Contact Characteristics Research Articles

Study on the influence of non-Gaussian honing surface on contact and flow characteristics

PurposeThe contact and lubrication performances, which were previously estimated assuming a Gaussian surface, are insufficient due to the non-Gaussian surface characteristics of the honing liner. The purpose of this study is to analyze the liner honing surface and examine its effects on the contact and flow performance.Design/methodology/approachThe fast Fourier transform (FFT) method was used to generate the liner honing texture. Subsequently, an elastoplastic contact model based on boundary element theory was constructed and simulated for the honing surface. The results were compared with those obtained using a Gaussian surface. In addition, flow factors of the honing surfaces were also compared.FindingsThe contact pressure and flow factors demonstrate significant disparities when dealing with non-Gaussian surfaces. In the deterministic model, the pressure exhibits considerably diminished magnitudes and a more evenly distribution. Moreover, when the gap between surfaces is narrow, the discrepancy in flow factor across different directions on the real honing surface becomes more prominent compared with the Gaussian surface.Originality/valueThe model incorporates the influence of the non-Gaussian honing surface, thereby enabling more accurate prediction.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2023-0198/

Adherens junctions as molecular regulators of emergent tissue mechanics.

Tissue and organ development during embryogenesis relies on the collective and coordinated action of many cells. Recent studies have revealed that tissue material properties, including transitions between fluid and solid tissue states, are controlled in space and time to shape embryonic structures and regulate cell behaviours. Although the collective cellular flows that sculpt tissues are guided by tissue-level physical changes, these ultimately emerge from cellular-level and subcellular-level molecular mechanisms. Adherens junctions are key subcellular structures, built from clusters of classical cadherin receptors. They mediate physical interactions between cells and connect biochemical signalling to the physical characteristics of cell contacts, hence playing a fundamental role in tissue morphogenesis. In this Review, we take advantage of the results of recent, quantitative measurements of tissue mechanics to relate the molecular and cellular characteristics of adherens junctions, including adhesion strength, tension and dynamics, to the emergent physical state of embryonic tissues. We focus on systems in which cell-cell interactions are the primary contributor to morphogenesis, without significant contribution from cell-matrix interactions. We suggest that emergent tissue mechanics is an important direction for future research, bridging cell biology, developmental biology and mechanobiology to provide a holistic understanding of morphogenesis in health and disease.

Synthesis, spectroscopic characterization, crystal structure, DFT calculations and Hirshfeld surface analysis of 3-acetyl-30-N2, N2-dimethyl-1′, 3′, 5′-triazine-2′, 4′-diamine of substituted 18β-Glycyrrhetinic compound

18β-glycyrrhetinic acid (GA) compounds, exhibiting good biological activity, are widely present in drug molecules. Many literatures reported on antitumor activity of derivatives of 18β-GA, and some of these compounds showed better anti-tumor activity than 18β-GA itself and Gefitinib. The compound 1 that one of the 18β-glycyrrhetinic acid compounds (4-amino-6-(dimethylamino)-1,3,5-triazin-2-yl)methyl (2S,6aS,8aR,12bR)-10-acetoxy-2,4a,6a,6b,9,9,12a-heptamethyl-13-oxo-1,2,3,4,4a,5,6,6a,6b,7,8,8a,9,10,11,12,12a,12b,13,14b-icosahydropicene-2-carboxylate was designed and synthesized, and the structure was characterized by spectroscopic techniques including UV-vis, FT-IR, Raman, NMR(1H,13C) and HRMS. The precise structure of 1 were analyzed using single-crystal X-ray diffraction and showed interesting intermolecular NH…O and NH...N hydrogen bonding which was the most important factor in the crystal stacking interaction. The molecular structure was further calculated using density functional theory (DFT), which were compared with the X-ray diffraction value. The results of the conformational analysis indicate that the molecular structure optimized by DFT were consistent with the crystal structures determined by single crystal X-ray diffraction. The molecular electrostatic potential and frontier molecular orbitals of the title compound were further investigated by DFT, and some physicochemical properties of the compound are revealed. In additional, the intermolecular interactions in the crystal were investigated through the Hirshfeld surface analysis to understand the characteristics of the close contacts, and the 2D-fingerprint plot data exposed that a significant contributions to the crystal packing are from N…H/H…N contacts.

