Width-diameter Ratio Research Articles

Behavior of high-strength U-shaped bolt shear connector in prefabricated composite beams

This paper presents a novel high-strength U-shaped bolt (HUB) shear connector, which can enhance the integrity, disassembly ease, construction quality, and efficiency of prefabricated steel–concrete composite beams. Seventeen push-out tests were conducted to investigate the effect of the bolt diameter, reserved aperture ratio of concrete slab, bolt width–diameter ratio, bolt length–diameter ratio, and concrete slab thickness on the shear performance of the HUB shear connector. Specimens with a short length–diameter ratio (h/d ≤ 3) exhibit damage characterized by bolt pull-out and bolt bending, while those with a long length–diameter ratio (h/d ≥ 4) experienced bolt shear damage. Subsequently, a finite element model was developed for the push-out tests, enabling a comprehensive study of the shear transfer mechanism, failure mechanism, and stress distribution of the HUB shear connector. Finally, the shear resistance models from different codes were verified. The total slip and simplified load–slip models were proposed.

Mechanical properties analysis of carbon fiber composite bond-rivet hybrid joints of maglev train body in different service environments

Carbon fiber reinforced composites have the advantages of high specific strength and stiffness, which are widely used in rail vehicles. As one of the most commonly used connection forms for maglev train bodies, it is important to ensure the strength and reliability of the joint under different temperatures. Therefore, the paper takes the perspective of carbon fiber composites in the lightweight application of high-speed train bodies. The optimal geometric parameters (end-diameter ratio e/D, width-diameter ratio w/D) of the bond-rivet hybrid joint connection are investigated. The influence laws on structural strength and load-bearing failure forms are found under typical temperatures such as room temperature environment, high-temperature environment, and alternating high and low-temperature environment. Failure specimens and tensile load-displacement curves were analyzed. At the three-room temperatures, the joint structure with an end-diameter ratio e/D of about 3:1 and a width-diameter ratio w/D of about 6:1 had the highest strength, and the failure form was the ideal extrusion damage around the nail hole. The high-temperature environment has little effect on the overall load-bearing capacity of the connected structure in a short period, but it changes the morphology of the adhesive layer. The structure is more prone to shear and peel failure of the adhesive layer. The strength of the alternating high and low-temperature treated joints is slightly higher than that of the untreated specimens when tensile at room temperature. The epoxy resin and carbon fibers are more closely fitted by the environment, enhancing the ability of the composite laminate to withstand tensile and torsional loads.

The Influence of Sagittal Angle of Posterior Malleolus Fracture on Ankle Joint Stability: A Retrospective Study of 120 Cases.

Due to the different force exerted during the posterior malleolus fracture (PMF), the difference in sagittal angle (SA) between the fracture fragments may affect ankle stability. But this aspect is less well studied and the aim of this study was to investigate the relationship between SA and the stability of PMF. The imaging data of 120 patients with PMFs from January 2014 to November 2022 were collected retrospectively and reconstructed. We first measured SA, posterior fragment area (PFA) and fragment area ratio (FAR), reanalyzing the correlation of SA with PFA and FAR, respectively. To better describe the morphological characteristics of the fracture fragments, we further measured the fragment width diameter ratio (FWR), the fragment length ratio (FLR), fragment height (FH), contact area (CA), and finally carried these data into the regression model of SA versus FAR to conduct the intermediary role. SA was negatively correlated with PFA(s) (r = -0.583, P < 0.001), with regression equation s = -0.063SA + 3.066; SA was negatively correlated with FAR (r = -0.204, P < 0.05), with regression equation FAR = -0.002SA + 0.198; A significant correlation was found between FWR, FLR, FH, CA and SA (P < 0.05), as well as between FWR, FLR, FH and FAR (P < 0.05); Further intermediary role analysis showed that FWR, FLR, FH had a partial intermediary role between SA and FAR. As SA increased, PFA and FAR decreased, so the larger the SA was due to the effect of vertical shear force, reflecting higher ankle stability, meanwhile, FWR, FLR and FH should also be considered on the fixation method of fracture fragments.

