Abstract The rolling is an efficient and economical approach for the manufacturing of strip or plate metals, it plays an important role because of its versatility and its high production rate in the manufacture of various products with uniform cross-sectional area. Without the knowledge of the influences of the variables such as friction conditions, material properties, and workpiece geometry on the process mechanics, it will not be possible to design and control the equipment adequately, or to predict and prevent the occurrence of failures. According to modeling by numerical has become a major tool in rolling research. By using the proper criterion, de-pending upon the production requirements along with the modeling results, the process efficiency, productivity and quality can be increased and the down time of the mill and cost operation can be reduced. In this study, investigated that it do not consider to work hardening and consider to work hardening during the rolling process from Von Karman theory. We can realize friction coefficient, reduction ratio, rolling force, rolling torque, neutral point, and pressure distribution relation, then from measuring rolling force, torque, neutral point can inverse to solve friction coefficient and pressure distribution. Result that we found the error of direct and inverse solution about rolling friction coefficient was less than 5 %, and the coef-ficient of friction was found to increase with reduction and rolling force and neutral point.

ABSTRACT The objective of this study is to obtain the friction coefficient of lubricants in tube hydroforming of guiding zone. Lubricants, universal testing machine, and friction test machine in tube hydroforming of guiding zone are used to carry out the experiments of aluminum alloy tubes. Lubricants are categorized according to their performance as follows: (1) oils, (2) emulsions, and (3) slide lacquer. Different lubricants tests, it is known that the best lubrication is derived from slide lacquer, while oils showed the poorest behavior. Different internal pressure tests, it is known that greater internal pressure causes the coefficient of friction decreasing. Different sliding velocity, it is known that sliding velocity does not affect the coefficient of friction at 100mm/min. And using CCD which is an optical instrument obtains the surface of tubes after experiments.

Smectite clay minerals are among the most common minerals in subduction zone megathrusts faults at shallow depth and in landslide decollements. Consequently, deformation processes at seismic slip rates (ca. 1 m/s) in smectites contribute to control the mechanics of megathrust earthquakes and landslide collapses. To investigate the deformation processes, rotary shear experiments on smectite-rich gouge layers (70/30 wt.% Ca-montmorillonite/opal) were performed. The experiments were conducted at ambient temperature and at 5 MPa normal stress. The gouges were sheared under vacuum (<0.001 mbar) and room humidity (i.e., water depleted) or in the presence of liquid water (i.e., water rich) conditions, at slip rates of 0.0003 <V <1.5 m/s and displacements of 0.1 <d <30 m. The temperature evolution with slip was measured with thermocouples and modelled numerically. Permeability of the gouge layer was measured with the pore pressure oscillation method prior to the rotary experiments. Before and after the experiments, the mineral and amorphous material content in wt.% were determined via quantitative X-ray powder diffraction and the microstructures investigated via scanning and transmission electron microscopy. The activation of deformation processes was strongly controlled by the water content of the gouge layers. Under water depleted conditions, grainsize reduction producing nanoparticles controlled the evolution of the friction coefficient f at all slip rates. Coseismic dynamic weakening (f = 0.2 - 0.3) occurred by combined thermal decomposition or melting (with decreasing water content) and pressurization of water released by dehydration of smectite interlayer. Under water rich conditions, grain size reduction was minor and development of nano-foliations occurred. At all slip rates, the friction coefficient rapidly decreased at the onset of slip. The large initial weakening (to f <0.15) was due to the presence of a film of water lubricating the surfaces of the sub-parallel smectite grains forming the nano-foliation in combination with shear-enhanced water pressurization. Then, friction coefficient evolved depending on the balance between dissipation of pore pressures, dehydration of smectite interlayer and thickening of the nano-foliation layers. At higher displacement and slip rates, sustained dynamic weakening was aided by vaporization of pore water. Expulsion of water determined a switch to deformation processes typical of water depleted conditions. In nature, the presence of liquid water in smectites has a lubricating effect, pressurizes the slipping zone and renders the smectite-rich gouges prone to accommodate large seismic slips. During megathrust earthquakes, such lubricating effect may result in the easy propagation of seismic ruptures in smectite- and water-rich sediments at shallow depths. Similarly, the presence of water can promote large displacements during landslide collapse.

