Using finite element to estimate vibration energy loss by cracks in thermosonic phenomenon under chaotic and non-chaotic vibrations

Thermosonic tests are capable of detecting surface defects such as fatigue cracks. The mechanism of its operation is based on the stimulation of structural vibration of the test piece which generates detectable displacements between crack surfaces. The main problem with using a thermosonic test is the uncertainty caused by chaotic and non-reproducible vibrations of the test piece. Consequently, the study of effective parameters such as, for example, the frequency and amplitude of vibration, crack size, vibration damping around the crack, and acoustical chaos could play a major role in improving this method to make it a highly reliable non-destructive test. In this study, an algorithm has been used to estimate the wasted vibration energy caused by extra damping due to the presence of cracks in the sample. Initially, the validity of the discussed algorithm is studied and findings compared with the results of other experimental studies available in the literature. Subsequently, a simulation process of the thermosonic test in a beam in two conditions of chaotic and non-chaotic vibrations take place. Then, findings are compared with the desired algorithm. Results indicate that in a non-chaotic vibration condition, the measured wasted energy by the algorithm is confirmed by the results obtained from the finite element. However, in a chaotic vibration condition, when the crack size is large enough, there is considerable difference between the results of the finite element method and the algorithm. This difference is due to the occurrence of acoustic chaos while stimulating the test piece. The used algorithm was unable to predict this.

[1]  Stephen Pierce,et al.  A comparison of methods used to predict the vibrational energy required for a reliable thermosonic inspection , 2010, NDT 2010.

[2]  Golam Newaz,et al.  Finite element modeling of the heating of cracks during sonic infrared imaging , 2006 .

[3]  Ap Bovsunovsky,et al.  The Shape of Mechanical Hysteresis Loops for Metals Under Harmonic Loading , 1998 .

[4]  P. Cawley,et al.  The Relationship between Vibration Level and Minimum Detectable Defect Size in Sonic-IR Inspection , 2006 .

[5]  S. N. Rasband,et al.  Chaotic Dynamics of Nonlinear Systems , 1990 .

[6]  D. J. Ewins,et al.  Modal Testing: Theory and Practice , 1984 .

[7]  P. Cawley,et al.  A Comparison of the Natural Frequency Changes Produced by Cracks and Slots , 1988 .

[8]  A. Bovsunovsky.  The mechanisms of energy dissipation in the non-propagating fatigue cracks in metallic materials , 2004 .

[10]  C F Beards,et al.  STRUCTURAL VIBRATION: ANALYSIS AND DAMPING , 1996 .

[11]  R. Adams,et al.  A Vibration Technique for Non-Destructive Testing of Fibre Composite Structures , 1979 .

[13]  K. Kainer,et al.  Measurement of crack induced damping of cast magnesium alloy AZ91 , 2004 .

[14]  Lawrence D. Favro,et al.  Thermosonic imaging of cracks: applications to teeth , 2001, European Conference on Biomedical Optics.

[15]  C. Surace,et al.  Considerations regarding superharmonic vibrations of a cracked beam and the variation in damping caused by the presence of the crack , 2005 .

[16]  Jose M. Roesset.  Nondestructive Dynamic Testing of Soils and Pavements , 1998 .