The Experts below are selected from a list of 7815 Experts worldwide ranked by ideXlab platform

Kazuhiro Nakata - One of the best experts on this subject based on the ideXlab platform.

  • effect of welding parameters on microstructure in the stir zone of fsw joints of Aluminum Die casting alloy
    Materials Letters, 2006
    Co-Authors: Hidetoshi Fujii, Takuya Tsumura, Tamu Komazaki, Kazuhiro Nakata
    Abstract:

    The effect of the welding speed and the rotation speed on the microstructure in the stir zone has been investigated by measuring the Si particle distribution in the ADC12 alloy. The stir zone has fine recrystallized grains without dendritic structures, and the eutectic Si was uniformly dispersed in the stir zone. The size of the Si particles was statistically determined in the stir zone using image processing. The number of finer Si particles, which is formed by stirring of the tool probe, increases during the FSW. Finer Si particles are distributed more in the bottom than in the other regions, though the size of the Si particles in the base metal is the same in all the regions. The size of the Si particles decreases with increasing welding speed. However, it is not significantly affected by the rotation speed.

  • improvement of mechanical properties of Aluminum Die casting alloy by multi pass friction stir processing
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006
    Co-Authors: Kazuhiro Nakata, Hidetoshi Fujii, Takuya Tsumura, Tamu Komazaki
    Abstract:

    Abstract An improvement in the mechanical properties was accomplished due to the microstructural modification of an Aluminum Die casting alloy by multi-pass friction stir processing (MP-FSP), which is a solid-state microstructural modification technique using a frictional heat and stirring action. The hardness of the MP-FSP sample is about 20 Hv higher than that of the base metal. The tensile strengths of the MP-FSPed specimens were significantly increased to about 1.7 times versus that of the base metal. This is due not only to the disappearance of the cold flake in the base metal, but also to a structural refinement, such as uniform distribution of Si particles. Thus, the application of the MP-FSP is a very effective method for the mechanical improvement of Aluminum Die casting alloys.

  • three defect types in friction stir welding of Aluminum Die casting alloy
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006
    Co-Authors: Young Gon Kim, Hidetoshi Fujii, Takuya Tsumura, Tamu Komazaki, Kazuhiro Nakata
    Abstract:

    For different tool plunge downforces, the optimum FSW conditions of Aluminum Die casting alloy were examined. The higher the tool plunge downforce is, the wider the range of the optimum FSW conditions is. The following three different types of defects are formed, depending on the FSW conditions. (1) A large mass of flash due to the excess heat input; (2) cavity or groove-like defects caused by insufficient heat input; and (3) cavity caused by the abnormal stirring. As for the abnormal stirring, it is clearly seen that the shape of the top part on the advancing side in the stir zone is completely different. For this type of defect, the effect of the tool plunge downforce is small, though the size of the defect due to insufficient heat input significantly decreases with the increasing downforce.

  • effect of tool plunging downforce on friction stir welding of adc12 Die cast alloy
    Transactions of J W R I, 2003
    Co-Authors: Kazuhiro Nakata, 中田 一博, 村上 太一, 駒崎 徹, Tamu Komazaki, Taichi Murakami, Masao Ushio, 牛尾 誠夫
    Abstract:

    Friction Stir Welding (FSW) has been attracting attention as a useful joining process for casts with superior characteristics to conventional fusion welding. It is well known that arc welding of Aluminum Die cast alloy isvery difficult because of the formation of blowholes and cracks. In this research, the effect of the tool plunge downforce on FSW joints of SDC12 was evaluated for establishing the range of the optimum welding conditions in FSW. The range of the optimum FSW conditions for sound joints expanded with increasing tool plunge downforce, because the area of contact of the tool shoulder with the workpiece increased and plastic metal flow was activated.

Nobuhiro Yoshikawa - One of the best experts on this subject based on the ideXlab platform.

