A cumulative damage experiment, also called a varying-stress experiment, is an accelerated life test where the stress levels can change over time. The stress can be applied by many different forces: load, temperature, pressure. A typical cumulative damage experiment consists of multiple test units. Each unit has an initial stress level, and the stress level can be changed throughout the experiment.

The most common cumulative damage experiment is a step-stress experiment. A step-stress experiment uses multiple units with varying levels of stress applied. Stress can be applied using factors such as temperature, pressure, or voltage. For each unit, there is an initial stress level. At specified time points, the stress levels are adjusted based on different patterns of stress levels. Between stress level changes, the stress level remains constant.