What is the stress term called that is induced by pulling apart in a longitudinal direction?

The stress term induced by pulling apart in a longitudinal direction is accurately described as tension parallel to the grain. This type of stress arises when a force is applied that stretches a material, causing its fibers to separate along the direction of the grain. In materials such as wood, which have a directional grain structure, tension affects the material's properties significantly, especially along the grain, as it interacts with the molecular bonds holding the fibers together.

In contrast, compression refers to stress that occurs when materials are pushed together, leading to a decrease in length or volume. Bending involves the application of a moment that causes curvature in a material, and this results in a combination of tension and compression occurring at different points along the structure. Shear occurs when forces are applied parallel to a surface, causing layers of material to slide past one another. Each of these terms identifies different kinds of mechanical stress, but for the scenario of pulling apart, tension parallel to the grain is the most relevant and correct term.