Contour method for residual stress measurements

The contour method is a destructive technique to characterize the distribution of residual stresses in a part section. It is often used to optimize manufacturing and forming process.

The contour method is a technique relatively easy to apply compared to the high value of the results. It allows to to map  residual stress in a part section, to realize measurements on thick part and to simplify comparison with numerical simulation of several processes.

This method is applied on a large range of materials and parts :

• Aluminium plate and profile
• Steel bar
• Forged steel ring
• Titanium fatigue sample
• Inconel welded cylinder
• Welded part

…

Method principle

This method is based on Bueckner superposition principle. It supposes to cut the part in half and to measure the deformation of the cutting plane due to relaxation of the residual stress. The noticed deformations are used to define the residual stresses field through a finite element simulation model.

(a) Initial state of stresses in the material

(b) Deformation of the cutting plane by stress relaxation

(c) Finite element stress calculation