No. 13124

HIGH-MOBILITY MULTIPURPOSE WHEELED VEHICLE (HMMWV) FRAME

WITH PROPOSED .DRAIN HOLES

oCH 1991

Stephen C. LambrechtRoberto P. GarciaU.S. Army Tank-Automotive CommandAMSTA-RYC

By Warren, MI 48397-5000

APPROVED FOR PUBLIC RELEASE:DISTRIBUTION IS UNLIMITED ao()l z~

U.S. ARMY TANK-AUTOMOTIVE COMMANDRESEARCH, DEVELOPMENT & ENGINEERING CENTERWarren, Michigan 48397-5000

LU

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1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED

1 15 March 1991 Final 10 Sep 90 - 26 Oct 904. TITLE AND SUBTITLE 5. FUNDING NUMBERS

Finite Element Analysis of High Mobility-MultipurposeWheeled Vehicle (HMNWV) Frame with Proposed Drain Holes

6. AUTHOR(S)

Stephen G. LambrechtRoberto P. Garcia

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION

REPORT NUMBER

U.S. Army Tank-Automotive CommandAMSTA-RYCWarren, MI 48397-5000 13524

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSORING/MONITORINGAGENCY REPORT NUMBER

11. SUPPLEMENTARY NOTES

12a. DISTRIBUTION/AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE

Approved for Public Release:Distribution is Unlimited

13. ABSTRACT (Maximum 200 words)

It was reported that High-Mobility Multipurpose Wheeled Vehicle (HMMWV) frames

were rusting out in tropical climates due to salt water resting in the frame

rails. In order to alleviate this problem, a proposal to drill four drain holes

into the HMM1WV frame rail was made. The purpose of this report was to perform

finite element analysis (FEA) on the HMNWV frame to determine if the proposed

drain holes lower the structural integrity of the frame.

14. SUBJECT TERMS 15. NUMBER OF PAGES

Finite Element Analysis, HNMWV, Vehicle Frame 3416. PRICE CODE

17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION 20. LIMITATION OF ABSTRACT

OF REPORT OF THIS PAGE OF ABSTRACT

Unclassified Unclassified Unclassified

NSN 7540-01 -280-5500 Standard Form 298 (Rev 2-89)1Prscrib. d bV ANSI Stll 39-18

2

TABLE OF CONTENTS

Section Page

1.0. INTRODUCTION .............. ................. 5

2.0. OBJECTIVE ................. .................. 5

3.0. CONCLUSIONS ............... ................. 5

4.0. RECOMMENDATIONS ............. ............... 7

5.0. DISCUSSION ................ ................. 75.1. Finite Element Method .. ............ . . . 75.2. Finite Element Software ......... ........... 85.2.1. I/FEM ................... .................... 85.2.2. PATRAN .................. ................... 85.2.3. ABAQUS . . .......... ................... 85.3. Finite Element Models ........... ............ 85.3.1. Geometry and Elements ........... ............ 85.3.2. Materials ............................. .. 115.3.3. Loading Conditions and Constraints ........ . 115.4. Discussion of Results ....... ............ 12

APPENDIX A, Result Plots of Standard Frame ... ...... A-1

APPENDIX B, Result plots of Frame with Drain Holes . B-1

DISTRIBUTION LIST .......... ................. Dist-i

3

LIST OF ILLUSTRATIONS

Figure Title Page

1-1. M1026 HMMWV ............. ... ................. 51-2. Proposed Drain Hole Locations ....... ........ 65-1. Finite Element Model of HMMWV Frame ... ..... 95-2. Model of HMMWV Frame with Four Drain Holes . 105-3. Constraints and Mass Loading Locations . ... 13

LIST OF TABLES

Table Title Page

5-1. ASTM A607 Grade 50 Properties ... ........ 115-2. Breakdown of Frame Loadings ... ......... 115-3. HMMWV Frame Analysis Results ... ......... 12

4

1.0. INTRODUCTION

The High-Mobility Multipurpose Wheeled Vehicle (HMMWV) iscurrently being used at various military bases around theworld. These vehicles are the replacement of the MI51 JeepVehicle. They come in various configurations such as theM998 pickup truck, the M996 ambulance and the M1026 four-door hardtop version. These vehicles utilize full framesto which the body, engine, and suspension are attached.Figure 1-1 below depicts a typical HMMWV.

Figure 1-1. M1026 HMMWV

According to field reports, the HMMWV frames are rustingout beyond repair in Hawaii within five years of service.This was thought to be caused by salt water resting in theframe rails. In order to remedy this problem, AMSTA-MTC atthe U. S. Army Tank-Automotive Command (TACOM) proposed thedrilling of four, two per frame rail, 0.5-inch drain holesin the bottom of the frame rails. Figure 1-2 illustratesthe drain hole locations. The Computer-Aided EngineeringBranch (AMSTA-RYC) was tasked to perform a structuralanalysis of the frame with the drain holes to determine ifthis solution was feasible.

