Liner Samples Research Articles

Influence of the geometry fidelity of resonant sound-absorbing liner samples on their acoustic characteristics

Samples of sound-absorbing Helmholtz resonator-type liners of circular shape were manufactured from two types of ABS plastic and nylon on the basis of 3D modeling and 3D printing technology. Check samples were made of metal on a numerically controlled machine. Deviations of geometric parameters of the manufactured samples from the design values were determined by visual and dimensional inspection using high-precision equipment. The minimum deviations were obtained for check samples made of metal. The acoustic characteristics of the samples were experimentally determined using an interferometer with normal wave incidence at high sound pressure levels. Numerical simulation of the acoustic processes in the interferometer for the given samples was carried out on the basis of solving full Navier-Stokes equations with account for compressibility. The obtained values of the resonant frequency, impedance and sound absorption coefficient were compared with the experimental ones. It was noted that the impedance values are most sensitive to the deviations of the geometric parameters of the samples from the design values, while the deviations in the sound absorption coefficient and resonance frequency are not so sensitive to them.

Friction Performance of Aluminum-Silicon Alloy Cylinder Liner after Chemical Etching and Laser Finishing

In order to enhance the surface friction performance of the aluminum-silicon (Al-Si) alloy cylinder liner, chemical etching and laser finishing techniques are applied to improve the friction performance. The cylinder liner samples are worn against a Cr-Al2O3 coated piston ring by a reciprocating sliding tribotester. The friction coefficient and weight loss are measured to determine the friction performance; a stress contact model is developed to ascertain the wear mechanism. The results show that the optimal etching time is 2 min for the chemical etching treatment and the optimal laser power is 1000 W for the laser finishing treatment. The chemical etching removes the surface aluminum layer and exposes the silicon on the surface, thereby avoiding metal-to-metal contact. The laser finishing results in the protrusion and rounded edges of the silicon particles, which decreases the stress concentration. The laser finishing results in better friction performance of aluminum-silicon alloy cylinder liner than the chemical etching.

DETERMINATION OF ACOUSTIC CHARACTERISTICS OF FULL-SCALE SAMPLE OF SINGLE LAYERED HONEYCOMB LINER BASED ON NUMERICAL SIMULATION

The acoustic characteristics of a full-scale sample of an actual single-layer liner are determined by numerical simulation of physical processes in normal incidence interferometer. Numerical simulation is performed based on solving the unsteady Navier-Stokes equations with allowance for compressibility in three-dimensional statement. It is noted the good agreement of the acoustic characteristics of the liner sample obtained in numerical simulation and in experiment. It is shown that conducting numerical simulation on single cell sample of the liner also gives results that are in good agreement with the experiment. It allows predicting the acoustic characteristics of samples of locally reacting liners with a more complex geometry in further.

Comparative Experimental Study of Tribo-Mechanical Performance of Low-Temperature PVD Based TiN Coated PRCL Systems for Diesel Engine

Piston ring and cylinder liner (PRCL) interface is a major contributor to the overall frictional and wear losses in an IC engine. Physical vapor deposition (PVD) based ceramic coatings on liners and rings are being investigated to address these issues. High temperature requirements for applications of conventional coating systems compromise the mechanical properties of the substrate materials. In the current study, experimental investigation of tribo-mechanical properties is conducted for various titanium nitride (TiN) coated PRCL interfaces in comparison with a commercial PRCL system. Low-temperature PVD based TiN coating is successfully achieved on the grey cast iron cylinder liner samples. Surface roughness of the grey cast iron cylinder liner substrates and the thickness of TiN coating are varied. A comprehensive comparative analysis of various PRCL interfaces is presented and all the trade-offs between various mechanical and tribological performance parameters are summarized. Coating thickness between 5 and 6 micrometres reports best tribo-mechanical behaviour. Adhesion and hardness are found to be superior for the TiN coatings deposited on cylinder liner samples with higher roughness, i.e., ~ 5-micron Ra. Maximum 62 % savings on the COF is reported for a particular PRCL system. Maximum 97% saving in cylinder liner wear rate is reported for another PRCL system.

