Subjects: Mechanics >> Other Disciplines of Mechanics submitted time 2024-06-17 Cooperative journals: 《应用力学学报》
Abstract：
The combined resonance of superharmonic resonance and 1:3 internal resonance of a rectangular thin plate in transverse magnetic field is studied.For the rectangular thin plate with one side fixed and three sides simply supported,the two degree of freedom nonlinear vibration differential equations are obtained by the Galerkin method.Then the multiple-scale method is employed to solve equations,and amplitude frequency response equations of the first two modes are obtained.Through calculation examples,the relationship between the first two order response amplitudes and parameters when superharmonic internal resonance occurs in system is obtained,in which the influence of parameters e.g.,external excitation amplitude and magnetic field intensity on the vibration of system is discussed.The results show that the high-order modes are indirectly excited when internal resonance is considered,and there is energy exchange in the system,and the resonance of system can be controlled by changing the magnetic field intensity.
Subjects: Mechanics >> Other Disciplines of Mechanics submitted time 2024-06-17 Cooperative journals: 《应用力学学报》
Abstract：
In order to study the tensile rate dependence of EPDM mechanical behavior,uniaxial tensile tests of EPDM at 3 mm/min,30 mm/min,300 mm/min and 500 mm/min were carried out,respectively.The nonlinear mechanical behavior laws and tensile rate characteristics of EPDM were analyzed.Based on the fractional-order Kelvin-Vogit,ZWT and OGDEN models,the experimental curves of different tensile rates at 160% strain were fitted,and the characterization ability of the models was compared and studied.The results show that the whole loading curve of EPDM presents a typical “S” shape,and has significant nonlinear hysteresis characteristics.The larger the tensile rate,the larger the area of hysteresis loop,and the stronger the damping loss capacity.When the strain is greater than 68%,the tensile rate has a significant effect on the mechanical properties of EPDM,and hardening occurs.The fractional Kelvin-Vogit and OGDEN models are suitable for the characterization of mechanical behavior of viscoelastic materials of EPDM when the strain is less than 68% at a low tensile rate,while the ZWT model is suitable for the characterization of mechanical behavior of viscoelastic materials of EPDM when the strain is more than 100% at a high tensile rate.The ZWT model also has a good fitting effect at low tensile rate.The results can provide a useful reference for the performance evaluation and optimization of EPDM products.
Subjects: Mechanics >> Other Disciplines of Mechanics submitted time 2024-06-17 Cooperative journals: 《应用力学学报》
Abstract：
Inspired by transportation using rolling logs,a compound-pendulum-hump interaction mechanism was designed.Through constructing an array of pendulum wheels and humps on the two surfaces,respectively,smooth relative sliding between the surfaces can be achieved.To investigate the relationship between the normal force and the tangential force in the sliding,the dynamical differential equations of the wheel-hump mechanism were established.An iterative algorithm was proposed based on Runge-Kutta method to solve the equations to calculate the sliding resistance induced by the collision between the pendulum wheels and the humps.The simulation results indicated that the energy loss in the sliding could be reduced by setting proper geometrical parameters of the proposed mechanism,so that the ratio of the normal load to the equivalent transversal resistance could be improved significantly.Based on the theoretical analysis,a prototype was fabricated for experimental verification.The results showed that smooth sliding could be achieved.Meanwhile,the tangential driving force could be less than one percent of the normal load,verifying the feasibility of the mechanism.
Subjects: Mechanics >> Other Disciplines of Mechanics submitted time 2024-06-17 Cooperative journals: 《应用力学学报》
Abstract：
Earthquake is one important factors which affect the stability of red mud yard.According to the current codes and the finite element strength reduction method,the static stability of Longtayagou red mud yard is analyzed.The position and shape of slip surface,and the safety factor is determined.Based on the safety factor of pseudo static method with different seismic intensity,the displacement,acceleration and dynamic safety factor of the red mud yard under two measured seismic waves are analyzed.The calculation results meet the specification requirements,and it can be determined to be stable.By comparing with the evaluation requirements of different methods and different specifications,the calculation results of the finite element strength reduction method can be judged as the evaluation criterion of stability analysis.
