Abstract
A broaching technique for thick-walled pipes has been investigated. The proposed technique implies the deformation of a hollow workpiece without a mandrel. The procedure has been devised to conduct theoretical studies using FEM. The procedure is aimed at determining the thermal, stressed state and a shape change in the workpiece while forging pipes without the use of a mandrel. The variables applied were the internal diameter of a hollow workpiece, which ranged in the interval of 0.30; 0.55; 0.80. Based on the finite-element modeling, the following was established: the distribution of temperatures and intensity of logarithmic deformations within the volume of a pipe after broaching without the use of a mandrel. The diameter of a pipe’s hole has been determined, which is formed at broaching when applying a given technique. The dependences of intensity of lengthening and thickening of the wall of a pipe have been established. A special indicator was devised to estimate the elongation rate of a pipe. It was determined that increasing the inner diameter increases the lengthening of a pipe and decreases the intensity of the hole forging. The common dependence for the simulated broaching schemes is that the magnitude of elongation of a hollow workpiece changes insignificantly for different degrees of reductions at constant relative sizes of a pipe. It has made it possible to establish a recommended feed in order to increase the elongation of a hollow forging and to decrease the degree of closing a hole. The rational feed shall be (0.05...0.15)D. The results from the finite element modeling were verified by experimental study using lead samples. An experimental modeling procedure has been devised. It was established that at an inside diameter of the workpiece of (0.5...0.6)D one observes a maximum of the wall thickening. It was established that the results for a workpiece shape change, obtained from a theoretical study using FEM, exceeded those acquired experimentally by 9.14 %. The validity of results from theoretical modelling is confirmed by data from experiments on decreasing the internal diameter of the pipe. Difference between the theoretical and experimental results amounts to 9...12 %. The established patterns make it possible to determine the resulting diameter of a pipe’s hole. It was found based on the results from modeling that it is impossible to broach pipe workpieces without a mandrel. This technique extends the possibilities of technological processes aimed at manufacturing pipe workpieces.
Highlights
A priority task for the development of power engineering is to reduce the cost of parts and to improve their mechanical properties [1,2,3]
Procedure of experimental modeling We experimentally studied the process of pipe forging using lead samples
We investigated of the process of pipe deformation without the use of a mandrel by peens cut at 115° and a feed of 50 % of the original diameter of the workpiece (Fig. 4)
Summary
A priority task for the development of power engineering is to reduce the cost of parts and to improve their mechanical properties [1,2,3]. These forgings must be produced by forging on a mandrel. The thick-walled pipes are manufactured from solid shafts by using the operation of drilling a hole [4].
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