The Foundations of Statistics By Prof. Leonard J. Savage. (Wiley Publications in Statistics.) Pp. xv + 294. (New York; John Wiley and Sons, Inc.; London: Chapman and Hall, Ltd., 1954.) 48s. net.

Probability and Statistical Inference

The Journal of the Acoustical Society of America

Ultrasonic testing of materials: Josef and Herbert Krautkramer Springer-Verlag Publishing Company, Berlin, Heidelberg, New York (1975) 669 pp, $63.00

Review of progress, QNDE

In this review, the use of x-ray computed tomography (XCT) is examined, identifying the requirement for volumetric dimensional measurements in industrial verification of additively manufactured (AM) parts. The XCT technology and AM processes are summarised, and their historical use is documented. The use of XCT and AM as tools for medical reverse engineering is discussed, and the transition of XCT from a tool used solely for imaging to a vital metrological instrument is documented. The current states of the combined technologies are then examined in detail, separated into porosity measurements and general dimensional measurements. In the conclusions of this review, the limitation of resolution on improvement of porosity measurements and the lack of research regarding the measurement of surface texture are identified as the primary barriers to ongoing adoption of XCT in AM. The limitations of both AM and XCT regarding slow speeds and high costs, when compared to other manufacturing and measurement techniques, are also noted as general barriers to continued adoption of XCT and AM.

/pdf/x-ray-computed-tomography-for-additive-manufacturing-a-1ouio0owzb.pdf

X-ray computed tomography for additive manufacturing: a review

The proposed 1D elastic metamaterial rod finds application in non-destructive evaluation, as a filter in the transduction side, where only the torsional and flexural modes need to be generated by isolating longitudinal modes. In this Letter, this is achieved by obtaining a wide bandgap in low-frequency ultrasound regime. The novelty of the proposed design arises from the use of a high impedance mismatch between the materials selected for the rod. The proposed concept is demonstrated and verified with numerical simulations. The effectiveness of the proposed technique is confirmed by comparing the results obtained from the rod made of a single material.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/el.2020.1576

Elastic metamaterial rod for mode filtering in ultrasonic applications

Horizontally polarized shear (SH) ultrasonic guided wave modes are considered to infer adhesion changes at different interfaces. In this study, the SH0 interaction with different lap joints are investigated. Experiments were performed on aluminium lap joint samples. Aluminium surfaces were prepared in a specific way to vary the adhesion. SH modes are generated and received using periodic permanent magnet (PPM) electromagnetic acoustic transducers (EMATs), the periodicity of which is equal to the wavelength of the transducer. SH0 is generated in the plate that comprises the lap joint and received in transmission mode. Distinct signatures were observed for different samples. To investigate the physics of interaction with tri-layer and to corroborate the experiment results, three dimensional finite element (FE) models were developed. Different cases of interfacial adhesion were simulated by changing the boundary condition at both aluminium-epoxy-aluminium interfaces. This work shows the potential of SH modes for quantifying properties at adhesive interfaces.

Interfacial adhesion (kissing bond) detection using shear horizontal (SH) waves

There is much interest in improving the resolution of ultrasonic guided wave NDE towards defect sizing for applications where access is difficult. This paper presents a study of the interaction of the cylindrical crested fundamental shear horizontal (SH0) mode with a through thickness crack in an isotropic plate. The study examines the reflection and diffraction of the wave at the crack, in order to gain understanding for the development of imaging procedures. Circular wavefronts are used to imitate the field from individual elements of a transducer array, which behave as point sources. Finite element (FE) simulations are used to gain an insight into the problem and the relative strengths of the diffraction and reflection fields for various crack lengths are assessed.

Interaction of the Fundamental Shear Horizontal Mode with a Through Thickness Crack in an Isotropic Plate

This paper demonstrates an approach for rapid non-contact air-coupled ultrasonic inspection of composite ailerons with complex cross-sectional profile including thickness changes, curvature and the presence of a number of stiffeners. Low-frequency plate guided ultrasonic modes are used in B-scan mode for the measurements in pitch-catch mode. Appropriate probe holder angles suitable for generating and receiving lower order guided wave modes are discussed. Different embodiments of the pitch-catch tandem positions along and across stiffener and curved regions of the test sample enable a rapid test campaign capturing the feature-rich sample profile. Techniques to distinguish special features in the stiffener are presented.

Prabhu Rajagopal

Papers

Elastic metamaterial rod for mode filtering in ultrasonic applications

Interfacial adhesion (kissing bond) detection using shear horizontal (SH) waves

Interaction of the Fundamental Shear Horizontal Mode with a Through Thickness Crack in an Isotropic Plate

Rapid non-contact inspection of composite ailerons using air-coupled ultrasound

A new approach to inversion of surface wave dispersion relation for determination of depth distribution of non-uniform stresses in elastic materials