An automatic welding system using Tungsten Inert Gas (TIG) welding with vision sensor for welding of aluminum pipe was constructed. This research studies the intelligent welding process of aluminum alloy pipe 6063S-T5 in fixed position and moving welding torch with the AC welding machine. The monitoring system consists of a vision sensor using a charge-coupled device (CCD) camera to monitor backside image of molten pool. The captured image was processed to recognize the edge of molten pool by image processing algorithm. Neural network model for welding speed control were constructed to perform the process automatically. From the experimental results it shows the effectiveness of the control system confirmed by good detection of molten pool and sound weld of experimental result.

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In several engineering fields including biological, sports, aeronautical and aerospace identification of pressure distribution applied to structures is a very important issue. Several experimental techniques have been suggested to measure the distributed load with piezo-electric sensors or films. Such direct measurement often meets with difficulty because the geometry or rigidity of the contact surface may be altered by attaching the sensors to it. To overcome this difficulty, this paper discusses the estimation of pressure distribution applied to structures by the inverse analysis technique. A transmission matrix is introduced which provides a linear relation between distributed load and internal strain. Tikhonov regularizaton and truncation of singular value decomposition (TSVD) are used to stabilize the solutions of the inverse analysis. A numerical demonstration for the estimation of foot pressure applied to a rectangular plate is conducted to illustrate the effectiveness of the present numerical formulation to identify the pressure distribution.

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Indentation analysis based on the representative strain offers an effective way of obtaining material elastoplastic properties from the reverse analysis of indentation load-displacement curve. In this paper, its approach is employed to analyze the unloading force-depth curves obtained from a sharp microindentation test. By using the unloading work and residual penetration depth as parameters characterizing unloading, two different formulations of representative strain/stress are proposed, respectively, with very simple functional forms. When combined with the established framework of loading curves, the plastic properties and/or elastic properties of a material can be derived in closed-form using the loading curvature, unloading work, and residual depth measured from one sharp indentation test.

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The objective is to characterize the effect of the microstructure of the micro pores inside the matrix on the mechanical properties of the thermoplastic syntactic polypropylene (PP) foams at the intermediate and high strain rates. Tensile tests are conducted at the nominal strain rates from 3 x 10^-1 to 10² s^-1. In addition, the dart impact tests are conducted at the impact velocities of 0.1, 1 and 10 m/s. Then, the constitutive law with craze evolution is modified by introducing the relative density, the stress concentration coefficient and the volume fraction of cell edge, and then applied to the dart impact test mode for simulating the macroscopic load displacement history of the dart impact process. Moreover, the microstructural finite element analysis is conducted to characterize the local stress states in the microstructure. In the tensile loading, the elastic modulus is not influenced by the shape of the micro pores in the PP matrix while the yield stress and the strain energy up to failure are relatively influenced by the shape of micro pores. The microstructural finite element analysis shows that the magnitudes of the localized stresses at the edges and the ligaments of the elliptical-shape micro pores are larger than those at the spherical micro pores, leading to the early yielding and the small material ductility. In the case of the dart impact loading, the microstructure of pores has strong effect on the absorbed energy. This is because the elliptical-shape micro pores are very sensitive to the shear deformation, which is revealed by the microstructural finite element analysis. The modified constitutive law with the stress concentration coefficient and the volume fraction of the cell edges successfully predicts the load-displacement curve of the dart impact loading in the spherical micro-porous PP foam. It is concluded that the micro porous shape has strong effect on the material ductility especially in the dart impact test, leading to the possibility to control the material ductility by the shape of the micro pores in the polymeric foams.

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Guided waves, i.e., ultrasonic wave packets propagating in the longitudinal direction, are a promising technique for rapid long-range nondestructive inspection of bar-like structures such as pipes and rails. Guided wave inspection requires determining guided wave velocities (dispersion curves) and wave structures. A computational technique is available to obtain the dispersion curves and wave structures for structures with complex cross-sections. This study develops a more accurate technique using the mirror relation of guided wave modes and an iteration method for solving the eigenproblem. Experimental studies of a JIS 6-kg rail verify that dispersion curves and wave structures can be obtained with sufficient accuracy for typical out-of-plain vibration modes. Wave structures were obtained by measuring waveforms at several points on the curved surface of the rail with a laser interferometer controlled by robot arms.

