新FM锻造法压实疏松缺陷效果的研究

通过模拟试验 ,对新 FM锻造法锻后钢锭内部疏松缺陷的效果及机理进行了试验研究 ,通过各种检测指标 ,得出了该工艺与常规工艺在不同变形参数条件下所需锻比的当量关系 ,为该新工艺在实际生产中应用时工艺参数的确定提供了试验依据。     

Numerical and experimental investigation into effect of temperature field on sensitization of Alloy 690 butt welds fabricated by gas tungsten arc welding and laser beam welding

This study examines the effects of the temperature field on the sensitization of Alloy 690 butt welds fabricated using the gas tungsten arc welding (GTAW) method and the laser beam welding (LBW) method, respectively. The welding thermal cycles of the two welding methods are simulated using ANSYS software based upon a moving heat source model and the high-temperature thermal physical property data maintained in the JMatPro database. The validity of the numerical model is confirmed by comparing the simulation results with the corresponding experimental findings. It is found that the agreement between the numerical results for the temperature field and the experimental temperature measurements by utilizing the value of the thermal diffusivity (α) in the thermal model for the GTAW and LBW weldments. In addition, it is shown that the LBW weldment experiences a more rapid heating and cooling effect than the GTAW weldment, and therefore has both a smaller heat-affected zone (HAZ) and a narrower sensitization region. Overall, the simulation results presented in this study are found to be in good agreement with the experimental findings. Thus, the validity and general applicability of the thermal welding model are confirmed.     

凝固模拟所用砂型热物性参数的测定和研究

采用反算法对砂型的热物性参数进行实验研究，并用自制的实验测温装置对工厂实际生产的硅砂的热物性参数进行测量，测量值得到模拟结果的验证；为本厂生产汽车后制动鼓铸件进行数值模拟，提供了实用和可靠的热物性参数。     

Gleeble3500热机械模拟试验系统及其数控热扭转单元

热机械模拟是在不同加热一受力的高温动态条件下研究材料力学性能、变形行为和物理冶金的经济而高效的实验手段。概述了热机械物理模拟中所常用的单轴加载模式,在大应变量试验条件下的应用局限以及扭转模拟试验所具备的优势和特点;介绍了Gleeble3500热机械模拟试验系统的数控热扭转单元及其性能参数;讨论了热扭转模拟技术在冶金产品及其工艺研发中的应用。     

某汽轮机叶片材料热变形行为及锻坯参数优化

为提高某叶片锻件质量和生产效率、减少模具磨损,采用热模拟试验研究了叶片材料的热变形行为,建立了材料的高温流动应力方程;以此方程作为材料模型,对叶片的锻造过程进行了数值模拟,优化了制坯工艺参数.试验分析表明,该材料热变形行为符合双曲正弦函数关系;数值模拟结果表明,采用叶根与叶冠成40°角的坯料较优,成形质量与成形载荷对坯...     

Thermal Expansion,Elastic and Magnetic Properties of FeCoNiCu-Based High-Entropy Alloys Using First-Principle Theory

The effects of V, Cr, and Mn on the magnetic, elastic, and thermal properties of FeCoNiCu high-entropy alloy are studied by using the exact muffin-tin orbitals method in combination with the coherent potential approximation. The calculated lattice parameters and Curie temperatures in the face-centered-cubic structure are in line with the available experimental and theoretical data. A significant change in the magnetic behavior is revealed when adding equimolar V, Cr, and Mn to the host composition. The three independent single-crystal elastic constants are computed using a finite strain technique, and the polycrystalline elasticity parameters including shear modulus, Young’s modulus, Pugh ratio, Poisson’s ratio, and elastic anisotropy are derived and discussed. The effects of temperature on the structural parameters are determined by making use of the Debye–Grüneisen model. It is found that FeCoNiCuCr possesses a slightly larger thermal expansion coefficient than do the other alloys considered here.     

