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.

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X-ray computed tomography for additive manufacturing: a review

Modeling tools to represent the entire inspection process are much desirable in the context of practical ultrasonic NDE. However with increasing sophistication of practical ultrasonic inspection the development and usage of a single method for the entire process is becoming difficult. The authors discussed the merits of a generic hybrid modeling procedure at the QNDE conference in 2009; first results from a single‐frequency implementation of this interface were also presented. This paper reports progress in this work, applying it to problems of interest to practical inspection. First the concept of a generic time‐domain hybrid prototype is introduced. This hybrid interface is then demonstrated and validated through the examples cases of simple wave propagation through the bulk of an infinite medium, and ultrasound scattering by a realistic defect.

Generic time‐domain hybrid models for ultrasonic nde

Interaction of the Shear Horizontal Bend Guided Mode (SHB) with Transverse Cracks

Inspection of practical plate assemblies is challenging due to the presence of complex features such as bends and corners. The objective is to investigate the influence of bends or curvature in the transverse direction on the propagation of guided waves in plates. A 3D finite element (FE) simulation shows that bends in plates can concentrate and guide ultrasonic energy along the direction of wave propagation. An interesting feature-guided mode that is surprisingly similar to the A0 (fundamental antisymmetric) Lamb mode in normal plates was identified when the bent plate is subjected to 'in-plane' excitation as the generation of this type of mode for a thicknesswise symmetric excitation is unexpected. These results are validated with experiments and discussed using Semi Analytical Finite Element (SAFE) models.

Ultrasonic waves guided by transverse bends in plates subjected to symmetric axial excitation

Reflection and Mode Conversion of Fundamental Torsional Guided Wave Mode From Lack of Bonding in Induction Pressure Welding

In recent years, metamaterial/ phononic crystal (PnC) based energy harvesters are gaining interest due to their excellent elastic wave manipulation and energy trapping capabilities. Here, we propose a novel PnC comprising of Tungsten Carbide (WC) spheres embedded in epoxy resin matrix. The sphere-epoxy composite is encapsulated by Aluminum (Al) holey structure and the device is sandwiched between two Al plates. Numerical analysis of band structure reveals a wide phononic band gap (BG) from 50.65 kHz to 71.12 kHz. These BGs can be engineered by varying geometric parameters of the unit cell viz., the radius of the sphere and thickness of Al plates. A point defect is introduced by removing the central sphere of the 5 × 5 PnC to facilitate the robust localization of evanescent wave defect modes within the bandgap. Moreover, it is observed that, by altering the radius of the defect sphere, the number of defect modes and their shift can be reconfigured. A PnC based energy harvester is implemented by attaching a piezoelectric disk (PZT-5H) onto the defect PnC just above the defect site. This arrangement of PZT disk converts the highly resonant mechanical defect mode into electrical energy, thereby allowing vibration energy harvesting. Finally, we show that the power enhancement can be achieved by ∼12 times with the proposed PnC compared to the bare Al block.

Prabhu Rajagopal

Papers

Generic time‐domain hybrid models for ultrasonic nde

Interaction of the Shear Horizontal Bend Guided Mode (SHB) with Transverse Cracks

Ultrasonic waves guided by transverse bends in plates subjected to symmetric axial excitation

Reflection and Mode Conversion of Fundamental Torsional Guided Wave Mode From Lack of Bonding in Induction Pressure Welding

Enhanced piezoelectric energy harvesting based on sandwiched phononic crystal with embedded spheres