The Numerical Simulation And Experimental Study Of Residual Stress Of Heavy Rail Press Straightening

Rail is the important parts of the railway, the magnitude and distribution of residual stresses which exist in the rail directly affect the service performance of rail. Straightening which is the final craft of the heavy rail production plays a decisive function of the straightness and the magnitude of residual stresses. The paper mainly researches the forming mechanism and law of distribution of residual stress during roller straightening by studying of the press straightening.The basis of paper is elastoplastic finite element method of large deformation, simulate the press straightening process of the heavy rail by static contact analysis of the finite element software ANSYS. The roller straightening was simplified as the continual process of seven times reverse bend, the alternating bend model of press straightening was established, the three-dimensional simulation was simulated considering the influence of the contact press. It analyzed the law of strain-stress and the distribution of residual stresses during the straightening process. On the basis of the simulation, the photoplasticity experiment of press straightening process was carried out.According to the simulations model,it analyzed the equivalent residual stress distribution situation of middle cross sections which went through seven times of alternating bending, the longitudinal residual stress magnitude of middle cross section and distribution. The analysis result indicated that, the equivalent residual stresses magnitude and the distribution are all related to the reduction, when the reduction is bigger, the rail interior has had the bigger elastic-plastic deformation, all has the certain influence to the equivalent residual stress magnitude and distribution; when the reduction is smaller, the rail interior has not had the plastic deformation, the equivalent residual stress magnitude and the distribution do not have the big change. The elastic-plastic deformation mechanism of heavy rail press straightening process is explained in the stress, the stress-strain relations of the press straightening process are obtained. And by contrast the equivalent residual stress and the section longitudinal residual stress of three different straightening regulations, obtained that the residual stress distribution of the present straightening regulations to be more reasonable. And it has obtained the process contact stress distribution of the straightening.A photoplastic experiment was carried on Used the photoplastic material polymethyl methacrylate (PMMA) which simulates the press straightening curving process. Experimental results indicated that: because elastic-plastic deformation quantity of straightening process is not big at room temperature, it can't hold the residual deformation after straightening in the experiment according to standard regulations. But the clear colorized stripes could observe in straightening process, it show that the straightening press process have certain quantity plastic deformation. We can get the relations between press distribution and the reduction by the isochromatic stripes.