基于突变理论的棒材分离机理与高效离心下料技术研究

According to the low-stress cropping having some defects, such as instable crack initiation and propagation, serious wear of high-speed rotating parts and big extrusion deformation of bar end face, the low-stress precision cropping method with centrifuge technology and hydraulic compensation technique is proposed. The crack size mutation effect is proposed to explain why the loading force acted on the bar is failure at the moment of crack initiation and cumulative expansion. The catastrophe theory and micro crack theory are presented and used to establish the relationship between the loading force acted on the metal bar and the crack length. By means of hydraulic compensation technology and closed-loop control technology, the variation trend of blanking force can be stabilized accurately and the blanking flexibility can be controlled effectively. The wear-resisting bearing, whose inner surface has spaced slots, is studied and the antifriction antiwear mechanism of higher pair between the wear-resisting bearing and the bar surface is described in detail. By virtual prototyping coupling method, 3D model of high-efficiency centrifugal low-stress blanking is built and the dynamic characteristic of key components in the cropping machine is also analyzed. Taking product quality of cropping bar, energy consumption, wear and environmental friendliness as the objective function, the comprehensive evaluation index of equivalent precision blanking quality is proposed. The high-efficiency centrifugal low-stress blanking experiment system is developed and the optimal blanking process parameters are also obtained. The above research has the important theoretical basis and practical significance for improving the cropping technology level of metal bar and achieving the large scale utilization as soon as possible.

针对低应力下料时存在裂纹起裂扩展不稳定、高速旋转部件磨损较大、棒料端面挤压变形等问题，提出基于离心技术和液压补偿技术的高效离心低应力精密下料方法。提出裂纹尺寸突变效应的概念，解释裂纹起裂和累积扩展瞬间作用力失效的原因和影响因素；提出采用突变理论和微裂纹理论，建立棒料受力与裂纹长度之间的确切关系。提出采用液压补偿技术和闭环控制技术，精确稳定下料力变化趋势和有效控制下料挠度。研发内表面具有等间隔槽的耐磨轴承，阐述耐磨轴承与棒料接触曲面高副减摩抗磨机理。利用虚拟样机耦合方法，建立低应力下料机构三维实体模型，对其关键部件进行动态特性仿真分析。以产品质量、能耗、磨损量和环境友好度为目标函数，提出当量精密下料质量的综合评价指标。研制高效离心低应力精密下料试验系统，获得最佳下料工艺参数。该研究对提高我国金属棒材下料技术水平并尽早实现规模化利用具有较好的理论基础和实践意义。

在机械加工中，下料是金属成形加工的第一道工序。国内每年需精密下料的棒材量达上千万吨，需求量较大。然而，低应力下料时存在裂纹起裂扩展不稳定、高速旋旋转部件磨损较大、棒料断面挤压变形等问题，为此本项目开展了基于液压补偿的高效低应力精密下料方法研究。. 1、针对棒料V型槽尖端应力分布的复杂性，提出采用折线形截面假设法计算V型槽的应力集中效应。建立了折线形截面假设方法构建的棒料几何模型，获得了修正后的棒料V型槽的应力集中系数计算公式，并分析了V型槽底角半径对应力集中系数的影响规律。. 2、为解决棒料V型槽尖端起裂瞬间所需临界加载力的突变问题，在起裂阶段，建立了临界起裂加载力与棒料V型槽参数和加载参数的计算公式；在裂纹扩展阶段，建立了扩展临界加载力与裂纹长度、加载参数和棒料直径的计算公式。设计了多组变频加载曲线，解决了加载力突变难题。. 3、提出基于液压补偿的低应力精密下料技术，设计了新型低应力下料系统。该技术提高了系统的加载稳定性。利用虚拟样机技术，建立了下料机仿真模型，获得了关键部件的动力学性能。研制了裂纹可控式低应力高效精密分离下料机样机，进行了不同材质的金属棒料下料试验研究，给出了当量精密下料质量的综合评价指标。. 4、利用声发射技术和摩擦学原理，搭建了基于声发射的摩擦磨损试验设备，来进一步检测下料锤头-棒料摩擦副的摩擦磨损状态。分析了下料机耐磨轴承与棒料接触曲面高副的减摩抗磨机理，获得了最佳减摩抗磨效果的纳米二硫化钼添加剂的质量分数。. 通过该项目研究，实现了对直径15mm-45mm的金属棒料的近净成形下料。获政府类省级技术发明一等奖1项，厅局级技术发明一等奖1项。共发表论文19篇，其中SCI/EI收录3篇(SCI二区1篇，影响因子超过2的2篇)，EI会议收录1篇；发表EI期刊论文1篇，录用EI期刊论文2篇。申请国家发明专利8项，其中授权发明专利3项，获软件著作权8项。参编学术专著1项。协助组织国际学术会议1次。培养研究生12名。