Browse Topic: Erosion
Storms contain a lot of energy, which can cause coastal erosion and damage when they reach unprotected coastlines. According to Michael Triantafyllou, Professor in Ocean Science and Engineering in the Department of Mechanical Engineering at the Massachusetts Institute of Technology, there are islands in the Pacific that are surrounded by reefs that protect them from much of that damage
As current courses through a battery, its materials erode over time. Mechanical influences such as stress and strain affect this trajectory, although their impacts on battery efficacy and longevity are not fully understood
Stainless Steel 304 (SS304) is a nickel–chromium–based alloy that is regularly used in valves, refrigeration components, evaporators, and cryogenic containers due to its greater corrosion resistance, high ductility, and non-magnetic properties, as well as good weldability and formability. Multiple regression analysis was used to establish empirical relationships between process variables. Additionally, the established regression equations are employed to predict and compare experimental data. Due to the increasing demands for high-quality surface finishes and complex geometries, traditional methods are being replaced by non-conventional techniques such as wire EDM. This process, which emerged from the electrical discharge machining concept, mainly involves creating intricate components. WEDM results in a high degree of precision and excellent surface quality. Due to the complexity of WEDM, the processing parameters cannot be selected by using the trial-and-error method. The various
In recent years, bearing electrical failures have been a significant concern in electric cars, restricting electric engine life. This work aims to introduce a coating approach for preventing electrical erosion on 52100 alloy steel samples, the most common material used on manufacturing bearings. This paper discusses the causes of shaft voltage and bearing currents, and summarizes standard electrical bearing failure mechanisms, such as morphological damages and lubrication failures. Alumina coatings are suitable for insulating the 52100 alloy steel samples because alumina coatings provide excellent insulation, hardness, and corrosion resistance, among other characteristics. The common method to coat an insulated alumina coating on the bearing is thermal spraying, but overspray can cause environmental issues, and the coating procedures are costly and time-consuming. Based on the research, this article briefly discusses employing plasma electrolytic aluminating to coat 52100 alloy steel
Numerous military aircraft and shipboard surfaces, such as radomes, antennas, gun shields, wing leading edges, and helicopter blade leading edges, are coated with a specialized erosion-resistant protective coating possessing strict performance requirements. These protective coatings must provide excellent rain erosion resistance, superior mechanical properties, good adhesion to the substrate and meet a host of other metrics outlined in MIL-PRF-32239 and SAE AMS-C- 83231A
Slag, generated from basic oxygen furnace (BOF) or Linz-Donawitz (LD) converter, is one of the recyclable wastes in an integrated steel plant. The present work aims at utilization of waste LD slag to develop surface coatings by plasma spraying technique. This study reveals that LD slag can be gainfully used as a cost-effective wear-resistant coating material. A prediction model based on an artificial neural network (ANN) is also proposed to predict the erosion performance of these coatings. The 2.27% error shows that ANN successfully predicts the erosion wear rate of the coatings both within and beyond the experimental domain. In addition to it, a novel optimization algorithm called imperialist competitive algorithm (ICA) is used to obtain minimum erosion wear rate of 12.12 mg/kg. This algorithm is inspired by the imperialistic competition and has several advantages over other revolutionary algorithms like its simplicity, less computational time, and accuracy in predicting the results
Recent experimental studies on the behavior of adhesively-bonded steel double-hat section components under axial impact loading have produced encouraging results in terms of load-displacement response and energy absorption when compared to traditional spot-welded hat- sections. However, it appears that extremely limited study has been carried out on the behavior of such components under transverse impact loading keeping in mind applications such as automotive body structures subject to lateral/side impact. In the present work, lateral impact studies have been carried out in a drop-weight test set-up on adhesively-bonded steel double-hat section components and the performance of such components has been compared against their conventional spot-welded and hybrid counterparts. It is clarified that hybrid components in the present context refer to adhesively-bonded hat-sections with a few spot welds only aimed at preventing catastrophic flange separations. For gaining confidence on
Innovators at NASA's Glenn Research Center have developed several new technological innovations to improve the capability of Hall-effect thrusters, which are used primarily on Earth-orbiting satellites and can also be used for deep-space robotic vehicles. Hall thrusters are susceptible to discharge channel erosion from high-energy ion impingement, which can reduce operational thruster lifetimes. Glenn researchers have developed several approaches to mitigate this problem. One is a magnetic circuit design that minimizes discharge chamber ion impingement. Another successful improvement developed by Glenn is a means of replacing eroded discharge channel material via a channel wall replacement mechanism. A third innovation is a propellant distributor that provides both a high degree of flow uniformity, and shielding from back-sputtered contamination and other potential contaminants. All of these advances work toward increasing the operational lifetime and efficiency of Hall thrusters
