Toshiharu Nomoto

Information models and functions for CIM in shipbuilding

In order to make significant progress in design and manufacturing systems, all industries must consider integration. This paper considers information models and functions for a computer integrated design and manufacturing system in shipbuilding. The authors propose the product model and several alterative functions for designing a ships structure, and develop a “ship definition system for computer integrated design and manufacturing.” This system is called SODAS (System of Design and Assembly for Shipbuilding). An object-oriented concept is used to develop this system. In order to define a ships structure, the authors propose the product models of “parts member” and “parts connection,” and the product models of “Room,” “Unit,” and “Module” are introduced to define the compartments, internal structures and intermediate products of a ship. Therefore, all information about a product from the design to the production stage is stored in the product model. As well as the product model, the “design function,” “cutting function,” and “virtual assembling function” are introduced. By using the design function, any type of ships structure can be designed, and by using the cutting function, the design of a ships structure can be cut into smaller elements. By using the virtual assembling function, a simulation of the manufacture of a ships structure can be carried out.

Life-cycle simulation model for large scale welded structure-a basic study on welded joint model with consideration of the welded joint corrosion

Corrosion of the welded joint has been singled out as a main cause of damage to ships. Insufficient maintenance of ships causes severe accidents due to the deterioration of products. These accidents lead to serious problems ranging from environmental pollution caused by oil spills to loss of lives. In order to prevent such accidents, we should design the products life cycle before designing the product, evaluate the life of the product, and make effective maintenance plans by computer simulation. Additionally, we should think of realizing the best product design front the viewpoint of life-cycle management. This paper presents a welded joint model that considers the effect of corrosion of the welded joint of a ship structure and presents a scenario for the collapse of a ship. In addition, a simulation method for evaluating product deterioration by corrosion of the welded joint is shown. In order to support a life-cycle design that takes corrosion into account, the authors have implemented a life-cycle simulation system based on a product model for computer-aided design and production.

A study on the simulation of water cooling process for the prediction of plate deformation due to line heating

Abstract In a line heating process for hull forming, the phase of the steel transforms from austenite to martensite, bainite, ferrite, or pearlite depending on the actual speed of cooling following line heating. In order to simulate the water cooling process widely used in shipyards, a heat transfer analysis on the effects of impinging water jet, film boil-ing, and radiation was performed. From the above simulation it was possible to obtain the actual speed of cooling and volume percentage of each phase in the inherent strain region of a line heated steel plate. Based on the materi-al properties calculated from the volume percentage of each phase, it should be possible to predict the plate de-formations due to line heating with better precision. Compared to the line heating experimental results, the simu-lated water cooling process method was verified to improve the predictability of the plate deformation due to line heating. Keywords: Line Heating Process; Heat Transfer Analysis; Cooling Speed; Phase Transformation; Inherent Strain; Plate Defor -mation

Safety Information Management System in the Assembly Stage of Shipbuilding

In order to carry out manufacturing operations more safely, it is necessary to acquire the safety information at the manufacturing planning stage. With the development and spread of IT in recent years, the database of various industrial accident examples is built in a company and the environment which can easily browse and share industrial accident example data is developed using computer networks. However, it is very difficult to acquire the appropriate safety information considering the industrial accident cases relevant to the assembly operations.This paper proposes a framework of information system for safety management, by assessing the risk of accident and the cost of safety. In this system, a database of industrial accident cases is introduced and integrated with the virtual assembly simulation. A planner of safety management can make the scenario of assembly operations using the virtual assembly simulation, and get hazards from simulations. Then, the system checks each case of accident using the database and show alternative measures for accidents with the value of risks and costs. He/She can interactively select appropriate measures and the system can show a statement of work to make the assembly operations safer.

A Study of Structural Optimization Design System Based on Product Model in Shipbuilding

Recently, a structural optimization design system linked with a FEM analysis system is going to be useful for a structural design, by a radical development of a computer environment. But, when structural engineers use this design system in practice, complicated operations are required to make an input-data. So this design system is not “a Practical Tool” for designers, we have to develop the structural optimization design system which is used easily for designers.Authors research the CIM for shipbuilding and develop a prototype CIM system. We call this system SODAS (System Of Design and Assembling for Shipbuilding). In the SODAS, designers can design a ship structure by design parameters and evaluate a designed structure by FEM directly.In this study, authors try to integrate a commercial structural optimization design system (GENESIS : which is developed in NASA) with the SODAS. We make relations clear between design parameters in the SODAS and design variables in the structural optimization design system. And we propose the method of system integration used by these relations. In the concrete, we develop the structural optimization design system based on the Product Model which supports designers powerfully by presenting optimal design-values.

The Analysis of Radial Deformation on Annular Local Heating Processed Pipe. Study of fitted pipe's manufacturing method due to annular local heating process (Report 2).

