bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effects of Hail Damage on the Fatigue Strength of a Graphite/Epoxy Composite Laminate
Authors: Skordahl Richard A. , Mahinfalah Mohammad 
Published: July 2023

Abstract
An investigation was undertaken to determine the effects of hail damage on the fatigue strength of a graphite/epoxy composite laminate. Sixteen-ply coupons were subjected to simulated hail impact by iceballs of 25.4 mm or 38.1 mm in diameter. Upon impact, the 25.4 mm diameter iceball possessed 7.1 J of kinetic energy, while the 38.1 mm diameter iceball possessed a kinetic energy of 27.4 J. For further comparison, additional coupons were impacted with a 12.7 mm diameter aluminum sphere with either 7.1 J or 27.4 J of kinetic energy. Inspection revealed that neither iceball impact event caused any internal damage, while each aluminum sphere impact caused delaminations within each coupon. After being impacted and inspected, each coupon was subjected to constant amplitude tension-tension fatigue. It was determined that neither the 25.4 mm diameter iceball impact nor the 38.1 mm diameter iceball impact affected the fatigue performance of this particular laminate. The 7.1 J aluminum sphere impact also did not affect this laminate, while the 27.4 J aluminum impact did adversely affect the fatigue performance of this material.
Modeling Delamination Growth in Composites
Authors: Reedy E. David , Mello Frank J. 
Published: July 2023

Abstract
A method for modeling the initiation and growth of discrete delaminations in shell-like composite structures is presented. The laminate is divided into two or more sublaminates, with each sublaminate modeled with four-noded quadrilateral shell elements. A special, eight-noded hex constraint element connects opposing sublaminate shell elements. It supplies the nodal forces and moments needed to make the two opposing shell elements act as a single shell element until a prescribed failure criterion is satisfied. Once the failure criterion is attained, the connection is broken, creating or growing a discrete delamination. This approach has been implemented in a three-dimensional finite element code. This code uses explicit time integration, and can analyze shell-like structures subjected to large deformations and complex contact conditions. The shell elements can use existing composite material models that include in-plane laminate failure modes. This analysis capability was developed to perform crashworthiness studies of composite structures, and is useful whenever there is a need to estimate peak loads, energy absorption, or the final shape of a highly deformed composite structure.
This paper describes the eight-noded hex constraint element used to model the initiation and growth of a delamination, and discusses associated implementation issues. Particular attention is focused on the delamination growth criterion, and it is verified that calculated results do not depend on element size. In addition, results for double cantilever beam and end notched flexure specimens are presented and compared to measured data to assess the ability of the present approach to model a growing delamination.
Failure Development in Particulate Composites
Authors: Rubinstein Asher A. , Wang Peng 
Published: July 2023

Abstract
We present a model capable of evaluation of principal micromechanical processes taking place in brittle matrix composites reinforced by ductile particles. The reinforcing mechanism is based on formation of a system of restrictive forces imposed on the crack surfaces by the plastic particles behind the propagating crack front. The particles form the bridging zone and, thus, constrain the crack opening. This is the principal aspect of the toughening mechanism in these systems. The developed model addresses the effects associated with the discrete particle distribution and particle-matrix interface properties. The developed analytical approach allows us to trace the crack propagation through this system at any intermediate step. This detailed analysis explains certain aspects of the particulate reinforcement mechanism not discussed in the literature previously. The crack growth resistance curves are presented for several composite systems.
Creep Behaviour of Hot Isostatically Pressed Metal-Matrix Composite
Authors: Lim C. S. , Hung N. P. , Tan Y. C. , Loh N. L. 
Published: July 2023

