加热、冷却下变物性梯度功能材料板瞬态热应力

用非线性有限元法分析由ZnO2和Ti-6Al-4V组成的变物性梯度功能材料板在加热、冷却过程中的瞬态热应力问题,检验方法的正确性,给出不同力学边界条件下该材料板的瞬态热应力场分布,并与常物性时的结果进行比较。结果表明,考虑变物性比常物性时的最大拉应力减少26％,最大压应力减少23．2％;在冷却初瞬时,陶瓷侧出现很大拉应力;此外,材料组分的分布形状系数M的变化和力学边界条件对该材料板的加热、冷却瞬态热应力场分布的影响显著。此结果为该材料的设计、制备提供了准确的理论计算依据。     

非均匀温度场下变物性二维功能梯度材料板的瞬态热应力分析

研究了非均匀温度场下变物性二维功能梯度材料板的瞬态热应力分布问题。并且建立了Al1100-Ti6Al4V-ZrO_2的二维功能梯度材料板的结构模型,构造了二维功能梯度板的有限元求解方法,计算得到了:1)二维功能梯度材料板在不同时刻的瞬态热应力分布规律;2)变物性(组分系数沿板长度和宽度方向变化)二维功能梯度材料板的瞬态热应力分布;3)非均匀温度场下(线性温度分布、非线性温度分布及周期性温度分布)的二维功能梯度材料板的瞬态热应力分布。     

换热边界下梯度功能材料板稳态热应力

用有限元和辛普生法研究了由ZrO2和Ti-6Al～4V组成的梯度功能材料板的稳态热应力问题，检验了孔隙度P为零时数值模拟模型的正确性，给出了对流换热边界下的稳态热应力场分布。结果表明：材料组分的分布形状系数M、孔隙度P、对流换热系数和环境介质温度的变化对该材料板的稳态热应力场分布均有明显的影响；在设定条件下，当P=0时，该材料无限自由长板在金属和陶瓷附近板内为压应力，而在板中部为拉应力；当A=3.99时，陶瓷侧拉应力最大。     

换热边界下梯度功能材料板稳态温度场研究

用有限元法分析了由ZrO2和Ti-6Al—4V组成的梯度功能材料板在对流换热边界条件下的稳态温度场问题，检验了方法的正确性，给出了对流换热边界下的稳态温度场分布。结果表明：材料组分的分布形状系数M、孔隙度P、对流换热系数和环境介质温度的变化对梯度功能材料板的稳态温度场分布均有明显的影响。此结果为材料设计和进一步的热应力分析提供了准确的计算依据。     

基于有限元法分析影响钻机液压刹车盘温度场和应力场的因素

针对石油钻机液压刹车盘瞬态温度场,建立了有限元仿真分析模型,并运用ABAQUS对模型进行热-机耦合仿真计算,重点研究了参数改变对温度场和应力场分布的影响。在不改变刹车条件的情况下,仅仅改变对流换热系数、制动时间、热膨胀系数、热传导系数、摩擦因数等参数,得到的温度场、应力场分布及相关结论是一致的;对于刹车盘,降低整体的温度和应力,可以通过增大对流换热系数、减小热膨胀系数、增大热传导系数、减小摩擦因数来实现。仿真分析结论为研制性能更好的刹车盘提供理论指导。     

城市轨道交通车辆踏面制动热应力仿真分析

分析了城轨列车在踏面制动方式下车轮踏面热疲劳裂纹产生的机理,并建立了车轮制动过程瞬态温度场三维有限元模型,采用整体输入热流和对流换热的简化模式为基础的传统理论的热应力计算方法,计算车轮在连续两次紧急制动工况下的热温度场及热应力场,为确定城轨列车制动方式及列车制动距离等技术规范提供计算依据。     

