Stress relaxation of braze joints
Calculations of residual stresses in braze joints are required to validate designs for a variety of metal/ceramic joining applications. In particular, finite element analysis (FEA) codes have the capability of incorporating either elastic-plastic or minimum creep rate constitutive models for the braze material. This paper presents both elevated temperature mechanical properties correlations for the eutectic Ag-Cu alloy, along with FEA results which use this data in calculating residual stresses in a generic metal/ceramic shear'' type braze joint. Three constitutive relations have been developed for eutectic Ag-Cu alloy: (1) an elastic/plastic correlation incorporating temperature-dependent yield stress and work hardening data, (2) a high temperature minimum creep rate correlation with a temperature-dependent stress exponent and (3) a minimum creep rate correlation using the Garofalo hyperbolic sine (sinh) equation. FEA calculations are presented for a eutectic Ag-Cu braze joint between metallized alumina ceramic and either Fe-29Ni-17Co or Fe-27Ni-25Co alloys using the three different constitutive relations for the brazement. The two creep correlations, since they are time-dependent, permit a study of the effect of various cooldown cycles on the maximum residual stress in the alumina ceramic. For the cooldown profiles studied in this paper, lower residual stresses are predicted in the ceramic -- relative to the elastic-plastic model -- when either of the two creep models are used as the constitutive law for the eutectic Ag-Cu braze joint. A second important result is that the simulations which incorporate the Fe-29Ni-17Co alloy show higher peak stresses than the Fe-27Ni-25Co alloy at 420{degree}C, along with much lower peak stresses compared to Fe-27Ni-25Co alloy at room temperature. The reason for this somewhat surprising behavior can be understood in terms of the coefficient of thermal expansion for the two Fe-Ni-Co alloys. 20 refs.
- Research Organization:
- Sandia National Labs., Albuquerque, NM (United States)
- Sponsoring Organization:
- USDOE; USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 5846543
- Report Number(s):
- SAND-92-0190C; CONF-920452-3; ON: DE92007989
- Resource Relation:
- Conference: American Society of Mechanical Engineers/Japan Society of Mechanical Engineers (ASME/JSME) joint conference on electronic packaging, San Jose, CA (United States), 9-12 Apr 1992
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BRAZED JOINTS
STRESSES
COPPER ALLOYS
CREEP
SILVER BASE ALLOYS
ALUMINIUM OXIDES
CERAMICS
CHROMIUM ALLOYS
FINITE ELEMENT METHOD
IRON BASE ALLOYS
MECHANICAL TESTS
NICKEL BASE ALLOYS
STRAINS
ALLOYS
ALUMINIUM COMPOUNDS
CHALCOGENIDES
IRON ALLOYS
JOINTS
MATERIALS TESTING
MECHANICAL PROPERTIES
NICKEL ALLOYS
NUMERICAL SOLUTION
OXIDES
OXYGEN COMPOUNDS
SILVER ALLOYS
TESTING
WELDED JOINTS
360103* - Metals & Alloys- Mechanical Properties