Acoustic/drag interaction and its impact on future aircraft design

For several decades, acoustic liner technology has substantially reduced the noise created by commercial jet engines. Conventional placement of the perforate-over-honeycomb liner is in the fore and aft bypass duct of an engine nacelle; however, future aircraft design may incorporate liners on additional surfaces, such as the underside of wings and the fuselage. In order to use liner technology in novel locations, the impact of the porous facesheet and core of the liner on the aerodynamic drag of the craft must be fully understood. Work conducted at the University of Notre Dame has experimentally evaluated this drag, as well as the impact of acoustic fields on the aerodynamic drag produced by acoustic liners. Measurements of several quantities across the full boundary layer profile show this impact is substantial and quantifiable. Such results for several liner facesheets will be presented. Through further testing of the acoustic impedance of various facesheets at the University of Hartford, the goal of striking design balance between acoustic performance and aerodynamic reliability can become more clear. Fluid mechanic, acoustic, and direct aerodynamic measurements for several liner samples will be presented and discussed.

SILVER-NANOPARTICLES MODIFIED SOFT LINER MATERIAL FOR OBTURATOR WEARERS WITH ACQUIRED PALATAL DEFECT. MICROBIOLOGICAL CROSSOVER STUDY

Aim: This research aimed to clinically investigate the microbecidal power of silver nano-par­ticles modified autopolymerized soft lining material for acquired palatal defect obturator wearers. Materials and methods: A total of sixteen patients with acquired palatal defect were selected from the Mansoura Oncology center and referred to the Removable Prosthodontics Department, Faculty of Dentistry, Mansoura University. For each patient, immediate surgical obturator was constructed and then replaced by temporary obturator two weeks after the surgery. At definitive abturator construction, random assigning of patients into two equal groups (eight patients each) was done. Within patient cross over study design was followed with respect to silver nanoparticles (AgNps) percentages added to the self-cure soft liner material where: Patient’s obturators in group I were lined with untreated soft liner followed by modified soft liner with 0.05 % loading by weight of AgNps added to 5gm of the polymer powder followed by modified soft liner with 0.2 % loading by weight of AgNps for one month of each soft liner application. In group II the sequence was reversed. Microbiological investigation was performed to identify bacterial colonization count related to different soft liner samples. Results: The highest mean of bacterial count was recorded with the soft liner samples without AgNps additives [mean =( 762.5 ± 85.08) x103]; while the lowest mean recorded with soft liner with 0.2% AgNps by weight [mean = (0.634 ± 0.73) x103]. (ANOVA) test indicated a significant reduction in bacterial count within increased AgNps concentration. Wilks’ lambda = 0.14, f = 40.75 and p = 0.001. Conclusions: Within parameters of this study, it could be concluded that: Modification of autopolymerized acrylic-based soft liner with AgNps is a simple reliable method to enhance its bactericidal activity especially for obturator wearers. The antimicrobial efficacy of AgNps modified soft liner seemed to be concentration dependent.

1.4 GHz on the Fundamental Plane of black hole activity

The fundamental plane of black hole activity is an empirical relationship between the OIII/X-ray luminosity depicting the accretion power, the radio luminosity as a probe of the instantaneous jet power and the mass of the black hole. For the first time, we use the 1.4 GHz FIRST radio luminosities on the optical fundamental plane, to investigate whether or not FIRST fluxes can trace nuclear activity. We use a SDSS-FIRST cross-correlated sample of 10149 active galaxies and analyse their positioning on the optical fundamental plane. We focus on various reasons that can cause the discrepancy between the observed FIRST radio fluxes and the theoretically expected core radio fluxes, and show that that FIRST fluxes are heavily contaminated by non-nuclear, extended components and other environmental factors. We show that the subsample of 'compact sources', which should have negligible lobe contribution, statistically follow the fundamental plane when corrected for relativistic beaming, while all the other sources lie above the plane. The sample of LINERs, which should have negligible lobe and beaming contribution, also follow the fundamental plane. A combined fit of the low-luminosity AGN and the X-ray binaries, with the LINERs, results in the relation log L$_R$ = 0.77 log L$_{OIII}$ + 0.69 log M. Assuming that the original fundamental plane relation is correct, we conclude that 1.4 GHz FIRST fluxes do not trace the pure 'core' jet and instantaneous nuclear activity in the AGN, and one needs to be careful while using it on the fundamental plane of black hole activity.

