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Quick Search     Adv Search 2021 Vol. 42, No. 5 Published: 2021-10-28 501 Study on Mechanical Behavior and Force Transfer Mechanism of Bamboo Bolt Anchorage Interface in Earthen Sites DOI: 10.19636/j.cnki.cjsm42-1250/o3.2020.048 The anchorage technology of bamboo bolt is an important means to deal with the stability problem of large-scale earthen sites caused by longitudinal crack. However, the force transfer mechanism of such anchoring system is still unclear, which has become the bottleneck restricting its scientific and large-scale application. The mechanical behavior of the bamboo bolt anchorage interface is studied through in-situ pull-out test in Gao Chang Ruins. The main control interface causing the slip failure and the critical anchorage length range of anchorage system are clarified. By comparing the load-displacement relationship, stress, strain and slip distribution obtained from the test, the complete de-bonding phenomenon is identified when the relative slip of anchorage segment interface exceeds 22.56mm. Then the complete de-bonding phenomenon is characterized by the non shear stress section after the friction section, and a modified tri-linear bond-slip model suitable for this type of anchorage interface is established. On this basis, the simulation method of mechanical behavior of anchorage interface based on nonlinear spring element in ANSYS is proposed, and the force transfer mechanism of anchorage system is studied systematically. Finally, the reliability of the simulation method proposed is verified by comparing with the experimental results. The results show that the slip failure of the bolt / anchoring agent interface is the main reason for the failure of the anchorage system. The stress evolution process of the interface segment can be divided into four stages: elasticity, softening, friction and complete de-bonding; With the increase of pull-out load, the high stress zone of the anchorage interface gradually transfers from the loading end to the anchorage end; After the interface enters the stage of complete de-bonding, the shear stress tends to zero, and there are critical values for the ultimate anchoring force and effective anchoring length; The shear stress transferred from the 1st to the 2nd anchoring interface is very limited, and the sites soil stress is relatively low. The results of the study can provide a reference for the optimal design of anchorage of earthen sites based on the principle of "safety first, minimum intervention". 2021 Vol. 42 (5): 501-517 [Abstract] ( 177 ) HTML (1 KB)  PDF   (0 KB)  ( 129 ) 518 The improvement of kinematic hardening rule of 316L stainless steel DOI: 10.19636/j.cnki.cjsm42-1250/o3.2021.018 316L stainless steel can produce kinematic hardening effect under cyclic loading, resulting in the accumulation of ratcheting strain and thus greatly reducing the fatigue life of the material. The generation of kinematic hardening can be considered as the movement of the yield surface in the stress space during the loading process, which leads to the asymmetry of the yield strength in tension and compression. Based on the results of cyclic loading tests, many kinematic hardening rules have been proposed. Some rules are suitable for the simulation of uniaxial cycle loading case. However, for the multiaxial non-proportional variable amplitude histories, the calculation results of existing models have large overestimation compared with test results. In this work, the evolution of back stress of several classic kinematic hardening models are studied. And the moving direction of back stress is discussed as well. The stress-controlled ratcheting experiments of 316L stainless steel under uniaxial and multiaxial loading paths are conducted to verify the influences of mean stress, stress amplitude and loading history. The strain-controlled cyclic loading is also conducted to verify the stress relaxation. It is demonstrated that the axial ratcheting is obvious under symmetrical shear loading path, and the ratcheting strain increases with the increasing stress amplitude and mean stress. The influences on the direction of back stress component increment, which are induced by the uniaxial and multiaxial parameters in Chen-Jiao and Jiang-Sehitoglu kinematic hardening rules, are discussed. Based on the experimental results, Chen-Jiao’s kinematic hardening rule is improved by replacing the multiaxial parameter with a surface saturated ratio, and a new parameter is introduced for correcting the plastic modulus coefficients. The calculated results show that the improved rule predicts a similar mean stress with Chen-Jiao’s rule, and coincides with experimental data much better than Chen-Jiao’s kinematic hardening rule under multiaxial loading case, which also proves the improvement is correct and valid. 