Academic literature on the topic 'Changing preload'
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Journal articles on the topic "Changing preload"
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Wu, Qiong, Lei Li, and Yi-Du Zhang. "Simulations and Experiments on Vibration Control of Aerospace Thin-Walled Parts via Preload." Shock and Vibration 2017 (2017): 1–7. http://dx.doi.org/10.1155/2017/8135120.
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Thin-walled parts primarily comprise the entire piece of rough machining, and the material removal rate can surpass 95%. Numerous components with thin-walled structures are preferred in the aerospace industry for their light weight, high strength, and other advantages. In aerospace thin-walled workpiece machining processes and practical applications, they are excited by the vibration. The preload changing the modal stiffness of the part is found and this change causes continuous changes in the natural frequency. Researching on the influence of pretightening force on dynamic characteristics of thin-walled components is highly significant for controlling vibration. In this study, the typical aviation thin-walled part is the research object. Finite element numerical simulation and experimental verification are employed to analyze the dynamic characteristics of 7075 aluminum alloy thin-walled plates under different preloads for exploring the relationship between natural frequency and preload. The relationship is validated by comparative results. Both the simulation and experimental results show that the natural frequencies of plates increase following the augmentation of the preload. Thus, this research introduces the method where vibration of aerospace thin-walled parts is reduced by preload. For practical engineering application, a program showing the relationship between natural frequency and preload is written using Visual Basic language.
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Xia, Zhongxian, Yuhou Wu, Hua Wei, Kexuan Ren, Longfei Gao, Jian Sun, and Songhua Li. "Experimental Research on the Influence of Working Conditions on Vibration and Temperature Rise of Si3N4 Full-Ceramic Bearing Motors." Shock and Vibration 2021 (November 8, 2021): 1–16. http://dx.doi.org/10.1155/2021/1176566.
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Working conditions such as lubrication, preload, and rotational speed have important influence on vibration and temperature rise of the spindle motor. In this study, controlled variable experiments are carried out on the silicon nitride (Si3N4) full-ceramic ball bearing and steel bearing of the same type, and the vibration signal characteristics and temperature rise of the spindle motor are tested and analysed, by changing the lubrication conditions, preloads, and rotational speeds of the spindle motor. Through the research, it is found that as the rotational speed increases, the vibration velocity of the Si3N4 full-ceramic bearing spindle motor under different preloads and lubrication conditions shows an overall increasing trend; kurtosis generally presents a downward trend and gradually flattens, indicating that although the vibration velocity increases at high speeds, the vibration signal shows a relatively stable state. As the rotational speed increases, the difference of vibration velocity under the condition of applying preload and no preload decreases, indicating that the influence of preload on the vibration of full-ceramic bearing spindle motor decreases with the increase in rotational speeds. At the same time, it is found that fr and 5fr have greater impact on the vibration of full-ceramic bearing spindle motor, where fr is the frequency of the bearing in normal operation, and 5fr is 5 times of the normal operating frequency. Lubrication conditions have little effect on the temperature rise of full-ceramic bearing spindle motor, and the temperature rise under nonlubricated conditions is even slightly lower than that under grease lubrication conditions. The research results show that the vibration velocity and temperature rise of Si3N4 full-ceramic bearing spindle motor are less than those of steel bearing with the same type, indicating that full-ceramic bearing has better performance than steel bearing under the same working conditions.
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Li, Xiao-hu, Yan-fei Zhang, Jun Hong, Hong Zhao, and Huan-feng Li. "Experiment analysis of spindle performance with rolling bearing under non-uniform preload." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 230, no. 17 (August 8, 2016): 3135–46. http://dx.doi.org/10.1177/0954406215605867.
