Únavovà pevnost defektních svaru v potrubí

Cyclic tests with the maximum force in a cycle F max = 5,5 kN and the cycle asymmetry ratio R = F min/ F ma x = 0,1 were carried out on flat specimens of 5mm in thickness. The specimens were cut out from a weldment of X52 steel sheet ∼ 10 mm thick perpendicularly to the weld seam. The results showed that the cyclic strenght of a welded joint is strongly dependent not only on the depth of a defect but also on its position. The effect of the weld root appeared to be much more unfavorable than the effect of the weld cap. For blunt cracks of the same depth the life of specimens with cracks in the weld root was shorter by an order than that of specimens with cracks in the weld cap. It is therefore very important in welding to pay an increased attention to mainly the root of the weld and to minimize here the risk of the occurence of defects.