基于油膜力的油膜厚度补偿模型的研究与应用

为了满足轧制中带钢厚度精度的控制要求,必须对由轧制速度变化引起的带钢厚度波动进行油膜补偿.提出了一种基于油膜力的油膜厚度补偿方法,并进行推证,得到适合现场应用的数学模型.以此数学模型为基础,开发了一套完整的数据采集、数据处理和现场应用方法,并将该模型成功应用于热连轧生产中.实际应用表明,对热连轧机组采用该油膜厚度补偿算...     

板料成形摩擦特性的实验研究与有限元分析

采用MPX-2000盘-销式摩擦试验机研究了边界润滑条件下滑动速度与界面载荷对304不锈钢与SKD11模具钢之间摩擦系数的影响。运用Matlab软件对实验数据进行处理分析,得出摩擦系数随滑动速度与界面载荷变化的规律,建立了基于滑动速度与界面载荷的变摩擦系数模型。并对典型U形件进行了实际冲压实验与有限元仿真,比较了定摩擦系数模型和变摩擦系数模型的回弹预测结果与测量值之间的误差。分析结果表明:滑动速度为30.615~44.22 mm·s~(-1)时,304不锈钢与SKD11模具钢之间的摩擦系数随滑动速度的增加而逐渐减小;界面载荷为2.038~4.076 MPa时,摩擦系数随界面载荷的递增而递减,且随着载荷的增加,摩擦系数减小的趋势逐渐变缓。采用修正后摩擦模型的回弹预测结果与测量值之间误差较小,预测精度较高。     

板料成形过程中成形速度对B340/590DP摩擦性能的影响

基于伺服压力机技术,采用板料滑动拉伸摩擦试验,研究了在板料成形过程中成形速度对B340/590DP板料摩擦性能的影响,分析了成形速度对摩擦性能的作用机理.结果表明,板料初始成形速度越小,初始摩擦力越小;速度变化瞬间摩擦力急剧变化,然后逐渐稳定;前后成形速度设置相差越大,摩擦力变化越大.因此,为了获得良好的成形性能和加工效率,可以选取较小的初始成形速度,保证较小的摩擦力以利于材料的塑性流动,然后采用较大的后续成形速度以保证加工效率.     

塑性成形中摩擦的研究进展和发展趋势(英文)

塑性成形中的摩擦是影响成形力、材料变形、成形质量和模具寿命的关键因素,也是受到多因素影响的高度非线性的物理问题,国内外学者在塑性成形摩擦机理研究和摩擦控制等方面做了大量的研究。从四方面总结和讨论塑性成形中摩擦的研究进展,分别是:摩擦测试方法、摩擦行为表征、摩擦模型以及摩擦优化/控制。并基于航空航天和汽车等高技术领域对高性能轻量化复杂构件的绿色、高效和精确成形制造的迫切需求,提出塑性成形中摩擦研究的发展趋势和挑战。     

基于ABAQUS的板料成形数值模拟摩擦模型的二次开发

对近年来兴起的板料成形过程数值模拟新技术研究,提出了一种基于ABAQUS的板料成形数值模拟摩擦模型的二次开发及实现的方法.对于进一步研究板料成形摩擦模型,在基于ABAQUS的板料成形数值模拟中加入新的摩擦模型提供了一种途径.     

基于SVM的轧机油膜厚度补偿模型的建立

研究单机架热轧中厚板轧机的油膜厚度补偿问题,利用SVM方法建立了轧机油膜厚度补偿模型,并对回归预测结果进行分析,同时与成熟的基于Reynolds方程的轧机相对油膜厚度补偿方法进行比较,结果表明:采用基于SVM的轧机油膜厚度补偿模型可以对轧机油膜厚度进行良好的补偿,补偿精度较好.     

基于现场实验支撑辊油膜厚度补偿模型的应用

热轧机支撑辊多采用油膜轴承,由于在轧制过程中支撑辊油膜轴承内油膜厚度发生变化,会造成轧机有载辊缝发生变化,从而导致产品厚度出现偏差。基于现场设备使用范围,提出支撑辊油膜厚度补偿模型的实验方案,根据实际采集不同压力下速度变化引起的辊缝变化量,使用Matlab拟合得到油膜厚度变化量与轧制力变化量、轧制速度变化量的关系,计算出轧制过程中不同轧制速度、压力条件下支撑辊油膜厚度的变化量,进一步对轧机有载辊缝进行补偿。实际应用表明,该支撑辊油膜厚度补偿方法取得了预期效果,轧机运行稳定可靠,可以有效提高带钢的厚度命中率。     

