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Author: Taylor Knuth Publisher: ISBN: Category : Languages : en Pages :
Book Description
A physics-based analytical model to predict the adhesion shear strength of impact ice on varying surface morphologies was developed and validated experimentally. The model focuses on the surface morphology effects on ice adhesion strength. As super-cooled water droplets, having a typical median volume diameter ranging from 10 to 80 [mu]m, impact and freeze on the leading edges of aircraft, it is hypothesized that the small drops expand and clamp to surface discontinuities, contributing to the ice adhesion strength of the material. The derivation of a Newtonian mechanics model to calculate the forces required for the removal of ice that has expanded and clamped inside macro surface structures is presented. The model requires knowledge of the macro-scale (10-6 m) surface geometry. Newtonian mechanics accounted for the expansion and clamping of freezing ice including temperature dependent ice properties. The model is dependent on Young's modulus, the thermal coefficient of expansion of ice, and the coefficient of static friction between ice and the adhering substrate. All of these properties are dependent on the variation of temperature. The research validated the developed model experimentally. Firstly, the individual parameters as functions of temperature were obtained from literature review and experimental measurements. Previous research revealed the correlation with temperature of the Young's modulus and the thermal coefficient of expansion for ice. The relationship for the thermal coefficient of expansion found is valid for temperatures ranging between -193.15 and 6.85 °C (-315.67 and 44.33 °F). The Young's modulus temperature relationship was obtained from tests presented in the literature that used sea ice. Secondly, the static coefficient of friction is dependent on the surface interaction between the accreted ice and the surface material. Through bench top testing, it was determined that the coefficient of friction of ice is also dependent on temperature. The coefficient of friction was experimentally acquired for a mercaptan and amine blended epoxy (Great Planes 30 Minute Pro Two-Part) applied to an aluminum substrate. The coefficient of friction varied from 0.046 with a standard deviation of 0.015 at -5.8 °C (21.6 °F) to 0.190 with a standard deviation of 0.019 at -15.7 °C (3.7 °F), a change of 420%, and is dependent on loading conditions and the test environment.The final phase of the research was the experimental validation of the ice adhesion model through adhesion strength testing on the Adverse Environment Rotor Test Stand (AERTS). To conduct validation testing, controlled surfaces were created. The surfaces were coated with the same mercaptan and amine epoxy blend to create a surface that approached a Ra of zero. The actual surface roughness measured was a Ra of 0.01 [mu]m (3.94 x 10-7 in.). This pristine coating provided a baseline against other surface of the same coating that had controlled surface roughness. The epoxy surfaces were ablated using a laser at differing intensities to create surfaces with varying roughness depths. The laser etched the coatings at 0.35, 0.6, and 1.2 W, each with a respective surface roughness of 1.13, 1.95, and 5.11 Ra (4.45 x 10-5, 7.68 x 10-5, and 2.01 x 10-4 in.). All of these coatings were tested within the Federal Aviation Regulation Part 25 and Part 29 Appendix C icing envelope to recreate realistic environmental icing conditions. The pristine surface was had an adhesion strength of 4.11 psi (28.3 kPa) with a standard deviation of 0.75 psi (5.17 kPa) at -8 °C (17.6 °F) and 7.99 psi (55.1 kPa) with a standard deviation of 0.94 psi (6.48 kPa) at -16 °C (3.2 °F). While, for example, the coating with the most severe ablation (Ra of 5.11 [mu]m) was had an adhesion strength of 22.7 psi (156.8 kPa) with a standard deviation of 2.70 psi (18.62 kPa) at -8 °C and 42.4 psi (292.5 kPa) with a standard deviation of 3.45 psi (23.79 kPa) at -16 °C. These measured values were then compared to the model predictions. The maximum discrepancy between prediction and experimental results was 9% for the 25 experimental tests conducted using the 1.2 W ablation surface.
