Final answer:
The proportional limit is the maximum stress or force that a material can withstand without deviating from its linear elastic behavior. To calculate the proportional limit, plot a stress-strain graph and find the stress value at which the linear portion of the graph ends.
Step-by-step explanation:
The proportional limit is the maximum stress or force that a material can withstand without deviating from its linear elastic behavior. It is the point on a stress-strain curve where the material begins to show permanent deformation.
To calculate the proportional limit, you need to plot a stress-strain graph and find the stress value at which the linear portion of the graph ends. This can be done by dividing the change in stress by the change in strain.