Effect of sizes of forming rolls on cold ring rolling by 3D-FE numerical simulation

During cold ring rolling process, changing the sizes of forming rolls including driver roll and idle roll will lead to a change of amount of feed Ah and contact areas between ring blank and forming rolls, thus a change of the shape and dimension of deformation zone located in the gap of forming rolls is found. It has a significant effect on metal flow and the forming quality of deformed ring. So the size effect of forming rolls on cold ring rolling was investigated by three-dimensional dynamic explicit FEM under ABAQUS environment. The obtained results thoroughly reveal the influence laws of the sizes of forming rolls on the average spread, fishtail coefficient, degree of inhomogeneous deformation and force and power parameters etc not only provide an important basis for design of the forming rolls and optimization of cold ring rolling process, but also reveal the plastic deformation mechanism of cold ring rolling.

Comparison of evolution laws of stress and strain fields in hot rolling of titanium alloy large rings with different sizes

For hot rolling of titanium alloy large rings,evolution laws of stress and strain fields in rings with various sizes were explored and compared based on a reliable coupled thermo-mechanical three-dimensional （3D） finite element （FE） model.The results show that for forming processes of different rings,as γ^-（the equivalent distribution ratio of feed amount per revolution of a process） decreases,the final peak Mises stress may transfer from the biting point at the driver roll side to that at the idle roll side,and the final peak equivalent plastic strain may transfer from the outside surface to the inside surface;as L^- （the equivalent deformation zone length of a process） increases,the final peak Mises stress may appear in the middle layer.The final positions of peak Mises stress and equivalent plastic strain are the combined effects of the above two aspects.In the deformation zone of a deformed ring,the surface layers are in the 3D compressive stress state,while the middle layer is in the 1D compressive and 2D tensile stress state or 2D compressive and 1D tensile stress state;the whole ring is in the 1D compressive and 2D tensile strain state.

Modeling and Simulation of Radial-Axial Large Ring Rolling

Finite element model is constructed according to the principle and characteristics of radial-axial large ring rolling technology. Dynamic explicit finite element method is used to simulate the rolling process. An effective modeling method of guide roller is proposed. Simulation indicates that high quality ring product could be obtained when rational rotational speed of rollers and feed rate in the radial and axial rolling are assigned.

Thermo-mechanical coupled analysis of hot ring rolling process

A 3D rigid-plastic and coupled thermo-mechanical FE model for hot ring rolling(HRR) was developed based on DEFORM 3D software,then coupled heat transferring,material flow and temperature distribution of the ring in HRR were simulated and the effects of process parameters on them were analyzed.The results show that the deformation nonuniformity of ring blank increases with the increase of the rotational speed of driver roll and friction factor or the decrease of the feed rate of idle roll and initial temperature of ring blank.The temperature nonuniformity of ring blank decreases with the increase of the feed rate of idle roll or the decrease of initial temperature of ring blank and friction factor.There is an optimum rotational speed of driver roll under which the temperature distribution of ring blank is the most uniform.The results obtained can provide a guide for forming parameters optimization and quality control.

Finite element analysis of deformation characteristics in cold helical rolling of bearing steel-balls

Due to the complexity of investigating deformation mechanisms in helical rolling(HR) process with traditional analytical method, it is significant to develop a 3D finite element(FE) model of HR process. The key forming conditions of cold HR of bearing steel-balls were detailedly described. Then, by taking steel-ball rolling elements of the B7008 C angular contact ball bearing as an example, a completed 3D elastic-plastic FE model of cold HR forming process was established under SIMUFACT software environment. Furthermore, the deformation characteristics in HR process were discovered, including the forming process, evolution and distribution laws of strain, stress and damage based on Lemaitre relative damage model. The results reveal that the central loosening and cavity defects in HR process may have a combined effect of large negative hydrostatic pressure(positive mean stress)caused by multi-dimensional tensile stresses, high level transverse tensile stress, and circular-alternating shear stress in cross section.

