Transverse Hole Research Articles

Fabrication and Performance Evaluation of Microneedle Devices with Through-type Transverse Holes

Fabrication and Performance Evaluation of Microneedle Devices with Through-type Transverse Holes

Three-dimensional reconstruction of transverse hole defect in plate based on TOFD inspection

ABSTRACT In this paper, aluminium plate specimens with circular transverse hole defect was prepared, and the specimen was subjected to ultrasonic non-destructive testing using the TOFD (Time-of-Flight Diffraction) inspection method. Simultaneously, addressing the issue of three-dimensional reconstruction of defect within the field of ultrasonic non-destructive testing, a method combining the least squares approach and volumetric rendering was proposed to process the B-scan images obtained from TOFD inspection. This method was used to reconstruct the three-dimensional shape of transverse hole defect. The result shows that processing defect information acquired through TOFD inspection using the integrated approach of least squares and volumetric rendering leads to clear three-dimensional reconstruction images. This research offers an efficient method for the three-dimensional visualisation of transverse hole defect in plate.

Laser ultrasonic frequency-domain imaging and phase weighted optimization based on full matrix capture

Far-field laser technology has greatly promoted the progress of nondestructive ultrasonic imaging of bulk structures. However, under thermoelastic excitation, the body waves exhibit a relatively low signal-to-noise ratio, resulting in images with low resolution and contrast. Based on the motivation, this paper developed a frequency-domain phase weighted imaging method to improve the quality of laser ultrasonic defect imaging. Firstly, laser ultrasonic scanning was performed on the sample with artificial transverse hole defects. The cylindrical lens focused line source was used to improve the intensity of the body wave signals, and ensure that there was no damage on the material surface under high laser energies. Then, the frequency-domain phase shift migration (PSM) algorithm was used to perform multimode imaging of defects, achieving frequency-domain synthetic aperture focusing technique (F-SAFT) and total focused method (F-TFM) imaging based on full matrix capture. Furthermore, the phase circular statistical vector (PCSV) was proposed for weighted optimization, which improved the image quality, suppressed the background noise and multimode artifacts. Finally, the imaging quality of several algorithms were discussed. The results indicate that frequency-domain images were superior to time-domain results. After phase weighting, the imaging quality can be further improved, and the detection blind zone was significantly reduced. This work will contribute to the rapid and high-quality defect imaging of laser ultrasonic.

Bending stresses in straight bars with a transverse centre hole: A case of beneficial notch effect?

The article investigates by finite elements the bending stresses around a centre transverse circular hole in straight bars with rectangular or circular cross-section. Four loading conditions are considered, pure bending and three variants of three-point bending (load concentrated on the bar surface above the hole, load directly applied to the hole as uniform pressure, load applied to the hole through a connecting pin). Mostly, the hole diameter is one-third of the section height and one-twentieth of the beam length. Holes of one-fourth and one half of the section on several beam lengths are also investigated for the flat bar in three-point bending to appraise the sensitivity to aspect ratios. The results show that, in all cases, the notch effect is mildly detrimental to the stress distribution and can even be beneficial in comparison with the unperforated bar. This is because the hole increases the stresses around the neutral axis, where the stresses are naturally low, thus taking away stresses from the surface where the bending stresses are naturally highest. The design of pivoted flexural machine elements like levers, yokes and balance arms can take advantage from this evidence.

Theory of Burstein–Moss effect in semiconductors with anisotropic energy bands

Abstract We study the peculiarities of the Burstein–Moss shift employing two-band model with an anisotropic valence band. There is a long wave tail which has a convex or concave shape depending on the ratio between the longitudinal and transverse hole masses. The width of this anisotropy-induced tail is temperature-independent and increases with increasing electron concentration and difference between the hole masses. This width also does not depend upon the value of the energy gap. Having experimentally evaluated the tail width and the position of the break in the optical absorption curve, one can deduce the values of the reduced hole masses.