Abstract
Castings usually contain defects such as shrinkage cavities and internal gas porosity. The application of hot isostatic pressing (HIPping) to cast metals can remove such defects through the synergistic effect of high isostatic pressure and high temperature. This paper investigates the effects of HIPping on creep of cast A359/SiC/20p composite. Although creep life was expected to improve due to removal of internal porosity in the castings, the creep results were contrary to expectations. Activation energy calculated for the cast composite, showed a decrease in activation energy for the material after HIPping. Creep life was noted to have improved with higher tensile strength as for the cast composite while creep strain at failure improved with an increase in elongation for the cast-HIPped composite. The effect of stress on creep properties are reported to show a decrease in creep life and creep strain at failure with an increase in stress, temperature remaining constant.
The Influence of Fiber Distribution and Voids on the Tensile Strength of Polymer Composite Materials
Authors: Generalis George , Sundaresan Mannur J. 
Published: July 2023

Abstract
Three types of material variations commonly introduced during the processing of polymeric matrix composite materials are considered. These are (i) deviations from the local fiber volume fraction from the design specifications, (ii) non-uniformity in the inter-fiber spacing, and (iii) the presence of substantial levels of local void distribution. The influence of these variabilities on the longitudinal tensile strength of unidirectional composite material is evaluated. For composite materials with uniform fiber distribution, the tensile strength slightly dropped as the fiber volume fraction was increased. The non-uniformity in the inter-fiber spacing and the presence of significant levels of voids was found to have a more adverse influence on the tensile strength.
Prediction of Axial Flow Fan Noise Spectrum
Authors: Su Shigong , Wu Sean F. , Shah Hemant 
Published: July 2023

Abstract
This paper presents a semi-empirical formula for predicting the noise spectra of axial flow fans in a free field. The basic assumption made in deriving this formula is that sound radiation from an axial flow fan in a free field is primarily due to the fluctuating pressure exerted on the fan blade surface. This fluctuating pressure is correlated to the lift force per unit length acting on the fan blade, and is subsequently approximated by pressure pulses that decay both in space and time. Accordingly, the radiated acoustic pressure is expressed in terms of superposition of contributions from these pressure pulses, and the line spectrum is obtained by taking a Fourier series expansion. To simulate the narrow and broad band sound spectra, a normal distribution-like shape function is designed which divides the frequency into consecutive bands centered at the blade passage frequency and its harmonics. The amplitude of this shape function at the center frequency of each band is unity but decays exponentially. The decay rate decreases with an increase in the number of bands. Thus, at high frequencies the narrow bands merge to form broad bandlike spectra. The noise spectra thus obtained are compared with the measured ones from four different types of axial flow fans running under various conditions, and a favorable agreement in each case is obtained.
The Application of Finite Element Method in Analyzing the Noise Reduction Effect of Helmholtz Resonator Attachments
Authors: Koai Kwang-Lu , Yang Tachung , Chen Jean 
Published: July 2023

Abstract
This paper is devoted to the study of muffling effect of Heimholtz resonators installed in different environments. A finite element approximation is employed to simulate a general acoustic environment of three (3) dimensional nature, while the Helmholtz resonators are represented by boundary conditions with a suitable amount of impedance at the frequency of interest. Using a variational formulation of the acoustic wave equation, the impedance boundary condition turns out to be damping terms in the second order matrix equations. Examples are given to quantitatively show the noise reduction effects of various Helmholtz resonator arrangement. Discussions on the damping coefficients based on lumped parameter and distributed model formulation are made.
The Characteristics of Ceramic Spool Valve Piloted Water Hydraulic Proportional Valve
Authors: Koskinen K. T. , Uusi-Heikkilä J. K. , Vilenius M. J. 
Published: July 2023

