Abstract: Provided is a method for rapidly, surely, and easily identifying a factor of a shape defect of an artifact attributed to elastic recovery of deformation upon molding by using the numeric value simulation technique, thereby eliminating lowering of dimension accuracy.

Abstract: Provided is a method for rapidly, surely, and easily identifying a factor of a shape defect of an artifact attributed to elastic recovery of deformation upon molding by using the numeric value simulation technique, thereby eliminating lowering of dimension accuracy.

Abstract: A press forming method which can prevent a stretch-flange crack while using conventional press forming equipment at a time of press forming a formed member with flange includes steps of constructing a blank for press forming with a base body blank portion corresponding to flat base body of the formed member, and a concave flange blank portion formed by bending on a concave outer peripheral edge of the base body blank portion. The concave blank portion is constituted by a convex flange blank portion in which a stretch-flange deformation is generated, and an adjacent flange blank portion which is adjacent thereto. An outer peripheral edge of the convex flange blank portion is formed such that one end exists between two points on a profile line corresponding to an outer peripheral edge of the adjacent flange blank portion, the other end exists between two other points, and the one end and the other end are smoothly connected between the straight lines.

Abstract: The invention provides a press forming method which can prevent a stretch-flange crack while using conventional press forming equipment, at a time of press forming a formed member with flange. The method of the invention is characterized by a shape of a blank for press forming, and a blank in accordance with the invention is constructed by a base body blank portion corresponding to a flat base body of the formed member, and a concave flange blank portion formed by bending on a concave outer peripheral edge of the base body blank portion. The concave blank portion is constituted by a convex flange blank portion in which a stretch-flange deformation is generated, and an adjacent flange blank portion which is adjacent thereto.

Abstract: In a first forming step, a metal sheet placed on, and held by a provisional horizontal flat forming portion of a first forming die part is bent along a provisional bend forming portion of the first forming die part to execute bent-forming such that two arch parts of the metal sheet, having respective protuberances oriented in directions opposite from each other, with protuberance surfaces being butted against a provisional inclined flat forming portion of a second forming die part, and a provisional inclined flat forming portion of the first forming die part, respectively, are coupled with each other, thereby obtaining a provisional formed member comprising a provisional inclined flat portion without any warpage, formed continuously from a provisional horizontal flat portion via a provisional bend, and a flange portion formed continuously from the provisional inclined flat portion so as to form a target angle.

Abstract: A die set for press forming a metal sheet is provided, which comprises: at least a punch; and a die, wherein a punch-die clearance CL2 corresponding to a site to be formed immediately after the initial stage of press forming and a punch-die clearance CL1 corresponding to a site to be formed in the initial stage of press forming are set so as to satisfy the following expressions (1) and (2), respectively: 0.8×t?CL1?1.2×t ??(1) CL2?CL1+t ??(2) where t denotes the thickness of the metal sheet to be formed. This configuration implements a die set for press forming capable of stably generating the reverse bending deformed portion due to overrun even when the die radius is large, minimizing the phenomenon such as wall warp, and enhancing the dimensional accuracy in press forming of a metal sheet, and a press forming method using the die set.

Abstract: In a first forming step, a metal sheet placed on, and held by a provisional horizontal flat forming portion of a first forming die part is bent along a provisional bend forming portion of the first forming die part to execute bent-forming such that two arch parts of the metal sheet, having respective protuberances oriented in directions opposite from each other, with protuberance surfaces being butted against a provisional inclined flat forming portion of a second forming die part, and a provisional inclined flat forming portion of the first forming die part, respectively, are coupled with each other, thereby obtaining a provisional formed member comprising a provisional inclined flat portion without any warpage, formed continuously from a provisional horizontal flat portion via a provisional bend, and a flange portion formed continuously from the provisional inclined flat portion so as to form a target angle.

Abstract: Disclosed is a method wherein when a steel sheet is subjected to warm or hot forming to produce a formed product by drawing with a punch and a die, the steel sheet is formed while the forming start temperature is controlled in accordance with the heating temperature of the steel sheet. By this method, when a steel sheet is subjected to warm or hot forming, good formability is obtained without the occurrence of fracture, cracking or the like during forming and also a formed product having good ductility is obtained.

