Abstract
It is known that expansion is the final operation on the production lines of large diameter pipes (LDP), it is used to correct deviations in the size and shape of pipes. However, after expansion, products often have a high uneven distribution of the stressed-strain over the cross sections of their wall, and this can significantly reduce the reliability, safety of operation and also pipe resources in harsh conditions. In the present work, a mathematical dependence is made between the degrees of stress-strain non-uniformity with the mechanical properties of the pipe material (such as elastic modulus, yield strength, tensile strength, ...) and the friction condition during expansion. On the basis of this dependence, a method of mathematical simulation on a computer has been established for evaluating and classifying the quality of LDP with the mechanical properties of the material and friction friction, which are considered random variables in accordance with the given distribution laws. The results of mathematical simulation when studying the process of expanding pipes with a diameter of 1420 mm made of K60 steel showed that: with the elastic modulus and tensile strength shifting toward large values, and the yield strength, elongation after break and friction coefficient - towards lower values, the uniformity of the stress distribution deformation and also the quality of the LDP is improved, and the possibilities of classifying a batch of input materials and the choice of lubricant during expansion are given to obtain high quality pipe products.
Keywords
Large diameter pipe, expansion, uneven distribution, stress, strain, mathematical simulation, random variable.