Articles de revues : « Search friction »

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Keymolen, Esther. « In Search of Friction ». Techné : Research in Philosophy and Technology 25, n^o 3 (2021) : 354–78. http://dx.doi.org/10.5840/techne20211124150.

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Considering the key mediating role that smartphones play in everyday life, a postphenomenological analysis to better understand how we have power over these devices, how these artifacts empower and simultaneously can overpower us, seems highly relevant. This article will show that in order to engage in such a much-needed postphenomenological analysis, we will first have to address three fundamental, methodological challenges. The first challenge is brought forth by the personalized interface of smartphones, hindering postphenomenologists to unravel the so-called multistability of the device through variational analysis, which typically is an anchoring point in their analysis. The second challenge is that the networked ontology of smartphones disrupts the ideal-typical hermeneutic relationship end-users have with their smartphone. The third, closely related challenge, comes with the general focus of postphenomenology on the everyday life, first-person experience of users, which leaves many, significant stabilities hidden behind the smartphone’s interface.

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Kou, Bin, Yao Huang, Pengpeng Wang, Dongcheng Ren, Jie Zhang et Shijie Guo. « A New Parameter Identification Method for Industrial Robots with Friction ». Machines 10, n^o 5 (9 mai 2022) : 349. http://dx.doi.org/10.3390/machines10050349.

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Commonly used intelligent algorithms that are used to identify the parameters of friction of industrial robots have poor accuracy or involve complex coding, which is not conducive to their use in engineering. This paper uses the random wandering simulated annealing-based variable-step beetle antennae search (RWSAVSBAS) algorithm to identify the parameters of friction of industrial robots. The moment of friction of the third joint of the robot is experimentally obtained and used to establish a Stribeck friction model. Following this, the RWSAVSBAS algorithm is used to identify the frictional parameters of the industrial robot. These parameters can be used to accurately predict the friction-induced torque of the robot.

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Shao, Liang, Chi Jin, Arno Eichberger et Cornelia Lex. « Grid Search Based Tire-Road Friction Estimation ». IEEE Access 8 (2020) : 81506–25. http://dx.doi.org/10.1109/access.2020.2991792.

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Othman, M. O., et A. Seireg. « A Procedure for Evaluating the Friction Properties of Hertzian Contacts Under Reciprocating Sliding Motion ». Journal of Tribology 112, n^o 2 (1 avril 1990) : 361–64. http://dx.doi.org/10.1115/1.2920265.

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The study reported in this paper presents an empirical procedure for evaluating the frictional properties in Hertzian contacts subjected to sinusoidal sliding motion. It utilizes the friction induced lateral vibration of a rod to evaluate the parameters of the frictional function using a gradient search which minimize the error between the analytical response and the friction-induced experimental vibrations. The use of sinusoidal sliding motion at the resonant frequencies of the vibrating rod is found to considerably minimize the effect of external vibrations on the experimental results.

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Hiki, Y., M. Tanahashi et Shin Takeuchi. « Search for High Damping Metallic Glasses ». Key Engineering Materials 319 (septembre 2006) : 151–56. http://dx.doi.org/10.4028/www.scientific.net/kem.319.151.

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In a hydrogen-doped metallic glass, there appear low-temperature and high-temperature internal friction peaks respectively associated with a point-defect relaxation and the crystallization. The high-temperature-side slope of low-temperature peak and also the low-temperature-side slope of high-temperature peak enhance the background internal friction near the room temperature. A hydrogen-doped Mg-base metallic glass was proposed as a high-damping material to be used near and somewhat above the room temperature. Stability of the high damping was also checked.

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Cebul, Randall D., James B. Rebitzer, Lowell J. Taylor et Mark E. Votruba. « Unhealthy Insurance Markets : Search Frictions and the Cost and Quality of Health Insurance ». American Economic Review 101, n^o 5 (1 août 2011) : 1842–71. http://dx.doi.org/10.1257/aer.101.5.1842.

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We analyze the effect of search frictions in the market for commercial health insurance. Frictions increase insurance premiums (enough to transfer 13.2 percent of consumer surplus from fully insured employer groups to insurers—approximately $34.4 billion in 1997); and increase insurance turnover (by 64 percent for the average policy). This rent transfer harms consumers and—when combined with heightened turnover—reduces incentives to invest in future health. We also find that a publicly financed insurance option can improve the efficiency of private insurance markets by reducing search friction induced distortions in pricing and marketing efforts. (JEL D83 G22, I18)

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Mortensen, Dale T. « Markets with Search Friction and the DMP Model ». American Economic Review 101, n^o 4 (1 juin 2011) : 1073–91. http://dx.doi.org/10.1257/aer.101.4.1073.

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Nourinejad, Mehdi, Amir Gandomi et Matthew J. Roorda. « Illegal parking and optimal enforcement policies with search friction ». Transportation Research Part E : Logistics and Transportation Review 141 (septembre 2020) : 102026. http://dx.doi.org/10.1016/j.tre.2020.102026.

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Ehsani, Sayeh, Marie-Alice Mandich, Tarek H. El-Bialy et Carlos Flores-Mir. « Frictional Resistance in Self-Ligating Orthodontic Brackets and Conventionally Ligated Brackets ». Angle Orthodontist 79, n^o 3 (1 mai 2009) : 592–601. http://dx.doi.org/10.2319/060208-288.1.

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Abstract Objective: To compare the amount of expressed frictional resistance between orthodontic self-ligating brackets and conventionally ligated brackets in vitro as reported in the literature. Methods: Several electronic databases (Medline, PubMed, Embase, Cochrane Library, and Web of Science) were searched without limits. In vitro studies that addressed friction of self-ligating brackets compared with conventionally ligated brackets were selected and reviewed. In addition, a search was performed by going through the reference lists of the selected articles to identify any paper that could have been missed by the electronic searches. Results: A total of 70 papers from the electronic database searches and 3 papers from the secondary search were initially obtained. After applying the selection criteria, only 19 papers were included in this review. A wide range of methods were applied. Conclusions: Compared with conventional brackets, self-ligating brackets produce lower friction when coupled with small round archwires in the absence of tipping and/or torque in an ideally aligned arch. Sufficient evidence was not found to claim that with large rectangular wires, in the presence of tipping and/or torque and in arches with considerable malocclusion, self-ligating brackets produce lower friction compared with conventional brackets.

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Ding, Li, Xingcheng Li, Qilin Li et Yuan Chao. « Nonlinear Friction and Dynamical Identification for a Robot Manipulator with Improved Cuckoo Search Algorithm ». Journal of Robotics 2018 (2018) : 1–10. http://dx.doi.org/10.1155/2018/8219123.