Subjects: Mechanics >> Other Disciplines of Mechanics submitted time 2024-06-17 Cooperative journals: 《应用力学学报》
Abstract：
In order to further study the response law of mid-story isolation structure considering SSI effect subjected to three-dimensional long-period earthquake and the difference with ordinary ground motion,one-dimensional,two-dimensional and three-dimensional ordinary ground motions and long-period ground motion are input respectively.Aiming at the more serious stress overrun problem of bearing subjected to three-dimensional long-period earthquake,the reliability of three-dimensional isolation structure subjected to long-period earthquake is further verified by adding three-dimensional isolation bearing.It is found that the seismic response of inter-story isolation structure considering SSI effect is greater than that subjected to ordinary ground motion input under long-period ground motion.The structural seismic response subjected to three-dimensional long-period earthquake is greater than that subjected to one-dimensional and two-dimensional inputs.The three-dimensional isolation structure can still effectively isolate the vertical earthquake under the action of long-period earthquake,the bearing stress is effectively reduced,the foundation soil stress is optimized,and the isolation effect is obvious.
Subjects: Mechanics >> Other Disciplines of Mechanics submitted time 2024-06-17 Cooperative journals: 《应用力学学报》
Abstract： Natural internode bamboo tubes are commonly used in engineering,and it is of great significance to investigate the impact resistance of such natural thin-walled tube structures.The impact resistance of natural bamboo tubes was investigated,and a finite element analysis was carried out with a split Hopkinson pressure bar(SHPB).The three-dimensional Hashin and Puck unidirectional fiber composite failure criterion was applied in ABAQUS and combined with the correction of the strain rate effect on strength to establish a bamboo tube constitutive model to simulate the natural internode bamboo tubes under impact loading.The dynamic stress-strain curves and damage modes obtained were close to those obtained from the SHPB experiments,proving the accuracy of the finite element model.The results show that the experimental and simulated ultimate compressive strengths have a minimum error of2.19 percent and a maximum error of 8.68 percent; under different impact compression loads,the bamboo tubes show end face crushing,axial splitting,and other forms of damage; displacement,velocity,and acceleration responses at the nodes of the outer wall of the bamboo tubes increase with the increase of the impact load.The incident energy,reflected energy,absorbed energy,and specific absorbed energy all increase with time,whereas the transmitted energy does not.The peak load of internode bamboo tubes is significantly lower than that of GFRP thin-walled round tubes,but the specific absorbed energy is similar,indicating that internode bamboo tubes are not suitable for high-speed impact protection fields that require large impact energy.The preliminary findings may provide some theoretical guidance for the use of bamboo tubes in engineering structural protection.
Subjects: Mechanics >> Other Disciplines of Mechanics submitted time 2024-06-17 Cooperative journals: 《应用力学学报》
Abstract： The dynamic snap-through behavior of isotropic shallow shells under thermal shock loading was studied in the present work.The transient heat conduction through the thickness of shell was analyzed first; the thermally induced membrane forces and bending moments were also derived.The classical shell theory was adopted to model the shell and the derived equations of motion accounts for the Karman’s geometrically nonlinear strain.The equations of motion were then transformed into coupled time-dependent nonlinear algebraic equations via the Ritz method,and the latter was numerically solved with the Newmark method and Newton-Raphson’s iterative method.The critical thermal shock condition for the occurrence of dynamic snap-through was identified by the Budiansky-Hutchinson criterion while the computational results were analyzed.It was demonstrated that dynamic snap-through occurs in the shallow shell subjected to strong enough thermal shock,and thermally induced vibration exists during the whole snap-through process.The modeling and analysis methods provided by this study have important reference value for accurately evaluating the stability and dynamic response of engineering shallow shells under thermal shock.
