Contact Width Research Articles

A Theoretical Method for Calculating the Internal Contact Pressure of Parallel Wire Cable during Fretting Wear

Fretting wear of the stay cable is an important factor affecting the service life of the cable. To accurately calculate the extent of fretting wear, it is necessary to calculate the internal contact pressure in the cable. Although there are many theories and experiments on the contact behavior between wires, there are still no theoretical formulations for calculating the distribution of contact pressure in stay cables. In this paper, by studying the transfer effect of contact pressure in the cable, the PIC (parallel wire cable internal point contact pressure) model for calculating the contact pressure in the parallel wire cable is proposed, considering the effects of wire twisting, sheath compression, and cable bending on the contact pressure. A finite element model corresponding to the contact mode between steel wires is established, and the effectiveness of the PIC model is verified through numerical simulation analysis and a comparison of the existing contact models. The results indicate that contact pressure caused by wire twisting (CWT) is superimposed layer by layer inwards, with the contact pressure increasing closer to the inner layers, and its magnitude is mainly related to the axial tension and twist angle. Simultaneously, on the same layer, contact points along the diagonal experience the greatest contact pressure. Contact pressure caused by sheath compression (CSC) is assumed to conform to the Boussinesq distribution, with the outer layers exhibiting greater contact pressure compared to the inner layers. Contact pressure caused by cable bending (CCB) conforms to the two-dimensional closely arranged contact force transmission model, has a clear layering phenomenon, and the contact pressure within the same layer does not change significantly. The magnitude of the contact pressure is exponentially related to the curvature of the cable and proportional to the tension of the cable, which explains the reason why the slip occurs later for the cables with high tensile forces. Among these three types of contact pressure, CWT is the greatest, followed by CCB, while CSC is the smallest. The theoretical analysis results show that factors such as wire radius, tension, torsion angle, and wire position have an impact on contact pressure. Contact pressure is transmitted along force chains within the cable, following the superposition law between layers. It is uncertain whether slip occurs in the neutral axis or in the outermost layer because of the different distributions of tangential force and interlayer frictional resistance between the layers of wires. Fretting wear simulations of two wires demonstrate that contact pressure has a significant influence on wear patterns, and the “averaging” of contact pressure is a major reason for achieving uniform interface wear. While the contact width increases proportionally with the contact pressure, excessive contact pressure can complicate the problem by changing the contact mode from gross slip to partial slip. This study provides a theoretical method for calculating contact pressures at any contact point within the cables in engineering practice.

Experimental characterisation and statistical modelling of woven carbon fibre weld conductors for electrical resistance welding of thermoplastic composites

Resistance welding of high-performance thermoplastic composites is a promising joining technique for the structural assembly of aerospace components. Knowledge of the weld conductor resistance as a function of its dimensions, as well as external boundary conditions such as contact preparation and pressure, can be used to scale welding parameters. This paper presents a comprehensive review on the weld conductor contact preparation, length, width and contact pressure dependent resistance with respect to the Toray 5HS T300JB carbon woven prepreg 281 gsm fibre architecture. The study is based on a 4-wire resistance measurement of the carbon fibre fabric weld conductors and was conducted to provide a solid basis for defining the weld conductor’s resistance, considering the dependence on length, width and contact pressure. The experimentally determined resistance values were approximated using linear and non-linear regression functions and combined into a general formulation with respect to the investigated carbon fibre fabric architecture. The least squares fit of experimental versus model data confirmed a very high model confidence. Thus, the model allows a simplified transfer of electrical properties for process pre-design and scaling considering weld conductors with the same fibre architecture.

