Effect Of Deflection Research Articles

Extending interfacial toughness and thermal cycling lifetime of thermal barrier coatings via interfacial 3D pattern

AbstractWeak interface bonding is a critical factor that compromises the long‐term durability of the thermal barrier coatings. To mitigate this, we introduce an innovative interface‐strengthening approach by integrating four types of 3D patterns at the top coat/bond coat interface using the laser cladding technique. Tensile tests demonstrate a significant enhancement in interfacial bonding strength, increasing by over 139.2% from 21.6 ± 1.7 MPa for conventional thermal barrier coatings without patterns to 51.67 MPa for the patterned coatings. Moreover, the thermal cycling lifetime has been extended by 41%, from 1026 ± 25 cycles for the conventional coating to 1936 ± 164 cycles for the patterned coating. This enhancement in interfacial toughness and thermal cycling lifetime is primarily because of the blocking and deflection effects of 3D patterns on interfacial crack propagation. Besides, the geometric parameters of the patterns play a crucial role in determining the failure behavior of the thermal barrier coatings. This strategy presents a practical solution for the development of durable thermal barrier coatings and provides the valuable insights for the optimization of other heterogeneous interfaces.

The Influence of Sino-US Trade Friction on the Export Volume of China's High-tech Products

With the rapid development of economy, witnessing the extraordinary progression of the economy, China has ascended as the second largest economy globally, and the gap with developed countries is getting smaller and smaller. For a long time, there has been a huge trade deficit from China to the United States. The United States provoked trade friction on the grounds of trade protectionism, restricting trade with China, high-tech industries being the focus. Employing the difference-in-differences (DID) methodology, this paper scrutinizes the influence of Sino-US trade frictions on the export value of China's high-tech industries, utilizing the export data of China's high-tech industries to the United States spanning from 2012 to 2022. It is found that after the Sino-US trade friction began, China's exports of high-tech products to the United States have declined significantly, which has caused trade destruction effect and trade deflection effect from China to the United States.

A New Framework for Understanding Systematic Errors in Cluster Lens Modeling. III. Deflection from Large-Scale Structure

Interpreting and reconstructing distant sources that are gravitationally lensed by galaxy clusters requires accurate and precise lens models. While high-quality data sets have reduced statistical errors in such models, systematic errors remain important. We examine systematic lensing effects caused by density fluctuations due to large-scale structure along the line of sight. We use a multiplane ray-tracing algorithm with the IllustrisTNG 100-3 cosmological simulation of matter distribution and compute the statistical distributions of shear, convergence, and higher-order deflections using two Hubble Frontier Field clusters as examples (A2744 and MACS J0416.1−2403). The cosmic shear distribution is Gaussian in each component, while the cosmic convergence distribution is skewed such that 1 + κ is consistent with a log-normal distribution; the standard deviations for these quantities are at the level of a few to 10%, depending on the redshift of the source. The deflection from higher-order terms beyond convergence and shear has significant scatter: the rms deflection is ∼15″, considerably larger than the image position residuals for current lens models. These results indicate that line-of-sight deflection effects due to large-scale structure can significantly impact lens models and should not be neglected. We present results in forms that can be incorporated into future cluster lens models.

Exceptional strength-toughness-hardness integrated B4C ceramics with synergistic reinforcement of nano-BN and in-situ ceramic phases

Boron carbide (B4C) ceramics with enhanced mechanical properties were fabricated by incorporating nano boron nitride (nano-BN), obtained through high-energy ball milling (HEBM) using ZrO2 balls as the medium, and utilizing the spark plasma sintering (SPS) technique. During the densification process of B4C/nano-BN composite powders, an in-situ reaction between the B4C matrix and ZrO2 resulted in the formation of ZrB2 ceramic phases at 1200–1300 °C. Additionally, the rapid sintering densification temperature of composites is reduced to 1500–1700 °C, approximately 80 °C lower than that required for pure B4C ceramics. Notably, while maintaining a high relative density (99.5 %), the Vickers hardness, flexural strength, and fracture toughness of B4C ceramics reinforced with synergistic effects of nano-BN and ZrB2 fabricated at 1750 °C are significantly improved to reach values of 36.8 ± 0.15 GPa, 701 ± 12 MPa, and 5.01 ± 0.13 MPa m1/2 respectively; representing an increase of 3.5 GPa (10.5 %), 225 MPa (47.3 %), and 1.72 MPa m1/2 (52.3 %) compared to pure B4C ceramics alone. The multiple reinforcement mechanisms including pinning effects provided by nano-BN and in-situ formed ZrB2 ceramic phases, B4C/ZrB2 grain boundary pressure and intracrystalline pressure within B4C, interlayer dislocations of nano-BN and turbulent layer of B4C/BN boundaries contribute to energy dissipation during fracture processes, such as crack deflection, bridging, propagation hindrance and branching effect; ultimately resulting in exceptional strength-toughness-hardness integrated B4C-based ceramics.