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This paper concerns the problem of dynamical identification for an industrial robot manipulator and presents an identification procedure based on an improved cuckoo search algorithm. Firstly, a dynamical model of a 6-DOF industrial serial robot has been derived. And a nonlinear friction model is added to describe the friction characteristic at motion reversal. Secondly, we use a cuckoo search algorithm to identify the unknown parameters. To enhance the performance of the original algorithm, both chaotic operator and emotion operator are employed to help the algorithm jump out of local optimum. Then, the proposed algorithm has been implemented on the first three joints of the ER-16 robot manipulator through an identification experiment. The results show that (1) the proposed algorithm has higher identification accuracy over the cuckoo search algorithm or particle swarm optimization algorithm and (2) compared to linear friction model the nonlinear model can describe the friction characteristic of joints better.

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Sarasiri, Nuapett, Kittiwong Suthamno et Sarawut Sujitjorn. « Bacterial Foraging-Tabu Search Metaheuristics for Identification of Nonlinear Friction Model ». Journal of Applied Mathematics 2012 (2012) : 1–23. http://dx.doi.org/10.1155/2012/238563.

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This paper proposes new metaheuristic algorithms for an identification problem of nonlinear friction model. The proposed cooperative algorithms are formed from the bacterial foraging optimization (BFO) algorithm and the tabu search (TS). The paper reports the search comparison studies of the BFO, the TS, the genetic algorithm (GA), and the proposed metaheuristics. Search performances are assessed by using surface optimization problems. The proposed algorithms show superiority among them. A real-world identification problem of the Stribeck friction model parameters is presented. Experimental setup and results are elaborated.

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Paul, Harold R., et James A. Scherocman. « Friction Testing of Tack Coat Surfaces ». Transportation Research Record : Journal of the Transportation Research Board 1616, n^o 1 (janvier 1998) : 6–12. http://dx.doi.org/10.3141/1616-02.

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In response to litigation because of an accident case involving tack coat on a construction project, a field trial was evaluated to determine frictional characteristics of tack-coated surfaces. When a literature search on this topic returned little information, state Department of Transportation materials engineers were surveyed to determine the state of the practice with respect to tack coat operations. On the basis of the survey responses and the existing litigation, a field trial was conducted to evaluate friction numbers on tack coat materials. Variables included residual asphalt content (three levels); test time (three levels); combinations of wet, dry, and flushed surface conditions (seven levels); and replicate testing. It was found that at typical residual asphalt rates reported by states and specified in Louisiana, reduced friction capability existed for up to 7 h after application. With the friction numbers obtained, traffic should be maintained only at controlled low speeds if at all. However, the residual asphalt content appeared heavier than in typical practice. At residual application rates that were typical of practice, friction properties were produced that would allow traffic at moderate speeds. After several days, friction numbers returned to the original condition because of traffic or weather abrasion.

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Sun, Qinqin, Xiuye Wang et Ye-Hwa Chen. « Modern explorations of the Brachistochrone-related problem : using the Udwadia–Kalaba approach ». Mathematics and Mechanics of Solids 24, n^o 6 (11 novembre 2018) : 1849–72. http://dx.doi.org/10.1177/1081286518808070.

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Modern explorations regarding the search for a curve subject to a minimization principle and its inverse, namely the search for the minimization object based on a given curve, are made. By using the Udwadia–Kalaba theory, which subsumes the Coulomb friction force as a non-ideal constraint, we obtain the analytic expression of the equation of motion for a particle moving along the Brachistochrone cycloid curve under Coulomb friction. Then we perform the inverse problem for the moving particle. That is, while the Brachistochrone cycloid curve is given, we seek the corresponding minimization object. Both the situations with and without friction are addressed. Finally, we return to the search for a curve subject to a minimization principle to complete the loop. However, this time we presume the minimization object is the total travel time, which was addressed in the classical Brachistochrone problem (hence, frictionless), while recognizing the presence of Coulomb friction. All three analyses come to meet at the special case when there is no friction. Our research reveals profound insights that have not been reported previously. The loop analysis also suggests a new angle for the study of dynamic systems.

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Mazur, Jacek, Renata Różyło, Monika Wójcik, Marian Panasiewicz, Kazimierz Zawiślak et Paweł Sobczak. « Development of an Innovative Attachment Determining Friction Parameters for Quality Assessment in Sustainable Processing ». Sustainability 14, n^o 20 (11 octobre 2022) : 12986. http://dx.doi.org/10.3390/su142012986.

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New trends forcing the attractiveness of products in sustainable processing make it necessary to search for innovative methods of measuring their quality. For various biological materials, their physical properties, such as friction parameters in addition to their texture, are very important. Friction determines the course of many technological operations, e.g., transport, cleaning, sorting, fractionation, storage, and dosing of materials. An innovative friction adapter was developed for biological raw materials and tested on samples of self-produced soap. A 3D printing method for the production of this attachment was used. The soap sample loads were 100, 200, and 500 g, and the measurements of frictional resistance were carried out in contact with dry or water moistened synthetic leather, in comparison with sandpaper. For all tested variants (surfaces × loads), the initial friction of soap ranged from 0.853 N to 5.316 N, dynamic friction from 0.123 N to 3.542 N. The static and dynamic friction coefficients ranged from 0.019 to 0.151 and 0.006 to 0.131, respectively. The developed adapter for testing the friction coefficient ensures easy and quick assembly of the analyzed sample, its quick exchange and stable operation in both measurement directions, i.e., pushing and pulling the sample, as well as the possibility of using a lower applied load.

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Kula, Piotr, Robert Pietrasik, Sylwester Pawęta et Jarosław Komorowski. « MOS2/WS2/FINELPN COMPOSITE LAYERS – A NEW APPROACH TO LOW FRICTIONAL COATINGS FOR PISTON RINGS ». Tribologia 301, n^o 3 (30 novembre 2022) : 49–58. http://dx.doi.org/10.5604/01.3001.0016.1024.

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In the search for alternative processes of technologically difficult and environmentally dangerous galvanic chromium coatings on cast iron piston rings, composite coatings of low-friction nanoparticles MoS2, WS2 and/or rGO embedded in a hard matrix of iron nitrides have been investigated. Laboratory tribological and operational tests on a real aircraft engine have been carried out to select the optimal technological parameters and microstructures of low frictional layers. A dry friction coefficient of 0.13 has been obtained for the best of the processes, i.e., four times lower than for raw reference samples (0.55). According to that technological option, the low-friction layers were produced for a set of rings for three cylinders of a Boxer aircraft engine and tested comparatively in an operational test with the rings in the other three cylinders. The experimental engine has passed the operational test obtaining the assumed power performance, fuel consumption and admission criteria of exhaust purity and oil purity.

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Тихомиров, Виктор, Viktor Tikhomirov, Надежда Новикова et Nadezhda Novikova. « Application of neurocomputing robust design to optimize the friction sintered powder material. » Bulletin of Bryansk state technical university 2014, n^o 3 (30 septembre 2014) : 81–84. http://dx.doi.org/10.12737/23225.

