Relevant bibliographies by topics / Under-platform damper

Academic literature on the topic 'Under-platform damper'

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Published: 14 March 2023

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Journal articles on the topic "Under-platform damper"

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Zhao, Da Hai, and Jing Lin Zhang. "Vibration Control of Offshore Platform Structure with Friction Dampers." Applied Mechanics and Materials 638-640 (September 2014): 318–21. http://dx.doi.org/10.4028/www.scientific.net/amm.638-640.318.

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The performance of friction dampers to mitigate waves and earthquakes in tower-type offshore platform is investigated in this paper. Taking the offshore platform of TOWER-1 as an example, the equation of motion of offshore platform structure under earthquake and wave loads was established. The response reductions of offshore platform structure by different peak earthquakes were analyzed. The results show that the responses of the tower-type offshore platform structure under wave and earthquake could be effectively reduced by friction damper, and the energy dissipation ability of the friction damper differs in the different floors. The friction dampers give good response reductions in different peak earthquakes, and the response reductions of displacement are better than those of acceleration.
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Mirzai, Nadia M., Reza Attarnejad, and Jong Wan Hu. "Analytical investigation of the behavior of a new smart recentering shear damper under cyclic loading." Journal of Intelligent Material Systems and Structures 31, no. 4 (December 19, 2019): 550–69. http://dx.doi.org/10.1177/1045389x19888786.

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Shear recentering polyurethane friction damper is a type of passive control device, including the shape memory alloy plates, polyurethane springs, and friction devices. This damper can be employed in the shear link of an inverted Y-shaped braced frame. As the failure mode is a shear failure, in this study, the shear recentering polyurethane friction damper is proposed to remove the residual deformation of the structure that remains after a strong earthquake and causes considerable damage to the structure. The shear recentering polyurethane friction damper can help the structure to return to the initial position. Furthermore, as compared to many other dampers, this new damper is of low cost, and its assembling requires a simple technology. In order to evaluate the performance of the damper, four different cases are considered. Furthermore, the effect of each component is investigated in each case, and a finite element analysis is performed under cyclic loading using the ABAQUS platform. In addition, for the sake of comparison, the shape memory alloy plates are replaced by steel ones, and a comparison for the results demonstrates that the recentering shear dampers can significantly decrease residual deformation, while there is a large amount of residual deformation in the steel damper. Due to using the polyurethane springs, the ultimate capacity of the shear shape memory alloy polyurethane friction damper is 500 kN; however, in the shear steel polyurethane friction damper, it is only about 300 kN. Furthermore, the energy dissipation by the shear shape memory alloy polyurethane friction damper is larger than the shear steel polyurethane friction damper. The results show that the steel plates cannot effectively increase energy dissipation.
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Botto, Daniele, and Muhammad Umer. "A novel test rig to investigate under-platform damper dynamics." Mechanical Systems and Signal Processing 100 (February 2018): 344–59. http://dx.doi.org/10.1016/j.ymssp.2017.07.046.

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Wu, Qiong, Xilu Zhao, Shuai He, Wenxian Tang, and Rencheng Zheng. "A Bufferable Tuned-Mass Damper of an Offshore Platform against Stroke and Response Delay Problems under Earthquake Loads." Shock and Vibration 2016 (2016): 1–12. http://dx.doi.org/10.1155/2016/9702152.

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A tuned-mass damper (TMD) is applied to ensure the safety and stability of an offshore platform in practice; however, damper stroke and response delay problems always result in intractable performances of vibration control while exposed to large earthquake loads. Therefore, this paper proposes a bufferable TMD, a passive TMD with buffers on both sides, to improve the performance of offshore platforms subjected to large seismic waves. A comprehensive simulation and experimental study was executed to investigate the dynamic performances of the bufferable TMD, by application of a 1 : 200-scale offshore platform prototype. It is verified that the bufferable TMD can be effective in absorbing the stroke energy, while the damper exceeds limitations of motion. Meanwhile, the bufferable TMD can maintain high-response characteristics. In conclusion, the experimental results indicate that the displacement, acceleration, and frequency performances of an offshore platform can be significantly decreased, and the evaluation indices show that the method is effective in reducing overall vibration levels and maximum peak values, with the application of the bufferable damper system.
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Yang, Jiajia, Erming He, and Yaqi Hu. "Vibration Mitigation of the Barge-Type Offshore Wind Turbine with a Tuned Mass Damper on Floating Platform." Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University 36, no. 2 (April 2018): 238–45. http://dx.doi.org/10.1051/jnwpu/20183620238.

