Subjects: Mechanics >> Solid Mechanics submitted time 2024-04-19 Cooperative journals: 《应用力学学报》
Abstract： Considering that research of circumferential horizontal shear wave(SH wave)has been published on the solid cylinders and cylindrical shell structures,aiming to discuss the existence of SH surface waves on the cylindrical cavity.Since it is impossible to directly obtain the analytical solution of SH surface wave propagating in cylindrical cavity,we compare the tendency of wave structures,strain energy density varying along thickness of SH waves on the surface of cylinders and various cylindrical shells.The governing equation of SH wave of homogeneous elastic material and functionally graded material in cylindrical coordinate system is established.The Bessel functions solution and the power series asymptotic solution of the governing equations of homogeneous elastic materials and functionally graded materials are obtained,respectively.Furthermore,the dispersion curves,the wave structures and the strain energy density are calculated.The results show that the power series method can be employed for solving wave governing equations with variable coefficients with high accuracy,the energy of circumferential SH waves in cylindrical structures is concentrated on the outer surface or subsurface,and the phenomenon of energy concentration is more obvious along thickness.It can be deduced from the distribution of strain energy density that the circumferential SH surface wave cannot propagate in the cylindrical cavity.Finally,for homogeneous material structure and functionally graded material structure,the inverse method is used to prove that any analytical solution cannot satisfy the attenuation condition of SH surface wave in the cavity.
Subjects: Mechanics >> Solid Mechanics submitted time 2024-04-19 Cooperative journals: 《应用力学学报》
Abstract：
The autoclaved aerated concrete block developed by desert sand is a new type of masonry material.A pseudo-static test considering the different vertical compressive stresses and constraints of structural columns is carried out on four pieces of desert sand wall made of autoclaved aerated concrete block in order to study the application of this new block in village buildings.The failure characteristics i.e.,force-displacement curve,skeleton curve,stiffness degradation curve and ductility of the four walls under low cyclic loading arecompared and analyzed. The test results show:1)The wall is mainly shear failure.The main crack of the wall without structural columns runs through the entire wall is about 45°,and the main crack of the wall with structural columns is in the shape of “inverted eight”.And when the vertical compressive stress increases,the seismic capacity of the wall increases,the lateral stiffness improves,but the ductility decreases. 2)Under the same vertical compressive stress,comparative analysis shows that the ultimate bearing capacity of the wall with structural columns is increased by about 2.22 times that of plain wall,ductility increased by about 60%,and the stiffness is also improved. 3)Based on the principal tensile stress theory and Coulomb failure theory,the calculation formulas for the seismic bearing capacity of the new block wall are established, and the calculation formula of seismic bearing capacity established by Coulomb failure theory is more reasonable in application. 4)The skeleton curve of the established restoring force model can reflect the experimental characteristics of the desert sand autoclaved aerated concrete block wall well.
Subjects: Mechanics >> Solid Mechanics submitted time 2024-04-19 Cooperative journals: 《应用力学学报》
Abstract：
In order to study the propagation characteristics of type Ⅰ fractures of concrete with different aggregate sizes,concrete three-point bending beam fracture tests with the maximum aggregate size of 10,20,30,40 mm were carried out,and the data of full-field strain and displacement changes in the calculated area on the specimen surface were measured by using digital image correlation techniques to investigate the changes and development of fracture energy,fracture toughness and fracture process zone of concrete with different aggregate sizes.The relationship between the FPZ extension process and the post-peak loading was investigated.The results show that with the increase of the aggregate size,the compressive strength,peak load and fracture parameters of the specimens show a trend ofincreasing first and then decreasing,and the change of FPZ length of M20 specimens has a strong correlation with post-peak load,and the aggregate has the best restraint effect on microcracks,In addition,by analyzing the development law of FPZ of concrete specimens with different aggregate sizes,it can be learned that specimens with the aggregate size of 20 mm have an improved local deformation capacity after peaking,enhanced fracture energy and fracture toughness,higher bearing capacity and smaller FPZ in the fracture process than other aggregate sizes concrete; therefore,the suitable aggregate size is 20 mm.
