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2025 Vol. 46, No. 3
Published: 2025-06-26
297
Research progress in fractional generalized thermoelastic problems
The recent research progress on fractional generalized thermoelastic problems has been summarized in this paper, covering advances in fractional generalized thermoelasticity theory, the effects of magneto-electro-multiphysics coupling, diffusion, viscoelasticity, and fractional heat conduction in biological tissues. Through this summary, a comprehensive understanding of the current state and future trends in fractional generalized thermoelastic problems is provided, facilitating researchers in advancing to higher-level studies in this field.
2025 Vol. 46 (3): 297-313 [
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314
Thermal Warping Analysis and Control of Heterogeneous Stepped Double-Layer Plate Structures
In microelectronic package, thermal warping deformation caused by the mismatch of the thermal expansion coefficient between chips and substrates is a main reason for the failure of chip package structures. In this paper, the chip package structure is simplified into a heterogeneous stepped double-layer plate model, and the thermal warping deformation is calculated using the finite element method during heating. The thermal warping deformation is also measured using three-dimensional digital image correlation (DIC) to verify the simulation results. Furthermore, a thermal warping control method based on the frame substructure is proposed, and it has been proven effective by using finite element method and experimental methods. The influence of geometric parameters such as the thickness and width of the frame, as well as material parameters like elastic modulus and thermal expansion coefficient on the thermal warping control effect, is discussed in detail. The research results show that the thermal warping deformation measured by DIC technology is in agreement with the simulation results. The warping control method using the frame substructure can effectively reduce the thermal warping deformation of the heterogeneous stepped double-layer plate structure. The thermal expansion coefficient, width, and thickness of the frame have a significant impact on the thermal warping deformation, while the elastic modulus has a relatively minor effect.
2025 Vol. 46 (3): 314-328 [
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329
FREE VIBRATION OF ONE-DIMENSIONAL HEXAGONAL PIEZOELECTRIC QUASI-CRYSTAL DISCS
Piezoelectric quasi-crystal materials possess excellent piezoelectric and phonon-phason coupling effects, ensuring they have promising applications in piezoelectric devices, such as sensors. For the design and optimization of piezoelectric sensors, the free vibration of one-dimensional hexagonal piezoelectric quasi-crystal discs is investigated using three-dimensional electro-elasticity theory and the improved double Legendre orthogonal polynomial method. The influence of the diameter-height ratio and phonon-phason coupling effect on the resonance frequency is analyzed. Based on the finite element method, a simulation program for the free vibration of piezoelectric quasi-crystal discs was developed to verify the theoretical calculation results. The results show that changing the diameter-to-height ratio significantly influences the normalized frequency of the phason modes, and the higher-order modes are more sensitive to the change of the diameter-to-height ratio. The influence of phonon-phason coupling coefficients on the phason modes is more significant.
2025 Vol. 46 (3): 329-342 [
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356
Reduced-Order Homogenization of Soft Composites Based on Clustering Analysis
Soft composites exhibit significant potential in advanced engineering applications but face critical computational challenges due to their inherent heterogeneity and geometric nonlinearity. Traditional meso-scale finite element analysis suffers from low efficiency, rendering macro-meso coupled multiscale analysis impractical for real-world engineering scenarios. To address this limitation, this study develops a clustering-based reduced order homogeni-zation method that synergistically integrates reduced-order homogenization techniques with clustering analysis, achieving remarkable computational efficiency while maintaining sufficient accuracy. First, we establish a two-scale analysis framework for soft composites on the basis of finite deformation theory. On the meso-scale, an energy density function is used to describe the constitutive behavior of the micro constituents. Then, we perform clustering analysis on the microscale representative volume element (RVE) to partition it into uniform subdomains called clusters. The clustering analysis groups regions with similar mechanical behavior and thereby reduces the system's complexity and related computational cost. After that, proper orthogonal decomposition (POD) is employed to generate reduced bases for approximating the mesoscopic deformation gradient fields. An efficient sampling strategy is used for both snapshot generation and model validation. A clustered version of reduced order model (CROM) is established based on the principle of minimum energy. Numerical examples demonstrate that the developed CROM can maintain a high level of accuracy while achieving a computational acceleration of about 10^4 compared to traditional finite element methods. A comparison to an existing clustering approach named self-consistent clustering analysis (SCA) is also given. Although the computational cost of the offline phase for the CROM is relatively high, the online analysis is rather fast. This significant improvement in efficiency makes the method highly suitable for problems that require frequent microscale RVE predictions, such as multiscale analysis or multiscale parameter identification. In conclusion, the developed CROM offers a promising and practical tool for engineers, which can be further applied in the design, optimization and analysis of soft composites.