Effects of fretting wear on rolling contact fatigue

In this study, a three-dimensional (3D) continuum damage mechanics (CDM) finite element (FE) model was developed to investigate the effects of fretting wear on rolling contact fatigue (RCF) of bearing steels. In order to determine the fretting scar geometry, a 3D arbitrary Lagrangian-Eulerian (ALE) adaptive mesh (AM) FE model was developed to simulate fretting wear between two elastic bodies for different initially pristine fretting pressures (0.5, 0.75 and 1 GPa) and friction coefficients (0.15, 0.175 and 0.25) resulting in stick zone to contact width ratios, c/a = 0.35, 0.55 and 0.75. The resulting wear profiles were subjected to various initially pristine RCF pressures (1, 2.2 and 3.4 GPa). The pressure profiles for RCF were determined by moving the contact over the fretted wear profiles in 21 steps. These pressure profiles were then used in the CDM-FE model to predict the RCF life of fretted surfaces. The CDM-FE model uses Fatemi-Socie (FS) criteria for damage evolution and accounts for scatter in RCF life by implementing material topological variation through Voronoi tessellation. The results from CDM-FE RCF model indicate that fretting scar generated at 1 GPa with c/a = 0.35 has the most detrimental effect on RCF life at 1 GPa, reducing life by as much as 99.8% from pristine condition. However, it is to be noted that the remaining life expectancy at this RCF pressure (1 GPa) is significant and more than 17 billion cycles. As the RCF pressure increases (PRCF ≥ 2.2 GPa), the effect of fretting on RCF life decreases for all fretting pressures and c/a values, indicating that life is primarily governed by the RCF pressure. The results from CDM-FE model were also used to develop a life equation for evaluating the L10 life of fretted M-50 bearing steel for the range of tested conditions.

Parametric investigation and optimization in laser based directed energy deposition of tungsten carbide-cobalt

Cemented carbide (WC-Co), the widely used tool-die material, is difficult to be machined by conventional and nonconventional techniques. This inspired exploring additive manufacturing (AM) of this material. However, porosity, brittleness due to cobalt depletion, etc. have been reported in the literature with rare success. For the AM of WC-Co, the current work focuses on directed energy deposition, which can be implemented with existing laser cutting-welding workstations, with modifications. To ensure the retention of cobalt even after inevitable vaporization of some of its initial content during deposition, 20 wt. % of Co was mixed with WC powder by low-energy ball milling. Laser power, scan speed, and powder flow rate were varied following a full-factorial design of experiments. The analysis of variance revealed that the experimental model and most of the parameters were significant. Only the laser power came out to be insignificant for the contact angle. The track height and width increased with the laser power and reduced with the scan speed. The contact angle increased with the scan speed and reduced with the powder flow rate. Cross sections of the deposited track showed no pores or cracks. Multiobjective optimization with gray relational analysis was conducted to get the parameter combination giving high values of the contact angle, track height, and width simultaneously. The optimum parameter combination, thus, obtained is 700 W laser power, 5 mm/s scan speed, and 5 g/min powder flow rate. This yielded 305 ± 40 μm track height, 2132 ± 33 μm width, and 152° ± 2° contact angle.

Grain-Level Numerical Simulations for the Effective Elasticity of Weakly Cemented Sandstones.

Weakly cemented sandstones are characteristic of loose-bonding contacts, large porosities, and high-clay contents. This study presents a discrete element method (DEM)-based numerical study for the effective elasticity of such rocks that mainly depends on the mechanical behavior of intergranular contact regions. The DEM scheme employs a set of normal and shear springs to phenomenologically describe the mechanical behavior of intergranular finite-sized cements defined by three morphological parameters: cement thickness, bonding radius, and grain radius. Applications to two digital models established in terms of contact-bonding and distant-bonding modes, respectively, where spherical quartz grains are randomly packed together with adding cements under the specified confining pressure, are compared with the theoretical predictions by the contact-bonding and distant-bonding cement theories, which demonstrates a good agreement generally for small contact widths, small contact thicknesses, and large-magnitude moduli, especially for the effective shear modulus. Applications to a series of artificial sandstone samples made in terms of different proportions of quartz grains and clays (a mixture of epoxy and kaolinite) under loose compaction for weak cementation demonstrate a good agreement with ultrasonic measurements. Numerical investigations for the micromechanical characteristics (differential stress fields, force chains, and fabric tensors) of artificial samples subject to applied axial strains demonstrate that the strong mechanical behavior of weakly cemented sandstones tends to appear inside the cohesive aggregates of stiff grains because of their relatively large sizes with loose compaction.

Theoretical study on the nonlinear contact mechanism of reinforced self‐centering bridge pier system based on the Winkler model

