扭转预载荷下原位三点弯曲测试装置的设计分析与试验研究

发布时间：2018-06-24 22:18

本文选题：弯曲 + 扭转　；参考：《吉林大学》2016年硕士论文

【摘要】：传统的材料力学性能测试方法往往对被测材料样品施加拉伸、弯曲或扭转等单一载荷作用,结合检测手段测量这类单一载荷作用下材料的基本力学参数与力学行为。随着科技的进步,为保证材料服役过程中的可靠性、耐久性、学术界和工程界对材料性能测试要求不断提高,传统单一载荷的测试方法已不能满足需求。同时,在测试过程中,研究人员希望通过扫描电子显微镜、金相显微镜、X射线衍射仪等材料性能表征手段动态监测载荷作用下材料的力学行为和微观组织结构演化情况,即原位(In situ)测试。为此,开展复杂载荷条件下材料微观力学性能原位测试技术的研究,显得尤为重要且迫切。面向上述需求,本文以扭转预载荷下原位三点弯曲测试装置的设计分析与试验研究作为选题开展研究。论文在对材料力学性能测试相关领域现状进行综述分析的基础上,设计提出了能够施加扭转预载荷的原位三点弯曲测试装置,再对被测试件施加扭转预载荷的基础上,通过大减速比减速机构实现准静态的弯曲加载。论文采用ABAQUS软件对弯曲加载装置的关键机构与整机进行了静力学分析和模态分析,仿真分析结果显示所设计的装置在刚度与强度方面基本满足要求。针对研制的测试装置,论文分别对弯曲力传感器、扭转力传感器进行了标定试验,通过激光位移传感器标定了电机编码器的输出精度。在此基础上,论文分别对装置结构机架柔度以及底座偏转角度误差进行了理论计算与仿真分析。通过对黄铜、7075铝合金的重复性试验验证了弯曲测试装置的稳定性,通过误差修正与产业化试验机结果对比验证了装置的精确性。通过有限元仿真分析,研究了扭转预载荷对材料弯曲力学响应的影响。针对6061铝合金和45钢样品材料分别开展了扭转弹性阶段与扭转塑性阶段等预载荷条件下的弯曲性能测试分析。从弯曲弹性阶段、弯曲强化阶段以及被测试样回弹能力三个方面进行研究。验证了扭转预载荷的增大会增强材料样品的抗弯强度与回弹性能。针对脆性铸铁材料,论文不仅开展了扭转预载荷的弯曲力学响应的研究,同时分析了铸铁断口的宏观失效形式。证明了弯曲载荷断裂角度会随预扭转载荷的增大向轴线偏移。利用CCD显微镜对Q235材料的金相组织变化,分析扭弯复合应力对材料微观组织失效机理,揭示了预扭转载荷作用下材料样品的金相组织变形更早进入微观失效形式。
[Abstract]:The traditional testing methods of mechanical properties of materials often apply single load such as tensile bending or torsion to the samples under such a single load. The basic mechanical parameters and mechanical behaviors of the materials under this kind of single load are measured by means of testing. With the development of science and technology, in order to ensure the reliability and durability of the material in service, the academic and engineering circles have been increasing the requirements of material performance testing, the traditional method of single load testing can not meet the demand. At the same time, during the testing process, the researchers hope to dynamically monitor the mechanical behavior and microstructure evolution of the materials under loading by means of scanning electron microscope, metallographic microscope and X-ray diffractometer. In situ test. Therefore, it is very important and urgent to study the in-situ testing technology of material micromechanical properties under complex loading conditions. In order to meet the above requirements, the design, analysis and experimental study of the in-situ three-point bending test device under torsional preload are studied in this paper. On the basis of summarizing and analyzing the current situation in the field of material mechanical performance testing, this paper designs a three-point bending in-situ testing device which can apply torsional preload, and then applies torsional preload to the tested part. The quasi-static bending loading is realized by the deceleration mechanism of large deceleration ratio. The static analysis and modal analysis of the key mechanism and the whole machine of the bending loading device are carried out by Abaqus software. The simulation results show that the designed device basically meets the requirements in terms of stiffness and strength. In this paper, the bending force sensor and the torsional force sensor are calibrated, and the output precision of the motor encoder is calibrated by the laser displacement sensor. On this basis, the flexibility of the frame and the deflection angle error of the base are calculated and simulated respectively. The stability of the bending test device was verified by the repeatability test on the brass alloy 7075 aluminum alloy. The accuracy of the device was verified by comparing the error correction with the results of the industrial testing machine. The effect of torsional preload on bending mechanical response of materials was studied by finite element simulation. The bending properties of 6061 aluminum alloy and 45 steel samples were tested and analyzed under preloading conditions such as torsional elastic stage and torsional plastic stage respectively. In this paper, the springback ability of tested samples is studied from three aspects: bending elastic stage, bending strengthening stage and springback ability of tested samples. It is verified that the increase of torsional preload will enhance the flexural strength and springback of the material. For brittle cast iron, not only the bending mechanical response of torsional preload is studied, but also the macroscopic failure mode of cast iron fracture is analyzed. It is proved that the fracture angle of bending load deviates to the axis with the increase of pretorsion load. The microstructure of Q235 material was changed by CCD microscope, and the failure mechanism of torsional and flexural composite stress on microstructure of Q235 material was analyzed. It was revealed that the deformation of metallographic microstructure of the material under pretorsion load entered the microfailure mode earlier.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TH87

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