Locomotive Fuel Tank Structural Safety Testing 

Program: Passenger Locomotive Fuel Tank 

Side Impact Load Test

U.S. Department of 

Transportation

Federal Railroad 

Administration

Office of Research

and Development

Washington, DC 20590

DOT/FRA/ORD-10/09 Final Report

August 2010
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1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE

August 2010

3. REPORT TYPE AND DATES COVERED

Technical Report

4. TITLE AND SUBTITLE

Locomotive Fuel Tank Structural Safety Testing Program: Passenger Fuel Tank Side Impact

Load Test

5. FUNDING NUMBERS

6. AUTHOR(S)

Abdullatif K. Zaouk, Basant Parida, and Mark Silver

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

Foster-Miller, Inc./QinetiQ North America

350 Second Avenue

Waltham, MA 02451-1196

8. PERFORMING ORGANIZATION 

REPORT NUMBER

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

U.S. Department of Transportation 

Federal Railroad Administration

Office of Research and Development

Washington, DC 20590

10. SPONSORING/MONITORING

AGENCY REPORT NUMBER

DOT/FRA/ORD-10/09

11. SUPPLEMENTARY NOTES

Program Manager: John Punwani

12a. DISTRIBUTION/AVAILABILITY STATEMENT

This document is available to the public online through the FRA Web site at http://www.fra.gov. 

12b. DISTRIBUTION CODE

13. ABSTRACT (Maximum 200 words)

This report represents a passenger fuel tank load test simulating a Side Impact Collision. The test is based on the Federal Railroad 

Administration’s (FRA) requirements for locomotive fuel tanks in the Title 49 Code of Federal Regulations (CFR), Part 238, 

Appendix D. This test covers Section (a) (3) of Appendix D, which states that in a side impact collision by an 80,000-pound Gross 

Vehicle Weight tractor/trailer at the longitudinal center of the fuel tank, the fuel tank shall withstand, without exceeding the ultimate 

strength, a 200,000-pound load (2.5g) distributed over an area of 6 inches (in) by 48 in (half the bumper area) at a height of 30 in 

above the rail (standard DOT bumper height). 

This report presents the test data, which showed that the resulting displacement of the tank sidewall corresponding to a maximum side 

impact load of nearly 300 kilopounds was approximately 0.5 in. This comprised of mostly elastic deformation and very little plastic 

deformation. Upon unloading, no local residual plastic deformation was noticeable to the naked eye although plotted test data 

revealed a small residual plastic deformation of 0.1 in. No crack or tank breach was observed near the side impact load application

zone or elsewhere in the tank. Therefore, from the FRA regulatory perspective, the tank is considered to have satisfied the structural 

integrity requirement set forth in 49 CFR Part 238, Appendix D, Section (a) (3). 

14. SUBJECT TERMS

Passenger locomotive fuel tank, side impact load condition

15. NUMBER OF PAGES

44 

16. PRICE CODE

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NSN 7540-01-280-5500 Standard Form 298 (Rev. 2-89)

Prescribed by ANSI Std. 239-18

298-102
ii

METRIC/ENGLISH CONVERSION FACTORS

ENGLISH TO METRIC METRIC TO ENGLISH

LENGTH (APPROXIMATE) LENGTH (APPROXIMATE)

1 inch (in) = 2.5 centimeters (cm) 1 millimeter (mm) = 0.04 inch (in)

1 foot (ft) = 30 centimeters (cm) 1 centimeter (cm) = 0.4 inch (in)

1 yard (yd) = 0.9 meter (m) 1 meter (m) = 3.3 feet (ft)

1 mile (mi) = 1.6 kilometers (km) 1 meter (m) = 1.1 yards (yd)

1 kilometer (km) = 0.6 mile (mi)

AREA (APPROXIMATE) AREA (APPROXIMATE)

1 square inch (sq in, in2) = 6.5 square centimeters (cm2) 1 square centimeter (cm2) = 0.16 square inch (sq in, in2) 

1 square foot (sq ft, ft2) = 0.09 square meter (m2) 1 square meter (m2) = 1.2 square yards (sq yd, yd2) 

1 square yard (sq yd, yd2) = 0.8 square meter (m2) 1 square kilometer (km2) = 0.4 square mile (sq mi, mi2) 

1 square mile (sq mi, mi2) = 2.6 square kilometers (km2) 10,000 square meters (m2) = 1 hectare (ha) = 2.5 acres

1 acre = 0.4 hectare (he) = 4,000 square meters (m2) 

MASS - WEIGHT (APPROXIMATE) MASS - WEIGHT (APPROXIMATE)

1 ounce (oz) = 28 grams (gm) 1 gram (gm) = 0.036 ounce (oz)

1 pound (lb) = 0.45 kilogram (kg) 1 kilogram (kg) = 2.2 pounds (lb)

1 short ton = 2,000 pounds 

(lb)

= 0.9 tonne (t) 1 tonne (t) =

=

1,000 kilograms (kg)

1.1 short tons

VOLUME (APPROXIMATE) VOLUME (APPROXIMATE)

1 teaspoon (tsp) = 5 milliliters (ml) 1 milliliter (ml) = 0.03 fluid ounce (fl oz)

1 tablespoon (tbsp) = 15 milliliters (ml) 1 liter (l) = 2.1 pints (pt)

1 fluid ounce (fl oz) = 30 milliliters (ml) 1 liter (l) = 1.06 quarts (qt)

1 cup (c) = 0.24 liter (l) 1 liter (l) = 0.26 gallon (gal)

1 pint (pt) = 0.47 liter (l)

1 quart (qt) = 0.96 liter (l)

1 gallon (gal) = 3.8 liters (l)

1 cubic foot (cu ft, ft3) = 0.03 cubic meter (m3) 1 cubic meter (m3) = 36 cubic feet (cu ft, ft3) 

1 cubic yard (cu yd, yd3) = 0.76 cubic meter (m3) 1 cubic meter (m3) = 1.3 cubic yards (cu yd, yd3)

TEMPERATURE (EXACT) TEMPERATURE (EXACT)

[(x-32)(5/9)] °F = y °C [(9/5) y + 32] °C = x °F

QUICK INCH - CENTIMETER LENGTH CONVERSION

0 1 2 3 4 5

Inches

Centimeters 0 1 2 3 4 5 6 987 1110 1312

QUICK FAHRENHEIT - CELSIUS TEMPERATURE CONVERSION

 -40° -22° -4° 14° 32° 50° 68° 86° 104° 122° 140° 158° 176° 194° 212°

 

°F

 °C -40° -30° -20° -10° 0° 10° 20° 30° 40° 50° 60° 70° 80° 90° 100°

For more exact and or other conversion factors, see NIST Miscellaneous Publication 286, Units of Weights and Measures.

