+----------------------+-----------------------------------------------+
| *                    | **Design Procedures and Analysis**            |
| *DOT/FAA/AR-96/121** |                                               |
|                      | **of Turbine Rotor Fragment**                 |
| Office of Aviation   |                                               |
| Research             | **Hazard Containment**                        |
|                      |                                               |
| Washington, D.C.     | March 1997                                    |
| 20591                |                                               |
|                      | Final Report                                  |
|                      |                                               |
|                      | This document is available to the U.S. public |
|                      |                                               |
|                      | through the National Technical Information    |
|                      |                                               |
|                      | Service, Springfield, Virginia 22161.         |
|                      |                                               |
|                      | ![](me                                        |
|                      | dia/image1.emf){width="0.34305555555555556in" |
|                      | height="0.3548611111111111in"}                |
|                      |                                               |
|                      | U.S. Department of Transportation             |
|                      |                                               |
|                      | **Federal Aviation Administration**           |
+----------------------+-----------------------------------------------+

**NOTICE**

> This document is disseminated under the sponsorship of the U.S.
> Department of Transportation in the interest of information exchange.
> The United States Government assumes no liability for the contents or
> use thereof. The United States Government does not endorse products or
> manufacturers. Trade or manufacturer\'s names appear herein solely
> because they are considered essential to the objective of this report.

**Technical Report Documentation Page**

+----------------------+-----------+-----------+-----------+-----------+
| 1\. Report No.       | 2\.       |           | 3\.       |           |
|                      | G         |           | Rec       |           |
| DOT/FAA/AR-96/121    | overnment |           | ipient\'s |           |
|                      | Accession |           | Catalog   |           |
|                      | No.       |           | No.       |           |
+----------------------+-----------+-----------+-----------+-----------+
| 4\. Title and        |           |           |           |           |
| Subtitle             |           |           |           |           |
|                      |           |           |           |           |
| DESIGN PROCEDURES    |           |           |           |           |
| AND ANALYSIS OF      |           |           |           |           |
| TURBINE ROTOR        |           |           |           |           |
| FRAGMENT             |           |           |           |           |
+----------------------+-----------+-----------+-----------+-----------+
| HAZARD CONTAINMENT   |           |           |           |           |
+----------------------+-----------+-----------+-----------+-----------+
| 7\. Author(s)        |           |           |           |           |
|                      |           |           |           |           |
| Dr. J.A. Mathis      |           |           |           |           |
+----------------------+-----------+-----------+-----------+-----------+
| 9\. Performing       |           |           |           |           |
| Organization Name    |           |           |           |           |
| and Address          |           |           |           |           |
|                      |           |           |           |           |
| Mechanical           |           |           |           |           |
| Engineering          |           |           |           |           |
| Department           |           |           |           |           |
|                      |           |           |           |           |
| Wichita State        |           |           |           |           |
| University           |           |           |           |           |
+----------------------+-----------+-----------+-----------+-----------+
| Wichita, KS          |           |           |           |           |
| 67260-0133           |           |           |           |           |
+----------------------+-----------+-----------+-----------+-----------+
| 12\. Sponsoring      |           |           |           |           |
| Agency Name and      |           |           |           |           |
| Address              |           |           |           |           |
|                      |           |           |           |           |
| U.S. Department of   |           |           |           |           |
| Transportation       |           |           |           |           |
|                      |           |           |           |           |
| Federal Aviation     |           |           |           |           |
| Administration       |           |           |           |           |
+----------------------+-----------+-----------+-----------+-----------+
| Office of Aviation   |           |           |           |           |
| Research             |           |           |           |           |
|                      |           |           |           |           |
| Washington, DC 20591 |           |           |           |           |
+----------------------+-----------+-----------+-----------+-----------+
| 15\. Supplementary   |           |           |           |           |
| Notes                |           |           |           |           |
|                      |           |           |           |           |
| .                    |           |           |           |           |
+----------------------+-----------+-----------+-----------+-----------+
| 16\. Abstract        |           |           |           |           |
|                      |           |           |           |           |
| Containment design   |           |           |           |           |
| procedures are       |           |           |           |           |
| reviewed through an  |           |           |           |           |
| extensive literature |           |           |           |           |
| summary that spans   |           |           |           |           |
| 23 years of research |           |           |           |           |
| from 1970 to 1993.   |           |           |           |           |
| Sixty-four reports   |           |           |           |           |
| are summarized and   |           |           |           |           |
| cross referenced to  |           |           |           |           |
| provide a useful     |           |           |           |           |
| bibliography on the  |           |           |           |           |
| subject. Comments    |           |           |           |           |
| from industry and    |           |           |           |           |
| government agencies  |           |           |           |           |
| are included along   |           |           |           |           |
| with a study of      |           |           |           |           |
| existing analytical  |           |           |           |           |
| methods. These       |           |           |           |           |
| analytical methods   |           |           |           |           |
| have substantiated   |           |           |           |           |
| that system level    |           |           |           |           |
| engine and nacelle   |           |           |           |           |
| evaluations are      |           |           |           |           |
| research areas that  |           |           |           |           |
| require future       |           |           |           |           |
| development and      |           |           |           |           |
| standardization.     |           |           |           |           |
+----------------------+-----------+-----------+-----------+-----------+
| 17\. Key Words       |           | 18\.      |           |           |
|                      |           | Dis       |           |           |
| Turbine engine,      |           | tribution |           |           |
| Rotor, Containment   |           | Statement |           |           |
|                      |           |           |           |           |
|                      |           | This      |           |           |
|                      |           | document  |           |           |
|                      |           | is        |           |           |
|                      |           | available |           |           |
|                      |           | to the    |           |           |
|                      |           | public    |           |           |
|                      |           | through   |           |           |
|                      |           | the       |           |           |
|                      |           | National  |           |           |
|                      |           | Technical |           |           |
|                      |           | In        |           |           |
|                      |           | formation |           |           |
|                      |           | Service   |           |           |
|                      |           | (NTIS),   |           |           |
|                      |           | Spr       |           |           |
|                      |           | ingfield, |           |           |
|                      |           | Virginia  |           |           |
|                      |           | 22161.    |           |           |
+----------------------+-----------+-----------+-----------+-----------+
| 19\. Security        | 20\.      |           |           |           |
| Classif. (of this    | Security  |           |           |           |
| report)              | Classif.  |           |           |           |
|                      | (of this  |           |           |           |
| Unclassified         | page)     |           |           |           |
|                      |           |           |           |           |
|                      | Unc       |           |           |           |
|                      | lassified |           |           |           |
+----------------------+-----------+-----------+-----------+-----------+

**Form DOT F1700.7** (8-72) Reproduction of completed page authorized

TABLE OF CONTENTS

Page

EXECUTIVE SUMMARY v

1\. INTRODUCTION

2\. LITERATURE SURVEY

2.1 Comprehensive Literature Summary

2.2 Index of Key Topics

3\. COMMENTS FROM INDUSTRY AND REGULATORY GROUPS

3.1 Large Engine Manufacturers

3.2 Small Engine and APU Manufacturers

3.3 Large Airframe Manufacturers

3.4 Small Airframe Manufacturers

3.5 Research Institutions and Government Agencies

4\. ANALYSIS OF CONTAINMENT/SHIELDING STRUCTURES

5\. CONCLUSIONS

LIST OF FIGURES

Figure Page

1 Flat Plate---Inconel 625 and A286 Steel Displacement Versus Impactor
Energy

2 Flat Plate---Inconel 625 Maximum Total Reaction Force Versus Impactor
Energy

3 Flat Plate---Inconel 625 and A286 Steel Time of Maximum Plate
Deflection

4 Steel Rings Internal Energy Time Histories

LIST OF TABLES

Table Page

1 Material Properties

2 Containment Experiment Results

EXECUTIVE SUMMARY

The Wichita State University Department of Mechanical Engineering was
tasked by the Federal Aviation Administration (FAA) William J. Hughes
Technical Center to evaluate the existing literature and procedures used
to design engine rotors and containment of engine rotors for hazard
mitigation. This report presents an extensive literature summary of 64
reports covering 23 years of research from 1970 to 1993. The reports are
cross referenced to an index of key topics for future researchers. The
final sections of the report provide industry viewpoints and examples of
work performed. To date there is no industry standard for assessing the
containment capability of a combined engine and nacelle with proven
numerical methods. Additional finite element code development is
necessary to match the numerical results with the growing body of
experimental data.

