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Quick Search     Adv Search 2024 Vol. 45, No. 4 Published: 2024-08-28 427 Data-Driven and Continuum Damage Mechanics-based Approach for Predicting Fatigue Life in Additive Manufacturing DOI: 10.19636/j.cnki.cjsm42-1250/o3.2024.010 Traditional mechanics models and emerging data-driven models have been widely used to predict the fatigue life of additive materials. However, traditional models represented by Continuum Damage Mechanics (CDM) suffer from low accuracy and limited applicability, while data-driven models represented by Artificial Neural Networks (ANN) cannot be applied to small-sample operating conditions. To address these issues, the knowledge-data dual-driven models that integrate physical knowledge and data information have received extensive attention in recent years. To compare and analyze the predictive capabilities of these models, this study takes the AlSi10Mg alloy in Laser Powder Bed Fusion (LPBF) as the research object. Initially, an automatically calibrated CDM model is constructed and compared with the ANN-based data-driven model under various working conditions. Furthermore, three types of knowledge-data dual-driven models based on CDM and ANN are constructed using feature fusion, parameter fusion, and output fusion methods. The performance of these models is quantitatively analyzed in terms of predictive accuracy and data requirements. The research results indicate that the parameter fusion-based model exhibits a significant effect in correcting the training data and shows minimal sensitivity to the CDM model in terms of predictive accuracy, even when the CDM model fitting results are poor. The feature fusion-based model maximizes the utilization of information from the CDM model and achieves the highest predictive accuracy when data is abundant. The output fusion-based model, which is primarily based on the results of the CDM model and corrected using ANN, demonstrates the best extrapolation performance in non-training domains. These findings provide valuable references for further developing knowledge-data dual-driven models for high-precision fatigue life prediction in additive manufacturing. 2024 Vol. 45 (4): 427-440 [Abstract] ( 89 ) HTML (1 KB)  PDF   (0 KB)  ( 18 ) 441 A Semi-analytical Model of Stress Interaction with Inclusions and Cracks in an Infinite Plane DOI: 10.19636/j.cnki.cjsm42-1250/o3.2024.016 The mechanical properties of the material are affected by the inevitable defects such as inclusions and cracks. In order to study the mutual interference of cracks and inclusions in isotropic full-space, the heterogeneous inclusions are approximated as homogeneous inclusions with the same elastic modulus as the matrix and containing unknown eigenstrain, and the I/II mixed cracks are approximated as climb dislocations and slide dislocations of unknown densities based on the method of combining the equivalent inclusion method and the distributed dislocation technology. A semi-analytical model that can simulate the interference of inclusions and cracks in isotropic full-space is established, and the stress intensity factor of the crack tip is solved based on the dislocation distribution. The conjugate gradient method is used in this model to iteratively solve the unknowns, and the fast Fourier transform algorithm is introduced to improve the computational efficiency, and finally, the effectiveness of the model developed in the study is verified by the finite element method . This model can provide an insight for the interference scheme of various defective structures and fracture behavior of the material. 2024 Vol. 45 (4): 441-455 [Abstract] ( 59 ) HTML (1 KB)  PDF   (0 KB)  ( 24 ) 456 Interaction Between a Screw Dislocation and Circular Arc Cracks in Magnetoelectroelastic Composites DOI: 10.19636/j.cnki.cjsm42-1250/o3.2024.006 The interaction between the circular arc crack with penetrating type and the screw dislocation is studied in magnetoelectric composites. Firstly, according to the basic equations of magnetoelastic composites and the theory of complex function，the relationship between the anti-plane shear stress, the normal component of the electric displacement and the normal component of the magnetic induction along the boundary arc c is derived. Then, based on conformal mapping technique, the complex form of generalized stress field is obtained by analyzing the stress conditions of the dislocation. In order to discuss the dislocation, dislocation shielding effect and crack shielding effect at the crack tip, we further deduce the force-electric-magnetic field intensity factors and the image forces acting on the dislocation. By analyzing the analytical solutions and numerical examples, the results show that the shielding effect of the field strength factor decreases with the increasing of the distance between the tip of the circular arc cracks and the dislocation point, and the angle formed by their connecting line and the positive half axis of the x-axis, which indicates that the dislocation has shielding effect on the crack. Then, the effect of dislocation on circular arc cracks is more obvious than that on straight crack. Besides, the image force on the dislocation is affected by the surface condition of the circular arc cracks. Finally, the screw dislocation can reduce the stress intensity factor of the circular arc cracks tip, and the shielding effect is rapidly weakened with the increase of the angle. The shielding effect of the screw dislocation on the crack tip is strengthened with the increase of the ratio of the distance from the dislocation point to the crack tip and the half-chord length of the circular arc cracks. These conclusions have a certain significance for fracture mechanics research, and provide a theoretical basis for improving and evaluating the performance of electromagnetic devices. 