Subjects: Mechanics >> Other Disciplines of Mechanics submitted time 2024-06-17 Cooperative journals: 《应用力学学报》
Abstract： The ABAQUS general finite element software is used to model concrete bridge piers constrained by assembled square steel tubes and calculate the load-displacement hysteresis curve and skeleton curve characteristics of the bridge piers.Axial compression ratio,slenderness ratio,confinement coefficient,yield strength of square steel tube,concrete strength,ratio of embedded depth of steel tube to side length of pier,and ratio of diameter of nested steel tube to side length of pier,and ratio of thickness of nested steel tube to side length of pier are taken as extended parameters.The influences of various parameters on the load-displacement skeleton curve of the concrete bridge piers confined by assembled square steel tubes are studied.Referring to the calculation framework of steel tube confined reinforced concrete column,the calculation formula of each characteristic value(elastic stiffness,horizontal load peak,peak load displacement and descending segment stiffness)of concrete piers confined by prefabricated square steel tubes is fitted.The calculation formula is in good agreement with the results of finite element analysis.The average value of the ratio between the finite element analysis value and the calculated value of the formula is 1.004～1.035,and the mean square error is 0.133～0.162.The actual project is selected to verify the algorithm.The calculation results are in good agreement with the finite element value.
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Subjects: Mechanics >> Other Disciplines of Mechanics submitted time 2024-06-17 Cooperative journals: 《应用力学学报》
Abstract： The circular ring vibration isolator is a nonlinear vibration isolator based on a circular ring structure.The circular ring produces a nonlinear restoring force due to the coupling of the tension and the curvature caused by stretching.The key to studying the performance of the vibration isolator is the accurate modeling of the nonlinear restoring force of the circular ring.In this paper,the circular ring structure is equally divided into several segments of curved beams.The force-displacement relationship model considering geometric nonlinearity is established for each segment of the curved beam using the beam constraint model.Combined with the force transfer relationship and geometric constraint relationship between curved beams,the nonlinear restoring force model of the whole circular ring during the compression process is established.The normal stress at all segment points during the deformation of the circular ring can be calculated via the beam constraint model.The restoring force of the circular ring structure in the compression process is measured by an electronic servo fatigue testing machine,and the modeling accuracy of the beam constraint model is verified.The research results show that the nonlinear restoring force characteristics of the circular ring can be characterized by the beam constraint model.The modeling accuracy of the beam constraint model is comparable to that of the elliptic integration method,but the model expression and solution process are simpler than those of the elliptic integration method.When the compression of the circular ring is the largest,the normal stress is the largest,and the maximum normal stress is obtained at the upper and lower end points of the circular ring.The modeling accuracy of the beam constraint model increases with the increase of the number of segments.When the number of segments is greater than 12,the restoring force calculation error of the beam constraint model is less than 2%.
YES
Subjects: Mechanics >> Other Disciplines of Mechanics submitted time 2024-06-17 Cooperative journals: 《应用力学学报》
Abstract： Hydrogels hold great promise in various high-tech fields such as biomedicine,brain-machine interfaces,flexible sensors,and soft actuators.However,they still face mechanical challenges when encountering different application environments,including susceptibility to tensile fracture,plastic deformation,and fatigue failure,which severely limit their application range.To enhance the mechanical properties of hydrogels to adapt to different working conditions,this study makes a comprehensive review of the mechanical properties of current hydrogel formulations and typical applications of various mechanically reinforced hydrogels.First,the composition of hydrogels is introduced,including natural polymer hydrogels and synthetic polymer hydrogels.Then,by systematically summarizing the mechanical characteristics and reinforcement methods of different hydrogels,the optimization pathways of mechanical properties such as tensile strength,adhesive strength,and fatigue threshold are analyzed in depth.Last,potential application scenarios for hydrogels with excellent mechanical properties are identified,and future development directions are discussed.This review provides a diverse perspective and solutions for enhancing the mechanical properties of hydrogels,providing scientific guidance for designing novel hydrogel materials tailored to specific requirements.