Fundamental Study of Phased Array Ultrasonic Cavitation Abrasive Flow Polishing Titanium Alloy Tubes

A new method of machining ultrasonic cavitation abrasive flow based on phase control technology was proposed for improving the machining efficiency of the inner wall of TC4 (Ti-6Al-4V) titanium alloy tubes. According to ultrasonic phase control theory and Hertzian contact theory, a model of ultrasonic abrasive material removal rate under phase control technology was established. Using COMSOL Multiphysics 6.1 software, the phase control deflection effect, acoustic field distribution, and the size of the phase control cavitation domain on the inner wall surface were examined at different transducer frequencies and transducer spacings. The results show that the inner wall polishing has the most excellent effect at a transducer frequency of 21 kHz and spacing of 100 mm. In addition, the phased deflection limit was explored under the optimal parameters, and predictive analyses were performed for voltage control under uniform inner wall polishing. Finally, the effect of processing time on polishing was experimented with, and the results showed that the polishing efficiency was highest from 0 to 30 min and stabilized after 60 min. In addition, the change in surface roughness and material removal of the workpiece were analyzed under the control of the voltage applied, and the experimental results corresponded to the voltage prediction analysis results of the simulation, which proved the viability of phase control abrasive flow polishing for the uniformity of material removal of the inner wall of the tube.

Study of Unsymmetrical Magnetic Pulling Force and Magnetic Moment in 1000 MW Hydrogenerator Based on Finite Element Analysis

The large dimensions of the 1000 MW hydroelectric generator sets require high mounting accuracy. Small deviations can lead to asymmetry, which in turn triggers unbalanced magnetic pulls and moments. Therefore, symmetry is a central challenge in the installation and operation of giant hydroelectric generators. In this paper, the effects of radial eccentricity, axial offset, and rotor shaft deflection on the unbalanced magnetic pull and moment are investigated by transient finite element analysis of the asymmetric magnetic field. The results of the time-domain and frequency-domain analyses show that asymmetric operation generates unbalanced magnetic forces and moments. These forces and moments increase linearly with increasing offset or deflection rate. When the eccentricity meets the installation criteria, the unbalanced magnetic pull forces are small and within acceptable limits. This study helps to understand the relationship between asymmetry and unbalanced magnetic pulling forces in large hydroelectric generators, and provides a theoretical basis for standardizing installation deviation control.

Effect of shaft deflection on the dynamic behaviors of the ceramic bearing rotor system within wide temperature ranges

The shaft deflection has great impact on the dynamic characteristics of the ceramic bearing rotor system, which cannot be ignored within wide temperature ranges. This paper establishes a model considering the shaft deflection, and the impact of shaft deflection appears along with changes in bearing attitude. The interaction between the various components of the bearing is recalculated, and the dynamic behavior of the full ceramic bearing rotor system in wide temperature ranges is obtained based on the thermal deformation difference. The trends of dynamic behaviors with rotor mass, rotation speed and shaft length-diameter ratio are investigated, and comparisons between simulation and experimental results are conducted for verification. It is found that the shaft deflection makes impact by bringing in extra centrifugal force, and the effects are reflected in frequency components and trajectories. The simulation results with shaft deflection fit well with the experimental results, which proves that the dynamic model considering the shaft deflection better illustrates the dynamic behavior of the ceramic outer ring when the contact situations change with working temperature. The research carries out deep insight into the running of ceramic bearing rotor system, and provides guidance for the improvement of dynamic behaviors in wide temperature ranges.