Subjects: Mechanics >> Solid Mechanics submitted time 2024-04-19 Cooperative journals: 《应用力学学报》
Abstract：
Basalt fiber reinforced composite(BFRP)has the advantages of strong corrosion resistance,high specific strength and environmental protection.The correct evaluation of the reliability and bearing capacity of BFRP pipeline is the basis for its application in the field of high value-added oil and gas transportation.For composite pipes wound by the basalt fiber(BF),the strength of impregnated fiber bundles is obtained on a meso scale firstly.Then,both axial and circumferential specimens were cut from a pipe and the tensile strength of the two kinds of specimens were measured.Based on both experimental measurement and finite element simulation,damage evolution of structure layers of the pipe wall was studied under conditions of tension,compression and shearing,and the constitutive model of the structure layer is obtained.Finally,a finite element model of the BF-wound composite pipe was established,and influences of fiber performances on the pipe’s carrying capacity were studied.It is shown that the effective fiber content exerts a great influence on the bearing capacity of the pipe.It is important to reduce the dispersion of fiber reinforcement from aspects such as fiber production and pipe forming process for predicting load-bearing reliability accurately and promoting BF composites application in oil and gas pipeline field.
Subjects: Mechanics >> Solid Mechanics submitted time 2024-04-19 Cooperative journals: 《应用力学学报》
Abstract：
Blind bolted T-shaped plate joints with good force transfer performance and high seismic performance,can make full use of the section characteristics of double steel tubes in composite concrete-filled steel tubular columns.Cyclic loading tests and numerical simulations on five blind bolted joints were conducted.There were three types of deformation characteristics of the T-shaped plate due to its different ribbed forms,but all the failure modes of the joints were plastic deformation of steel beams after T-shaped plates yielded.Numerical simulation results agreed well with the experimental results.A tensile model of the T-shaped plate was established according to the force-transferring mechanism based on the results of experiments and simulations.The bending bearing capacity of T-shaped plate flanges and stiffeners was calculated respectively,and the ultimate bearing capacity of the joint was calculated.The error between the calculated results and the experimental results is very small,and they are very close to the numerical simulation results.The results show that the calculation formula based on the tensile model of a T-shaped plate is suitable for the case of strength matching between T-shaped plates and blind bolts.The rib form of T-shaped plates has the greatest influence on the ultimate bearing capacity of the joint,followed by the flange thickness of T-shaped plates,and the web thickness of T-shaped plates has little influence.The maximum critical value and the best matching value between the diameter of the blind bolt and the flange thickness of T-shaped plates are obtained,which provides a theoretical reference and design basis for the application of this type of joint in composite structures.
Subjects: Mechanics >> Solid Mechanics submitted time 2024-04-19 Cooperative journals: 《应用力学学报》
Abstract：
To explore the influences of section types(rectangular,1/4 arch,1/2 arch)and the groove-width ratio(B/b=1.5:1,2:1,3:1,4:1)on the earth pressure of the hill-filled cut-and-cover tunnel(HFCCT),this paper used the discrete element software PFC2D to simulate and analyze the evolution laws of the average vertical earth pressure(VEP)on the top of the cut-and-cover tunnel(CCT),the settlement difference between inner and outer soil columns,and the contact force chains among particles.Moreover,the paper analyzed the correlation between the settlement difference and the earth pressure based on the earth pressure theory of culvert and pipe,which was put forward by Gu Anquan,and further modified the function of the above-mentioned theory so as to make it applicable to the different section types and groove-width ratio (B/b).The results show that ①when the B/b is determined,the contact force chains will distribute on the top of the CCT and the average vertical earth pressure(VEP)is greater if the CCT adopts a rectangular section.The average VEP will decrease if the CCT adopts an arched section.However,there is partly stress concentration at the top of the arched section.② When the section is determined,the average VEP and settlement difference on the top of CCT both increase with the increase of B/b.As the B/b decreases,the slope effect is enhanced,the settlement of the outer soil column reduces gradually,and the interaction between the inner and outer soil columns declines,which makes the VEP on the top of the CCT decrease.③ The settlement difference between the inner and outer soil columns is linearly related to the additional earth pressure.Compared with the rectangular section,the same additional earth pressure under the arched section is generated by a smaller differential settlement,which benefits the stability of the structure.
