Shock Resistance Ability Research Articles

The Effect of Surface Roughness of Inconel 738 Superalloy on the Adhesive Properties of 8YSZ Coatings Deposited by Electrophoretic Deposition (EPD)

The electrophoretic deposition coating method has recently received attention as a new method for thermal barrier coating due to its advantages such as the simplicity of the method, controllability of the process, and the need for simple equipment. In this study 8 wt % yttria- stabilized zirconia was deposited on Inconel 738 substrate at room temperature by electrophoretic deposition. Before deposition, the substrates were treated by sand blasting treatment (by silica sands with different sizes) and roughness in the range of Ra=1 and Ra=3 was achieved on the substrate surfaces. The coated samples were sintered at 1100 °C temperature under controlled atmosphere (Ar atmosphere). X-Ray diffraction, scanning electron microscopy and thermal shock resistance technics were used to investigating of structural and phase properties and adhesiveness between coatings and substrates. Results from thermal shock resistance test show that by increasing roughness number, the thermal shock resistance ability first increased and then decreased. In addition, according to SEM images, increasing of roughness number, causes decrease the microcracks that creating in the coating surface. The best result was observed for coatings deposed on substrate with Ra=2.

Optimum relative frequency and fluctuating substrate selection in reinforcing anammox-mediated anabolic adaptation

Adaptation to substrate fluctuations is a life actuality of microbes in global municipal wastewater treatment plants (WWTPs). Yet there remains a lack of definite information on how influent changes with different alternation frequencies shape the stability of anammox consortia and the metabolic regulations they feedback. According to human rhythmic activity, day-fluctuant fed (every 6 h, alternating between 50 and 100 mg NH4+-N/L) substantially diminished the robustness of nitrogen removal efficiency (NRE; 84.1 ± 7.0%, left-skewed distribution [R2 = 0.87]) and shock-resistance ability (>30% effluent variability). Unexpectedly, the anammox ecosystem under week-fluctuant mode (every 6 d) displayed adapted growth (NRE 86.6 ± 3.1%, normal distribution [R2 = 0.97]), higher extracellular polymeric substances (EPS) yields, and superior tolerance (juggling the shortest recovery time and highest NRE, tightest protein secondary structure facing long-term load shocks) than steady-state (75 mg NH4+-N/L). 16S sequencing showed that the influent disturbance led to increased levels of bacterial diversity, however, a similar microbiota composition between week-fluctuant and steady systems was detected. Notably, K strategist Candidatus Kuenenia was more sensitive to substrate fluctuations, with the lower relative abundance at day-fluctuant (23.4 ± 5.1%) and week-fluctuant (39.5 ± 4.3%) than at steady-state community (47.5 ± 4.2%). Conversely, Candidatus Jettenia had higher relative abundance at day-fluctuant (i.e., 1.3 ± 0.1%) compared to that at week-fluctuant (0.2 ± 0.04%) and steady-state (0.05 ± 0.03%). Importantly, untargeted metabolomics revealed that week-fluctuant grown anammox microbiota increased protein synthesis and transporter expression while decreasing expression of catabolic pathways (citric acid cycle and bypass) as a strategy for efficient substrate uptake and utilization, which clearly different to day-fluctuant and steady-state survival ways. Overall, we predictively reported an “anabolic adaptation growth state” for the anammox consortia and put forward the associated reinforcement control strategy.

Preparation and Thermal Shock Resistance of Gd2O3 Doped La2Ce2O7 Thermal Barrier Coatings

As one of the promising thermal barrier coating (TBC) candidates, stoichiometric (La0.8Gd0.2)2Ce2O7 (LGC) coatings were prepared by atmospheric plasma spraying (APS), using (La0.8Gd0.2)2Ce2.5O8 as a spray powder and optimized spray parameters. It was found that spray distance and spray power both play an important role in the phase composition and microstructure of the coating. The LGC coating exhibited lower thermal conductivities than that of La2Ce2O7 (LC) coating, which is ~0.67 W/m·K at 1200 °C. Double-ceramic-layer (DCL) optimum (La0.8Gd0.2)2Ce2O7/YSZ (LGC/YSZ) thermal barrier coating was prepared and its thermal shock behavior was investigated. The LGC/YSZ DCL TBCs had better thermal shock resistance ability than that of LC/YSZ TBCs, which was around 109 cycles at 1100 °C. However, the failure mode was similar to that of LC/YSZ DCL TBCs, which was still layer-by-layer spallation in the top ceramic layer due to the sintering of the ceramic coating.

