复杂应变场测量实验方法研究
发布时间：2018-11-17 19:36
【摘要】：开缝钢板剪力墙、开孔钢板剪力墙、圆孔蜂窝梁、梁腹板开圆孔节点、节点焊接处等,都存在复杂应变场。钢结构中这些复杂应变区域存在同向的二维或者三维应变场以及低温环境往往导致钢材脆化、造成钢结构脆性破坏。因此复杂应变场的产生机理有重要的研究意义。复杂应变场的研究有很多,并形成了许多的理论方法。然而,只有少量的边界条件和几何形状相对简单的情形能够得到弹性力学的解析解；更多的情况下需要用有限元法近似求解；而对于更复杂的情况往往就只能借助实验方法了。事实上结构的实验分析方法非常重要：既可以对解析解进行验证,还可以解决很多理论方法不能解决的复杂实际问题。本文研究复杂应变场测量实验方法,并且通过基于重叠贴片法的复杂应变场电测实验验证本文方法的可行性。主要内容如下：1、归纳、总结常规电阻应变测量技术,讨论基于重叠贴片的电测法测量复杂应变场的基本原理和测量方法。通过三个不同栅长的应变片重叠的方法得到点应变值,然后利用获得的应变实测值通过牛顿插值拟合某个轴上的复杂应变场；模拟分析发现：对复杂应变场中的一点,通过重叠粘贴多个不同栅长应变片的方法比单片粘贴应变片测量方法能更加准确地反映出被测点的应变值。而对于在测点区间外的测点(即外推的数据)误差较大。所以,通过构造牛顿插值多项式函数的应变场测量方法需要进行改进。2、在重叠三片贴片法的基础上,模拟分析重叠四片和五片不同栅长应变片的测量方法。得出了重叠粘贴四片应变片测量效果最为理想的结论。3、提出一种关于复杂应变场测量的基于重叠贴片的双三次样条插值曲面拟合方法。即通过重叠贴片的电测法得到复杂应变场区域的点应变值,再通过双三次样条插值的曲面拟合方法得到复杂应变区域的应变场。本文结果表明：通过重叠应变片测量的方法得到获得测点处高精度的应变实测值,再利用双三次样条插拟合应变场较最小二乘拟合的曲面场相对误差小、效果更理想。4、以一典型的带孔拉伸板为实验对象,获得重叠贴片的实测数据；分别进行最小二乘拟合与双三次样条插值曲面拟合求解应变场；最后对ANSYS结果、实测数据、牛顿插值结果、最小二乘拟合与双三次样条插值曲面拟合以及数字图像相关分析方法实测结果等进行综合分析比较。本文关于复杂应变场测量的基于重叠贴片和双三次样条插值曲面拟合方法应变电测方法精度高、是有效实用的。
[Abstract]:The complex strain field exists in the slotted steel plate shear wall, the perforated steel plate shear wall, the circular honeycomb beam, the web opening joint of the beam, the joint welding, and so on. In these complex strain regions of steel structures there are two or three dimensional strain fields in the same direction and the low temperature environment often leads to steel embrittlement resulting in brittle failure of steel structures. Therefore, the mechanism of complex strain field is of great significance. There are many researches on complex strain field, and many theoretical methods have been formed. However, only a small number of boundary conditions and relatively simple geometric shapes can obtain the analytical solution of elastic mechanics; in more cases, it is necessary to use the finite element method to approximate solution; but for more complex cases, it is often only by means of experimental methods. In fact, the experimental analysis method of the structure is very important: it can not only verify the analytical solution, but also solve many complex practical problems which can not be solved by the theoretical method. In this paper, the experimental method of measuring complex strain field is studied, and the feasibility of this method is verified by electrical measurement of complex strain field based on overlap patch method. The main contents are as follows: 1. The basic principle and method of measuring complex strain field by electrical measurement based on overlapped patch are discussed. The point strain values are obtained by the method of overlapping strain gauges with three different gate lengths, and the complex strain field on an axis is fitted by Newton interpolation. The simulation results show that the strain values of the measured points can be more accurately reflected by the method of overlapping multiple strain gauges with different gate lengths than by the method of single piece sticking strain gauges for a point in a complex strain field. However, the error of measuring points (i.e. extrapolated data) outside the interval is large. Therefore, it is necessary to improve the method of strain field measurement by constructing Newton interpolation polynomial function. 2. Based on the method of overlapping three patches, the measurement method of overlapping four pieces and five pieces of strain gauges with different gate lengths is simulated and analyzed. It is concluded that the effect of overlapping paste four pieces of strain gauges is the most ideal. 3. A fitting method of double cubic spline interpolation surface based on overlapping patches is proposed for complex strain field measurement. The point strain of the complex strain field is obtained by the electrical measurement of the overlapped patch, and the strain field of the complex strain region is obtained by the surface fitting method of the double cubic spline interpolation. In this paper, the results show that the high precision strain measurements are obtained by the method of overlapping strain gauges, and the bicubic spline interpolation is used to fit the strain field with less relative error than the surface field fitted by the least square method. 4. Taking a typical stretching plate with holes as the experimental object, the measured data of the overlapped patch were obtained. The strain field is solved by least square fitting and bicubic spline interpolation respectively. Finally, the ANSYS results, the measured data, the Newton interpolation results, the least square fitting, the bicubic spline interpolation surface fitting and the digital image correlation analysis results are comprehensively analyzed and compared. In this paper, the method based on overlapped patch and bicubic spline interpolation surface fitting method for measuring complex strain field has high accuracy and is effective and practical.