Price $2.50 SD Catalog No. C13 10286 Updated 6/17/98
iii

Acknowledgments

This report discusses full-scale passenger fuel tank test simulating a side impact loading condition. 

Foster-Miller/QinetiQ North America performed this work under contract DTFR53-07-00003 Task 

Order 004 from the Federal Railroad Administration (FRA) for the Locomotive Fuel Tank Safety 

Improvement Program.

John Punwani, FRA Office of Research and Development, is the contract officer’s technical 

representative, and the authors thank him for his technical direction and involvement in the project. 

The support of Claire Orth, (retired) Chief of Equipment and Operating Practices, FRA’s Office of 

Research and Development, and of Magdy El-Sibaie, Former Director of the FRA Office of 

Research and Development, is gratefully acknowledged.

The authors would like to express their gratitude to Gopal Samavedam for his encouragement and 

guidance, wish to thank Norm Dana for the computer-aided design drawings, and thank John Kidd 

and John Flynn for help with test setup.
iv

Contents

Executive Summary......................................................................................................................... 1

1. Introduction ............................................................................................................................. 2

1.1 Background ......................................................................................................................... 2

1.2 Objectives ............................................................................................................................ 2

2. Technical Approach ................................................................................................................. 3

2.1 Test Condition ..................................................................................................................... 3

2.2 Test Fixture .......................................................................................................................... 3

2.3 Fuel Tank Load and Displacement Measurement Method ................................................... 5

2.4 Test Article .......................................................................................................................... 5

2.5 Test Instrumentation and Data Acquisition .......................................................................... 7

2.6 Test Methodology ................................................................................................................ 9

3. Test Results and Discussions ................................................................................................. 13

4. Results of Simulation and FEA ............................................................................................. 16

4.1 Mechanical Properties Evaluation of F59 Tank Material ................................................... 16

4.1.1 Test Sample Preparation and Testing ......................................................................... 16

4.1.2 Tensile Test Results ................................................................................................... 16

4.2 FEA for Side Impact Load Case ........................................................................................ 18

5. Conclusions ........................................................................................................................... 23

6. References ............................................................................................................................. 24

Appendix A – Summary of F59 Tank Material Tensile Properties Data ......................................... 25

Abbreviations and Acronyms......................................................................................................... 37
v

Illustrations

Figure 1. Schematic of FRA Side Impact Load Applied to the Tank Sidewall ................................. 3

Figure 2. Locomotive Fuel Tank Test Fixture .................................................................................. 4

Figure 3. Test Fixture and F59 Tank Configuration for Side Impact Load Case .............................. 5

Figure 4. External Dimensions of F59 PHI Passenger Locomotive Tank ........................................ 6

Figure 5. F59 Tank Interior Details Including Component Wall Thicknesses .................................. 6

Figure 6. Test Control and Data Acquisition System Setup ............................................................. 7

Figure 7. F59 Tank Loading Face String Potentiometer Attachment to Load Lever ........................ 8

Figure 8. Two String Potentiometer Attachments to the Unloaded Sidewall of the Tank ................. 9

Figure 9. Configuration of Servohydraulic Actuator for Side Impact Load Application ................ 11

Figure 10. A Closeup View of Tank Sidewall and the Load Lever following 

Complete Unloading .................................................................................................... 12

Figure 11. Applied Side Impact Load vs. Load Lever and Tank UnloadedSidewall Displacements ............................................................................................... 13

Figure 12. Variation of Load Lever Displacement with Applied Side Impact Load ....................... 14

Figure 13. Effective Load Point Deformation of Tank Sidewall with Applied Side Impact Load .. 14

Figure 14. Tensile Stress vs. Strain Curve for Tank Top Plate Material.......................................... 17

Figure 15. Extracted True Stress vs. True Strain Data for Tank Top Plate Material........................ 18

Figure 16. FEM of F59 Tank under Side Impact Loading: (a) Inverted Tank and a Bumper 

Attached to the Load Lever and (b) a Cutaway View of Tank Internal Structure ......... 19

Figure 17. Von Mises Stress Contours Corresponding to Applied Maximum Side Impact Load: 

(a) in the Sidewall of F59 Tank and (b) in the Internal Structures ................................ 20

Figure 18. FEM and Experimental Force vs. Displacement Data .................................................. 21

Figure 19. Detail of Cutaway FEM Results Showing von Mises Stresses in the Buckled 

Transverse Baffle Directly behind the Side Impact Bumper ........................................ 22
1

Executive Summary

As a part of the Federal Railroad Administration (FRA) Fuel Tank Safety Improvement Program, 

the structural integrity of an Electro-Motor Diesel, Inc. (known as EMD)-F59 PHI passenger 

locomotive fuel tank was evaluated under the side impact load case. The quasi-static load test was 

performed in a custom-designed fuel tank test fixture located at the Foster-Miller/QinetiQ North 

America (QNA) Transportation Research Center in Fitchburg, MA. This report presents the details 

of the test setup, instrumentation, methodology, and results. Correlations of test results with those 

obtained from finite element analysis (FEA) using ABAQUS are also shown.

The results of side impact load test reveal that the supplied F59 PHI tank is capable of 

withstanding quasi-static load as specified by the Title 49 Code of Federal Regulations (CFR) Part 

238, Appendix D, Section (a) (3), which states that in a side impact collision by an 80,000-pound

(lb) gross vehicle weight tractor/trailer at the longitudinal center of the fuel tank, the fuel tank shall 

withstand, without exceeding the ultimate strength, a 200,000-pound load (2.5g) distributed over 

an area of 6 inches (in) by 48 in (half the bumper area) at a height of 30 in above the rail (standard 

Department of Transportation bumper height).

