Liner Interface Research Articles

Characteristic Curves for Deep Circular Tunnels in Poroplastic Rock

A complete analytical solution for an axisymmetric deep tunnel excavated in a saturated poroplastic rock is presented. Results are found for short- and long-term analyses and for different drainage conditions at the rock–liner interface. In the derivation, the following assumptions are made: (1) circular cross-section, (2) deep tunnel, (3) plane strain conditions on a cross-section perpendicular to the tunnel axis, (4) axisymmetric loading, (5) the rock is saturated, homogeneous and isotropic, and (6) the rock is elastic-perfectly plastic with brittle failure and non-associated flow rule. The results obtained indicate that, if the rock remains elastic during construction, the stresses of the liner and the tunnel deformations are the same for short- and long-term conditions and are independent of the drainage conditions at the rock–liner interface and on the magnitude of Biot’s parameter α. If the rock yields, the stresses in the liner and the tunnel deformations strongly depend on the type of analysis. Effective radial and tangential stresses inside the rock decrease with Biot’s parameter α, while radial displacements increase. The response of the liner in terms of stresses and deformations strongly depends on its stiffness relative to the rock, yielding of the rock, groundwater and drainage conditions, and construction operations, while it is somewhat less sensitive to the rock’s poroplastic properties. Stresses and deformations inside the rock, however, show a much stronger dependency.

Measurement of dynamic lubricating oil film thickness between piston ring and liner in a motored engine

The interface between the piston rings and cylinder liner plays an important role in total frictional losses and mechanical wear of internal combustion engines and is increasingly coming under scrutiny as legislated particulate emission standards are becoming more and more stringent. The capacitance method is used for measurement of minimum oil film thickness at the piston ring–liner interface in the present investigations. Measurement of capacitance formed between the piston ring and a probe mounted flush with the liner provides an accurate measurement of oil film thickness provided that the region between the probe and liner is flooded with lubricating oil whose dielectric constant is known. This paper presents detailed design of sensor, instrumentation and measurement of lubricating oil film thickness using capacitive micro-sensor. The present investigation is carried out in a motored engine in order to validate the sensor and instrumentation and it can be directly employed in a firing engine also. The oil film thickness was measured at different speeds at three different locations, i.e. close to TDC, mid stroke position and close to BDC position and the results are accordingly presented in this paper. Lubricating oil film thickness is found to vary between 0.2 and 8 μm in the motored engine. At a particular position, lubricating oil film thickness varies significantly in upward and downward stroke of the engine due to reversal in direction of piston tilt.

Misalignment effects on steady‐state and dynamic behaviour of compliant journal bearings lubricated with couple stress fluids

AbstractThis work concerns the steady‐state and dynamic analysis of misaligned compliant journal bearings considering the effects of couple stresses arising from the lubricant blended with polymer additives. Based on the Stokes micro‐continuum theory, a modified form of the Reynolds equation is derived. The displacement field at the fluid film–bearing liner interface due to pressure forces is determined using the elastic thin liner model. The effects of the misalignment and the couple stress parameters on static and dynamic performances such as pressure distribution, load‐carrying capacity, power loss, side leakage flow, misalignment moment, critical mass and whirl frequency are presented and discussed. Copyright © 2008 John Wiley & Sons, Ltd.

Effect of Progressive Failure on Measured Shear Strength of Geomembrane/GCL Interface

This paper presents experimental data and numerical modeling results that illustrate the effects of progressive failure on the measured shear strength of a textured geomembrane/geosynthetic clay liner (GMX/GCL) interface. Large direct shear tests were conducted using different specimen gripping/clamping systems to isolate the effects of progressive failure. These tests indicate that progressive failure causes a reduction in measured peak shear strength, an increase in the displacement at peak, an increase in large displacement shear strength, and significant distortion of the shear stress–displacement relationship. A numerical model was developed to simulate progressive failure of a GMX/GCL interface. Measured and simulated shear stress–displacement relationships are in good-to-excellent agreement at four normal stress levels. The model was then used to investigate mechanisms of progressive interface failure and factors that control its significance. The results indicate that accurate measurements of shea...

