Simulation of drip-rain effects by tribofatigue loading

2020 ◽  
Author(s):  
A.A. Aliev ◽  
A.Yu. Ampilogov
Keyword(s):  
Polymer Coating ◽  
High Speed ◽  
Erosion Resistance ◽  
High Water ◽  
Contact Spot ◽  
Vertical Load ◽  
Rigid Substrate ◽  
Rain Drop ◽  
The Impact ◽  
Rain Erosion

The outer surfaces of aircraft are periodically subjected during flight to intense rain causing hydroerosion of the outer paintwork. The experimental evaluation of hydroerosion resistance is based on testing in high-speed water flow. The main drawback of such research is the bulkiness of the stands, high water and energy consumption, and, as a result, increased cost. As an alternative to drip-rain tests, their simulation by kinetically similar tribofatigue test according to the “ball on plate” scheme is proposed (vertical load is applied to the polymer coating on a rigid substrate through a steel ball). The process is cyclically repeated until the coating is worn to the specified thickness. The experimentally obtained tribofatigue characteristics then can be converted into close-meaning estimates of erosion resistance. CAAPCOAT-B274-ASP108 polyurethane, previously tested for rain erosion, was selected as the sample. For quantitative evaluation of the transition from drip-rain loading to equivalent tribofatigue one the contact mechanics formulas were used by calculating the force of the drip impact and the stress in the contact spot. Tribofatigue tests were conducted on the UMT-2 TriboLab unit. At equal calculated contact stress levels the wear rate under tribofatigue loading was almost 7 times higher compared to the conditions of rain-drop erosion. The reason may be a scale factor due to the actual difference in contact areas under drip and tribofatigue loading, as well as the failure to take into account the dynamics of waves after the impact of drops. The obtained results of tribofatigue tests can give an estimated value of the hydroerosion resistance of the coating.

scholarly journals The impact of raindrops on Salvinia molesta leaves: effects of trichomes and elasticity

2021 ◽  
Vol 18 (185) ◽  
Author(s):  
Wilfried Konrad ◽  
Anita Roth-Nebelsick ◽  
Benjamin Kessel ◽  
Tatiana Miranda ◽  
Martin Ebner ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
High Speed ◽  
Water Repellency ◽  
High Water ◽  
Rain Water ◽  
Residual Water ◽  
Intense Rainfall ◽  
Salvinia Molesta ◽  
Aquatic Fern ◽  
The Impact

The floating leaves of the aquatic fern Salvinia molesta are covered by superhydrophobic hairs (=trichomes) which are shaped like egg-beaters. These trichomes cause high water repellency and stable unwettability if the leaf is immersed. Whereas S. molesta hairs are technically interesting, there remains also the question concerning their biological relevance. S. molesta has its origin in Brazil within a region exposed to intense rainfall which easily penetrates the trichome cover. In this study, drop impact on leaves of S. molesta were analysed using a high-speed camera. The largest portion of the kinetic energy of a rain drop is absorbed by elastic responses of the trichomes and the leaf. Although rain water is mostly repelled, it turned out that the trichomes hamper swift shedding of rain water and some residual water can remain below the ‘egg-beaters’. Drops rolling over the trichomes can, however, ‘suck up’ water trapped beneath the egg-beaters because the energetic state of a drop on top of the trichomes is—on account of the superhydrophobicity of the hairs—much more favourable. The trichomes may therefore be beneficial during intense rainfall, because they absorb some kinetic energy and keep the leaf base mostly free from water.

A discussion on deformation of solids by the impact of liquids, and its relation to rain damage in aircraft and missiles, to blade erosion in steam turbines, and to cavitation erosion - Rain erosion properties of materials

1966 ◽  
Vol 260 (1110) ◽  
pp. 168-181 ◽  
Keyword(s):  
High Speed ◽  
Cavitation Erosion ◽  
High Speed Photography ◽  
Steam Turbines ◽  
Quantitative Measurements ◽  
Wide Range ◽  
Erosion Properties ◽  
Properties Of Materials ◽  
The Impact ◽  
Rain Erosion

A rotating arm apparatus capable of circumferential speeds up to 475 m/s (Mach 1.4) has been used to make quantitative measurements of the velocity and angle dependence of ram erosion for a wide range of materials. It has been possible to relate the mechanical properties of some materials with their rain erosion resistance. The behaviour of the drops during impact has been studied by high speed photography.

