薄壁管材连续矫直拉伸失稳极限弯曲半径模型

 薄壁管材连续矫直拉伸失稳极限弯曲半径作为重要的工艺参数,直接决定了设备结构和产品质量。而目前现场仍沿用经验图表结合人工经验和反复试矫对其进行估定,为此基于薄壳理论的相关假设,确定了变形区的应力应变,运用Swift分散失稳准则建立了塑性拉伸失稳极限弯曲半径的解析模型,并进行了有限元仿真验证。研究结果表明：解析模型可正确计算薄壁管材矫直时拉伸失稳的极限弯曲半径,该半径随初始弯曲半径的增大而减小,并与管材直径和金属塑性加工能力有关,为继续深入研究矫直相关工艺参数的合理设置、完善薄壁管材矫直理论体系奠定基础。     

薄壁管材多斜辊等曲率矫直工艺方案与实现

针对薄壁管材在连续矫直过程中矫直方案与等曲率矫直辊弯曲半径难以定量确定的实际问题。基于多斜辊统一矫直机理与薄壁管材弹复方程建立了等曲率矫直辊统一曲率半径的判断方法,提出了最小统一曲率半径的搜索方法,针对不同初始弯曲程度的薄壁管材给出了具体矫直方案,其中对于无法一次统一的具有大初始变形的管材提出了先预弯曲再统一后矫直的方法,确定了薄壁管材可矫直判断条件,采用VB开发程序通过算例证明了上述方法的有效性,发现了若针对某一初始弯曲半径的统一曲率半径存在则其并不唯一必在一定范围之内,同时发现初始曲率半径在一定范围内的管材无法应用二斜辊实现曲率统一。     

六辊薄壁管材矫直机参数设计与仿真分析

以原有的六斜辊矫直机为基础进行了辊型的改进,将第二对的双曲线辊型设计为凹凸辊,并针对薄壁管特性设计相应的辊型参数。在以往矫直机设计中,矫直辊的压下行程和压下量都是人工调整,这就大大降低了工作效率,而且矫直精度也不是很高。通过在压下系统中安装伺服机构可以实现自动补偿机架变形,保证机架能稳定工作,从而使被矫直的薄壁管材具有较高的矫直精度。通过对原有矫直力学模型的分析和计算,建立一种适合等曲率反弯辊型的力学简化模型。在ANSYS有限元软件中模拟薄壁管材的矫直过程,进行了管材变形仿真分析。通过仿真分析判断薄壁管材在矫直过程中能否正常运转。     

十辊管材高精度矫直机参数设计与仿真分析

针对薄壁管矫直过程中废品率较高的问题,本文设计矫直精度较高的十辊薄壁管矫直机,对其辊形和机架结构进行了创新设计。矫直机的第二对和第四对矫直辊采用凹凸辊形曲线,使管材在辊矩和辊间都发生弯曲,以较小的压弯量获得较长的塑性变形区域;并且,压下系统采用伺服自动控制机构,可以实现自动补偿机架变形。最后对矫直过程进行动力学分析,获得薄壁管与矫直辊之间的接触情况,分析管材在各矫直辊间的应力应变分布情况,验证本文矫直参数,辊型以及矫直机整体设计的合理性。     

薄壁管材连续矫直截面扁化动态仿真分析

薄壁管材在连续矫直过程中会在大弯曲变形阶段发生截面扁化（即Bazier效应）,截面最大扁化量和残留扁化量作为重要工艺参数,用以控制截面变形程度和管材的圆度。而目前现场仍沿用经验图表结合人工经验和反复试矫对其进行估定,为此运用ANSYS/LS-DYNA对薄壁管材弯曲扁化的过程进行动态仿真,得到了最大扁化量和残留扁化量数据,并通过现场实验证明了分析结果的正确性和可信性,为现场矫直过程相关工艺参数的合理设置提供有效手段。     

镀锡板开平线矫直机插入量对板形控制的影响

基于镀锡板开平线矫直机结构形式,分析了矫直机结构特点及带材矫直机理。通过建立开平线矫直机有限元仿真模型,研究带材矫直过程的变形机理,分析各矫直辊组插入量对板形质量的影响。结合带材矫直过程仿真分析规律,建立了不同规格开平线矫直机插入量参数优化表,并针对不同来料板形制定矫直参数。参数优化后,带材浪形及翘曲缺陷基本消除,实现了镀锡板开平后板形质量的大幅提升,取得了良好的实用效果。     

