Search Results (1,655)

During jacking construction of prefabricated utility tunnels, asynchronous jack output and interface friction may induce internal force redistribution and deformation amplification at the leading end. Taking a triple-cell prefabricated utility tunnel in Xiong’an New Area as a case study, a three-dimensional finite element model was established considering inter-segment contact, equivalent bolted connections, and bottom-slab-bedding friction. Jack asynchrony was idealized as a quasi-static thrust imbalance, and a synchronous case, asynchronous cases with thrust differences of 5–30%, and varying friction coefficients were analyzed. For the 30% thrust-difference condition, structural responses were examined at both the gasket-compression stage and the maximum jacking-force stage. The results show that jacking loads attenuate along the tunnel length in a staged manner, with the leading end acting as the primary load-transfer zone. Increasing thrust imbalance drives the response from axial compression toward eccentric compression-bending, accompanied by monotonic increases in principal stresses and vertical displacement. Higher friction further amplifies the leading-end response; nevertheless, for the investigated configuration, stresses and deformations under a 30% thrust imbalance remain within engineeringly acceptable limits. The findings provide a basis for identifying critical leading-end locations, arranging monitoring schemes, and supporting construction control under asynchronous jacking. Full article

We introduce a class of parametric operators acting on the space of Bayesian games with continuous utility functions. Each operator induces a structured perturbation of agents’ utilities while preserving the underlying informational primitives, strategy spaces, and Bayesian updating. This construction generates a family of utility-perturbed Bayesian games that can be interpreted as continuous deformations of classical incomplete-information games in the space of payoff functions. The contribution of the paper is purely mathematical. First, we formally define a utility perturbation operator and characterize the associated class of perturbed Bayesian games. Second, under standard compactness and continuity assumptions, we prove the existence of Nash equilibria for all admissible perturbations. Third, we show that the equilibrium correspondence of the perturbed games converges upper hemicontinuously to the classical Bayesian Nash equilibrium correspondence as the perturbation parameter vanishes. Under additional differentiability and strict concavity assumptions, we establish a structural stability result: in a neighborhood of the unperturbed game, equilibria are locally unique and depend smoothly on the perturbation parameter. The equilibrium mapping is continuous, locally Lipschitz, and differentiable, implying that utility perturbations generate a stable deformation of the classical equilibrium structure rather than a qualitative departure from it. Taken together, the results identify a new operator-based framework for studying equilibrium stability and sensitivity in Bayesian games. The analysis shows that parametric perturbations of utility functions define a mathematically well-posed deformation of classical game-theoretic equilibria, providing a foundation for further work on equilibrium equivalence, stability, and comparative statics in non-cooperative games. Full article

Tetra-missing rib honeycombs (TMRHs), characterized by monoclinic geometry, exhibit high elastic stiffness but suffer from poor deformation stability and reduced axial load-bearing capacity, which limit their applicability in energy-absorbing and load-sensitive engineering structures. To address these inherent drawbacks, this study proposes two symmetry-enhanced tetra-missing rib honeycomb configurations through overall axisymmetric design and subunit-level symmetric optimization. A finite element model was established in Abaqus/Explicit and validated against quasi-static compression experiments, demonstrating good agreement in deformation modes and mechanical responses. Systematic numerical investigations were then conducted to compare the mechanical properties and deformation behaviors of three honeycomb layouts, including the conventional TMRH and the proposed symmetric designs. Furthermore, the effects of impact velocity on mechanical performance were examined to evaluate the dynamic response characteristics of the structures. Finally, the influence of subunit angle parameters on the stiffness, energy absorption, and deformation stability of the tetra-missing rib honeycombs was comprehensively analyzed. The results provide insight into the role of symmetry and geometric parameters in improving the mechanical performance of TMRH-based structures and offer guidance for the design of high-performance auxetic honeycombs. Full article

Monocular dynamic scene reconstruction is a challenging task due to the inherent limitation of observing the scene from a single viewpoint at each timestamp, particularly in the presence of object motion and illumination changes. Recent methods combine Gaussian Splatting with deformation modeling to enable fast training and rendering; however, their performance in real-world scenarios strongly depends on accurate point cloud initialization. When such initialization is unavailable and random point clouds are used instead, reconstruction quality degrades significantly. To address this limitation, we propose an optimization strategy that relaxes the requirement for accurate initialization in Gaussian-Splatting-based monocular dynamic scene reconstruction. The scene is first reconstructed under a static assumption using all monocular frames, allowing stable convergence of background regions. Based on reconstruction errors, a subset of Gaussians is then activated as dynamic to model motion and deformation. In addition, an annealing jitter regularization term is introduced to improve robustness to camera pose inaccuracies commonly observed in real-world datasets. Extensive experiments on established benchmarks demonstrate that the proposed method enables stable training from randomly initialized point clouds and achieves reconstruction performance comparable to approaches relying on accurate point cloud initialization. Full article