An Improved Finite Element Model to Study Stress Concentration Around an Elliptical Cutout in Pressure Vessel : Application- Part II

The application of finite element method (FEM) to the solution of cutout and inclusion problems in Filament Wound Fibre Reinforced Plastic (FWFRP) pressure vessel is considered. The analysis of pressurised laminated composite shell, which can be regarded as a heterogeneous body consisting of a finite number of orthotropic layers bonded together, with an elliptical hole is carried out. The influence of uniform shear force distribution along the hole boundary is studied. The numerical results of pressurised laminated composite shell with transverse elliptical hole filled by edge bonded elastic cover are also presented. Predicted stress distribution through the thickness of composite shell with cutout/inclusion at critical locations on the hole boundary is presented in graphical form and discussed.

The correlation of fractal dimension to fracture surface slope for fatigue crack initiation analysis under bending-torsion loading in high-strength steels

In this study, the fractal dimension of fatigue fracture surfaces is investigated in order to find an alternative failure loading indicator. Some of many metrological factors are generalized by reducing the fracture surface structure to one factor and develop an entire fracture surface procedure by analyzing the impact of surface slope and calculation resolution. Three notched geometries are studied under cyclic bending-torsion: 34CrNiMo6 high-strength steel bars with transverse blind holes; (ii) 34CrNiMo6 high-strength steel bars with lateral U-shaped notches; and (iii) 18Ni300 maraging steel hollow bars with transverse holes produced by selective laser melting. The surface topographies of fatigue fractures were measured with an optical profilometer. The bending-torsion ratio, maximum local von Mises equivalent stress and the number of cycles to crack initiation are examined using the fractal dimension. Moreover, a comparison was also made for conventional surface topography parameters such as root mean square height and void volume. A fatigue crack initiation model based on surface topography and loading conditions is proposed. The model relies on the product of the maximum local von Mises equivalent stress and the fractal dimension divided by the root mean square height to void volume ratio. The results show that the fracture plane geometry, expressed by the fractal dimension Df, can facilitate the estimation of post-failure loading history. In particular, the analysis based on the enclosing boxes method (EBM) is more accurate when it is used as an extra-fine resolution without any plane leveling.

Clinical Evaluation of a New Surgical Augmentation Technique for Transarticular Atlantoaxial Fixation for Treatment of Atlantoaxial Instability.

The feasibility of a newly developed augmentation of ventral fixation technique for surgical stabilization of atlantoaxial instability was clinically evaluated in a cohort of eleven dogs, and long-term clinical outcomes were retrospectively analyzed. The new technique combines wire/suture fixation through a transverse hole in the axis anchored by two screws placed in the alae atlantis or at the cranial end of plates used to bridge the atlantoaxial joint ventrally. A previous biomechanical study demonstrated good stability of this technique during shear loading, comparable to the stability achieved with other standard techniques. Ten dogs improved clinically after surgery and returned to a normal life within 3-6 months of surgery. One dog developed aphonia, dysphagia, and died of aspiration pneumonia three days after surgery. The augmentation of conventional ventral atlantoaxial fixation with the transverse bony corridor of the proximal axis body may be a valuable way to enhance stabilization of the atlantoaxial joint.

Numerical Simulations on the Flexural Behaviours of Reinforced Concrete Girders Strengthened with Bolts

