Data processing: measuring – calibrating – or testing – Measurement system – Temperature measuring system
Reexamination Certificate
2002-11-12
2004-07-20
Bui, Bryan (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system
Temperature measuring system
C702S042000, C702S099000, C700S207000, C700S165000
Reexamination Certificate
active
06766268
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for calculating a heating procedure of a linear heating, in which an arrangement and heating conditions for heating lines are determined in order to carry out bending work such as work for a plate into an outer bending plate constituting a vessel shell (work for a metal plate into a target shape of a curved surface) in shipbuilding.
2. Description of the Related Art
In recent years, a method of bending work by a linear heating has been adopted for the bending work for a metal plate for use in a vessel or the like.
The linear heating is a technology of utilizing a property of a metal plate, in which the metal plate generates a plastic strain and deforms itself upon being restricted from a periphery thereof when the metal plate is linearly heated by a point heat source such as a gas burner. In addition, the linear heating is a technology of carrying out bending work for a metal plate as an object into a target shape of a curved surface by arranging heating points on respective spots on a metal plate.
Conventionally, it has been conceived that the bending work for a metal plate by the linear heating is a technique to be acquired through a long-term experience. Heating positions, directions, conditions and the like have been determined by senses and skills of skilled workers, and the bending work has been carried out. However, such a conventional method depending on the work of the skilled workers has involved problems that a long time is required for acquiring the skill and of a lack of successors. Further, a problem of a large variation in working precision has occurred. Therefore, in recent years, a method for mechanically carrying out the linear heating has been proposed.
As this type of method for mechanically carrying out the linear heating, there is a method to be described below. Namely, the surface of a metal plate to be subjected to the bending work is divided into a large number of regions by applying the Finite Element Method (FEM). Moreover, a target specific strain required for executing the bending work into the target shape of a curved surface is obtained for each of the divided regions. Curved heating lines are arranged in a crossing manner on the divided regions of one surface of the metal plate, and the metal plate is locally heated so as to receive a specified supplied heat with a moving velocity of a heat source as a control parameter while moving the heat source along the heating lines. In this manner, the membrane-shrinkage and bending strain components of the target specific strain are given, thereby bending each of the divided regions to the target shape and bending the entire metal plate to a target curved surface.
Note that a plurality of strains (i.e., four strain components including membrane-shrinkage strains along the neutral surface of the plate in two principal axes perpendicular to each other, and bending strains operating to the external direction of the plate surface in the two principal axes perpendicular to each other) are concerned in the bending work for the metal plate by the linear heating.
Meanwhile, strains generated by one heating line includes four components: a membrane-shrinkage strain in the perpendicular direction of the heating line; a membrane-shrinkage strain in the tangential direction of the heating line; a bending strain in the perpendicular direction of the heating line; and a bending strain in the tangential direction of the heating line. These four strain components are determined simultaneously for one heating condition. Therefore, in the case of using a method for heating a plate from one surface thereof by controlling only one control parameter in the above-described moving velocity of the heat source and the like, the four strain components to be obtained cannot be satisfied entirely even if two heating lines are arranged in combination perpendicularly to each other.
Therefore, a method for obtaining a heating procedure has been adopted heretofore, which is realized by: (a) a method for arranging heating lines, disclosed in Japanese Patent Application Laid-Open No. H10-230326; (b) a method for obtaining a membrane strain, disclosed in Japanese Patent Application Laid-Open No. 2001-071041; (c) a method for obtaining a heating condition, in which deformations of a plurality of adjacent heating lines are added together, and four strain components to be obtained from a deformation amount obtained by the addition are obtained averagely and approximately by use of an optimization method and so on; or the like. The above-described Japanese Patent Application Laid-Open No. H10-230326 discloses the method for arranging heating lines by paying attention only to one deformation component affecting the formation of a curved surface most, such as a bending or membrane-shrinkage deformation perpendicular to the heating line, among the four deformation components generated by the heating lines (i.e., bending and membrane-shrinkage deformations in the perpendicular direction of the heating line and bending and membrane-shrinkage deformations in the tangential direction thereof). The above-described Japanese Patent Application Laid-Open No. 2001-071041 discloses the following method including the steps of: dividing a target shape of a curved surface into fine grid regions; assuming a membrane strain in each grid region; obtaining a second-order finite difference approximating second-order differential of membrane strains between a membrane strain in the grid region and a membrane strain in a region surrounding the grid region; forming simultaneous equations on the assumption that the second-order finite difference in the membrane strains and a degree of incompatibility R in a region composed of both the grid region and the region surrounding the same are equal to each other; and determining the membrane strain based on these simultaneous equations. The degree of incompatibility R has already been determined at a point of time when the curved surface was given. The degree of incompatibility R is a value obtained from a distribution of the bending strains or a curvature of the curved surface.
However, the method for arranging a heating line by paying attention only to one component affecting the formation of a curved surface most among four deformation components generated by the heating line has the following problem. Namely, the three remaining deformation components operate as disturbances, whereby a difference between the formed surface and the target shape increases. Accordingly, a case may possibly occur, where a heating condition for approximating the strain distribution giving the target shape of a curved surface precisely is not obtained.
Further, the method for obtaining a heating condition, in which the deformations of the plurality of adjacent heating lines are added together, and four strain components to be determined from the deformation amount given by the addition of the deformations are obtained averagely and approximately by use of an optimization method or the like, has the following problem. That is, magnitudes of deformations given by individual heating lines adjacent to each other are significantly different from each other. Therefore, an extra residual stress is induced around the heating lines, thereby deteriorating local precision of the curved surface.
Moreover, there has been the following problem in the method including the steps of: dividing a target shape of a curved surface into fine grid regions; assuming a membrane strain in each grid region; obtaining a second-order finite difference approximating second-order differentials of membrane strains between a membrane strain in the grid region and a membrane strain in a region surrounding the grid region; forming simultaneous equations on the assumption that the second-order finite difference in the membrane strains and a degree of incompatibility R in a region composed of both the grid region and the region surrounding the same are equal to each other; and obtain
Ishiyama Morinobu
Kobayashi Jun
Bui Bryan
IHI Marine United Inc.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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