2.0. OBJECTIVE

The objective of this project was to compare the standardHMMWV frame to one with the four 0.5-inch drain holes.Finite Element Analysis (FEA) was to be used to determineif the drain holes would damage the structural integrity ofthe frame.

3.0. CONCLUSIONS

The result of the finite element analysis showed no adversestress condition on the frame with the 0.5-inch drain holes

5

FRONT

Drain hole, 6 inches Drain hole, 6 inchesaft. construction aft. constructionhole hole

Drain hole, 8 inches Drain hole, 8 inchesaft.trans. cross- aft.trans. cross-member holes member holes

Figure 1-2. Proposed Drain Hole Locations

6

as compared to the one without. None of the resultsindicate a reduction in frame integrity due to the drainholes for the simulation conducted.

The results of this report are based on a steady-statestatic analysis only. No fatigue analysis or prototypetests were performed for this project.

4.0. RECOMMENDATIONS

Though the drain holes do not reduce the strength of theframe, they are a source for oxidation to begin. This isespecially true if the holes are drilled after the rust-proofing is applied, leaving bare exposed metal. It isrecommended that extra rustproofing be applied around thedrain holes.

5.0. DISCUSSION

5.1. Finite Element Method

The finite element method is an analysis technique forsolving the differential equations of complex problems. Thefinite element method has become a valuable tool formodeling structural, mechanical, thermal, and fluidsystems. Basically, the finite element method is thesubdividing of complex continuous structures into discreteregions, or finite elements. The elements have specificpoints called nodes that define the geometry of the elementas well as provide points at which physical information canbe entered, and received from, the element. Suchinformation which can be entered include force,temperatures, and flow rates. Information which couldresult include stress, flux, and pressure. Behavior ofeach finite element can be described by a set of functionsinvolving the nodal displacements in that element.

It is desirable that the behavior of the model closelyexhibits the behavior of the actual physical structure.For this reason, there are many types of elements whichdiffer in their geometries and their allowable degrees offreedom. Such element types include truss, beam, shell,and solid elements. The choice of element shape is left tothe skill of the engineer. The more regular, that is,square in shape the element is, the more accurate theresults. This project used shell elements which, unlikesolid elements, are two-dimensional and needed a numericalvalue for the thickness to be assigned.

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5.2. Finite Element Software

5.2.1. I/FEM. The Intergraph Finite Element ModelingSystem, (I/FEM) is a computer-aided engineering softwarepackage for general-purpose finite element modeling andanalysis. I/FEM uses interactive graphics allowing theanalyst to create the model, perform the analysis, andevaluate the results. I/FEM was developed by IntergraphCorp. For this project, I/FEM was used as a modeler only.

5.2.2. PATRAN. Patran is a pre/postprocessing softwarepackage developed by PDA Engineering. For this project,PATRAN was used to translate the I/FEM model to an ABAQUSinput deck. PATRAN was also used as a postprocessor whichallows the analyst to view the results of the analysis ingraphical form. All of the stress and displacement colorcontour plots in this report were created using PATRAN.

5.2.3. ABAQUS. ABAQUS is a large-scale finite elementanalysis program capable of analyzing complex structures.The analyst first needs an input file, which in this casewas created using PATRAN. The input file defines the shapeand material properties of the model as well as boundaryconditions and loads. The program then assembles andsolves a system of equations and outputs the results.ABAQUS was developed by Hibbitt, Karlsson, & Sorensen, Inc.

5.3. Finite Element Models

The finite element model contains all the informationneeded to run the analysis for the frame. This modeldefines the actual shape and dimensions of the frame, thematerials used and their properties, and any boundaryconditions and force loadings. Two different models wereused for this project: the standard HMMWV frame and theframe with the four 0.5-inch drain holes. The two modelswere identical except for the addition of the four 0.5-inchdrain holes.

5.3.1. Geometry and Elements. The geometry, or actualshape and dimensions of the frame, was constructed first.This geometry was done using I/FEM which uses Intergraph'sEngineering Modeling System (I/EMS) to create the model.The geometry was created using surfaces.

Once the geometry was completed, the nodes and elementswere made, also using I/FEM. Four and three-noded shellelements were used for this project. The standard HMMWVframe model contained 1747 nodes and 1728 elements. Themodel of the HMMWV frame with the 0.5-inch drain holescontained 2074 nodes and 2007 elements. Figure 5-1 showsthe completed finite element model of the frame withoutdrain holes. Figure 5-2 shows the finite element model ofthe HMMWV frame with drain holes. The frame in Figure 5-2is upsidedown so the drain holes are visible.

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5.3.2. Materials. The material and property assignmentswere done using I/FEM. The entire model was assigned theone material. The HMMWV frame is made of ASTM A607 Grade50 steel. The properties used are listed in TABLE 5-1below.

