The Experts below are selected from a list of 39111 Experts worldwide ranked by ideXlab platform
Ken-ichiro Mori - One of the best experts on this subject based on the ideXlab platform.
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Hemming for Joining High Strength Steel Sheets
Procedia Engineering, 2020Co-Authors: Z. Hamedon, Ken-ichiro MoriAbstract:A high Strength Steel sheet is used to make the hollow sections for the body structure of automobiles. The hollow sections, which are typically joined by resistance spot welding have insufficient energy absorption because the joins are not continuous. Thus, to overcome this problem, the hollow section is joined using the hemming process. The hemming of the high Strength Steel sheet was successfully performed using punch with stopper. The high Strength Steel hollow sections joined by hemming and resistance spot welding were then examined by tensile and fatigue tests. The hollow section with hemmed joins showed better performance in both tests. The overlapping joins of the hemmed hollow section have greater Strength as compared to the resistance of spot welding joins.
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Bending process for producing uniform angle distribution from ultra-high Strength Steel sheets having thickness distribution
The International Journal of Advanced Manufacturing Technology, 2020Co-Authors: Wataru Ijichi, Ken-ichiro Mori, Sadao MiyazawaAbstract:Because of the elastic deformation of rolling mills in rolling, the edge drop in thickness of rolled ultra-high Strength Steel sheet was remarkable, thus the thickness distribution was not uniform. The distribution of angle before and after unloading in V-bending of the ultra-high Strength Steel sheets having such a thickness distribution was measured. The bend angle was nonuniformly distributed by the insufficient bend angle at the bottom dead centre and springback during unloading. The effects of the bent angle and thickness distribution on the springback in thin and thick edges were discussed. The distribution of bend angle was reduced by bottoming with a three-piece die using a rubber pad. It was found that bottoming with a divided die using a rubber pad in bending is effective in improving the dimensional accuracy of ultra-high Strength Steel sheets having a thickness distribution by finite element simulation and experiment.
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Improvement of Joinability in Mechanical Clinching of Ultra-High Strength Steel Sheets Using Counter Pressure
Advanced Materials Research, 2014Co-Authors: Shoma Nishino, Ken-ichiro Mori, Toru KatoAbstract:A mechanical clinching using counter pressure of a rubber disk was developed to join the ultra-high Strength Steel sheets having low ductility. In the proposed process, the interlock was increased by the increment of metal flow with the counter pressure of rubber disk in the die cavity. The two kind of ultra-high Strength Steel sheets having different ductility were used in the mechanical clinching. The effect of the shape of rubber disk on the deforming behaviour of the sheets was investigated. The joinability was improved under the appropriate shape of rubber disk for both sheets, and then the sheets having 56% of reduction area were successfully joined whereas the sheets were not joined without the counter pressure. Although the joinability of the sheets having 43% of reduction area was improved, the cracks occurred in the upper sheet around the punch sidewall. The maximum static load and the fatigue limit of the joined sheets were measured in the tension-shearing and cross-tension tests. It was effective for the improvement of joinability in the mechanical clinching of ultra-high Strength Steel sheets to use the counter pressure of the rubber disk.
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Improvement of Joinability in Mechanical Clinching of Ultra-high Strength Steel Sheets Using Counter Pressure with Ring Rubber
Procedia Engineering, 2014Co-Authors: Shoma Nihsino, Ken-ichiro Mori, Takato SaitoAbstract:Abstract A mechanical clinching using counter pressure of a rubber ring was developed to join the galvanised ultra-high Strength Steel sheets having low ductility. In the proposed process, the interlock was increased by the increment of metal flow with the counter pressure of rubber ring in the die cavity. The ultra-high Strength Steel sheets having 45% of reduction area was used in the mechanical clinching. The effect of the shape of rubber ring on the deforming behaviour of the sheets was investigated. The joinability was improved under the appropriate shape of rubber ring, and then the sheets were successfully joined with the counter pressure. The maximum static load and the fatigue limit of the joined sheets were measured in the tension-shearing and cross-tension tests. It was effective for the improvement of joinability in the mechanical clinching of ultra-high Strength Steel sheets to use the counter pressure of the rubber ring.
