ISO 18489 Cracked Round Bar Test Method

In long term applications of thermoplastic materials such as polyethylene (PE) pipes or fittings it is important to rank and pre-select materials based on their resistance to long-term failure mechanics as a result of slow crack growth (SCG). Developments in modern raw materials has led to a significant increase in resistance of PE to crack initiation and SCG so that testing with previous methods exceeded practical time frames. ISO 18489 achieves a significant reduction in testing time at ambient temperatures more relevant to the temperature range of many applications and that do not change the structural status of the polymer. Acceleration of material testing is achieved by specimen geometry and cyclic loading regime resulting in a relatively short test time.

CHALLENGE - TESTING TO ISO18489 CRACKED ROUND BAR TEST METHOD

Need to determine long-term failure mechanics as a result of crack initiation and slow crack growth

Cylindrical specimens notched and cyclically loaded to failure, avoid static loading pre-test, may cause creep at notch tip

Number of cycles to failure recorded as function of stress range