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[en] Shape memory effect is the most effectively performed on NiTi shape memory alloy. The shape memory effect phenomena are related to solid-state phase transformation so the atomic neighbourhood orientation keeps during the phase transformation process. Stress and energy release during the phase transformation have effects on orientations of the atomic structure. However, if SMAs are exposure to repeated regular deforming and shape recovery cyclings, this will eventually cause some loses in their shape memory recoverability. In this study, the shape memory effect loss ratio of Ni46.84Ti53.16 (at%) alloy was investigated by systematic stress-strain mechanical tests and significant shifts was recorded on shape recovery ratios. (paper)
[en] Among the applications of Materials Science and Engineering carried out by the Center for Technological Applications and Nuclear Development (CEADEN) is the use of various physical techniques to support the restoration and maintenance of buildings and other work objects of historical, cultural and social interest in Havana city. The field of Defectoscopy is addressed in this paper, where the applied Nondestructive testings also contributed to restore the cultural heritage, to upgrade the structural conditions at an important sport facility in Havana, and in a greater extent, to the safety of facilities of social significance, such as amusement parks. In this regard, three examples are presented: the inspection of structures during the restoration of the City Hall in the Museum of the Havana City at the Palace of Captains General; the welded joints testing during the restoration of the lighting system and the installation of the digital screen at the Latin American Stadium in Cerro municipality; and finally, the inspection systematically performed at maintenance works to critical elements and related devices at amusement parks.
[en] A probe that can examine a ferromagnetic heat-exchanger finned tube with a curved part is proposed in this paper. The distortion in the electromagnetic field due to the existence of flaws and tube support plate (TSP) was measured using an active-type excitation coil, a bobbin-type Hall sensor array, and a passive-type pick-up coil. The active-type excitation coil could recognize the existence and location of flaws. The Hall sensor array could recognize the existence, location, and distribution of flaws. The passive-type pick-up coil could recognize the position of TSP, which was used as a landmark. The effectiveness and TSP-recognition ability of the proposed probe were verified using a finned-tube specimen made of STS 439 with various types of artificial defects
[en] Applications of additive manufacturing (AM) are diversified, but found with preponderance in the automotive, aerospace, and medical fields. The field of additive manufacturing/material 3D printing is advancing extremely fast, and covers a broad range of materials, spanning from plastics to metals, ceramics, and even to biological tissue. In the aerospace industry one of the main points of attraction is that parts with complex shapes can be built on demand while reducing the weight at the same time. The process can also aid in the fabrication of rare parts and replacement components that are no longer in production. It is commonly understood that AM parts would have different types of defects than those found in conventionally manufactured ones, while major gaps in knowledge exists in terms of the defect type, the effect-of-defect, and the critical defect size and location. One of the shortcomings is related to the lack of physical reference blocks for calibration and performance verification of proposed non-destructive evaluation (NDE) techniques. Also, there are no standards for NDE techniques as applied to AM. This article discusses how NDE could better position itself to help AM gain the trust of aerospace industry. (author)
[en] Currently, thin plate-type materials are widely used as structural materials in various industries. Defects in such a thin plate cause destruction of the structure, resulting in human and material damage. The ultrasonic inspection technique is the most widely used non-destructive inspection method to detect such defects. However, it is difficult to detect micro defects in a thin plate with thickness ≤ 5mm and analyze their signals. In this study, electromagnetic acoustic transducer-based resonant ultrasonic spectroscopy was applied to detect micro defects. Through finite element analysis, the change of the resonance frequency and output voltage depending on the presence or absence of defects was determined, and a test specimen was fabricated by incorporating fine defects to an actual aluminum plate. Our results indicate that it is possible to identify the presence of micro defects using this technique and to recognize the scanned image by changing the resonance frequency and output voltage
[en] Structural health monitoring has been a growing business in the past few decades in infrastructure sector, particularly when multi-billion-dollar structures were built. These may include television towers, over hundred storey high skyscrapers, suspension bridges, cable stayed bridges, tunnels and dams. In the industrial sector, owners' mindset has also gradually changed from reactive maintenance to proactive monitoring and preventive measures. In smelting industries, each day of shutdown due to maintenance can cost millions of dollars. This provides the incentive for owners to take the proactive approach to reduce the frequencies and periods of unscheduled shutdowns. In view of the demand, Hatch Ltd. has developed a package for structural health assessment for smelters and various industrial structures. This included a non-destructive testing (NDT) program to identify the weak zones of a structure and a structural assessment to check the soundness of the major-structural components. The non-destructive testing program include the determination of remaining lining thickness or vessel shell thickness, and the determination of the extent of damaged zones and potential runout/leak regions. Furthermore, ground penetrating radar and impact echo are used for identifying corrosion and delamination of reinforced concrete and to locate any voids and cracks within the concrete structures. A case study is provided in this paper to illustrate the effectiveness of the structural health assessment program on silo structures. (author)
[en] The connections of precast beam and column elements plays a major role in implementation of this technology in seismic regions through which the lateral stability and structural integrity will be maintained. So far the review papers published on precast beam-column connections concisely outlines the concepts, development and suitability of different form of connections in seismic regions. However review works related to seismic behaviour of different precast beam-column connections with analyses and discussion compared to their monolithic connection in a single platform were limited. Hence, this paper presents the overall review of the precast beam-column connection's experimental results by correlation with their monolithic connections in terms of the load carrying capacity, ductility, energy dissipation capacity, stiffness degradation and the failure mode. The different forms of connections were grouped under wet and dry connections (post-tension and mechanical device). The performances of various connection systems are analysed and compared based on the connection construction detail and seismic behaviour. Overall, the seismic performance of wet connection and post-tension connection are acceptable with some major construction drawbacks. Despite of the poor seismic performances, the mechanical device connections may be implemented in construction field with the benefit of economy and simplicity in construction. However, certain innovative ideas and or modification are to be performed to the existing systems to suit the regions of high seismicity. (author)
[en] Miniaturized mechanical tests are commonly utilized to evaluate properties of materials, including thin films, nanostructured, and irradiated materials. However, the specimen size effect occurs when miniaturized sample geometries contain too few dislocation sources, resulting in elevated yield stresses. The size effect is controlled by extrinsic (specimen dimensions) and intrinsic (microstructure) factors. Here, we summarize extrinsic and intrinsic size effects from micro-compression pillar, micro-cantilever bend, and flexure studies reported in the archival literature. We find an approximately linear relationship between intrinsic and extrinsic size effects. Meaningful mechanical properties can be measured when extrinsic size dominates the intrinsic size.