请翻译此段意思 The maximum stress for which stress and strain are proportional is called the proportional limit . The action is said to be elastic limit , it is found that a portion of the deformation remains after the load is removed. The deformation remaining after an applied load is removed is called plastic deformation . Plastic deformation independent of the time duration of the applied load is known as slip . Creep is plastic deformation that continues to increase under a constant stress . In many instances creep continues until fracture occurs ; however, in other instance the rate of creep decreases and approaches zero as a limit. Some materials are much more susceptible to creep than are others , but most materials used in engineering exhibit creep at elevated temperatures.