Abstract: Provided are a steel sheet having a predetermined chemical composition, and a steel microstructure comprising, by vol %, ferrite: 1 to 50%, ratio of nonrecrystallized ferrite in the ferrite: 0 to 50%, tempered martensite: 1% or more, retained austenite: 5% or more, fresh martensite: 0 to 10%, total of pearlite and cementite: 0 to 5%, and balance: bainite, and, when analyzing the surface by an EPMA, an area ratio of regions with an AlS/SiS ratio of 0.2 or less is 50% or less, and a tensile strength is 980 MPa or more, and a method for producing the same.

Abstract: Provided are a steel sheet having a predetermined chemical composition, and a steel microstructure comprising, by vol %, ferrite: 1 to 50%, ratio of nonrecrystallized ferrite in the ferrite: 0 to 50%, tempered martensite: 1% or more, retained austenite: 5% or more, fresh martensite: 0 to 10%, total of pearlite and cementite: 0 to 5%, and balance: bainite, and, when analyzing the surface by an EPMA, an area ratio of regions with an AlS/SiS ratio of 0.2 or less is 50% or less, and a tensile strength is 980 MPa or more, and a method for producing the same.

Abstract: In an automotive structural member, weight efficiency of impact resistance is improved. An automotive structural member includes: a hollow member having plane portions; and an FRP member joined to at least one section of the plane portions, wherein: the FRP member is joined to a region of at least 0.1L1 to 0.9L1 of a length L1 in a longitudinal direction of the hollow member; the plane portion is formed with an FRP joint portion being a portion to which the FRP member is joined and an FRP non-joint portion being a portion to which the FRP member is not joined, in the region of 0.1L1 to 0.9L1; a total width of the FRP joint portion is 8 to 60% of a full width of the plane portion, in the plane portion; and a flexural rigidity of the FRP member in the FRP joint portion is 30 times or more a flexural rigidity of the plane portion excluding the FRP member in the plane portion.

Abstract: The present impact absorbing member includes: a hat-shaped member having a hat top section; and a plate-shaped member facing the hat top section. A deformation guidance section is provided on a wall section of at least one of the hat top section and the plate-shaped member. The deformation guidance section includes: a first high strength section having relatively higher buckling resistance in the wall section; and a pair of low strength sections having relatively lower buckling resistance and arranged on both sides of the first high strength section therebetween in a view along the longitudinal direction. Furthermore, the impact absorbing member includes a pair of second high strength sections disposed on both sides of the deformation guidance section to be adjacent to the pair of low strength sections in a view along the longitudinal direction and having a higher buckling strength relative to the low strength sections.

Abstract: A break prediction method according to the present invention predicts a break of a joint portion of an object to be analyzed including a pair of members joined to each other by using a finite element method, and includes a first step of acquiring at least an element size of a base material portion, from among parameters set in an element model for the object to be analyzed; a second step of calculating, as a break discernment standard, a break limit moment defined by a function including the element size of the base material portion as a variable; and a third step of discerning whether the moment applied to the joint portion in a deformation analysis of the element model for the object to be analyzed exceeds the break limit moment, and outputting the result of the discernment as a break prediction result for the joint portion.

Abstract: In an automotive structural member, weight efficiency of impact resistance is improved. An automotive structural member includes: a hollow member having plane portions; and an FRP member joined to at least one section of the plane portions, wherein: the FRP member is joined to a region of at least 0.1L1 to 0.9L1 of a length L1 in a longitudinal direction of the hollow member; the plane portion is formed with an FRP joint portion being a portion to which the FRP member is joined and an FRP non-joint portion being a portion to which the FRP member is not joined, in the region of 0.1L1 to 0.9L1; a total width of the FRP joint portion is 8 to 60% of a full width of the plane portion, in the plane portion; and a flexural rigidity of the FRP member in the FRP joint portion is 30 times or more a flexural rigidity of the plane portion excluding the FRP member in the plane portion.