Subjects: Mechanics >> Other Disciplines of Mechanics submitted time 2024-05-07 Cooperative journals: 《应用力学学报》
Abstract：
In order to study the growth of convective disturbance and heat transfer characteristics of rectangular cavity with sinusoidal periodic heating, the hydrodynamic equations were numerically simulated.The results showed that with the increase of Grashof number Gr, the growth rate of maximum amplitude Amax of convective disturbance increases while the time of linear growth phase decreases. For a cavity with aspect ratio A=10 and a width d=2 cm and for the fluid with Prandtl number Pr=6.949, the empirical formula of the growth rate γm of convective disturbance varying with Graschof number is γm=9×10-8Gr1.234 3. For a cavity with A=10 and d=6 cm and for the fluid with Pr=0.703, the empirical formula of the growth rate γmvaring with Graschof number is γm=8×10-4Gr0.52. At Pr=0.027 2, the correlation between the average Nusselt numberNu^- of the hot wall and Graschof number isNu^-=0.000 02Gr1.17; at Pr=6.949,the correlation is Nu^-=0.000 24Gr1.05.The heat transfer capacity of the right wall increases with the increase of Graschof number.
Subjects: Mechanics >> Other Disciplines of Mechanics submitted time 2024-04-19 Cooperative journals: 《应用力学学报》
Abstract：
A new form of assembled beam-column joint is proposed,and in order to study the mechanical properties of this joint,the parametric analysis of the assembled new beam-column joint with cantilever beam segment splicing is carried out by ABAQUS software on the basis of the preliminary experimental research.First,the test model of the assembled beam-column joint was established by ABAQUS,and the test results were compared and verified. Then,the parametric analysis of the spliced joint with cantilevered beam segments was carried out and the mechanical properties of the joint under different parameters were obtained by considering the number of stiffening ribs,thickness of cross-plate,thickness of plates,and length of L-shaped angle steel.
Subjects: Mechanics >> Other Disciplines of Mechanics submitted time 2024-04-19 Cooperative journals: 《应用力学学报》
Abstract：
The existence of complex microscopic features in the bolted structure leads to inevitable uncertainty in the numerical model.Aiming at the quantification of parameter uncertainty in bolt design,this paper proposes a stochastic model updating method for assembled structures with bolted joints based on a high-precision modal synthesis method.First,considering the influence of higher-order residual modes,a high-precision modal synthesis method suitable for the elastic interface of bolted joints is derived.Then,under the framework of Bayesian inference,using the natural frequency and mode shape probability distribution of the assembled structure,the posterior probability density function of the bolt parameters is established,and the parameter uncertainty is quantified with delayed rejection adaptive metropolis(DRAM)sampling method.The numerical examples indicate that for structures with large differences in natural frequencies among the substructures,compared with the general modal synthesis methods,the method proposed in this paper can ensure good model updating performance in the case of using a small number of substructure modes.
Subjects: Mechanics >> Other Disciplines of Mechanics submitted time 2024-04-19 Cooperative journals: 《应用力学学报》
Abstract：
In order to study the dynamic mechanical characteristics and stress wave propagation law of filled joint rocks under different confinement angles and different confining pressures,the impact test was carried out on sandstone specimens with a filling joint thickness of 8 mm by using the modified dynamic and static combination loading(split hopkinson pressure bar,SHPB)device.The dynamic mechanical characteristics and stress wave propagation laws of filled joints under different confining pressure grades(0,4,6 and 8 MPa)and different joint inclination angles(0°,15°,30° and 45°)were studied,and the stress wave oblique emission theory was used and verified.The experimental results show that ①The reflected amplitude of intact sandstone is the smallest.Taking 0 MPa as an example,the reflected amplitude increases from 0.194×10-3 to 0.299×10-3,which is positively correlated with the inclination,and the transmission amplitude is negatively correlated with the inclination angle from 0.169×10-3 to 0.053×10-3.Taking 0° as an example,the reflected amplitude is negatively correlated with the confining voltage,which decreases from 0.194×10-3 to 0.074×10-3 and the transmitted amplitude increases from 0.169×10-3 to 0.257×10-3.②Under the action of impact dynamic load,a certain degree of confining pressure can limit deformation,inhibit cementation surface separation,and improve bearing capacity.The larger the inclination angle of the joint,the greater the deformation of the filling joint,and the worse the bearing state.③With the increase of confining pressure,the reflectivity decreases and the transmission capacity increases.The reflection coefficient of the 0° inclination specimen decreases from 0.603 to 0.147,and the transmission coefficient increases uniformly from 0.569 to 0.789.With the increase of inclination angle,the reflection capacity of the confining pressure specimen increases,while the transmission capacity decreases,which is consistent with the theoretical analysis law.④The joint inclination angle is negatively correlated with the absorption energy density of the sample,but the confining pressure is positively correlated with the absorption energy density of the sample,which is consistent with the transmission reflection law under the action of confining pressure.
