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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components attached to the hull and chassis have more limited life spans and by design become damaged, worn-out, or outdated and are repaired, replaced, and/or upgraded.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.

Bearing press fits have a wide range of application in ground vehicles and are typically governed by longstanding rules of thumb for designs that conform to past successful design geometries and practice. However, in unusual applications such as a gear box designed to also bear external loads, the combined stress states require finite element analysis (FEA) that accounts for the press fit, the bearing loads due to torque transmission, and the external loading. Therefore accurate prediction of press fit stress states are required to construct complete solutions to gear box fatigue life prediction and in particular to predict mean stress states. Current FEA tools provide a variety of analysis methods with which to approach the problem of press fit mechanics.