The arc breakdown phase in automotive spark-plugs is a sub-microsecond event that precedes the main spark event. This phase is typically characterized by strong non-equilibrium plasma phenomena with high voltage and currents. The nature of the initial breakdown phase has strong implications for the successful spark formation and the electrode erosion/lifetime. There are evidently very few studies that seek to characterize this phase in detail. The goal of this work is to investigate this non-equilibrium plasma arc breakdown phase, using high-fidelity computational modeling. We perform studies using the VizGlow non-equilibrium plasma modeling tool. During the early breakdown phase, the plasma forms thin filamentary streamers that provide the initial conductive channel across the gap. Once the streamers bridge the gap, the plasma begins to transition to a thermal arc. The redistribution of electrostatic potential across the gap during the breakdown phase causes a large electric field
A hybrid drilling process of multi material stacks with one shot drilling recently emerge as an economical and time efficient method in aerospace industry. Even though the comprehensive experience and knowledge is available for the cutting parameters of composites and metals alone, significant gap exist for the hybrid drilling parameters. Determination of these parameters such as feed rate, spindle speed and pecking depth has vital importance so as to provide a robust and optimal process to ensure dimensionally high quality, burr and delamination free holes. Main challenge of hybrid drilling operation is to obtain required hole diameter with adequate homogeneity and repeatability. In this study, effect of cutting parameters on dimensional hole quality was investigated. In addition to the hole diameter tolerances, CFRP hole enlargement phenomena which is encountered as a specific drawback of metal-exit stack configurations is also addressed within the scope of this study. Statistical
This document establishes the requirements for physical and chemical properties and the minimum tests to evaluate suitability of phosphate ester hydraulic fluids for use in aircraft systems where fire resistance is required. Additional tests may be specified by the qualifying agency to demonstrate compliance with their specific requirements. The "qualifying agency" will be defined herein to be the airframe manufacturer submitting certification approval for use of the fluid in a specific model airplane. Fluids meeting the requirements of this specification may be approved by a qualifying agency for use on specific airplane models. Data used to show compliance to this specification can be used by the qualifying agency to show compliance to the applicable regulations for the appropriate certifying authority; e.g., FAA, EASA, etc
This paper describes the establishment of a new method for predicting piston skirt scuffing in the internal combustion engine of a passenger car. The authors previously constructed and reported a method that uses 3D piston motion simulation to predict piston slap noise and piston skirt friction. However, that simulation did not have a clear index for evaluation of scuffing that involves piston skirt erosion, and it impressed shortage of the predictive accuracy of a scuffing. Therefore, the authors derived a new evaluation index for piston skirt scuffing by actually operating an internal combustion engine using multiple types of pistons to reproduce the conditions under which scuffing occurs, and comparing with the results of calculating the same conditions by piston motion simulation. In addition, it was clarified that in these calculations it is important to accurately predict the behavior of the oil film between the piston skirt and cylinder liner, and that this requires
Despite numerous research efforts, there is no reliable and widely accepted tool for the prediction of erosion prone material surfaces due to collapse of cavitation bubbles. In the present paper an Erosion Aggressiveness Index (EAI) is proposed, based on the pressure loads which develop on the material surface and the material yield stress. EAI depends on parameters of the liquid quality and includes the fourth power of the maximum bubble radius and the bubble size number density distribution. Both the newly proposed EAI and the Cavitation Aggressiveness Index (CAI), which has been previously proposed by the authors based on the total derivative of pressure at locations of bubble collapse (DP/Dt>0, Dα/Dt<0), are computed for a cavitating flow orifice, for which experimental and numerical results on material erosion have been published. The predicted surface area prone to cavitation damage, as shown by the CAI and EAI indexes, is correlated with the experiments. EAI predictions indicate
This SAE lab test procedure should be used when performing the following specialized weathering tests for wheels; Florida Exposure, QUV, Xenon and Carbon Weatherometer. In addition to these procedures, some additional post-weathering tests may be specified. Please refer to customer specifications for these requirements
When the planing craft with outboard motor is running, cavitation occurs around the surface of propeller and lower unit of outboard motor. Cavitation has been classified under several categories by the feature and cause of occurrence. Among them, cloud cavitation and root cavitation lead to erosion damage on the surface of lower unit and propeller. To prevent from poor appearance or performance deterioration of outboard motor by erosion damage, it is important problem to predict the erosion occurrence. Currently we can predict the cavitation phenomena sufficiently, but the area of cavitation does not necessarily correspond with the area of erosion. In this study, we present the new method to predict the area of erosion due to cavitation using CFD (computer fluid dynamics) analysis. In order to evaluate the accuracy of erosion occurrence simulation, the simulation results are compared against the result of a full-scale cruising test. Comparison between simulation and experiment suggests
