Yield Maps for Single and Bilayer Thin Films Under Scratch

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
Abhish Chatterjee ◽  
Ali Beheshti ◽  
Andreas A. Polycarpou ◽  
Pascal Bellon
Keyword(s):  
Stainless Steel ◽  
Film Thickness ◽  
Contact Pressure ◽  
Thickness Ratio ◽  
Interfacial Stress ◽  
Yield Zone ◽  
Advantages And Disadvantages ◽  
Fe Simulations ◽  
Film Substrate ◽  
Maximum Contact

Finite element (FE) simulations were performed to study yielding in single and bilayer (BL) film systems using a “yield zone map” approach. Onset of yielding was observed at the interface, substrate, surface, and film in HfB2/silicon and HfB2/stainless steel systems. The interface yield zone in HfB2/stainless steel system was found to be larger due to the dominant effect of interfacial stress gradients. Based on the FE simulations, empirical equations were derived for the maximum contact pressure required to initiate yield at the interface. For BL/substrate systems, onset of yield at the lower film/substrate interface occurred when film thickness ratio was in the range 0.5–5. The maximum contact pressure associated with the initial yielding at this interface is minimum compared to other locations. From the design point of view, for a BL system the preferable film thickness ratio was found to be 20, whereas the optimum hardness ratio ranges from 2 to 4. For these values, maximum contact pressure is very high (∼30 GPa), and thus, yield onset can be avoided at lower film/substrate interfaces. In addition, based on the obtained results, the advantages and disadvantages of using a BL film as compared to a single film and their relevance to practical applications are discussed.

Investigation of Parameters Affecting the Limiting Shear Stress-Pressure Coefficient: A New Model Incorporating Temperature

1994 ◽  
Vol 116 (3) ◽  
pp. 612-620 ◽  
Author(s):  
Victoria Wikstro¨m ◽  
Erik Ho¨glund
Keyword(s):  
Shear Stress ◽  
Film Thickness ◽  
Contact Pressure ◽  
Pressure Coefficient ◽  
Oil Viscosity ◽  
New Model ◽  
Lubricated Contacts ◽  
Limiting Shear Stress ◽  
Essential Parameter ◽  
Maximum Contact

When calculating film thickness and friction in elastohydrodynamically lubricated contacts, assuming a non-Newtonian fluid, the lubricant limiting shear stress is an essential parameter. It influences minimum film thickness and determines traction in the contact. The limiting shear stress is pressure dependent according to the Johnson and Tevaarwerk equation: τL=τ0+γp The limiting shear stress-pressure coefficient γ has in a previous screening investigation been shown to depend on several parameters: oil type, oil viscosity at + 40°C, maximum contact pressure and temperature. In the present investigation, the preliminary data is used together with response surface methodology. With these results in mind, further experiments are made and an empirical model is built. This paper presents a new model for γ which is valid for two types of oil (a polyalphaolefine with diester and a naphthenic oil) with different viscosities at +40°C. The model incorporates the influence of maximum contact pressure and oil temperature on γ. The measurements on which the model is based were carried out at temperatures ranging from −20 to + 110°C. The pressure range was 5.8–7 GPa and the shear rate was about 106 s−1.

Paper 18: Effect of Interface Geometry on the Wear of Graphite Sliding against Stainless Steel

1966 ◽  
Vol 181 (15) ◽  
pp. 11-15
Author(s):  
J. E. Houghton ◽  
L. A. Mitchell ◽  
T. S. Crawford
Keyword(s):  
Stainless Steel ◽  
Brittle Fracture ◽  
Wear Rate ◽  
Contact Pressure ◽  
Graphite Surface ◽  
Specific Wear Rate ◽  
Maximum Contact ◽  
Contact Pressures ◽  
Very High ◽  
Interface Geometry

The specific wear rate of reactor-grade graphite discs, sliding against En 58B stainless-steel cylinders, was determined for a range of theoretical contact pressures for unidirectional, constant-speed sliding in laboratory air. In many instances, wear was found to be discontinuous and associated with blistering of the graphite surface; the severity of blistering increased with increasing maximum contact pressure, but became negligible at low contact pressures, when the specific wear rate tended to a constant value—the microscopic component. At very high contact pressures, wear resulted predominantly from ploughing, i.e. instantaneous brittle fracture.