  • empirical formulation of stress concentration factor around an arbitrary sized spherical dual cavity system and its application to Aluminum Die castings
    Applied Mathematical Modelling, 2015
    Co-Authors: Sujit Bidhar, Ikumu Watanabe, Takao Utsunomiya, Yoshihiko Hangai, M. Nomura, Osamu Kuwazuru, Yoshinori Shiihara, Nobuhiro Yoshikawa
    Abstract:

    Abstract An empirical formula for the stress concentration factor is developed for an unequal-sized cavity pair in an arbitrary orientation. Three-dimensional finite element linear elastic analyses are performed to evaluate the stress concentration factors for different sizes, orientations, and separations of cavities. A suitable mathematical function is chosen to fit the numerical results of the finite element analyses. An application is given for evaluating the maximum stress concentration factor, which governs fatigue crack initiation in Aluminum Die cast test pieces from an engine block. From the X-ray CT image, the location and geometry of the gas pores are evaluated so as to develop the proposed empirical formula for this actual multi-pore system simplified to a dual spherical pore system. A proof of the formula is shown by comparison with voxel finite element analysis. The proposed empirical formula can be satisfactorily used as a scientific guideline for selecting a casting method for car engine blocks from a fatigue crack initiation perspective.

  • practical application of empirical formulation of the stress concentration factor around equally sized dual spherical cavities to Aluminum Die cast
    Applied Mathematical Modelling, 2015
    Co-Authors: Sujit Bidhar, Ikumu Watanabe, Takao Utsunomiya, Yoshihiko Hangai, Osamu Kuwazuru, Yoshinori Shiihara, Nobuhiro Yoshikawa
    Abstract:

    Abstract An empirical method is developed for obtaining the stress concentration factor for a pair of equally sized spherical cavities embedded in a large continuum in three-dimensional space. For practical applications such as Die-cast materials containing many pores, we construct a simple and robust closed-form equation to evaluate the stress concentration factor considering the interaction between two cavities. The stress concentration factor can be used to evaluate the effect of pores on the material strength and the probable location of pores that will initiate a fatigue crack. Three-dimensional finite element linear elastic analysis was carried out to evaluate the stress concentration factors for arbitrary locations of the two cavities. The effects of the inter-cavity distance and the orientation of the inter-cavity axis with respect to the loading direction on the stress concentration factor are numerically obtained by systematically changing each of these parameters. Two empirical equations are proposed to fit the stress concentration factor data calculated by finite element analysis after considering various boundary conditions from a mechanical standpoint, and the parameters of the empirical formula are obtained by non-linear curve fitting with regression analysis.

Tamu Komazaki - One of the best experts on this subject based on the ideXlab platform.

  • effect of welding parameters on microstructure in the stir zone of fsw joints of Aluminum Die casting alloy
    Materials Letters, 2006
    Co-Authors: Hidetoshi Fujii, Takuya Tsumura, Tamu Komazaki, Kazuhiro Nakata
    Abstract:

    The effect of the welding speed and the rotation speed on the microstructure in the stir zone has been investigated by measuring the Si particle distribution in the ADC12 alloy. The stir zone has fine recrystallized grains without dendritic structures, and the eutectic Si was uniformly dispersed in the stir zone. The size of the Si particles was statistically determined in the stir zone using image processing. The number of finer Si particles, which is formed by stirring of the tool probe, increases during the FSW. Finer Si particles are distributed more in the bottom than in the other regions, though the size of the Si particles in the base metal is the same in all the regions. The size of the Si particles decreases with increasing welding speed. However, it is not significantly affected by the rotation speed.

