Kliknij ten link, aby zobaczyć inne rodzaje publikacji na ten temat: Transient friction measurement.
Artykuły w czasopismach na temat „Transient friction measurement”
Utwórz poprawne odniesienie w stylach APA, MLA, Chicago, Harvard i wielu innych
Sprawdź 50 najlepszych artykułów w czasopismach naukowych na temat „Transient friction measurement”.
Przycisk „Dodaj do bibliografii” jest dostępny obok każdej pracy w bibliografii. Użyj go – a my automatycznie utworzymy odniesienie bibliograficzne do wybranej pracy w stylu cytowania, którego potrzebujesz: APA, MLA, Harvard, Chicago, Vancouver itp.
Możesz również pobrać pełny tekst publikacji naukowej w formacie „.pdf” i przeczytać adnotację do pracy online, jeśli odpowiednie parametry są dostępne w metadanych.
Przeglądaj artykuły w czasopismach z różnych dziedzin i twórz odpowiednie bibliografie.
1
Li, Yufeng, i Aric Kumaran Menon. "A Theoretical Analysis of Breakaway Friction Measurement". Journal of Tribology 116, nr 2 (1.04.1994): 280–86. http://dx.doi.org/10.1115/1.2927210.
Pełny tekst źródłaStreszczenie:
The transient response of an I-beam friction measurement system to a constant disk acceleration is theoretically analyzed. The friction measurement system is modeled as a single-degree-of-freedom system. It is found that the true breakaway friction is different from the measured breakaway friction, and that the true breakaway time is also different from the measured breakaway time. The system measurement error is evaluated as a function of the acceleration, the effective mass, the spring stiffness, as well as the static and kinetic coefficients of friction. A closed-form dimensionless solution is derived for the system measurement error. If the dynamic effect of the measurement system can be neglected by selecting an appropriate effective mass and acceleration, the maximum possible discretization error can be estimated as a dimensionless function of the discretization frequency, the breakaway friction, the spring stiffness, and the acceleration.
2
Prölß, Maximilian, Hubert Schwarze, Thomas Hagemann, Philipp Zemella i Philipp Winking. "Theoretical and Experimental Investigations on Transient Run-Up Procedures of Journal Bearings Including Mixed Friction Conditions". Lubricants 6, nr 4 (1.12.2018): 105. http://dx.doi.org/10.3390/lubricants6040105.
Pełny tekst źródłaStreszczenie:
This paper focuses on the operating behavior of journal bearings for industrial machinery application during run-ups. For this purpose, a numerical simulation code that is based on a two-dimensional extended and generalized Reynolds equation and a full three-dimensional energy equation, was advanced by a theoretical model considering the effects of mixed friction and warming of journal components during start-up. The mixed friction routine contained the elastic half-spaces model proposed by Boussinesq, which considers the influence of rough surfaces by implementing flow factors and calculates additional stiffness and dissipation in areas with solid interactions. Furthermore, a transient term was added in the energy equation to consider the thermal inertia of journal, and bearing to ensure a realistic heating during run-ups. Results of the prediction were compared to experimental data taken from a special test rig built up for validation procedures. Besides the conventional sensors for temperature, oil flow, and relative motion between shaft and stator, a contact voltage measurement was installed to determine the intensity of mixed friction. The evaluation of experimental data by Stribeck curves, based on a shaft torsion measurement, indicated a significant influence of run-up time on frictional moment. The friction coefficient of the rotor bearing system was strongly influenced by the run-up time. A short run-up time reduced the frictional coefficient in the mixed lubrication regime while the opposite behavior was observed in the hydrodynamic lubrication regime. The numerical code predicted these tendencies in good agreement with experimental data, however, only if the transient energy model was applied.
3
Hoić, Matija, Alen Miklik, Milan Kostelac, Joško Deur i Andreas Tissot. "Analysis of the Accuracy of Mass Difference-Based Measurement of Dry Clutch Friction Material Wear". Materials 14, nr 18 (16.09.2021): 5356. http://dx.doi.org/10.3390/ma14185356.
Pełny tekst źródłaStreszczenie:
The paper demonstrates that the dry clutch friction plate wear rate, measured based on the plate mass difference method, exhibits a transient behavior after each change of friction interface temperature level. The effect is hypothesized to be caused by a temperature-dependent change in the moisture content/mass level in the friction material. To test this hypothesis, a series of synchronized characterization experiments have been conducted by using two friction plates, one for wear tests and the other for drying in an oven under the same temperature conditions. Based on the analysis of test results, a moisture content compensation procedure, which reduces the transient wear rate from being 100% to being 50% higher compared to stabilized wear rate, is proposed and verified. The gained insights are used to set recommendations on the organization of routine wear characterization experiments aimed at avoiding the effect of moisture content influence on the accuracy of wear measurement. The main recommendations are to minimize the number of temperature target level changes through proper design of the experiment, insert a run-in test after every long test pause, and execute a pre-heat, blind wear test at the beginning of each test day.
4
Hwang, J. J., G. J. Hwang, R. H. Yeh i C. H. Chao. "Measurement of Interstitial Convective Heat Transfer and Frictional Drag for Flow Across Metal Foams". Journal of Heat Transfer 124, nr 1 (15.05.2001): 120–29. http://dx.doi.org/10.1115/1.1416690.
Pełny tekst źródłaStreszczenie:
Convective heat transfer and friction drag in a duct inserted with aluminum foams have been studied experimentally. The combined effects of foam porosity (ε=0.7, 0.8, and 0.95) and flow Reynolds number (1900⩽Re⩽7800) are examined. Frictional drags for flow across the aluminum foam are measured by pressure taps, while interstitial heat transfer coefficients in the aluminum foam are determined using a transient single-blow technique with a thermal non-equilibrium two-equation model. Solid material temperature distribution is further measured for double check of the heat transfer results. To understand the frictional drag mechanisms, smoke-wire flow visualization is conducted in the aluminum-foam ducts. Results show that both the friction factor and the volumetric heat transfer coefficient increase with decreasing the foam porosity at a fixed Reynolds number. In addition, the aluminum foam of ε=0.8 has the best thermal performance under the same pumping power constraint among the three aluminum foams investigated. Finally, empirical correlations for pore Nusselt number are developed in terms of pore Reynolds number under various foam porosities.
5
Wei, Wei, Jian Wei Yu, Tao You, Xiao Fen Yu i Yong Hong Wang. "Evaluation of the Transient Temperature Distribution of End-Face Sliding Friction Pair Using Infrared Thermometry". Key Engineering Materials 613 (maj 2014): 213–18. http://dx.doi.org/10.4028/www.scientific.net/kem.613.213.
Pełny tekst źródłaStreszczenie:
A real-time temperature measurement system was designed for end-face sliding friction pairs with an infrared (IR) probe and IR thermography installed on it. The approximate temperature of contact surface was measured by the probe while non-contact surface’s temperature distribution was determined with the IR thermography. Two experiments with constant load but varied rotational speeds were carried out, and a preliminary study was made to analyze the variation of temperature in the friction process. Furthermore, the probe data was used as thermal load to calculate the temperature field by the FEM model and the result was verified using IR images. The experimental results showed that the infrared measurement system can detect and record the interface-temperature variation accurately. The probe data showed a good dynamic performance with the variation of friction coefficient. In addition, the calculated temperature field showed good accordance with the IR thermography data.
6
Gulino, R., S. Bair, W. O. Winer i B. Bhushan. "Temperature Measurement of Microscopic Areas Within a Simulated Head/Tape Interface Using Infrared Radiometric Technique". Journal of Tribology 108, nr 1 (1.01.1986): 29–34. http://dx.doi.org/10.1115/1.3261139.
Pełny tekst źródłaStreszczenie:
This study concerns the infrared measurement of steady-state and transient temperatures of microscopic areas within the contact region formed by a magnetic tape passing over a simulated recording head. This research demonstrates that the tape surface temperature can be measured within specific limits of response time and sensitivity. Due to its high tranmissivity in the relevant infrared band, sapphire was chosen as the material to be used in the fabrication of a simulated recording head. A Barnes RM2A infrared microscope was the principle radiometer used, while a best effort was made in scanning with an AGA Thermovision 750. The friction force versus load characteristics of the head-magnetic tape interface were also observed. The high speed measurements were divided into two regimes; non-contact hydrodynamic film region, and tape-head contact regime. The temperature measurements displayed a strong correlation with the measured friction force versus load curve. Almost no temperature rise was found in the noncontact hydrodynamic film region while a temperature rise of a few degrees Celsius was found when there was tape-head contact. The results with the AGA Thermovision 750 were consistent with the measurements obtained with the Barnes RM2A.
7
Meng, Fei, i Junqiang Xi. "Numerical and Experimental Investigation of Temperature Distribution for Dry-Clutches". Machines 9, nr 9 (3.09.2021): 185. http://dx.doi.org/10.3390/machines9090185.