Axial piston pumps and motors are widely used in heavy-duty applications and play a fundamental role in hydrostatic and power split drives. The mechanical power losses in hydraulic piston pumps come from the friction between parts in relative motion. The improvement, albeit marginal, in overall efficiency of these components may significantly impact the global efficiency of the machine. The friction between slipper and swash plate is a functional key in an axial piston pump, especially when the pump (at low rotational speed or at partial displacement) works in the critical areas where the efficiency is low. The application of special surface treatments have been exploited in pioneering works in the past, trying different surface finishing or adding ceramic or heterogeneous metallic layers. The potential of structured coatings at nanoscale, with superhydrophobic and oleophobic characteristics, has never been exploited. Due to the difficulty to reproduce the real working conditions of axial piston pump slippers, it has been made a hydraulic test bench properly designed in order to compare the performance of nano-coated slippers with respect to standard ones. The nano-coated and standard slippers have been subjected to the following working conditions: a test at variable pressure and constant rotational speed, a test at constant pressure and variable rotational speed. The comparison between standard and nanocoated slippers, for both working conditions, shows clearly that more than 20% of friction reduction can be achieved using the proposed nano-coating methodology.

This thesis deals with tests of forming operations, which are used to determine coefficient of friction. In the theoretical part of thesis, the individual tests are described in details, with the greatest emphasis on the upsetting test. In the experimental part of thesis was perform upsetting test on the cylindrical and ring samples. Coefficient of friction of the cylindrical samples was determined by a calculation method and ring samples were evaluated using diagram of calibration. The thesis includes comparison of the result received on lubricant and unlubricated samples and method for determined coefficient of friction. Graphite Delta 144 was used as a lubricant. This result show that the lubricant has a positive effect on forming process.

<p>The work material in metal working operations always showssome kind of anisotropy. In order to simplify the theoreticalanalysis, especially considering bulk deformation processes,anisotropy is usually neglected and the material is assumed tobe isotropic. On the other hand, the analysis that consideredthe influence of anisotropy seldom incorporates the influenceof friction. For predicting the material flow during plasticdeformation and for predicting the final material properties ofthe product, adequate descriptions of both flow stress curvesand coefficients of friction have to be developed.</p><p>In the present work a number of experimental methods fordetermining the anisotropy have been utilized and compared:Yield loci, strain ratios (R-values) and establishing flowstress-curves in different directions. The results show thatthe yield loci measurements are weak in predicting anisotropywhen the material strain hardening is different in differentdirections. It is concluded that also the strain ration(R-value) measurements are unreliable for describinganisotropy. The most trustable and useful results were foundfrom multi-direction determinations of the flow stresses.</p><p>Three typical cases of ring upsetting conditions wereanalyzed by theory (3D-FEM) and experiments:</p><p>    An anisotropic ring, oriented 900 to the axis ofrotational symmetrical anisotropy. The friction coefficientwas the same in all directions</p><p>    An isotropic ring. The friction coefficient was differentin different directions</p><p>    An anisotropic ring oriented 00 to the axis of rotationalsymmetrical anisotropy. The friction coefficient was the samein all directions</p><p>The cases 1) and 2) reveal that the influence of anisotropyon the ring deformation is quite similar to that obtained bychanging the frictional condition. The case 3) exposes that ifthe material flow caused by anisotropy is incorrectly referredto friction, the possible error of the friction coefficient canbe as high as 80% for a pronounced anisotropic material. Amodified two-specimen method (MTSM) has been establishedaccording to an inverse method. Experiments were carried ascylinder upsetting. Here both ordinary cylinders were used aswell as so-called Rastegaev specimen. Also plane straincompression tests were utilized. The results show that MTSM isable to evaluate the validity of a selected mathematical modelwhen both the friction coefficient and the flow stress areunknown for a certain process. MTSM can also be used toestimate the friction coefficient and flow stress provided thatthe selected mathematical model is adequate.</p><p><b>Key words:</b>Anisotropy, friction coefficient, flowstress, modified two-specimen method and FE-analysis</p>