Property Value

Young's Modulus, E 29 x 106 psiDensity, 9 0.284 lb/in. 3

Poisson's Ratio, ) 0.30Ultimate Strength 65 ksiYield Strength 50 ksiShear Strength 30 ksi

TABLE 5-1. ASTM A607 Grade 50 Properties'

Since shell elements were used, the thicknesses had to beassigned. The frame rails, braces, and crossmembers were0.1196-in. thick. The actual brackets that hold thecrossmenbers to the frame rails were not modeled, but inthe areas that they were located, the thickness wasincreased to simulate their presence. After the materialsand thicknesses were assigned, the models were translatedfrom I/FEM to a PATRAN data file.

5.3.3. Loading Conditions and Constraints. The currentHMMWV frame rail configuration was designed to withstand aconstant steady load of approximately 3.9 g's. This wasthe test that was used to compare the two frame models, a3.9 g acceleration in the gravitational direction, whichsimulates an air drop. A total vehicle weight of 5640 lbwas used. TABLE 5-2 below shows the breakdown of theweights. The "REST" item below includes the body, cargo,and driver.

ENGINE = 650 lbTRANSMISSION = 182 lbFRAME = 754.431 lbREST 4053.569 lbTOTAL = 5640 lb

TABLE 5-2. Breakdown of Frame Loadings

The above weights were added to the models as mass loadsand were applied using PATRAN.

lMarks' Standard Handbook for Mechanical Engineers,8th Edition, McGraw-Hill Book Company, 1978, p 6-28.

11

The frame was constrained at the suspension spring mountingbrackets. The vehicle was considered to be bottomed outbefore accelerations were applied for a worst-casecondition. Figure 5-3 shows the locations of theconstraints and mass loading points.

At this point the models were optimized and a PATRANnetural file was created. Model optimization is therenumbering of nodes and elements to reduce the number ofcalculations needed to solve the system of equations. Thenusing a translator, an ABAQUS input file was created. ThePATRAN/ABAQUS translator writes information from PATRANinto a format that ABAQUS can read.

5.4. Discussion of Results

After the models were completed and the ABAQUS input filecreated, the analysis was run on a Cray-2 Supercomputer.The actual analysis took about 10 minutes. Several outputfiles are created from the results. The ABAQUS.FIL filewas translated back to PATRAN on the VAX 8800. TABLE 5-3below lists the results of the analysis for the two HMMWVframes.

Standard Frame Frame W/Holes

Von Mises Stress 16,243 psi 16,245 psiMax Shear Stress 3,754 psi 3,754 psiMax Principal 16,407 psi 16,412 psiMax Deflection 0.0894 in. 0.0894 in.

TABLE 5-3. HMMWV Frame Analysis Results

As can be seen from the results above, the drain holes haveno effect on the overall strength of the frame. The slightdifferences between the stresses are within the error boundof the analysis, therefore no realistic difference existsbetween the two cases. The Von Mises stress above takesinto account the shear stress effect, as well as the normalstress. The Von Mises criterion, also known as the MaximumDistortion Energy criterion, is a yield criteria forductile materials under plane stress. According to thecriterion, a given structural component is safe as long asthe maximum value of the distortion energy per unit volumein that material remains smaller than the distortion energyper unit volume required to cause yield in the standardtensile test specimen of the same material. 2 The Von

2 Beer, F. P. and E. R. Johnston, Jr., Mechanics of

Materials, McGraw-Hill Book Company, 1981, p. 316

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Mises stresses from this analysis are below the yieldstrength of the material, therefore there is no indicationof a failure.

There are two sets of color contour plots of the results ofthis analysis. Appendix A shows the results of thestandard HMMWV frame and Appendix B shows the plots of theresults of the frame with the drain holes. As can be seenby the color plots, the largest displacement on bothmodels, occurred at the center of the transmissioncrossmember. The highest stresses occurred at the fourconstrained locations, as was expected.

There was a stress concentration at the drain holes,especially the left front drain hole, as can be seen by thelast plot in Appendix B. The highest Von Mises stress atthis hole was 11,736 psi, which is well below the higheststress of the whole frame, which was 16,245 psi.

14

APPENDIX A

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Copies

Commander 12Defense Technical Information CenterBuilding 5, Cameron StationATTN: DDACAlexandria, VA 22304-9990

Manager 2Defense Logistics Studies Information ExchangeATTN: AMXMC-DFort Lee, VA 23801-6044

Commander 2U.S. Army Tank-Automotive CommandATTN: ASQNC-TAC-DIT (Technical Library)Warren, MI 48397-5000

Commander 1U.S. Army Tank-Automotive CommandATTN: AMSTA-CF (Dr. Oscar)Warren, MI 48397-5000

Director 1U.S. Army Material Systems Analysis ActivityATTN: AMXSY-MP (Mr. Cohen)Aberdeen Proving Grounds, MD 21005-5071

Commander 10U.S. Army Tank-Automotive CommandATTN: AMSTA-RYC (Mr. Lambrecht)Warren, MI 48397-5000

Commander 5U.S. Army Tank-Automotive CommandATTN: AMSTA-MTCWarren, MI 48397-5000

Commander 19 U.S. Army Tank-Automotive Command

ATTN: AMSTA-TD (Mr. Adlam)Warren, MI 48397-5000

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