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Fatigue is a structural failure mode that must be recognized and understood to develop products that meet life cycle durability requirements. In the age of lightweighting, fatigue strength is an important vehicle design requirement as engineers struggle to meet stringent weight constraints without adversely impacting durability. This technical concept course introduces the fatigue failure mode and analysis methods. It explains the physics of material fatigue, including damage accumulation that may progress to product failure over time, and it provides the needed foundation to develop effective fatigue prediction capabilities.

l. ACKNOWLEDGMENT: A vendor must mention this specification number and its last revision in all quotations and when acknowledging purchase orders. 2. FORM: Bars, billets, forgings, tubing, or as ordered.

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Parts, such as bolts, turbine wheels, discs, buckets, and blades, for high strength and oxidation resistance up to 1500 F when suitably heat treated.

A combination of laboratory reactor measurements and vehicle FTP testing has been combined to demonstrate a method for diagnosing the formation of NO2 from a diesel oxidation catalyst (DOC). Using small cores from a production DOC and simulated diesel exhaust, the laboratory reactor experiments are used to support a model for DOC chemical reaction kinetics. The model we propose shows that the ability to produce NO2 is chemically linked to the ability of the catalyst to oxidize hydrocarbon (HC). For thermally damaged DOCs, loss of the HC oxidation function is simultaneous with loss of the NO2 production function. Since HC oxidation is the source of heat generated in the DOC under regeneration conditions, we conclude that a diagnostic of the DOC exotherm is able to detect the failure of the DOC to produce NO2. Vehicle emissions data from a 6.6 L Duramax HD pick-up with DOC of various levels of thermal degradation is provided to support the diagnostic concept.