ZG20Mn2钢摇臂断裂分析

通过宏，微观检验，成分分析及力学性能测试，得出ＺＧ２０Ｍｎ２钢摇臂断裂是由于晶粒粗化和铸造缺陷的存在使强度和塑性急剧下降所致。     

MG750／1800-WD滚筒式采煤机摇臂壳体的有限元分析

大功率滚简式采煤机摇臂壳体承受载荷大,受力状况复杂,其结构的合理与否直接会影响整机的使用寿命和生产效率。本文采用有限元软件Ansys／Workbench对MG750／1800-WD型采煤机的摇臂壳体进行了静力学分析,获取了壳体的应力和应变分布特性,为大功率采煤机摇臂壳体的结构设计和改进提供了理论参考。     

轮类壳体铸造工艺研究及质量控制

本文介绍了某轮类壳体铸件的铸造工艺设计和制造过程。通过相对合理的工艺设计,并通过实际生产检验来验证工艺的合理性,成功进行了产品的开发,并对产品的生产过程进行了质量控制,取得了很好的效果。     

基于多场耦合的采煤机摇臂壳体分析

 为对大型装备壳体类零件进行创新设计,建立了大采高采煤机铸、锻、焊结合摇臂壳体的柔性虚拟样机耦合模型,研究截割部齿轮系统热平衡过程,确定温度载荷和边界条件,加载动力学仿真软件ADAMS输出的载荷文件．应用有限元软件ANSYS对摇臂壳体进行温度 结构耦合分析及疲劳寿命预测,得到了壳体的温度场及结构场云图,发现了摇臂壳体疲劳寿命的薄弱环节,并提出了改进措施．结果表明,温度场的影响使摇臂壳体的最大应力增加了11.707%.研究结果为大型壳体类零件的设计与优化提供了明确的量化依据,可有效提高该类零件的工作可靠性．     

发动机活塞裙铸造过程模拟及工艺优化

目的优化发动机活塞裙铸件铸造工艺。方法采用UG等软件设计活塞裙铸件浇注系统以及采用MAGMA铸造仿真软件对铸造工艺进行仿真预测,分析铸件凝固温度场,预测缩孔、疏松等铸造缺陷,进一步优化铸造工艺。结果铸件整体上实现了自下而上的顺序凝固,虽然通过冒口获得了一定程度的补缩,但凝固温度梯度不明显,冒口疏松缺陷依然延伸至铸件上端面。通过合理设置冷铁,增加冒口和内浇口数量,从而实现铸件顺序凝固,使补缩效果更为明显,可有效降低缩孔、疏松缺陷。结论采用MAGMA铸造仿真软件分析凝固过程并预测缺陷,通过改进和优化工艺,可以有效预防活塞裙铸件缺陷的产生,提高铸件合格率。     

挤压铸造替代压铸制造的铝合金壳体的工艺改进策略

本文主要探讨挤压铸造替代压铸制造的铝合金壳体工艺改进方法。由于在实际产品加工、生产过程中,发现某压铸铝合金壳体件在铸造过程中存在气孔等瑕疵。因此,本文通过对该铝合金壳体件存在气孔铸造缺点的具体成因进行分析,最终决定采用挤压铸造方法取代压铸制造方法,对铝合金壳体加工生产技术工艺进行优化改进。实践研究表明,采用挤压铸造技术工艺进行产品加工、生产,能够满足生产技术质量标准,力学性能较好,产品无明显的结构性缺陷,符合相关铸造技术要求。     

基于计算机模拟的支架铸钢件铸造工艺设计及优化

目的对ZG270-500铸钢支架的铸造工艺进行优化设计,以达到工艺简单、成本低、操作简便、质量良好等要求。方法使用三维CAD软件和铸造模拟软件对相应铸造工艺方案进行了三维建模和铸造过程的模拟。针对工艺初始浇注系统设计了正放、倒放,底注式、阶梯式共4种不同组合的浇注方案。在对充型温度场进行模拟后,选择了倒放阶梯式与正放底注式浇注系统进行后续模拟。在对凝固进行模拟后,最终选择了正放底注式的方案并进行后续优化。在设计补缩系统时,通过多次调整冒口的位置与尺寸,以及冷铁的位置、尺寸与形状,达到工艺优化的效果。结果 4种初始方案中,倒放阶梯式浇注系统有利于顺序凝固,正放底注式浇注系统较为经济环保。凝固过程中,正放底注式浇注系统的疏松疏孔液相孤立区存在于铸件顶部,有利于补缩。初始补缩系统有效补缩了顶面两孔中心缺陷,优化后可使顶板和肋板的连接处,凝固最晚区域的缺陷大为改善。结论模拟表明,最终方案可基本消除铸件中的缺陷,保证铸件的质量与良好的工艺性。     

