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Laser beam drilling has been widely applied in various industries due to its high efficiency and low cost. However, machining defects like obvious taper, heat affected zone (HAZ), and spatter may generate as hidden perils. In order to investigate generation mechanism of these phenomena and explore a proper solving method, a three-dimensional finite element model which describes the temperature field distribution and interaction between continuous laser and metal was put forward. Simulations on laser cutting with steady and moving focal point on carbon steel C45 workpiece with thickness of 1 and 4 mm were conducted. The comparison of hole morphology under initial simulation and experiments illustrated that the established finite element model is able to predict taper formation and size of HAZ in continuous laser drilling process. Moreover, using a moving focal point during laser drilling process is conductive to the reduction of taper and size of HAZ through contrast experiments. Both numerical simulations and experimental results indicated that the cylindricity and quality of deep holes can be significantly improved with a moving focal point.

Copper-laminated REBCO tape is one of the best choices for manufacturing high-current-carrying cables in fusion projects and particle accelerator designs due to their excellent current-carrying performance in high magnetic fields. In order to maximize the electromechanical properties of the cable after winding, the bending properties of three kinds of copper-laminated REBCO tapes are analyzed. The experimental results show that the bending properties of the three REBCO tapes are different from each other. A three-dimensional finite element simulation model is also established to study the strain field of the superconducting layer under different bending radius and bending states (REBCO layer is inside/outside of bending). The simulation results are in good agreement with the calculated formula, which verifies the correctness of the finite element model. The edge effect is found by the simulation results of strain distribution along tape width. The influence on strain field distribution by changing the tape width and the thickness of the copper-laminated layer is investigated under two bending states. Finally, the critical strain values of each tape under two bending states are obtained by combining the results of experiments and the finite element model. In addition, the finite element model can study the stress and strain field distribution of each functional layer of REBCO tape along axis a, b and c.

Fully coupled soil–structure analyses were performed for a building of strategic importance located in the city of Messina (Sicily, Italy). The structure was built after the destructive 1908 earthquake, also known as the ‘Messina and Reggio Calabria earthquake’, which caused severe ground shaking. A parametric study considering three seismograms of this earthquake was performed. Deep in situ and laboratory investigations allowed the definition of the geometric and geotechnical model of the subsoil. Numerical analyses were performed with PLAXIS3D finite element software (Version 21.01.00.479). The Hardening Soil model with small-strain stiffness was accurately calibrated using laboratory and field data. The dynamic response was investigated in terms of accelerations, response spectra, amplification functions, displacements and stress–strain hysteretic loops. The findings show that many aspects must be investigated for the retrofitting of buildings with shallow foundation in areas characterized by a medium to high level of seismic risk: (i) a key role is played by an accurate investigation of the soil; taking into account the specific conditions of the soil, it was possible to investigate its filtering effects; (ii) the dynamic response of the fully-coupled soil–structure system deviates from the free field-site response analysis; (iii) the results reveal the importance of considering the soil nonlinearity in seismic soil–structure interaction problems.

The influence of kinematic excitation of vibrations on vibration stress in a disk–blade system with a violation of cyclic symmetry when one blade is damaged is evaluated. To assess the trouble-free operation, it is relevant to determine their stress state when the blade shape changes due to erosion damage. The results of calculations of the maximum stresses in the blades under power and kinematic excitation of oscillations are presented. The three-dimensional finite element models of the disk–blade system and the corresponding mathematical software are used to determine the parameters of stationary vibrations and blade stresses. The force effect of a steam flow with a frequency of 2100 Hz (the number of guide blades is 42) and kinematic excitation when the center of the disk moves along an elliptical trajectory in its plane with a frequency of 50 Hz, which is caused by rotor vibration in sliding bearings in stationary operating conditions, is taken into account. The load from the steam flow on each blade was set to be linearly variable from zero at the root of the blades to 1 and 5 kPa at the periphery and for a uniformly distributed 2.5 kPa along their length, acting normally at the points of the blade working surfaces. It is assumed that the physical and mechanical properties of the damaged blade material are preserved after repair and surface treatment. The change in the maximum equivalent stresses in the impeller blades for different loading conditions is determined. The amplitude-frequency characteristics for the maximum stresses in the region of rotational speeds and the action of the load on the blades are given. The results are compared for the system with and without kinematic excitation of oscillations. The studies confirmed the practicality of considering the influence of kinematic excitation when assessing the stress state of the last stage blades of a powerful steam turbine.

