S-N Compare

S-N Compare converts a one-dimensional rainflow spectrum from stress range – bin cycle count into a cumulative cycle count – stress range curve, then overlays it with up to three reference S-N curves.

Input and display

• Accepts matrix_1d Histogram input only; configure one to six Histogram input pads.
• The histogram x values are stress ranges and its y values are the bin cycle counts.
• Both axes default to linear scale and can be switched independently between linear and logarithmic display from the operation toolbar. The horizontal axis is cumulative cycles; its lower bound is 0.5, and its upper bound is automatically taken from the larger of the input's maximum cumulative cycle count and Nfc×100 from valid reference curves unless manually set. The vertical stress axis has a default lower bound of 0; its automatic upper range includes the reference curves.
• Display is always overlay. Paging changes only calculated curves; reference curves stay visible.

Reference S-N parameters

Each of the three rows defines one reference curve. FAT is the stress at 2e6 cycles. Slope m1 applies up to Nc; m2 applies from Nc to Nfc; the curve is horizontal after Nfc. Its defined X range is 1 through Nfc×100.

Every reference curve is black and has markers at 1, 2e6, Nc, Nfc, and Nfc×100. Choose a Circle, Square, or Triangle marker and a width from 1 to 8 (default 3); marker size is three times the selected line width. The legend label is Ref: FAT <FAT> and remains at the top right.

The Advanced tab also provides Custom Axis Range and X/Y cursor positions. The range table opens with the plot's current visible range.