Shock Signal Trend Term Error Correction Method Based on Discrete Wavelet Transform and Low-Frequency Oscillator Combination

Shock response spectrum (SRS), calculated according to shock loading signal, is the primary metric for assessing the shock resistance ability of shipborne equipment. Nevertheless, the measured shock acceleration signal contains a trend term error that severely distorts the low frequency of the SRS. The accuracy of present correction methods cannot be assured due to a lack of reference. A discrete wavelet transform (DWT) and low-frequency oscillator combination method is proposed for correcting shock signals in this paper. The optimal wavelet parameters can be selected according to a low-frequency spectrum baseline fitted by the measured relative displacement to reject low-frequency trend term errors. Shock machine test results show that the average difference between the low-frequency spectrum baseline and uncorrected SRS is reduced from 89.8% to 3.2%, while the SRS slope rolled off to 5.8 dB/oct after imposing the proposed correction. The corrected SRS can faithfully show the actual shock loading characteristics of shipborne equipment in shock tests.

High shock resistance and self-healing ability of graphene/nanotwinned Cu nanolayered composites

Graphene/metal matrix composites have attracted intense interest because of superior mechanical properties, while introducing graphene into the nanotwinned metal matrix has been rarely studied. Here, a nanolayered composite is constructed by introducing single-layer graphene sheets into the nanotwinned Cu (nt-Cu) matrix. The shock response of the composite is investigated using molecular dynamics simulations. Compared to nt-Cu and single-crystal Cu, the graphene/nt-Cu composite possesses higher shock resistance and better self-healing ability simultaneously. It is found that the wrinkling of graphene can act as an initiator for rapid nucleation of numerous dislocations in the composite at the impact velocity of 4.5 km/s, while only an elastic wave is observed in the metal matrix under the same conditions. The subsequent propagation of dislocations effectively absorbs the impact force, leading to a rapid decline of shock stresses and particle velocities. There is a synergistic effect between graphene and twin boundaries on increasing the plastic sensitivity of the composite at a higher impact velocity, resulting in the larger dislocation density with higher shock resistance. Moreover, a fast and smooth self-healing process is observed with the propagation of the reflected wave. As graphene cannot be easily perturbed by dislocations due to high in-plane stiffness, the integrity of the crystal lattice in the graphene/nt-Cu composite is slowly degraded with a better self-healing performance.

Energy Storage and Dissipation of Human Periodontal Ligament during Mastication Movement.

As a layer of soft fibrous tissue, the periodontal ligament (PDL) protects against mechanical shock when transmitting mastication force from tooth to its surrounding alveolar bone. Currently, no quantitative method is available to estimate the shock resistance ability of the PDL. To solve this problem, in the present study we developed a finite element (FE) model of the tooth-PDL-bone complex and analyzed the energy storage and dissipation during the mastication movements. Displacement and Mises stress of tooth-PDL-bone complex show that the PDL is able to protect the alveolar bone from mechanical shock by shielding the transfer of deformation and stress. During mastication, the energy of the PDL is stored up to ∼161.5 J/mm3 at the period of loading and dissipated about one-tenth of the stored energy when unloading. The energy storage is displacement-dependent but time-independent because of the hyperelasticity of PDL. However, the energy dissipation is time- and displacement-dependent because of the viscoelasticity of PDL. The present study helps to understand the periodontal potential and the origin of dental diseases such as tooth concussion and occlusal trauma from the view of energy conversion.

A novel oxidation protective SiC-ZrB2-ZrSi2 coating with mosaic structure for carbon/carbon composites

An oxidation protective SiC-ZrB2-ZrSi2 coating with mosaic structure was designed to improve the oxidation resistance of carbon/carbon composites by a combined method of hydrothermal electrophoretic deposition and pack cementation. The phase composition, microstructure, thermal shock resistance and oxidation protective ability of the coating were investigated. Results show that the as-prepared SiC-ZrB2-ZrSi2 coating was dense and crack-free. After 50 thermal cycles between 1773 K and room temperature, the weight gain of the coated samples was 15.2 g m−2. The weight loss of the coated samples was only 15.6 g m−2 after oxidation in air at 1773 K for 580 h. The good thermal shock resistance and oxidation protective ability of the coated samples were attributed to the synergetic effect of the glass layer protection, compressive stress restraint and pinning role of ZrSiO4 inlaid phase.

What is the suitable segmentation crack density for atmospheric plasma sprayed thick thermal barrier coatings with the improved thermal shock resistance?