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As a result of the manufacturing errors in the main parts of spindle, and the errors in assembly process of spindle, as well as the non-uniform heat distribution during spindle operation, the non-uniformly distributed preload in rolling bearing is inevitable. The non-uniform preload has not only axial force on the rolling bearing, but also the bending moment around the rolling bearing center. The effect of preload in bearing being non-uniform on the spindle performance is still unclear. In order to analyze the spindle performance with rolling bearing under non-uniform preload, a spindle test system with adjustable non-uniform distribution preload is built. By changing the magnitude of preload force on each action point, it can make the preload force distribute non-uniformly. In the static state of spindle, upon the change of non-uniformly distributed preload, the radial displacement of spindle shaft end is also changed, while in the dynamic state of spindle, it will lead to the change of the rotation center of spindle as a result of bending moment accompanying the non-uniform preload. Furthermore, the dynamic and static results show that when the preload is under non-uniform distribution, the spindle performance is significantly different from that under uniform preload. So this study would have certain reference value to check the spindle performance and explore novel preload method for rolling bearing.
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Chen, Kai, Li Zu, and Li Wang. "Prediction of preload attenuation of ball screw based on support vector machine." Advances in Mechanical Engineering 10, no. 9 (September 2018): 168781401879916. http://dx.doi.org/10.1177/1687814018799161.
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Ball screw is a mechanical device widely used in mechanical field. The reverse clearance of ball screw will reduce its precision. In order to eliminate the reverse clearance, it is necessary to apply preload to the ball screw. It is very difficult to measure the preload in real time, and the data are large and time-consuming. By using machine learning method to predict and supervise preload, the changing trend of working condition of ball screw can be evaluated in advance, and the working precision of screw is controlled, which has important engineering significance. In this article, the relationship between the preload and the friction torque is obtained through theoretical derivation and experimental verification. Then, the support vector machine is used as a tool to model the friction torque of ball screw with the parameters of material, lubrication, and revolution, and predict the value and trend of preload to complete the supervision and prediction of the preload of the ball screw. By comparing the experimental results, it is proved that the support vector machine is feasible in predicting and supervising the attenuation of the preload of ball screw.
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Scallan, Joshua P., John H. Wolpers, Mariappan Muthuchamy, David C. Zawieja, Anatoliy A. Gashev, and Michael J. Davis. "Independent and interactive effects of preload and afterload on the pump function of the isolated lymphangion." American Journal of Physiology-Heart and Circulatory Physiology 303, no. 7 (October 1, 2012): H809—H824. http://dx.doi.org/10.1152/ajpheart.01098.2011.
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We tested the responses of single, isolated lymphangions to selective changes in preload and the effects of changing preload on the response to an imposed afterload. The methods used were similar to those described in our companion paper. Step-wise increases in input pressure (Pin; preload) over a pressure range between 0.5 and 3 cmH2O, at constant output pressure (Pout), led to increases in end-diastolic diameter, decreases in end-systolic diameter, and increases in stroke volume. From a baseline of 1 cmH2O, Pin elevation by 2–7 cmH2O consistently produced an immediate fall in stroke volume that subsequently recovered over a time course of 2–3 min. Surprisingly, this adaptation was associated with an increase in the slope of the end-systolic pressure-volume relationship, indicative of an increase in contractility. Lymphangions subjected to Pout levels exceeding their initial ejection limit would often accommodate by increasing diastolic filling to strengthen contraction sufficiently to match Pout. The lymphangion adaptation to various pressure combinations (Pin ramps with low or high levels of Pout, Pout ramps at low or intermediate levels of Pin, and combined Pin + Pout ramps) were analyzed using pressure-volume data to calculate stroke work. Under relatively low imposed loads, stroke work was maximal at low preloads (Pin ∼2 cmH2O), whereas at more elevated afterloads, the optimal preload for maximal work displayed a broad plateau over a Pin range of 5–11 cmH2O. These results provide new insights into the normal operation of the lymphatic pump, its comparison with the cardiac pump, and its potential capacity to adapt to increased loads during edemagenic and/or gravitational stress.