# 1. INTRODUCTION.

The general topic of containment of rotating parts in gas turbine
engines and protection of the aircraft in the case of noncontainment
remains an active area for industry research and development and
regulatory interest. The work summarized in this report was to determine
some sense of whether a state of the art exists for the problem of
designing structural components for containment or shielding functions.

This report is divided into three sections. The first is a literature
summary of reports and articles published on rotor fragment containment
and deflection. The literature citations are organized chronologically
and each is accompanied by a brief summary. A keyword index also
accompanies the literature summary section, so that interested designers
might find a convenient means to locate relevant technical reports.

In the second section, the results of many discussions with aircraft
engine manufacturers, aircraft airframe manufacturers, and related
governmental and research institutions are presented. Included are
statements from technical personnel about general and specific design
methods in use. Comments offered about the overall topic of rotor burst
containment, minimization of damage from uncontained rotor bursts, and
the relation of these topics in the overall concept of aircraft safety
are also reported.

In the final section, some results of containment/shielding structure
analysis are presented. This work was accomplished with commercially
available general purpose finite element structural codes and the
purpose of engaging in this task was to determine the suitability of
such tools for the design problem. Some examples are provided, showing
the types of design information which can be obtained from these codes.

# 2. LITERATURE SURVEY.

## 2.1 COMPREHENSIVE LITERATURE SUMMARY.

This section is a bibliography, including a short summary of each
article, of reports and articles published on rotor burst containment
and related issues. The time period covered is from 1970 to 1993. The
citations are limited to those directly addressing the subject, hence
more general articles on topics such as high velocity impact, for
example, are not included. The ordering of references is chronological.

In section 2.2, an index of key words and topics contained in these
references is provided. The index numbers refer to the RECORD NUMBERS in
this section.

RECORD NO. N001

Title: Simplified Analysis of a Trifragment Rotor Disk Interaction with
a Containment Ring

Author: R. Bruce McCallum

Date: May 1970

Report No.: [Journal of Aircraft]{.underline}, Vol. 7, No. 3

SUMMARY: The report discusses the JET 1 program developed at MIT for
predicting the large deflection transient response of a containment ring
structure. Compares predicted shear stress values with material ultimate
shear stress values and discusses applicability of a shear stress
failure criteria.

RECORD NO. N002

Title: Designing Rotor Burst Protection

Author: A.A. Martino

Date: April 1971

Report No.: ASME 71-GT-70

Gas Turbine Conference and Products Show

Houston, Texas, March 28-April 1, 1971

SUMMARY: The report describes the NASA sponsored Rotor Burst Protection
Program including a summary of MIT computer code development and the
test program carried out at the Naval Air Propulsion Test Center. The
test facility and test procedures are described and several factors
important in the design of containment systems, shown from the test
data, are presented.

RECORD NO. N003

Title: Status of Engine Rotor Burst Protection Program for Aircraft

Author: Patrick T. Chiarito

Date: May 1971

Report No.: NASA SP-270

SUMMARY: The report discusses the NASA program and describes the
experimental facility at the Naval Air Propulsion Test Center for
testing containment rings. Parameters noted to be especially relevant
include early experimental results on the deformation characteristics of
the ring, the effect of the number of fragments on the containment
capability of the ring (i.e., is a four-way rotor burst worse than a
three-way burst), and the relative performance of candidate containment
ring materials including several steels and ballistic nylon cloth. The
use of partial rings as deflector shields is discussed. Some
nondimensional parameters affecting containment ring performance are
identified.

RECORD NO. N004

Title: Dimensional Analysis Considerations in the Engine Rotor Fragment
Containment/ Deflection Problem

Author: John W. Leech, Emmett A. Witmer, and Raffi P. Yeghiayan

Date: December 1971

Report No.: NASA CR-120841

SUMMARY: The use of dimensional analysis to design effective containment
experiments is discussed. An example illustrates the technique used to
determine parameters necessary to design simple circular containment
rings impacted by bladed rotor fragments. Use of a parameter called the
containment threshold is discussed for characterizing performance.
Suggestions are made for the design of a testing program to investigate
material effects.

RECORD NO. N005

Title: Examination of the Collision Force Method for Analyzing the
Responses of Simple Containment/Deflection Structures to Impact by One
Engine Rotor Blade Fragment

Author: Robert M. Zirin and Emmett A. Witmer

Date: May 1972

Report No.: NASA CR-120952

SUMMARY: Describes the theory and applicability of the (MIT developed)
Collision Force Method (CFM). The method predicts collision forces and
ring and fragment responses. The report includes a section addressing
the use of this method in deducing blade structural behavior during
impact, e.g., elastic-plastic curling.

RECORD NO. N006

Title: Development and Modifications of the RB211 Engine

Author: Anon

Date: May 1972

Report No.: Aircraft Engineering Vol. 44

SUMMARY: Narrative of blade containment considerations in engine design.
Lists containment ring general features.

RECORD NO. N007

Title: Rotor Burst Protection Program: Statistics on Aircraft Gas
Turbine Engine Failures That Occurred in Commercial Aviation During 1971

Author: R.A. DeLucia and G.J. Mangano

Date: February 1973

Report No.: NASA-CR-131525

SUMMARY: One of an annual series. (Refer to Record No. N061.)

RECORD NO. N008

Title: Application of the Collision-Imparted Velocity Method for
Analyzing the Responses of Containment and Deflector Structures to
Engine Rotor Fragment Impact

Author: Thomas P. Collins and Emmett A. Witmer

Date: August 1973

Report No.: NASA-CR-134494

SUMMARY: Presents theory, application, and example problems of
fragment/containment ring response calculated with the
collision-imparted velocity method (CIVM). Includes a detailed user's
guide to the MIT-developed CIVM-JET-4A program. The program calculates
transient response for complete and partial rings which may have a
number of boundary conditions subject to impacting fragments specified
by initial dynamical properties. The report includes comparisons with
experiments.

RECORD NO. N009

Title: Experimental and Data Analysis Techniques for Deducing
Collision-Induced Forces From Photographic Histories of Engine Rotor
Fragment Impact/Interaction With a Containment Ring

Author: Raffi P. Yeghiayan, John W. Leech, and Emmett A. Witmer

Date: October 1973

Report No.: NASA-CR-134548

SUMMARY: Describes experiments and data analysis for obtaining transient
response data (force and deformation history) of containment rings. Data
is intended to be used as input for a structural response computer code
to estimate the forces which would have been required for the measured
input to be produced.

