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 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: 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 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.