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Oblique impact excitation has been introduced in Experimental Modal Analysis (EMA), with the great advantage of reducing the conventional EMA's testing time by a factor of three. One major constraint of this technique is the investigation of the effect of various oblique impact directions towards its accuracy in determining the structural dynamic characteristic. This feasibility study is difficult to be achieved in practice, as it involves a lengthy amount of experimental works using various oblique impact directions. To solve this problem, a mathematical model has been developed to synthesize the FRF due to oblique impact (i.e. oblique FRF) in this study. The synthesized oblique FRFs show great agreement with the measured oblique FRFs in various oblique impact directions, which validate the reliability of the usage of the proposed synthesis method. The performance of the oblique impact testings using various impact angles is investigated. The results show that the oblique impact testing has a high success rate to extract directional modes in many impact directions, however wrong selection of the impact direction will lead to mode estimation failure. Good selection of impact direction based on force and modal strengths are demonstrated to ensure an accurate estimation of the structural dynamic characteristics. [ABSTRACT FROM AUTHOR]

This paper presents the elastoplastic behavior of beam-to-column connections with horizontally oblique angles under cyclic loading. We conducted a full-scale experiment and an element test to predict the critical sections of flanges subjected to tensile loading. Four element specimens were tested at different oblique angles. In the element test, strain concentration caused earlier failure of the specimens with oblique angles. Notably, the ductility of specimens with a 45° oblique angle decreased by 50% compared to those without an oblique angle. In the full-scale experiment, four specimens were tested. The hysteretic responses, skeleton curves, failure modes, and ductile performances of the specimens were analyzed. The experimental results from the full-scale experiment showed that all specimens, regardless of the oblique angles, exhibited stable hysteresis behavior and similar skeleton curves. Regarding failure modes, fractures occurred where local buckling developed, albeit with varying locations based on the oblique angle. However, strength deterioration behaviors following local buckling remained the same. A strain concentration phenomenon was observed at the beam end with analyzing strain range. Owing to local buckling, no apparent decrease in ductility with a change in the oblique angle was observed. • Oblique angles had little effect on the behavior of beam-to-column connections. • Larger oblique angles caused strain concentration in obtuse angle zones. • With increasing oblique angles, strength deterioration behavior was not affected. • Fatigue life with oblique angles was similar to that without oblique angles. • Premature fracture might appear at the obtuse angle zone of the beam end. [ABSTRACT FROM AUTHOR]

• In this manuscript, a new unidirectional SH wave EMAT with oblique permanent magnet for the inspection of the aluminum plate is presented for the first time.The oblique angle of the permanent magnet enhances the guided signal on one side and weakens the ultrasonic signal on the other side. • Therefore, the angled bias magnetic field can improve the focusing ability of the SH guided wave transducers effectively. • It is concluded that the oblique PPM can improve the focusing ability of the unidirectional point-focusing SH guided wave EMAT and suppress the influence of the reflected signal, and then improve the resolution of the ultrasonic signal at the focusing point. • In the study of the influence of the oblique angle of the permanent magnet on the focusing SH guided wave EMAT, the displacement amplitude at the focal point increases as the angle increases while the growth rate decreases. • For the other side of the focal position, the displacement amplitude at that point decreases linearly as the angle increases. We propose a new unidirectional point focusing shear horizontal (SH) guided wave electromagnetic ultrasonic transducer (EMAT) with an angled periodic permanent magnet (PPM) in this work. The angled PPM developed here provides an angled bias magnetic field to achieve the EMAT's unidirectional focusing capability. The characteristics of the magnetic field distribution are analyzed by numerical and theoretical calculations. The simulation and experimental results are proven to be in good agreement when studying the bidirectional normalized amplitudes of the displacement of the single-coil SH-guided EMAT with oblique permanent magnets. Both the proposed angled transducer structure and the traditional paralleled transducer structure are performed and simulated using the three-dimensional Finite Element Method (FEM) to compare their unidirectional focusing capabilities. The results show that the SH guided wave EMAT of the focusing coils with an oblique permanent magnet enhances the signal on the focusing side and weakens the signal on the other side effectively. This performance can suppress the influence of the reflected signal from the unfocused side and further improve the ultrasonic signal's resolution. Moreover, it is shown in the study that increasing the oblique angle of the PPM makes it difficult to increase the signal strength at the focal point when the angle reaches a certain value, but it is still effective at weakening the signal on the unfocused side. [ABSTRACT FROM AUTHOR]

