Integrated structural analysis system with on-line coordinate-measuring machines for car body panels

Abstract

This paper deals with computer graphics applications for developing new types of steel sheets for car body panels, which would contribute to car milage improvement by weight reduction. This computer system in which structural analysis system is implemented, has been primary developed for CAD/CAM application to ROLL PASS design of grooved rolls with which rails, seamless pipes, beams and other steel sections are produced. On line 3-D coordinate measuring machines, graphic displays, a digitizer, a high speed/accuracy drafting machine and an on line ultrasonic thickness meter are the major devices of the computer graphics system of which mini-computers are linked to main frame computers where general purpose Finite Element programs, e.g. NASTRAN, MARC, are installed for structural analysis of pressed steel sheets for car body panels. The functions of this system could be categorized into the following three: 1. (1) Profile measurement and analysis of pressed steel sheets to visualize and quantify even minute unfavourable shape due to inadequate material properties and pressing conditions. 2. (2) An on line ultrasonic thickness meter built in the graphic system plays an important role for analysing plastic deformation behaviour by graphical representation of panel thickness data which is also valuable for geometric description of the structure. 3. (3) An integration of data preparation facility through extensive use of on line 3-D coordinate measuring machines and every variety for Finite Element programs in bigger computing resources are the key feature of this system. These computer analyses, of press formability, vibration behaviour and stiffness performance which would vary with material properties and pressing conditions could add invaluable information to research and development of both forming technique and new steel quality. This paper also contains a discussion on performance properties of newly developed steel sheets, i.e. anisotropic steel which shows high stiffness because of a virtual Young's modulus and non-uniform thickness steel sheets with slight convexo-convex sectional profile for reducing material volume without decreasing the stiffness. Computer Graphics and computer utilization in automobile industry have often been reported so far, from clay model measurement to car body design and die manufacturing. Compared with this situation, profile measurement and analyses for material development of steel sheets are still being done with dial gauges or offline position sensors where tedious data processing work is still required. The Computer Graphics system described in this paper features on-line 3-D coordinate measuring machines and an on-line ultrasonic thickness meter which enable one to do effective research work for improvement of press formability and performance of steel sheets. Panel stiffness and dynamic performance analyses by FEM are to be the major objectives of this paper. As the fruitful results derived from an extensive use of this integrated system anisotropic high Young's modulus steel sheets and intentionally slight-convexo-convex profiled (non flat) steel sheets have become into practical use for energy saving car body building.