Author: Taylor Knuth Publisher: ISBN: Category : Languages : en Pages :
Book Description
A physics-based analytical model to predict the adhesion shear strength of impact ice on varying surface morphologies was developed and validated experimentally. The model focuses on the surface morphology effects on ice adhesion strength. As super-cooled water droplets, having a typical median volume diameter ranging from 10 to 80 [mu]m, impact and freeze on the leading edges of aircraft, it is hypothesized that the small drops expand and clamp to surface discontinuities, contributing to the ice adhesion strength of the material. The derivation of a Newtonian mechanics model to calculate the forces required for the removal of ice that has expanded and clamped inside macro surface structures is presented. The model requires knowledge of the macro-scale (10-6 m) surface geometry. Newtonian mechanics accounted for the expansion and clamping of freezing ice including temperature dependent ice properties. The model is dependent on Young's modulus, the thermal coefficient of expansion of ice, and the coefficient of static friction between ice and the adhering substrate. All of these properties are dependent on the variation of temperature. The research validated the developed model experimentally. Firstly, the individual parameters as functions of temperature were obtained from literature review and experimental measurements. Previous research revealed the correlation with temperature of the Young's modulus and the thermal coefficient of expansion for ice. The relationship for the thermal coefficient of expansion found is valid for temperatures ranging between -193.15 and 6.85 °C (-315.67 and 44.33 °F). The Young's modulus temperature relationship was obtained from tests presented in the literature that used sea ice. Secondly, the static coefficient of friction is dependent on the surface interaction between the accreted ice and the surface material. Through bench top testing, it was determined that the coefficient of friction of ice is also dependent on temperature. The coefficient of friction was experimentally acquired for a mercaptan and amine blended epoxy (Great Planes 30 Minute Pro Two-Part) applied to an aluminum substrate. The coefficient of friction varied from 0.046 with a standard deviation of 0.015 at -5.8 °C (21.6 °F) to 0.190 with a standard deviation of 0.019 at -15.7 °C (3.7 °F), a change of 420%, and is dependent on loading conditions and the test environment.The final phase of the research was the experimental validation of the ice adhesion model through adhesion strength testing on the Adverse Environment Rotor Test Stand (AERTS). To conduct validation testing, controlled surfaces were created. The surfaces were coated with the same mercaptan and amine epoxy blend to create a surface that approached a Ra of zero. The actual surface roughness measured was a Ra of 0.01 [mu]m (3.94 x 10-7 in.). This pristine coating provided a baseline against other surface of the same coating that had controlled surface roughness. The epoxy surfaces were ablated using a laser at differing intensities to create surfaces with varying roughness depths. The laser etched the coatings at 0.35, 0.6, and 1.2 W, each with a respective surface roughness of 1.13, 1.95, and 5.11 Ra (4.45 x 10-5, 7.68 x 10-5, and 2.01 x 10-4 in.). All of these coatings were tested within the Federal Aviation Regulation Part 25 and Part 29 Appendix C icing envelope to recreate realistic environmental icing conditions. The pristine surface was had an adhesion strength of 4.11 psi (28.3 kPa) with a standard deviation of 0.75 psi (5.17 kPa) at -8 °C (17.6 °F) and 7.99 psi (55.1 kPa) with a standard deviation of 0.94 psi (6.48 kPa) at -16 °C (3.2 °F). While, for example, the coating with the most severe ablation (Ra of 5.11 [mu]m) was had an adhesion strength of 22.7 psi (156.8 kPa) with a standard deviation of 2.70 psi (18.62 kPa) at -8 °C and 42.4 psi (292.5 kPa) with a standard deviation of 3.45 psi (23.79 kPa) at -16 °C. These measured values were then compared to the model predictions. The maximum discrepancy between prediction and experimental results was 9% for the 25 experimental tests conducted using the 1.2 W ablation surface.
Author: Yan Li Publisher: BoD – Books on Demand ISBN: 1837690146 Category : Technology & Engineering Languages : en Pages : 120
Book Description
This book includes six chapters on wind turbine icing. For wind turbines operating in cold regions, icing often occurs on blade surfaces in winter. This ice accretion can change the aerodynamic shape of the blade airfoil, causing performance degradation and loss of power generation, even leading to operational accidents. This book focuses on the recent research progress on wind turbine icing. Chapters address such topics as the effect of icing conditions on the icing distribution characteristics of a blade airfoil for vertical-axis wind turbines, power loss estimation in wind turbines due to icing, wind turbine icing prediction methods, especially those using machine learning, the icing process of a single water droplet on a cold aluminum plate surface, the main theories of the icing adhesive mechanism, and theoretical and experimental studies on the ultrasonic de-icing method for wind turbine blades. This book is a valuable reference for researchers and engineers engaged in wind turbine icing and anti-icing research.