Subjects: Materials Science >> Composite Material Subjects: Mechanics >> Solid Mechanics Subjects: Aviation & Aerospace >> Manufacture Technology of Aerocraft submitted time 2024-04-09
Abstract： The mechanical properties of unidirectional fiber-reinforced plastic (UD-FRP) are affected by internal micro-defects, such as random fiber arrangement, fiber misalignment, and micro#2;voids. This study aims to investigate how these multiple micro-defects interact with each other and how they affect the strength and failure mechanisms of UD-FRP through computational micromechanics. The failure behavior was simulated by the finite element analysis of a representative volume element; both matrix and interface failure were considered for the different loadings and their combinations. It was found that these micro-defects significantly weakened the compressive strength of UD-FRP along the longitudinal direction. Especially the fiber misalignment magnified the effect of fiber arrangement, while the micro-voids reduced the effect. Besides, the fiber arrangement and micro-voids significantly weakened the tensile and compressive strength of UD-FRP along the transverse direction. Moreover, transverse and longitudinal shear strengths are significantly affected by micro-voids, but only longitudinal shear is affected by fiber arrangement, and this effect is also weakened by micro-voids. Finally, the damage envelope under the combined longitudinal compression and transverse loads was obtained and compared with the Tsai-Wu failure criterion. The results showed that the Tsai-Wu criteria can provide an effective estimation for the failure locus under this biaxial loading condition.
Peer Review Status:
Awaiting Review
Subjects: Mechanics >> Solid Mechanics submitted time 2024-02-07 Cooperative journals: 《应用力学学报》
Abstract：
Since the column in precipitator casing mainly presents buckling failure,the stability strengthening method for column was investigated so as to improve its buckling capacity and optimize the structural design of precipitator equipment.For the structure system composed of stiffened wallboard and H-Shaped steel column in precipitator casing,in consideration of initial imperfection,the buckling mechanism of column was investigated by non-linear finite element method first.Since being influenced by the wall stressed skin effect,the buckling of column occurs on the high compressive stress region adjacent to the column top.The column presents the interactive buckling that the overall flexural-torsional buckling occurs on the front half section composed of the front flange and the web and the local buckling occurs simultaneously on the web.Based on the buckling characteristics,the strengthening configuration measurement for enhancing column buckling capacity was proposed,that is,the strengthening steel plates would be welded on both sides of the front flange of the column in top region,and its upper and lower sides would be welded with the L-shaped diaphragms.The influences of several configuration parameters on the column buckling capacity were investigated,including the width,thickness and the locating range of the strengthening steel plates and the L-shaped diaphragm thickness.Consequently,a rational design method of the strengthening configuration for enhancing column buckling capacity was proposed.The buckling capacity of the column can be increased significantly by employing the strengthening configuration measurement.
Subjects: Mechanics >> Solid Mechanics submitted time 2024-02-07 Cooperative journals: 《应用力学学报》
Abstract：
The seepage direction inside the dam usually changes due to the different seepage positions and the fluctuation of upstream and downstream water levels.The infiltration angle of the seepage flow on the contact surface between the protected soil and the filter is not orthogonal.Because of the great difference of permeability coefficient between the dam material and the filter,the seepage angle causes the change of hydraulic properties of the contact surface,which will affect the filter performance.In this paper,the PFC-3D is used to establish the numerical models of 30°,45°,60° and 90° between the seepage direction and the contact surface.By simulating the real-time invasion rate of the protected soil particles and the depth of their movement into the filter,the contact erosion and filter effect under the action of different seepage directions are studied.The results show that in the initial stage of seepage,the difference of invasion rate and invasion depth of protected soil particles in different seepage directions is small; with the increase of seepage time,the invasion rate at 90°is relatively stable and the value is small,the invasion depth and seepage velocity at the contact surface are the smallest,and the filter has a strong ability to block the movement of protected soil particles.The filter effect decreases at 60°,45° and 30°,indicating that the larger the angle between the seepage direction and the contact surface,the better the filter effect.The reasonableness of the calculation results is discussed by using the principle of seepage refraction,and compared and analyzed with the experimental results of relevant literature,and it is considered that the change of seepage infiltration angle at the contact surface between the fill and the filter should be paid attention to in water conservancy projects such as embankment dams,especially the fact that the small angle of infiltration flow at the interface has a greater influence on the filter effect.
