磁场淬火过程热弹塑性本构方程研究及其数值模拟

【作者】 李自良；

【导师】 陈君若；

【作者基本信息】 昆明理工大学 ， 材料加工工程， 2002， 硕士

【摘要】 在前期工作中已提出的包含变物性系数、过冷沸腾边界、相变和磁场作用的热磁耦合热传导控制方程组的基础上，根据热非弹性理论、传热学原理、相变原理和电磁场理论，利用相变点附近铁磁材料热膨胀系数反常和磁致弹(性)变效应现象，建立了考虑变物性、磁场作用、相变的热弹塑性本构关系。考虑了弹塑性矩阵、材料的力学性能参数随温度变化的因素，从热弹塑性本构理论出发，应用热弹塑性增量理论建立了热弹塑性有限元方程。 采用大型有限元分析软件ANSYS对45钢外加磁场淬火冷却过程进行计算机数值模拟分析，定量求解热磁耦合作用下，碳钢试件的瞬态应力和残余应力分布。计算结果表明，与普通淬火相比，外加磁场淬火后的试件内应力及组织应力低，变形小，残余应力少，力学性能高， 实验方面，进行了硬度测试、拉伸试验和冲击试验。结果表明，与普通淬火相比，外加磁场淬火后的试件硬度变化不大，但塑性、韧性有较大提高。说明外加磁场淬火能获得较好的综合机械性能。 计算和实验的结果说明：(1)外加磁场淬火能有效地改善金属材料的组织形态及构成，提高材料的综合机械性能，是一种极有发展前途的热处理新工艺；(2)运用热传导理论、热弹塑性理论和计算机技术来模拟外加磁场淬火过程在理论上是可行的，所得结果与实测情况基本吻合，证明本文所采用的方法是基本正确的。更多还原

【Abstract】 In this paper, based on a heat conduction governing equations involves variant thermal physical properties, phase transformation, sub-cooling boiling boundary and the effect of magnetic field which is obtained in earlier work, according to the theory of thermal non-elasticity, heat transfer, phase transformation and electromagnetic, taking advantage of the abnormal phenomena of heat expansion coefficient of iron-magnetism nearby the Curie terrperature and magneto-elasticity, a new constitutive equation considering effects of phase transformation is proposed. And then, the change of elastoplastic matrix, parameters of material mechanics performance with temperature were considered, from thermal elastoplastic constitutive relation and applying the theory of thermal elastoplastic increment, the theoretical finite element equation was established.Using the large-scale FEM analysis software ANSYS to simulate the quenching process by additional magnetic field of 45 steel workpiece, and the distributing of transient thermal stress and residual stress are obtained and the influencing factors on the thermal stress are analyzed and discussed. Through the calculation, we make out that additional magnetic field reduces the sample’s internal stress and diminish the residual stress and deformation, so we can get a workpiece with high mechanics properties.In the course of experiments, we measure the tensile strength, impact strength and hardness of the sample. The result of experiments show that after magnetic field quenching, the hardness of sample waves slightly, but its plasticity and tenacity increased significantly, i.e. we can get a workpiece with high synthesis mechanical properties by means of magnetic quenching.Through the results of calculation and experiments, we can discover that when using magnetic quenching, internal texture stress low, deformation and residual austenite less and mechanic properties better. So the study of magnetic quenching has more extensive perspective. Meanwhile, we also can discover that utilizing heat transfer theory and computer technology to simulate magnetic field quenching process is feasible. The corresponding result is fit to practicality measuring value. It proves that the method used in this paper is correct by and large.更多还原