Abstract
Water hydraulics is one of the most rapidly growing areas in the field of fluid power. Environmental and safety aspects have strong effect to the use of water hydraulics. Also high level material technology and intelligent control systems enable better characteristics for water hydraulic components. Computer simulation is very efficient way to get information of the operation of a component and a system before the prototype or the system really exists. Especially in the research of water hydraulic systems simulation is effective, because water hydraulic components are still very expensive.
Proportional valves used in water hydraulics are normally ball seat valves, seat valves or spool valves. The latest development is ceramic spool valve, which has a spool made of industrial ceramics. Today the valves are still mainly 2/2-way or 3/2-way valves and the more complex controls must be build by using these basic elements. The control accuracy of the valves can be improved by using electrical position feedback from the control element. In some cases this is also essential for the proper operation of the valve. In this paper the simplified mathematical model for 3/2-way ceramic spool valve is presented and verified. Different control methods for the two-stage throttle valve are examined.
Formation of Pressure Gain in Hydraulic Servovalves and its Significance in System Behavior
Authors: Ellman Asko , Virvalo Tapio 
Published: July 2023

Abstract
The pressure gain of hydraulic servovalves is caused by an internal leakage. The leakage flow occurs because of the spool construction and finite radial clearance of the spool. The internal leakage results in unwanted properties such as crawling of a loaded actuator in open loop systems and position error of a P-controlled loaded actuator. On the other hand system damping increases. This paper presents a robust model for internal leakage that can be identified according to known pressure gain. The importance of the valve’s pressure gain on steady state and dynamic behaviour is studied by a well verified simulation model.
Elastic-Plastic Strain Acceptance Criterion for Structures Subject to Rapidly Applied Transient Dynamic Loading
Authors: Solonick William R. 
Published: July 2023

Abstract
Rapidly applied transient dynamic loads produce stresses and deflections in structures that typically exceed those from static loading conditions. Previous acceptance criteria for structures designed for rapidly applied transient dynamic loading limited stresses to those determined from elastic analysis. Different stress limits were established for different grades of structure depending upon the amount of permanent set considered acceptable. Structure allowed to sustain very limited permanent set is designed to stress limits not significantly greater than yield stress. Greater permanent set in structure under rapidly applied transient dynamic loading conditions is permitted by establishing stress limits that are significantly greater than yield stress but still provide adequate safety margin (with respect to failure).
This paper presents a strain-based elastic-plastic (i.e., inelastic) analysis criterion developed as an alternative to the more conservative stress-based elastic analysis stress criterion for structures subjected to rapidly applied transient dynamic loading. The strain limits established are based on material ductility considerations only and are set as a fraction of the strain at ultimate stress obtained from an engineering stress/strain curve of the material. Strains limits are categorized by type as membrane or surface and by region as general, local, or concentrated.
The application of the elastic-plastic criterion provides a more accurate, less conservative design/analysis basis for structures than that used in elastic stress-based analysis criteria, while still providing adequate safety margins.
Simple Structures Test for Elastic-Plastic Dynamic Analysis Validation
Authors: Trimble Thomas F. , Krech Gregory R. 
Published: July 2023

Abstract
A Simple Structures Test Program was performed where several cantilevered beam and fixed-end beam test specimens were subjected to a series of analytically predetermined rapidly applied transient dynamic input loads. The primary objective of the test program was to obtain dynamic nonlinear response for simple structures subjected to these load inputs. Data derived from these tests was subsequently used to correlate to analysis predictions to assess the capability to analytically predict elastic-plastic nonlinear material behavior in structures using typical time-dependent (transient) design methods and the ABAQUS finite element analysis code.
The installation of a significant amount of instrumentation on these specimens and post-test measurements enabled the monitoring and recording of strain levels, displacements, accelerations, and permanent set. An assessment of modeling parameters such as the element type and mesh refinement was made using these test results. In addition, currently available material models and the incremental time step procedure used in the transient analyses were evaluated.
Elastic-Plastic Finite Element Analysis-to-Test Correlation for Structures Subjected to Dynamic Loading
Authors: Hodge Scott C. , Minicucci Jay M. 
Published: July 2023