微成形摩擦研究进展

评述了微成形在微细加工领域中的优势及存在的挑战。介绍了近年来体积微成形和板材微成形在摩擦的尺寸效应、摩擦模型、数值模拟中对摩擦的处理以及润滑方法等方面的研究进展。分析了当前微成形摩擦研究中存在的问题。展望了微成形摩擦有待研究的方向。     

载荷和滑动速度对块体镁基非晶合金干摩擦性能的影响

目的以制备的Mg_(59.5)Cu_(22.9)Ag_(6.6)Gd_(11)块体镁基非晶合金为基础,探索法向载荷和滑动速度影响镁基非晶合金干摩擦行为的规律和机制,为进一步研究镁基非晶合金提供实验依据。方法采用UMT-2多功能摩擦磨损机,改变法向载荷和滑动速度的大小,进行摩擦磨损实验。通过白光干涉轮廓仪测出磨损轨迹的宽度和深度,再根据公式计算出磨损体积和磨损率。利用扫描电镜和EDS能谱分析磨损轨迹,揭示非晶合金的磨损机制。结果随着载荷的增加,磨损率先减小后稳定,摩擦系数略有减小。随着滑动速度的增加,磨损率先减小后增大,在相对滑动速度为120 mm/s时出现最小值。载荷小于20 N时,磨痕表面布满犁沟和小颗粒状磨屑;载荷大于20 N时,磨痕表面出现层叠状非均匀塑性变形层,对磨球表面转移膜粘连明显。滑动速度低时,磨痕表面布满犁沟,随着速度的增加,先是软化均匀流变,接着出现熔化、剥落。结论块体非晶镁基合金在低载荷下以磨粒磨损为主,还伴随着氧化、少量的粘着;载荷大于20 N时,变为粘着磨损为主。低滑动速度下以磨粒磨损为主,当滑动速度为180 mm/s时,试样表面熔化失效,磨损方式为剥落和磨粒磨损的综合。     

拉延成形中拉延筋的摩擦分析

此文建立了一种用拉延筋单元模拟试验器测试拉延筋摩擦系数的方法，同时对成形中的摩擦润滑进行了试验研究和分析。     

高润滑皮膜钢板的成形特性及在汽车覆盖件中的应用

高润滑皮膜钢板通过固化手段在合金化熔融镀锌钢板(GA钢板)表面的GA层形成固态润滑皮膜,紧密附着在钢板表面,从而降低钢板的表面摩擦系数,改善润滑性能,达到提高钢板成形性、削减原材料成本的目的。本研究采取适当方法对高润滑皮膜钢板和普通GA钢板的滑动性能、拉伸性能以及胀形性能进行了对比试验,并提出以成形余裕度作为成形性的评价参数,结合在实际汽车覆盖件生产中的成形余裕度测试。结果表明:高润滑皮膜钢板的各项性能对比普通GA钢板均有较大地提高;在成形稳定性方面,对比普通GA钢板提升了60%以上。目前,高润滑皮膜钢板已经在丰田、本田等汽车制造厂中被广泛使用。     

Advance and trend of friction study in plastic forming

Friction is a critical issue in plastic forming which influences forming force, metal flow, forming quality and service life of die. Since friction is a highly nonlinear physical phenomenon which is interactively affected by so many factors, great efforts have been made to study the friction mechanism and controlling. The research progress of friction issues in plastic forming was summarized and discussed from four aspects: testing, characterizing, modeling and optimization /controlling. Considering urgent demands for green, efficient and precise forming of high-performance, lightweight and complex components in high-tech industries such as aerospace and automotive, the trends and challenges of friction study in plastic forming were proposed.     

金属塑性成形中摩擦模型的研究进展

详细论述了当前有关塑性成形摩擦建模现状的几点研究展望。摩擦是塑性成形中一项重要且复杂的边界条件,直接影响成形过程。鉴于目前塑性成形摩擦模型的发展状况,将它们分为经典摩擦模型、基于粘附理论的摩擦模型、引入相对滑动速度的摩擦模型、考虑表面粗糙度的摩擦模型和基于专用测试装置的摩擦模型等五类进行总结,并对各模型的构成、特点和适用范围进行了较为详细的论述。经典摩擦模型由于经典理论的自身不足,很难准确描述塑性成形中的摩擦行为;粘附理论从微观层面更好地解释了摩擦现象,General摩擦模型改善了摩擦模型适用性,但植入有限元程序较为困难;反正切修正提高了摩擦模型的可植入性,IFUM摩擦模型较为真实地反映了相对滑动速度的影响,这类模型已经作为商业化软件中的可选模型;与基于粘附理论的摩擦模型相比,考虑表面粗糙度的摩擦模型更细致地描述了真实接触表面对摩擦的影响。     

