金属材料动态力学性能的动压痕测试表征研究

Taking the broad requirements for dynamic mechanical properties of advanced materials with small size and micro area of material surface as the study background, this research project focuses on developing and improving the dynamic indentation technique with the establishment of mechanical analysis model through systematic investigations of experimental tests, numerical simulations and theoretical analysis. In addition, the reasonable definition of indentation representative strain and strain-rate will be pinpointed as well as the corresponding physical significance and range of applications. Relationships between the hardness-depth curves and uniaxial stress-strain curves of materials under different loading rates will be obtained, as well as the mechanics parameters of elasticity, plasticity, stress, strain and strain-rate. The feasibility of establishment of metals’ power law constitutive relation and the uniqueness of numerical inversion result will be investigated by applying indentation test under different cone angles combined with the reverse inversion optimization. Meanwhile, a systematic investigation about adiabatic shear, strain gradient effect and plastic flow localization of tested materials under dynamic indentation are carried out. The effectiveness and reliability of test results under dynamic indentation will be evaluated by comparing with those of traditional dynamic test methods. An overall understanding of materials deformation behavior under high strain-rate and complex stress states will be presented. This project will enrich and improve the test method of dynamic mechanical properties, as well as the evaluation means of strain rate sensitivity.

项目以小尺寸先进材料和材料表面微区动态力学性能测试表征的广泛需求为背景，通过系统的实验研究、数值模拟及理论分析，发展和完善动态压痕测试技术并建立其力学分析模型；合理化定义压入特征应变、特征平均应变率并明确其物理意义和适用范围，获得不同压入速度下硬度-深度曲线与单轴应力-应变曲线之间的对应关系，提取材料的弹塑性及应力-应变-应变率相关力学参量；采用不同锥角压头测试并结合逆向反演优化探讨典型金属材料动态幂本构关系构建的可行性以及数值反演结果的唯一性；同时对动态压入过程所伴随的绝热剪切行为、应变梯度效应及可能出现的塑性流动局域化等进行系统研究；并将其与传统动态力学性能测试技术所得结果进行对比分析，对动态压痕测试方法的有效性与可靠性进行评估。试图全面认识高应变率下处于多向应力状态的材料在绝热过程中发生强迫变形的力学行为，丰富和完善材料的动态力学性能测试方法及相应的率敏感性评价手段。

动态压痕测试技术相比于传统的材料动态力学性能测试方法具有无损、便捷、试样加工方便及可实现原位测试等优势，鉴于该技术已表现出的良好发展前景及其相关基础问题尚未完全厘清的现状，本项目通过实验测试、理论分析和数值模拟系统开展了金属动态压入测试技术及表征方法的研究：通过分离式霍普金森压杆系统搭建了动态压入测试装置，有效实现了金属材料的动态压入测试，并建立了相应的动态压入有限元分析模型，结合实验测试与数值模拟分析验证了“三波法”用于获取动态压入响应的准确性，进而给出了相应的压入数据分析表征方法；给出了不同加载条件、不同半锥角圆锥压头下实时动态压入硬度和平均压入硬度的获取方法并结合实验测试与数值模拟对其有效性进行了验证，采取撞击杆动量恒定的加载方式并结合Cowper-Symonds模型给出了有效获取金属率相关塑性参数的方法；基于Johnson-Cook模型结合不同热转化率和不同场温度环境工况下的动态压入数值模拟研究，评估了绝热温升对动态压入响应数据的影响且可予以忽略；通过采用柱形压头结合两种锥角压头测试及基于晶体细观机制的应变梯度塑性理论给出了保证唯一性与有效性的金属幂强化弹塑性本构关系确定方法；研究成果丰富和完善了材料的动态力学性能测试技术，为我国在新实验方法与仪器、提供科学研究新颖手段和有力工具及提高科研装备自给水平等方面的重大战略需求提供了相应的理论与技术支持，具有广泛的应用前景。