Abstract: A high strength steel sheet has a yield-point elongation of 1% or greater and a tensile strength of 980 MPa or greater. The high strength steel sheet has a specific chemical composition and microstructure. A ratio of retained austenite grains adjoining a retained austenite grain having a different crystal orientation to total retained austenite grains is 0.60 or greater, the ferrite has an average grain size of 5.0 ?m or less, and the retained austenite has an average grain size of 2.0 ?m or less. A value obtained by dividing a volume fraction V?a by a volume fraction V?b is 0.40 or greater, where the volume fraction V?a is a volume fraction of retained austenite in a fractured portion of a tensile test specimen after a warm tensile test at 150° C., and the volume fraction V?b is a volume fraction of retained austenite before the warm tensile test at 150° C.

Abstract: A hot-pressed member having excellent bending collapsibility, a method for manufacturing the same, and a method for manufacturing a steel sheet for the hot-pressed member. The hot-pressed member includes a steel sheet as a base material, the steel sheet having a specified chemical composition. The hot-pressed member has a microstructure in which a martensite microstructure is present in a volume fraction of 70% or greater, and a number density of inclusions having a longest diameter of 25 ?m or greater is 0.02/mm2 or less. The hot-pressed member has a tensile strength of 1.8 GPa or greater.

Abstract: A strain state of a bending outside surface of a test specimen is photographed by use of a camera without falling out of focus during a bending test. A bending test facility for a metal sheet material for an automobile body includes a supporting member that supports two supported portions of a flat test specimen formed of the metal sheet material for an automobile body, a punch for performing a bending test in which an area between the two supported portions of the test specimen is pressed from an opposite side to the supporting member so that the test specimen is bent to be deformed, and a camera for photographing, from the side of the supporting member, a bending outside surface of the test specimen during the bending test using the punch, with relative positions of the punch and the camera during the bending test being fixed.

Abstract: An object of the present invention is to provide a collision performance evaluation test method and apparatus that achieve a part collision test that satisfactorily reproduces the state of an actual automobile body collision, allow the test to be performed in a high-speed region, and increase the economic rationality of the test. A motion control mechanism formed of a translation control mechanism or a rotation control mechanism is provided in at least one of a support jig that supports one end portion of an automobile body part and a support jig that supports the other end portion of the automobile body part. The motion control mechanism includes a fixed member fixed to a motion restriction member in the support jig and a movable member so connected to the fixed member as to be movable and fixed to the one end portion or the other end portion of the automobile body part.

Abstract: A translation control and rotation control mechanism support jig for supporting a front end portion of an automobile body part includes a pair of support members, a rotary box having an L-shaped plate, a rotary shaft pin, a compression pin, and a connection plate. The translation control mechanism includes a support plate, a slide guide, an automobile body part securing disk, a translation plate, and a compression pin. Energy-absorbing members are disposed in an arcuate guide groove on a side surface of the rotary box and a linear guide groove arranged on the support plate or the translation plate. A collision punch collides at a test speed with the L-shaped plate of the rotary box. The compression pin deforms the energy-absorbing members to apply torque opposite to a rotation direction and a reaction force in an opposite direction to a translation direction.

Abstract: A collision resistance performance of a structural member is effectively improved while suppressing an unnecessary increase in mass of the structural member. The structural member includes a hollow member and a tension member. The hollow member forms a closed cross-sectional shape by a top sheet portion, a pair of sidewall portions each continuous to each side of the top sheet portion in a width direction, and a bottom sheet portion arranged to face the top sheet portion. The tension member is formed by a metal sheet extending along the width direction of the top sheet portion and being thinner than the sheet thickness of the hollow member, and connects inner surfaces of the pair of sidewall portions facing each other to each other to restrain the distance between the pair of sidewall portions from increasing.

Abstract: Disclosed is a hot-pressed steel sheet member having a tensile strength of 1780 MPa or more and excellent bending collapsibility. The hot-pressed steel sheet member includes: a specific chemical composition; a microstructure in which an average grain size of prior austenite grains is 8 ?m or less, a volume fraction of martensite is 90% or more, and a solute C content is 25% or less of a total C content; and a tensile strength of 1780 MPa or more.

