Influence Of Contact Area Research Articles

Influence of Contact Area on Memristive Characteristics of Parylene-Based Structures in Single and Crossbar Geometry

Influence of Contact Area on Memristive Characteristics of Parylene-Based Structures in Single and Crossbar Geometry

On the lack of influence of contact area on the solid–liquid lateral retention force

We experimentally show that, unlike the solid–solid frictional force, the solid–liquid retention force is determined by interactions at the triple line rather than over the solid–liquid contact area, as predicted by theory. We have prepared drops whose triple line enclosed a uniform surface, a hydrophobic island, and topographical inhomogeneities, and measured the same retention force for all three cases. We have also studied the retention force on drops whose initial triple line was non-circumferential and measured different retention forces for different shapes, also as predicted by theory. The experiments with non-circumferential drops provide (1) another way to show that the retention force is not proportional to the contact area, and (2) a manner to falsify a recent theory on drop depinning.

A Three-Dimensional Transition Interface Model for Bolt Joint

Bolt connection is an important component in mechanical structure which significantly affects the dynamic property of the whole structure. In this paper, a three-dimensional transition interface model which contains geometric and physical parameters is proposed to model the bolted joint based on the contact analysis. The geometric parameters and the physical parameters are used to characterize the influence of contact area and contact pressure which are related to connection parameters such as material, roughness, connection thickness, and tightening force, respectively. After that, the geometric parameter identification method is proposed, and the geometric parameter database of bolt joints for machine tools is constructed based on the Kriging interpolation method. Then, the model updating method based on the combination of modal parameters and frequency response function is proposed to identify the physical parameters and thickness of the three-dimensional transition interface model. The database of the transition interface model is constructed after verifying the validity of the proposed model. Finally, an engineering example of an engraving machine tool is used to check the practicability of the proposed transition interface model and the usage of the constructed parameter database.

Investigation into the transmission of guided waves across bolt jointed plates

Bolt joints are extensively used in aerospace and civil engineering. Online monitoring of bolt looseness is crucial to ensure the function and safety of these structures. Understanding the interaction between guided waves and the joint interfaces can aid in the design and optimization of such monitoring systems, and hence becomes important. However, the influence of contact area on guided wave energy passing through these jointed plates is still not clear. In this paper, a semi-analytic method, which combines finite element models with a wave superposition method, is proposed to predict the transmission of guided waves in joint interfaces. The wave mode conversions in the contact area are included. The model was validated by comparison with independent finite element models. In addition, the influence of the contact length on transmission coefficients of guided waves passing through the joint interface is investigated. The results were experimentally validated by wire electrical discharge machined specimens with various contact areas. Then, the transmitted guided wave and the contact area in a bolt jointed plate under different torques were measured experimentally and compared with the present method. The results of the two different experiments agree well with those predicted using the semi-analytic method, respectively. In particular, the experimental results of the bolt jointed plate show that the direct S0 wave packet energy decreases with the bolt preload, which can be explained by the proposed model. Thus, the proposed semi-analytic method demonstrates efficiency in the prediction of the power transmission coefficient and has potential applications in the selection of excitation frequencies in the online monitoring of jointed structures. On this basis, a normalized power transmission coefficient can be directly calculated by the energy of the first S0 wave packet in the received signal to monitor bolt torque.

A smart ball sensor fabricated by laser kirigami of graphene for personalized long-term grip strength monitoring

Grip strength is an important indicator of health conditions and needs to be monitored for health management. However, different populations (e.g., babies and rehabilitation patients) have different hand sizes and different levels of grip strengths, requiring a personalized sensor to monitor grip strength. In this paper, we developed a smart ball sensor by laser kirigami of graphene for personalized grip strength monitoring. To realize the rational utilization of space, a transparent pill shell embedding all electronic accessories is installed in the center of the ball sensor with a spiral-sensing unit fabricated by laser kirigami of graphene on the surface. Furthermore, we assessed the influence of contact area between hand and ball on grip strength using finite-element analysis (FEA), which was then considered in our results readout. The grip strength can be continuously read by a mobile phone in a wireless manner. The smart ball sensor demonstrated a high performance in vitro against gold-standard method in diseased and healthy subjects. It would be a powerful tool for personalized long-term monitoring of grip strength, especially suitable for specific populations such as babies and sensitive enough for samll grip strength.

