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High temperatures in a gas turbine may lead to severe blade rubbing failure for the bladed thin drum rotor. It is essential to demonstrate such rubbing features. This paper established a bladed drum rotor model with blade rubbing induced by high temperatures. The analytical function of a coupled axial-radial temperature in the drum according to the actual thermal field analysis is obtained. The equations of motion for this rotor are derived. The dynamic model and its solution method are verified through the natural frequency comparison and the rub-impact response analysis. Thereafter numerical simulations are carried out. Results show that the heat at the turbine is transferred from its outer surface to its inner surface, then to the compressor's inner surface along the axial direction, and finally from the compressor's inner surface to its outer surface. This is a novel coupled axial-radial thermal effect for the gas turbine, which causes special axial and radial thermal gradients. The effect is induced by high temperatures in a gas turbine and intensifies a blade rubbing fault. Increasing the exhaust temperature aggravates the coupled axial-radial thermal effect, which causes more severe blade rubbing. Fortunately, introducing a lower temperature on the drum's inner surface can prevent blade rubbing caused by this thermal effect. [ABSTRACT FROM AUTHOR]

• A rubbing blade-drum model under high time-varying temperature is proposed. • Paroxysmal vibrations caused by sudden temperature rise induce a rubbing fault. • The rub-impact fault is induced or intensified during fluctuating temperature rise. • Reducing a proper exhaust temperature weakens tip-rub and avoids shock vibrations. In a gas turbine, the multistage bladed drum rotor often operates under high time-varying ambient temperature. Thermal deformations of the thin drum could lead to the rub-impact fault between multistage blade rows and the outer casing, which may cause damage to the blades or even the whole machine. Due to the complexity of the thermoelastic coupling solution, rub-impact characteristics of this kind of rotor system are not clear. This study develops a multistage bladed drum rotor model with the rub-impact fault induced by high time-varying temperature. A solution process for the thermoelastic dynamics analysis of the multistage bladed drum rotor system is proposed, combining experimental, numerical, and analytical methods. According to temperature characteristics in a gas turbine, the effect of the high-temperature environment, heating, fluctuating temperature rise, and cooling on the rub-impact fault is the main emphasis of the study. The high-temperature environment could cause a rub-impact fault for the multistage bladed drum rotor. The sudden increase of the exhaust temperature leads to paroxysmal vibrations, which could induce tip rub or make a slight rub-impact fault into a severe accident. Large fluctuation during temperature rise induces the rub-impact fault and even leads to the continuous aggravation of the rub-impact fault. Fortunately, reducing an appropriate exhaust temperature can eliminate or weaken the rub-impact fault and avoid shock vibrations induced by the sudden drop of the high ambient temperature at the same time. Besides, more blade rows could aggravate this kind of rub-impact phenomenon for the multistage bladed drum rotor. Graphical abstract [Display omitted]. [ABSTRACT FROM AUTHOR]

Thermal shock load has an important influence on dynamic characteristics of blades in turbomachines. Due to higher level operating thermal shock for improving the efficiency, the damage to the blades has greatly increased. Considering the major effect of variable thickness and large deflection on thermal dynamic behavior of blades, their thermo-large deflection-variable thickness coupled dynamic characteristics are unknown. This paper develops a thermo-large deflection coupled semi-analytical model based on a rotating variable thickness plate under thermal shock. Geometric nonlinear governing equation and an analytical solution of heat transfer equation are derived. Numerical examples of natural frequencies are investigated to validate the proposed model. The non-uniform temperature distribution features of the rotating variable thickness plate are found. Besides, when the thermal shock is serious, the large deflection theory must be considered to analyze thermo-large deflection coupled dynamic characteristics. Based on theoretical and experimental results, deformation characteristic of the cantilever plate subjected to thermal shock is obtained, which is helpful to find the optimal thickness distribution. Finally, the effect of variable thickness on thermo-large deflection coupled dynamics of the rotating plate is demonstrated. The vibration induced by thermal shock can be reduced by thickening the plate on its free side or both fixed–free sides. However, when thickening other positions, the vibration is either intensified or unchanged. Results are helpful to reduce blade's vibrations under thermal shock. • A thermo-large deflection coupled analytical model of rotating variable thickness plates under thermal shock is developed. • The non-uniform temperature distribution due to the plate's variable thickness is obtained under thermal shock. • Thermo-large deflection is divergent as increasing time, and the divergent degree depends on severity of thermal shock. • Thickening on free side or both fixed–free sides weakens thermo-large deflection coupled responses caused by thermal shock. [ABSTRACT FROM AUTHOR]