Investigation of a self-lubricating coating for diesel engine pistons, as produced by combined microarc oxidation and electrophoresis

The purpose of this work was to improve reliability and durability of high-silicon aluminum alloy piston skirts for diesel engines. Novel ceramic matrix composites were fabricated on ZL109 aluminum alloy substrates by two steps combining microarc oxidation (MAO) with electrophoresis deposition (EPD). MoS2 is incorporated into an aluminum oxide matrix during processing. The effects of the ceramic matrix composites on anti-wear and self-lubricating were investigated using a reciprocating test method and cylinder liner samples (boron copper cast iron) as the sliding partner. Compared to the high-silicon aluminum alloys substrate, the friction coefficient of ceramic matrix composites against the liner material was reduced by 35% under dry sliding, the wear loss was decreased by 95%, the worn surfaces were flat and smooth, and friction coefficient was relatively stable. The mechanisms by which the observed advantages were produced are discussed.

Acoustic excitation impact on aerodynamic drag measured in aeroacoustic liners

Research interest has steadily grown for understanding the aerodynamic drag produced by acoustic liners for commercial turbofan engines. This is driven by an aim to understand the phenomena fundamentally as well as for application in flight. Stringent government regulations on aircraft noise and next generation aircraft designs that may include liners on more surfaces are key drivers for industry involvement. While the conventional perforate-over-honeycomb liner has proven effective acoustically for decades, liner drag production has not been fully understood. When an acoustic liner sample is excited with sound pressure levels above 140dB re: 20 micropascals, a measurable drag increase is observed at flight velocity. Recent measurements have shown that tonal noise at the same level can produce more than a 50 percent increase in drag coefficient for a liner sample at lower test speeds. By testing liner samples at low speed in the Notre Dame Hessert Laboratory, detailed hotwire probe measurements near the wall have been made and drag coefficient comparisons have been made with the use of a linear air-bearing force balance. The development of the measurement setup, the results produced, and a discussion of implications will be included in this paper.

An improved impedance eduction technique based on impedance models and the mode matching method

The problem of determining the acoustic impedance of liners used in turbofan engines of commercial aircraft has been a point of interest for the scientific community for decades, especially in the presence of grazing flows, similar to operational conditions. Different techniques have been developed to determine liner acoustic impedance under grazing flow. More recent research have been focused on inverse methods, which consist of two steps: (i) measurement of the acoustic field in a rectangular duct with flow and a liner sample located at one or two walls of the duct and (ii) modelling of the acoustic field and application of an optimization procedure to find the impedance that minimize the difference between experimental and analytic results. The process is usually carried on using optimization techniques and performed at each frequency step, which can lead to discontinuous impedance curves and large computational costs. In this work, the mode matching method is discussed in detail, and a new technique for impedance determination is proposed, which incorporates a mathematical impedance model to the optimization process as a mean to improve the impedance curve, therefore suppressing measurements error and convergence issues at single frequencies. The impedance models considered here are given in the frequency domain and satisfy passivity, reality and causality conditions, which allows the use of the educed impedance in time domain simulations. Three models are considered and compared regarding different liner samples, flow velocities and wave propagation direction. The results show that the impedance models can successfully suppress convergence errors close to the liner resonance frequency.

Friction and wear of liner and grinding ball in iron ore ball mill

To understand the friction and wear of working mediums in iron ore ball mills, experiments were conducted using the ball cratering method under dry and wet milling conditions, which mimic the operating conditions in ball mills. The liner sample is made of Mn16 steel, the ball had a diameter of 25 mm and was made of GCr15 steel, and the iron ore powder was screened from the magnetite particles with mesh number of 20. The results indicate that a different wear condition makes the COF change in a converse way and causes a different wear pattern in wear craters, followed by the corresponding temperature rise.

