Studies on Digital Shearography for Testing of Aircraft Composite Structures and Honeycomb-Based Specimen
This paper reviews shearography and its applications for testing of aircraft composite structures and honeycomb-based specimen. Shearography is a laser-based interferometry in conjunction with the digital imaging processing technique for full-field measurement of surface deformation. It reveals defects in an object by looking for defect-induced deformation anomalies. It does not require special vibration isolation, and with the development of a small and mobile measuring device (portable inspection system), it can be employed easily in field/factory environments.
A combined fiber optic digital shearography and holography system for defect inspection in Si-wafers
The present work relates to surface and/or subsurface defects inspection system for semiconductor industries and particularly to an inspection system for a defect such as swirl defects and particles in an unpolished silicon wafer before the wafer fabrication process by a combined fiber optic digital shearography and holography technique. The dual purpose camera described in this paper gives the possibility of using either digital shearography or holography (DSPI) techniques depending on application needs. The sub-surface defects in a wafer normally create strain concentrations subjected to loading (stressing) which are translated into anomalies in the fringe pattern. A real time technique with the use of Lab view Express 7 software is developed to detect defects in Si-wafer with the application of thermal oading as a stressing method. The results obtained by applying a real time fiber optic shearography technique are described in this paper. The method described here relates specifically to semiconductor wafers, but may be generalized to any other samples.
Experimental study on bond behavior between high-strength grout and deformed steel bars
Abstract Engineers use high-strength grout to connect precast concrete members for its low shrinkage and good fluidity. This paper designed 87 central pull-out specimens using the control variable method to investigate the influence of factors on the rebar-grout bond property such as compressive strength, steel grade, bar diameter, transverse stirrups, and bond length. The test result showed that improving grout compressive strength (85.8 MPa–122.7 MPa) cannot improve the bond strength, which was different from the previous conclusions of concrete pull-out tests. Simplified formulas were presented for calculating the characteristic values of bond strength, residual strength, peak slip, and relative slip of load-holding platform based on parameter analysis. Then, a constitutive model was proposed to predict the full-range bond stress-slip curve of high-strength grout and steel bar specimens from bearing to failure. Finally, FEA models were established to evaluate the applicability and accuracy of the constitutive model.