Subjects: Mechanics >> Solid Mechanics submitted time 2024-02-07 Cooperative journals: 《应用力学学报》
Abstract：
Small diameter pipelines are widely distributed in oil and gas fields,but the traditional corrosion detection methods are difficult and expensive,and the corrosion degree can only be quantitatively evaluated after the sampling points are excavated.In order to make up for this deficiency,quantitative evaluation under trenchless condition is realized:the magnetic signal characteristics of leakage magnetic field near corrosion defects are obtained by analyzing the magnetic dipole model; the relationship between the depth and width of corrosion defects and the magnetic signal is obtained by finite element simulation; SY/T 6151—2009 “evaluation method for corrosion damage of steel pipeline”,the defect width and depth parameters required for corrosion evaluation are combined with the magnetic dipole model theory to deduce the relationship between calculation and magnetic signal characteristic parameters,and a quantitative evaluation method for pipeline corrosion under trenchless condition by weak magnetic field detection is obtained,which is verified in an oil field pipeline project,and is suitable for Trenchless condition It provides a theoretical basis for the quantitative evaluation of pipeline corrosion detection.
Subjects: Mechanics >> Solid Mechanics submitted time 2024-02-07 Cooperative journals: 《应用力学学报》
Abstract：
Under the action of asymmetrical load,the internal bracing foundation excavation will skew to the small side of the load,which will be deleterious to the stability of the foundation pit,so it is necessary to optimize its design.A unsymmetrical loaded pipe gallery foundation pit is used as an example in this paper,and the finite element software plaxis 2D was used to simulate this foundation pit.The simulation results are in good agreement with the measured data,which verifies the validity of the model.Then the supporting structure parameters of the foundation pit are analyzed,and the influence of the length,equivalent thickness and elastic modulus of the supporting structure on the deformation of the supporting structure and the safety of the foundation pit is studied.The research results show that when the supporting structures on both sides are designed according to the biased side,the maximum horizontal displacement of a side supporting structure increases with the equivalent thickness of the side supporting structure.And with the increase of the equivalent thickness and elastic modulus of the supporting structure on both sides,the maximum horizontal displacement of the side supporting structure and the reverse displacement of the top of the non-biased side supporting structure will decrease.Finally,a simple and economical optimization idea for asymmetric load foundation pits is proposed by parameter analysis,and the optimization effect is analyzed through numerical simulation,which proves the effectiveness of the optimization idea.The conclusions and optimization idea can provide references for similar projects.
Subjects: Mechanics >> Solid Mechanics submitted time 2024-02-07 Cooperative journals: 《应用力学学报》
Abstract：
Based on the cyclic load testing of steel reinforced recycled concrete filled circular steel tube columns,the hysteretic performance of composite columns was numerically analyzed by using OpenSees software,and the hysteretic curves and performance indexes of composite columns were obtained. Compared with the experimental results,the rationality of the numerical model of the composite column was verified. On this basis,the influence levels of parameters on the hysteretic performance of composite columns were analyzed. The results showed that the replacement rate of recycled aggregate increased from 0 to 100%,the peak load of composite columns decreased by 7.78%,and the ductility decreased slightly. Improving the strength of recycled concrete,section steel and circular steel tube was beneficial to improving the bearing capacity and stiffness of composite columns,but it also increased the brittleness of composite columns. With the growth of axial compression ratio,the bearing capacity of composite columns increased first and then decreased,and the ductility decreased gradually. The steel ratio of section steel rose from 5.54% to 9.99%,and the peak load of composite columns increased by 24.34%,but it did not obviously improve the ductility of composite columns. Increasing the wall thickness of steel tube was beneficial to the bearing capacity and ductility of composite columns.
Subjects: Mechanics >> Solid Mechanics submitted time 2024-02-07 Cooperative journals: 《应用力学学报》
Abstract：
Soft dielectric thin films are widely used in electrical and electronic systems due to their low modulus,large deformation and strong adaptability.However,due to the low dielectric constant of the material,they usually need to serve in high electric field environment.Under high electric field,soft dielectric film is prone to instability and electrical breakdown.It affects the application range and stability of the material.In this paper,the stability of this kind of device is studied under the condition that the electrode’s constraint on the soft dielectric film.First,the evolution law of the instability morphology in the process of voltage loading and unloading is described when the electrode has no constraint on the dielectric.Then,the inhibition of electromechanical instability by soft electrodes such as lithium chloride hydrogel is discussed.The chemical bonding method was used to strengthen the constraint of hydrogel electrode on the dielectric film,and the critical breakdown field strength of the dielectric film was increased.