2025 Vol. 46 (3): 356-367 [
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368
Analysis of the Mechanical Behavior of Bolted Connections Subjected to Transverse Vibration
The purpose of this paper is to study the variation law of threaded joints loosening under transverse vibration, and examine the mechanical behavior during the loosening process. A single-bolted and single-lap joint structure was adopted as the research specimen. Based on this structure, a preload degradation model for bolted connections was developed.Subsequently, the friction torque and friction shear models of the bearing surface and thread surface were established. After that, the friction-shear model of the bearing surface and the thread surface caused by the additional bending moment is also established. Thereafter, the impacts of vibration amplitude, thread pitch and initial preload on the variation of bolt preload were analyzed, and the failure mechanism of bolt loosening is explored through case studies. In the end, a transverse vibration test bed was designed and fabricated, and the preload decline curves under different parameters were obtained, which verified the rationality of the theoretical model between the loosening factors and the preload. The results indicate that when the loosening torque exceeds the combined friction torque of the bolt head's bearing surface and the threaded surface, the bolt reaches the critical condition for loosening. The friction torque between the bearing surface of the bolt head and the thread pair's surface decreases when the vibration amplitude increases. And when the vibration amplitude reaches the critical value, the loosening of the bolt will be further accelerated. The greater the initial preload of the bolt, the more difficult it is to reach the critical condition of bolt loosening, and the slower the preload decay. Under the same conditions, the larger the vibration amplitude and thread pitch, the faster the preload declines.
2025 Vol. 46 (3): 368-379 [
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380
The Failure Analysis and Experimental Study of Steel Wires in Cable Structures under Coupling Effect of Corrosion and Fatigue
In cable structures, the coupled corrosion-fatigue failure mode of steel wires is a common and critical form of failure. However, due to the presence of protective sheaths, corrosion and fatigue do not occur synchronously, posing challenges for failure analysis. Traditionally, methods based on damage mechanics and fracture mechanics have been widely used in the analysis of fatigue fracture. However, damage mechanics methods are limited in engineering practice due to their complexity, while fracture mechanics methods are often based on the premise of the existence of pre-cracks.To overcome the limitations of existing studies, this paper first employs the S-N curve of high-strength steel wires under non-corrosive conditions to evaluate the fatigue damage state of steel wires when the protective sheath is intact. Subsequently, utilizing a corrosion kinetics model, the growth of corrosion pits in steel wires after damage to the protective sheath is calculated, and the critical fatigue cycles for the transition of corrosion pits to cracks are predicted. Based on this, the crack propagation is further analyzed using fracture mechanics principles and the Franc3D software, which facilitates the prediction of the fatigue life of steel wires.To validate the accuracy of the above theoretical calculations, this paper also designs and implements an experiment on the coupled effect of fatigue and corrosion fatigue in high-strength steel wires, with fatigue preceding corrosion. By comparing the experimental results with the theoretical predictions, a small error is observed, thereby verifying the correctness and effectiveness of the proposed theoretical calculation method.In summary, the failure analysis theory proposed in this paper for steel wires in cable structures under coupled corrosion-fatigue failure mode is not only simple to calculate and easy to apply, but also aligns well with experimental results. It provides an important reference for the design, operation, and maintenance of cable structures.
2025 Vol. 46 (3): 380-393 [
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394
Study on the Mechanical Properties and Numerical Simulation of Anisotropic Tough Hydrogels Inspired by Muscle Training
Hydrogels have received increasing attention for their wide range of applications in flexible wearable devices, bionic actuators and biomedicine. However, the mechanical properties of conventional hydrogels are poor. Inspired by muscle training, this paper proposes a new method combining the ice template method and mechanical training to prepare anisotropic strong hydrogels, and analyses the effects of different training times on their mechanical properties. In the preparation process, PVA was first dispersed in deionised water and heated and stirred to form a homogeneous solution, which was then slowly dripped into a mould and frozen with liquid nitrogen from the bottom up to form a PVA hydrogel with a fibrous structure. This hydrogel was then immersed in a glycerol-water mixture and mechanically trained using a homemade cyclic tensile tester. The mechanical properties of hydrogels prepared by different methods were tested. The results showed that the anisotropic hydrogels prepared by the ice template method had a distinct fiber structure, but their fiber orientation was significantly dispersed. After mechanical training, the fiber orientation of the hydrogels became highly consistent and more compact. The mechanical properties of the hydrogels were significantly improved by the combination of the ice template method and the mechanical training method. In addition, an anisotropic hyperelastic constitutive model is proposed, which takes into account compositional variations and fiber orientation. By comparing with the experimental results, it is verified that the model can effectively describe the mechanical behaviour of hydrogels. This study provides a new method for preparing anisotropic strong hydrogels and a theoretical basis for predicting and analysing their mechanical responses.