The present study has the objective of evaluating the effect of lubricant features on the friction coefficient by using three different lubricants (two synthetics and one mineral), which are used in automotive transmissions. In order to perform experiments, it was used a ball-on-disc system. The disc was manufactured with the same mechanical properties as transmission gears and the ball was made of 52100 SAE steel. The test parameters were defined based on a dynamic analysis conducted using \"ISOCAD\" which takes into account the geometry of the gear and vehicle dynamics (applied force and speed) during the tribological experiments. In order to set the temperature parameter, the lubricant testing temperature of a standard fuel economy was used. Experiments were conducted in two different lubrication conditions: i (starved) and ii (fully flooded). After the parameters were defined, it was possible to calculate the oil film thickness and, thus define the lubrication regime reached in each condition. Mixed and/or boundary lubrication was obtained in all the tests. Results showed the relationship between the speed and the specific oil film using a Khonsari and Masjedi formulation (2014), which takes into account the effect of surface roughness and, it is based on Downson and Higginson\'s (1981) formulation. The chemical analysis of the lubricant showed a relationship between friction coefficient and the additives used in lubricants. These results also showed the oil performance under different temperatures, speeds and loads. The best results were obtained for a synthetic lubricant. / O presente estudo tem o objetivo de avaliar o efeito de propriedades dos lubrificantes sobre o coeficiente de atrito. Para tanto foram testados três lubrificantes diferentes (dois sintéticos e um mineral), que são utilizados em transmissões automotivas. Os experimentos foram conduzidos utilizando um sistema tribológico denominado \"ball-on-disc\". Os discos foram fabricados com as mesmas propriedades mecânicas das engrenagens de transmissão, já as esferas foram fabricadas com aço SAE 52100. Os parâmetros de teste foram definidos com base na análise dinâmica conduzida utilizando o software \"ISOCAD\", que leva em conta a geometria da engrenagem e a dinâmica do veículo (força aplicada e velocidade) durante os ensaios tribológicos. Para definir os parâmetros de temperatura, foram utilizadas as mesmas temperaturas encontradas durante o ensaio de economia de combustível padronizado. Experimentos foram realizados em duas condições de lubrificação diferentes: i) fornecimento limitado de lubrificante, ou \"Starved\" e ii) condição de lubrificação imersa, ou \"Fully flooded\". Depois dos parâmetros definidos, foi possível calcular a espessura de filme de óleo, de forma a definir o regime de lubrificação alcançado em cada condição. Lubrificação mista e limítrofe foi obtida todas as condições de testes. Os resultados mostraram a relação entre a velocidade e o filme de óleo específico usando uma formulação de Khonsari e Masjedi (2014), que leva em conta o efeito da rugosidade da superfície e baseia-se na formulação de Downson e Higginson (1981). A análise química do lubrificante mostrou que existe uma relação entre o coeficiente de atrito e os aditivos utilizados nos lubrificantes. Estes resultados também mostram o desempenho dos lubrificantes em diferentes temperaturas, velocidades e cargas. Os melhores resultados foram obtidos para um lubrificante sintético.

