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The service life of a military ground vehicle is measured in decades and throughout its life it is expected to see several theaters with severe terrain and complex evolving operating conditions. The core of the vehicle, like the chassis and the hull, are often in continuous use, undergoing routine repair, reset, and re-fielding. Other components attached to the hull and chassis have more limited life spans and by design become damaged, worn-out, or outdated and are repaired, replaced, and/or upgraded. New components like armor, weapons, and sensor packages are frequently added to the existing structure for improved mission performance (survivability, lethality, etc.) as threats and strategies change. Designing military vehicles for durability is therefore very challenging and should not end when the product is designed, validated with hardware tests, manufactured, and sold.

Ring gear bolts in differentials are often modified in size to accommodate the additional clamp load that is required due to an increase in torque from a vehicle's powertrain. Depending on a given program several constraints need to be considered. These include cost, validation time, reliability / durability and timing for implementation. In this paper, a Finite Element Analysis (FEA) procedure for analyzing stresses in ring gear bolts within a rear differential assembly is outlined and the computational results are then compared to quasi-static bench test results that were developed to measure bending and tension loads in the ring gear bolts during loading and unloading of the axle pinion. A dynamometer test is then developed to duplicate the failure mode and provide a comparison of the design changes proposed and the expected improvement in durability.

A simple and robust path follower has been developed for use in road loads simulations as required for virtual evaluation of vehicle durability and strength. The path follower is described as simple because it has a single tunable parameter and minimal control logic. It is deemed robust because the same gain setting can be used over a wide range of terrains, paths, and speeds. Path following performance is successfully demonstrated with a multibody vehicle model of a generic heavy truck for a variety of terrains, paths, and speeds. The convergence to the desired path during parameter tuning is observed to be monotonic. A physical interpretation of the gain as a maximum centripetal acceleration further enables vehicles in the same or similar classes of mobility characteristics (all off-road trucks for example) to utilize the same gain value.

An essential part of the SHM validation effort is to check the presence and adequacy of the methods required to validate the correct functionality of each SHM task, which can be targeted at detecting structural faults. The ultimate proof of the correct functionality is validation evidence, e.g. crack detection evidence, observed during the operation of the aircraft. However, the occurrences of structural faults such as cracks are infrequent, and hence, years of flight tests might be required to collect validation evidence; small numbers of flights would be only sufficient to prove the system's “fitness for flight” and would be insufficient to prove “fitness for purpose”. Validation evidence can be collected during laboratory tests by inducing faults in structural specimens and examining the SHM detection capability.

Quality has been the illustrious word of the 80s and 90s as we speak organizations are chasing quality problems through the engineering teams and into production. Taskforces of workers in white coats are being sent on to the production line to furiously check components, monitoring process capability in an attempt to improve product quality. Unfortunately it's only after several years of production that the first “real” data gets back to the engineering teams, when it is often too late to remove the causes of these quality problems. The organization is left kicking itself over the same old catch twenty-two situations, “If only the team knew this process data before they decided to engineer it like that!”