Structural Engineering & Statics
where the load goes
Generator

The sn-curve generator

Rendered here at the parameters it defaults to, with every essay that calls it — which is the same list as the blast radius of changing it.
Three details, and no material anywhere on the plotStress range against cycles to failure for three detail categorys — 160, 90, 36 N/mm² at two million cycles. The lines are parallel because they share a slope of three, and the spread between them is a factor of 4.4 in stress and therefore 88 in life. Nothing on this plot depends on the strength of the steel: the same detail in a grade twice as strong lies on the same line. No working stress range is marked. The knee in each line is the constant-amplitude limit, past which the slope becomes five.10⁴10⁵10⁶10⁷10⁸2050100200500cycles to failurestress range, N/mm²category 160category 90category 36

1 essay calls sn-curve. The drawing above is what it returns with no arguments at all; every call below passes it something, because a placement that passes nothing draws whichever member of the family the generator happens to default to rather than the one its essay argues about.

Where it is called

Changing this generator changes every one of these figures.

10⁴10⁵10⁶10⁷10⁸2050100200500cycles to failurestress range, N/mm²category 160category 90category 366.8e+74.3e+62.7e+5working range 70 N/mm² — the lives are marked Materials

The load that never came near failing anything

A detail survives sixty-eight million cycles at a stress range that another detail in the same steel survives two hundred and seventy thousand of. The two lie a factor of two hundred and fifty apart, and the material is not on the plot anywhere.

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