Pełny tekst źródłaStreszczenie:
The temperature rise of the engaging clutch during shifting depends heavily on the transmitted torque. Precisely estimating the clutch temperature not only improves clutch control but also the optimal design of the clutch. However, the contact surface of the friction lining is closed, and the surface temperature is often difficult to measure accurately. In this study, a theoretical model of a two-dimensional transient temperature field for the friction disc has been established. In the radial and axial directions under different launching conditions, the temperature field of a friction disc is investigated. Four stages of clutch engagement have been determined, and finite-element analysis has been used to study the temperature field of a single clutch and to determine its duration.Then, the latest internationally developed distributed optical fiber sensing technology is used to perform measurement tests on the designed dry clutch friction characteristic test rig. The distributed fiber-optic temperature measurement technology can accomplish accurate temperature measurement with fast response speed and can acquire temperature value on different radii of friction discs with high spatial resolution. Such temperature sensing technology is very suitable for clutch working conditions. By analyzing the simulation and experimental results of temperature variation of different radii, different working conditions and different components, an important reference is provided for the establishment of the clutch temperature model and the optimization of the clutch heat dissipation structure design.
8
Hu, Yusheng, Rongting Zhang, Jinquan Zhang, Qifeng Song i Guangxiong Chen. "Friction-Excited Oscillation of Air Conditioner Rotary Compressors: Measurements and Numerical Simulations". Lubricants 10, nr 4 (25.03.2022): 50. http://dx.doi.org/10.3390/lubricants10040050.
Pełny tekst źródłaStreszczenie:
The oscillation of a rotary compressor was measured and analyzed in the frequency and time domains. The harmonic wavelet transform was used to dissolve the oscillation signal into a series of single-frequency components. A power spectrum analysis of the single-frequency components shows that there are many vibration components whose frequencies are one, double, triple, quadruple, and even tens of times the rotating frequency. An envelope spectrum analysis shows that some single-frequency components originate from the friction-excited oscillation of the compressor. A full-size mode-coupling model of the rotary compressor was established to forecast the friction-excited oscillation of the compressor using the transient dynamics method and the complex eigenvalue method. The measurement results are consistent with the predictive results. A sensitivity analysis of the main parameters shows that the coefficient of friction has a major impact on the development tendency of the friction-excited oscillation of rotary compressors.
9
Irawan, Yudy Surya, Moch Agus Choiron i Wahyono Suprapto. "Tensile strength and thermal cycle analysis of AA6061 friction weld joints with different diameters and various friction times". Eastern-European Journal of Enterprise Technologies 2, nr 12 (110) (30.04.2021): 15–21. http://dx.doi.org/10.15587/1729-4061.2021.227224.
Pełny tekst źródłaStreszczenie:
The paper reports measurement of tensile strength and the thermal cycle of AA6061 aluminum alloy circular bar friction weld with different diameters and various friction times. A continuous drive friction welding (CDFW) of AA6061 was conducted to weld the AA6061 circular bar with different diameters of 30 mm for the rotating part and 15 mm for the stationary part. The CDFW process was carried out with the revolution speed of 1,600 rpm, the initial compressive force of 2.8 kN during the friction stage for various friction times of 10, 12, and 14 seconds, and an upset force of 28 kN for 60 seconds. The flash temperature was measured using a digital infrared thermometer gun. Computer simulation using the finite element method was also done by coupling transient thermal and static structural methods. The flash temperature becomes higher along with increasing friction time based on the digital infrared thermometer gun measurement and finite element analysis. The results of tensile strength testing show that the specimen with a friction time of 12 seconds has the highest tensile strength. Based on the hardness testing result, it is found that the specimen with a friction time of 10 seconds has higher hardness, but it has an incomplete joint flash so that the tensile strength is lower than that of the specimen with a friction time of 12 seconds. Besides, the hardness of the specimen with a friction time of 12 seconds is higher than that of the specimen with a friction time of 14 seconds. The flash size becomes bigger along with the increase of the friction time based on the macrostructure observation on the longitudinal section of the CDFW specimen. It is confirmed by the temperature measurement and finite element analysis that the specimen with a friction time of 12 seconds has heat input to form the CDFW joint that has a maximum tensile strength in the range of this study
10
Chen, Chao, i Chongmin She. "Creep Effect Analysis at the Friction Interface of a Rotary Ultrasonic Motor". International Journal of Applied Mechanics 07, nr 02 (kwiecień 2015): 1550031. http://dx.doi.org/10.1142/s1758825115500313.
Pełny tekst źródłaStreszczenie:
Theoretical and experimental studies for the creep mechanism at the friction interface between rotor and stator of traveling wave type rotary ultrasonic motors (TRUM) are performed in this work. A modeling method is developed to investigate the creep and the distributed contact pressure in the friction interface for the piezoelectric composite stator with complex geometries. The annular laminated structure of the stator is discretized into a semi-analytical plate element in the radial direction, and the teeth on top of the stator are modeled by the finite element (FE) method. Then a coupled approach for the continuous plate and FE discretized teeth is proposed to investigate the interface contact mechanism. Finally, the accelerated aging tests for TRUM are conducted to study the creep effect in the friction layer during the long-term storage, the startup state is investigated experimentally by the transient characteristics measurement system. It is shown that transient characteristics of TRUM are strongly affected by the creep effect at the friction interface. The vibration response of the stator is weakened by the creep of the contact layer, and the amplitude of the piezoelectric composite plate decreases with increasing creep percentage. It is theoretically and experimentally proved that the creep percentage of over 20% can lead to the startup failure of TRUM.
11
Wang, Xudong, Zhaofeng Wang i Man Yao. "Online Measurement for Transient Mold Friction Based on the Hydraulic Oscillators of Continuous-Casting Mold". Metallurgical and Materials Transactions B 44, nr 6 (7.08.2013): 1499–508. http://dx.doi.org/10.1007/s11663-013-9919-4.
Pełny tekst źródła
12
Keong, Le-Onn, i Choe-Yung Teoh. "Topology Analysis of Bicycle Rim Brake Pad to Improve Braking Performance". MATEC Web of Conferences 217 (2018): 04004. http://dx.doi.org/10.1051/matecconf/201821704004.
Pełny tekst źródłaStreszczenie:
Various parameters of rubber brake pad tribology will affect the braking performance of a rim brake system of a bicycle. Out of those, three main parameters are contact length of brake pad, surface topology of friction surface, and the thickness of rim brake pad. the goals of this study are to improve the braking performance of rim brakes to have better friction performance while retaining its simplicity of manufacturing and to investigate the effect on friction performance through the modifications of external dimensions and surface topology of rim brakes. Moreover, through this study, it can reveal which topology modifications of the rubber brake pad will have the most significance effect towards friction performance. Experimental measurement is used to obtain the friction properties and then parametric study was carried out numerically to obtain the braking performance of the rubber brake pad. the parametric study was simulated in ANSYS Transient Structural analysis. Taguchi design method was used for quantitatively identifying the right inputs and parameter levels. the results showed that smaller groove and smaller width contribute to higher friction performance. Stress concentration occurs at the edge of groove; hence, by reducing number of groove, it allows higher braking force to be generated. Location of groove concentration appears to have insignificance effect to the friction performance. Through the topology modifications, it improves the braking performance by 3%. As for external dimension, thick rubber brake pad will not demonstrate any improvement and longer contact length will demonstrate higher friction force. However, it has to be bounded by the practicality of the dimension. Upon modifications at the external dimension, it has an improvement of 64% in braking performance.
13
Ma, Kuikui. "Field Measurement and Mechanism Analysis of Rail Corrugation on Steel Spring Floating Slab Track Section". Sustainability 14, nr 18 (19.09.2022): 11790. http://dx.doi.org/10.3390/su141811790.
Pełny tekst źródłaStreszczenie:
In this study, a combination method of field measurements and numerical simulations is used to investigate the mechanism of rail corrugation in the curve’s inner rail in urban rail transit. Firstly, field measurements on rail corrugation and rail vibration characteristics were conducted on the steel spring floating slab track (SSFST) section of a metro line; secondly, a three-dimensional finite element model of the wheelset-SSFST was established, and complex eigenvalue analysis and transient analysis were conducted. It was found that the main frequency of measured rail vertical vibration and the simulated wheel–rail—which simulated normal contact force on the inner rail—correspond to the first wheel–rail unstable vibration mode, as well as to the field-measured rail corrugation passing frequency. Therefore, the strong agreement between the results of the field measurements and the numerical simulation further verifies that the frictional, self-excited vibration of the wheelset-SSFST system on a sharply curved track can cause rail corrugation. When the vertical and lateral fasteners’ stiffness increases, the possibility of rail corrugation decreases. The decrease in vertical stiffness of the steel spring leads to an increase in the possibility of rail corrugation, but the lateral stiffness changes in the steel spring have almost no effect on the possibility of rail corrugation. The increase in the wheel–rail contact friction coefficient leads to a sharp increase in the trend of rail corrugation occurrence and causes a decrease in the rail corrugation wave-length.
14
Skadsem, Hans Joakim, Amare Leulseged i Eric Cayeux. "Measurement of Drilling Fluid Rheology and Modeling of Thixotropic Behavior". Applied Rheology 29, nr 1 (1.03.2019): 1–11. http://dx.doi.org/10.1515/arh-2019-0001.
