Academic literature on the topic 'Eccentricity crank mechanism'
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Journal articles on the topic "Eccentricity crank mechanism"
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Tuleshov, Amandyk, Recep Halicioglu, Azhar Shadymanova, and Moldir Kuatova. "Kinematic synthesis method and eccentricity effects of a Stephenson mechanism." Mechanical Sciences 12, no. 1 (January 11, 2021): 1–8. http://dx.doi.org/10.5194/ms-12-1-2021.
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Abstract. When implementing the technological process on crank presses, it is necessary to provide a predetermined working cycle of the slider motion: fast lifting, dwell, and slow lowering. The cycle cannot be realized without controlling the motor. In addition, using controllable motors increases the manufacturing cost. Due to the geometric and kinematic capabilities of the mechanism, changing the kinematics of the working link is the best choice. Thanks to the use of the Stephenson II mechanism, the slider skew is eliminated due to the parallel connecting rods and the increased area of slider contact. This study presents a numerical method for kinematic synthesis of the Stephenson mechanism that has kinematic advantages. The method is based on mean square deviation which is the minimizing of an objective function. Thanks to the proposed synthesis method, approximate dwell movement can be performed when the slider is on the bottom dead center. In this study, values of the crank length and parallel connecting rods' lengths, angular coordinates of the crank and connecting rods, and the eccentricity of the guide slider relative to the crank rotation axis were obtained. It is observed that eccentricity affects the lower forward and higher backward speed of the slider. The kinematic results of the slider movement are comparatively presented in this article.
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Long, Jiang Qi, Si Jia Zhou, and Ping Yu. "Experimental Investigation of Vibration and Noise Control of Reciprocating Compressors." Advanced Materials Research 443-444 (January 2012): 837–42. http://dx.doi.org/10.4028/www.scientific.net/amr.443-444.837.
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The reciprocating compressor contains crank-rod mechanism whose unbalanced inertia force mainly accounts for mechanical noise and vibration during the working process. Through the analysis of fit between the diameter of the compressor piston and the crank eccentricity, influence of imbalance force on the compressor vibration and noise is obtained under no change in other parts. The tests of vibration and noise are followed for the purpose of verification. The results show that the vibration and noise control will be better if a small piston diameter and a big crank eccentricity are utilized.
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Zhao, Man, Shurong Yu, Chao Li, and Yang Yu. "Effect of Mechanism Error on Input Torque of Scroll Compressor." International Journal of Rotating Machinery 2013 (2013): 1–5. http://dx.doi.org/10.1155/2013/438127.
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Based on the fundamental principle of plane four-bar mechanism, the force on the equivalent parallel four-bar mechanism was analyzed for scroll compressor with mini-crank antirotation, and the formula of input torque was proposed. The change of input torque caused by the mechanism size error was analyzed and verified with an example. The calculation results show that the mechanism size error will cause large fluctuation in input torque at the drive rod and connecting rod collinear and the fluctuation extreme value increases with rotational speed. Decreasing of the crankshaft eccentricity errors is helpful for reducing the effects of dimension error on input torque but will increase the friction loss of orbiting and fixed scroll wrap. The influence of size error should be considered in design in order to select suitable machining accuracy and reduce the adverse effect caused by size error.
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Sun, Tao, and Lu Fang Qin. "The Virtual Optimization Design on the Variable-Pitch Actuator of Wind Turbine." Advanced Materials Research 827 (October 2013): 302–8. http://dx.doi.org/10.4028/www.scientific.net/amr.827.302.
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According to the load calculation of blade, the required maximum torque of rotational blade is obtained. A mathematic analysis method can be used to deduce the following results: the thrust of hydraulic cylinder is related to crank length, the connecting rod length, the eccentricity, the installation angle, and the variable-pitch driving force. Finally, the optimal values of pitch-controlled actuator are obtained. Based on three-dimensional modeling, assembly and dynamic simulation analysis, the virtual design of variable blade pitch mechanism is completed by using the software Pro/E. By means of dynamic simulation analysis, the rationality of this design is verified, facilitating the further on development mechanism's optimized design.