Influence of Contact Area on Tribo Response of Al 6061 in Ambient and Vacuum Environment

Aluminium alloys are used in spacecraft and aerospace industries because of their unique properties which are lightweight and high strength. The components of aluminium alloys used in aerospace and space environment are subjected to relative motion which results in the tribo-phenomenon. The designer needs tribo response data for designing components geometrical dimensions. The literature reports inadequate tribo response data, more particularly in a vacuum environment (adverse environment). In the present investigation, experiments were conducted using Al 6061 aluminium alloy pins with different diameters. The cylindrical pin diameters were 2mm, 4mm and 6 mm. The cylindrical pins were slid against a hardened En-8 steel disc. The normal pressure was maintained at 0.625 MPa and the sliding speed was 0.5 ms-1. The estimated friction coefficient from monitored frictional force and normal force and the dependency of estimated friction coefficient on sliding distance for cylindrical pins of different diameters were analysed.

Non-Fickian Solute Transport in Rough-Walled Fractures: The Effect of Contact Area

The influence of contact area, caused by normal deformation, on fluid flow and solute transport through three-dimensional (3D) rock fractures is investigated. Fracture surfaces with different Hurst exponents (H) were generated numerically using the modified successive random addition (SRA) method. By applying deformations normal to the fracture surface (Δu), a series of fracture models with different aperture distributions and contact area ratios (c) were simulated. The results show that the contact area between the two fracture surfaces increases and more void spaces are reduced as deformation (Δu) increases. The streamlines in the rough-walled fractures show that the contact areas result in preferential flow paths and fingering type transport. The non-Fickian characteristics of the “early arrival” and “long tail” in all of the breakthrough curves (BTCs) for fractures with different deformation (Δu) and Hurst parameters (H) were determined. The solute concentration distribution index (CDI), which quantifies the uniformity of the concentration distribution within the fracture, decreases exponential as deformation (Δu) and/or contact area ratios (c) increase, indicating that increased contact area can result in a larger delay rate of mass exchange between the immobile zone around the contact areas and the main flow channel, thus, resulting in a longer time for the solute to fill the entire fracture. The BTCs were analyzed using the continuous time random walk (CTRW) inverse model. The inverse modeling results show that the dispersion exponent β decreases from 1.92 to 0.81 as c increases and H decreases, suggesting that the increase in contact area and fracture surfaces enhance the magnitude of the non-Fickian transport.

The Influence of Contact Area on Oil Film Thickness

The Influence of Contact Area on Oil Film Thickness

Influence of contact area on the sliding friction and wear behaviour of an electrochemical jet textured Al-Si alloy

Environmental legislation continues to drive optimisation of internal combustion engines in the automotive sector in an effort to reduce harmful emissions and promote fuel efficiency. Significant frictional losses occur at the ring pack, prompting research on reducing sliding friction at the ring – liner interface through the use of surface texturing. This study assesses the influence of contact area on the friction and wear behaviour of light-weight monolithic hyper-eutectic Al-Si alloy with a textured surface generated by electrochemical jet texturing. Flat rectangular samples were prepared from a cast cylinder liner via electro-discharge machining and flat lapped to 6 µm diamond finish prior to immersion in a 1 mol solution of NaOH for 120 s to simulate the mechanical honing process. Surfaces were electrochemically jet textured using a 2.3 mol solution of NaCl and current density of 220 A/cm2. An offset array of 1.3 × 0.3 mm rectangular features at 1.2 mm spacing was created with an average depth of 39 µm. Lubricated reciprocating sliding was carried out at a stroke length of 25 mm in a bath of PAO (4 cSt) at 100 °C against a 6 mm diameter, 13 mm long 52100 steel cylinder with three different contact areas corresponding to initial contact pressures of 157, 12 and 4 MPa. Sliding frequencies were varied between 1 and 15 Hz at a load of 50 N in order to establish the influence of both the contact pressure and velocity on the friction behaviour as a function of the lubrication regime. Textured features were observed to reduce the average coefficient of friction by up to 37% via a lubricant reservoir mechanism if the counter-surface contact width was greater than the feature dimension. Increases in contact pressure prevented a micro-EHL effect due to adhesive wear rather than pressurization of textured features.

