[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Freedom of design, mass customisation, waste minimisation and the ability to manufacture complex structures, as well as fast prototyping, are the main benefits of additive manufacturing (AM) or 3D printing. A comprehensive review of the main 3D printing methods, materials and their development in trending applications was carried out. In particular, the revolutionary applications of AM in biomedical, aerospace, buildings and protective structures were discussed. The current state of materials development, including metal alloys, polymer composites, ceramics and concrete, was presented. In addition, this paper discussed the main processing challenges with void formation, anisotropic behaviour, the limitation of computer design and layer-by-layer appearance. Overall, this paper gives an overview of 3D printing, including a survey on its benefits and drawbacks as a benchmark for future research and development.

Additive manufacturing (3D printing): A review of materials, methods, applications and challenges

The American Society for Testing and Materials (ASTM) is an independent organization devoted to the development of standards.

American Society for Testing and Materials

A review of shape memory alloy research, applications and opportunities

The unique electrical, mechanical and physical properties of two-dimensional materials make them attractive candidates in flexible nanoelectronic systems. Here Akinwande et al. review the literature on two-dimensional materials in flexible nanoelectronics, and highlight barriers to their full implementation.

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Two-dimensional flexible nanoelectronics.

On the optimal sensor placement techniques for a bridge structure

Prediction of Young's modulus of single wall carbon nanotubes by molecular-mechanics based finite element modelling

Active infrared thermography is a fast and accurate non-destructive evaluation technique that is of particular relevance to the aerospace industry for the inspection of aircraft and helicopters’ primary and secondary structures, aero-engine parts, spacecraft components and its subsystems. This review provides an exhaustive summary of most recent active thermographic methods used for aerospace applications according to their physical principle and thermal excitation sources. Besides traditional optically stimulated thermography, which uses external optical radiation such as flashes, heaters and laser systems, novel hybrid thermographic techniques are also investigated. These include ultrasonic stimulated thermography, which uses ultrasonic waves and the local damage resonance effect to enhance the reliability and sensitivity to micro-cracks, eddy current stimulated thermography, which uses cost-effective eddy current excitation to generate induction heating, and microwave thermography, which uses electromagnetic radiation at the microwave frequency bands to provide rapid detection of cracks and delamination. All these techniques are here analysed and numerous examples are provided for different damage scenarios and aerospace components in order to identify the strength and limitations of each thermographic technique. Moreover, alternative strategies to current external thermal excitation sources, here named as material-based thermography methods, are examined in this paper. These novel thermographic techniques rely on thermoresistive internal heating and offer a fast, low power, accurate and reliable assessment of damage in aerospace composites.

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Recent Advances in Active Infrared Thermography for Non-Destructive Testing of Aerospace Components.

The structural health monitoring (SHM) of structures is acquiring a key role in the present time. An in situ system able to assess the health state of bolted joints would save money and maintenance time, by allowing quick assessment of residual life and degradation state of structures. In the last decades, SHM systems based on linear acoustic/ultrasound methods have been investigated extensively. The scope of this study was to develop a reliable index able to assess the loosening/tightening health state of a bolted structure based on linear and nonlinear acoustic/ultrasound parameters. In particular, for the linear acoustic/ultrasound method, a tightening/loosening state index based on the first-order acoustic moment was developed. This method is based on the assumption that a change of signal energy would be recorded for different loosening/tightening states. As for the nonlinear methods, under single- and multi-frequency excitation, high-harmonics generation and sidebands modulation indices were develop...

Structural health monitoring of bolted joints using linear and nonlinear acoustic/ultrasound methods

Modern aerospace structures make increasing use of fibre reinforced plastic composites, due to their high specific mechanical properties. However, due to their brittleness, low velocity impact can cause delaminations beneath the surface, while the surface may appear to be undamaged upon visual inspection. Such damage is called barely visible impact damage (BVID). Such internal damages lead to significant reduction in local strengths and ultimately could lead to catastrophic failures. It is therefore important to detect and monitor damages in high loaded composite components to receive an early warning for a well timed maintenance of the aircraft. Non-linear ultrasonic spectroscopy methods are promising damage detection and material characterization tools. In this paper, two different non-linear elastic wave spectroscopy (NEWS) methods are presented: single mode nonlinear resonance ultrasound (NRUS) and nonlinear wave modulation technique (NWMS). The NEWS methods were applied to detect delamination damage due to low velocity impact (<12 J) on various composite plates. The results showed that the proposed methodology appear to be highly sensitive to the presence of damage with very promising future NDT and structural health monitoring applications.

Michele Meo

Papers

On the optimal sensor placement techniques for a bridge structure

Prediction of Young's modulus of single wall carbon nanotubes by molecular-mechanics based finite element modelling

Recent Advances in Active Infrared Thermography for Non-Destructive Testing of Aerospace Components.

Structural health monitoring of bolted joints using linear and nonlinear acoustic/ultrasound methods

Detecting Damage in Composite Material Using Nonlinear Elastic Wave Spectroscopy Methods