Impact Wear Resistance of Nanocomposite Coatings for Aircraft Components

2019 ◽  
Vol 813 ◽  
pp. 387-392 ◽  
Author(s):  
Giovanna Gautier ◽  
Maria Giulia Faga ◽  
Vincenzo Tebaldo
Keyword(s):  
High Speed ◽  
Erosion Resistance ◽  
High Speed Steel ◽  
Ceramic Coatings ◽  
Landing Gear ◽  
Erosion Wear ◽  
Test Volume ◽  
Impact Speed ◽  
Structural Part ◽  
The Impact

Landing gear is an aircraft component often subjected to wear, fracture, mechanical failure and erosion, principally caused by impact with sand and other small particles. Erosion wear can cause deformation and material removal with consequent efficiency reduction. Coatings can protect stressed structural part and impede the erosion of the metallic components. This work focus on the investigation of the erosion resistance of two ceramic multilayer coatings, AlSiTiN and AlSiCrN, deposited by Physical Vapour Deposition (PVD) on a high speed steel (H11) usually used for landing gear application. Erosion test were carried out with an erosion machine using alumina particles. Powder was directed to the specimens (coatings and substrate) at nominal impingement angles of 90° and 20° with different impact speed (50, 75, 100 and 125 m/s at 90° and 100, 125, 150 and 175 m/s at 20°), at a nozzle-specimen distance of 10 mm. All the tests were performed for two minutes. Hardness and Young's modulus were obtained by nanoindentation, and adhesion between coating and substrate was evaluated by scratch test. Volume lost was measured with Taylor Hobson profiler while cracking behaviour and microstructure modifications were examined with a scanning electron microscope (SEM). AlSiCrN coating significantly enhanced the erosion resistance of H11 substrate, showing higher resistance also with respect to AlSiTiN coating. Indeed, the coating was not completely removed from the surface neither at 90° nor at 20°. The erosion wear rapidly increased by increasing the impact speed in the case of substrate and AlSiTiN, while such parameter was not significantly influent in the case of AlSiCrN. The results suggest that adhesion should play an important role to explain the highest erosion resistance of AlSiCrN coating. Erosion mechanism was principally driven by the intrinsic brittleness of both ceramic coatings.

Assessment of Diaphragm Wall's Structural Impact on Groundwater Hydrology

2011 ◽  
Vol 250-253 ◽  
pp. 1098-1104
Author(s):  
Te Hsing Chang
Keyword(s):  
Groundwater Level ◽  
High Speed ◽  
Vibration Reduction ◽  
High Water ◽  
Diaphragm Wall ◽  
Wall Structure ◽  
Groundwater Hydrology ◽  
Groundwater Levels ◽  
Diaphragm Walls ◽  
The Impact

The Southern Taiwan Science Park (STSP) is located between Hsinshi Township and Shanhua Township of Tainan County, with the newly-built, high-speed railway running through its eastern side. The low-frequency vibration which was generated by passing high-speed trains causes environmental disturbances to industries within the Park. To address this issue, the implementation of vibration-reduction project with detailed design and construction was provided. The diaphragm wall-type vibration reduction walls will be built along the borderline between Hsinshi Township and Shanhua Township to reduce the impact on industries. The diaphragm wall structure will block groundwater from flowing to affect the underground hydrology. This study was aimed to discuss and assess the best configuration for the vibration reduction effects and environmental impacts. Numerical analysis of the impacts on groundwater hydrology was conducted in two cases. The simulation results indicated that both sides of diaphragm walls developed gaps in groundwater levels. Hence, diaphragm walls effectively reduced adverse impacts on groundwater hydrology with openings at locations where underground pipelines ran. Such variations were within the scope of groundwater level of high water and low water periods. Therefore, surface runoff and land subsidence resulting from the diaphragm wall construction were not severe. As diaphragm walls were made of impermeable materials, pumping water nearby made the groundwater level drawdown effects worse. Groundwater level variations resulting from pumping water were far greater than the regional groundwater level variations after the establishment of diaphragm walls. Special attention must be paid to this situation in follow-up management.

A discussion on deformation of solids by the impact of liquids, and its relation to rain damage in aircraft and missiles, to blade erosion in steam turbines, and to cavitation erosion - Practical aspects of rain erosion of aircraft and missiles

1966 ◽  
Vol 260 (1110) ◽  
pp. 161-167 ◽  
Keyword(s):  
High Speed ◽  
Protective Coatings ◽  
Material Surface ◽  
Steam Turbines ◽  
Functional Requirements ◽  
Design Problems ◽  
Factors Affecting ◽  
Practical Applications ◽  
The Impact ◽  
Rain Erosion

All-weather operational requirements have added considerably to aircraft and missile design problems as the effects of various meteorological hazards, predominantly rain, are aggravated by high speed flight. Typical damage patterns are reproduced and discussed. The problem of rain erosion is reviewed with regard to the functional requirements of the components, the flight plan of the vehicle and the occurrence of rain over the geographical terrain of operation. The factors affecting rain erosion characteristics such as type of material, surface finish, shape of component, speed and rainfall intensity are discussed and empirical data derived. The translation of significant results into practical applications is described with particular reference to supersonic transport aircraft. Details given of equipment for the simulation of rain erosion are concerned principally with the R. A. E. ‘whirling arm’ and rocket runway high speed sled techniques. Correlation of test results from these facilities with those from flight tests are briefly discussed. Degree of erosion of a material is defined in relation to the particular application of the material and details are given of the characteristics of numerous materials, both metals and non-metals. The utilization of these materials for such applications as radomes, transparencies, high temperature materials, de-icing systems are briefly discussed together with methods of extending the rain erosion ‘life’ of materials by design or by use of protective coatings.