2021 Vol. 42 (5): 518-531 [Abstract] ( 176 ) HTML (1 KB)  PDF   (0 KB)  ( 131 ) 532 A data-driven model of the relationship between polymer molecular chain microstructure and mechanical properties DOI: 10.19636/j.cnki.cjsm42-1250/o3.2021.019 Polymers are generally composed of randomly distributed macromolecular chains. The distribution, entanglement, and cross-linking of molecular chains significantly affect the mechanical and physical properties of the polymer. In this paper, a data-driven method was used to establish the relationship between the microstructure and mechanical properties of polymer molecular chains. Using the finite element method, the random microstructure models of two molecular chains were established and their mechanical properties were obtained. A data set was established based on the relationship between microstructure and mechanical properties, with the random molecular chain microstructure of the polymer as input, and the elastic stiffness of the polymer as the response output, to train and verify the data-driven model. We have obtained the analysis results of the microstructure-mechanical properties relationship with satisfactory accuracy. The result shows that it is reliable to study the elastic stiffness of polymers through data-driven methods. 2021 Vol. 42 (5): 532-542 [Abstract] ( 230 ) HTML (1 KB)  PDF   (0 KB)  ( 165 ) 543 Dynamic analysis of the buckled thin film in island-interconnector structure under thermal effect DOI: 10.19636/j.cnki.cjsm42-1250/o3.2021.013 The flexible electronic devices based on the island-interconnector structure have been used in health monitoring and skin electronics. However, flexible electronic devices are extremely affected to vibration caused by changes in operating temperature during operation, which in turn affect the sensitivity and reliability of the device. Therefore, this paper studies the dynamic behaviours of the buckled thin films which serve as interconnects in island-interconnector structure flexible electronic devices under the thermal effect. Firstly, the dynamic equations of the buckled thin films under thermal effect are derived based on the Euler-Bernoulli beam theory. Secondly, by introducing new variables, the dynamic equations are introduced into the Hamilton system, and the corresponding Hamilton regular equations are obtained. Then, the symplectic Runge-Kutta method is used to solve the Hamilton regular equations. Compared with the traditional Runge-Kutta method, the symplectic algorithm has the advantages of high precision and high numerical stability in solving nonlinear dynamic equations. Finally, the effects of temperature change, pre-strain, and damping coefficient on the dynamic response of the buckled thin film are analyzed. This study would provide a theoretical reference for the dynamic design of flexible electronic devices. 2021 Vol. 42 (5): 543-551 [Abstract] ( 154 ) HTML (1 KB)  PDF   (0 KB)  ( 133 ) 552 Analytical solution for the Eshelby problem of an inhomogeneous inclusion with the same shear module as the matrix and arbitrary shape in an infinite plane DOI: 10.19636/j.cnki.cjsm42-1250/o3.2021.037 The elastic fields of the matrix in two-dimensional space with an inhomogeneous inclusion undergoing a uniform eigenstrain and/or due to a uniform remote load are studied, where the inclusion shaped by the Laurent polynomial has distinct properties to the matrix but shares the same shear modulus. The equivalent method is used to convert the problem of the perturbance field due to the remote uniform loadings into that of an equivalent uniform eigenstrain, and the interface continuity conditions are expressed by the K-M potentials. Then, by virtue of the Riemann mapping theorem, the exterior of the inclusion is mapped on to the exterior of the unit disk by the Laurent polynomial and making use of the Cauchy integral formula and the Faber polynomial, the explicit analytical solutions of the K-M potentials are carried out in the inclusion and the matrix, where the relative rigid-body displacement of the inclusion to the matrix is considered. The obtained results are compared with those of previous literatures, to show that the method and results of this paper are effective and correct. 