Research For The J_IC Test Method Of Construct Steel Welded Joint

In this paper, the J-integral test of 16Mn and 907A has been done with three-point bend specimen. The specimens have different dimensions. The method of J-integral test is studied. The results show that there are many problems inpresent JIC testing, such as the form of blunting line, the method ofdetermine JIC, the condition of validness of J-integral and plane-strain and so on.All these problems have been discussed in this paper and the methods for resolving these problems are raised.The data processing system of fracture toughness is programmed with Visual PoxPro6.0. The testing data can be calculated and saved and managed by the system.A new blunting and cracking model is founded by analyzing the process of specimen's blunting and cracking.On the basis of path-independence of J-integral, a new form of blunting lineis obtained. The result is as followed: J-- x 2 a0.Through analyzing the method for determining J1C, this paper proposes a new rule to determine JIC. The method is as followed: construct the vertical line,which passes the point (Aa0, 0). Plot J versus crack extension. Mark J1C at theintersection of the two lines.It is necessary to use a new standard specimen to do J-integral test. The dimension of standard specimen is 10 mnx20 nsnxiOO mm .The results from this specimen are satisfied with the condition of validness of J-integral as well as the condition of plane-strain. The reason is explained.Because of the particularity of welded joints, it is difficult to get the &s and b, of different positions of welded joints, it is the most difficult tiling in testingJIC , so the form of blunting line can not be obtained and it is difficult to get theJIC of welded joints with present method of J-integral test. After discussing allthe problems proposed, this paper proposes a new method of J-integral test. This method can be used to measure the JIC of welded joint. In this paper, the Jof welded joint of 907A steel is obtained by this method.