RECORD NO. N010

Title: General Specification for Engines, Aircraft, Turbojet, and
Turbofan

Author: U.S. Military Specification

Date: October 1973

Report No.: MIL-E-5007D

SUMMARY: This is a generic specification for all departments and
agencies of the Department of Defense. Containment criteria are
specified, consisting primarily in the ability of the engine to
completely contain a single fan, compressor or turbine blade, and all
parts damaged and released by the failure of the blade. The means of
demonstrating that containment criteria have been met is also specified.

RECORD NO. N011

Title: Rotor Burst Protection Program: Statistics on Aircraft Gas
Turbine Engine Rotor Failures That Occurred in U.S. Commercial Aviation
During 1972

Author: R.A. DeLucia and G.J. Mangano

Date: March 1974

Report No.: NASA-CR-136900

SUMMARY: One of an annual series. (Refer to Record No. N061.)

RECORD NO. N012

Title: The Containment of Disk Burst Fragments by Cylindrical Shells

Author: A.C. Hagg and G.O. Sankey

Date: April 1974

Report No.: ASME 73-WA-Pwr-2

ASME Winter Annual Meeting, Detroit, Michigan, November 11-15, 1973

SUMMARY: The paper discusses containment of steel disk fragments by a
steel cylindrical shell. Test results support an analytical development
that describes containment in terms of a two-stage process---a localized
inelastic impact and momentum transfer followed (if penetration does not
occur) by development of large tensile strains in large areas of the
shell. It also includes criteria for containment and test results for
cylindrical shells.

RECORD NO. N013

Title: Analysis of Rotor Fragment Impact on Ballistic Fabric Engine
Burst Containment Shields

Author: J.H. Gerstle

Date: September 1974

Report No.: ISSN: 0021-8669

Symposium on Propulsion System Structural Integration and Engine
Integrity

Naval Postgraduate School, Monterey, California, September 3-6, 1974

SUMMARY: This report discusses the development of a material model for
ballistic fabrics in which fabric is modeled as a single or multilayered
membrane which can support loads along the fibers. It also includes a
comparison with experimental test data.

RECORD NO. N014

Title: Rotor Burst Protection Program: Statistics on Aircraft Gas
Turbine Engine Rotor Failures That Occurred in U.S. Commercial Aviation
During 1973

Author: R.A. DeLucia and G.J. Mangano

Date: August 1975

Report No.: NASA-CR-134854

SUMMARY: One of an annual series. (Refer to Record No. N061.)

RECORD NO. N015

Title: Rotor Burst Protection Program: Statistics on Aircraft Gas
Turbine Engine Rotor Failures That Occurred in U.S. Commercial Aviation
During 1974

Author: R.A. DeLucia and G.J. Mangano

Date: September 1975

Report No.: NASA-CR-134855

SUMMARY: One of an annual series. (Refer to Record No. N061.)

RECORD NO. N016

Title: Structural Effects of Engine Burst Noncontainment

Author: T.W. Coombe

Date: October 1975

Report No.: ISSN: 0549-7191

Spec Meeting on Impact Damage Tolerance of Structures

Ankara, Turkey, September 28-October 3, 1975

SUMMARY: This report discusses the general problem of designing to
minimize structural damage and contains an empirical correlation for
energy absorbed by full penetration for several ductile metals.

RECORD NO. N017

Title: Design Considerations for Minimizing Damage Caused by Uncontained
Aircraft Turbine Engine Rotor Failures

Author: Federal Aviation Administration

Date: November 1975

Report No.: Order 8110.11 (FAA)

SUMMARY: This order outlines design considerations in terms of engine
location, location of critical systems and components, and protective
armor and deflectors.

RECORD NO. N018

Title: User's Guide to Computer Program CIVM-JET 4B to Calculate the
Transient Structural Responses of Partial and/or Complete Structural
Rings to Engine-Rotor-Fragment Impact

Author: Thomas R. Stagliano, Robert L. Spilker, and Emmett A. Witmer

Date: March 1976

Report No.: NASA-CR-134907

SUMMARY: This detailed user's guide includes a FORTRAN IV listing of the
program. The CIVM-JET 4B program, developed at MIT under contract to
NASA, was developed to predict the large-deflection elastic-plastic
structural responses of single layer partial or complete ring
containment structures.

RECORD NO. N019

Title: Development of Fiber Shields for Engine Containment

Author: R.J. Bristow and C.D. Davidson

Date: March 1977

Report No.: NASA CP-2017

SUMMARY: Empirical work done at the Boeing Company is described. Two
models were developed from the experimental work. The first relates the
weight of the shield with projectile sizes and velocities. The second
relates the shield mount load to the mount dynamic stiffness and
attachment method.

RECORD NO. N020

Title: Federal Aviation Administration's Approach to Engine Rotor
Integrity

Author: A.K. Forney

Date: March 1977

Report No.: NASA CP-2017

SUMMARY: This report summarizes the FAA policy and philosophy at the
time of the conference. It also discusses the three-fold approach of (1)
designing engines not to fail, (2) designing engines for containment
when they fail, and (3) designing aircraft for minimum damage when
engines fail and containment fails. The FARs pertinent to this
philosophy are cited and summarized.

RECORD NO. N021

Title: Ceramic Composite Protection for Turbine Disc Bursts

Author: P.B. Gardner

Date: March 1977

Report No.: NASA CP-2017

SUMMARY: This report discusses the design and testing of a shield
developed to protect the tail section of the A300B from auxiliary power
unit compressor rotor fragment attack. The design, consisting of boron
carbide panels backed with woven fiberglass in a high-temperature resin,
is stated to have been very successful in terms of economics and minimum
weight penalty.

RECORD NO. N022

Title: Analysis Method for Kevlar Shield Response to Rotor Fragments

Author: J.H. Gerstle

Date: March 1977

Report No.: NASA CP-2017

SUMMARY: This report describes the theory of a Boeing Company developed
finite difference large deflection plate/shell code. Comparisons of
predicted and measured peak displacements are shown.

RECORD NO. N023

Title : Engine Noncontainment---The UK CAA View

Author: G.L. Gunstone

Date: March 1977

Report No.: NASA CP-2017

SUMMARY: This report presents the CAA philosophy on designing for engine
noncontainment. Worldwide accident histories are discussed as rationale
for the regulations. Some background is presented explaining the
implementation of a probability figure (probability of catastrophic
failure as a result of uncontained failure) as part of the design
criteria.

RECORD NO. N024

Title : Metallic Armor for Ballistic Protection From Steel Fragments

Author: Donald F. Haskell

Date: March 1977

Report No.: NASA CP-2017

SUMMARY: This report describes experimental data collected for
cylindrical steel fragments impacting on six different alloys.
Experimental data is available in unclassified reports of the U.S. Army
Ballistic Research Laboratory.

RECORD NO. N025

Title: Concepts for the Development of Lightweight Composite Structures
for Rotor Burst Containment

Author: Arthur G. Holms

Date: March 1977

Report No.: NASA CP-2017

SUMMARY: This report summarizes lessons learned from previous rotor
burst containment experiments and uses these observations to form
guidelines for an effective testing program.

