Framework Member

Abstract: A skeleton member (100) includes a closed cross-section portion (10) and a stress concentration portion (20). The closed cross-section portion (10) includes flat portions (41, 42, 311, 312) and ridge portions (313, 314, 32, 33, 43, 44, 45, 46). The flat portions (41, 42, 311, 312) have widths (W1, W2, W3, W4) of 70.0 mm or less. The stress concentration portion (20) is provided in at least one of the flat portions (41, 42, 311, 312) and the ridge portions (313, 314, 32, 33, 43, 44, 45, 46). The Vickers hardness of central portions in the thickness direction of the flat portions (41, 42, 311, 312) is 350 Hv or more. When the standard deviation of the frequency distribution of Vickers hardness in surface layer portions of the flat portions (41, 42, 311, 312) is divided by the standard deviation of the frequency distribution of Vickers hardness in the center portions in the thickness direction of the flat portions (41, 42, 311, 312), the resulting standard deviation ratio is greater than 1.0.

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