2024 Vol. 45 (4): 456-465 [Abstract] ( 59 ) HTML (1 KB)  PDF   (0 KB)  ( 22 ) 466 Adaptive Phantom Node Method for Three-Dimensional Dynamic Stress Intensity Factor DOI: 10.19636/j.cnki.cjsm42-1250/o3.2024.007 Stress intensity factor is a crucial parameter for modeling and predicting structural fracture failure. The evaluation of the dynamic stress intensity factor for three-dimensional dynamic fracture problem is studied by the adaptive phantom node method. This method combines the phantom node method with adaptive mesh refinement, automating the generation of dense mesh around the crack. In this approach, strong discontinuities at cracks are modeled using the technique of phantom nodes without the crack tip enrichment functions or the corresponding extra degrees of freedom. The theoretical framework of this technique is straightforward and easy to implement based on the finite element method, but it requires a relatively dense mesh to ensure computational accuracy. Adaptive mesh refinement technology and criterion suitable for crack problems are introduced into the phantom node method, thus the globally dense mesh with high computational consumption is not needed and the computational accuracy and efficiency are improved. A concise approach, known as constrained approximation, is adopted to deal with hanging nodes presented in the locally refined mesh. It is convenient to implement numerically, does not involve special elements or complex shape functions and retains the interpolation and numerical integration of the standard finite element method. The stress intensity factors for several three-dimensional crack problems are evaluated using the adaptive phantom node method and compared with the theoretical solutions and numerical results obtained by the standard phantom node method. It is found that the numerical results of this method are in good agreement with the theoretical solutions, and the computational accuracy is effectively improved compared to the standard phantom node method. Additionally, compared to locally pre-refined mesh with equivalent accuracy, adaptive refined mesh exhibits higher computational efficiency and reduced computational consumption. This holds considerable potential value for the efficient simulation and prediction of dynamic fracture failure in large-scale complex engineering structures. 2024 Vol. 45 (4): 466-476 [Abstract] ( 45 ) HTML (1 KB)  PDF   (0 KB)  ( 18 ) 477 Asymmetric Bristle Model for Steel Brush and its Application DOI: 10.19636/j.cnki.cjsm42-1250/o3.2024.014 In this paper, an asymmetric bristle model based on the combination of bristle model and LuGre model is proposed to explain the phenomenon of direction-dependent friction(asymmetric friction) exhibited by steel brush. In this model, the friction is generated through the horizontal frictionless contact between the asymmetric bristles and the contacted substrate. It is shown from the numerical simulation and expreimental results that the asymmetric bristle model can illustrate the phenomenon of the direction-dependent friction pretty well. Furthermore, in the simulation study of planar biped robot, the results show that with the application of this model, the maximum motion speed of the planar biped robot can be improved compared to the symmetric friction model. Besides, the exmprimental resutls indicate that compared to rubber materials the steel brush possesses the advantages of high friction and abrasion resistance. Thus, based on these propterties, the steel brush structure may have great application prospects and potential advantages in the field of legged robots. 2024 Vol. 45 (4): 477-487 [Abstract] ( 48 ) HTML (1 KB)  PDF   (0 KB)  ( 26 ) 488 Ultra-high Cycle Fatigue Life Prediction Considering Loading Frequency DOI: 10.19636/j.cnki.cjsm42-1250/o3.2024.012 Ultra-high cycle fatigue experiments can be conducted using traditional testing methods such as electromagnetic vibration (30-3000 Hz) and ultrasonic vibration (20 kHz). Differences in fatigue life for the same material may arise when tested under varying loading frequencies. To fully utilize the ultra-high cycle fatigue life data obtained from different testing systems, the impact of loading frequency on the ultra-high cycle fatigue life of materials needs to be studied imperatively. This paper presents novel prediction models for ultra-high cycle fatigue life, taking into account loading frequency. The models incorporate the crack initiation life prediction model based on Tanaka’s dislocation dipole accumulation theory and the Paris crack growth life prediction model. The influence of loading frequency is integrated into effective stress and fatigue strength. The proposed models are verified using available very high cycle fatigue test data for titanium alloy TC17 and nickel-based superalloy GH4169 under different loading frequencies. The results show that the models proposed in this work can reasonably characterize the ultra-high cycle fatigue test data of materials under varying loading frequencies, offering a valuable approach for utilizing fatigue life data of titanium alloy and nickel-based superalloy under different frequencies. 