A study of grease film thicknesses in elastorheodynamic rolling point contacts

An elastorheodynamic analysis and a numercial solution are presented for grease film thicknesses in rolling point contacts for fully flooded, isothermal and steady state conditions. The contact surfaces are smooth and a grease four-parameter rheological model is considered. A modified Reynolds equation is established and a complete numerical solution, including surface deformations, piezoviscous, and compressional effects is given.     

The effects of deformations by rolling and uniaxial tension on the structure and the magnetic and mechanical properties of armco iron,steel 12X18H10T,and a steel 12X18H10T-Armco Iron-Steel 12X18H10T composite material

The effects of elasto-plastic deformations by rolling and uniaxial tension on the structure and the magnetic and mechanical properties of Armco Iron, 12X18H10T steel, and a three-layer Steel 12X18H10T-Armco Iron-Steel 12X18H10T model composite material are investigated. The magnetic characteristics, which vary uniquely during elasto-plastic deformations, thus allowing their use as parameters for estimating mechanical properties and the degree of deformation by rolling and uniaxial tension in items made of these materials, are determined.     

ANALYSIS OF CREEP FORCES OF WHEEL/RAIL

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Linear Complementarity Framework for 3D Steady-State Rolling Contact Problems Including Creepages with Isotropic and Anisotropic Friction for Circular Hertzian Contact

In this article, the problem of 3D steady-state rolling contacts with dry friction for circular Hertzian contacts is formulated mathematically as a linear complementarity problem (LCP). The complementarity variables are the traction and the relative slip of contact regions, in which a polyhedral friction law is employed. The present work uses the general expressions describing the surface deformations due to uniform traction over a rectangular area on an elastic half-space to derive the influence coefficient matrix for rolling contact problems. Three possible creepage types—that is, longitudinal, lateral, and spin creepage—are considered in this work. Firstly, the numerical results are verified against the existing numerical solutions and good agreement has been found. Secondly, the anisotropic friction is studied by the verified approach. Some numerical examples are provided to illustrate the current LCP method for both isotropic and anisotropic friction in which the combined effects of the three kinds of creepage on the traction distribution are shown.     

Stream surface strip element method for simulation of the three-dimensional deformations of plate and strip rolling

A new method—the stream surface strip element method (SSSEM)—for simulating the three-dimensional deformations of plate and strip rolling process is proposed. The rolling deformation zone is divided into a number of stream surface (curved surface) strip elements along metal flow traces, and the stream surface strip elements are mapped into the corresponding plane strip elements for analysis and computation. The longitudinal distributions of the lateral displacement and the altitudinal displacement of metal are constructed respectively to be a quartic curve and a quadratic curve, the transverse distributions of them are expressed as the third-power spline function, and the altitudinal distributions of them are fitted to be a quadratic curve. Based on the flow theory of plastic mechanics, the three-dimensional deformations and stresses of the deformation zone are analyzed and formulated. Compared with the streamline strip element method, the SSSEM considers the uneven distributions of stresses and deformations along altitudinal direction, and realizes an accurate three-dimensional analysis and computation. The simulation examples indicate that the method and the model of this paper are in accord with facts, and provide a new reliable engineering-computation method for the three-dimensional mechanics simulation of plate and strip rolling process.     

大变形量下高碳钢环件冷轧变形过程模拟与试验研究

研究了大变形量下高碳钢环件冷轧变形行为,利用有限元模拟方法分析了环件冷轧过程中的形变规律,采用光学显微镜、SEM等材料表征手段研究了大变形量下环件冷轧过程中的组织演化特点。结果表明：在较小的变形量下,环件内外侧应变较中间应变大,且变形首先发生在环件外侧;整个环件变形过程中,环件中间层的晶粒变形程度最小,外层次之,内层的变形最为剧烈;铁素体基体沿轧制方向呈现明显的方向性,碳化物颗粒分布更为均匀,且数量变少;随着变形量的增大,环件内层的应变明显大于外层的应变,且最小应变的位置偏移至靠外层比较近的区域,其组织中碳化物颗粒脱落加重;当变形量达到625%时,环件达到塑性极限,在内侧表面产生裂纹发生破坏。     

