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•Erosion-damage-induced vibration response of rotor system is studied innovatively.•A new data extraction method for erosion damage based on DC-SP is proposed.•Unbalance excitation of ...rotor caused by erosion damage of blade is characterized.•Vibration response of rotor caused by distributed erosion damage are revealed.
When a turboshaft engine operates in harsh environments such as deserts, plateaus, and coastal areas, the erosion damage to compressor blades leads to uneven mass distribution of the blade disk of the gas generator and further induces unbalance fault vibration of the rotor system, which seriously endangers helicopter flight safety and mission execution. The vibration characteristics of the rotor system of the gas generator of an aero-turboshaft engine under blade erosion damage are studied innovatively in this paper. The theoretical formula for the blade erosion damage depth is derived. The key parameters for the calculation of the erosion damage to the blades are obtained by combining the particle impact velocity test, Ti-6Al-4 V alloy erosion wear test, and finite element analysis. A new data extraction method for erosion damage based on distribution characteristics and the sparseness–denseness path (DC-SP) is proposed. The unbalance fault mechanism of the rotor system caused by erosion damage is revealed. Using a turboshaft engine as an example, a dynamic model of the rotor system of a gas generator is developed. Unbalance load samples caused by erosion damage are applied, and the whirl trajectory and vibration spectrum characteristics of the rotor system analyzed. The results show that the unbalance magnitude of 1-stage and 3-stage rotor blades caused by erosion damage is 2.33 times and 1.22 times that of 2-stage rotor blades, respectively. The vibration response of the supporting position of the rotor changes with the unbalance phase difference of the rotor blade disk. The vibration amplitude of the supporting position is the lowest when the unbalance phase difference is 0°-180°-180° and is the highest when the unbalance phase difference is 0°-0°-0°. At design speed, the vibration amplitude fluctuation range of the left side of the supporting position is concentrated, whereas that of the right side is large. When the unbalance magnitude increases from 20 to 120 g·mm, the vibration amplitudes of the left and right sides of the supporting position increases by 97% and 263%, respectively.
In the desert region of northwest China, the frequency of wind-sand disasters is high. All types of concrete buildings built in this area face severe wind erosion due to high wind speed, resulting in ...varying degrees of wind-erosion damage to concrete. To accomplish intelligent identification of concrete wind-erosion damage, a concrete wind erosion experiment was conducted in the laboratory, and a concrete wind-erosion damage dataset was generated under the interference of water stains, scratches, shooting distance, and background noise. This paper combined with transformer theory to improve YOLO-v4 and proposed an object detection algorithm called MHSA-YOLOv4 suitable for wind-erosion damage of concrete. The results demonstrate that MHSA-YOLOv4 exhibits improved object detection performance than YOLO-v3, improved YOLO-v3, and YOLO-v4. On the test set, ACC, Precision, Recall, and mAP of MHSA-YOLOv4 are 91.30%, 91.52%, 92.31%, and 0.89, respectively. MHSA-YOLOv4 can accurately identify wind-erosion damage of concrete images under different test conditions, which reflects strong robustness. The applicability of computer vision technology to the intelligent identification of wind-erosion damage on concrete has been verified.
•The dataset of wind-erosion of concrete was established to simulate the spalling of concrete.•A object detection algorithm called MHSA-YOLOv4 was proposed based on Transformer.•MHSA-YOLOv4 can detect concrete wind-erosion damage with high-precision.
A series of experimental techniques were used to study the erosion-damage effect of a silica-filled silicone rubber coating exposed to simulated space environment (atomic oxygen and ultraviolet ...irradiation). The elastomer is known to be chemically and thermally stable, but there are insufficient data on its durability in the space environment. In the present work, atomic oxygen doses up to 3.8 × 1021 atoms·cm−2 and ultraviolet irradiation doses up to 360 equivalent sun-hours (ESH) were applied from Space Environment Simulation Measurement System, respectively. Since the aging and failure processes of the filled silicone rubber relate to different aspects of chemical structure and physics form, therefore, this study explored the use of chemical-mechanics methods to comprehensively evaluate the erosion-damage effect of materials. Morphology and chemical changes due to radiation were investigated by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), and nanoindentation test probed surface mechanical properties changed with exposure dose. Results demonstrated that, with increased exposure time and irradiation-induced free radicals，the aggregation state and molecular chain structure of the silica-filled silicone rubber have changed, which caused an increase in surface hardness and modulus. Taken together, the results indicated that oxidative cross-linking was the dominant degradation mechanism under the irradiation dose in this paper.