Test results showed that the sidewall of the tank safely resisted the applied maximum load of 

317,000 lb without fracture or cracking. The tank exhibited evidence of undergoing very little local 

plastic deformation in the contact region with the side-impacting bumper. The rest of the tank was 

practically undamaged, including the tank attachment fixtures. Hence, from the FRA regulatory 

perspective, it may be concluded that the tank has passed the structural integrity requirement set 

forth in 49 CFR Part 238, Appendix D, Section (a) (3).
2

1. Introduction

1.1 Background

Ensuring the structural integrity of locomotive fuel tanks in railroad accidents is crucially 

important to improving the safety of train crews and passengers. Damage to tanks and associated 

fuel system components can lead to leaks, potential fires, and cause pollution, resulting in loss of 

property as well as passenger injuries. The FRA Fuel Tank Safety Improvement Program was 

being pursued to address these safety concerns.

FRA specified the loads a typical fuel tank must withstand for safety under minor derailment

(MD), jackknife derailment (JD), and side impact. Full-scale tests to validate passenger fuel tank 

strength to safely resist these loads following derailment have not been performed to date, except 

for a few tests on freight locomotive tanks by Foster-Miller/QNA at its Transportation Research 

Center in Fitchburg, MA. 

1.2 Objectives 

Foster-Miller/QNA performed this test with following objectives:

(a) Simulate the side impact loading condition on the F59 PHI passenger locomotive fuel tank

by using the full-scale fuel tank test fixture located at the Transportation Research Center, 

(b) Instrument the test setup with load cell and transducers for displacement measurement, 

(c) Determine the load versus displacement data, identifying salient points related to plastic 

yielding, peak load, and corresponding displacements, 

(d) Determine the unloading behavior of the tank when the load is removed,

(e) Identify the permanent deformation in the tank sidewall and cracking, if any, and

(f) Correlate the test data with those obtained from FEA and explain reasons for discrepancy, 

if any.
3

2. Technical Approach

2.1 Test Condition

All primary locomotive fuel tanks are required to resist certain loading conditions without failure

per FRA regulations that reference American Association of Railroads (AAR) Standard S-5506. 

These regulations originated through collaborative efforts of AAR and FRA and were introduced in 

1995 as Recommended Practice RP-506 for new manufacture. These guidelines have been used by 

industry after that time. In 2007, they became the AAR Standard S-5506 and were subsequently

referenced in 49 CFR Part 238. These requirements incorporate application of three static load 

conditions that are applied by railhead surfaces to the tank exterior, representing exposure to three 

different accident scenarios, namely MD, JD, and side impact. This report covers the test condition 

involving the side impact loading case only.

This test covers Section (a) (3) of Appendix D of 49 CFR Part 238 which states that “in a side 

impact collision by an 80,000-pound Gross Vehicle Weight tractor/trailer at the longitudinal center 

of the fuel tank, the fuel tank shall withstand, without exceeding the ultimate strength, a 200,000-

pound load (2.5g) distributed over an area of 6 × 48 in (half the bumper area) at a height of 30 in 

above the rail (standard DOT bumper height).” This represents one of the severe loading cases of a 

grade-crossing accident scenario in which the front bumper of a heavy road vehicle or tractor

trailer hits near the longitudinal center of one side of the locomotive fuel tank, shown in Figure 1.

Figure 1. Schematic of FRA Side Impact Load Applied to the Tank Sidewall

2.2 Test Fixture

The testing outlined in this document was performed by using the full-scale fuel tank test fixture 

illustrated in Figure 2.

The fixture was designed and developed by Foster-Miller/QNA to test a fuel tank in all standard 

derailment configurations, and is located at its Transportation Research Center. The modular nature 

of the fixture allows for different tank types to be tested in multiple load configurations with 

minimal modifications to the fixture.
4

Figure 2. Locomotive Fuel Tank Test Fixture 

The test fixture was designed to enable application of all three types of FRA derailment load 

conditions to a wide range of full-size production locomotive fuel tanks. The tanks are tested 

upside-down relative to their position in actual locomotives. Movable support beams are used to 

reposition tanks relative to the loading levers, which incorporate a segment of actual rail or 

bumpers for contact with the tank. The levers swing in large-radius arcs, to closely reflect the 

translational movement of the railhead or bumper into the tank implied by the regulations. Use of 

widely spaced supports and stiff arms assures stability of the fixture under the unpredictable 

crushing behavior that might occur when large deflections (of several inches) are produced on the 

tank walls. The test fixture is, therefore, designed to be capable of stable operation under the

extreme loading conditions.

The tank mounting brackets are also accommodated, because these are part of the tank attachment 

system and are also subjected to the impact loads. The tests tax these important components as they 

must function satisfactorily under the required load conditions. Figure 3 shows the test fixture and 

fuel tank configuration for application of FRA side impact load to the F59 passenger locomotive 

fuel tank.
5

Figure 3. Test Fixture and F59 Tank Configuration for Side Impact Load Case

Shakedown testing was conducted to prove out the integrity of test fixture, instrumentation, and to 

refine test procedures. Additionally, a separate calibration test was performed for the evaluation of 

pivot joint reaction force of the load lever. 

2.3 Fuel Tank Load and Displacement Measurement Method

For the side impact load case, the fuel tank is mounted near the middle portion of the test fixture 

and anchored down to the transverse floor beams at both ends. The load lever is positioned at the 

longitudinal middle of the tank on one side. It is suspended from an upper transverse beam such 

that its lower end containing a bumper (6 in deep and 48 in long) touches the tank sidewall at the 

desired height, as shown in Figure 3. For side impact load application, an Enerpac servohydraulic 

actuator is used that is positioned horizontally between an upright column and lower end of the 

load lever having its axis coincide with the midplane of the bumper.

