Pan Meichen, Chen Xin, He Meiling, Kong Yi, Du Yong, Hartmaier Alexander, Zheng Xiaoyu, Liu Yuling
State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China.
Interdisciplinary Centre for Advanced Materials Simulation (ICAMS), Ruhr-Universität Bochum, 44801 Bochum, Germany.
Materials (Basel). 2024 Jul 1;17(13):3210. doi: 10.3390/ma17133210.
As a new type of high-performance material, gradient structural steel is widely used in engineering fields due to its unique microstructure and excellent mechanical properties. For the prevalent fatigue failure problem, the rate of change in the local grain size gradients along the structure (referred to as the gradient rate) is a key parameter in the design of gradient structures, which significantly affects the fatigue performance of gradient structural steel. In this study, a new method of 'Voronoi primary + secondary modeling' is adopted to successfully establish three typical high-strength steel models corresponding to the convex-, linear-, and concave-type gradient rates for gradient structures, focusing on the stress-strain response and crack propagation in structural steel with different gradient rates under cyclic loading. It was found that the concave gradient rate structural model is dominated by finer grains with larger volume fraction, which is conducive to hindering fatigue crack propagation and has the longest fatigue life, which is 16.16% longer than that of the linear gradient rate structure and 23.66% longer than that of the convex gradient rate structure. The simulation results in this study are consistent with the relevant experimental phenomena. Therefore, when regulating the gradient rate, priority should be given to increasing the volume fraction of fine grains and designing a gradient rate structure dominated by fine grains to improve the fatigue life of the material. This study presents a new strategy for designing engineering materials with better service performance.
作为一种新型高性能材料，梯度结构钢因其独特的微观结构和优异的力学性能而在工程领域得到广泛应用。针对普遍存在的疲劳失效问题，沿结构的局部晶粒尺寸梯度变化率（简称梯度率）是梯度结构设计中的关键参数，它对梯度结构钢的疲劳性能有显著影响。本研究采用一种“Voronoi 一次 + 二次建模”的新方法，成功建立了对应于梯度结构的凸型、线性和凹型梯度率的三种典型高强度钢模型，重点研究了不同梯度率的结构钢在循环加载下的应力 - 应变响应及裂纹扩展情况。研究发现，凹型梯度率结构模型以体积分数较大的细晶粒为主导，有利于阻碍疲劳裂纹扩展，疲劳寿命最长，比线性梯度率结构长 16.16%，比凸型梯度率结构长 23.66%。本研究的模拟结果与相关实验现象一致。因此，在调节梯度率时，应优先增加细晶粒的体积分数，并设计以细晶粒为主导的梯度率结构，以提高材料的疲劳寿命。本研究为设计具有更好服役性能的工程材料提供了一种新策略。