Precast reinforced concrete (RC) girders with dapped ends are used in order to reduce the overall depths of concrete floors and bridge decking and meet architectural requirements. The structural requirements by reducing the depths of these girders result in stress concentrations within the recessed zones. Thus, girders with dapped ends require special details for the strengthening systems. The use of open transverse holes in RC sections is for the passage of various service lines such as telecommunication cables, gas lines, water pipes, electricity cables, etc. The behaviours of RC girders with dapped ends and openings strengthened by bolts subjected to two vertical concentrated loads were numerically simulated by utilising commercial finite element software ANSYS. The numerical results from the simulated models were identical and compatible with those experimental results stated in literature. The validation of the numerical results with those experimental ones was based on the statistical analysis by including the calculations of the correlation coefficients, arithmetic means, and standard deviations for all the simulated girder models in terms of loads and deflections. The obtained numerical results showed that an increase in the compressive strength of concrete by 20% would cause an increase in the loading resistance of the models by 13% and a decrease in the deflection by 21%, respectively. Also, it was indicated that the type of section, i.e., the change of the section from solid to open (with transverse openings), would decrease the resistance of the section by 8–16% and increase the deflections by 15–20%. Similarly, an increase in the number of holes would result in the decreases in the load resistance by up to 6% and the increases in the deflections by up to 24% under the same applied loads. Strengthening openings using vertical bolts has an important role in enhancing the resistance of the models by 8–20% and decreasing the deflections by 20–30%. The failure patterns were hybrid, e.g., flexure and shear, and identical with the experimental ones. Finally, the effect of using the cylindrical compressive strength of concrete as a mechanical parameter on the structural behaviours of the simulated models was investigated, which could improve the resistance loading and decrease the deflections of the models.

Scour Reduction around Bridge Pier Using the Airfoil-Shaped Collar

Scouring around the bridge pier is a natural and complex phenomenon that results in bridge failure. Failure of bridges have potential devastation and public safety and economic loss, which lead to political consequences and environmental impacts. Therefore, it is essential to countermeasure the scour around the bridge pier. This paper studies the effects of four different airfoil-shaped collars (i.e., bc1 = 1.5b, bc2 = 2.0b, bc3 = 2.5b and bc4 = 3.0b, where bc and b are the diameter of the airfoil-shaped collar and pier, respectively) as a scour countermeasure. All the experiments are conducted under clear water conditions with uniform sediment and a constant water depth (y) of 10 cm. Airfoil-shaped collar is placed at four elevations, i.e., bed level, y/4, y/2 and 3y/4 above the sediment bed level. It is observed that the maximum percentages of scour reduction of 86, 100 and 100% occurred due to protection provided by the collar bc2, bc3 and bc4, respectively, at sediment bed level. So, collars bc2, bc3 and bc4 are efficient at the sediment bed level. The profiles of scour hole show that the length of the transverse scour hole is greater than that of the longitudinal one. Numerical investigation of the morphological changes in sediment bed and scour depth contours is developed using the FLOW-3D for the pier with and without the airfoil-shaped collar.

A combined cooling structure consisting of serrated trench and V-shaped surface for film holes: Flow structure and effectiveness improvement

Film cooling is a commonly used thermal protection technology for turbine airfoils. However, due to the counter-rotating vortex pair (CVP) generated by the interaction between the cooling jet and the mainstream, the coolant gradually breaks away from the wall, which is particularly evident at high blowing ratios. For the sake of improving the film cooling effectiveness (FCE) under high inlet temperature conditions, a novel film cooling structure (SerrTrench-VSS) that combines serrated trench film holes with shark skin-inspired V-shaped surface (VSS) is proposed. The RANS method and realizable k-ε model are used for the simulations. The flow characteristics, adiabatic FCE, and resistance loss are analyzed in detail when the blowing ratio (BR) is 0.5–1.5 and then compared with the traditional cylindrical film hole and transverse trench film hole. In addition, the impact of VSS height on the cooling performance is investigated and the best height of the structure is determined. The results show that the SerrTrench-VSS has better FCE. The serrated trench can destroy the CVP and improve the spanwise spreading ability of the coolant. Also, the VSS can converge the cooling jet downstream of the film hole toward the centerline, thereby improving its extension ability along the flow direction. In the studied range of blowing ratio, the SerrTrench-VSS has the best FCE, and the spanwise-averaged FCE increases by up to 10.50% when BR = 0.5. The empirical correlations between the globally-averaged FCE and the height ratio within the range of the present study are also given. For the serrated trench, the cooling jet has the best spanwise spreading and flow extension ability when the VSS height is 0.5D. The proposed novel film cooling structure (SerrTrench-VSS) can effectively improve the FCE and provide feasible means for the efficient cooling of a turbine blade under practical conditions.

