Browse Topic: Erosion
Cold spray deposition is a kinetic-based deposition method that uses an inert gas flow to accelerate particles, where kinetic energy causes plastic deformation upon impact with a substrate, as discussed in Reference 1. Cold spray has been investigated as a method to deposit metal coatings on polymer-based composites, such as aerospace carbon-fiber-reinforced plastics (CFRP's), as discussed in Reference 2. These methods also exhibit low deposition efficiency (15-45%) as shown in Reference 3. In this work, to achieve high deposition efficiency and create an erosion-resistant coating, we use metal-polymer composite powders for cold spray, to make polymer-on-polymer bonding the dominant and effective bonding mechanism; this method lowers impact velocities relative to pure metal deposition to avoid substrate damage. The polymer can also lower the effect of material mismatch, while the nickel can help enhance the erosion performance of the final coating above that of pure polymer. This paper discusses the development of the cold spray deposition process, sample post-processing, erosion testing, and characterization of the samples. The results validate that this method successfully creates a method of depositing a coating with erosion resistance approaching that of bulk titanium without substrate damage on PEEK substrates. Further work is needed to address the issues with depositing on CF-PEEK substrates.
Composite materials have become widely adopted in commercial aviation, as aerospace manufacturers look to use them to drive weight reduction and improved fuel efficiency in new aircraft designs. In the case of aircraft rotary blades, the poor wear properties of these materials have necessitated the development of metal leading edge guards that can provide critical protection against erosion and impact damage during flight. Electroforming has been a leading process for the manufacture of these protective guards, with nickel parts providing excellent wear resistance that significantly extends the service life of the rotary blade assembly. Currently there has not been a focus on utilizing direct electrodeposition of metal on to carbon filled epoxy composite structures, as traditional plating-on-plastics approaches require considerable effort in surface preparation and normally do not provide adequate adhesion to the underlying structure. Alpha Metalcraft Group has been working in cooperation with aerospace suppliers in the design of an electroplating ready composite structure that would allow for direct nickel deposition, provide excellent adhesion, and significantly reduce both the time and cost for the manufacture of ready-to-assembly rotary blade structures. Test panels were constructed of commercially available prepreg materials or by resin infusion of dry fabrics that incorporated different metal containing conductive layers to allow for the direct deposition through a nickel sulfamate electrodeposition process. Different surface modification strategies were investigated to expose the metal conducting layer and thereby provide the metal-to-metal bonding surfaces required for successful electrodeposition.
Quieter cabins in an automobile are the new era, they provide customers with pleasurable driving experience. Squeak and Rattle are spoil sport for any OEM that aim to improvise customer driving experience. Their nonlinear nature makes it difficult to formulate design frontloading methods. The issue of seals rubbing against the body & door interface is a clear sign of seal squeak & seal chucking. Seals are applied with anti-friction coatings to avoid stick slip phenomena between EPDM and painted panel. Primary root cause for seal squeak is coating erosion. The challenge lies in determining whether the body or the closure side contributes to the seal issue. This paper presents a distinctive approach for identifying the seal squeaking noise and enriches on the new modelling methods for seal interaction with door and body interfaces using FE software. The proposed method was able to highlight the locations along the door-body interface for squeak noise. The approach for reducing the relative displacements was tackled by checking the contributing modes at every interface. A simulation-driven approach of “Panel Contribution Analysis” (PCA) has been introduced analyzing the contribution of several BIW & Closure panels. The optimized panel thicknesses minimized the displacement and reduced the likelihood of squeaking and chucking. The key highlight is a method of DOE followed to minimize experimental runs with a weighted optimization of panel thickness. This method enables engineers to achieve the ideal trade-off between structural integrity, weight, cost, and performance.
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 parameters that are used in a process such as machining will have a huge impact on the production rate and quality of a component. In addition to the surface finishes, the other factors that affect the performance of a machine are also taken into account. This study aims to analyze the three pulse on time (‘Ton’), pulse off (‘Toff’), and applied current parameters of WEDM. An experimental study of WEDM of SS304 alloy was conducted utilizing Taguchi’s response analysis technique, with a particular emphasis on the building of multiple regression models. The results of this study show that the predicted values are almost similar to the experimental values. The findings of this study will provide manufacturers with a comprehensive guide on how to improve the quality and production rate of their components using the WEDM method.
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 samples, an eco-friendly and high-efficiency coating process. Coating experiments were conducted over different coating periods to determine the most appropriate thin film for 52100 alloy steel samples. Scanning electronic microscopy observations indicated that pores reduced as their size and porosity rose with the increased treatment time. Longer treatment period resulted in thicker coating layers, but a rougher surface. The results indicated that extending the coating period increased the insulating characteristics of the ceramic coating on 52100 alloy steel samples. The single piece of 20-minute coated sample had the best insulation property, compared with other single pieces. Two 20-min coatings sample combinations provided the best resistance (121-143 MΩ) and the highest breaking voltage (914-935 V). Coatings remained in good condition after thermal shock tests.
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. A 2.39% error is noticed while comparing the erosion wear rate result of ICA with the experimental outcome.
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 experimental responses, steel tubes of square cross-section have at first been subjected to transverse impact tests. Good correlation has been found between experimentally determined peak and mean loads for a square-section steel tube and those predicted numerically. The performance of adhesively-bonded components under lateral impact is found to degrade somewhat compared to conventional spot-welded hat-sections in terms of mean loads sustained, although not alarmingly for the current test conditions. It is, however, noted that flange separation observed in purely adhesively-bonded hat-sections can be an issue in terms of erosion in confidence on structural integrity of such members which can be restored by adding sparse spot-welds to adhesively-bonded flanges as also shown in the current study.
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 intensification near the cathode. This leads to significant ion bombardment on the electrode surface and fast gas heating, both of which can be attributed to electrode erosion.
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 evaluation of hole quality was conducted with calculation of process capability (Cp). Effect of different cutting parameters was compared with respect to these quality variables and optimum parameter set was acquired. In order to demonstrate the effect of cutting parameters on CFRP erosion tendency, number of excessively out of tolerance holes are used and corresponding chip characteristics are evaluated. This paper presents the results for individual contributions of drilling parameters to the hole quality as well as optimum combination of these parameters specific to given stacking configuration. This publication summarizes a part of TAI’s research and activities within the context of LOCOMACHS Project funded by EC 7th Framework Program.
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 understanding of the piston skirt surface property parameters, so a method of applying these parameters was indicated. Furthermore, the newly obtained evaluation index was confirmed to be effective even for pistons of different shapes, which validated the general versatility of this prediction method. Use of this prediction method made it possible to clearly distinguish and predict wear and scuffing of the piston skirt.
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 the minimum bubble size above which erosion starts as also its location along the injector wall. The proposed methodology is also tested in an actual Diesel injector, operating under realistic injection cycles and pressure levels for which erosion data are available.
This paper reports the results of a limited flight loads survey focusing on the increase in oscillatory loads caused by a degraded erosion protection coating. Load increase was on average between 10-20% leading to estimations of a significant reduction in fatigue lives. Lessons learned and various analytical studies are presented which emphasize the potential for erosion protection coatings to impact fatigue lives. The Aviation Engineering Directorate currently emphasizes the minimum requirement to performance flight test the coating in the worst authorized condition. An increase in power required of greater than 2% would require flight loads survey to demonstrate airworthiness.
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