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→5.1.7.2 Fatigue Strength
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====<!--5.1.7.2 -->Fatigue Strength====
The fatigue strength is a measure of maximum alternating bending force, symmetrical to the zero position, which a sample – for example a relay spring – can be exposed to for an “unlimited” number of cycles without breaking. (Rule of thumb: Fatigue strength = 1/3 of Tensile strength). The measurement is conducted using so-called Woehler– diagrams . With increasing bending force 7 the number of alternating cycles before breaking decreases. Above 10 cycles the influence of further cycling numbers becomes insignificant and therefore 7 the force value reaching 2x10 cycles can be used to define the fatigue strength.
The multi-component alloys CuZn23Al3.5Co and CuSn1CrNiTi show high values of fatigue strength while CuFe2P and CuZn30 exhibit low ones [[#figures9|(Figs. 2 – 3)]] <!--(Figs. 5.39 and 5.40)-->.
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<xr id="fig:Woehler curves for selected copper based materials"/> <!--Fig. 5.39: --> Woehler curves for selected copper based materials. Strip samples: 0.3 mm thick, cold worked; Testfrequency; 1,500 / min (Wieland)
<xr id="fig:Ranges of fatigue strength for selected copper materials Wieland"/> <!--Fig. 5.40: --> Ranges of fatigue strength for selected copper materials (Wieland)
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