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ZANNOLI, ROMANO, IVAN CORAZZA, PAOLA CACCIAFESTA, and ANGELO BRANZI. "EVALUATING THE MECHANICAL BEHAVIOR OF A VENTRICULAR SIMULATOR." Journal of Mechanics in Medicine and Biology 05, no. 02 (June 2005): 369–73. http://dx.doi.org/10.1142/s0219519405001503.
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The mechanical performance of a ventricular simulator was characterized by recording Pressure-Volume loops for different preload and afterload conditions. The End Systolic Pressure-Volume Relationship was drawn to demonstrate a "physiological" behaviour. The external work of the artificial ventricle was calculated by the P-V loop area and the presence of the Frank–Starling mechanism was demonstrated. The P-V loop was obtained by recording the internal pressure and by integrating the flow signal recorded at the orifice of the artificial ventricular chamber. The preload was modified by increasing the level of the filling reservoir and the afterload was modified by shortening the thin tube that represents the hydraulic resistance. The measurements were repeated at two different volumes of the ventricular external chamber. The ventricular external work was calculated by measuring the P-V loop area in the different loading conditions. The sequence of the loops obtained by changing the preload and afterload show a well defined End Systolic Pressure-Volume Relationship that changes its slope by changing the volume of the ventricular external chamber. The ventricular mechanical simulator shows a "physiological" behaviour.
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Alfares, Mohammed, Omar Saleem, and Majed Majeed. "Analytical study of thermal variation impact on dynamics of a spindle bearing system." Proceedings of the Institution of Mechanical Engineers, Part K: Journal of Multi-body Dynamics 233, no. 4 (May 2019): 871–98. http://dx.doi.org/10.1177/1464419319841687.
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Changes in the thermal status of machine tools spindle-bearing system can have a noticeable effect on the performance of the machine itself, and therefore studying the thermal effect on the performance ball bearing during service is important. For this purpose, a study was carried out where a simple rotating shaft system supported by two angular contact ball bearings was taken into consideration. Heat was generated due to the contact between the balls and rings of the bearing. This thermal effect on the dynamics of the system was studied using a transient thermal model. The system was divided into nodes; each was assumed to be a uniform temperature. Thermal energy balance was used on each node to obtain a set of differential equations. ODE solver in MATLAB was used to solve the resulting system of differential equations. The thermal model considered an initial preload as well as the thermal preload that is caused by the uneven expansion of bearing components. In this research, a 5 DOF nonlinear dynamical system model is integrated with a spindle-bearing thermal model and then utilized to study the impact of preload variations on the spindle-bearing system of a grinding machine. The effect of different system parameters such as speed of rotation, type of bearing, ambient temperature, type of oil, initial preload on temperature output and thermal growth within the system was studied. The study shows that the heat generation rate is directly proportional to the rotational speed of the shaft and higher thermally induced preload is reached at higher speeds. It is also noticed that initial preload has a small effect on the heat generation, thermally induced preload, and temperature of the bearing. Also, the dominant frequency values of the spindle system generally increase with changing thermally induced preload values. This study is useful in predicting the thermal profile as well as preload value resulting in the bearing assembly, which in turn will be used to predict variation in the dynamics of the system.
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Yang, Xue, Chang Geng Shuai, and Shen Lin Yang. "Magnetorheological Effect of NDI Polyurethane-Based MR Elastomers." Advanced Materials Research 750-752 (August 2013): 832–35. http://dx.doi.org/10.4028/www.scientific.net/amr.750-752.832.
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The dynamic magnetorheological (MR) effects of 1,5-Naphthalene diisocyanate (NDI) polyurethane-based MR elastomers were tested by changing excitation frequency, excitation amplitude, magnetic strength, or preload. NDI polyurethane-based elastomers show high dynamic mechanical property, and were used as base material to prepare MR elastomers, whose mechanical performance and dynamic MR effect were tested. The results show that: (1) the prepared NDI polyurethane-based MR elastomers have high mechanical performance and MR effect; (2) their MR effect was reduced with the increase in excitation amplitude or preload, but did not change obviously with the increase in excitation frequency. Therefore, MR elastomer devices should be reasonably designed to maximize MR effect.