The pressure transducer output of the hydraulic pump unit provides the magnitude of applied load 

during a test. For tank displacement measurement, one string potentiometer (string pot) was 

connected to the lever in the plane of loading. Two more string pots were connected to the backside 

(opposite to the loading sidewall). One was attached near one end of the tank and the other near the 

middle. In the event of likely rigid-body displacement (lateral sliding along the loading direction) 

of the tank because of applied side impact load, the difference of readings between that of the 

string pot attached to the load lever and the average reading of the back-face string pots provides 

the tank displacement under side impact load application. 

2.4 Test Article

The test article used in this testing program is a F59 PHI passenger locomotive fuel tank. This was

reported to have been manufactured using corrosion-resistant (COR-TEN) steel material. Its
6

overall shape and major external dimensions are shown in Figure 4. The interior construction 

details including baffle configurations and wall thicknesses are shown in Figure 5. 

Figure 4. External Dimensions of F59 PHI Passenger Locomotive Tank

Figure 5. F59 Tank Interior Details Including Component Wall Thicknesses
7

The side impact load is intended to be applied at the middle of one side of the fuel tank with the 

bumper touching one side plate covering a 6 × 48-inch band. The bumper is configured to straddle 

both sides of the three-eighths-inch-thick lateral center baffle, supported by a 0.5-inch-thick 

sidewall. This is expected to permit evaluation of the tank structural integrity under worst case side 

impact conditions. 

2.5 Test Instrumentation and Data Acquisition

All test data for the fuel tank structural improvement program were acquired through National 

Instruments (NI) signal conditioners integrated to a high-end PC (Figure 6) using Laboratory 

Virtual Instrumentation Engineering Workbench (LabVIEW) version 8.2.1 software (NI, 2008a). 

LabVIEW is a powerful graphical programming environment for measurement and automation 

developed by NI for applications to test and measurement. 

Figure 6. Test Control and Data Acquisition System Setup

In addition, the following instrumentation was used in this test:

Instrumentation for measurement of applied load

Load is applied through an Enerpac hydraulic cylinder with a maximum capacity of 10,000 pounds 

per square inch (psi). To determine the applied piston load, a calibrated Setra 201 pressure 

transducer with a maximum pressure rating of 10,000 psi was used. This permits continuous 

monitoring of pressure as well as applied piston load data by using LabVIEW software for 

acquisition and recording for later processing.

Instrumentation for measurement of tank deformation

To measure the tank sidewall horizontal deformation because of side impact load applied by the 

load lever, a Celesco string potentiometer was attached to the load lever as shown in Figure 7. Two 

additional Celesco string pots were attached to the unloaded (back face) sidewall of F59 tank. One

string pot was attached near one end of tank and the other to the (back face) sidewall near the 
8

location of lateral center baffle. This arrangement of string-pot mountings permitted measurement 

of the overall tank horizontal displacement due to sliding motion and/or bending in the horizontal 

plane under side impact load. The string potentiometer attachments to the back face sidewall of the 

inverted tank are shown in Figure 8. All three string potentiometers were connected to one NI 

SCXI-1121 signal conditioning module (NI, 2008b) for automated data acquisition by using 

LabVIEW. 

Figure 7. F59 Tank Loading Face String Potentiometer Attachment to Load Lever
9

Figure 8. Two String Potentiometer Attachments to the Unloaded Sidewall of the Tank

As mentioned, all data were acquired through NI signal conditioners integrated with the high-end 

PC by using LabView version 8.2.1 with NI-Daq 4.3 software (NI, 2008a) that permitted data 

acquisition, real-time display, and recording for later analysis. The test control and data acquisition 

system was shown in Figure 6. 

2.6 Test Methodology

The test preparation and methodology for conducting side impact load test comprised the following 

steps:

• The F59 tank was positioned over the test fixture in an inverted position.

• Two transverse floor beams were anchored down to the test fixture per the computer-aided 

design (CAD) and the inverted tank was mounted over them with the help of tank-attachment 

fixtures located at both ends of the tank. 

• The load lever was repositioned relative to the tank so that while anchored and suspended from 

an upper transverse beam, the bumper attached to its lower end just made contact with one 

sidewall of the tank, as required for FRA side impact load case. This was determined from the 

CAD drawing of test setup shown in Figure 3.

• The hydraulic actuator was positioned between the lower-end back face of the load lever and 

an upright column of the test fixture as shown in Figure 9. Before commencement of the test, 

the actuator piston was at its minimum travel position and just made contact with the back 

surface of the load lever under unloaded condition. 
10

• One string potentiometer was attached between the back face of the load lever and an upright 

column of the test fixture as shown in Figure 7.

• Two more string pots were attached to the opposite-side unloaded sidewall of the tank as 

shown in Figure 8. One of them was attached near one end of tank and the other was attached 

near the location of central transverse baffle of the tank. These two string pots were meant to 

measure average sliding displacement, if any, of the tank because of side impact load. 

• The hydraulic hoses of the actuator were connected to the power pack, and the output of all 

transducers, such as load cell, pressure transducer, and string potentiometers, was connected to 

the NI data acquisition hardware. 

• The output of NI-Daq modules was connected to the high-end PC loaded with LabVIEW 

version 8.2 software for real-time display of all transducer output data and for recording all 

data to the hard drive.

• To start the test, all transducers were reset to show zero output without load application. 

• Hydraulic power pack was started and its pressure increased in steps to apply the desired load 

by the actuator on the load lever that was transmitted to the sidewall of tank through the 

“bumper.” 

• The applied load was gradually raised up to and beyond the required maximum of 200 

kilopounds (kip), as the test condition stated. All transducer output data were automatically 

recorded at a sampling rate of 1 kilohertz onto the hard disk of the PC. 

• After the maximum load application up to about 300 kip, the actuator load was gradually 

reduced to zero and the residual displacement of the tank sidewall and the unloaded position of 

load lever were recorded. 

• The F59 tank sidewall was photographed after completion of unloading (Figure 10). Hardly 

any noticeable residual deformation was in the tank sidewall even though a peak SI load well 

above the required 200 kip was applied.
11

Figure 9. Configuration of Servohydraulic Actuator for Side Impact Load Application
12

Figure 10. A Closeup View of Tank Sidewall and the Load Lever 

following Complete Unloading
13

3. Test Results and Discussions

The test procedure outlined in Section 2.6 was followed to conduct the side impact load test. 

