Examples of time-dependent viscoelastic properties. a. If a material or structure is suddenly stressed and that stress is maintained at a constant afterward, the tissue continues to deform due to the phenomenon called creep. Primary creep: reversible decelerating strain rate ± benign damage via delamination and interfiber fracture. Secondary creep: reversible constant strain rate ± benign and/or early harmful damage via delamination and interfiber fracture. Tertiary creep: irreversible accelerating strain rate + gradual or progressive harmful damage via delamination and interfiber fracture. b. When a material or structure is suddenly strained and then that strain is held constant afterward, the stress in the tissue decreases with time. This phenomenon is called stress relaxation.