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Chu, Zhi Bing, Qing Xue Huang, Zhi Yuan Zhang, and Dan Li. "Study of Structure and Properties of New Rolling-Cut Shear." Advanced Materials Research 146-147 (October 2010): 991–95. http://dx.doi.org/10.4028/www.scientific.net/amr.146-147.991.
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Based on rolling-cut shear simulation, using a kind of single-shaft and double eccentricity rolling-cut shear, which adopts a new structure of asymmetric feature and negative bias, as the calculating model by establishing motion path equation of spatial shear mechanism, comparing with the steel shear forces, link forces and horizontal link force components with or without asymmetric feature, the asymmetric formulation is deduced. Such asymmetric crank structure can decrease horizontal force component between the linkages during rolling-cut process, increase the effective drive force on links while it comes to the maximum shear force, and decrease the extrusion of blade arc on steel edge as well. Theoretical analysis and steel-shearing quality at site indicate that asymmetric and negative bias is an important and efficient way to prolong the lifetime of blade, decrease blade wear, improve shearing quality, and maintain the constant clearance between blades.
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Moskvichev, V. V., and E. A. Chaban. "Analysis of the fatigue cracks development in crane girders and assessment of their residual life." Industrial laboratory. Diagnostics of materials 84, no. 7 (August 8, 2018): 47–54. http://dx.doi.org/10.26896/1028-6861-2018-84-7-47-54.
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The results of analysis of the residual life of crane girders with operational defects based on numerical studies of the stress-strain state, equations of limiting states, and kinetic dependences of the fatigue crack development, based on the criteria of deformation and fracture mechanics are presented. High level of wear of the fixed capital assets of engineering constructions and metal structures as well as operation of the facilities in beyond-design-basis terms contribute to origination of the emergency situations caused by damage accumulation. Crane girders operated under emergency conditions due to the fatigue cracks of different lengths present in the most dangerous zones of the beam wall with an eccentric application of crane load are studied. The results of the numerical experiment revealed the lines of tension intensity impact at the crack tip appeared at the upper zone of the wall at different values of the loading eccentricity attributed to the rail shift from the vertical axis of the beam. The dependence of the length of the fatigue crack and stress intensity in the crack tip on the number of load cycles of the beam is determined. To assess the bearing capacity of crane girders operated in emergency conditions, it is suggested to use the effective values of the stress intensity factors calculated for the specific loading conditions, taking into account the structural features of the beams, size of the fatigue cracks and their location in the crane girders. Proceeding from the results of analysis the diagrams which provide of the remaining residual life of crane girders with a crack are constructed. Using traditional methods of structure calculation for cyclic fracture toughness we developed and implemented the calculation algorithm for individual lifetime of the crane girders which includes the obligatory analysis of the stress-strain state of the crane girders with a crack at the upper zone of the wall.
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Xiao, Chenglong, Renshu Yang, Chenxi Ding, Cheng Chen, Yong Zhao, Yiqiang Kang, and Guoli Shi. "Dynamic Fracture Experiment of Medium with Defects under Impact Loading." Shock and Vibration 2021 (February 16, 2021): 1–9. http://dx.doi.org/10.1155/2021/8860929.