Abstract
A test program was undertaken to demonstrate the ability of elastic-plastic finite element methods to predict dynamic inelastic response for simple structural members. Cantilever and fixed-beam specimens were tested to levels that produced plastic straining in the range of 2.0% to 3.0% and permanent sets. Acceleration, strain, and displacement data were recorded for use in analytical correlation.
Correlation analyses were performed using the ABAQUS finite element code. Results of the correlation show that current elastic-plastic analysis techniques accurately capture dynamic inelastic response (displacement, acceleration) due to rapidly applied dynamic loading. Peak elastic and inelastic surface strains are accurately predicted. To accurately capture inelastic straining near connections, a solid model, including fillet welds, is necessary.
The hardening models currently available in the ABAQUS code (isotropic, kinematic) do not accurately capture inelastic strain reversals caused by specimen rebound. Analyses performed consistently underpredicted the peak strain level of the first inelastic reversal and the rebound deflection and overpredicted the permanent set of structures experiencing inelastic rebound. Based on these findings, an improved hardening model is being implemented in the ABAQUS code by the developers. The intent of this model upgrade is to improve the ability of the program to capture inelastic strain reversals and to predict permanent sets.
A Nodal-Based Stable Time Step Predictor for Transient Dynamics With Explicit Time Integration
Authors: Heinstein Martin W. , Mello Frank J. , Dohrmann Clark R. 
Published: July 2023

Abstract
A procedure for estimating the maximum stable time step for explicit finite element codes using central time difference is presented. The method is based on an estimate of maximum nodal stiffness and lumped nodal mass. The estimate of maximum nodal stiffness makes use of the finite element assembly operator and the maximum eigenvalue estimates of the finite elements being considered (in this case Flanagan’s mean quadrature hexahedron). The nodal-based stable time step calculated by this method is shown to be greater than or equal to an element based estimate alone.
Overview of the Trainline Communication Network and Associated Systems
Authors: Nast Thomas E. 
Published: July 2023

Abstract
The Staff of the Association of American Railroads in cooperation with the railroad supply industry are specifying a network of intelligent control devices to aid freight train handling and railway operations. This trainline control network has the potential to host electronically controlled pneumatic (ECP) brake systems, distributed locomotive power control (DP) systems, and a wide assortment of vehicle health monitoring systems.
This paper highlights some of the system level considerations of this project and provides and overview of component “black box” definitions.
NUCARS Modeling of Locomotive Bogies
Authors: Ahmadian Mehdi , DeLorenzo Michael W. 
Published: July 2023

Abstract
NUCARS is an industry standard dynamic simulation package that has been used extensively for railcar modeling. Locomotives can also be modeled in NUCARS, reducing the cycle time for problem solving and product development. This paper discusses NUCARS modeling, and how it is applied to a typical freight locomotive.
Effects of Yarn Undulation on the Stress and Deformation of Textile Structural Composites
Authors: Chou Tsu-Wei , Ito Makoto , Kostar Timothy D. 
Published: July 2023

Abstract
This paper reports the effects of yarn undulation on the stress and deformation of plain weave composites. The findings from a number of sources2 are reviewed and compiled here. Existing micromechanical analyses of woven fabric composites have been conducted using mostly either simplifying mathematical models or elaborate three-dimensional finite element analysis. For example, Ishikawa and Chou proposed the mosaic model, crimp model, and bridging model for analyzing the thermoelastic and failure behavior of woven fabric composites. On the other hand, finite element analysis by Whitcomb and Foye, for example, can provide detailed stress analysis under specific boundary conditions. The recent work of Ito and Chou expands the analytical capability to modeling of the strength and failure behavior of woven fabric composites. In their studies, the geometrical characteristics of yarn shape, laminate stacking configuration, fiber volume fraction, and yarn packing fraction are investigated using three-dimensional micromechanical models. Based on the geometrical characteristics, an iso-strain approach is then developed to predict the elastic properties, local stress distributions, and failure strengths under tensile loading for four laminate stacking configurations: a single lamina, an iso-phase laminate, an out-of-phase laminate, and a random-phase laminate.
On Predicting Dynamic Compressive Properties of Some Composite Materials
Authors: Vinson Jack R. 
Published: July 2023

