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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] The authors conducted research to find methods of nondestructive testing for preliminary determination of detonation of thin-layer nanostructured explosives obtained by thermal vacuum sublimation. It was necessary for detecting the relationship between the microstructure and its detonation. It is shown that the specific length of crystals correlates with its detonation and can be used for nondestructive testing of thin-layer nanostructured explosives obtained by thermal vacuum sublimation
[ru]С целью разработки методов неразрущающего контроля для предварительного определения детонационной способности взрывчатых веществ по термовакуумной технологии (ВВ-ТТ) проведено исследование по установлению взаимосвязи между микроструктурой гексогена-ТТ и его детонационной способностью. Показано, что удельная длина границ раздела кристаллов гексогена-ТТ коррелирует с его детонационной способностью и может использоваться для неразрушающего контроля ВВ-ТТ
[en] Acoustic characteristics of a pulse detonation engine (PDE) with and without an ellipsoidal reflector are numerically and experimentally investigated. A two-dimensional (2D) non-splitting unstructured triangular mesh Euler solver based on the space-time conservation element and solution element (CE/SE) method is employed to simulate the flow field of a PDE. The numerical results clearly demonstrate the external flow field of the PDE. The effect of an ellipsoidal reflector on the flow field characteristic near the PDE exit is investigated. The formation process of reflected shock wave and reflected jet shock are reported in detail. An acoustic measurement system is established for the PDE acoustic testing. The experimental results show that the ellipsoidal reflector changes the sound waveform and directivity of PDE sound. The reflected shock wave and reflected jet shock result in two more positive pressure peaks in the sound waveform. The ellipsoidal reflector changes the directivity of PDE sound from 20° to 0°. It is found that the peak sound pressure level (PSPL) and overall sound pressure level (OASPL) each obtain an increment when the PDE is installed with a reflector. The maximum relative increase ratio of PSPL and OASPL are obtained at the focus point F 2, whose values are 6.1% and 6.84% respectively. The results of the duration of the PDE sound indicate that the reflecting and focusing wave generated by the reflector result in the increment of A duration and B duration before and near focus point F 2. Results show that the ellipsoidal reflector has a great influence on the acoustic characteristic of PDE sound. The research is helpful for understanding the influence of an ellipsoidal reflector on the formation and propagation process of PDE sound. (paper)
[en] Highlights: • The yield-point phenomenon (YPP) was analysed in relation with cyclic plasticity. • Uniaxial cyclically-loaded specimens made of EN 42CrMo4 were analysed in normalized and tempered state. • Digital image correlation was used for observing the strain field of specimens during monotonic and cyclic experiments. • In specific conditions, the YPP is present during the whole lifetime of uniaxial specimens. • The YPP can affects the lifetime of a cyclically-loaded specimen, when material exhibits cyclic softening. The article presents the influence of the yield-point phenomenon (YPP) on the cyclic plasticity of the uniaxial cyclically-loaded specimens based on observation of stress–strain responses and imaging of strain fields. The phenomenon and its dependence on cyclic material hardening or softening was studied through experiments conducted on the low-alloy EN 42CrMo4 steel in its normalised state (184 HV), which exhibits cyclic hardening, and in its tempered state (296 HV), which is subject to cyclic softening. The results of the study express the influence of the YPP on cyclic plasticity through inhomogeneous strain field when specimens are loaded with strain amplitudes within the yield plateau. The YPP is well expressed in uniaxial cyclic experiments of cyclically softening material.
[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] In this work, the evaluation of damage area due to low-velocity impact tests at different impact energy values and different temperatures on glass fiber-reinforced plate laminates was investigated by two nondestructive evaluation (NDE) techniques, electronic speckle pattern interferometry (ESPI) and ultrasound testing (UT). Composites are characterized by several interacting failure modes such as matrix breakage, fiber failure and delaminations, which can be simultaneously induced by low-velocity impacts and can be different depending on the temperature. It can be complicated to detect by visual inspections of the structures for such phenomena. This paper aims to investigate the dependence of the damaged area with respect to temperature variation on glass fiber composite laminates. GF composite laminates were impacted with three energy levels (5, 10, 20 J) and at different temperatures (room temperature, − 25, − 50 °C) by a drop weight impact machine. The results show that at decreasing temperature, a decrease in the damage extension was observed, which is more evident at increasing impact energy. Moreover, as expected, the results confirm UT and ESPI techniques are able to identify the barely visible low-velocity impact damage. However, some limitations for detection were found in ESPI. Nonetheless, the ESPI technique can be considered as one of the useful NDE methods if the calibration and the post-processing methods are improved.