2025 Vol. 46 (3): 394-402 [
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403
A Load-combination Modulation-based Transfer Printing Method in Flexible Electronics
The superior electrical and mechanical properties of flexible electronics enables the breading of the limitations of traditional electronic devices, and promises wide applications in the fields of bionic electronics and medical monitoring. Transfer printing is the mainstream technology for the fabrication of flexible electronics, realizing the process of picking up electronic devices from the donor substrate and printing them onto the receiver substrate. The existing transfer printing process has problems such as complex stamp preparation or damage to electronic devices caused by external excitation, which greatly limits the application of transfer printing. In this paper, a load-combination modulation-based transfer printing method is proposed to control the loading sequences for the rigid pillars on the stamp, modulate the displacement/stress distribution at the stamp/device interface, realize the interface adhesion control, and finally complete the transfer printing on different rigid/flexible substrates. Based on the theoretical model and finite element analysis, the nonlinear relationship between the geometric parameters and the energy release rate of the stamp in the transfer printing process is explored to provide a guidance for the stamp design in transfer printing. Physical experiments show that the transfer printing method not only has a high compatibility with the morphology of electronic devices and receiver substrates, but also supports the large-scale, multi-layer and multi-time integration of micro-silicon wafers on flexible substrates.
2025 Vol. 46 (3): 403-411 [
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412
Analysis of crack propagation in drill pipe joints based on drill string dynamics
The drilling environment and tool assembly in deep and ultra deep wells are more complex, leading to increased vibration loads underground, which can cause fatigue crack propagation and failure of drill pipe joints, leading to early scrapping of drill pipes. In response to the above issues, this article conducts the following research: establishing a dynamic calculation model for drill pipe joints, analyzing the axial force, torque, and bending moment loads borne by drill pipe joints underground; Conduct a finite element analysis model of the drill pipe joint to determine whether the stress on the drill pipe joint meets the material strength requirements; Establish a crack propagation model for drill pipe joints and analyze the remaining life of the joints. Conclusion: By comparing with indoor experiments, it has been proven that the established dynamic calculation model is effective. It is found that in the target environment, the drill pipe joint is subjected to three loads: 13.11kN axial force, 35 torque (including make-up torque), and 0.75 bending moment; Through composite load analysis, the maximum Mises stress borne by the male and female joints is 551.2MPa and 323.2MPa, which meets the material strength requirements; The thread extension of drill pipe joints is mainly characterized by open type cracks, and their depth has a greater impact on crack propagation than their length; Under current operating conditions, the minimum crack propagation size is 3x2mm, and the remaining life at this size is 126820 times.
2025 Vol. 46 (3): 412-422 [
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423
The interaction of dislocation and crack in body-centered crystal under hydrogen environment
In order to study the microscopic mechanism of the influence of hydrogen atoms on the fracture of metallic materials, this paper builds a model of crack - dislocation interaction under the influence of hydrogen atoms infiltrating at the crack tip within multiple grains based on the discrete dislocation theory. On the basis of this model, the influence of hydrogen atoms on the dislocation distribution on the slip planes in grains is considered. Further, the effects of hydrogen atoms on the dislocation penetration at the grain boundaries and the initiation of wedge cracks at the grain boundaries are obtained. This model is applicable to both body centered cubic (BCC) and face centered cubic (FCC) crystals. Through calculations, the influence of different hydrogen infiltration concentrations and ranges at the crack tip on the dislocation distribution in front of the crack is analyzed. It is found that hydrogen atoms at the crack tip can promote dislocation emission and increase the driving force for dislocation movement on the slip planes, making it easier for dislocations to penetrate the grain boundaries. The relationship between the initiation of wedge cracks at the grain boundary and hydrogen atoms at the crack tip is presented. It is found that when the grain boundary angle is large, an increase in the hydrogen infiltration concentration and range at the crack tip makes it easier for wedge cracks to initiate at the grain boundaries. The influence of hydrogen infiltration at the crack tip on the shear stress in the dislocation - free zone in front of the main crack is analyzed. It is found that an increase in the hydrogen infiltration range and concentration at the crack tip will enlarge the dislocation - free zone in front of the crack, thereby reducing the shielding effect of dislocations on the crack and making it easier for the main crack to propagate. This model effectively demonstrates how hydrogen atoms at crack tip influence dislocations in crystals, providing a foundation for studying metal fracture in hydrogen environments.
2025 Vol. 46 (3): 423-436 [
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