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The paper presents a methodology for selecting the optimal composition of the friction sintered powder material to the safety of the friction devices using a neurocomputer robust design to reduce the search time and reduce the cost of the experiment and the analysis of the computational experiment.

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Wang, Yuxiang, Zhangwei Chen, Hongfei Zu et Xiang Zhang. « An Optimized RBF Neural Network Based on Beetle Antennae Search Algorithm for Modeling the Static Friction in a Robotic Manipulator Joint ». Mathematical Problems in Engineering 2020 (12 février 2020) : 1–10. http://dx.doi.org/10.1155/2020/5839195.

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Friction is a nonlinear effect that occurs in all mechanical systems which may cause limit cycles, tracking errors, and other undesirable effects. Traditional static friction models cannot characterize all the friction situations. In recent years, neural network (NN) technique has been widely used to approximate the nonlinear function. In this paper, a new method which combines radical basis function neural network (BRFNN) with beetle antennae search (BAS) algorithm for modeling friction in a robotic joint is proposed. Velocity, load, and temperature are considered as the three factors that influence the static friction. It is shown that the proposed BAS-RBFNN possesses better performance in terms of faster convergence rate and higher accuracy.

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Willems, Phil, Corinne Lamb, Alastair Heptonstall et Jim Hough. « Search for stress dependence in the internal friction of fused silica ». Physics Letters A 319, n^o 1-2 (décembre 2003) : 8–12. http://dx.doi.org/10.1016/j.physleta.2003.09.070.

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Huang, Shiuh Jer, Chun Ming Chiu et M. C. Huang. « LuGre Friction Model Estimation of a Precision Table and Sliding Mode Control Design ». Solid State Phenomena 147-149 (janvier 2009) : 264–71. http://dx.doi.org/10.4028/www.scientific.net/ssp.147-149.264.

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Piezoelectric friction actuating mechanism is chosen to construct long traveling range sub-micro X-Y positioning table. LuGre friction model is employed to simulate the friction dynamics of this positioning mechanism. The optimization scheme of Matlab toolbox is adopted to search the optimal friction model parameters. However, this piezoelectric actuating system has obvious nonlinear and time-varying dead-zone offset control voltage due to the static friction and preload. The estimated LuGre dynamic model is still not accurate enough for model-based precision control design. Hence, the adaptive sliding mode control (SMC) with robust behavior is employed to design the nonlinear controller for this piezoelectric friction actuating mechanism. The Laypunov-like design strategy is adopted to achieve the system stability criterion. The dynamic experimental results of the proposed nonlinear controllers are compared with that of a model-based PID controller, too.

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Rosyid, Abdur, et Bashar El-Khasawneh. « Identification of the Dynamic Parameters of a Parallel Kinematics Mechanism with Prismatic Joints by Considering Varying Friction ». Applied Sciences 10, n^o 14 (14 juillet 2020) : 4820. http://dx.doi.org/10.3390/app10144820.

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This study proposed a novel approach for the offline dynamic parameter identification of parallel kinematics mechanisms in which the friction is significant and varying. Since the friction is significant, it should be incorporated to provide an accurate dynamic model. Furthermore, the varying normal forces as a result of the changing posture of the mechanism lead to varying friction forces, specifically varying static and Coulomb friction forces. By considering this variation, the static and Coulomb friction parameters are identified as coefficients instead of forces. A bound-constrained optimization technique using an iterative global search tool was employed in this work to minimize the residual errors while maintaining the physical feasibility of the solutions. Moreover, the friction was modeled by using the nonlinear Stribeck friction model since a linear friction model was not sufficient, whereas the variation of the friction followed the variation of the normal forces, which were evaluated through the Lagrange multipliers in the constrained dynamic model of the mechanism. The solutions obtained were verified by using some trajectories that were different from those used in the identification.

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Lin, Chih Jer, Shen Kai Yu, Bo Yen Ho et Chin Sheng Chen. « Identification on Nonlinear Friction Model and Tracking Control for a Ball-Screw Actuated Stage Using Modified Charge System Search ». Key Engineering Materials 625 (août 2014) : 423–29. http://dx.doi.org/10.4028/www.scientific.net/kem.625.423.

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High precise positioning and high-speed performance are demanded for servo mechanical systems in recent industry. However, the nonlinear friction is a main factor to make the positioning mechanism imprecision. To improve the positioning the positioning precision of stages driven by ball-screws, there are two types of compensations including model and non-model based methods. In this study, the LuGre friction Model is applied to model the nonlinear friction behavior for a ball-screw driven stage. A Modified Charge Search System (MCSS) was proposed to identify the system’s parameter. After the system’s parameters are obtained, a feed-forward control integrated with a disturbance observer is proposed to eliminate the external disturbance and improve its tracking performance.

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Trzepiecinski, Tomasz, et Hirpa G. Lemu. « Recent Developments and Trends in the Friction Testing for Conventional Sheet Metal Forming and Incremental Sheet Forming ». Metals 10, n^o 1 (25 décembre 2019) : 47. http://dx.doi.org/10.3390/met10010047.

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Friction is the main phenomenon that has a huge influence on the flow behavior of deformed material in sheet metal forming operations. Sheet metal forming methods are one of the most popular processes of obtaining finished products, especially in aerospace, automobile, and defense industries. Methods of sheet forming are carried out at different temperatures. So, it requires tribological tests that suitably represent the contact phenomena related to the temperature. The knowledge of the friction properties of the sheet is required for the proper design of the conditions of manufacturing processes and tools. This paper summarizes the methods used to describe friction conditions in conventional sheet metal forming and incremental sheet forming that have been developed over a period of time. The following databases have been searched: WebofKowledge, Scopus, Baztool, Bielefield Academic Search Engine, DOAJ Directory of Open Access Journals, eLibrary.ru, FreeFullPdf, GoogleScholar, INGENTA, Polish Scientific Journals Database, ScienceDirect, Springer, WorldCat, WorldWideScience. The English language is selected as the main source of review. However, in a limited scope, databases in Polish and Russian languages are also used. Many methods of friction testing for tribological studies are selected and presented. Some of the methods are observed to have a huge potential in characterizing frictional resistance. The application of these methods and main results have also been provided. Parameters affecting the frictional phenomena and the role of friction have also been explained. The main disadvantages and limitations of the methods of modeling the friction phenomena in specific areas of material to be formed have been discussed. The main findings are as follows—The tribological tests can be classified into direct and indirect measurement tests of the coefficient of friction (COF). In indirect methods of determination, the COF is determined based on measuring other physical quantities. The disadvantage of this type of methods is that they allow the determination of the average COF values, but they do not allow measuring and determining the real friction resistance. In metal forming operations, there exist high local pressures that intensify the effects of adhesion and plowing in the friction resistance. In such conditions, due to the plastic deformation of the material tested, the usage of the formula for the determination of the COF based on the Coulomb friction model is limited. The applicability of the Coulomb friction model to determine the COF is also very limited in the description of contact phenomena in hot SMF due to the high shear of adhesion in total contact resistance.

