Subjects: Mechanics >> Oscillation and Wave submitted time 2023-06-21 Cooperative journals: 《应用力学学报》
Abstract：
With the increasing demand for oil and gas,horizontal wells are used more and more frequently.The lateral vibration of the drillstring in horizontal wells will directly affect drilling efficiency and safety.Different from vertical wells,horizontal wells have buildup and horizontal sections besides vertical section; thus the initial deformation and stress conditions of the drillstring are more complicated.In order to accurately predict the lateral vibration of the drillstring in horizontal wells,based on the lagrange equation,a finite element model of drillstring system is established with consideration of the 3D borehole trajectory,drilling parameters and contact between the borehole and drillstring.The model is discretized and solved by the finite element method.Then,the lateral vibration characteristics of the drillstring are verified by the field data of a horizontal well in Sichuan.Finally,the influence of the weight on bit,rotation speed and stabilizer is analyzed.The results show that in the drilling process,the lateral vibration of the drillstring in the vertical section is slight; the drillstring lateral vibration in the buildup and the horizontal sections is violent,and the closer to the bit is,the more violent the lateral vibration is; the weight on the bit has small effect on the lateral vibration in the vertical section,but it has significant effect in the buildup and horizontal sections.the larger the weight on bit,the more violent the lateral vibration of the drillstring.Under the actual drilling conditions(the rotation speed is 30-120 r/min),the change of the lateral vibration of all drillstring sections are not obvious.The stabilizer can limit the lateral displacement of the drillstring in the horizontal section,and its location can greatly affect the stabilizer effect.The model can also be used to study the dynamic characteristics of drillstring in cured wells,and the results can provide theoretical guidance for improving drilling efficiency and ensuring drillstring safety.
Subjects: Mechanics >> Oscillation and Wave submitted time 2023-06-21 Cooperative journals: 《应用力学学报》
Abstract：
The concrete multi-ribbed conical reticulated shell is a new spatial structure formed by dividing the conical surface into multi-ribbed flat plates.The multi-ribbed flat plates meet at the valley(ridge)line.In order to understand the stability of the structure,the arc length method is used for geometric nonlinear analysis on the basis of elastic stability analysis.The effects of rise-span ratio,boundary beam rigidity and initial geometric defects on the structural bearing capacity are discussed.The results show that the weak part of the structure is mainly the intersection between the valley line and the multi-ribbed slab.The buckling instability has the characteristics of a shell structure,and the ultimate bearing capacity drops sharply after jumping instability.The increase of the rise-span ratio will reduce the structural bearing capacity.As the boundary beam is the main force transmission member of,increasing its rigidity can effectively improve the overall rigidity of the structure.Changing the rigidity of the ridge(valley)beam and the thickness of roof plate has little contribution to improving the overall stability of the structure.Increasing the rigidity of the multi-ribbed beam will effectively enhance the structure's ability to resist instability.The initial geometric defects have little effect on the ultimate bearing capacity of the structure.The amplitude L/300 is regarded as the largest initial defect acceptable to the structure.The stability bearing capacity formula is fitted to the structure,and the calculation error is within acceptable engineering accuracy.
Subjects: Mechanics >> Oscillation and Wave submitted time 2023-06-21 Cooperative journals: 《应用力学学报》
Abstract：
Recent experiments have shown that the stress-strain relation of graphene is nonlinear under finite displacements.Theoretically,the stress-strain relation of single-walled carbon nanotubes(SWCNTs)with big tube diameters are consistent with that of graphene because the SWCNTs are formed by rolling graphene.In the present paper,we propose a new Euler-Bernoulli beam model of the SWCNTs based on the nonlinear stress-strain relation of graphene.Then,the static bending and forced vibrations of the SWCNTs are studied by the Galerkin method and the multi-scale method for the case of a hinged-hinged beam.The results indicate that the nonlinear terms of stress-strain relation can soften the stiffness of the SWCNTs during static bending.In the case of forced vibration,the nonlinear terms of stress-strain relation can change the position of the amplitude bifurcation points.Therefore,the nonlinear term in nonlinear constitutive cannot be ignored.
