Journal articles: 'Torsional oscillations of the crank mechanism'

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Pasricha, M. S. Pasricha, and F. M. Hashim. "Effect of the reciprocating mass of slider-crank mechanism on torsional vibrations of diesel engine systems." ASEAN Journal on Science and Technology for Development 23, no. 1&2 (October 30, 2017): 71. http://dx.doi.org/10.29037/ajstd.94.

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The torsional vibration phenomenon in the running gear of reciprocating engine systems isusually dealt with by considering a series of constant inertias connected by sections of massless shafting. However in reality, a slider crank mechanism is a vibrating system with varying inertia because the effective inertia of the total oscillating mass of each crank assembly varies twice per revolution of the crankshaft. Large variations in inertia torques can give rise to the phenomenonof secondary resonance in torsional vibration of modern marine diesel engines which can not be explained by conventional theory incorporating only the mean values of the varying inertias. In the past associated secondary resonances and regions of instability tended to be dismissed by most engineers as interesting but of no importance. The situation changed in recent years since there is evidence of the existence of thesecondary resonance effects which could have contributed to a number of otherwise inexplicable crankshaft failures in large slow speed marine engines. The cyclic variation of the polar moment of inertia of the reciprocating parts during each revolution causes a periodic variation of frequency and corres ponding amplitude of vibration of reciprocating engine systems. It also causes an increase in the speed range over which resonance effects are experienced and only a partial explanation of the behaviour of the systems has been worked out. It is impossible to avoid these instabilities by changes in thedesign , unless of course the variations in mass and spring constant can be made zero. In the present paper a critical appraisal of the regions of instability as determined from the equation of motion which takes into account variation of inertia is given. The motion in the form of complex waveforms is studied at different speeds of engine rotation. A comparison of theoretical results with Goldsbrough’s experimental resultsand Gregory’s analysis is included.

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Cheng, Shouguo, and Shulin Liu. "Dynamic Analysis of Slider-Crank Mechanism with a Cracked Rod." Mathematical Problems in Engineering 2018 (September 2, 2018): 1–7. http://dx.doi.org/10.1155/2018/8540546.

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The dynamical equation of the slider-crank mechanism is established by using Lagrange equation and Newton’s second law. The slider-crank mechanism with an open crack rod is investigated and then establishes the equivalent mechanics model by a massless torsional spring to simulate the influence of the crack in the rod, and the mechanism of a cracked rod is divided into two subsystems. The dynamical equation of the slider-crank mechanism with a crack rod is established. Comparing the dynamic analysis results between with and without crack in the rod, the results show that the existence of the crack leads to a great change in the motion characteristics of the slider. The calculated maximum Lyapunov exponent is positive, which shows that the movement of the slider in the crank slider mechanism with a cracked rod is chaotic.

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Adiletta, G., and A. R. Guido. "Dynamical behaviour of a torsional system with parametric and external excitations." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 214, no. 7 (July 1, 2000): 955–73. http://dx.doi.org/10.1243/0954406001523182.

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The dynamic behaviour of a torsional system with a one-cylinder, reciprocating compressor driven by an asynchronous motor is studied using a two degrees-of-freedom (2 DOF) lumped-parameter theoretical model. The model takes into account the variability of the mass moment of inertia of the crank mechanism and the presence of pressure forces loading the compressor piston. The influence of the ratio of the variable to the constant part of inertia in the crank mechanism and the effect of the load torque due to pressure forces acting on the piston are examined in relation to system dynamic behaviour. Experimental data, obtained with the adoption of a suitable rig, show that the theoretical indications can be considered reliable, despite the approximation that was given to the mathematical model as far as the treatment of the damping and the absence of clearances were concerned.

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Guzzomi, A. L., D. C. Hesterman, and B. J. Stone. "Variable inertia effects of an engine including piston friction and a crank or gudgeon pin offset." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 222, no. 3 (March 1, 2008): 397–414. http://dx.doi.org/10.1243/09544070jauto590.

