Frictional heat analysis of mine hoist and numerical simulation on temperature field of gasket

The frictional performance of gaskets is greatly affected by frictional heat in operational mine hoists. Based on frictional mechanism and heat transfer theory, the mathematical model of the temperature field of the PVC gasket in an operational mine hoist was investigated, a numerical simulation using ANSYS is presented and the distribution of the temperature and heat flux were studied under basic assumptions. The results show that the temperature gradually decreases as the radius of the model increases and the isotherms are arcs of concentric semi-circle. The heat flux is of bilateral symmetry in the model and decreases radially. The theoretical values correspond with the measured values for a short time (τ≤ 100 s) when the steel wire rope slides.

SIMULATION ON TEMPERATURE FIELD OF FRICTION STIR WELDED JOINTS OF 2024-T4 Al

The thermal model of FSW based on the thermal elastic-plastic finite element method, and the transient temperature distribution of FS welded joints of 2024-T4 Al was simulated by using this model, which provides useful information for the investigation of FSW process. Simulation resuits show that the temperature distribution of the weld gradually decreases toward periphery in a radiate format, whose center is the probe, and the highest temperature in the weld can reach about 400℃. The initial terminal of the weld is a zone, in which the temperature gradient is great, and defects of the welding are easily produced in this zone. Temperature change at the end of the welded joint is as layer variation, the local serious defects are not easy to produce in this zone.

THE COUPLED FEM ANALYSIS OF THE TRANSIENT TEMPERATURE FIELD DURING INERTIA FRICTION WELDING OF GH4169 ALLOY

The inertia friction welding process is a non-linear process because of the interaction between the temperature field and the material properties as well as the friction force. A thermo-mechanical coupled finite element model is established to simulate the temperature field of this process. The transient temperature distribution during the inertia friction welding process of two similar workpieces of GH4169 alloy is calculated. The region of the circular cross-section of the workpiece is divided into a number of four-nodded isoparametric elements. In this model, the temperature dependent thermal properties, time dependent heat inputs, contact condition of welding interface, and deformation of the flash were considered. At the same time, the convection and radiation heat losses at the surface of the workpieces were also considered. A temperature data acquisition system was developed. The temperature at some position near the welding interface was measured using this system. The calculated temperature agrees well with the experimental data. The deformation of the flash and the factor affecting the temperature distribution at the welding interface are also discussed.

Artificial-neural-network-based storage method for three-dimensional temperature field data during friction stir welding

In this paper,a new storage method for the three-dimensional temperature field data based on artificial neural network(ANN)was proposed.A multilayer perceptron that takes the coordinate(x,y,z)as inputs and temperature T as output,is used to fit the three-dimension-al welding temperature field.Effect of number of ANN layers and number of neurons on the fitting errors is investigated.It is found that the errors decrease with the number of hidden layers and neural numbers per layers generally.When the number of hidden layers increases from 1 to 6,the maximum temperature error decreases from 74.74℃to less than 2℃.The three-dimensional temperature field data is obtained by finite element simulation,and the experimental verification is completed by comparing the simulation peak temperatures with the measured results.As an example,an ANN with 4 hidden layers and 12 neurons in each layer were applied to test the performance of the proposed method in storage of the three-dimensional temperature field data during friction stir welding.It is found that the average error between the temperature data stored in ANN and the original simulation data that stored point-by-point is 0.517℃,and the error on the maximum temper-ature is 0.193℃,while the occupied disk space is only 0.27%of that is required in the conventional point-by-point storage.

Effect of Rotation Speed on Temperature Field and Axial Shortening of Inertia Friction Welded GH4169 Joints by Numerical Simulation

A 2D finite element model was established for inertia friction welding of GH4169 nickel-base superalloy based on the ABAQUS environment.The remeshing and map solution techniques were adopted to solve the problem of element distortion.The effect of rotation speed on the temperature field and axial shortening of joints was investigated.The results show that the interface temperature increases rapidly to higher than 900℃within 1s.And then,it increases slowly to a quasi-stable value.The axial shortening begins to augment quickly when a uniform interface temperature field has formed and the plasticized material is extruded from the interface to form an obvious flash.The rotation speed of the flywheel controls the welding process and has a significant influence on the temperature evolution and axial shortening of joints.