Author: K. L. Mittal Publisher: John Wiley & Sons ISBN: 1119640377 Category : Technology & Engineering Languages : en Pages : 704
Book Description
This unique book presents ways to mitigate the disastrous effects of snow/ice accumulation and discusses the mechanisms of new coatings deicing technologies. The strategies currently used to combat ice accumulation problems involve chemical, mechanical or electrical approaches. These are expensive and labor intensive, and the use of chemicals raises serious environmental concerns. The availability of truly icephobic surfaces or coatings will be a big boon in preventing the devastating effects of ice accumulation. Currently, there is tremendous interest in harnessing nanotechnology in rendering surfaces icephobic or in devising icephobic surface materials and coatings, and all signals indicate that such interest will continue unabated in the future. As the key issue regarding icephobic materials or coatings is their durability, much effort is being spent in developing surface materials or coatings which can be effective over a long period. With the tremendous activity in this arena, there is strong hope that in the not too distant future, durable surface materials or coatings will come to fruition. This book contains 20 chapters by subject matter experts and is divided into three parts— Part 1: Fundamentals of Ice Formation and Characterization; Part 2: Ice Adhesion and Its Measurement; and Part 3: Methods to Mitigate Ice Adhesion. The topics covered include: factors influencing the formation, adhesion and friction of ice; ice nucleation on solid surfaces; physics of ice nucleation and growth on a surface; condensation frosting; defrosting properties of structured surfaces; relationship between surface free energy and ice adhesion to surfaces; metrology of ice adhesion; test methods for quantifying ice adhesion strength to surfaces; interlaboratory studies of ice adhesion strength; mechanisms of surface icing and deicing technologies; icephobicities of superhydrophobic surfaces; anti-icing using microstructured surfaces; icephobic surfaces: features and challenges; bio-inspired anti-icing surface materials; durability of anti-icing coatings; durability of icephobic coatings; bio-inspired icephobic coatings; protection from ice accretion on aircraft; and numerical modeling and its application to inflight icing.
Author: Shivrajsinh Jadeja Publisher: ISBN: Category : Languages : en Pages :
Book Description
Ice accretion to aircraft and other civil structures has led to the cost of billion dollars every year. The icing clouds are controlled by temperature, liquid water content (LWC), and median volumetric diameter (MVD). De-icing systems are required to mitigate ice accretion and reduce damages to the structure from icing events. The de-icing systems design require ice adhesion strength which is controlled by temperature, LWC, MVD, and impact velocity of the droplet. For aircraft applications, discrepancies on the value of ice adhesion strength are reported by different sources. Current testing methodologies are not testing and reporting all of the icing cloud conditions that define an icing cloud. The icing cloud conditions affect the ice adhesion strength. To design an effective ice protective coating, the factors that contribute to changes in ice adhesion strength must be understood. In flight ice accretion, there are three types of ice encountered on wings and rotors: glaze, mix, and rime ice. In this research, it is shown that ice adhesion strength varies for each of the ice types. In this research, a non dimensional parameter typically used in the modeling of ice shapes, called freezing faction, was used to summarize affects of icing parameters on ice adhesion strength. The freezing fraction and ice adhesion strength are both functions of icing cloud conditions. Freezing fraction is a function of MVD, LWC, temperature, impact velocity and collection efficiency of the structure. The affects of freezing fraction variation on impact ice adhesion strength is evaluated in this work. A modified instrumented centrifugal adhesion testing rig (ICATR) was used to vary freezing fraction and measure ice adhesion strengths of three surfaces. The ICATR is part of the Adverse Environment Research and Testing Systems (AERTS) located at The Pennsylvania State University. Flat circular disks with an average surface roughness, Sa, of 331, 12.6 and 9.5 nm were tested at -8, -12, and -16 $^{\circ}$C. Two cloud water droplet sizes (20 $\mu$m and 50 $\mu$m median volumetric diameter, MVD) were tested at a liquid water content of the icing cloud (LWC) of 0.28 g$/$m$^3$ and 0.41 g$/$m$^3$, respectively. The freezing fraction was also varied with the variation of the droplet impact velocity (54.6, 60.0, and 68.2 m$/$s). For the first time, it is demonstrated that freezing fraction variations affected ice adhesion strength of the ice, making it possible to obtain multiple different ice adhesion strength values at identical temperatures and material substrate conditions. The impact ice density of both clouds at -20 $^{\circ}$C were measured for the calculation of collection efficiency. The average impact ice density of the 20 and 50 $\mu$m MVD cloud were 526.34 and 623.84 kg$/m^3$. The impact ice density increased linearly as impact velocity increased for the respective MVD tested. The impact ice density increased by 17.8 \% and 10.16 \% for the 50 and 20 $\mu$m MVD clouds. By a decrease in either temperature, LWC, MVD and impact velocity the freezing fraction is increased. As the freezing fraction is increased, the ice adhesion strength of the 331, 12.6 and 9.5 nm surface roughness is affected. For the MVD 50 $\mu$m cloud, the ice adhesion strength increased by 390.41\%, 1,122.93\%, and 1,540.22\%, respectively as freezing fraction varied from 0.49 to 1.18. The 20 $\mu$m MVD testing condition increased the ice adhesion strength by 591.64\%, 430.88\%, and 273.95\% for the respective surfaces for freezing fraction increases of 1.14 to 2.73. The research conducted demonstrates that all icing cloud parameters need to be considered and reported to specify the ice adhesion strength of impact ice to a surface, since these values affect the freezing fraction and subsequent type of ice accreted.