  • improvement of mechanical properties of Aluminum Die casting alloy by multi pass friction stir processing
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006
    Co-Authors: Kazuhiro Nakata, Hidetoshi Fujii, Takuya Tsumura, Tamu Komazaki
    Abstract:

    Abstract An improvement in the mechanical properties was accomplished due to the microstructural modification of an Aluminum Die casting alloy by multi-pass friction stir processing (MP-FSP), which is a solid-state microstructural modification technique using a frictional heat and stirring action. The hardness of the MP-FSP sample is about 20 Hv higher than that of the base metal. The tensile strengths of the MP-FSPed specimens were significantly increased to about 1.7 times versus that of the base metal. This is due not only to the disappearance of the cold flake in the base metal, but also to a structural refinement, such as uniform distribution of Si particles. Thus, the application of the MP-FSP is a very effective method for the mechanical improvement of Aluminum Die casting alloys.

  • three defect types in friction stir welding of Aluminum Die casting alloy
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006
    Co-Authors: Young Gon Kim, Hidetoshi Fujii, Takuya Tsumura, Tamu Komazaki, Kazuhiro Nakata
    Abstract:

    For different tool plunge downforces, the optimum FSW conditions of Aluminum Die casting alloy were examined. The higher the tool plunge downforce is, the wider the range of the optimum FSW conditions is. The following three different types of defects are formed, depending on the FSW conditions. (1) A large mass of flash due to the excess heat input; (2) cavity or groove-like defects caused by insufficient heat input; and (3) cavity caused by the abnormal stirring. As for the abnormal stirring, it is clearly seen that the shape of the top part on the advancing side in the stir zone is completely different. For this type of defect, the effect of the tool plunge downforce is small, though the size of the defect due to insufficient heat input significantly decreases with the increasing downforce.

  • effect of tool plunging downforce on friction stir welding of adc12 Die cast alloy
    Transactions of J W R I, 2003
    Co-Authors: Kazuhiro Nakata, 中田 一博, 村上 太一, 駒崎 徹, Tamu Komazaki, Taichi Murakami, Masao Ushio, 牛尾 誠夫
    Abstract:

    Friction Stir Welding (FSW) has been attracting attention as a useful joining process for casts with superior characteristics to conventional fusion welding. It is well known that arc welding of Aluminum Die cast alloy isvery difficult because of the formation of blowholes and cracks. In this research, the effect of the tool plunge downforce on FSW joints of SDC12 was evaluated for establishing the range of the optimum welding conditions in FSW. The range of the optimum FSW conditions for sound joints expanded with increasing tool plunge downforce, because the area of contact of the tool shoulder with the workpiece increased and plastic metal flow was activated.

Hidetoshi Fujii - One of the best experts on this subject based on the ideXlab platform.

  • effect of welding parameters on microstructure in the stir zone of fsw joints of Aluminum Die casting alloy
    Materials Letters, 2006
    Co-Authors: Hidetoshi Fujii, Takuya Tsumura, Tamu Komazaki, Kazuhiro Nakata
    Abstract:

    The effect of the welding speed and the rotation speed on the microstructure in the stir zone has been investigated by measuring the Si particle distribution in the ADC12 alloy. The stir zone has fine recrystallized grains without dendritic structures, and the eutectic Si was uniformly dispersed in the stir zone. The size of the Si particles was statistically determined in the stir zone using image processing. The number of finer Si particles, which is formed by stirring of the tool probe, increases during the FSW. Finer Si particles are distributed more in the bottom than in the other regions, though the size of the Si particles in the base metal is the same in all the regions. The size of the Si particles decreases with increasing welding speed. However, it is not significantly affected by the rotation speed.

  • improvement of mechanical properties of Aluminum Die casting alloy by multi pass friction stir processing
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006
    Co-Authors: Kazuhiro Nakata, Hidetoshi Fujii, Takuya Tsumura, Tamu Komazaki
    Abstract:

    Abstract An improvement in the mechanical properties was accomplished due to the microstructural modification of an Aluminum Die casting alloy by multi-pass friction stir processing (MP-FSP), which is a solid-state microstructural modification technique using a frictional heat and stirring action. The hardness of the MP-FSP sample is about 20 Hv higher than that of the base metal. The tensile strengths of the MP-FSPed specimens were significantly increased to about 1.7 times versus that of the base metal. This is due not only to the disappearance of the cold flake in the base metal, but also to a structural refinement, such as uniform distribution of Si particles. Thus, the application of the MP-FSP is a very effective method for the mechanical improvement of Aluminum Die casting alloys.

