Loads- externally applied force. Due to: - Service conditions Environment in which the component works (wind load) Through contact with other members Fluid pressure Gravity or inertia forces (mass) Externally applied forces in mechanics of deformable solids- acts on a body and body will suffer a deformation. - This action should be opposed or reacted by internal forces which are set up within the particles or material due to cohesion. - (equilibrium point of view) internal forces- give rise to a concept of stress. Stress- force intensity or force per unit area. 𝜎= 𝑃 𝐴 - P- applied normal load in Newton A- area in mm2 Maximum stress in tension or compression- occurs over a section normal to the load. TYPES OF STRESS: - Normal stress- if stresses are normal or perpendicular to the area concerned. - denoted by a Greek letter (𝜎) - can be either tensile or compressive stress - uniaxial state of stress- stress acts on one direction. - rarely exist stress. - biaxial- stress acts on two sides - triaxial state- stress acts on three sides Either the two is mutually perpendicular normal stresses acts or three mutually perpendicular normal stresses. Tensile or compressive stresses Tensile stress- stress acts out of the area. (strectches) Compressive stress- stress acts intro the area. (compresses)
