Final answer:
Elastic behavior occurs when a material returns to its original shape after removal of an applied load and persists up to the yield point. Beyond this point, the material exhibits plastic behavior, where deformation is permanent. This progression of material deformation from elastic to plastic and finally to the failure point can be analyzed on a stress-strain diagram.
Step-by-step explanation:
Materials exhibit different behaviors when exposed to external forces. These behaviors are generally categorized as elastic or plastic based on the material's ability to return to its original form after the external force is removed. Elastic behavior is observed when a material returns to its original shape and size upon removal of the load. This occurs as long as the stress applied does not exceed the material's proportionality limit, meaning stress is proportional to strain. When stress is increased beyond the proportionality limit, the behavior may still be elastic but becomes nonlinear until the elastic limit or yield point is reached.
When the stress exceeds the yield point, the material no longer springs back to its original shape and size, entering the plastic behavior region. Here, the deformation will be permanent, and the material will exhibit a new shape and size when the load is removed. This plastic deformation continues until the stress reaches the failure point, or fracture point, where the material ultimately breaks and cannot sustain further deformation.
The elastic modulus, also known as Young's modulus, and the elastic limit are two principal parameters that determine a material's elasticity. A high elastic modulus indicates that a material is hard to deform, requiring a higher load to produce a significant strain, whereas a low elastic modulus signifies a material that deforms easily under lesser load. The transition from elastic to plastic behavior, and eventually to failure, can be analyzed using a stress-strain diagram.