Effective modulus, fatigue testing

Increasing temperature decreases the modulus of elasticity of elastomers at the same time that accelerated chemical effects occur. In our constant strain fatigue tests it has been found that the effect on the modulus (lower stress at the same strain) is significantly more important than chemical degradation effects, as shown in Figure 2. Thus, failure occurred much more rapidly at 4°C than at 37°C or 60°C. This may be one manner in which fatigue... 

Figure 4 shows the results of rolling-contact fatigue tests. The fatigue property was evaluated by the parameter NP which was determined from the mean effective load, Rm in kN times the number of contacts, N in millions. It is obvious that material A and Dl (bearing grade) showed superior NPm values than those of other samples. Material C2 showed the smallest value, which was easily expected from both lowest Young s modulus and hardness, Hv values. 

The mechanical damping of a polymer is related to impact, vibration, and similar dynamic stresses. Although mechanical damping has been correlated with fatigue performance, neither it nor torsion modulus can be used to determine design data, because creep effects are not included in the test. 

The resultant tensile modulus values for the RT testing done are shown in Table 1. Even though the material was tested in 3 lots, lot effects were not reviewed since fatigue effects were known to have larger influences than lot effects [9]. 

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