Author: Rebekah Douglass Publisher: ISBN: Category : Languages : en Pages :
Book Description
In-flight ice accretion on fixed-wing aircraft and rotorcraft can be catastrophic if not mitigated. Most modern ice protection systems are active systems, which require electrical or mechanical power to remove accreted ice. Despite their proven capability to protect aircraft from ice accretion, these methods can reduce the aerodynamic efficiency of the vehicle and increase its weight, cost, and complexity. Scientists and engineers now seek passive, erosion-resistant materials and coatings with low ice adhesion strength. Ideally, such materials, when applied to vulnerable components of an aircraft, would cause any ice to shed off the surface under normal aerodynamic loading. To aid in the development of low-ice-adhesion-strength materials, the growth and structural behavior of impact ice in a wide range of atmospheric conditions must be characterized. Facilities such as the NASA Icing Research Tunnel (IRT), the Anti-Icing Materials International Laboratory (AMIL), and the Penn State Adverse Environment Research Testing Systems (AERTS) laboratory, to name a few, have spent decades investigating the relationship between ice adhesion strength, temperature, surface roughness, airspeed, and other parameters. The structural behavior of ice has been examined under pure shear, tension, and compression, and mixed-mode loading. However, one important loading consideration that has not been widely investigated on atmospheric ice is strain rate. Very few published ice adhesion studies report the strain rate applied to the ice samples. Several previous studies of laboratory-prepared ice in compression revealed that ice undergoes a ductile-to-brittle transition under high strain rate conditions, and that the adhesion strength is a power function of the strain rate. Other studies, in which lab-prepared ice was loaded in pure shear, reported similar trends. It is unclear whether the same behavior can be expected of dynamically-accreted atmospheric impact ice. Knowledge of the relationship between impact ice adhesion strength and strain rate is important because it can be used to design future ice protection systems, and it may dictate the appropriate course of action for a pilot flying through icing conditionsfor instance, whether a helicopter pilot should increase the rotor speed rapidly or slowly to induce shedding of the ice. NASA Glenn Research Center funded the design and construction of a new centrifuge-style ice adhesion test rig (AJ2) by the Penn State AERTS lab. The ice is accreted dynamically by spinning flat metal test coupons at high speed inside a simulated icing cloud environment, so the water droplet sizes and impact speed are representative of in-flight icing, without the need for a wind tunnel. The rig motor allows for user-defined acceleration rates, so the strain rate on the ice can be controlled. The adhesion strength of the ice is calculated from the voltage output of strain gauges mounted on the cantilever beams holding the test coupons. Unlike other small-scale adhesion test methods, AJ2 allows researchers to collect real-time adhesion data and control the testing environment without any direct interaction with the ice, thus preserving the fidelity of the data. As per NASA requirements, ballistic and structural analysis was performed on the rig to verify its safety. The design and analysis of the AJ2 rig is described in detail in this paper. Many experiments were performed at Penn State to investigate how the adhesion strength of impact ice related to the strain rate applied to it. Stainless steel test coupons of known surface roughness were tested in a range of environmental temperatures. The strain rates applied to the ice ranged between 5x10-7 and 5x10-5 s-1. It was discovered that a similar power function exists between strain rate and adhesion strength as found in the freezer-ice studies described in the literature. Despite scatter in the data, regression analysis determined the trends to be statistically significant. The data suggests that strain rate has a stronger effect on adhesion strength for smoother surfaces as opposed to rougher surfaces. The power 1/n for a coupon roughness of 64 nm (Sa) was double that of the 80-nm coupon; this was the case for both tested temperatures. Similarly, lower temperatures caused a higher power 1/n and coefficient c in the power function. The variation of the coefficient with temperature is consistent with Glens power law for the creep of glacier ice in compression. However, Glen did not observe a variation of the power with temperature. The value of n in the current study ranged from 2.5 for the smoothest sample at the coldest temperature, to 9.7 for the roughest sample at the warmest temperature. In most cases, n was within the range of previously-reported values in literature (1.5 to 6). These findings suggest that the creep behavior of atmospheric impact ice in shear is similarbut not identicalto freezer ice in compression. The proven strain rate testing capabilities of the AJ2 rig will aid icing research efforts by yielding baseline prediction data for future design of ice-resistant materials.