Subjects: Mechanics >> Solid Mechanics submitted time 2024-02-07 Cooperative journals: 《应用力学学报》
Abstract： Compared with shallow buried tunnel,the high stress caused by the increase of buried depth makes the safety evaluation of deep buried tunnel more complicated.Therefore,this paper designs and optimizes the bolt support mode of deep buried tunnel under impact load with the premise of in-situ stress balance by combining the finite and infinite elements.This paper not only studies the deformation characteristics of surrounding rock under impact load,but also analyzes the influence of length,density,length interval arrangement and key support of arch foot on the safety of tunnel.The results show that the Mises stress has almost no change before and after the in-situ stress balance,but the displacement is highly affected.When impact wave is loaded,the Mises stress first increases slightly with the increase of bolt length and density.When the length and density of the bolt increase to a certain value,the Mises stress no longer increases.The displacement and plastic strain of the cavern wall reach their minimum.In this case,the surrounding rock of the tunnel reaches a relatively safe state.Regarding to the bolt spacing,reasonable arrangement of short dense bolts is beneficial to the safety of tunnel,and the increase of the number of long anchors can improve the safety of the tunnel.This is due to the wide reinforcement range of long anchor to the surrounding rock.A high strength bearing layer is formed above the tunnel.It can withstand a large load,and transfer the load to the bottom of the straight wall.When the arch foot of the cavern is mainly supported,the displacement of the arch foot as well as the whole wall is reduced.
Subjects: Mechanics >> Solid Mechanics submitted time 2024-02-07 Cooperative journals: 《应用力学学报》
Abstract：
Cutterhead of a tunnel boring machine(TBM),the main weighted part in the process of tunneling,bears loadings in different directions.A fatigue failure of cutterhead would severely affect the construction progress and safety.Therefore,it is of great importance to study the fatigue reliability of its cracks.In this paper,the critical point of the cutterhead was found using the static strength analysis,and we analyzed the dynamic stress characteristics.In addition,the stress intensity factor of cutterhead crack was calculated using the sub model technique,and the crack propagation mechanism and damage characteristics of cutterhead crack were also analyzed.Then,combined with crack fatigue theory,we proposed a fatigue reliability evaluation method based on JC method,and the effects of different factors on the reliability were discussed for different geological conditions.The results show that the crack propagation has open-type and tear-type in the deepest part of the crack tip,but there are three kinds of propagation modes at both ends.As the initial crack depth increases,the fatigue reliability of the cutterhead decreases significantly.The reliability is positively correlated with the crack shape ratio.However,there are no significant relationships between the reliability and depth of the critical crack.
Subjects: Mechanics >> Solid Mechanics submitted time 2023-12-18 Cooperative journals: 《应用力学学报》
Abstract：
Catenary theory is increasingly widely used in the design of large-span space flexible pipelines.However,the application mainly considers in-plane vertical force or horizontal force,and the study of using catenary theory to directly solve out-of-plane problems is still not perfect.In response to this problem,this paper starts from the two-dimensional catenary theory,establishes a nonlinear equation system in which the out-of-plane normal concentrated force acts on the horizontal catenary at any position,and obtains the analytical solution of the out-of-plane normal concentrated force acting on the midpoint ofcatenary.The dichotomy and the Newton-Raphson iterative method are used to solve the analytical solutions and nonlinear equations respectively.The results of this paper are verified by flexible cable test device and finite element calculation.The results show that the configuration and characteristic tension obtained by experiments and finite element calculations are in good agreement with the configuration and characteristic tension calculated by theoretical calculations.The theoretical research results in this paper can solve the common problem of the vertical distributed force and the out-of-plane normal concentrated force of the flexible pipeline.The initial configuration form-finding and characteristic tension calculation problems under the action.