矿井提升机制动盘温度场与应力场的数值模拟

基于热传导理论和热弹性力学理论,对矿井提升机的制动过程进行了数值模拟。分析了制动过程中制动盘表面上边界条件的变化规律,并着重探讨了制动过程中制动盘表面对流换热系数的计算方法。在变物性的前提下,依据实际的几何尺寸,建立矿井提升机制动盘循环对称三维有限元模型,研究不同制动工况下制动盘的温度场和应力场分布。文中还对热应力的计算方法进行了探讨,并分析比较了各种方法的优劣性。研究结果表明:制动盘的温度应力分布与制动初始速度和加速度的大小密切相关。本研究为提升机提升速度和制动加速度的优化和高性能制动系统的设计开发提供了重要的参考依据。     

基于STAR-CCM+与ABAQUS的排气歧管流场及热应力分析

基于STAR-CCM+与ABAQUS软件,对排气歧管的稳态流动进行了数值模拟,计算各歧管流动压力损失、压损不均匀度、出口端面速度均匀度。采用流固耦合方法计算排气歧管的温度场及热应力,首先利用STAR CCM+对流体进行稳态计算,利用同时进气法计算流场温度分布和壁面对流换热系数,将流场外壁面热边界条件映射至排气歧管固体内壁面,固体外壁面的热边界条件对流换热系数和环境温度设定为定值,采用ABAQUS软件计算排气歧管的温度场和热应力。     

三维热弹耦合场作用下汽车制动鼓的性能分析

将制动中的辐射换热等效为对流换热,建立汽车鼓式双领蹄制动器三维热弹耦合模型。考虑制动摩擦力矩的影响,对多次连续制动工况下的制动鼓瞬态温度场、应力场、变形场进行有限元数值模拟,获得制动鼓的内外表面的温度、热应力及热机耦合强度变化规律。     

圆柱齿轮淬火过程温度场的计算机模拟

应用有限元分析软件ANSYS模拟了材料为20CrMnTi复杂结构圆柱内齿轮淬火冷却过程的温度场,得到了温度场随时间的分布关系;在模拟中考虑了热物性参数和表面换热系数的非线性和相变,模拟结果与实际过程相符合,为进一步精确计算淬火过程中的热应力和残余应力打下了基础.     

Simulation of thermal stresses due to grinding

An efficient finite element procedure has been developed to calculate the temperatures and stresses arising due to a moving source of heat. The procedure is applied to calculate the thermal stresses produced in hardened steels during grinding. The thermal load during grinding is modeled as a uniformly or triangularly distributed, 2D heat source moving across the surface of a half-space, which is insulated or subjected to convective cooling. The grinding of elastic and elastic–plastic workpiece materials has been simulated. The calculated transient stresses and temperatures in an elastic solid are found to be in good agreement with prior analytical and numerical results. In an elastic–plastic workpiece material, for which no analytical solution is available for the residual stress distributions, the finite element calculations show that the near surface residual stress is predominantly tensile and that the magnitude of this stress increases with increasing heat flux values. Based on an analysis of the effects of workpiece velocity, heat flux magnitude and convective cooling, on the residual stress distributions in an elastic–plastic solid, it is seen that the calculated thermal stress distributions are consistent with experimentally measured residual stresses on ground surfaces. Furthermore, the results explain often cited observations pertaining to thermally induced grinding stresses in metals.     

Three-dimensional solution for transient thermal stresses of functionally graded rectangular plate due to nonuniform heat supply

This paper is concerned with the theoretical treatment of transient thermoelastic problem involving a functionally graded rectangular plate due to nonuniform heat supply. The thermal and thermoelastic constants of the rectangular plate are assumed to vary exponentially in the thickness direction. The transient three-dimensional temperature is analyzed by the methods of Laplace and finite cosine transformations. We obtain the three-dimensional solution for the simple supported rectangular plate. Some numerical results for the temperature change, the displacement and the stress distributions are shown in figures. Furthermore, the influence of the nonhomogeneity of the material is investigated.     

