Influence of roughness on contact interface in fretting under dry and boundary lubricated sliding regimes

This paper presents experimental results of wear process under dry and boundary lubricated metallic (AISI 1034/AISI 52100) contacting bodies with different surfaces morphologies subjected to a wide range of kinematic fretting conditions. Analysis of damage mode observed under such fretting conditions is elucidated in context of surfaces morphologies therefore associated with surface manufacturing processes. Various surface topographies due to specific machining processes (cutting and abrasive modes) have been investigated. Under boundary lubricated (ZDDTP zinc-dialkyl-dithiophosphate) fretting contact paradoxally has a high coefficient of friction at the transition between Partial and Full slip sliding regime. This paper attempts to bridge the gap between the damage mode, sliding conditions and surface roughness to provide an approach to evaluate the surface finishing as a factor in friction and wear damage processes

Interface roughness effect on friction map under fretting contact conditions

In many industrial applications where fretting damage is observed in the contact (e.g. rotor/blade, electrical contacts, assembly joint, axe/wheel, clutch) the external loadings or geometry design cannot be changed. Therefore, the surface preparation and finishing process become essential to control and reduce the damage caused by fretting. In this paper, the authors present the experimental study of the initial surface roughness and machining process influence on fretting conditions in both partial and full sliding regimes. Surfaces prepared by milling and smooth abrasive polishing processes have been analysed. The influence of roughness on sliding behaviour and analysis of friction have been reported. Also, the contact pressure influence and qualitative analysis of fretting wear scar have been presented

RELATIVE PROFITABILITY OF VINE-RIPE TOMATOES IN NORTH CAROLINA AND TENNESSEE

Crop Production/Industries,

Roughness and wettability of surfaces in boundary lubricated scuffing wear

The diversity of multidisciplinary approaches suggests that fundamentals of scuffing require systemic, complex multi-scale and multi-physics analysis of an irreversible process as it is postulated in present study. That is probably one of the reasons of lack of unequivocal model of this irreversible transitional process from stable more or less lubricated wear to scuffing described only by one or few authors in equation(s) form. Therefore, it is useful to characterize the tribological surface properties in frame of systemic approach looking simultaneously for the optimal compromise between rheological, morphological and physicochemical features of contacting surface's layer. Hypothetical role connected to any group of features in the topological approach is elucidated and experimentally confirmed via the wettability, strongly combined with surface roughness and surface free energy. Due to the fact that the free energy is directly related to the surface wettability it can as well affect the scuffing activation process. For scientific and rhetoric reasons some selected results of limited boundary lubrication investigations under double blind trial conditions in case of gear oil with anti-wear (AW) and extreme pressure (EP) additives are elucidated here. The results issued from scuffing tests on AISI 4140 ground steel burnished under different forces in order to generate different surface roughness, residual stresses and surface energy are analysed. It was stated and numerically correlated that the wettability by lubricating medium influences the scuffing resistance. Additionally, the dependence of wettability on selected parameters of roughness and a time to scuffing activation have been stated. On that basis, it is proposed to reinforce concept of "oleophilic" and "oleophobic" properties of metallic surfaces as autonomous invariants determining the activation of catastrophic wear process under boundary lubricated conditions

Pharmaceutical product cross-contamination: industrial and clinical pharmacy practice

Therapeutic consultation by patients is made complete by drug management which is expected to solve the patients’ problems. Pharmaceutical product cross-contamination is a serious problem which has been detected as an obstacle towards successful therapeutic goals. In the pharmaceutical care of patients in developed countries, cross-contamination of drugs has been well addressed and controlled unlike in most developing countries including Tanzania. This review intends to provide insight into this problem, aiming at increasing awareness on the health impacts of crosscontamination on patients in order to promote preventive strategies employed in combating cross-contamination in both industrial and clinical pharmacy practice

Geological evaluation of posidonia and wealden organic-rich shales : geochemical and diagenetic controls on pore system evolution

