Elastohydrodynamic Lubrication Analysis of Pure Squeeze Motion on an Elastic Coating/Elastic Substrate System

2015 ◽  
Vol 137 (1) ◽  
Author(s):  
Li-Ming Chu ◽  
Chi-Chen Yu ◽  
Qie-Da Chen ◽  
Wang-Long Li
Keyword(s):  
Young’S Modulus ◽  
Elastic Deformation ◽  
Maximum Stress ◽  
Young's Modulus ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Von Mises Stress ◽  
Rigid Sphere ◽  
Elastic Substrate ◽  
Asymptotic Value

A rigid sphere approaching a lubricated flat surface with a layer of elastic coating on the elastic substrate is explored under constant load conditions. The transient pressure profiles, film shapes, elastic deformation, von Mises stress (σvon) during the pure squeeze process under various operating conditions in the elastohydrodynamic lubrication (EHL) regime are discussed. The simulation results reveal that the greater the Young's modulus of coating is, the greater the pressure distribution is, the smaller the contact area is, and the greater the maximum stress (σvon) value is. As the Young’s modulus of coating decreases, the central elastic deformation at the surface (Z = 0) increases and the deformation at the interface of coating/substrate (Z = −1) decreases. For hard coating cases, the maximum central pressure increases to an asymptotic value and minimum film thickness decreases to an asymptotic value as the coating thickness increases. For soft coating cases, this phenomenon reverses. A thicker and stiffer coating leads to a higher maximum stress. At the deformation recovery stage, the positions of the maximum stress would begin to offset downwards and closer to the coating/substrate interface. Moreover, the position of maximum stress varies from the coating to the subsurface as the Young’s modulus of coating increases. The EHL with stress analysis can prevent the chance of fracture in coating or substrate. These characteristics are important for the lubrication design of mechanical elements with coatings.

Plasto-Elastohydrodynamic Lubrication in Point Contacts for Surfaces With Three-Dimensional Sinusoidal Waviness and Real Machined Roughness

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Tao He ◽  
Ning Ren ◽  
Dong Zhu ◽  
Jiaxu Wang
Keyword(s):  
Plastic Deformation ◽  
Rough Surface ◽  
Mechanical Design ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Von Mises Stress ◽  
Asperity Contacts ◽  
Lubrication Characteristics ◽  
Von Mises

Efficiency and durability are among the top concerns in mechanical design to minimize environmental impact and conserve natural resources while fulfilling performance requirements. Today mechanical systems are more compact, lightweight, and transmit more power than ever before, which imposes great challenges to designers. Under the circumstances, some simplified analyses may no longer be satisfactory, and in-depth studies on mixed lubrication characteristics, taking into account the effects of 3D surface roughness and possible plastic deformation, are certainly needed. In this paper, the recently developed plasto-elastohydrodynamic lubrication (PEHL) model is employed, and numerous cases with both sinusoidal waviness and real machined roughness are analyzed. It is observed that plastic deformation may occur due to localized high pressure peaks caused by the rough surface asperity contacts, even though the external load is still considerably below the critical load determined at the onset of plastic deformation in the corresponding smooth surface contact. It is also found, based on a series of cases analyzed, that the roughness height, wavelength, material hardening property, and operating conditions may all have significant influences on the PEHL performance, subsurface von Mises stress field, residual stresses, and plastic strains. Generally, the presence of plastic deformation may significantly reduce some of the pressure spikes and peak values of subsurface stresses and make the load support more evenly distributed among all the rough surface asperities in contact.

Size-Dependent Young's Modulus of the FCC Metallic Films

2012 ◽  
Vol 499 ◽  
pp. 76-79
Author(s):  
Ming Li ◽  
G.H. Su
Keyword(s):  
Young’S Modulus ◽  
Elastic Deformation ◽  
Young's Modulus ◽  
Energy Curve ◽  
Fundamental Parameter ◽  
Deformation Capacity ◽  
Metallic Films ◽  
Size Dependent ◽  
Simulation Results ◽  
Young Equation

Young's modulus is one of the most fundamental parameter to depict the elasticity of a given material. It determines the basic elastic deformation capacity of a structure under a bear load. When the diameter of nanocrystals is in the scale of several nanometers, the Young's modulus is quite different from that of bulk. In order to determine elastic deformation capacity of nanocrystals, it is necessary to study the size dependent Young's modulus. Based on above consideration, a simple thermodynamic model is developed for size dependent Young's modulus of nanocrystals according to the “universal” binding energy curve and Laplace-Young equation. According to this model, the Young's modulus of several FCC metallic films is predicted and the Young's modulus increases with the size reduction. The prediction is agreed with computer simulation results.