Evolution of residual stress field in 6N01 aluminum alloy friction stir welding joint

Based on the characteristics of friction stir welding( FSW) and Coulomb friction work theory,the residual stresses field of FSW joints of 6 N01 aluminum alloy( T5),which was used in high speed train,were calculated by using the ANSYS finite element software. During the FEM calculation,the dual heat source models namely the body heat source and surface heat source were used to explore the evolution law of the welding process to the residual stress field. The method of ultrasonic residual stress detecting was used to investigate the residual stresses field of the 6 N01 aluminum alloy FSW joints. The results show that the steady-state temperature of 6 N01 aluminum alloy during FSW is about 550 ℃,and the temperature mutates at the beginning and at end of welding. The longitudinal residual stress σ_x is the main stress,which fluctuates in the range of-25 to 242 MPa. Moreover,the stress in the range of shaft shoulder is tensile stress that the maximum tensile stress is 242 MPa,and the stress in the outside of shaft shoulder is compressive stress that the maximum compressive stress is 25 MPa. The distribution of the tensile stress in the welding nugget zone( WNZ) is obviously bimodal,and the residual stress on the advancing side is higher than that on the retreating side. With the increasing of the welding speed,the maximum temperature decreased and the maximum residual stress decreased when the pin-wheel speed kept constant. With the increasing of the pin-wheel speed,the maximum temperature of the joint increased and the maximum residual stress increased when the welding speed was constant. The experimental results were in good agreement with the finite element results.

Plastic flow and interfacial bonding behaviors of embedded linear friction welding process:Numerical simulation combined with thermophysical experiment

In this study,a new linear friction welding(LFW)process,embedded LFW process,was put forward,which was mainly applied to combination manufacturing of long or overlong loadcarrying titanium alloy structural components in aircraft.The interfacial plastic flow behavior and bonding mechanism of this process were investigated by a developed coupling EulerianLagrangian numerical model using software ABAQUS and a novel thermo-physical simulation method with designed embedded hot compression specimen.In addition,the formation mechanism and control method of welding defects caused by uneven plastic flow were discussed.The results reveal that the plastic flow along oscillating direction of this process is even and sufficient.In the direction perpendicular to oscillation,thermo-plastic metals mainly flow downward along welding interface under coupling of shear stress and interfacial pressure,resulting in the interfacial plastic zone shown as an inverted“V”shape.The upward plastic flow in this direction is relatively weak,and only a small amount of flash is extruded from top of joint.Moreover,the wedge block and welding components at top of joint are always in un-steady friction stage,leading to nonuniform temperature field distribution and un-welded defects.According to the results of numerical simulation,high oscillating frequency combined with low pressure and small amplitude is considered as appropriate parameter selection scheme to improve the upward interfacial plastic flow at top of joint and suppress the un-welded defects.The results of thermo-physical simulation illustrate that continuous dynamic recrystallization(CDRX)induces the bonding of interface,accompanying by intense dislocation movement and creation of many low-angle grain boundaries.In the interfacial bonding area,grain orientation is random with relatively low texture density(5.0 mud)owing to CDRX.

前卡式液压千斤顶往复密封摩擦生热分析

针对千斤顶内油膜摩擦生热问题,提出了一种基于前卡式液压千斤顶内活塞往复密封摩擦生热分析方法。首先,在摩擦生热热源条件下,利用计算流体力学(CFD)数值计算规则,根据活塞往复运动方程进行了用户自定义函数(UDF)编程;然后,结合油液黏温特性建立了千斤顶往复密封摩擦生热仿真计算模型,并给出了千斤顶活塞往复运动油膜摩擦生热建模分析方法;最后,分析了千斤顶油缸内摩擦阻力,并对千斤顶摩擦生热特性进行了仿真分析,得到了千斤顶内温度场分布,并把关键点温度仿真结果与试验数据进行了对比、分析。研究结果表明:前卡式液压千斤顶进行多次张拉工作时,其温度上升趋势和理论分析以及仿真数据基本吻合,在初次张拉工作时,温度上升速度较快;但是在张拉15次后,温度达到29℃左右时,后续温度上升趋势基本相同。前卡式液压千斤顶内温度场分布规律可以为液压千斤顶密封材料选取、结构改进和张拉系统油压表温度补偿提供理论和技术方面的支持。

盘式制动器温度场的分析研究

针对制动器温度场的研究分析,建立额定起重量32 T的钳盘式制动器三维模型,同时在Workbench中添加制动器材料的各个参数,设置摩擦副间的接触关系,施加制动盘和制动衬片载荷、约束,对制动器制动过程产生的温度场进行仿真。使用LM算法建立包括时间、摩擦因数、制动压力、初始转速的多元非线性数学模型,通过Matlab进行回归分析。最终拟合结果和有限元仿真结果吻合,验证了起重机制动器温度模型的正确性。