  • three defect types in friction stir welding of Aluminum Die casting alloy
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006
    Co-Authors: Young Gon Kim, Hidetoshi Fujii, Takuya Tsumura, Tamu Komazaki, Kazuhiro Nakata
    Abstract:

    For different tool plunge downforces, the optimum FSW conditions of Aluminum Die casting alloy were examined. The higher the tool plunge downforce is, the wider the range of the optimum FSW conditions is. The following three different types of defects are formed, depending on the FSW conditions. (1) A large mass of flash due to the excess heat input; (2) cavity or groove-like defects caused by insufficient heat input; and (3) cavity caused by the abnormal stirring. As for the abnormal stirring, it is clearly seen that the shape of the top part on the advancing side in the stir zone is completely different. For this type of defect, the effect of the tool plunge downforce is small, though the size of the defect due to insufficient heat input significantly decreases with the increasing downforce.

Sujit Bidhar - One of the best experts on this subject based on the ideXlab platform.

  • empirical formulation of stress concentration factor around an arbitrary sized spherical dual cavity system and its application to Aluminum Die castings
    Applied Mathematical Modelling, 2015
    Co-Authors: Sujit Bidhar, Ikumu Watanabe, Takao Utsunomiya, Yoshihiko Hangai, M. Nomura, Osamu Kuwazuru, Yoshinori Shiihara, Nobuhiro Yoshikawa
    Abstract:

    Abstract An empirical formula for the stress concentration factor is developed for an unequal-sized cavity pair in an arbitrary orientation. Three-dimensional finite element linear elastic analyses are performed to evaluate the stress concentration factors for different sizes, orientations, and separations of cavities. A suitable mathematical function is chosen to fit the numerical results of the finite element analyses. An application is given for evaluating the maximum stress concentration factor, which governs fatigue crack initiation in Aluminum Die cast test pieces from an engine block. From the X-ray CT image, the location and geometry of the gas pores are evaluated so as to develop the proposed empirical formula for this actual multi-pore system simplified to a dual spherical pore system. A proof of the formula is shown by comparison with voxel finite element analysis. The proposed empirical formula can be satisfactorily used as a scientific guideline for selecting a casting method for car engine blocks from a fatigue crack initiation perspective.

  • practical application of empirical formulation of the stress concentration factor around equally sized dual spherical cavities to Aluminum Die cast
    Applied Mathematical Modelling, 2015
    Co-Authors: Sujit Bidhar, Ikumu Watanabe, Takao Utsunomiya, Yoshihiko Hangai, Osamu Kuwazuru, Yoshinori Shiihara, Nobuhiro Yoshikawa
    Abstract:

    Abstract An empirical method is developed for obtaining the stress concentration factor for a pair of equally sized spherical cavities embedded in a large continuum in three-dimensional space. For practical applications such as Die-cast materials containing many pores, we construct a simple and robust closed-form equation to evaluate the stress concentration factor considering the interaction between two cavities. The stress concentration factor can be used to evaluate the effect of pores on the material strength and the probable location of pores that will initiate a fatigue crack. Three-dimensional finite element linear elastic analysis was carried out to evaluate the stress concentration factors for arbitrary locations of the two cavities. The effects of the inter-cavity distance and the orientation of the inter-cavity axis with respect to the loading direction on the stress concentration factor are numerically obtained by systematically changing each of these parameters. Two empirical equations are proposed to fit the stress concentration factor data calculated by finite element analysis after considering various boundary conditions from a mechanical standpoint, and the parameters of the empirical formula are obtained by non-linear curve fitting with regression analysis.