RECORD NO. N026

Title: Rotor Burst Protection Program---Experimentation to Provide
Guidelines for the Design of Turbine Rotor Burst Fragment Containment
Rings

Author: G.J. Mangano, J.T. Salvino, and R.A. DeLucia

Date: March 1977

Report No.: NASA CP-2017

SUMMARY: This report discusses results of experimentation done at the
Naval Air Propulsion Test Center. Guidelines were developed for
designing optimum weight containment rings for turbine disk fragments.

RECORD NO. N027

Title: Types of Rotor Failure and Characteristics of Fragments

Author: D. McCarthy

Date: March 1977

Report No.: NASA CP-2017

SUMMARY: This report presents statistics on engine noncontainment
collected by Rolls Royce. Discusses in detail the possible failure modes
of engine components. Describes characteristics of fragments in terms of
size, velocity, energy, and angle of deflection.

RECORD NO. N028

Title: Rotor Burst Protection Criteria and Implications

Author: Ralph B. McCormick

Date: March 1977

Report No.: NASA CP-2017

SUMMARY: This report reviews, without specifics, aircraft design methods
for minimizing damage from uncontained rotor burst and the effect of
noncontainment and noncontainment protection on aircraft design.
Presents brief results of a Boeing study of noncontainment accident
statistics. A point made is that if additional containment (weight)
measures will contain low-energy fragments but be ineffective against
high-energy fragments, the improvement to aircraft safety will be
minimal.

RECORD NO. N029

Title: Blade Fragment Energy Analysis

Author: M.A. O'Connor, Jr.

Date: March 1977

Report No.: NASA CP-2017

SUMMARY: This document generally discusses work done at Douglas Aircraft
but with no details. It also describes the development of analytical
methods to describe blade fragment dynamics and a testing program to
determine the effectiveness of Kevlar cloth containment systems.

RECORD NO. N030

Title: Numerical Analysis of Impact in Woven Textile Structures

Author: D. Roylance

Date: March 1977

Report No.: NASA CP-2017

SUMMARY: This report describes the theory and application of a computer
code designed to predict the impact response of woven fabrics. User
input consists of material properties, weave geometry, and projectile
velocity. Experiments are compared to the computed predictions for
single layer Kevlar 29 fabric and small projectiles with velocities up
to 700 meters per second. A comparison of Kevlar 29, Kevlar 49, nylon,
and graphite based on the results of the computer model is also
examined.

RECORD NO. N031

Title: Engine Noncontainment---UK Risk Assessment Methods

Author: J.C. Wallin

Date: March 1977

Report No.: NASA CP-2017

SUMMARY: A detailed technical discussion of the calculation of risk to
the aircraft from uncontained rotor burst including the use of a
detailed engine failure model as part of the calculation process. It
also discusses some specific measures implemented in the Concorde.

RECORD NO. N032

Title: Lightweight Engine Containment

Author: A.T. Weaver

Date: March 1977

Report No.: NASA CP-2017

SUMMARY: This paper summarizes the Pratt & Whitney work done for
development of Kevlar fabric containment systems for blade containment.
The work included ballistic impact evaluations, laboratory tests, spin
pit tests, and engine tests. Key results included the efficiency of
Kevlar compared to hardened steel, the result that Kevlar efficiency
decreases if the fabric deflection is constrained, and the fact that
Kevlar fabric can absorb multiple hits. Wicking and flammability tests
to define the fire resistance of Kevlar are also reported.

RECORD NO. N033

Title: Analysis of Simple 2-D and 3-D Metal Structures Subjected to
Fragment Impact

Author: E.A. Witmer, T.R. Stagliano, R.L. Spilker, and J.J.A. Rodal

Date: March 1977

Report No.: NASA CP-2017

SUMMARY: This report describes analytical work done at the MIT
Aeroelastic and Structures Research Laboratory. It also discusses the
merits and limitations of the collision force method versus the
collision imparted velocity method. Analytical predictions are compared
with experimental data obtained at the Naval Air Propulsion Center (both
single-blade fragment and trihub turbine rotor burst) and impact
experiments done with solid spherical impactors against aluminum panel
and beam targets.

RECORD NO. N034

Title: Rotor Burst Protection Program: Statistics on Aircraft Gas
Turbine Engine Rotor Failures That Occurred in U.S. Commercial Aviation
During 1975

Author: R.A. DeLucia and G.J. Mangano

Date: May 1977

Report No.: NASA-CR-135304

SUMMARY: One of an annual series. (Refer to Record No. N061.)

RECORD NO. N035

Title: Study to Improve Airframe Turbine Engine Rotor Blade Containment

Author: C.O. Gunderson

Date: July 1977

Report No.: FAA-RD-77-44

SUMMARY: This study, performed by McDonnell Douglas Corporation for the
FAA, examines the range of energies and trajectories of various blade
fragments and tests the energy absorption capability of various
candidate materials to provide protection from the blade fragments. The
necessary armor weights are determined, and the economics of installing
such armor is discussed.

RECORD NO. N036

Title: Report on Aircraft Engine Containment

Author: Society of Automotive Engineers/Committee on Engine Containment

Date: October 1977

Report No.: AIR 1537

SUMMARY: This report contains detailed statistics on noncontained
failures including classification by degree of damage, fragment type,
flight mode, and cause of failure. It also contains a discussion on
potential for improvement of aircraft safety in terms of engine design,
aircraft design, and increased containment capability.

RECORD NO. N037

Title: Rotor Fragment Protection Program: Statistics on Aircraft Gas
Turbine Engine Rotor Failures That Occurred in U.S. Commercial Aviation
During 1976

Author: R.A. DeLucia and J.T. Salvino

Date: July 1978

Report No.: NASA-CR-159474

SUMMARY: One of an annual series. (Refer to Record No. N061.)

RECORD NO. N038

Title: Two-Dimensional Finite-Element Analyses of Simulated
Rotor-Fragment Impacts Against Rings and Beams Compared with Experiments

Author: Witmer

Date: August 1978

Report No.: NASA-CR-159645

SUMMARY: The report presents a detailed theoretical description of the
CIVM-JET 4B computer code. The response of containment ring response to
a trihub burst is analyzed and discussed. It also includes dimensional
analysis considerations and the use of deflectors for fragment control.

RECORD NO. N039

Title: Containment of Composite Fan Blades

Author: C.L. Stotler and A.P. Coppa

Date: July 1979

Report No.: NASA-CR-159544

SUMMARY: Prepared by General Electric under a NASA contract, this
document describes (1) an analytical determination of blade impact
behavior; (2) scaled blade impact tests conducted on containment rings
formed of Kevlar/epoxy fins mated to an aluminum ring, Kevlar cloth
faced with an aluminum ring, aluminum honeycomb, and stainless steel
ring; and (3) design and fabrication of a containment system utilizing
results of testing and final testing of the design concept. A graph
showing Kevlar thickness required for containment versus blade kinetic
energy is included.

RECORD NO. N040

Title: Composite Containment Systems for Jet Engine Fan Blades

Author: G.T. Smith

Date: February 1981

Report No.: NASA-TM-81675

Thirty-Sixth Annual Conference of the Reinforced Plastics/Composites
Institute of the Society of the Plastics Industry, Inc., Washington,
D.C., February 16-20, 1981

SUMMARY: The report describes the testing of composite containment
structures that include Kevlar/epoxy fins mounted on an aluminum ring,
an aluminum honeycomb, and a Kevlar cloth filled ring. It also includes
the curve of Kevlar thickness required versus blade kinetic energy.