Silicon nitride (Si₃N₄) ceramic bearings inevitably contain crack-like defects, yet their compressive capacity degradation and crack-driven failure mechanisms remain unclear. This study proposes a discrete element method (DEM) numerical framework within PFC2D to simulate a bearing containing a single prefabricated crack. First, a bearing DEM model was established and calibrated to reproduce the compressive mechanical response. Then, particle deletion introduced controllable central cracks in the ball and raceway with prescribed inclination angles. Finally, displacement-controlled compression-splitting simulations, serving as a surrogate for a quasi-static overload scenario relevant to quality screening, tracked crack initiation, propagation, and failure modes; under a fixed raceway-crack inclination, crack length was varied to quantify size effects. Results show that a single crack markedly reduces compressive strength. Failure progresses through elastic deformation, crack propagation, and final fracture, with cracks initiating at stress concentrators near crack tips. Crack inclination significantly regulates capacity: raceway cracks are most detrimental near 45°, while ball cracks exhibit an overall decrease in initiation and peak stresses with increasing inclination (with local non-monotonicity). Crack length has a stronger weakening effect than inclination, with accelerated capacity loss beyond 0.3 mm and a pronounced drop in initiation stress beyond 0.6 mm. The framework enables controllable defect parametrization and micro-scale failure interpretation for defect sensitivity assessment under compressive overload. Thus, this study focuses on simulating monotonic fracture events to elucidate fundamental defect–property relationships, which provides a foundation distinct from the prediction of rolling contact fatigue life under cyclic service conditions. Full article

This study presents the development, calibration, and validation of cohesive zone models (CZMs) for epoxy-based adhesive joints connecting stainless steel and CFRP composites. The objective of this study is to develop and rigorously validate cohesive zone models for epoxy-based adhesive joints between stainless steel and CFRP composites, ensuring their reliability for numerical simulations of structural failure under quasi-static and large-deformation conditions. The work focuses on accurately describing the quasi-static behaviour and failure mechanisms of hybrid adhesive interfaces, which are crucial for multimaterial structures in modern transportation systems. Experimental tests in Mode I (DCB) and Mode II (ENF) configurations were performed to determine the cohesive parameters of the structural adhesive SikaPower 1277. The obtained data were further analysed through analytical formulations and validated numerically using PAM-CRASH. Excellent agreement was achieved between experiments, analytical predictions, and simulations, confirming the reliability of the proposed material definitions under large deformations. The validated models were subsequently implemented in a large-scale numerical simulation of a bus rollover according to UN/ECE Regulation No. 66, demonstrating their applicability to real structural components. The results show that the developed cohesive zone models enable accurate prediction of failure initiation and propagation in adhesive joints between dissimilar materials. These findings provide a robust foundation for the design of lightweight, crashworthy structures in transportation and open new perspectives for integrating epoxy-based adhesives into additively manufactured hybrid metal–composite systems. Full article

This paper investigates the impact of lubrication and thermal effects on the performance of single-metal seals in roller cone bits, and it establishes the geometric, material, and operating parameter models for the single-metal seal. Based on the theory of statistics, the Greenwood–Williamson (G–W) model is employed to predict the contact stress of micro-protrusions on the sealing pair surface. This study establishes a Thermal Elastohydrodynamic Lubrication (TEHL) coupling model for single-metal seals, which utilizes the deformation matrix method to characterize the microscopic deformation of the sealing interface. The central difference method is applied to solve the oil film thickness and temperature distribution in the axial and film thickness directions of the sealing surface. The results indicate that the sealing zone is predominantly under rough peak contact pressure, operating in a mixed-lubrication state. Oil film thickness negatively correlates with static contact pressure, and seal pressure and pre-compression displacement significantly influence lubrication performance. Experiments validate the numerical simulation results, with a mean relative error of less than 15%, confirming the model’s effectiveness. This study offers a theoretical basis for optimizing single-metal seal design, enhancing the reliability and lifespan of roller cone bits in harsh conditions. Full article