Pełny tekst źródłaStreszczenie:
Abstract Drilling fluids perform a number of important functions during a drilling operation, including that of lifting drilled cuttings to the surface and balancing formation pressures. Drilling fluids are usually designed to be structured fluids exhibiting shear thinning and yield stress behavior, and most drilling fluids also exhibit thixotropy. Accurate modeling of drilling fluid rheology is necessary for predicting friction pressure losses in the wellbore while circulating, the pump pressure needed to resume circulation after a static period, and how the fluid rheology evolves with time while in static or near-static conditions. Although modeling the flow of thixotropic fluids in realistic geometries is still a formidable future challenge to be solved, considerable insights can still be gained by studying the viscometric flows of such fluids. We report a detailed rheological characterization of a water-based drilling fluid and an invert emulsion oilbased drilling fluid. The micro structure responsible for thixotropy is different in these fluids which results in different thixotropic responses. Measurements are primarily focused at transient responses to step changes in shear rate, but cover also steady state flow curves and stress overshoots during start-up of flow. We analyze the shear rate step change measurements using a structural kinetics thixotropy model.
15
Stąsiek, Jan, Adam Stąsiek i Marek Szkodo. "Modeling of Passive and Forced Convection Heat Transfer in Channels with Rib Turbulators". Energies 14, nr 21 (28.10.2021): 7059. http://dx.doi.org/10.3390/en14217059.
Pełny tekst źródłaStreszczenie:
The main goal of the research presented in this paper was the experimental and numerical analysis of heat enhancement and aerodynamic phenomena during air flow in a channel equipped with flow turbulators in the form of properly configured ribs. The use of ribs intensifies the heat transfer and at the same time increases not only the flow resistance but also the energy costs. Therefore, designing modern heat exchangers with optimal thermal and flow parameters requires the knowledge of the theory of heat exchangers as well as measurement methods and numerical calculations. Bearing in mind the above, the liquid crystal techniques (LCT), particle image velocimetry (PIV) and digital image processing (DIP) for temperature, velocity, friction factor and heat transfer coefficient measurements are presented herein. These three optical tools (using desktop computers) create an extremely powerful and advanced measuring technique that has not been available anywhere before. Brief histories of these measurement methods and techniques are discussed and some examples are presented. In order to assess and select the value of the measurement technique, local and average distributions of Nusselt numbers (in the measurement section) obtained by the transit analysis method on the inter-rib regions of a plate coated by thermochromics liquid crystal and heated by air as an alternative to the steady-state analysis. In the parallel, numerical calculation was performed with the use of the ANSYS Fluent software code and supported by laser anemometry-computed turbulence intensity of air flow. Comparison of the Nusselt number distributions was determined by three methods, i.e., steady state, the transient method and CFD simulation. Up to three-fold enhancement of the local heat transfer capability was observed. Failure to take into account the surface of the ribs in heat transfer causes differences in the obtained results of the Nusselt number depending on the method used. Apart from the heat transfer data, the pressure drop in the form of friction factors is also presented. On the basis of the conducted research, it can be stated that both qualitative and quantitative coherence was obtained between the experimental and computational studies.
16
Chen, Wei, Yuelin Shen, Rongbing Chen, Zhengxin Zhang i Sheldon Andre Rawlins. "Simulating Drillstring Dynamics Motion and Post-Buckling State with Advanced Transient Dynamics Model". SPE Drilling & Completion 36, nr 03 (22.02.2021): 613–27. http://dx.doi.org/10.2118/199557-pa.
Pełny tekst źródłaStreszczenie:
Summary As drilling sections become deeper and longer, transferring more weight downhole to improve rate of penetration is the primary concern for the operator. Drillstring dynamics and buckling are some primary limiters for drilling efficiency. Aggressive drilling parameters may lead to severe downhole dynamics, which leads to cutter breakage and tool damage. When axial compression exceeds a certain threshold, the drillstring buckles sinusoidally inside the wellbore first, followed by helical buckling. Buckling leads to accelerated joint wear, tool fatigue failures, and lower drilling efficiency. To better manage drillstring dynamics and buckling, we propose a method of simulating drillstring dynamics motion and postbuckling state using an advanced transient dynamics model. An analysis methodology was developed on the basis of the finite element transient dynamics model. The model captures the enriched physics of drillstring dynamics and loading: the large deformation of buckled drillstring, the strong nonlinearity of contact and friction forces, and the dynamically triggered instability caused by drilling rotation. Transient dynamics simulations are conducted for drillstring with the actual well trajectory and rotation speed. The weight on bit (WOB) is ramped up gradually, and the drillstring deformation is monitored to detect the onset of buckling or dynamics instability. To conduct the model validation, the buckling inception loads predicted by the model are compared against the analytical equation of critical buckling loads. A field extended reach drilling (ERD) job was simulated by the model. The downhole weight and torque data from the measurement-while-drilling (MWD) tool was used to validate the weight transfer prediction by the model. Most existing buckling theories use the analytical equations of critical buckling load, which were normally derived on the basis of the idealized assumptions, such as perfect wellbore shape and uniform tubular geometry. The proposed method simulates the drillstring behaviors in the field drilling conditions and aims to capture effects of wellbore friction and string rotation. The transient dynamics model is capable of simulating drillstring dynamics movement (whirling and snaking) and weight lockup under severe helical buckling. An automatic method is proposed to interpret the drillstring behaviors from the simulation results. Using the transient dynamics model, the procedure presented in this article can simulate the dynamics and buckling behaviors of drillstring and help mitigate associated risks in well-planning and execution phases.
17
Kamaludin, Khairun Najmi, Lokman Abdullah, Syed Najib Syed Salim, Zamberi Jamaludin, Nur Aidawaty Rafan, Mohd Fua'ad Rahmat i Rprakash Ramanathan. "TRIPLE NONLINEAR HYPERBOLIC PID WITH STATIC FRICTION COMPENSATION FOR PRECISE POSITIONING OF A SERVO PNEUMATIC ACTUATOR". IIUM Engineering Journal 24, nr 2 (4.07.2023): 315–36. http://dx.doi.org/10.31436/iiumej.v24i2.2766.
Pełny tekst źródłaStreszczenie:
Accurate and precise positioning control is critical in designing a positioning servo pneumatic system. The internal friction force of the pneumatic is one of the disturbances that make it challenging to achieve accurate and precise positioning. Dynamic friction identification and modelling are usually very complex and computationally exhaustive. In addition, pneumatic actuators are nonlinear systems, and applying linear control to the system is a mismatch. This study proposes an enhanced triple nonlinear hyperbolic PID controller with static friction (T-NPID+FSS) feedback module. T-NPID is integrated with nonlinear hyperbolic functions at each PID gain, hence the name. The reference in designing the T-NPID is the Popov stability criterion. Meanwhile, static friction (comparatively more straightforward than dynamic friction) is identified by measuring the actuator's internal friction at various velocities and applying it to the static friction model. T-NPID+FSS is compared to a classical PID, a PID with static friction (PID+FSS), and T-NPID without the friction module. With the comparisons, the performance gains of each module are clear. While most previous research focuses on the sinusoidal wave tracking performance (measuring the maximum tracking error, MTE, and root mean square error, RMSE), the analysis in this research focuses on obtaining precise positioning; steady-state analysis is the primary measurement. However, transient response and integral of absolute error (IAE) analysis are also observed to ensure no significant drawback in the controller's performance. T-NPID+FSS achieved the best precise positioning control, with 88.46% improvement over PID, 71.15% over PID+FSS, and 59.46% over T-NPID. The final controller is also on par with T-NPID for transient responses compared to the base PID. Although the FSS model caters to friction compensation, optimizing the FSS parameter by applying artificial intelligence, such as Neural Networks (NN) and Genetic Algorithm (GA), will increase the friction modeling‘s accuracy, and improve the compensation. ABSTRAK: Kawalan kedudukan yang tepat dan jitu adalah kitikal dalam mereka bentuk sistem pneumatik servo penentududukan. Daya geseran dalaman pneumatik adalah salah satu gangguan yang menyukarkan untuk mencapai kedudukan yang tepat dan jitu. Penentuan daya geseran dinamik dan pemodelannya selalunya kompleks dan pengiraan menyeluruh yang sukar. Selain itu, pneumatik ialah sistem tak linear, menggunakan kawalan linear pada sistem adalah tidak padan. Kajian ini mencadangkan PID hiperbolik tiga fungsi tak linear yang dipertingkatkan dengan modul suapan-balik geseran statik (T-NPID+FSS). T-NPID diintegrasikan dengan tiga fungsi hiperbolik tidak linear pada setiap pendarab PID, member pada nama. T-NPID direka bentuk dengan kriteria kestabilan Popov. Manakala geseran statik (secara perbandingan lebih mudah daripada geseran dinamik) dikenal pasti dengan mengukur geseran dalaman penggerak pada pelbagai halaju dan menerapkannya pada model geseran statik. T-NPID+FSS dibandingkan dengan PID klasik, PID dengan geseran statik (PID+ FSS) dan T-NPID tanpa modul geseran. Dengan perbandingan, prestasi peningkatan setiap modul adalah jelas. Walaupun kebanyakan penyelidikan terdahulu memfokuskan pada prestasi penjejakan gelombang sinusoidal (mengukur ralat penjejakan maksimum, MTE dan ralat purata kuasa dua akar, RMSE), analisis kajian ini memberi tumpuan kepada mendapatkan kedudukan yang tepat; oleh itu, analisis keadaan akhir ialah ukuran utama. Walau bagaimanapun, tindak balas sementara dan analisis kamiran ralat mutlak (IAE) juga diperhatikan untuk memastikan tiada kelemahan ketara dalam prestasi pengawal. T-NPID+FSS mencapai kawalan penentududukan tepat terbaik, dengan peningkatan 88.46% berbanding PID, 71.15% berbanding PID+FSS dan 59.26% berbanding T-NPID. Pengawal yang dicadangkan juga setanding dengan T-NPID untuk respons sementara berbanding PID asas. Walaupun model FSS telah ditunjukkan untuk memenuhi pampasan geseran, mengoptimumkan parameter FSS dengan menggunakan kecerdasan buatan (artificial intelligence, AI) seperti Neural Networks, NN dan Genetic Algorithms, GA akan meningkatkan ketepatan dan pampasan pemodelan geseran.