Thermal conductive materials with low dielectric constant under high frequencies play an important role in high-power integrated circuits packaging. The application of Cu in the packaging substrates is limited due to the high dielectric constant. In this paper, the AlN coatings were deposited on the Cu substrates to maintain the high thermal conductivity and obtain excellent electrical properties for the first time. The microstructure, thermal conductivity and electrical properties of the AlN/Cu systems were adjusted by duty cycles. The results show that improving the duty cycle reduced the hcp-AlN (002) preferred orientation degree of the coatings. The growth structure of the coatings could be regulated by increasing the duty cycle, which induced the grain and particle size first increasing and then decreasing. AlN/Cu systems improved the thermal conductivity of Cu. All coatings show far higher resistivity than Cu and 0.006–0.24 low dielectric loss. The minimum dielectric constant (5.6) of the coating at 2000 kHz frequency was obtained. The AlN/Cu systems in this paper realize high thermal conductivity and excellently dielectric properties, meeting the application in high-power integrated circuit packaging. [ABSTRACT FROM AUTHOR]

• A rubbing rotor model with multiple wide-chord blades is developed. • The localized rub-impact phenomenon of blades by synchronous forces is found. • The asynchronous force makes all blades rub in turn with a phase difference Δ φ = 2 π / Ω ± ω N b . • The swing motion intensifies steady tip-rub, but weakens unstable tip-rub. • The gyroscopic effect weakens the swing motion and the stable rub-impact fault. In turbo-machinery, wide-chord blades are widely used due to the advantages of improving fan efficiency and aerodynamic performance. The rotor with multiple wide-chord blades is spaced from the outer casing. The small clearance may cause rub-impact fault between wide-chord blades and the casing, which induces different damage severity or the destruction of the whole machine. Numerical simulation is necessary to analyze this kind of rub-impact fault, but the solution process becomes complicated because of the coupling of geometric nonlinearity, local vibrations of wide-chord blades and gyroscopic motion of the rotor. This paper develops a rubbing rotor model with multiple wide-chord blades considering the gyroscopic effect and geometric nonlinearity induced by rub-impact. Based on the rub-impact model established for wide-chord blades, the high-order nonlinear governing equations of the bladed rotor are derived. Vibration responses are solved, and a series of dynamic characteristic analysis is carried out. The results reveal that high-order nonlinearity has a little effort on vibrations during slight rub-impact. But with the increase of transverse deformation induced by severe tip-rub, its influence cannot be ignored. Besides, localized rub-impact phenomenon of blades induced by external synchronous forces is found. Instead, external asynchronous force makes all blades rub, one after another along the circumferential direction of the disk, and there is a phase difference Δ φ = 2 π / Ω ± ω N b between the vibration responses of adjacent blades. Then, we found that the swing motion intensifies the difference of transverse deformations along the chord direction of wide-chord blades with tip-rub, which may induce the edge failures. Also, the swing motion intensifies the steady rub-impact fault. It could weaken or eliminate its divergence and instability when the rotor with multiple wide-chord blades is unstable. The gyroscopic effect could weaken the swing motion, and then weakens the stable rub-impact fault. [ABSTRACT FROM AUTHOR]

Abstract: This paper uses a semi-analytical approach to investigate the frequency response, bifurcation, and chaos of a rotating large deflection plate subjected to rub-induced non-linear vibrations. The general equations are coupled with the lateral displacement and two in-plane stretch variables and were derived using Hamilton's principle with consideration given to the centrifugal stiffening effect. The accuracy of the solution method is demonstrated through a comparison of modal characteristics found in the literature. Special attention is given to the influence of friction coefficients, the rubbing force amplitude and the contact load time on rub-induced non-linear vibrations. The results show that the frictional effect in tip-rub is the main source of rub-induced non-linear vibrations for the rotating large deflection plate. Increases in the rubbing force amplitude and the contact load time produce more non-linear effects such as more paths to chaos and a jump phenomenon, and intensify the vibration of the system. [Copyright &y& Elsevier]

