金属铸造凝固过程的界面传热系数的研究与应用
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摘要
在金属铸造凝固过程中,在铸件/铸型界面间会产生空隙即热阻。热阻的大小随时间和空间变化,常常主导着热传导的过程,通常将热阻的影响表示为界面传热系数。在温度场数值模拟中,铸件与铸型间的界面传热系数是关键的参数。
本文通过利用大型通用有限元分析软件ANSYS对金属铸造凝固过程的温度场进行了数值模拟分析,利用“反问题”的方法对界面传热系数进行了求解,并通过试验证明了这种方法的正确性和通用性。主要研究工作如下:
1、利用ANSYS软件从是否考虑热阻(或界面传热系数)的角度来对同一铸造凝固过程的温度场进行模拟分析,进而判定接触热阻的存在对温度场分布的影响;在考虑界面热阻情况下,对当界面传热系数取不同值时的铸造凝固过程的温度场进行模拟,对比分析模拟结果与试验结果,得到界面传热系数对铸造凝固过程温度场的影响;
2、由于重力和铸型表面散热情况等因素的影响,处于铸件/铸型界面处的竖直方向产生的空隙大于水平方向,模拟时考虑以上因素,界面传热系数根据铸件与铸型接触面所处位置不同取不同值,并将模拟结果与试验结果进行对比分析;
3、采用“测点温度计算界面传热系数”和“0.618法直接搜索界面传热系数”两种方案同时利用“反问题”的数学方法来求解界面传热系数,并应用ANSYS软件、0.618法和最小二乘法得出了界面传热系数随时间变化的规律并建立其数学模型。基于以上的方法和所得结论,可以扩展到考虑接触应力、不同厚度、不同时间(或温度)等情况,建立关于应力、厚度、时间(或温度)等的界面传热系数的数学模型。
An air-gap could be generated at the interfaces between the solidifying metal and surrounding mould during casting solidification.The air-gap produces a heat resistance which is traditionally described by an interfacial heat transfer coefficient.It varies with time and space and takes important part in the thermal transfer.The effect of heat transfer is described by an interfacial heat transfer coefficient.The interfacial heat transfer coefficient is the key parameter in the simulation of temperature field.
As finite element software, ANSYS is used to analyze the solidification of metal casting in the paper.The interfacial heat transfer coefficient is determined using the inverse method.The correctness and convenience of this method is proved using experiments.
The main tasks of this paper are as follows:
1、ANSYS is used to simulate the temperature fields of the same casting solidification under two kinds of condition of considering the effect of heat resistance or ignoring its effect,and to analyze the influence of the heat resistant on the temperature distribution.Under the condition of considering the heat resistant, all of the simulated results with varying interfacial transfer coefficients are compared with the experimental results.Then the effect of the interfacial heat transfer coefficient on the temperature fields of solidification is received.
2、Owing to the effect of gravity and the mold-environment heat transfer, the air-gap at the vertical interface is larger than that at the horizontal.Considering all above factors, the values of the interfacial heat transfer coefficients vary with the different locations of the boundary between the metal and mould.After simulation, the recorded cooling curves are compared with the simulated cooling curves.
3、The interfacial heat transfer coefficient is determined using the Inverse Method by means of two transient techniques, which includes mathematically solving the interfacial heat transfer coefficient by thermocouple measurements and using 0.618 method to search the best fitting interfacial heat transfer coefficient directly.By applying ANSYS software, 0.618 method and the least-squares method, the rule and the mathematical model of the interfacial heat transfer coefficient with time can be made up.Based on all the methods and conclusions above, the model of the interfacial heat transfer with the contacting pressure, the thickness and the times or temperatures can be made up when it is extended to consider the respective factors.
