Benchmarking of Direct and Indirect Friction Tests in Micro Forming

2012 ◽  
Vol 504-506 ◽  
pp. 581-586 ◽  
Author(s):  
Rasmus Solmer Eriksen ◽  
M. Calaon ◽  
Mogens Arentoft ◽  
Nils Bay
Keyword(s):  
Friction Coefficient ◽  
Friction Force ◽  
Visual Inspection ◽  
Sliding Friction ◽  
Continuous Measurement ◽  
Work Piece ◽  
Friction Test ◽  
Micro Forming ◽  
Micro Scale ◽  
Flat Tool

In this study the application of a simulative sliding friction test at micro scale is suggested. Two work piece specimens are upset against opposing sides of a flat tool element. The tool element is then pulled out while the resulting friction force F is measured. The test principle offers several advantages when compared against the DEC-test, including easy visual inspection of tool and work piece surfaces, continuous measurement of friction coefficient over the complete sliding length and less sensitivity to mechanical tolerance deviations of work piece and tool elements.

scholarly journals Analysis of the Variation of Friction Coefficient of Sandstone Joint in Sliding

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Guochao Zhao ◽  
Laigui Wang ◽  
Na Zhao ◽  
Jianlin Yang ◽  
Xilin Li
Keyword(s):  
Friction Coefficient ◽  
Sliding Friction ◽  
Rock Joints ◽  
Amplification Coefficient ◽  
Test Results ◽  
Friction Test ◽  
Test Device ◽  
Wear Area ◽  
The Stability ◽  
Good Agreement

The friction coefficient of rock joints is closely related to the stability of the slope. However, it is difficult to predict the friction coefficient due to the influence of surface roughness and mechanical properties of rocks. In this study, we use a method that combines theoretical analysis with a sandstone sliding friction test and propose a model to predict the friction coefficient of Sandstone Joint. A sandstone sliding friction test was performed on a self-made reciprocating sliding friction test device. Good agreement between the estimated values and test values verified the validity of the friction coefficient prediction model. Through an analysis of the friction coefficient in sandstone sliding, it was established that the larger the wear mass, the larger the friction coefficient in sliding, and the larger the wear area, the smaller the friction coefficient. With the cycles increasing of sandstone, the friction coefficient gradually decreased before finally reaching a stable value. Comparisons between the estimated value and test results showed that when the wear difference coefficient c = 2.0 and the meshing friction amplification coefficient K = 1.4, the minimum error was 2.89%. The results obtained are significant in the control of slope sliding.

scholarly journals Effect of Axial Vibration on Sliding Frictional Force between Shale and 45 Steel

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Wu Hao ◽  
Chen Ping ◽  
Liu Yang ◽  
Ma Tianshou
Keyword(s):  
Friction Coefficient ◽  
Friction Force ◽  
Sliding Friction ◽  
Complex Structure ◽  
Drill String ◽  
Friction Reduction ◽  
Vibration Velocity ◽  
Model Parameters ◽  
Axial Vibration ◽  
Friction Reducing

Activating drill string vibration is an effective means to mitigate the excessive drag encountered during drilling complex-structure wells. However, the Coulomb model cannot describe the sliding friction behavior between drill string and borehole rock with imposed axial vibrations. To solve this problem, a specially designed experimental setup was utilized to investigate the characteristics of axial vibrating-sliding coupling friction. The results indicate that when vibration velocity is greater than sliding velocity, axial vibration can significantly reduce friction force between contact surfaces. Its friction reduction mechanism embodies not only the changes of instantaneous friction force, but also friction coefficient. Meanwhile, a friction coupling model was established based on the Hertz contact theory and Dahl model. The corresponding computational program was developed in Matlab/Simulink environment. The calculation results are in good agreement with the experimental results, verifying the validity of the present method. Furthermore, to overcome the shortcoming of Dahl model, a dynamic friction coefficient model was proposed to evaluate the friction-reducing effect of axial vibration using dimensional analysis method. The model parameters under different lubrication conditions were retrieved through inverse calculation with experimental data. This method provides a new solution for evaluating the friction-reducing effect of hydraulic oscillator and optimizing its placement.

