□ Question 4 5 pls Select all the correct answers from the list below. If a statement includes a fact and a reason. both must be correct for the statement to be correct. There is an unspecified number (N) of correct answers. For each correct answer, you will receive 5/N marks, but you will lose 5/N marks for any incorrect answer selected. Your total mark will not go negative. Brittle failure in pipes tends to happen with cracks running along the pipe length and the main reason is that the polymer is weaker in this direction from the extrusion process. Miner's rule is based on a detailed analysis of crack growth behaviour. The critical stress intensity factor is a material property whereas the stress concentration factor depends purely on the geometry. With low stress applied, normally ductile polymers can fail due to cracking and this is almost always due to chemical degradation.

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