基于Marc的角钢矫直过程有限元仿真研究

针对某厂10辊800型钢矫直机,基于大型非线性有限元分析软件Marc,建立了角钢矫直过程的三维动态有限元仿真模型,模拟了20角钢在小变形矫直方案、不同相对原始曲率情况下的矫直过程,研究分析了矫直过程中角钢特定点应力应变的变化规律以及各矫直辊的矫直力分布规律,为优化矫直工艺提供依据。     

Q46020号角钢9辊矫直过程有限元仿真

根据大变形小残差的矫直理论得到矫直机压下量,通过建立9辊矫直过程有限元仿真模型,对Q460 20号角钢矫直过程进行模拟,考虑了材料的加工硬化得到了其矫直过程的应力应变分布,以及各矫直辊矫直过程中矫直力、矫直力矩的动态变化过程,为开发设计新型矫直机提供了理论依据。     

大圆坯连铸带液芯矫直过程的应力、应变有限元模拟

应用Marc有限元软件对圆坯连铸的连续矫直变形过程进行模拟.以马鞍山钢铁公司大圆坯连铸机为原型,考虑铸坯与辊子的接触状态,建立了圆坯矫直变形模型;模拟分析了大圆坯连铸带液芯矫直过程中坯壳的应力、应变,得到了铸坯在矫直过程中的变形规律,可为铸机矫直工艺及设备设计提供参考依据,从而进一步优化铸坯的矫直变形,以提高圆坯的内部质量和表面质量.     

薄壁管材等曲率矫直辊形曲线与设计平台研发

针对薄壁管材等曲率矫直辊形曲线无精确数学模型的实际问题,运用空间曲线、曲面相关几何关系和坐标变换,以管材在辊缝中单曲率弯曲为出发点,建立了辊形曲线的解析模型,通过算例证明了模型的可操作性,并运用VB和Solidworks开发了等曲率矫直辊设计平台,实现矫直辊的快速设计.     

Setting and realizing process plan for straightening thin- walled tube by multiple cross rolls of equal curvature

Since it was difficult to setting the plan and the unifying curvature- radius precisely when the thin- walled tubes were straightened continuously by the rolls of equal curvature. Therefore, based on the mechanism of unifying- straightening for the multiple cross- rolls straightening machine, the judgment method of the unifying curvature- radius was presented firstly in view of the bending and springback equation of the thin- walled tube, and then the searching method of the minimum unifying curvature- radius was presented subsequently, finally the straightening plans were drawn up for different thin- walled tubes with different initial curvature radii, especially for the thin- walled tube with the large initial deformation which could not be unified by the two cross rolls, the new method was pre- bending, unifying, and straightening, and it was also presented whether a thin- walled tube could be straightened. Some procedures were developed by VB to calculate the example, which is shown that the methods are effective, meanwhile it is found that if the unifying curvature- radius exist for an initial curvature- radius, it will not be sole and will be within a scope, and it is also found that there must be a scope of the initial curvature- radius within which the thin- walled tubes can??t be unified by the two cross rolls.     

Prediction of Maximum Section Flattening of Thin-walled Circular Steel Tube in Continuous Rotary Straightening Process

Cross-sectional ovalization of thin-walled circular steel tube because of large plastic bending,also known as the Brazier effect,usually occurs during the initial stage of tube′s continuous rotary straightening process.The amount of ovalization,defined as maximal cross section flattening,is an important technical parameter in tube′s straightening process to control tube′s bending deformation and prevent buckling.However,for the lack of special analytical model,the maximal section flattening was determined in accordance with the specified charts developed by experienced operators on the basis of experimental data;thus,it was inevitable that the localized buckling might occur during some actual straightening operations.New normal strain component formulas were derived based on the thin shell theory.Then,strain energy of thin-walled tube(per unit length)was obtained using the elastic-plastic theory.A rational model for predicting the maximal section flattening of the thin-walled circular steel tube under its straightening process was presented by the principle of minimum potential energy.The new model was validated by experiments and numerical simulations.The results show that the new model agrees well with the experiments and the numerical simulations with error of less than 10%.This new model was expected to find its potential application in thin-walled steel tube straightening machine design.     

