Camshaft in the service process will bear alternating bending and torsion. Three-point bending fracture test and Weibull statistical analysis of three-point bending fracture loads have been used to two Citroen camshafts contained 0.21％Cr or traces of Cr (0.02％Cr) to evaluate the reliability. The results showed that the three-point bending fracture loads of the two camshafts were in line with the three parameter Weibull model, their shape parameters m were 14.3 (the camshaft contained 0.21％ chromium) and 11.4 (the camshaft contained 0.02％Cr) respectively, which shows the former has a higher reliability. The average fracture Ioad were 7.0kN (the camshaft contained 0.21％ chromium) and 6.5kN (the camshaft contained 0.02％ Cr) respectively, which shows Cr can improve the fracture resistance of the camshaft. Preliminary analysis of the reasons for the above-mentioned phenomena has been done.%凸轮轴在服役过程中承受弯曲和扭转的复杂交变载荷,凸轮轴异常断裂是严重的失效形式.本文采用Weilbull统计分析方法研究了两种(其中一种含0.02%Cr,另一种含0.21%Cr)神龙富康激冷灰铸铁凸轮轴的三点弯曲断裂载荷.结果表明,上述两种凸轮轴三点弯曲断裂载荷的Weibull模量分别为11.4和14.3;其三点弯曲断裂载荷平均值分别为6.5kN和7.0kN;表明含Cr凸轮轴比不含Cr凸轮轴的可靠性更高.作者初步分析了产生上述现象的原因.
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