The influence of contact area between implant and its adjacent teeth on finite element analysis

The aim of this work is to investigate the influence of contact area between the first molar implant and its adjacent teeth on finite element analysis. Five types of finite element contact models containing implant and its adjacent teeth were established: non-contact model (C0), contact models with different contact area (C1, C2, C3, C4). An occlusal force was applied to finite element models to calculate the stress of implant and bone interface on mandible. Compared with the group C0, the stress of alveolar bone surrounding the implant in other groups decreased 88.08 % at most, but the stress of cancellous bone surrounding the natural teeth increased 59.42 %. In summary, a proper small contact area can not only reduce the stress concentration on the implant region, but also can avoid an excessive stress in the periodontal ligament and alveolar bone around the natural teeth. The finite element results revealed that it is effectively to distribute the load implant suffered, especially to reduce the stress generated by the lateral load when the first molar implant has a small contact with its adjacent teeth.

Modeling for Distribution of Compressive Stress from Loading Platens in Diametrical Compression Test

Diametrical Compression test is one of indirect tests to investigate the tensile strength of brittle materials. This test is spread because of easiness to perform. However, results from this test are not stable. Traditionally, calculations for this test are performed under a pair of opposite concentrated loading on the diameter of specimen. However, contact areas appear just before fracture of specimen in the fact and the stress distribution from loading platens is not obvious. It seems be one of reasons why the result from this test is not stable. In this study, the attempt to establish the modeling for distribution on loading platens in the diametrical compression test is shown. The aim of this modeling is to calculate stresses and displacement of specimen using complex stress function by Lekhnitskii. Therefore, this model is expanded in Fourier expansion. Accuracy of calculation using Fourier expansion depends on the number of terms. Therefore, the influence of contact area and number of terms to accuracy is also discussed.

Investigation of Nanotribological Characterization of Stretched European Hair Using Atomic Force Microscopy

In order to understand the influence of stretching on the nanotribological properties of human hair, the European hair with stretching ratios at 20, 40, 60 and 80% were studied using atomic force microscopy (AFM). The results show that appropriate stretching ratios (40-60%) make the European hair surface smoother and the friction measurements also verify the result. When the stretching ratio is 80%, the European hair has the highest coefficient of friction. The reason is that cuticle damages lead to the local ratchet and collision between AFM tip and the sample obviously increased. With the increase of stretching ratios, the adhesive force of European hair is nonlinear change, which is attributed to the influence of contact area, water molecules absorbed and the amount of polar molecules.

Improving the quality of Schottky contacts on ZnO microwires using Cu-contained silver paste electrode

High-quality Schottky devices based on ZnO microwires (MWs) by using a simple and effective method are reported. Cu-contained silver paste (SPC) was used as the contact electrodes of one end of ZnO MW-based metal-semiconductor-metal structures instead of the conventional method, in which customised silver paste was used as the contact electrodes of both ends of the structure. The experimental results reveal that SPC used in this study can increase the opportunity for obtaining the device with rectifying behaviour. The best-produced device exhibited a very high rectifying ratio of 105 at ±1 V. In addition, the rectifying I–V characteristics were greatly improved after annealing treatment because of the elimination of the bubbles in the conductive pastes. Moreover, the influence of contact area on the electrical properties was also investigated. It was shown that the contact area between ZnO MW and the electrode also played an important role in determining the rectifying performance.

