Combined temperature, humidity and vibration testing applies three environmental stresses - temperature, humidity and vibration - simultaneously. The combined environment reflects the field performance of a product more realistically and exposes product defects more effectively.
While a single environmental stress can trigger product failures, applying three different environmental stresses can easily achieve an acceleration factor of 3 to 5 times. Moreover, combining different environmental stresses can also reveal failures that cannot be produced by any single stress applied alone.
In a combined test where temperature, humidity and vibration are applied simultaneously, the failure mechanism is as follows: during temperature cycling, the internal parts of the product expand and contract owing to differences in the coefficients of thermal expansion of the materials, causing looseness at the joints. If humidity is then applied, moisture will penetrate through the gaps and reduce the friction coefficient at the joints and connections. When vibration stress is further applied, resonance of the product will occur at specific frequencies. Through this repeated process of movement, moisture absorption, freezing and resonance, new failure modes become possible - caused by the strongly accelerated single-factor failure modes and by the combined superposition of the three factors.
Combined temperature, humidity and vibration testing is widely used for complete products and components in aerospace, military, electrical and electronic applications. It is an essential test method throughout product and material development, prototype testing and product qualification.
Reference standards for combined testing: GB/T2423.35, GB/T2423.36, IEC/EN60068-2-50, IEC/EN60068-2-51.