Abstract: A hot-pressed member having excellent bending collapsibility, a method for manufacturing the same, and a method for manufacturing a steel sheet for the hot-pressed member. The hot-pressed member includes a steel sheet as a base material, the steel sheet having a specified chemical composition. The hot-pressed member has a microstructure in which a martensite microstructure is present in a volume fraction of 70% or greater, and a number density of inclusions having a longest diameter of 25 ?m or greater is 0.02/mm2 or less. The hot-pressed member has a tensile strength of 1.8 GPa or greater.

Abstract: An object of the present invention is to provide a collision performance evaluation test method and apparatus that achieve a part collision test that satisfactorily reproduces the state of an actual automobile body collision, allow the test to be performed in a high-speed region, and increase the economic rationality of the test. A motion control mechanism formed of a translation control mechanism or a rotation control mechanism is provided in at least one of a support jig that supports one end portion of an automobile body part and a support jig that supports the other end portion of the automobile body part. The motion control mechanism includes a fixed member fixed to a motion restriction member in the support jig and a movable member so connected to the fixed member as to be movable and fixed to the one end portion or the other end portion of the automobile body part.

Abstract: A collision performance evaluation test with few variations in test results with high accuracy in which a complicated phenomenon that actually occurs can be reproduced in a simple manner by considering the history of deformation in both the press forming and a collision. A collision performance evaluation test method for a metal sheet material for an automobile body is characterized in that a press working apparatus first forms a flat test specimen made of a metal sheet material to be tested into a V shape by primary bending, a bending test apparatus then deforms, by secondary bending, the test specimen formed by the primary bending in a direction intersecting with the primary bending direction, and a bending load and a bending stroke for the test specimen during the secondary bending deformation are recorded and evaluated.

Abstract: Disclosed is a hot-pressed steel sheet member having a tensile strength of 1780 MPa or more and excellent bending collapsibility. The hot-pressed steel sheet member includes: a specific chemical composition; a microstructure in which an average grain size of prior austenite grains is 8 ?m or less, a volume fraction of martensite is 90% or more, and a solute C content is 25% or less of a total C content; and a tensile strength of 1780 MPa or more.

Abstract: Disclosed is a hot-pressed steel sheet member having a tensile strength of 1780 MPa or more and excellent bending collapsibility. The hot-pressed steel sheet member has: a specific chemical composition where a ratio of a C content in mass % to a Nb content in mass %, C/Nb, is from 22 to 100; a microstructure in which an average grain size of prior austenite grains is 8 ?m or less, a volume fraction of martensite is 90% or more, and a solute C content is 25% or less of a total C content; and a tensile strength of 1780 MPa or more.

Abstract: A high-strength hot-dip galvanized steel sheet excellent in formability includes, on the basis of mass percent, 0.05-0.3% C, 1.4% or less (including 0%) Si, 0.08%-3% Mn, 0.003-0.1% P, 0.07% or less S, 0.1-2.5% Al, 0.1-0.5% Cr, and 0.007% or less N, Si+Al?0.5%, and the balance being Fe and incidental impurities, wherein the steel sheet has a retained austenite content of 3% or more by volume fraction, a stretch-flange formability ?>50% and wherein the average aspect ratio (major axis/minor axis) of retained austenite grains is less than 2.5.

Abstract: A method of measuring panel stiffness of an automobile part outer panel by pushing an indenter onto a surface of the panel in a pushing direction intersecting the surface under a load to deform the panel and measuring deformation of the panel includes arranging grids in a lattice form to a surface of a site of the panel; arranging markers previously knowing three-dimensional position information on a periphery of the site; pushing the indenter onto the surface of the site under the load and moving the indenter in a direction perpendicular to the pushing direction, during which the grids on the surface deformed by loading of the indenter are simultaneously and repeatedly shot from plural positions by plural cameras; and calculating position information of the grids corresponding to the markers based on the image data to measure change in deformation of the panel associated with movement of the indenter.