薄带材浪形缺陷生成与拉伸矫直过程数值仿真

基于ABAQUS有限元软件建立了薄带材浪形生成与拉伸过程有限元模型,研究了带材在初应变作用下的浪形缺陷生成规律及其在张力拉伸作用下的应力特性及其变形行为,并进一步分析了浪形缺陷拉伸矫直矫平功效的主要影响因素及其影响规律.薄带钢变形过程可分为浪形生缺陷生成、拉伸矫直和弹性回复三个阶段.针对薄钢带弹性后屈曲浪形和铝带弹塑性后屈曲浪形两类典型浪形形式,研究了浪形缺陷在后屈曲和拉伸变形阶段的浪形陡度变化与系统能量变化规律.研究表明:弹性后屈曲浪形在拉伸矫直过程中浪数和浪高均发生变化,而弹塑性后屈曲浪形仅发生浪高的连续变化.弹性后屈曲浪形矫直后的残余应力分布形式与初始应力分布类似,而弹塑性后屈曲浪形的残余应力分布发生显著差异.浪形缺陷的残余陡度随初始浪形陡度增大而增大,随带厚增加而减小,且弹塑性后屈曲浪形缺陷的矫直效果更为显著.      

Tube Reversing and Extrusion (TRE) as a Novel Method for Producing UFG Thin Tubes

In the present research, a new severe plastic deformation method has been introduced for producing thin walled tubes with ultrafine grained substructure. The tube reversing and extrusion (TRE) technique was applied to a CP-aluminum and thin walled tubes with ultra-fine grained microstructure were successfully processed. The obtained results from tensile tests at room temperature showed the significant increase in mechanical properties of TRE processed thin walled tubes including yield and ultimate strengths and micro-hardness due to grain refinement. The microstructure evolution and deformation behaviour of commercially pure aluminium under TRE processing was simulated by the constitutive model as a micromechanical approach implemented in the finite element framework. The continuous dynamic recrystallization (the evolution of dislocation density and grain size) of aluminum tubes during TRE was considered as the main grain refinement mechanism in micromechanical constitutive model. Also, the flow stress of material in macroscopic scale was related to microstructure quantities. This was in contrast to the previous approaches in FEM simulations of SPD methods where the microstructure parameters such as grain size were not considered at all. The FEM simulated grain refinement behavior was consistent with the experimentally obtained results.     

Q345B低温变形抗力模型及在矫直工艺中的应用

通过Gleeble-1500热模拟试验机对低合金钢Q345B φ10 mm × 30 mm圆件体试样在450～650℃以0.001～0.1s^-1变形速率进行真应变为0.15拉伸试验。结果表明,低温低变形速率状态下的变形抗力处于弹塑性变形区,线性段较长,当变形量大于0.06以后出现较明显塑性变形,变形抗力的变化规律与较高温状态基本类似。通过采集实验数据,应用Origin软件通过多元非线性回归建立了Q345B钢变形抗力的数学模型。应用该模型结合矫直理论公式计算了中厚板9辊矫直机矫直力,计算结果的相对误差为0.01%～6.71%。     

Continuous bending and straightening technology of Q345c slab based on high-temperature creep deformation

A new continuous bending and straightening casting curve with the aim of full using of high-temperature creep deformation was proposed.The curvature of bending and straightening segment varies as sine law with arc length.The basic arc segment is shortened significantly so that the length of bending and straightening area can be extended and the time of creep behavior can be increased.The distance from solidifying front in the slab was calculated at 1 200°C by finite element method.The maximum strain rate of new casting curve at different locations inside the slab is 6.39×10~(-5) s~(-1) during the bending segment and it tends to be 3.70×10-5 s~(-1) in the straightening segment.The minimum creep strain rate is 7.45×10~(-5) s~(-1)when the stress is 14 MPa at 1 200°C.The strain rate of new casting machine can be less than the minimum creep strain rate.Thus,there is only creep deformation and no plastic deformation in the bending and straightening process of steel continuous casting.Deformation of slabs depending on creep behavior only comes true.It is helpful for the design of the new casting machine and improvement of old casting machine depending on high temperature creep property.     

φ15～70mm液压管材矫直机机架工作状态有限元研究

φ15 ～ 70mm液压管材矫直机为十二辊矫直机,采用有限元方法分析矫直过程中机架受力变形情况.研究建立了矫直机机架的三维模型,用最大理论矫直力作为工作载荷,对机架的形变进行有限元仿真分析研究.得出了机架的各单元、节点的变形值及应力值,找到了机架的应力和位移分布规律,并据此提出了机架的改进措施,为保证矫直精度打下基础.