Residual Stress Research Paper

INTRODUCTION
Residual stress is a “locked-in” stress present within the material independent of external load. Residual stress is self-equilibrating. It creates compressive and tensile stresses sum to zero force within the volume of the material. Residual stress distribution through the thickness of material without application of external load always present inside the material. Manufacturing process also influences residual stress such as welding, casting, rolling, heat treatment, forging. Where residual stresses present in a metal component can seriously affect life of the material. In which during welding process component experience issues on residual stress as shrinkage occurs during the process. Mechanism of residual stress formation

The destructive and semi destructive techniques, called also mechanical method. Mechanical methods are stress relaxing methods. These methods relay on the measurement of deformations due to the release of residual stresses upon removal of material from the specimen. Sectioning, contour, hole-drilling, ring-core and deep-hole are based on destructive and semi destructive techniques used to measure residual stresses in structural members. Non-destructive methods include X-ray or neutron diffraction, ultrasonic methods and magnetic methods. These techniques usually measure residual stress. For the assessment of fatigue related damage. become increasingly important since many structural components, e.g. bridges, aircraft structures or offshore platforms, need to be inspected periodically to prevent major damage or even failure. In hole-drilling method hole is drilled in a series of steps at geometric center of the strain gauge rosette. In which associated relived strain are measured at sequence of steps of hole depth using recording instrument. The principle of sectioning technique technique is based on the fact that if a portion of a residually stressed body is cut away and the resulting deformation of the body is carefully measured, then the residual stress which existed at the component surface can be

It is convenient to use. Hole-drilling method has standardized procedures with improved accuracy and reliability.
This method is based on the principle that a stressed material causes a redistribution of the residual stresses in surrounding material of hole and associated local deformation. Residual stress may remain approximately constant depth in case of uniform stresses and they may vary with depth in case of non-uniform stresses. Varying stress distribution with increase in depth.
MEASUREMENT RANGE:
This method gives accurate results in localized measurement of stress relived area within the boundaries of hole drilled area. Residual stress is identified on surface of the specimen. It is observed that residual in a material should not exceed 60% of yield stress.
STRAIN GAUGE