A tricarbide foam fuel material has been developed that can operate at temperatures near 3,000 °C, without substantial hydrogen erosion, while providing highly efficient heat transfer to the coolant or propellant. A tricarbide foam fuel matrix of zirconium carbide (ZrC), niobium carbide (NbC), and uranium carbide (UC) has been successfully deposited and hydrogen tested. It shows that high-temperature, high-porosity foams can be produced that resist hydrogen corrosion and prevent the diffusion of fission products from the matrix. Chemical vapor deposition (CVD) technology was applied to nuclear materials systems that may be used in thermal propulsion and very high-temperature gas reactors
This coating demonstrates high emittance above 80% or better at broad wavelengths within the infrared spectrum. It has shown to have an extremely stable emittance at lower wavelengths within the infrared (IR) spectrum, where energy dissipation is critical at elevated temperatures. The coating has demonstrated increases in surface texturing, and ultimately an increase in emissivity when exposed to temperatures up to 2,050 °F (≈1,120 °C). It is also stable at continuous run, elevated temperatures, and shows no signs of spalling or erosion
In present paper, the process of joining aluminum alloy 6111T4 and steel HSLA340 sheets by self-piercing riveting (SPR) is studied. The rivet material properties were obtained by inverse modeling approach. Element erosion technique was adopted in the LS-DYNA/explicit analysis for the separation of upper sheet before the rivet penetrates into lower sheet. Maximum shear strain criterion was implemented for material failure after comparing several classic fracture criteria. LS-DYNA/implicit was used for springback analysis following the explicit riveting simulation. Large compressive residual stress was observed near frequent fatigue crack initiation sites, both around vicinity of middle inner wall of rivet shank and upper 6111T4 sheet
The anodic oxide films are formed to improve the corrosion resistance on aluminum alloy that used as the parts of engines and car bodies. Because these films are porous structure, it is necessary to seal the pores to further improve the corrosion resistance. The pores are sealed with hydrated alumina by treating the films in boiling water or solution that added sealing additives. These hydration sealing has a problem that energy consumption is large because of long sealing time and high temperature of solution. In this study, the authors have developed a new sealing treatment (Lithium sealing) using a lithium hydroxide solution to solve above problem. Lithium sealing mainly sealed the pores with lithium aluminate double salt (LiH(AlO2)2·5H2O). This salt was rapidly formed in strong alkaline solution at room temperature, so that the sealing time was reduced to about 1/10 compared with the conventional sealing. This salt was formed from the surface of the film to the depth part
Ice adhesion on critical aircraft surfaces is a serious potential hazard that runs the risk of causing accidents. For this reason aircraft are equipped with active ice protection systems (AIPS). AIPS increase fuel consumption and add complexity to the aircraft systems. Reducing energy consumption of the AIPS or replacing the AIPS by a Passive Ice Protection System (PIPS), could significantly reduce aircraft fuel consumption. New coatings with superhydrophobic properties have been developed to reduce water adherence to surfaces. Superhydrophobic coatings can also reduce ice adhesion on surfaces and are used as icephobic coatings. The question is whether superhydrophobic or icephobic coatings would be able to reduce the cost associated with AIPS. To address this concern, this paper reviews the current knowledge on superhydrophobic and icephobic coatings, proposes a parameter to quantify the coating hydrophobicity level and presents methods to adapt available experimental data to aircraft
This SAE Recommended Practice presents standardized test methods developed for use in testing with hydrocarbon fuels or their surrogates and those same fuels when blended with oxygenated fuel additives. Hydrocarbon fuels include Gasoline and Diesel fuel or their surrogates described in SAE J1681. Oxygenated additives include Ethanol, Methanol Methyl Tertiary Butyl Ether (MTBE) and Fatty Acid Methyl Esters (FAME or Biodiesel
Development of reliable magnesium (Mg) to steel joining methods is one of the critical issues in broader applications of Mg in automotive body construction. Ultrasonic spot welding (USW) has been demonstrated successfully to join Mg to steel and to achieve strong joints. In this study, corrosion test of ultrasonic spot welds between 1.6 mm thick Mg AZ31B-H24 and 0.8 mm thick galvanized mild steel, without and with adhesive, was conducted. Adhesive used was a one-component, heat-cured epoxy material, and was applied between overlapped sheets before USW. Corrosion test was conducted with an automotive cyclic corrosion test, which includes cyclic exposures of dipping in the 0.5% sodium chloride (NaCl) bath, a constant humidity environment, and a drying period. Lap shear strength of the joints decreased with the cycles of corrosion exposure. Good joint strengths were retained at the end of 30-cycle test. Failure mode of joints without adhesive was Mg nugget pull-out, but was interfacial
Items per page:
50
1 – 50 of 225