搅拌摩擦焊过程热-力-流全耦合仿真:不同本构方程的仿真效果对比

本构方程是搅拌摩擦焊过程热-力-流全耦合仿真模型的重要部分。针对6 mm铝合金6061-T6板材FSW过程开展热-力-流全耦合仿真分析。为分析本构方程的形式对仿真效果的影响,在模型中分别采用Chen-Liu本构模型、Sellars-Tegart模型和Johnson-Cook模型,并对仿真结果进行对比分析。仿真结果表明,Chen-Liu模型计算得到的FSW温度场及流动场与实验结果的吻合程度均高于Sellars-Tegart模型和Johnson-Cook模型。究其原因,在搅拌头-工件界面附近的温度条件下,Sellars-Tegart模型和Johnson-Cook模型预测的流变应力较高,使得材料流动困难,搅拌头与工件之间的界面状态主要为滑动摩擦。相比之下,Chen-Liu模型能够体现材料在温度升高时的迅速软化现象,在搅拌头-工件界面附近的温度条件下,材料的剪切流变应力低于搅拌头/工件界面的摩擦应力,因而在摩擦作用下工件发生塑性流动,这降低了搅拌头/工件之间的滑动摩擦速度,从而使得滑动摩擦产热减少,且其减少量大于工件发生塑性流动产生的额外热量,从而使得采用Chen-Liu模型预测得到的焊接温度更低。综合来看,FSW过程温度场与材料流动速度场受材料本构模型影响归因于FSW的热-力-流全耦合效应。

惯性摩擦焊高温区温度特征仿真与实验研究

目的定量分析影响惯性摩擦焊接头质量的关键因素——焊接过程高温区的温度特征。方法选取TC4钛合金为研究对象,综合运用有限元仿真及界面组织观察的研究方法,分析确定惯性摩擦焊过程中高温区的温度特征。针对初始转速分别为1000 r/min及1200 r/min的2种惯性摩擦焊工况开展实验,并建立了热-力耦合有限元仿真模型对惯性摩擦焊过程进行仿真分析。结果仿真得到的温度分布与焊接过程摩擦界面附近的测温结果吻合良好,仿真模型与实验分析结果均表明,与初始转速为1000 r/min相比,初始转速为1200 r/min时的接头的飞边更大,2种焊接工况下仿真得到的轴向缩短量均与实验结果吻合良好,表明了仿真模型对TC4钛合金惯性摩擦焊热-力过程分析的准确性。结论在TC4钛合金圆棒样品惯性摩擦焊过程中,摩擦界面附近存在高温区,高温区内的温度呈现出芯部低、外围高的特点,最高温度约出现在沿半径方向1/2半径处。在初速转速为1000 r/min及1200 r/min的焊接工况下,芯部温度约为720℃与780℃,外围的最高温度分别约为850℃与920℃。接头组织观察结果进一步证实了仿真得到的高温区的温度数值的准确性。

6061-T6铝合金高速搅拌摩擦焊数值模拟

基于耦合欧拉-拉格朗日方法,建立了6061-T6铝合金薄板的高速搅拌摩擦焊数值模型,研究高速焊接工艺条件下的温度场及变形场特点,采用示踪粒子方法研究焊接区材料塑性流动规律。开展高速搅拌摩擦焊试验,分别从温度场、宏观样貌和内部缺陷对数值模型进行验证。结果表明,采用该模型能够准确描述高速搅拌摩擦焊过程的温度场及变形场,也能精准预测焊接缺陷出现的位置及尺寸。相较于常规搅拌摩擦焊,高速搅拌摩擦焊在焊接方向和横截面都具有更密集的温度梯度,塑性应变区域也较为集中,其热影响区更小。

2219-T8铝合金搅拌摩擦沉积增材初始进料阶段数值模拟研究

研究了高强铝合金2219-T8在搅拌摩擦沉积过程中初始进料阶段的温度、应变和塑性流动,并深入探讨了主轴转速和进料速度对材料流动性的影响规律。采用Arrhenius材料定律建立了三维有限元热力学模型。实验结果表明,在不同的工艺参数下,同一区域的沉积时间存在差异。在当前工艺参数设定下,主轴转速为350 r/min,进料速度为0.2 mm/s时,沉积速度最快,增材效率最高;随着主轴转速的增加,进料杆的升温速率增大,材料发生塑性变形的最高温度增加,应变速率也增大;随着进料速度的增加,材料流动性减弱,填补中空旋转工具与基板之间的间隙所需时间增加。

差厚铝合金2024∕7075搅拌摩擦焊的温度场数值模拟

利用Abaqus有限元软件,建立差厚7075和2024铝合金的有限元模型和改进热源模型,进行模拟搅拌摩擦焊的焊接过程,分析了不同厚度比的温度分布,以及对焊核区和热力影响区的宽度变化的影响,并验证了所建模型应用的可行性。结果表明,铝合金焊件中的温度峰值随着厚度比的变化而改变,且温度在铝合金板上呈不对称的倒“V”形分布,板材上的温度峰值随着板材厚度变大而减小。焊接过程中温度越高焊件上的热力影响区就越宽。较大的厚度比会使得焊件的热力影响区宽度和焊核区宽度偏大。模拟得到的温度值和试验数据比较,两者的误差在8%以内,验证了模型的可行性。