Subjects: Mechanics >> Other Disciplines of Mechanics submitted time 2024-04-19 Cooperative journals: 《应用力学学报》
Abstract：
In order to obtain the tri-dimensional seismic ground motion time histories which are compatible with the corresponding floor response spectra,the eigenfunctions of the sixth order ordinary differential equation are used as the basis functions to decompose and reconstruct the real recorded earthquake ground motion.By constructing the influence matrix,the amplitude coefficient of the eigenfunction is gradually adjusted through iterative calculation,and the preset fitting accuracy threshold is finally achieved.The orthogonalization procedure is introduced to ensure the statistical independence between the tri-directional time histories,and two sets of numerical examples are provided.The examples show that it is capable of achieving high matching accuracy between the response spectra of generated time histories and the target spectra.During the iteration,the time history response spectrum uniformly approaches the target spectra.The iterative process converges; the generated seismic time histories are drift-free and satisfy the code requirements.
Subjects: Mechanics >> Other Disciplines of Mechanics submitted time 2024-04-19 Cooperative journals: 《应用力学学报》
Abstract：
This article studies the free vibration of a functionally graded piezoelectric porous cylindrical microshell resting on elastic foundation under thermo-electro-mechanical loads.First,the dynamic model of the functionally graded piezoelectric porous cylindrical microshell resting on elastic foundation was established.Then the analytical solution of modal frequencies of the functionally graded piezoelectric porous cylindrical microshell resting on elastic foundation was derived using the third-order shear deformation shell theory and the modified couple stress theory.Last the factors affecting model frequency were discussed by numerical case studies.The results show that the Pasternak foundation is preferred to improve the modal frequencies of the shell to the Winkler foundation.The modal frequencies of the cylindrical microshell could be adjusted via changing the stiffness coefficients of the elastic foundation,axial load,applied voltage,porosity distribution,material volume fraction indexes,and structure dimensions.The larger the porosity volume fraction,the greater the influence of temperature and axial load on the modal frequency,and the smaller the influence of applied voltage on the modal frequency.The change trends of modal frequency with increasing porosity volume fraction are obviously different with different material volume fraction indexes.The elastic foundation can weaken the influence of temperature,axial load and applied voltage on the modal frequency,and its influence on the modal frequency of thin or short cylindrical shell is more significant.
Subjects: Mechanics >> Other Disciplines of Mechanics submitted time 2024-04-19 Cooperative journals: 《应用力学学报》
Abstract：
The damage of transmission and transformation tower system under wind-rain coupling often attributes to wind load, ignoring the amplification effect of rain load coupling excitation. Based on the tensioning tower system model of a transmission line, the time-history loads of wind and rain in a normal weather field and a wet downburst field are simulated. The dynamic response analysis of the tower-line system is carried out. The results show that the rainfall has a significant impact on the response of the transmission tower-line system. With the increase of rainfall intensity, the response of the tower-line system increases obviously. Under the condition of extreme rainfall, the displacement of tower top in wet downburst field increased by 31.30% in X direction and 33.93% in Y direction, respectively. The displacement and acceleration power spectral density of the tower top increased significantly in both wind and rain fields,and the resonance response of the system was enhanced. The stress of the main material at the key position of the tower increased by 11.64% and 37.07%,respectively. In different wind fields, the increasing incentive effect of raindrop impact on tower-line system during heavy rainfall cannot be ignored.