How to Help Older Adults Navigate Through VR? Effects in Outdoor–Indoor Transition Environments

In more complex outdoor–indoor transition scenarios, people were more prone to getting lost due to difficulties in effectively integrating proprioceptive cues and external navigation cues. Previous research had mostly focused on spatial perception driven by head or limb movements, with less discussion on locomotion methods that involved significant visual discrepancies. The challenge in designing navigation systems lies in balancing the enhancement of wayfinding performance with the potential negative impact on spatial cognition. We believe that navigation legibility might be a key optimization approach. Additionally, the differences in performance between different age groups were also worth investigating. Therefore, this study aimed to explore how locomotion methods and navigation legibility affected wayfinding performance, navigation interaction, navigation regression, and spatial cognition in younger and older adults during outdoor–indoor transition scenarios. Twenty-four younger (aged 19–27) and 24 older adults (aged 60–83) underwent VR wayfinding tasks. Participants initially followed virtual phone navigation from outdoor starting points to indoor endpoints, then drew cognitive route maps. Five main findings emerged: Continuous teleportation positively affected navigation performance and global representation of routes. Improving navigation legibility boosted navigation interaction, navigation regression, and global representation of routes. Older adults engaged more in navigation interaction but less in navigation regression, exhibiting poorer performance and route representation. Location-specific differences were observed in locomotion, legibility, and age effects. Furthermore, most older adults and over half of younger adults displayed a deflection effect based on outdoor–indoor (OI) space in route representation. These findings indicated that continuous teleportation and enhanced navigation legibility could improve user experience and spatial cognition, highlighting the importance of considering user age and the characteristics of outdoor–indoor transition scenarios when optimizing navigation methods.

Biomimetic structure-driven high strength and toughness in continuous SiC skeleton-reinforced graphite composites

Graphite-matrix structural composites with excellent mechanical properties and long-term reliability are ungently required in aerospace and nuclear industries. However, the enhancement of graphite-matrix composites by mainstream surface coating techniques or second-phase particle reinforcement is rather limited. Inspired by the structural-functional feature of plant cells, silicon carbide (SiC, cytoderm) coated mesocarbon microbeads (MCMB, cytoplasm) powders were prepared by combustion synthesis (CS), which were then densified via spark plasma sintering (SPS) to obtain the biomimetic cellular-structured SiC-reinforced MCMB (M@SiC) composites. The in-situ formed SiC ‘cytoderm’ ensures good interfacial bonding and contributed to the densification of the composites. Additionally, the continuous SiC skeleton and cellular-structured configuration improved the mechanical properties of M@SiC composites. Owing to the complex crack deflection, branching and bridging effects at the MCMB/SiC interfaces and graphite nanoflakes inside MCMB, the biomimetic M@SiC composite with SiC content of 47 vol% exhibited strengthening and toughening, with flexural strength and fracture toughness of 245 MPa and 3.82 MPa m1/2, respectively. The developed biomimetic graphite-matrix composites with excellent mechanical properties are expected to be applied in reusable spacecrafts and high-temperature gas-cooled reactors.

A comprehensive analysis on coast side contact behaviour of thermoplastic gears against steel gear: a FEA approach

PurposeThe research paper comprehensively investigates the gear tooth deflection of standard thermoplastic gears with steel gear as the driver and driven companions. An accurate mapping of characteristic contact regions between the meshing gears was done, and the behaviour of the gear tooth in the premature and prolonged contact zones was studied.Design/methodology/approachThe study employs the finite element method to conduct a quasi-static 2D analysis of meshing gear teeth. The finite element model was created in AutoCAD and analysed using the ANSYS 19.1 simulation package.FindingsIn the polymer-polymer gear combinations, premature and prolonged contact primarily occurs along the addendum radii of meshing gears, whereas a novel contact phenomenon was observed in the coast side for polymer-metal and metal-polymer combinations, exhibiting a path perpendicular to the standard drive side contact. As well, the deflection of the tooth alters the load distribution across the interlocking gears, leading to a decrement in the root stresses.Originality/valueThe Lewis bending equation demonstrates that bending stresses depend solely on the applied load and the geometry of the tooth. It does not consider the effects of deflection. However, the computational results showed that the gear tooth deflection caused by different gear pair combinations also affects the bending stresses. The contact stresses observed in the polymer-polymer gear combination were observed to be within the material’s proportional limit. However, when a steel gear is paired with a polymer gear, the contact stresses exceed the proportional limit due to coast side contact.

