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扭转是一种常用的冷作硬化方法。本文通过实心圆轴扭转实验和预扭试件的单向拉伸实验,研究了扭转塑性变形程度对6063铝合金拉伸力学性能的影响。通过理论研究和硬度分析探究了造成这一影响的内在机理。结果表明,试件扭转后其内部形成的以屈服强度为特征参数的梯度结构,是造成预扭试件力学性能得到改善的根本原因。并且,扭转不同的角度,材料内部产生的梯度结构也是不同的。而不同的梯度结构对试件力学性能的影响则表现为后继拉伸屈服强度随预扭角度的增大而增大。为了预测预扭试件的后继拉伸力学行为,验证前述结论的正确性,建立了由内到外屈服强度逐渐变化的有限元模型。此模型代表了预扭转变形试件,对其施加位移载荷,模拟后继单向拉伸加载过程。模拟所得材料力学性能随扭转角的变化趋势与实验结果基本吻合,从而验证了扭转冷作硬化后,圆轴试件内部产生了以屈服强度为特征参数的梯度结构这一结论。同时,也提供了一种有效的预测材料扭转后拉伸力学性能的数值模拟方法。
Torsion is a commonly used method of cold work hardening. In this paper, through the solid circular shaft torsion test and the uniaxial tensile test of the pre-torsion test piece, the effect of the degree of torsional plastic deformation on the tensile mechanical properties of 6063 aluminum alloy was studied. Through theoretical research and hardness analysis to explore the underlying mechanism of this impact. The results show that the gradient structure with the yield strength as the characteristic parameter formed after the torsion of the specimen is the fundamental reason that the mechanical properties of the pre-torsion specimen are improved. And, to reverse the different angles, the gradient structure produced inside the material is also different. However, the influence of different gradient structures on the mechanical properties of the specimens shows that the yield strength of the subsequent tensile increases with the increase of the pre-twist angle. In order to predict the subsequent tensile mechanical behavior of pre-torsion specimens and verify the correctness of the above conclusions, a finite element model with gradual change of internal-external yield strength was established. This model represents a pre-torsional deformation specimen, to which a displacement load is applied to simulate the subsequent uniaxial tension loading process. The simulation results show that the change trend of the mechanical properties with the torsional angle basically agrees with the experimental results, which verifies the conclusion that the gradient structure with the yield strength as the characteristic parameter is produced inside the round shaft specimen after torsion cold hardening. At the same time, it also provides an effective numerical simulation method for predicting tensile mechanical properties of materials after torsion.