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This paper evaluates the application of a passive control technique with a tuned mass damper on platform for the barge-type offshore wind turbine. First of all, the three degrees of freedom mathematical model for the floating wind turbine is established based on Lagrange's equations, and the Levenberg-Marquardt algorithm is adopted to estimate the parameters of the wind turbine. Then, the method of frequency tuning which is utilized in engineering projects and genetic algorithm are employed respectively to simulate the optimum parameters of the tuned mass damper. The vibration mechanism about the phase-angle difference between tuned mass damper and floating platform is analyzed. Finally, the dynamic responses of floating wind turbine with/without tuned mass damper are calculated under five typical wind and wave load cases, and the vibration mitigation effects are researched in marine environment. Partial ballast is substituted by the equal mass of tuned mass damper due to the mass of floating platform with tuned mass damper would increase obviously, which would change the design of the wind turbine, and the vibration mitigation is also simulated in five typical load cases. The results show that the suppression rate of standard deviation of platform pitch is up to 47.95%, after substituting the partial mass of ballast, the suppression rate is 50%. Therefore, the dynamic responses of the barge-type floating wind turbine would be reduced significantly when the ballast is replaced by the equal mass of the tuned mass damper on floating platform.
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Liu, Yu Li, He Yang, and Tao Gao. "Effects of Friction on Precision Forging Process of Blade with a Damper Platform." Materials Science Forum 561-565 (October 2007): 831–34. http://dx.doi.org/10.4028/www.scientific.net/msf.561-565.831.

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A blade with a damper platform, with excellent anti-vibration characteristic and high efficiency, has become one of the most important types of blades being developed in the aeronautical engines. During the precision forging process of this blade, the friction between dies and workpiece has important effects on metal flow, deformation defects, load and energy etc. So researching the effects of friction conditions on the forging process of blade with a damper platform has been a crucial problem urgent to be resolved. In this paper, the precision forging process of titanium alloy blade with a damper platform under different friction conditions has been simulated and analyzed based on the DEFORM-3D software platform. The obtained results reveal the influence laws of friction on temperature field and load-stroke curves, and provide a significant basis for determining technological parameters of the blade forging process.
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Chandrasekaran, Srinivasan, Deepak Kumar, and Ranjani Ramanathan. "Dynamic response of tension leg platform with tuned mass dampers." Journal of Naval Architecture and Marine Engineering 10, no. 2 (December 27, 2013): 149–56. http://dx.doi.org/10.3329/jname.v10i2.16184.

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Tension Leg Platform (TLP) is a taut-moored compliant offshore platform that deploys tethers under high initial pretension to counteract the excess buoyancy. TLPs show large amplitude responses under the encountered lateral forces, which challenges the serviceability of the platform in critical sea states. One of the passive control device i.e. Tuned Mass Damper (TMD) is attempted in the present study to control large amplitude motion of TLPs. In the present study, response control of TLP using single and multiple TMDs is compared. Optimized parameters of multiple tuned mass dampers (MTMD) are obtained using H2 optimization algorithm for the maximum control of the motion of the platform. Based on the studies conducted, it is seen that MTMD systems show better response control in comparison to the single TMD. Higher robustness of the MTMD system is also examined to highlight the use of MTMD over a wide range of excitation frequencies in extreme sea states.DOI: http://dx.doi.org/10.3329/jname.v10i2.16184
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Sun, Yu Hong, Qun Niu, Li Wu Nie, and Ji Gang Zhang. "Vibration Control of Offshore Platform Based on Outrigger Damping System." Applied Mechanics and Materials 351-352 (August 2013): 1112–16. http://dx.doi.org/10.4028/www.scientific.net/amm.351-352.1112.

