'Weld Cracking In Ferrous Alloys' Will Be A Valuable Source Of Reference For All Those Concerned With Improving The Quality Of Welding And Welded Components

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  ennio curto

  11/08/09 | Report as spam

  NON DESTRUCTIVE RESIDUAL STRESS EVALUATION

  
  
  
  NEW TECHNIQUE FOR RESIDUAL STRESS MEASUREMENT NDT
  
  
  
  
  
  Introduction
  
  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.
  
  
  Description
  
  Elastic oscillations (also called vibrations) of an elastic material consisting of elementary masses alternately moving around their respective balance positions; these movements cause a transformation of the potential energy into kinetic energy. This phenomenon takes place due to reactions (elastic forces) that the aforementioned masses produce in opposition to elastic movements; these reactions are proportional according to Hooke?s Law to the same movements. The elastic waves that are produced propagate according to a fixed speed that depends on how rapidly the elemental masses begin to oscillate.
  Elastic waves of this type are called ?permanently progressive?, and they propagate at a constant speed which is absolutely independent of the speed with which the elemental masses move during the oscillating motion, and therefore also their respective oscillations.
  
  
  
  
  Impact with the metallic surface results an elastic deformation energy.
  
  Ed = Ei ? ( Ek + Ep )
  
  Ei = Impact energy Ek = Kinetic energy
  
  Ed = elastic deformation energy Ep = plastic deformation energy + lost energy
  
  Ed = ? K dx? = ? m ?? dx? K = constant elastic material (stiffness)
  
  
  
  Behavior elastic metals, due to new discovery
  
  
  Fig. 1 Fig.2
  
  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 ?. For non-magnetic metals, wax or gel will be used to mount the accelerometer.
  The system doesn?t recognize the compressive from tensile stress.
  
  Fig .3
  
  Conclusion
  
  You will realize the convenience of this technique.
  1) Portable system easy to use and very swift.
  2) NDT non-destructive test.
  3) Repeatable in unlimited number of points.
  4) All metals type (a-magnetic)
  5) Don?t expensive. Effective for welding, hardened treatments, vessels control,
  bridges, pipes line, aeronautics, NDT inspection for every metal types.
  
  
  p.i. Ennio Curto.
  
  Web site: www.scribd.com/doc/6067883/New-Technique-for-Residual-Stress-Measurement-NDT-