某产品组合壳体机加工艺改进

某产品为分体组合结构,由上壳体和下壳体组成,采用螺纹连接,其中下壳体为装配焊接件,结构较为复杂,且组合壳体又有较高同轴度精度要求,在加工时易出现同轴度超差,加工废品率较高。 通过优化调整加工工艺,减少装夹次数,消除了累积装夹误差;通过调整装夹定位基准,改进夹具结构,提高了装夹精度;通过延长下壳体套筒焊接后自然时效时间,消除焊接残余应力,避免了因焊接应力引起的壳体加工变形;通过优化切削参数,降低切削力,防止了下壳体装配件薄壁套筒的加工变形。 通过以上工艺技术改进,提高了壳体加工精度,使组合壳体同轴度加工精度满足了产品设计要求。     

基于ProCAST的ZL114A尾段壳体凝固成形数值模拟与工艺优化

目的 针对ZL114A尾段壳体研制需求,利用低压充型液态成形工艺与数值仿真计算,预测疏松缺陷分布位置及严重程度,通过改进工艺来减少疏松缺陷,进而提高生产合格率。方法 基于Pro CAST软件对ZL114A尾段壳体低压充型凝固过程进行仿真计算,分析充型凝固过程中的流动场与温度场分布、充型时间、流动长度与凝固时间,预测疏松缺陷分布位置及严重程度,结合枝晶相干点双电偶热分析法测试结果,对低压充型工艺进行设计优化。结果 由尾段壳体凝固疏松缺陷的仿真计算结果与枝晶相干点温度测试结果可知,低压充型增压速度得到提高,保压时间有所延长,对安装凸台冷铁材质与厚度进行设计优化后,疏松缺陷得到显著改善。结论 通过数值仿真计算指导了铸造工艺设计,制备得到了满足技术指标要求的ZL114A尾段壳体。     

镁合金挤压铸造凝固过程数值模拟

利用有限元法对镁合金挤压铸造凝固过程进行数值模拟,分析了铸件的凝固收缩和凝固时间,预测铸件可能发生缺陷的位置,对比挤压压力对铸件缺陷的影响。 结果发现,与重力铸造相比,挤压铸造的凝固收缩小,铸件在挤压铸造的压力作用下可缩短凝固时间;缺陷模拟结果与实验相符,加大挤压铸造压力有助于减少缺陷的产生。     

高强钢控制臂件冲压工艺优化及稳健性分析

为获得高强钢控制臂件冲压工艺参数最优解,提高冲压工艺稳健性,基于6sigma稳健设计理论,采用数值模拟方法分析预成形模具间隙、局部翻边模间隙、预成形压边力、摩擦系数、板料轮廓尺寸等对拐角处材料减薄率的影响规律;将坯料位置、料片厚度、摩擦系数、塑性应变比、屈服强度、抗拉强度、板料尺寸等作为噪声变量输入,分析工艺的稳健性;根据敏感性分析结果,选用局部翻边模间隙、预成形模具间隙为变量,3σ水平设为目标,成形过程能力Cp值为1.0,进行优化计算;最后采用优化后的局部翻边模间隙、预成形模具间隙值,其他噪音变量不变,再次进行稳健性分析.研究发现,影响控制臂局部过度减薄甚至开裂的主要因素为预成形模具间隙及局部翻边模具间隙.根据模拟结果试模,零件的壁厚分布与模拟结果相比,最大误差小于6%.通过对关键参数的敏感性分析以及考虑噪声因素的稳健性分析,优化工艺参数后,成形质量水平提高,成形结果可靠.     

电磁超声横波测量连铸钢坯壳厚度

为解决连铸坯壳厚度在线检测问题,提出采用电磁超声横波反射法检测连铸坯壳厚度。对电磁超声横波换能器的激发和接收过程进行模拟仿真,分析横波在连铸坯中的传播情况,获得横波在连铸钢坯内固液两相区分界面处的反射回波。以坯壳厚度为10～50 mm的Q460连铸小方坯为研究对象,通过有限元仿真软件COMSOL,仿真得出温度在800～1300℃范围内时横波速度随温度的变化曲线。根据被测对象内部的温度场分布,得出坯壳内平均声速。利用回波时间与平均声速计算坯壳厚度。实验证明,上述方法可用于测量连铸坯壳厚度,当声时测量误差在1～2μs时,厚度测量误差为2～5 mm。     

ProCAST软件在熔模铸造工艺优化中的应用

为解决企业生产中某精铸件存在的缺陷问题,利用数值模拟软件ProCAST对其充型过程和凝固过程进行模拟,并预测缩孔和缩松的存在情况.根据数值模拟的结果对该铸件工艺方案进行相应的改进,显著降低了缩孔和缩松缺陷,并提高了产品的合格率.应用表明:铸造模拟软件能够准确地预测充型凝固过程中可能产生的缺陷,从而辅助工艺人员进行工艺优化.     

脱硫泵叶轮铸造工艺的优化设计

脱硫泵叶轮的铸造成型由于铸件结构扭曲大,材质脆性高在铸造行业是一个难题,本文通过铸造工艺优化来避免铸造缺陷的产生,从而使铸件达到要求.     