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Giustolisi, O., L. Berardi et T. M. Walski. « Some explicit formulations of Colebrook–White friction factor considering accuracy vs. computational speed ». Journal of Hydroinformatics 13, n^o 3 (26 octobre 2010) : 401–18. http://dx.doi.org/10.2166/hydro.2010.098.

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The Colebrook–White formulation of the friction factor is implicit and requires some iterations to be solved given a correct initial search value and a target accuracy. Some new explicit formulations to efficiently calculate the Colebrook–White friction factor are presented herein. The aim of this investigation is twofold: (i) to preserve the accuracy of estimates while (ii) reducing the computational burden (i.e. speed). On the one hand, the computational effectiveness is important when the intensive calculation of the friction factor (e.g. large-size water distribution networks (WDN) in optimization problems, flooding software, etc.) is required together with its derivative. On the other hand, the accuracy of the developing formula should be realistically chosen considering the remaining uncertainties surrounding the model where the friction factor is used. In the following, three strategies for friction factor mapping are proposed which were achieved by using the Evolutionary Polynomial Regression (EPR). The result is the encapsulation of some pieces of the friction factor implicit formulae within pseudo-polynomial structures.

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Choi, S. H., C. O. Lee et H. S. Cho. « Friction compensation control of an electropneumatic servovalve by using an evolutionary algorithm ». Proceedings of the Institution of Mechanical Engineers, Part I : Journal of Systems and Control Engineering 214, n^o 3 (1 mai 2000) : 173–84. http://dx.doi.org/10.1243/0959651001540546.

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A poppet-type electropneumatic servovalve developed in this study utilizes a poppet directly operated by a moving-coil actuator in the metering stage and is controlled by a digital controller. This servovalve is insensitive to air contamination and has no problem of air leakage at null, but it has relatively large friction between the O-rings installed in the peripheral grooves of the balance pistons and the valve sleeve. For friction compensation control, a static friction model that enables simulation of the stick-slip phenomena and a dynamic model that captures the friction behaviour such as presliding displacement and varying break-away force are presented. The parameters for the friction models are identified by utilizing an evolution strategy, one of the evolutionary algorithms, which is a probabilistic global search algorithm based on the model of natural evolution. These friction models are then used in designing a non-linear friction compensation controller. It is found in the experiment that the electropneumatic servovalve has almost no hysteresis and that the friction compensation control significantly improves valve performance. The experimental results of the open loop test on poppet positioning agree well with simulation results of the valve model with identified friction parameters. It is also shown that the experimental results of friction compensation control using a static friction model show a small steady state error but those using a dynamic friction model show almost no such error.

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Chainarong, Suppachai, Thanatkij Srichok, Rapeepan Pitakaso, Worapot Sirirak, Surajet Khonjun et Raknoi Akararungruangku. « Variable Neighborhood Strategy Adaptive Search for Optimal Parameters of SSM-ADC 12 Aluminum Friction Stir Welding ». Processes 9, n^o 10 (11 octobre 2021) : 1805. http://dx.doi.org/10.3390/pr9101805.

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In this study, we present a new algorithm for finding the optimal friction stir welding parameters to maximize the tensile strength of a butt joint made of the semisolid material (SSM) ADC 12 aluminum. The welding parameters were rotational speed, welding speed, tool tilt, tool pin profile, and rotational direction. The method presented is a variable neighborhood strategy adaptive search (VaNSAS) approach. The process of finding the optimal friction stir welding parameters comprises five steps: (1) identifying the type and range of friction stir parameters using a literature survey; (2) performing experiments according to (1); (3) constructing a regression model using the response surface method optimizer (RSM optimizer); (4) using VaNSAS to find the optimal parameters for the model obtained from (3); and (5) confirming the results from (4) using the parameter levels obtained from (4) to perform real experiments. The computational results revealed that the tensile strength generated from VaNSAS was 3.67% higher than the tensile strength obtained from the RSM optimizer parameters. The optimal parameters obtained from VaNSAS were a rotation speed of 2200 rpm, a welding speed of 108.34 mm/min, a tool tilt of 1.23 Deg, a tool pin profile of a hexagon, and a rotational direction of clockwise.

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Liu, LL, et ZY Wu. « A new identification method of the Stribeck friction model based on limit cycles ». Proceedings of the Institution of Mechanical Engineers, Part C : Journal of Mechanical Engineering Science 228, n^o 15 (2 février 2014) : 2678–83. http://dx.doi.org/10.1177/0954406214521604.

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This paper presents a new parameter identification method of the Stribeck friction model based on limit cycles. A single degree of freedom mass spring system driven by a belt is studied, and the Stribeck friction model is established between the mass and belt. Limit cycle oscillation will occur when the system is unstable. The limit cycle curve is described by some main shape characteristic parameters using the modified Freeman chain code method. Thus, the Stribeck friction parameters can be identified by using the ergodic search method to minimize the Euclidean distance of the theoretical and identified limit cycle shape characteristic parameters. The parameter identification method based on limit cycles is different from the traditional identification methods. It only needs the displacement and velocity responses of the system instead of the measurement of the friction force or motor voltage/current. All of these works can provide the reference for the research work of the friction parameter identification.

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Mistakidis, E. S., et P. D. Panagiotopoulos. « The search for substationarity points in the unilateral contact problems with nonmonotone friction ». Mathematical and Computer Modelling 28, n^o 4-8 (août 1998) : 341–58. http://dx.doi.org/10.1016/s0895-7177(98)00126-5.

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Frens, M. A., et J. N. Van der Geest. « Scleral Search Coils Influence Saccade Dynamics ». Journal of Neurophysiology 88, n^o 2 (1 août 2002) : 692–98. http://dx.doi.org/10.1152/jn.00457.2001.

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The scleral search coil technique is commonly used for recording eye movements. The goal of this paper is to investigate to what extent the placement of scleral search coils onto the eyes influences the kinematics of saccades. To that end saccadic eye movements of human subjects were recorded with an infrared video system, while they wore coils and we compared the main sequence properties with recordings in which no coils were mounted on the eyes. It was found that saccades last longer (by about 8%) and become slower (by about 5%) when both eyes wear coils. This is truly due to the fact that the coils are on the eyes and not due to other factors that are part of this method, such as the scleral anesthesia. The influence of coils in both eyes was also observed when one coil was mounted on one eye only. Therefore the effect that the coils have on the eye movements cannot be attributed to purely mechanical factors, such as inertial load on the eyeball or increased friction. Rather the coils appear to change the oculomotor command signals that drive the saccadic eye movements.