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Turek, Paweł, Wacław Skoczyński, and Marek Stembalski. "Controlling the preload adjustment system of bearings in the machine spindle model using the LabVIEW environment." Mechanik 92, no. 11 (November 12, 2019): 698–700. http://dx.doi.org/10.17814/mechanik.2019.11.92.
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A test stand with a high speed spindle equipped with an active support, which provides the possibility of changing the preload of the bearings, was presented. The LabVIEW software environment was used for control. The benefits resulting from the use of the active system to reduce the amplitude of the vibration displacement of the spindle tip are presented.
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Long, Lian Chun, Zhong Ying Chen, and Zhi Guang Yang. "Research on Pre-Loaded Composite Irradiated by Laser Beam." Key Engineering Materials 462-463 (January 2011): 872–77. http://dx.doi.org/10.4028/www.scientific.net/kem.462-463.872.
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This paper investigates failure behavior tests of T300/AG80 composite laminated specimens under tensile and compressive preload using a load holding device and laser irradiation from an Nd: YAG laser. By changing the magnitudes of the preload and the power densities of the laser, the effects of preload and laser power density on the time-to-failure of the specimens were observed. The response process of specimens was synchronized taken in using high-speed camera in experiment. The experimental results showed that tensile mechanical properties of T300/AG80 composite laminated specimens were obviously superior to ones in compression test. The relational expressions between the time-to-failure of specimens and pre-loads as well as with laser power densities were acquired through fitting experiment data. The time-to-failure reduced with the pre-load increasing, the relationship is approximating linear when the laser power density kept invariable. When the pre-load kept unchanged, the time-to-failure reduced as the laser power density increased. The relationship is approximating exponential. A basis for life prediction of structure mechanically loaded in either tension or compression during the irradiation by laser is provided by fitting expression.
Conference papers on the topic "Changing preload"
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Lu, Mingjian, Haipeng Geng, Guohui Xu, Lie Yu, and Weimin Wang. "Analytical and Experimental Study of Dynamic Characteristics of Rod Fastened Rotor-Bearing System Under Preload Saturation." In ASME Turbo Expo 2013: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/gt2013-95397.
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This paper investigates the dynamic characteristics of a composite rotor fastened by rods. Contact stiffness and equivalent bending stiffness between discs with different rod preloads of the rotor are obtained respectively by using the elastic and elastic-plastic contact theory. The finite element model of rotor-bearing system is built with Timoshenko beam elements. Critical speeds are respectively calculated with and without the consideration of contact effect, including the changing bearing dynamic coefficients. A test rig of rod fastening rotor-bearing system has been constructed to verify the numerical model results. The results show that the critical speed increases with rod preload and it keeps almost constant when the rod preload reaches a certain value, called preload saturation. The experiments demonstrate that the rod fastening rotor under preload saturation has the similar dynamic characteristics as integral rotor, such as the critical speed and backward whirl with asymmetric support stiffnesses. This kind of rotors which are under preload saturation can be analyzed and designed as an integral one without considering the contact effect. The study gives referential recommendations for analysis and design of a class of composite rotors which contain discs and rods.
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Mak, Robin, Ali Amoozandeh Nobaveh, Giuseppe Radaelli, and Just L. Herder. "A Curved Compliant Differential Mechanism With Neutral Stability." In ASME 2022 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/detc2022-89406.