MEASUREMENT AND APPLICATION OF PHYSICAL PARAMETERS IN UNSTEADY HEAT CONDUCTION

1.IntroductionPhysicalsimulatingandnumericcalculatingaremainrespectsofapplicationofcomputerinscienceandtechnology.Theaccuracyofsimulatingandcalculatingisaprincipleproblemforstudyanddiscussion.Obviously,toadoptareasonablemodelandmethodforcalculatingtemperaturefieldisaessentialpremisetopledgeaccuracyofcalculation.Oncethemodelforcalculationhasbeenestablished,itisadecisivefactortoselectthevaluesofphysicalparameters.Itisnecessarytoobtaintheparameterssuchasspecificheat,thermalconductivity,latenthea…     

凝固模拟热物性参数数据库系统的研究与开发

针对凝固模拟中热物性参数数据量大、种类多,数据查找困难、更新不便的问题,研究开发了一套热物性参数数据库系统.系统包括参数录入、数据更新、数据查询和液固相线温度计算模块,实现了对参数数据的集中有效管理.     

The numerical analysis of thermal effect and weld shaping of DE-GMAW under composite heat

The action of the composite heat source model in DE-GMAW has been carried out according to the characteristics of the DE-GMA W process,and the distribution of surface and body heat source was analyzed.The weld temperature field distribution has been derived from the appropriate boundary conditions and the thermal physical property parameters by COMSOL software.The effects of the positions of the surface and body heat source on the crosssectional shape were investigated by studying the experimental welding thermal cycle curve.The simulated results are fully compliant with the experimental data under the same conditions.This illustrates that the composite heat source model is correct.It reflects the thermal mechanism of DE-GMAW process,and reveals the internal influence of weld shaping.     

基于Matlab磁流变阻尼器Bouc-Wen模型的参数识别

为解决磁流变阻尼器Bouc-Wen模型参数识别方法复杂、不易实现的难题,采用Matlab中的Simulink Design Optimization工具,在Simulink中搭建Bouc-Wen模型,利用磁流变阻尼器力学特性试验得到的试验数据,对Bouc-Wen模型进行参数识别。结合各参数的物理意义对得到的识别结果进行分析,确定出阻尼力调控参数,并在Matlab中进行线性拟合,得到其与电流的函数关系。最后搭建考虑阻尼力调控参数的Bouc-Wen仿真模型,用不同幅值和频率的正弦激励进行仿真,并将仿真结果和试验数据进行对比。结果表明:仿真结果和试验数据能够很好的吻合,得到的参数满足要求。     

Cr9Mo钢热压缩试验结果的标定及验证

在Gleeble 1500D热模拟机上进行了Cr 9Mo钢的热压缩试验。通过对变形前后试样轮廓尺寸的定量分析发现,仅考虑摩擦的影响来进行试验结果的标定是不充分的,标定结果存在较大误差,因为试样上温度梯度的影响不可忽略。使用平均摩擦系数和试验中监测的温度梯度参数,通过有限元软件模拟不同变形条件下的热压缩过程,进而使用迭代法标定了试验结果。对物理试验和有限元数值模拟的结果比较证明,在进行热压缩试验数据标定时,同时考虑摩擦和温度梯度两个因素,可取得较高精度的结果。     

DSC测量中基线的准确确定

DSC分析作为材料测试中的重要方法之一,常用于分析材料在加热及冷却过程中热量、热焓及比热容的变化等物理参数,具有其他方法不可替代的作用.主要介绍了DSC测量试验中基线的测量与应用效果,对减小误差起到关键作用.结果证明,不同质量的坩埚会对基线产生不同的影响,并进一步影响到试验数据的分析.     

The numerical analysis of thermal effect and weld shaping of DE-GMAW under composite heat source

The action of the composite heat source model in DE-GMAW has been carried out according to the characteristics of the DE-GMAW process,and the distribution of surface and body heat source was analyzed.The weld temperature field distribution has been derived from the appropriate boundary conditions and the thermal physical property parameters by COMSOL software.The effects of the positions of the surface and body heat source on the crosssectional shape were investigated by studying the experimental welding thermal cycle curve.The simulated results are fully compliant with the experimental data under the same conditions.This illustrates that the composite heat source model is correct.It reflects the thermal mechanism of DE-GMAW process,and reveals the internal influence of weld shaping.     

汽车尾气后处理系统铝泵体的精锻工艺智能优化

为了提高铝泵体精锻过程中的材料利用率和模具使用寿命,建立了目标参数与工艺参数的响应面模型,提出了基于人工蜂群算法的参数优化方法.介绍了汽车尾气后处理系统中铝泵体的中间体和坯料,并设计了开式模锻模具.使用中心复合实验法设计了4因素5水平的30组实验,基于Deform-3D有限元软件得到了实验结果.使用二阶响应面模型建立了...     