Design, performance evaluation and calibration of an indirectly-excited piezoelectric wind energy harvester via a double-bluffbody exciter

Using piezoelectric wind energy harvester to harvest energy from fluids has been an effective way to power wireless sensing systems in the last decade. In order to solve the problems of low reliability, poor environmental adaptability and narrow operating bandwidth of existing piezoelectric wind energy harvesters, a piezoelectric wind energy harvester with a double-bluffbody exciter (DE-PWEH) is proposed in this research. By summarizing the disadvantages of traditional piezoelectric wind energy harvester with upwind structure, a downwind structure was adopted to improve the ability of PWEH to adapt to high wind speed environment. In order to further improve the reliability of the DE-PWEH, a wind isolation structure and an indirect excitation structure was adopted, which means the piezoelectric element was installed inside a cylindrical shell. Therefore, this 2-DOF indirectly excited DE-PWEH could possess both high reliability and broad working bandwidth. To verify the principle feasibility and design regarding the proposed DE-PWEH, a prototype of the DE-PWEH was fabricated and tested in terms of output and operating bandwidth. The results showed that the relative size and position of the adjustable plate and cylindrical shell brought significant effects on the output and operating bandwidth. When the distance-diameter ratio was 0.6, the width-diameter ratio was 1 and the height ratio was 1, the maximum output voltage was 90.35 V and the critical wind speed was 0.96 m/s. The maximum increase of the critical wind speed was 550%, and the minimum was −85.67%. With a wind speed of 15 m/s and the optimal load resistance of 2000 kΩ, a maximum power of 2.57 mW was attained. In order to quantitatively study the performance of DE-PWEH, a data fitting method based on polynomial was proposed for the first time to calibrate PWEH performance. The sixth order polynomial fitting equation can be used to characterize the output characteristics of DE-PWEH. And in practice, 80 LEDs in series were successfully driven by the DE-PWEH. The DE-PWEH could charge the 470 μF, 1000 μF, 2200 μF and 3000 μF commercial capacitors to 2 V in 60 s, 128 s, 340 s, and 400 s, respectively.

Micropolar lubricant effects on the performance of partial journal bearings

Present work deals with the computation of static performance of partial journal bearing, operated with micropolar lubricant. The non-dimensional Reynolds equation governs the lubricant flow in clearance space and finite element method is used to solve it. Static characteristics including bearing load capacity, attitude angle, friction force, friction factor, and side flow are presented. Input parameters are chosen such as partial angles 120° and 180° and a width-diameter ratio (1.0), for a range of micropolar fluid parameters. The numerically simulated results show that the bearing geometry and lubricant micropolar parameters on higher side, provide an improved static performance of partial journal bearing system.

Experimental and numerical research on opening size effect of novel short fiber reinforced composite laminates

This study investigates the opening size effect of a novel short fiber reinforced quasi-isotropic composite laminate with unidirectionally arrayed chopped strands (UACS) under tensile load by approaches of simulations and experiments. The layup of [45/0/-45/90]s was used to fabricate novel carbon fiber laminates with various central hole diameter from 4 mm to 10 mm. Low notch sensitivity and strength reduction rate were observed in UACS open-hole laminates. It was found that when the width diameter ratio (d/w) of UACS laminate with open-hole is less than 20%, 80% of the original strength can be maintained, which can greatly reduce the design safety factor. Compared with continuous fiber laminates, high increase rate of strength reduction rate was induced by bi-angled slits with the increasing of open hole diameter. The strain distribution around the hole was affected significantly by bi-angled slits, which also inhibited the initiation and propagation of delamination effectively. The strain concentration factor of UACS laminates increases with the increasing open hole diameter. The damage progression of notched and unnotched UACS laminates were analyzed by simulation method, which are consistent well with experimental results.

