Student_report.doc

Final Design ProjectME 380

Fall 1999

Submitted to: Dr. Michael Day

University of LouisvilleMechanical Engineering Department

Submitted on:12/7/1999

Written By:Kevin Murphy: Introduction, Ford background, Ford methodologyColleen O’Connor: Hummer background, Hummer methodology

Dale Mason: Final design solution, Conclusions, Recommendations

Contributors:Doug Fervan

Chuck GreenwellJason VittitoeBrian Grant

Daniel Graham Brian Block

Dan Vo Bryan Leonard Damon Pleasant

David Leone Mark Medley

INTRODUCTION

For this project, the Ford F150 (2000 model), the current AM General HMMWV, and a

conceptual prototype were modeled in CAD (Computer Aided Design) using IDEAS Master Modeler

software. These designs were then analyzed under a static body load using ANSYS finite element analysis

software. The purpose of this analysis was to benchmark existing F-150 and HMMWV models, and to

develop and analyze the feasibility of a new design per request of Ford and the Department of Defense.

The prototype frame developed in this project is intended for use as the frame for a lightweight

military tactical vehicle, and as the frame for future Ford F150 model trucks. The new frame will be

manufactured using high-strength steel composed of lighter and stronger materials. It will support a body

composed of laser-welded blanks and materials with improved corrosion resistance.

This report gained insight into the frame response of the existing Ford F-150 and HMMWV

designs under a static body load. The results of these analyses were used to highlight possible problem

areas, and/or predict case failure. With these results, a lightweight, multipurpose frame was designed.

This reports consists of multiple sections. Background information for this project follows the

introduction. The report then moves into a discussion of methodology and a presentation of results for the

Ford and HMMWV models, on to a discussion of the final design solution, conclusions, and

recommendations. Attached to this report are appendices containing ANSYS results.

BACKGROUND INFORMATION

This analysis was oriented to redesign/modify the HMMWV and/or Ford F150 for military use.

The results of this project are discussed in this report and online at http://athena.louisville.edu/~kpmurp01.

The basic truck produced for the United States Army and other military units is known as a High

Mobility Multipurpose Wheeled Vehicle, or HMMWV, which the military refers to as a Humvee. The

HMMWV (M998 Truck) supplies a wide variety of wheeled vehicle platforms for the U.S. military. These

platforms include a cargo/troop carrier, an armament carrier, a TOW missile system carrier, a shelter carrier

and two ambulance variants. The HMMWV will is also the prime mover for the AN/TRC-170 Radio

Digital Terminal and the Pedestal Mounted Stinger System.

The M998 is the baseline vehicle for a series of 1 1/4-ton trucks, which are known as the

HMMWV vehicles. These vehicles include eleven. All of which are designed for use over all types of

roads, in all weather conditions and are extremely effective in the most difficult terrain. The HMMWV’s

high power-to-weight ratio, four-wheeled drive and high ground clearance combine to give it outstanding

cross-country mobility. The Humvee’s “look” is a simple case of form following function. The unique

design reflects the U.S. Army’s long list of requirements for this vehicle.

Figure 1. The military’s HMMWV

The box shape allows for a number of platforms to be integrated with the body, allowing the

military to have more than 50 different combat, combat support and custom designed systems to be

installed. This versatility translates well into general industry also. Commercial Hummers are sold to

construction, mining, electrical utility, fire and rescue, oil and gas, forestry and other industries requiring

the same versatility that the Humvee offers the military. The overall weight of the HMMWV is 10,300

pounds and the Department of Defense is looking to create a lightweight tactical vehicle.

The F-series trucks are the Ford Motor Company's current heavy-duty vehicles. Its heaviness

(4700 lbs) and low fuel efficiency have left the F150 at a disadvantage with its lighter more fuel-efficient

competitors. In the interest of serving a more environmentally conscious clientele, and the needs of a fuel

conscious military, the Ford Motor Company has undertaken the development of a lighter, stronger truck,

the P2000.

Figure 2. Ford F-150 2000 model

The goals of Ford's P2000 development project are to reduce the F150's overall weight by 25%, creating a

lighter and more fuel-efficient vehicle, and to increase corrosion resistance and strength of the materials

used. The P2000 will be a civilian based platform capable of performing in military tactical operations.

The P2000 will phase out the US Military's current light tactical vehicle, the AM General HMMWV.

The design project is sponsored by the TACOM's National Automotive Center. Major participants

in the program include Ford Motor Company, the American Iron and Steel Institute, Oak Ridge National

Laboratory, Mississippi State University and the University of Louisville. To begin the design of the new

multipurpose vehicle, it is necessary to examine the existing F150 and HMMVW model frames under

loading conditions to determine the advantages of each.

METHODOLOGY

FORD

Frame dimensions for the Ford F-150 were obtained from, the Ford F-150 (1999) brochure, and

physical measurements. Using physical measurements and the brochure, an overall sketch of the frame was

rendered using Auto-CAD 2-D software (Figure 3).

