Creep testing is used to measure how a material deforms over time while subjected to constant stress at a constant temperature. Long-term mechanical creep testing is especially valuable for assessing materials with high temperature service applications, such as engines, ovens, and boilers.
The experts at the Smithers rubber and plastic testing labs use two different methods to measure creep performance of rubber and polymer materials:
Creep strain testing is performed by applying a constant tensile load to the test specimen and measuring the resulting straight in order. The stress is applied using a lever system with dead weights, and the strain is measured using precision extensometers which allow the strain to be recorded to computer. Creep strain testing can be carried out in a controlled environment up to temperatures of 80°C. The resulting data is used to calculate the creep modulus.
Creep rupture is a measure of failure time as a function of applied stress. A range of applied stresses are used to generate failure times, typically from 100s to 106s. From this data, a plot of stress versus log failure time can be generated. A minimum of 20 data points are required to produce a creep rupture plot. Plots can be generated in over a range of temperatures up to 80°C. Strain is not recorded.
If plots of fatigue versus log failure time are produced over at least three different temperatures, then it is possible to predict longer failure times at the lower temperature by time-temperature superposition.
The expert team at Smithers has years of experience with industry standards for creep testing and designing custom protocols to meet your needs. Creep strain and creep rupture tests are normally performed on tensile
dumbbells which can be machined or molded. Our experienced sample prep
technicians can excise samples from production samples and most whole products to simplify the process for our clients.
BS EN ISO 899-1—Plastics -- Determination of creep behavior -- Part 1: Tensile creep