scholarly journals Sliding Interaction for Coated Asperity with Power-Law Hardening Elastic-Plastic Coatings

Materials ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2388
Author(s):  
Bin Zhao ◽  
Hanzhang Xu ◽  
Xiqun Lu
Keyword(s):  
Friction Coefficient ◽  
Yield Strength ◽  
Young’S Modulus ◽  
Contact Force ◽  
Young's Modulus ◽  
Contact Forces ◽  
Geometrical Parameters ◽  
Asperity Contact ◽  
Strength Ratio ◽  
Modulus Ratio

Sliding between asperities occurs inevitably in the friction pair, which affects the efficiency and reliability in both lubricated and non-lubricated conditions. In this work, the contact parameters in the coated asperity sliding process are studied, and the universal expressions of the average contact force and the friction coefficient are obtained. The effect of the interference between asperities, the material and geometrical parameters including the Young’s modulus ratio and yield strength ratio of the coating and substrate, and the hardening exponent and thickness of the coating on the average contact forces and friction coefficient is considered. It shows both normal and tangential contact forces increase with the increasing interference, increasing Young’s modulus ratio, decreasing yield strength ratio, and decreasing coating thickness; while the trend is different for the effect of the hardening exponent of the coating. The normal force increases and the tangential force decreases as the hardening exponent increases. Based on this, the influence of these parameters on the effective friction coefficient is obtained further. It reveals that the friction coefficient increases as the interference and Young’s modulus ratio enlarge and decreases as the yield strength ratio, the coating’s hardening exponent, and thickness increase. The universal expressions for the contact force and friction coefficient in the sliding process are obtained. This work might give some useful results to help choose the optimum coatings for specific substrates to reduce friction in cases where the asperity contact exists, especially in the focused field of the journal bearing in the marine engine under poor lubrication conditions.

Friction Analysis in Needle Insertion Into Soft Tissue

2021 ◽  
Author(s):  
Yingda Hu ◽  
Murong Li ◽  
Yong Lei
Keyword(s):  
Friction Coefficient ◽  
Young’S Modulus ◽  
Friction Force ◽  
Young's Modulus ◽  
Surface Friction ◽  
Needle Insertion ◽  
Contact Forces ◽  
Diagnostic Methods ◽  
Tissue Pressure ◽  
Preoperative Diagnostic

Abstract As one of the preoperative diagnostic methods, needle insertion is widely used for its safety and effectiveness. Recently, robotic needle insertion systems have been under active developments. Hence needle insertion experiments are essential for system verifications, in which the interactions between needle and tissue is a major focus for needle-tissue interactive models, and the friction between the needle and tissue is an important factor. In these experiments, the friction coefficient can be affected by many factors, such as insertion speed, needle-tissue deformation and contact forces. In this paper, to study and analyze the influence of various variables on friction force and friction coefficient, three variables, i.e., tissue pressure on needle, needle insertion velocity and Young’s modulus of the tissue, are systematically studied by constructing a testbed, in which the radial surface friction is converted into equivalent plane friction based on the assumption that the distribution of the normal force and friction force on the needle is uniform for the whole needle outer surface. The experimental results show that the variation range of friction coefficient is 0.122–0.341. The friction coefficient decreases with the increase of pressure and increases with the increase of velocity, while Young’s modulus have a small effect on the friction coefficient.

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.

scholarly journals Tensile strengths and Young’s modulus of thin copper and copper-nickel (CuNi44) substrates

2008 ◽  
Vol 6 (4) ◽  
pp. 535-541 ◽  
Author(s):  
Oliver Staller ◽  
Christina Mitterbauer ◽  
Katharina Mayr
Keyword(s):  
Yield Strength ◽  
Young’S Modulus ◽  
Pole Figure ◽  
Vickers Hardness ◽  
Young's Modulus ◽  
Coated Conductors ◽  
Test Method ◽  
Tensile Yield Strength ◽  
Reducing Atmosphere ◽  
Cold Worked

AbstractIn this paper we report a method to determine tensile strengths and Young’s modulus of cubic biaxial textured metal tapes used as substrate materials for coated conductors (CC). Simplicity, rapidity and reproducibility of the procedure are important for the evaluation of continuous in-house productions. Our approach is based on the EN 10002-1 B tensile test method. A key role for satisfactory results is the sample preparation of 100–250 μm thick tapes, which will be described in detail. Copper (E-Cu57) can be successfully transformed to cubic biaxial textured substrates. Best results were achieved by annealing between 750°C and 850°C in reducing atmosphere. Best FWHM values for the ψ scan are 5.51° and for the ϕ scan are 4.5°. Pole figure analysis verified the sharp {001} texture of the tape. Vickers hardness measurements (HV 0.1) for the cold worked material yielded values of 135 and for the annealed tape, values of 37. The ultimate tensile yield strength Rm of the textured substrate is 150 MPa and thus significantly lower than that for the cold worked material (413 MPa). Cubic biaxial substrates could be manufactured from Isotan CuNi44 (WM49) bars. Best results were achieved by annealing at 1200°C in reducing atmosphere. Pole figure analysis verified the {001} texture with other low intensity texture components. Vickers hardness measurements (HV 0.1) for the cold worked material yielded values of 236 and for the annealed tape values of 92. The ultimate tensile yield strength R m of the textured substrate is 300 MPa and thus significantly lower than that for the cold worked material (723 MPa).