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Outrigger damping system is used in JZ20-2 north high wellhead platform, making simulation analysis to the whole structure subjected to pushing ice load by finite element software ANSYS, calculating displacement and acceleration response under different length of horizontal pole and different height of damper. The height of the damper has great influence on displacement and acceleration. The damping effect of horizontal bar length has an impact on the damping system, and the main influencing factor is the damper height, and when the height is H2 the damping effect is the most ideal.
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Peng, Y. B., Z. K. Zhang, J. G. Yang, and L. H. Wang. "Full-Scale Simulations of Magnetorheological Damper for Implementation of Semi-Actively Structural Control." Journal of Mechanics 35, no. 4 (August 2, 2018): 549–62. http://dx.doi.org/10.1017/jmech.2018.26.

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ABSTRACTFull-scale simulations of a (Magnetorheological) MR damper are carried out for revealing its hysteretic behaviors associated with implementation of semi-active control using the routine of computational fluid dynamics. By virtue of the structural symmetry of the MR damper, a two-dimensional configuration for finite element simulation is built up. Herschel-Bulkley model is employed to represent the property of the MR fluid, of which the control parameters and their relevances to the input current are addressed. Typical cases involving sinusoidal and irregular displacements, steady and transient currents loaded upon the MR damper are investigated. Numerical investigations reveal that the damper force has a positive correlation with input current, excitation amplitude and excitation frequency. The full-scale simulation is proved to exhibit a sound accuracy through the validation of experimental data. It provides a logical manner revealing the true performance of MR dampers under desirable operating modes in practice, and can be readily integrated with the gain design of the associated semi-actively controlled structure. This progress bypasses the technical challenge inherent in the traditional tests with low-frequency cyclic loadings due to the limitation of experimental setup. Besides, comparative study between two-dimensional and three-dimensional configuration simulations of the MR damper shows that former has a better applicability, which can be carried out on a low-cost platform.
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Gastaldi, Chiara, and Muzio M. Gola. "Estimation accuracy vs. engineering significance of contact parameters for solid dampers." Journal of the Global Power and Propulsion Society 1 (July 4, 2017): VLXC9F. http://dx.doi.org/10.22261/vlxc9f.

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AbstractAll numerical models of friction-damped bladed arrays require knowledge or information of contact-friction parameters. In the literature, these parameters are typically tuned so that the experimental Frequency Response Function (FRF) of a damped blade matches its numerical counterpart. It is well known that there exist multiple combinations of contact parameters capable of satisfying a given experimental-numerical FRF match. A better approach towards a finer tuning could be based on directly measuring contact forces transmitted between blade platforms through the damper: in this case friction coefficients are estimated through tangential over normal force components during those hysteresis segments which are safely identified as being in a slip condition. This has been applied by these authors to rigid bar (solid) dampers. Unfortunately, the four contact stiffness values (left and right damper-platform contact, normal and tangential) are more than the measurements available in the technique presented by these authors. Therefore, the problem is underdetermined. The purpose of this paper is twofold,i.e., to propose an alternative way to estimate contact stiffness values (i.e.thus solving the under-determinacy mentioned above) and to check the effective significance of such estimates from a practical engineering point of view. The contact parameter estimation technique proposed by these authors produces, for each contact parameter, a best-fit value and an uncertainty band. It will be shown that the uncertainty affecting each contact parameter results in an uncertainty on the equivalent damping and stiffness indicators at blade level which is lower than 5%.
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Dissertations / Theses on the topic "Under-platform damper"

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LIU, TONG. "Investigation of under-platform damper kinematics and dynamics." Doctoral thesis, Politecnico di Torino, 2013. http://hdl.handle.net/11583/2507354.

