A Study On Spring Back And Length Extension Of Pipe Bending

Spring back and length extension are the most important factors influencing the forming quality of bending pipe. In this paper, in order to improve the quality in accurate pipe bending, the theories of elastic deformation and plastic deformation are studied and large amount of test have been carried out. Based on the above predicting of spring back and length extension precisely are the key to obtaining the accuracy of bending pipe.It is difficult for design engineers to predict spring back and length extension because many variables affect it, such as material properties, die geometry, pipe outer diameter, pipe thickness, and so on. In this paper, there are many records containing the spring back and extension properties of various pipe materials and pipe sizes at different angles of bend.However, the smaller the bending radius are, the smaller the spring back, and the greater the bending angel, the greater the spring back. The final bending angle after spring back is smaller than that before spring back, and the final bending radius after spring back is larger than that before spring back. In order to achieve the accurate bending angle as target figure, for practical purposes the actual bending die radius may be smaller than the target radius, i.e. about 97%, and the actual angle of bending for the certain die is slightly larger than the desired angle based on the pipe size and wall thickness and desired angle.On the basis of bending experiments with various pipe size classed, various wall thicknesses and angles of bend, length extension information recorded in this paper are created, and the pipe is bent according to the created bending instructions.