Investigation of the surface integrity and fatigue strength of Inconel718 after wire EDM and machine hammer peening
Investigation of the surface integrity and fatigue strength of Inconel718 after wire EDM and machine hammer peening
复制标题
DOI：
10.1007/s12289-015-1249-4
复制
发表时间：
2016-11
影响因子：
2.4
通讯作者：
D. Trauth;F. Klocke;D. Welling;M. Terhorst;P. Mattfeld;A. Klink
中科院分区：
文献类型：
--
作者：
D. Trauth;F. Klocke;D. Welling;M. Terhorst;P. Mattfeld;A. Klink
高应力涡轮叶片由Inconel718 （DIN NiCr19NbMo(2.4668)）制成；ASTM B637;UNS N07718)必须满足严格的耐久性和可靠性要求。表面完整性对工件材料疲劳强度的影响已被证明是非常重要的。采用表面精加工机锤击技术对Inconel718线材电火花加工后的表面完整性进行优化。机械锤击强化是一种渐进成形过程，在平滑表面粗糙度的同时，可能会产生残余压应力和应变硬化。由于机锤强化对表面完整性的影响尚未完全研究，本文对机锤强化对Inconel718疲劳强度的未知影响进行了描述和建模。提出了电火花线切割和机锤强化的最佳疲劳强度参数。实验测量进行量化的表面完整性，特别是表面粗糙度，压缩残余应力和应变硬化，经过电火花加工和随后的机器锤击。利用弯曲疲劳强度试验机对表面完整性对疲劳强度的影响进行了评价。此外，还建立了有限元模型来分析载荷作用下的表面完整性，揭示难以测量的特性对疲劳强度的影响。在此基础上，提出了一种基于相似理论的疲劳强度预测模型。与先前分析的表面完整性和疲劳强度之间的相关性一起，这允许机器锤强化参数的建设性设置。从而为了解机锤强化对Inconel718表面完整性和疲劳强度的影响做出了重要的新贡献。所提出的方法可以很容易地转移到其他材料和工件几何形状。
Highly stressed turbine blades made of Inconel718 (DIN NiCr19NbMo (2.4668); ASTM B637; UNS N07718) have to satisfy stringent requirements regarding durability and reliability. The impact of surface integrity on the fatigue strength of the workpiece material has proven to be of significant importance. An optimization of the surface integrity after wire EDM of Inconel718 can be achieved using the surface finishing process machine hammer peening. Machine hammer peening is an incremental forming process which has the potential to induce residual compressive stresses and strain hardening while smoothing surface asperities. As the effect of machine hammer peening on surface integrity has not yet been completely investigated, this paper deals with its description and modeling of the unknown impact of machine hammer peening on the fatigue strength of Inconel718. Wire EDM and machine hammer peening parameters maximizing the fatigue strength are presented. Experimental measurements are performed to quantify the surface integrity, especially surface roughness, compressive residual stresses and strain hardening, after wire EDM and subsequent machine hammer peening. The evaluation of the effect of surface integrity on the fatigue strength is carried out using a bending fatigue strength testing machine. Additionally, a finite element model is developed to analyze the surface integrity under load and to reveal the effects of difficult-to-measure properties on the fatigue strength. Based on the new knowledge gained during this work, a model to predict the fatigue strength using similitude theory is presented. Along with the previously analyzed correlations between surface integrity and fatigue strength, this allows a constructive setting of machine hammer peening parameters. Thereby, a significant new contribution to knowledge about the influence of machine hammer peening on surface integrity and fatigue strength of Inconel718 is made. The presented approach can be easily transferred to other materials and workpiece geometries.