A downwind-vibrating piezoelectric energy harvester under the disturbance of a downstream baffle

Wind energy harvesting using piezoelectric transduction is becoming a promising alternative for battery-free wireless electronics. To offer a promising solution for low structure reliability of Piezoelectric Wind-induced Vibration Energy Harvesters (PWVEHs) under fairly high wind speed, a Downwind-Vibrating Piezoelectric Energy Harvester under the disturbance of a downstream baffle (DVPEH) is proposed in this paper. Unlike the most existing PWVEHs of which the bluff body swung against the wind, the structure reliability of energy harvester was improved with the downstream structure of the DVPEH. A downstream baffle was introduced to adjust the working characteristics of DVPEH to avoid the disadvantage of small amplitude of downwind structure. Meanwhile, the dynamic and electrical characteristics of the DVPEH under the disturbance of a downstream baffle was explored to enhance the power generation capacity. To prove the structural feasibility and ascertain the influence of the downstream baffle, theoretical investigation, simulation, fabrication and experimental testing were conducted. The results showed that the interaction of vortex-induced vibration and galloping was induced by the downstream baffle to accelerate the oscillation of the bluff body. Besides, the distance-diameter ratio, width-diameter ratio and length ratio brought significant effects on the performance in terms of electric output and cut-in wind speed. A maximum power of 0.42 mW was achieved at the optimal load resistance of 100 kΩ with the wind speed of 16 m/s and 20 blue LEDs in series was successfully driven by the DVPEH. It was expected that this study could provide a reference for improving the structure reliability and electric output of traditional PWVEHs.

Model Experiment Exploration of the Kinetic Dissipation Effect on the Slit Dam with Baffles Tilted in the Downstream Direction

Slit dams can eliminate the risk of particle overload accumulation, which can be safer in controlling debris flow compared with a completely closed dam. In attempting to better use the energy dissipation effect of particle collision and reduce the impact of the dam body, referring to the traditional slit dam, this paper proposed one with tilted baffles in the downstream direction. Discrete element simulation and several flume model experiments were carried out herein to verify the advantages and explore the applicable conditions of this tilted baffle slit dam, in which the particle trapping efficiency and the change law of impact force of the tilted baffles under the conditions of different inclined angles, opening sizes, and particle sizes were studied. The results show that: 1. when the inclination angle is 30° ≤ θ ≤ 45°, the tilted baffles can dissipate more particle kinetic energy than the transverse baffles; 2. the maximum impact force and trapping efficiency of the tilted baffles decrease with the increase in the width diameter ratio b/d, with the opening width b of the slit to the particle diameter d; 3. with the given particle size of 6 mm ≤ d ≤ 14 mm, the range that the tilted baffles can effectively intercept the particles flowing down is 0 ≤ b/d ≤ 4, and it reaches the ideal interception state near 1 ≤ b/d ≤ 2, where, relatively, the impact force is weak, and the interception efficiency is high.

A Novel Magnetic-Coupling Non-Contact Piezoelectric Wind Energy Harvester With a Compound-Embedded Structure

Herein, we propose a magnetic-coupling non-contact piezoelectric wind energy harvester with a compound-embedded structure to improve the power generation performance, environmental adaptability, and reliability. It is mainly composed of a cylinder, a fixed square plate, and a generator which is embedded inside a square shell and indirectly excited by the magnetic force. Unlike most existing harvesters where the performance improvement was achieved by changing cylinder geometry, this harvester realized the enhancement and suppression of the power generation performance via the interference effect of the square plate on the cylinder. The feasibility of the structure and principle of the harvester was proved through simulations and experiments. At the distance-diameter ratio of 2 and the width-diameter ratio of 3, the corresponding Strouhal number of the cylinder varied from 0.223 to 0.113, realizing the conversion from vortex-induced vibration to galloping vibration with larger amplitude. Thus, the maximum voltage of the proposed harvester increased from 7.5 V to 14.8 V, and the corresponding excitation wind speed was reduced by 10.5 m/s. Besides, according to two evaluation indicators proposed in this paper, the performance improvements on the proposed harvester could be characterized as 201.57% and 97.33%, respectively. As a result, the proposed harvester could output a maximum power density of 2.139 mW/cm3, which was 289.62 % higher than the 0.549 mW/cm3 of the harvester with a single cylinder.