Fe-3%Si钢CSP工艺轧制的热模拟试验

针对Fe-3%Si钢,根据CSP生产线的工艺特点,模拟现场CSP工艺条件进行加热、轧制和卷取热模拟试验,采用Gleeble-1500D热模拟试验机研究Fe-3%Si钢在模拟CSP工艺热轧过程中的再结晶行为。结果表明,道次压下量为45%-40%-40%-20%-35%-35%的压下工艺条件下,获得的晶粒尺寸较为细小,动态再结晶完成较好;随着卷取温度的提高,晶粒平均尺寸减小,且卷取温度在650℃时,晶粒相对均匀。研究结果可为CSP工艺取向硅钢热变形行为的研究提供试验依据。

Al-5Fe-1.2Si-1Mg-0.6Cu-0.5Mn合金轧制变形行为及组织性能

为了细化Al-5%Fe基合金中粗大的脆性针状或针片状富铁相,采用电磁搅拌及固态挤压技术制备Al-5%Fe-1.2%Si-1%Mg-0.6%Cu-0.5%Mn合金轧制坯锭,研究Al-5%Fe基合金的轧制变形能力及合金的组织性能,并用热压缩实验模拟了铝铁合金在783～693 K、变形速率为0.01～10 s-1条件下的热变形行为.结果表明:该合金高温变形时存在明显的稳态流变特征,流动应力对应变速率和温度敏感.板材力学性能较挤压态有大幅度提升,其室温下的抗拉强度和伸长率最高达到354.5 MPa和7.6%,比挤压态分别提高了105.6%和184.6%.轧制对铝铁合金中富铁相的破碎作用十分明显.

On a plastic instability criterion for ultra-large radial-axial ring rolling process with four guide rolls

A dynamic mechanical model is proposed to describe the complexing actions of all the rolls on the ring during the ultra-large radial-axial ring rolling(RARR)process with four guide rolls.Based on the model,the calculation models for bending moment and normal stress at any section of the ring are deduced by force method.If the maximum section bending normal stress exceeds the yield stress of the ring materials,the ring will be distorted thus leading to the instability of the RARR process.According to this,a plastic instability criterion for the ultra-large RARR process with four guide rolls is developed,based on which a mathematical model to calculate the critical guide force for avoiding plastic instability of ring is obtained.The influence rule of the position of guide roll on the dangerous ring section of plastic instability is revealed,from which it is found the dangerous ring section mainly appears at the radial and axial deformation regions and the contact positions of the guide rolls and ring.The optimized layout of guide roll around the ring in favor of stability is determined to be about a1=61°and a2=119°.The plastic instability criterion is proven to be reliable from the aspects of the critical guide force,the section bending moment and normal stress and the dangerous ring section of plastic instability.Intelligent simulation case studies for the RARR process of ultra-large aluminum alloy ring indicate that the stable forming of the process can be effectively realized by regulating the guide force based on the plastic instability criterion.This work could provide a valuable guidance for the control of guide rolls and the optimization of the ultra-large RARR process with four guide rolls.

Numerical Simulation of Deforming Manufacture Process for Automobile Bevel Gear Blank

Aiming at solving the difficulties of deforming manufacture of the automobile rear axle bevel gear blank,the paper presented to adopt the numerical simulation method to study the rolling process of the bevel gear blank instead of the traditional expensive trail-and-error method. A three-dimensional simulation model of the Φ500 bevel gear blank radial ring rolling machine was firstly created based on the general dynamic explicit finite element code ANSYS/LS-DYNA,and then realized the virtual simulation of the entire rolling process of the bevel gear blank within a producing cycle. The simulation results displayed the real-time blank enlarging and fleck generating as well as the stress,strain and displacement contours,which are in good agreements with the real ring rolling process. It is concluded that this numerical simulation method is feasible and can be used to guide the practical rolling process of the bevel gear blank as well as other profile-shaped annular blanks.

