Effect of Thermal cycles and Dimensions of the Geometry on Residual stress of the Alumina-Kovar Joint

7th National Conference on Processing and Characterization of Materials

Mishra, Srishti^1 ; Pal, Snehanshu^1 ; Karak, Swapan Kumar^1 ; Shah, Sejal^2 ; Venakata Nagaraju, M.^2 ; Chakraborty, Arun Kumar^2

Metallurgical and Materials Engineering Department, National Institute of Technology, Rourkela

769008, India^1

ITER-India, Indian Plasma Research, Sangath Skyz, Bhat-Koteshwar Road, Koteshwar, Ahmedabad, Gujarat

380 005, India^2

关键词: Ansys workbenches;    Augmented Lagrange method;    Brazed joint;    Brazing temperature;    Comparative studies;    Heating and cooling rates;    Height-to-diameter ratio;    Representative volume element (RVE);   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/338/1/012001/pdf
DOI  :  10.1088/1757-899X/338/1/012001

来源: IOP

【 摘 要 】

Finite element method is employed to determine the effect of variation of residual stress with dimension and the stress generated under its working condition along the Kovar. 3 different dimensions of Alumina-Kovar joint with height to diameter ratio of 3/10, using TiCuSil as a filler material. Transient Structural Analysis is carried out for three different dimensions (diameter × height) (i) 60mm × 20mm (Geometry 1) (ii) 90mm × 20mm (Geometry 2) (iii) 120mm × 20mm (Geometry 3). A comparative study has been carried out between the residual stresses developed in the brazed joint that have undergone 5 thermal cycles subsequent to brazing and that between the brazed joint. The heating and cooling rates from the brazed temperature is 10°C/up to room temperature. The brazing temperature and holding time considered for the analysis are 900°C and 10 minutes. Representative Volume Element (RVE) model is used for simulation. Sparse Matrix Direct Solver method is used to evaluate the results, using Augmented Lagrange method formulation in the contact region. All the simulations are performed in ANSYS Workbench 15.0, using solver target Mechanical APDL. From, the above simulations it is observed high concentration of residual stress is observed along the filler region i.e. in between Alumina and Kovar, as a result of difference in coefficient of thermal expansion between Alumina and Kovar. The residual stress decreases with increasing dimensions of the geometry and upon application of thermal cycles, subsequent to brazing.