Effective Contact Length Research Articles

Modeling and contact analysis for spur gear pair with modification and localized crack failure

The modified teeth are deliberately manufactured to mitigate the stress concentration generated by offset components, which makes equipment more susceptible to localized failures. Therefore, this paper presents a model aimed at investigating the meshing characteristic of gear pair with modification and crack failure. In this model, the tooth deformation and force transmission are determined based on slice coupling theory. The torsional deformation of teeth produced by eccentric load distribution is considered and complemented to the calculation method. Finally, the approach is proven through the experimental tests and FE model. The result shows that when the equipment is operated in misalignment condition, eccentric load distribution, and stress concentration at tooth edge are generated, the meshing stiffness will be reduced drastically, which can be suppressed by appropriate modification, and the rapid decline of meshing stiffness is weakened by increasing the effective contact length. Although the contact stiffness would be further reduced by the crack failure and the tooth surface deformation is increased, it seems to alleviate the stress concentration and eccentric load effectively.

Sealability Analyses of Premium Connections Characterized by a Surface Fractal Function

With the development of high-pressure, high-temperature wells, the sealability of premium connections is being threatened by heavy loads. For the sake of researching the sealability of premium connections at the microlevel on the sealing surface, a rough profile was characterized according to a fractal function, and the influence of the fractal parameters of contact behavior on the rough surface was analyzed. A full-size premium connection model with a fractal surface FEM was established using ABAQUS software to analyze the Von Mises stress and contact pressure, and the sealability was then analyzed using contact strength theory. It was found that utilizing fractal functions to describe the rough morphology on the sealing surface of premium connections could reveal the contact behavior of the sealing surface more realistically. The premium connection’s fractal FEM was closer to the actual situation, considering the effect of the asperities’ elastic–plastic deformation on the sealability. The fractal dimension D had a greater influence on the contact area and contact pressure than the scale coefficient G. When the fractal dimension D was less than 2.5, the maximum Von Mises stress and maximum contact pressure on the sealing surface were 8.81 × 108 Pa and 1.20 × 109 Pa, respectively, making the surface prone to gluing. The sealability of the premium connection was primarily affected by the axial tension. When the axial tension was 1.2 × 106 N, the sealing surface experienced significant displacement along the axial direction, the effective contact length reduced from 2.72 × 10−3 m to 2.24 × 10−3 m, and the maximum contact pressure reduced from 8.10 × 108 Pa to 6.39 × 108 Pa, which led to a 30% decrease in sealing strength, which may pose a high risk of sealing failure. When the internal pressure reached 1 × 108 Pa, the effective contact length increased from 9.08 × 10−3 m to 1.06 × 10−2 m, the maximum contact pressure increased from 8.67 × 108 Pa to 1.37 × 109 Pa, and the sealing strength increased by 23%.

High-Performance Organic Source-Gated Transistors Enabled by the Indium-Tin Oxide–Diketopyrrolopyrrole Polymer Interface

Source-gated transistors are a new driver of low-power high-gain thin-film electronics. However, source-gated transistors based on organic semiconductors are not widely investigated yet despite their potential for future display and sensor technologies. We report on the fabrication and modeling of high-performance organic source-gated transistors utilizing a critical junction formed between indium-tin oxide and diketopyrrolopyrrole polymer. This partially blocked hole-injection interface is shown to offer both a sufficient level of drain currents and a strong depletion effect necessary for source pinch-off. As a result, our transistors exhibit a set of outstanding metrics, including an intrinsic gain of 160 V/V, an output resistance of 4.6 GΩ, and a saturation coefficient of 0.2 at an operating voltage of 5 V. Drift-diffusion simulation is employed to reproduce and rationalize the experimental data. The modeling reveals that the effective contact length is significantly reduced in an interdigitated electrode geometry, eventually contributing to the realization of low-voltage saturation.

