External forces acting on a component
External forces ("loads") acting on a component cause stress in the material. In order to determine stress caused by loads in a complex component, you should always assume a biaxial stress state with unknown principal directions.
In this case, experimental stress analysis is a means to determine the absolute value and direction of the principal normal stresses σ 1 and σ 2.
Three steps toward determing loading stress
- Install a strain gage rosette at the spot to be examined.
- The measuring grids of the strain gage rosette are designated a, b and c.
They are connected to a matching amplifier in a so-called quarter bridge circuit. Thus, a minimum of three amplifier channels must be available for each strain gage rosette to enable the three individual strains to be measured independently of each other.
- The measured strains ε a, ε b and ε c are used as the basis for determining the absolute value and direction of the mechanical stresses.