Abstract Slope surface is unavoidable and has an important effect on the quality of final fabricated product in the selective laser melting (SLM) process. In this paper, finite element simulation and experimental research on the effect of slope surface with different oblique angles are performed. In the finite element model, the difference in thermal physical properties between the fabricated part and powder material are taken into account. The temperature distribution, melt pool shape, slope surface morphology, roughness and dimensional accuracy are investigated. It shows that the melt pool depth and length are significantly influenced by the oblique angle and the tail of melt pool trends to one side as the oblique angle becomes small. The quality of slope surface increases and the dimensional deviation decreases with the increasing oblique angle. Based on the results, large oblique angle is recommended when designing part, and rotation in the vertical direction is prompted for obtaining large oblique angle when fabricating product. In addition, large dimension compensation and intensified post processing are suggested for slope surface with small oblique angle. [ABSTRACT FROM AUTHOR]

In the present work, the effect of channel cross section on the heat transfer performance of an oblique finned micro-channel heat sink was investigated. Water and Al 2 O 3 /water nanofluid of volume fraction 0.25% were used as a coolant. The oblique finned microchannels are designed with three channel cross-sections namely square, semicircle and trapezoidal. The primary work of this paper is to study the heat transfer and hydrodynamic characteristics in the oblique finned microchannel. The experimental setup and procedure are validated using water as coolant in a micro-channel heat sink. Heat transfer and flow characteristics are examined for three cross-sections of varying mass flux. The trapezoidal channel cross-section increases the considerable heat transfer rate improvement for both water and nanofluid by 3.133% and 5.878% compared to square and semicircle cross section. Also, the pressure drop is higher in the trapezoidal cross-section over the square and semicircle cross section. This is due to increase in friction loss of trapezoidal cross section. The results indicate that trapezoidal cross-section oblique finned micro-channel is more suitable for heat transfer in the electronic cooling application. [ABSTRACT FROM AUTHOR]

Laboratory experiments were conducted to investigate the dynamics of oblique particle cloud in stagnant water. Previous laboratory studies on vertically downward particle clouds indicated the importance of nozzle diameter d o and mass of sand particles in form of an aspect ratio of L o / d o where L o is the length of occupied sand particle in a pipe. In addition, particle size plays an important role in mixing capability of particle clouds. 30 laboratory experiments were carried out to consider the effects of L o / d o , particle size D 50 , angle of release θ , and release height H . In order to generalize the outcome of the present study, both particle size and release height were normalized to form Stokes number S t and release number η . Three classes of particle size were identified for 0 < S t < 1 and a relatively wide range of aspect ratio 0.8 ≤ L o / d o ≤ 40.1 was formed by changing the mass of sand particles. To consider the effects of release angle and release height, four release angles of θ = 15°, 30°, 45°, and 60° were chosen and three release numbers of η = 8.5, 13.2, and 17 were selected. Trajectories of particle clouds were identified based on the position of cloud front. Empirical formulations were developed to model the path of the frontal head of oblique particle clouds. Using a theoretical approach, the location of particle fall out was estimated within ± 10% accuracy. Variations of the frontal velocity of particle clouds in vertical direction were investigated and an empirical equation was proposed based on dimensional analysis to predict the frontal velocity at different initial conditions. Mixing efficiency of particle clouds was characterized by entrainment coefficient α e . The entrainment coefficients of particle clouds were computed using the theoretical entrainment hypothesis. It was found that the Stokes number can significantly alter the mixing capability of particle clouds. The influence of controlling parameters on particle−particle interactions can be studied by estimating the drag reduction due to particle grouping effects. The averaged drag coefficients C d of particle clouds were calculated from momentum equation and a semi-empirical model was proposed to estimate the drag reduction of particle clouds. Significant drag reduction occurred in particle clouds in comparison with individual particles. [ABSTRACT FROM AUTHOR]

