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2024 Vol. 45, No. 3
Published: 2024-06-28
289
Study on the Interaction between Stacking Fault Pyramid and Point Defects in Zirconium
Hai DongFan
DOI: 10.19636/j.cnki.cjsm42-1250/o3.2024.004
Zirconium and its alloys are widely used as fuel cladding in nuclear reactors because they have good mechanical properties, good corrosion resistance, and small thermal neutron absorption cross-section. Under irradiation, a large number of irradiation-induced defects are generated, which greatly reduce the mechanical properties and service life of zirconium alloys. In this work, molecular dynamics method is used to study the interaction between stacking fault pyramid (SFP) and point defects (self-interstitial atoms (SIAs), vacancies). At 0 K and 300 K, the SFP absorbs SIAs only; At 600 K, the SFP absorbs both SIAs and vacancies. In addition, the size of SFP has a negligible effect on the interaction mechanism. The binding energy between SIAs/vacancies and SFP is calculated. The binding energy of SIAs is much higher than that of vacancies, and SIAs are absorbed easily. Current work provides new insight into understanding the growth mechanism of irradiation-induced defects in zirconium.
2024 Vol. 45 (3): 289-301 [
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302
A Neural Network-Assisted Theoretical Constitutive Model to Predict the High Temperature Flow Behavior of High-Entropy Alloys
DOI: 10.19636/j.cnki.cjsm42-1250/o3.2023.053
Metals and alloys are widely used in industry due to their excellent mechanical properties, and researchers are committed to finding new materials with better properties or mechanisms to enhance properties of materials. In the forming process of metal and alloy materials, the hot deformation can refine the grain effectively to improve the mechanical properties such as yield strength and tensile strength. Therefore, it is necessary to study the deformation behavior of metal and alloy materials at high temperature. Hyperbolic–sinusoidal Arrhenius-type model is widely used by researchers because of its good simulation effect at high temperatures. This paper studies the building process of the model and optimizes the modeling process with the help of neural network model. A neural network model is constructed to efficiently determine the hyperbolic–sinusoidal Arrhenius-type equations, based on which the flow stress of high-entropy alloys (HEAs) for different high temperatures and strain rates can be well predicted. In this study, the reported hot deformation behaviors of Al0.3CoCrFeNi HEAs are examined by current model. The results show that the coefficients obtained by the neural network method can better describe the experimental hot flow stress, especially at high strain rate or low temperature conditions. The root mean square error (RMSE) and the correlation coefficient(R) are used to assess the degree of difference between the results. The RMSE and R of the neural network method at total data are 27.7 and 0.985, respectively, which are better than 33.1 and 0.979 of the traditional method. To show the general applicability of the model, the hot deformation behaviors of (CoCrNi)94Ti3Al3, FeCrCuNi2Mn2 and AlCrCuFeNi are analyzed by the model. The research work in this paper can improve the efficiency and accuracy of hyperbolic–sinusoidal Arrhenius-type model, reduce the difficulty of establishing the model, and has positive significance for the wide use of the model.
2024 Vol. 45 (3): 302-312 [
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313
Bandgap Coupling Characteristics of Tunable Metamaterial with Double Magnetic Resonators
DOI: 10.19636/j.cnki.cjsm42-1250/o3.2023.060
Elastic wave metamaterials are artificial periodic structures can control elastic waves. It can be used in aeronautics and astronautics, vehicle engineering and other fields. In this paper, a kind of tunable metamaterial with two magnetic resonators are proposed. The stainless steel plate is used to connect the magnetic resonator to the external frame in this structure. Adjusting the distance between the magnets can affect the in-plane stress of the stainless steel plate to affect the internal stiffness. By adjusting the cell structure, the double-cell system with different internal stiffness can be formed to achieve a wider coupling band gap. First, the trend of the stiffness of thin plate and the negative stiffness of magnetic force with distance between two magnetic resonators are obtained. The dispersion relationship and the transmissibility of the double magnetic resonators single cell metamaterial and two-cell metamaterial formed by adjusting the distance between magnets are obtained via theoretical model. Then, the effect of distance between two magnetic resonators on metamaterial bandgap and double-cell coupled bandgap in a specific case are further studied. Last, the experimental model was designed and manufactured by 3D printing technology. The transmissibility curves at different distance between two magnetic resonators were measured. The bandgap coupling results of double-cell metamaterial structures are verified. The theoretical prediction bandgap of the metamaterial agrees well with experimental results. This adjustment method can provide a new idea for the active control of restraining elastic wave transmission.