Sensor-Enhanced Thick Laminated Composite Beams: Manufacturing, Testing, and Numerical Analysis.

This study investigates the manufacturing, testing, and analysis of ultra-thick laminated polymer matrix composite (PMC) beams with the aim of developing high-performance PMC leaf springs for automotive applications. An innovative aspect of this study is the integration of Fiber Bragg Grating (FBG) sensors and thermocouples (TCs) to monitor residual strain and exothermic reactions in composite structures during curing and post-curing manufacturing cycles. Additionally, the Calibration Coefficients (CCs) are calculated using Strain Gauge measurement results under static three-point bending tests. A major part of the study focuses on developing a properly correlated Finite Element (FE) model with large deflection (LD) effects using geometrical nonlinear analysis (GNA) to understand the deformation behavior of ultra thick composite beam (ComBeam) samples, advancing the understanding of large deformation behavior and filling critical research gaps in composite materials. This model will help assess the internal strain distribution, which is verified by correlating data from FBG sensors, Strain Gauges (SGs), and FE analysis. In addition, this research focuses on the application of FBG sensors in structural health monitoring (SHM) in fatigue tests under three-point bending with the support of load-deflection sensors: a new approach for composites at this scale. This study revealed that the fatigue performance of ComBeam samples drastically decreased with increasing displacement ranges, even at the same maximum level, underscoring the potential of FBG sensors to enhance SHM capabilities linked to smart maintenance.

Improved interfacial mechanical properties between PZT piezoelectric ceramic and Ag metallization layer by in-situ-formed CuO nanoparticles

In-situ-formed CuO nanoparticles were used to improve the interfacial mechanical properties between lead zirconate titanate (PZT) ceramic and metallization layer. The effects of CuO particles on the mechanical properties of PZT/Ag interfaces were studied, and the damage evolutions of the PZT-CuO/Ag interfaces were analyzed. The results showed that both the maximum peeling stress σmax and shear stress τmax of the PZT-CuO/Ag interfaces increased by approximately 200 %, while the critical fracture energy GIC of the interface was increased at most by seven times. The enhanced mechanical properties of the PZT-CuO/Ag interfaces originated from the high bonding strength between CuO and Ag layer and the effective stress concentration relief. Crack deflection and crack pinning effects promoted the enhancement of interfacial fracture toughness. The optimal size of the CuO particles at the PZT/Ag interface was approximately 100 nm. Notably, the electron transport between the PZT ceramic and Ag layer was not degraded with the introduction of CuO nanoparticles.

Centrifuge modelling of dry granular run-out processes under deflective Coriolis condition

Coriolis effects, encompassing the dilative, compressive, and deflective manifestations, constitute pivotal considerations in the centrifugal modelling of high-speed granular run-out processes. Notably, under the deflective Coriolis condition, the velocity component parallel to the rotational axis exerts no influence on the magnitude of Coriolis acceleration. This circumstance implies a potential mitigation of the Coriolis force's deflective impact. Regrettably, extant investigations predominantly emphasize the dilative and compressive Coriolis effects, largely neglecting the pragmatic import of the deflective Coriolis condition. In pursuit of this gap, a series of discrete element method (DEM) simulations have been conducted to scrutinize the feasibility of centrifugal modelling for dry granular run-out processes under deflective Coriolis conditions. The findings concerning the deflective Coriolis effect reveal a consistent rise in the run-out distance by 2%–16%, a modest increase in bulk flow velocity of under 4%, and a slight elevation in average flow depth by no more than 25%. These alterations display smaller dependence on the specific testing conditions due to the granular flow undergoing dual deflections in opposing directions. This underscores the significance and utility of the deflective Coriolis condition. Notably, the anticipated reduction in error in predicting the final run-out distance is substantial, potentially reaching a 150% improvement compared to predictions made under the dilative and compressive Coriolis conditions. Therefore, the deflective Coriolis condition is advised when the final run-out distance of the granular flow is the main concern. To mitigate the impact of Coriolis acceleration, a greater initial height of the granular column is recommended, with a height/width ratio exceeding 1, as the basal friction of the granular material plays a crucial role in mitigating the deflective Coriolis effect. For more transverse-uniform flow properties, the width of the granular column should be as large as possible.