CuIn 0.8 Ga 0.2 Se 2 (CIGS) is a chalcogenide semiconducting material used as absorbing layer in photovoltaic cell. In the present study, CIGS thin films were deposited on bare soda lime glass substrate by RF magnetron sputtering at various oblique angles. The structural, surface morphological, film surface roughness, optical, and electrical properties of CIGS thin films were studied at various oblique angles. Films were characterised by X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), Atomic force microscopy (AFM), UV-Vis-NIR spectrophotometer and four probe method. XRD revealed that all the deposited thin films were polycrystalline with preferred peak intensity along (112) plane. The film deposited at 0° (target- substrate parallel) exhibited larger crystallite size (28 nm) with low dislocation density (1.2×10 15 lines m -2 ). The film surface at this angle was more compact and uniform in comparison to the films deposited at other deposition angles. The optical data revealed that the film exhibits more transparency (23%) at higher oblique angle (60°). The optical band gap of developed film was found to be 1.33 eV at 60° while 1.14 eV at 0°. Slanting morphology was observed at higher oblique angle. The electrical resistivity was following an increasing trend with rise in oblique angle. [ABSTRACT FROM AUTHOR]

Abstract: A novel cylindrical oblique fin minichannel heat sink was proposed and studied for cooling heat source with cylindrical surfaces. To optimize and analyze the heat transfer performance of the heat sink, a similarity analysis and parametric study on the geometric dimensions of the heat sink were performed. Three dimensional conjugated heat transfer simulation using CFD (Computational Fluid Dynamics) approach was used to analyze the laminar convective heat transfer and apparent friction characteristics for 43 different cylindrical heat sinks with varied geometric dimensions. The studies were performed by varying the oblique angle from 20° to 45°, secondary channel gap from 1mm to 5mm and Reynolds number from 200 to 900. In this paper, the flow distribution was also investigated and reported, as the secondary channel gap, oblique angle and Reynolds number were varied. Based on the 259 numerical data points, multiple correlations for the average Nusselt number and the apparent friction constant were formulated, verified and presented. The average deviation for the approximation of average Nusselt number is from −5.8% to 7.0% while it is from −5.1% to 7.1% for the apparent friction constant. These correlations can be used for further studies such as performance prediction or geometrical optimization. [Copyright &y& Elsevier]

Abstract: Oblique angle ion etching at incidences of 30° and 75° from surface normal were used to produce sharp tipped topographical features on Ti6Al4V alloy. The 30° etching resulted in a random distribution of needles raising ~4μm from the base surface, while needles from the 75° etching laid closer to the surface. The cellular response of these surfaces was evaluated by a weeklong culture of hFOB 1.19 cells. It was shown that the features of the 30° etch prevented cells from spreading while cells on the 75° etched surface displayed preferential elongation in the direction of the needles. [Copyright &y& Elsevier]

Abstract: Piezoelectric composite materials, an important part of smart structure, have the ability to perform both sensing and actuating functions. The 1–3 piezoelectric composite consists of piezoelectric rods embedded across the polymer. Such materials have been applied effectively in the pulse-echo transducers used in medical ultrasonic imaging. The composite can also be used for underwater vibration or noise controlling with its high coupling factor and low acoustic impedance, for both the shear and the compression damping characteristics can be controlled by inclining the piezoelectric rods. In this paper, a simple physical model of 1–3 piezoelectric composite was developed to illustrate the material''s properties that are relevant to the hydrostatic response. It evaluated the influences of the oblique angles, volume fraction and the parameters of PZT rods and polymer to its hydrostatic properties and came up with a solution to maximize the electromechanical coupling factor and the acoustic impedance. [Copyright &y& Elsevier]

Abstract: An experimental study is performed to determine the combined effects of oblique angle (θ) and heating height (H) on the flame structure, temperature field and thermal efficiency of a laminar premixed methane–air flame impinging on a plane surface. A double-flame burning of a Bunsen flame under a fuel-rich condition is used. It is found that the flame structure, temperature distribution and thermal efficiency depend strongly on the oblique angle and heating height. The influence of the oblique angle on flame structure is stronger for lower heating heights but is relatively weak for higher heating heights. For normal impingement, axisymmetric temperature distributions are found, which is attributed to the axisymmetric flame structure. However, a jet flame impinging at an angle onto the horizontal plate creates an asymmetric flame structure and, thus, results in asymmetric temperature distributions. The results show that as the oblique angle is reduced from 90° to 60°, the high-temperature zone shifts toward the major flow region. An optimum operating condition of the burner, identified by the widest high-temperature zone and the highest thermal efficiency, is achieved under the condition of θ=60° and H=12 mm. In general, a decrease of the oblique angle leads to a decrease in thermal efficiency. However, for the cases of lower heating heights (i.e. H⩽12 mm), the trend may be reversed. Furthermore, for a fixed oblique angle, as the heating height is increased, the thermal efficiency first increases to a maximum value and then decreases. [Copyright &y& Elsevier]