During the test, the side impact load experienced by one sidewall of inverted F59 tank was

continuously monitored and recorded. The load point horizontal displacement was measured from 

the output of a string potentiometer connected to the back face of the load lever, coinciding with 

the initial line of contact with the tank sidewall. The variation of applied actuator load, representing 

side impact load, and consequent horizontal displacement of the load lever in contact with tank 

sidewall is shown in Figure 11. The output of two string potentiometers—representing horizontal 

displacements or sliding motion/bending in horizontal plane of the tank due to application of side 

impact load—is also plotted. The load lever displacement behavior with variation in applied side 

impact load is shown in Figure 12. The effective load point deformation of the tank sidewall is

computed by subtracting the average value of the two string pot outputs, SP-2 and SP-3 (attached 

to the unloaded sidewall) from that of SP-1 (attached to the back face of load lever). This effective 

load point deformation of tank sidewall versus the applied SI load is shown in Figure 13. 

F59 Tank Side Impact Load Test: Applied Load Vs. Load Lever and Tank 

Displacements

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

0 50 100 150 200 250 300 350

Applied Side Impact Load (Kip)

Displacement (String Pot Output in Inches)

SP-1 Output SP-2 Output SP-3 Output

Figure 11. Applied Side Impact Load vs. Load Lever and Tank 

Unloaded-Sidewall Displacements
14

F59 Tank Side Impact Load Test: Load Versus Displacement of Lever Arm 

0

50

100

150

200

250

300

350

0 0.5 1 1.5 2 2.5

Displacement of Lever Arm (in)

Applied Side Impact Load (Kip)

Figure 12. Variation of Load Lever Displacement with Applied Side Impact Load

F59 Side Impact Load Test: Load Versus Effective Displacement 

0

50

100

150

200

250

300

350

0 0.1 0.2 0.3 0.4 0.5 0.6

Effective Load-Point Deformation (in)

Applied Side Impact Load (Kip)

Figure 13. Effective Load Point Deformation of Tank Sidewall with 

Applied Side Impact Load
15

Following FRA guidelines for test conditions outlined in Section 2.1, the magnitude of applied 

quasi-static side impact load was increased gradually to 200 kip and beyond up to a maximum 

value of about 300 kip. From the test results shown in Figures 11–13, it is observed that:

• The applied side impact load and corresponding displacement of the load lever exhibit an 

almost linear relationship. The horizontal displacement of the tank (unloaded) back 

sidewall increased with increased applied load on tank front sidewall, although there were 

signs of intermittent “slip and stick” of the tank during this process. One likely reason for 

this sliding motion of tank under horizontal loading condition could be the existing gap 

between the oversized holes in tank attachment brackets and the large fastener bolts used 

for anchoring the tank. Despite adequate tightening of the nuts over large washers, there 

seems to have been appreciable sliding along the direction of loading. 

• Effective local deformation of the tank sidewall with side impact load point is shown in 

Figure 13. The peak side impact load of slightly over 300 kip caused elastoplastic 

deformation in the tank sidewall of about 0.5 in. Upon unloading, the residual plastic 

deformation on the sidewall is seen to be only about 0.12 in. This confirmed the barely 

visible slight depression in the sidewall after unloading and removal of load lever.

• The tank sidewall at the point of loading as well as all other walls were found to be 

undamaged owing to side impact load, and no breach was detected anywhere in the tank. 

On the basis of these test results, the F59 PHI passenger locomotive tank is considered to

demonstrate adequate strength and structural integrity against applied FRA side impact load

without any failure or breach in its walls. Furthermore, the applied side impact load versus load 

lever displacement behavior offers clear indication of greater-than-statutory side impact load 

bearing capacity of the tank.
16

4. Results of Simulation and FEA

4.1 Mechanical Properties Evaluation of F59 Tank Material

Foster-Miller/QNA carried out coupon-level testing to obtain reliable material properties, 

especially true stress versus true strain tensile data for the components of the tank. These data were 

necessary as material input parameters for FEA of the side impact load case. Material testing was 

performed by fabricating F59 tank component specimens, machined to the American Society for 

Testing Materials (ASTM) specifications, and applying tensile load in an Instron test machine. The 

load was monotonically increased slowly (quasi-static loading) from its initial value of zero to its 

final value just before breaking, so that the cross-section necking area and the corresponding 

tensile force could be measured for the computation of true stress. Through the examination of the 

tensile stress in the specimen as a function of the strain, material properties such as the elastic 

modulus, yield stress, ultimate stress and percent elongation at or near break condition of the 

coupons were obtained. Additionally, to represent sheet metal in ABAQUS, linear isotropic 

plasticity material model was used. This material model required the true stress versus true strain 

relationship as input parameters for the postyield segment of the stress–strain curve. That 

necessitated generation of tensile properties data on small samples of plate materials obtained from 

various sheet metal components of F59 PHI tank.

4.1.1 Test Sample Preparation and Testing

Initially, small-size plates were cut from different components of F59 tank, such as the top, bottom, 

and side plates, central and outer longitudinal baffles, and transverse central baffle. The end plates, 

which were 0.75-inch thick were identical to those of SD-70 tank tested previously so were not 

tested. Depending on the plate thickness of the retrieved material from components, tensile test 

coupons were fabricated per ASTM standards. For those plates having 0.25-inch thickness or less, 

tensile test coupons were fabricated according to ASTM-E8 Standard for subsize (SS) coupons. 

These SS test coupons were machined to be 6 in long to allow for the use of an extensometer for 

accurate measurement of strain and percent elongation. The coupons were tested in a calibrated 

Instron 1332 servohydraulic test machine. For consistency, the test machine crosshead-separation 

speed was maintained constant at 0.044 in/min and the data rate was 300 samples per minute. An 

MTS extensometer with 1.0-inch range of travel was used to continuously monitor and record 

percent elongation of the gage section almost up to the breaking point. This feature of the test was 

useful in computation of “true stress versus true strain” deformation behavior of the material 

beyond nominal ultimate stress point, which provided the necessary plastic strain component input 

into the ABAQUS FEA model.