RECORD NO. N041

Title: Development of Advanced Lightweight Systems Containment

Author: C.L. Stotler

Date: May 1981

Report No.: NASA CR-165212

SUMMARY: This report describes testing done by General Electric (NASA
contract) with dry weave Kevlar for blade containment for a CF6-size
engine. Experimental data is used to construct a curve of amount of
Kevlar cloth required versus blade impact energy.

RECORD NO. N042

Title: Rotor Fragment Protection Program: Statistics on Aircraft Gas
Turbine Engine Rotor Failures That Occurred in U.S. Commercial Aviation
During 1978

Author: R.A. DeLucia and J.T. Salvino

Date: September 1981

Report No.: NASA-CR-165388

SUMMARY: One of an annual series. (Refer to Record No. N061.)

RECORD NO. N043

Title: Rotor Fragment Protection Program: Statistics on Aircraft Gas
Turbine Engine Rotor Failures That Occurred in U.S. Commercial Aviation
During 1979

Author: R.A. DeLucia and J.T. Salvino

Date: October 1982

Report No.: NASA/CR-168163

SUMMARY: One of an annual series. (Refer to Record No. N061.)

RECORD NO. N044

Title: Statistics on Aircraft Gas Turbine Engine Failures That Occurred
in U.S. Commercial Aviation During 1981

Author: R.A. DeLucia, J.T. Salvino, and T. Russo

Date: March 1987

Report No.: DOT/FAA/CT-86/42

SUMMARY: One of an annual series. (Refer to Record No. N061.)

RECORD NO. N045

Title: Report on Aircraft Engine Containment

Author: Society of Automotive Engineers/Committee on Engine Containment

Date: September 1987

Report No.: AIR 4003

SUMMARY: This report presents detailed statistical data on noncontained
rotor failures including classification by degree of damage, engine
type, flight mode, engine and rotating part component, and cause. It
also includes rotorcraft and general aviation data not included in a
similar report issued in 1977. This report also discusses potential
improvements in the areas of engine design, aircraft design, bird
threat, and maintenance. This report provides an overview of related FAA
regulations and certification procedures.

RECORD NO. N046

Title: Design Considerations for Minimizing Hazards Caused by
Uncontained Turbine Engine and Auxiliary Power Unit Rotor and Fan Blade
Failures

Author: Federal Aviation Administration

Date: March 1988

Report No.: Advisory Circular AC 20-128

SUMMARY: This AC recommends design consideration be directed at location
of rotating sections relative to critical components and suggests a
maximum fragment size and energy level for design purposes. It also
suggests that the airframe designer obtain fragment energies and
trajectories from the engine manufacturer's data.

RECORD NO. N047

Title: A Turbine Wheel Design Story

Author: Wilson R. Taylor, Keith Wheless, and Lee G. Gray

Date: June 1988

Report No.: ASME 88-GT-316

Gas Turbine and Aeroengine Congress

Amsterdam, The Netherlands, June 6-9, 1988

SUMMARY: Design considerations relating to containment issues for a Jet
Fuel Starter used in the F-15 Fighter Aircraft are discussed.
Consideration is given to limiting the power turbine containment ring by
designing the power turbine wheel to break into small pieces.

RECORD NO. N048

Title: Statistics on Aircraft Gas Turbine Engine Rotor Failures That
Occurred in U.S. Commercial Aviation During 1982

Author: R.A. DeLucia and J.T. Salvino

Date: July 1988

Report No.: DOT/FAA/CT-88/23

SUMMARY: One of an annual series. (Refer to Record No. N061.)

RECORD NO. N049

Title: Experimental Guidelines for the Design of Turbine Rotor Fragment
Containment Rings

Author: James T. Salvino, Robert A. DeLucia, and Tracy Russo

Date: July 1988

Report No.: DOT/FAA/CT-88/21

SUMMARY: Experiments performed at the Naval Air Propulsion Center are
described. In the first set of experiments, containment rings
constructed of Kevlar fabric and ballistic nylon are tested for
containment of trihub turbine rotor failures. In the second set,
containment rings constructed of aluminum, 304 stainless steel, and
A-286 steel are tested for their ability to contain single and triple
blade release events. Test results include findings that a minimum
casing thickness of 0.375 inch is required to contain the tested JT8D
and JT3D blades.

RECORD NO. N050

Title: Statistics on Aircraft Gas Turbine Engine Rotor Failures That
Occurred in U.S. Commercial Aviation During 1983

Author: R.A. DeLucia and J.T. Salvino

Date: March 1989

Report No.: DOT/FAA/CT-89/5

SUMMARY: One of an annual series. (Refer to Record No. N061.)

RECORD NO. N051

Title: Statistics on Aircraft Gas Turbine Engine Rotor Failures That
Occurred in U.S. Commercial Aviation During 1984

Author: R.A. DeLucia, J.T. Salvino, and B.C. Fenton

Date: June 1989

Report No.: DOT/FAA/CT-89/6

SUMMARY: One of an annual series. (Refer to Record No. N061.)

RECORD NO. N052

Title: Statistics on Aircraft Gas Turbine Rotor Failures That Occurred
in U.S. Commercial Aviation During 1985

Author: R.A. DeLucia, J.T. Salvino, and B.C. Fenton

Date: July 1989

Report No.: DOT/FAA/CT-89/7

SUMMARY: One of an annual series. (Refer to Record No. N061.)

RECORD NO. N053

Title: Development of an Advanced Fan Blade Containment System

Author: Alan D. Lane

Date: August 1989

Report No.: DOT/FAA/CT-89/20

SUMMARY: Ceramic-based blade containment systems are studied. Such a
system is designed for minimum weight and compared with metal systems
for weight and cost effectiveness. Kevlar and B~4~C/Spectra systems are
examined.

RECORD NO. N054

Title: Statistics on Aircraft Gas Turbine Engine Rotor Failures That
Occurred in U.S. Commercial Aviation During 1986

Author: R.A. DeLucia, J.T. Salvino, and B.C. Fenton

Date: January 1990

Report No.: DOT/FAA/CT-89/30

SUMMARY: One of an annual series. (Refer to Record No. N061.)

RECORD NO. N055

Title: Development of Helicopter Modular Armor Systems and Installation
Techniques

Author: U.S. Army Materials Technology Laboratory

Date : March 1990

Report No.: MTL TR 90-11

SUMMARY: Not summarized.

RECORD NO. N056

Title: An Overview of Propulsion System Risks 1959 Through 1989

Author: G.P. Sallee

Date: November 1990

Report No.: Boeing Commercial Airplane Company D6-55456

SUMMARY: A comprehensive study of all propulsion-type risks, which
includes statistics on uncontained turbojet and turbofan engine
failures.

RECORD NO. N057

Title: Titanium Rotating Components Review Team Report

Author: Federal Aviation Administration/Aircraft Certification
Service/Engine and Propeller Directorate

Date: December 1990

Report No.: N/A

SUMMARY: This report describes the results of a project to collect data
and provide a review of industry practices relevant to titanium rotating
parts in aircraft turbine engines. Aspects of design, manufacturing,
quality control, and inspection procedures were investigated. Detailed
recommendations are made.

RECORD NO. N058

Title: Statistics on Aircraft Gas Turbine Engine Rotor Failures That
Occurred in U.S. Commercial Aviation During 1987

Author: R.A. DeLucia, B.C. Fenton, and Janine Blake

Date: January 1991

Report No.: DOT/FAA/CT-90/19

SUMMARY: One of an annual series. (Refer to Record No. N061.)