The optimization and control of the segmentation crack density (Ds) for the thick thermal barrier coatings (TTBCs) with the improved thermal shock resistance has been performed via finite element modeling. The simulation results based on the current property parameters of each layer of the TTBCs fabricated by atmospheric plasma spraying (APS) are well consistent with the experimental results of thermal shock test. The investigation results indicate that too large or too low Ds will be not beneficial to the improvement of the thermal shock resistance of the TTBCs. The Ds must be located at a suitable range, and this paper has revealed the objective law quantitatively. Based on our simulation and experimental results, the appropriate segmentation crack density is in the range of 2.38–4.76 cracks/mm which will be beneficial to improve the thermal shock resistance ability. It has been found that the as-sprayed TTBCs exhibited superior thermal shock resistance when the segmentation crack density is about 4mm−1. The stress intensity factor (KI) and energy release rate (J integration) will increase with the increasing of segmentation crack length. The existence of segmentation crack will improve the strain tolerance of TTBCs. The strain tolerance has been characterized by Ds and segmentation crack length quantitatively. The failure mechanism of APS-TTBCs can be attributed to the propagation of segmentation crack at the top-coat of the TTBCs, formation and propagation of the horizontal crack at the top-coat/TGO (thermally grown oxide) interface. The propagation rate of the main segmentation crack has been calculated and the life prediction model of the TTBCs during thermal cycle has been established. The possible methods which can prolong the service life of the TTBCs have also been proposed.

Force Analytic Method for Rolling Gaits of Tensegrity Robots

This paper proposes an analytic method based on finite-element method (FEM) for the rolling gaits of tensegrity robots. By analyzing forces during the rolling motions, the following problems can be solved. First, the relation between the actuator combinations (AC) and the rolling directions is discovered for controlling the rolling motions. Second, the influence of the driving parameters on the deformations is found out for obtaining the optimized control strategy. Third, the influence of the material parameters on the rolling motions is achieved as guidance to design physical robots. Tensegrity robots were proposed as novel mobile robots based on tensegrity structures that consist of discrete rigid struts and continuous elastic cables. The tensegrity structures process the shock resistance ability and high deformation capacity, and can be used to build lightweight mobile robots. The tensegrity robots can generate multiple gaits and multiple deformations. Rolling gaits are more stable than jumping and more efficient than crawling. Aiming at rolling gaits, to solve the three problems mentioned earlier, force analysis is required. The internal forces of the tensegrity structures always keep balance to maintain the shape of the structures, however, as the structures are highly coupled, the variation of one force will change the rest of the forces and generates feedback effects to this force. As the number of the forces increase with the growing number of struts, the force analysis becomes more and more complicated. The existing exhaustive experimental method can obtain the relation between the AC and the rolling directions through massive experiments, but this method cannot tell the influence of the driving parameters on the deformations and the experiment results based on certain robots are not suitable for other robots without analyzing the influence of the material parameters. In this paper, an analytic method based on FEM is introduced. A six-strut tensegrity model is used as an example to test the feasibility of the method. Experiments on a physical robot are performed to verify the reliability of the computation results.

Shock mitigation effects of cellular cladding on submersible hull subjected to deep underwater explosion

Warships and submarines can be severely damaged by underwater explosion (UNDEX) shock loadings, so improving shock resistance ability of such weapons is of great importance. However, studies on the shock resistance ability of submersible hull subjected to deep UNDEX shock wave are rare. In this paper, the transient response of bare/coated submersible hull subjected to combined loads of hydrostatic pressure and shock wave is analyzed numerically by Abaqus, with special attention on shock mitigation capability of cellular cladding coated on the pressure hull. The local cavitation in water and transient response of bare and coated hulls are obtained. Additionally, the effects of the initially applied hydrostatic pressure on the system response are discussed. The results indicate that the cellular cladding coated on the pressure hull is very effective on reducing hull deformation, velocity and acceleration response, and the soft cladding is more effective than the strong cladding if the cladding is not fully densified. Otherwise, the stress enhancement appears which can amplify the local response of coated hull. The research results are useful in designing surface shields for submersible hull so as to enhance its resistance to underwater shock damage.

Establishment of Motion Model for Wave Capture Buoy and Research on Hydrodynamic Performance of Floating-Type Wave Energy Converter

Abstract Floating-type wave energy converter has the advantages of high wave energy conversion efficiency, strong shock resistance ability in rough sea and stable output power. So it is regarded as a promising energy utilization facility. The research on hydrodynamic performance of wave capture buoys is the precondition and key to the wave energy device design and optimization. A simplified motion model of the buoys in the waves is established. Based on linear wave theory, the equations of motion of buoys are derived according to Newton’s second law. The factors of wave and buoys structural parameters on wave energy absorption efficiency are discussed in the China’s Bohai Sea with short wave period and small wave height. The results show that the main factor which affects the dynamic responses of wave capture buoys is the proximity of the natural frequency of buoys to the wave period. And the incoming wave power takes a backseat role to it at constant wave height. The buoys structural parameters such as length, radius and immersed depth, influence the wave energy absorption efficiency, which play significant factors in device design. The effectiveness of this model is validated by the sea tests with small-sized wave energy devices. The establishment methods of motion model and analysis results are expected to be helpful for designing and manufacturing of floating-type wave energy converter.