4.1.2 Tensile Test Results

Two or three identical coupons were tested in tension up to or near breaking point and the results 

were found to be consistent. Figure 14 shows a sample tensile stress versus strain curve, plotted in 

terms of engineering stress versus engineering strain. The results of all three test coupons tested 

showed that the average engineering yield stress of the material was 65,957 psi, the corresponding 

ultimate stress was 72,810 psi, and the average percent elongation at break was 21.7.

The test data were then used to compute the corresponding true stresses and true strains, on the 

basis of the actual cross-section area of the specimen, including necking, in the postyield regime 
17

associated with higher rate of elongation. Assuming that zero change occurs to the total volume of 

the specimen gage section during the tensile test, the relationship between true and engineering 

stresses and strains can be derived as:

σT = σE (1 + ЄE) (1)

ЄT = Ln (1 + ЄE) (2)

where σE and ЄE are engineering stresses and strains, respectively, and σT and ЄT are true stresses and 

true strains, respectively.

0

10000

20000

30000

40000

50000

60000

70000

80000

-0.05 0 0.05 0.1 0.15 0.2 0.25

Engineering Strain ( in/in )

Engineering Stress ( psi )

Figure 14. Tensile Stress vs. Strain Curve for Tank Top Plate Material

The computed true stress versus true strain data derived from the test data of a sample tensile test 

coupon is shown in Figure 15. In this figure the last point of the curve represents the true stress at 

the necking region of the gage section, accurately computed by measuring actual cross-sectional 

dimensions of an unbroken specimen and with the known magnitude of applied load close to the 

termination of test. For a failed specimen, the reconstituted cross-section necking area and the 

magnitude of tensile load just before its sudden drop at break were considered to compute the true 

stress, which offered the last data point of the test. Because the true stress magnitudes from 

necking and associated reduction in cross-section area increase beyond the ultimate stress point up 

to the breaking point, the interim true stress values were interpolated corresponding to true strain 

values. The tensile test data of the top plate suggest that its material is likely to be an enhancedstrength quenched and tempered steel, COR-TEN B-QT70, or high-strength low-alloy (HSLA) 

steel such as ASTM A656.

The results of all the tensile coupon tests performed on materials retrieved from different 

components of the tank are included in Appendix A – Summary of F59 Tank Material Tensile 

Properties Data. 
18

0

10000

20000

30000

40000

50000

60000

70000

80000

90000

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16

True Strain ( in/in)

True Stress ( psi )

Figure 15. Extracted True Stress vs. True Strain Data for Tank Top Plate Material

4.2 FEA for Side Impact Load Case 

A static finite element model (FEM) was developed in ABAQUS to model the side impact load 

case using 85749 shell and solid elements and kinematic constraints. The full model and the model 

with the outer wall elements removed are shown in Figure 16 (a) and (b). Material properties used 

in the model were the same as those used in the JD FEM, as shown in the table below. 

Component Thickness 

(in) Likely Material Modulus (Msi)

Yield Stress 

(ksi) Source

Top plate 0.25 HSLA steel 30.5 65.9 Test

Bottom plate 0.491 CORTEN-B-QT70 29.4 70.4 Test

Side plates 0.491 CORTEN-B-QT70 29.4 70.4 Test

End plates 0.75 CORTEN-B 29.7 51.6 Test (SD-70)

Rail N/A High-strength steel 30.0 110.0 Handbook

Transverse 

baffles 0.3705 AISI 1030 or CORTEN-A 29.5 50.9 Test

Longitudinal 

baffle (outer) 0.1825 CORTEN-A 28.7 50.1 Test

Longitudinal 

baffle (center) 0.2265 Cast iron 13.0 31.0 Test
19

Figure 16. FEM of F59 Tank under Side Impact Loading: (a) Inverted Tank and a Bumper 

Attached to the Load Lever and (b) a Cutaway View of Tank Internal Structure

FEM predictions of deformation and von Mises stress in the F59 tank under side impact loading 

are shown in Figure 17. The load/displacement history, analogous to that of the experiment, was 

also determined in the FEM. These results are shown along with the experimental data in

Figure 18. 
20

Figure 17. Von Mises Stress Contours Corresponding to Applied Maximum Side Impact 

Load: (a) in the Sidewall of F59 Tank and (b) in the Internal Structures
21

Figure 18. FEM and Experimental Force vs. Displacement Data

The test data in this case were postprocessed to assess the effects of tank slipping in the test setup. 

Therefore, the resulting data are seen to be very nonlinear, especially during the loading part. 

Taking this into account, as can be seen in Figure 18, it is conceivable that the actual tank 

deformation response would have been stiffer had it not slipped during loading. Accounting for this 

artifact, the FEM results may be considered to generally agree with the experimental data. 

However, some variations can be identified between the two sets. First, the FEM seems to be stiffer 

initially, up to about 0.04 in of deformation. This discrepancy is most certainly due to initial 

slipping and settling of the tank in the test. Second, after about 0.25 in of deflection, the FEM 

softens slightly and, thereafter, offers a very low-stiffness plastic response. This most likely occurs 

because the central transverse baffle directly behind the fuel tank sidewall and at the center of the 

side-impacting bumper is found to have buckled and is capable of offering only lower stiffness 

through bending. This can be seen in the cutaway detail shown in Figure 19. The unloading part of 

FEM results also differ from those of the test, showing a faster elastic recovery and a small lateral 

shift for the FEM result. However, upon complete unloading, the residual plastic deformation of 

nearly 0.12 in agrees with the measured value from the test.
22

Figure 19. Detail of Cutaway FEM Results Showing von Mises Stresses in the Buckled 

Transverse Baffle Directly behind the Side Impact Bumper
23

5. Conclusions 

The F59 PHI passenger locomotive fuel tank was subjected to simulated quasi-static side impact

load at Foster-Miller/QNA’s full-scale fuel tank test facility. It was observed that the effective

horizontal deformation of the sidewall of the inverted tank, corresponding to a maximum side 

impact load of 317 kip, was 0.5 in. This comprised both elastic and plastic components of the tank 

sidewall deformation. Upon unloading, the local residual plastic deformation of the sidewall at the 

bumper location was found to be approximately 0.12 in, with no cracks or breach observed within 

the plastically deformed zone or elsewhere. Despite the applied side impact load being more than 

50 percent of the statutory test load, the residual plastic deformation or the ‘permanent set’ was 

negligibly small and not discernible to the naked eye. Hence, from the FRA regulatory perspective, 

the tank was deemed to have passed the structural integrity requirement and be considered safe 

against side impact load (FRA, 2005) under 49 CFR Part 238, Appendix D, Section (a) (3). 
24

6. References

1. National Instruments. (2008a). LabVIEW Version 8.2.1 w/ NI-Daq 4.3

http://www.ni.com/labview/. 