This report summarizes the study on numerical analysis of thermal elastic-plastic deformations of steel pipes due to annular local heating process. This process in which while the local area is heated annularly the adjacent sections are cooled can be applied to reduce the diameter of steel pipes.The results of this study are as follows ;(1) While the circumferential plastic strains generated during heating period are compressive, they are tensile during cooling.(2) When the compressive plastic strains remain after cooling, the pipe shrinks. The remaining tensile plastic strains cause the pipe to expand.(3) The variation of the longitudinal temperature distribution controls whether the pipe shrinks or expands.(4) Since the effect of the parameters on deformation of pipe, namely the distribution of temperature, the cross section shape of pipe and the number of themal cycles, can be determined by performing thermal elastic-plastic numerical analysis one can control the deformation of the pipe caused by a forementioned process.(5) The numerical predictions show good agreement with experimental results. Moreover, it is found that the value of pipe shrinkage can be represented by the parameter αTmax/βLc.

System of Parts Design Based on Product Definition System

To define parts in shipbuilding, much information is required such as plate thickness, groove shape and slot shape. To support the work of parts definition, the authors have developed a system for parts design, using a prototype system of CIM for shipbuilding, called SODAS (system of design and assembling for shipbuilding). In this paper, a new concept is proposed: superiority and inferiority of parts for the description of the relationship between two parts. The information is inputted into parts as attribute data. Because of the recognition of the relation between parts by this information at the design stage, the detailed shape of parts can be designed.

Study of Fitted Pipe's Manufacturing Method due to Annular Limited Heating. (Part 1). Shrinkage of Pipe due to Annular Limited Heating.

Thermal plastic process for reducing a diameter of metal pipe by heating an annular limited section of the pipe while cooling adjacent sections has been developed.This report is concerned with the method of the process, its principle and the effect of parameters for shrinkage of pipe.The principle of shrinkage of pipe is explained that the limited section of pipe heated by an annular induction coil tends to radially expand outwardly. However, due to the self-restriction against thermal expansion and reducing the yielding strength because of high temperature condition, the heated sections diameter is not increased so much as that of free expansion. As a result, a diameter of thermal plastic processed part is reduced in comparison with initial one after cooling.As for the parameters, maximum temperature, coil length, diameter, wall-thickness and number of repetition are given. Effects of parameters for shrinkage of pipe are as follows.As maximum temperature becomes higher and coil length becomes shorter, the shrinkage of pipe is increased. And as diameter and wall-thickness of the pipe become bigger respectively, the shrinkage is increased slightly.Furthermore, if this process is repeated for the same pipe, the shrinkage is increased.

Plane Elastic-Plastic Analysis of Perforated Plates based on Complex Stress Functions

The problem of stress distribution around a hole or a crack belongs to the very important one in the field of fracture mechanics. In this paper, the problem of an infinite plate with a circular or elliptic hole under simple tension was investigated.Basic equations were derived from complex stress functions introduced by E. Goursat and developed by N. I. Muskhelishvili and S. Moriguchi. As a first step, stress function FX (x, y;x0, y0) for a unit force in x-direction valid for a infinite plate without any discontinuity was derived. Then, by the use of principle of reflection (proposed by S. Moriguchi), the stress function FXH (x, y;x0, y0) for a plate with a hole was deduced.Two dimensional elastic-plastic analysis was conducted by using the “Modified Initial Strain Method” introduced by T. Fujimoto in the field of welding dynamics.In order to derive stress function Fex* (x, y;x0, y0) for unit initial strain e*x atpoint (x0, y0), the concept of thermo-elastic theory was used.The calculated results show that the applied analytical method is more useful in stress calculation than F. E. M.

Studies on Prevention of End Cracking in One Side Automatic Welding (2nd Report)

Recently one sided automatic welding has widely been prevailed in the assemble stage of Japanese shipyards. As one of the problems of welding procedure, as well as any other welding techniques, cracking which sometimes occurs near the end of weld, has become an important problem.The authors have proposed the calculation technique in the seam welding. The most significant feature of the method differing from the ordinary welding thermal stress analysis is that the conditions of calculation are simulated to be those of more realistic welding procedures.Then, the following assumptions are imposed in order to calculate stress and strain during welding.(1) Before welding, specimens are connected by tack welds and prepared edges are free boundaries.(2) Molten region containing arc tip is free from stress.(3) After the arc passed by, the plates are connected by solidifying of the molten pool, that is, free prepared edge changes to supported one as temperature is cooled down.(4) When the arc passed through a tack weld, it should be melted away and free from stress.In order to calculate the thermal stress analysis during welding, firstly we solved un-stationary heat conduction problems and obtained temperature distribution during welding. Based on the calculated temperature distribution, we analysed uncoupled thermal stress problems by using the finite element method, and conclusively showed that one of the main causes of end cracking is the transient tensile stresses generated near the end part of weldment when the stress re-distribution is taken place due to the melting of the last tack weld.To endorse the numerical calculation by the proposed method, experiments are carried out and it is confirmed that the method could be applicable to this kind of transient welding stress-strain state with time depending varying boundary conditions.