What differentiates engineering strain from true strain?

Engineering strain is defined as the measure of deformation representing the displacement between particles in a material body. It is calculated based on the original length of the material before any deformation. This is the key differentiating factor, as engineering strain utilizes the original dimensions of the material to assess how much it has been stretched or compressed.

In contrast, true strain accounts for the actual length of the material at any given point during the deformation process. It continuously updates as the material is deformed, which reflects more accurately the changes occurring within the material. Thus, focusing on the original length allows engineering strain to provide a simpler, initial perspective on strain, which is particularly useful for many engineering applications where precise material behavior at large deformations is less critical.

By understanding this, it becomes clear why the relationship to original length defines engineering strain and sets it apart from true strain, which adjusts for the deformation throughout the material's response to stress.