[成形过程仿真优化与集成计算材料工程]限动芯棒连轧管机轧制过程轧件变形行为及规律仿真

基于ABAQUS有限元软件建立了180 mm限动芯棒连轧管机组钢管连轧过程仿真模型。通过仿真模拟展现了连轧各机架连续轧制过程中轧制区钢管横截面上应力、应变及位移的分布和壁厚形成演变过程,揭示了轧制压力分布和轧辊上总轧制力的变化规律以及轧件温度与轧制区摩擦因数对壁厚与轧制力的影响。使用三次样条插值方法从仿真结果数据中提取钢管壁厚和直径,通过研究对象机组的工业生产实测数据验证了有限元模型的正确性。仿真发现:连轧过程中,金属在纵向上先发生减径变形后发生减壁变形,横向上金属主要从孔顶区流向开口区;前三机架接触压力主要集中在孔顶区,变形量较大,是主变形机架,第四五机架接触压力最大在侧壁区,变形量较小,主要起到精整和归圆作用;随着轧制温度的升高,出口壁厚增大,轧制力减小,随着芯棒与轧件之间摩擦因数的增大,壁厚减小,轧制力减小。仿真研究结果支撑了针对该机组的关键轧机结构参数设计、轧制工艺参数确定以及工程调试中工艺参数优化。     

模拟板带轧制三维变形的流面条元法

提出模拟板带轧制过程三维变形的一种新的数值方法——流面条元法。沿着金属的流动轨迹,将变形区划分为若干流面(曲面)条元,为方便分析和计算,又将其映射为平面条元。横向位移和高向位移的纵向分布被分别构造为四次曲线和二次曲线,其横向分布均用三次样条插值函数表示,高向分布均用二次曲线拟合。根据塑性力学流动理论,分析推导了变形区三维变形和应力的数学模型。与曾经提出的流线条元法相比,考虑了应力与变形沿高向的不均匀分布,实现了精确的三维分析和计算。仿真实例表明,该方法和模型符合实际,为板带轧制过程的三维力学仿真提供了一个新的实用工程数值方法。     

Experimental study of the disturbed layer generation during hot rolling contact of aluminum with steel

Effects of rolling passes and forward speed on the generation of disturbed layer on aluminum alloy sheet surfaces were investigated using a hot rolling simulator at forward speeds of −1% and 12% in presence of spraying emulsion. The results showed that at higher forward speed and number of rolling passes, the localized shear deformations become more pronounced on the surface. However, when the two rolling passes were in opposite directions, the localized shear deformations did not stick out, but were embedded into the aluminum surface. The defects generated were representative of the initial stages of the disturbed layer formation.     

Methods for Determining Pressure Distributions in Lubricated Rolling Contact

Two methods have been evolved for finding pressure distributions in lubricating rolling contact. In the first method, the circumferential profile of the gap between rolling disks is found by using an X-ray technique, and the pressures are inferred from the observed deformations of the disks. Several profiles have been obtained for a range of loadings, temperatures, and rolling speeds by using steel disks with polyphenyl ether as the lubricant, and plausible (though not greatly detailed) pressure distributions were derived from some of them. The second method uses a strip of manganin coaling on a glass disk which is loaded into lubricated, rolling contact with a second glass disk. The change in electrical resistance of the manganin due to film pressures is measured. The data recorded by this technique also appear to be reasonably reproducible and consistent.     

轮轨结构横向变形对轮轨滚动接触蠕滑力的影响

从数值方面详细分析轮轨结构横向弹性变形对轮轨蠕滑力的影响。借助于有限元方法分析计算轮对和轨道结构横向弹性变形与横向作用力的关系，确定轮轨接触斑处横向单位作用力引起轮轨横向变形的影响系数。用这些影响系数修正Kalker非赫兹滚动接触理论中无限弹性半空间上单位力的影响系数，并分别用没有修正的和修正了的Kalker三维弹性体非赫兹滚动接触理论分析计算轮轨滚动接触蠕滑力。从数值结果看，轮轨的结构变形对轮轨蠕滑力的影响是十分大的。因此，用现有基于弹性半空间理论的滚动接触理论分析轮轨蠕滑力，其结果大于实际轮轨滚动接触蠕滑力。     

Plastic deformations of wheel-rail surfaces

Experimental investigations into the interactions between surface pressure, tangential tractions and plastic deformations during rolling gave the following results.

• 1.(1) The most intensive plastic deformations are caused by lateral frictional forces, followed by longitudinal frictional forces. The material flow is smallest with pure rolling.
• 2.(2) In agreement with Johnson's theory for a steel with a carbon content of 0.6% (similar to those used for wheels and rails) the shakedown limit was found at a maximum hertzian surface pressure of about 1600 N mm⁻².