Dynamic characteristics of helical gear with root crack and friction

Helical gear transmission is smooth and has many advantages. However, long-term operation will cause root cracks, which will reduce the time-varying meshing stiffness (TVMS) of the gears, increase the transmission error (LSTE), and reduce the load distribution ratio (Lsr). According to the slice method and the energy method, a TVMS calculation model for a helical gear pair with cracks was established, and the effects of the crack initiation width, termination width, effective contact length and crack propagation angle on the gear were studied. Then, the changes of TVMS, LSTE, and Lsr under the time-varying friction and crack are considered. Build failure dynamics model, and fourth-order Runge-Kutta solution for vibration and amplitude-frequency characteristics. And wavelet transform and variational mode decomposition (VMD) are used to analyze the vibration signal, and statistical indicators are used to analyze the sensitivity of vibration. The results show that the TVMS with tooth root cracks will gradually decrease, LSTE will increase, the Lsr will decrease, and the vibration displacement (VD) will increase. When the two faults are combined, due to the damping characteristics of friction, the TVMS will increase, the LSTE and the VD will decrease. This offers a theoretical foundation for studying the dynamic characteristics of the coupling of gear cracks and friction faults, as well as vibration and noise reduction.

A multifunctional TENG yarn integrated into agrotextile for building intelligent agriculture

Raining as a common phenomenon in agricultural environment sometimes may bring adverse effects on agricultural production, to remedy this, agrotextiles are extensively utilized. In this study, the technology of triboelectric nanogenerator (TENG) is firstly integrated into agrotextiles. To construct a robust TENG yarn, a facile and effective method for the fabrication of stretchable electrode is developed, i.e. coating an elastic fibre with MXene ink, followed by spontaneous growth of Ag nanoparticles (AgNPs). By consecutively coating the conductive fibre with PDMS, the final developed triboelectric yarn (diameter of ~400 μm) is demonstrated to possess extraordinary output performance, generating a voltage of 7.7 V with a effective contact length of 3 cm. Moreover, the excellent mechanical property, highly stretchability, outstanding robustness, and considerable hydrophobicity of the TENG yarn also make it be capable of being woven into net or integrated into agrotextile. Thus, in the meantime of providing protection for crop plantation and animal husbandry to improve the quality and yield of agricultural products, the raindrop energy can also be harvested. Moreover, it can also act as a self-powered sensor to monitor dynamic force, which provide a basic information of weather condition. All in all, this developed TENG yarn enables many promising advantages such as being easily engineered and scaled up, therefore possessing great potential to apply in agrotextile for building intelligent agriculture. • A facile method for fabricating highly stretchable electrode is firstly presented. • The TENG yarn is easily engineered and scaled up for various applications. • The technology of TENG is firstly proposed to combine with the agrotextile. • The TENG yarn can harvest raindrop energy and protect crops at the same time. • The constructed TENG yarn can self-powered monitor dynamic forces.

Uncemented, curved, short endoprosthesis stem for distal femoral reconstruction: early follow-up outcomes

BackgroundUncemented endoprosthetic knee replacement has become a mainstream treatment for malignant tumours of the distal femur. Most femoral stems, however, are straight and therefore poorly fit the anteriorly bowed curvature of the femur. To address this issue, we used a short, curved, uncemented press-fit femoral stem and evaluated its short-term outcomes after reconstruction of the distal femur.MethodsForty-two patients underwent distal femur replacement using curved press-fit stem. To assess the interface, we measured the axial length of the press-fit area and the perpendicular distance of the radiolucent area between the stem and bone on digital images obtained using tomosynthesis with Shimadzu Metal Artefact Reduction Technology (T-SMART). Postoperative complications and oncological outcomes were monitored at each follow-up visit.ResultsOf the 42 patients enrolled in the study, two had cancer-related deaths and one had local tumour recurrence. The minimum follow-up time of the surviving patients was 24 months, with no incidence of aseptic loosening or mechanical failure of the prosthesis. The average effective contact length between the press-fit stem and bone was 74.0 mm, with nearly undetectable radiolucent gaps between the implant and the bone on medial-lateral and anteroposterior views.ConclusionsOver the short term, uncemented, curved, short stem provides a stable bone-prosthesis interface without any aseptic loosening.