成形速度及载荷对高强钢板回弹影响的研究

回弹问题一直是高强钢板弯曲成形的难点。本文基于伺服压力机对成形速度、载荷以及滑块行程的可控性,通过控制高强钢板弯曲成形过程中的成形速度、载荷以及滑块的行程位移,在试验的基础上探讨了成形速度及载荷等工艺条件对高强钢板弯曲回弹的影响,并通过ABAQUS有限元软件进行了相关的成形模拟。研究结果表明,随着成形载荷的增大回弹量明显减小,多次折弯可有效减小回弹。另外,成形速度和凸模保压时间对回弹影响不大。因此,在伺服压力机工作环境下,可以通过精确控制成形载荷以及折弯次数来控制高强钢板弯曲回弹量。     

A friction model for cold forging of aluminum, steel and stainless steel provided with conversion coating and solid film lubricant

Adopting a simulative tribology test system for cold forging the friction stress for aluminum, steel and stainless steel provided with typical lubricants for cold forging has been determined for varying normal pressure, surface expansion, sliding length and tool/work piece interface temperature. The results show, that friction is strongly influenced by normal pressure and tool/work piece interface temperature, whereas the other process parameters investigated show minor influence on friction. Based on the experimental results a mathematical model has been established for friction as a function of normal pressure and tool/work piece interface temperature. The model is verified by process testing measuring friction at varying reduction in cold forward rod extrusion.     

Effect of rotary direction and speed on mechanical properties in friction stir spot welding of A6061 sheets e

Friction stir spot welding of A6061 sheets was conducted using a tool with thread pin. The hook geometries, hook formation and mechanical properties of the joints welded with different rotary directions and speeds were investigated. The results show that the hook in the joint welded in clockwise was curved upwards and that in anticlockwise was curved downwards. The hook formation was related to the plastic material flow in the joint. With increasing the rotary speed in clockwise direction, the hook moved upwards and far way from the center of the keyhole, resulting in an increase in the effective weld width and a decrease in the effective sheet thickness. Three types of fractuces were observed and they were affected by the hook geometries. The tensile shear load increased firstly and then decreased when the rotary speed increased in clockwise direction, which was related to the hook geometries.     

基于MSC.SuperForm的金属体积成形数值模拟摩擦模型的二次开发

针对金属体积成形数值模拟,在反正切摩擦模型基础上,建立了考虑温度、压力和变形程度等的多因素摩擦模型,可以充分地考虑体积成形过程中速度、温度、单位压力和变形程度对变形体与模具之间界面的影响.采用该多因素摩擦模型对体积成形软件MSC.SuperForm进行了二次开发,通过实际算例分析,并与已有的文献结果对比,说明了提出的多因素摩擦模型的合理性.     

An efficient thermal analysis for the prediction of minimum film thickness in inlet zone at high speed lubricated cold strip rolling

The main objective of this work is to develop a formula for the prediction of thermal minimum film thickness at the roll/strip contact in terms of operating parameters particularly at the elevated roll speeds. The film thickness at the exit of inlet zone and at the entry of contact zone is common. Therefore, in order to compute minimum film thickness accurately at the contact, an efficient thermohydrodynamic analysis of fully flooded inlet zone has been carried out. The effects of rolling speed, reduction ratio, material parameter and slip on minimum film thicknesses (isothermal and thermal) and maximum film temperature rise (in the inlet zone only) are rigorously investigated. The performance parameters in the lubricated domain have been evaluated for rolling speeds (up to 20.0 m/s), reduction ratios (0.05–0.20), and slip values varying up to 20%. Significant reduction in minimum film thickness (thermal) has been observed with the increase in the rolling speed and slip. Based on this study, empirical relations are developed for the prediction of minimum film thicknesses (isothermal and thermal) at the contact. A relation for evaluation of maximum film temperature rise in the inlet zone has been also developed. Authors believe that the empirical relations presented herein may be useful for designers and practicing engineers.     

板料拉深成形数值模拟摩擦模型及参数化实现研究

对板料拉深成形过程数值模拟新技术进行了研究，提出现有的摩擦模型的不足之处，拟提出一种全面考虑板料及模具的材质、表面粗糙度、接触应力、变形温度、变形程度、所用润滑剂的组分等情况的新摩擦模型，并拟用新摩擦模型来实现板料拉深成形过程数值模拟的的参数化研究。