【学位授予单位】：长沙理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU317
，
本文编号：2338841
[Abstract]:The complex strain field exists in the slotted steel plate shear wall, the perforated steel plate shear wall, the circular honeycomb beam, the web opening joint of the beam, the joint welding, and so on. In these complex strain regions of steel structures there are two or three dimensional strain fields in the same direction and the low temperature environment often leads to steel embrittlement resulting in brittle failure of steel structures. Therefore, the mechanism of complex strain field is of great significance. There are many researches on complex strain field, and many theoretical methods have been formed. However, only a small number of boundary conditions and relatively simple geometric shapes can obtain the analytical solution of elastic mechanics; in more cases, it is necessary to use the finite element method to approximate solution; but for more complex cases, it is often only by means of experimental methods. In fact, the experimental analysis method of the structure is very important: it can not only verify the analytical solution, but also solve many complex practical problems which can not be solved by the theoretical method. In this paper, the experimental method of measuring complex strain field is studied, and the feasibility of this method is verified by electrical measurement of complex strain field based on overlap patch method. The main contents are as follows: 1. The basic principle and method of measuring complex strain field by electrical measurement based on overlapped patch are discussed. The point strain values are obtained by the method of overlapping strain gauges with three different gate lengths, and the complex strain field on an axis is fitted by Newton interpolation. The simulation results show that the strain values of the measured points can be more accurately reflected by the method of overlapping multiple strain gauges with different gate lengths than by the method of single piece sticking strain gauges for a point in a complex strain field. However, the error of measuring points (i.e. extrapolated data) outside the interval is large. Therefore, it is necessary to improve the method of strain field measurement by constructing Newton interpolation polynomial function. 2. Based on the method of overlapping three patches, the measurement method of overlapping four pieces and five pieces of strain gauges with different gate lengths is simulated and analyzed. It is concluded that the effect of overlapping paste four pieces of strain gauges is the most ideal. 3. A fitting method of double cubic spline interpolation surface based on overlapping patches is proposed for complex strain field measurement. The point strain of the complex strain field is obtained by the electrical measurement of the overlapped patch, and the strain field of the complex strain region is obtained by the surface fitting method of the double cubic spline interpolation. In this paper, the results show that the high precision strain measurements are obtained by the method of overlapping strain gauges, and the bicubic spline interpolation is used to fit the strain field with less relative error than the surface field fitted by the least square method. 4. Taking a typical stretching plate with holes as the experimental object, the measured data of the overlapped patch were obtained. The strain field is solved by least square fitting and bicubic spline interpolation respectively. Finally, the ANSYS results, the measured data, the Newton interpolation results, the least square fitting, the bicubic spline interpolation surface fitting and the digital image correlation analysis results are comprehensively analyzed and compared. In this paper, the method based on overlapped patch and bicubic spline interpolation surface fitting method for measuring complex strain field has high accuracy and is effective and practical.
【学位授予单位】：长沙理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU317
，
本文编号：2338841
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