Influence of Experimental Parameters on Fatigue Crack Growth and Heat Build-Up in Rubber

Abstract

Loading parameters (frequency, amplitude ratio and waveform) are varied to determine their influence on fatigue crack growth in rubber. Up to three different rubber blends are investigated: one actual engineering material and two model materials. Fatigue crack growth curves and strain distributions of pure shear and faint waist pure shear samples are compared for a model material. Fatigue behavior is studied for three different frequencies (1 Hz, 3 Hz and 5 Hz). Amplitude ratio appears to be another important influence factor concerning fatigue crack growth in rubber. The beneficial effect of positive amplitude ratios (tensional loading conditions) is shown for different materials. However, fatigue crack growth is considerably increased for negative amplitude ratios (tensional-compressional loading conditions). Furthermore, the influence of the waveform is determined for three different waveform shapes. One is sinusoidal, and two have a square shape, including dwell periods and sinusoidal slopes. Special focus lies on heat build-up, which is substantial, especially for large loads, high frequencies and/or highly filled rubber blends. Plateau temperatures are determined for various loading conditions and rubber blends. A very simple linear relationship with dissipated energy per time and unit area is obtained. Results gathered with dynamic mechanical analyses show, likewise, a linear trend, but the heat build-up is very small, due to different sample geometries.

Review on Heat Generation of Rubber Composites

“…It is noticeable that the heat conduction acts a critical role in deciding temperature rise. Consequently, the heat generation is not only related to the stress and deformation involved in the rubber material, but also to the frequency of the applied loading and the environmental temperature [8,22].…”

Characterizing the Intrinsic Strength (Fatigue Threshold) of Natural Rubber/Butadiene Rubber Blends

“…window within which cracks grow due to the application of cyclic deformation. The crack growth behavior in this fatigue damage accumulation regime is affected by frequency, nature of the waveform (e.g., pulse versus sine wave), and maximum and minimum cyclic load limits [10][11][12][13][14]. There have not been enough detailed studies to know the effects of these testing variables on the fatigue threshold, T 0 .…”