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Under-platform damper is a device used in turbo engines to attenuate forced vibration amplitude and prevent high cycle fatigue of turbine blades, which are caused by hot gas flow and the vibration of engine rotor. The device itself is a piece of metal and during service it is loaded by centrifugal force against the platform underside of two adjacent blades. The relative movement of the blade platforms produces possible slip on the damper surfaces that dissipates the vibration energy through heat induced by friction. Although the damper is a simple device, it is difficult to predict and optimize its performance in the blades system by combining blade FE model, contact model and kinematic model due to marked nonlinearity of friction force, geometry coupling of two contact surfaces and uncertainties of contact surface conditions. As concluding from literature, the important parameters controlling damper effectiveness include damper mass, friction coefficient, contact stiffness and damper geometry. All numerical models require knowledge or information of contact and friction parameters, which are established either through direct single interface frictional measurements, done with the help of correct test arrangements or by fine tuning the parameters in numerical model and comparing the calculated response against the experimental response of damped blade(dummy or real) in vibration. What happen in detail on the damper kinematics and contact forces on the interface are not experimentally observed. In this thesis, an alternative experimental way of investigating and evaluating under-platform damper behavior is proposed. By measuring relative movement between two simulated platforms, the movement of damper and forces transmitted through the damper, a record of the contact events(stick, slip, separation) which take place during the cycle is expected to provide information of friction coefficient, contact stiffness to better understand the damper behavior. It is paid attention to guarantee that the response determined by damper itself and contact interfaces should not be disturbed by test rig structure. The test rig is a trial to experimentally observe the damper kinematics and contact details , and furthermore reduce the ambiguity and complexity in optimizing damper geometry and performance .
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UMER, MUHAMMAD. "Analisi sperimentale e teorica dell'effetto degli smorzatori sottopala sullo smorzamento delle vibrazioni nelle palette di turbina." Doctoral thesis, Politecnico di Torino, 2019. http://hdl.handle.net/11583/2739921.

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Book chapters on the topic "Under-platform damper"

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Gola, Muzio M., and Chiara Gastaldi. "Under-Platform Damper Measurements at Politecnico di Torino." In The Mechanics of Jointed Structures, 181–204. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-56818-8_13.

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Conference papers on the topic "Under-platform damper"

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Denimal, E., C. Wong, L. Salles, and L. Pesaresi. "On the Efficiency of a Conical Under-Platform Damper for Turbines." In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-14642.

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Abstract Underplatform Dampers are commonly used in aircraft engines to limit the risk of High-Cycle Fatigue of turbine blades. The latter is located in a groove between two consecutive blades. The dry friction contact interface between the damper and the blades dissipates energy and so reduces the vibration amplitudes. Two common geometries of dampers are used nowadays, namely wedge and cylindrical dampers, but their efficiency is limited when the blades have an in-phase motion (or a motion close to it), since the damper tends to have a pure rolling motion. The objective of the present study is to analyse a new damper geometry, based on a conical shape, which prevents from this pure rolling motion of the damper and ensures a high kinematic slip. The objective of this study is to demonstrate the damping efficiency of this geometry. Hence, in a first part, the kinematic slip is approximated with analytical considerations. Then, a nonlinear dynamic analysis is performed, and the damping efficiency of this new geometry is compared to the wedge and the cylindrical geometries. The results demonstrate that the conical damper has a high damping capacity and is more efficient and more robust than the two others.
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Botto, Daniele, Muhammad Umer, Chiara Gastaldi, and Muzio M. Gola. "An Experimental Investigation of the Dynamic of a Blade With Two Under-Platform Dampers." In ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-64928.

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Several experimental apparatus have been designed in the past to evaluate the effectiveness of under-platform dampers. Most of these experimental setups allow to measure the overall damper efficiency in terms of reduction of vibration amplitude in turbine blades. The experimental data collected with these test rigs do not increase the knowledge about the damper dynamics and therefore the uncertainty on the damper behavior remains a big issue. In this paper a different approach to evaluate the damper-blade interaction has been put forward. A test rig has been purposely designed to accommodate a single blade and two under-platform dampers. One side of each damper is in contact with a ground support specifically designed to measure two independent forces on the damper. In this way both the normal and the tangential force components in the damper-blade contact can be inferred. Damper kinematics is rebuilt by using the relative displacement measured between damper and blade. This paper describes the concept behind the new approach, shows the details of the new test rig and discuss the blade frequency response from a new point of view.
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Gola, Muzio M., Marcelo Braga dos Santos, and Liu Tong. "Design of a New Test Rig to Evaluate Under-Platform Damper Performance." In ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2010. http://dx.doi.org/10.1115/esda2010-24268.