Normal contact mechanism of flexible film/substrate bilayer structure: Experimental and numerical insight

The film/substrate bilayer structure design plays a crucial role in enhancing the adaptability of flexible tactile sensors in complex environments. Nonetheless, as the cornerstone for machine tactility, the normal contact mechanism of the film/substrate bilayer structure remains elusive. Herein, the normal contact characteristics of polydimethylsiloxane film/sponge bilayer structure (PF/SBS) with different structural parameters, including substrate porosity, film mass ratio, and relative thickness between film and substrate, are investigated by experimental and numerical methods. The roles of the film and substrate structure parameters of PF/SBS in the normal contact process are analyzed by a cohesive contact model from the energy perspective. The results demonstrate that PF/SBS not only modulates the maximum normal force by substrate porosity but also exerts a substantial impact on the critical contact state by the film mass ratios. The contribution of film thickness to the critical separation state can be enhanced up to 90% with increasing relative thickness.

Achieving Ohmic Contacts in NbS2/MoSe2 van der Waals Heterostructure: A First‐Principles Study

AbstractThe functionality of electronic and optoelectronic devices relying on two‐dimensional (2D) materials can be substantially influenced by the characteristics of their electrical contacts. Herein, a metal–semiconductor electrical contact between metallic NbS2 and semiconducting MoSe2 monolayer is constructed using first‐principles calculations. The electronic properties and contact characteristics of the NbS2/MoSe2 heterostructure as well as the effects of electric fields and in‐plane strains are also explored. These results indicate that the NbS2/MoSe2 heterostructure exhibits the ‐type Schottky contact (ShC) with low Schottky barriers and possesses low contact resistance of the tunneling barrier. Furthermore, the electronic properties and contact characteristics of the NbS2/MoSe2 heterostructure can be fine‐tuned through the application of in‐plane strains and electric fields. The electric fields give rise to the transformation from ‐type to ‐type ShC as well as the conversion from ShC to Ohmic contact (OhC) in the NbS2/MoSe2 heterostructure. Similarly, in‐plane strains play a role in direct‐to‐indirect band gap transitions and further contribute to the conversion from ShC to OhC in the NbS2/MoSe2 heterostructure. These findings offer valuable theoretical insights that can guide the practical utilization of the NbS2/MoSe2 vdW‐MSH in the development of next‐generation electronic and optoelectronic devices.

Research on the Contact Characteristics Between Armature and Rail of the Enhanced Electromagnetic Rail Gun Based on the New Aluminum Alloy Armature

Research on the Contact Characteristics Between Armature and Rail of the Enhanced Electromagnetic Rail Gun Based on the New Aluminum Alloy Armature

Middle trapezius tendon transfer using Achilles allograft for irreparable isolated supraspinatus tendon tears effectively restores the superior stability of the humeral head without restricting range of motion: a biomechanical study