本文通过利用大型通用有限元分析软件ANSYS对金属铸造凝固过程的温度场进行了数值模拟分析,利用“反问题”的方法对界面传热系数进行了求解,并通过试验证明了这种方法的正确性和通用性。主要研究工作如下:
1、利用ANSYS软件从是否考虑热阻(或界面传热系数)的角度来对同一铸造凝固过程的温度场进行模拟分析,进而判定接触热阻的存在对温度场分布的影响;在考虑界面热阻情况下,对当界面传热系数取不同值时的铸造凝固过程的温度场进行模拟,对比分析模拟结果与试验结果,得到界面传热系数对铸造凝固过程温度场的影响;
2、由于重力和铸型表面散热情况等因素的影响,处于铸件/铸型界面处的竖直方向产生的空隙大于水平方向,模拟时考虑以上因素,界面传热系数根据铸件与铸型接触面所处位置不同取不同值,并将模拟结果与试验结果进行对比分析;
3、采用“测点温度计算界面传热系数”和“0.618法直接搜索界面传热系数”两种方案同时利用“反问题”的数学方法来求解界面传热系数,并应用ANSYS软件、0.618法和最小二乘法得出了界面传热系数随时间变化的规律并建立其数学模型。基于以上的方法和所得结论,可以扩展到考虑接触应力、不同厚度、不同时间(或温度)等情况,建立关于应力、厚度、时间(或温度)等的界面传热系数的数学模型。
An air-gap could be generated at the interfaces between the solidifying metal and surrounding mould during casting solidification.The air-gap produces a heat resistance which is traditionally described by an interfacial heat transfer coefficient.It varies with time and space and takes important part in the thermal transfer.The effect of heat transfer is described by an interfacial heat transfer coefficient.The interfacial heat transfer coefficient is the key parameter in the simulation of temperature field.
As finite element software, ANSYS is used to analyze the solidification of metal casting in the paper.The interfacial heat transfer coefficient is determined using the inverse method.The correctness and convenience of this method is proved using experiments.
The main tasks of this paper are as follows:
1、ANSYS is used to simulate the temperature fields of the same casting solidification under two kinds of condition of considering the effect of heat resistance or ignoring its effect,and to analyze the influence of the heat resistant on the temperature distribution.Under the condition of considering the heat resistant, all of the simulated results with varying interfacial transfer coefficients are compared with the experimental results.Then the effect of the interfacial heat transfer coefficient on the temperature fields of solidification is received.
2、Owing to the effect of gravity and the mold-environment heat transfer, the air-gap at the vertical interface is larger than that at the horizontal.Considering all above factors, the values of the interfacial heat transfer coefficients vary with the different locations of the boundary between the metal and mould.After simulation, the recorded cooling curves are compared with the simulated cooling curves.
3、The interfacial heat transfer coefficient is determined using the Inverse Method by means of two transient techniques, which includes mathematically solving the interfacial heat transfer coefficient by thermocouple measurements and using 0.618 method to search the best fitting interfacial heat transfer coefficient directly.By applying ANSYS software, 0.618 method and the least-squares method, the rule and the mathematical model of the interfacial heat transfer coefficient with time can be made up.Based on all the methods and conclusions above, the model of the interfacial heat transfer with the contacting pressure, the thickness and the times or temperatures can be made up when it is extended to consider the respective factors.
引文
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[5]李维特,黄保海,毕仲波.热应力理论分析及应用[M].北京:中国电力出版社,2004.
[6]王勖成,邵敏.有限元法基本原理与数值方法[M].北京:清华大学出版社,1988.
[7]陈海清,李华基,曹阳著.铸件凝固过程数值模拟[M].重庆:重庆工业出版社,1991,4.
[8]郭宽良.计算机传热学[M].合肥:中国科学技术大学出版社,1988,13-86.
[9]大中逸雄著,许云详译.计算机传热凝固解析入门[M].北京:机械工业出版社,1988,3.
[10]许肇钧.传热学[M].北京:机械工业出版社,1980.
[11]李景湧．有限元法[M].北京:北京邮电大学出版社,1999,3-4.
[12]谭建国.使用ANSYS6.0进行有限元分析.北京:北京大学出版社,2002,1-13.
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[15]孔祥谦.有限单元法在传热学中的应用[M].北京:科学出版社,1998.
[16] [美]Daryl L.Logan著.有限元方法基础教程(第三版)[M].电子工业出版社,2003,8.