Rolling-Friction Behavior of Sub-Micron Polystyrene-Sphere Arrays under Very Light Loads

2013 ◽  
Vol 321-324 ◽  
pp. 174-178
Author(s):  
Jiao Qu ◽  
Shi Rong Ge
Keyword(s):  
Friction Coefficient ◽  
Friction Force ◽  
Self Assembly ◽  
Sliding Friction ◽  
Rolling Friction ◽  
Polystyrene Sphere ◽  
Si Substrate ◽  
Friction Behavior ◽  
Layer Film ◽  
Colloidal Spheres

The uniform sub-micron colloidal spheres were arrayed on the surface of a Si substrate via self-assembly to forming a sphere-layer film (monolayer), with emphasis on the application of rolling friction in the presence of rolling spheres on the surface of micro- or nano-equipment. It was found that the arrayed spheres on the substrate are mobile arising from rolling, and they can significantly reduce the friction force through changing the sliding friction to rolling one, thus exhibiting a smaller friction coefficient value than that of pure substrate. On the other hand, the elastic deformation of polystyrene (PS) spheres also contributes to the reduced friction force. In the absence of lubricant, the optimal friction coefficient of sphere-layer film was found to be 0.059 at the load of 3500 µN, at which the friction force of sphere-layer film was only 68% that of substrate. The friction coefficient of sphere-layer film decreases with increasing the applied load up to 3500 µN, followed by an increase with a further enhanced load, which has been ascribed to the transition from elastic contact to plastic one.

Application of Energy Principle to Dry Sliding Friction

2005 ◽  
Author(s):  
Zhongming Xu ◽  
Ping Huang
Keyword(s):  
Friction Coefficient ◽  
Friction Force ◽  
Sliding Friction ◽  
Critical Value ◽  
New Method ◽  
Dry Sliding ◽  
Operational Parameters ◽  
Energy Principle ◽  
Dry Sliding Friction ◽  
Elastic Surfaces

A new method named as energy principle method is used to calculate and research the friction force and friction coefficient of two flat elastic surfaces. The studies reveal the relationships between friction coefficient and parameters of a tribo-system such as microstructure of interface, performance of material, operational parameters and geometry parameters. When the height of an asperity increases in the model, the friction coefficient increases rapidly to a critical value, and then hardly increases after that.

Analysis of Sliding Friction for Surface with Micro-Scale Circumferential Grooves

2015 ◽  
Vol 642 ◽  
pp. 222-226 ◽  
Author(s):  
Hsin Chih Wang ◽  
Jhy Cherng Tsai
Keyword(s):  
Theoretical Analysis ◽  
Friction Force ◽  
Sliding Friction ◽  
Stable Condition ◽  
Sliding Surface ◽  
Crucial Issue ◽  
Micro Scale ◽  
Sliding Mechanism ◽  
Depth Analysis ◽  
Plain Surface

Friction is a crucial issue for the performance of a machine with sliding mechanism. While the sliding surface is often manually scraped to improve its tribological properties, the quality is not stable nor the efficiency of the scraping process. This study investigated the influences of micro-scale circumferential grooves on the frictional characteristics of a sliding surface through theoretical analysis and numeric simulations. The study found that sliding surface with micro grooves can reduce the friction, compared to plain surface. An in-depth analysis indicated that the slider with micro-scale grooves was uplifted when it slides, thus reduced the sliding friction. Moreover, as the amount of lubricant collected on the grooves increased, the friction force decreased with time and approached a stable condition.

Friction Force and Stresses Analysis for Contact of Assembled Details

2006 ◽  
Vol 113 ◽  
pp. 334-338
Author(s):  
Z. Dreija ◽  
O. Liniņš ◽  
Fr. Sudnieks ◽  
N. Mozga
Keyword(s):  
Mechanical Properties ◽  
Surface Roughness ◽  
Plastic Deformation ◽  
Friction Force ◽  
Sliding Friction ◽  
Friction Model ◽  
Contact Interface ◽  
Finite Element Program ◽  
Elastic Plastic ◽  
Element Program

The present work deals with the computation of surface stresses and deformation in the presence of friction. The evaluation of the elastic-plastic contact is analyzed revealing three distinct stages that range from fully elastic through elastic-plastic to fully plastic contact interface. Several factors of sliding friction model are discussed: surface roughness, mechanical properties and contact load and areas that have strong effect on the friction force. The critical interference that marks the transition from elastic to elastic- plastic and plastic deformation is found out and its connection with plasticity index. A finite element program for determination contact analysis of the assembled details and due to details of deformation that arose a normal and tangencial stress is used.

