Plastic Pipes Conference Association # 2021 Amsterdam
S. Nestelberger, J. Cheng
The Point Load Test (PLT) [ 1, 2] was designed to simulate the SCG (slow crack growth) failure initiated by a rock pressing into the exterior wall of a polymer pipe. Today’s PE materials sustain long PLT testing times, due to its high SCG resistance design. Consequently, an accelerated “PLT+” with the support of enhanced detergents and higher temperatures was introduced [ 3].
Unexpectedly, discrepancies between failure modes of 32mm vs. 110mm PE pipes in the PLT+ method is noticed. The study examines possible root causes of noticed discrepancies via applied Finite Element Methods (FEM), focusing on the effects of different material models (elastic, elasto-plastic) and different pipe geometries. Considering those effects in the Finite Element simulations opens an unique possibilityfor detailed analysis of stress/strain fields close to the relevant regions of fracture of pipe material. Different pipe sizes clearly show distinct deformation states at the location of the point load. Either the deformation is more compression or lateral bending dominated. The computed deformations states as well as the computed stress concentration locations fit very well the observed locations of crack initiation zones in laboratory tests.
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