利用塑性5εt与中性层偏移的二辊矫直辊型设计方法
Design Method of Roller Shape for Bar Two？？Roll Straightener Based on Plastic 5εt and Neutral Layer Offset

为了提高棒材二辊矫直机的矫直精度,依据棒材矫直工艺特点和矫直辊磨损区域分析,提出了“凹三凸二”的矫直辊组合形式及辊型设计方法。在辊型设计过程中,根据棒材矫直的实际变形规律,提出了塑性5εt矫直应力应变拟合原则,更加准确地描述了棒材矫直变形的应力应变关系;结合微元法对矫直棒材内部金属的受力状态及中性层偏移进行分析,推导出了含有硬化系数与中性层偏移的新弯矩比公式。在此基础上,通过对矫直力与辊面磨损关系以及残余应力和弹性芯对隐患挠度影响的综合分析,精确给出了矫直不同规格棒材时辊腰段的反弯曲率比范围,从而能最大限度地降低辊面磨损,克服因残余应力回复而导致矫直质量不稳定的缺陷。基于上述理论和方法,给出了具体设计实例,并对矫直过程进行了数值模拟分析,给出了矫直过程中影响棒材矫后精度的各参量状态。结果表明:设计辊型的残余直线度为0.64 mm/m,隐患挠度为0.202 4 mm/m,预测弹复后直线度小于0.85 mm/m,从而显著提高了棒材的矫后精度及其稳定性,同时也验证了该设计理论与方法的正确性及有效性。
According to the bar straightening process features and wear area of straightening roll, the design method of “three？？stage concave roll and two？？stage convex roll” was put forward to improve the straightening accuracy of two？？roll straighter. In the design process, based on the bar deformation rule, the principle of 5εt fitting was put forward to describe the stress？？strain relationship more accurately and effectively. On the basis of fitting rule and micro？？element method, the stress state of metal inside the bar and the neutral layer offset were analyzed, then the bending moment ratio including hardening coefficient and neutral layer offset was deduced. From the comprehensive analysis of the relation of straightening force with the roller wear, as well as the effects of residual stress and elastic core on the hidden deflection, the range of reverse bend curvature ratio of roller lumbar segment was determined for different bar sizes, and hence the wear of roller surface could be slowed down, and the defect of unstable straightening quality caused by residual stress response was overcome greatly. Based on the proposed theory and method, the specific design example was provided to simulate the straightening process, and each parameter which might affect the straightening accuracy was analyzed. It can be found that the straightening accuracy of the designed roll shape could reach to 0.64 mm/m, the hidden deflection was 0.202 4 mm/m, and the prediction accuracy after straightening was less than 0.85 mm/m. The stability and reliability of the bar straightening were guaranteed, and the correctness and effectiveness of the theory and design method were verified