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joining of high Strength Steel and aluminium alloy sheets by mechanical clinching with dies for control of metal flow
Journal of Materials Processing Technology, 2012Co-Authors: Ken-ichiro Mori, Toru KatoAbstract:Abstract High Strength Steel and aluminium alloy sheets were joined by mechanical clinching with dies for control of metal flow. Since the sheets undergo plastic deformation for the joining during the mechanical clinching, the high Strength Steel sheets tend to fracture due to the small ductility. For the upper high Strength Steel sheet, fracture was caused by the concentration of deformation around the corner of the punch, and cracks were caused by the tensile stress generated in the bulged bottom into the groove of the die for the lower high Strength Steel sheet. To prevent these defects, metal flow of the sheets was controlled by optimising a shape of the die. For the upper high Strength Steel sheets, the depth of the die was decreased to prevent the concentration of deformation around the corner of the punch. On the other hand, the groove of the die was eliminated to reduce the tensile stress for the lower high Strength Steel sheets. The sheets below SPFC780 and SPFC980 were successively joined with the aluminium alloy sheet for the upper and lower high Strength Steel sheets, respectively.
Toru Kato - One of the best experts on this subject based on the ideXlab platform.
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Improvement of Joinability in Mechanical Clinching of Ultra-High Strength Steel Sheets Using Counter Pressure
Advanced Materials Research, 2014Co-Authors: Shoma Nishino, Ken-ichiro Mori, Toru KatoAbstract:A mechanical clinching using counter pressure of a rubber disk was developed to join the ultra-high Strength Steel sheets having low ductility. In the proposed process, the interlock was increased by the increment of metal flow with the counter pressure of rubber disk in the die cavity. The two kind of ultra-high Strength Steel sheets having different ductility were used in the mechanical clinching. The effect of the shape of rubber disk on the deforming behaviour of the sheets was investigated. The joinability was improved under the appropriate shape of rubber disk for both sheets, and then the sheets having 56% of reduction area were successfully joined whereas the sheets were not joined without the counter pressure. Although the joinability of the sheets having 43% of reduction area was improved, the cracks occurred in the upper sheet around the punch sidewall. The maximum static load and the fatigue limit of the joined sheets were measured in the tension-shearing and cross-tension tests. It was effective for the improvement of joinability in the mechanical clinching of ultra-high Strength Steel sheets to use the counter pressure of the rubber disk.
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joining of high Strength Steel and aluminium alloy sheets by mechanical clinching with dies for control of metal flow
Journal of Materials Processing Technology, 2012Co-Authors: Ken-ichiro Mori, Toru KatoAbstract:Abstract High Strength Steel and aluminium alloy sheets were joined by mechanical clinching with dies for control of metal flow. Since the sheets undergo plastic deformation for the joining during the mechanical clinching, the high Strength Steel sheets tend to fracture due to the small ductility. For the upper high Strength Steel sheet, fracture was caused by the concentration of deformation around the corner of the punch, and cracks were caused by the tensile stress generated in the bulged bottom into the groove of the die for the lower high Strength Steel sheet. To prevent these defects, metal flow of the sheets was controlled by optimising a shape of the die. For the upper high Strength Steel sheets, the depth of the die was decreased to prevent the concentration of deformation around the corner of the punch. On the other hand, the groove of the die was eliminated to reduce the tensile stress for the lower high Strength Steel sheets. The sheets below SPFC780 and SPFC980 were successively joined with the aluminium alloy sheet for the upper and lower high Strength Steel sheets, respectively.
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self piercing riveting of high tensile Strength Steel and aluminium alloy sheets using conventional rivet and die
Journal of Materials Processing Technology, 2009Co-Authors: Toru Kato, Ken-ichiro MoriAbstract:Abstract High tensile Strength Steel sheets having different Strengths were joined with an aluminium alloy sheet by a self-piercing rivet. In the joining, a conventional rivet and die used for aluminium alloy sheets were employed in order to have the versatility for various Steel sheets. The effects of the flow stress of the high Strength Steel sheets and the combination of the sheets on the joinability of the sheets were investigated by finite element simulation and an experiment. As the tensile Strength of the high Strength Steel sheet increases, the interlock for the upper high Strength Steel sheet increases due to the increase in flaring during the driving through the upper sheet, whereas that for the lower high Strength Steel sheet decreases. The joint Strength for the lower high Strength Steel is comparatively smaller than that for the upper high Strength Steel sheet. It was found that the high tensile Strength Steel sheets below 590 MPa were fully joined with the aluminium alloy sheet even with the conventional self-piercing rivet and die.