Effect of misaligned bearing support performance on natural frequencies of marine propulsion shafting

The influences of bearing support performance which would be affected by the quality of shafting alignment apparently on the lateral vibration natural frequencies of marine propulsion shafting are analyzed in this paper. A three dimensional finite element model representing the entire propulsion shafting, including the bearings, shaft and propeller, has been developed using finite element software for lateral vibration analyses. The effects of the number of bearings, the stiffness and effective contact length of the bearings on the natural frequencies of the shaft are studied respectively. The simulation analysis show that the bearing of a certain position often only has a significant impact on the frequencies of a certain order or a few orders, and the natural frequencies of the shaft can be transferred to avoid the resonance speeds through the reasonable arrangement and performance design of the shaft bearings. In addition, the curve alignment technology is also presented to improve the current shafting alignment quality and misalignment angle error, so as to ensure the design performance of radial bearings. Experimental results show that the curve alignment technology is an effective method to reduce the uneven load and eccentric wear of the bearings, which are beneficial to avoid the resonance vibration and improve the life and stability of shaft system.

Optical Polishing Using Fiber Based Tools

Novel, polymer based fiber tools were utilized to polish BK7 glass. Initial tests with these tools investigated the factors affecting the material removal rates. Fiber type and count, polishing pressure and tool rotational speed were all found to affect the removal rates. Abrasive particle size affects the effective contact length whereby smaller particles resulted in narrower tool processing widths. On a sample with an imparted sinusoidal pattern (amplitude = 100nm, wavelength = 2mm), it was found that the surface roughness on the higher regions were higher than the lower regions thus emphasizing the importance of the fiber-abrasive interaction.

Carbon nanotube–Cu/parylene nanowire array electrical fasteners with high adhesion strength

The preparation of room-temperature electrical fasteners with high adhesion strength presents a major challenge at the micro- or nanoscale. A carbon nanotube (CNT)–Cu/parylene core/shell nanowire (NW) array room-temperature electrical fastener was therefore prepared, and is described herein. The shear adhesion strength of the CNT–Cu/parylene NW array electrical fastener reached a maximum of 50.72 N/cm2, which is six times higher than that of a metallic NW electrical fastener. A theoretical analysis indicated that the adhesion force of such a fastener can potentially be further improved by increasing the effective contact length between the CNTs and the Cu/parylene NW. The resistance of the fastener is 45.4 Ω, which indicates that it has good electrical conductivity.

Improved efficiency of photoconductive THz emitters by increasing the effective contact length of electrodes

We study the effect of a surface modification at the interface between metallic electrodes and semiconducting substrate in Semi-Insulating GaAs (SI-GaAs) based photoconductive emitters (PCE) on the emission of Tera-Hertz (THz) radiation. We partially etch out a 500 nm thick layer of SI-GaAs in grating like pattern with various periods before the contact deposition. By depositing the electrodes on the patterned surface, the electrodes follow the contour of the grating period. This increases the effective contact length of the electrodes per unit area of the active regions on the PCE. The maxima of the electric field amplitude of the THz pulses emitted from the patterned surface are enhanced by up to more than a factor 2 as compared to an un-patterned surface. We attribute this increase to the increase of the effective contact length of the electrode due to surface patterning.

Origin of bias stress induced instability of contact resistance in organic thin film transistors

We report a study on the contact resistance instability induced by the bias stress in staggered pentacene thin film transistors, combining the bias stress measurements with the transfer line method. The contact resistance is increasing with the stress time, and two device parameters are found to contribute to this contact resistance instability: one is the threshold voltage increase due to the charge trapping in the charge accumulation layer; the other is the effective contact length increase due to the charge trapping in the pentacene bulk in the contact region. The gold contact shows lower contact resistance stability compared with the copper contact, which is ascribed to higher density of the deep trap states at the gold contact. This work suggests that the time-dependent charge trapping is responsible for the bias stress effect in organic thin film transistors.

