more information about residual stresses

[ennio curto]

More information about residual stress measurement NDT/NDE

The residual stress in a metal do not depend on it hardness, but from the module of elasticity or Young module and from its chemical composition (density).
The hardness of a metal indicates its ability to absorb energy elastic, plastic or kinetic energy, but through it not possible to determine the value of residual stress. In a metal with the same hardness we will have a different values of this stress. Therefore, the problem will be to measure the values that vary so exactly proportional to the residual stress values in a given metal.
The residual stresses tend to equilibrate themselves in the surface of the material.
The measurement made with all the major methods, X-ray, string gauge (destructive), optical etc. the residual stress is determined between the measuring the displacement of the equilibrium point the reticule crystalline.
The method discovered analyzes the value of acceleration vibratory generated by an impulse to constant energy with the subsequent reaction elastic (elastic field) from the metal, The equipment does not recognize the value of compression from that of tensile stress. It gives the value of the space resulting or volume but with the applying of a triaxial accelerometer we can have forces values axis x, y, z.

You will realize the convenience of this system.
1) Portable and easy to use and very rapid, high accuracy.
2) NDT/NDE non-destructive testing.
3) Repeatable in unlimited number of times.
4) Not dangerous (X-ray).
5) Do not expensive. Effective for welding, hardened treatments, vessels control, bridges, pipes line, aeronautics, NDT inspection for every metal types.

p.i Ennio Curto.

[ennio curto]

TECHNICAL PAPER
57th DEFENSE WORKING GROUP ON NONDESTRUCTIVE TESTING
17 through 19 November, 2009

NEW TECHNIQUE FOR RESIDUAL STRESS MEASUREMENT NDT

p.i. Ennio Curto.

Ennio Curto
Via E. di Velo, 84
36100 Vicenza (Italy)
[e-mail]

This type of non-destructive method NDT provides the possibility to measure residual stress and the effect of the service load with an impact device and a vibration measurement sensor. Internal stresses are to be considered as the following: 1) Operational strains referring to loads that the material is subject and calculated 2) Residual stresses in the material caused by heat treatments or stresses caused by welding, forging, casting, etc. The new technique is able to measure the applied load and residual stress that are balanced on the surface of the material, and in a relatively large volume, at times even the same size as the entire structures. This stress is part of the metal’s elasticity field and has a three axis spatial orientation. The system works through the accelerometer mounted with a magnetic base to generate the acceleration value of the vibrations created by the device impacting on the metal surface.
The acceleration value, in combination with other parameters, permits obtaining the exact value of the residual stress or load applied in the desired point. This value will appear on the display directly in N / mm ². For non-magnetic metals, wax or gel will be used to mount the accelerometer.
This new system, for buildings, bridges steel inspection is very simple for to use , portable ,measure exact values of residual stress due to welding and the applied loads. After many years of research and tests, and between e discover about elastics behavior in field of metal steel now is very practice inspection point to point building and bridge constructions. This new system let bridges steel inspection in very simple mode, is portable instrument and let to measure exact values of residual stress due to welding and the applied loads.



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