Superhydrophobic coatings often face challenges related to poor friction and corrosion resistance. In this study, composite coatings were developed, featuring a top layer of SiO 2 nanoparticles and a bottom layer of epoxy resin (EP) and polydimethylsiloxane (PDMS). As the number of SiO 2 nanoparticles layers increased, surface roughness escalated, and the coating structure transitioned from SiO 2 nanoparticles entirely encapsulated by EP and PDMS to a small fraction of SiO 2 exposed on the coating surface. Leveraging the rough surface and low-free-energy properties endowed by Si-(CH 3) 2 and Si-O-Si hydrophobic groups, coatings comprising 3–5 layers SiO 2 nanoparticles exhibited superhydrophobicity and self-cleaning capabilities. These coatings retained their superhydrophobic properties even after enduring heavy friction from sandpaper, and demonstrated robust corrosion resistance over extended periods. Increasing the number of SiO 2 layers not only enhanced superhydrophobicity, corrosion and friction resistance, but also improved the coating-substrate adhesion. The designed coating structure exhibited superior corrosion resistance and coating-substrate adhesion compared to those of EP/PDMS + SiO 2 double-layer and EP + PDMS + SiO 2 mixed coatings. Moreover, the coatings displayed a self-healing ability, regaining superhydrophobicity following O 2 or Ar etching, facilitated by the upward movement of hydrophobic groups/bonds and intensity recovery. Coatings subjected to Ar etching exhibited better self-healing properties due to higher Si-O-Si and lower C-C/C-H bond intensities. This research presents novel insights for the practical application of superhydrophobic coatings. • Coating structure with all or a part of SiO 2 surrounded by EP and PDMS was designed. • Rough surface with low surface energy led to coating superhydrophobic and self-clean. • Improving SiO 2 layers number achieved good adhesion, corrosion and friction durability. • Coatings present better corrosion durability and adhesion than other structure design. • Hydrophobic groups floating up and intensity recovery were coating self-heal reason. [ABSTRACT FROM AUTHOR]

[Display omitted] • New idea to analyse atom distribution and interface structure of ultrathin multilayer. • Actual composition and distribution of Pt/Co/W multilayers are obtained by ARXPS. • Atom diffusion of Co and W in Pt/Co/W multilayers is reflected through MD simulation. • Growth modes, surface and interface roughness of Pt/Co/W multilayers are exhibited. • Surface/interface structure adjust multilayers magnetic anisotropy and coercivity. Characterizing ultrathin multilayer films' atom distribution and interface structure remains challenging. This paper innovatively characterized the chemical composition and distribution of Pt/Co/W ultrathin multilayer films by ARXPS. Molecular dynamics simulated the growth process of films to correspond to that in experiment. The results show that through ARXPS, the actual structure of Pt (2 nm)/Co (t = 0.5–3 nm)/W (2 nm) film could be obtained. For Pt (2 nm)/Co (2 nm)/W (2 nm) film, the actual structure was Pt/Co (1.73 nm)/W (0.78 nm)/WO 3 + WO 2 (1.48 nm). W at the top layer significantly diffused to the bottom layers, and oxidized W reduced from the surface to the interior of multilayer films. Molecular dynamics simulation confirmed that the interdiffusion degree of Co and W atoms was improved with the increase of Co atoms. The growth modes of Co and W layers were respectively layer-by-layer and island. As the number of Co atoms increased, the relative surface roughness of Co and W layers and the relative interface roughness of Co/W were increased. The in-plane magnetic anisotropy and coercivity were respectively enhanced and decreased due to the change in the surface/interface structure. This paper provides a new idea for analyzing ultrathin multilayer films' atom distribution and interface structure. [ABSTRACT FROM AUTHOR]