[en] The optimum distance parameters obtained int testing the surface condition of the PEB cladding using a variety of ultrasonic test immersion probes. The use of ultrasonic testing equipment, especially in the PIE activities (Post irradiation examination), is one of the testing methods at the test stage which does not damage nuclear fuel in Radiotherapy Metallurgical Installation of PTBBN-BATAN. The method used is to compare % FSH (Full Screen High) output signal data at certain distance variations (28 -42 mm) on IK-56, IK-5-10, and IW-10-6 probes using PEB cladding samples with 6400 m/s velocity. The result obtained are that each of these probes has an optimum distance of 32 mm, 38 mm, and 32 mm against the sample with highest % FSH on the IK-5-6 probe. So that the optimization of the parameters of the variation of probes on the PEB cladding is normal and result in the probes IK-5-6 being the best probe in interpreting the surface conditions of the PEB cladding if there are defects/anomalies.(author)
[en] Laser-induced breakdown spectroscopy (LIBS) is an analytical technique allowing the determination of elemental concentrations in a variety of matrices in the solid, liquid, and gaseous phases. Because of the inherent complexity of the signal and to the high dimensionality of experimental data, chemometrics has been more and more applied in LIBS to perform samples identification or quantitative measurements. But multivariate methods can also be used for the description and physical interpretation of the plasma, particularly to exploit the temporal dimension of the LIBS signal, which is usually neglected in spectrochemical measurements. In this work, time-resolved spectra of a pure aluminum sample were treated with 2 methods, mean field-independent components analysis and multivariate curve resolution- alternating least squares, applying non-negativity constraints for scores and components in both cases. Results obtained were compared with reference univariate measurements of the emission of the species of interest (ions, neutral atoms, and molecules). The interpretation of scores and components provided a physical description of phenomena that take place between species in the plasma, like ionic recombination and molecules formation. Overall, mean field-independent components analysis and multivariate curve resolution-alternating least squares yield equivalent solutions with our dataset. This new approach is very promising for the treatment of time-resolved data obtained by LIBS. (authors)
[en] Various tubular objects are utilized for strategic and critical applications in nuclear, aviation, space and petrochemical industries. Major tubular objects employed in these industries are tubes, pipes and vessels which are inspected for planar and volumetric defects hidden inside the material. Various Non-Destructive Testing (NDT) techniques are used for the inspection of such circular objects both during fabrication as well as during in-service stages. Non-Destructive Evaluation (NDE) of these components is carried out in conformance with various codes and standards such as ASME, ASTM and IIW etc. Ultrasonic Testing (UT) is a well-known NDT technique to perform flaw detection, sizing and characterization of tubular objects. Other than the accurate measurement of loss of wall thickness, measurement of variation in Inner Diameter (ID) and Outer Diameter (OD) is also an important requirements of tubes and pipes. Ultrasonic imaging systems are utilized for volumetric inspection of the desired region of tubes and pipes. Imaging systems provide both the gauging and imaging operations. Such a high-speed generic system capable of both, B/C-Scan imaging and high resolution gauging of tubes and pipes, is the requirement of critical applications. Ultrasonic Testing (UT) method, currently used for tube inspection, is not always adequate for flaw characterization. Utilities occasionally experience problems trying to characterize a flaw (particularly, crack or an off-axis flaw) and define its shape, orientation and size. Typically, the Normal Beam (NB) longitudinal waves and angle beam shear waves employing the Pulse-Echo (PE) or Pitch-Catch (PC) technique are used for tube/pipe testing to detect, characterize and size the flaws located within the tube wall or on the ID region or the OD region of tube/ pipe. (author)