scholarly journals Tire–Road Contact Area on Asphalt Concrete Pavement and Its Relationship with the Skid Resistance

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 615 ◽  
Author(s):  
Di Yun ◽  
Liqun Hu ◽  
Cheng Tang
Keyword(s):  
Traffic Safety ◽  
Contact Area ◽  
Three Dimensional ◽  
Real Contact Area ◽  
Skid Resistance ◽  
Test Machine ◽  
Multi Scale ◽  
Asphalt Concrete Pavement ◽  
The Impact ◽  
Scale Roughness

Sufficient pavement skid resistance is one of the essential factors to ensure traffic safety. The real contact area (Ar) between the tire and road is significant for understanding and improving the skid resistance performance. In this study, the tire–road contact area is measured by squeezing a smooth underside-dyed rubber block into the specimens, using a self-designed fixture mounted on the universal test machine. The three-dimensional (3D) printing technology is used to separate the specimens with multi-scale roughness. Surface texture on 29 AC pavements is obtained by a 3D scanner and qualified by the root-mean-square surface height (Sq), to investigate the impact of pavement texture on the Ar. The skid resistance on 23 AC road sections is measured using the T2GO system, and the pavement texture is recorded, to discuss the influence of the Ar on the skid resistance. The results indicate that the multi-scale roughness rarely affects the measured contact area once the concerned wavelength is less than 0.6 mm. The Ar decreases with the Sq following a power function but has weak correlation with the friction coefficient. This study could provide an in-depth understanding of the tire–road contact and lays a foundation for optimizing the contact-related pavement performance.

scholarly journals Contact pressures and the impact of farm equipment on Latosol with the presence and absence of sugarcane straw

2016 ◽  
Vol 40 (3) ◽  
pp. 265-278 ◽  
Author(s):  
Reginaldo Barboza da Silva ◽  
Piero Iori ◽  
Zigomar Menezes de Souza ◽  
Danilo de Moraes Gomes Pereira ◽  
Oswaldo Julio Vischi Filho ◽  
...  
Keyword(s):  
Contact Pressure ◽  
Contact Area ◽  
Structural Changes ◽  
Front Axle ◽  
Real Contact Area ◽  
Digital Measurement ◽  
Farm Equipment ◽  
Presence And Absence ◽  
The Impact ◽  
Contact Pressures

ABSTRACT High contact pressures applied to soil result in a greater degree of compaction, in addition to promoting other negative effects. The objective of this study was to quantify contact areas by using different methodologies, and pressures of farm equipment employed in production activity and evaluate structural changes caused in a Red Latosol with the presence and absence of straw cover. The design was completely randomized in a factorial scheme of type 4 (tire on front axle, tire on rear axle, tire on a sugarcane wagon and metallic track of sugar cane Harvester) x 2 (presence and absence of straw). The contact area (CA) of the run was obtained by three procedures: analytical measure of the area of an ellipse (CA1); digital measurement of area of an ellipse (CA2); and measurement of real contact area (RCA), with digital resources. The contact pressure was calculated from the ratio of mass of each machine's axle and the contact area of the run. The contact area obtained according to the procedure of the ellipse (CA1 and CA2) is overrated when compared to actual area obtained digitally (RCA). The straw reduces the contact pressure in the soil, due to the deep tire treads and consequently, increased contact area. Areas where the traffic of the machines occurred with soil covered with the presence of straw showed reduced soil resistance to penetration, cone index and pre-consolidation pressure, confirming that the increased contact area produced by straw reduced the pressure applied and the compression power dissipated in the soil.

scholarly journals ATFL repair alone versus combined repairs of ATFL and CFL

2017 ◽  
Vol 2 (3) ◽  
pp. 2473011417S0002
Author(s):  
Kenneth Hunt ◽  
Judas Kelley ◽  
Richard Fuld ◽  
Nicholas Anderson ◽  
Todd Baldini
Keyword(s):  
Contact Area ◽  
Peak Pressure ◽  
Plantar Flexion ◽  
Weight Bearing ◽  
Three Dimensional ◽  
Lateral Ligament ◽  
Joint Stability ◽  
Intact Specimen ◽  
Significant Difference ◽  
The Impact

