Feasibility of introducing compositional gradients to the core of a sandwich structure and the resulting fracture behavior under impact loading conditions is the primary focus of the study. Model sandwich structures comprising of graded core with bilinear variation of volume fraction of hollow microballoons are considered for experimental and numerical simulations. Conventional sandwiches with ...

Damage detection and calibration in beams by wavelet analysis involve some key factors such as the damage model, the choice of the wavelet function, the effects of windowing and the effects of masking due to the presence of noise during measurement. A numerical study has been performed in this paper addressing these issues for single and multispan beams with an open crack. The first natural mod...

This paper describes a new method developed for the discrimination of acoustic emission (AE) events based on the similarity of their parameters. The method should help to locate the sources of AE events which are related to failure of the material’s integrity (the crack propagation). Early detection of crack growth is critical for the prevention of catastrophic failure, especially for metallic ...

Introduction: There are several electromagnetic techniques that can be used for detecting surface-breaking cracks in metals, including potential drop, AC field measurement and eddy current methods. Each method possesses its own advantages and limitations in a specific application. In recent years, the use of microwaves has shown an increasing potential and success as a new technique for non-des...

This paper explores theoretically the possibility of using caustics, formed in the ultrasonic field diffracted by defects, as an approach to the inverse scattering problem, The case of crack-like defects is considered in detail, using the geometrical theory of diffraction. The involute of the far field caustic reproduces the projection of the crack edge in the incident beam direction, for a pla...

The dynamic behaviour of a structure changes when it is subject to damage such as cracking. Recently research has been directed at employing conventional Modal Analysis techniques to investigate this change in simple structures and to study the dependency on the location and size of a crack. The use of the modeshapes to characterise the dynamic behaviour of the structure would require several a...

This Note describes the suitability of a number of techniques of potential use in studying cracking in lead-free solder joints, and hence their use in assessing joint lifetimes. Cracks induced into solder joints of chip resistors on FR4 substrates, were studied using micro-sectioning, dye penetration, mechanical test and thermal conductivity techniques. The work previously reported [1] has been...

The objectives of this work were to develop an electromagnetic scattering model that can be used to predict the microwave scattering from a crack in a metallic surface, and to evaluate the potential of using microwave scattering measurements to determine the dimensions of the crack. The .initial approach to this problem has been to model the surface crack as a section of rectangular waveguide s...