Study on microstructure and thermal shock resistance of plasma sprayed Cr2O3/8YSZ composite coating

In order to explore the high temperature performance of Cr2O3/8YSZ composite coating, four kinds of Cr2O3/8YSZ composite coatings were prepared on the surface of Q235 steel by using the plasma spraying technology (the content of 8YSZ is 50%, 30%, 20% and 0%, respectively). The morphology of the coating was characterized through thermal field emission scanning electron microscopy, and the distribution of elements in the section of the coating was scanned by using EDS line. The phase composition of the composite coating was analyzed by using X-ray diffractometer, and the surface roughness of the composite coating was measured by using surface profilometer. The microhardness of the coating was measured by using automatic micro-Vickers hardness tester, and the scratch resistance of the coating was compared by using scratch tester. The thermal shock resistance of the coating was tested in Gleeble-3800 thermal physical simulator, and the cross section morphology after thermal shock was observed and analyzed. The results show that when the ratio of Cr2O3 to 8YSZ is 7∶3, the sample coating has good thermal shock resistance due to the deflection effect of 8YSZ on the vertical cracks and the thermal stress release effect of the pores and cracks in the coating.

Fracture Propagation of Multi-Stage Radial Wellbore Fracturing in Tight Sandstone Reservoir

Radial wellbore fracturing is a promising technology for stimulating tight sandstone reservoirs. However, simultaneous fracturing of multiple radial wellbores often leads to unsuccessful treatments. This paper proposes a novel technology called multi-stage radial wellbore fracturing (MRWF) to address this challenge. A numerical model based on the finite element/meshfree method is established to investigate the effects of various parameters on the fracture propagation of MRWF, including the azimuth of the radial wellbore, the horizontal stress difference, and the rock matrix permeability. The results show that previously created fractures have an attraction for subsequently created fractures, significantly influencing fracture propagation. A conceptual model is proposed to explain the variations in the fracture propagation of MRWF, highlighting three critical effect factors: the attraction effect, the orientation effect of the radial wellbore, and the deflection effect of the maximum horizontal principal stress. Fracture geometry is quantitatively assessed through the deviation distance, which indicates the radial wellbore’s ability to guide fracture propagation along its axis. As the azimuth increases, the deviation distances can either increase or decrease, depending on the specific radial wellbore layouts. Decreasing the horizontal stress difference and increasing the rock matrix permeability both increase the deviation distance.

Enhanced mechanical properties of boron carbide ceramics prepared by spark plasma sintering with boron nitride nanosheets addition

Boron carbide (B4C) ceramics with enhanced mechanical properties have been fabricated with boron nitride nanosheets (BNNSs, 1.5–5 wt%) as reinforcement via spark plasma sintering. The densification temperature of the B4C ceramic containing 3 wt% BNNSs (B4C-3 %BNNSs) was reduced to 1480–1700 °C, approximately 100 ℃ lower than the pure B4C ceramic. The B4C-3 %BNNSs composites with a density of 98.9 % and associated Vickers hardness of 34.4 GPa, flexural strength of 654 MPa, and fracture toughness of 4.86 MPa·m1/2 that represent a respective increased by 1.1 GPa (3.3 %), 178 MPa (37.4 %) and 1.57 MPa·m1/2 (47.7 %) relative to pure B4C. The reinforcement mechanisms due to BNNSs combined with B4C involves a synergistic effect of the decrease in densification temperature where the BNNSs promote B4C grain rearrangement, B4C twin grain boundaries, and BNNSs pull-out, crack branching and crack deflection effects.