RECORD NO. N059

Title: The Impact Load on Containment Rings During a Multiple Blade Shed
in Aircraft Gas Turbine Engines

Author: T.B. Dewhurst

Date: June 1991

Report No.: ASME 91-GT-163

> International Gas Turbine and Aeroengine Congress and Exposition,
> Orlando, Florida, June 3-6, 1991

SUMMARY: Using experimental data of ring displacement during a multiple
blade shed event in a medium sized gas turbine engine, the finite
element code ANSYS is used to develop an impact load record. Reaction
force results are presented. Details and problems with the numerical
analysis are discussed. Observations of field experience are presented
regarding failure modes, with brittle tensile failure identified as the
most common mode.

RECORD NO. N060

Title: Statistics on Aircraft Gas Turbine Engine Rotor Failures That
Occurred in U.S. Commercial Aviation During 1988

Author: R.A. DeLucia, B.C. Fenton, and E.R. Chapdelaine

Date: March 1992

Report No.: DOT/FAA/CT-91/28

SUMMARY: One of an annual series. (Refer to Record No. N061.)

RECORD NO. N061

Title: Statistics on Aircraft Gas Turbine Engine Rotor Failures That
Occurred in U.S. Commercial Aviation During 1989

Author: E.R. Chapdelaine, B.C. Fenton, R.A. DeLucia, and M. Muller

Date: June 1992

Report No.: DOT/FAA/CT-92/5

SUMMARY: The statistics contained in this report were taken from the FAA
Flight Standards Service Difficulty Reports. The reports were analyzed
to establish the number of contained and uncontained rotor bursts, the
distribution of failures among engine components and fragment types, and
the cause of failure. Also included is the distribution of incidents by
engine type and the flight condition at the time of failure. An analysis
of engine failure rate according to engine fleet hours is included. The
incidence of uncontained rotor bursts in the years 1962 through 1984 is
presented.

RECORD NO. N062

Title: The Use of Imposed Displacements to Determine Impact Forces in a
Multiple Blade Shed Incident

Author: T.B. Dewhurst

Date: May 1993

Report No.: ASME 93-GT-127

International Gas Turbine and Aeroengine Congress, Cincinnati, Ohio

SUMMARY: The report presents an approach to finding forces exerted on
containment rings by blades. Experimental data on containment ring
deflection is used with the ANSYS finite element code. The report also
focuses on the correct use of the numerical parameters required for
accurate modeling.

RECORD NO. N063

Title: Fiber Reinforced Structures for Turbine Engine Fragment
Containment

Author: J. Pepin

Date: June 1993

Report No.: AIAA 93-1816

29th Joint Propulsion Conference, Monterey, CA

SUMMARY: The report describes experimental program to test fiber
reinforced systems for containment of turbine rotor disks. The effect of
construction details is investigated. Hybrid sandwich panels were found
to perform comparably to honeycomb panels. Polybenzbisoxazole (PBO) is
tested as an option for hot-section containment.

RECORD NO. N064

Title: Analysis of Turbine Engine Rotor Containment and Shielding
Structures

Author: J.A. Mathis, S.C. Parduhn, and P. Alvarez

Date: June 1993

Report No.: AIAA 93-1817

29th Joint Propulsion Conference, Monterey, CA

SUMMARY: Applies commercial finite element codes to geometries and
fragment energies typical of containment problems. Describes results
available from analysis such as displacement, reaction force, and energy
absorption histories.

## 2.2 INDEX OF KEY TOPICS.

The following index accompanies the record number list in section 2.1.
Key topics from the bibliographic record are arranged here in
alphabetical order. The index numbers refer to the RECORD NUMBERS in
section 2.1.

Analytical research---001, 005, 008, 009, 018, 022, 024, 033, 039, 059,
062

Fabric---013, 022, 030

Failure criteria---001

Finite element codes---059, 062, 064

Armor

Helicopter---055

Metallic---024

Auxiliary power unit---021

Blade fragments

Deformation---002

Dynamics---029, 035

Impact structural behavior---039

Ceramic

Ceramic composite---021, 053

Ceramic composite, environmental test---021

Ceramic composite resin, high temperature---021

Ceramic composite armor---021

Civil Aviation Authority (CAA)---016, 023, 031

Containment

Blades---002, 003, 006, 010, 032, 049, 059, 062

Containment criteria---004, 022, 026, 028, 040

Military engines---010

Disk fragments---001, 003, 026, 024, 049, 063

Engine casing thickness required---049

Fan blades---039, 040, 041, 053

Parameter study---004, 025

Threshold---004

Containment ring

Axial length---026

Clearance from rotor---002

Deformation of---013

Failure mode---001, 012, 059

Finned---022

Restraints---002, 003

Sandwich panel (hybrid structural)---063

Stiffening ribs---006

Weight of---013

Deflectors---017

Disk fragment---024

Design

Aircraft considerations---016, 017, 020, 028, 035, 036, 045

Containment rings---041, 049

Experimental guidelines---026, 049

Engine considerations---006, 036, 045, 047, 049, 057

Dimensional Analysis---003, 004, 039

Disk failure mode---012, 027

Empirical Models---016, 019, 035, 049

Environmental testing---021, 032

Experimental research---002, 012, 019, 035, 039, 040, 041, 049, 063

Ceramic composites---021

Comparison with analytical work---009

Engine containment test---032

Planning for experiments---004, 025, 053

Spin pit testing---002, 009, 019, 026, 040, 063

Federal Aviation Administration Policy---020, 036, 045

Fragments

Deflection of---003, 027

Energy---002, 012, 027, 029

Geometry---002, 027, 053

Number of---003, 026

Residual velocity---012

Retention---039, 040

Spread angle---016, 027

Trajectory---013

Honeycomb materials---029, 041

Containment structure, aluminum---035, 039

Containment structure, steel---035

Kevlar---019, 022, 032, 035, 039, 040, 041, 049, 053, 063

Environmental tests---032

Fire resistance---032

Restraint of fabric---040

Weave geometry---030, 032, 049, 063

Weight required---032, 035, 039, 040, 053

Material

Material comparisons---002, 022, 053, 063

Material models---004

Fabric---013, 022, 030

Strain rate---024

Materials

Alumina---021, 053

Aluminum---002

Ballistic nylon---002, 003, 049

Boron carbide---021, 026, 053

Ceramics---053

Ceramic/polymer fiber composite---053

E-glass---002, 003

Rubber/metal composite---021

PBO (polybenzbisoxazole)---063

S-glass---013, 022

Spectra

TRIP steel---002, 003

Military Containment Criteria---010

Risk, calculation of---016, 023, 031, 056

Shields---002, 017, 019

Mounting---019

Statistics

Uncontained failures---002, 007, 011, 014, 015, 023, 034, 036, 037, 042,

043, 044, 045, 048, 050, 051, 052, 054, 056, 058

060, 061

Cause---007, 011, 014, 023, 027, 034, 036, 037, 042, 043, 044, 045

048, 050, 051, 052, 054, 056, 058, 060, 061

Damage severity---028, 036, 045

Propulsion related---056

United Kingdom---027

Worldwide---023, 056

Testing

Verification of containment criteria---010, 020

Turbine Wheel

Frangible---047

Uncontained failure

Energy absorption by aircraft structure---035

Engine failure model---031

Structural damage---016, 028, 031

Weight of containment structures---013, 023, 026, 035

# 3. COMMENTS FROM INDUSTRY AND REGULATORY GROUPS.

A portion of this research task included visiting with and gathering the
opinions and comments of a variety of airframe and engine manufacturers
and agencies involved in the issue of containment. An initial list of
companies involved was developed, however not everyone contacted wished
to participate in discussions.