The present work investigates the role of surface hardening and roughening on the damage accumulation during the incubation period in water droplet erosion (WDE). Water droplet erosion tests were ...carried out on Ti–6Al–4V alloy at an impact velocity of 250 m/s. The evolution of hardness and surface roughness during the incubation period were evaluated using microhardness tester and Confocal Laser Scanning Microscope (CLSM). Scanning Electron Microscopy (SEM) was conducted on the impact area at several intervals during the incubation period. Finite Element (FE) simulations were performed to obtain the impact stresses on both smooth and rough surfaces. It was found that the solid surface plastically deforms by the action of the initial impingements, and as a result, hardness and surface roughness increase progressively until the end of the incubation period. The cyclic increase in hardness results in gradual improvement in the erosion strength, making the surface more resistant to the subsequent droplet impacts. However, the finite element results revealed that the dynamic surface roughening process results in higher impact stresses for the same impact pressure due to geometrical stress concentration. It is concluded that the increase in impact stresses resulting from surface roughening negates the improvement in the erosion resistance due to hardening. Hence, cyclic hardening and roughening are crucial parameters in the damage accumulation process during the incubation period.
•Cyclic hardening and roughening play crucial roles in WDE damage.•Hardening results in increasing the incubation period in WDE.•Surface roughening accelerates the WDE damage.•FE simulation is used to observe the impact stresses on smooth and rough surfaces.
When an aircraft passes through a rainy area at high speed, the coating on the front edge of the fuselage will be continuously eroded by raindrops, causing the coating to wear, crack or even peel ...off. This paper uses carbon fiber T300 material as the base material, and at the different impact speeds and impact numbers, water cutting equipment was used to simulate the erosion of the coating caused by the continuous impact of water droplets. The damage morphology of samples at different damage stages was observed by digital microscope and Scanning Electron Microscope (SEM), and the damage evolution curve was established to analyze and reveal the damage behavior and damage mechanism of rain erosion. The results show that the degree of damage experienced an increasing trend with the increase of impact numbers and speed, until circular peel damage was formed; no damage occurred during the incubation period, and the curvature of the damage evolution curve increased significantly after the expansion period and eventually showed a stable expansion trend. The mechanical properties of the coating material were the main influencing factors of its rain corrosion resistance. Moreover, the axially symmetric unsteady contact problem of droplets impacting the surface of a solid deformable body was studied. And the contact area was determined based on the iterative algorithm boundary positioning method. A mathematical model and closed mathematical formula describing the unsteady interaction between a droplet and a solid deformable obstacle were proposed.
To mitigate the restraining effect of basalt fiber on the sulfate erosion damage in basalt fiber reinforced concrete, sulfate erosion experiments were carried out on both ordinary concrete and basalt ...fiber reinforced concrete. Changes in concrete strength in relation to sulfate erosion depth under various sulfate solutions and erosion ages were recorded. The mechanical relationship between the compressive strength and sulfate erosion depth was proposed. The results showed that the inflection point on the strength-erosion age curve for basalt fiber reinforced concrete appeared significantly later than that in ordinary concrete, indicating that basalt fiber can delay sulfate erosion and enhance concrete durability. Using the measured sulfate erosion depth, remaining compressive strength can be predicted.
•Long term sulfate erosion experiments on both OC and BFRC were carried out, in which the longest erosion age was 12 months.•Studied the sulfate corrosion resistance of BFRC and OC through ion concentration test and compression test.•The theoretical model for the relationship between compressive strength and the sulfate erosion depth was generated.
In the present work, the high-velocity oxygen fuel spraying technology was used to fabricate the (AlCoCrFeNi)x/(WC-10Co)1-x x = 100 (C1), 75 (C2), and 50 (C3) wt% composite coatings and the 316 ...stainless steel was used as substrates. The main BCC phase and the minor FCC phase were primary components of the AlCoCrFeNi coating. The average hardness of the C1, C2 and C3 coatings was 646 HV0.2, 741 HV0.2, and 823 HV0.2, respectively. After being eroded for 15 h, the average hardness of the eroded coatings increased. WC enhanced the erosion performance and significantly decreased the volume loss of the coatings. The volume loss rate of the coatings decreased with the erosion process owing to both the dislocation strengthening of high-entropy alloy (HEA) and embeddedness of WC. For the AlCoCrFeNi coating, the erosion mechanism consisted of a mainly ductile failure such as cutting, plowing and removed squeeze lip, and a minorly brittle failure, in which crack and spalling of BCC phase appeared. The primary erosion destruction mechanism of WC in the composite coatings was brittle fatigue wear since crack and spalling contributed to the erosion damage of WC. The ductile removal of WC was also observed in this work, such as micro-scratch.
