Bryła Jakub, Martowicz Adam
Department of Robotics and Mechatronics, Faculty of Mechanical Engineering and Robotics, AGH University of Krakow, al. A. Mickiewicza 30, 30-059 Krakow, Poland.
Materials (Basel). 2025 Jul 15;18(14):3333. doi: 10.3390/ma18143333.
Loading and clamping schemes significantly influence the behavior of shape memory alloys, specifically, the course of their solid-state transformations. This paper presents experimental and numerical findings regarding the nonlinear response of samples of the above-mentioned type of smart materials observed during tensile tests. Hysteretic properties were studied to elucidate the superelastic behavior of the tested and modeled samples. The conducted tensile tests considered two configurations of grips, i.e., the standard one, where the jaws transversely clamp a specimen, and the customized bollard grip solution, which the authors developed to reduce local stress concentration in a specimen. The characteristic impact of the boundary conditions on the solid phase transformation in shape memory alloys, present due to the specific clamping scheme, was studied using a thermal camera and extensometer. Martensitic transformation and the plateau region in the nonlinear stress-strain characteristics were observed. The results of the numerical simulation converged to the experimental outcomes. This study explains the complex nature of the phase changes in shape memory alloys under specific boundary conditions induced by a given clamping scheme. In particular, variation in the martensitic transformation course is identified as resulting from the stress distribution observed in the specimen's clamping area.
加载和夹紧方案对形状记忆合金的行为有显著影响，具体而言，会影响其固态转变过程。本文介绍了在拉伸试验中观察到的上述类型智能材料样本非线性响应的实验和数值研究结果。研究了滞后特性以阐明测试样本和建模样本的超弹性行为。所进行的拉伸试验考虑了两种夹具配置，即标准配置（夹爪横向夹紧试样）和作者开发的定制系船柱夹具解决方案，以减少试样中的局部应力集中。使用热像仪和引伸计研究了由于特定夹紧方案而导致的边界条件对形状记忆合金固相转变的特征影响。观察到了马氏体相变和非线性应力 - 应变特性中的平台区。数值模拟结果与实验结果收敛。本研究解释了在给定夹紧方案引起的特定边界条件下形状记忆合金相变的复杂性质。特别是，马氏体转变过程的变化被确定为由试样夹紧区域中观察到的应力分布引起。