2021 Vol. 42 (5): 552-566 [Abstract] ( 117 ) HTML (1 KB)  PDF   (0 KB)  ( 126 ) 567 Frictionless Contact of Thermoelectric Materials Under the Rigid Circular Punch DOI: 10.19636/j.cnki.cjsm42-1250/o3.2021.022 Thermoelectric materials can convert thermal energy into electricity, and vice versa. This excellent performance will contribute to the development of more cost-effective equipment and devices. The contact problem of thermoelectric materials has aroused widespread concern due to its possible application in various structures of practical significance. The frictionless contact problem of rigid conductive circular punch acting on half plane of thermoelectric materials is studied in this paper. Assume that the punch is an electric conductor and a thermal conductor, and the depth of the pressure and the width of the contact area are unknown. First, for the electric fields and temperature fields, starting from the constitutive equation of the thermal electric field, the analytical expressions of potential function, temperature, electric current density and energy flux are obtained by using Fourier transform. Then, for the elastic field, starting from the Duhamel-Neumann constitutive relations for plane thermoelasticity, the thermoelastic contact problem is transformed into the first kind of singular integral equation and solved numerically by using integral transformation and boundary conditions. The effects of the punch radius and thermoelectric load on the normal contact stress, electric current intensity factor and energy flux intensity factor are discussed. The results show that the normal electric current density and the normal energy flux of thermoelectric materials show high singularity in the vicinity of the contact edge, while the normal contact stress of the surface is zero at the contact edge. It is found that the research model established in this paper helps to understand the contact behavior of thermoelectric materials in a deeper level. It is a great significance to explore methods to suppress contact deformation and contact damage and to realize the optimal design of materials. 2021 Vol. 42 (5): 567-575 [Abstract] ( 111 ) HTML (1 KB)  PDF   (0 KB)  ( 134 ) 576 Symplectic elasticity method for local longitudinal buckling of thin and wide strips DOI: 10.19636/j.cnki.cjsm42-1250/o3.2021.033 Local longitudinal buckling is a flatness defect commonly found in the production process of thin and wide strips, and it is a difficult point in buckling research. An accurate analytical solution method is very important for the research of local longitudinal buckling formation mechanism and the improvement of strip flatness quality. In this paper, the local arbitrary longitudinal buckling of the strip is divided into two types: the edge and the interior of the strip. The symplectic elastic method is used to directly derive the critical buckling stress and buckling deflection function when the local longitudinal buckling area is subjected to different boundary constraints and the solution results are compared with the finite element and related literature. The result shows that the symplectic elasticity method has the same calculation accuracy and higher calculation efficiency than the finite element method, and the calculation accuracy is higher than that of the energy method in the reference; The critical buckling stress, buckling area geometry and buckling deflection function are affected by the strip boundary constraint conditions, which verifies the shortcomings of energy method and helps to improve the accuracy of local buckling calculation. 2021 Vol. 42 (5): 576-585 [Abstract] ( 139 ) HTML (1 KB)  PDF   (0 KB)  ( 137 ) 586 Study on the Snap Characteristics of Bistable Plate Actuated by MFC Intelligent Material DOI: 10.19636/j.cnki.cjsm42-1250/o3.2021.012 Due to the residual stress, asymmetric cross-ply bi-stable laminates can show two different stable deformation states at room temperature. In this paper, the stable configurations and the snap through behaviors of the bi-stable laminate actuated by MFC with center point fixed is studied. Considering the effect of mechanical-electric coupling, the mechanical model of the system is constructed. Based on the classical laminate theory of Krichhoff hypothesis, the potential energy of the system is obtained according to the Von-Karman strain-displacement relationship, and the Rayleigh-Ritz technique is used to obtain the configuration of the bi-stable laminate with MFC actuator. Using numerical method, systematic parametric analyses are conducted to investigate the influences of aspect ratio, ply thickness and laminate size on the