Study Of The 3D Digital Photoelasticity Method And Its Application

Photoelascity is an effective method to solve two-dimensional and three-dimensional stress analysis in engineering and a focus today. Stress components at any point of the three-dimensional model can be calculated by it.With the development of computer technique, automatic whole-field measurement of photoelasticity has been focused. Based on the work which was reported before, some urgent problems of digital photoelasticity have been discussed,and automatic data processing and stress separation of photoelasticity are realized. The problem of isoclinic and isochromatic interaction is important in phase-shifting techniques in photoelasticity. A technique named eight-step phase shifting technique is presented to solve the problem of isoclinic fringe pattern influenced by isochromatic fringe patterns of integer order and half-integer order. Isoclinic parameter in the range of [ 0,Ï€2] of the frozen slice is given by the method.Based on the eight-step phase shifting technique, three methods to determining the first principal stress direction of the slice are discussed. Isoclinic angle information of whole-field first principal-stress direction can be analyzed and obtained by two rules of arctan calculation. The feasibility of this method was proved by the experiments of disk and ring under radial compression.The influence of time edge effect is analyzed. On the premise of exiting time edge effect, mechanic model is founded and proved by simulation and experiment. Two methods for erasing time edge effect are put forward in the experiments.Automatic technique of stress separation is discussed after obtaining the value and direction of secondary principal stress of every frozen slice.Three-dimensional contact stress of turbine between roots and rims are analyzed by the three-dimensional digital photoelasticity. Six stress components and equivalent Von Mises stress of any point in the model are calculated and the contact area of roots and rims are discussed. Finally, the loading values of every tooth of rims are obtained. Three-dimensional digital photoelasticity can be used widely in engineering field and the field of application is widened.