18
Tu, Jay F., i Jeffrey L. Stein. "On-Line Preload Monitoring for Anti-Friction Spindle Beatings of High-Speed Machine Tools". Journal of Dynamic Systems, Measurement, and Control 117, nr 1 (1.03.1995): 43–53. http://dx.doi.org/10.1115/1.2798522.
Pełny tekst źródłaStreszczenie:
Catastrophic and premature bearing failure caused by excessive thermally-induced bearing preload is a major design problem for spindle bearings in high-speed machine tools. Due to a lack of low cost and easy to maintain on-line preload measuring techniques, the traditional solution is to limit the maximum spindle speed and the initial bearing preload. This solution is incompatible with the trend of high-speed machining, which requires increasing both spindle speed and spindle stiffness. Therefore, it would be valuable if thermally-induced preload can be monitored on-line for regulating bearing thermal behavior at high speeds. This paper proposes using a dynamic state observer based on a preload model to estimate the spindle bearing preload via low cost thermocouples attached to the bearing outer ring and the spindle housing. The observer is based on a state-space model capable of describing the transient preload behavior of the spindle bearing. The temperatures of the outer ring and housing are used as the feedback signals for the preload observer. The observer gains are determined systematically to account for modeling errors, unknown parameters, nonlinearities, and measurement noise. In particular, the modeling errors due to unexpected factors such as bearing skidding, wear, and lubricant deterioration are compensated by a Modeling Error Compensator (MEC). By using the MEC, the error dynamics of the observer can be converted into a form suitable for applying existing observer techniques such as the Extended Kalman Filter (EKF). This preload observer has been successfully validated on two different bearing configurations operated at different speeds. The results show that the model-based monitoring technique, which combines the measurement of outer ring and housing temperature and a robust state observer, can be an effective and low-cost solution for preload monitoring in high-speed machine tools.
19
Ji, Jiandu, Rongjing Hong, Fuzhong Sun i Xiaodiao Huang. "Thermal characteristic analysis of Z-axis guideway based on thermal contact resistance". Advances in Mechanical Engineering 10, nr 10 (październik 2018): 168781401880532. http://dx.doi.org/10.1177/1687814018805321.
Pełny tekst źródłaStreszczenie:
The Z-axis feeding system of large computer numerical control (CNC) gear grinding machine tools generates lots of heat during processing, which leads to tilt and pitch deformation of the Z-axis guideway and reduces the machining accuracy. In view of this situation, a three-dimensional finite element analysis method is proposed to conduct transient thermal-structural coupling analysis of the Z-axis guideway and feeding system. Considering the microscopic contact state on machine tool joint surfaces and using the root mean square measurement method, the fractal parameter is identified and the thermal contact resistance at the joints is calculated. The friction heat on the guideway is calculated and the thermal value of the motor is obtained. Then, the heat generation rate of the bearing and the screw nut is calculated according to the friction torque. The convective heat transfer coefficient is determined according to the Reynolds number and the Nusselt number. The finite element model is established to obtain the finite element simulation results of thermal error. Finally, the experimental platform for measuring the temperature and thermal deformation of the large computer numerical control gear grinding machine tool is set up, and the accuracy and reliability of the method is verified.
20
Zhao, Wenping, i Przemyslaw Zagrodzki. "Study of Wet Friction Material Test Under Severe Thermal and Mechanical Loading (“Bump Test”)". Journal of Tribology 123, nr 1 (1.08.2000): 224–29. http://dx.doi.org/10.1115/1.1331056.
Pełny tekst źródłaStreszczenie:
One of the fatigue tests used for friction materials is the so called “bump test”. In this test, one of the reaction disks in a pack of disks has machined bumps across the contact surface. These bumps generate locally high contact pressure and temperature. In this way, severe contact conditions like that arising in service can be reproduced. The major difficulty in utilizing the “bump test” is estimation of the local pressure and temperature. In this paper, a model is developed and experimental verification of thermoelastic contact is presented. The model represents a multi-surface contact problem for a pack of disks. Due to the presence of bumps, contact surfaces are not conforming. To solve this strongly nonlinear contact problem, a robust finite element code is used. The model also includes thermal effects generated by frictional heating. The coupled elastic contact and thermal problems are solved sequentially. Contact pressure at interfaces is measured in static conditions (without sliding) using pressure sensitive film. Good agreement between the model and the measurement is observed in sense of contact length and magnitude of pressure. In order to verify the full thermoelastic model, the transient temperature inside one of the disks is measured by thermocouples. The results agree with model predictions. The study shows that the local contact pressure is an order of magnitude higher than nominal pressure. Also temperatures are much higher than that predicted for uniform contact conditions. The developed model helps to understand complex thermoelastic effects accompanying the test and to control the test parameters.
21
Krasnov, M. L., P. L. Kachurin, S. G. Vishnyakov, Yu I. Savchenko, V. A. Vasilyev, A. Yu Nitskiy i A. I. Ivanov. "SELF-OSCILLATION OF THE TENSION STATIONS OF AN ETCHING UNIT COMBINED WITH THE TANDEM COLD-ROLLING MILL 2000". Bulletin of the South Ural State University series "Mechanical engineering industry" 23, nr 2 (2023): 61–71. http://dx.doi.org/10.14529/engin230206.
Pełny tekst źródłaStreszczenie:
On multi-cage cold rolling mills combined with a continuous etching unit, self-oscillations can occur not only on the mill stands but also on the tensioning stations of the etching unit. Fatigue cracks can appear on the rollers of the tension stations, and characteristic defects can appear on the surface of the polyurethane-coated roller. To measure self-oscillations, MEMS accelerometers are installed on the roller bearing supports. The collection of vibrational data takes place in parallel with the measurement of technological parameters. Time series databases are used for data storage. The hybrid database allows the simultaneous processing of technological and vibrational parameters. When an emergency situation occurs, it is possible to chart the dependence of self-oscillations on the technological parameters. Using the results of an industrial experiment, it was possible to obtain the characteristic of the friction of the rolled strip on the roller of the tension station at low strip movement speeds. At band speeds from 0.5 m/s to 1 m/s, the friction characteristic is in a transient mode and can be either positive or negative. With a negative characteristic of friction, self-oscillation appears, with a positive characteristic, the movement of the belt stabilizes. Signal processing was carried out using Fast Fourier Transform (FFT). According to the spectral characteristic, it is possible to determine the number of complete cycles acting on the oscillatory system. Having a sufficient amount of information in time, it is possible to calculate the number of cycles and estimate the residual resource before cracks appear on the end surfaces of the roller of the tensioning station.
22
Antipov, A. S., i S. A. Krasnova. "Stabilization System of Convey-Crane Position Via Sigmoidal Function". Mekhatronika, Avtomatizatsiya, Upravlenie 20, nr 10 (10.10.2019): 609–14. http://dx.doi.org/10.17587/mau.20.609-614.
Pełny tekst źródłaStreszczenie:
In this paper, we consider the convey-crane system, which can transport loads for industrial purposes. The mathematical model, describing the motion of convey-crane, is presented by a Lagrangian mechanical system of nonlinear equations with two degrees of freedom and one control action. It is supposed that the rope has no mass, its stiffness is not taken into account, and there is no friction in the joints. The stabilization problem of the desired convey-crane position is posed underuncertain mass inertia characteristics, an action of non-smooth bounded disturbances and incomplete measurements. Based on the passivity property, the control law with linear and sigmoidal parts is constructed for the solution of the problem. The only measurement of the convey-crane position is available without a noise in the measurements. We use the low order observer with sigmoidal corrective action to obtain the needed velocity estimates for the control law. It is shown that the using of sigmoidal function as a prelimit realization of sign-function provides disturbances invariance with the given accuracy. With respect to the smoothness and boundness, sigmoidal function helps to avoid overshoot in the transient responses and excessive consumption of control resources. Moreover, unlike the sign-function, a sigmoidal function is realized in the electromechanical systems with actuator dynamics, in which the physical restrictions on the forces and general moments are posed. The constructed control law with linear and sigmoidal parts is simulated for the convey-crane system in MATLAB- Simulink. The classical PD-controller is simulated too for the purpos e of comparison. The results of modeling are proved the effectiveness of the proposed approach.
23
Koch, Sebastian, Holger Gödecker i Utz von Wagner. "On the interrelation of equilibrium positions and work of friction forces on brake squeal". Archive of Applied Mechanics 92, nr 3 (25.11.2021): 771–84. http://dx.doi.org/10.1007/s00419-021-02071-4.
