Abstract

The main purpose of this paper is to examine the applicability of spot welded dissimilar steel sheets to ultrasonic testing, because resistance spot welding of the steel sheets is widely used in the car bodies and transport fields and ultrasonic testing is a good way to evaluate the fatigue life of the spot welds. Methodology of this paper is that two different steel sheets AISI 304 type austenitic stainless steel sheet and Galvanized steel sheet were welded to each other by using resistance spot welding. Some pre welding tests were made to obtain suitable and optimum weld nugget diameter and the welding current vs. nugget diameter curve were obtained. By using this curve and keeping constant welding parameters such as current, electrode pressure, weld time, etch. Fully identical four spot welded specimens having 5 mm ±0.16 nugget diameter were obtained. The specimens and nugget diameters were tested by using a special ultrasonic test apparatus which is designed for spot welded joints. Findings are that after the first ultrasonic tests, the four identical spot welded sheets which have AISI 304 – Galvanized steel sheet combination were subjected to the fatigue test in four different numbers of cycles. There is no any rupture or fracture in spot welded joints after fatigue tests. The spot welded specimens subjected to fatigue test were tested in ultrasonic test apparatus to observe the variation in the weld nugget and joint. The ultrasonic test results before fatigue and after fatigue were compared with each other and the decreasing of the weld nugget diameter were observed while increasing the number of cycles. The results were shown in figures and discussed. Spot welding of different steel sheets forms different microstructures which respond different values to ultrasonic testing. Evaluation of these responses are quiet difficult. Only a few spot welds can be evaluated among approximately 5 thousands of spot welds on a car body. Only selected spot welds can be ultrasonically tested. Resistance spot welding of AISI 304 and galvanized steel forms austenitic, martensitic and ferritic microstrucutre in the same weld region. Ultrasonic testing of austenitic microstructures is different than the other microstructures. In this study the response of different microstructures to ultrasonic waves are investigated. Chilla Veera Venkata Satyanarayana | Uppada Komali "Performance of Ultrasonic Testing for Different Steel Sheets which are joined by Spot Welding" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-4 , June 2019, URL: https://www.ijtsrd.com/papers/ijtsrd23598.pdf Paper URL: https://www.ijtsrd.com/engineering/mechanical-engineering/23598/performance-of-ultrasonic-testing-for-different-steel-sheets-which-are-joined-by-spot-welding/chilla-veera-venkata-satyanarayana

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