Jfe Steel Corporation

Satoshi Sumikawa

Akinobu Ishiwatari

Masaki Urabe

Jiro Hiramoto

Fumiaki Tamashiro

A method for identifying a necking limit strain of a metal sheet includes a step of measuring the distribution of strain in a tensile orthogonal direction in a tensile deformation process of a notch root for two or more types of sheet specimens having a notch geometry in a portion of a sheet edge; a step of obtaining a strain increment ratio of the notch root in the tensile deformation process and a strain gradient in the tensile orthogonal direction; a step of obtaining necking limit strain at which necking occurs in the notch root based on the strain increment ratio in the tensile deformation process; and a step of identifying the necking limit strain as a function of the strain gradient from the relation between the necking limit strain obtained for the two or more types of sheet specimens and the strain gradient at that time.

Method for identifying necking limit strain of metal sheet

A press forming method forms a press-formed product having a hat-shaped cross section and includes: a first forming process of press-forming a preformed part in which a portion corresponding to web corresponding to a web portion, and a portion corresponding to side wall corresponding to a side wall portion and including a twisted side wall portion of a twisted shape along the longitudinal direction, are formed, the preformed part including a portion corresponding to convex curve corresponding to a convex curved portion; and a second forming process of press-forming the preformed part into the press-formed product. The twisted side wall portion at the first forming process is twisted such that an angle between the twisted side wall portion and the portion corresponding to web is larger on an end portion side than at a center of the portion corresponding to convex curve in the longitudinal direction.

Press forming method

A method includes: forming either one or both of convex and concave bead portions at surface portions corresponding to sites of a side wall portion on both sides of a convex curve site and to sites of a side wall portion on both sides of a concave curve site; and squashing the bead portions, wherein the bead portions formed on both sides of the convex curve site are tilted such that an end part of the bead portion positioned on the convex curve site side is farther from a baseline and the other end part is closer to the baseline; and the bead portions formed on both sides of the concave curve site are tilted such that an end part of the bead portion positioned on the concave curve site side is closer to the baseline and the other end part is farther from the baseline.

A press forming method forms a press-formed product having a hat-shaped cross section and includes: a first forming process of press-forming a preformed part in which a portion corresponding to web corresponding to a web portion, and a portion corresponding to side wall corresponding to a side wall portion and including a twisted side wall portion of a twisted shape along the longitudinal direction, are formed, the preformed part including a portion corresponding to concave curve corresponding to the concave curved portion; and a second forming process of press-forming the preformed part into the press-formed product. The twisted side wall portion at the first forming process is twisted such that an angle between the twisted side wall portion and the portion corresponding to web is smaller on an end portion side than at a longitudinal center of the portion corresponding to concave curve.

A press forming method according to the present invention includes: a first forming step of forming the press formed part by using the first press forming tool having a line length in the cross-sectional direction of the joining portion contacting with a flange portion subjected to stretch flange deformation or a flange portion subjected to shrink flange deformation is a line length Lin the cross-sectional direction that is shorter than a line length L, where the line length Lis a line length in a cross-sectional direction of the joining portion of the second press forming tool for making the product shape; and a second forming step of forming the press formed part in the product shape by crash forming by using the second press forming tool in which the line length in the cross-sectional direction of the joining portion is L

Press forming method and press forming tool

A method of press forming includes: forming a trench-shaped portion into a product shape with a die and a punch until reaching a first bottom dead center, and forms at least one of: a flange portion subject to shrink flange deformation such that a linear length of the flange portion subject to the shrink flange deformation in a longitudinal direction is shorter than a linear length of a flange portion in the product shape; and a flange portion subject to stretch flange deformation such that a linear length of the flange portion subject to the stretch flange deformation in the longitudinal direction is longer than the linear length of the flange portion in the product shape; and forming the formed flange portion into the product shape with the die and a flange forming die until reaching a second bottom dead center.

Method of press forming and press forming apparatus

Displacement or a load is applied to an elastic-plastic material to deform the elastic-plastic material plastically to acquire experimental values of a stress-strain relation. With a kinematic-hardening incremental vector d&#x3b1;of a yield surface in an elastic-plastic constitutive model as a predetermined first equation, the elastic-plastic constitutive model being defined as a function of stress and back stress, a computer identifies material constants contained in the elastic-plastic constitutive model with the acquired experimental values. The computer identifies material constants contained in a predetermined second equation on the basis of the acquired experimental values and the predetermined first equation into which the identified material constants are substituted. The computer simulates the stress-strain relation of the elastic-plastic material with the predetermined first equation, the predetermined second equation, and the elastic-plastic constitutive model into which the identified material constants are substituted.

Stress-strain relation simulation method, springback-amount prediction method, and springback analyzer

A method of identifying a cause of springback includes a step of performing a press forming analysis, a step of performing a springback analysis on the basis of information acquired by the press forming analysis, a step of dividing a shape of a press forming product acquired by the press forming analysis into a plurality of regions, a step of changing Young's modulus in a designated direction in any region of the divided regions, a step of performing the springback analysis on the press forming product whose Young's modulus is changed, a step of acquiring springback amount differences on the basis of multiple springback analysis results, and a step of identifying the cause of the springback on the basis of the acquired springback amount differences.

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Tokyo, Japan

Satoshi Sumikawa