During layered mining of extra-thick coal seams in deep rock-burst-prone mines, a thick bottom coal layer facilitates the accumulation of elastic strain energy in the floor strata. This stored energy may be released under mining-induced disturbances during retreat, thereby triggering rock-burst events. To mitigate floor energy accumulation at the lower-slice working face of extra-thick coal seams, previous studies have primarily adopted floor blasting for pressure relief. However, conventional blasting is often associated with poor energy utilization and limited controllability of the pressure-relief range, which hampers achieving the intended relief performance. Accordingly, this study proposes a shaped charge blasting scheme to reduce floor energy accumulation. ANSYS/LS-DYNA simulations and UDEC-based energy analyses, together with theoretical analysis and field validation, were conducted to clarify the mechanism of directional fracture propagation and the evolution of floor elastic energy before and after blasting. The results showed that the synergistic effects of the high-velocity jet and quasi-static pressure in shaped charge blasting generated a through-going fracture aligned with the maximum horizontal principal stress. This fracture effectively segmented the high-stress region in the floor and increased the maximum fracture length along the shaped charge direction to 10–13 times that achieved by conventional blasting. UDEC simulations and theoretical analysis indicated that the peak elastic energy in the floor was reduced by up to 54.08% after shaped charge blasting. Field measurements further showed that shaped charge blasting limited the maximum roadway floor heave to 300 mm and reduced floor deformation by 35–42% compared with the case without pressure relief. Overall, shaped charge blasting effectively blocks stress-transfer pathways and improves energy dissipation efficiency, providing theoretical support and a practical technical paradigm for safe and efficient mining of deep extra-thick coal seams. Full article

Aiming at analyzing the load characteristics and friction torque of triple-row hub bearings for new energy vehicles, this work established a comprehensive theoretical and experimental methodology for predicting the internal load distribution and friction torque. Firstly, considering the preload effect via an initial negative clearance, deformation coordination and force balance equations for the triple-row bearing under axial load were formulated, to analyze the external loads under various driving conditions. Based on contact deformation theory, a quasi-static model was developed to combine radial, axial, and moment loads. The Newton–Raphson iterative algorithm was employed to solve the ball load distribution equations, and the correctness was verified by using the finite element method. Furthermore, accounting for the elastic hysteresis, differential sliding, and spin sliding, the theoretical models for friction torque components were established, to investigate the influence of structural parameters and the total friction torque under different driving conditions. Finally, to confirm the effectiveness and the precision of the model, a finite element simulation and experimental measurements of friction torque were conducted, respectively, which showed good agreement with theoretical calculations. The main innovations include proposing a mechanical modeling method for triple-row hub bearings that accounts for preload effects, and establishing an integrated friction torque analysis model applicable to multiple driving conditions. This work provides theoretical support and a methodological foundation for the design of next-generation hub bearings for new energy vehicles. Full article

This study investigates the design, numerical analysis and manufacturing-oriented evaluation of two-dimensional energy-absorbing lattice structures. Several lattice geometries, including conventional honeycomb and non-conventional auxetic layouts, were modelled using CAD tools and analysed through static and explicit dynamic finite element simulations. The mechanical response was evaluated in terms of deformation behaviour, reaction forces and energy dissipation. Results indicate that auxetic and anti-tetrachiral lattices exhibit more progressive deformation and reduced transmitted forces compared with honeycomb configurations. Manufacturing aspects were assessed through additive manufacturing simulations, providing a first screening of feasible geometries. The proposed workflow supports the selection of lattice families suitable for further experimental validation. Full article

A fractal approach for the Timoshenko beam theory by applying differential vector calculus in a three-dimensional continuum with a fractal metric is developed. First, a summary of the tools needed, mathematical relationships, and background of fractal continuum mechanics is presented. Then, the static and dynamical parts of the Timoshenko beam equation are extended to fractal manifolds. Afterwards, an intrafractal beam constructed as a Cartesian product is suggested and the fractal dimensionalities of the Balankin beam are scrutinized. This allows comparing both intrafractal beams when they have the same Hausdorff dimension but different connectivity. Finally, the effects of fractal attributes on the mechanical properties of the deformable fractal medium are highlighted. Some applications of the developed tools are briefly outlined. Full article

Accurate determination of a vehicle’s centre of gravity (CoG) is fundamental to driving dynamics, safety, and engineering design. However, existing static CoG estimation methods often neglect tyre deflection and detailed wheel geometry, which can introduce significant errors, particularly in electric vehicles, where the low and concentrated mass of the battery pack increases the sensitivity of vertical CoG calculations. This study presents a refined static axle-load-based method for electric vehicles, in which the influence of tyre deformation and lifting height on the accuracy of the vertical centre of gravity coordinate is explicitly considered and quantitatively justified. To minimise human error and accelerate the evaluation process, a custom-developed Python (Python 3.13.2.) software tool automates all calculations, provides an intuitive graphical interface, and generates visual representations of the resulting CoG position. The methodology was validated on a Volkswagen e-Golf, demonstrating that the proposed approach provides reliable and repeatable results. Due to its accuracy, reduced measurement complexity, and minimal equipment requirements, the method is suitable for design, educational, and diagnostic applications. Moreover, it enables faster and more precise preparation of vehicle dynamics tests, such as rollover assessments, by ensuring that sensor placement does not interfere with vehicle behaviour. Full article