Motion of Transverse Shock Tester Guided by Parallelogram Mechanism

The transverse shock tester is an important device to assess the shock resistance ability of ship equipments. Because of the shock point and the gravity center of the tester are not on the same horizontal, the device may generate huge overturning moment. We adopt the finite element method to do the dynamics analysis of the transverse shock tester, using the parallelogram mechanism as its guide device, to analysis its output waveform and other problems, and find: it will appear saw-tooth acceleration waveform result from the oscillation caused by the overturning moment during the impact process; the oscillation will greatly increases the hinge load--changed following the oscillation amplitude periodically--of the parallelogram mechanism; the hinge inner friction almost has no effect on the impact tester movement or the output waveform. From the above statements, we can see that the parallelogram mechanism can not only share the overturning moment generated by the transverse impact, but also can ensure to get the desired output waveform, thus it suits to be used as the guide device of the transverse shock tester.

Strength and Movement of Flexible Plate Oriented Horizontal Shock Testing Platform

Horizontal shock testing table can be used to evaluate shock resistance ability of warship equipments. Based on this theory, the level of flexible plate oriented shock testing platform is raised. Using the finite element method, the output waveform of the testing platform and the stress distribution of the flexible plate are analyzed in this paper. It can be concluded that flexible plate can be used to store elastic potential energy during the impact and have a certain impact on test waveforms. Theoretical maximum displacement of the platform body is 94mm, the calculated value is 89.5mm, decrease by 4. 8%; theoretical maximum speed of the platform body is 4m/s, the calculated value is 3.93m/s, reducing to1.75%; theoretical, the value of positive wave peak acceleration of platform body is 571m/s2, the calculated value is 532 m/s2, decrease by 6.8%; theoretical platform body negative wave peak acceleration values is 175m/s2, the calculated value of 183 m/s2, an increase of 4.6%. The research shows that flexible plate as a guide device can meet the impact test table for error waveform requirements..

Method to seek the deformed shape and to find the rolling direction of tensegrity robots

Tensegrity structures which are widely used on architecture have high strength-mass ratio, strong deformation ability and pressure and shock resistance ability, so they can be used in design of deformable tensegrity robots which can adapt to complex and dangerous terrestrial environment. The deformable robots use different gaits to adapt to different terrestrial environment. The rolling gait of the deformable robots is efficient and stable on the flat ground. This paper proposes a method to predict rolling direction of the deformable robots to avoid the limitation of the exhaustive experimental method. The method uses the finite element analysis to get deformational shape of the robots, and analyze torque of struts during this state to predict rolling direction of the robots. The experiment on a real model has been performed to check validity of the method.

超低噪声单频可调谐光纤激光器

A tunable single frequency laser with ultralow-noise and high vibration resistance is developed,and its working principle and structure design are introduced.The laser worked at 1 550 nm is consisted of a single frequency laser resonant cavity,a polarization containing optical fiber amplifier and a monitoring feedback optical path.By using a closed-loop temperature control technology,the laser shows a higher precision and stability,and its extremely temperature control resolution is up to 0.001 ℃.Using frequency components and a matched closed-loop system,the locked output frequency and power of the laser are implemented.The closed loop system not only gives the stability of wavelength and power,but also greatly reduces the low frequency noise of the laser system and effectively improves the laser damage threshold.As a result,the fiber laser can provide the long-term power stability better than 1% and the relative intensity noise better than-130 dBc/Hz.By selecting different types of seed light source cavities,the laser line-width can be controlled in the 1-400 kHz.Furthermore,the output power of fiber laser is 1 W and tunable wavelength is 3 nm.At 1 Hz,the phase noise is less than 10 μrad·Hz-1 2/m OPD and the shock resistance ability is 0.1g(g for the acceleration of gravity).