Figure 3. Diagram

The IDEAS model was created without width variations between the main beams. Simplifying the frame in

this manner was necessary for a timely analysis. Further detail would only complicate the design process,

and yield only slightly different results. Using the CAD sketch, a 3 dimensional model of the frame was

rendered in IDEAS Master Modeler Software, seen below in figures(4-6) .

Figure 4. Isometric view of F150 frame modeled in IDEAS

Figure 5. Top view of F150 frame modeled in Ideas

Figure 6. Front view of F150 frame modeled in Ideas

Figure 7. Side view of F150 frame modeled in Ideas

As seen above, five cross-members with varying geometry support the frame. Because of the varying cross-

sectional dimensions of the frame, the length geometry of the frame (219 in.), seen in figure (6), was

defined first and extruded 36 in. Following the extrusion, the middle portion that separated the main beams

was removed and the remaining beams were shelled to the “c-channel” thickness of .10904 in. The middle

Cross-members were modeled by first modeling rectangles and then extruding them to the require lengths.

The resulting beams were then modified through cuts to have the correct curvature, shelled to the “c-

channel” thickness, and joined to the main frame. For the “X” cross member at the rear of the truck, the

cross-section was defined as an extruded solid, modified with subtractions of the inner and outer arcs (see

Figure), then shelled to the cross-sectional thickness, and joined to the frame.

From this model, the frame weight was calculated using the IDEAs Measurement command. The

material was defined as generic isotropic steel. At 361.084 lbs, the frame weighs slightly less than that of

the HMMWV discussed later. With the IDEAS model completed and weight calculated, the project then

moved into Finite Element Analysis using ANSYS.

For analytical purposes (and time saving), the cross-section is assumed to be constant throughout

the length beams, with exceptions at the curves. However, the cross-sections of the cross-members were

varied to accurately portray the IDEAS model. Because of the limited modeling capabilities of ANSYS,

these variations were made during the definition of the element properties.

Figure 8. Frame geometry modeling in ANSYS.

The ANSYS frame geometry was created by first defining keypoints. Keypoints were placed

where variations in cross section occurred. Other key-points were placed at cross-member locations. The

keypoints were then connected with lines (Figure 8), and defined by an element type BEAM4 (3-D).

ANSYS requires certain user-defined variables such as Moment of Inertia, Modulus of Elasticity, cross-

sectional area and Shear Modulus. Variables defined during the ANSYS analysis of the Ford model are

shown in Table 2.

Table 2. Defined variables for ANSYS analysis

Note: moments of inertia and cross sectional area varied. Seventeen sets of element properties were

initialized to accurately define the lengths, widths and moments of inertia. The modeled lines were meshed

into element sections based on the real constants for that section. Based off the F150 brochure, estimates

were made of constraint and force locations. These constraints (all degrees of freedom) were located at the

approximate axel locations (Figure 9).

Figure 9. Loading conditions for ANSYS model frame.

As seen above, four 959.00 lb forces were applied at approximated body mounting locations to simulate the

body weight of the truck. The magnitudes of the applied forces were derived by subtracting the frame and

engine weights from the total truck weight (4700- 361-500 lbs). Then the loads were applied uniformly

over the four mounting locations. The uniform pressure loads (seen in Figure (9) as redlines with

downward arrows) were placed at engine and bed locations. For the engine location, 200 lbs. were

distributed in 20 psi. uniform pressures over a portion of the front of the main beams. An additional 100lbs

was distributed over the cross-sectional member at the front of the frame in 20psi increments. At the rear

of the frame, the last thirteen elements, created by the mesh, have 20 psi. of pressure force applied along

the lengths. The rear cross-members also held 20 psi. of pressure force per element. These forces represent

an additional bed loading of 2,632 lbs. These loading conditions exceed the current maximum loading

conditions for the current F150 of 1,675 lbs of total bed load as described in the brochure. The following

images show the results of the loading conditions per ANSYS post processing FEA.

Figure 10. Maximum bending deformation plot.

Figure 11. Moment about the z-axis

Figure 12. Von Mises stress.

As shown in above figures, the result of these loading conditions was a maximum

deflection of 0.445268 inches. Other results are listed below in Table 3.

Maximum displacement 0.446 inMaximum bending stress (+y side) 38508 psiMaximum bending moment -66422    

Table 3. ANSYS loading conditions results.

HUMVEE

The HMMWV’s frame dimensions were obtained from the Kentucky National Guard.

Using these dimensions an overall sketch of the frame was rendered using Ideas Master Modeler software

(Figure 1).

Figure 13. Diagram

Figure 14. Isometric and side views of HMMWV frame modeled in IDEAS

As seen in the diagrams above, five cross-members support the frame. From this model, the frame weight

was calculated using the IDEAs Measurement command. The material was defined as generic isotropic

steel. The frame weighs in at 395 lbs, slightly more than the F-150 frame. At this time we began the Finite

Element Analysis on ANSYS.

Figure 15. Frame geometry modeling in ANSYS.