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In order to obtain greater accuracy in simulation, more sophisticated models are often required. When it comes to the torsional vibration of reciprocating mechanisms the effect of inertia variation is very important. It has been shown that the inclusion of this variation increases model accuracy for both single-cylinder and multi-cylinder engine torsional vibration predictions. Recent work by the present authors has revealed that piston-to-cylinder friction may modify an engine's ‘apparent’ inertia function. Kinematic analysis also shows that the piston side force and the dynamic piston-to-cylinder friction are interdependent. This has implications for engine vibration modelling. Most modern engines employ a gudgeon pin offset, and there is a growing interest in pursuing large crank offsets; hence, the effect of these on inertia variation is also of interest. This paper presents the derivation of the inertia function for a single engine mechanism, including both piston-to-cylinder friction and crank or gudgeon pin offset, and investigates the effect of each through predictions. The effect of crank offset on the variable inertia function is also verified by experiment.

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Fabbri, Luca, and Stefano Vignolo. "A torsional completion of gravity for Dirac matter fields and its applications to neutrino oscillations." Modern Physics Letters A 31, no. 03 (January 18, 2016): 1650014. http://dx.doi.org/10.1142/s0217732316500140.

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In this paper, we consider the torsional completion of gravitation for an underlying background filled with Dirac fields, applying it to the problem of neutrino oscillations: we discuss the effects of the induced torsional interactions as corrections to the neutrino oscillations mechanism.

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Wang, Mingyuan, and Lubin Hang. "Research and application of variable DOF compliant five-bar mechanism based on novel compliant torsion joint in vehicle side door latch." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 234, no. 19 (April 20, 2020): 3789–808. http://dx.doi.org/10.1177/0954406220917423.

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In this paper, a novel compliant joint with torsion spring (CJTS) is proposed in order to realize the power release (Note: The “power release” feature means that the closure system with a latch assembly including a pawl-ratchet release mechanism is controlled by at least one electric actuator.) feature of the vehicle side door latch. A new type of variable degree of freedom (DOF) compliant five-bar mechanism (VDCM) based on the novel compliant joint is constructed. The novel compliant mechanism is characterized by multiple motion modes of planar five-bar mechanism and four-joint, crank-shaper, crank-oscillating block mechanism. These motion modes can be switched through the different choices of driving joints and limiting stoppers. This compliant mechanism is effectively implanted into a vehicle side door latch as a sub-branch to perform power release function. The force-adaptive characteristic of the VDCM ensures compatibility with extant manual release branches. Drifting displacement of the CJTS’s torsion spring rotation center in the groove is proposed as a compliant index to describe the compatibility and force-adaptive characteristics under various working modes. The relationship between torsion spring stiffness and mechanism characteristic point motion trajectory or position recovery time duration or motion accuracy is studied. The results show that the introduction of compatibility and force-adaptive characteristics is able to reduce the shaking forces exerted on the mechanism frame. The shaking forces will be further reduced by changing equivalent mass center position of the component. Furthermore, the practicability of the novel compliant mechanism is experimentally validated on the force-displacement test platform. The work in this paper provides a reference for the multi-mode motion mechanical design in a confined space of the latch.

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Nehme, H., N. G. Chalhoub, and N. Henein. "Development of a Dynamic Model for Predicting the Rigid and Flexible Motions of the Crank Slider Mechanism." Journal of Engineering for Gas Turbines and Power 120, no. 3 (July 1, 1998): 678–86. http://dx.doi.org/10.1115/1.2818199.

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A continuous model is developed to predict the rigid and flexible motions of the piston assembly/connecting rod/crankshaft mechanism for a single cylinder engine. The model accounts for the torsional vibration and the out-of-plane transverse deformation of the crankshaft along with the out-of-plane transverse deformation of the connecting rod. The eigenvalue problem of the crankshaft, including the counterweights, the flywheel, and the crank gear, is solved to obtain the analytical expressions for the elastic modes of the crankshaft. The resulting mode shapes are then used in the assumed modes method to approximate the structural flexibility terms. The differential-algebraic equations of motion are obtained by implementing the Lagrange principle. The digital simulation results illustrate the role played by the topological nonlinearities inherent in the system and reveal the relationships with which the rigid and flexible motions of the crank-slider mechanism would interact.