BackgroundMiddle trapezius tendon (MTT) transfer has been suggested for promising treatment of irreparable isolated supraspinatus tendon tears (IISTTs). However, there have been no attempts to assess the biomechanical efficacy of MTT transfer. This study aims to evaluate the biomechanical efficacy of MTT transfer in the setting of IISTTs. MethodsEight fresh-frozen cadaveric shoulders were tested in three conditions (1) intact rotator cuff, (2) IISTTs, and (3) Middle trapezius tendon transfer (MTT) using Achilles allograft for IISTTs. Total humeral rotational range of motion, superior translation of the humeral head, and subacromial contact characteristics were measured at 0°, 20°, and 40° glenohumeral abduction (representing 0°, 30°, and 60° shoulder abduction). Superior translation and subacromial contact pressures were measured at 0°, 30°, 60° and 90° external rotation (ER). Two different MTT muscle loading conditions were investigated. A linear mixed-effects model and Tukey post hoc test were used for statistical analysis. ResultsTotal range of motion was significantly increased after IISTT at 20° abduction (P =.037). There were no changes in total ROM following MTT transfer compared to the IISTT condition (P>.625 for all comparisons). The IISTT condition significantly increased superior translation compared to the intact rotator cuff condition in 0° and 20° abduction with all ER angles (P<.001), 40° abduction/30° ER (P=.016), and 40° abduction/60° ER (P=.002). MTT transfer significantly decreased superior translation of the humeral head at all abduction angles compared to the IISTTs condition (P<.026). MTT transfer significantly decreased peak contact pressure by 638.7 kPa (normal loading) and 726.8 kPa (double loading) at 0° abduction/30° ER compared to the IISTTs condition (P<.001). Mean contact pressure was decreased by 102.8 kPa (normal loading) and 118.0 kPa (double loading) at 0° abduction/30° ER (P<.001) and 101.0 kPa (normal loading) and 99.2 kPa (double loading) at 0° abduction/60° ER (P<.001). MTT transfer at 20° abduction/30° ER with 24N loading significantly decreased contact pressure by 91.2 kPa (P=.035). ConclusionsThe MTT transfer biomechanically restored the superior humeral head translation and reduced the subacromial contact pressure in a cadaveric model of IISTT, while not restricting total ROM. These findings suggest that MTT transfer may have potential as a surgical treatment for IISTTs.

Combined influence mechanism of the flexible free outer ring on contact characteristic in heavy-load cam roller bearings

The cam roller bearing (CRB) is widely used in the cam mechanism of various machinery due to its low friction loss under heavy loads. Such high loads easily cause flexible deformation and free tilting of the outer ring, thereby affecting the contact characteristic and fatigue life. For that, an innovative quasi-static model considering the flexible deformation and free tilting of the outer ring is established to calculate the load distribution of CRBs. Based on the model, the combined influence mechanism of the flexible free outer ring is revealed. Finally, a loading experiment of the CRB is conducted to investigate the contact characteristic of the CRB and validate the proposed model, which demonstrates the necessity of considering the flexible free outer ring in modeling the heavy-load CRB.

Coaxial Flexible Fiber-Shaped Triboelectric Nanogenerator Assisted by Deep Learning for Self-Powered Vibration Monitoring.

Self-powered vibration sensor is highly desired for distributed and continuous monitoring requirements of Industry 4.0. Herein, a flexible fiber-shaped triboelectric nanogenerator (F-TENG) with a coaxial core-shell structure is proposed for the vibration monitoring. The F-TENG exhibits higher adaptability to the complex surfaces, which has an outstanding application prospect due to vital compensation for the existing rigid sensors. Initially, the contact characteristics between the dielectric layers, that related to the perceiving performance of the TENG, are theoretically analyzed. Such a TENG with 1D structure endows high sensitivity, allowing for accurately responding to a wide range of vibration frequencies (0.1 to 100Hz). Even applying to the real diesel engine, the error in detecting the vibration frequencies is only 0.32% compared with the commercial vibration sensor, highlighting its potential in practical application. Further, assisted by deep learning, the recognition accuracy in monitoring nine operating conditions of the system achieves 97.87%. Overall, the newly designed F-TENG with the merits of high-adaptability, cost-efficiency, and self-powered, has offered a promising solution to fulfill an extensive range of vibration sensing applications in the future.

