Computer simulation of the forging of fine grain IN-718 alloy
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I.
INTRODUCTION
IN recent years, the field of metal forming has witnessed great emphasis on technologies associated with process modeling in manufacture. Traditional build and test methods for die design and selection of process variables have resulted in high tooling and setup costs and in long lead times before production. The development of simulation programs, such as ABAQUS, ADINA, ALPID, and MARC, has moved some of the trial-anderror involved in the conventional process design procedure from the shop floor to the computer, where many options can be investigated economically prior to an actual build-and-test. The key to the success of any simulation is accurate knowledge of the properties, both thermal and mechanical, of the major components of the metal-forming system under the operating conditions of a manufacturing process. Handbooks of material properties report the properties of materials under service conditions. For an alloy such as IN-718, these include elastic moduli, thermal expansion coefficients, fatigue, and creep data over a temperature range from room temperature to about 650 ~ (! 200 ~ However, forging of nickel-base alloys is carried out at temperatures of about 980 ~ (1800 ~ and to large plastic strains (E > 1.0) under nonisothermal conditions, and the handbook data is of little value for computer modeling under these processing conditions. A study to determine the data required to model the forging of IN-718 using H- 13 steel dies was carried out. These data were then used to simulate the deformation R. SRINIVASAN, Assistant Professor, U. DESHPANDE, Graduate Student, and 1. WEISS, Professor, are with the Mechanical and Materials Engineering Department, Wright State University, Dayton, OH 45435. V. R A M N A R A Y A N , formerly Graduate Student, Mechanical and Materials Engineering Department, Wright State University, is Associate Engineer, Concurrent Technologies Corporation, Johnstown, PA 15904. V. JAIN, Professor, is with the Mechanical and Aerospace Engineering Department, University of Dayton, Dayton, OH 45409. Manuscript submitted April 24, 1992. METALLURGICAL TRANSACTIONS A
of "double-cone" shaped specimens with the computer program ALPID. Physical forging experiments were conducted on an industrial forging press. The results of the computer simulation and the physical modeling experiments are discussed in this article.
II.
FORGING PROPERTY DATA
A considerable effort has been undertaken to determine the flow behavior of workpiece materials, and a data base suitable for use in simulation programs is being developed. However, other necessary properties, such as thermal expansion coefficients, thermal conductivity, and elastic properties at elevated temperatures, are not readily available, especially at temperatures encountered in the forging process. Thermal and mechanical properties of die materials are needed in order to predict die stresses and distortions which affect the workpiece metal flow and final dimensions of the forged part. These properties are also needed to predict
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