中文摘要：

以标准材料试样和实际汽车零件为对象，探索两种比较典型的表面工艺强化对材料强度特性的影响．研究结果表明：材料经工艺强化后强度特性发生较大的变化，不能用先前在工程上广泛应用的查图表法准确预测工艺处理后材料强度特性．40Cr材料经中频淬火后静强度提高197％，疲劳强度提高89．8％．20MnCr5材料经碳氮共渗后静强度提高145％，疲劳强度提高73．5％，S—N曲线向上移动，其斜率变大，转折点循环数降低．从而设计时有限寿命区域减少，无限寿命区域增大．

英文摘要：

Taking the standard material specimen of a vehicle joint and an actual auto part as study objects, the strength characteristics of materials after two typical surface strengthening processes were investigated. The results show that the material＇s strength can be greatly developed after surface strengthening. However, the checking charts method which is used widely in engineering cannot accurately forecast material＇ s strength characteristics after surface treatment. The 40Cr material＇s static strength and fatigue strength can be increased by 197% and 89.8% respectively after medium frequency induction hardening. The 20MnCr5 material＇s static strength and fatigue strength can be increased by 145 % and 73.5 % respectively after carbonitriding hardening and S - N curve moves up, the slope becomes steeper and the turning point reduces after strengthening technology. The limited life area reduces and the unlimited life area increases.