2024 Vol. 45 (4): 488-495 [Abstract] ( 32 ) HTML (1 KB)  PDF   (0 KB)  ( 17 ) 496 Modeling and Analysis on Case II Diffusion Coupled with Swelling Deformation Behavior in Polymers DOI: 10.19636/j.cnki.cjsm42-1250/o3.2024.013 For some polymers at temperatures near or below their glass transition temperature, one particular instance of non-Fickian solvent diffusion is usually observed, which is called Case II diffusion. In order to describe the coupling effect of Case II diffusion and swelling deformation in polymers, a set of theoretical models are established based on the continuum mechanics framework. Here, the governing equations for solvent penetration into polymer are derived and then specialized in reference configuration, including the mechanical-chemical equilibrium state equation, the concentration-dependent diffusion equation, and the molecular number conservation equation. Besides, the visco-hyperelastic constitutive equation taking into account the time-dependent deformation characteristics of material is integrated, which can reflect the competition mechanism between relaxation rate of polymeric network and migration of solvent in case II diffusion. This modeling approach is used to analyze the transient free swelling process for two material systems, so as to investigate the behavior of unidirectional Case II diffusion in columnar and tabular polymer specimens without constraint. According to those appropriate boundary conditions and initial conditions, the concentration, stress and deformation field variables during the unidirectional diffusion are directly obtained. The distribution and evolution of these calculation results are compared with the experimental observations, which moderately verifies the effectiveness and adaptability of the proposed coupling analysis method concerning with polymer swelling. The theory developed in this article may provide important guidance for practical applications (such as membranes designing or drug-delivery systems), in which Case II diffusion can commonly occur. It is also helpful to enhance understanding on combination of different polymer-solvent diffusion, from Fickian to non-Fickian circumstances. 2024 Vol. 45 (4): 496-507 [Abstract] ( 40 ) HTML (1 KB)  PDF   (0 KB)  ( 19 ) 508 Research on Functional Characteristics of Perceptual Structures Based on Three-Unit Configuration DOI: 10.19636/j.cnki.cjsm42-1250/o3.2024.011 Using fused deposition modeling (FDM) 3D printing technology, the lattice structure was created. After adhering composite conductive materials to the surface of its structural elements, the 3D lattice structure with sensing capability (LSS) was fabricated. Based on three unit configurations, the study was conducted to investigate both the mechanical properties and piezoresistive characteristics of different lattice structures in LSS. Utilizing the conductive percolation phenomenon in conductive composites, this study research on the patterns of piezoresistive behavior in LSS with varying structures and composites under both small and large strain conditions. The stress caused by structural deformation and the self-contact that occurs between lattice surfaces are two key factors. These factors lead to the observed three-stage trend in the change of electrical resistance response. By analyzing the experimental data from compression stress tests, the optimal lattice structure and composite mass fraction for the LSS were determined. This provides a reliable basis for realizing deformation monitoring capabilities in perceptual structures The approach of creating a 3D structure and then incorporating conductive composites offers advantages such as structural controllability and good mechanical performance. The sensing structure can be used for detecting compressive stress in objects, while also serving as a high-quality buffering or damping material that effectively absorbs vibration and energy. Therefore, this research has broad application prospects. 