There are several common stress (σ) states that occur frequently in engineering applications. Simple tension: Forces are applied outwards in opposing directions at either end of the specimen on a single axis.
Imagine a force acting on a block, F, which is resting on the floor. The floor exerts an equal and opposite force back on the block. If this didn’t happen the block would move.
Another important material property is toughness. Toughness is a measure of how much energy a material can absorb to fracture. Fracture is based on crack growth within a material.