Optimum location of silicide/Si interface in ultra-thin body SOI MOSFETs with recessed and elevated silicide source/drain contact structure

Optimization of the series resistance of silicide contact structure in ultra-thin body (UTB) silicon-on-insulator (SOI) MOSFET with elevated source/drain (S/D) is examined through theoretical analysis and 2-dimensional simulation. It is found that the optimum silicide/Si interface position, which exhibits lowest parasitic series resistance, can be located at inside of SOI layer under the surface as the effective contact length is scaled down further below 100 nm regime. The closed-form analytical expressions derived from modified transmission line model principle provide a guideline for optimum design of silicide thickness and contact parameters in self-aligned silicide technology.

Logarithmic Profile of Rollers in Roller Bearing and Optimization of the Profile

When a bearing roller is in contact with raceways, excessive pressure peaks occur at the ends of the contact rectangles. They are called edge loading. Roller and/or raceway profiles are usually crowned to prevent edge loads. Lundberg developed a logarithmic function as a crowned profile. The profile gives an axially uniform pressure distribution. Johns-Gohar improved the function for convenience of manufacturing. However, the Johns-Gohar profile yields edge loading when the roller is tilted. Also, the profile allows no straight portion on the roller surface although it is desirable to have a flat region from the viewpoint of machining. In this study, we modified the Johns-Gohar logarithmic function to exclude edge loading even when the roller is tilted allowing a flat region. Three parameters, K1, K2 and zm, are introduced into the Johns-Gohar function. These have the following meanings : K1 : coefficient of load, K2 : ratio of crowning length to effective contact length, Zm : crown drop at edge of effective contact length zone. In addition, a mathematical optimization method is used to efficiently determine a set of the parameters. An optimization problem is considered to minimize the maximum contact pressure Pmax, or to maximize the rolling fatigue life L10. A Rosenbrock method is adopted as the optimization algorithm. The method requires no evaluation of gradients of the objective function. Pressure distribution is calculated by making use of a multilevel method. Some examples are demonstrated to verify the proposed method for both Pmax and L10.

Experimental Investigation of Heat Transfer in Grinding

New findings are presented for temperatures, heat flux distribution and the implications for workpiece damage and partition ratio. Workpiece temperatures were measured using a 25 u.m single pole thermocouple assembly. It was found that the critical temperature for the onset of temper colours for ferrous materials lies within the range 450 to 500 deg.C. Measured temperature distributions in the contact zone compared best with theory assuming a square law heat flux. The effective contact length for vitrified CBN and alumina wheels was confirmed to be greater than the geometric value. Substantially lower partition ratios were found with CBN compared to alumina.

EXPERIMENTAL STUDY FOR HEAT AND MASS TRANSFER IN WAVY FILM ABSORPTION WITH THE PRESENCE OF NON-ABSORBABLE GASES

Experimental measurements for the heat and mass transfer in laminar wavy film absorption with the presence of non-absorbables are presented. Water vapor was absorbed into a falling film of aqueous lithium chloride solution on a vertical tube with the air present in the gas phase acting as the non-absorbable whose concentration was accurately detected by a mass spectrometer gas analyzer. Although the depressing effect of the air on the absorption rate was much more significant in the low air concentration range, the absorption reduction rate with increasing air concentration was found to be lower than that reported previously. The reduction was found to be continuous even up to 30% of air content. Besides the non-absorbables, the effects of other operational parameters such as solution flow rate, inlet solution temperature, inlet solution concentration, absorber wall temperature, absorber water vapor pressure, and effective contact length on the absorption rate were also tested. These effects were shown to...