复合恒温构件热变形控制技术研究

研究了复合恒温构件在机床热变形控制中的应用,在分析相变热传导的基础上,研究了包含相变过程的二维传热特性,利用自适应变网格有限方法计算相变材料复合恒温构件机床立柱及主轴箱的温度场和热变形值,并将之与实测值比较,二者基本吻合。试验结果对精密数控机床热变形控制具有一定的参考价值。     

INDUCTION-HEATED TOOL MACHINING OF ELASTOMERS—PART 1: FINITE DIFFERENCE THERMAL MODELING AND EXPERIMENTAL VALIDATION

Experiments and finite difference thermal modeling of the induction-heated tool for end milling of elastomers are investigated. Three sets of experiments are designed to calibrate the contact thermocouple for the tool tip temperature measurement, study the effect of tool rotational speed on induction heat generation and convective heat transfer, and measure the tool temperature distribution for finite difference inverse heat transfer solution and validation of modeling results. Experimental results indicate that effects of tool rotation on induction heat generation and convective heat transfer are negligible when the spindle speed is below 2000 rpm. A finite difference thermal model of the tool and insulator is developed to predict the distribution of tool temperature. The thermal model of a stationary tool can be expanded to predict the temperature distribution of an induction-heated rotary tool within a specific spindle speed range. Experimental measurements validate that the thermal model can accurately predict tool tip peak temperature.     

Some studies on temperature profiles in AISI 304 stainless steel sheet during laser beam welding using FE simulation

The investigation of transient temperature profiles of a weld joint produced by the laser welding process is presented. A three-dimensional finite element model is developed using a commercial finite element code ANSYS in order to obtain the behavior of temperature field and molten pool shape during the welding process. A three-dimensional conical Gaussian heat source is employed as a heat source model for performing a non-linear transient thermal analysis. The temperature-dependent material properties of AISI 304 stainless steel sheet are taken into account, which has a great influence on the temperature fields indicated by the simulation results. The effect of latent heat and the convective and radiative boundary conditions are also included in the model. A series of laser welds are performed using a 2-kW continuous wave Nd:YAG laser welding system. The experimental trials are conducted by varying the laser input parameters namely beam power, welding speed, and beam incident angle to validate the model. The results show that there is a good agreement between the finite element simulation and the experimental observations.     

FEM-based prediction of workpiece transient temperature distribution and deformations during milling

In high-speed dry milling of thin-walled parts, the cutter-workpiece temperature rises asymptotically with cutting speed, causing excessive cutter tooth wear and workpiece thermal expansion, which in turn reduces the cutter life and produces dimensional and geometrical variabilities in the machined part. Therefore, a basic understanding of the thermal aspect of machining and the effecting parameters is essential for achieving better part quality with improved productivity. This paper presents a transient milling simulation model to assist manufacturing engineers in gaining in-depth understanding of the thermomechanical aspects of machining and their influence on resulted part quality. Based on the finite-element method approach, the model can predict transient temperature distributions and resulted elastic-plastic deformations induced during the milling of 2.5D prismatic parts comprising features like slots, steps, pockets, etc. The advantages of the proposed model over previous works are that it (1) performs feature-based machining simulation considering transient thermomechanical loading conditions; (2) allows modeling the effects of coolant on convective heat transfer rate; and (3) considers the nonlinear behavior of the workpiece due to its changing geometry, inelastic material properties, and flexible fixture–workpiece contacts. The prediction accuracy of the model was validated with experimental results obtained during the course of the research work. A good agreement between the numerical and experimental results was found for different test cases with varying part geometries and machining conditions.     

INDUCTION-HEATED TOOL MACHINING OF ELASTOMERS—PART 1: FINITE DIFFERENCE THERMAL MODELING AND EXPERIMENTAL VALIDATION

ABSTRACT

Experiments and finite difference thermal modeling of the induction-heated tool for end milling of elastomers are investigated. Three sets of experiments are designed to calibrate the contact thermocouple for the tool tip temperature measurement, study the effect of tool rotational speed on induction heat generation and convective heat transfer, and measure the tool temperature distribution for finite difference inverse heat transfer solution and validation of modeling results. Experimental results indicate that effects of tool rotation on induction heat generation and convective heat transfer are negligible when the spindle speed is below 2000 rpm. A finite difference thermal model of the tool and insulator is developed to predict the distribution of tool temperature. The thermal model of a stationary tool can be expanded to predict the temperature distribution of an induction-heated rotary tool within a specific spindle speed range. Experimental measurements validate that the thermal model can accurately predict tool tip peak temperature.