An inclined straight combination support pile can play a better role in deep foundation pit support, especially for the protection of adjacent structural pile foundations. We take a section of the construction of a deep foundation pit project in Wuhan City, Hubei Province as the research object. This paper studies the influence of inclined and straight combination support piles on the bending moment and displacement behavior of adjacent pile foundations during the construction of foundation pits under the influence of different factors such as distance from the excavation surface, pit angle effect, inclined pile tilt angle, pit depth to width ratio, and construction conditions on the adjacent pile foundation using a three-dimensional finite element model. According to the research results, as the distance from the excavation surface increases, the bending moment of the adjacent pile foundation decreases, and the closer the pile is to the foundation pit, the greater the horizontal displacement of the pile; the bending moment and displacement of the pile foundation are supported by the pit angle effect. Moreover, the pile bending moment increases with the increase of the pit depth–width ratio, and the maximum displacement point of the pile body gradually moves down from the middle of the pile body to the bottom of the pile foundation as the excavation depth of the pit increases. In addition, the minimum displacement of the adjacent pile foundation is at the top of the pile, and the maximum displacement is at the middle of the pile. Finally, compared with the static analysis, the whole process of dynamic simulation can reflect the dangerous working conditions in the project construction process, and make a more complete safety control construction plan for the project construction process.

Background Cleft palate is a prevalent oral and maxillofacial malformation that requires complex surgical interventions. In cleft palate repair, managing flap tension is critical to avoid complications such as flap rupture and impaired healing. Additionally, excessive flap movement can compromise blood supply, affecting postoperative outcomes. A thorough understanding of these biomechanical factors is crucial for surgical success. Methods A three-dimensional finite element model was developed using CT scan data to simulate the biomechanical behavior of the cleft palate under surgical conditions. The model was constructed and analyzed using ANSYS Workbench and related software, incorporating material properties of bone, mucosa, and muscle. Stress and deformation distributions were calculated to evaluate surgical incision points and flap movement. Results The model identified critical areas of high tension and movement along the surgical incisions on both oral and nasal surfaces. The maximum deformation observed was 3.9885 mm, with stress concentration points along the suture lines and flap edges. The results highlighted specific regions prone to mechanical stress, which are crucial for optimizing surgical strategies. Conclusion This study demonstrates the potential of a 3D finite element model in predicting mechanical responses of the cleft palate during surgical repair. The findings provide surgeons with valuable insights for improving incision placement, flap design, and suturing techniques to minimize tension and enhance healing. This personalized approach could significantly improve surgical outcomes and reduce postoperative complications in cleft palate repair.

A reliable assessment and design of engineering structures requires appropriate estimation and consideration of different sources of uncertainty. The randomness of seismic ground motion is one major uncertainty that needs to be considered from the perspective of performance-based earthquake engineering. To properly account for this uncertainty and its corresponding effect on pile foundations, a stochastic seismic response analytical framework based on a probability density evolution method and a stochastic ground motion model is proposed for the nonlinear stochastic seismic response analysis of pile foundations. A three-dimensional finite element model of a reinforced concrete pile with a large diameter embedded in the soil foundation is firstly established and calibrated using the full-scale lateral load test results from the literature, in which the nonlinear behavior of soil, the soil–pile interaction, the concrete damaged plasticity, and the steel yielding of the pile are properly modeled. Then, the calibrated three-dimensional numerical model is employed as an illustrative example for the stochastic seismic response analysis using the proposed framework. The mean, standard deviation, and probability density function of pile settlement and the dynamic reliabilities of the pile concerning various performance requirements are obtained in the present study. The settlements of the pile show great variability under the excitation of various stochastic ground motions, and the maximum mean value of the pile settlements is about 8 mm. The changing shape of the settlement probability density functions in every moment demonstrates that it is unreasonable to use assumed probabilistic distribution models to characterize the seismic responses of pile foundations during a seismic reliability analysis. Based on the proposed method, it is found that the dynamic reliabilities of the selected reinforced concrete pile concerning four different performance levels are 0, 0.1293, 0.8247, and 1, respectively. The proposed stochastic seismic response analytical method in the present study can provide a proper and comprehensive way to quantify various uncertainties and their corresponding effects on the seismic performance of pile foundations. It can also be used to estimate the actual reliability level of pile foundations that are designed by the current codes when they are subjected to seismic loads.