Asymmetric Schottky Barrier in Rubrene Transistor via Monolayer Graphene Insertion toward Self-Powered Imaging

Organic semiconductor materials featuring lightweight, and flexibility may play a significant role in various future applications, such as foldable displays, wearable devices, and artificial skin. For developing high-performance organic devices, organic crystals are highly desired, while a remaining fundamental issue is their contact problem. Here, we have grown a high-quality rubrene single crystal by utilizing a simple in-air sublimation technique. The contact characteristics (barrier height and contact resistance) are detail-studied by resist-free transfer electrodes (Au metal or graphene/Au). The Schottky barrier of the rubrene/graphene interface is lower and can be also modulated by gate bias, which is confirmed by spatial photocurrent mapping. Finally, we demonstrated the zero-bias photocurrent imaging application by constructing the asymmetrical device employing different electrode contacts. Our work would be of significance for studying the contact issue of organic crystals and wireless imaging.

Modelling Friction-Induced Dynamic Instability Dedicated for Isogeometric Formulation

Flutter-type dynamic instability induced by friction is a highly nonlinear phenomenon and computationally expensive to model through transient analysis. An efficient way to make inference of such instabilities in a dynamical system is through analyzing the first-order effect of a perturbation at one of its equilibrium with eigenvalue analysis. The contact characteristics of such dynamical systems are typically modelled through the normal compliance approach with inference from experiments. In this case, the dynamical response of the system is implied to be sensitive to the contact stiffness modelled through the normal compliance approach. Typically, with the normal compliance approach, the continuum of the contact interface is approximated through a set of nonlinear springs which can be interpreted as a collocation method. Such approximations or the numerical implication of contact formulations in general for such problems is not largely studied. We focus on a variational formulation-based contact formulation without domain decomposition which is computationally efficient with small sacrifice in accuracy, where we imply that the dynamical response can be robustly modelled with the given accuracy. Further, we expose the inadequacy of the collocation method for such problems, where the dynamical system is observed to be sensitive to the extent of inaccuracy as a result of collocation for low values of contact stiffness. The inferences numerically imply the characteristics of the dynamical system for variation in contact stiffness.

Tunable Electronic Properties, Carrier Mobility, and Contact Characteristics in Type-II BSe/Sc2CF2 Heterostructures toward Next-Generation Optoelectronic Devices.

Conducting heterostructures have emerged as a promising strategy to enhance physical properties and unlock the potential application of such materials. Herein, we conduct and investigate the electronic and transport properties of the BSe/Sc2CF2 heterostructure using first-principles calculations. The BSe/Sc2CF2 heterostructure is structurally and thermodynamically stable, indicating that it can be feasible for further experiments. The BSe/Sc2CF2 heterostructure exhibits a semiconducting behavior with an indirect band gap and possesses type-II band alignment. This unique alignment promotes efficient charge separation, making it highly promising for device applications, including solar cells and photodetectors. Furthermore, type-II band alignment in the BSe/Sc2CF2 heterostructure leads to a reduced band gap compared to the individual BSe and Sc2CF2 monolayers, leading to enhanced charge carrier mobility and light absorption. Additionally, the generation of the BSe/Sc2CF2 heterostructure enhances the transport properties of the BSe and Sc2CF2 monolayers. The electric fields and strains can modify the electronic properties, thus expanding the potential application possibilities. Both the electric fields and strains can tune the band gap and lead to the type-II to type-I conversion in the BSe/Sc2CF2 heterostructure. These findings shed light on the versatile nature of the BSe/Sc2CF2 heterostructure and its potential for advanced nanoelectronic and optoelectronic devices.

MODELING OF CUTTING TEMPERATURE IN SCREW WHIRLING MILLING DURING THE TWO CUTTING STAGES

Temperature analysis in the manufacturing phase of the product is necessary for improving the operational performance of the workpiece. In screw whirling milling, the analysis of cutting temperature is different from turning or milling due to the complicated contact characteristics between the tool, workpiece and chip. In this study, a temperature model is developed for predicting the temperature distribution of the cutting area in screw whirling milling at the two cutting stages. Temperature experiments on the ball screw shaft are carried out in whirling milling machine under different cutting conditions to verify the proposed model. The maximum temperature of the cutting area increases with the cutting speed at first and decreases subsequently. The maximum temperature increases with the rotation of the tool ring and then decreases in one cut.