Effect of bending-torsion on fracture and fatigue life for 18Ni300 steel specimens produced by SLM

In this study, different fracture surfaces caused by fatigue failure were generated from 18Ni300 steel produced by selective laser melting (SLM). Hollow round bars with a transverse hole were tested under bending-torsion to investigate the crack initiation mechanisms and fatigue life. Next, the post-failure fracture surfaces were examined by optical profilometer and scanning electron microscope. The focus is placed on the relationship between the fatigue features (e.g., bending-torsion ratio, fatigue crack initiation angles, and fatigue life) and the fracture surface topography parameters (e.g., height parameter Sx, volume parameters Vx, maximal pit and valley angles). The analysis was carried out using the entire fracture surface of the tested specimens. It was found that the decrease of the shear stress level significantly reduces the value of the fracture surface parameters. A fatigue life prediction model based on both the surface topography values and the applied load was proposed. Fatigue life predictions for different loading ratios agreed well with the experimental results and were slightly better than those of other existing models. The proposed model can be helpful for post-mortem analysis of engineering components subjected to multiaxial fatigue.

Loop Anchor Tension Band Fixation for Olecranon Fractures and Chevron Olecranon Osteotomy.

Although tension band wiring is effective for treating olecranon fractures, it is associated with a high reoperation rate because of hardware-related problems. The loop anchor tension band technique is a novel modification of the Arbeitsgemeinschaft für Osteosynthesefragen (AO)-modified tension band wiring technique. This technique is suitable for treating olecranon fractures without severe comminution and olecranon osteotomy. In the current case series, 2 intramedullary 1.25-mm Kirschner wires (K wires) were inserted as temporary fixation into the ulnar shaft from the olecranon after anatomical reduction. The proximal end of each K-wire was bent into a loop shape and advanced deep into the triceps tendon. A transverse hole was drilled distal to the fracture site, and a 1.0-mm metal wire was passed through the bone tunnel and the loops. The wire was tightened to form a figure-of-eight tension band construct. In total, 10 patients with a mean age of 49 (range: 19 to 85) years were included in this pilot series. The mean and minimum follow-up periods were 13.9 and 12 months, respectively. All fractures achieved favorable union, both radiographically and clinically. The mean QuickDASH score was 15.4 (range: 13.6 to 18.2) and the mean Mayo elbow performance score was 94 (range: 85 to 100). None of the patients experienced K-wire migration. The loop anchor tension band technique is a simple, cost effective modification of conventional tension band wiring and exhibited no implant migration in a pilot series.

Self-mixing interference in a thin-slice solid-state laser with few feedback photons per observation period

Formation of a peculiar lasing pattern leading to a TEM00-like mode accompanied by a nonzero bright outer-ring emission (namely, a modified TEM00 mode) was observed in a 300-\mu m-thick LiNdP4O12 (LNP) laser with reflective flat end mirrors that was pumped with a laser diode whose focused spot size was larger than the lasing beam spot size determined by the thermal lens effect. The photon lifetimes of the laser oscillations were found to be greatly shortened to \tau_{p} = 6.74 ps as compared with those in pure TEM00 mode operation, while the fluorescence lifetime was \tau = 130 \mu s. The formation of the peculiar transverse mode was theoretically treated in terms of the pump-intensity-dependent thermal lens effect, which yields the lasing beam spot sizes in the resultant optical cavity. In addition, transverse spatial hole burning of population inversions due to the preceding transverse eigenmode intensity and the associated anti-guidance of the pure TEM00 field leading to formation of the TEM00 with an emergent outer ring emission was shown to appear with increasing pump power through the electric lens (i.e., population lens) effect, in which almost all of the population inversion contributes to lasing with a pronounced effective modal gain. Self-mixing laser Doppler velocimetry (LDV) experiments and numerical simulations revealed that spontaneous emission factors in the peculiar mode oscillations were greatly decreased in comparison with those in pure TEM00 mode operation. The present thin-slice solid-state laser possessing a large fluorescence-to-photon lifetime and decreased spontaneous emission factor enabled us to detect LDV signals in the regime of few feedback photons per observation period.

