The Experts below are selected from a list of 267 Experts worldwide ranked by ideXlab platform
Joakim Schon - One of the best experts on this subject based on the ideXlab platform.
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Coefficient of Friction and wear of a carbon fiber epoxy matrix composite
Wear, 2004Co-Authors: Joakim SchonAbstract:Abstract The objective is to measure the Coefficient of Friction for composite in contact with composite in reciprocal sliding as it is important for modeling bolted joints and predicting their failure load. The wear mechanisms have been studied using scanning electron microscope and contact surfaces from a fatigue-loaded joint have been studied on a carbon fiber/epoxy matrix composite, HTA-6376. While the value of initial Coefficient of Friction recorded was 0.65 that for the peak after wear in was 0.74, suggesting that a significant part of the applied load to a joint at quasi-static failure will be transferred by Friction force. Since all wear mechanisms observed in the Friction specimen were also observed in the joint specimen it is possible to use the measured Coefficient of Friction from the Friction specimens on the joints. The main wear mechanisms were slow wear of the matrix on the original surface and cracking of the fiber–matrix interface, causing both the matrix and fibers to exhibit fracture.
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Coefficient of Friction for aluminum in contact with a carbon fiber epoxy composite
Tribology International, 2004Co-Authors: Joakim SchonAbstract:Abstract In bolted joints, a large part of the load is transferred by Friction. The objective of this investigation is to measure the Coefficient of Friction for carbon fiber epoxy matrix composite, HTA-6376, in contact with aluminum, 3637-77, in reciprocal sliding. During testing, the Coefficient of Friction increased initially with number of cycles and after reaching a maximum, slowly decreased. The initial Coefficient of Friction is approximately 0.23 and the peak Coefficient of Friction after wear in is approximately 0.68. The Coefficient of Friction is independent of normal load. During wear, cracks are formed at the fiber–matrix interface, which causes the matrix layer on the original composite surface to break off in pieces. It also causes single fibers or groups of fibers to be broken off and removed from the surface. Pieces of carbon fiber caused depressions in the aluminum surface. The wear debris is reattached to the composite surface but not to the aluminum surface.
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Coefficient of Friction of composite delamination surfaces
Wear, 2000Co-Authors: Joakim SchonAbstract:The Coefficient of Friction of delamination surfaces from graphite fiber/epoxy matrix (IM7/8552) composites has been measured in reciprocating sliding. The worn surfaces were examined with a scanning electron microscope and the Friction and wear mechanisms were studied. The results show that after an initial wear-in of the surfaces the Coefficient of Friction will decrease with increasing number of reciprocal cycles as more load is carried by fiber/fiber and fiber/matrix contacts. The evolution of the Coefficient of Friction is related to whether the starting surfaces are covered with a matrix layer or if the fibers are visible. Any matrix layer will flow to the sides of the contact region, causing fibers to become visible. More of the load will be carried by fiber/fiber and fiber/matrix contacts and the Coefficient of Friction will decrease. The effective Coefficient of Friction depends on the amount of load carried by matrix/matrix, fiber/matrix and fiber/fiber contacts and their respective Coefficient of Friction. of the three types of contact, the matrix/matrix contact has the highest Coefficient of Friction, approximately 0.6. Matrix debris formed at the boundary of the contact regions and no wear of the fibers was observed.
J. G. Lenard - One of the best experts on this subject based on the ideXlab platform.
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The Effect of Temperature on the Coefficient of Friction in Flat Rolling
CIRP Annals, 2008Co-Authors: J. G. Lenard, S. KalpakjianAbstract:While it is acknowledged that one of the most important parameters affecting the magnitude of the Coefficient of Friction in metal forming processes is the temperature, relatively few experimental studies have been published that detail their exact relationship. The objective of the present work is 10 develop the required data that will allow the choice of the Frictional Coefficient to be made with confidence. In the present study the effect of temperature on the roll separating forces, roll torques and forward slip are measured during warm and hot rolling of commercially pure aluminum strips. The magnitude of the Coefficient of Friction is inferred by machine measured and predicted roll forces. The results indicate the μ is indeed a strong function of the temperature. In general, increasing the temperature leads to higher values of the Coefficient.