Forming tools adjustable by tensile elastic deformations offer opportunities for improved process control and reduced wear in high-volume metal forming processes such as ironing. However, the lack of tensile and fatigue data for hardened cold-work tool steels limits their broader adoption. This study investigates the mechanical performance of three tool steels—Vanadis^®4 Extra SuperClean, Vancron^® SuperClean, and Caldie^®—through uniaxial tensile and fatigue testing, supplemented by destructive static and fatigue/wear tests on specimens representative of an adjustable ironing punch. Non-coated specimens exhibited ultimate tensile strengths above 2700 MPa with approximately 2% plastic strain, while coated specimens fractured in a brittle manner between 1600–1900 MPa. Fatigue life at stress ranges between 1450–1750 MPa varied from several thousand to over four million cycles, with crack initiation linked to non-metallic inclusions and precipitates 10–30 μm in size. Finite element simulations accurately linked failure observed in uniaxial tests to the component-level tests, confirming that first principal stress is a reliable predictor for punch failure. All punch specimens withstood 10⁶ cycles at diameter changes up to 140 μm (4‰), with coated punches exhibiting minimal wear and non-coated ones showing localized surface damage. The findings support material and coating selection for adjustable forming tools and highlight opportunities for further optimization. Full article

Geometric discontinuities are unavoidable in additively manufactured polymer components and can significantly alter their mechanical response; however, their effects are rarely quantified in a systematic and geometry-comparative manner. In this study, the tensile behavior of FDM-printed PLA+ specimens with three different geometries—dog-bone, circular-hole, and U-notched (manufactured and tested in accordance with ASTM D638 (Type IV))—was experimentally and numerically investigated. Tensile tests were conducted using a universal testing machine equipped with an extensometer, while finite element simulations were performed using an experimentally calibrated Ramberg–Osgood-based elastic–plastic material model. The dog-bone specimens exhibited an ultimate tensile strength (UTS) of 41–43 MPa and a Young’s modulus of 3.06 GPa, representing the intrinsic material response under nearly homogeneous stress conditions. Circular-hole specimens maintained comparable strength (38–42 MPa) but showed reduced ductility (1.4–1.6%) and a slightly increased apparent modulus of 3.17 GPa due to localized deformation. In contrast, U-notched specimens displayed the highest apparent modulus (≈5.30 GPa) and nominal UTS (46–49 MPa), accompanied by a pronounced reduction in ductility (0.9–1.0%), indicating severe stress concentration and predominantly brittle fracture behavior. Finite element analysis showed excellent agreement with experimental results, with peak von Mises stresses reaching approximately 42 MPa for all geometries, corresponding closely to the experimentally measured tensile strength. These results demonstrate that geometric discontinuities strongly govern stress localization, apparent stiffness, and fracture initiation in FDM-printed PLA+ components. The validated Ramberg–Osgood-based modeling framework provides a reliable tool for predicting geometry-dependent mechanical behavior under quasi-static loading and supports geometry-aware design of additively manufactured polymer structures. Full article

Large-scale frames are increasingly used in engineering structures, particularly in aerospace structures. Among them, planar phased array satellite antennas used for global observations and target tracking have received much attention. Considering that structural deformation will degrade the coherence of antennas, a frame with inherent diagonal cables that serves to control the antennas’ static configuration is thoroughly studied. These inherent cables of planar phased arrays are pre-tensioned to preserve the structural integrity and increase the stiffness of the antenna. However, they are also used as actuators in our research; in this way, additional control devices are not needed. As a result, the antenna’s mass will decrease, and its reliability will increase. For high observation accuracy, the antennas tend to be very large. Accordingly, there is a significant deformation of space antennas when they are loaded. For this reason, a nonlinear finite element method is used to consider the structures’ geometrical nonlinearity. In order to achieve shape adjustment, the difference between active and passive cables must be carefully investigated. Furthermore, for the nonlinear structure in this paper, the active cables will deform in tandem with the structure as a whole so that the direction of the active cables’ control forces will also change during the entire control process. This paper elaborates on this problem and proposes a nonlinear optimization method considering this characteristic of the cables. Simulations of a simplified 2-bay and 18-bay satellite antenna are performed to validate the proposed method. Results of the numerical simulation demonstrate that the proposed method can successfully adjust the large-scale antenna’s static shape and achieve high precision. Full article