Influence of cavity structure on gas explosion characteristics in coal mine

Through theoretical analysis, experimental research and numerical simulation, the influence of cavity structure on explosion wave propagation is explored. The mathematical model of shock wave propagation in the cavity is established to verify the feasibility of cavity explosion suppression and isolation technique. The explosion shock wave and flame isolation experiments of eight different sizes of cavities were carried out by a self-built large gas explosion experimental system. The results show that the length and width of the cavity jointly affect the explosion shock wave isolation effect, and the flame isolation effect is more obviously affected by the width of the cavity. Through the analysis, it is suggested that the cavity with length-diameter ratio of 2.5, width-diameter ratio of 4 and height-diameter ratio of 1 should be used as the flameproof cavity. The propagation process of explosive shock wave in cavities with different sizes is explored by numerical simulation.

Influence of Cavity Width on Attenuation Characteristic of Gas Explosion Wave

This study aimed to investigate the influence of cavity width on the attenuation characteristic of gas explosion wave. Attenuation mechanism of gas explosion wave through cavity was obtained by numerical simulation. The gas explosion shock wave energy can be greatly attenuated through the cavity structure in five stages, namely, plane wave, expansion, oblique reflection, Mach reflection, and reflection stack, to ensure that it is eliminated. Cavities with various width sizes, namely, 500 ∗ 300 ∗ 200, 500 ∗ 500 ∗ 200, and 500 ∗ 800 ∗ 200 (length ∗ width ∗ height, unit: mm), were experimented to further investigate the attenuation characteristics through a self-established large-size pipe gas explosion experimental system with 200 mm diameter and 36 m length. Results showed an evident attenuation effect on flame duration light intensity (FDLI) and peak overpressure with increasing cavity width. Compared with 300 mm, the overall FDLI decreased by 83.0%, and the peak overpressure decreased by 71.2% when the cavity width was 800 mm. The fitting curves of the FDLI and peak overpressure attenuation factors to width-diameter demonstrated that the critical width-diameter was 2.19 when the FDLI attenuation factor was 1. The FDLI attenuation factor sharply decreased at the width-diameter ratio range from 1.5 to 2.5 and basically remained steady at 0.17 at the width-diameter ratio range from 2.7 to 4.0. The peak overpressure attenuation factor gradually decreased with the increase of width-diameter ratio and changed from 0.93 to 0.28 with width-diameter ratio from 1.5 to 4.0. The research results can serve as a good reference for the design of gas explosion wave-absorbing structures.

Influence of Geometrical Parameters on Heat Transfer of Transversely Corrugated Helically Coiled Tube for Deicing Fluid

In order to ensure flight safety in cold winter, aircraft ground deicing is crucial and necessary. In Chinese deicing fluid heating system, the helically coiled tube is paramount exchanger to heat deicing fluid. The deicing fluid is ethylene-glycol-based mixture with high viscosity. Aiming at heat transfer enhancement of deicing fluid, ring rib is formed by an embossed tube wall toward the internal of the tube; thus, transversely corrugated helically coiled tube (TCHC) is achieved. Depth and width are two key geometrical parameters of ring rib. Based on field synergy principle, the influence of depth–diameter ratio (H/D) and width-diameter ratio (w/D) is investigated through numerical simulation. The results show that outlet temperature, mean convection heat transfer coefficient, and Nusselt number have similar trends, which first increase and then decrease nonlinearly. The variation of flow resistance coefficient is inversely proportional to Reynolds number. Especially, the effect of H/D is more significant than that of w/D. Field synergy angle and velocity field are also analyzed to reveal the mechanism of heat transfer. TCHC performs better than the original tube. Orthogonal experiment calculates the outlet temperature of TCHC when H/D and w/D change. The combination of H/D=0.075 and w/D=0.5 is best solution. TCHC effectively enhances heat transfer of deicing fluid. Therefore, TCHC is beneficial to improve the deicing efficiency and ensure the flight punctuality.

