非接触测量技术在航空金属材料形变分析中的应用研究

发布时间：2018-04-11 07:03

本文选题：Vic-3D非接触测量技术 + 正交试验　；参考：《中国民航大学》2016年硕士论文

【摘要】：研究飞机材料损伤变形过程及机理具有非常重要的现实意义,是民用航空领域十分关注的问题之一。传统的形变测量使用应变片、引伸计等接触式测量方法,由于直接作用于试样表面,不可避免地对试样造成损伤,而且测量效率较低。Vic-3D(Video Image Correlate-3 Dimension)非接触全场应变测量系统,作为一种新型的形变测量工具,因其非接触性、高效、准确、无损伤等优势,得到广泛的关注,但在我国民航领域尚未得到应用。本论文通过使用非接触测量技术对航空用2024铝合金进行形变研究,为该方法在民航领域的应用奠定基础。使用Instron电子万能试验机对2024铝合金板材进行静态拉伸试验,Vic-3D系统测量拉伸过程中应变场变化。首先,通过正交试验的方法对散斑质量参数、图像测试系统参数进行优化。其次,对无孔试样裂纹两侧取点,研究裂纹扩展趋势。再次,研究长短轴之比及开孔面积对试样力学性能的影响,并沿孔径方向取点,研究局部应变情况。然后,对比分析Vic-3D非接触测量方法、引伸计法及Patran建模仿真方法测得试验结果。最后,使用扫描电镜对无孔和开孔试样进行微观断口分析。研究结果表明,影响散斑质量的主次因素及最优结果分别为:散斑半径(0.02in),散斑密度(50%),散斑分布随机性(69%);影响图像测试系统的主次因素及最优结果分别为:子集大小(59个像素),步长值(12个像素),相机之间的角度(20°~25°),光圈值(5.6~8)。对比裂纹两侧数据点应变及应变速率变化情况判定裂纹源,预测试样失效部位及相应载荷。越靠近试样开孔位置,应变越集中。减小试样开孔面积,降低开孔的长短轴之比,可以有效降低试样的应变集中系数,延长使用寿命。对比三种试验方法,Vic-3D系统不仅可以记录拉伸全过程应变情况,而且可以以云图的形式显示实际试验结果,更具有优越性。使用扫描电镜观察试样断口,断口形貌以韧窝为主,韧窝底部含有铝铜合金等第二相硬质颗粒。裂纹源均出现在开孔内侧,在试样靠近表面处有快速撕裂的痕迹。
[Abstract]:It is of great practical significance to study the damage and deformation process and mechanism of aircraft material, and it is one of the most concerned problems in civil aviation field.The traditional contact measuring methods such as strain gauge and extensometer are used in the traditional deformation measurement. Because of the direct action on the surface of the specimen, the damage of the specimen is inevitable, and the measurement efficiency is low. Vic-3DX Video Image Correlate-3 dimensional) non-contact full-field strain measurement system.As a new kind of deformation measurement tool, it has been widely concerned because of its advantages of non-contact, high efficiency, accuracy and no damage, but it has not been applied in the field of civil aviation in China.This paper studies the deformation of 2024 aluminum alloy for aviation by using non-contact measurement technology, which lays a foundation for the application of this method in civil aviation.The static tensile test of 2024 aluminum alloy sheet was carried out by using Instron electronic universal testing machine. The strain field was measured by using Vic-3D system.First, the parameters of speckle quality and image testing system are optimized by orthogonal test.Secondly, the crack propagation trend is studied by taking points on both sides of the specimen without holes.Thirdly, the influence of the ratio of long and short axis and the area of opening on the mechanical properties of the specimen is studied, and the local strain is studied by taking the points along the aperture direction.Then, the test results of Vic-3D non-contact measurement, extensometer and Patran modeling and simulation are compared and analyzed.Finally, SEM was used to analyze the microfracture of the porous and open samples.The results show thatThe primary and secondary factors affecting speckle quality and the optimal results are as follows: speckle radius 0.02 inn, speckle density 50m, speckle distribution randomness 690.The primary and secondary factors affecting the image testing system and the optimal results are as follows: subset size (59 pixels, step)The long value (12 pixels), the angle between cameras is 20 掳/ 25 掳, and the aperture value is 5. 6 / 8 / 0.The source of the crack is determined by comparing the variation of strain and strain rate of the data points on both sides of the crack, and the failure position and the corresponding load of the specimen are predicted.The closer it is to the opening position of the specimen, the more concentrated the strain is.The strain concentration coefficient can be reduced effectively and the service life can be prolonged by reducing the opening area and reducing the ratio of the long and short axis of the opening.Compared with the three test methods, the Vic-3D system can not only record the strain of the whole tensile process, but also show the actual test results in the form of cloud diagram, which is more advantageous.The fracture surface of the specimen was observed by scanning electron microscope. The fracture morphology was mainly dimple, and the second phase hard particles such as Al-Cu alloy were found in the bottom of the dimple.The source of the crack appeared in the inner part of the hole and there was a rapid tear near the surface of the specimen.
【学位授予单位】：中国民航大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：V252

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