Abstract: The present impact absorbing member includes: a hat-shaped member having a hat top section; and a plate-shaped member facing the hat top section. A deformation guidance section is provided on a wall section of at least one of the hat top section and the plate-shaped member. The deformation guidance section includes: a first high strength section having relatively higher buckling resistance in the wall section; and a pair of low strength sections having relatively lower buckling resistance and arranged on both sides of the first high strength section therebetween in a view along the longitudinal direction. Furthermore, the impact absorbing member includes a pair of second high strength sections disposed on both sides of the deformation guidance section to be adjacent to the pair of low strength sections in a view along the longitudinal direction and having a higher buckling strength relative to the low strength sections.

Abstract: A structure design support device includes: an evaluation point information acquisition unit which acquires evaluation point information representing a position in a first state and a position in a second state, of an evaluation point provided in a structure which is configured of a plurality of parts, and a part to which the evaluation point belongs, among the plurality of parts; and an evaluation value calculation unit which calculates an evaluation value representing the magnitude of a change between the first state and the second state, of a positional relationship between a first evaluation point belonging to a first part and a second evaluation point belonging to a second part different from the first part to which the first evaluation point belongs, by using the evaluation point information acquired in the evaluation point information acquisition unit.

Abstract: The deformation analysis device includes: a storage unit (12) which stores analysis data of a material; a state variable calculating unit (152) which calculates stresses and other state variables of respective elements of the material at each point in time of deformation of the material, based on the analysis data; a fracture determining unit (153) which, based on the calculated state variables, determines whether or not a fracture has occurred in each of the elements of the material, based on a fracture limit stress curve which is found in advance for the material; and a stress correcting unit (154) which, regarding an element in which it is determined that the fracture has occurred, out of the elements of the material, reduces ? by the following expression ?=(1?D)?? where ? is a stress with a rigidity decrease taken into consideration, D is a damage variable (note that 0?D?1) in continuum damage mechanics, and ?? is a stress with the rigidity decrease not taken into consideration, to thereby decrease rigidi

Abstract: A break prediction method according to the present invention predicts a break of a joint portion of an object to be analyzed including a pair of members joined to each other by using a finite element method, and includes a first step of acquiring at least an element size of a base material portion, from among parameters set in an element model for the object to be analyzed; a second step of calculating, as a break discernment standard, a break limit moment defined by a function including the element size of the base material portion as a variable; and a third step of discerning whether the moment applied to the joint portion in a deformation analysis of the element model for the object to be analyzed exceeds the break limit moment, and outputting the result of the discernment as a break prediction result for the joint portion.

Abstract: A structure design support device includes: an evaluation point information acquisition unit which acquires evaluation point information representing a position in a first state and a position in a second state, of an evaluation point provided in a structure which is configured of a plurality of parts, and a part to which the evaluation point belongs, among the plurality of parts; and an evaluation value calculation unit which calculates an evaluation value representing the magnitude of a change between the first state and the second state, of a positional relationship between a first evaluation point belonging to a first part and a second evaluation point belonging to a second part different from the first part to which the first evaluation point belongs, by using the evaluation point information acquired in the evaluation point information acquisition unit.

Abstract: The deformation analysis device includes: a storage unit (12) which stores analysis data of a material; a state variable calculating unit (152) which calculates stresses and other state variables of respective elements of the material at each point in time of deformation of the material, based on the analysis data; a fracture determining unit (153) which, based on the calculated state variables, determines whether or not a fracture has occurred in each of the elements of the material, based on a fracture limit stress curve which is found in advance for the material; and a stress correcting unit (154) which, regarding an element in which it is determined that the fracture has occurred, out of the elements of the material, reduces ? by the following expression ?=(1?D)?? where ? is a stress with a rigidity decrease taken into consideration, D is a damage variable (note that 0?D?1) in continuum damage mechanics, and ?? is a stress with the rigidity decrease not taken into consideration, to thereby decrease rigidi