Effect of shape/size and distribution of microgeometries of textures on tribo-performance of crankpin bearing

2021 ◽  
pp. 135065012110105
Author(s):  
Nguyen Van Liem ◽  
Wu Zhenpeng ◽  
Jiao Renqiang
Keyword(s):  
Friction Coefficient ◽  
Friction Force ◽  
Contact Force ◽  
Distribution Density ◽  
Hydrodynamic Lubrication ◽  
Operating Conditions ◽  
Asperity Contact ◽  
Combined Model ◽  
Obvious Effect ◽  
Area Density

The effect of the shape/size and distribution of microgeometries of textures on improving the tribo-performance of crankpin bearing is proposed. Based on a combined model of the slider-crank mechanism dynamic and hydrodynamic lubrication, the distribution density, area density, and shape of spherical textures, square-cylindrical textures, wedge-shaped textures, and a hybrid between spherical texture and square-cylindrical texture on the crankpin bearing's tribo-performance are investigated under different operating conditions of the engine. The tribological characteristic of the crankpin bearing is then evaluated via the indexes of the oil film pressure p, asperity contact force, friction force, and friction coefficient of the crankpin bearing. The research results show that the distribution density with n = 12 and m = 6, and area density with α = 30% of various microtextures have an obvious effect on ameliorating the crankpin bearings tribo-performance. Concurrently, at the mixed lubrication region, the shape of the square-cylindrical texture on improving the tribo-performance is better than the other shapes of the spherical texture, wedge-shaped texture, and spherical and square-cylindrical texture. Particularly, all the average values of the asperity contact force, friction force, and friction coefficient with a square-cylindrical texture are significantly reduced by 14.6%, 19.5%, and 34.5%, respectively, in comparison without microtextures. Therefore, the microtextures of the spherical texture applied on the bearing surface can contribute to enhance the durability and decrease the friction power loss of the engine.

Stress Analysis of Bonded-Interface Technique on Subsurface Damage Observations of Brittle Porcelains

2007 ◽  
Vol 353-358 ◽  
pp. 864-867 ◽  
Author(s):  
Hai Yang Yu ◽  
Zhen Sun ◽  
Hua Zhao ◽  
Min Hao Zhu
Keyword(s):  
Sliding Friction ◽  
Wear Behavior ◽  
Subsurface Damage ◽  
Work Piece ◽  
Interface Plane ◽  
Bottom Line ◽  
Load Effect ◽  
Depth Direction ◽  
Bonded Interface ◽  
Sliding Test

In the subsurface damage observations on the wear behavior of brittle dental porcelains, it still remains unsolved that how to distinguish the cracks that develops accidentally during the preparing sample process from those actually produced in the tests. In the sliding friction tests, the bonded-interface technique (BIT) was successfully used for subsurface damage evaluations. The profile of wear scar was easily observed on the cemented section of the blocks without inducing any cracks. The stresses on the surface and internal of dental porcelains were calculated with the contact element method (CEM) by ABAQUS software. The model of rectangular dental porcelain and Si3N4 ball were developed based on sliding friction tests. The Si3N4 ball modeled in this study was of the diameter of 4mm and 12 mm. The size of Vita VMK 95 porcelain blocks was 5 mm wide, 2 mm thick and 15 mm long. The glue layer thickness values are 10 .m, 20 .m and 30 .m. The loading of the Si3N4 ball was modeled as a constant distributed vertical load applied across the bonding line of the porcelain. Stresses and displacements of all nodes of the model, especially at the bonding interface, were analyzed and compared. The results of the study indicated that stress values correlated strongly to the applied loads. Stress distribution was symmetric about the bonded-interface plane. The maximum occurred in surface layer and the minimum on the bottom line in the porcelain blocks. Along the interface, stresses decreased with the distance from the surface of porcelain. On the other hand, high stresses focus on the surface part and go sharply down in the internal region along the depth direction. Among the parameters of sliding test on the stresses, the load effect is prominent. The BIT model experiences a different, non-axisymmetric stress field than that of real work-piece. So the BIT should not be considered as a reliable source of quantitative analysis but as a qualitative method for observing the form of the damage modes with more visible information than the conventional tools.