Category: Ankle Introduction/Purpose: The standard for lateral ligament stabilization is direct repair of the ATFL by open or arthroscopic technique. The implications and necessity of repairing the CFL are not well understood. The purpose of this study was to assess the impact of repairing the ATFL alone compared to repairing both the ATFL and CFL, in a biomechanical cadaver model. We hypothesized that repairing the CFL will substantially augment ankle and subtalar joint stability during weight-bearing ankle inversion compared to ATFL repair alone. Methods: Ten matched pairs of fresh frozen human cadaveric ankles were dissected to expose intact ATFL and CFL. Ankles were mounted to an Instron at 20° plantar flexion and 15° of internal rotation. Each ankle was loaded to body weight and then tested from 0 to 20° of inversion for three cycles; stiffness and torque were recorded, peak pressure and contact area were recorded using a calibrated Tekscan sensor system, and rotational displacement of the talus and calcaneus relative to the ankle mortise was recorded using a three-dimensional motion capture system. Ankles then underwent sectioning of ATFL and CFL and were randomly assigned to ATFL only repair using two arthroscopic Broström all-soft anchors, or combined ATFL and CFL repair. Testing was repeated after repair to 20° of inversion, then load-to-failure (LTF). Results: The predominant mode of failure after repair was at the tissue/suture. There were no instances of anchor pullout. There was an 11.7% increase in stiffness in combined repairs, and only a 1.6% increase in ATFL-only repairs. CFL failed at lower torque and rotation than the ATFL in combined repairs. There were strong correlations between intact stiffness and stiffness after repair (r=.74) and ATFL torque in LTF testing (r=.77), across both groups. There was no significant difference in peak pressure or contact area in the tibiotalar joint between the intact ankle and ATFL or combined repair. Conclusion: We found a greater increase in stiffness following combined ATFL and CFL repair compared to ATFL repair alone. This added stability is due to complimentary contributions of the CFL, not augmented LTF strength of the ATFL. Intact specimen stiffness correlated strongly with stiffness after repair and LTF torque, suggesting that a patient’s inherent tissue laxity or inelasticity is likely a meaningful predictor of strength after repair. Restoring the CFL plays a relevant role in lateral ligament repair, however sufficient time for ligament healing should be allowed before substantial inversion stresses are applied.

scholarly journals Meningioma Segmentation in T1-Weighted MRI Leveraging Global Context and Attention Mechanisms

2021 ◽  
Vol 1 ◽  
Author(s):  
David Bouget ◽  
André Pedersen ◽  
Sayied Abdol Mohieb Hosainey ◽  
Ole Solheim ◽  
Ingerid Reinertsen
Keyword(s):  
Three Dimensional ◽  
Specific Treatment ◽  
Primary Brain Tumor ◽  
University Hospital ◽  
Patient Specific ◽  
Entire Volume ◽  
Global Context ◽  
Multi Scale ◽  
Magnetic Resonance Imaging Mri ◽  
The Impact

Purpose: Meningiomas are the most common type of primary brain tumor, accounting for ~30% of all brain tumors. A substantial number of these tumors are never surgically removed but rather monitored over time. Automatic and precise meningioma segmentation is, therefore, beneficial to enable reliable growth estimation and patient-specific treatment planning.Methods: In this study, we propose the inclusion of attention mechanisms on top of a U-Net architecture used as backbone: (i) Attention-gated U-Net (AGUNet) and (ii) Dual Attention U-Net (DAUNet), using a three-dimensional (3D) magnetic resonance imaging (MRI) volume as input. Attention has the potential to leverage the global context and identify features' relationships across the entire volume. To limit spatial resolution degradation and loss of detail inherent to encoder–decoder architectures, we studied the impact of multi-scale input and deep supervision components. The proposed architectures are trainable end-to-end and each concept can be seamlessly disabled for ablation studies.Results: The validation studies were performed using a five-fold cross-validation over 600 T1-weighted MRI volumes from St. Olavs Hospital, Trondheim University Hospital, Norway. Models were evaluated based on segmentation, detection, and speed performances, and results are reported patient-wise after averaging across all folds. For the best-performing architecture, an average Dice score of 81.6% was reached for an F1-score of 95.6%. With an almost perfect precision of 98%, meningiomas smaller than 3 ml were occasionally missed hence reaching an overall recall of 93%.Conclusion: Leveraging global context from a 3D MRI volume provided the best performances, even if the native volume resolution could not be processed directly due to current GPU memory limitations. Overall, near-perfect detection was achieved for meningiomas larger than 3 ml, which is relevant for clinical use. In the future, the use of multi-scale designs and refinement networks should be further investigated. A larger number of cases with meningiomas below 3 ml might also be needed to improve the performance for the smallest tumors.