A H Clausen - One of the best experts on this subject based on the ideXlab platform.
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axial crushing of thin walled high Strength Steel sections
International Journal of Impact Engineering, 2006Co-Authors: V Tarigopula, M Langseth, Odd Sture Hopperstad, A H ClausenAbstract:Abstract Quasi-static and dynamic axial crushing tests were performed on thin-walled square tubes and spot-welded top-hat sections made of high-Strength Steel grade DP800. The dynamic tests were conducted at velocities up to 15 m/s with an impacting mass of 600 kg in order to assess the crush behaviour, the deformation force and the energy absorption. Typical collapse modes developed in the sections and the associated energy absorbing characteristics were examined and compared with previous studies on high-Strength Steel. A significant difference was observed between the quasi-static and the dynamic crushing tests in terms of the deformation force and impact energy absorption. As this difference is attributed to strain-rate and inertia effects, material tensile tests at elevated strain rates have been carried out. A comparison is made with analytical methods and the response was under-predicted. In addition, numerical simulations of the axial crushing of the thin-walled sections were performed and comparisons with the experimental results were satisfactory. The validated numerical model was used to study the energy absorption capacity of thin-walled sections with variations in the yield Strength, sheet thickness, flange width and spot-weld spacing. Structural effectiveness differences have been captured through simulations between spot-welded top-hat sections made of mild Steel and high-Strength Steel.
Hidekazu Murakawa - One of the best experts on this subject based on the ideXlab platform.
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numerical and experimental study on nugget formation in resistance spot welding for three pieces of high Strength Steel sheets
Journal of Materials Processing Technology, 2010Co-Authors: Hidekazu MurakawaAbstract:Abstract A resistance spot welding for three pieces of high Strength Steel sheets was selected as a research subject and the nugget formation processes at the various welding conditions were investigated by both experimental measurement and FEM simulation. The FEM program developed by the authors considered the coupling of the electrical field, thermal field and mechanical field. The interface elements were used to model the transient contact states between two worksheets or between a worksheet and an electrode. The electrical resistance and thermal–mechanical properties of the interface elements change with the contact state, and can have different values from the worksheets and electrodes. The nugget sizes and its formation process predicted by FEM agreed very well with experimental results. The welding conditions (current, cycles and force) to produce sound nuggets for both two pieces and three pieces of high Strength Steel sheets were accurately estimated by the simulation.
Renata Kovacevic - One of the best experts on this subject based on the ideXlab platform.
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Hybrid laser/arc welding of advanced high Strength Steel in different butt joint configurations
Materials and Design, 2014Co-Authors: M. Mazar Atabaki, G Yang, J. Ma, Renata KovacevicAbstract:An experimental procedure was developed to join thick advanced high Strength Steel plates by using the hybrid laser/arc welding (HLAW) process, for different butt joint configurations. The geometry of the weld groove was optimized according to the requirements of ballistic test, where the length of the softened heat affected zone should be less than 15.9. mm from the weld centerline. The cross-section of the welds was examined by microhardness test. The microstructure of welds was investigated by scanning electron microscopy and an optical microscope for further analysis of the microstructure of fusion zone and heat affected zone. It was demonstrated that by changing the geometry of groove, and increasing the stand-off distance between the laser beam and the tip of wire in gas metal arc welding (GMAW) it is possible to reduce the width of the heat affected zone and softened area while the microhardness stays within the acceptable range. It was shown that double Y-groove shape can provide the optimum condition for the stability of arc and laser. The dimensional changes of the groove geometry provided substantial impact on the amount of heat input, causing the fluctuations in the hardness of the weld as a result of phase transformation and grain size. The on-line monitoring of HLAW of the advanced high Strength Steel indicated the arc and laser were stable during the welding process. It was shown that less plasma plume was formed in the case where the laser was leading the arc in the HLAW, causing higher stability of the molten pool in comparison to the case where the arc was leading.