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Defects have a significant effect on the dynamic fracture characteristics of the medium. In this paper, the dynamic fracture experiment of specimens with bias precracks is designed by utilizing the digital laser dynamic caustics system, and the effect of defect eccentricity on the dynamic fracture behavior is studied. Research shows that crack propagation can be divided into four stages: crack initiation stage, attraction stage, repulsion stage, and specimen fracture stage. The change of defect eccentricity has no obvious effect on the crack propagation behavior in the crack initiation stage and penetration stage but has a significant effect on the attraction stage and specimen fracture stage. In the process of the interaction between defect and crack, mode I stress intensity factor decreases at first and then increases. The decrease of mode I stress intensity factor reduces with the increase of defect eccentricity. The value of mode II stress intensity factor changes from negative to positive. With the increase of defect eccentricity, the symbol of mode II stress intensity factor no longer changes. The fractal dimension and the deflection angle of crack trajectory both decrease with the increase of defect eccentricity. In addition, a numerical simulation of the experiment is conducted by ABAQUS, which provides results that are in good agreement with the experimental results.
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ЧУРИЛОВ, Д. Г., И. С. АРАПОВ, А. В. СТАРУНСКИЙ, and С. Д. ПОЛИЩУК. "JUSTIFICATION OF APPLICATION MODES OF MACHINING ATTACHMENTS FOR PROCESSING PARTS BY THE METHOD OF PLASTIC DEFORMATION." VESTNIK RIAZANSKOGO GOSUDARSTVENNOGO AGROTEHNOLOGICHESKOGO UNIVERSITETA IM P A KOSTYCHEVA, no. 2(50) (June 30, 2021): 136–41. http://dx.doi.org/10.36508/rsatu.2021.50.2.019.
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Проблема и цель. Установлено, что функциональное действие машин в значительной мере определяется параметрами качества их поверхностного слоя. Цель работы – обеспечение качества поверхностного слоя деталей одним из наиболее эффективных способов, обеспечивающих управление в широком диапазоне показателями качества обработки деталей поверхностным пластическим деформированием (ОУО ППД). Одни и те же параметры качества поверхностного слоя можно получить, используя различные методы и режимы ОУО ППД. Для их оценки необходимо определение трудоемкости операции. Следовательно, имеет место совокупность научно-технических задач, решение которых позволяет разработать методологию, алгоритм и программу выбора оптимального метода и условий ОУО ППД, обеспечивающих требуемые параметры качества поверхности при минимальной технологической себестоимости, что дает значительный экономический эффект. Методология. Одним из способов обработки деталей при восстановлении служит алмазное выглаживание после процесса шлифования. Выглаживатель – кристаллический алмаз – перераспределят металл поверхностного слоя, при этом меняется микрорельеф. После алмазного выглаживания увеличивается надежность, долговечность деталей, износостойкость. Для достижения цели предлагается использование двухзвенных оправок, которые позволяют исключить биение обрабатываемой поверхности. Структурный эквивалент механизма близок к кривошипно-шатунному механизму, в отличие от которого радиус обрабатываемой детали распределяется по дуге. Изменения силы выглаживания устанавливают связь между статической силой и силой инерции. Статическую силу сглаживания можно определить, зная основные технологические параметры и процессы. Сила инерции зависит от массы подвижного звена оправки. Результаты. Результаты настоящего исследования показали: к числу задаваемых параметров относятся масса подвижного звена оправки, диаметр детали, скорость скольжения, эксцентриситет, постоянная механизма и сила инерции. Найдены разрешенные частоты вращения в зависимости от диаметра детали. Заключение. Данная методика может быть применена для восстановления рабочих поверхностей поршневых пальцев автотракторных дизельных двигателей сельскохозяйственного назначения и позволяет снизить уровень шероховатости поверхности обрабатываемых деталей. Problem and purpose. Problem and purpose. It has been established that the functional action of machines is largely determined by the quality parameters of their surface layer. The purpose of the work is to ensure the quality of the surface layer of parts by one of the most effective methods that provides control over a wide range of quality indicators for processing parts by surface plastic deformation (SPD). The same parameters of the quality of the surface layer can be obtained using different methods and modes of SPD. To assess them, it is necessary to determine the complexity of the operation. Consequently, there is a set of scientific and technical problems, the solution of which makes it possible to develop a methodology, an algorithm and a program for choosing the optimal method and conditions for SPD, which provide the required surface quality parameters at a minimum technological cost, that gives a significant economic effect. Methodology. One