空间滚动轴承MoS_(2)薄膜润滑分子动力学模拟

针对空间滚动轴承往复运动状态下二硫化钼薄膜润滑失效机理不明的难题,提出了采用分子动力学对薄膜润滑过程进行分析的方法。建立了单层二硫化钼薄膜摩擦原子模型,针对载荷和环境温度这2个空间滚动轴承的重要影响因素展开了二硫化钼薄膜的往复摆动模拟,得到了摩擦过程中二硫化钼薄膜的摩擦力、粘附力和磨损情况。模拟结果表明:Fe-Ni-Cr合金探针在单层二硫化钼薄膜上的摩擦为黏滑运动,载荷在20~100 nN范围内探针的摩擦过程不会对薄膜造成磨损,但在往复运动过程中润滑性能有所提高;载荷从200 nN开始探针的摩擦过程会对薄膜造成磨损,往复运动过程中摩擦系数不断提高,润滑性能下降;400 nN为单层薄膜的载荷极限,在该载荷下探针会刺穿薄膜与基底接触此时薄膜迅速磨损失去润滑作用。环境温度在1 773.15 K以下对薄膜的润滑作用影响不明显,但达到该温度后薄膜边界处开始缓慢熔化,当环境温度达到二硫化钼熔点时薄膜的熔化速度加快并失去润滑作用。从这些发现得到如下结论:二硫化钼单层薄膜在接触载荷8 GPa以下拥有优异的耐磨性和润滑性;在薄膜未破损的条件下,反复摩擦过程提升了润滑性能;二维层状结构对单层二硫化钼薄膜润滑性能有重要的影响,高温和重载都会对薄膜层状结构造成破坏。

环件轧制技术的研究现状及发展趋势

环件轧制是各类形状尺寸无缝环形零件的先进制造技术,在航空航天、装备制造业和核工业等领域应用前景广阔。本文针对环件轧制技术方面的相关文献进行了系统性的分析、总结与论述,介绍了环件轧制的分类及工作原理、工艺与设备,综述了近年来国内外学者在环件轧制实验、理论和有限元模拟三个方面的研究进展;并指出了当前研究存在的主要问题,展望了环件轧制技术未来的发展趋势,以期为环件轧制技术的研究和实践提供思路及借鉴。

铝冷轧油雾捕集用环吸式、条缝式排风罩性能的对比研究

针对铝冷轧工艺过程产生大量烟气污染环境的问题,文章结合铝冷轧工艺现场,建立了用于铝轧油雾捕集的环吸罩和条缝罩物理模型。通过计算流体力学方法建立了两种排风罩流场的数值计算模型,对比了两种排风罩罩口处附近特征风速和污染物捕集效果,并通过实际物理模型实验,给出了两种形式排风罩捕集污染物的可视化结果。结果表明,环吸式排风罩对污染物的捕集性能优于条缝式排风罩的捕集效果。

环件径-轴双向轧制数值模拟及其多轧辊的联合控制

环件轧制过程是热力耦合作用下高度非线性、非稳态的热成形工艺,其工艺参数多,轧辊控制复杂,难变形材料的环件轧制技术还缺乏高效、便捷的数值研究手段。以轧制曲线为基本变量,建立了各轧辊之间的运动学和动力学关系,随后基于FORGE有限元软件平台,依据Φ3000 mm数控环轧机建立了环件轧制的有限元模型。模型采用力及力矩控制抱辊,通过多轧辊联合控制,能够成功实现对偏心、椭圆等弱刚度现象的预测。通过Inconel718合金全尺寸环件轧制实验,验证了所建有限元模型的可靠性。该模型预测结果的相对误差小于3%,并在机匣等典型薄壁件的研制中得到了工程化应用。

环模制粒模、辊挤压过程影响因素分析

环模制粒装备是饲料加工装备使用最广泛、最重要的设备,环模制粒装备中的模、辊直接接触物料,十分容易磨损,为探究磨损机理,根据物料在挤压过程中的状态分为供料区、变形压紧区和挤压成型区,并对挤压过程进行受力分析,计算出成功攫取公式,并通过ABAQUS/Explicit对模、辊辊轧过程进行有限元分析,得到不同摩擦系数和模、辊间隙情况下压辊受力情况,为环模制粒设备设计提供了参考。

