Understanding of Materials State and its Degradation using Non-Linear Ultrasound (NLU) Approaches

Abstract

NLU response at six different locations along the gage length of dog-bone sample is captured with fair degree of accuracy. Nonlinear ultrasonic technique has been used to characterize fatigue damage by Jayrao et.al. (2008), Komareddy et.al. (2006), Cantrell and Yost (2001). The maximum load was 80% of the yield stress with load ratio 0.1. A2/A12, ratio of second harmonic amplitude and square of fundamental amplitude, was taken as a measure of nonlinearity parameter. In case of piezoelectric transducer as receiver, A2/A12 found to increase as the number of fatigue cycle increases up to 47% of fatigue life and it remains constant till 70% of fatigue life. After that it decreases till 93% of fatigue life and it shoots up near the fracture site. Similar results are obtained in low input wave amplitudes. Transmission Electron Microscopy was carried out for samples fatigued for zero%, 47%, and 100% fatigue life. TEM images show that there is increase in dislocation density as the fatigue life of the material increases. Hikata et.al. (1965) reported that nonlinearity parameter (A2/A12) increases as the dislocation density increases. Results showed that there was an increase of around ~250% in the nonlinear parameter A2/A12 in completely fatigued sample when compared to the as received sample for high input wave amplitudes. It was also observed that for low input wave amplitudes this change was ~450%. Laser vibrometer was also used as receiver to carry out comparative study between contact type and non-contact type receivers. . A2/A12 showed an increment of 36.2% and 30.3% from the virgin state of the material for samples fatigued up to 47% and 93% of fatigue life respectively in high amplitude regime whereas in the low amplitude regime this percentage increment is 35.7% and 38.3%.

Open PDF

Document Details

Document Type
Technical Report
Publication Date
Jan 01, 2011
Accession Number
ADA536521

Entities

People

  • Krishnan Balasubramaniam

Organizations

  • Indian Institute of Technology Madras

Tags

Communities of Interest

  • Air Platforms
  • Energy and Power Technologies

DTIC Thesaurus Topics

  • Acoustic Waves
  • Doppler Effect
  • Elastic Properties
  • Electron Microscopy
  • Fatigue Life
  • Literature Surveys
  • Materials
  • Measurement
  • Mechanical Properties
  • Mechanics
  • Modulus Of Elasticity
  • Piezoelectric Transducers
  • Stress Strain Relations
  • Stresses
  • Transmission Electron Microscopy
  • Ultrasounds
  • Wave Propagation

Readers

  • Atmospheric Science / Meteorology, specifically Wind Wave Turbulence.
  • Mechanical Engineering/Mechanics of Materials.
  • Women's Health and Cancer Risk Research: African American Women and Pregnancy Outcomes.

Technology Areas

  • Directed Energy
  • Microelectronics