18.1 : מתח רגיל תחת עומס צירי

A rod subjected to a load undergoes elongation. A load-deformation diagram can represent the elongation but cannot predict deformation in different rods.

For example, a rod with double the cross-sectional area requires twice the load for the same deformation, and a rod twice as long deforms two times under the same load. The ratio of deformation to length remains constant, introducing the concept of strain.

The normal strain refers to a deformation of material when subjected to axial loading. It is quantified as the change in length divided by the unit length of the object, providing a unit-less ratio of deformation.

The axial load causes stress within a material, which is directly related to the strain experienced by the object.

The relationship between stress and strain is governed by the modulus of elasticity or Young's Modulus, which indicates the stiffness of the material. A higher Young's modulus means less deformation under an axial load.

Understanding the normal strain helps ensure that the structures can withstand their exposed forces without deforming excessively or failing.