PhD ThesisFree gas in shales occurs mainly in larger mesopores (width >6 nm) and macropores (width >50 nm) and is likely to be the first or even main contributor to gas production. Because evaluation of the storage capacity and final recovery of gas depends on distribution and connectivity of these pores, their correct quantification has become a focus point of advanced research. A major step for understanding pore systems in organic rich shales was made by recognition that under increasing thermal stress, decomposition of kerogen should progressively lead to development of organic porosity. Despite this, many questions concerning fate of organic porosity in organic rich rocks still remain unresolved. To date, several important attempts to link evolution of organic pores with maturation and organic matter content gave inconclusive and contradictory results. In this study, pore systems of the Lower Jurassic Posidonia and Lower Cretaceous Wealden shale, representing different mudrock types and covering a range of maturities, have been characterised. By integrating geochemical and petrophysical measurements, and with a detailed analysis of microscopic images we offered a unique approach for measuring porosity and pore characteristics on micrometre and centimetre scales with thorough understanding for a micrometer lithological variation. Key aims were to quantify the evolution of porosity associated with both organic matter and inorganic rock matrix as a function of maturity, and address the influence of mudrock heterogeneity on porosity change. Our experiments revealed a non-linear trend of porosity change with maturity in pores of all sizes, with an initial drop in the oil window as a result of mechanical compaction, chemical diagenesis, as well as pore-filling oil and bitumen. At comparable maturities, porosity and distribution of pores depend on the content of clays, organic matter, microfossils, silt grains and pore filling cement. In both Posidonia and Wealden, macropores (> 50 nm) account for merely up to 20% of total porosity physically measured, with the lowest percentage in the least mature samples. It was also demonstrated that gas sorption micropores are controlled by the amount of organic matter and clay minerals, and thus their microporous nature was confirmed. In terms of organic porosity development, we provided evidence that organic matter content and the path of its thermal decomposition control total porosities of the gas window shale. Importantly, neoformed intraorganic porosity is highly heterogeneous with 35% of organic particles containing visible pores (> 6 nm in diameter), and porosities of individual particles ranging from 0–50%. As a key result, we confirmed that porous zones in the gas window are associated with sites of bitumen retention and degradation. That indicates iii that the location of potential reservoirs of free gas should be linked to rigid zones, such as fossiliferous faecal pellets, or compaction shadows of mineral grains. Combined mercury injection and SEM data also showed that visible but potentially isolated macropores are connected, but only through throats below 20 nm. With the evolution of the porous network of bitumen saturating the shale matrix in the gas window, connectivity of the system changes from inorganic to organic dominated. The size of the pore throats, and the connectivity of the organic system in shales are likely key controls on the delivery of gas from pore to fracture and then to wellbore.Gas Shales in Europe projec

Avaliação do estado funcional e dos sintomas apresentados por pacientes internados na enfermaria clínica de um hospital universitário

Trabalho de Conclusão de Curso - Universidade Federal de Santa Catarina. Curso de Medicina. Departamento de Clinica Medica

Wetting of anisotropic sinusoidal surfaces - experimental and numerical study of directional spreading

Directional wettability, i.e. variation of wetting properties depending on the surface orientation, can be achieved by anisotropic surface texturing. A new high precision process can produce homogeneous sinusoidal surfaces (in particular parallel grooves) at the micro-scale, with a nano-scale residual roughness five orders of magnitude smaller than the texture features. Static wetting experiments have shown that this pattern, even with a very small aspect ratio, can induce a strong variation of contact angle depending on the direction of observation. A comparison with numerical simulations (using Surface Evolver software) shows good agreement and could be used to predict the fluid-solid interaction and droplet behaviour on textured surfaces. Two primary mechanisms of directional spreading of water droplets on textured stainless steel surface have been identified. The first one is the mechanical barrier created by the textured surface peaks, this limits spreading in perpendicular direction to the surface anisotropy. The second one is the capillary action inside the sinusoidal grooves accelerating spreading along the grooves. Spreading has been shown to depend strongly on the history of wetting and internal drop dynamics

Narcotics in rheumatology

Patients with rheumatic conditions often suffer from related chronic pain. When first-line traditional medications such as acetaminophen and anti-inflammatory medications do not suffice, then other options are needed. The traditional medications may ultimately not provide sufficient pain relief, or alternatively, they can pose as a contraindication due to underlying hypertension, renal, and/or hepatic disease. Therefore, narcotics are an alluring alternative, which if used in a multidisciplinary and systematic approach to the patient, can prove to be quite beneficial in the lives of these patients

Surface morphology in engineering applications: Influence of roughness on sliding and wear in dry fretting

Influence of initial surface roughness on friction and wear processes under fretting conditions was investigated experimentally. Rough surfaces (Ra=0.15-2.52 [mu]m) were prepared on two materials: carbon alloy (AISI 1034) and titanium alloy (Ti-6Al-4V). Strong influence of initial surface roughness on friction and wear processes is reported for both tested materials. Lower coefficient of friction and increase in wear rate was observed for rough surfaces. Wear activation energy is increasing for smoother surfaces. Lower initial roughness of surface subjected to gross slip fretting can delay activation of wear process and reduce wear rate; however, it can slightly increase the coefficient of friction