Study of Micromotion in Modular Acetabular Components During Gait and Subluxation: A Finite Element Investigation

Polyethylene wear after total hip arthroplasty may occur as a result of normal gait and as a result of subluxation and relocation with impact. Relocation of a subluxed hip may impart a moment to the cup creating sliding as well as compression at the cup liner interface. The purpose of the current study is to quantify, by a validated finite element model, the forces generated in a hip arthroplasty as a result of subluxation relocation and compare them to the forces generated during normal gait. The micromotion between the liner and acetabular shell was quantified by computing the sliding track and the deformation at several points of the interface. A finite element analysis of polyethylene liner stress and liner/cup micromotion in total hip arthroplasty was performed under two dynamic profiles. The first profile was a gait loading profile simulating the force vectors developed in the hip arthroplasty during normal gait. The second profile is generated during subluxation and subsequent relocation of the femoral head. The forces generated by subluxation relocation of a total hip arthroplasty can exceed those forces generated during normal gait. The induced micromotion at the cup polyethylene interface as a result of subluxation can exceed micromotion as a result of the normal gait cycle. This may play a significant role in the generation of backsided wear. Minimizing joint subluxation by restoring balance to the hip joint after arthroplasty should be explored as a strategy to minimize backsided wear.

Surface improvement of EPDM rubber by plasma treatment

The surface of ethylene-propylene-diene monomer (EPDM) rubber was treated in N2/Ar and N2/H2/Ar RF plasmas in order to achieve similar or better adhesion properties than NBR (acrylonitrile-butadiene) rubber, nowadays used as thermal protection of rocket chambers. The surface properties were studied by contact angle measurements and by x-ray photoelectron spectroscopy (XPS). The treated surfaces of the EPDM samples show a significant reduction in the contact angle measurement, indicating an increase in the surface energy. XPS analyses show the incorporation of polar nitrogen- and oxygen-containing groups on the rubber surface. After plasma treatment the presence of oxygen is observed due to surface oxidation which occurs when the samples are exposed to the air. Atomic force microscopy and scanning electron microscopy analyses indicate a decrease in the EPDM rubber surface roughness, promoted by surface etching during the plasma treatment. Strength tests indicate improvement of about 30% and 110% in the adhesion strength for the plasma treated EPDM/polyurethane liner interface and for the EPDM/epoxy adhesive interface, respectively. The adhesion strength of the EPDM/liner is similar to that obtained for the NBR/liner, which indicates that EPDM rubber can safely be used as thermal protection of the solid propellant rocket chamber.

Effect of liner surface properties on wear and friction in a non-firing engine simulator

The performance of a combustion engine is closely related to the friction force and wear between cylinder liner and piston rings. It is believed that this friction force can be significantly reduced by optimizing the surface topography of cylinder liners. Therefore, it is necessary to understand how liner surface topography affects wear, friction and lubricating oil consumption. Several experimental studies have been carried out for evaluating wear and friction in simulated engine conditions using Cameron–Plint wear testers, Pin-on-disk testers, SRV testers, etc. However, these studies do not reflect the true behaviour of inside the engine because of stroke length limitations. In this paper, a non-firing engine simulator has been developed in order to simulate engine conditions to a closer extent compared to these machines. This simulator can operate at similar linear speed, stroke, and load as real engine and can simulate almost all engine operating conditions, except firing pressures. In the present study, a production grade cylinder liner has been used for the experiments conducted using a custom-made non-firing engine simulator. The wear and surface property behaviour were evaluated at several locations in the liner and found that after running-in an engine, surface of cylinder liner exhibits plateau-honed-like characteristic. Energy dispersive analysis (EDS) has been carried out of liner and top ring for evaluating materials transfer. Coefficient of friction between three different liner segments and ring was evaluated using an SRV wear tester. Coefficient of friction in the piston ring–liner interface increases with increasing average surface roughness for liner.