Performance Optimization Two-Node Support Structure of Free Beam Vibration Gyro

Establishing the system model of free beam vibration gyro under the influence of the Support structure, deriving and analyzing its vibration performance, comparison between model simulation through ANSYS software and relative theoretical calculation indicates that the relative error is less than 0.25%. Researches on the relations among system sensitivity, bandwidth, shock resistance and anti-interference ability of its model and sizes of Support structure contribute to principles of system optimization design and a set of design parameters: free beam (50mm×4.1mm×4.12mm), cylindrical Support structure(radius0.25mm×2.46mm), the performance of model is as: system driving frequency (8589.8HZ), bandwidth (39.4HZ), shock resistance (411.02g) and anti-interference frequency (above2381.3HZ).

Mechanical Shock Ability of Different Potting Materials and Packaging Processes for Electronic Components

In the paper, the mechanical shock abilities of the three potting materials of hard material, silicone and paraffin wax for the ceramic packaging capacitors and metal packaging capacitors are investigated by mechanical shock tests. Results show that the mechanical shock resistance ability of the hard epoxy resin potting material is the strongest, and the mechanical shock resistance ability of the metal packaging component is more than the ceramic packaging. The mechanical shock resistance value of the epoxy resin potting material for metal packaging capacitors is in 20000g above.

Thermal shock behavior of 8YSZ and double-ceramic-layer La2Zr2O7/8YSZ thermal barrier coatings fabricated by atmospheric plasma spraying

The single-ceramic-layer (SCL) 8YSZ (conventional and nanostructured 8YSZ) and double-ceramic-layer (DCL) La2Zr2O7 (LZ)/8YSZ thermal barrier coatings (TBCs) were fabricated by plasma spraying on nickel-based superalloy substrates with NiCrAlY as the bond coat. The thermal shock behavior of the three as-sprayed TBCs at 1000°C and 1200°C was investigated. The results indicate that the thermal cycling lifetime of LZ/8YSZ TBCs is longer than that of SCL 8YSZ TBCs due to the fact that the DCL LZ/8YSZ TBCs further enhance the thermal insulation effect, improve the sintering resistance ability and relieve the thermal mismatch between the ceramic layer and the metallic layer at high temperature. The nanostructured 8YSZ has higher thermal shock resistance ability than that of the conventional 8YSZ TBC which is attributed to the lower tensile stress in plane and higher fracture toughness of the nanostructured 8YSZ layer. The pre-existed cracks in the surface propagate toward the interface vertically under the thermal activation. The nucleation and growth of the horizontal crack along the interface eventually lead to the failure of the coating. The crack propagation modes have been established, and the failure patterns of the three as-sprayed coatings during thermal shock have been discussed in detail.

Finite element simulation of stress distribution and development in 8YSZ and double-ceramic-layer La2Zr2O7/8YSZ thermal barrier coatings during thermal shock

In this paper, the thermal stress of the double-ceramic-layer (DCL) La2Zr2O7/8YSZ thermal barrier coatings (TBCs) fabricated by atmospheric plasma spraying (APS) during thermal shock has been calculated. The residual stress of the coating after being sprayed has been regarded as the initial condition of the first thermal cycle. The characteristic of the stress development during the thermal cycle has been discussed, and the influence of the defects on the failure mode during the thermal cycle has also been discussed systematically. Finite element simulation results show that there exist higher radial thermal shock stresses on the ceramic layer surface of these two coatings. There also exist higher thermal stress gradient at the interface between the ceramic layer and the metallic layer. Higher thermal stress in 8YSZ/NiCoCrAlY coating lead to the decrease of thermal shock property as compared to that of LZ/8YSZ/NiCoCrAlY coating. The addition of LZ ceramic layer can increase the insulation temperature, impede the oxygen transferring to the bond coating and can also reduce the thermal stress. Considering from the aspects of thermal insulation ability and the thermal shock resistance ability, DCL type LZ/8YSZ TBCs is a more promising coating material compared with the single-ceramic-layer (SCL) type 8YSZ TBCs for the application.

Synthesis of (TiC)<sub>p</sub>Ni/TiAl/Ti Graded Material via Field-Activated and Pressure-Assisted Combustion Process

In this paper, the synthesis of four-layered functionally graded materials (FGMs) samples of (TiC)pNi/TiAl with titanium substrate by field-activated and pressure-assisted synthesis process (FAPAS) was investigated. It was shown that the TiC particles formed by in-situ combustion synthesis process were fine and distributed uniformly. Moreover, the imposition of the electric field and the combustion reaction of TiAl is the key for the successful synthesis of the FGMs during the process. The microstructure, phase composition of the interfaces and mechanical properties of the graded material were characterized. Moreover, the sample has an excellent thermal shock resistance ability and gradient distribution of micro-hardness across the substrate layers and the surface layer.