Fatigue Comparison
Fatigue strength and resistance to fatigue failure is a highly important property when comparing common bicycle frame materials. Fatigue failure is defined as the progressive, localized, and permanent structural change that occurs in a material subjected to fluctuating stresses below the yield strength. Riding a bicycle produces fluctuating stresses on the frame that in some cases, cause fatigue failures to occur. As seen in Table 2, the aluminum alloys have much lower fatigue strengths when compared to 4130-steel and titanium, and are thus much more susceptible to fatigue failure. This means that 6061 requires much lower stresses and cycles to induce a fatigue failure. Both steel and titanium have fatigue strengths of 250 MPa at 50,000 cycles while the aluminum alloys have fatigue strengths of only about 75 MPa at 50,000 cycles.