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Kim, Young-Wann, and Kyung-Jo Park. "The interaction of fundamental torsional guided waves from axial and oblique defects in pipes." Insight - Non-Destructive Testing and Condition Monitoring 63, no. 6 (June 1, 2021): 334–40. http://dx.doi.org/10.1784/insi.2021.63.6.334.

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A quantitative study of the interaction of the T(0,1) torsional mode with axial and oblique defects in a pipe is presented in this paper. A mode decomposition technique employing the chirplet transform is used to separate the multimodal signals reflected from the defects. Reflection signals are obtained from experiments on a carbon steel pipe. The influence of the crack length and inclination angle on the reflection is investigated. The reflection from an axial defect is found to consist of a series of wave pulses with gradually decaying amplitude. The results show that the reflection coefficient of an axial crack initially increases with the crack length but finally reaches an oscillating regime. Furthermore, for an oblique crack, it is revealed that the reflection coefficient is linearly dependent on the equivalent circumferential extent of the defect and is independent of the axial length.

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Zaqarashvili, T., and B. Roberts. "Swing Coupling between Stellar Pulsations and Torsional Alfvén Oscillations." International Astronomical Union Colloquium 185 (2002): 484–85. http://dx.doi.org/10.1017/s0252921100016894.

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AbstractWe suggest a mechanism of energy transmission from stellar radial pulsations into torsional oscillations in a dipole-like magnetic field. We show that the stellar radial pulsations cause a periodical variation of the Alfén speed which leads to the Mathieu equation for torsional Alfén waves. Harmonics with half the frequency of the pulsations have exponentially growing amplitudes. Then the energy supporting the various type of pulsations can be transformed into purely electromagnetic oscillations of the star.

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Liu, Siyuan, Wanyou Li, Zhijun Shuai, and Meilong Chen. "Vibration Analysis of a Single-Cylinder Reciprocating Compressor considering the Coupling Effects of Torsional Vibration." Shock and Vibration 2019 (April 1, 2019): 1–9. http://dx.doi.org/10.1155/2019/3904595.

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A piston slap is one of the main vibration sources of the reciprocating machinery. Much work has been done in this field, most of which was based on a constant rotating speed. However, in practice, the speed of a crankshaft may always fluctuate due to the uneven load or excitation. The inertia forces of moving components are much different at the fluctuating rotating speed comparing with that at a constant speed. In this paper, the piston slap and the induced vibration are analyzed based on the instantaneous angular speed measured on a single-cylinder reciprocating compressor. Firstly, the dynamics of a crank-connecting rod mechanism is analyzed based on the measured instantaneous angular speed which contains the torsional vibration of the air compressor. The time histories of piston slap impact forces considering and without considering torsional vibration are compared. Then, in order to correlate the piston slap impact with the slap-induced vibration, the corresponding transfer functions between the middle stroke of the outer surface of the cylinder liner and the excitation points are measured. And the excitation force on the main bearing is also taken into account to bring the simulation closer to the experimental results. The effects of a torsional vibration on the vibration of the cylinder liner are analyzed, and the simulation results show that the torsional vibration is a factor that must be taken into account in the vibration analysis of the single-cylinder reciprocating compressor.

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Teed, R. J., C. A. Jones, and S. M. Tobias. "Torsional waves driven by convection and jets in Earth’s liquid core." Geophysical Journal International 216, no. 1 (October 9, 2018): 123–29. http://dx.doi.org/10.1093/gji/ggy416.

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SUMMARY Turbulence and waves in Earth’s iron-rich liquid outer core are believed to be responsible for the generation of the geomagnetic field via dynamo action. When waves break upon the mantle they cause a shift in the rotation rate of Earth’s solid exterior and contribute to variations in the length-of-day on a ∼6-yr timescale. Though the outer core cannot be probed by direct observation, such torsional waves are believed to propagate along Earth’s radial magnetic field, but as yet no self-consistent mechanism for their generation has been determined. Here we provide evidence of a realistic physical excitation mechanism for torsional waves observed in numerical simulations. We find that inefficient convection above and below the solid inner core traps buoyant fluid forming a density gradient between pole and equator, similar to that observed in Earth’s atmosphere. Consequently, a shearing jet stream—a ‘thermal wind’—is formed near the inner core; evidence of such a jet has recently been found. Owing to the sharp density gradient and influence of magnetic field, convection at this location is able to operate with the turnover frequency required to generate waves. Amplified by the jet it then triggers a train of oscillations. Our results demonstrate a plausible mechanism for generating torsional waves under Earth-like conditions and thus further cement their importance for Earth’s core dynamics.

