Crack Failure Mode Analysis for Cam-Housing Rocker Arm and Pin 2017-01-0358
During the extensive testing under NATO and Commercial Standards, crack is observed in camshaft housing to initiate from the eccentric shaft bore and go toward the hold down bolt hole. Hence lab test proposal is originated to induce similar failure in a controlled method and then to compare new design alternatives. CAE analysis follows the same set up as the lab test to duplicate failure mode in stress analysis and fatigue analysis with duty cycle loads, and then figures out two strategies on how to improve the design, including geometry change and material change. In geometry wise, four new design iterations are evaluated for comparison. In material wise, one new material for camshaft housing and five manufacturing effect parameters for pin and rocker arm are compared, including ground, machined, machined and decarburization, casting, as well as casting and nitride. With those comparisons, all manufacturing parameters are compared based on effectiveness to affect the fatigue life. Besides design change, manufacturing cost is also prone to be a relatively critical factor. By all means above, the new architecture is decided and successfully validated by the following testing and can meet production criteria as well. The CAE software applied in the analyses are Abaqus for stress analysis and nCode DesignLife for fatigue analysis.