Pełny tekst źródłaStreszczenie:
AbstractBrake noise, in particular brake squeal, is a permanent topic both in industry and academia since decades. Nonlinearities play a decisive role for this phenomenon. One nonlinear effect widely ignored so far is that the brake can engage multiple equilibrium positions with severe consequences on the noise behavior. In fact in an automotive disk brake, the essential elements carrier, caliper and pad are elastically coupled with each other and their behavior is nonlinear that multiple equilibrium positions are possible. The engaged equilibrium position depends, for example, on the initial conditions, external disturbances, and the transient application of the brake pressure, and in consequence configurations with or without self-exciting characteristics of the friction forces result. Obviously, a self-exciting characteristic of the friction force is a necessary precondition for the occurrence of squeal. The authors recently published some corresponding results (Koch et al. FU Mech Eng, 2021. https://doi.org/10.22190/FUME210106020K) demonstrating that for same operating parameters with respect to brake pressure (i.e., brake torque), rotational speed and temperature the engaged equilibrium position has decisive influence whether squeal occurs or not. While in Koch et al. (2021) it has just been detected whether there is squeal or not, the excitation characteristic of the friction forces becomes, beside the engaged equilibrium position, the additional focus in the present paper. Therefore, a work criterion already successfully applied in earlier publications for squeal tendency is considered. For the experimental application of the work criterion, accelerometers have to be mounted. The accelerometers’ location to be applied can be determined in the chosen setup by the camera system anyway necessary for the measurement of the engaged equilibrium position. With this refined setup, it is possible to specify the states squeal, close to squeal and far from squeal. The test series again demonstrate the decisive influence of the engaged equilibrium position (for constant operation parameters) on the occurrence of the respective state. These findings can have consequences for simulations (consideration of multiple equilibrium positions in models and respective linearization with consequences on system’s eigenvalues), but also for the design (avoidance of equilibrium positions suspicious for squeal) and experimental setups (determination of special positions) of brakes.
24
Prashu, Raj Nandkeolyar, Premful Kumar, Vivek Kumar Sinha i Vivek Sangwan. "Entropy Generation and Regression Analysis of Magnetohydrodynamic Stagnation Point Flow of a Casson Fluid with Radiative and Dissipative Heat Transfer and Hall Effects". Mathematical Problems in Engineering 2023 (19.01.2023): 1–17. http://dx.doi.org/10.1155/2023/8154625.
Pełny tekst źródłaStreszczenie:
The phenomenon of heat transfer is prevalent in industries and has an extensive range of applications. However, mostly the discussion of heat transfer problems is limited to the study of the first law of thermodynamics, which deals with energy conservation. It is just restricted to the quantity of energy, not to its quality; i.e., there is no difference between the work (high-grade energy) and the heat (low-grade energy). A measurement of the degree of randomness of energy in a system is known as entropy. It is unavailable for doing useful work because work takes place only from ordered molecular motion. Even though many boundary layer models exist in the literature to investigate the flow and heat transfer of various fluids along a stretching surface, they have not yet been used at their maximum ability. The main motive of the current research is to discuss entropy generation or its minimization during heat transfer. This work presents an entropy generation analysis for the transient three-dimensional stagnation point flow of a hydromagnetic Casson fluid flowing over a stretching surface in the existence of Hall current, viscous dissipation, and nonlinear radiation. The physical configuration of the present work is described in terms of partial differential equations (PDEs) of nonlinear nature. Furthermore, these PDEs are converted into ordinary differential equations by using some relevant similarity transformations. An efficient numerical method named as the spectral quasilinearization method (SQLM) is used to solve this model. The expression of the Bejan number and volumetric entropy generation rate is also computed. A parametric analysis, including the essential physical parameters, is performed to examine the influences of distinct flow parameters on the velocity profile, temperature profile, Bejan number, entropy generation number, and the coefficients of skin friction and the Nusselt number. In order to further insight into the emerging physical quantities of engineering interest, multiple quadratic regression models are used to estimate the coefficients of skin friction and heat transfer.
25
Tal, Yuval, Vito Rubino, Ares J. Rosakis i Nadia Lapusta. "Illuminating the physics of dynamic friction through laboratory earthquakes on thrust faults". Proceedings of the National Academy of Sciences 117, nr 35 (17.08.2020): 21095–100. http://dx.doi.org/10.1073/pnas.2004590117.
Pełny tekst źródłaStreszczenie:
Large, destructive earthquakes often propagate along thrust faults including megathrusts. The asymmetric interaction of thrust earthquake ruptures with the free surface leads to sudden variations in fault-normal stress, which affect fault friction. Here, we present full-field experimental measurements of displacements, particle velocities, and stresses that characterize the rupture interaction with the free surface, including the large normal stress reductions. We take advantage of these measurements to investigate the dependence of dynamic friction on transient changes in normal stress, demonstrate that the shear frictional resistance exhibits a significant lag in response to such normal stress variations, and identify a predictive frictional formulation that captures this effect. Properly accounting for this delay is important for simulations of fault slip, ground motion, and associated tsunami excitation.
26
Nygaard, Gerhard Haukenes, Erlend H. Vefring, Kjell Kåre Fjelde, Geir Naevdal, Rolf Johan Lorentzen i Saba Mylvaganam. "Bottomhole Pressure Control During Drilling Operations in Gas-Dominant Wells". SPE Journal 12, nr 01 (1.03.2007): 49–61. http://dx.doi.org/10.2118/91578-pa.
Pełny tekst źródłaStreszczenie:
Summary To obtain an underbalanced pressure condition, nitrogen gas can be injected into the drillstring. Simultaneous injection of liquids and gases leads to a highly dynamic flow system. During pipe connections, pressure transients can cause the bottomhole pressure to rise above the pore pressure of the reservoir or fall below the reservoir collapse pressure. Migration of gas during pipe connection and inflow from the reservoir will also cause bottomhole pressure changes. This paper presents a methodology for controlling the bottomhole pressure during drilling operations in gas-dominant wells. The methodology incorporates a dynamic model of the well fluid flow and the well-reservoir interaction. Available control actions during the drilling process are the gas injection rate prior to the pipe connection and choke valve settings during the pipe connection. Measurement of the pump rates, pump pressures, choke pressure and the bottomhole pressure are also available to support the control actions. However, during pipe connections and in the event of transient signal failures, the bottomhole pressure measurements will be suppressed. The control methodology used is based on a nonlinear model predictive control system, which predicts the near-future behavior of the well, and uses these predictions to obtain the optimal choke settings. The model parameters are calibrated using measurements from the well to ensure that the model is suitable for the predictions. A field-based case with gas injection has been examined using this control methodology. The results indicate that model based control can be utilized in developing an automated and integrated pump rate and choke-control system for underbalanced drilling operations. Introduction Injection of nitrogen gas into the drillstring while drilling is often used to obtain underbalanced pressure conditions in the reservoir section of the well. When drilling into a low-pressure reservoir, where the reservoir pore pressure is substantially lower than 1 SG, a large amount of nitrogen gas is needed to achieve underbalanced conditions. This causes the gas properties of the fluid mixture to be dominant in the well. During pipe connection, where the fluid velocity is reduced, gas and liquid segregate because of gravitational forces. In addition, loss of friction pressure causes the pressure difference between the reservoir pressure and the bottomhole well pressure to increase. This results in a larger influx of reservoir fluids into the well. To achieve more stable pressure conditions in the well, the choke setting and the circulation pump rates can be adjusted (Perez-Tellez et al. 2004; Nygaard et al. 2004). This paper evaluates a method for controlling the bottomhole pressure during the whole drilling operation, including operations related to pipe connections.
27
Minas, I., N. Morris, S. Theodossiades, M. O’Mahony i J. Voveris. "Automotive dry clutch fully coupled transient tribodynamics". Nonlinear Dynamics 105, nr 2 (lipiec 2021): 1213–35. http://dx.doi.org/10.1007/s11071-021-06605-x.
Pełny tekst źródłaStreszczenie:
AbstractDetermining the root causes of Noise, Vibration and Harshness (NVH) phenomena in modern automotive drivetrains is a task of critical importance. This research investigates the stability of dry clutch systems vibrational behaviour during engagement. A fully coupled dry clutch numerical model including the influence of friction is presented and validated using vehicle measurements. The clutch component frictional properties are measured using parts that exhibit aggressive NVH behaviour using representative tribometric experiments. The validated numerical tool highlights the occurrence of instabilities which are caused by modal couplings, particularly between the input shaft bending and clutch disc radial motions. Such a validated transient dynamics model of a dry clutch system has not hitherto been presented in the open literature.
28
Xizhi, Ma, i Wang Gang. "Study on temperature rise in the screw pair under high frequent oscillation". Industrial Lubrication and Tribology 68, nr 2 (14.03.2016): 197–205. http://dx.doi.org/10.1108/ilt-07-2015-0102.