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Carrara, Valdemir, et Hélio Koiti Kuga. « Estimating Friction Parameters in Reaction Wheels for Attitude Control ». Mathematical Problems in Engineering 2013 (2013) : 1–8. http://dx.doi.org/10.1155/2013/249674.

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The ever-increasing use of artificial satellites in both the study of terrestrial and space phenomena demands a search for increasingly accurate and reliable pointing systems. It is common nowadays to employ reaction wheels for attitude control that provide wide range of torque magnitude, high reliability, and little power consumption. However, the bearing friction causes the response of wheel to be nonlinear, which may compromise the stability and precision of the control system as a whole. This work presents a characterization of a typical reaction wheel of 0.65 Nms maximum angular momentum storage, in order to estimate their friction parameters. It used a friction model that takes into account the Coulomb friction, viscous friction, and static friction, according to the Stribeck formulation. The parameters were estimated by means of a nonlinear batch least squares procedure, from data raised experimentally. The results have shown wide agreement with the experimental data and were also close to a deterministic model, previously obtained for this wheel. This model was then employed in a Dynamic Model Compensator (DMC) control, which successfully reduced the attitude steady state error of an instrumented one-axis air-bearing table.

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Jassim, Najwa Wasif, et Shaymaa alsafi. « Study The Consequence of Fly Ash on Some of Physical Soil Characteristics ». IOP Conference Series : Earth and Environmental Science 961, n^o 1 (1 janvier 2022) : 012089. http://dx.doi.org/10.1088/1755-1315/961/1/012089.

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Abstract Study the consequence of adding fly ash (FA) on the Atterberg limit; cohesions and internal friction of angles of the verified soil was the aim of this search. The tested soil according to the system of unified soil classification was (CH) group. Fly ash (FA) was added to the tested soil samples in 1, 3, 6, 9, 12, 15 & 18 % by weight of samples. This study shows that once the tested soil mixed with (FA); the values of cohesion reduced; while the values of the angles of internal frictions increases. The drop in the soil sample cohesion when mixed with 18% of (FA) was 34%, were noteworthy increase in the angles of internal friction. For all soil samples as the percentages of adding (FA) increase, the decrease in the index of plasticity amounts increase also at different rates. The adding of (FA) produced a reduction in the liquid limits; plastic limits and henceforth the plasticity index of the tested soil sample at rate of 43%, 48% and 37% correspondingly. The plasticity index losses took place at the first 3%, at a lesser rate, then the rate increased at 18% of additive and because nearly constant.

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Härtwig, Fabian, Lars Lorenz, Stefan Makowski, Matthias Krause, Carsten Habenicht et Andrés Fabián Lasagni. « Low-Friction of ta-C Coatings Paired with Brass and Other Materials under Vacuum and Atmospheric Conditions ». Materials 15, n^o 7 (30 mars 2022) : 2534. http://dx.doi.org/10.3390/ma15072534.

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Vacuum environments provide challenging conditions for tribological systems. MoS2 is one of the materials commonly known to provide low friction for both ambient and vacuum conditions. However, it also exhibits poor wear resistance and low ability to withstand higher contact pressures. In search of wear-resistant alternatives, superhard hydrogen-free tetrahedral amorphous carbon coatings (ta-C) are explored in this study. Although known to have excellent friction and wear properties in ambient atmospheres, their vacuum performance is limited when self-paired and with steel. In this study, the influence of the paired material on the friction behavior of ta-C is studied using counterbodies made from brass, bronze, copper, silicon carbide, and aluminum oxide, as well as from steel and ta-C coatings as reference materials. Brass was found to be the most promising counterbody material and was further tested in direct comparison to steel, as well as in long-term performance experiments. It was shown that the brass/ta-C friction pair exhibits low friction (µ < 0.1) and high wear in the short term, irrespective of ambient pressure, whereas in the long term, the friction coefficient increases due to a change in the wear mechanism. Al2O3 was identified as another promising sliding partner against ta-C, with a higher friction coefficient than that of brass (µ = 0.3), but considerably lower wear. All other pairings exhibited high friction, high wear, or both.

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Peng, Li, Zhan, Wang et Yang. « Finite Element Method-Based Skid Resistance Simulation Using In-Situ 3D Pavement Surface Texture and Friction Data ». Materials 12, n^o 23 (21 novembre 2019) : 3821. http://dx.doi.org/10.3390/ma12233821.

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Skid resistance is an important surface characteristic that influences roadway safety. Various studies have been performed to understand the interaction between pavement and tires through numerical simulation for skid resistance prediction. However, the friction parameters required for simulation inputs are generally determined by objective assumptions. This paper develops a finite element method (FEM)-based skid resistance simulation framework using in-situ 3D pavement surface texture and skid resistance data. A 3D areal pavement model is reconstructed from high resolution asphalt pavement surface texture data. The exponential decay friction model is implemented in the simulation and the interface friction parameters required for the simulation are determined using the binary search back-calculation approach based on a trial process with the desired level of differences between simulated and observed skid numbers. To understand the influence of texture characteristics on interface friction parameters, the high-resolution 3D texture data is separated into macro- and micro-scales through Butterworth filtering and various areal texture indicators are calculated at both levels. Principal component analysis (PCA) regression analysis is conducted to quantify the relationship between various texture characteristics and the interface friction parameters. The results from this study can be used to better prepare the inputs of friction parameters for FEM simulation.

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Despard, Erin. « Photographic social media, designed landscapes and urban, place-based visibilities : in search of friction ». Journal of Aesthetics & ; Culture 7, n^o 1 (1 janvier 2015) : 28242. http://dx.doi.org/10.3402/jac.v7.28242.

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Lu, Yongzhong, Danping Yan et David Levy. « Friction coefficient estimation in servo systems using neural dynamic programming inspired particle swarm search ». Applied Intelligence 43, n^o 1 (10 janvier 2015) : 1–14. http://dx.doi.org/10.1007/s10489-014-0621-2.

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Beroun, Stanislav, Pavel Brabec, Ondřej Dráb et Robert Voženílek. « Influence of the Mean Friction Pressure on the Temperatures of the Combustion Engine ». Applied Mechanics and Materials 390 (août 2013) : 350–54. http://dx.doi.org/10.4028/www.scientific.net/amm.390.350.

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The development of a new combustion engines is connected with endeavor for escalation of the total efficiency. Escalation of the total efficiency can be: minimization of the mechanical losses in the combustion engines or minimization of the unsuitable equipment capacity of accessories. Now research and development programs of a manufacturer of the combustion engines search effectual equipment and method for this escalation of the total efficiency. The escalation of the total efficiency is important for a minimization fuel consumption and consequently for lower emissions. The paper deals with the problem of frictional losses in internal combustion engines. It is described by measuring station built and further are shown measured values for a small car. Furthermore, in the paper presented to the selected function to approximate the measured values of friction losses, depending on the temperatures of the work fluids for a concrete RPM mode.