Lubrication performance analysis of crankshaft bush in compressor

Abstract The instability of lubricating oil film has a great effect on the wear of friction pairs and carrying capacity of the parts as well as smooth running of the machine. The lubrication system of crankshaft bush plays an important role in the good operation of compressor unit, reduces production cost while improving production efficiency. In this paper, lubrication performance of the crankshaft bush in compressor was investigated. Parameters involved in the lubrication of bush are studied and analyzed systematically during the stable rotation of crankshaft. Effects of lubrication parameters, such as width diameter ratio, crankshaft speed, inlet pressure, attitude angle and the minimum oil film thickness, on the pressure and distribution of lubricant film were discussed. At last, the optimum value and recommended range of some parameters of bush are determined, and the quantization is carried out within a certain range. The results show that two symmetrical distributions of positive and negative high pressure concentrated areas on both sides of bush oil groove can be formed when the crankshaft is stable. The speed and width diameter ratio have a great effect on the maximum pressure value of oil film. The inlet oil pressure and the minimum oil film thickness are the second, and the inlet attitude angle has little effect. With the increase of width diameter ratio, the maximum pressure value of the positive high pressure concentrated area increases, and the negative areas decreases. With the increase of oil inlet pressure, the maximum oil film pressure increases too but the influence is small. With the increasing of minimum oil film thickness, the maximum pressure and carrying capacity of oil film decrease. If the clearance between crankshaft and bush is too small, oil film can't be formed. For the analysis model in this paper, it is recommended that the radius clearance of bush is 0.04 mm. The inlet oil pressure range of lubricating oil is 0.32–0.36 MPa. Those results can be used in the design, testing and evaluation of the crankshaft system in compressor.

Theoretical research of dynamic characteristics of Tc bearing of measurement while drilling

In this paper, through analyzing Tc bearing by the theory of Hydrodynamic lubrication, the unsteady Reynolds equation of Tc bearing under the dynamic-state condition is initially established. The formula of Tc bearing’s liquid-film dimensionless stiffness coefficient and damping coefficient is derived. Furthermore, two kinds of the distribution curves of Tc bearing’s liquid-film dimensionless stiffness coefficient, damping coefficient against Tc bearing’s eccentricity ratio and width-diameter ratio are displayed respectively, and the stability criterion of liquid film is worked out and the angular speed of instability of bearing shaft is calculated. Overall, conclusions are drawn: downhole system improves the entire system’s stability by enhancing the stiffness of bearing shaft itself. The improvement of the stability of bearing shaft itself, which can be done by altering the structure of Tc bearing and adopting better spiral flutes and ellipse groove can strengthen the whole system’s stability. The high width-diameter ratio of Tc bearing increases the liquid film’s stiffness coefficient and damping coefficient of Tc bearing. The rotational rate of rotary table is lower than half of that of the supporting system of Tc bearing.

An Annulus-Sector Segmented Primary Mirror

Ultrahigh resolution optical imaging with large aperture is increasingly desired in space-based remote sensing and imaging system, but it is usually limited by volume and mass constraints of launch vehicle due to size and weight of the imaging system. In this paper, an annulus-sector segment primary mirror is presented, which is in high obscuration with circularity symmetrical annulus-sector around. The different structure types of the annulus-sector segment aperture are discussed, while two important parameters, width–diameter ratio and the subaperture angle are also studied. An annulus-sector optical lens is processed to verify the image performance. Experimental results show that modulation transfer function of annulus-sector segment optical system can be up to 0.23(50 lp/mm), which approaches the optical resolution of full aperture optical system with smaller size and lighter weight.