Lubricin, or proteoglycan 4 (PRG4), is a secreted, glycosylated protein that binds to cartilage surfaces, which functions as a boundary lubricant. The loss of lubricin from cartilage is identified as a major pathogenic factor in post-traumatic osteoarthritis (PTOA) that has now been the aim of therapeutic intervention. Intra-articular injection of PRG4 protein provides short-term benefits that might be extended using sustained delivery methods such as in gene therapy. Here we describe the development and testing of such therapy using adeno-associated virus (AAV) as a vector for the transfer of PRG4-green fluorescent protein (GFP) fusion gene. Our recombinant PRG4 gene produces a PRG4-GFP fusion protein to facilitate tracking of its expression and distribution on joint surfaces. We hypothesized that PRG4-GFP is fully functional as a cartilage lubricant and that PRG4-GFP produced in vivo is expressed by synoviocytes and other joint cells, and cartilage surfaces remained coated for several weeks up to months after intra-articular injection of the virus. PRG4-GFP showed lubricin-like cartilage binding in vitro, and lubrication immunoblot analysis confirmed that purified PRG4-GFP from cultured media conditioned by PRG4-GFP-transduced synoviocytes was heavily glycosylated, while confocal microscopy revealed binding of the fluorescent fusion protein to cartilage surfaces. Metal-on-cartilage friction tests showed that PRG4-GFP reduced friction coefficients to a degree comparable to that of synovial fluid and had strong chondro-protective effects in explanted cartilage exposed to shear loading. The chondrocyte viability after shear loading showed that PRG4-GFP had a strong chondro-protective effect on par with that of the synovial fluid. Confocal microscopy and immunohistology confirmed that cartilage surfaces in the stifle joints of mice injected with viruses were coated with PRG4-GFP for up to 2 or 4 weeks after the treatment. The overexpression of PRG4-GFP and coating of cartilage surfaces in the stifle joints of mice injected with Adeno-Associated Virus for the transfer of PRG4-GFP fusion gene (AAV-PRG4-GFP) was confirmed by confocal microscopy and immunohistology for up to 2 or 4 weeks post-injection. The μCT imaging and immunohistology in AAV-PRG4-GFP injected rabbit knees showed stronger inhibition in degeneration of damaged tissues than in AAV-GFP injected control group. Collectively these findings indicate that AAV-PRG4-GFP transduction is a valuable new tool for evaluating the effects of long-term lubricant supplementation on PTOA in animal models.

Diamond and diamond-like carbon films, with their exceptionally good mechanical, chemical, and optical properties, are the best materials as protective hard coatings for electronic devices and cutting tools. The biocompatibility of these materials makes it suitable for bone implants. The wide range applications of these films are hindered because of the high compressive stresses developed during the deposition. Use of carbide and nitride interfacial layers has emerged as one of the methods to reduce the compressive stresses.The present research focuses on the study of different materials as the interfacial layers for diamond and tetrahedral amorphous carbon films. For tetrahedral amorphous carbon AlN, Ta, TiN, TiC, TaN and W were investigated as the interlayer materials. The interlayer was deposited at different substrate temperatures to study the temperature induced changes in the residual stress. The tetrahedral amorphous carbon with TiN interlayer deposited at 300°C and 600°C exhibited a maximum reduction in the stress.TiN and TiC were deposited as interlayer for the diamond films on Ti-6Al-4V alloy. TiC has improved the adhesion of diamond with the substrate and exhibited less compressive stresses compared to TiN.

Small punch test (SPT) has been widely used to evaluate in-service materials in nuclear fusion facilities. Early use of SPTs is largely based on empirical relations or curve fitting from experimental data, while recent applications of SPTs take advantage of finite element methods. In this study, an improved inverse finite element analysis procedure is proposed to obtain constitutive relations from load-displacement curves recorded in SPTs. In addition, a parametric study is performed to evaluate the effects of SPT parameters including friction coefficient, punch head diameter, sample thickness, specimen scale and boundary conditions. The proposed inverse finite element (FE) method improves the accuracy of existing inverse FE methods, and the current parametric study provides a basis for the standardization of SPT procedures in the future.