仿生制动盘表面温度场与应力场的计算机模拟

根据天然生物与生俱有的高效散热原理,设计三种可抑制温升,从而预防磨损和疲劳的仿生车辆制动盘,并建立三维计算模型。借助于有限元分析软件ANSYS,研究比较这三种表面形态的仿生制动盘和常规制动盘在紧急制动工况下,温度场和应力场的大小及变化趋势。结果表明,仿生制动盘能够降低制动盘表面的温度梯度和应力集中,从而可减小由于循环应力而导致的热疲劳趋势,其降低幅度从大到小依次为具有网格状凹槽的仿生制动盘、具有放射状凹槽的仿生制动盘和具有环形凹槽的仿生制动盘。摩擦生热降低和散热性的提高是温度梯度下降的主要原因。该模拟研究为今后仿生制动盘的优化设计和试验研究提供了重要参考依据。

基于摩擦功率法的列车制动盘瞬态温度场分析

针对在已有的制动盘瞬态温度场模拟中,摩擦表面摩擦生热热流密度的计算没有考虑摩擦热流在摩擦面上分布的差异,提出用摩擦功率法及摩擦副周向接触长度确定制动盘摩擦面摩擦生热热流密度的方法。根据温度场分析时的载荷和边界条件,建立制动初速200 km.h-1条件下列车紧急制动过程中制动盘瞬态温度场的有限元模型并进行数值分析,结果表明:在制动过程中,制动盘高温区域集中在制动盘摩擦半径至外径区域,温度最高可达289.9℃;摩擦热流对盘体内径附近区域的影响较小;能反映出制动盘和闸片周向接触长度径向分布对制动盘表面温度场分布产生的影响。

低温环境下轮轨材料滚动磨损模拟试验研究

针对高寒地区温度环境特点,设计了低温环境轮轨磨损模拟试验装置,实现了低温环境下轮轨滚动磨损模拟试验,对比研究了室温（23~25℃）及–60℃试验温度下轮轨试样的滚动摩擦系数、磨损量、硬度及表面损伤等变化情况.结果表明：与室温环境条件相比,低温环境条件下轮轨材料的摩擦系数、磨损量均明显增大;低温环境下试验后轮/轨硬度比较室温环境下增大,车轮硬化情况严重;随温度的降低,轮轨试样的表面磨痕呈现出不同的损伤机制;所设计低温环境轮轨磨损模拟试验机可用来评价不同低温环境下车轮与钢轨材料摩擦磨损行为.

热量自适应搅拌摩擦焊热源模型

当前采用的温度场热源数值模型在准确表征焊接过程材料性能和产热机制与温度变化关系上存在困难。依据摩擦学原理,以材料屈服强度ReL为产热基本参数建立新型热源模型,产热量随温度、材料性能改变,实现搅拌摩擦焊产热自适应过程,更准确地描述了搅拌摩擦焊过程物理现象的本质。温度场试验与模拟结果的比较表明,该热量自适应热源模型具有较高的计算精度。

搅拌头压入速度和停留时间对2024铝合金搅拌摩擦焊接温度场的影响

针对2024铝合金对接焊,基于Abaqus软件平台,建立了搅拌摩擦焊接过程的有限元分析模型。模拟了焊接过程中搅拌头的压入、停留过程以及整个温度场的瞬态变化。模拟结果表明,降低搅拌头的压入速度以及延长搅拌头的停留时间都能使焊接压入端的温度峰值升高,但压入速度的影响相对不大。适当延长停留时间能使搅拌头压入端达到材料熔点温度的70%左右,有利于获得良好的焊接质量;但停留时间也不能过长,否则会造成焊接过程中的温度过高,甚至超过焊材的熔点。

GH4169高温合金惯性摩擦焊接温度场的数值模拟

根据惯性摩擦焊接过程的特点,结合摩擦学理论在研究了摩擦焊接摩擦面生热变化规律的基础上,建立了一个基于二维轴对称的有限元法传热计算模型。利用该模型可以模拟计算惯性摩擦焊接瞬态温度场的分布。并对同质材料GH4169-GH4169焊接进行了实例计算。用热电偶点焊在工件的表面的方法对GH4169-GH4169焊接过程中的温度变化进行了计算机实时多点测量。结果证实:计算结果与试验数据符合良好。从而该模型可为进一步研究惯性摩擦焊接应力场、应变场和缩短量以及优化焊接工艺参数提供有效的依据。