Abstract
A need exists to employ high strain rate mechanical properties of composite material systems when designing or structurally analyzing products and vehicles that are subjected to dynamic loadings. This is due to the fact that for many materials some properties vary by factors of two or three from the static mechanical properties which are so often used in design. The result is that some structures may be significantly overweight from what they could be if dynamic material properties were used in their design, while in other instances unexpected failures can occur which are difficult to diagnose if the high strain rate properties of the materials involved were unknown.
An ultimate goal might be to develop the capability to predict high strain rate properties from static material properties, but that capability does not exist today. However, it is helpful to develop the capability to predict the needed high strain rate material properties over the entire strain rate range of interest from a minimum number of dynamic tests performed, because high strain rate property testing is time consuming, expensive, and requires sophisticated equipment.
From the testing of numerous polymer matrix composite materials in compression utilizing a Split Hopkinson Pressure Bar, repeated patterns have emerged involving yield strength, yield strain, ultimate strength, strain to failure, modulus of elasticity, elastic strain energy density and strain energy density to failure. These are the properties needed for proper design, structural analysis and materials selection. By studying these patterns, a procedure is suggested by which these properties can be obtained through performing a minimum number of tests.
Delamination Induced Buckling in Orthotropic Plate Structures
Authors: Jiang W. , Bao G. 
Published: July 2023

Abstract
Delamination in composite laminates can cause buckling of the debonded layer; the subsequent delamination cracking can in turn be buckle-driven. To aid the failure analysis of composite structures, this article presents a critical review of analytic solutions for buckling of rectangular, orthotropic thin plates. Considered are plates with all edges simply supported, two edges simply supported/two edges clamped, and all edges clamped. The material orthotropy is characterized by two non-dimensional parameters, λ = D22/D11 and η=(D12+2D66)/D11D22. Systematic comparisons with finite element results are made for the critical buckling load of a plate under in-plane uniaxial compression. It is found that for plates with all edges clamped, the analytic solution for critical buckling load is neither accurate nor conservative. Buckling of orthotropic plates with other boundary conditions is briefly discussed.
Influence of Ply Orientation on Delamination in Composite Laminates
Authors: Tao Jianxin , Sun C. T. 
Published: July 2023

Abstract
An experimental investigation in interlaminar fracture behavior and toughness of multi-directional composite laminates was conducted. Based on the result of this investigation, an experimental method to determine mode II dominated interlaminar toughness of was proposed and used to obtain interlaminar toughnesses of 0/θ interfaces in AS4/3501-6 composite material with various θ’s. It was found that the critical strain energy release rate decreases as the off-axis angle θ increases.
Modeling the Effects of Translaminar Reinforcements on Mode II Fracture Toughness
Authors: Sonik V. , Sankar B. V. 
Published: July 2023

Abstract
Translaminar reinforcements in the form of stitching is an effective solution to suppress delaminations in laminated composites. An analytical study is conducted on the unidirectional graphite/epoxy laminates to examine the effects of stitching and the various geometric parameters associated with stitching on the apparent interlaminar fracture toughness. End-notched flexure tests were conducted to study the Mode II fracture toughness of the laminates. Shear deformable beam theory was applied to model the sublaminates where the stitches were smeared as equivalent foundation springs. Only elastic behavior of this equivalent spring system was assumed. Load-deflection patterns were obtained and the fracture toughness, GIIc, as a function of the apparent crack propagation was computed. The fracture toughness, GIIc was determined by evaluating the area under the load-deflection curve at every instant of crack propagation. The effects of mechanical properties of the smeared stitches on the crack extension was studied. The analytical model was verified by comparing with the experimental results. The effects of stitch stiffness, density, initial starter crack length and various geometric parameters were examined.