하중재하 패턴을 고려한 강바닥판의 정적거동 평가

강박스거더의 바닥틀은 바닥강판, 종방향 리브 및 횡방향 리브로 구성된다. 강바닥판 교량은 용접 접합부의 개소가 많고 중차량 접지하중과 반복응력의 증가에 의해 피로손상의 발생 가능성이 매우 높다. 일반적으로 강바닥판의 피로균열은 중차량 트럭하중의 반복적인 재하하중으로 인한 국부응력에 의하여 발생한다. 또한 중차량 통행량의 증가 및 통행차량의 대형화는 피로균열 발생 가능성을 촉진한다. 따라서 교량에 영향을 미치는 실제 통행 차량하중의 하중재하 패턴을 고려한 하중 접지면적에 따른 교량의 거동을 정확히 평가하는 것은 매우 중요하다. 본 연구는 강바닥판 교량에서 통행 차량의 접지면적과 하중재하 효과를 고려하여 설계하중에 의한 접지면적과 실제 통행 차량의 접지면적을 유한요소해석을 통하여 비교 평가하였다. 유한요소해석은 강바닥판 교량의 4가지 하중 재하패턴에 대하여 수행하였다, 또한 해석은 다이아프램의 설치 유무에 따른 통행트럭의 접지면적 영향을 비교 평가하였다. 유한요소해석 결과, 실제 싱글타이어의 하중재하면적이 설계하중의 접지면적보다 보다 큰 국부응력을 보였고, 바닥강판은 전륜하중인 싱글타이어 재하에 의해 가장 큰 영향을 받는 것으로 나타났다. 또한 다이아프램의 설치 유무는 탄성영역에서 다이아프램 설치가 강바닥판 가로리브와 세로리브 교차부의 피로저항에 대한 구조성능 개선에는 효과가 없는 것으로 나타났다. The deck of steel box girder bridges is composed of deck plate, longitudinal rib, and transverse ribs. The orthotropic steel decks have high possibility to fatigue damage due to numbers of welded connection part, the heavy contact loadings, and the increase of repeated loadings. Generally, the local stress by the repeated loadings of heavy vehicles causes the orthotropic steel deck bridge to fatigue cracks. The increase of traffic volume and heavy vehicle loadings are promoted the possibility of fatigue cracks. Thus, it is important to exactly evaluate the structural behavior of bridge considering the contact loading area of heavy vehicles and real load patterns of heavy trucks which have effects on the bridge. This study estimated the effect of contact area of design loads and real traffic vehicles through the finite element analysis considering the real loading conditions. The finite element analysis carried out 4 cases of loading patterns in the orthotropic steel deck bridge. Also, analysis estimated the influence of contact area of real truck loadings by the existence of diaphragm plate. The result of finite element analysis indicated that single tire loadings of real trucks occurred higher local stress than one of design loadings, and especially the deck plate got the most influence by the single tire loading. It was found that the diaphragm attachment at joint part of longitudinal ribs and transverse ribs had no effects on the improvement of structural performance against fatigue resistance in elastic analysis.

Thermotactile thresholds at the fingertip: Effect of contact area and contact location

Thresholds for the detection of changes in temperature are used to indicate neuropathy, but a variety of different contact areas and contact locations are used. This study was designed to determine the effects of variations in contact area and contact location on both warm and cool thresholds at the fingertip. With 20 healthy subjects (10 females and 10 males aged 20–30 years), warm thresholds and cool thresholds were determined in two separate sessions using the method of limits. In the first part of each session, thresholds were determined around the centre of the whorl using circular contactors with five different diameters (3, 6, 9, 12, and 55 mm). In the second part of each session, thresholds were determined using two contactors (6- and 12-mm diameter) at three locations along the fingertip: (i) distal (5 mm from the nail), (ii) middle (centre of whorl), and (iii) proximal (3 mm from the distal interphalangeal joint). With increasing contact area, the warm thresholds decreased, the cool thresholds increased, and the inter-subject variability in both warm and cool thresholds decreased. Using the 6-mm diameter contactor, warm thresholds were independent of location but cool thresholds increased from distal to proximal locations. It is concluded that temperature sensitivity at the fingertip increases with increasing area of contact, with the variability in thresholds consistent with the existence of warm and cool “insensitive fields”. The findings show that the influence of contact area and contact location should be considered when assessing thermotactile thresholds at the fingertip.

