Durable Design and Maintenance of Military Vehicles -Crack Initiation and Crack Growth Applications 2011-01-1047

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components attached to the hull and chassis have more limited life spans and by design become damaged, worn-out, or outdated and are repaired, replaced, and/or upgraded.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. Changes in operational use, upgrade kits, and the overall growth of such vehicles mandates that the life of any such platform be continuously assessed by virtual methods to anticipate and mitigate failures. Surface and sub-surface defects induced during manufacture (and re-manufacture) in welds, forgings, and castings also pose significant challenges as these defects may grow rapidly under repeated operations resulting in ultimate failure of parts well before reaching the design life. To address the design and maintenance of military ground vehicles from cradle to grave, a comprehensive virtual durability process is presented which uses in-house tools and commercial software applications to predict crack initiation and crack growth. Application of this process to predict and extend the residual life of a fielded vehicle for different operating conditions, duty cycles, and vehicle configurations (additional weight) is demonstrated.