AbstractSelf‐centering (SC) bridge piers generally set one or several gaps to avoid the occurrence of plastic hinges and mitigate both damage and residual drifts during major earthquakes. However, the gap opening mechanism also produces new problems in theoretical analyses, such as the strong nonlinear contact motion behavior between adjacent segments. An accurate contact mechanism is therefore significant to describe the gap‐opening process and evaluate the mechanical properties of rocking systems. Firstly, for the low‐damage SC bridge pier system especially with different reinforcement measures in contact segment, this study investigated the nonlinear contact mechanism by decoupling the linear and nonlinear motions of the SC bridge pier system, which were elastic‐body rotation and contact segment bending‐to‐yielding, respectively. Secondly, the entire gap opening process was divided into three stages, and force analysis of the contact segment in each stage was conducted. Subsequently, the differential equations and rotation equation of the contact segment were established and derived based on the Winkler model. The corresponding contact parameters in the equations were obtained. The proposed equation was verified using published experimental data. In addition, finite element analysis (FEA) results showed that the rotation equation can accurately describe the contact state at each moment during the entire nonlinear contact process. Finally, the key parameters describing the contact state is investigated including the contact width, rotation posture, rotation angle, and contact stress. The results show that proposed theory can accurately predict the improvement effect of hysteretic performance for different reinforced measures on the rocking interface, which will be helpful and efficient for the optimal design of reinforced SC bridge pier system.

Preliminary characterization on the dynamic mechanism of asphalt mixture under on-site vibratory compaction

Compaction is the final critical step in the construction of asphalt pavements, but the dynamic response of the mixtures at the particle scale and its correlation with the compaction degree have received limited in-depth investigations. Based on the SmartRock sensor technique, this study is aimed for this inadequacy and to further understand the interaction characteristics (e.g., rolling speed, vibration range and contact width) between the steel drums and pavement surface during compaction at the particle scale. Meanwhile, the dynamic responses (i.e., acceleration frequency and amplitude) of the aggregates in the asphalt mixture were comprehensively investigated to establish the correlation between the acceleration amplitude and compaction degree of pavement. According to the results, the vibrating drum shows a higher compaction effectiveness than the driving drum in the z-direction. The acceleration frequency reflects the energy attenuation of vibration waves during vibrational compaction, and the attenuation of vibration acceleration is normally distributed with the distance from the SmartRock. Lastly, an empirical relationship was developed between the maximum acceleration and pavement compaction degree and can be used to provide reasonable estimations for the in-situ density. The findings are expected to shed light on the compaction mechanism of asphalt pavement, and to provide a potential approach/basis for improving the on-site quality control and decision-making during compaction.

Influence of the wettability dividing line on bubble growth and detachment behavior in a von Kármán swirling flow field

The contact-angle (CA) hysteresis generated by the difference between the advancing and receding CAs of a droplet on an inclined surface generates an adhesion force that can hold the droplet on the surface. Similarly, the CA hysteresis generated by a wettability dividing line (WDL) between the superhydrophobic and superhydrophilic regions can improve the anti-shear stability of bubbles in water, with a maximum range of more than 150° for the difference between the advancing and receding CAs. Based on this mechanism, the influence of a WDL on the growth and detachment behavior of bubbles at different Reynolds numbers (Re) in a von Kármán swirling flow field was experimentally studied. The results show that the WDL significantly improves the anti-shear stability of bubbles when compared to uniform superhydrophobic and hydrophilic surfaces. Furthermore, the detachment volume and maximum contact width decrease with increasing Re, while the tilt angle and asymmetry ratio increase significantly. The fluctuation amplitudes of these parameters gradually increase with rising Re. Based on variations in these parameters, bubbles' growth behavior can be classified into three modes: stabilization, transition, and oscillation. Additionally, the constraint mechanism of a WDL on a bubble was analyzed based on variations in the CA hysteresis generated by the WDL and the maximum contact width. Finally, the detachment dynamics of bubbles in the three modes were analyzed based on a force–balance model.

Kinetic drop friction

Liquid drops sliding on tilted surfaces is an everyday phenomenon and is important for many industrial applications. Still, it is impossible to predict the drop’s sliding velocity. To make a step forward in quantitative understanding, we measured the velocity (U), contact width (w), contact length (L), advancing ({theta }_{{{{{{rm{a}}}}}}}), and receding contact angle ({theta }_{{{{{{rm{r}}}}}}}) of liquid drops sliding down inclined flat surfaces made of different materials. We find the friction force acting on sliding drops of polar and non-polar liquids with viscosities ({eta }) ranging from 10−3 to 1 {{{{{rm{Pa}}}}}}cdot {{{{{rm{s}}}}}} can empirically be described by {F}_{{{{{{rm{f}}}}}}}(U)={F}_{0}+beta weta U for a velocity range up to 0.7 ms−1. The dimensionless friction coefficient (beta ) defined here varies from 20 to 200. It is a material parameter, specific for a liquid/surface combination. While static wetting is fully described by {theta }_{{{{{{rm{a}}}}}}} and {theta }_{{{{{{rm{r}}}}}}}, for dynamic wetting the friction coefficient is additionally necessary.