Contact area of solid bodies: calculations compared to measured results

AbstractA novel attempt is made to directly measure the contact area of solid bodies by relating it to the electrical contact resistance. This method was used by F. P. Bowden and D. Tabor in the 1930s already. We confined the setup by use of low conductive thin film coatings. This way it is possible to point out the influence of contact area in contrast to incidental contaminations. By use of wear resistant coatings it will be possible to measure the contact area in sliding contacts as well. New measurements and calculations are compared with the original setup and model for contact resistance and contact area, respectively. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The effect of contact area on nano/micro-scale friction

The effect of contact area on nano/micro-scale friction was experimentally studied. Glass balls with various radii were used in order to change the contact area. Borosilicate glass balls (radii—0.32 μm, 0.5 μm, 1.25 μm and 2.5 μm) attached on the top of AFM tip (NPS, DI) were applied for nano-scale contact and Soda Lime balls with radii 0.25 mm, 0.5 mm and 1 mm were applied for micro-scale contact. At the nano-scale, the friction between ball and surface was measured with the applied normal load using an atomic force microscope (AFM), and at the micro-scale it was measured using a ball-on-flat type micro-tribotester. All experiments were conducted on silicon wafer and diamond-like carbon (DLC) coated silicon samples, at controlled conditions of temperature of 24 ± 1 °C and relative humidity of 45 ± 5%. Friction was measured with the applied load in the range of 0–160 nN at the nano-scale and at 1000 μN, 1500 μN, 3000 μN and 4800 μN at the micro-scale. Results at the nano-scale showed that the friction increased with the applied normal load and tip size, for both kinds of samples. Similar behavior of friction with the applied normal load and ball size was observed for silicon at the micro-scale. However, for DLC friction decreased with the ball size. This distinct difference in the behavior of friction in DLC at the nano- and micro-scale was attributed to the difference in the operating mechanisms. At nano-scale, friction in DLC was affected by adhesion, whereas at the micro-scale it was affected mainly by plowing. Evidences of the operating mechanisms at micro-scale were obtained using scanning electron microscope (SEM). At micro-scale, solid–solid adhesion was dominant in silicon, while DLC showed plowing. Contrary to the nano-scale that is almost a ‘wear-less’ situation, wear was prominent at the micro-scale. At both the nano- and micro-scales, the effect of applied normal load and the tip/ball size on friction was discussed as the influence of contact area on these parameters.

The influence of contact area on the deformation of chalk

Chalk rock masses contain natural discontinuities that are largely parallel and perpendicular to the ground surface. In terms of foundation loading, it is the normal deformation of the horizontal discontinuities, which are of particular interest. This paper considers the influence of discontinuity contact area on the deformation behaviour of chalk. A suite of unconfined compressive strength tests is described, which comprises an intact specimen and five discontinuous specimens. The contact area at the discontinuity ranges from 57% of the initial cross-sectional area of the specimen to 17% contact area. The deformation processes are modelled analytically and the experimental results are compared with the predicted values. The experimental results show excellent agreement with the proposed model and identify a critical contact area, between 44% and 51%, which determines the mode of deformation behaviour.

Influence of contact area on service life of gears with crack in tooth root

AbstractThe paper describes the influence of contact area on the service life of dynamically loaded gears with a crack in a tooth root. Numerical results obtained with the finite element method using the program package BERSAFE are compared with the experimental results obtained on the universal testing machine INSTRON 1255. Numerical and experimental results are in good agreement. The analysis shows that the contact area directly influences the speed and direction of the crack propagation and the service life of the gear with a crack in a tooth root.

Electrical Analogy of Hydraulic Flow Through Rock Fractures

Abstract Electrical analogy is used to study the influence of contact areas on the hydraulic flow through rock fractures. The investigation has shown that in the case of radial flow the location of contact zones, as well as the total contact area, influences the flow rate. It is also demonstrated that when injection tests are conducted in boreholes, where the fracture close to the borehole is partially plugged by loose particles or other debris, the flow rate may be substantially underestimated.