2024 Vol. 45 (4): 508-519 [Abstract] ( 45 ) HTML (1 KB)  PDF   (0 KB)  ( 21 ) 520 Research on Vibration Characteristics of Functionally Gradient Stepped Cylindrical Shells with Arbitrary Boundary Conditions DOI: 10.19636/j.cnki.cjsm42-1250/o3.2024.017 The vibration characteristics of metal-ceramic functionally graded material stepped cylindrical shells with arbitrary boundary conditions are studied. Firstly, Voigt model and power function volume fraction are used to obtain the properties of metal-ceramic functionally graded materials. Secondly, the artificial spring technology is introduced to simulate the continuous coupling between the shell segments and the boundary conditions at both ends of the shell, and the energy expression of the shell is derived based on the first-order shear deformation theory. Finally, Chebyshev polynomial is selected to construct the admissible function. Based on Rayleigh-Ritz method, the dynamic differential equation of shell under arbitrary boundary conditions is solved. Compared with the existing literature, the effectiveness and convergence of this method are verified. The results show that the natural frequency of shell increases with the exponential increase of volume fraction. The influence of aspect ratio and thickness-diameter ratio on the vibration characteristics of the shell is different, the natural frequency of the shell decreases with the increase of aspect ratio, and increases with the increase of thickness-diameter ratio; Compared with the rotating spring, the stiffness of the translational spring has a significant influence on the vibration characteristics of the shell. 2024 Vol. 45 (4): 520-532 [Abstract] ( 66 ) HTML (1 KB)  PDF   (0 KB)  ( 22 ) 533 Multi-resolution Topology Optimization Method for Composite Structures with In-plane Periodicity DOI: 10.19636/j.cnki.cjsm42-1250/o3.2024.015 Composite materials have complex structural forms at the microscopic scale, and their structural analysis and design require refined finite element mesh discretization, resulting in a large computational scale. As a common structural form of composites, the in-plane periodic structure can withstand arbitrary directional loads on the macroscopic scale, but it is difficult to characterize its performance and difficult to design and analyze. In this paper, an efficient topology optimization method for in-plane periodic structures is established based on the thick plate assumption and multi-resolution mesh strategy. Firstly, the rough mesh is used to decouple the macro and micro structures, solve the micro edge-value conditions, and carry out the equivalent characterization of the mechanical properties of the non-homogeneous single cell; secondly, the macroscopic edge-value conditions are solved based on the homogenized equivalent properties, and the fine mesh is used to update the design variables and map the density variables. On the one hand, the assumption of thick plate considering out-of-plane shear deformation makes the two-scale topology optimization design more in line with the actual load-bearing scenarios; on the other hand, the multi-resolution modeling strategy is utilized to avoid the problem of limited solvable problem size due to excessive finite element computation without sacrificing the resolution of the optimized configuration. 2024 Vol. 45 (4): 533-546 [Abstract] ( 78 ) HTML (1 KB)  PDF   (0 KB)  ( 24 ) 547 Analysis of Pullout Failure Mode and Group Anchor Effect of Two-anchor System of EBTP Anchor in Earthen Sites DOI: 10.19636/j.cnki.cjsm42-1250/o3.2024.009 The study takes the two-anchor system of EBTP (Extension Type Bamboo/Rebar Tension-Pressure Anchor Rod) anchors in earthen sites as the research object. Indoor two-anchor DIC (Digital Image Correlation) pullout tests with anchor spacing of 0.3m and 0.6m are conducted to clarify the load-displacement relationship and typical failure modes. First, based on the characteristics of anchor slip failure mode, a 2D FEM (Finite Element Method) simulation method for the two-anchor system is proposed. The simulation of contact pairs and nonlinear springs is then employed to the pressurised section slurry/soil interface and rod/pulp interface in tension. It is found that, at a 0.3m spacing, the primary failure mode involves horizontal cracking along the rammed earth layer. While at 0.6m spacing, a conical cracking pattern emerges with a transition between tension and compression at an angle of 30~45°, yielding a maximum crack radius of soil top is approximately 24cm. The bearing capacity decreases by approximately 7% at 0.3m spacing compared to 0.6m. The simulation analysis illustrates that anchor spacing has a significant influence on the group anchor effect. For one thing, when the spacing exceeds 0.6m, the group anchor effect is more limited, which is consistent with experimental results. For another, the depth of the expansion body demonstrates an approximately linear correlation with the ultimate bearing capacity of the anchor. Therefore, as anchor length increases, the bearing capacity initially increases sharply, followed by a more moderate increase. The experimental results indicate the group anchor effect gradually strengthens. Yet the increment in bearing capacity due to increased anchor length outweighs the loss caused by the group anchor effect. These findings provide valuable insights for the design of EBTP anchor groups in earthen sites. The simulation methodology in this study can be used to predict and optimize the anchorage design parameters in the design of anchoring works at earthen sites. 2024 Vol. 45 (4): 547-564 [Abstract] ( 44 ) HTML (1 KB)  PDF   (0 KB)  ( 24 )

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