2. National Instruments. (2008a). Data Acquisition Model SCXI-1121/1120tb. 

http://sine.ni.com/nifn/cds/view/main/p/sn/n24:SCXI/lang/en/nid/1036/ap/daq. 

3. Requirements for External Fuel Tanks on Tier I Locomotives, Section (a) (3), Appendix D to 

Part 238, 49 CFR Ch. II (10-1-05 Edition), Federal Railroad Administration, Department of 

Transportation, 2005. 
25

Appendix A. 

Summary of F59 Tank Material Tensile Properties Data

F59 Tank Materials Tensile Properties Data

1. Outer Longitudinal Baffle Plate

Nominal plate thickness = 0.1825 in

Coupon F59-C1/2

Young’s modulus, E = 28.7 × 106 psi

UTS = 69,432 psi

Elongation at UTS = 10.4 percent

Elongation at break = 22 percent

True stress at yield = 50,081.8 psi

True strain at yield = 0.001745

F59 Tank Outer Longitudinal Baffle Plate: Engineering Stress Versus Strain [C - 1/2 ]

0

10000

20000

30000

40000

50000

60000

70000

80000

0 0.05 0.1 0.15 0.2 0.25

Engineering Strain (in / in )

Engineering Stress ( psi ) P. L.

Figure A1. Engineering Stress vs. Strain Curve for Outer Longitudinal Baffle Plate
26

F59 Tank Outer Longitudinal Baffle: True Stress Vs. True Strain [C-1/2] 

{ Extracted Data (Based on Final Necking ACS) for FEA}

0

20000

40000

60000

80000

100000

120000

140000

0 0.05 0.1 0.15 0.2 0.25

True Strain (in/in)

True Stress ( psi )

Figure A2. True Stress vs. True Strain Curve for Outer Longitudinal Baffle

F59 Tank Outer Longitudinal Baffle: Plastic Strain Vs.True Stress [ C-1/2 ] 

{ True Stress Extrapolated to Include Final Necking ACS - For FEA }

0

20000

40000

60000

80000

100000

120000

140000

0 0.05 0.1 0.15 0.2 0.25

Plastic Strain ( in/in )

True Stress ( psi )

Figure A3. True Stress vs. Plastic Strain Curve for Outer Longitudinal Baffle
27

2. F59 Tank Central Longitudinal Baffle Plate

Nominal plate thickness = 0.2265 in

Coupon F59-C2/1

Young’s modulus, E = 13.0 × 106 psi (average value of 2 coupons tested)

UTS = 53,669 psi

Elongation at UTS = 16.75 percent

Elongation at break = 29.2 percent

True stress at yield = 31,014.8 psi

True strain at yield = 0.00238

F59 Tank Central Longitudinal Baffle Material: Engineering Stress Vs. Strain [C-2/1]

-10000

0

10000

20000

30000

40000

50000

60000

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35

Engineering Strain (in/in)

Engineering Stress (psi) Uppe

r

Figure A4. Engineering Stress vs. Strain Curve for Central Longitudinal Baffle Plate
28

F59 Tank Central Longitudinal Baffle: True Stress Vs. True Strain [C-2/1] 

{ Extracted for FEA - Including Final Necking ACS }

0

20000

40000

60000

80000

100000

120000

0 0.05 0.1 0.15 0.2 0.25 0.3

True Strain ( in/in )

True Stress ( psi )

Figure A5. True Stress vs. True Strain Curve for Central Longitudinal Baffle

F59 Tank Central Longitudinal Baffle: True Stress Vs. Plastic Strain [ C-2/1 ] 

{True Stress Extrapolated to Include Final Necking ACS - For FEA}

0

20000

40000

60000

80000

100000

120000

0 0.05 0.1 0.15 0.2 0.25 0.3

Plastic Strain ( in/in )

True Stress ( psi )

Figure A6. True Stress vs. Plastic Strain Curve for Central Longitudinal Baffle
29

3. F59 Tank Central Transverse Baffle Plate

Nominal plate thickness = 0.3705 in

Coupon F59-C3/1

Young’s modulus, E = 29.513 × 106 psi

UTS = 69,475 psi

Elongation at UTS = 19.2 percent

Elongation at break = 37.9 percent

True stress at yield = 50,891.81 psi

True strain at yield = 0.001671

F59 Tank Central Transverse Baffle: Engineering Stress Vs. Strain [ C-3/1 ]

-10000

0

10000

20000

30000

40000

50000

60000

70000

80000

-0.05 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4

Engineering Strain ( in/in )

Engineering Stress ( psi )

Upper 

Y. P.

Figure A7. Engineering Stress vs. Strain Curve for Central Transverse Baffle Plate
30

F59 Tank Central Transverse Baffle: True Stress Vs. True Strain [ C-3/1 ] 

{ Extracted Data Including Final Necking ACS For FEA }

0

20000

40000

60000

80000

100000

120000

140000

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35

True Strain ( in/in )

True Stress ( psi )

Figure A8. True Stress vs. True Strain Curve for Central Transverse Baffle

F59 Tank Central Transverse Baffle: Plastic Strain Vs. True Stress [ C-3/1 ] 

{True Stress Extrapolated to Include Final Necking ACS - For FEA }

0

20000

40000

60000

80000

100000

120000

140000

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35

Plastic Strain ( in/in )