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Rempel, Matthias. "Flux‐Transport Dynamos with Lorentz Force Feedback on Differential Rotation and Meridional Flow: Saturation Mechanism and Torsional Oscillations." Astrophysical Journal 647, no. 1 (August 10, 2006): 662–75. http://dx.doi.org/10.1086/505170.

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13

Svoboda, Antonín, Milan Chalupa, and Taťána Šrámková. "Mechanical Medical Device for Generating Vibration and Stimulation of the Neuron Pathways." Symmetry 13, no. 1 (December 31, 2020): 62. http://dx.doi.org/10.3390/sym13010062.

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This article describes a medical device uses precisely generated vibrations to obtain genetic material (sperm) in injured men, tetraplegics, and paraplegics. A significant advantage is the absence of general anesthesia of the patient. The DC motor of a medical device works with a safe voltage powered by rechargeable or AA cells. The principle of generation of vibration is a crank mechanism. Rotation of the flywheel is converted to rectilinear reciprocating motion. The amplitude is set in the range between 1–4 mm and the frequency is controlled by the RPM of the DC motor. If the stimulation will be followed preciously with the methodology, the process will be completed within 12 min from the beginning of stimulation. The success rate of the device is in the range between 65–85% depending on the patient’s condition and the extent of the spinal cord lesion. The measurement of sinusoidal oscillations was performed by using a stand in which the device was mounted. The amplitude was measured with an accelerometer and then mathematically converted by software Matlab and MS-Excel to the magnitude of the deviation in mm. Measurements have shown that the proposed design meets the requirements for amplitude and frequency.

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Li, Wenjie, and Shujin Laima. "Experimental Investigations on Nonlinear Flutter Behaviors of a Bridge Deck with Different Leading and Trailing Edges." Applied Sciences 10, no. 21 (November 3, 2020): 7781. http://dx.doi.org/10.3390/app10217781.

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Recently, the nonlinear flutter behavior of long-span suspension bridges has attracted attention. Unlike the classical theory of bridge flutter, the stable limit cycle oscillations (LCO) have occurred for some bluff aerodynamic configurations when the inflow velocity exceeded a specific critical value. To explore the influence of aerodynamic configurations on flutter behaviors a series of flutter tests for spring-suspended sectional models were conducted. When the leading edges and trailing edges with various shapes were installed at the sectional models, different flutter types occurred. In the test, the self-excited forces and flutter responses were measured. Then, the characteristics of coupling vibration and aerodynamic hysteresis of the two kinds of flutter were analyzed and compared. Finally, the role of the phase difference between self-excited forces and displacements was discussed in the mechanism difference of the classical flutter and the postflutter LCO. As the leading edge became the bluffer, the results showed that the type of flutter gradually transformed from classical divergent flutter to postcritical LCO and the torsional mode played a more important role in the flutter than in the vertical mode. For the postflutter LCO, there was a negative feedback pattern, i.e., as the vibration amplitude increased, the phase difference gradually decreased, and the energy input to the dynamic system did not grow rapidly, which limited the further vibration divergence and resulted in a stable LCO.

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Simard, Corinne, and Paul Charbonneau. "Grand Minima in a spherical non-kinematic α2Ω mean-field dynamo model." Journal of Space Weather and Space Climate 10 (2020): 9. http://dx.doi.org/10.1051/swsc/2020006.