• A periodic incoming wake model is developed considering pressure variations. • A wake-induced nonlinear vibration model based on varying thickness plates is established. • Increasing thickness on the fixed end is a better way to decrease vibration induced by wakes. • Increasing maximum thickness in chord is another way to reduce wake-induced vibrations. Incoming wakes significantly affect vibration characteristics of rotating blades in turbomachines. This paper develops a periodic incoming wake mathematical model to consider the influence of pressure variations. Considering thickness variations along both the chord to reduce vibrations and the span to decrease centrifugal stress, a wake-induced vibration model based on rotating large deformation cantilever plates is established. Natural frequencies calculated by different methods show that the present method has a high degree of accuracy. And analysis of incoming wake-induced vibrations indicates the incoming wake model can analyze effects of important parameters of such wakes on vibration characteristics. With the aggravation of wakes induced-vibrations, geometric nonlinear vibrations become more remarkable, which indicates the necessity of large deflection analysis. Discussions on variable thickness demonstrate that increasing thickness on the fixed end or maximum thickness along the chord not only reduces vibrations caused by incoming wakes, but also decreases the centrifugal stress, which are two better ways to reduce this kind of vibrations. Image, graphical abstract [ABSTRACT FROM AUTHOR]

A tip-rub model is developed for nonlinear dynamics analysis of contact-induced vibrations of the rotating variable thickness plate under large deformations. Variable thickness, coupled with large deformations, contact-impact and centrifugal stiffening, increases complexity of the nonlinear system. Natural frequencies for different variable thickness are compared to indicate a great precision of the present method. Solution procedure for tip-rub has been proved to be in good agreement with existing experimental results. Numerical simulation for tip-rub reveals the requirement of large deformation analysis. Then special attention is given to nonlinear characteristics of the rotating rubbing plate with variable thickness. Results show that there are very rich and complex nonlinear dynamics of contact-induced vibrations of the rotating variable thickness plate under large deformations such as multi-period, bifurcation and chaotic motions. And effects of thickness strategies of exponential and linear decrease along the span used in engineering on nonlinear characteristics induced by tip-rub are investigated. Numerical results reveal that smaller thickness at the free end used to reduce centrifugal stress should not be too small to avoid aggravation of contact-induced bifurcation and chaos. Moreover, in order to obtain less centrifugal stress and weak chaotic behavior, there is an optimal thickness at the fixed end when the smaller thickness at the free end is unchanged. As the order of thickness function increasing, the trend of bifurcation and chaotic motions is gradually aggravated. It is better to choose a small order of thickness function to ensure stable operation. • Tip-rub model of rotating variable thickness plate with large deflection is developed. • Large thickness at free end can avoid aggravation of bifurcation and chaos in tip-rub. • There is an optimal thickness at fixed end for less centrifugal stress and weak chaos. • It is good to choose small order of thickness function to ensure stable operation. [ABSTRACT FROM AUTHOR]

The dielectric loss of Cu with high thermal conductivity is large at high frequency, which cannot meet the performance requirements in high-integrated circuits. There is an urgent need for materials to reduce its dielectric loss. In this paper, the thermal conductivity and dielectric properties of the AlN coating-Cu substrate system were controlled by changing the N2 pressure. The results showed that the crystallinity of hcp-AlN in AlN coating increased significantly when the proportion of N2 pressure was increased. With the increase of the N2 pressure, the particle size on the surface and the roughness of the coating improved. The AlN coating prepared at high N2 pressure had high dielectric constant and low dielectric loss at high frequency compared to those of the coatings prepared at low N2 pressure. At the same time, the AlN coating prepared under high N2 pressure on the Cu substrate did not decrease the thermal conductivity of Cu substrate. The AlN-Cu system prepared in this paper had high thermal conductivity and good dielectric properties, providing theoretical guidance for integrated circuit packaging and capacitor applications. [ABSTRACT FROM AUTHOR]