A New Method Developed for Brittle and Ductile Materials to Evaluate Mechanical Properties of a Lump Specimen in the Use of Indentation Test

2006 ◽  
Vol 129 (2) ◽  
pp. 284-292 ◽  
Author(s):  
Pal Jen Wei ◽  
Jen Fin Lin
Keyword(s):  
Yield Strength ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Elastic Recovery ◽  
Indentation Test ◽  
New Method ◽  
Ductile Materials ◽  
Conventional Material ◽  
Loading And Unloading ◽  
Logarithm Function

In this study, the load-depth (P‐h) relationships matching the experimental results of the nanoindentation tests exhibited at the subregions of small and large depths are obtained, respectively. The relationships associated with these two subregions are then linked by the hyperbolic logarithm function to attain a single expression that is applied in the evaluation of the specimen’s elastic recovery ability, as shown in the unloading process. A new method is developed in the present study to evaluate both Young’s modulus and the yield strength of either a ductile or brittle material through the uses of the appropriate P‐h relationships developed in the load and unloading processes. The results of the Young’s modulus and the yield strength achieved by the present method are compared to those obtained from the conventional material tests for a lump material. The scattering of the experimental data shown in the loading and unloading processes are also interpreted by different causes.

scholarly journals Evaluation of the effectiveness of representative methods for determining Young's modulus and hardness from instrumented indentation data

2006 ◽  
Vol 21 (1) ◽  
pp. 225-233 ◽  
Author(s):  
Dejun Ma ◽  
Taihua Zhang ◽  
Chung Wo Ong
Keyword(s):  
Young’S Modulus ◽  
Young's Modulus ◽  
Maximum Error ◽  
Instrumented Indentation ◽  
Modulus Ratio ◽  
Material Parameters ◽  
Correction Scheme ◽  
Single Standard ◽  
Hardness Values ◽  
Hardening Coefficient

The effectiveness of Oliver & Pharr's (O&P's) method, Cheng & Cheng's (C&C’s) method, and a new method developed by our group for estimating Young's modulus and hardness based on instrumented indentation was evaluated for the case of yield stress to reduced Young's modulus ratio (σy/Er) ≥ 4.55 × 10−4 and hardening coefficient (n) ≤ 0.45. Dimensional theorem and finite element simulations were applied to produce reference results for this purpose. Both O&P's and C&C's methods overestimated the Young's modulus under some conditions, whereas the error can be controlled within ±16% if the formulation was modified with appropriate correction functions. Similar modification was not introduced to our method for determining Young's modulus, while the maximum error of results was around ±13%. The errors of hardness values obtained from all the three methods could be even larger and were irreducible with any correction scheme. It is therefore suggested that when hardness values of different materials are concerned, relative comparison of the data obtained from a single standard measurement technique would be more practically useful. It is noted that the ranges of error derived from the analysis could be different if different ranges of material parameters σy/Er and n are considered.

Local Mechanical Properties of Highly Porous Si3N4 for Trabecular Bone Replacement

2015 ◽  
Vol 662 ◽  
pp. 142-146
Author(s):  
Zuzana Pramuková Vilčeková ◽  
Monika Kašiarová ◽  
Magdaléna Precnerová Domanická ◽  
Miroslav Hnatko ◽  
Pavol Šajgalík
Keyword(s):  
Mechanical Properties ◽  
Silicon Nitride ◽  
Yield Strength ◽  
Trabecular Bone ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Polyurethane Foams ◽  
Strength Increase ◽  
Bone Replacement ◽  
Highly Porous

The study deals with the development of highly porous undegradable ceramics based on silicon nitride as potential replacement of trabecular bone. These materials were produced using replication method with polyurethane foams as pore-forming agents to achieve similar porous structure to trabecular bone. Prepared porous ceramics had a bimodal pore structure with macro-pores larger than 200 μm and micro-pores smaller than 1 μm in diameter, which are necessary for tissue ingrowths, cell adhesion, adsorption of biological metabolites and nutrition delivery in organism. The microstructure and local mechanical properties (Young’s modulus and Yield strength) were evaluated and compared with human trabecular bone. Results showed that studied porous materials have satisfactory porosity and pore sizes for trabecular bone replacement. Young’s modulus of bone was 12.6 ± 2.23 GPa and porous silicon nitride samples ranged from 10.9 ± 3.38 GPa to 12.9 ± 1.13 GPa. The values of Yield strength of trabecular bone was determined as 493 ± 30.7 MPa and the values of porous samples varied from 250 ± 19.3 MPa to 558 ± 36.5 MPa. Young’s modulus and Yield strength increase with increasing of the pre-sintering temperature and multiple infiltrations.

Assessment of Container Mountings in Modular Offshore Platform Designs for Arctic Regions

2012 ◽  
Author(s):  
Josefine Michel ◽  
Patrick Kaeding
Keyword(s):  
Friction Coefficient ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Offshore Platform ◽  
Harsh Environment ◽  
Offshore Platforms ◽  
Friction Coefficients ◽  
Cold Temperatures ◽  
Elastic Range ◽  
Arctic Regions

Regularly the twistlock system is used to mount containers on container vessels or on offshore platforms as service containers in normal climate regions. In this paper the twistlock system is analyzed with respect to mounting auxiliary systems as well as accommodation and service modules to the deck of offshore platforms in arctic regions. When the twistlock systems are used in harsh environment it is also important that the twistlocks withstand the acting forces without great displacements and without exceeding the elastic range. But in arctic regions the mountings must resist additional forces due to ice interaction, cold temperatures and small friction coefficients. Because the existing rules do not include regulations how to analyze the strength of these mountings in arctic regions the influence of the friction coefficients and the Young’s modulus were of interest in this study. This paper summarizes some numerical works on these new discoveries. The results of the computations show that the Young’s modulus has no influence on the stress and the displacement of the bodies. However, the friction coefficient has influence on the stress specified in the simulations for large roll angles.

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