Elastohydrodynamic Lubrication of Soft, Highly Deformed Contacts

1972 ◽  
Vol 14 (1) ◽  
pp. 34-48 ◽  
Author(s):  
C. J. Hooke ◽  
J. P. O'Donoghue
Keyword(s):  
Film Thickness ◽  
Contact Pressure ◽  
Journal Bearing ◽  
Elastohydrodynamic Lubrication ◽  
Theoretical Solution ◽  
Minimum Film Thickness ◽  
Ring Seal ◽  
The Relationship ◽  
Maximum Contact

Part 1 presents a theoretical solution to the problem of lubrication of soft, highly deformed surfaces. It is argued that with this type of contact the inlet and outlet regions can be separated and analysed independently. This approach leads to a single value of non-dimensional film thickness at the point of maximum contact pressure and to a non-dimensional minimum film thickness dependent on the relationship between the inlet and outlet parameters. In Part 2, these results are applied to the problems of a cylinder sliding on an elastomer lined surface, an elastomer lined journal bearing and a sliding O-ring seal.

Effects of Film Thickness and Annealing Temperature on the Stress in Amorphous Gd-Fe Alloy Thin Films

1993 ◽  
Vol 308 ◽  
Author(s):  
Zhi-feng Zhou ◽  
Yu-dian Fan
Keyword(s):  
Thin Films ◽  
Film Thickness ◽  
Annealing Temperature ◽  
Amorphous Structure ◽  
Growth Stress ◽  
Interfacial Stress ◽  
Inhomogeneous Distribution ◽  
Structure Model ◽  
Glass Substrates ◽  
Film Substrate

ABSTRACTGd-Fe films were deposited by magnetron sputtering on glass substrates. The results shoved that the stress is compressive in most cases, and a larger compressive stress exists at the film-substrate interface. The stress is independent on the film thickness when the film thickness is greater than 0.20 μm. The stress becomes tensile only when the annealing temperature attains 400ºC. Therefore, the interfacial stress and the growth stress coexist in the Gd-Fe films, and the former will not be dominant when the film thickness is greater than 0. 2μm. The interfacial stress may originate from the inhomogeneous distribution of film composition at the interface, and the origin of growth stress can be explained by the atomic peening effect. The relation between the stress and the annealing temperature can be comprehended with the amorphous structure model.

Experimental and Theoretical Study of the Contact Mechanics of Five Total Knee Joint Replacements

1995 ◽  
Vol 209 (4) ◽  
pp. 225-231 ◽  
Author(s):  
T Stewart ◽  
Z M Jin ◽  
D Shaw ◽  
D D Auger ◽  
M Stone ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Knee Joint ◽  
Contact Pressure ◽  
Contact Stress ◽  
Linear Elasticity ◽  
Contact Area ◽  
Elasticity Analysis ◽  
Joint Replacements ◽  
Total Knee ◽  
Maximum Contact

The tibio-femoral contact area in five current popular total knee joint replacements has been measured using pressure-sensitive film under a normal load of 2.5 kN and at several angles of flexion The corresponding maximum contact pressure has been estimated from the measured contact areas and found to exceed the point at which plastic deformation is expected in the ultra-high molecular weight polyethylene (UHMWPE) component particularly at flexion angles near 90°. The measured contact area and the estimated maximum contact stress have been found to be similar in magnitude for all of the five knee joint replacements tested. A significant difference, however, has been found in maximum contact pressure predicted from linear elasticity analysis for the different knee joints. This indicates that varying amounts of plastic deformation occurred in the polyethylene component in the different knee designs. It is important to know the extent of damage as knees with large amounts of plastic deformation are more likely to suffer low cycle fatigue failure. It is therefore concluded that the measurement of contact areas alone can be misleading in the design of and deformation in total knee joint replacements. It is important to modify geometries to reduce the maximum contact stress as predicted from the linear elasticity analysis, to below the linear elastic limit of the plastic component.

Analysis and Comparison of Seal Ability of Premium Tubing Connections under Axial Alternating Load

2013 ◽  
Vol 423-426 ◽  
pp. 2035-2039
Author(s):  
Long Cang Huang ◽  
Yin Ping Cao ◽  
Yang Yu ◽  
Yi Hua Dou
Keyword(s):  
Contact Pressure ◽  
Oil And Gas ◽  
Element Analysis ◽  
Gas Well ◽  
Cycle Number ◽  
Compression Load ◽  
Well Production ◽  
Maximum Contact ◽  
Contact Pressures ◽  
Better Than

In the process of oil and gas well production, tubing connection stand the axial alternating load during open well, shut well and fluid flow. In order to know premium connection seal ability under the loading, two types of P110 88.9mmx6.45mm premium tubing connections which called A connection and B connection are performed with finite element analysis, in which contact pressures and their the regularities distribution on sealing surface are analyzed. The results show that with the increasing of cycle number, the maximum contact pressures on sealing surface of both A connection and B connection are decreased. The decreasing of the maximum contact pressures on B connection is greater than those on A connection. With the increasing of cycle number of axial alternating compression load, the maximum contact pressure on sealing surface of A connection is decreased, and the maximum contact pressure on sealing surface of B connection remains constant. Compared the result, it shows that the seal ability of A connection is better than B connection under axial alternating tension load, while the seal ability of B connection is better than type A connection under axial alternating compression load.