Reduced aerodynamic drag concepts for acoustic liners

The objective of this paper is to describe the development of reduced aerodynamic drag concepts for acoustic liners in turbofan engine nacelles. Conventional acoustic liners help aircraft to achieve U.S. governmental noise regulations, however they are responsible for a measurable increase in the total aerodynamic drag of the aircraft. As regulations on commercial aircraft noise become more strict, additional surfaces may be covered with acoustic liner, heightening the need for the understanding and reduction of aerodynamic drag caused by liners. A linear force balance has been designed at the Mach 0.6 Wind Tunnel at the University of Notre Dame to evaluate the aerodynamic and acoustic characteristics of both conventional and 3D-printed liner samples. Through multi-parameter characterization, reduced drag concepts for future liners have been created. This paper will discuss the experimental work done to develop these reduced drag concepts, outline the future work to be done, and discuss the potential acoustic coupling effect on aerodynamic drag.

Study of Nano-Kaolinite Properties in Clay Liner Application

This paper reports the outcome of the laboratory investigation conducted on new clay liners modified with kaolinite combined with various content of lime-treated, various content of bentonite and admixture of kaolinite adding with 3% nano-kaolinite for composition. The 3% nano-kaolinite was chosen based on earlier finding by S.V.Netethu (2013). The various content of lime-treated and bentonite adopted are 2.0%, 5.0%, 7.5% and 10.0% by total weight of the kaolinite. Compaction tests was performed on the resulted modified clay liner samples to evaluate the best percentage that gives optimum moisture content (OMC) and maximum dry density (MDD) . The best percentage of each bentonite and lime-treated are chosen and be added into kaolinite and the physical properties of samples are tested and compared to the other two samples which are kaolinite only and kaolinite added with 3 % of nano-kaolinite. Nano-kaolinite was produced using a mill machine and the sized of nano-kaolinite (1nm-100nm) were examined under Scanning Electron Microscope (SEM) machine.The addition of 3% nano-kaolinite to the kaolinite gives the best compaction result compared to bentonite or lime-treated. The value of dry density is increased to give the reduction of air voids, thereby reducing the hydraulic conductivity by concept. Based on the compaction test value, it clearly observed that admixture of kaolinite adding with 3% nano-kaolinite gives the best results from the other samples due to required less water to achieve maximum dry density of 1.39 Mg/m3 and 27.34% of optimum moisture content resulted positive effect in soil properties.

Development of Standardized Material Testing Protocols for Prosthetic Liners.

A set of protocols was created to characterize prosthetic liners across six clinically relevant material properties. Properties included compressive elasticity, shear elasticity, tensile elasticity, volumetric elasticity, coefficient of friction (CoF), and thermal conductivity. Eighteen prosthetic liners representing the diverse range of commercial products were evaluated to create test procedures that maximized repeatability, minimized error, and provided clinically meaningful results. Shear and tensile elasticity test designs were augmented with finite element analysis (FEA) to optimize specimen geometries. Results showed that because of the wide range of available liner products, the compressive elasticity and tensile elasticity tests required two test maxima; samples were tested until they met either a strain-based or a stress-based maximum, whichever was reached first. The shear and tensile elasticity tests required that no cyclic conditioning be conducted because of limited endurance of the mounting adhesive with some liner materials. The coefficient of friction test was based on dynamic coefficient of friction, as it proved to be a more reliable measurement than static coefficient of friction. The volumetric elasticity test required that air be released beneath samples in the test chamber before testing. The thermal conductivity test best reflected the clinical environment when thermal grease was omitted and when liner samples were placed under pressure consistent with load bearing conditions. The developed procedures provide a standardized approach for evaluating liner products in the prosthetics industry. Test results can be used to improve clinical selection of liners for individual patients and guide development of new liner products.

Численное моделирование акустических процессов в интерферометре с образцами многослойных звукопоглощающих конструкций

Численное моделирование акустических процессов в интерферометре с образцами многослойных звукопоглощающих конструкций

Сравнительный анализ акустических интерферометров на основе расчетно-экспериментальных исследований образцов звукопоглощающих конструкций

Сравнительный анализ акустических интерферометров на основе расчетно-экспериментальных исследований образцов звукопоглощающих конструкций

A study on cycling life and failure mode of type3 cylinder treated with autofrettage pressure

