Surviving in the Field by Developing Proper Durability Test Schedules

Principal Investigator
John B. Ferris (Virginia Tech)

Industry
Jerry Larsen (Chrysler Corporation)

Government
Alexander Reid (TARDEC)

Student
Trey Smith (Virginia Tech)

Our primary objective is to improve the survivability of military vehicles in the field by developing durability test schedules, based on the characterization of the terrain, that reflect those conditions. The project will build on existing work done by the quad members and others in the field of terrain characterization and development of durability test schedules . Implementation of this research will create a major improvement in the ability of the Army to test military vehicles, allowing the Army to move away from dependence on response based measurements. This research will eliminate currently held assumptions about the character of the terrain that should be tested, assumptions about how major design changes will affect the wheel loading, and eliminate the practice of accelerating damage by simply increasing the amplitude of the excitation.

This project will focus on identifying parameters that characterize terrain (that is, characterizing the bumps that excite the vehicle suspension) and ensuring that the excitations that are used to test the vehicle for durability are of the same character of those excitations that are experienced in the field. This approach fundamentally differs from pseudofatigue methods that seek to find equal levels of damage to select locations of select components. In this way, this project does not assume that the appropriate durability test can be scaled from field data (i.e., is it not assumed that 10 small bumps in the field can be adequately represented by one large bump in the laboratory). Using this technique, the fundamental excitation to the vehicle, the terrain, remains constant throughout the design cycle (e.g., an 8 inch bump will remain an 8 inch bump regardless of the suspension being tested). Wheel forces are vehicle responses, not excitations. If wheel forces are used as surrogate excitations, they must be adjusted for each new design iteration. Implementation of this research would eliminate the use of wheel forces as surrogate excitations and eliminate the errors resulting from the required adjustments. The final validation of this project, however, will depend on the ability of similar terrain to produce similar responses (including wheel forces) in the vehicle. The ability to accurately measure terrain and model vehicles and tires is critical to the success of this project. Again, the project will build on existing work done by the quad members and others in the field of terrain measurement , and vehicle and tire modeling.

This project will provide the US Army with techniques by which durability test schedules can be developed for both physical testing at proving ground locations as well as techniques to find the proper combinations of excitations (terrain sets) for simulation. In this way, the physical tests that are performed will emulate the actual conditions that are encountered when military vehicles are deployed in the field. In addition to the benefit for physical testing, there is a major advantage for simulation. It is impractical for both the automotive industry and the US Army to perform hundreds of miles of simulations for vehicle durability prediction purposes. If a reduced set of characteristic terrain sets can be created, then durability test schedules can be generated and used for timely and efficient simulations. Vehicle design decisions regarding survivability can be made in a timely manner based on the best information available at the time. As part of this project, simulations will be used to test the technologies that are developed. At the completion of this project, physical experiments should be conducted to verify the technology that was developed.