Define in Plane Stresses

Define in Plane Stresses

• A. Stresses that occur equally in all directions
• B. Stresses associated with the primary forces of the member
• C. Stresses caused by thermal expansion
• D. Stresses due to external fluid pressure

Answer: (B)

In-plane stresses are the two‑dimensional stress state that results from the member’s primary internal forces acting within its plane. For thin members, we focus on the stresses caused by axial forces, bending, and shear that act in the plane of the member, while any stress through the thickness is neglected. That’s why the best description is stresses associated with the primary forces of the member—these are the internal stresses you encounter when analyzing and designing the member in its in-plane load path. Stresses caused by thermal expansion or external fluid pressure are different sources of stress and don’t define the typical in-plane state, and stresses that are equal in all directions describe an isotropic (hydrostatic) condition, not the standard in-plane loading scenario.

In-plane stresses are the two‑dimensional stress state that results from the member’s primary internal forces acting within its plane. For thin members, we focus on the stresses caused by axial forces, bending, and shear that act in the plane of the member, while any stress through the thickness is neglected. That’s why the best description is stresses associated with the primary forces of the member—these are the internal stresses you encounter when analyzing and designing the member in its in-plane load path.

Stresses caused by thermal expansion or external fluid pressure are different sources of stress and don’t define the typical in-plane state, and stresses that are equal in all directions describe an isotropic (hydrostatic) condition, not the standard in-plane loading scenario.