Operation Parameters' Effect on Gaseous Bubbles in Lubricant of Groove Textured Journal Bearing

Operation parameter influences on the behavior of the gaseous bubble in the lubricant for a groove textured journal bearing are studied under the consideration of the thermal effect of the bearing–shaft system. The influence is analyzed by simultaneously solving Rayleigh–Plesset (RP), energy, and Reynolds equations. The computer code for the analyzing the bubble behavior is validated. Numerical results show that appropriately increasing the width–diameter ratio of the bearing and rotational speed of the shaft, or decreasing the applied load and inlet temperature of the lubricant, can decrease the maximum radius, collapse pressure, and temperature of the bubble.

Influence of Surface Texture on Lubrication Performance of Hydrodynamic Journal Bearing

A finite-difference numerical model is used to study the influence of surface texture on lubrication performance of hydrodynamic journal bearing. Reynolds equation is adopted to calculate the bearing load carrying capacity, friction force and friction coefficient under different width-diameter ratio, different eccentricity ratio and different texture location. Results show that partial texture along the circumferential direction on the bearing with small width-diameter ratio will increase bearing performance appreciably. Partial texture along the axial direction will decrease friction coefficient effectively, especially at the film inlet zone or the position of film pressure trending to zero.

Numerical Analysis of Static Characteristics of Herringbone Grooved Hydrodynamic Journal Bearing

By means of the finite differential method, the Reynolds equation is solved and the static characteristics of herringbone grooved hydrodynamic journal bearing are numerically analyzed by presenting the circumferential and axial pressures. The influences of parameters such as the eccentricity, width-diameter ratio of bearing, spiral angle, depth and number of grooves, on the static characteristics of herringbone grooved bearing are discussed. The results indicate that the normal pressure of oil film and the load carrying capacity as well, of herringbone grooved bearing will decrease with the increase of groove number and depth. On the other hand, as the pressure distributes in wider area in the circumferential direction, the stability of bearing can be improved. In consideration of these two aspects, the optimal groove number is 8-12, and the selection of depth and screw angle of grooves should also be chosen carefully to obtain the significant performance of herringbone grooved bearing.

Bearing-Rotor Coupled System Stability Optimization Design Based on Genetic Algorithm

The structure parameter of sliding bearing has significant influence on entire shafting. The structural optimization of elliptical sliding bearing based on the genetic algorithm theory is studied in the paper. Shafting logarithmic decrement is taken as the objective function, the bearing width-diameter ratio, relative clearance and main design parameters such as ellipticity is taken as design variables. Mutual coupling effect between sliding bearing and rotor is considered in the optimization model. An elliptical sliding bearing of shafting has been optimized, and the solution result shows that the shafting stability has been increased, it indicates this method is feasible.

Effect of Detachment and Attachment of Top Foil on Predicted Maximum Load Carrying Capacity of Bump Foil Journal Bearings(Part 2: Extensive Survey of Bearing Design Variables)

Bump foil journal bearings are prospective applicants that can support small-sized high-speed rotating machinery. In the previous report, the maximum load carrying capacity of the bearing was predicted, considering the detachment of top foil and the style of attachment of its trailing edge to the bearing housing, and these effects on the capacity were shown to be small. However, the result was obtained only from a base case of the bearing design variables. In this report, the capacity is presented extensively in other cases of the bearing design variables. It is found that the result is applicable to the capacity of the bearing where an excessive static friction acts between the top and the bump foils. On the other hand, the effects of the detachment and the attachment on the capacity of the bearing without the friction between the two foils could be large in the cases of larger values of rigidity of top foil, preload factor, attached angle of top foil, width diameter ratio and pitch angle of bump-equivalent springs.