A novel technique for modeling friction behavior in knitted fabric simulation

2017 ◽  
Vol 29 (6) ◽  
pp. 776-792
Author(s):  
Vajiha Mozafary ◽  
Pedram Payvandy
Keyword(s):  
Friction Coefficient ◽  
Uniform Distribution ◽  
Friction Force ◽  
Experimental Result ◽  
Knitted Fabric ◽  
Friction Behavior ◽  
Content Type ◽  
Novel Technique ◽  
Fabric Structure ◽  
Fabric Surface

Purpose Fabric-object friction force is a fundamental factor in cloth simulation. A large number of parameters influence the frictional properties of fabrics such as fabric structure, yarn structure, and inherent properties of component fibers. The purpose of this paper is to propose a novel technique for modeling fabric-object friction force in knitted fabric simulation based on the mass spring model. Design/methodology/approach In this technique, unlike other studies, distribution of friction coefficient over the fabric surface is not uniform and depends on the fabric structure. The main reason for considering non-uniform distribution is that in various segments of fabric, contact percent of fabric-object is different. Findings The proposed technique and common methods based on friction coefficient uniform distribution are used to simulate the frictional behavior of knitted fabrics. The results show that simulation error values for proposed technique and common methods are 2.7 and 9.4 percent as compared with the experimental result, respectively. Originality/value In the existing methods of the friction force modeling, the friction coefficient of fabric is assumed uniform. But this assumption is not correct because fabric does not have an isotropic structure. Thus in this study, the friction coefficient distribution is considered based on fabric structure to achieve more of realistic simulations.

Comparison in Tribological Properties of YBa2Cu3OX/Ag and Bi2Sr2CaCu2OX/Ag Self-Lubricating Composites

2011 ◽  
Vol 291-294 ◽  
pp. 34-40
Author(s):  
Hua Tang ◽  
Wen Jing Li ◽  
Chang Sheng Li
Keyword(s):  
Friction Coefficient ◽  
Tribological Properties ◽  
Room Temperature ◽  
Superconducting Transition ◽  
Friction Test ◽  
Average Value ◽  
Structure And Morphology ◽  
Disk Friction ◽  
Pin On Disk ◽  
Self Lubricating Composites

The YBa2Cu3Ox/Ag and Bi2Sr2CaCu2Ox/Ag self-lubricating composites were prepared using powder metallurgic method. The crystal structure and morphology of the as-synthesized samples were characterized by XRD and SEM. The YBa2Cu3Ox/Ag and Bi2Sr2CaCu2Ox/Ag self-lubricating composites were found to compose of superconductor phase and Ag phase. The tribological properties from ultra-low temperature to room temperature of the composites were studied by pin-on-disk friction test. It was found that the friction coefficients of pure YBa2Cu3Ox(YBCO) and Bi2Sr2CaCu2Ox(BSCCO) were both dropped abruptly when the temperature cooled below the superconducting transition temperature. At room temperature, the friction coefficient of pure YBa2Cu3Oxis 0.68~0.95, when mixing 15wt% Ag, the friction coefficient of the sample decreased to the lowest value 0.11. The friction coefficient of pure Bi2Sr2CaCu2Ox is 0.15~0.17, When Ag content reach 10wt%, the coefficient was lowest (average value is 0.13). The addition of appropriate amount of Ag obviously improve the tribological property of YBCO, while only slightly meliorate that of BSCO. On the other hand, the YBCO/Ag composites exhibit better tribological properties than BSCCO/Ag composites at higher load under the same experimental condition.

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