Abstract: A high-strength hot-dip galvanized steel sheet excellent in formability includes, on the basis of mass percent, 0.05-0.3% C, 1.4% or less (including 0%) Si, 0.08%-3% Mn, 0.003-0.1% P, 0.07% or less S, 0.1-2.5% Al, 0.1-0.5% Cr, and 0.007% or less N, Si+Al?0.5%, and the balance being Fe and incidental impurities, wherein the steel sheet has a retained austenite content of 3% or more by volume fraction, a stretch-flange formability ?>50% and wherein the average aspect ratio (major axis/minor axis) of retained austenite grains is less than 2.5.

Abstract: A method of measuring panel stiffness of an automobile part outer panel by pushing an indenter onto a surface of the panel in a pushing direction intersecting the surface under a load to deform the panel and measuring deformation of the panel includes arranging grids in a lattice form to a surface of a site of the panel; arranging markers previously knowing three-dimensional position information on a periphery of the site; pushing the indenter onto the surface of the site under the load and moving the indenter in a direction perpendicular to the pushing direction, during which the grids on the surface deformed by loading of the indenter are simultaneously and repeatedly shot from plural positions by plural cameras; and calculating position information of the grids corresponding to the markers based on the image data to measure change in deformation of the panel associated with movement of the indenter.

Abstract: A method for manufacturing includes a polygonal shape closed structure part with a bent shape in the longitudinal direction only by press forming. The method uses two metal plates for manufacturing a curvilineal closed structure part and includes a press forming process of forming straight or bent folding lines in the longitudinal direction of the two metal plates at positions corresponding to a polygonal bent shape with a flange formed at least at one of the ends of the width direction of each plate, a process of forming a closed structure by laying the two metal plates to overlap each other flange to flange and end to end for ends without flanges and by welding the portions laid to overlap each other in the longitudinal direction of the metal plates, and a process of forming a polygonal shape closed structure having a bent shape in the longitudinal direction by holding both ends of the closed structure and by compressing it toward its central axis.

Abstract: A method for manufacturing includes a polygonal shape closed structure part with a bent shape in the longitudinal direction only by press forming. The method uses two metal plates for manufacturing a curvilineal closed structure part and includes a press forming process of forming straight or bent folding lines in the longitudinal direction of the two metal plates at positions corresponding to a polygonal bent shape with a flange formed at least at one of the ends of the width direction of each plate, a process of forming a closed structure by laying the two metal plates to overlap each other flange to flange and end to end for ends without flanges and by welding the portions laid to overlap each other in the longitudinal direction of the metal plates, and a process of forming a polygonal shape closed structure having a bent shape in the longitudinal direction by holding both ends of the closed structure and by compressing it toward its central axis.

Abstract: A curved-part forming method for obtaining a curved part by performing forming on a blank formed of a single metal plate, the method including a bending process in which the blank having a curved outline corresponding to a curve of the curved part in a longitudinal direction is bent into a sectional shape corresponding to a division portion of a sectional shape of the curved part; and a joining process in which two or more portions obtained by the bending process are joined together.

Abstract: A method for producing a galvanized steel sheet including (a) melting a steel having a steel composition comprising 0.005 to 0.04 mass % C, 1.5 mass % or lower Si, 1.0 to 2.0 mass % Mn, 0.10 mass % or lower P, 0.03 mass % or lower S, 0.01 to 0.1 mass % Al, less than 0.008 mass % N and 0.2 to 1.0 mass % Cr, wherein Mn (mass %)+1.29 Cr (mass %) is 2.1 to 2.8, and the balance being iron and unavoidable impurities, (b) hot rolling and cold rolling the steel from step (a) to provide a steel sheet, and (c) annealing the steel sheet from step (c) at an annealing temperature of at least the Ac1 point and not more than the Ac3 point, wherein the galvanized steel sheet has a structure which includes a ferrite phase and a martensite phase with a volume fraction being at least 3.0% and less than 10%, the average particle diameter of the ferrite is larger than 6 ?m and not more than 15 ?m, and 90% or more of the martensite phase exists in a ferrite grain boundary.