Case history of liner veneer instability

Construction conditions experienced during installation of a landfill geocomposite liner system led to two slides on a 3H:1V slope during construction. The landfill was being developed for final disposal of flue gas desulfurization by-product material (FGD). The slides occurred in two different areas of the 3H:1V slope and encompass 10,500 and 20,235 m2 in the Fall of 1996 and Summer of 1997, respectively. The slides developed by movement along the PVC geomembrane/compacted clay liner interface during or shortly after placement of the protective FGD cover material over the drainage sand layer. Laboratory direct shear tests revealed that the shear strength of this interface is sensitive to the moisture content of the exposed compacted clay liner. The direct shear tests revealed reductions in the available shear strength of 35% and 37% for the peak and large displacement values as the compacted clay liner moisture content increased by 8 percentage points. In addition, shear stresses induced by surface traffic activities might result in shear displacements along the interface, which in some cases were large enough to lower the available shear resistance of the geomembrane/compacted clay interface to a post-peak or large displacement value. This paper discusses the slides, direct shear testing, slope stability analyses used to evaluate the mobilized interface shear strength parameters, the relationship between moisture content and geomembrane/compacted clay liner interface strength, and the effect of shear displacement on the mobilized shear strength.

Lubrication regime transitions at the piston ring-cylinder liner interface

An experimental apparatus and an analytical model have been developed to investigate and determine the lubrication condition and frictional losses at the interface between a piston ring and cylinder liner. In order to obtain a solution for the lubrication condition between the piston ring and cylinder liner, the system of Reynolds and film thickness equations subject to boundary conditions were simultaneously solved. The effects of boundary and mixed lubrication conditions were implemented using the Greenwood-Tripp stochastic approach. The Elrod cavitation algorithm was used to investigate the effects of fluid rupture and reformation at the top and bottom dead centres. The experimental results indicate that the piston ring and liner experience all the different lubrication regimes (i.e. boundary, mixed, and hydro-dynamic lubrication) during a stroke. A comparison between experimental and analytical results indicated that they are in good agreement and the analytical model developed for this study can capture the different lubrication regimes that the piston ring and liner experience.

Effect of pore water pressure on tunnel support during static and seismic loading

The support of underground structures must be designed to withstand static overburden loads as well as seismic loads. New analytical solutions for a deep tunnel in a saturated poroelastic ground have been obtained for static and seismic loading. The static solution accounts for drainage and no-drainage conditions at the ground–liner interface. Linear elasticity of the liner and ground, and plane strain conditions at any cross-section of the tunnel are assumed. For tunnels in which ground stresses and pore pressures are applied far from the tunnel center, the drainage conditions at the ground–liner interface do not affect the stresses in the liner. The analytical solution shows that the stresses in the liner are exactly the same whether there is drainage or not at the ground–liner interface. Hence, if the drainage conditions in the tunnel are changed from full drainage to no-drainage or vice versa the stresses in the liner are not affected. However, the stresses and displacements in the ground change significantly from drainage to no-drainage conditions. For seismic loading a new analytical formulation is presented which provides the complete solution for the ground and the liner system for both dry and saturated ground conditions. The formulation is based on quasi-static seismic loading and elastic ground response; for a saturated ground, undrained conditions are assumed which indicate that the excess pore pressures generated during the seismic event do not dissipate. The results show that the racking deformations of a liner in dry or saturated ground are highly dependent on the flexibility of the liner.

Effect of thermocycling on tensile bond strength of six silicone-based, resilient denture liners

