Kriechtests

Kriechtests, or creep tests, are mechanical experiments that evaluate the time-dependent deformation of materials under a constant load at elevated temperature. They quantify how a material deforms slowly over time when exposed to sustained stress in a high-temperature environment, providing data essential for assessing long-term performance in service conditions.

A typical creep curve shows three stages: primary creep with a decreasing rate, secondary creep at approximately constant rate, and tertiary creep that accelerates toward failure. From the curve one extracts the steady-state creep rate, time to a specified strain, and sometimes the time to rupture. These measurements help characterize material resistance to creep and inform life predictions for components expected to operate under high stress for extended periods.

In a uniaxial creep test, a specimen is held at a fixed geometry, placed in a furnace at the designated temperature, and loaded with a constant force. Deformation is recorded with extensometers or strain gauges. Tests span from hundreds to thousands of hours, and may be conducted in air or controlled atmospheres to accommodate reactive materials. Replicates and geometry are chosen to reflect the material’s service conditions.

Results are presented as creep curves and creep-life data, enabling the construction of creep-rupture curves and the development of life-prediction models. Standards across ISO, EN, and ASTM define specimen geometry, temperature control, and data reporting for various materials, including metals, ceramics, and polymers.

Kriechtests are widely used in aerospace, power generation, and chemical processing to rate materials for high-temperature applications. Limitations include long test durations, potential differences between laboratory and service environments, and the need for model assumptions when extrapolating long-term behavior.