•The (AlCoCrFeNi)x/(WC-10Co)1-xcomposite coatings were bonding well with the substrates by applying HVOF spraying technology.•The addition of WC significantly improved the erosion performance of AlCoCrFeNi coating.•The volume loss rate of coatings decreased with the erosion process by the dislocation strengthening.•The erosion mechanism of the (AlCoCrFeNi)x/(WC-10Co)1-x composite coatings was studied.
•An improved YOLO-v3 was proposed.•Based on computer vision, the wind erosion to concrete was studied.•Intelligent recognition of erosion damage to concrete was realized.
Concrete is one of the most ...common building materials in civil engineering. Buildings in Northwest China are facing strong wind erosion. Due to wind erosion, the surface of concrete peels off and erosion damage occurs, which has a very adverse impact on both the appearance of buildings and their safe use. Therefore, it is of great significance to carry out an intelligent identification of the erosion area of concrete. A deep learning dataset was established through a concrete erosion test to realize accurate recognition of erosion damage to concrete, and an improved YOLO-v3 algorithm model was proposed. Compared with other mainstream target detection algorithms, the improved version of YOLO-v3 is found to be able to achieve more accurate concrete erosion damage recognition, and the accuracy, precision, and map of the algorithm are 96.32%, 95.68%, and 75.68%, respectively, which verifies the applicability of deep learning to the research of concrete erosion damage.
The 3-D numerical simulation method is coupled with erosion and particle rebound models based on the results of high temperature erosion tests to systematically study the gas-solid two-phase flow ...characteristics of a flue gas turbine for the first time. The aerodynamic loss characteristics of the flue gas-steam mixtures and particle erosion mechanism in the flue gas turbine cascade under design and non-design conditions are investigated. The results indicate that the mixing loss of cooling steam and gas, secondary flow loss, and separation loss significantly affect the entropy increment of the rotor cascade. The isentropic efficiency of the flue gas turbine under the design condition is 78.74%. The radial inflow of wheel cooling steam from the axial clearance has a radial impact and mixing effect on the mainstream flue gas, enhancing the generation and development of the secondary flow vortex in the rotor cascade. When the dimensionless cooling steam flow rate is reduced from 1 to 0.6, the isentropic efficiency of the flue gas turbine increases by approximately 0.9%. By contrast, when the dimensionless cooling steam flow rate increases from 1 to 2, the isentropic efficiency decreases by 0.42%. The erosion rate of the leading and trailing edges of the rotor is higher than those at other streamwise locations. The erosion of the rotor leading edge and the blade-tip trailing edge is caused by the high speed impact of particles above 10 ?m, while the erosion of the rotor root is caused by the grinding of 1-5 ?m particles carried by the secondary flow.
A practical, predictive equation for estimating erosion damage caused by solid particle impact, which can be utilized under any impact conditions and for any type of material, is proposed. Impact ...parameters, which affect erosion mechanisms and damage to materials are the size, shape and properties of particles in addition to the important parameters of impact velocity and angle. The material parameters are mechanical properties such as material hardness. Correlative equations with erosion damage are generally derived from particle impact energy, but cannot be applied to the selection of suitable materials in practical service or for estimating erosion damage to newly developed materials. However, another correlative equation derived from indentation behavior, which relates to material hardness, is useful for this purpose of the estimation. The mechanical properties of a material can be therefore regarded as a key parameter for estimating erosion damage. The effects of impact parameters on the correlative equation were investigated in detail for several aluminum 3003, 5052, 2017 copper, carbon steel and stainless steel 304H specimens. The impact angle dependence of erosion damage to these materials was also discussed. It was concluded that material hardness was clearly an essential parameter and should be a dependent variable in terms of impact velocity dependence and impact angle dependence in the practical, predictive equations.