Generally, the companies and agencies visited could be placed in the
following categories: large engine manufacturers, small engine and APU
manufacturers, large airframe manufacturers, small airframe
manufacturers, research institutions, and governmental agencies. Since
issues involving rotor burst containment are considered by most to be
highly sensitive, the comments presented in this report are left
anonymous in the above categories. Most companies were unsure of our
motives in talking with them, especially in light of the research
project being funded by the FAA and the fact that the preparation of the
AC on minimizing the hazards from engine rotor burst noncontainment was
still ongoing.

## 3.1 LARGE ENGINE MANUFACTURERS.

A typical opinion expressed by large engine manufacturers was that their
extensive research and development efforts into rotor containment
advances had cost them a lot of money. Hence, they did not wish to
reveal any technical details or discuss company philosophy. One company
indicated that analytical modeling of fragments impacting containment
structures was a research effort that has spanned at least 10 years and
has been conducted in part with a version of DYNA‑3D.

## 3.2 SMALL ENGINE AND APU MANUFACTURERS.

One company discussed their computational modeling efforts with us which
consisted of using a version of DYNA-3D to simulate the interaction of a
typical containment ring with fragments released from a trihub rotor
burst. However, they stated that this research effort is still in a
developmental stage and most of their design guidelines come from test
data generated in-house. A problem mentioned with use of this type of
modeling is that of finding a failure model. Continuing research effort
is directed toward correlating and nondimensionalizing the data in
useful ways.

## 3.3 LARGE AIRFRAME MANUFACTURERS.

Manufacturers interviewed in this category included civilian transport
and military aircraft manufacturers. On the question of the
appropriateness of the fragment size/spread angle data included in the
proposed Advisory Circular, different opinions were offered. While one
manufacturer felt that the historical data well supported this fragment
definition, another manufacturer felt that the data was not realistic
nor conservative. This company is supporting analytical research to
address this question. When questioned on design methods used when
dealing with uncontained rotor burst (URB) events, the approach of
designing redundant systems and relocating critical components to areas
outside of an expected fragment trajectory envelope was mentioned as a
primary method. One company related some design work involving the
possible use of structural shielding. They mentioned that a possible
drawback to the use of shields is that in certain cases, more serious
structural damage results as a consequence of using the shield, because
the shield transfers the impact reaction to more structural members.
Another manufacturer has devoted some number of years of research into
the use of analytical codes (DYNA-3D) that can be used to model the
interaction of released URB fragments with the aircraft structure.

Military manufacturers stressed their compliance with generic military
specifications for dealing with URB threats and typically suggested the
relocation of critical components as their primary design tool. In
compliance with the military specifications, this is one item addressed
on a required program plan where apparently the operating history of the
engine is taken into consideration. Finally, one company felt that a
probability number for design would be more desirable than the proposed
Advisory Circular approach of minimizing the hazard.

## 3.4 SMALL AIRFRAME MANUFACTURERS.

An opinion expressed is that the smaller airplane, if required to have
the same degree of protection as the large transport airplane, would be
penalized because the structural components themselves are less massive.
The companies surveyed basically rely presently on geometric analysis
and the relocation of critical components out of the trajectory path as
a means of minimizing the hazard from and URB event. The question of the
role of maintenance was addressed by more than one company. If, for
example, the engine of a general aviation business jet is inspected with
a frequency of three times that to which a transport jet engine is
inspected, or if the engine is monitored in a formalized trend
monitoring program, why should both the small jet and transport category
jet be subject to the same criteria for protection from URB events? Some
reservations about the use of the words "minimize the hazard" in the
draft Advisory Circular were expressed with a stated preference for a
specific quantitative probability number in lieu of the more general
term minimize. If this approach were adopted, what merit should be given
to field histories?

Another small company interviewed retrofitted various fixed and rotary
wing aircraft with small gas turbine engines. The status of policy for
minimizing damage from uncontained rotor bursts was of great interest to
this company. Such questions as how to demonstrate that a certain
shielding material and configuration would be adequate were stated by
this company to be of critical interest, as the necessity of extensive
testing would make the conduct of business impossible.

## 3.5 RESEARCH INSTITUTIONS AND GOVERNMENT AGENCIES.

Opinions offered by various individuals employed at civilian and
military airworthiness agencies are grouped under this category. Some
individuals offered suggestions for the direction of future research
efforts. These included investigating the effect of the engine case
pressurization of the fragment trajectories, the design of disks to
limit the mass of fragments by breaking into small pieces, and the
design of directed failure paths. Some concern was voiced that if more
stringent requirements for containment were required, less emphasis
would be directed to engine part integrity and or monitoring. The
repeatability of containment tests was questioned, with a suggestion
that this be investigated. Finally, an opinion was received that
follow-up on the recommendations of the Titanium Rotating Components
Review Team would result in overall enhanced safety by providing
improved materials and inspection techniques which will reduce the
probability of manufacturing defects.

# 4. Analysis of Containment/Shielding Structures.

A review of the past work accomplished reveals many previous analytical
studies. Some computer codes have been especially developed for modeling
of containment rings and deflector shields, notably the codes developed
by MIT as part of the NASA-sponsored Rotor Burst Protection Program (see
Record Numbers N001 and N008 in section 1.1). However, these codes do
not appear to have been adapted for widespread use in the aerospace
industry. Part of the present research effort involved examining the use
of currently available general commercial finite element codes for the
design of containment structures and related structural components.

The availability, capability, and workability of commercially available
finite element codes has increased dramatically in recent years. These
codes offer the ability to accurately perform the dynamic, nonlinear,
high-velocity impact analyses required to model containment and
shielding problems. Such tools allow the impact and energy transfer
mechanisms and the time dependent development of stress patterns to be
studied in detail for various materials and geometries. Two such codes
were evaluated for their capability to model various structural
configurations representative of containment rings or shielding
components. No attempt was made to model any specific engine components;
rather, a generalized study was made with fragment kinetic energies
representative of gas turbine engine sizes ranging from auxiliary power
units (APU) through 50,000 pound thrust engines (lb.t). Only metallic
structures were modeled in this research. The geometries studied were
circular containment rings and flat plates subject to direct impact. One
of the goals of this research was to determine if the use of such
commercially available codes could be useful in modeling and providing
design information for the high-velocity impact problems encountered in
containment and shielding.

The flat plate was 12 x 24 x 1 in. thick. It was meshed with
quadrilateral shell elements with minimum edge dimensions of 1 inch. The
element dimensions were minimum in the center of the plate, where impact
occurs, and a maximum of 3 inches near the edge of the plate, resulting
in a total number of degrees of freedom (including variables associated
with contact elements) of 1776. All edges of the plate were fixed
against displacement in three directions. The plate was impacted with a
rigid flat cylindrical disk 8 inches in diameter and 2.2 inches thick.
The impactor mass was 6.36 slugs; its velocity was varied from 25 in/sec
to as high as 700 in/sec resulting in a kinetic energy range of 170 to
130,000 in-lb. The ratio of impactor mass to plate mass was
approximately 2.5.