Subjects: Mechanics >> Oscillation and Wave submitted time 2023-06-21 Cooperative journals: 《应用力学学报》
Abstract：
Aiming at the analysis of the swing laws of the cable lifting system(CLS),the dynamic characteristics of the CLS are studied by combining theoretical modeling and visual simulation.The dynamic model is derived using D' Alembert's principle.It contains the effect of horizontal motion and lifting motion on the system motion status,and also takes into account the quality of the cable to improve the accuracy of model.The Runge-Kutta method is used to solve model numerically,and simulation is conducted within ADAMS environment to verify the dynamic model.Based on the dynamic model and numerical calculation,the effect of horizontal motion,lifting motion and system parameters on swing was studied.The results show that the dynamic model and numerical calculations are accurate,which can be used to plan more reasonable motion and explore swing control technology and method.During the movement,the payload oscillation is mainly affected by the initial acceleration,sudden change of acceleration and lifting speed.The larger initial acceleration or the sudden change of acceleration or the greater velocity of lifting,the greater swing and the velocity of lifting makes the oscillation increased exponentially with time.After the lifting point stops moving,the payload oscillation is affected by the velocity,acceleration and frequency of the lifting at the stopping moment.The greater the speed,the greater the cardinality of the swing of lifting payload; the greater the acceleration and the longer the time of acceleration,the greater the increased swing of lifting payload.The length of steel cable and the mass of lifting payload determine the frequency of the CLS,which does not affect the payload oscillation during the movement.The oscillation and frequency are affected by the lifting laws of the steel cable.And the study of acceleration laws of the lifting point affecting the oscillation can be used to guide the design and control of the CLS.
Subjects: Computer Science >> Other Disciplines of Computer Science Subjects: Mechanics >> Oscillation and Wave submitted time 2023-06-15
Abstract： This paper proposes a modal analysis strategy based on dilated residual convolutional broad network. In modal analysis, vibration analysis of large-scale structures or complex systems usually requires processing large amounts of data and complex calculations.The dilated residual convolution width architecture can reduce the number of parameters and computational complexity of the network, reduce the computational burden, and improve the efficiency of analysis.The dilated residual convolutional broad network applied to modal analysis tasks can improve the extraction ability of vibration features, improve the accuracy of modal identification, and enhance the sensitivity of structural damage detection, and has high computational efficiency and parameter efficiency. The experimental results show that our model achieves excellent performance in the regression task of modal analysis prediction.
Peer Review Status:
Awaiting Review
Subjects: Mechanics >> Oscillation and Wave submitted time 2022-12-21 Cooperative journals: 《应用力学学报》
Abstract：
The QZSID system consisting of parallel Quasi-Zero-Stiffness(QZS),damper and inerter is studied.In order to study the dynamic response mechanism of QZSID isolation system under near-fault vertical earthquake,an analysis model of QZSID system under vertical earthquake is established.The response control effect of QZSID isolation system is analyzed by nonlinear time-history response.The results show that the seismic response control effect of inerter is related to predominant period of near-fault vertical earthquakes.The inerter has a good control effect on the acceleration of long-period near-fault earthquakes.However,there is a poor control effect on the displacement.Although the resonance period is not prolonged under the action of long-period ground motion,the system can avoid the resonance frequency of ground motion.The system can still obtain good isolation effect.The vertical natural vibration period of the system should not be too large.The damping ratio and static equilibrium height can be helpful to the seismic response control of the system.Seismic responses are not proportioned to the mass parameters of inerter.The isolation effect of the inerter is related to the characteristics of ground motions.
Subjects: Mechanics >> Oscillation and Wave submitted time 2022-11-01 Cooperative journals: 《应用力学学报》
Abstract： The energy dissipation of stress wave propagation through rock masses with microdefects and macrojoint considering unloading effects was investigated.The combined effects of microdefects and macrojoints with different unloading and loading models on stress wave propagation were considered.First,the transmission properties of five waveforms of incident waves(rectangular wave,half-sinusoidal wave,triangular wave,left-triangular wave and right-triangular wave)propagating through the rock masses with microdefects and macrojoint were analyzed.Then,the differences in the energy transmission properties of stress waves propagating through rock masses with microdefects and macrojoint considering unloading effects and those not considering unloading effects were compared.Finally,the effects of propagation distance and incident wave amplitude on the energy transmission coefficient were discussed.The effects of propagation distance and incident wave amplitude on the difference of energy transmission coefficient with and without considering unloading effect were further revealed.The results show that the energy transmission coefficient considering unloading effect is always smaller than the energy transmission coefficient not considering unloading effect.In addition,the energy transmission coefficient of the rectangular wave is the largest while the energy transmission coefficient of the right-triangular wave is the smallest.The difference of energy transmission coefficient of the rectangular wave is the smallest whereas the difference of energy transmission coefficient of the left-triangular wave is the largest.The energy transmission coefficient decreases with the increase of propagation distance but increases with the increase of incident wave amplitude.The difference of energy transmission coefficient increases with the increase of propagation distance and decreases with the increase of incident wave amplitude.