Author: Masoud Farzaneh Publisher: Springer Science & Business Media ISBN: 1402085303 Category : Computers Languages : en Pages : 388
Book Description
This is a comprehensive book that documents the fundamentals of atmospheric icing and surveys the state of the art in eight chapters, each written by a team of experienced and internationally renowned experts. The treatment is detailed and richly illustrated.
Author: K. L. Mittal Publisher: John Wiley & Sons ISBN: 1119162327 Category : Technology & Engineering Languages : en Pages : 515
Book Description
This book is based on the 13 review articles written by subject experts and published in 2014 in the Journal Reviews of Adhesion and Adhesives. The rationale for publication of this book is that currently the RAA has limited circulation, so this book provides broad exposure and dissemination of the concise, critical, illuminating, and thought-provoking review articles. The subjects of the reviews fall into 4 general areas: 1. Polymer surface modification 2. Biomedical, pharmaceutical and dental fields 3. Adhesives and adhesive joints 4. General Adhesion Aspects The topics covered include: Adhesion of condensed bodies at microscale; imparting adhesion property to silicone material; functionally graded adhesively bonded joints; synthetic adhesives for wood panels; adhesion theories in wood adhesive bonding; adhesion and surface issues in biocomposites and bionanocomposites; adhesion phenomena in pharmaceutical products and applications of AFM; cyanoacrylate adhesives in surgical applications; ways to generate monosort functionalized polyolefin surfaces; nano-enhanced adhesives; bonding dissimilar materials in dentistry; flame treatment of polymeric materials—relevance to adhesion; and mucoadhesive polymers for enhancing retention of ocular drug delivery.
Author: K. L. Mittal Publisher: John Wiley & Sons ISBN: 111984665X Category : Technology & Engineering Languages : en Pages : 914
Book Description
With the voluminous research being published, it is difficult, if not impossible, to stay abreast of current developments in a given area. The review articles in this book consolidate information to provide an alternative way to follow the latest research activity and developments in adhesion science and adhesives. With the ever-increasing amount of research being published, it is a Herculean task to be fully conversant with the latest research developments in any field, and the arena of adhesion and adhesives is no exception. Thus, topical review articles provide an alternate and very efficient way to stay abreast of the state-of-the-art in many subjects representing the field of adhesion science and adhesives. The 19 chapters in this Volume 6 follow the same order as the review articles originally published in RAA in the year 2020 and up to June 2021. The subjects of these 19 chapters fall in the following areas: Adhesives and adhesive joints Contact angle Reinforced polymer composites Bioadhesives Icephobic coatings Adhesives based on natural resources Polymer surface modification Superhydrophobic surfaces The topics covered include: hot-melt adhesives; adhesively-bonded spar-wingskin joints; contact angle hysteresis; fiber/matrix adhesion in reinforced thermoplastic composites; bioadhesives in biomedical applications; mucoadhesive pellets for drug delivery applications; bio-inspired icephobic coatings; wood adhesives based on natural resources; adhesion in biocomposites; vacuum UV surface photo-oxidation of polymers and other materials; vitrimers and their relevance to adhesives; superhydrophobic surfaces by microtexturing; structural acrylic adhesives; mechanically durable water-repellent surfaces; mussel-inspired underwater adhesives; and cold atmospheric pressure plasma technology for modifying polymers. Audience This book will be valuable and useful to researchers and technologists in materials science, nanotechnology, physics, surface and colloid chemistry in multiple disciplines in academia, industry, various research institutes and other organizations.
Author: Taylor Knuth
Author: Taylor Knuth
Author: Yan Li
Author: K. L. Mittal
Author: Shivrajsinh Jadeja
Author: Rebekah Douglass
Author: Grant M. Schneeberger
Author: Masoud Farzaneh
Author: K. L. Mittal
Author: Cold Regions Research and Engineering Laboratory (U.S.)
Author: K. L. Mittal