[17]杨泉,张真.金属凝固与铸造过程数值模拟[M].杭州:浙江大学出版社,1996.
[18]博弈创作室编.ANSYS9.0经典产品基础教程与实例详解[M].北京:中国水利水电出版社,2006.
[19]陈玲,王鹏林,张敬宇.金属型铸造温度场的有限元数值模拟及物理参数的“逆方法”.机械设计,2003,20(12):29-31.
[20] Abel-WAHED M, ASSAR. On the interfatial heat transfer coefficient for fylindrical ingot casting in a metal mould[J]. Journal of Materials Sciences Letters, 1992, vol 11: 601-602.
[21]马兆敏.复杂铸件三维温度场有限元分析[M].广西工学院学报,2002,14(1):54-58.
[22] Non-Linear Analysis Guide.Realease 5.4[R]. ANSYS, Inc. is a UL registered ISO 9001:1994 company.
[23]安晓卫,王承志.铸件温度场有限元分析中界面热阻的处理[J].计算力学学报,2005,22(1):100-103.
[24]王国强.实用工程数值模拟技术及其在ANSYS上的实践[M].西安:西北工业大学出版社,2000,1-187.
[25]宋广胜,王承志,安晓卫等.金属型铝合金凝固过程的数值模拟[J].铸造设备研究,2001(1): 8- 11.
[26]陈进,丁忠军,付秀玲等.基于MATLAB的氮化铝和铜界面热阻仿真[J].低温与特气,2005,23(4):13-15.
[27]饶荣水.固体表面之间接触热阻的辨识研究[J].工程加热,2003,2:16-18.
[28] KAI HO and ROBERT D.PEHLKE. Metal-Mold Interfacial Heat Transfer[J].METALLURGICAL TRANSATION, 1985, vol 16:585-594.
[29] Ce-Wen Nan, Xiao-Ping Li, R.Birringer. Inverse Problem for Composites with Imperfect Interface: Determination of Interfacial Thermal Resistance, Thermal Conductivity of Constituents, and Microstructural Parameters[J]. Journal of the American Ceramic Society-Nan et al., 2000, 83(4): 848-854.
[30]沙明红,郑贤淑.连续铸钢结晶器温度场的试验研究及数值模拟[J].铸造,2005,54(2):182-186.
[31]张洪武,廖爱华,张昭等.具有界面热阻的接触传热耦合问题的数值模拟[J].机械强度,2004,26(4):393-399.
[32]黄光远,刘小军.数学物理反问题[M].山东科学技术出版社,1993.
[33] K.S.Alfredsson and B.L.Josefson.Harmonic Response of a spot Welded Box Beam-Influence of Welding Residual Stresses and Deformations[J]. Proc.IUTAM Symposium on the Mechanical Effects of Welding.Lulea, Sweden, June, 1991:1-8.
[34] K.Ho,R.D.Pehlke. Mechanisms of Heat Transfer at a Metal-Mold Interface[J]. AFS Transactions, 1984, vol 92:587-598.
[35] S.M.H.Mirbagheri, M.Dadashzadeh, S.Serajzadeh, ect. Modeling the effect of mould wall roughness on the melt flow simulation in casting process[J]. Applied Mathematical Modelling,2004,vol 28:933-956.
[36] R.W.Lewis, R.S.Ransing. The optimal design of interfacial heat transfer coefficients via a thermal stress model[J].Finite Elements in Analysis and Design,2000, vol 34:193-209.
[37] C.P.HALLAM, W.D.GRIFFITHS. A Model of the Interfacial Heat-Transfer Coefficient for the Aluminum Gravity Die-Casting Process[J].METALLURGICAL AND MATERIALS TRANSACTION,2004,VOL 35:721-733.
[38]石零,王惠龄,赵琰.调制光热法低温接触界面层热阻研究[J].低温工程,2006,2:7-10.
[39]卢义,巫英伟,索晓娜等.板坯连铸二冷表面传热系数预测与仿真软件[J].工业传热,2005, 34(6):4-7.
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