Subjects: Mechanics >> Other Disciplines of Mechanics submitted time 2024-04-19 Cooperative journals: 《应用力学学报》
Abstract：
This paper innovatively provides a coherence function model,specially adapted for water-covered canyon-hill composite topography and for simulating the multi-support seismic motions.First,a new coherence function model considering the soil filtering effect and vertical distance is proposed and derived.The characteristics of coherence and physical meaning of the proposed model are further investigated and summarized.Then,the multi-support underground seismic motions are generated by decomposing the underground power spectral density matrix,which is formed by combining the coherence function based on the derived model with the transfer function.Subsequently,the reasonability and rationality of the simulated results are verified by comparing the simulated power spectrum and the coherence function to the theoretical ones.Finally,the influence of the presented coherence function model on the differential effect of multi-support seismic motions and the dynamic response of a continuous rigid frame bridge is specially analyzed,respectively.The results show that the coherence among the simulated variable seismic motions is relatively reduced,but the variability of seismic motions at each foundation is increased,which leads to the enlargement of the structural responses.
Subjects: Mechanics >> Other Disciplines of Mechanics submitted time 2024-04-19 Cooperative journals: 《应用力学学报》
Abstract：
Aiming at the problem that it is difficult for the existing modeling and analysis methods of soft finger based on fin ray effect to meet the requirements of high precision and small amounts of calculation,we proposed approximately regarding the soft finger as concatenated four-bar mechanisms by observing the soft finger deformation.The theoretical model to solve contact force and actuating torque was established based on the principle of virtual work when the deformation state is given.The deformation recovery torque was modeled using linearly elastic torsional spring,and then an improved particle swarm algorithm was programmed to solve the stiffness coefficient of the torsional spring of each phalanx.Based on the Abaqus finite element model and combined with the secondary development,the relationship between actuating torque and pressure,joint angle was obtained,and then fitted with the aid of BP neural network.Last,an experiment platform was built to measure the grip force of the soft robotic picking hand.The results showed that the absolute relative error of the model was less than 8.6%,which was equivalent to that of the finite element model.The values of actuating torque calculated by BP neural network shared the same trend with the values measured and the relative error was under 12.7%.
Subjects: Mechanics >> Other Disciplines of Mechanics submitted time 2024-04-19 Cooperative journals: 《应用力学学报》
Abstract：
An experimental study on the dynamic mechanical properties of polyurea was carried out by using a low impedance split Hopkinson pressure bar and pull rod test device.The dynamic compression and dynamic tensile tests of polyurea 8380 at room temperature(T=18 ℃)and high temperature(50,80 ℃)and low temperature(-40,-20 ℃)were carried out respectively.The dynamic compression and dynamic tensile properties of the material were studied,and the effects of strain rate and temperature on the dynamic mechanical properties of the material were studied.The results show that:the dynamic mechanical properties of polyurea 8380 have significant strain rate effect at different temperatures.With the increase of loading strain rate,the strength,deformation capacity and energy dissipation capacity of the material are improved to varying degrees.The dynamic mechanical properties of polyurea 8380 have obvious temperature dependence.The dynamic compressive properties of polyurea 8380 show different changes at high and low temperatures.The dynamic compressive strength of polyurea 8380 is much lower than that at room temperature.With the increase of temperature,the dynamic compressive strength of the material decreases.At a low temperature,the dynamic compressive strength and energy dissipation capacity of polyurea 8380 are significantly improved compared with those at room temperature.With the decrease of temperature,the dynamic compressive strength of the material increases.
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