Pełny tekst źródłaStreszczenie:
Purpose – This paper aims to study the mechanism of heat generation in a screw, and investigates the heat flux in the connection screw pair under high frequent oscillation along the axial direction. Heat generated in the screw under high frequent oscillation could be observed in a lot of situations and was significant, and it could cause damage of screw joining and transmission. Design/methodology/approach – A heat flux model in a screw pair under high frequent oscillation along the axial direction is established. Bulk temperature field in the connected parts is calculated by means of finite element methods. A testing device aimed to temperature rise measurement in a thread pair under high frequent oscillation is built. Temperature rises under different operation conditions are measured. Findings – The heat flux generated in the screw pair because of friction between the contact surfaces of the screw thread is obtained. The effects of oscillating amplitude and frequency on heat flux are obtained. It is found that amplitude and frequency have a significant influence on the heat generated under high frequent oscillation. The numerical results show good agreement with the numerical results. Research limitations/implications – This study has some limitations; for example, the friction coefficient and the relative sliding displacement between the thread surfaces need further accurate research. Practical implications – Heat generated in a screw under high frequent oscillation is very rarely mentioned in previous research papers. The methods used in this paper could be used to evaluate the heat flux and temperature under high frequent oscillations. The temperature could be used to calculate the thermal stress and expansion in the screw thread under high frequent oscillation. The screw connections need to be protected from the damage because of heat stress and from getting loose because of heat expansion of the connected parts. Originality/value – The mechanisms of heat generation in the screw pair under high frequent oscillation are studied. The model of heat flux in the screw under high frequency oscillation is established, and it could be used to calculate the heat flux under different operating conditions. The transient temperature field of the connected parts is given. A test facility was built and the experiment to measure the temperatures of the bolt and nut was carried out. The results had good agreement.
29
Price, G. R., R. K. McBrien, S. N. Rizopoulos i H. Golshan. "Evaluating the Effective Friction Factor and Overall Heat Transfer Coefficient During Unsteady Pipeline Operation". Journal of Offshore Mechanics and Arctic Engineering 121, nr 2 (1.05.1999): 131–36. http://dx.doi.org/10.1115/1.2830078.
Pełny tekst źródłaStreszczenie:
This paper presents a method to determine the effective friction factor and overall heat transfer coefficient for a high-pressure, natural gas pipeline during fully transient flow conditions. Time-varying SCADA (supervisory control and data acquisition) measurements at the pipeline boundaries (i.e., inlet and outlet) provide boundary conditions for a transient flow model, as well as additional information which is utilized to determine these parameters. The resulting friction factor and overall heat transfer coefficient minimize the least-squared difference between the additional SCADA measurements at the pipeline outlet and the corresponding values predicted from the transient flow model. This concept is referred to as parameter estimation. The transient flow model is based on a numerical solution of the one-dimensional conservation equations (i.e., continuity, momentum, and energy) which are discretized using a highly accurate compact finite-difference scheme. The transient flow model and parameter estimation is incorporated into a computer program that is initially tested on a simple pipeline with steady flow conditions. The predicted outlet pressure and temperature using the estimated friction factor and overall heat transfer coefficient exactly matches the corresponding prescribed values. Subsequently, a portion of the Foothills Pipe Line Ltd. transmission system in Alberta is considered using time-varying SCADA flow measurements. The resulting outlet pressure and temperature from the transient flow model are in good agreement with SCADA measurements for this pipeline section.
30
Polycarpou, Andreas A., i Andres Soom. "Boundary and Mixed Friction in the Presence of Dynamic Normal Loads: Part II—Friction Transients". Journal of Tribology 117, nr 2 (1.04.1995): 261–66. http://dx.doi.org/10.1115/1.2831240.
Pełny tekst źródłaStreszczenie:
The normal dynamic model of the sliding system developed in Part I of this paper is combined with a friction model, obtained separately from the same apparatus, to provide estimates of the friction under dynamic loading conditions. The two-dimensional friction model, developed from measurements at constant normal load and slowly varying sliding speeds, includes the normal approach of the sliding bodies as a key variable. From the combined model, estimates of friction under harmonic loading and of friction transients associated with short duration impacts are compared with measurements. The very good agreement between estimates and measurements indicates that, while a good friction model is required, the crucial and most variable aspect of the modeling of dynamic friction is the representation of the normal dynamics of the sliding system.
31
Rubino, Vito, Yuval Tal, Ares J. Rosakis i Nadia Lapusta. "Evolution of dynamic shear strength of frictional interfaces during rapid normal stress variations". EPJ Web of Conferences 250 (2021): 01016. http://dx.doi.org/10.1051/epjconf/202125001016.
Pełny tekst źródłaStreszczenie:
Pressure shear plate impact tests have revealed that when normal stress changes rapidly enough, the frictional shear resistance is no longer proportional to the normal stress but rather evolves with slip gradually. Motivated by these findings, we focus on characterizing the dynamic shear strength of frictional interfaces subject to rapid variations in normal stress. To study this problem, we use laboratory experiments featuring dynamic shear cracks interacting with a free surface and resulting in pronounced and rapid normal stress variations. As dynamic cracks tend to propagate close to the wave speeds of the material, capturing their behavior poses the metrological challenge of resolving displacements on the order of microns over timescales microseconds. Here we present our novel approach to quantify the full-field behavior of dynamic shear ruptures and the evolution of friction during sudden variations in normal stress, based on ultrahighspeed photography (at 1-2 million frames/sec) combined with digital image correlation. Our measurements allow us to capture the evolution of dynamic shear cracks during these short transients and enable us to decode the nature of dynamic friction.
32
Chen, W., R. Mills i R. S. Dwyer-Joyce. "Direct load monitoring of rolling bearing contacts using ultrasonic time of flight". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 471, nr 2180 (sierpień 2015): 20150103. http://dx.doi.org/10.1098/rspa.2015.0103.
Pełny tekst źródłaStreszczenie:
The load applied by each rolling element on a bearing raceway controls friction, wear and service life. It is possible to infer bearing load from load cells or strain gauges on the shaft or bearing housing. However, this is not always simply and uniquely related to the real load transmitted by rolling elements directly to the raceway. Firstly, the load sharing between rolling elements in the raceway is statically indeterminate, and secondly, in a machine with non-steady loading, the load path is complex and highly transient being subject to the dynamic behaviour of the transmission system. This study describes a method to measure the load transmitted directly by a rolling element to the raceway by using the time of flight (ToF) of a reflected ultrasonic pulse. A piezoelectric sensor was permanently bonded onto the bore surface of the inner raceway of a cylindrical roller bearing. The ToF of an ultrasonic pulse from the sensor to the roller–raceway contact was measured. This ToF depends on the speed of the wave and the thickness of the raceway. The speed of an ultrasonic wave changes with the state of the stress, known as the acoustoelastic effect. The thickness of the material varies when deflection occurs as the contacting surfaces are subjected to load. In addition, the contact stiffness changes the phase of the reflected signal and in simple peak-to-peak measurement, this appears as a change in the ToF. In this work, the Hilbert transform was used to remove this contact dependent phase shift. Experiments have been performed on both a model line contact and a single row cylindrical roller bearing from the planet gear of a wind turbine epicyclic gearbox. The change in ToF under different bearing loads was recorded and used to determine the deflection of the raceway. This was then related to the bearing load using a simple elastic contact model. Measured load from the ultrasonic reflection was compared with the applied bearing load with good agreement. The technique shows promise as an effective method for load monitoring in real-world bearing applications.
33
Watton, J. "The Dynamic Performance of an Electrohydraulic Servovalve/Motor System With Transmission Line Effects". Journal of Dynamic Systems, Measurement, and Control 109, nr 1 (1.03.1987): 14–18. http://dx.doi.org/10.1115/1.3143811.
Pełny tekst źródłaStreszczenie:
The transient response of an electrohydraulic servovalve coupled to an axial piston ball motor is analyzed. In particular, the effect of long lines between the servovalve and motor is studied together with coulomb friction effects at the motor. The dynamic characteristics of the basic system with short lines is first established via frequency response measurements coupled with a small signal linearized analysis. Longer lines are then added and the method of characteristics, coupled with a quasi-analytical solution for the motor-end equations, is used to predict the large signal transient response. The importance of coulomb friction damping is established together with damping due to servovalve dynamics.
34
Gassenfeit, E. H., i A. Soom. "Friction Coefficients Measured at Lubricated Planar Contacts During Start-Up". Journal of Tribology 110, nr 3 (1.07.1988): 533–38. http://dx.doi.org/10.1115/1.3261670.
Pełny tekst źródłaStreszczenie:
Measurements of instantaneous coefficients of friction and associated motions during start-up at a planar contact are presented for four different lubrication conditions. The various patterns of transient behavior are discussed. Difficulties in interpreting static friction coefficients during rapidly applied tangential loads are described in relation to the motion data. It is shown that a molybdenum disulphide grease yields a friction characteristic that is quite different from either dry or boundary lubricated conditions in the presence of liquid lubricants. Transition distances from a static or maximum initial friction to kinetic conditions are examined and found to be considerably longer than had been previously found for concentrated contacts. Some suggestions regarding future studies of unsteady friction behavior are made.
35
Taniguchi, Koichi, Yong Chae Lim, Alexis Flores-Betancourt i Zhili Feng. "Transient Microstructure Evolutions and Local Properties of Dual-Phase 980 MPa Grade Steel Via Friction Stir Spot Processing". Materials 13, nr 19 (2.10.2020): 4406. http://dx.doi.org/10.3390/ma13194406.