Modeling of Tread Block Contact Mechanics Using Linear Viscoelastic Theory3

2008 ◽  
Vol 36 (3) ◽  
pp. 211-226 ◽  
Author(s):  
F. Liu ◽  
M. P. F. Sutcliffe ◽  
W. R. Graham
Keyword(s):  
High Speed ◽  
Slip Rate ◽  
Material Model ◽  
Contact Forces ◽  
Block Modeling ◽  
Rate Dependent ◽  
Linear Viscoelastic Material ◽  
Linear Viscoelastic ◽  
The Impact ◽  
Good Agreement

Abstract In an effort to understand the dynamic hub forces on road vehicles, an advanced free-rolling tire-model is being developed in which the tread blocks and tire belt are modeled separately. This paper presents the interim results for the tread block modeling. The finite element code ABAQUS/Explicit is used to predict the contact forces on the tread blocks based on a linear viscoelastic material model. Special attention is paid to investigating the forces on the tread blocks during the impact and release motions. A pressure and slip-rate-dependent frictional law is applied in the analysis. A simplified numerical model is also proposed where the tread blocks are discretized into linear viscoelastic spring elements. The results from both models are validated via experiments in a high-speed rolling test rig and found to be in good agreement.

Case study: Prediction and field tests of railway noise and effects of a low-height noise barrier

2020 ◽  
Vol 68 (4) ◽  
pp. 303-314
Author(s):  
Yuna Park ◽  
Hyo-In Koh ◽  
University of Science and Technology, Transpo ◽  
University of Science and Technology, Transpo ◽  
University of Science and Technology, Transpo ◽  
...  
Keyword(s):  
High Speed ◽  
Field Tests ◽  
Residential Areas ◽  
Railway Systems ◽  
Railway Noise ◽  
Sound Levels ◽  
Noise Barrier ◽  
The Difference ◽  
Reduction Effect ◽  
The Impact

Railway noise is calculated to predict the impact of new or reconstructed railway tracks on nearby residential areas. The results are used to prepare adequate counter- measures, and the calculation results are directly related to the cost of the action plans. The calculated values were used to produce noise maps for each area of inter- est. The Schall 03 2012 is one of the most frequently used methods for the production of noise maps. The latest version was released in 2012 and uses various input para- meters associated with the latest rail vehicles and track systems in Germany. This version has not been sufficiently used in South Korea, and there is a lack of standard guidelines and a precise manual for Korean railway systems. Thus, it is not clear what input parameters will match specific local cases. This study investigates the modeling procedure for Korean railway systems and the differences between calcu- lated railway sound levels and measured values obtained using the Schall 03 2012 model. Depending on the location of sound receivers, the difference between the cal- culated and measured values was within approximately 4 dB for various train types. In the case of high-speed trains, the value was approximately 7 dB. A noise-reducing measure was also modeled. The noise reduction effect of a low-height noise barrier system was predicted and evaluated for operating railway sites within the frame- work of a national research project in Korea. The comparison of calculated and measured values showed differences within 2.5 dB.

The Impact of High-Speed Rail on the Spatial Structure of Chinese Urban Agglomerations

2020 ◽  
Vol 46 (3) ◽  
pp. 379-397
Author(s):  
Chunyang Wang
Keyword(s):  
High Speed ◽  
River Delta ◽  
City Size ◽  
High Speed Rail ◽  
Local Conditions ◽  
Urban Agglomerations ◽  
Large Cities ◽  
Spatial Systems ◽  
Economic Concentration ◽  
The Impact

This paper measures the spatial evolution of urban agglomerations to understand be er the impact of high-speed rail (HSR) construction, based on panel data from fi ve major urban agglomerations in China for the period 2004–2015. It is found that there are signi ficant regional diff erences of HSR impacts. The construction of HSR has promoted population and economic diff usion in two advanced urban agglomerations, namely the Yang e River Delta and Pearl River Delta, while promoting population and economic concentration in two relatively less advanced urban agglomerations, e.g. the middle reaches of the Yang e River and Chengdu–Chongqing. In terms of city size, HSR promotes the economic proliferation of large cities and the economic concentration of small and medium-sized cities along its routes. HSR networking has provided a new impetus for restructuring urban spatial systems. Every region should optimize the industrial division with strategic functions of urban agglomeration according to local conditions and accelerate the construction of inter-city intra-regional transport network to maximize the eff ects of high-speed rail across a large regional territory.

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