煤矿双齿辊破碎机破碎齿及齿环座的强度分析

基于煤矿双齿辊破碎机破碎齿及齿环座基本结构构建破碎齿和齿环座有限元仿真模型,并以此为基础开展仿真分析,确认煤矿双齿辊破碎机破碎齿及齿环座强度性能水平。此外,研究中还会将此仿真分析方法应用于煤矿双齿辊破碎机破碎齿和齿环座强度分析检测工程实践中,通过实际检测结果与仿真分析结果的匹配对比确认仿真分析方法的可用价值。

大型台阶环件分步轧制成形工艺模拟研究

大型环锻件作为风电、航空航天等领域的关键零部件,其制备质量和效率已成为行业发展的重要因素。针对台阶环件的精准轧制问题,采用热模拟试验与数值模拟相结合的方法,研究了Q345E钢不同工艺参数下的热变形行为,分析了不同轧制方式下金属的流动规律。结果表明:当变形温度在1100℃以上时,应力-应变曲线呈现出动态再结晶特征。同时,确定了最优变形工艺参数,即温度在1050~1250℃之间,应变速率在0.1~1 s^(-1)之间。特别地,针对大型内台阶环件的成形,提出了矩形毛坯逐步产生轴向壁厚差的分步轧制新方法。

环件冷辗扩中单辊随动导向运动规律研究

根据立式单导向辊随动导向冷辗环机的实际工况,建立了矩形截面环件和深沟球截面环件冷辗扩的运动学模型,分析两种环件的直径变化规律,研究了一定辗扩工艺条件下导向辊的运动规律。建立根据冷辗扩工艺来确定导向辊运动的一整套设计方法,并用MATLAB编写求解程序以求解所有的设计参数。精确地控制导向辊的运动规律有利于提高环件冷辗扩的精度。研究结果为冷辗环机的设计制造提供了依据。

滚压强化的残余应力的数值仿真及工艺分析

表面滚压强化,由于在表层引起加工硬化和残余压应力,可以十分有效地提高构件、零件疲劳强度,而滚压强化的有限元数值仿真,将成为分析优化滚压强化工艺的重要手段。本文建立了连续多、圈滚压工艺的有限元数值仿真模型,获得了比较合理的滚压变形与残余应力结果。在此基础上对滚压工艺做了进一步分析。结果表明,滚压变形的进给量太大、滚压的转速太快都容易造成工件表层残余应力分布的不均匀甚至形成残余拉应力;在滚压与未滚压的过度区域,从表面到心部的近1mm范围内,均未出现人们通常所担心的残余拉应力。这将在工程生产实践中,为滚压工艺制订提供重要的依据。

内台阶锥形环件轧制三维有限元模拟和工艺优化设计

以Abaqus三维有限元模拟软件为平台,对内台阶锥形环件的轧制过程进行了数值模拟,通过模拟计算揭示了内台阶锥形环件轧制缺陷的形成机理。根据轧制难度分析和有限元模拟结果,对轧制毛坯尺寸和轧制孔型进行了优化。采用铅环件试样在D51-160轧环机上进行了内台阶锥形环件的轧制试验,轧制了合格的内台阶锥形环件。模拟和试验结果表明,轧制毛坯尺寸和轧制孔型优化方案是合理的,基于变形模拟的轧环工艺优化方法是有效的。

大型环件的径轴向轧制工艺模拟和研究

研究了大型环件的径轴向轧制工艺。利用有限元模拟试验对具体的大型环件产品进行模拟轧制,通过对不同的毛坯和不同的工艺参数的选取进行试验和分析,找出了毛坯设计及工艺参数选取与控制的基本方法和规律,揭示了大型环件径轴向轧制过程的变形规律和机理,分析了轧制过程中产生的问题和缺陷的实质,为实际的工业生产提供了依据。