bifurcation phenomenon of the bi-stable laminate with MFC. The critical size of bi-stable laminate and the snap-through voltage are predicted. It is found that the out-of-plane displacement of the corner point of the bi-stable laminate with MFC bifurcates with the increase of the side length of the laminate, and the bi-stable critical length increases with the increase of the aspect ratio. The critical thickness of the bi-stable laminate with MFC decreases with the increase of the aspect ratio. Using a specific MFC to actuate asymmetric laminates, there is a certain range of requirements for the size of the laminate. If the size of the laminate is too small, it will lose the bi-stable state, and if the size of the laminate is too large, it will exceed the actuating capability of the MFC. Compared with unidirectional actuating asymmetric laminates, adding MFC on the other side can achieve bidirectional actuating, but the snap-through voltage needs to increase. The snap through behavior of bi-stable laminates is a nonlinear behavior with large deformation, and the study of realization and control of snap behavior are very important for its application in engineering. Bi-stable laminate actuated by MFC is an intelligent deformable structure with fast response, easy control and strong reliability. The results of this paper provide a certain theoretical reference for the structural design of bi-stable laminates actuated by new piezoelectric materials. 2021 Vol. 42 (5): 586-598 [Abstract] ( 146 ) HTML (1 KB)  PDF   (0 KB)  ( 126 ) 599 Torsional Vibration Analysis of Nano-Round-Shaft in Elastic Medium DOI: 10.19636/j.cnki.cjsm42-1250/o3.2021.032 The torsional free vibration of the nano-shaft embedded in an elastic medium is investigated based on the nonlocal strain gradient theory. Firstly, the governing equations and boundary conditions are derived by Hamilton principle. Then the discrete form of the governing equations and boundary conditions are obtained by the differential quadrature method. Finally the torsional vibration characteristics are analyzed from the numerical results. The influence of two small-scale parameters and the stiffness of elastic media on vibration frequency are discussed. The coupling effect of the two scale parameters on vibration frequency is reflected through the influence of the scale parameter ratio. The results show that the torsional free vibration frequency decreases due to the increase of non-local parameters, and increases when the strain gradient scale parameter or elastic medium stiffness increase. When the non-local parameter is larger, the scale utility is reflected as a non-local effect , on the contrary, it is reflected as a strain gradient effect. 2021 Vol. 42 (5): 599-611 [Abstract] ( 123 ) HTML (1 KB)  PDF   (0 KB)  ( 124 ) 612 The Frequency Prediction of the Hybrid Structure of Wind Turbine Foundation Based on BP Neural Network DOI: 10.19636/j.cnki.cjsm42-1250/o3.2021.001 The natural frequency design of wind turbine tower structure is the basis of wind power generation structure system. To overcome the disadvantages of traditional theoretical and finite element method (FEM), a new approach based on BP neural network algorithm is proposed to efficiently predict the natural frequency of the newly designed hybrid Steel-Concrete cylinder tower. First, the features and labels of the training model are determined by FEM calculation and analysis. And then, 32 FEM calculation samples are used train the frequency prediction model of hybrid Steel-Concrete cylinder tower, using the BP neural network algorithm. It has been verified that this method has a high accuracy of the first-order frequency prediction, whose error is limited within only about 1.0E-3. On the other hand, all of the prediction results using the models trained with different sample sets agree well with the FEM calculation, implying the algorithm has a high stability. In addition, the BP neural network algorithm training method can also be used to predict the multi-order frequencies of hybrid Steel-Concrete cylinder tower, which still has the high accuracy. In addition, compared with frequency calculation based on FEM method, this new approach has outstanding efficiency. From the above aspects, it is proved the frequency prediction model based on the BP neural network is efficient and workable, which can provide important guidance for the design of wind power generation structure system. 2021 Vol. 42 (5): 612-622 [Abstract] ( 291 ) HTML (1 KB)  PDF   (0 KB)  ( 132 )

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