Pełny tekst źródłaStreszczenie:
Friction stir processing is a novel solid-state process to modify microstructures and their properties by intense, localized plastic deformation. However, little research has been reported for microstructure evolutions of advanced high-strength steels during the process. The present work focuses on the study of transient microstructure changes and local mechanical properties for friction stir spot processed dual-phase (DP) 980 MPa grade steel (DP980) under different peak temperatures. A pinless silicon nitride ceramic tool was used to produce relatively simple material deformation and flow near the tool. Friction stir spot processed steel samples were characterized by optical and electron microscopies. Furthermore, Vickers microhardness and nano-indentation measurements were used to study local mechanical properties for correlation with microstructures. A swallow layer of refined grains (<0.6 µm) was obtained with a low peak temperature (under 400 °C), whereas higher peak temperatures (>Ac1) led to a change in grain size with different microstructures (fine-grained DP or martensite). Electron back-scattered diffraction characterizations revealed a large deformation in the as-received microstructures (mixture of ferrite and tempered martensite) induced by friction stir spot processing, leading to recrystallization and grain refinement around the stirred zone. Also, nano-indentation measurements showed a higher hardness than the hardness of the as-received DP980. Friction stir processing with different process conditions effectively changed microstructures and local mechanical properties.
36
Fan, D., i A. Tijsseling. "Fluid-Structure Interaction With Cavitation in Transient Pipe Flows". Journal of Fluids Engineering 114, nr 2 (1.06.1992): 268–74. http://dx.doi.org/10.1115/1.2910026.
Pełny tekst źródłaStreszczenie:
The interactions between axial wave propagation and transient cavitation in a closed pipe are studied. Definitive experimental results of the phenomenon are produced in a novel apparatus. The apparatus is characterized by its simplicity and its capability of studying transient phenomena in a predictable sequence. The influence due to friction is small and the representations of the boundary conditions are straightforward. Measurements with different severity of cavitation are provided to enable other researchers in the area to compare with their theoretical models. A new cavitating fluid/structure interaction cavitation model is proposed. The measurements are compared with the column separation model of Tijsseling and Lavooij (1989) and the new model to validate the experimental results.
37
Grolman, Eric, i Jan M. H. Fortuin. "Transient Gas-Liquid Flow in Upward Sloping Pipes, Approaching the Wavy-to-Slug Flow Transition". Journal of Fluids Engineering 118, nr 4 (1.12.1996): 729–35. http://dx.doi.org/10.1115/1.2835502.
Pełny tekst źródłaStreszczenie:
A model is presented for transient, cocurrent gas-liquid pipe flow in the stratified-smooth and stratified-wavy flow regimes. It is based on the equations of continuity and motion in the direction of flow and results in two hyperbolic partial differential equations, which are solved numerically using the combined methods of lines (Schiesser, 1991) and characteristics (Stoker, 1957). In wavy gas-liquid pipe flow, three different interfacial areas and corresponding shear stresses are identified. Three friction-factor correlations were derived on the basis of an extensive set of 2500 steady-state measurements. The transient behavior of inclined gas-liquid pipe flow is successfully simulated and compares well with the results obtained from on-line measurements, right up to the onset of slug flow.
38
Kucinschi, B., i M. Fillon. "An Experimental Study of Transient Thermal Effects in a Plain Journal Bearing". Journal of Tribology 121, nr 2 (1.04.1999): 327–32. http://dx.doi.org/10.1115/1.2833940.
Pełny tekst źródłaStreszczenie:
The present study deals with the experimental determination of temperature distribution in a plain, steadily loaded journal bearing, during transient thermal periods such as start-up or slow changing in velocity. A number of chromel-alumel thermocouples, placed circumferentially in the median section of the bearing, are used in order to carry out the measurements. The temperature at film-shaft interface is also measured by means of a chromel-alumel thermocouple and a mercury transmitter. The effects of journal speed and load on bearing temperature and fluid friction torque are analyzed. The bearing temperature increases considerably with the increase of rotational speed. In addition, for slight bearing loads the bearing temperatures are greater than for higher loads, due to the oil recirculation. The fluid friction torque increases at start-up and afterwards tends to decrease because of the temperature rise which decreases the oil viscosity.
39
Slabka, Iryna, Sören Henniger, David Kücükkaya, Michael Dawoud i Hubert Schwarze. "Influence of Rheological Properties of Lithium Greases on Operating Behavior in Oscillating Rolling Bearings at a Small Swivel Angle". Lubricants 10, nr 7 (19.07.2022): 163. http://dx.doi.org/10.3390/lubricants10070163.
Pełny tekst źródłaStreszczenie:
In this study, the behavior of greases during oscillating bearing operation with a small oscillation angle and high frequency was investigated. This mode of operation entails demands on the lubrication system that differ significantly from those for continuously rotating bearings. In order to determine the variables influencing the suitability of a lubricating grease for small angle oscillating operation, the grease samples were examined with particular regard to their rheological properties. The focus of this investigation was to find a relationship between the rheological parameters and the real behavior in the bearing. Therefore, rheological and physical parameters, which influence the long-term structural changes and lubrication conditions, were identified. For this purpose, the viscosity was measured over a wide shear-rate range. The storage and loss modulus, the work of deformation, and the adhesion force jump are also determined. Afterward, rotational transient flow measurements were performed. These allowed us to analyze the development of the shear stress over time, at a constant shear rate, and to examine the internal friction behavior by evaluating the energy density. Subsequently, grease-lubricated four-point bearings were used in component tests, while the frictional torque was measured. These bearings operated in oscillating motion. Moreover, the yield point of mechanically aged greases was measured and compared with that of fresh greases to examine the influence of the oscillating operation on the lubricant condition. Finally, correlations between grease composition, rheological measurements, and component tests were investigated. Thereby, parameters influencing the frictional behavior of greases in rolling bearings during oscillating operation at small swivel angles were identified.
40
McNelley, Terry R., Keiichiro Oh-ishi i Alexandre P. Zhilyaev. "Microstructure Evolution and Microstructure-Property Relationships in Friction Stir Processing of NiAl Bronze". Materials Science Forum 539-543 (marzec 2007): 3745–50. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.3745.
Pełny tekst źródłaStreszczenie:
Friction stir processing (FSP) has been employed for localized modification and control of microstructures in NiAl bronze materials, which are widely utilized for marine components. The thermomechanical cycle of FSP results in homogenization and refinement and the conversion of microstructures from a cast to a wrought condition within stir zones in the material. However, the direct measurement of stir zone temperatures, strains, strain rates and cooling rates is difficult due to steep gradients and transients in these quantities, and this is an impediment in the assessment of FSP-induced microstructures and properties. Quantitative microstructure analyses following FSP of cast NiAl bronze materials have been used to develop estimates of stir zone thermomechanical cycles. The estimation procedures will be reviewed and the microstructure-based estimates will be compared to results from computational models and embedded thermocouples measurements. Stir zone microstructures comprise a mixture of primary α grains and transformation products of the β that formed during processing. Recrystallization in the primary α occurred due to particle-stimulated nucleation in this low stacking fault energy material. Factors that influence the distribution of strength and ductility in the stir zone appear to include the mixture of microstructure constituents and gradients in microstructure due to gradients in processing conditions.
41
Fares, Y. R. "Transient bottom topography changes in alluvial streams". Canadian Journal of Civil Engineering 27, nr 2 (1.04.2000): 309–18. http://dx.doi.org/10.1139/l99-063.
Pełny tekst źródłaStreszczenie:
The development of a quasi two-dimensional computational model for simulating the transient variations of bed topography profiles in alluvial river channels is reported. The formulation of the model is based on combining the longitudinal flow momentum with the continuity principle of the sediment bed load. The Engelund-Hansen formula is employed in estimating the total sediment bed load along the reach of a river channel. The lateral bed load contribution from the total load is calculated in the same way as in calculating the lateral secondary currents from the main flow velocities. The numerical scheme and the computational procedure used in the study are described in detail. The simulated bed level profiles are verified through comparisons with experimental and field measurements taken from case studies in the literature for different flow conditions, channel characteristics, and sediment properties. The correlation between flow discharge, bed load, boundary friction, and channel slope is discussed. On the basis of the reasonably good comparisons with field data, it may be deduced that the model can be used for predicting the bottom topography variations in river channels.Key words: meandering rivers, bottom topography, sediment transport, bed load, boundary roughness, field measurements, experimental data, computational modelling, finite difference method.
42
Potdar, Yogesh K., i Alan T. Zehnder. "Measurements and Simulations of Temperature and Deformation Fields in Transient Metal Cutting". Journal of Manufacturing Science and Engineering 125, nr 4 (1.11.2003): 645–55. http://dx.doi.org/10.1115/1.1596571.
Pełny tekst źródłaStreszczenie:
Advanced finite element software makes it possible to perform accurate simulations of orthogonal metal cutting provided all input parameters such as material properties, friction and material separation criteria are known. In principle, such properties can be determined by performing a series of cutting experiments and mechanical property tests, and then iterating the finite element simulations until acceptable agreement is reached. Cutting measurements have generally included only cutting forces and tool-chip temperatures. We hypothesize that by closely coupling simulations to conventional cutting force measurements and with fine scale spatial and temporal experimental measurements of temperature and strain fields, questions related to the choice of parameters in finite element simulations can be resolved. As a step towards that resolution a method for high resolution experimental measurements of temperature and strain fields is presented here. Temperatures of the workpiece and chip are measured during transient metal cutting over areas of 27×27μm and time scales of 200 ns by using infrared detectors. Three different materials, 1018CR steel, Al6061-T6 and Ti-6Al-4V are tested. A grid method is used to measure deformations in steel with a spatial resolution of 50 μm.
43
Mishra, P. C., H. Rahnejat i P. D. King. "Tribology of the ring—bore conjunction subject to a mixed regime of lubrication". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 223, nr 4 (11.12.2008): 987–98. http://dx.doi.org/10.1243/09544062jmes1220.
