Residual stress can cause premature failures in structures and equipment and is a significant contributor in crack growth calculations. It is created by a variety of sources including welding (thermal), fabrication (force fit), manufacturing (cold forming), and structural loads (thermal ratcheting, pressure overload, and excessive force). Corrosive environments are particularly detrimental to metals in tension. In some situations, heat-treating reduces the impact of residual stress, but these procedures often are neither practical nor specified.
Stress Engineering Services can measure residual or ambient stress using strain gages with the Blind Hole Drilling Method (ASTM E-837). This technique measures deformation as a small hole is drilled into the surface. As the new hole expands or contracts in response to the local stresses, the surface complies with the deformation. Principal stress is calculated from the measurements of a three-element strain gage oriented radially around the hole. The tiny-drilled hole is typically within the corrosion allowance and can be easily removed by blend grinding.