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This study was conducted to investigate the effect of DLC (diamond-like carbon) coating on fatigue properties of austenitic stainless steel SUS304. For the DLC coating, UBMS (unbalanced magnetron sputtering) equipment was used. The generated surface layer of about 2 μm thickness was composed of both the DLC layer possessing high hardness and a very thin intermediate layer to improve adhesion force between the DLC layer and the substrate. DLC coating, which was carried out at a relatively low temperature, had no influence on the microstructure so that the mechanical properties of the stainless steel were unchanged by the coating. The results of the plane-bending fatigue test showed that the DLC coating improved fatigue strength by 18%. From the results of detailed observation conducted on the fatigue fracture surface, it was suggested that the improvement in fatigue strength resulted from the suppression of fatigue crack initiation due to the surface layer, which had high adhesion force and strength.

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In order to validate the applicability of the direct current potential difference method (DC-PDM) to the identification of interface cracks, electric field analysis was carried out for a copper plate with a solder ball joined on its surface by the finite element method. The analysis was carried out for different crack depths under the following four conditions: (a) when the shape of interface crack between solder ball and copper changes, (b) when the radius of solder ball changes, (c) when the distance between the bottom of inserted copper wire and the interface changes, and (d) when the angle of inserted copper wire changes. It was found from the analysis results that a large crack area ratio gave a large increase in the potential difference and that the effect of crack shape and the angle of copper wire on the potential difference was small. Finally, the relationship between the crack area ratio and the increase in potential difference was given by a single formulated curve for all the conditions discussed in the present analysis.

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Macroscopic deformation of biological tissue shows the various behaviors of nonlinear, aeolotropic and so on. The mechanics of the deformation generally depend on the character of the microscopic cells which have complicated structures like substratum, membrane and wall. In the cells, the strain caused by macroscopic deformation is unevenly distributed because of its structures. However, the structures cause difficulty in the observation of the strain distribution and the study on the deformation mechanics of the tissue. In this study, a birefringence microscope is applied to observe the uneven distribution of the strain. The technique of the microscope with CCD has abilities to evaluate the phase difference and the azimuthal direction, and to observe the value distribution. The uniaxial and biaxial tensile testings and the some considerations are carried out to investigate the deformation mechanics of the tissue of a plant by using the microscope system.

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Local approach to fracture based on continuum damage mechanics and finite element method is a powerful method to estimate fatigue strength, which can reduce computing time and cost for the analysis of fatigue crack initiation and propagation. In the present study, this approach has been applied to the analysis of the behaviors of ring-shaped cracks in stainless steel pipes under thermal cyclic loading. The obtained solutions have been compared with the experimental results to discuss the accuracy of uncoupled, locally-coupled and fully-coupled approaches. A new technique to remove the mesh-dependence of the solutions has been proposed and its validity has been discussed through numerical studies on the low-cycle fatigue crack propagation.

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Considering a rule for the rationalization of maintenance of Light Water Reactor piping, reliable flaw evaluation criteria are essential for determining how a detected flaw will be detrimental to continuous plant operation. Ductile fracture is one of the dominant failure modes that must be considered for carbon steel piping and can be analyzed by elastic-plastic fracture mechanics. Some analytical efforts have provided various flaw evaluation criteria using load correction factors, such as the Z-factors in the JSME codes on fitness-for-service for nuclear power plants and the section XI of the ASME boiler and pressure vessel code. The present Z-factors were conventionally determined, taking conservativity and simplicity into account; however, the effect of internal pressure, which is an important factor under actual plant conditions, was not adequately considered. Recently, a J-estimation scheme, LBB.ENGC for the ductile fracture analysis of circumferentially through-wall-cracked pipes subjected to combined loading was developed for more accurate prediction under more realistic conditions. This method explicitly incorporates the contributions of both bending and tension due to internal pressure by means of a scheme that is compatible with an arbitrary combined-loading history. In this study, the effect of internal pressure on the flaw evaluation criteria was investigated using the new J-estimation scheme. The Z-factor obtained in this study was compared with the presently used Z-factors, and the predictability of the current flaw evaluation criteria was quantitatively evaluated in consideration of the internal pressure.

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