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The Coefficient of Friction During Hot Rolling of Low Carbon Steel Strips
Journal of Tribology-transactions of The Asme, 2002Co-Authors: John G. Lenard, J. G. Lenard, Leon Barbulovic-nadAbstract:Hot rolling tests were performed on low carbon steel strips with the objective of determining the Coefficient of Friction as a function of the process variables. The growth of the scale prior to rolling was controlled and the thickness of the layer of scale at the entry remained in the range of 20-100 μm, somewhat higher than in the finishing train of a hot strip mill. Roll separating forces, roll torques, the speed, the reduction and the entry temperature were monitored. The effective Coefficient of Friction was determined by using a one-dimensional model of the flat rolling process. The Coefficient was chosen to allow matching the measured and calculated roll force and the roll torque. An empirical relation, connecting the Coefficient of Friction to process variables was obtained by non-linear regression analysis.
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The effect of lubricant additives on the Coefficient of Friction in cold rolling
Journal of Materials Processing Technology, 1998Co-Authors: J. G. LenardAbstract:The effect of four boundary additives—lauryl alcohol, stearyl alcohol, lauric acid and stearic acid—in mineral seal oil, on the roll separating forces, roll torques and the Coefficient of Friction was investigated. The independent variables were the rolling speed, reduction and the concentration of the additives. Lauryl alcohol was the most effective in reducing the roll separating force while stearyl alcohol caused the largest reduction of the roll torque. The Coefficient of Friction, obtained by the use of Hill’s empirical relation, was the lowest when lauryl alcohol was used.
Simo-pekka Hannula - One of the best experts on this subject based on the ideXlab platform.
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effects of fabricated method on the Coefficient of Friction of al2o3 15 wt zro2 3 wt solid lubricant composites
Materials Science Forum, 2011Co-Authors: Erkin M Cura, Outi Söderberg, Simo-pekka HannulaAbstract:The Coefficient of Friction was very important factor for the applications of high temperature parts. In vehicles, the Coefficient of Friction was decreased due to lubricants as like engine oil etc. Lubricant such as oils is difficult to apply at high temperature. To apply high temperature parts, lubricants were demanded for high temperature stability. This work is to use the pulsed electric current sintering (PECS) technique and the atmospheric plasma spraying (APS) method in order to make self-lubricating Al2O3-15wt% ZrO2-solid lubricant composites. We focused on the Coefficient of Friction for the fabrication method of self-lubricating Al2O3-15wt% ZrO2-solid lubricant composites. We compared with the Coefficient of Friction of PECSed and APSed composites. The surface roughness of PECSed Al2O3-15wt% ZrO2-solid lubricant composites were 0.06 ~ 0.31 μm of Ra and 10.16 ~ 33.12 μm of Ry. In the case of APSed Al2O3-15wt% ZrO2-solid lubricant composites, as-coated samples were 6.56 ~ 11.42 μm of Ra and 59.68 ~ 81.79 μm of Ry, and polished samples were 1.12 ~ 3.70 μm of Ra and 11.66 ~ 32.22 μm of Ry. The Coefficient of Friction of PECSed and APSed Al2O3-15wt% ZrO2-solid lubricant composites were 0.19 ~ 0.49 and 0.41 ~ 0.61, respectively.
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Effects of Fabricated Method on the Coefficient of Friction of Al2O3-15 wt% ZrO2-3 wt% Solid Lubricant Composites
Materials Science Forum, 2011Co-Authors: M. Erkin Cura, Outi Söderberg, Simo-pekka HannulaAbstract:The Coefficient of Friction was very important factor for the applications of high temperature parts. In vehicles, the Coefficient of Friction was decreased due to lubricants as like engine oil etc. Lubricant such as oils is difficult to apply at high temperature. To apply high temperature parts, lubricants were demanded for high temperature stability. This work is to use the pulsed electric current sintering (PECS) technique and the atmospheric plasma spraying (APS) method in order to make self-lubricating Al2O3-15wt% ZrO2-solid lubricant composites. We focused on the Coefficient of Friction for the fabrication method of self-lubricating Al2O3-15wt% ZrO2-solid lubricant composites. We compared with the Coefficient of Friction of PECSed and APSed composites. The surface roughness of PECSed Al2O3-15wt% ZrO2-solid lubricant composites were 0.06 ~ 0.31 μm of Ra and 10.16 ~ 33.12 μm of Ry. In the case of APSed Al2O3-15wt% ZrO2-solid lubricant composites, as-coated samples were 6.56 ~ 11.42 μm of Ra and 59.68 ~ 81.79 μm of Ry, and polished samples were 1.12 ~ 3.70 μm of Ra and 11.66 ~ 32.22 μm of Ry. The Coefficient of Friction of PECSed and APSed Al2O3-15wt% ZrO2-solid lubricant composites were 0.19 ~ 0.49 and 0.41 ~ 0.61, respectively.
