Slit-type cross-shaped tensile test specimen, and method for manufacturing a slit-type cross-shaped tensile test specimen

Abstract

To provide a cruciform tensile specimen with slits, when a biaxial tensile test is performed, capable of preventing fracture by reinforcing arms, and manufacturing method of the cruciform tensile specimen with the slits.SOLUTION: A cruciform tensile specimen 1 with slits comprising a square measurement part 3, and arms 5 extending from four sides of the measurement part 3 in a direction of applying a tensile load to the measurement part 3 and including a plurality of slits 7 formed parallel to the extending direction, is used for a biaxial tensile test for applying the tensile load in two orthogonal directions to the measurement part 3 via the four arms 5 to acquire a stress-strain relation under biaxial stress. The cruciform tensile specimen 1 with the slits comprises reinforcing materials 11 joined to cover the respective arms 5 and reinforcing the arms 5, where the reinforcing materials 11 are longer than at least the slits 7 in the direction applying the tensile load in the arms 5, and formed not to close the slits 7 by covering the arms 5.SELECTED DRAWING: Figure 1

Claims

1. A slitted cross-shaped tensile test specimen used in a biaxial tensile test to determine the stress-strain relationship under biaxial stress by applying a tensile load in two orthogonal directions to the measurement section, comprising a square measuring section and four arms extending from the four sides of the measuring section in two orthogonal directions from which a tensile load is applied to the measuring section via the four arms, wherein a tensile load in two orthogonal directions is applied to the measuring section via the four arms, Each of the aforementioned arms is joined to a reinforcing member that reinforces the respective arm, The reinforcing material consists of a single plate material that is at least longer than the slit in the direction in which the tensile load is applied and has a reinforcing material side slit that does not block the slit, and the reinforcing material side slit is characterized in that the tip on the measuring portion side is open and the end on the opposite side of the measuring portion is closed.

2. A slitted cross-shaped tensile test specimen used in a biaxial tensile test to determine the stress-strain relationship under biaxial stress by applying a tensile load in two orthogonal directions to the measurement portion, comprising: a square measuring portion; and four arms extending from the four sides of the measuring portion in two orthogonal directions to apply a tensile load to the measuring portion, with a plurality of slits formed in the arms parallel to the directions of extension, wherein a tensile load in two orthogonal directions is applied to the measuring portion via the four arms. Each of the aforementioned arms is joined to a reinforcing member that reinforces the respective arm, The reinforcing member is joined such that it is at least longer than the slit in the direction in which the tensile load is applied, and does not block the slit. A slitted cross-shaped tensile test specimen is characterized in that, when the plate thickness of the slitted cross-shaped tensile test specimen is t1, the maximum value of the equivalent plastic strain generated at the center of the measurement portion in the biaxial tensile test is ε1, the equivalent plastic strain generated in the arm portion and the reinforcing material when the equivalent plastic strain of the measurement portion is ε1 is ε2, the width of the measurement portion and the arm portion is w1, and the width of the reinforcing material is w2, the plate thickness t2 of the reinforcing material is set such that ε2 is less than or equal to the uniform elongation of the reinforcing material and satisfies the following formula. t2=(ε1 / ε2-1)×(w1 / w2)×t1...(1)

3. The slitted cross-shaped tensile test specimen according to claim 1 or 2, characterized in that the material of the slitted cross-shaped tensile test specimen is a steel plate with a tensile strength of 1470 MPa or higher.

4. A method for manufacturing a slitted cross-shaped tensile test specimen according to claim 1 or 2, A plate thickness setting step in which the temporary plate thickness of the reinforcing material is set, A CAE analysis is performed on the biaxial tensile test of the slit-equipped cross-shaped tensile test specimen, for which a provisional plate thickness of the reinforcing material has been set, and a strain calculation step is performed to calculate the strain generated at the tip of the slit formed in the arm portion. A crack occurrence determination step, which determines whether or not a crack has occurred at the tip of the slit based on the calculated strain at the tip of the slit, If it is determined that a crack has occurred at the tip of the slit, a plate thickness change step is performed to change the plate thickness of the reinforcing material. The process involves repeatedly performing the plate thickness change step, the strain calculation step, and the crack occurrence determination step until it is determined that no crack has occurred at the tip of the slit. A method for manufacturing a slitted cross-shaped tensile test specimen, characterized by including a plate thickness determination step, in which, if it is determined in the crack occurrence determination step that no crack has occurred at the tip of the slit, the plate thickness of the reinforcing material in that case is determined to be the plate thickness of the reinforcing material joined to the arm portion.

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