2024 Vol. 45 (3): 313-325 [
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40
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326
Peridynamic Modeling of Corrosion Fatigue in Metallic Materials
DOI: 10.19636/j.cnki.cjsm42-1250/o3.2024.003
Fatigue failure is the most common form of failure in engineering. Under the interaction between corrosive environments and fatigue load, the fatigue performance of structures will be significantly reduced. It often consumes a lot of time and economic costs to evaluate the fatigue properties of materials or structures by corrosion fatigue experiments. Therefore, establishing a reliable numerical prediction model for scientific research and engineering design is significant. In this paper, we develop a peridynamic corrosion fatigue model, which combines the peridynamic fatigue crack model and the peridynamic stress-corrosion model, according to the superposition model of corrosion fatigue. In this model, corrosion fatigue damage is a linear superposition of corrosion damage and fatigue damage, and the coupling between stress and corrosion is considered. We simulate the corrosion fatigue failure process (including crack initiation and crack growth phase) of stainless steel compact tensile specimens. The numerical results show that the peridynamic corrosion fatigue model can describe the damage evolution process of corrosion fatigue, and the introduced mechano-chemical damage model captures the fatigue life reduction and loading frequency sensitivity of specimens.
2024 Vol. 45 (3): 326-340 [
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341
Free Vibration Analysis for Anisotropic Plates Based on Peridynamic Operator Method
DOI: 10.19636/j.cnki.cjsm42-1250/o3.2023.058
Anisotropic materials find widespread applications across various engineering domains, and the investigation of their vibrational properties holds significant significance for structural vibration mitigation and safety design. This paper introduces a novel approach, peridynamic operator method (PDOM), to construct a non-local anisotropic model and applies it to the analysis of free vibrations in anisotropic plates. This model incorporates the unique feature of PDOM, which transforms local differentials and their products into non-local integrals, thereby reformulating the strain energy density from its local form to a non-local form within classical anisotropic theory. Additionally, by employing a variational principle and introducing the free vibration equation, a PDOM solution is developed for addressing anisotropic free vibration problems. Through three numerical examples: anisotropic rectangular thin plate, anisotropic rectangular plate with cracks, and anisotropic rectangular plate with holes in free vibration, the results are compared with finite element results, demonstrating the convergence, stability, and high computational accuracy of the model when dealing with the free vibration of anisotropic plates with defects and discontinuities.
2024 Vol. 45 (3): 341-351 [
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352
Numerical Analysis on the Local Stress-Strain Response of U75V Notched Bar Considering Ratchetting
DOI: 10.19636/j.cnki.cjsm42-1250/o3.2024.001
Based on the finite element simulation on the cyclic deformation of notched bar made from U75V steel under the asymmetrical uniaxial stress-controlled cyclic loading condition, the stress/strain distributions and correspondent stress/strain concentration coefficients at the notch root as well as their evolutions during the cyclic deformation are studied. Then, the applicability of Neuber rule to analyze the local stress-strain response at the notch root of the notched component is discussed with the ratchetting considered. The results show that during the cyclic deformation, the local stress at the notch root relaxes, and the stress concentration coefficient decreases accordingly; while, the ratchetting strain concentrates at the notch root and the strain concentration coefficient increases with increasing the number of cycles; The geometrical mean of the stress and strain concentration coefficients gradually increases with the number of cycles, and is significant different from the theoretical stress concentration coefficient. It is indicated that the Neuber rule cannot accurately describe the stress-strain response at the notch root of notched component if obvious ratchetting occurs.