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This work presents the development of a test rig capable of measuring the forces transferred between the blade platforms through the under-platform damper. This test rig is composed of two distinct parts each one representing a platform. The static part contains the load cells, which measure the forces in two perpendicular directions; the moving part controlled using two piezoelectric actuators reproduces any in-plane relative displacement between two adjacent platforms. In this scheme, the damper is placed between these two platforms and loaded by dead weights that reproduce the effects of centrifugal force. The hysteresis cycle, of the damper system, is obtained using the measured forces and the imposed displacement. In addition, two laser beams can be used to measure the damper displacement and its tilt angle, which allows validating dynamic models of the damper. Moreover, the test rig is designed to allow heating the specimens up to temperatures which are normally found in real operation. Finally, the test rig provides necessary variables to study the damper performance and to evaluate some contact models used to simulate under-platform dampers.
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Gastaldi, Chiara, and Muzio M. Gola. "TESTING, SIMULATING AND UNDERSTANDING UNDER-PLATFORM DAMPER DYNAMICS." In VII European Congress on Computational Methods in Applied Sciences and Engineering. Athens: Institute of Structural Analysis and Antiseismic Research School of Civil Engineering National Technical University of Athens (NTUA) Greece, 2016. http://dx.doi.org/10.7712/100016.2134.11184.

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Umehara, Ryuichi, Sotaro Takei, Tomohiro Akaki, and Hiroki Kitada. "New Modeling Combining Kinematic and Stiffness Nonlinearity in Under Platform Dampers." In ASME Turbo Expo 2021: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/gt2021-58445.

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Abstract Turbine blades are used under increasingly severe conditions in order to increase the thermal efficiency of the gas turbines in operation. Friction dampers are often used to reduce the vibration of the blade and improve the plant reliability. Under platform dampers designed to generate friction between platforms and dampers have been widely adopted in gas turbines as one of the friction dampers. It is important to predict the vibration characteristics of such damper blades analytically during the design phase, and many analysis methods have been proposed vigorously. However, the phenomenon of the friction damper is not fully understood because of its complicated behavior due to nonlinearity such as contact and sliding. One of them is the variability of frequency generated in the under platform dampers. Recently, it has been reported on the variability of frequency in the mock-up blade test greatly under small excitation force, due to variability of contact surfaces. As different approach, mechanism of the variability of frequency is explained even if each damper pin has the same dimensions and characteristics of stiffness each other under the range of small vibration without slipped phenomena. In this paper, the phenomenon of this frequency variation is shown based on two physical phenomena. First, it shows the geometric nonlinear characteristics in which the normal load changes by the friction coefficient of the pin and the pin angle. Second, it shows the stiffness nonlinear characteristics in which the contact stiffness changes with the normal load of the pin. Based on the new proposed modeling of combining the geometric nonlinear characteristics and nonlinear stiffness characteristics, the phenomenon is shown in which the relative displacement of the pin changes the load and contact stiffness, and the frequency changes. It also shows that the maximum normal load before sliding is different depending on the friction coefficient and the pin angle, and that when the friction coefficient is large and the damper angle is large, the change in contact stiffness due to the normal load is large and the variability of frequency is large.
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Gastaldi, Chiara, Teresa M. Berruti, Muzio M. Gola, and Andrea Bessone. "Experimental Investigation on Real Under-Platform Dampers: The Impact of Design and Manufacturing." In ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-90416.

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Abstract The focus of this paper is on underplatform dampers (UDPs), friction damping devices commonly used in turbines for power generation. Given the nonlinear and highly complex nature of dry friction, model validation of bladed disks with UPDs still relies heavily on experimental verification, which is typically performed using the Frequency Response Function. The AERMEC research group has, in the last ten years, promoted an additional experimental/numerical comparison, based on evidence gathered directly at the blade platform/UPD interface to increase the understanding of friction and damper mechanics. A new test rig for the direct experimental investigation of UPDs at frequencies and contact pressures in line with real working condition has been developed. The geometry of the test rig and its technical features are described in detail in the paper. Different real dampers (real shape and material) are tested. The results analysis includes a complete understanding of the contact states undergone by each damper during a period of vibration and an estimation of its contact parameters. The influence of the damper shape together with the precision of the surface manufacturing and finishing on the damper effectiveness is addressed.
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Bessone, Andrea, Federico Toso, and Teresa Berruti. "Investigation on the Dynamic Response of Blades With Asymmetric Under Platform Dampers." In ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-42597.