The effect of longitudinal hole shape and size on the flexural behavior of RC beams

The building's electro-mechanical piping systems can pass through transverse or longitudinal holes inside the reinforced concrete (RC) secondary beams, thus increasing the available floor height. These holes induced a reduction in the beam stiffness and strength. This work analytically and experimentally investigates the impact of longitudinal hole shape on the flexural behavior of RC beams. The interaction between hole shape and hole location has also been studied. The test program includes nine beams with the same cross section dimensions and steel reinforcement. Holes have been made using two circular PVC pipes (50 and 75 mm in diameter), and wooden medium-density fiberboard (MDF) square tubes (50×50 mm) and rectangular tubes (50×100 mm). Each hole shape was installed at two locations (90 and 160 mm) from the top of the beam. All beams were tested to failure using a four-point bending test. The results show that the hole shape and size up to half the beam width does not affect the failure mode compared to the solid control beam. The reduction in the ultimate strength of hollow beams compared to the control beam depends on the hole shape and size, with a maximum reduction of 20%. The developed analytical models were validated using experimental test results and can be employed to accurately predict the full flexural behavior of hollow RC beams, including cracking, yielding, and ultimate moments/loads.

Fracture Surface Behavior of 34CrNiMo6 High-Strength Steel Bars with Blind Holes under Bending-Torsion Fatigue.

The present study evaluates the fracture surface response of fatigued 34CrNiMo6 steel bars with transverse blind holes subjected to bending with torsion loading. The analysis of the geometric product specification was performed by means of height parameters Sx, functional volume parameters Vx, and fractal dimension Df. Surface topography measurements were carried out using an optical profilometer with focus variation technology. The experimental results show that the doubling the bending to torsion moment ratio B/T from B/T = 1 to B/T = 2, maintaining the same normal stress amplitude, greatly reduces both Sa, Vv as well as the fractal dimension Df of the analyzed specimen fractures by 32.1%, 29.8%, and 16.0%, respectively. However, as expected, a two-fold increase in the B/T ratio, maintaining the same normal stress amplitude, resulted in a larger number of cycles to fatigue crack initiation, Ni, which can be explained by the lower shear stress level. These experiments prove that parameters Sx, Vx, Df are smaller for larger Ni values, which is an important finding. In addition, it was found a high consistency of surface topography measurements for the two sides of the broken specimens. The proposed methodology is both reliable and applicable for other engineering applications involving different geometries and loading conditions.

Hydrodynamic drag reduction of shear-thinning liquids in superhydrophobic textured microchannels

Super-hydrophobic textured surfaces reduce hydrodynamic drag in pressure-driven laminar flows in micro-channels. However, despite the wide usage of non-Newtonian liquids in microfluidic devices, the flow behaviour of such liquids was rarely examined so far in the context of friction reduction in textured super-hydrophobic micro-channels. Thus, we have investigated the influence of topologically different rough surfaces on friction reduction of shear-thinning liquids in micro-channels. First, the friction factor ratio (a ratio of friction factor on a textured surface to a plain surface) on generic surface textures, such as posts, holes, longitudinal and transverse ribs, was estimated numerically over a range of Carreau number as a function of microchannel constriction ratio, gas fraction and power-law exponent. Resembling the flow behaviour of Newtonian liquids, the longitudinal ribs and posts have exhibited significantly less flow friction than the transverse ribs and holes while the friction factor ratios of all textures has exhibited non-monotonic variation with the Carreau number. While the minima of the friction factor ratio were noticed at a constant Carreau number irrespective of the microchannel constriction ratio, the minima have shifted to a higher Carreau number with an increase in the power-law index and gas fraction. Experiments were also conducted with aqueous Xanthan Gum liquids in micro-channels. The flow enhancement (the flow rate with super-hydrophobic textures with respect to a smooth surface) exhibited a non-monotonic behaviour and attenuated with an increase in power-law index tantamount to simulations. The results will serve as a guide to design frictionless micro-channels when employing non-Newtonian liquids.

