20-10-2012, 10:57 AM
Fatigue Behavior and Life Predictions of Forged Steel and Powder Metal Connecting Rods
ABSTRACT
This study investigates and compares fatigue behavior of forged steel and powder metal connecting rods. A literature review on several aspects of connecting rods in the areas of load and stress analysis, durability, manufacturing, and optimization is also provided. The experiments included strain-controlled specimen testing, with specimens obtained from the connecting rods, as well as load-controlled connecting rod bench testing. Monotonic and cyclic deformation behaviors, as well as strain-controlled fatigue properties of the two materials are evaluated and compared.
Experimental S-N curves of the two connecting rods from the bench tests obtained under
R = -1.25 constant amplitude axial loading conditions are also evaluated and compared. Fatigue properties obtained from specimen testing are then used in life predictions of the connecting rods, using the S-N approach. The predicted lives are compared with bench test results and include the effects of stress concentrations, surface finish, and mean stress. The stress concentrations factors were obtained from FEA, and the modified Goodman equation was used to account for mean stress effect.
Comparative study of forged steel connecting rods versus powdered metal connecting rods. Validation of fatigue life prediction analytical tools based on baseline material properties and S-N approach. Element size of 1.25 mm (0.05”) was finalized by mesh sensitivity. Tetrahedral Element type was used, Analysis was linear elastic.Specimens from C-70 connecting rods were also tested and results compared with forged steel and powder metal connecting rods. C-70 connecting rod is considered to be an economical alternative to powder metal and conventional steel connecting roD.