Contact mechanical behavior and leakage prediction of metal lenticular gaskets in bolt flange joints of ultrahigh pressure pipelines

Metal lenticular gaskets have been widely applied in the bolt flange joints of high and ultrahigh pressure pipelines due to their semi-self-tightening sealing properties. However, research on the leakage prediction of the metal lenticular gaskets is still lacking, which limits their further optimal design and sealing performance improvement. In this paper, an elastoplastic contact mechanics analysis of a metal lenticular gasket used in the bolted flange joint of ultra-high pressure polyethylene pipelines was firstly carried out. The analytical formulas of contact stress and contact width were derived and compared with corresponding numerical results. Then, based on the surface topography measurement, a leakage model was established, in which the pipe surface was simplified to a smooth rigid flat surface, and the gasket surface was simplified to an equivalent rough surface composed of identical wedges. Finally, an analytical leakage prediction formula for the metal lenticular gasket was proposed. In addition, the effects of influence factors on leakage rate were discussed. It is shown that the analytical formulas can accurately calculate the contact stress and contact width in elastoplastic contact. The leakage rate increases with the decrease of the bolt load and the increase of internal pressure. For the ultrahigh pressure pipeline with internal pressure of 200 MPa, the minimum bolt load should be ensured to be higher than 120 kN in order to meet the T5 tightness level. In addition, the initial contact diameter is basically proportional to the leakage rate, while the change of gasket inclination angle has little effect on the leakage rate. Therefore, the contact diameter can be designed to be as small as possible within a reasonable range. This work can provide a theoretical basis for the sealing optimal design of metal lenticular gaskets.

A new analytical model for compressive amounts of metallic sealing gasket of subsea connectors

ABSTRACT The compression deformations of subsea connectors’ sealing gasket dominate the sealing performance. Based on the previous study which has presented an analytical model for calculating compression deformations, a new analytical model that considers the deviations is proposed to predict compression deformations more exactly and effectively. The mathematical contact model of the metallic sealing structure is built on the basis of Hertz contact mechanics theory. Theoretical relationships between contact loads and contact pressure as well as contact width are established, and stress components equations under different loads are obtained. The compression displacements equation is presented by considering constitutive equations and geometric equations. Finite element method is adopted to verify predicted values in the new analytical model and the results show good agreement. This work will provide a theoretical method and guidance for designing structural parameters of the metallic lenticular gasket of the subsea connector in the subsea production system.

Response of elastic/viscoelastic layers on an elastic half-space in rolling contacts: Towards a new modeling approach for elastohydrodynamic lubrication

The 3D quasi-static contact problem of a rigid sphere rolling on an elastic half-space covered by a thin viscoelastic/elastic layer is studied as representative of soft layered contacts in engineering, physics, and biomedical applications, as well as for its potential merit to model Elasto-Hydrodynamically Lubricated (EHL) contacts in specific EHL film behavior suggested in earlier research. The viscoelastic layer behavior is modeled with a standard linear solid (SLS) model with a single relaxation time. Two approaches are used, the foundation (Winkler) reduced model assuming unidirectional stress–strain behavior normal to the surface only and the Papkovich–Neuber potential model which, based on the complete Navier–Cauchy equations, accounts for non-local support and bending effects. The models are validated against literature and compared. Whereas coated/layered contact problem studies mostly consider relatively thick coatings, and results focus on the pressure distribution and the contact area size, in this paper we consider layers with a thickness much smaller than the contact radius, i.e. of the order of a thickness of a conventional EHL film. The details of the layer deformation, pressure profiles and subsurface stresses are presented and interpreted in terms of the underlying physics, in particular the thin layer limit common also in thin fluid layers. It is shown that two dimensionless parameters, the ratio of the elastic modulus between the layer and the substrate and the ratio of the layer thickness to the corresponding Hertz contact width, dominate the systematic response for elastic layered contact problems. And four dimensionless parameters with two extras, the Deborah number based on the Hertz contact width and the ratio of the two elastic limits of the SLS viscoelastic material, are needed and analyzed for viscoelastic layered contacts. The results presented provide a good framework for the understanding and interpretation of the effects of viscoelastic layers on the deformation and pressure distribution of contact problems. Finally, the capability of actually modeling EHL film behavior via a viscoelastic layer suggested by van Emden et al. (2017) is discussed.