of the methods of processing parts during restoration is diamond burnishing after the grinding process. The smoother or the crystal diamond will redistribute the metal of the surface layer, thus changing the microrelief. After diamond burnishing, reliability, durability of parts, and wear resistance increase. To achieve the goal, it is proposed to use two-link mandrels, which allow to exclude the beating of the treated surface. The structural equivalent of the mechanism is close to the crank gear, in contrast to which the radius of the workpiece is distributed along the arc. Changes in the smoothing force establish a relationship between static force and inertial force. The static smoothing force can be determined by knowing the basic technological parameters and processes. The force of inertia depends on the mass of the moving link of the mandrel. Results. The results of this study showed that the parameters set included the mass of the movable link of the mandrel, the diameter of the part, the sliding speed, the eccentricity, the constant of the mechanism and the force of inertia. The permitted speeds were found depending on the diameter of the part. Conclusion. This technique can be used to restore the working surfaces of the piston pins of automotive diesel engines for agricultural purposes and can reduce the level of surface roughness of the processed parts
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Malíková, Lucie, Petr Miarka, and Hana Šimonová. "Propagation conditions of an eccentric crack in a semi-circular disk loaded in I+II mixed mode." MATEC Web of Conferences 310 (2020): 00017. http://dx.doi.org/10.1051/matecconf/202031000017.
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Multi-parameter fracture mechanics concept is applied to investigate crack propagation conditions during a three-point bending (3PB) test performed on an asymmetrical semi-circular disk under I+II mixedmode loading. The asymmetry is represented by an eccentricity of the angled crack as well as by different distances of both supports during the 3PB test from the middle of the specimen. The Williams series expansion is used for the crack-tip stress field approximation and fracture response of the crack is assessed by means of the combination of the numerical and analytical solution. Comparison between the individual configurations is carried out and discussion on the importance of the higher-order terms considered in the Williams expansion for various cases of asymmetry is presented.
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Spagnuolo, Roberto. "Out-of-plane local mechanism analysis with finite element method." Curved and Layered Structures 8, no. 1 (January 1, 2021): 130–36. http://dx.doi.org/10.1515/cls-2021-0012.
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Abstract The stability check of masonry structures is a debated problem in Italy that poses serious problems for its extensive use. Indeed, the danger of out of plane collapse of masonry walls, which is one of the more challenging to evaluate, is traditionally addressed not using finite element models (FEM). The power of FEM is not properly used and some simplified method are preferred. In this paper the use of the thrust surface is suggested. This concept allows to to evaluate the eccentricity of the membrane stresses using the FEM method. For this purpose a sophisticated, layered, finite element with a no-tension material is used. To model a no-tension material we used the smeared crack method as it is not mesh-dependent and it is well known since the early ’80 in an ASCE Report [1]. The described element has been implemented by the author in the program Nòlian by Softing.
Dissertations / Theses on the topic "Eccentricity crank mechanism"
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Ducheček, Martin. "Čtyřválcový řadový vznětový motor s excentrickým klikovým mechanismem pro užitková vozidla." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-232116.
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The purpose of this thesis is to evaluate the influence of eccentricity of crank mechanism to the force between the piston and the cylinder liner for appointed crank mechanism. Furthermore the influence of eccentricity to balancing crankshaft is verified and for selected value of eccentricity is realized balance. For the construction check was realized stress analysis of crank mechanism included torsion vibration.
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Černohous, Tomáš. "Dvouválcový řadový vznětový motor s excentrickým klikovým mechanismem pro užitková vozidla." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-232050.
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The goal of this master’s thesis is to examine the influence of eccentricity on the behaviour of forces between the piston and cylinder liner and on balancing of the crank mechanism for given parameters of the diesel engine. Another aim of this paper is to propose an appropriate balancing of the crank mechanism followed by stress analysis considering torsional vibration for a chosen value of eccentricity.