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We present a non-kinematic axisymetric α2Ω mean-field dynamo model in which the complete α-tensor and mean differential rotation profile are both extracted from a global magnetohydrodynamical simulation of solar convection producing cycling large-scale magnetic fields. The nonlinear backreaction of the Lorentz force on differential rotation is the only amplitude-limiting mechanism introduced in the mean-field model. We compare and contrast the amplitude modulation patterns characterizing this mean-field dynamo, to those already well-studied in the context of non-kinematic αΩ models using a scalar α-effect. As in the latter, we find that large quasi-periodic modulation of the primary cycle are produced at low magnetic Prandtl number (Pm), with the ratio of modulation period to the primary cycle period scaling inversely with Pm. The variations of differential rotation remain well within the bounds set by observed solar torsional oscillations. In this low-Pm regime, moderately supercritical solutions can also exhibit aperiodic Maunder Minimum-like periods of strongly reduced cycle amplitude. The inter-event waiting time distribution is approximately exponential, in agreement with solar activity reconstructions based on cosmogenic radioisotopes. Secular variations in low-latitude surface differential rotation during Grand Minima, as compared to epochs of normal cyclic behavior, are commensurate in amplitude with historical inferences based on sunspot drawings. Our modeling results suggest that the low levels of observed variations in the solar differential rotation in the course of the activity cycle may nonetheless contribute to, or perhaps even dominate, the regulation of the magnetic cycle amplitude.

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Thomsen, M., A. Go¨rtz, U. V. Na¨gerl, D. Kubein-Meesenburg, W. Go¨rtz, J. Fangha¨nel, and H. Na¨gerl. "Bending Vibrations of the Femur and the Oscillatory Behavior of a Cemented Femoral Hip Endoprosthesis." Journal of Biomechanical Engineering 122, no. 4 (February 28, 2000): 416–22. http://dx.doi.org/10.1115/1.1286317.

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The paper presents a novel method for recording amplitude and phase of 6D-vibrations of a spatial pendulum over a wide frequency range (10 Hz up to 20 kHz). The six degrees of freedom of the pendulum mass were monitored by three electrodynamic stereo pickups. At rest, the tips of the needles and the pendulum’s center of mass defined the reference system with respect to which the oscillations of the mass were recorded in terms of their amplitudes and phases. Its small dimensions, constant transfer characteristics, linearity, high dynamics, and virtual lack of reaction onto the moving system over the entire frequency range provided the advantages of the measuring system. This method was used to analyze the spatial 6D-vibrations of the head of a cemented femoral hip endoprosthesis when the femur was stimulated to bending vibrations. The head of the prosthesis carried out axial rotational vibrations at every frequency used to stimulate the femur. The amplitudes of the axial rotations of the cortical bone were small in comparison to the ones of the prosthesis head, indicating that axial rotational vibrations following femur bending vibrations mainly stressed the spongiosa and the cement layer. This was observed over the entire frequency range, including at the low frequencies relevant for gait. Over the low-frequency range, as well as at some of the higher resonance frequencies, stationary instantaneous helical axes characterized the vibrations. The measurements suggest the mechanism that the interface “implant-bone” may already be stressed by axial torsional loads when the femur is loaded by bending impacts that are known to occur during walking. [S0148-0731(00)01604-6]

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Ferrell, Devin B., Yanal F. Isaac, Spencer P. Magleby, and Larry L. Howell. "Development of Criteria for Lamina Emergent Mechanism Flexures With Specific Application to Metals." Journal of Mechanical Design 133, no. 3 (March 1, 2011). http://dx.doi.org/10.1115/1.4003538.

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This paper develops new design criteria for lamina emergent mechanism (LEM) flexures with particular application to sheet-metal-formed metal flexures. The LEM flexure design criteria are based on the relative performance between the LEM flexure and a section of lamina that is of the same overall length, width, and thickness as the LEM flexure. Novel metal revolute and torsional LEM flexures are presented and evaluated against the LEM flexure design criteria. Both flexures meet the proposed criteria, and their performance is evaluated in the design of a basic crank-slider mechanism. When compared with unformed flexures of the same dimensions, the revolute and torsional metal LEM flexures are found to improve the crank-slider performance.

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Pasricha, MS, and FM Hashim. "Effect of the Reciprocating Mass of Slider-Crank Mechanism on Torsional Vibrations of Diesel Engine Systems." ASEAN Journal on Science and Technology for Development 23, no. 1 (July 26, 2007). http://dx.doi.org/10.3125/asean.v23i1.408.

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19

Xu, Da. "Application of the Crank–Nicolson time integrator to viscoelastic wave equations with boundary feedback damping." IMA Journal of Numerical Analysis, October 14, 2020. http://dx.doi.org/10.1093/imanum/draa071.

