In this paper,we present a method to expedite multi-wavelength photoelasticity for efficient stress analysis.By modulating two slightly different-wavelength illumination beams and simultaneously capturing dark-field and bright-field images,our approach acquires four essential polarized images.Spatial filtering of Fourier transforms streamlines inner stress computation,enabling multi-wavelength photoelasticity with a single detector exposure.Theoretical foundations are outlined,and proof-of-principle experiments validate the feasibility with a measurement error below 6.4%.The high measurement speed,determined by the detector’s frame rate,facilitates dynamic sample measurements at video frequency,offering promising advancements in material stress analysis.
Pengfei ZhuSuhas P.VeetilXiaoliang HeZhilong JiangYan KongAihui SunShouyu WangCheng Liu
Stress separation is usually achieved by solving differential equations of equilibrium after parameter determination from isochromatics and isoclinics.The numerical error resulting from the stress determination is a main concern as it is always a function of parameters in discretization.To improve the accuracy of stress calculation,a novel meshless barycentric rational interpolation collocation method(BRICM)is proposed.The derivatives of the shear stress on the calculation path are determined by using the differential matrix which converts the differential form of the equations of equilibrium into a series of algebraic equations.The advantage of the proposed method is that the auxiliary lines,grids,and error accumulation which are commonly used in traditional shear difference methods(SDMs)are not required.Simulation and experimental results indicate that the proposed meshless method is able to provide high computational accuracy in the full-field stress determination.
The quantitative characterization of the full-field stress and displacement is significant for analyzing the failure and instability of engineering materials.Various optical measurement techniques such as photoelasticity,moiréand digital image correlation methods have been developed to achieve this goal.However,these methods are difficult to incorporate to determine the stress and displacement fields simultaneously because the tested models must contain particles and grating for displacement measurement;however,these elements will disturb the light passing through the tested models using photoelasticity.In this study,by combining photoelasticity and the sampling moirémethod,we developed a method to determine the stress and displacement fields simultaneously in a three-dimensional(3D)-printed photoelastic model with orthogonal grating.Then,the full-field stress was determined by analyzing 10 photoelastic patterns,and the displacement fields were calculated using the sampling moirémethod.The results indicate that the developed method can simultaneously determine the stress and displacement fields.