The influence of kinematic excitation of rotor vibrations of a powerful steam turbine without and with disturbance of blade vibration frequencies on the extension of their trouble-free operation is evaluated. The results of determining the maximum equivalent stresses of the blades under the condition of power and kinematic excitation of stationary oscillations are presented. A system with cyclic symmetry is considered. The three-dimensional finite element models of the disk–blade system and the corresponding mathematical support for calculating stationary harmonic oscillations are used. Computational studies to determine the maximum equivalent stresses of the blades were carried out under the condition of simultaneous action of power excitation of oscillations from the steam flow with a frequency of the forcing force of 2100 Hz (with the number of guide blades of 42) and kinematic excitation due to rotor vibration on sliding bearings with a frequency of 50 Hz. The load from the steam flow on each blade was set to be linearly variable from zero at the root to 1 kPa and 5 kPa at the apex, as well as a uniformly distributed 2.5 kPa along the blade, acting normally at points on their working surface. The kinematic excitation was set as an ellipse describing the motion of the disk center in its plane. It is assumed that the physical and mechanical properties of the blade material are preserved after their repair and surface treatment. The change in the maximum equivalent stresses for different variants of blade loading in a cyclic-symmetric disk–blade system under kinematic excitation of oscillations is evaluated. The obtained results are compared with the data for the system with all damaged blades after restorative repair in their lower part under the condition of kinematic excitation of vibrations and without repair. These results confirm the practicality of assessing the stress state of the last stage blades of a powerful steam turbine, considering the disk–blade system’s kinematic excitation when determining their operation’s reliability.

Thermal barrier coatings (TBCs) and air film-cooling technology have been extensively utilized in nickel-based, single-crystal turbine blades to enhance their heat resistance. However, structural complexity and material property mismatches between layers can affect residual stresses and potentially lead to coating failure. In this study, a three-dimensional finite element model with atmospheric plasma-spraying thermal barrier coatings (APS-TBCs) deposited on air-cooled, nickel-based, single-crystal blades was established to investigate residual stress character under centrifugal load, considering the effect of temperature, crystal orientation deviation angle, oxide layer thickness, and the number of cycles. The results show that when the centrifugal load is increased from 300 MPa to 700 MPa, the absolute value of the residual stress at the crest of the interface between Top Coat (TC) and Thermally Grown Oxide (TGO) increases by only 8.5%, whereas in the region of compressive to tensile stress conversion, residual stress decreases by 100.9%. As the crystal orientation deviation angle increases, the absolute value of the residual compressive stress increases and the absolute value of the residual tensile stress decreases, but the performance is more special in the valley region, where the absolute value of the residual stress increases with the increase in the deviation angle. Special attention is required, as the increase in temperature leads to a rise in the absolute value of residual stress. For example, at the trough of the TC–TGO interface, when the temperature increases from 910 °C to 1100 °C, the residual stress increases by 9.8%. The effect of the number of cycles on residual stress is relatively weak. For instance, at the wave crest of the TC–TGO interface, the residual stress differs by only 0.6 MPa between one cycle and three cycles. The effect of oxide layer thickness on residual stress in the TBCs after a single cycle is nonlinear. When the oxide layer thickness is 0, 4, and 7 μm, the residual stress undergoes a transition between tensile and compressive directions at different locations. The exploration of these results has yielded some valuable laws that can provide a reference for the study of the damage mechanism of TBCs, as well as a guide for the optimization of nickel-based turbine blades in the manufacturing and use processes.