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Abstract We study the numerical solutions for a boundary feedback mechanism on torsional vibrations of a homogeneous viscoelastic rod. The problem is discretized by the Crank–Nicolson scheme based on the trapezoidal rule: while the time derivative is approximated by the trapezoidal rule in a two-step way, a convolution quadrature formula, constructed again from the trapezoidal rule, is used to approximate the integral term. Error estimates of the numerical scheme are derived in the $ l^{\infty }_{t}(0,~\infty ;~L^{2}(0,~1)) $ norm. Results from some numerical experiment are presented.

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Loi, Shyeh Tjing, and John C. B. Papaloizou. "Torsional Alfvén resonances as an efficient damping mechanism for non-radial oscillations in red giant stars." Monthly Notices of the Royal Astronomical Society, February 2, 2017. http://dx.doi.org/10.1093/mnras/stx281.

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Kulke, Vincent, and Georg-Peter Ostermeyer. "Energy transfer through parametric excitation to reduce self-excited drill string vibrations." Journal of Vibration and Control, July 13, 2021, 107754632110310. http://dx.doi.org/10.1177/10775463211031065.

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Drilling a wellbore can result in several types of vibration that lead to inefficient drilling and premature failure of drill string components. These vibrations are subdivided based on their operating direction into lateral, torsional, and axial vibrations. Especially in hard and dense formations, high-frequency torsional oscillations are found in the bottom-hole assembly (BHA). These critical vibrations are induced by a self-excitation mechanism caused by the bit–rock interaction. Self-excitation mechanisms are regenerative effects, mode coupling, or a velocity-dependent torque characteristic at the drill bit. To increase drilling performance and reduce tool failure due to high-frequency torsional oscillations, the critical vibration amplitudes localized at the bottom-hole assembly need to be minimized. Increasing the damping of self-excited systems to affect the energy output during vibration is a common approach to mitigate self-excited vibrations. In drilling systems, the achievable damping is naturally limited by the small installation space due to the drilled borehole diameter. Therefore, alternative methods to influence vibrations are necessary. Applying parametric excitation in self-excited systems can result in a parametric anti-resonance and therefore in an energy transfer within different modes of the structure. This allows, among other benefits, improved utilization of the structural damping. In this article, the influence of additional stiffness–based parametric excitation on self-excited torsional vibration in downhole drilling systems is investigated. For this purpose, a finite element model of a drill string is reduced using the component mode synthesis and analyzed with the goal to mitigate torsional vibrations. The multiple degree of freedom drill string model is investigated regarding the additional energy transfer due to the parametric excitation. Robustness of various parameters, especially with regard to the positioning within the bottom-hole assembly, is analyzed and discussed. Additionally, the problem of multiple unstable self-excited modes due to the nonlinear velocity-dependent torque characteristic in drilling systems is addressed.

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Liu, Wen, Chunji Ren, Tengjiao Lin, and Yanjun Zhang. "Study on vibration characteristics of hydraulic planetary transmission considering engine and torque converter excitation." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, September 23, 2021, 095440702110477. http://dx.doi.org/10.1177/09544070211047790.

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Large-size vehicle loaders are mainly used in various construction projects with complex working environment, which has a serious impact on the internal vibration of the whole system. In this study, the vibration characteristics of hydraulic planetary transmission of vehicle loader considering the influence of the external excitation are evaluated theoretically and experimentally. The output torque of the four-stroke six-cylinder diesel engine is obtained by force calculation of crank and connecting rod mechanism. The equivalent stiffness and damping of the torque converter are solved according to the torsional dynamic equation of the torque converter. The trapped oil area, oil pressure, and flow rate of gear meshing part are extracted to obtain the trapped oil pressure of variable-speed pump. Then, the multi-degree-of-freedom gear system dynamic model is established to calculate the meshing force, which is applied to vibration response analysis model by using mode superposition method. Lastly, the vibration response test is performed on the experimental prototype to verify the calculation method. The conclusion shows that the generation principle of external excitation and its calculation method in this paper are feasible in the analysis of dynamic characteristics of hydraulic planetary torque converter.

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Journal articles on the topic 'Torsional oscillations of the crank mechanism'

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