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Petr, David. "Hydrodynamická ložiska vznětového traktorového motoru." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-228924.
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This thesis deals with the hydrodynamic plain bearings tractor diesel engine. The first part is closer acquainted with the hydrodynamic bearing, its principles and materials used. The next part work deals with the multibody system adams-engine. The main part of this work is to model the crank mechanism and its storage in hydrodynamic bearings in the MBS program and the subsequent simulation under different operating conditions.
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Süttő, Daniel. "Pětiválcový řadový vznětový motor s excentrickým klikovým mechanismem." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2014. http://www.nusl.cz/ntk/nusl-231456.
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The aim of this thesis is to find out the influence of eccentricity of crank mechanism on the duration of the force between the piston and the cylinder liner. At the same time I wanted to find out its influence on the balance of the whole system. It is important to design the balance for the selected value of the eccentricity and subsequently put through the crank shaft to stress analysis with torsional vibrations. I got so interested in this problem that in addition to the whole topic I designed a torsional vibration damper.
Conference papers on the topic "Eccentricity crank mechanism"
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Su, D. N., Q. Song, Y. X. Dou, and K. M. Zhong. "Light-Load Linear Reciprocating Motion Device Based on Servo Motor and Small Eccentricity Crank Mechanism." In ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-11241.
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Here designs innovatively a kind of NC light-load straight reciprocating motion device which has relative fully technical function. It is driven by a low-power servo motor to actuate small eccentricity crank mechanism to rotate or swing. The rotation or swing drives piston to move linearly short distance. With the help of the simple and functional device, the internal-reflux area-differential hydraulic stroke amplifying device, the small linear displacement of the piston can be amplified dozens times or even more than one hundred times, so the output plunger can obtain relative large linear displacement to meet the required output force and motion. This device of hydrau-electromechanial integration has the following advantages: (1) easy to control the frequency of straight reciprocating motion by editing the program to control the rotating/swing frequency of the servo motor; (2) easy to get the needed stroke of the output plunger by editing program to control the oscillation angle of the servo motor; (3) higher precision in motion and displacement than pneumatic/hydraulic transmission device while the same good buffering as in pneumatic/hydraulic transmission device.
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Sharashenidze, Guri, Nikoloz Mgebrishvili, Pavle Kurtanidze, Mamuka Dolidze, and Sergo Sharashenidze. "Improvement of Reliability of Executive Mechanisms of Railway Ice-Cars Compressors." In 2009 Joint Rail Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/jrc2009-63007.
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A compressor of the ice-car refrigerating plant is characterized by uninterrupted operation that is necessary to maintain a refrigerating cycle in the car. A problem of operating lifetime, unfailing operation and reliability of the compressor depends on functional operation of its basic executive mechanism — crank mechanism. An original dynamic model of the executive crank mechanism is elaborated by the authors. Research of dynamical parameters of the executive crank mechanism according to real dynamic model is carried out. Phenomenon of variable eccentricity caused by the wear of hinges and conditions of its existence are established. Expressions corresponding to dynamical analysis are obtained. Use of the elaborated dynamic model in modern ice-car refrigerating plants ensures a significant economic effect — it decreases: planned repair expenses of refrigerating plants and compressors, ice-car downtime. At the same time it increases the length of the repair period and improves operating characteristics.
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Flores, Paulo, Margarida Machado, Eurico Seabra, and Miguel Tavares da Silva. "A Parametric Study on the Baumgarte Stabilization Method for Forward Dynamics of Constrained Multibody Systems." In ASME 2009 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/detc2009-86362.