In this study, series of experiments and finite element method analyses were conducted, and the results were used to demonstrate the effect of the autofrettage pressure on the cycling life and the failure mode, and to determine an optimal condition of autofrettage process for self-contained breathing apparatus. Total 20 vessels went through different autofrettage pressures, i.e., 1.0, 1.1, …, 2.9 times the test pressure. Then, each vessel was subjected to the ambient hydraulic cycling test of the same condition until fluid leaks. Cycling life of a vessel was estimated based on the stress-strain diagram and stress-cycle curve that were obtained by the tensile test and the fatigue test, respectively, of the liner sample. By using ABAQUS code, the compressive residual stress and the maximum strain distribution at each autofrettage pressure were computed. As a result, the failure modes were in good agreements with the computations. And it is concluded that the proportionality factor of 1.7 or above should be applied in the autofrettage process for significant extension of the cycling life, and, with the factor of 2.5, the maximum cycling life and the desired failure mod are achieved simultaneously.

МОДИФИЦИРОВАННАЯ ЭНЕРГЕТИЧЕСКАЯ МОДЕЛЬ ТРЕНИЯ И ИЗНАШИВАНИЯ ПРИМЕНИТЕЛЬНО К ТРИБОСОПРЯЖЕНИЯМ ДВС

For the description and wear prediction in tribicouplings there are theoretical formulae and also empirical models. Most of well-known regulations may be used only under specific conditions of contacting. The purpose of this work is the investigation of tribicoupling “piston guide – cylinder liner” in an internal combustion engine (ICE). In particular, for that there were carried out experimental investigations on a tribometer realizing a reciprocal motion of piston and cylinder liner samples. The results of experimental investigations were analyzed with the use of a wear model which is the most applicable for the description of this type of tribocouplings. This model is based on the combination of energetic theory and molecularmechanical method with a precise definition of friction surface topography parameters. Such a modified model of friction and wear allows combining the prognostication of a layer worn with fatigue theory that gives a possibility of its use as applied to the life analysis of any reciprocating tribosystem.

The Influence of Salt Solution on Morphological Changes in a Geosynthetic Clay Liner

Morphological variations of geosynthetic clay liner (GCL) samples, hydrated with two different permeates, distilled water and NaCl solution (100 mM concentration), were observed in detail using microscopic analysis. After the GCL samples were hydrated with the NaCl solution, they were observed with an optical microscope. While the surface of the treated GCL samples was similar to the surface of the untreated GCL, a crystal deposit was found on the surface of the treated samples. Using a scanning electron microscope (SEM), a more solid appearance was observed for the bentonite particles contained in the GCL after the sample was hydrated with distilled water in comparison to the GCL sample that was hydrated with the NaCl solution. It appears that salt solution hydration results in less swelling of the bentonite particles. Furthermore, the energy-dispersive X-ray spectrometer (EDS) results showed that distilled water hydration had no effect on the distribution of the elements contained in the GCL samples. However, bound chlorine was observed, which demonstrated that the bentonite particles had absorbed the NaCl solution. In addition, changes in the hydraulic conductivity of the hydrated GCL samples were also observed.

Time Dependent Effect of a Denture Cleanser on the Sorption and Solubility of Four Soft Liners-An Invitro Study.

Soft liner materials, when used with ill fitting dentures, are constantly kept in a wet environment of either saliva or denture cleanser that affects their sorption and solubility. These inturn have detrimental effect on other properties. To evaluate the influence of different exposure times of a commonly used denture cleanser on sorption and solubility of four soft liners. Metal disc was fabricated to make the mould space for soft liner samples. Four materials were used, long term and short term acrylic liners; long term and short term silicone liners. Each of these were divided into four groups: first control group- all liners were kept in artificial saliva for entire period of study. Second group- liners were immersed daily in cleanser for 1 hour and then transferred to artificial saliva for rest of the day. Similarly samples of third and fourth groups were immersed in cleanser for 4 and 8 hours respectively and transferred to artificial saliva. Sorption and solubility tests were conducted and statistical analysis done. One-way ANOVA followed by Post-hoc Tukey's test for pair wise comparisons was done. Significance was set at the probability level of p < 0.05. Solubility values of all groups were higher than the quoted ADA specifications. Overall, silicones performed better than acrylics. Long term silicone was most stable. Short term acrylic was most unstable. The 8 hour immersion in denture cleanser caused significantly high sorption and solubility.