Prediction of Contact Area and Frictional Behaviour of Rubber on Rigid Rough Surfaces

2014 ◽  
Author(s):  
Hagen Lind ◽  
Matthias Wangenheim
Keyword(s):  
Contact Area ◽  
Surface Texture ◽  
Rough Surfaces ◽  
Scale Model ◽  
Real Contact Area ◽  
Contact Friction ◽  
Sliding Velocity ◽  
Normal Contact ◽  
Multi Scale ◽  
Frictional Behaviour

In the tire-road contact friction depends on several influencing variables (e.g. surface texture, real contact area, sliding velocity, normal contact pressure, temperature, tread block geometry, compound and on the existence of a lubrication film). A multi-scale model for prediction of contact area and frictional behaviour of rubber on rigid rough surfaces at different length scales is presented. Within this publication the multi-scale approach is checked regarding convergence. By means of the model influencing parameters like sliding velocity, compound and surface texture on friction and contact area will be investigated.

Unloading Process in Elastic-Plastic Contact of a Rough Surface With a Flat

2008 ◽  
Author(s):  
A. Sepehri ◽  
K. Farhang
Keyword(s):  
Finite Element ◽  
Rough Surface ◽  
Contact Force ◽  
Contact Area ◽  
Three Dimensional ◽  
Integral Form ◽  
Real Contact Area ◽  
Elastic Plastic ◽  
Real Contact ◽  
Approximate Equations

Three dimensional elastic-plastic contact of a nominally flat rough surface and a flat is considered. The asperity level Finite Element based constitutive equations relating contact force and real contact area to the interference is used. The statistical summation of asperity interaction during unloading phase is derived in integral form. Approximate equations are found that describe in closed form contact load as a function of mean plane separation during unloading. The approximate equations provide accuracy to within 6 percent for the unload phase of the contact force.

On the Mechanism of Contact Between Metal Surfaces: Part 2—The Real Area and the Number of the Contact Points

1968 ◽  
Vol 90 (1) ◽  
pp. 81-88 ◽  
Author(s):  
T. Tsukizoe ◽  
T. Hisakado
Keyword(s):  
Contact Area ◽  
Three Dimensional ◽  
Real Contact Area ◽  
Load Range ◽  
The Real ◽  
Real Contact ◽  
Contact Points ◽  
Theoretical Analyses ◽  
Total Contact Area ◽  
Real Area

Assuming that the distribution curve obtained from the profile curve of the surface has a normal distribution, the relation between the real contact area and the separation is obtained theoretically in the case of ideal plastic flow of the microcontacts. If the asperities are cones of the same angle which depends on the surface roughness, the three-dimensional number and the distribution of the radii of contact points are also deduced theoretically. The results of the theoretical analyses are compared with the experimental results for the real contact areas and the numbers of the contact points. Results show that over the wide load range the average radii of contact points are almost constant; consequently, the total contact area is increased mainly owing to the increase in the number of the contact points.

An FFT Deterministic Simulation of Elastic Rough Surfaces in Three-Dimensional Contact and Model Analysis

2009 ◽  
Author(s):  
Robert L. Jackson ◽  
Itzhak Green
Keyword(s):  
Contact Area ◽  
Thermal Contact Resistance ◽  
Thermal Contact ◽  
Three Dimensional ◽  
Real Contact Area ◽  
Real Contact ◽  
Contact Models ◽  
Surface Profiles ◽  
Rough Surface Contact ◽  
Mathematical Foundations

For practicing engineers in industry it is important to have closed-form, easy to use equations that can be used to predict the real contact area, and relate it to friction, wear, adhesion, and electrical and thermal contact resistance. There are quite a few such models in the literature, but their agreement or their effectiveness has not been determined. This work will use several measured surface profiles to make predictions of contact area and contact force from many elastic contact models and compare them to a deterministic FFT based rough surface contact model. The results show that several of the models show good quantitative and qualitative agreement despite having very different mathematical foundations.