     

点接触弹流润滑条件下表面弹性变形研究

为研究弹流润滑条件下点接触表面变形及其对表面性能的影响,采用激光微织构法制备了一组不同形貌参数的滚动轴承滚道表面试件,基于表面频谱分析和弹流润滑快速算法（幅值缩减法）分析了试件在不同工况参数下的弹性变形。使用ISO 25178三维形貌参数体系对变形前后表面进行表征,研究了点接触弹流润滑状态下表面形貌的弹性变形与载荷、转速的关系。研究结果表明,弹流接触使表面形貌发生显著的弹性变形,载荷、转速等工况参数对变形量影响较大,表面弹性变形使得形貌参数发生显著变化。     

Mechanical behavior of an asymmetrically rolled and annealed 1050-O sheet

In this work, 1050-O aluminum alloy sheets are asymmetrically rolled and annealed. The asymmetric rolling process imposes intense shear deformations across the sheet thickness, leading to the development of shear texture and also grain refinement. The shear texture obtained is found to be retained after annealing. The improvements of the mechanical response and the texture evolution after heat treatment processing are inferred based on experimental shear tests and numerical simulations. It is proven that it is difficult to spread shear texture through the entire sheet thickness from a general asymmetric rolling process. Based on the fact, future research is discussed at closure.     

A mixed-EHL analysis of effects of misalignments and elastic deformations on the performance of a coupled journal-thrust bearing system

This paper presents a mixed-EHL analysis of effects of misalignments and elastic deformations on the performance of a coupled journal-thrust bearing system. Two types of misalignment (axial and twisting) are considered. The JFO's mass conserving cavitation conditions are applied to the governing Reynolds equations. The performance of a typical coupled journal-thrust bearing system is numerically studied and the effects of elastic deformations and misalignments are investigated.     

环件径轴向轧制毛坯尺寸设计方法

毛坯尺寸设计是环件径轴向轧制过程优化设计的前提和基础,合理的毛坯尺寸设计,对于成功建立环件径轴向轧制过程、通过包括毛坯在内的过程优化设计以获得精确的环件尺寸和良好性能,具有十分重要的意义.为此,提出一种基于轧比和径轴向变形量分配比的矩形截面环件径轴向轧制毛坯尺寸设计方法,给出毛坯尺寸的计算公式与确定流程,阐明该毛坯尺寸设计方法的特点及应用范围.该方法基于体积不变原理,针对同一环件的轧制,可以设计不同轧比和变形量分配比的多个环坯,为研究不同环坯下的环件径轴向轧制变形行为、工艺规律以及包括毛坯在内的工艺过程优化设计、成形成性一体化调控提供了重要的方法和基础.     

基于流面条元法的四辊热带钢连轧机整机仿真

用流面条元法分析带材的三维塑性变形，用影响系数法分析辊系的弹性变形，将二者联立，组成板形和板凸度的分析和计算模型，对1450mm四辊热带钢连轧机的轧制过程进行了仿真，仿真结果与实测结果吻合良好，为四辊热带钢连轧机板形分析与控制的仿真提供了模型和方法。     

Oscillations in the Mechatronic System of a Multi-Stand Rolling Mill

The mechatronic system of the DUO-300 rolling mill is analyzed. The influence of the roller’s linear velocity on the distribution of frictional forces in the rolling region is studied. A nonlinear relation is found between the load and the roller speed. The conditions of self-oscillation in rolling are determined. Methods of damping the self-oscillation are considered.     

Thermal model of high-speed spindle units

For the purpose to facilitate development of high-speed spindle units (SUs) running on rolling bearings, we have developed a beam element model, algorithms, and software for computer analysis of thermal characteristics of SUs. The thermal model incorporates a model of heat generation in rolling bearings, a model of heat transfer from bearings, and models for estimation of temperature and temperature deformations of SU elements. We have carried out experimental test and made quantitative evaluation of the effect of operation conditions on friction and thermal characteristics of the SUs of grinding and turning machines of typical structures. It is found out that the operation conditions make stronger effect on SU temperatures when rpm increases. A comparison between the results of analysis and experiment proves their good mutual correspondence and allows us to recommend application of the models and software developed for design and research of high-speed SUs running on rolling bearings.     

铝钢复合材料冷轧变形规律的研究

研究了铝钢复合材料冷轧变形特性,对试验结果进行理论分析和回归分析,得出了一个描述变形特性的方程.研究结果表明,在冷轧过程中,铝钢复合材料的塑性变形、厚度和变形抗力相互影响,对于双金属轧制计算以及双金属冷轧生产过程具有指导意义.