http://ieeexplore.ieee.org/iel5/5/31047/01444179.pdf

Fundamentals of acoustics

Normal and oblique impact of small arms bullets on AA6082-T4 aluminium protective plates

Ballistic performance of composite metal foams

An investigation of the constitutive behavior of Armox 500T steel and armor piercing incendiary projectile material

Effects of heat treatment on the ballistic properties of AA6070 aluminium alloy

Defect detection around rebars in concrete using focused ultrasound and reverse time migration

3D numerical simulations of sharp nosed projectile impact on ductile targets

Two different techniques for ultrasonic imaging of concrete are presented, namely a weighted sum technique and a statistical technique. The techniques utilize both the scattered elastic compressional and the mode converted shear wave fields. Since the conventional imaging techniques utilize either the compressional or the shear wave mode to generate the subsurface image, information contained in the scattered ultrasonic field is partially utilized. The proposed techniques intend to use more information contained in the scattered field leading to an improvement in the final image. Synthetic full matrix data is generated using the finite difference in time domain scheme for simulation of elastic wave propagation in concrete with embedded rebars and aggregates. The proposed imaging techniques are then used to generate the subsurface image of the medium. Experiments were also performed to generate full matrix data on two concrete slabs with different geometry, sizes and distribution of rebars. The applicability of the proposed imaging techniques is demonstrated on the experimentally acquired data. The images when compared to the ones generated by the conventional single mode approach, show improvement in resolution and distinction between the embedded features, e.g. closely spaced rebars. It is also observed that the weighted sum technique performs slightly better in comparison to the statistical technique with respect to suppression of background noise.

Ultrasonic imaging of concrete using scattered elastic wave modes

Reference free imaging of subsurface cracks in concrete using Rayleigh waves

The objective of this article is to assess the feasibility of detection of delaminations around rebars in cement mortar using focused ultrasound. The focused field is used to insonify the medium and subsequent image reconstruction is done using the Synthetic Aperture Focusing Technique. The attenuation and scattering of ultrasonic waves by cement mortar can be partially circumvented by focusing the ultrasonic energy towards a particular region of interest. This increases the chances of detection of delaminations around rebars in the chosen region of interest. Artificial delaminations of submillimeter dimensions wrapped around rebars are found to be detectable using this approach. The operational time associated with focusing with an ultrasonic array and subsequent image formation is shown to be less in comparison to the Total Focusing Method. This makes the proposed method an attractive diagnostic technique for rapid nondestructive evaluation of cement-based materials.

Surendra Beniwal

Papers

Defect detection around rebars in concrete using focused ultrasound and reverse time migration

3D numerical simulations of sharp nosed projectile impact on ductile targets

Ultrasonic imaging of concrete using scattered elastic wave modes

Reference free imaging of subsurface cracks in concrete using Rayleigh waves

Localized Condition Monitoring Around Rebars using Focused Ultrasonic Field and SAFT