Study on contact and vibration characteristics of composite cylindrical roller bearings

PurposeThe purpose of this paper is to establish a dynamic analysis model of composite cylindrical roller bearings, investigate the effects of different working conditions on the kinematic characteristics of composite bearings and compare the differences between them and solid roller bearings.Design/methodology/approachThis paper establishes a dynamic analysis model for composite cylindrical roller bearings and proves the correctness of the established model by establishing dynamic vibration experiments and contact theory for composite roller bearings. Comparative analysis was conducted on the effects of coupling changes in rotational speed, load, number of rollers and filling ratio on parameters such as bearing static stiffness, contact stress and vibration acceleration.FindingsThe composite roller can enhance the bearing’s operational stability and minimize contact stress, but that a higher filling ratio is going to increase the bearing’s stiffness. The acceleration degree of bearing vibration, the load on the outer raceway nodes and the bearing stability all decrease as inner ring speed rises.Originality/valueA dynamic calculation model of composite cylindrical roller bearings is established, and the influence of multiparameter coupling changes on bearing vibration and contact is studied, which lays a foundation for the structural improvement of the bearings.

Key role of initial interface on contact characteristics of Pd/p-GaN

Sequential three-layers of Pd/Pt/Au were deposited on p-GaN by magnetron sputtering under high vacuum (HV, ∼1.33 × 10−4 Pa) and ultra-high vacuum (UHV, ∼1.33 × 10−7 Pa) background conditions, respectively, for investigating the electrical contact properties. Linear I–V curves are observed in the samples deposited under the UHV conditions, whereas nonlinear I–V characteristics are obtained in the samples deposited under the HV vacuum. The depth profiles of X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) of the as-deposited samples were probed in detail. It is found that the amounts of O and OH as well as Pd oxide of the sample deposited under the HV background condition are larger than those of the sample deposited under the UHV conditions due to the higher residual gases such as water in the HV chamber. The oxide layer leads to an extra barrier, influencing the electrical characteristics of Pd/Pt/Au/p-GaN contact. This study demonstrates that metal deposition under the UHV environmental conditions can reduce and even prevent formation of oxide on p-GaN surface, and hence favor making a good ohmic contact on p-GaN.

Numerical simulation of mechanical characteristics and tension-torsion coupling effect of tension-type anchor cable

PurposeThe purpose of this paper is to simulate the tension process of tension-type anchor cable and to explore the mechanical characteristics and tension-torsion coupling effect of anchor cable subjected to tension.Design/methodology/approachABAQUS numerical software is applied to construct the numerical models of tension-type anchor cables with different diameters. Through explicit contact, the characteristics of contact between grouting body-anchor cable and grouting body-rock mass are determined. Confining pressure is applied to the model through surface pressure, and drawing force is applied to the model by displacement loading so as to simulate the tension process of the anchor cable.FindingsThe results show that the stress is transmitted in both axial and radial directions in the anchorage section and distributed in a cone. The shear stress in the grouting body is unevenly distributed, and its peak value increases with the rise in confining pressure and anchor cable diameter. The stress characteristics of torque and axial force are basically consistent and evenly distributed in the free section; they gradually decrease in the anchorage section. Due to the tension-torsion coupling effect, the internal stress characteristics of the anchor cable structure vary. On average, the anchorage performance of each anchor cable model is improved by 6.19%.Originality/valueThe proposed method of numerical modelling is effective in addressing the interface contact between the anchor cable and the grouting body and in solving the problem with convergence of calculation. Compared with the indoor test, this method is more suited to collecting the internal mechanical data of the anchor body.

Modeling and simulation study on the ablation characteristics of DC contactor contact

The DC contactor can frequently break the high current control circuit, and the arc motion characteristic in the current breaking process is closely related to its electrical life and reliability. In this paper, a three-dimensional magnetohydrodynamic arc model of the DC contactor considering contact motion and external circuit characteristics is established. On this basis, the influence of the vapor produced by the contact ablation on the arc behavior is studied, and the ablation rate of the cathode in a single breaking process is calculated. The results show that the arc temperature is reduced, the motion speed is slowed down, and the arc burning time is shortened due to the presence of copper vapor produced by ablation. The ablation rate of the cathode during a single arc is 8.9 µg/C.