Scanning Scratch Tests for Evaluating the Adhesion of Thin Oxide Films on Stainless Steel

1994 ◽  
Vol 356 ◽  
Author(s):  
V. A. C. Haanappel ◽  
H. D. van Corbach ◽  
T. Fransen ◽  
P. J. Gellings
Keyword(s):  
Mechanical Properties ◽  
Growth Rate ◽  
Stainless Steel ◽  
Film Thickness ◽  
Critical Load ◽  
Deposition Temperature ◽  
Chemical Vapour ◽  
Organic Chemical ◽  
Thin Oxide Films ◽  
Type Aisi

AbstractAmorphous alumina films were deposited by metal-organic chemical vapour deposition (MOCVD) on stainless steel, type AISI 304. The MOCVD experiments were performed in nitrogen at low pressure (0.17 kPa (1.25 torr)).The effect of deposition temperature (200 − 380 °C), growth rate, film thickness, and post-deposition thermal treatment on the mechanical properties was studied. The experiments were performed with a scanning-scratch tester. The experiments are based on the estimation of the film adhesion to the substrate by determining a critical load, Lc: the load where the film starts to spall or to delaminate.The best mechanical properties were obtained with unannealed samples. After thermal annealing the critical load decreases. Regarding the unannealed samples, the critical load increased with increasing film thickness. The deposition temperature and the growth rate had no effect on the critical load.

Analysis of Premium Connection of Connecting and Sealing Ability Loaded by Axial Tensile Loads

2012 ◽  
Vol 268-270 ◽  
pp. 737-740
Author(s):  
Yang Yu ◽  
Yi Hua Dou ◽  
Fu Xiang Zhang ◽  
Xiang Tong Yang
Keyword(s):  
Finite Element ◽  
Contact Pressure ◽  
Tensile Load ◽  
Element Model ◽  
Sealing Ability ◽  
Axial Tensile ◽  
High Level ◽  
Maximum Contact ◽  
Contact Pressures ◽  
The Finite Element Model

It is necessary to know the connecting and sealing ability of premium connection for appropriate choices of different working conditions. By finite element method, the finite element model of premium connection is established and the stresses of seal section, shoulder zone and thread surface of tubing by axial tensile loads are analyzed. The results show that shoulder zone is subject to most axial stresses at made-up state, which will make distribution of stresses on thread reasonable. With the increase of axial tensile loads, stresses of thread on both ends increase and on seal section and shoulder zone slightly change. The maximum stress on some thread exceed the yield limit of material when axial tensile loads exceed 400KN. Limited axial tensile loads sharply influence the contact pressures on shoulder zone while slightly on seal section. Although the maximum contact pressure on shoulder zone drop to 0 when the axial tensile load is 600KN, the maximum contact pressure on seal section will keep on a high level.

Weldability and machinability of the dissimilar joints of Ti alloy and stainless steel – A review

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Yan Zhang ◽  
YuanBo Bi ◽  
JianPing Zhou ◽  
DaQian Sun ◽  
HongMei Li
Keyword(s):  
Residual Stress ◽  
Stainless Steel ◽  
Bonding Temperature ◽  
Fusion Welding ◽  
Research Progress ◽  
Diffusion Welding ◽  
Ti Alloy ◽  
Dissimilar Joints ◽  
Advantages And Disadvantages ◽  
Fe Intermetallics

Abstract As two important industrial manufacturing materials, titanium alloys and stainless steel have their own advantages and disadvantages in terms of physical, chemical, and mechanical properties. The field of materials manufacturing has witnessed efforts to develop technical processes that can properly combine these two alloy types, aiming to effectively use their respective advantages. The welding technology for Ti alloy and stainless steel, as a research topic with broad prospects, is comprehensively and deeply analyzed in this review. The current research progress in this field was analyzed from different process perspectives such as fusion welding, brazing, diffusion welding, friction welding, explosive welding and vacuum hot-rolling welding. The results of the review showed that the greatest challenges of fusion welding are low ductility of the material, high residual stress, high cooling rate, and the formation of numerous brittle Ti-Fe intermetallics. By using appropriate intermediate materials between these two materials, the residual stress and brittle intermetallics near the interface of the transition joint can be minimised by solving the thermal expansion mismatch, reducing the bonding temperature and pressure, and suppressing the diffusion of elements such as Ti and Fe.

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