The ring model was circular and unflanged with dimensions chosen to
match experiments performed at the Naval Air Propulsion Laboratory (see
Record Number N049 in section 1.1). The ring had an inside diameter of
28 inches, an axial length of 9 inches, and a thickness which varied in
different runs from 0.187 to 0.390 inch. The total number of elements in
the ring model was 810. Quadrilateral shell element dimensions were 1
inch, and the top and bottom edges of the ring were fixed against
displacement in three directions. The ratio of impactor mass to ring
mass ranged from 2.3 to 6.4. In both the flat plate and ring models, the
mesh sizes were coarse compared with the rigid impactor contact area,
hence its geometry was somewhat irrelevant.

Problems were run with two codes: ABAQUS (Hibbett, Karlsson, and
Sorensen, Version 4.9) and DYTRAN (MacNeal-Schwendler, Version 2.0).
ABAQUS is a finite element direct integration implicit code that solves
the nonlinear equilibrium equations. The implicit time integration
operator is a modification of the trapezoidal rule called the
Hilbert-Hughes-Taylor operator. This formulation contains a parameter
used to introduce artificial damping and can be used to eliminate the
high frequency noise that is generated as a result of the time step
being changed in the automatic time stepping procedure. A force
tolerance and moment tolerance are entered by the user to define the
accuracy with which equilibrium must be satisfied. Time stepping can be
user defined or an automatic incrementation scheme is applied which
adjusts the time step after comparing the equilibrium residuals half way
through the time step with those at the end of the time step.

The second code, DYTRAN, is an analysis code for analyzing dynamic,
nonlinear behavior of structures, using explicit time integration. It is
an adaptation of the DYNA-3D code developed at Lawrence Livermore
National Laboratory. Time steps are controlled automatically to assure
stable solutions. The default automatic time step is calculated by the
program to be smaller than the time taken for a stress wave to cross the
smallest element; a user adjustable safety factor (typically of 2) is
then applied to this calculation to determine the actual time step. Both
codes were operated on a HP9000 Series 730 workstation.

Simple bilinear elastic-plastic material models were used for the
materials studied, A286 Steel and Inconel 625. Required parameters
include the yield point, elastic modulus, hardening modulus, and
Poisson's ratio. Values are summarized in table 1.

Table 1. Material Properties

  ----------------------------------------- -------------- ---------------
  ParameterInconel                          Steel          

  Yield Stress (psi)                        4.40E4         9.00E4

  Elastic Modulus (psi)                     29.8E6         22.5E6

  Hardening Modulus (psi)                   25.3E5         20.3E5

  Poisson's Ratio                           0.29           0.25

  Density (lbf sec~2~ /in)                  7.82E-4        7.40E-4
  ----------------------------------------- -------------- ---------------

Generally, both codes were found to be effective in modeling problems of
this nature, and both compared well, providing some verification of one
another. Time histories of maximum deflection and energy summaries from
both programs proved to be nearly identical. For the models and dynamic
time period ranges studied, the explicit code ran in approximately
one-tenth the time required for the implicit code. Some convergence
problems with the implicit code were encountered. These occurred at
energy levels insufficient to produce plastic dissipation. Even maximum
values of artificial damping parameters proved insufficient to eliminate
the high frequency noise generated as a result of time step changes in
the automatic time stepping procedure.

The analysis results for the flat plate models include maximum
displacement that occurs at various impactor energy levels, time of
maximum displacement, plastic dissipation, and maximum total reaction
force. Maximum displacements occurred in the center of the plate in the
impact area, and for the two materials, these are plotted in figure 1.
The maximum displacement is seen to increase nonlinearly with impactor
energy. The displacement of the Inconel is, in the plastic region, less
than that of the steel; the ratio of Inconel deflection to steel
deflection is the same as the ratio of the respective material hardening
moduli---approximately 1.25.

For the Inconel plate, the maximum total reaction force and the sum of
all reaction forces in the direction of impactor travel are plotted
against impactor energy in figure 2. The value is seen to rise sharply
with energy and level off at approximately 200,000 lb. The time at which
maximum displacement occurs for both plates, is shown in figure 3. Times
are higher for the Inconel plate, and the ratio of time for the Inconel
to that for the steel is approximately 1.35. The increase scales with
the product of relative hardening modulus and density for the two
materials.

Containment ring models of A286 steel were also constructed with
geometries chosen to match experimental work performed earlier. A
summary of these experiments is shown in table 2.

TABLE 2. CONTAINMENT EXPERIMENT RESULTS

  ------------------- ------------------------------ ---------------------
  Thickness (in.)     Fragment Energy (in-lb)        Result

  0.140               23,490                         Not Contained

  0.187               29,900                         Contained

  0.250               98,900                         Not Contained

  0.390               116,000                        Contained
  ------------------- ------------------------------ ---------------------

These experiments were modeled numerically with the DYTRAN program.
Geometry models matched those of the experiment and impactor velocities
were chosen to result in identical energy levels. However, several
aspects of the experiments differed from the computer model. In the
experiments the rings were hanging free, suspended by chains, while in
the model the top and bottom edges were restrained. Also, in the
experiments the impactors were actual turbine blades, not rigid disks.
Curves showing the total amount of energy absorbed by the rings is shown
in figure 4 with the maximum values in good agreement with the fragment
initial energies.

![](media/image2.emf){width="6.49375in" height="3.432638888888889in"}

FIGURE 1. FLAT PLATE---INCONEL 625 AND A286 STEEL DISPLACEMENT VERSUS
IMPACTOR ENERGY

![](media/image3.emf){width="6.49375in" height="3.55625in"}

FIGURE 2. FLAT PLATE---INCONEL 625 MAXIMUM TOTAL REACTION FORCE VERSUS
IMPACTOR ENERGY

![](media/image4.emf){width="6.49375in" height="3.3673611111111112in"}

FIGURE 3. FLAT PLATE---INCONEL 625 AND A286 STEEL TIME OF MAXIMUM PLATE
DEFLECTION

![](media/image5.emf){width="6.49375in" height="3.8048611111111112in"}

FIGURE 4. STEEL RINGS INTERNAL ENERGY TIME HISTORIES

# 5. CONCLUSIONS.

Few published research results on design methods for the containment of
rotating parts within the gas turbine engine case have appeared in the
last 15 years. The nature of such research, requiring a large amount of
expensive test data, is such that most development has occurred at the
engine manufacturers. The work is considered to be highly proprietary
and details are not generally released by the companies involved.

Some research work has been carried out under various NASA, DOD, and DOT
programs. Experimental work has been performed at the Naval Air
Propulsion Center, which is publicly available and provides a wealth of
experimental spin pit testing results on many candidate containment ring
materials for rotor segment and blade containment. This work is
presently continuing under sponsorship of the FAA William J. Hughes
Technical Center and focusing on the application of fiber composite
materials.

A number of companies report using finite element codes to model
containment structures and shields; derivatives of the DYNA-3D program
are often mentioned. However, in no cases were these tools described as
a simple solution. Indeed, many companies described a substantial
research effort, consisting of years of development, to obtain useful
computational results. While time histories of deflection, stress
levels, and reaction forces are fairly simple to obtain, as shown by
some examples in this report. Selection of an appropriate failure model
and hence the ability to predict containment capability, remains a
problem.