Locking compression plate (LCP) is a common orthopedic instrument for internal fixation and healing of bone trauma. It is important to study on mechanical behavior and failure investigation of LCP because its failure leads to lots of cost and pain to the patient. In this paper, fatigue life of an eight-hole tibia LCP is evaluated under flexural loading. A four-point bending jig is manufactured and fatigue tests are performed for different compression loads. Fatigue life cycles are investigated for compression loads of 500, 600, 700, 800, 900 and 1000 N and relation between compression load and life cycles is estimated. 125 walking days is estimated for the patient during treatment period according to life cycle results. Post failure analysis results on fracture surface revealed that the crack initiated from the edge of compression hole and propagated from lower to the upper surface of LCP according to beach marks. Finally, Scanning electron microscopy (SEM) on the fracture surface revealed striations as a proof of fatigue crack growth. The striation spacing near the crack initiation site is found to be smaller than this spacing far from the initiation zone. The fatigue crack propagation life is estimated as 1600 cycles according to the number of striation spacings. تفاصيل المقالة

In this paper, a two-dimensional computational model is proposed for predicting the initiation position and propagation path of subsurface crack of spur gear tooth flank. In order to simulate the contact of teeth, an equivalent model of two contacting cylinders is used. The problem is assumed to be under linear elastic fracture mechanic conditions and finite element method is used for numerical study. An initial subsurface crack is considered in the model at different depths. For each position of the initial crack, moving contact loading is applied to the part and value of ∆KII is obtained for the crack tips. The position of maximum ∆KII is selected as the location of crack initiation. It is shown that the subsurface crack appears at the maximum shear stress point. The maximum tangential stress criterion is used to determine the crack growth angle. The crack is incrementally propagated until the crack tip reaches the part surface and a cavity is formed on the tooth surface. Analyzing the stress field and stress intensity factors are performed in ABAQUS software. The obtained results for the depth and shape of the spall are in good agreement with the experimental results reported in literature. تفاصيل المقالة