Three-Dimensional Contact Analysis of Elastic-Plastic Layered Media With Fractal Surface Topographies

2000 ◽  
Vol 123 (3) ◽  
pp. 632-640 ◽  
Author(s):  
K. Komvopoulos ◽  
N. Ye
Keyword(s):  
Contact Area ◽  
Three Dimensional ◽  
Homogeneous Medium ◽  
Real Contact Area ◽  
Rigid Sphere ◽  
Real Surface ◽  
Elastic Plastic ◽  
Real Contact ◽  
Fractal Parameters ◽  
Surface Topographies

Three-dimensional rough surfaces were generated using a modified two-variable Weierstrass-Mandelbrot function with fractal parameters determined from real surface images. The number and size of truncated asperities were assumed to follow power-law relations. A finite element model of a rigid sphere in normal contact with a semi-infinite elastic-plastic homogeneous medium was used to obtain a constitutive relation between the mean contact pressure, real contact area, and corresponding representative strain. The contact model was extended to layered media by modifying the constitutive equation of the homogeneous medium to include the effects of the mechanical properties of the layer and substrate materials and the layer thickness. Finite element simulations of an elastic-plastic layered medium indented by a rigid sphere validated the correctness of the modified contact model. Numerical results for the contact load and real contact area are presented for real surface topographies resembling those of magnetic recording heads and smooth rigid disks. The model yields insight into the evolution of elastic, elastic-plastic, and fully plastic deformation at the contact interface in terms of the maximum local surface interference. The dependence of the contact load and real contact area on the fractal parameters and the carbon overcoat thickness is interpreted in light of simulation results obtained for a tri-pad picoslider in contact with a smooth thin-film hard disk.

Computational Solid Mechanics Modeling of Asperity Deformation and Pad-Wafer Contact in CMP

2007 ◽  
Vol 991 ◽  
Author(s):  
Bo Jiang ◽  
Gregory P. Muldowney
Keyword(s):  
Finite Element ◽  
Contact Area ◽  
Solid Mechanics ◽  
Real Contact Area ◽  
Formation Mechanisms ◽  
Stress And Strain ◽  
Finite Element Software ◽  
Real Contact ◽  
Deformation Mechanics ◽  
The Impact

ABSTRACTAsperity-scale pad deformation and dynamic pad-wafer contact area are crucial to the fundamental understanding of material removal and defect formation mechanisms in CMP. Pad asperity stress and strain are also central to characterizing pad wear rate during polishing and cut rate during conditioning. While it is very difficult to isolate and measure stress and strain in individual asperities, finite element modeling may be used in conjunction with experimental surface characterization to predict asperity-scale deformation and pad-wafer contact. Asperity sub-domains up to 1270 microns across are reproduced from three-dimensional point cloud data on porous polyurethane CMP pads obtained by confocal microscopy, meshed to high resolution, and analyzed using ABAQUS finite element software. Physical properties are derived from dynamic mechanical experiments. Pad stacks are simulated both with and without sub-pads. Results show that while a sub-pad increases pad-wafer contact area overall, it limits the local spreading of individual contact regions as polishing load increases. This finding identifies a direct mechanical origin of the trade-off in pad design between wafer-scale and die-scale planarity. As expected, the real contact area between a pad and wafer is much smaller than the cross-sectional or “bearing” area, but the difference is notably greater when a sub-pad is present. Values of asperity stress and strain under typical CMP polishing pressures reveal that plastic deformation takes place both on and beneath the contacting surface. Hence upon release of the polishing load the asperities do not fully rebound to their pre-compressed shapes. Each pass under the wafer thus reshapes the pad asperities such that a slightly different texture is presented upon the next pass. These deformation mechanics clarify the impact of top pad and sub-pad properties on real contact area, allowing better optimization of CMP pad performance.

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