Unsteady Aerodynamics of Delta Kites for Airborne Wind Energy Under Dynamic Stall Conditions

ABSTRACTThree unsteady aerodynamic tools at different levels of fidelity and computational cost were used to investigate the unsteady aerodynamic behavior of a delta kite applied to airborne wind energy. The first tool is an in‐house unsteady panel method that is fast but delivers low to mid fidelity predictions. The second tool uses the open‐source CFD code SU2 to solve the unsteady Reynolds‐averaged Navier–Stokes equations with the SST turbulence model. At an intermediate level of fidelity, a semiempirical dynamic stall model that combines the panel method with a phenomenological dynamic stall module is proposed. The latter has free parameters that are fine‐tuned with CFD results from the second tool. The research on the dynamic stall model has been inspired by two flight test campaigns suggesting dynamic stall phenomena possibly driven by the periodic variation of the angle of attack (aerodynamic pitching motion) during crosswind maneuvers. The recorded inflow along the flight path was prescribed in the three aerodynamic tools. As expected, the price to pay for the low computational cost of the panel method is its inability to capture the dynamic stall phenomenon. The results from unsteady CFD qualitatively matched the experimental data identifying a leading‐edge vortex that forms and detaches cyclically during the pitching motion. Using RANS data, the semiempirical tool was fined‐tuned to reproduce the dynamic stall behavior, becoming an accurate and fast aerodynamic tool for coupling with any kite flight simulator. Further discussions on the effects of kite aerostructural deflections are included.

Wing deformation improves aerodynamic performance of forward flight of bluebottle flies flying in a flight mill.

Insect wings are flexible structures that exhibit deformations of complex spatiotemporal patterns. Existing studies on wing deformation underscore the indispensable role of wing deformation in enhancing aerodynamic performance. Here, we investigated forward flight in bluebottle flies, flying semi-freely in a magnetic flight mill; we quantified wing surface deformation using high-speed videography and marker-less surface reconstruction and studied the effects on aerodynamic forces, power and efficiency using computational fluid dynamics. The results showed that flies' wings exhibited substantial camber near the wing root and twisted along the wingspan, as they were coupled effects of deflection primarily about the claval flexion line. Such deflection was more substantial for supination during the upstroke when most thrust was produced. Compared with deformed wings, the undeformed wings generated 59-98% of thrust and 54-87% of thrust efficiency (i.e. ratio of thrust and power). Wing twist moved the aerodynamic centre of pressure proximally and posteriorly, likely improving aerodynamic efficiency.

Densification mechanism and thermal shock resistance improvement of MgF2‐doped Y2O3 ceramics

AbstractThis paper aims to improve the density and thermal shock resistance of Y2O3 ceramics for the preparation of ultra‐pure high‐temperature alloy crucible materials. The doping effect of MgF2 content on the densification behavior, physical properties, and thermal shock resistance of Y2O3 ceramics was systematically investigated in this paper. The results suggested that the presence of MgF2 greatly promoted the growth of Y2O3 grains and the transformation of the pore structure by liquid‐phase sintering. And the mechanical properties of the MgF2‐doped Y2O3 ceramics were significantly improved. Besides, the marked improvement in the thermal shock resistance of MgF2‐doped Y2O3 ceramics was attributed to the synergistic action resulting from the growth of grain size and the enhancement of the crack deflection effect. In particular, the relative density of Y2O3 ceramics doped with 1.5 wt% MgF2 reached 96.4% and the residual flexural strength ratio after thermal shock achieved 45.0%, showing an excellent application prospect.

An advanced design diagram of stiffened plate subjected to combined in-plane and lateral loads considering initial deflection effects

This study presents an advanced methodology for stiffened plates subjected to combined in-plane longitudinal compression and lateral loads. The proposed methodology is based on comprehensive numerical parametric analyses, and it utilises newly developed design curves for the lateral pressure limit and tailored empirical formulae for stiffened plates to increase the precision of ship structural designs. Plate–stiffener combination (PSC) members are used for the limit state analysis, which introduces various positions and initial deflection shapes specific to the PSC models. Local buckling-shaped deflections of the stiffener web are also incorporated into the analysis, which closely mirrors the real-world welding conditions of stiffened plates and provides deeper insight into their load-bearing capacities. These findings highlight the importance of accurately selecting the positions and initial deflections of stiffeners in PSC-based analyses to ensure that structural predictions are safe and reliable. The proposed method is grounded in conservative PSC models and represents a significant advancement in ship structural design in terms of safety and practicality.