Abstract: A method in which engineers having no experience and technical storage can preliminarily easily and accurately predict an amount of dimensional accuracy defect which occurs at the time of press-forming a metal sheet before press-forming without having expertise such numerical value simulations and mathematics. In predicting an amount of dimensional accuracy defect at the time of press-forming a metal sheet, as a stress-strain relationship, an elastic-perfectly plastic solid model having a fixed stress value after being yielded is adopted and a value which is equal to or less than a tensile strength and exceeds a yield strength is used as an apparent yield strength.

Abstract: A die set for press forming a metal sheet is provided, which comprises: at least a punch; and a die, wherein a punch-die clearance CL2 corresponding to a site to be formed immediately after the initial stage of press forming and a punch-die clearance CL1 corresponding to a site to be formed in the initial stage of press forming are set so as to satisfy the following expressions (1) and (2), respectively:

Abstract: A press die composed of an upper die having a concave part (with the peripheral surface of the opening of said concave part functioning as a first blank pressing face), a lower die having a convex part (to form the blank into a desired form in cooperation with said concave part), and a blank holder (which has a second blank pressing face), said press die working in such a way that said first blank pressing face and said second blank pressing face hold a blank between them while permitting it to flow into said concave part during pressing, characterized in that at least either of said first blank pressing face and said second blank pressing face has a roughened surface with a plurality of striated projections which are formed in the direction inclined in a range of −25° to +25° (preferably approximately parallel) toward the circumferential direction of the edge of the opening of said concave part.

Abstract: Disclosed is a method for bending a metal plate comprising: a first forming step (A) for obtaining a first formed member having a bent portion; and a second forming step (B) for bending the first formed member in a direction of a bending direction of the bent portion so as to allow the bent portion of the first formed member to receive bending-back force. In bending a metal plate by a forming punch relatively moving to a forming die side, the metal plate is bent in an arch shape round the bent forming portion of the forming die. The angle &thgr;p formed between an inclined flat forming portion and a horizontal flat forming portion of the forming die is set to &thgr;p>0, so that the bent arch portion abuts with the inclined flat forming portion of the forming punch and the inclined flat portion of the forming die simultaneously for a certain period of time.

Abstract: Disclosed is a method for bending a metal plate comprising: a first forming step (A) for obtaining a first formed member having a bent portion; and a second forming step (B) for bending the first formed member in a direction of a bending direction of the bent portion so as to allow the bent portion of the first formed member to receive bending-back force. In bending a metal plate by a forming punch relatively moving to a forming die side, the metal plate is bent in an arch shape round the bent forming portion of the forming die. The angle &thgr;p formed between an inclined flat forming portion and a horizontal flat forming portion of the forming die is set to &thgr;p>0, so that the bent arch portion abuts with the inclined flat forming portion of the forming punch and the inclined flat portion of the forming die simultaneously for a certain period of time.

Abstract: A press-formed product which is characterized by having a large number of linear concave portions 11 in the region (such as the side wall 31 of the press-formed product 30) which has undergone bending or bending-unbending deformation during press-forming, said linear concave portions satisfying the following requirements. D/P≦0.03×t/1.2 and 0.02t<D≦0.5t where, P (mm) is an interval between the linear concave portions 11, D (mm) is a depth of the linear concave portions, and t (mm) is a wall thickness of the press-formed product. A method of producing a press-formed product, said method being characterized by using a die having linear projections on its forming surface in such a way that the edges of said linear projections cut into the blank in the region which has undergone bending or bending-unbending deformation during press-forming, thereby correcting warpage at the same time of press-forming.

Abstract: A press die composed of an upper die having a concave part (with the peripheral surface of the opening of said concave part functioning as a first blank pressing face), a lower die having a convex part (to form the blank into a desired form in cooperation with said concave part), and a blank holder (which has a second blank pressing face), said press die working in such a way that said first blank pressing face and said second blank pressing face hold a blank between them while permitting it to flow into said concave part during pressing, characterized in that at least either of said first blank pressing face and said second blank pressing face has a roughened surface with a plurality of striated projections which are formed in the direction inclined in a range of −25° to +25° (preferably approximately parallel) toward the circumferential direction of the edge of the opening of said concave part.

Abstract: A method in which engineers having no experience and technical storage can preliminarily easily and accurately predict an amount of dimensional accuracy defect which occurs at the time of press-forming a metal sheet before press-forming without having expertise such numerical value simulations and mathematics. In predicting an amount of dimensional accuracy defect at the time of press-forming a metal sheet, as a stress-strain relationship, an elastic-perfectly plastic solid model having a fixed stress value after being yielded is adopted and a value which is equal to or less than a tensile strength and exceeds a yield strength is used as an apparent yield strength.