Single Symmetry Plane And Equal Cross-Section Profile Three-Point Bending And Its Straightening Technology

Reverse bending pressure straightening is a technology which erases or reduces bend of long steel parts. It is simple, flexible, economic and effective. In the process of traditional straightening technology to automatic straightening machine, although several vaileties of good automatic straightening machines have been developed by different manufacturers in few developed countries, their design development seems not to be backed up by a detailed theoretical analysis. Researches on straightening technology theory have not been developed very well. So it is important and significative to study pressure straightening theory. As the basic mechanical model of straightening process, three-point bending is the foundation of the pressure straightening theory. This paper, based on current researches, according to elasto-plastic mechanics, analyses the same cross-section profiles of single symmetric three-point bending of small deformation and its springback. And applying the results of analysis, attains new understanding, enriches the existing straightening theory.Firstly, the physical process of three-point bending were analyzed, which was divided into two stages: completely elastic stage and elastic-plastic stage, and the profile of elastic-plastic stage was carved up fully elastic region and elastic-plastic region.Secondly, based on analysis of physical processes of three-point bending, under certain assumptions, according to elastic-plastic mechanics, with the knowledge of mechanical property parameters and geometric parameters, this paper established deflection distribution equations of three-point bending and its springback, so as to gain their deflection relationship. And discussed effects of the fulcrum distance on the three-point bending and its springback. By with and without initial curvature of the profile three-point bending comparative analysis of physical processes, this paper obtained the conclusion that a cross-section suffered the same moment, the curvature variation are the same, as the basis for the establishment of the straightening deflection equation and a new straightening technology parameters calculation method.Finally, experiment methods and numerical analysis method were applied to verify the main conclusions of this paper. And proved the correctness and accuracy of the proposed deflection distribution equations, and the feasibility of new straightening technology parameters calculation method. And through error analysis, put forward the present problems and directions for improvement of the analysis model and calculation method.Studies of whole thesis will enrich straightening technology theory and have well engineering value. It will be helpful for design and development of automatic straightening machine.