2024 Vol. 45 (3): 352-362 [
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363
Optimization Study on the Width of Narrow Coal Pillar along the Goaf Tunnel with Peridynamics
DOI: 10.19636/j.cnki.cjsm42-1250/o3.2023.054
Coal-rock mass have extremely complex discontinuous deformation and heterogeneous characteristics. The traditional numerical methods represented by Finite Element Method (FEM) are difficult to accurately describe the whole process of damage accumulation and progressive failure. Based on the no-nlocal Peridynamics (PD) method, the corresponding micro-modulus function and critical elongation are derived by reconstructing kernel function of the constitutive force function. The heterogeneity characterized by random pre-breaking bond is introduced into the homogeneous discrete model, so that the Peridynamics can be applied to the simulation and analysis of deformation and failure of natural heterogeneous materials and structures. Taking Fucun Coal Mine as an example, heterogeneous Peridynamic simulation model is established. The deformation and failure laws of roadway surrounding rock and failure characteristics of coal pillars with different widths are analyzed. It is found that when the width of coal pillar is 5 m, the roadway is at the edge of the extrusion deformation zone. Due to the dramatic change of the abutment pressure, the roadway surrounding rock is seriously deformed and damaged; when the width of coal pillar increases to 6 m and 7 m, the roadway surrounding rock gradually moves away from the extrusion deformation area, the influence of the basic roof rotation movement of the goaf on coal pillar is relatively weak, and the deformation and damage of the roadway are small; when the width of coal pillar continues to increase, the roadway surrounding rock will enter the the stress increases area. Due to the large bearing pressure of the external stress field, the deformation and damage of the roadway will increase. Considering the deformation and damage characteristics of roadway surrounding rock and coal pillar, the reserved width of coal pillar is finally determined to be 7 m. The proposed Peridynamic simulation model provides a new and effective simulation tool for the optimization of coal pillar size in gob-side entry driving.
2024 Vol. 45 (3): 363-378 [
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379
Vibration Characteristics of Graphene-Reinforced Porous Cylindrical Shells with Arbitrary Boundary Conditions
DOI: 10.19636/j.cnki.cjsm42-1250/o3.2023.057
In order to investigate the vibration characteristics of graphene platelet reinforced porous composite (GPLRPC) cylindrical shells under arbitrary boundary conditions, a semi-analytical method using Gegenbauer polynomials as admissible functions is proposed in this paper. First, the effective material properties of the GPLRPC cylindrical shell are derived based on the Halpin-Tsai micromechanical model and closed-cell body theory. Artificial spring technique is utilized to simulate the boundary conditions at both ends of the shell and continuous coupling conditions between shell segments. Then, based on the first-order shear deformation shell theory, the motion equations of the structure are derived and it's dimensionless frequencies are obtained with Rayleigh-Ritz method. Hence, numerical calculations are performed to analyze the effects of boundary conditions, porosity coefficients, porosity types, graphene distribution patterns, graphene mass fractions, boundary spring stiffness, and geometrical parameters on the vibration characteristics of the shell structure. The results show that the Gegenbauer polynomials have excellent convergence and accuracy as admissible functions. It is also found that the boundary conditions have different effects on the frequency of cylindrical shells, and GPL-A and Type II have the best stiffness enhancement effect. Additionally, it is observed that the influence of translational springs on frequency is greater than rotational springs, and the effect of cylindrical shell length-to-diameter ratio is greater, but the effect of diameter-to-thickness ratio is less. Overall, applying graphene to cylindrical shells has a wide range of applications, and the research results can provide data support and theoretical reference for the engineering design.