中高碳钢试样堆焊冷却过程应力场数值模拟

采用红外热像仪和X射线应力仪分别测定了中高碳钢堆焊过程的温度场和残余应力场，根据实验数据和材料的物理、力学参数，采用二维有限元计算方法，建立了堆焊应力场模型，根据这一模型，对堆焊冷却过程应力进行了数值模拟分析。模拟结果表明：在堆焊冷却过程中，当发生马氏体相变时，试样表面出现压应力，随着冷却时间的延长，试样表面开始出现较大的拉应力，并保持到室温。     

An investigation into the forging of Bi-metal gears

This paper introduces a method for the production of bi-metal gears using the forging technique. To study the process, model materials of copper (tooth ring material) and lead (core material), were used for both experimentation and simulation. Firstly, experimental setup and test procedures are introduced and the bi-metal gears are forged with different thicknesses of the outer ring material. A simplified FE model is established based on the symmetry of a gear forging process, which enables the 3D FE analysis to be carried out in an efficient manner. The material flow and thickness distribution of the experimentally forged bi-metal gears are analysed and compared with FE predictions. The effect of friction on the axial lock caused by the material flow of the forged gears is also studied. Finally, simulations of different combinations of the inner core and outer ring materials, specifically steel (ring material), copper (ring and core material) and lead (core material) are performed. The numerical and experimental data showed that: thin rings can deform excessively, affecting the structure of the gear; and that both tooling friction and flow stress can significantly affect the relative material flow between the core and the ring.     

Performance Analysis and Modeling of Thermally Sprayed Resistive Heaters

Many processes and systems require hot surfaces. These are usually heated using electrical elements located in their vicinity. However, this solution is subject to intrinsic limitations associated with heating element geometry and physical location. Thermally spraying electrical elements directly on surfaces can overcome these limitations by tailoring the geometry of the heating element to the application. Moreover, the element heat transfer is maximized by minimizing the distance between the heater and the surface to be heated. This article is aimed at modeling and characterizing resistive heaters sprayed on metallic substrates. Heaters were fabricated by using a plasma-sprayed alumina dielectric insulator and a wire flame-sprayed iron-based alloy resistive element. Samples were energized and kept at a constant temperature of 425 °C for up to 4 months. SEM cross-sectional observations revealed the formation of cracks at very specific locations in the alumina layer after thermal use. Finite-element modeling shows that these cracks originate from high local thermal stresses and can be predicted according to the considered geometry. The simulation model was refined using experimental parameters obtained by several techniques such as emissivity and time-dependent temperature profile (infra-red camera), resistivity (four-probe technique), thermal diffusivity (laser flash method), and mechanical properties (micro and nanoindentation). The influence of the alumina thickness and the substrate material on crack formation was evaluated.     

采用近终形铸造制备高强6xxx铝合金控制臂

采用近终形铸锭配合热锻工艺制备高强6xxx铝合金控制臂。首先设计近终形铝合金锭坯的形状,采用Procast商业软件模拟研究近终形铝合金铸锭的铸造过程。结果表明,近终形铝合金铸锭的收缩行为与铸锭形状相关,经模拟计算优化后,铸造出无缺陷的近终形6xxx铝合金铸锭。为了获得优异的锻件性能,研究了6xxx铝合金的热压缩行为。结果表明,锻件组织中的亚晶百分数与Z参数值相关;中等Z参数（1．09×10^16MS^-1）有利于获得较高的亚晶百分数,从而保证锻件产品具有更优的性能。     

阀体的锻造工艺改进

针对阀体锻造后存在的质量问题如裂纹、端面缩孔、折叠以及参差不齐等缺陷进行分析讨论,认为:在锻造过程中,由于阀体锻件端面温度比较低,截面变化比较大,材料的分配不够合理,导致了金属流动困难是造成质量问题的主要原因.通过对其进行工艺改进--即采用"两个一连"的锻造工艺,之后拔出中间圆棒部分,再用气割的方法将其一分为二.工艺改进后,用料减少了,原来存在的裂纹、缩口、以及接头处参差不齐的质量问题得到了彻底地解决,实验证明本方案是一种切实可行的好方法.