Statement of Problem. Adhesion failure between silicone resilient denture lining materials and denture base resin is commonly encountered in clinical practice. Adhesion failure results in localized unhygienic conditions at the debonded regions and often causes functional failure of the prosthesis. Purpose. The purpose of this study was to investigate the effect of thermocycling on the tensile bond strength of 6 soft lining materials. Material and Methods. Six commonly used silicone-based resilient denture liners (Ufigel C, Ufigel P, Mollosil, Molloplast B, Permafix, and Permaflex) were chosen for the investigation. The bond strength was determined, in tension, after processing to PMMA. The resilient denture liners for each group (n = 24) were 10 × 10 × 3 mm and were processed between 2 polymethyl methacrylate specimens according to manufacturer's instructions. Two PMMA specimens were prepared by investing brass dies with a 3-mm-thick spacer in a denture flask. Specimens were made by processing the resilient denture liners against the polymerized PMMA block. After polymerization, the brass spacer was removed from the mold, the 2 PMMA resin specimens were trimmed, and the surfaces to be bonded were smoothed. The PMMA block was placed back into the molds and the resilient denture liners were packed into the space made by brass spacer, trial packed, and polymerized according to the manufacturer's instructions. Half of the specimens for each group were stored in water for 24 hours, and the other half were thermocycled (5000 cycles) between baths of 5° and 55°C. All specimens were placed under tension until failure in a universal testing machine at a crosshead speed of 5 mm/min. The maximum tensile stress before failure and mode of failure were recorded. The mode of failure was characterized as cohesive, adhesive, or mixed mode, depending on whether the fracture surface was in the soft liner only, at the denture base-soft liner interface only, or in both. Failure strength was recorded in kg/cm2. Results were tested by multiple analysis of variance (ANOVA) for mode of failure (adhesive, cohesive, and mix), 2-way ANOVA (storage-products), and 1-way ANOVA (storage-products interaction, before and after thermocycling). Duncan's test was used to determine whether significant changes in the tensile bond properties of the materials occurred during thermocycling. Results. Varying degrees of bond strengths were found for soft lining materials and were significantly different (P<.05). Results of this study also indicated that the bond strengths of soft lining materials had significantly decreased after thermocycling except Ufigel C and Mollosil. Conclusions. Because the adequate adhesive value for soft lining materials is given 4.5 kg/cm2, all of the materials were acceptable for clinical use. (J Prosthet Dent 2003;89:303-10.)

The influence of non-uniform transmissivity vis-à-vis hole location

Almost all of the many technical papers on the quantification of advective flow rates through composite liners focus on uniform interface transmissivity and mathematical modelling. Few papers have addressed situations where the transmissivity is non-uniform or experimental validation of previously developed analytical or empirical equations. This paper therefore attempts to present both the results of a numerical survey based on previously developed equations addressing the case of non-uniform hydraulic transmissivity at the liner interface and an experimental survey conducted on large-scale tests. Even if the two aspects of this study are based on different assumptions—two-dimensional geometry, steady-state flow, saturated soil and interface for the numerical study and axi-symmetric geometry, transient flow and unsaturated soil and interface for the experimental study, both tend to show that the advective flow rate through the composite liner is greatly influenced by the position of a hole in a geomembrane in relation to the spatial distribution of transmissivities at the composite liner interface. It is also shown that the existence of two fluids in the interface, air and water or leachate for instance, will have an influence on the wetted area.

Polyethylene liner cementation into fixed acetabular shells

A patient presenting with a secure cementless acetabular component and with femoral head penetration through the polyethylene liner is a common clinical problem. Cementing a new liner into the fixed shell is one option. We evaluated this option in a clinical series of 17 cases and with a preliminary mechanical study. In the 1 clinical failure (5.9%), the failure occurred at the cement–liner interface. The most important variable in optimizing the mechanical strength of the cemented liner construct was adequate preparation of the cement–liner interface. This approach to treating the patient with a fixed cementless shell and a worn polyethylene liner can provide a durable construct with minimal morbidity. Copyright 2002, Elsevier Science (USA). All rights reserved.

Calculation of mixed lubrication at piston ring and cylinder liner interface

This paper reports on the theoretical analysis of mixed lubrication for the piston ring. The analytical model is presented by using the average flow and asperity contact model. The cyclic variations of the nominal minimum oil film thickness are obtained by numerical iterative method. The total friction is calculated by using the hydrodynamic and asperity contact theory. The effects of the roughness height, pattern, and engine speed on the nominal minimum film thickness, friction force, and frictional power losses are investigated. As the roughness height increases, the nominal oil film thickness and total friction force increase. Also, the effect of the surface roughness on the boundary friction is dominant at low engine speed and high asperity height. The longitudinal roughness pattern shows lower mean oil film pressure and thinner oil film thickness compared to the case of the isotropic and transverse roughness patterns.

