Acoustic waves or sound waves are a kind of mechanical vibration which propagates through a material medium such as solid, liquid and gas. The acoustic waves can carry the information of the excitation source and also collect the information about the environmental conditions in its propagation paths. Together with the impressively wide frequency range of 10-2-1010 Hz and travelling distance of 10-3-107 m, acoustic waves are an excellent tool for medical imaging, non-destructive testing (NDT) of materials and structures, underwater sonar and communication, oil and gas exploration, and seismological planet study.
Figure 1 Spectrum of sound waves.
In IMRE, we have deep expertise in acoustic-based NDT method, especially for defect imaging. We employs the generation, transmission, reflection, refraction and scatter of sound waves for practical industry applications. Besides the detection of macroscopic defects such as cracks, void and delamination, acoustic waves are also sensitive to the microscopic status of materials, such as dislocations, grain distribution and residual stresses. Our interests and expertise are centered around the controlled generation and improved detection of acoustic waves through innovative transducer technologies, as well as understanding of wave-defect interactions for high-resolution defect imaging and non-destructive evaluation of the status of the materials and structures. By combination of acoustic wave excitations with optical imaging methods, we have achieved novel NDT methods for fast and deep subsurface defect imaging with excellent detection speed, depth and sensitivity.
Acoustic Shearography imaging
Acoustic shearography technology developed in IMRE is a new NDT technique by integrating laser shearography with acoustic wave excitations. In acoustic shearography testing, ultrasonic waves generated by transducers or pulsed lasers are used as excitation in shearography. By comparing the changes of surface interferometric pattern due to wave-defects interaction, both surface and deep subsurface defects can be imaged in seconds. An acoustic shearography system has been established at IMRE and the detection of deep subsurface defects in metals and composites has been demonstrated as shown in Figure 2. This technology has combined advantages of fast and full-filed imaging of shearography and deep penetration of acoustic waves. The technology is suitable for fast inspection of thick materials and structures and has broad applications for NDT in aerospace, marine & offshore or general infrastructure industries.
Figure 2 Acoustic shearography system and examples of defect detection in metal and composite.
Advanced Acoustic Transducers
In many acoustic-based NDT applications, it is important to effectively generate and/or detect the desired acoustic waves. Thus, the design and development of advanced acoustic transducers is important for improving the detection sensitivity of acoustic-based NDT methods. We have broad and deep expertise in design, fabrication and implementation of advanced acoustic transducers including directed acoustic wave transducers and 2D phased array transducers for advanced NDT applications.
Highlights & Achievements
Our team has numerous publications and patents related to shearography technology. We have also worked on multiple industry related project in the use of such technology at industrial settings.
The team has demonstrated the use of acoustic waves as stress loading for successful shearography imaging.
The team has demonstrated the use of directed acoustic wave transducers in shearography testing for deep subsurface defect detection.
The team has evaluated performance of acoustic shearography for NDT in aerospace industry as part of the on-going A*STAR Aerospace Programme.
Publications related to acoustic shearography technology:
Liu H., Liu M., Zhang L., Chen Y. F., Tan C. Y., Guo S. and Cui F. (2018), “Directed acoustic shearography for crack detection around fastener holes in aluminum plates”, NDT & E International, Vol 100, 124-131.
Liu H., Guo S., Chen Y.F., Tan C.Y., and Zhang L. (2018), “Acoustic shearography for crack detection in metallic plates”, Smart Materials and Structures, Vol. 27, 085018.
Dr. Zhang Lei, email@example.com
Dr. Chiam Sing Yang, firstname.lastname@example.org
We welcome queries and collaboration partners for both the research and commercialization of acoustic NDT design, methods and technologies.