Repeated impact subjecting on the key components of equipment is always characterized by extremely high loading rate loading, while plastic deformation of most metals depends on loading rate. To ensure the reliability and security of these components, it is necessary to understand the loading rate effect on the fatigue performance. In this study, an automated impact fatigue system based on split Hopkinson bar technique was newly developed to investigate the materials’ impact fatigue behavior. Impact fatigue behavior and non-impact fatigue behavior of laser metal deposition 316L stainless steel were analyzed. The fatigue life decreases with the increasing loading rate, implying the significant loading rate dependence. The compression and fracture toughness tests combined with fractography analysis at high and low loading rates were also conducted to reveal the underlying mechanism of the difference between impact and non-impact fatigue life. Finally, microstructure of the laser metal deposition 316L stainless steel after impact and non-impact fatigue was characterized. It can be concluded that the fatigue crack is apt to initiate under impact fatigue due to the high density of dislocation entanglement, while under non-impact fatigue, a large number of twins are beneficial to delay the fatigue crack initiation.

中文翻译：

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采用基于分裂霍普金森杆技术的自动冲击疲劳系统的激光金属沉积 316L 不锈钢的冲击疲劳行为

设备关键部件受到的反复冲击往往具有极高的加载速率加载的特点，而大多数金属的塑性变形取决于加载速率。为了确保这些部件的可靠性和安全性，有必要了解加载速率对疲劳性能的影响。在本研究中，新开发了一种基于分裂霍普金森杆技术的自动冲击疲劳系统，以研究材料的冲击疲劳行为。分析了激光金属沉积316L不锈钢的冲击疲劳行为和非冲击疲劳行为。疲劳寿命随着加载速率的增加而降低，这意味着显着的加载速率依赖性。还进行了压缩和断裂韧性测试以及高负载率和低负载率下的断口分析，以揭示冲击和非冲击疲劳寿命之间差异的根本机制。最后，对激光金属沉积316L不锈钢在冲击和非冲击疲劳后的微观结构进行了表征。由此可见，冲击疲劳时由于位错缠结密度高，容易产生疲劳裂纹，而非冲击疲劳时，大量孪晶有利于延缓疲劳裂纹的产生。