Data processing: generic control systems or specific application – Specific application – apparatus or process – Product assembly or manufacturing
Reexamination Certificate
1999-10-28
2002-11-26
Von Buhr, Maria N. (Department: 2125)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Product assembly or manufacturing
C700S110000, C073S804000, C703S009000
Reexamination Certificate
active
06487468
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of Japanese Patent Application No. HEI 10-309920 filed on Oct. 30, 1998 and No. HEI 11-223755 filed on Aug. 6, 1999, each including the specification, drawings and abstract, is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to analysis of a forging process of a material and, more specifically, to a technology for analyzing and/or predicting deformation of a workpiece caused due to the forging process performed thereon by setting fiber flow lines in the interior of the workpiece and calculating displacements of the fiber flow lines caused by the forging process. The invention relates particularly to a technology capable of analysis taking three-dimensional information into account.
2. Description of the Related Art
Forging processes, such as pressing or the like, sometimes suffer from defects, such as forging defects, dead metal, buckling or the like, depending on the combination of whether the workability of a material is good and how the material is processed. To analyze such defects, a fiber flow line is conventionally observed. Observation of a fiber flow line makes it possible to identify the type of the defect and detect the condition of friction between the workpiece and a die. In order to observe a fiber flow line, however, it is necessary to prepare a die, forge a material with the die, cut out a sample piece for the observation from the forged material, grind and etch the sample piece, and place it under a microscope. Results of the observation are fed back to the die designing or the production process designing. A single cycle of this procedure of observation and feedback consumes a long period of time, for example, several months. Therefore, the process designing cannot be quickly accomplished.
To avoid consumption of a long time, computer simulation of a forging process is often employed to predict the state of a fiber flow line occurring after the process. In many cases, such a simulation is performed by a finite element method. In a conventional manner of simulation based on the finite element method, a workpiece is divided into many elements by setting a grid mesh in the workpiece, and the displacements of individual element-forming nodes (grid points) are sequentially calculated to simulate the deformation of the entire workpiece.
However, the aforementioned conventional arts have the following problems. That is, the method in which a fiber flow line in an actually processed material is observed consumes an inconveniently long time as mentioned above. Furthermore, the method does not allow observation of material flowage in a cross section of a sample piece perpendicular to the length of the piece because a fiber flow line does not exist in such a section.
The conventional manner of computer simulation of a forging process is not able to provide a result whose fineness exceeds the fineness of the grid mesh set during an initial period of the analysis. This problem becomes remarkable particularly at sites of a workpiece that have high rates of surface area expansion. Furthermore, at a position between nodes, a left-behind phenomenon in which a deformed portion is left behind in a die sometimes occurs. This phenomenon makes it impossible to simulate a precise shape occurring after deformation.
SUMMARY OF THE INVENTION
Accordingly, the invention is intended to solve the aforementioned problems of the conventional technologies for analyzing a forging process. It is an object of the invention to provide a forging process analyzing method that allows simulation of a forging process within a short period of time, and also allows high-precision analysis with respect to a section perpendicular to the length of a workpiece and a site of a great expansion, and further allows display of results of the analysis in a three-dimensional manner, and to provide a medium storing a program for executing the method.
In the forging process analyzing method of the invention, a plurality of trace points for expressing at least one fiber flow line are set in a workpiece that is to be forged by a die. Furthermore, a displacement of each trace point involved in deformation of the workpiece is calculated. At least one post-deformation fiber flow line is expressed in the workpiece by connecting the trace points after displacement.
More specifically, trace points are set in the shape of a workpiece before a process is performed on the workpiece. The trace points provided for expressing fiber flow lines. That is, a bent or curved line obtained by connecting trace points expresses a fiber flow line. Arbitrary fiber flow lines can be set. That is, the fiber flow lines may be lines that match real fiber flow caused by the past processes actually performed on a workpiece or lines based on a simulation of real fiber flow. Furthermore, the fiber flow lines may also be imaginary lines that are irrelevant to real fiber flow. With regard to each trace point, a displacement involved in deformation caused by a process performed on the workpiece is calculated. Normally, this calculation is executed by iterative operation. Then, the post-displacement trace points are connected to form bent or curved lines that express fiber flow lines occurring after the workpiece has been processed.
Based on the post-process fiber flow lines, it is possible to predict whether the workability is good when the workpiece is actually subjected to the forging process. That is, it is possible to predict a possibility of occurrence of defects, such as a forging defect, dead metal, buckling and the like. This forging process analyzing method can be performed through computer processing. The computation time required by the method is only slightly longer than the computation time required when a normal finite element method is employed. Therefore, results of the analysis can be fed back to the die designing and the production process designing in a turn-around time of only one day or less. The forging process analyzing method thus contributes to quick process designing. Furthermore, the method of the invention achieves finer and closer results than a method in which fiber flow lines are formed by using element-forming nodes.
The forging process analyzing method of the invention is intended for the application to an analysis based on a Lagrangian method in which trace points are not fixed in a space but set as mobile points that move together with a workpiece material and the movement of the trace points caused by a workpiece process is tracked. Therefore, it is not essential to place trace points on a surface of a workpiece during the setting of trace points. Trace points belong to the same elements before and after being displaced.
In the forging process analyzing method of the invention, a new trace point may be set between trace points in a portion that has a high rate of expansion caused by deformation. That is, when calculation of a displacement of each trace point finds that the distance between post-displacement trace points has become equal to or greater than a certain value, a new trace point is set between those trace points. Then, the subsequent calculating process is performed. Therefore, it becomes possible to perform fine and close analysis even at a site of a high rate of expansion caused by the workpiece process (typically interpreted as a high rate of expansion of surface area).
The additional setting of a new trace point may be performed in the following manner. That is, a distance between adjacent trace points present on a fiber flow line is compared with a predetermined critical value. When the distance between the adjacent trace points exceeds the critical value, a new trace point is set. This manner of setting a new trace point prevents the distance between trace points from exceeding the critical value even at a site of expansion caused by deformation. Therefore, it becomes possible to perform fine and close analysis even at a site of a high expansion rate.
Furthermore, in the
Akashi Tadao
Atsumi Yoshitaka
Matsuoka Naoki
Nakanishi Kokichi
Takeuchi Masahiko
Bahta Kidest
Pillsbury & Winthrop LLP
Toyota Jidosha & Kabushiki Kaisha
Von Buhr Maria N.
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