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


SOLUTION - ELECTROPULS E3000 - DETERMINATION OF RESISTANCE TO SLOW CRACK GROWTH UNDER CYCLIC LOADING

  • Capable of imposing and recording cyclic load varied by time between accurately defined limits, constant values +/- 1%
  • Determines resistance of PE material to slow growing brittle cracks
  • Quickly predict life expectancy of pipe
  • Custom fixture designed and developed with customer


THE INSTRON ADVANTAGE

  • Multiple operators produce repeatable and reliable results, made possible with the patented stiffness based tuning
  • ElectroPuls is a reliable test instrument that can be run uninterrupted with no need to stop and restart, saving time and hassle of preparing new samples
  • Confidence in data through accurate loading during test across a range of frequencies
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