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Kersten, Mik, et Gail C. Murphy. « Reducing Friction for Knowledge Workers with Task Context ». AI Magazine 36, n^o 2 (21 juin 2015) : 33–41. http://dx.doi.org/10.1609/aimag.v36i2.2581.

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Knowledge workers perform work on many tasks per day and often switch between tasks. When performing work on a task, a knowledge worker must typically search, navigate and dig through file systems, documents and emails, all of which introduce friction into the flow of work. This friction can be reduced, and productivity improved, by capturing and modeling the context of a knowledge worker’s task based on how the knowledge worker interacts with an information space. Captured task contexts can be used to facilitate switching between tasks, to focus a user interface on just the information needed by a task and to recommend potentially other useful information. We report on the use of task contexts and the effect of context on productivity for a particular kind of knowledge worker, software developers. We also report on qualitative findings of the use of task contexts by a more general population of knowledge workers.

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Skorynina, P. A., A. V. Makarov, V. V. Berezovskaya, E. A. Merkushkin et N. M. Chekan. « THE INFLUENCE OF NANOSTRUCTURING FRICTION TREATMENT ON MICROMECHANICAL AND CORROSIVE CHARACTERISTICS OF STABLE AUSTENITIC CHROMIUM-NICKEL STEEL ». Frontier materials & ; technologies, n^o 4 (2021) : 80–88. http://dx.doi.org/10.18323/2782-4039-2021-4-80-88.

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Friction treatment is an effective method to increase the strength and wear resistance of austenitic chromium-nickel steels. Previously, the authors identified that the high level of mechanical properties of metastable austenitic steels is achieved at the intensive development of deformation γ→α'-transformation. However, the presence of deformation martensite in the austenitic steel structure can negatively affect its anti-corrosion properties. The search for ways to improve the strength characteristics of stable austenitic chromium-nickel steel while maintaining high resistance to corrosion destruction is the up-to-date line of research. In this paper, to evaluate the mechanical properties of 03Cr16Ni14Mo3Ti steel in the hardened condition and after friction treatment, the authors applied the technique of measuring the hardness using the restored print and the method of instrumental micro-indentation, which allows recording the indenter loading and unloading diagrams. The corrosion failure resistance of steel was studied in general corrosion tests. The authors compared the corrosion rate of austenitic steel after grinding, electropolishing, and friction treatment; using scanning electron microscopy and optical profilometry, studied steel surfaces subjected to these treatments and determined their roughness. Nanostructuring friction treatment provides surface hardening of stable austenitic steel up to 570 HV 0.025. The study showed the high efficiency of friction treatment application to increase the strength characteristics and resistance of steel surface layer to elastic and plastic deformation. The authors identified that austenitic steel is characterized by similar corrosion rates km=(3.26–3.27)∙105 (g/cm2∙h) after electrolytic polishing (the structure of large-crystal austenite) and after frictional treatment (sub-micro/nanocrystalline austenite structure), while mechanical grinding leads to a twofold increase in the corrosion rate of 03Cr16Ni14Mo3Ti steel due to the occurrence of microcracks and metal breakouts on the polished surface. The research justified the determining role of the quality of the surface formed by various treatments (roughness, the presence of continuity defects) in ensuring the corrosion resistance of stainless steel.

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KAŁUŻNY, Jarosław, Jerzy MERKISZ, Aleksander STEPANENKO, Emil WRÓBLEWSKI, Bartosz GAPIŃSKI, Adam PIASECKI et Dawid GALLAS. « Piston assembly in the most powerful 2.0l diesel engine – case study of the current tribological system and innovative concepts for the future ». Combustion Engines 171, n^o 4 (1 novembre 2017) : 127–33. http://dx.doi.org/10.19206/ce2017-421.

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This article is a contribution to the ongoing debate on the scenario of the vehicle powertrains development. The directions of the internal combustion engines development in search of the possibility of effective economic and ecological indicators improvement have been indicated. It has been pointed out that this goal can be achieved through the use of nanotechnology in order to exceed the downsizing barriers resulting from the permissible mechanical loads for conventional materials. The article presents the study of the construction and materials used in the piston assembly of the most advanced four-cylinder, compression-ignition diesel engine currently in manufacture. Original concepts of nanotechnology have been proposed to reduce friction losses in major friction components of future engines with extremely high loads. The main idea is to verify the hypothesis that the sub-micron surface texture of the friction components obtained in the process of applying anti-wear outer layers can lead to an effective reduction of friction losses under real engine operating conditions. Computer simulations of the effects of introducing the surface texture in the upper sealing ring on friction loss confirm this hypothesis by showing friction value being reduced by 3-4% relative to the standard ring profile. In the summary, further advanced technologies designed to effectively utilize the unique properties of carbon nanotubes have been described.

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Ciavarella, Michele, et Antonio Papangelo. « SOME SIMPLE RESULTS ON THE MULTISCALE VISCOELASTIC FRICTION ». Facta Universitatis, Series : Mechanical Engineering 17, n^o 2 (26 juillet 2019) : 191. http://dx.doi.org/10.22190/fume190215025c.

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The coefficient of friction due to bulk viscoelastic losses corresponding to multiscale roughness can be computed with Persson's theory. In the search for a more complete understanding of the parametric dependence of the friction coefficient, we show asymptotic results at low or large speed for a generalized Maxwell viscoelastic material, or for a material showing power law storage and loss factors at low frequencies. The ascending branch of friction coefficient at low speeds highly depends on the rms slope of the surface roughness (and hence on the large wave vector cutoff), and on the ratio of imaginary and absolute value of the modulus at the corresponding frequency, as noticed earlier by Popov. However, the precise multiplicative coefficient in this simplified equation depends in general on the form of the viscoelastic modulus. Vice versa, the descending (unstable) branch at high speed mainly on the amplitude of roughness, and this has apparently not been noticed before. Hence, for very broad spectrum of roughness, friction would remain high for quite few decades in sliding velocity. Unfortunately, friction coefficient does not depend on viscoelastic losses only, and moreover there are great uncertainties in the choice of the large wave vector cutoff, which affect friction coefficient by orders of magnitudes, so at present these theories do not have much predictive capability.

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Ghate, Chetan, et Debojyoti Mazumder. « Employment targeting in a frictional labor market ». Indian Growth and Development Review 12, n^o 2 (11 novembre 2019) : 242–62. http://dx.doi.org/10.1108/igdr-06-2018-0065.