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This paper presents and discusses the results obtained from a parametric study on the Baumgarte stabilization method for forward dynamics of constrained multibody systems. The main purpose of this work is to analyze the influence of the variables that affect the violation of constraints, chiefly the values of the Baumgarte parameters, the integration method, the time step and the quality of the initial conditions for the positions. In the sequel of this process the formulation of the rigid multibody systems is reviewed. The generalized Cartesian coordinates are selected as the variables to describe the bodies’ degrees of freedom. The formulation of the equations of motion uses the Newton-Euler approach that is augmented with the constraint equations that lead to a set of differential algebraic equations. Furthermore, the main issues related to the stabilization of the violation of constraints based on the Baumgarte approach are revised. Special attention is also given to some techniques that help in the selection process of the values of the Baumgarte parameters, namely those based on the Taylor’s series and Laplace transform technique. Finally, a slider crank mechanism with eccentricity is considered as an example of application in order to illustrated how the violation of constraints can be affected by different factors such as the Baumgarte parameters, integrator, time step and initial guesses.
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Zhao, J., H. A. DeSmidt, and W. Yao. "Nonlinear Breathing Behavior Study of Transverse Crack on a Jeffcott Rotor Under Torsional Excitation." In ASME 2014 Dynamic Systems and Control Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/dscc2014-5824.
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In this paper, Jeffcott rotor model is employed to explore the vibration response of breathing cracked system with unbalance mass. Based on the energy method and Lagrange principle, 6 degree-of-freedom equation of motion is derived in fixed coordinate system. The crack model is established using strain energy release theory of facture mechanics. The stiffness matrix induced by the crack is changing with the variation of crack open area. Zero stress intensity factor (SIF) method is used to determine the crack closure line by computing the SIF for opening mode. By integrating compliant coefficients over newly determined crack open area, the stiffness matrix is updated and vibration response is solved for every time step by Gear’s method. In addition, the breathing behavior of the crack is studied for multiple eccentricity phases and rotation speeds in order to provide effective guidance for damage detection. The paper explores the effect of external torsional loading on the crack breathing behavior. Finally, the coupling of lateral and torsional vibration is investigated to be used as an indicator of damage detection and health monitoring.
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Zhao, J., H. A. DeSmidt, and W. Yao. "Nonlinear Dynamics of Breathing Cracked Jeffcott Rotor Under Axial Excitation." In ASME 2014 Dynamic Systems and Control Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/dscc2014-6119.
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The rotor may operate at various working conditions in practice and the crack breathing behavior at different rotating speeds is essential for damage detection and health monitoring of rotor system. In this paper, the coupling of lateral and longitudinal vibration is investigated by building a Jeffcott rotor model with imbalance. By using D’Alambert Principle, four degree-of-freedom equation of motion is derived in fixed coordinate system and the crack model is built based on the fracture mechanics. Zero SIF method is used to determine the crack open area by computing the SIF of opening mode for every point in crack area. The stiffness matrix is updated every time step by integrating compliant coefficients over instantly calculated crack open area. In addition, the breathing behavior of the crack under axial excitation is studied in terms of several eccentricity phases and rotation speeds, which provide effective guidance for damage detection in such scenarios. The paper also explores the coupling effect of external axial loading on the vibration response and its effectiveness for damage detection.
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Fricke, Wolfgang. "Weld Root Fatigue Assessment of Fillet-Welded Structures Based on Structural Stresses." In 25th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/omae2006-92207.
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The problem of fatigue cracking is particularly significant for large welded plate structures being typical for ships and floating offshore structures. Here, fillet welding is applied to a large extent to join structural components. This leads to non-fused root faces, which can behave like initial cracks. In several cases the situation is even worse, when welding can be performed from one side only, resulting in a highly-stressed weld root on the other side. Although refined approaches exist for a fatigue assessment of such weld roots, for instance the crack propagation and the notch stress approaches, more practical approaches requiring less effort are demanded to handle typical problems occurring in practice. These problems are associated with locally increased load transfer, e.g. at crossing support structures and at fillet welded ends of attachments with additional stress concentrations. Also, pronounced bending can occur in fillet welds due to lateral loading of the attachment and/or the eccentricity of one-sided welds. In the paper, practical approaches for such problems are presented which have been developed in the recent past in different research projects and which are based on a structural stress or a local nominal stress in the weld. Their application is demonstrated by several examples taken from ship and offshore structures using relatively coarse finite element meshes for the stress analyses.