Creation of the ANSYS frame geometry began in defining key points. ANSYS requires certain

user-defined variables such as Modulus of Elasticity and Shear Modulus. Variables defined during the

ANSYS analysis of the HMMWV model are shown in Table 1.

MODULUS OF ELASTICITY 30 E6 psi

SHEAR MODULUS 0.3

Table 1. User-defined variables for analysis

The modeled lines were meshed into element sections based on the real constants for that section. Based on

the existing HMMWV frame constraint and force locations were estimated.

Figure 16. Loading conditions for ANSYS model frame

As seen in the above diagram, forces were applied along the beams in order to simulate the weight of the

truck. The loads were then uniformly applied over the mounting locations. The following images show the

results of the loading conditions per ANSYS post processing FEA.

Figure 17. Maximum bending deformation plot.

Figure 18. Von Mises stress plot of front and rear ends.

As shown in diagrams above, the result of these loading conditions was a maximum deflection of 0.001

inches. Other results are listed below in Table 2.

MAXIMUM DISPLACEMENT 0.005 in.

MAXIMUM BENDING STRESS (+y side) 5,600 psi

Table 2. ANSYS loading conditions results.

*Ford Motor Company: F-Series Ninety-Nine Brochure.

FINAL DESIGN SOLUTION

The final design was created by accumulating all drawings and valid information from the

modeling of the HMMWV and the Ford F-150. The final frame design had to be able to function as the

frame for both of these vehicles requiring only minor modification.

A few major design changes to the initial frame designs were required to make a universal frame.

The major desecrations in the frames were that the HMMWV has a very wide wheelbase; it is about as

wide as it is long. Another major difference was that the F-150 was quite a bit longer than the HMMWV to

accommodate the bed of the truck. These were major obstacles that had to be overcome before this idea

could become reality. To overcome the length and width discontinuity some assumptions had to be made.

The ford frame was established as the beginning design to modify. To accommodate the

HMMWV body the frame was shortened a little so that it could be universal. This modification also

allowed the frame to be lighter witch is desirable for Ford’s needs. The modified frame was then equipped

with necessary cross members incorporating both Ford’s, and HMMWV’s frames. This is a simple

explanation of how these frames here manipulated to make a single frame fit for both applications. Below

you will see a variety of views of the prototype frame and body that have been designed. We have also

included diagrams of how we intend to set up this vehicle when production begins.

Figure 22 wire frame diagram.

Figure 23 isometric solid model

Figure 24 dimensioning of the universal frame.

Figure 25 designed body

Figure 26 assembly diagram

Figure 27 full schematic of the undercarriage

Now that the final design was materialized it was prudent that the frame have a stress analysis

done in ANSYS. The frame was drawn up in ANSYS making the entire frame into elements and applying

simple loads. This is necessary just to get preliminary information about the durability of the redesigned

frame, and how it will withstand driving elements of both the consumer and the military.

To do this key points had to be assigned in the ANSYS software were the frame and cross-sections

meet. At this point lines were made to connect these points and all the properties and constants were

assigned prior to meshing. The lines were then meshed making the elements have the properties of Beam 4

3D. After meshing loads and constraints were applied the analysis was solved. At this point graphs were

produced of the von Mises stress, and the deformation. Using other tools in ANSYS many useful values of

this design were found. A picture of the redesign ANSYS diagram can be seen below and the output values

can be found in the Appendix. It has been found that the frame is able to hold up to loads presented in

everyday applications. It is definitely recommended that this frame be put through intensive complex stress

analysis prior to beginning production.

Figure 28 loaded frame analysis in ANSYS

Figure 29 deform vs. undeformed plot

Figure 30 von Mesis stress plot

To get an idea of the materials used and the geometric properties of the frame the IDEAS measuring tools

were used, the results can be seen below.

MEASURED BODY FRAME TOTALSURFACE AREA (in2) 60137.2 10219.2 70356.4VOLUME (in3) 19170.1 1238.8 20408.9WIEGHT (lb) 5412.18 349.744 5761.924

Table 6 body and frame results

CONCLUSION AND RECOMMENDATIONS

Although the goal of reducing the F-150 frame weight by 25% was not accomplished the weight

was decreased by 3% and retained stability. The best aspects of both frames have been combined into one

multipurpose design. There will be obvious modifications made prior to production as the implication

carries on, but this fame has been tested to be theoretically sound investment. This design has gone through

evaluations of only a static body load. Complex stress test are still needed to prove the frame’s fatigue

strength. It is imperative that before production begins that a team is formed to put this frame through a

analysis to ensure the safety of consumers. It is also prudent that test be run to ensure the safety of this

frame in crash situations. The design has had preliminary testing preformed but is still not ready for the

consumer.

The reduced weight of this design will economical template for multipurpose frames. In the near

future it may be a possibility to make all of our automobiles on just a few frames witch will save this

company millions. As a team it is very exciting to be involved with this project, and see the innovative

thinking in this cooperation that brought this about. With a little support this could be the future of

automotive design, and manufacturing.