Research On The Measurement Method Of Complex Strain Field

A lot of complex strain field appears on structures of civil engineering, such as Slotted steel-plate shear wall, steel-plate shear wall with opening, honeycomb beam with round holes, column connection with opening in beam web, node welding, etc. Therefore it’s significant to study the generating mechanism of complex strain field on which there is abundant research and theoretical methods. However, only in little boundary conditions and relative simple case can obtain the analytical solutions of elastic mechanics; More often using finite element method to obtain the approximate solutions is needed; For more complex situation often can only with the aid of experimental methods. In fact the experimental analysis method of structure is very important:not only validates the analytical solution, but also solves the complex practical problems that many theoretical methods cannot solve. In this paper, we study the experiment method to measure the complex strain, and verify the feasibility of the method based on the electrical measurement experiments by overlapped strips. The main contents are as follows:1% The conventional resistance strain measurement technique was concluded and summarized, and the basic principle and measuring method of experiment method to measure the complex strain based on the overlapped strips method were also discussed. Point strain values were obtained by overlapping the strain gauge method with three different gate lengths, then the obtained strain values were used to fit the complex strain field on some axis by Newton interpolation; Simulation analysis found that: As for one point in the complex strain field, method of overlapping strain gauges with different gate lengths reflected more accurately than that of monolithic paste. However, as for the measuring point outside the measuring range, which also can be expressed as the extrapolation of data, the error was bigger. So, measurements by constructing Newton interpolation polynomial function of the strain field need to be improved.2、On the basis of three overlapping strain gauges measurement, simulation analysis measuring methods of overlapping strain gauges with for and five different bar lengths were also adopted. The results by using the four lengths were the most ideal.3、Proposed a method of complex strain field measuring based on overlapped strips of double cubic spline interpolation curved surface fitting. By overlapping strips of electrical measuring method for complex strain field area of strain values, again by the double cubic spline interpolation curved surface fitting method for complex strain region strain field. In this paper, the results show that the obtained was formulated by using the method of overlapping strain gauge measurement precision of measured values of strain, using the double cubic spline interpolation fitting strain field is the least squares fitting surface of relative error is small, the effect is more ideal.4、Measured data with a typical tensile perforated plate as experimental subjects, obtain overlapping patches; respectively, least-squares fitting with bi-cubic spline interpolation curve fitting; Finally ANSYS result, the measured data, Newton interpolation results, least-squares fitting and bi-cubic spline interpolation curve fitting and digital image correlation method such as a comprehensive analysis of the measured results compared. This article about a complex strain field strain measurement fitting method based on high precision electrical measuring method overlapping patch and bicubic spline interpolation surface is an effective and practical.