Pełny tekst źródłaStreszczenie:
This paper provides a detailed analysis of the compression ring—bore/liner conjunction. The analysis includes ring—bore conformability and global in-plane deformation of ring fitted in situ. The analysis for fitted ring in an out-of-round bore shows very good agreement with precise measurements, using a coordinate measuring machine. The analysis also includes the lubricated conjunction under a transient regime of lubrication, taking into account combined elastohydrodynamics and asperity interactions. The transient nature of the tribological conjunction has been demonstrated, particularly the prevalent mixed/boundary regime of lubrication at the top and bottom dead centres. The analysis is applied to a high performance motorbike engine subjected to very high impact loads and engine speeds of the order of 13 000 r/min. Furthermore, the predictions of the model show good conformance to the measurements of friction reported by other research workers.
44
Assemien, Modeste, i Alain Le Bot. "Vibration level induced by the friction of two rough surfaces weakly loaded". INTER-NOISE and NOISE-CON Congress and Conference Proceedings 263, nr 5 (1.08.2021): 1261–66. http://dx.doi.org/10.3397/in-2021-1795.
Pełny tekst źródłaStreszczenie:
This paper presents an experiment to measure the vibration level generated when a light solid slides over a dry and rough surface. The experimental set-up is based on linear constant motion with speed range from 1 to 1000 mm/sec. The aim is to study the evolution of the vibration level as a function of the sliding speed and the friction area. Measurements show that the vibration level is a logarithmic increasing function of the sliding speed with a transient velocity. It is also observed that two regimes exist for the evolution of vibration level versus apparent contact area. On the one hand the vibration level is proportional to the friction area, but on the other hand this level is constant.
45
MOSS, E. A., A. KRASSNOKUTSKI, B. W. SKEWS i R. T. PATON. "Highly transient squeeze-film flows". Journal of Fluid Mechanics 671 (25.01.2011): 384–98. http://dx.doi.org/10.1017/s0022112010005756.
Pełny tekst źródłaStreszczenie:
The aim of this work was to investigate the flow evolution with time of fluid between two parallel disks and the corresponding pressure variations at the centre of the lower disk that occur subsequent to an impact-loading situation arising from dropping a mass onto the upper disk from a chosen height. During the event a fixed amount of energy is dissipated in the fluid between the disks through the action of friction. Therefore, this fundamental system may be regarded as a constant energy one, as distinct from one in which the upper disk is moving at a constant velocity, or is acted upon by a constant force. A test cell was set up to conduct the investigation, for which the separation between the disks was monitored, together with the pressure at the centre of the lower disk, over the duration of the experiment (about 8–10 ms). Glycerine was used as the test fluid. The equation of motion, based on a self-similarity approach, was reduced to a simpler (quasi-steady linear or QSL) form. Measured values of disk separation, velocity and acceleration were substituted as inputs into the full QSL model and two limiting cases, namely an inviscid and a viscous model. The QSL model provided excellent comparisons between the pressure measurements and data generated by a commercial computational fluid dynamics software package, throughout the duration of a typical experiment. The inviscid and viscous models achieved good correlations with measurements for the initial impact (during which disk accelerations exceeding 2 km s−2 occurred) and towards the end of the event, that were characterized by a small and much larger pressure rise, respectively. The former feature appears not to have been previously reported and is likely to typify that which would be observed in impact systems involving squeeze films.
46
Yao, Bin, i Masayoshi Tomizuka. "Adaptive Robust Motion and Force Tracking Control of Robot Manipulators in Contact With Compliant Surfaces With Unknown Stiffness". Journal of Dynamic Systems, Measurement, and Control 120, nr 2 (1.06.1998): 232–40. http://dx.doi.org/10.1115/1.2802414.
Pełny tekst źródłaStreszczenie:
High performance robust motion and force tracking control of robot manipulators in contact with compliant surfaces is considered in this paper. The robot parameters and the stiffness of the contact surface may not be known. The system may also be subjected to uncertain nonlinearities coming from the joint friction of the robot, external disturbances, the contact surface friction model, and the unknown time-varying equilibrium position of the contact surface. An adaptive robust motion and force tracking controller is proposed, which needs measurements of position, velocity, and interaction force only. The controller achieves a guaranteed transient performance and final tracking accuracy, a desirable feature for applications and for maintaining contact. In addition, the controller achieves asymptotic motion and force tracking without resorting to high-gain feedback when the system is subjected to parametric uncertainties.
47
Wang, Z., P. T. Ireland, S. T. Kohler i J. W. Chew. "Heat Transfer Measurements to a Gas Turbine Cooling Passage With Inclined Ribs". Journal of Turbomachinery 120, nr 1 (1.01.1998): 63–69. http://dx.doi.org/10.1115/1.2841390.
Pełny tekst źródłaStreszczenie:
The local heat transfer coefficient distribution over all four walls of a large-scale model of a gas turbine cooling passage have been measured in great detail. A new method of determine the heat transfer coefficient to the rib surface has been developed and the contribution of the rib, at 5 percent blockage, to the overall roughened heat transfer coefficient was found to be considerable. The vortex-dominated flow field was interpreted from the detailed form of the measured local heat transfer contours. Computational Fluid Dynamics calculations support this model of the flow and yield friction factors that agree with measured values. Advances in the heat transfer measuring technique and data analysis procedure that confirm the accuracy of the transient method are described in full.
48
Ramudu, Eshwan, Benjamin Henry Hirsh, Peter Olson i Anand Gnanadesikan. "Turbulent heat exchange between water and ice at an evolving ice–water interface". Journal of Fluid Mechanics 798 (7.06.2016): 572–97. http://dx.doi.org/10.1017/jfm.2016.321.
Pełny tekst źródłaStreszczenie:
We conduct laboratory experiments on the time evolution of an ice layer cooled from below and subjected to a turbulent shear flow of warm water from above. Our study is motivated by observations of warm water intrusion into the ocean cavity under Antarctic ice shelves, accelerating the melting of their basal surfaces. The strength of the applied turbulent shear flow in our experiments is represented in terms of its Reynolds number $Re$, which is varied over the range $2.0\times 10^{3}\leqslant Re\leqslant 1.0\times 10^{4}$. Depending on the water temperature, partial transient melting of the ice occurs at the lower end of this range of $Re$ and complete transient melting of the ice occurs at the higher end. Following these episodes of transient melting, the ice reforms at a rate that is independent of $Re$. We fit our experimental measurements of ice thickness and temperature to a one-dimensional model for the evolution of the ice thickness in which the turbulent heat transfer is parameterized in terms of the friction velocity of the shear flow. Applying our model to field measurements at a site under the Antarctic Pine Island Glacier ice shelf yields a predicted melt rate that exceeds present-day observations.
49
Chen, P.-H., i Z.-C. Chang. "Measurements of Thermal Performance of the Regenerator of a Cryocooler with a high Number of Transfer Units Value". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 210, nr 4 (lipiec 1996): 341–52. http://dx.doi.org/10.1243/pime_proc_1996_210_206_02.
Pełny tekst źródłaStreszczenie:
Hundreds of stacked wire screens are used in the regenerator matrix of a common cryocooler. The number of transfer units of such a matrix (denoted as NTUm) may well exceed 60. However, most of the earlier studies reported are limited to studies of regenerators with NTUm values less than 60, as the single-blow method was employed to measure the NTUm value of the regenerator matrix. Furthermore, in these earlier studies, the effect of heat transfer from the working fluid to the external tube and the Joule-Thomson effect were neglected. In the present study, three regenerators having high NTUm values have been constructed and a transient single-blow technique has been employed to measure the friction factor and the heat transfer performance of these regenerators. In addition, an improved model has been adopted to correct the shortcomings of the earlier studies. Empirical correlations have been provided for the relation between the friction factor and Reynolds number and between the Nusselt number and Reynolds number. The correlation with smaller NTUm values agreed well with those reported in earlier studies.
50
Pleskun, H., A. Syring i A. Brümmer. "Transient chamber filling in rotary positive displacement vacuum pumps". IOP Conference Series: Materials Science and Engineering 1267, nr 1 (1.11.2022): 012016. http://dx.doi.org/10.1088/1757-899x/1267/1/012016.
Pełny tekst źródłaStreszczenie:
Chamber model simulation is a common approach to simulate rotary positive displacement vacuum pumps. Therefore the pump is abstracted into working chambers and connecting clearances, whereby the clearance leakages can be identified as the major loss mechanism in such machines. The clearance mass flow rates are calculated with respect to the thermodynamic states in the adjacent chambers, which are inhomogeneous for rarefied gases due to the movement of the rotors which causes a pressure gradient within the chamber. This effect increases with higher Knudsen numbers, because of the increasingly dominant friction. It is shown that inhomogeneous chamber states cause a non-complete chamber filling. As a result the mass-averaged pressure within the suction chamber is lower than the pressure in the suction port. Due to the non-constant chamber volume over time three-dimensional transient simulations with a Computational Fluid Dynamics (CFD) solver are performed in order to investigate the mass within a geometrically abstracted suction chamber. Based on a dimensionless number, a regression analysis is done to provide a quantitative estimation of this effect by means of analytical calculations. This is implemented in a chamber model simulation software and results of a test machine are compared to measurements and to previous simulations.