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The paper presents the experimental activity about the dynamic response of the blades of a gas turbine for power generation carrying underplatform dampers. The final aim of the activity is to provide an experimental data base to validate the results of a numerical tool which calculates the response of the blades with underplatform dampers. The blades have fir tree attachments and an asymmetric damper is fitted between the blade platforms. The dynamic behavior of the blades is detected by an experimental campaign on two blades mounted in a test rig. Stepped sine measurements are performed with a closed-loop control system on the excitation amplitude. Different levels of excitation amplitude and centrifugal force on the damper are tested. The test campaign pointed out the presence of damping due both to the underplatform damper and to the blade attachment. The contribution of the different damping sources are discussed and analyzed. A method is suggested to identify the root damping which is not constant but proved to depend on the excitation force on the blades.
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Kaneko, Yasutomo. "Vibration Response Analysis of Mistuned Bladed Disk With Under-Platform Damper: Effect of Variation of Contact Condition on Vibration Characteristics." In ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-63027.

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Blades with a friction damper have been used in a steam turbine and a gas turbine to improve the blade reliability. In particular, for a gas turbine blade of the upstream stage, under-platform dampers have been widely used, where the damper pieces with various geometries are inserted into the platforms of the adjacent blades. The damper piece is designed so that its surface contacts the platform surface uniformly. However, the contact conditions of the damper piece (in other words, the equivalent stiffness and the damping caused by the damper piece) may change appreciably blade by blade because of the likes of manufacturing tolerance, blade deformation in operation, and wear of the damper piece. Therefore, it is essential to consider the mistuning effect caused by the variation of the contact condition of the damper piece in evaluating the vibration response of the bladed disk with the under-platform damper. In this study, a mistuned bladed disk with under-platform dampers is represented by the equivalent spring-mass model. Frequency response analysis and random response analysis are carried out using the direct method and Monte Carlo simulation. Carrying out an extensive parametric study, the effect of the variation of the contact condition caused by the damper piece on the vibration response of the bladed disk is clarified.
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Gola, Muzio M., and Chiara Gastaldi. "Understanding Complexities in Underplatform Damper Mechanics." In ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-25240.

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All numerical models of friction damped bladed arrays require knowledge or information of contact-friction parameters, which are established either through direct frictional measurements, done with the help of single contact test arrangements, or by fine tuning the parameters in the numerical model and comparing the experimental response of damped blade against its computed response. Some critical assumptions are necessary to the purpose, such as the position and extension of the real contact areas and the values of local friction coefficients. In the light of recent results from direct measurements on under-platform dampers [1–3] it became evident that a dedicated routine for the damper mechanics is a much more effective tool to capture those finer details which are essential to an appropriate description of damper behaviour. This was made possible by the successful effort of the present authors to accurately measure the forces transmitted between the platforms through the damper and to relate them with the relative platform movement [2]. Simulations, and the matching experiments which are here not described, are performed under so called out-of-phase (O-O-P) and in-phase (I-P) condition simulating the two basically important motion types. Damper forces and damper kinematics are discussed for two highly representative cases in the low frequency range. Diagrams are then used to show the sensitivity to contact parameters, input motion and initial conditions on damper behaviour, casting heavy doubts on the validity of oversimplified practices.
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Zucca, Stefano, Daniele Botto, and Muzio M. Gola. "Range of Variability in the Dynamics of Semi-Cylindrical Friction Dampers for Turbine Blades." In ASME Turbo Expo 2008: Power for Land, Sea, and Air. ASMEDC, 2008. http://dx.doi.org/10.1115/gt2008-51058.

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Under-platform dampers are used to reduce resonant stresses in turbine blades to avoid high cycle fatigue failures. In this paper a model of semi-cylindrical under-platform damper (i.e. with one flat side and one curved side) for turbine blades is described. The damper kinematics is characterized by three degrees of freedom (DOFs): in-plane translations and rotation. Static normal loads acting on the damper sides are computed using the three static balance equations of the damper. Non-uniqueness of normal pre-loads acting on the damper sides is highlighted. Implementation of the model in a numerical code for the forced response calculation of turbine blades with under-platform dampers shows that non-uniqueness of normal pre-loads leads to non-uniqueness of the forced response of the system. A numerical test case is presented to show the capabilities of the model and to analyze the effect of the main system parameters (damper mass, excitation force, coefficient of friction and damper rotation) on the damper behavior and on the system dynamics.
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