Jfe Steel Corporation

Kawasaki Steel Corporation

Hirotaka Kano

Osamu Sonobe

Akinobu Ishiwatari

Kazuhito Kenmochi

Ikuo Yarita

Masaki Urabe

Akihiko Fukuhara

Jiro Hiramoto

Nobuaki Gamo

A springback amount evaluation method evaluates an amount of springback after die release of a press forming product by a computer and includes: setting a plurality of section planes intersecting a shape of the press forming product at predetermined intervals; obtaining a sectional shape of the press forming product for each of the set section planes; and obtaining an orientation of each of the sectional shapes in each section plane as a direction of the each of the sectional shapes, wherein for each of a shape to be a reference of the press forming product and a shape after the die release, the above-described three steps are performed, and the amount of springback is evaluated by comparing, for all of the section planes, the obtained directions of the sectional shapes for the shape to be the reference and for the shape after the die release.

Springback amount evaluation method

A method for manufacturing a press formed part, the method including specifying stretch flange limit strain in a metal sheet by using strain gradient in a radial direction and strain gradient in a sheet thickness direction. The strain gradient in the radial direction being directed from an end portion of the metal sheet at a time a press load is applied. The strain gradient in the sheet thickness direction being a direction of the metal sheet that intersects a loading direction. Additionally, the stretch flange limit strain satisfies the formula &#x3f5;=A[a&#xb7;&#x394;&#x3f5;/&#x394;r+b&#xb7;&#x394;&#x3f5;/&#x394;t]+c, where &#x3f5;represents the stretch flange limit strain in a tangential direction of the sheet edge, &#x394;&#x3f5;/&#x394;r represents the strain gradient in the radial direction, &#x394;&#x3f5;/&#x394;t represents the strain gradient in the sheet thickness direction, A, a, and b represent influence coefficients, and c represents the limit strain at a time the strain gradient is zero.

Method for specifying stretch flange limit strain and method for determining feasibility of press forming

A method for press forming analysis includes (1) performing a coordinate transformation to calculate a distribution of stress (a) before a release from the press die in a local coordinate system; (2) performing a springback analysis which includes (i) calculating a distribution of residual stress after the release and performing the coordinate transformation to calculate a distribution of residual stress (b) in the local coordinate system, and (ii) calculating shape data (d) after the release; (3) calculating a difference (a-b) as SB effective stress, performing a coordinate transformation to calculate a distribution of SB effective stress in a global coordinate system, changing or removing the SB effective stress in an analysis target region and performing the springback analysis to calculate a shape data (c) after the release; and (4) calculating a difference (c-d) to determine a degree of influence of the analysis target region.

Method for press forming analysis

The present invention provides a composite roll for cold rolling capable of rolling a cold-rolled steel strip having little edge drop, a cold-rolled stainless steel strip or a bright finish steel strip having excellent surface brightness or a silicon steel strip excellent in magnetic properties without causing breakage of roll, which is a roll in which a sleeve is fitted at a surrounding of a shaft portion with the shaft portion as a central axis and its fabrication method, in which the sleeve is constituted by previously integrating a plurality of pieces of mold members divided by a face intersecting with the central axis of the roll. Further, this is a fit roll in which a sleeve member of an outermost layer is made of WC&mdash;Co series hard alloys having Young's modulus of 35000 kgf/mm or more and Co content of 12-50 weight % and is provided with a wall thickness of 3% or more of roll radius and a ratio L/D of a length L of a barrel of the sleeve to a diameter D of the roll falls in a range of 2-10. Further, when there are one layer or more of intermediate layers between the outermost layer of the sleeve and the shaft core, the intermediate layers are arranged such that Young's modulus of the layer on the outer side is larger than Young's modulus of the layer on the inner side.

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Chiba, Japan

Hirotaka Kano