True Stress ( psi )

Figure A9. True Stress vs. Plastic Strain Curve for Central Transverse Baffle
31

4. F59 Tank Top Skin Plate

Nominal plate thickness = 0.25 in

Coupon F59-1-1 

Young’s modulus, E = 30.517 × 106 psi

UTS = 72,935 psi

Elongation at UTS = 14 percent

Elongation at break = 24.6 percent

True stress at yield = 65,834.65 psi

True strain at yield = 0.0023617

0

10000

20000

30000

40000

50000

60000

70000

80000

-0.05 0 0.05 0.1 0.15 0.2 0.25

Engineering Strain ( in/in )

Engineering Stress ( psi )

F59-Tank Top Plate Material : Engineering Stress Versus Strain [ Coupon F59-1 / 1 ]

Figure A10. Engineering Stress vs. Strain Curve for F59 Tank Top Plate
32

F59 Tank Top Plate: True Strain Vs. Effective True Stress [F59-1/1]

{ Effective True Stress Extrapolated to Include Final Necking ACS - For FEA }

0

20000

40000

60000

80000

100000

120000

0 0.05 0.1 0.15 0.2 0.25

True Strain (in/in)

Effective True Stress (psi)

Figure A11. True Stress vs. True Strain Curve for F59 Tank Top Plate

F59 Tank Top Plate Material: Effective True Stress Vs. Plastic Strain [F59-1-1]

0

20000

40000

60000

80000

100000

120000

0 0.05 0.1 0.15 0.2 0.25

Plastic Strain ( in/in )

Effective True Stress ( psi )

Figure A12. True Stress vs. Plastic Strain Curve for F59 Tank Top Plate
33

5. F59 Tank Bottom and Side Plate

Nominal plate thickness = 0.491 in

Coupon F59-4-2 

Young’s modulus, E = 29.422 × 106 psi

UTS = 88,662 psi

Elongation at UTS = 5.45 percent

Elongation at break = 25.1 percent

True stress at yield = 70,400 psi

True strain at yield = 0.002542

F59 Tank Bottom and Side Plate: Engineering Stress Vs. Engineering Strain [C-4/2]

0

10000

20000

30000

40000

50000

60000

70000

80000

90000

100000

-0.05 0 0.05 0.1 0.15 0.2 0.25 0.3

Engineering Strain ( in/in )

Engineering Stress ( psi )

Figure A13. Engineering Stress vs. Strain Curve for F59 Tank Bottom and Side Plate
34

F59 Tank Bottom and Side Plate: True Strain Vs.True Effective Stress [F59-C4/2]

{ Effective True Stress Extrapolated to Include Final Necking ACS - For FEA }

0

20000

40000

60000

80000

100000

120000

140000

160000

0 0.05 0.1 0.15 0.2 0.25

True Strain (in/in)

Effective True Stress (psi)

Figure A14. Effective True Stress vs. True Strain Curve for F59 Tank Bottom and Side Plate

F59 Tank Bottom and Side Plate: Effective True Stress Vs. Plastic Strain [C-4/2 ] 

{ True Stress Extrapolated to Include Final Necking ACS - For FEA }

0

20000

40000

60000

80000

100000

120000

140000

160000

0 0.05 0.1 0.15 0.2 0.25

Plastic Strain ( in/in )

Effective True Stress ( psi )

Figure A15. True Stress vs. Plastic Strain Curve for F59 Tank Bottom and Side Plate
35

6. F59 Tank End Plate

Assumed same material as SD70 tank

Nominal plate thickness = 0.75 in

Coupon (SD70)-5/2

Young’s modulus, E = 29.7 × 106 psi

UTS = 73,546 psi

Elongation at UTS = 11.34 percent

Elongation at break = 21.6 percent

True stress at yield = 51,581 psi

True strain at yield = 0.00171

Fuel Tank End Plate Material: Engineering Stress Versus Strain [ Coupon 5 / 2]

0

10000

20000

30000

40000

50000

60000

70000

80000

-0.05 0 0.05 0.1 0.15 0.2 0.25

Strain (in/in)

Engineering Stress (psi)

Figure A16. Engineering Stress vs. Strain Curve for Fuel Tank End Plate
36

Fuel Tank End Plate Material : True Stress Vs. True Strain [Coupon 5 / 2 ]

0

10000

20000

30000

40000

50000

60000

70000

80000

90000

-0.05 0 0.05 0.1 0.15 0.2 0.25

True Strain ( in/in )

True Stress ( psi )

Figure A17. True Stress vs. True Strain Curve for Fuel Tank End Plate

Table A1. Summary of F59 Tank Materials Properties from Tensile Test Data

Component Thickness 

(in) Material Modulus 

(Msi)

Yield 

Stress (ksi)

Ultimate

(Msi)

Top plate 0.25 HSLA Steel 30.50 65.90 72.93

Bottom plate 0.491 CORTEN-B-QT70 29.40 70.40 88.66

Side plates 0.491 CORTEN-B-QT70 29.40 70.40 88.66

End plates 0.75 CORTEN-B 29.70 51.60 73.54

Transverse baffles 0.3705 AISI 1030/CORTEN-A 29.50 50.20 69.47

Longitudinal baffle (outer) 0.1825 CORTEN-A 28.70 50.10 69.43

Longitudinal baffle (center) 0.2265 Cast iron 13.00 31.90 53.70

Notes: 

COR-TEN A refers to corrosion-resistant steel material of thickness less than 0.5”

COR-TEN B refers to same material with thickness in the range of 0.5” to 2.0”

QT70 represents thermomechanically processed (quenched and tampered) COR-TEN steel material to raise 

the yield stress from 50 to 70 ksi.
37

Abbreviations and Acronyms

CAD computer-aided design

CFR Code of Federal Regulations

EMD Electro-Motive Diesel, Inc.

FEA finite element analysis

FEM finite element model

FRA Federal Railroad Administration

HSLA high-strength low-alloy

in inch

JD jackknife derailment

kip kilopound

ksi kilopound per square inch

MD minor derailment

Msi million pound per square inch

NI National Instrument

psi pound per square inch

SS subsize