2024 Vol. 45 (3): 379-391 [
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392
Design of Ultrahigh Cycle Fatigue Sample with Planar Section and Experimental Verification Through Fatigue Life Testing
DOI: 10.19636/j.cnki.cjsm42-1250/o3.2024.008
Ultrasonic resonance technology is the most effective method for studying the ultra-high cycle fatigue properties of metal materials. Ultrasonic fatigue specimens typically need a distinctive geometric design to fulfill the resonance requirements. Traditional specimens, such as round rod and dog bone, do not have planar characteristics, which makes microscopic characterization difficult. This paper presents an ultra-high-cycle tensile fatigue specimen with a featured plane based on a traditional dog-bone tensile-compression specimen design. Different from the traditional specimen design, the dog-bone specimen herein has a flat observation area, which is readily to implement microscopic characterization. This paper takes GH4169 nickel-based alloy as an example to verify the proposed plane featured dog-bone fatigue specimen design. As expected, the ultrasonic fatigue test results show that the proposed dog-bone plane specimen can resonate at 20kHz. The measured fatigue life data is basically consistent with available S-N results in the literature. The proposed method provides new ideas for the design of ultra-high cycle fatigue specimens, as well as helps in the study of micro-deformation mechanisms of ultra-high cycle fatigue.
2024 Vol. 45 (3): 392-400 [
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401
Design of Ultrasonic Fatigue Sample with Planar Section and Experimental Verification through Fatigue Life Testing
DOI: 10.19636/j.cnki.cjsm42-1250/o3.2024.005
This study investigates the mechanical behavior of binary Cu-Zr metallic glass under cyclic loading using the molecular dynamics simulation method. Firstly, simulations of single indentation are performed on metallic glasses with four different alloy ratios (Cu50Zr50, Cu54Zr46, Cu60Zr40, and Cu64Zr36), obtaining their corresponding force-depth curves. The evolution of their microstructures is analyzed using Voronoi indices. To further reveal the hardening mechanism of the metallic glasses under cyclic loading with different alloy ratios and loading rates, the hardness, average atomic volume, residual indentation depth, local shear strain and large strain atoms involved in indentation are analyzed. The results indicate that the yield capacity of metallic glass increases with the Cu content under different alloy ratios, primarily due to a higher Cu content resulting in more short-range ordered structures, thus enhancing the yield capacity. Simulation results also show that after cyclic loading, the average hardness at large depth indentation of metallic glass with the four different alloy ratios increases by 1.86% to 3.17% compared to that of single indentation. The generation and accumulation of shear bands during the cyclic process, as well as the decrease in the average atomic volume in the region beneath the indenter, lead to a denser structure, effectively resisting further deformation and serving as the main factors contributing to the hardening effect. After cyclic indentation of Cu50Zr50 metallic glass at different loading speeds (80m/s, 100m/s, 150m/s), it is found that the higher the loading rate, the more micro-plastic deformation, residual indentation depth and large strain atoms in the matrix. This leads to a higher average hardness and a more pronounced hardening effect in the metallic glass. The above work not only contributes to a better understanding of the plastic deformation mechanism of binary Cu-Zr metallic glass under cyclic loading, but also provides reference data for potential applications and the design of new nanostructured materials.
2024 Vol. 45 (3): 401-415 [
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416
High-Precision Numerical Analysis of the Angle of Repose in Particle Systems Using the Discrete Element Method
DOI: 10.19636/j.cnki.cjsm42-1250/o3.2023.059
The angle of repose of granular accumulation is a fundamental issue in granulometry, and our current understanding of its influencing factors and variation patterns is still incomplete. Experimental research methods are limited by the existing types of granules and measurement means, making it difficult to comprehensively reveal the influence of individual physical parameters on the angle of repose. The Discrete Element Method (DEM) is a commonly used computer simulation method for studying granular systems, allowing for direct modeling and calculation of the transient behavior of complex large-scale granular systems. In this paper, the DEM method was used to conduct a systematic numerical study on the angle of repose of granular accumulation, exploring the important granular physical parameters that can affect the angle of repose. Simulation results show that both sliding and rolling friction coefficients are positively correlated with the size of the angle of repose. The sliding friction coefficient can double the angle of repose, while the influence of the rolling friction coefficient on the angle of repose has an upper threshold value. Once this threshold is reached, it will no longer increase the size of the angle of repose; the effects of Young's modulus and the coefficient of restitution on the angle of repose are relatively minor.
2024 Vol. 45 (3): 416-426 [
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52
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