Study the Strength of Material and Composite Structures of Belly-Landing Mini UAV

2016 ◽  
Vol 842 ◽  
pp. 178-185 ◽  
Author(s):  
Maria Fransisca Soetanto ◽  
Rachmad Imbang Tritjahjono
Keyword(s):  
Tensile Strength ◽  
Composite Materials ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Von Mises Stress ◽  
Uniaxial Tensile ◽  
Specific Strength ◽  
Specific Stiffness ◽  
Von Mises ◽  
Material Composite

This paper consists of the design and analysis of the strength of material composite of the fuselage of a Belly-Landing Mini Unmanned Aerial Vehicle (UAV). A belly landing UAV occurs when an UAV lands without its landing gear and uses its underside, or belly, as its primary landing device. Belly landings carry the risk that the UAV may flip over, disintegrate, or catch fire if it lands too fast or too hard [1], so the more important designs parameters for materials used are the specific strength and specific stiffness. Specific strength is defined as the ultimate tensile strength divided by material density, and specific stiffness is defined as Young’s modulus of the material divided by density [Franklin, 2010]. The aim of this Belly Landing Mini UAV is for used in situations where manned flight is considered too risky or difficult and no runway for take-off or landing, such as fire fighting surveillance, while the term 'mini’ means the design of this UAV has a launch mass greater than 100 grams but less than 100 kilograms [2], the objective of this project is the development and design of materials fuselage of a mini UAV with two layer sandwich structures made from composite materials and epoxy resin. For that purposes, 3 variations of the composite materials tensile test specimens have been manufactured in accordance with ASTM D3039 standard and tested its strength. The results showed that the fibre glass and fibre carbon composite with resin epoxy has the maximum tensile strength and Young’s modulus, so that the fabrication and manufacturing of the fuselage component is made by using that material composite. The Von Mises stress is used to predict yielding of materials under any loading condition from results of simple uniaxial tensile tests by using software Autodesk Inventor 2012. The results show that the design is safe caused the strength of material is greater than the maximum value of Von Mises stress induced in the material. The results of flight tests show that this small UAV has successfully manoeuvred to fly, such as take off, some acrobatics when cruising and landing smoothly, which means that the calculation and analysis of structure and material used on the fuselage of the Mini UAV was able to be validated.

On the Relation between Indentation Hardness and Young's Modulus

1958 ◽  
Vol 31 (4) ◽  
pp. 896-906 ◽  
Author(s):  
A. N. Gent
Keyword(s):  
Young’S Modulus ◽  
Young's Modulus ◽  
Empirical Relation ◽  
Rigid Sphere ◽  
Indentation Hardness ◽  
Shore Hardness ◽  
Theoretical Relation ◽  
Classical Elasticity ◽  
British Standard ◽  
Classical Elasticity Theory

Abstract A relation between British Standard and International rubber hardness and Young's modulus is derived from classical elasticity theory, and compared with the empirical relation given in B.S.903:1950. An experimental examination of the load-indentation relationship for a rigid sphere pressed into a flat rubber pad is described ; it indicates that the theoretical relation is more appropriate than the empirical one for small indentations, corresponding to hardnesses exceeding about 60° B.S. & I.R.H., and equally valid for hardnesses between about 40° and 60°. Moreover, the numerical constants are not subject to experimental uncertainty. If reduced major loads are stipulated for determining the hardness of rubbers of less than 35° to 40° B.S. & I.R.H., the theoretical relation should apply over the entire useful range. An approximate relation between Shore hardness and Young's modulus is derived similarly. The approximate equivalence of the British Standard and International rubber hardness and Shore hardness scales over the major part of the hardness range is confirmed.

Fluid-Structure Interaction Simulation of an Aortic Phantom with Uncertain Young's Modulus Using the Polynomial Chaos Expansion

2015 ◽  
Vol 807 ◽  
pp. 34-44
Author(s):  
Jonas Kratzke ◽  
Michael Schick ◽  
Vincent Heuveline
Keyword(s):  
Numerical Simulations ◽  
Uncertainty Quantification ◽  
Young’S Modulus ◽  
Clinical Decision Making ◽  
Polynomial Chaos ◽  
Young's Modulus ◽  
Clinical Decision ◽  
Von Mises Stress ◽  
Strong Impact ◽  
Fluid Structure

To add reliability to numerical simulations, Uncertainty Quantification is considered to be a crucial tool for clinical decision making. This especially holds for risk assessment of cardiovascular surgery, for which threshold parameters computed by numerical simulations are currently being discussed. A corresponding biomechanical model includes blood flow, soft tissue deformation, as well as fluid-structure coupling. Thereby, structural material parameters have a strong impact on the dynamic behavior. In practice, however, particularly the value of the Young's modulus is rarely known in a precise way, and therefore, it reflects a natural level of uncertainty. In this work we introduce a stochastic model for representing variations in the Young's modulus and quantify its effect on the wall sheer stress and von Mises stress by means of the Polynomial Chaos method. We demonstrate the use of uncertainty quantification in this context and provide numerical results based on an aortic phantom benchmark model.

scholarly journals Finite Element Biomechanics of Optic Nerve Sheath Traction in Adduction

