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H型钢空冷过程中残余热应力的有限元分析 总被引:2,自引:0,他引:2
借助于LS-DYNA有限元软件,在H型钢轧制全程有限元分析的基础上,对轧后H型钢空冷过程进行了三维热力耦合有限元分析,分析了不同热定尺情况下H型钢残余热应力的分布.结果表明:该热轧H型钢因轧后断面温度场的分布不均匀导致空冷过程中残余热应力的分布状态复杂,其中沿轧件长度方向上的残余热应力在腹板部位整体表现为压应力,可达160 MPa以上,而翼缘中心和腰腿连接部位表现为拉应力;H型钢宽度方向的残余应力影响长度方向上的应力分布,当采用热锯定尺小于3 m时,随着长度的减小沿长度方向的残余热应力相应减小. 相似文献
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H型钢矫直过程的有限元仿真 总被引:1,自引:0,他引:1
以H型钢矫直过程为研究对象,建立了矫直辊与型钢三辊弯曲矫直的仿真模型;采用ANSYS软件,对上下、左右挠度和翼缘斜度矫直过程进行了仿真分析,计算了H型钢的应力与残余应力状态,分析了矫直时翼缘与腹板之间产生裂纹的原因,提出了改善H型钢矫直质量的合理工艺方案. 相似文献
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为了研究大规格H型钢产品冷却过程中热应力的分布规律,采用有限元数值分析和现场测试相结合的方法,对空冷过程H型钢产品的温度场变化历程,等效应力变化历程及冷却至矫直温度时,热应力的分布规律进行了研究。结果表明:现有生产工艺条件下,H型钢冷却至矫直温度时,其内部存在着分布极为不均的热应力场,必须对其采取有效地控制冷却措施,改善其热应力场分布,才能达到提高产品质量的目的。 相似文献
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热轧H型钢终轧后在空气中自然冷却,由于H型钢的翼缘和腹板散热性能不同,在冷却过程中H型钢端面会产生高达300℃的温差,影响产品最终的力学性能。为了改善H型钢冷却过程中的温度场分布,提高产品的力学性能,采用有限元仿真技术和现场测试技术相结合,提出了H型钢生产线轧后控制冷却系统的设计方案,如喷嘴布置方案、冷却设备的布置方案、冷却设备的控制方案、冷却方式等。该冷却方案现已成功装备生产现场,现场实测数据表明对热轧H型钢实现轧后控制冷却,在冷却过程中H型钢的温度场得到了明显改善.最终还提出了对该控制冷却系统方案进一步优化的措施。 相似文献
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上海大通钢结构有限公司H型钢生产线是采用高频焊接工艺连续生产H型钢的高效率生产线。原材料为卷料带钢,上翼缘、下翼缘和腹板各一条。包括开卷机、端焊机、平整机、储料器和夹送辊等设备组成的连续工艺线将材料连续输入高频焊机。焊机出口的H型钢经冷却、矫直、定长剪切直到成品收集打包。储料器可储存一定数量的卷料,以便在换新卷和端焊时使生产线保持连续生产。 相似文献
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利用有限元技术计算了沉积坯在生长形成过程及形成后的温度场,利用该温度场计算了沉积坯的瞬时热应力场和残余应力场,计算结果表明沉积坯在沉积的初始阶段冷却速度较大,沉积坯底部的残余应力和瞬时热应力最大。 相似文献
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莱钢大型H型钢轧线矫直机自动控制系统包括矫直机本体自控系统和矫直辊换辊自控系统,本体系统实现对轧件的矫直,换辊系统完成每种规格矫直辊的更换。两个独立的自控系统通过西门子SIMATICDP/DP Coupler网络耦合器进行连接,共同完成大型 H型钢的矫直工序。 相似文献
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Excessive heat generated at the machining zone, during Electro-discharge diamond grinding (EDDG), is the major cause of thermal stresses, untempered martensite, overtempered martensite, and cracks. Therefore, the key to achieve good surface integrity in a machined part is to prevent excessive temperature and thermal stresses generated during machining process. A finite element model has been developed to estimate thermal stresses during EDDG when the current is switched-off. First, the developed code calculates the temperature in the workpiece and then the thermal stress field is estimated using this temperature field. Computations were carried out in plane strain condition for different down feeds of the grinding wheel. The effects of time of grinding and feed on thermal stress distribution have been reported. The thermal stresses are found to be higher near top surface at initial time of grinding but shifted away towards bottom after some grinding time. 相似文献
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The automotive industry has traditionally used ceramic honeycomb substrates as catalyst carriers. The long-term durability
of a passenger car’s converter is assessed by examining the thermal stresses resulting from the temperature variations experienced
under various driving conditions. These thermal stresses constitute the majority of the total stress that the ceramic catalyst
substrate experiences while in service. The radial and axial temperature distributions were measured, and the thermal stress
was calculated by using the thermal expansion coefficient according to the measured temperature. The threshold stress was
determined from the fatigue constant, the required lifetime and the duration of the short term strength tests. The radial
temperature variation was higher than the axial temperature variation, and the axial stress was higher than the radial stress
because the thermal stress is dependent on the elastic modulus. The radial and axial stresses exist below the threshold thermal
stress over the entire engine speed range. 相似文献
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熔射成形中涂层的使用性能与其残余热应力密切相关,而残余热应力则是由于沉积过程中温度场分布不均匀导致的,因此,研究涂层温度场是分析其残余热应力的基础。针对现有涂层沉积温度场模拟普遍采用的增层模型不能考虑涂层孔隙的缺陷,提出一种基于显微照片的含孔隙涂层生长增层模型,并使用该模型对其温度场进行模拟。计算结果表明,孔隙不仅对沉积过程中的涂层温度场具有重要影响,而且对基体温度场也有影响。涂层中靠近孔隙的位置其温度下降比远离孔隙位置更慢,且沉积初期这种差异更明显。含孔隙涂层温度场的模拟为含孔隙涂层残余热应力的研究及涂层起翘、开裂和剥落等失效机理的分析提供了基础。 相似文献
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Residual stress analysis of the thermal barrier coating system by considering the plasma spraying process 总被引:2,自引:0,他引:2
Myung-Jae Lee Byung-Chai Lee Jang-Gyun Lim Moon-Ki Kim 《Journal of Mechanical Science and Technology》2014,28(6):2161-2168
The residual stress is the key factor causing the reliability problem of thermal barrier coating (TBC). The failure of plasma spray coatings due to residual stresses is a serious and recurring problem of TBC. The difference of thermal expansion coefficient between the substrate and each coating combined with temperature evolution and temperature gradients during deposition process determine the residual stress for the whole TBC system. The magnitudes and distributions of the residual stresses are affected by deposition process and deposition characteristics. Most of FEA (finite element analysis) has been performed under the assumption that the multilayer coating system is stacked at once without considering the deposition process during plasma spraying. In this research, FEA for a coupled heat transfer and elastic-plastic thermal stress was performed to obtain the more detailed and reliable result of residual stress of the TBC system using the element activation/deactivation technique. The residual stress variation from the start of plasma spraying to cooling stage with room temperature was obtained systematically considering the deposition process. It can be used as reference data to improve the performance of TBC. In addition, the relationship between residual stress and coating conditions such as cooling rate and time is also examined thoroughly. 相似文献
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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. 相似文献