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Purpose Governments in both developing and developed economies play an active role in labor markets in the form of providing both formal public sector jobs and employment through public workfare programs. The authors refer to this as employment targeting. The purpose of the paper is to consider different labor market effects of employment targeting in a stylized model of a developing economy. In the context of a simple search and matching friction model, the authors show that the propensity for the public sector to target more employment can increase the unemployment rate in the economy and lead to an increase in the size of the informal sector. Design/methodology/approach The model is an application of a search and matching model of labor market frictions, where agents have heterogeneous abilities. The authors introduce a public sector alongside the private sector in the economy. Wage in the private sector is determined through Nash bargaining, whereas the public sector wage is exogenously fixed. In this setup, the public sector hiring rate influences private sector job creation and hence the overall employment rate of the economy. As an extension, the authors model the informal sector coupled with the other two sectors. This resembles developing economies. Then, the authors check the overall labor market effects of employment targeting through public sector intervention. Findings In the context of a simple search and matching friction model with heterogeneous agents, the authors show that the propensity for the public sector to target more employment can increase the unemployment rate in the economy and lead to an increase in the size of the informal sector. Employment targeting can, therefore, have perverse effects on labor market outcomes. The authors also find that it is possible that the private sector wage falls as a result of an increase in the public sector hiring rate, which leads to more job creation in the private sector. Originality/value What is less understood in the literature is the impact of employment targeting on the size of the informal sector in developing economies. The authors fill this gap and show that public sector intervention can have perverse effects on overall job creation and the size of the informal sector. Moreover, a decrease in the private sector wage due to a rise in public sector hiring reverses the consensus findings in the search and matching literature which show that an increase in public sector employment disincentivizes private sector vacancy postings.

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Lu, Lianshan, et Dong Li. « Determination of Wall Friction Velocity of the Turbulent Boundary Layer by Two-Parameter Nonlinear Curve Fitting ». Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University 38, n^o 2 (avril 2020) : 253–60. http://dx.doi.org/10.1051/jnwpu/20203820253.

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Hot-wire anemometer is a fundamental tool for flow field measurement, and has been widely adopted in research of turbulent flow. A turbulent boundary layer was generated by a trip wire and a piece of sandpaper in the low-speed wind tunnel, and the time-averaged velocity profiles at three different streamwise stations in the boundary layer were measured with IFA-300 constant temperature anemometer. Targeting the dimensionless velocity profile model White Law of the turbulent boundary layer, a nonlinear curve fitting MATLAB program for two parameters, which were theoretical original point of wall coordinate y0 and wall friction velocity uτ, was developed. Based on the measured time-averaged velocity profiles, the program was adopted to determine y0 and uτ of the three streamwise stations. It is found that the initial search domain and search step size of y0 and uτ have no effect on the fitting results if the physical solutions are included in the domain. It is also found that the selected fitting velocities data are closely related to the results. The value of the friction velocity with high precision will be obtained by this nonlinear curve fitting method if the highest fitting velocity data point dose not fall into the wake region. The method given in this paper is simple in programming and reliable in fitting results, and it is of practical to obtain the wall friction velocity of the turbulent boundary layer.

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Kolesnikov, I. V., et P. A. Koropets. « ANALYSIS OF DYNAMIC PROCESSES IN GEARE COUPLING OF HELICOPTER TAIL ROTOR TRANSMISSION ». Journal of Dynamics and Vibroacoustics 6, n^o 1 (20 mars 2020) : 6–13. http://dx.doi.org/10.18287/2409-4579-2020-6-1-6-13.

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The operation of the Mi-26 helicopters has shown that the operating time for rejection of splined gear couplings of the tail rotor transmission can differ by about 30 times. This fact is the reason for the search for dynamic processes that violate the stationary of the loading modes of the transmission couplings. Based on the analysis of the kinematics and dynamics of the clutch, it is shown in this work that when sliding in "tooth-spline" friction pairs, frictional self-oscillations can develop, leading to additional dynamic loads in the transmission elements and, as a consequence, a decrease in the working life of the clutches. The type of self-oscillations, their parameters (frequency, amplitude), as well as the stability of the transmission in relation to frictional self-oscillations depend on the tribological characteristics of the "tooth-slot" contact, which require additional experimental research. The results of this work can be useful in planning field tests and processing the data obtained.

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IORDACHE, Daniela-Monica, Eduard-Laurenţiu NITU et Lia BOTILA. « Macroscopic and microscopic analysis of friction stir welding ofpolyethylene ». University of Pitesti. Scientific Bulletin - Automotive Series 30, n^o 1 (1 novembre 2020) : 1–6. http://dx.doi.org/10.26825/bup.ar.2020.006.

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The automotiveindustry is one of the most dynamic, advanced and innovative industries in Europe, being in constant search of solutions to reduce fuel consumption and pollutant emissions while maintaining or even improving the safety of passengers. One of the main directions in which the research of all car manufacturers is focused to reduce the weight of the car, through the increasing use of light metal alloys and polymeric materials. Polyethylene is one of the most widely used polymeric materials in the world, being widespread in many industries.The increasing use of this category of materials has led to the need to develop new reliable and efficient techniques for joining different materials to be used in complex structures. In the aeronautical and aerospace field, polymeric materials are used due to their low weight. The paper presents the macroscopic and microscopic analysis of the joining of these materials by FSW.

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Shankar, S., M. Manikandan et G. Raja. « Evaluation of tribological properties of Ceiba pentandra (kapok) seed oil as an alternative lubricant ». Industrial Lubrication and Tribology 70, n^o 3 (9 avril 2018) : 506–11. http://dx.doi.org/10.1108/ilt-04-2017-0103.

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Purpose The decrease in availability of mineral oils and their environmental hazards created the need to search for alternate bio-based oils. The aim of this study is to investigate the friction and wear characteristics of kapok (Ceiba pentandra) oil as a bio-lubricant. Design/methodology/approach The wear and friction characteristics between steel-steel contact under lubrication were found using a pin-on-disk tribometer under different loads and sliding speeds, respectively. The corrosion and oxidation stability of the test lubricants were also analyzed. The worn surfaces of the specimen are analyzed with the help of an optical microscope. The obtained results were compared with palm oil and mineral oil (SAE20W 40). Findings From the investigation, it is found that the kapok oil possess a lower coefficient of friction and wear rate than palm and mineral oil. It is also found that the coefficient of friction varies proportionally and the wear rate varies inversely with the sliding speed as expected. Originality/value The present results confirm that the kapok oil can be used as an alternative lubricant to reduce the demand for mineral-based oil lubricants.

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Pinevich, Elena, Yuriy Lazarev, Nikolay Bolgarov, Dmitry Altynov et Yuri Fatyushin. « Mathematical model of the influence of the rheology of lubricating compositions on the safety of rolling stock movement ». Journal of Physics : Conference Series 2131, n^o 2 (1 décembre 2021) : 022021. http://dx.doi.org/10.1088/1742-6596/2131/2/022021.