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
Andrew Shin ◽  
Lawrence Yoo ◽  
Joseph Park ◽  
Joseph L. Demer
Keyword(s):  
Finite Element ◽  
Optic Nerve ◽  
Young’S Modulus ◽  
Optic Neuropathy ◽  
Maximum Stress ◽  
Young's Modulus ◽  
Tensile Elongation ◽  
Glaucomatous Optic Neuropathy ◽  
Stress And Strain ◽  
Element Analysis

Historical emphasis on increased intraocular pressure (IOP) in the pathogenesis of glaucoma has been challenged by the recognition that many patients lack abnormally elevated IOP. We employed finite element analysis (FEA) to infer contribution to optic neuropathy from tractional deformation of the optic nerve head (ONH) and lamina cribrosa (LC) by extraocular muscle (EOM) counterforce exerted when optic nerve (ON) redundancy becomes exhausted in adduction. We characterized assumed isotropic Young's modulus of fresh adult bovine ON, ON sheath, and peripapillary and peripheral sclera by tensile elongation in arbitrary orientations of five specimens of each tissue to failure under physiological temperature and humidity. Physical dimensions of the FEA were scaled to human histological and magnetic resonance imaging (MRI) data and used to predict stress and strain during adduction 6 deg beyond ON straightening at multiple levels of IOP. Young's modulus of ON sheath of 44.6 ± 5.6 MPa (standard error of mean) greatly exceeded that of ON at 5.2 ± 0.4 MPa, peripapillary sclera at 5.5 ± 0.8 MPa, and peripheral sclera at 14.0 ± 2.3 MPa. FEA indicated that adduction induced maximum stress and strain in the temporal ONH. In the temporal LC, the maximum stress was 180 kPa, and the maximum strain was ninefold larger than produced by IOP elevation to 45 mm Hg. The simulation suggests that ON sheath traction by adduction concentrates far greater mechanical stress and strain in the ONH region than does elevated IOP, supporting the novel concept that glaucomatous optic neuropathy may result at least partly from external traction on the ON, rather than exclusively on pressure on the ON exerted from within the eye.

Wildhaber-Novikov Circular Arc Gears: Elastohydrodynamics

1993 ◽  
Vol 115 (3) ◽  
pp. 487-492 ◽  
Author(s):  
H. P. Evans ◽  
R. W. Snidle
Keyword(s):  
Film Thickness ◽  
Elastic Deformation ◽  
Elastohydrodynamic Lubrication ◽  
Major Axis ◽  
Operating Conditions ◽  
Circular Arc ◽  
Rolling Velocity ◽  
Oil Film ◽  
Practical Design ◽  
Thinning Effect

The paper describes an elastohydrodynamic lubrication (EHL) analysis of heavily loaded contacts between the teeth of Wildhaber-Novikov (W-N) circular arc gears. The contacts occurring in gears of this type are elliptical in shape with lubricant entrainment in the direction of the major axis of the contact. The results shown refer to a particular practical design and cover a range of operating conditions encountered in practice. Because of the high rolling velocity in W-N gears a relatively thick oil film is predicted over most of the contact. Severe thinning of the film occurs at the sides of the contact, however. Results of the full EHL analysis are compared with predictions using a published film thickness formula based upon analysis of moderately loaded elliptical contacts. It is suggested that the side-thinning effect is dependent upon the relative elastic deformation occurring in the contact.

Elastohydrodynamic Lubrication Between Rolling and Sliding Ceramic Cylinders: An Experimental Investigation1

2000 ◽  
Vol 122 (4) ◽  
pp. 721-724 ◽  
Author(s):  
T. Sperrfechter ◽  
R. Haller
Keyword(s):  
Thermal Conductivity ◽  
Film Thickness ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Elastohydrodynamic Lubrication ◽  
Ceramic Materials ◽  
Oil Film ◽  
Thin Film Sensors ◽  
Line Contacts ◽  
Clear Increase

The present work focuses on the investigation of the influence of bulk ceramic materials on the behavior of elastohydrodynamically (EHD) lubricated line contacts. The materials alumina Al2O3, zirconium oxide ZrO2 and aluminum nitride (AIN) are used. Comparative measurements were taken with steel disks made of 42CrMo4. Of primary importance are the material parameters Young’s modulus and thermal conductivity. The experimental variables pressure, temperature and oil film thickness in the EHD contact of a two disk test rig were measured with the aid of evaporated thin film sensors. As the results show, an increase in the Young’s modulus causes a clear increase of the pressure level. The oil film thickness distributions show a decline of the flattening width and of the constriction occurring at the contact outlet. The influence of the material with respect to its thermal conductivity dominates, above all, in the region of the load transmitting contact zone. The transition from a good to a bad conductor of heat causes a rise in temperature, more prominent for materials with lower thermal conductivities. This leads to viscosity decrease causing clearly reduced oil film thicknesses in the contact. [S0742-4787(00)01404-1]

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