An improved Artificial Neural Network for the direct prediction of fretting fatigue crack initiation lifetime

Fretting fatigue is a common type of problem in the aviation and other engineering fields. Due to its multiaxial characteristics, it leads to a shorter overall fatigue life compared to plain fatigue conditions. Fretting fatigue crack initiation lifetime is a crucial part of the total lifetime, and the currently dominant method for research on fatigue behavior is the combination of the theoretical and numerical models. With the advent of the era of data science, machine learning has been widely used to predict fatigue behavior, but there are no many applications in the field of fretting fatigue. This paper proposed an improved Artificial Neural Network (ANN) using Balancing Composite Motion Optimization (BCMO) for quick prediction of fretting fatigue crack initiation lifetime. Physical-mechanical reasoning parameters, axial stress amplitude, shear stress amplitude, half contact width, and half stick zone width are considered as input parameters, and fretting fatigue crack initiation lifetime is set as the output feature. The main aim of BCMO is to improve the robustness of the ANN based on the influential parameters, namely bias and weight. The provided results using ANN-BCMO are robust compared to ANN and traditional techniques from the literature. The Matlab code of improved ANN using BCMO can be found at https://github.com/Samir-Khatir/BCMO-ANN.git

Effect of Lubricant Properties and Contact Conditions on False Brinelling Damage

False brinelling is a type of fretting wear that occurs in rolling bearings when the contacts of bearing rings and rolling elements are subjected to small-amplitude oscillatory motion. It manifests itself as deep craters with relatively polished bottoms that are evenly spaced around the bearing rings. This work investigates the influence of lubricant properties and contact conditions, including oil viscosity, applied load, and amplitude and frequency of oscillations, on the onset and progression of false brinelling damage. Experiments were conducted with AISI 52100 bearing steel specimens in a ball-on-flat configuration under small-amplitude oscillating conditions. A set of base oils and a group of custom-made greases with systematically varying properties were employed. Importantly, the same ball-on-flat setup was adapted to allow optical access to the contact by employing a sapphire disc instead of a steel one. This allowed direct observation of the damage onset and progression to better elucidate the mechanisms taking place. Additional experiments were conducted with the same lubricants on a thrust ball bearing rig and the observed trends were compared to those from the ball-on-disc setup. Results show that false brinelling damage initiates locally at discrete asperity microcontacts and then spreads relatively quickly with continued rubbing to cover the whole contact area. Oscillation amplitudes shorter than the Hertz contact width (A/D < 1) were shown to be most damaging, while the damage reduces drastically for amplitudes larger than the Hertz contact width (A/D > 1). For the more important case of A/D < 1, oils and greases with lower viscosities produced less damage. Oils in general produced somewhat less damage than the equivalent lithium- or urea-thickened greases with the same base oil. Lower oscillation frequencies and lower contact pressures also produced less damage. The corresponding friction and electrical contact resistance measurements indicate that under these conditions of A/D < 1 the contact operates under boundary lubrication at best but can intermittently approach effectively dry conditions, depending on lubricant properties and applied conditions. These observations indicate that the key variable that controls damage when the oscillation amplitude is less than the contact width is the ability of the lubricant to penetrate and remain in the oscillating contact. Therefore, lubricant properties and contact conditions that promote this penetration, which may be different from those that promote hydrodynamic film formation, can mitigate against false brinelling.

The performance of double-layer rubber sealing ring under the action of low temperature environment

Aiming at the sealing failure of a water quality monitoring system in a low-temperature environment, a double rubber O-ring sealing structure was designed, and its sealing performance at low temperatures was studied. Finite element software ANSYS constructed the sealing structure, and the change of sealing performance of rubber O-ring in the process of standard temperature installation and low temperature was studied by a two-dimensional axisymmetric model. The results show that the equivalent strain and stress of the sealing structure show an increasing trend during the installation process. With the effect of the medium pressure, the maximum contact stress of the rubber seal ring increases from 2.6285 MPa at 20 ℃ to 2.6657 MPa at 0 ℃. The contact width decreases gradually with the decrease in temperature. With the initial compression rate increase, the maximum contact stress increases significantly. The simulation results show that the double-layer rubber O-ring structure still has good sealing performance at low temperatures.