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Abstract The article deals with the search for rational and balanced solutions to ensure maximum safety of rolling stock movement, taking into account the minimization of costs and technical measures. The paper presents a mathematical model for calculating the effect of rheological characteristics of lubricants on the service life of heavy-loaded friction units of rolling stock. The scheme of interaction of a wheel with a rail at a single-point contact is presented in the form of contacts of two cylinders of infinite length. The results of numerical analysis of the found analytical dependences of the influence of the plasticity parameter on the coefficient of friction, the influence of the plasticity parameter on the supporting force created by the lubricant layer during the movement of surfaces are presented. The influence of the coefficient of friction on the safety of rolling stock movement in the curved sections of the track is established.

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Petrov, E. P., et D. J. Ewins. « Analytical Formulation of Friction Interface Elements for Analysis of Nonlinear Multi-Harmonic Vibrations of Bladed Disks ». Journal of Turbomachinery 125, n^o 2 (1 avril 2003) : 364–71. http://dx.doi.org/10.1115/1.1539868.

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An analytical formulation for the vectors of contact forces and the stiffness matrix of the nonlinear friction contact interface is developed for the analysis of multi-harmonic vibrations in the frequency domain. The contact interface elements provided here an exact description of friction and unilateral contact forces at the interacting surfaces, taking into account the influence of the variable normal load on the friction forces, including the extreme cases of separation of the two surfaces. Initial gaps and interferences at the contact nodes, which affect the normal force, as well as the unilateral action of the normal force at the contact surface, are all included in the model. The accurate calculation of the force vector and the tangent stiffness matrix provides a very reliable and fast convergence of the iteration process used in the search for the amplitudes of nonlinear vibrations of bladed disks. Numerical investigations demonstrate excellent performance with respect to speed, accuracy and stability of computation.

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Grebenuk, G., et M. Veshkin. « Internal friction influence on the calculation results and rod system optimization under impulse action ». Journal of Physics : Conference Series 2131, n^o 3 (1 décembre 2021) : 032086. http://dx.doi.org/10.1088/1742-6596/2131/3/032086.

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Abstract An algorithm for calculating elastic rod systems under the action of impulse loads, using a complex model of internal friction in the material, has been developed and implemented in software. Very short (instantaneous) and extended in time impulses are considered as variants of impulse action. The importance of taking into account the vibration energy dissipation due to internal friction in the material of the structure is shown, considering impulse effects. The implemented software module is used to calculate the dynamic responses of the system in the search for the optimal solution of the control program for the selected variable parameters, target and restrictive functions. The problem of optimizing a flat frame system loaded with static and impulse loads has been posed and solved. An algorithm for finding an optimal solution is considered. Variants of dividing variable parameters into generalized groups are discussed. The minimum volume of material, spent on the structure, is taken as an optimality criterion. Analysis of the influence of the pulse duration of a given value on the calculation results without and with internal friction, as well as a comparative analysis of the optimal designs obtained without and with internal friction in the material and various tolerances for horizontal displacements. The results obtained indicate a significant effect of internal friction on the characteristics of the optimal design, especially with active movement restrictions.

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Liao, Jian, Fuming Zhou et Jianbo Zheng. « An Improved Parameter Identification Algorithm for the Friction Model of Electro-Hydraulic Servo Systems ». Sensors 23, n^o 4 (12 février 2023) : 2076. http://dx.doi.org/10.3390/s23042076.

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Friction is an inherent nonlinear disturbance that can lead to creeping, jitter, and decreased tracking precision in an electro-hydraulic servo system. In this paper, the LuGre friction model is used to describe the dynamic and static characteristics of the friction force of a servo system comprehensively. Accurate identification of model parameters is key to implementing friction compensation. However, traditional genetic identification algorithms have the shortcomings of a premature solution, slow convergence, and poor accuracy. To address these shortcomings, this paper proposes an improved adaptive genetic identification algorithm. The proposed algorithm selects evolutionary processes adaptively according to the population concentration in the initial stage of population evolution. Moreover, it adjusts the crossover probability and the mutation probability to identify a local optimum accurately and converge to the global optimum rapidly. During the late stage of population evolution, the accuracy of the global optimal solution can be improved by reducing the search range of identification parameters. The simulation results show that the relative error of the model parameter values identified by the proposed algorithm is reduced to less than 1% and the convergence speed is faster. Compared with the existing traditional genetic algorithm and adaptive genetic algorithm, the overall performance of the proposed method is better. This study provides a feasible and highly accurate identification method for parameter identification of friction models used in electro-hydraulic servo systems.

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Stoyanov, Pantcho, Rolf Merz, Markus Stricker, Michael Kopnarski et Martin Dienwiebel. « Achieving Ultra-Low Friction with Diamond/Metal Systems in Extreme Environments ». Materials 14, n^o 14 (7 juillet 2021) : 3791. http://dx.doi.org/10.3390/ma14143791.

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In the search for achieving ultra-low friction for applications in extreme environments, we evaluate the interfacial processes of diamond/tungsten sliding contacts using an on-line macro-tribometer and a micro-tribometer in an ultra-high vacuum. The coefficient of friction for the tests with the on-line tribometer remained considerably low for unlubricated sliding of tungsten, which correlated well with the relatively low wear rates and low roughness on the wear track throughout the sliding. Ex situ analysis was performed by means of XPS and SEM-FIB in order to better understand the underlying mechanisms of low friction and low-wear sliding. The analysis did not reveal any evidence of tribofilm or transferfilm formation on the counterface, indicating the absence of significant bonding between the diamond and tungsten surfaces, which correlated well with the low-friction values. The minimal adhesive interaction and material transfer can possibly be explained by the low initial roughness values as well as high cohesive bonding energies of the two materials. The appearance of the wear track as well as the relatively higher roughness perpendicular to the sliding indicated that abrasion was the main wear mechanism. In order to elucidate the low friction of this tribocouple, we performed micro-tribological experiments in ultra-high vacuum conditions. The results show that the friction coefficient was reduced significantly in UHV. In addition, subsequently to baking the chamber, the coefficient of friction approached ultra-low values. Based on the results obtained in this study, the diamond/tungsten tribocouple seems promising for tribological interfaces in spacecraft systems, which can improve the durability of the components.

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Dmitriev, Sergey, Vladimir Malikov et Anatoly Sagalakov. « Research on the welded seams of aluminum alloys using super-miniature eddy current transducers ». MATEC Web of Conferences 212 (2018) : 01001. http://dx.doi.org/10.1051/matecconf/201821201001.

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Based on the eddy current transducer of the transformer type, a measuring system has been developed that makes it possible to investigate the welded joints obtained by friction stir welding (FSW). The main technical information about the eddy current converter being used is given, and a measurement procedure is described that allows to search for defects in welded seams of aluminum plates. The device allows to automatically change the main operating frequency of the device and the cutoff frequency of the filtration system. The experiments were carried out on aluminum-magnesium alloy plates being connected by friction welding. In the article, the results of measurements are presented, allowing to estimate the quality of a welded seam and to answer a question on reliability of welding.

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