Kurt E Beschorner - One of the best experts on this subject based on the ideXlab platform.
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Coefficient of Friction testing parameters influence the prediction of human slips
Applied Ergonomics, 2018Co-Authors: Arian Iraqi, Rakie Cham, Mark S Redfern, Kurt E BeschornerAbstract:Abstract Measuring the available Coefficient of Friction (ACof) of a shoe-floor interface is influenced by the choice of normal force, shoe-floor angle and sliding speed. The purpose of this study was to quantify the quality of slip prediction models based on ACof values measured across different testing conditions. A dynamic ACof measurement device that tests entire footwear specimens (Portable Slip Simulator) was used. The ACof was measured for nine different footwear-contaminant combinations with two levels of normal force, sliding speed and shoe-floor angle. These footwear-contaminant combinations were also used in human gait studies to quantify the required Coefficient of Friction (RCof) and slip outcomes. The results showed that test conditions significantly influenced ACof. The condition that best predicted slip risk during the gait studies was 250 N normal force, 17° shoe-floor angle, 0.5 m/s sliding speed. These findings can inform footwear slip-resistance measurement methods to improve design and prevent slips.
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required Coefficient of Friction during level walking is predictive of slipping
Gait & Posture, 2016Co-Authors: Kurt E Beschorner, Devon L Albert, Mark S RedfernAbstract:The required Coefficient of Friction (RCof) is frequently reported in the literature as an indicator of slip propensity. This study aimed to further develop slip prediction models based on RCof by examining slips under moderately slippery conditions where the RCof was approximately equal to the available Coefficient of Friction. Baseline RCofs were found for normal walking trials and then an unexpected slip was introduced with a moderately slippery boot-floor contaminant combination for thirty-one subjects. Slip outcomes (i.e., whether a subject experienced a slip) were assessed based on the displacement of a marker placed on the heel. A logistic regression analysis was used to model the impact of RCof on slipping. Results showed that subjects who walked with a greater RCof were found to have a higher probability of slipping. The predicted probability of a slip across the RCof ranged from 3% to 95% and an increase of 0.01 in RCof was associated with a slipping odds ratio of 1.7. Thus, modest differences in RCof can have a dramatic impact on slip propensity. This study shows that RCof can be a sensitive and valid predictor of slipping in realistic Frictional environments.
Akira Azushima - One of the best experts on this subject based on the ideXlab platform.
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Coefficient of Friction at interface of lubricated upsetting process
Wear, 2012Co-Authors: Akira Azushima, Shigeki Yoneyama, Hiroshi UtsunomiyaAbstract:Abstract In the lubricated upsetting process, it is well known that the Coefficient of Friction over the contact surface between the tool and the workpiece is distributed nonuniformly and changes with the reduction in height and the position at the interface. In order to increase the reliability of the numerical simulation of cold forging processes, more precise input data of the Coefficient of Friction at the tool–workpiece interface have become necessary. In this study, in order to predict the Coefficient of Friction at the interface lubricated cylinder upset tests are carried out using a specimen of commercially pure aluminum and a liquid lubricant. The displacements of the points located at the interface are measured. The normal stress and the tangential stress acting on the interface are calculated by the finite element method, using the measured displacement. Then, the Coefficients of Friction are estimated using Amonton–Couloumb's Friction law. The Coefficients of Friction depend on the reduction in height and the position at the interface.