Subjects: Mechanics >> Oscillation and Wave submitted time 2022-11-01 Cooperative journals: 《应用力学学报》
Abstract： The dynamic stress concentration ascribed to the scattering of stress wave encountering underground structures is an important factor affecting the damage of deep rock mass.The analytical solution of a circular lined tunnel filled with fluid in an infinite elastic medium subjected to a plane P wave was derived based on the wave function expansion methods.The influence of an elastic and rigid lining on the dynamic stress concentration around the tunnel was investigated,respectively.Moreover,the analytical solution of the transient P wave with Fourier integral transformation was obtained based on the state-steady response.The δ (x)function and Heaviside step function are introduced to simplify the integral computation.Taking the unit of a half sin wave as an incident function,the influence of wavelength and time on dynamic response was analyzed.Further,the distribution of dynamic stress of lining and surrounding rock was simulated by the finite element program LS-DYNA.The results indicate that the numerical simulation results are consistent with theoretical calculations.Waveform parameters,lining thickness and elastic modulus of lining materials have different effects on dynamic response,increasing the lining thickness and properly adjusting the stiffness of lining materials can play a better supporting effect.The peak value of dynamic stress concentration appears in the vertical incident direction and the value of the dynamic stress concentration factor along the incident direction is 0 or negative.Under the action of transient disturbance,which will not only cause large compressive stress concentration in surrounding rock and lining,but also occur the phenomenon of the duration of tensile stress is long.
Subjects: Mechanics >> Oscillation and Wave submitted time 2022-11-01 Cooperative journals: 《应用力学学报》
Abstract： Studying stress wave propagation across jointed rock masses is essential for the stability of rock engineering.Rock masses in nature include many joints,which have great influence on stress wave propagation.During wave propagation across rock masses,both of the amplitude and speed of the wave attenuate.Meanwhile,the interaction between the stress wave and the joints usually results the joints open,close and slippery.Currently,some analytical methods have been successfully applied-for studying one-dimensional or two-dimensional wave propagation across rock joints.These analytical methods are divided into three types:the discontinuous medium method,the equivalent continuous medium methods and double-scale discontinuous method.Based on these two methods,the effect of linear and nonlinear joints on wave propagation has been studied effectively.The present paper is to introduce the discontinuous and equivalent continuous media methods,discuss their applicability,and suggest the further problems to study.
Subjects: Mechanics >> Oscillation and Wave submitted time 2022-11-01 Cooperative journals: 《应用力学学报》
Abstract： The unsteady flow field of an airfoil under the action of pulsed jet is numerically simulated based on the Reynolds average N-S equation.The proper orthogonal decomposition(POD)method is used to analyze the variation of small-scale vortex structure in the wake of low-frequency,medium-frequency,and high-frequency pulsed jet.The results show that with the help of the POD method,the motion state of the wake small-scale vortex structure can be effectively extracted.The low-order modes extracted by the POD method mainly reflect the static separation structure of the wake vortex with the greatest intensity in the wake,corresponding to the main frequency component of the pulsed jet.The higher-order modes mainly reflect the flow state inside or between the wake vortices,corresponding to the high-order frequency doubling components of the pulsed jet.The mutual stretching within the wake vortex contains a wide range of frequencies,and the traction decomposition between the wake vortices contains a single frequency.Only a pair of main wake vortices can be extracted from the wake at low frequency,and many pairs of wake vortices with the same intensity can be extracted from the wake at high frequency.At low frequency,the wake vortex is single and the interaction is simple.The first six modes can be used to characterize the flow field structure.At high frequency,the number of wake vortices is large and the interaction is complex,so higher order modes are needed to characterize the flow field structure.
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