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Abstract Differential mechanisms are remarkable mechanical elements that are widely utilized in various systems; nevertheless, conventional differential mechanisms are heavy and difficult to use in applications with limited design space. In this paper, a curved lightweight compliant type of differential mechanism is presented. This mechanism acquires its differential characteristic by having a high rotational stiffness when the mechanism is symmetrically actuated on two sides, while having a low rotational stiffness when actuated only on one side. The intrinsic elastic strain energy required for deformation of the compliant differential is compensated for by reintroduction of potential energy to make the mechanism neutrally stable. For the storage of potential energy, two preloaded linear springs were used. The rotational stiffness of the one-sided actuation around the neutral position of the compliant differential mechanism is hypothesized to be adjustable by changing the preload of the springs. The stiffness can be positive, zero, and negative, meaning that the mechanism can have neutral stability and bistability. The hypothesis is investigated using a simulated model in Ansys Parametric Design Language using optimized parameters to achieve the desired stiffness for the mechanism. The simulated model is validated using an experimental setup for both the one-sided and symmetrical actuation stages. The experimental results showed a high correlation with the simulations. The mechanism with optimized dimensions and preload showed neutral stability for a range of 16°. Bistability was found for preloads higher than the aforementioned optimized preload. A linear trend was found between the preload of the springs and the rotational stiffness of the mechanism at θ = 0. Furthermore, an output/input kinematic performance of 0.97 was found for the simulated results and 0.95 for the experimental results.
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Park, Jisu, and Kyuho Sim. "A Feasibility Study of Controllable Gas Foil Bearings With Piezoelectric Materials via Rotordynamic Model Predictions." In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-76273.
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This study presents a new concept of gas bearings consisting of controllable gas foil bearings (C-GFBs) in which piezoelectric actuators are applied to the GFBs. The C-GFB consists of a laminated top foil, bump foil, and piezo stacks and can simply change the bearing shape or film thickness locally and globally by varying the thickness of the piezo stacks by adjusting the input voltage. The working method of C-GFBs is as follows. First, the bearing clearance is adjusted by changing the overall piezo stack thickness (clearance control). Second, the bearing preload (preload control) is modulated by the thickness expansion of several piezo stacks. Bearing lubrication performance is predicted for four cases of C-GFBs that controlled to have different bearing clearances and preloads. The piezo stack control generates meaningful differences in the fluid-film thickness and pressure. Clearance control has a great effect on the dynamic force coefficients, but preload control slightly increases the dynamic stiffness and damping coefficients. Furthermore, the rotordynamic prediction of a rotor supported on two journal C-GFBs is conducted. As a result, both control mode for C-GFB is found to have a positive effect on rotordynamic performance in terms of synchronous motions. Finally, the C-GFB is controlled to have a small bearing clearance and large preload at critical speeds to make it possible to stably pass through the critical speeds. Consequently, it turns out that the C-GFB can generate meaningful performance change in terms of bearing lubrication and ro-tordynamic performances by controlling only the input voltage of the piezo stacks. In addition, the C-GFB can be used to form various shapes to meet the operation conditions of an applied system.
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Smith, Eric, and Al Ferri. "Shock Isolation in Finite-Length Dimer Chains With Linear, Cubic and Hertzian Spring Interactions." In ASME 2013 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/detc2013-13229.
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A numerical investigation to mitigate the effects of shock in finite 1:1 dimer chains is performed. Dimer chains consist of alternating light and heavy masses. Changing the mass ratio has provided interesting results in previous research. In particular, in the case of Hertzian contacts with zero-preload, certain mass ratios have revealed minimal levels of transmitted force. This paper examines this phenomena from the perspective of utilizing it in practical isolation systems. The zero-preload Hertzian contact case is contrasted with chains connected by linear or cubic springs. Through numerical simulations, tradeoffs are examined between displacement and transmitted force.
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Guan, Hanqing, Tianyu Liu, Tao Zhang, Kai Feng, and Zhiyang Guo. "Vibration Control for Rotor Mounted on a Novel Active Bump Type Foil Bearing With Controllable Mechanical Preloads." In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-75894.