Bragg scattering and local resonance are two fundamental mechanisms for bandgap (BG) formation of phononic crystals (PCs) and acoustic metamaterials (AMs). In this paper, a new class of motional two-dimensional (2D) hybrid Bragg-locally resonant (LR) meta-pipe model is developed, and the BG interaction behaviors of such a meta-structure are explored. The pipe is axially composed of alternate materials, and is periodically encircled with dual-layer rings, which are used to simultaneously trigger Bragg scattering and local resonance. Meanwhile, the pipe conducts an axially spinning motion, and a steady fluid flows inside the pipe. Compared to static periodic structures, the orthogonal traveling waves due to spin bring about a 2D meta-structure, and the spinning local resonators yield an additional centrifugal effect on the pipe. The results reveal the formation of hybrid Bragg-LR BGs in such a motional meta-structure, and further demonstrate their complicated evolutions with the location, number and geometry of the local resonators as well as the pipe material. The impacts of motional properties on the hybrid BGs are discussed, and they are compared with the behavior of Euler-Bernoulli model. This study provides a more in-depth interpretation for the interaction of Bragg and LR BGs, which is especially beneficial to the vibration and noise reduction of rotors and fluid-transporting devices. • A new class of motional hybrid Bragg-LR meta-pipe structure is constructed. • Bragg, LR and coupled BGs are all detected in the proposed structure. • Coupled effective BG is triggered when local resonators yield effects on Bragg effective BG. • Complicated evolutions of hybrid BGs with the location, number and geometry of local resonators are revealed. • Bragg effective BG and LR effective BG have different variations for Timoshenko model and Euler-Bernoulli model. [ABSTRACT FROM AUTHOR]

A new approach was adopted to improve the corrosion behavior of the chromium nitride (CrNx) hard coating through magnetron sputtering deposition at different nitrogen flow rates. The influence of the nitrogen flow rates on the chemical composition, microstructure, mechanical property and corrosion behavior in artificial seawater of the CrNx coatings was investigated. The results show that with the increase of the nitrogen flow rates, the growth structure of the coatings varied from dense granular growth to coarse columnar growth. Increasing the nitrogen flow rates was helpful to decrease the Cr/N ratio and induce the phase transforming from mixed hexagonal Cr2N and face-centered cubic CrN to single CrN. However, the coatings under different nitrogen flow rates significantly improved the corrosion resistance and hardness of the steel substrate. Furthermore, at high nitrogen flow rate, the coating had high corrosion velocity and low protective capability against the substrate corrosion due to the fast corrosion channels acted by the columnar grain boundaries. While at the middle nitrogen flow rate, the coating with CrN phase, densely granular growth structure and moderate grain size resulted in excellent corrosion resistance and highest hardness. [ABSTRACT FROM AUTHOR]

The lack of durability in superhydrophobic coatings has restricted the practical applications of coatings in the fields of marine and construction. In this paper, the composite coatings of epoxy resin (EP), polydimethylsiloxane (PDMS) and SiO 2 nanoparticles were prepared by using the room-temperature liquid spraying and laser curing methods. The effects of the laser curing powers on the microstructure, hydrophobicity, durability in terms of corrosion and friction of the coatings were researched. The results demonstrate that there were micropores and aggregated SiO 2 nanoparticles on the surface of coatings. The coatings had the growth structure with SiO 2 nanoparticles partially embedded into the PDMS and EP bottom layer, and PDMS in the bottom layer migrating upward. With the increase of laser curing powers, the nanoparticles gathered significantly and the micropores was decreased. Under different laser curing powers, the coatings had the Si-(CH 3) 2 hydrophobic group and exhibited superhydrophobicity. All the coatings showed excellent self-cleaning performance in muddy water and ink. As the laser curing power increased, the superhydrophobicity of the coating was increased (the maximum contact angle of the coating was up to 161.90 ± 1.85°). Moreover, the coatings had strong corrosion resistance after being immersed in artificial seawater for 72 h. The coatings still had the superhydrophobicity after 100 cycles of load friction. With the increase of laser curing power, the friction resistance of the coating was improved, and the corrosion resistance was first improved and then reduced. This study provides a new idea for obtaining superhydrophobic and strong durable coatings. [Display omitted] • Laser curing was effective applied to improve durability of EP + PDMS/SiO 2 coatings. • All the coatings exhibit superhydrophobic and self-cleaning performances in sewage. • Coatings still exhibit superhydrophobicity after 100 cycles of 200 g load friction. • Superhydrophobicity and friction resistance improve by increasing laser curing power. • Coatings are strong corrosion resistance against artificial seawater exceed 72 h. [ABSTRACT FROM AUTHOR]