Model development to Predict Dynamic Interactions of Roller and Geomaterial using Simulated Roller Compaction

Crushed rock or unbound granular materials constitute the top layer of geomaterial compacted in a pavement. These materials are required to be compacted using compactors or rollers at a designated target density or modulus for satisfactory performance. Studying the interaction between compactors and geomaterial is important for optimising these geomaterial layers’ construction. As field compaction is time-consuming and cumbersome, the study of material behaviour at a smaller scale is necessary. This study utilises a novel setup simulating the field compaction better to study the material's behaviour and dynamic interaction between the material and the compactor during compaction. A constitutive model was developed utilizing the geometric relationship between the contact width to plastic deformation during compaction, which can be easily measured. Using Hertzian theory, the estimation of contact width allows the estimation of contact stress. The developed model shows that it can model the experimental observation with very high accuracy (R2 > 0.98). The model is then used to predict other geomaterial properties during compaction, showing their dependence on the material state.

Process optimization of contact hole patterns via a simulated annealing algorithm in extreme ultraviolet lithography.

The critical dimension (CD), roughness, and sensitivity are extremely significant indicators for evaluating the imaging performance of photoresists in extreme ultraviolet lithography. As the CD gradually shrinks, tighter indicator control is required for high fidelity imaging. However, current research primarily focuses on the optimization of one indicator of one-dimensional line patterns, and little attention has been paid to two-dimensional patterns. Here, we report an image quality optimization method of two-dimensional contact holes. This method takes horizontal and vertical contact widths, contact edge roughness, and sensitivity as evaluation indicators, and uses machine learning to establish the corresponding relationship between process parameters and each indicator. Then, the simulated annealing algorithm is applied to search for the optimal process parameters, and finally, a set of process parameters with optimum image quality is obtained. Rigorous imaging results of lithography demonstrate that this method has very high optimization accuracy and can improve the overall performance of the device, dramatically accelerating the development of the lithography process.

Analytical calculation method for predicting compression deformations and sealing performance of subsea connector under operating condition

Keeping the sealing capacity under operating conditions is of vital importance for subsea connectors, which are the key connection facilities in subsea production systems. The finite element method (FEM) is usually adopted to evaluate the sealing performance and structural strength after determining structural design parameters. However, since the design is an iterative process, the efficiency of this evaluation method is relatively low. This paper proposes an analytical calculation method (ACM) which can quickly predict compression deformations and sealing performances of the gasket under operating conditions. Theoretical relationship equations are developed among the compression under preloading conditions, the variations of the compression and the unknown contact load under operating conditions. Consequently, the contact load under the operating condition is obtained first, then contact width, contact pressure and structural stresses are determined. Finally, compression deformations and sealing performances of the subsea connector under operating conditions are estimated explicitly. Case studies under various conditions are performed to verify the consistency of the FEM and the ACM. The predicted results including compression amount, sealing parameters and structural stress are in good agreement. This work provides a theoretical method and guidance for the engineering design of subsea connectors.

Effects of Make-Up Torque on the Sealability of Sphere-Type Premium Connection for Tubing and Casing Strings

The present investigations on sealability evaluation for tubing and casing premium connections depend on the FEM with testing. This paper proposed a theoretical model to evaluate the sealability of a sphere-type premium connection based on make-up torque, which combines Hertz contact pressure and the von Mises yield criterion for calculating elastic–plastic contact pressure distribution on sealing interface and adopts the gas sealing criterion obtained from Murtagian’s experimental results for deducing gas sealing capacity. With the proposed model, the effects of additional make-up torque from the sealing interface on the sealing contact pressure distribution and key sealability parameters, including contact width, yield width, average contact pressure and gas sealing capacity, were analyzed and compared. The results show that additional make-up torque from the sealing interface closely influenced sealability parameters’ variation and gas sealing capacity. The gas sealing index based on the sealing contact energy theory should be recommended for sealability evaluation other than average contact pressure on the sealing interface. For improving gas sealability, make-up torque should be controlled accurately for ensuring enough average contact pressure and contact width but a proper yield width, and a lager sphere radius should be selected for reducing the risk of yield sticking.

Specific pressure under roller squeezing of leather

The influence of factors on the width of the roller contact and the specific pressure under roller pressing of leather is analyzed in the article. As a result of experimental studies, the dependences of the width of the contact area and specific pressure on the intensity of the load, velocity, and diameter of the rollers were determined. It was revealed that the parameter of the technological specific pressure on the hide in the contact zone increases with an increase in the intensity of the load, the speed of rolls, the width of the contact area, and a decrease in the radius of rolls. An analytical dependence of the residual moisture content of leather on the specific pressure was determined. It was established that with an increase in specific pressure, the residual moisture content of leather decreases and asymptotically approaches a certain value of the function.