Abstract
The possibilities of using an energy method to forecast defect formation in the form of shrinkage depression in the combined extrusion processes have been investigated. We have proposed a mathematical model of the combined radial-reverse extrusion process of hollow details with a flange, taking into consideration the degeneration of the trapezoidal module into a rectangular one. Separate stages in the deformation process have been defined, depending on the magnitude of the active tool stroke compared with the thickness of the bottom of the cup. We have devised a generalized estimation scheme for the process of combined radial-reverse extrusion of parts with a flange taking into consideration the final stage of deformation ( H bottom < h 1 ). The magnitude of the reduced pressure of deformation has been derived as a function of the geometric, technological, and kinematic parameters of the extrusion process. A role of the kinematic parameter of the process belongs to a relative speed of metal flow in the vertical direction (filling the cup’s wall at the inverse flow of metal). The magnitude for the reduced pressure of deformation has been optimized based on this parameter. We have analyzed the character of change in the optimum magnitude of a relative speed of metal flow in the vertical direction in the course of the process. The differences have been established in the derived dependences of a given kinematic parameter for the process with the formation of shrinkage depression in the bottom part of a component and without defect formation. It has been substantiated that the use of combined extrusion in the manufacture of hollow parts with a flange, when compared with the application of simple schemes of deformation, improves the technological capabilities of the process. We have proven that the technologies for introducing combined extrusion had not been sufficiently studied and there is a lack of recommendations on predicting the formation of a defect in the form of shrinkage depression. The estimation scheme has been proposed for the radial-reverse extrusion process, taking into consideration the emergence of shrinkage depression at the final stage of deformation. We have modeled the process of combined extrusion of hollow parts with a flange and established the influence of friction conditions on the time of the emergence of shrinkage depression in the bottom part of a component. It has been confirmed that the proposed generalized estimation scheme makes it possible to predicting the occurrence of a defect in the form of shrinkage depression at all stages and under different technological conditions for a deformation process. Obtaining a preliminary assessment, based on it, of possible defect formation would facilitate the development of appropriate technological recommendations to avoid defects of this type
Highlights
The machining processes of metals, both hot and cold, are the preparatory base of machine engineering and metallurgy
Given the ability to form a metal at high performance and low waste, thereby improving its mechanical properties, the importance of pressure treatment in modern industry is enormous [1]. This increases the role of effective resource-saving methods for pressure metal treatment such as cold volumetric stamping [2]
Combining traditional schemes of longitudinal extrusion by radial or lateral extrusion methods opens up the possibility of manufacturing parts with a more complex
Summary
The machining processes of metals, both hot and cold, are the preparatory base of machine engineering and metallurgy. Combining the reverse and radial extrusion schemes in the manufacture of hollow parts with a flange improves technological capabilities of the processes of precision volumetric stamping by reducing the energy and labor intensity of production and increasing a metal utilization factor. Along with these advantages, there are a series of problems, primarily related to the issues of plasticity and hardening of metal under conditions of the complex stressed-deformed state [5, 6]. Special attention should be paid to building full-fledged mathematical models for calculating force parameters and shape formation that would make it possible to predict defect formation in the processes of combined extrusion
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