Study on the Effect of Different Design Parameters of Sidewall Insert Rubber on the Mechanical Characteristics of Self-Supporting Run-Flat Tires

Self-supporting run-flat tires (SSRFTs) achieve good zero-pressure driving ability by reinforcing the sidewalls, and the structural shape of sidewall insert rubber (SIR) is critical in influencing the mechanical characteristics of SSRFTs. In this paper, an SSRFT contour model is established by combining the radial tire contour theory and the design elements of SIR. The influence of two design parameters (maximum width L and maximum thickness H) of SIR on the tire stiffness characteristics and the contact characteristics is analyzed in depth, and the accuracy of the model is verified by the tire mechanics bench test. The results show that the radial stiffness of SSRFTs is positively correlated with two design parameters; an increase in L affects the stress concentration at the end of SIR, while a change in H has a more drastic effect on the stress distribution of SIR, leading to a large change in both the location of the deformation of SIR and the maximum equivalent stress; under rated pressure conditions, when L is less than 100 mm, the overlap between SIR and the tread decreases, which in turn makes the contact characteristics of SSRFTs closer to that of a normal tire, and obtains better comfort and abrasion resistance; under zero-pressure conditions, the maximum contact stress of the tread is the smallest when the H is 8 mm, but when H is less than 6 mm, the contact characteristics appear to deteriorate uniformly, and the maximum contact stress continues to rise. The results of the research provide a reference value for the selection of the design parameters for SIR and the optimization of the dynamic performance of SSRFTs.

Stiffness Constitutive Characteristics of Elastic Disordered Microporous Metal Rubber Considering Temperature Effects

Elastic disordered microcellular metal rubber (EDMMR) is a lightweight metal material widely employed for damping or support in high‐temperature environments, addressing the limitations of traditional polymer rubbers. Herein, three sets of solid finite element models of EDMMR with different relative densities are developed using virtual manufacturing technology (VMT). Thermal–mechanical coupled finite element simulations explore the dynamic evolution of two typical spatial topological structures in the material's microstructure: unit contact characteristics and angle distribution under temperature variations. Results indicate that the mechanical performance of the material under high‐temperature loads exhibits distinct spatial topological structures compared to those at room temperature. At 100, 200, and 300 °C, the material experiences internal stress distributions of up to 0.5, 1.2, and 1.8 MPa, respectively, due to expansion. Additionally, during the initial loading stage, stress differentials of approximately 0.4 MPa are observed between different temperatures due to boundary effects. Furthermore, the study investigates the probability density distribution of typical microstructural combinations of EDMMR along the forming direction based on VMT, enhancing the generality of the constitutive model. Finally, three groups of EDMMR samples with different relative densities are prepared using standardized processes, and the model is validated through high‐temperature quasistatic compression experiments.

Dynamic properties of sand with different contents of clay

In this study, a series of dynamic triaxial tests and corresponding simulations using discrete element method (DEM) were conducted on sand with different clay particle contents. The development of pore pressure, axial strain, stress path, and stress–strain curve were analyzed. The contact and pore structure characteristics were further examined through electron microscopy. Subsequently, the concept of a contact-to-particle ratio is proposed to describe the connection behavior. The results show that the influence of the clay particle content on the liquefaction resistance is not monotonous. With an increase in clay particle content, the effective stress of sand cannot reach zero. However, the increase in clay particles reduced the permeability coefficient of the sand, which resulted in weak liquefaction resistance of sand. When clay particle content reached 30–35%, the stress–strain curve failed at an early stage. The contact-to-particle ratio was the smallest when the clay particle content was 35%, that effective contact of the particles is only 15% of that in the pure sand sample. When clay content reached 40–50%, the sand sample gradually exhibited the characteristics of clay.