连铸板坯凝固过程的数值模拟

为得到连铸坯凝固末端的液相穴分布,以便选取轻压下参数,依据实际生产中二冷边界换热条件,采用有限元法对连铸厚板坯冷却传热过程进行数值模拟,并用远红外测温仪测试并校准Q235B300 mm×1650 mm铸坯表面温度,得到了连铸坯在任意段截面的温度场分布、凝固末端液相穴形状及铸坯中心纵截面固相率分布.结果表明,可以根据铸机...     

Enhancing mechanical properties and permeability of ceramic shell in investment casting process

In the present investigation, the mechanical properties and hot permeability of the ceramic shell used in investment casting process were improved by modifying the ingredients of conventional slurry. The modifications were made by adding a varying content of nano alumina, camphor and a mixture nano alumina and camphor (hybrid mixture) individually into the conventional slurry. The properties, viz. green strength, fired strength, corner strength, load bearing capacity, self-load deformation and permeability of the modified shells were investigated and compared with conventional shell. The experimental results revealed that the green strength of all the shells increased with an increment of the additives into the slurry. The maximum green, fired and corner strengths were exhibited by the nano alumina modified shell with 1 wt% nano alumina addition. The lowest self-load deformation at elevated temperature was also attained by the nano alumina modified shell with 1 wt% nano alumina addition. The addition of camphor significantly improved the permeability of the shell among all the developed shells. But, addition of camphor decreased the strength of the shell. It was also found that addition of hybrid mixture into the slurry simultaneously increased the mechanical properties and permeability of the shell.     

基于COMSOL连铸坯壳测厚横波EMAT优化

为了研究电磁超声传感器(Electromagnetic Acoustic Transducer,EMAT)横波测量连铸坯壳厚度的机理及横波在连铸坯中的传播情况,选取坯壳厚度为10~50 mm的Q235小方坯为研究对象,利用有限元软件COMSOL建立脉冲电磁铁和螺旋线圈的电磁超声模型,分析在不同EMAT结构参数下,连铸坯中电磁场、力场、声场的分布规律。研究结果表明:脉冲电磁铁和螺旋线圈组成的EMAT能够在连铸坯壳集肤层激发出超声波横波。脉冲电磁铁空心螺线管线圈匝数、内半径、线圈导线半径对换能效率的影响依次减小,且当脉冲电磁铁内半径尺寸大于螺旋线圈尺寸时,产生横波的效率最高。坯壳厚度越小,螺旋线圈最优激励频率越大,测量精度越高,信号衰减越快。因此,坯壳厚度为10~50 mm的Q235小方坯选择1.1 MHz为最佳激励频率。     

Numerical simulation of rotating bending process for U-tubes in heat exchangers

Heat exchangers comprise thousands of tubes having U-shaped portions. Rotating bending method has been widely utilized to make U-bends. Although this method shows an excellent performance, cracks have been frequently detected in the U-bends due to residual stresses induced by bending. In this paper, the bending process is simulated based on elastic–plastic finite element analyses in order to investigate the magnitude and distribution of the residual stresses including the effects of operating pressure. Analyses results show that the residual stress increases as the radius of U-bend decreases and that operating pressure has a detrimental effect in terms of stress corrosion cracking at the intrados of U-bend. It is thought that these results can be utilized for the estimations of fracture mechanics parameters such as limit load, stress intensity factor and J-integral, prevention of the cracking, and establishment of the optimum inspection strategy for the heat exchanger tubes.     

Modelling and simulation of the electric slag remelting guide vane casting (ESRC) process and its application

Modelling and experiment work is carried out for a large stainless steel casting with variable cross-section and a curved surface which is produced by the electric slag remelting casting process. The casting is part of a hydraulic runner generator at a power station of a big river.

Mathematical models of the heat transfer and melted rate from an expendable metallic electrode were established. The melted rate is related to some important parameters, such as electric current and voltage, temperature and the flow rate of the cooling water in a crystallizer. Electrode melting, the moving pattern of the melted pool and the slag pool and the melt solidification in the metal pool were simulated.

In order to make the enmeshment of the variable curved surface of the casting, a co-operation method of extended constructive solid geometry (CSG) from 9 to 21 uniform geometry with B-Spline surface functions is developed. By this method the guide vane casting is enmeshed. The boundary condition between the steel casting and the crystallizer cooled by water was measured.

Based on the above new content the solidification simulation software ESRC3D is developed. Using it to simulate the whole process of ESRC with different parameters, instead of exploring the technological parameters of casting production by the trail-and-error method, the optimized parameters from the simulation for production of the large stainless steel castings with variable cross-section and a curved surface, such as the guide vane castings, have been used to produce them. Economic benefit and good quality of castings are obtained. Guide vane castings are widely applied to the hydraulic runner generator at numerous river power stations.