High cycling performance electrodes of Co2+-doped sandwich structured woodceramics

In order to improve the electrochemical performance of biomass electrodes and prolong their service life, the Co2+ doped sandwich structure woodceramics composite electrode is prepared by utilizing cherry wood veneer and pine needle carbon powder as external cladding layer and core layer, respectively, accompanying with catalyst and dopant Co(NO3)2.6H2O. Scanning electron microscopy (SEM) reveals that a three-dimensional network can be obtained by an external cladding layer which maintains natural pore structures and pine needle toner core layer which possesses the hollow tubular structure attach with the transverse holes tube wall. Transmission electron microscopy (TEM) results exhibit that the doped Co nanoparticles are wrapped by graphitized carbon which improves the corrosion retardancy and prolongs the service life of electrodes. X-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) analysis indicates that the doped Co2+ exists mainly as metallic cobalt (Co) after a series of reactions, but also with a small amount of Co2+. The electrochemical measurements presents that the specific capacitance of the resultant electrodes can reach 319 F g−1 specific capacitance and capacitance retention rate can maintain 98.7% after 15,000 cycles under 0.1 A g−1 current density in the inorganic system (6 mol L−1 KOH). The practical assembled in symmetrical capacitor with the energy density of 33.86 Wh kg−1 has been performed at a power density of 100 W kg−1. Those enhanced performances explain that this novel sustainable sandwich electrode has a good potential for practical application with a long cycle life.

Enhancement behavior of reinforced concrete beam with transverse holes under combined twisting and bending using steel fiber

Openings in beams cause load path and stress discontinuities. Several research experiments have been conducted in recent years to improve the area surrounding the opening using various techniques. In this research investigate the effect of hybrid concrete (normal concrete and steel fiber reinforced concrete) on the beams with transfer opening subject to combined loading (torsion and bending). Six specimens of reinforced concrete beams with the same dimension and reinforcement were tested. The variable where distance of hybrid area around opening (150, 225, 450 and 1500) mm. The opening in reference concrete beams was decrease in the ultimate twisting moment (18.28%) with respect to solid one (without opening). The ultimate twisting moment increases by (32-68%) as steel fiber reinforced concrete is used around the opening. Simultaneously, the twist angle was increased by about (27.6- 46.7%). In addition, relative to the control specimen, the first crack was delayed by bout (41.6-75) %.

Spacially resolved coupled mode analysis for TMI threshold powers in quantum and Rayleigh scattering limits.

A 3D spatially resolved coupled mode and perturbation analysis for the transverse mode instability (TMI) threshold powers in Yb-doped fiber amplifiers is presented in this paper. Threshold powers are computed in the quantum and thermal Rayleigh scattering limits and are compared with those calculated by other coupled mode analyses. Quantum-limited threshold powers are found to be more than three times greater than those calculated with coupled-mode analyses that use uniform and/or average gain approximations. The analysis presented here includes pump depletion, gain saturation, and transverse hole burning. Simulations are applied to co-, cnt-, and bidirectionally pump amplifier configurations. The appearance of TMI is attributed to the formation of a dynamic thermal grating, which enables the exchange of optical power between the fundamental mode (FM) and higher-order mode (HOM). The sole approximation made is that the power in the HOM is much less than that in the FM. A distributed thermal Rayleigh scattering model is introduced that includes a ray-optic representation of the fiber mode structure that relates the Rayleigh power captured by the HOM to the waveguide structure. The location and strength of the thermal gratings are identified to assist in the application of mitigation techniques.