The effect of heat sinks in GTA microwelding
When miniature devices containing glass-to-metal seals are closure welded it is accepted practice to incorporate thermal heat sinks into the fixturing. This is intended to assure that the heat from gas tungsten arc (GTA) welding will not cause thermal stress-induced cracking of the seals and loss of hermeticity. The design of these heat sinks has never been systematically studied; instead only ''engineering horse sense'' has been applied. This practice has been successful in the past; however, the component being GTA welded have become smaller and more complex (i.e., more pins) and glass cracking problems are being encountered. The technology of producing glass seal-containing lids (called ''headers'') has benefited from finite element analyses in deciding how to optimally dimension pin-to-glass seal diameter ratios and glass-to-metal thickness ratios in order to minimize thermal stresses locked in during manufacture. It appeared likely that an analysts of the stresses generated by welding would also be beneficial. Recently, computer speed and code capabilities have increased to the point where finite element analysis of a close simulation of real hardware can be made, including the effect of external heat sinks. The work reported here involves an analysis (with some supporting experimental data) of a miniature thermal battery which encountered glass cracking problems. In the course of the analysis various heat sink practices were examined. Among other findings, through-thickness thermal gradients in a header with a heat sink were found to equal in-plane thermal gradients in a header without any heat sinking at the glass seal positions. Also noted were significant variations due to relatively minor changes in the weld preparation geometry. A summary of good practice for heat sinking will be presented. 4 refs., 6 figs., 2 tabs.
- Research Organization:
- Sandia National Labs., Albuquerque, NM (USA)
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 6338607
- Report Number(s):
- SAND-88-3025C; CONF-8905118-2; ON: DE89010330
- Resource Relation:
- Conference: 2. international conference on trends on welding research, Gatlinburg, TN, USA, 15 May 1989; Other Information: Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
42 ENGINEERING
99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
GAS TUNGSTEN-ARC WELDING
MATHEMATICAL MODELS
CRACKING
FINITE ELEMENT METHOD
GLASS
HEAT SINKS
METALS
STRESSES
WELDING
ARC WELDING
CHEMICAL REACTIONS
DECOMPOSITION
ELEMENTS
FABRICATION
JOINING
NUMERICAL SOLUTION
PYROLYSIS
SINKS
THERMOCHEMICAL PROCESSES
360101* - Metals & Alloys- Preparation & Fabrication
360601 - Other Materials- Preparation & Manufacture
420200 - Engineering- Facilities
Equipment
& Techniques
990230 - Mathematics & Mathematical Models- (1987-1989)