Subjects: Mechanics >> Solid Mechanics submitted time 2023-12-18 Cooperative journals: 《应用力学学报》
Abstract：
To study the influence of damage threshold on the damage mechanical properties of soft rock with natural defects,based on the damage threshold theory,combined with the modified Lade-Duncan strength criterion and the elastic Hooke’s law,we derived the expression of the damage threshold of soft rock.The statistical damage constitutive model of soft rock is constructed by using Weibull distribution theory and Lemaitre strain equivalence theory,and verified by a triaxial compression test.The results show that the damage threshold of soft rock based on the modified Lade-Duncan strength criterion and elastic Hooke’s law is too conservative,and the natural defects have a great influence on the axial strain of rock.Taking the natural defects in rock as modified variables,the damage variation law,failure process description,and stress-strain evolution of soft rock are more practical after modifying the damage threshold,which verifies the scientificity and rationality of the damage constitutive model of soft rock in this paper.
Subjects: Mechanics >> Solid Mechanics submitted time 2023-12-18 Cooperative journals: 《应用力学学报》
Abstract：
In order to expand the application scope of non-limit active earth pressure calculation before instability and failure of deep foundation pit,according to the effect of soil state transition effect before the instability of deep foundation pit,that is,the characteristics of viscous soil fluid and the division of wall back disturbance region,a calculation method of non-limit active earth pressure considering time and displacement was derived according to the rheological model of soil and the momentum equation of fluid movement.The COMSOL Multiphysics simulation software was used to solve the calculation equation,and the active earth pressure about time and displacement before instability and failure of deep foundation pit was calculated.The results show that the calculated results of non-limit active earth pressure based on the soil state transition effect before foundation pit failure are closer to the measured values,and the error is less than 3%.Through the analysis of the rheological parameters in the calculation model,the influence of instantaneous elastic modulus,viscoelastic modulus and viscosity coefficient on the non-limit active earth pressure is obtained,and the viscosity coefficient has the most significant influence on the non-limit active earth pressure.The analysis results have engineering guiding significance for the instability and failure prevention of deep foundation pit.
Subjects: Mechanics >> Solid Mechanics submitted time 2023-12-18 Cooperative journals: 《应用力学学报》
Abstract：
The backfill site is formed by short-term reconstruction.Compared with the natural site,factors such as backfill material significantly affect the internal force of the structure.In order to investigate the long-term safety of unloading high-filled cut-and-cover tunnels(HFCCT)during use process,the timeliness of the structural response needs to be analyzed.The authors established the model of HFCCT with the finite different software(FLAC3D)to analyze the variation of the soil arch shape and the structural response of HFCCT over time after its completion.The results show that when the creeping materials are filled,the soil arch inside the backfill soil gradually degenerates and disappears and the various aspects of the structure response change greatly.Besides,the rate of change is higher in the early stage,gradually declines in the middle stage,and finally basically stabilizes and becomes zero.The backfill height and backfill material have certain influence on soil arch shape and structural response.With the increase of backfill height,the shape of soil arch and the structure response will change obviously,but the changing height does not affect the overall change trend over time.If the creep properties of materials are weak,the shape of soil arch changes notably,but the structural response varies little as time goes by.The research results can provide reference for the design and safety monitoring of such structures.
Subjects: Mechanics >> Solid Mechanics submitted time 2023-12-18 Cooperative journals: 《应用力学学报》
Abstract：
To investigate the stress mechanism of pipe-roof pre-construction structure,the force performance of the double-steel-plate-concrete biased members was explored.The test of four double-steel-plate-concrete composite members was completed,and the finite element model was established.The correctness and reliability of the model were verified by comparing the calculation results with the test results.The numerical analysis took the form of end restraint,the form of interface connection,and eccentricity as parameters.The results show that in the steel-steel-concrete eccentric compression member,when the end restraint is strong enough,concrete and steel plates on both sides participate in the force work together,and there is no interface slip.Without considering the buckling,the setting of the connector does not affect the bearing capacity of the member,and the bearing capacity is the highest at this time.When the end restraint is not strong enough and the external load cannot act on the concrete and the steel plates on both sides at the same time,setting a connector between the steel plate and concrete can improve the bearing capacity of the member.When the coincident nodes on the interface between steel plate and concrete are combined into the same node,the bearing capacity is the highest.
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