Liquid Flow Through Composite Liners due to Geomembrane Defects: Nonuniform Hydraulic Transmissivity at the Liner Interface

Rates of liquid flow through composite liners are intimately linked with the existence of a transmissive layer between the soil liner and the geomembrane. The aim of this paper is to propose analytical solutions for estimating the rate of liquid flow through composite liners for the case where two zones of different hydraulic transmissivities coexist in the transmissive layer. Solutions are given for both the axi-symmetric and two-dimensional cases. The development of these analytical solutions is directly based on solutions that have been proposed previously for uniform hydraulic transmissivity. Results tend to show, for the simple cases evaluated, that, in situations where there is variable hydraulic transmissivity, neglecting the variability can result in a significant overestimation of the rate of liquid flow. This preliminary approach shows the importance of taking into account a realistic distribution of hydraulic transmissivity in attempts to estimate the rate of liquid flow through composite liners and highlights the need for more research in this area.

Motion at the Modular Acetabular Shell and Liner Interface A Comparative Study

Excessive polyethylene debris generated from a total hip arthroplasty can lead to osteolysis and premature revision. Most of this polyethylene debris comes from the concave articulation. However, abrasive wear on the convex side of a modular polyethylene component also may play a role in this problem. Motion of a modular polyethylene liner with respect to its shell can lead to such abrasive wear. Six samples of modular acetabular components from eight manufacturers were tested for motion between the shell and the liner. Motion at the shell liner interface was detected by five fiberoptic sensors in the x, y, and z planes. Micromotion occurred at the shell liner interface in all designs tested. The magnitude of motion varied between manufacturers, ranging from 5 to 311 microns. Design features that limit motion may be advantageous in limiting the amount of polyethylene debris.

Metal retention from landfill leachate by glacial clays: laboratory experiments

Abstract Two sets of laboratory experiments were carried out to investigate the role of clay liners on the retention of metals present in landfill leachate. In the first experiment leachate was passed through clay filled columns and comparisons made of the metal content in treatment columns (leachate) with that in the control columns (de-ionized water). The metals Na, K, Mg, Ca, Al and Fe show elevated concentrations when compared with the control columns. In addition, a black sludge was observed on the upper surface of the treatment columns. On analysis this sludge was found to be Fe-rich when compared with the surrounding leachate/clay matrix. In the second experiment a simple tank system was used to investigate sludge formation at the leachate: clay liner interface. The observed sludge was found to have elevated metal concentrations, with a corresponding decrease in metal levels in leachate samples, compared with analysis before the experiment. From these observations it was concluded that the sludge may be acting as a sink for key metal contaminants from leachate.

Closure to “Landfill Liner Interface Strengths from Torsional-Ring-Shear Tests” by Timothy D. Stark and Alan R. Poeppel

Closure to “Landfill Liner Interface Strengths from Torsional-Ring-Shear Tests” by Timothy D. Stark and Alan R. Poeppel

In vitro characterization of visible light-cured glass ionomer liners

The purpose of this study was to characterize the in vitro performance of three visible light-cured glass ionomer liners. The liners containing 2-HEMA showed significantly higher compressive strength, diametral tensile strength and Vickers hardness than the liner without 2-HEMA. Statistically significant differences were found in the optical properties of the materials tested. The liners containing 2-HEMA manifested higher shear strength at liner/composite than at dentin/liner interfaces. The acid-base reaction was significantly delayed after light exposure in all the liners tested. The liner without 2-HEMA presented the greatest maximum gap at the liner/dentin interface. Significant correlations were detected between the optical properties of the liners and the top-bottom differences in the extent of conversion, as well as between the maximum marginal gap at the dentin/liner interface and the bond strength with dentin and composite. These correlations suggest the following areas for further developments: incorporation of low molecular weight polyalkenoic acids or accelerating agents to increase the initial carboxylate yield, increase in total transmittance and reduction in diffuse reflectance to improve the in-depth conversion, and reinforcement of the dentin liner interface to prevent gap formation.

Smooth HDPE-clay liner interface shear strengths: compaction effects. Technical note : J Geotech Engng Div ASCE V117, N4, April 1991, P686–693

Smooth HDPE-clay liner interface shear strengths: compaction effects. Technical note : J Geotech Engng Div ASCE V117, N4, April 1991, P686–693