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A novel active bump type foil bearing (ABFB) is put forward aims at demonstrate the feasibility of applying active lubrication control of the aerodynamic gas bearing. The proposed active structure consists of (1) piezoelectric actuators (PZTs) amounted in the bearing housing to produce control forces, (2) flexure hinges machined in the bearing housing to produce pivot for the lever amplifier, (3) lever amplifier machined in the bearing housing to amplify the deformation of PZTs. The mechanical preloads of the ABFB can be actively adjusted by using lever amplifiers which is actuated and controlled by the controlling the driving voltage on PZTs to create variable multiple lobe clearance and realizing the real time shape changing of the lubricate gas film. The static load-deformation test of the ABFB is done to demonstrate that the preload of the bearing is significantly adjusted by changing the driving voltage on PZTs. The lift-off tests versus different driving voltages of the ABFB are done to illustrate that the change of the preloads can significantly affect the drag torque of the ABFB and illustrate the significance of the active control. Rotordynamic tests of the ABFB with different driving voltages have been conducted. Subsynchronous vibrations of the rotor have been suppressed significantly by increasing the driving voltage. The coast-down time increases with the increase of the driving voltage on PZTs. At the rotational speed of 33krpm, the amplitude of the whip motion can be suppressed timely and actively by controlling the driving voltage on PZTs.
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Sato, Koji, Akira Muramatsu, Takashi Kobayashi, and Toshiyuki Sawa. "FEM Stress Analysis and Sealing Performance of Bolted Flanged Connections Using PTFE Blended Gaskets Under Internal Pressure." In ASME 2015 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/pvp2015-45268.
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The objective of the paper is to examine mechanical characteristics of bolted flanged connection with newly developed PTFE blended gaskets under internal pressure such as the contact gasket stress distribution, the sealing performance, the load factor, reduction in axial bolt load due to creep and the flange hub stress. The relationship between the leak rate and the contact gasket stress for newly developed PTFE blended gasket were measured according to JIS B 2490 as well as the stress - displacement relationship of the gaskets. Then, the leak rate for bolted flanged connection with the PTFE blended gaskets (2inch nominal flange) was measured under internal pressure while changing the bolt preloads. In addition, the load factor and the hub stress were measured experimentally. The changes in each axial bolt force were measured using the strain gauges taking into account gasket creep. Using FEM, the gasket stress distribution, the load factor and the hub stress are analyzed taking into account the creep phenomenon of the PTFE blended gasket. The optimal maximum bolt preload is determined and the FEM results of the load factor and hub stress are in a fairly good agreement with the measured results. The predicted leak rate is fairly coincided with the measured results.
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Hayashi, Akio, Hiroto Ishibashi, Yoshitaka Morimoto, Yoshiyuki Kaneko, and Naohiko Suzuki. "Study on Method to Avoid Chatter Vibration Based on Machine Tool Rigidity." In JSME 2020 Conference on Leading Edge Manufacturing/Materials and Processing. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/lemp2020-8533.
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Abstract Chatter vibration decreases machining accuracy and thus presents a problem in manufacturing. In order to eliminate chatter vibration based on the estimation of stable cutting conditions from a stability limit diagram and to determine the cutting conditions accordingly has been proposed. However, changing the cutting conditions may lead to a decrease in productivity. The stability limit is estimated from the relationship between machine rigidity and the cutting conditions. In the present study, we proposed a system to avoid chatter vibration by changing the rigidity of the machine tool. We developed the desktop machine tool that can change its rigidity by varying the preload of a brace bar attached to the frame. In order to clarify the relationship between the chatter vibration and the rigidity of the desktop machine tool, the stability limit of the desktop machine tool was determined by conducting machining tests and comparing the results with a simulated stable limit diagram. We then investigated the frequency response function within the simulation. The results showed that the transition of the stability limit can be accomplished by changing the rigidity of the desktop machine tool, and indicate that chatter vibration can be avoided by simulation.