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El-Bagory, Tarek M. A. A., and Maher Y. A. Younan. "Crack Growth Behavior of Pipes Made From Polyvinyl Chloride Pipe Material." In ASME 2015 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/pvp2015-45657.
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The behavior of crack growth of polymeric materials is affected by several operating conditions such as, crosshead speed, specimen thickness, load line, and specimen configurations which reverse the behavior of crack from stable to unstable crack growth behavior. The main objective of the present paper is the determination of plane strain fracture toughness (KIC) for polyvinyl chloride (PVC) used in piping water transmission systems. The dimensions of the PVC pipe are outside diameter, Do=315 mm, standard dimensions ratio, SDR=13.23, ratio between outside to inside radii Ro/Ri =1.179 and pipe thickness, t =24 mm. Curved specimens are prepared from a pipe by cutting 12 mm thickness ring segments. The curved specimens are divided into two specimen configurations, namely curved three point bend, CTPB and C-shaped tension, CST specimens. All specimens are provided artificially with a pre-crack. CTPB specimen is further cut into five 72° sectors with each being centrally notched to a depth approximately a = 0.479 of the wall thickness. CST specimen configuration is characterized by the eccentricity X = 0, and 0.5W, of the loading holes from the bore surface. Linear elastic fracture mechanics theory (LEFM) is used to predict the plane strain fracture. The tests are carried out at room temperature, Ta equal 20 °C and different crosshead speeds of (10–500 mm/min). The fracture test results reveal that, the crosshead speed has been proven to affect the mode of failure and mode of fracture. At lower crosshead speeds the mode of failure is ductile, while at higher crosshead speeds it is brittle. The specimen configuration affects also on the fracture toughness. C-shaped tension specimens show higher fracture toughness in case of pin loading location X = 0.5W than X = 0 by about (12%). Transitional crosshead speed is affected by specimen geometry. C-shaped tension specimens (CST) at x= 0 and 0.5W have higher transitional crosshead speed compared with CTPB specimen configuration.
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Li, Yi, Duo-Yin Wang, and Shi-Liang Zhou. "On SIF and SCF of Circumferential Welds on Steel Tubular Piles Under Bending Moments." In ASME 2010 29th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2010. http://dx.doi.org/10.1115/omae2010-20842.
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Circumferential welds, also called splice welds, on steel piles installed in marine and offshore structures are potential fatigue hot spots, given harsh and cyclic loadings. This paper is devoted to linear elastic fracture mechanics (LEFM)-based fatigue assessment for pile splice welds under bending moments. Specifically, this paper studies two important factors for the LEFM analysis of surface crack at the circumferential welds, stress intensity factor (SIF) and stress concentration factor (SCF). So far, LEFM-based fatigue assessment has not been widely conducted for steel tubular piles. Particularly, the two factors have not been properly developed with regard to typical features of marine steel piles, i.e., small aspect ratio of crack shape, thin-walled condition, misalignments at splice, thickness transition, complicated loading effects including bending moments, etc. The determination of SIF heavily relies on a geometry function for the growth of a fatigue crack. Based on a literature review, this paper has identified a database of geometry functions that may be suitable in practice for the circumferential welds on tubular piles with a thickness ratio around 10 under bending moments. SCF is used to accommodate stress concentration effects due to assorted geometric misalignments at a pile splice, including diameter difference (or concentricity), center eccentricity, thickness difference, and out of roundness. Currently, SCFs for tubular connections are produced for axial forces. In this paper, a practical approximation to the SCF under bending moments is mathematically formulated on the basis of a flat-plate configuration. This paper presents practical information for LEFM-based fatigue assessment of steel piles installed in marine and offshore works.