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Effect of Scale on Coefficient of Friction in Hot Sheet Rolling of Steel
Isij International, 2010Co-Authors: Akira Azushima, Yoshifumi NakataAbstract:The effect of scale on Coefficient of Friction in hot rolling was investigated by changing the scale thickness of Si–Mn steel, using the simulation testing machine developed by the authors. The simulation testing machine for the evaluation of the lubrication behavior consisted of a main stand, a substand, a furnace and a tension device. The rolling force and the rolling torque were measured and the Coefficients of Friction were calculated by changing the scale thickness, the reduction and the emulsion concentration. The scale thicknesses were obtained by the control of the flow rate of Ar gas and the heating time at 800°C in the image furnace. The experiments were carried out at constant rolling conditions of a velocity ratio of 20, a rolling speed of 50 m/min and a furnace temperature of 800°C at the rolling reductions of 0.3, 0.5 and 1.0 mm. The colza oil was used as the base oil. The emulsion concentrations were 0.1 and 3.0 mass%. At an emulsion concentration of 3 mass%, the Coefficient of Friction at rolling reductions of 0.3 and 0.5 mm remains constant above 60 μm, whereas below 60 μm it increases with decreasing scale thickness. The Coefficient of Friction at a rolling reduction of 1.0 mm remains constant above 110 μm, whereas below 110 μm it increases with decreasing scale thickness. At an emulsion concentration of 0.1 mass%, the Coefficient of Friction at a rolling reduction of 0.3 mm increases with increasing scale thickness above 60 μm, whereas below 60 μm it increases with decreasing with scale thickness. The Coefficient of Friction at a rolling reduction of 0.5 mm increases with increasing scale thickness above 110 μm, whereas below 110 μm it increases with decreasing with scale thickness. The Coefficient of Friction at a rolling reduction of 1.0 mm remains constant above 110 μm, whereas below 110 μm it increases with decreasing scale thickness. The increase in the Coefficient of Friction for the specimens with a thinner layer of scale is due to the formation of white zones in which the scale is removed from the interface between scale and steel. For these specimens, the ratio of the Fe3O4 layer of the scale surface is higher and the black layer is observed on the roll surface after rolling.
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Prediction of effect of rolling speed on Coefficient of Friction in hot sheet rolling of steel using sliding rolling tribo-simulator
Journal of Materials Processing Technology, 2010Co-Authors: Akira Azushima, Yoshifumi Nakata, Takahiro ToriumiAbstract:Abstract In order to reduce the rolling force and the roll wear, the lubricants have been used in hot rolling of steel. In order to evaluate the tribological behavior at the interface between roll and workpiece in hot steel rolling, it is important to measure the Coefficient of Friction and examine the effect of the tribological factors on the Coefficient of Friction. In this paper, the effect of the rolling speed on the Coefficient of Friction is investigated using the tribo-simulator testing machine for hot rolling developed by the authors. The workpiece used is SPHC. The roll material is SKD11 and the surface roughnesses are 0.05 μm, 0.2 μm and 0.8 μm. The rolling tests are carried out at a temperature of 800 °C during a rolling distance of 400 mm, changing the rolling speed from 15 to 70 m/min. The colza oil is used as a base oil and the emulsion concentrations are 0.1% and 3.0%. The Coefficient of Friction at an emulsion concentration of 3.0% is independent on the rolling speed. On the other hand, the Coefficient of Friction at an emulsion concentration of 0.1% decreases with increasing rolling speed in the lower range of rolling speed, but it increases in increasing rolling speed in the higher range of rolling speed.
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effect of surface roughness of roll on Coefficient of Friction in hot rolling forming processing and thermomechanical treatment
Tetsu To Hagane-journal of The Iron and Steel Institute of Japan, 2008Co-Authors: Akira Azushima, Weidong Xue, Yoshiaki YoshidaAbstract:In order to understand the tribological behavior at the interface between roll and workpice in hot steel rolling, it is important to measure the Coefficient of Friction and examine the effect of the tribological factors on the Coefficient of Friction. In this paper, the effects of the surface roughness of roll on the Coefficient of Friction are investigated by using the tribo-simulatior testing machine for hot rolling developed by the authors. The workpice material used is SPHC. The roll material is SKD11 and the surface roughnesses are 0.1, 0.2, 0.4 and 0.8 μm Ra. The rolling tests are carried out at a temperature of 800°C during a rolling distance of 400 mm, changing the rolling speed from 50 to 70 m/min. The colza oil is used as a base oil and the emulsion concentrations are 0.1 and 3.0%. The Coefficient of Friction at an emulsion concentration of 3.0% dose not depend on the surface roughness of roll. However, the Coefficient of Friction at an emulsion concentration of 0.1% decreases with increasing surface roughness of roll up to a surface roughness of 0.3 μm Ra and over 0.3 μm Ra it increases with increasing surface roughness of roll.