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Balabina, Tat'yana, Mariya Karelina, and Aleksey Mamaev. "THE INFLUENCE OF THE LENGTHS OF THE LINKS OF THE HINGED FOUR-LINK ON THE ANGLE OF HEIGHT, RETURN ANGLE AND RELATIVE DISPLACEMENT OF LINKS CONNECTED BY THE ELASTIC ELEMENT DURING THE OUTPUT LINK STABILITY." In PROBLEMS OF APPLIED MECHANICS. Bryansk State Technical University, 2020. http://dx.doi.org/10.30987/conferencearticle_5fd1ed03b024e0.49570399.
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Toothed-lever and cam-toothed-lever mechanisms are widely used in technological equipment of automatic and semi-automatic action to convert the one-way rotational motion of the input link into one-way rotary motion of the output link with periodic stops. To ensure periodic rotation with a precise fixed length, an elastic element with a preload of two-sided action is introduced into the mechanism, as a result of which the mechanism has a variable structure. Compared to other mechanisms of periodic rotation, in gear-link mechanisms there is a wide possibility of influencing the function of the position of the output link, the angle of reverse rotation and the relative displacements of the links connected to each other by an elastic element by changing the lengths of the links of the basic hinged four-link
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Ting, Yung, Hui-Yi Feng, Han-Chih Hsieh, Li-Yen Wang, Chun-Chung Li, Yuan Kang, and Shihming Wang. "Internal Model Control Using EWMA for a Wedge-Type Piezoelectric Motor." In ASME 2007 International Manufacturing Science and Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/msec2007-31050.
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Wedge-type piezoelectric motor is easily subject to disturbance such as friction, preload and temperature change, which influences the performance significantly and reduces the positioning accuracy and reliability. In this study, Exponentially Weighted Moving Average (EWMA) method is considered to use for the velocity-feedback loop, which is included in an Internal Model Control (IMC) to achieve a Run-to-Run IMC (RtR-IMC) control structure. Such control scheme is able to adapt the control command following a changing system dynamics so that it can improve the tracking accuracy and robustness. Friction is also a problem of generating dead-zone area and causes serious nonlinear phenomenon especially while moving direction is changed. A feedforward controller is designed based on the friction model. Moreover, temperature increase appears in long-time operation, which is another factor influential to piezoelectric motor’ performance. Instead of using the Single EWMA method, which cannot efficiently deal with such environmental drift problem, a Double EWMA algorithm is developed. Practical experiment is carried out to verify the performance by using these proposed methods. It concludes that the Double EWMA associated with the friction-model-based feedforward controller is superior to the other methods.
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Housari, Basil A., and Sayed A. Nassar. "Effect of Coating and Lubrication on the Vibration-Induced Loosening of Threaded Fasteners." In ASME 2006 International Mechanical Engineering Congress and Exposition. ASMEDC, 2006. http://dx.doi.org/10.1115/imece2006-16185.
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This study provides an experimental and theoretical investigation of the effect of the bearing friction coefficient and the thread friction on the self-loosening of threaded fasteners that are subjected to cyclic transverse service loads. Coating and lubrication affect the thread and the underhead friction of the fastener, which affects the loosening rate when it is subjected to transverse loads. A mathematical model was developed to evaluate the self-loosening behavior in threaded fasteners when subjected to cyclic transverse loads. An experimental procedure and test set up are designed in order to collect real-time data on the rate of preload loss per cycle as well as the rotational angle of the bolt head during its gradual loosening. The values of the coefficients of friction under the bolt head and between the threads were changed in the mathematical model to monitor their effect on the loosening rate. Experimentally, the friction coefficients are modified by changing the coating or the lubrication applied to the fasteners. One coating and one solid film lubricant are used, namely, phosphate and oil coating and Olefin and Molydisulfide lubricated bolts. The theoretical and experimental results are presented and discussed.