The measurement of the adhesion of glaze ice.

Icing is a lethal and costly aviation hazard affecting aircraft of all sizes ranging from small UAVs to large commercial craft such as the Boeing 787, resulting in hundreds of deaths over the last century and resulting in billions of dollars of economic impact. Three predominant types of icing, namely, airframe icing, engine icing, and rotorcraft icing, dominate aircraft icing research. Each type poses unique challenges. In the case of rotor icing, attention needs to give to the rotating environment with large oscillatory loads and icing conditions. In the case of airframe icing, special attention needs to be paid to a variety of loading cases from the available options for de-icing and anti-icing equipment. In the case of engine icing, the formation mechanism is poorly understood and the structure of the ice needs to be studied in greater detail. Airframe icing requires However, all three share the same fundamental problem that ice sticks to surfaces. How strongly ice adheres to a surface dictates how hard it is to remove. The adhesion strength then regulates the primary threat from icing - the maximum aerodynamic penalty that accretion will have. It also dictates the threat of impingement from shed ice elsewhere on the aircraft, such that a piece of ice from the main rotor could strike the tail rotor on a helicopter, destroying it. There exist many methods to evaluate the adhesion of ice to a given substrate, the most common being pusher tests and centrifuge tests. These and other methods are problematic in evaluating the adhesive properties of ice to a substrate in aircraft icing conditions; no data in the literature exists that accounts for stress concentrations at the interface and the strain rate at the interface, and no data was found in the literature on the grain structure of impact ice at speeds relevant to aircraft icing. A new method to measure the adhesion of impact ice has been developed based on a lap joint shear test. Lap joint tests are common in adhesion measurements since they produce nearly uniform stress at the interface of interest. In support of this end, a new shear rig and a new wind tunnel model for the Icing Research Tunnel were designed and fabricated. Six nights of testing in the Icing Research Tunnel were conducted to obtain samples, which were later tested in a laboratory environment. The tests were displacement controlled and samples were tested at four crosshead speed rates. The grain structure of the ice was documented using a cross-polarized optical microscope for the first two nights of testing, showing significant differences in the grain structure dependent on velocity and whether the cloud was in the SLD range or not. Correlations with temperature and test section velocity are demonstrated. It was also demonstrated that residual stresses, which are unaccounted for in the literature, play a significant role in the adhesion of impact ice. Options to improve the test methodology further are discussed. Finally, a shedding model predicting the trajectory of ice at a shed event has been developed and validated against test data. This model successfully predicted the front of a multi-break shed event in the Icing Research Tunnel

Toward Polymer Coating with Easy Ice Release

Minimizing adhesion of ice has been the subject of extensive studies for applications such aircraft wings, wind turbine blades spacecraft, power transmission wires, while a growing interest concerns coatings for aerospace applications. The work described here describes progress for coatings and ice release test method development over the last few years. Major achievements include: (1) New Rigid Adherent-Resistant Elastomers (RARE), (2) A new Epoxied Cylinder (EC) adhesion test, (3) Validation of an ice release test, and (4) Study of ice adhesion strength on coating thickness for a PDMS elastomer. Rigid Adhesion-Resistance Elastomers (RARE) are comprised of 3F 1 terminated with triethoxysilane moieties and linear 3F polyurethane (U-3F). Hybrid compositions U-3F-x are designated by polyurethane weight percent “x”. Interestingly, RARE coatings spontaneously “self-stratify” during coating deposition and cure. Cured RARE coatings are comprised of (1) a nanoscale surface layer with low work of adhesion, (2) a low modulus mesoscale and (3) a tough U-3F bulk, where “Mesoscale” is defined as a near surface region with a depth ~ 1000 nm. An EC adhesion test was developed to evaluate the fouling release characteristics of RARE. EC adhesion testing was devised by using the commercially available instrument, TA RSA-3. The TA RSA-3 is well suited for these tests as the 3.5 kg load cell facilitates accurate measurements. This test gives peak force (Ps) for EC removal. A striking compositional dependence was found for EC adhesion. A U-3F-50 hybrid coating had the lowest adhesion (Ps = 0.078 MPa) with good toughness (6.2 MPa). Bulk and surface characterization together with adhesion measurements established U-3F-x hybrid coatings, and U-3F-50 in particular, as new fluorous rigid adherent-resistant elastomers (RARE) that are tough, oil resistant, and optically transparent. Inspired by the Epoxied Cylinder (EC) adhesion test, a laboratory method for ice adhesion measurement with a commercially available instrument was established in the Wynne Laboratory. This is the first laboratory ice adhesion test that does not require a custom built apparatus. The temperature controlled chamber on TA RSA-3 is an enabling feature that is essential for the test. The method involves removal of an ice cylinder from a polymer coating with a probe and the determination of peak removal force (Ps). To validate the test method, the strength of ice adhesion was determined for a prototypical glassy polymer, poly(methyl methacrylate). The distance of the probe from the PMMA surface has been identified as a critical variable for Ps. The new test provides a readily available platform for investigating fundamental surface characteristics affecting ice adhesion. In addition to the ice release test, PMMA coatings were characterized using DSC, DCA and TM-AFM. This new laboratory ice release test was then employed to obtain the thickness dependence of ice adhesion for Sylgard 184, a filled polydimethylsiloxane elastomer. A correlation between ice adhesion and coating thickness (t) was found, that follows a relationship developed by Kendall over 40 years ago for removal of a rigid object from an elastomer. In particular, a nearly linear relationship between peak removal stress (Ps) and 1/t1/2 was found, with Ps decreasing from 550 kPa to 100 kPa with coating thickness increasing from 12 μm to 800 μm. While work of adhesion, which is related to surface free energy, is recognized as an important factor that can affect ice release, the results reported herein show that coating thickness can override this single parameter for elastomeric substrates. Base on the result, a general model is proposed for the removal of ice from low modulus elastomers (~10 MPa)

Safety and Reliability - Safe Societies in a Changing World

The contributions cover a wide range of methodologies and application areas for safety and reliability that contribute to safe societies in a changing world. These methodologies and applications include: - foundations of risk and reliability assessment and management - mathematical methods in reliability and safety - risk assessment - risk management - system reliability - uncertainty analysis - digitalization and big data - prognostics and system health management - occupational safety - accident and incident modeling - maintenance modeling and applications - simulation for safety and reliability analysis - dynamic risk and barrier management - organizational factors and safety culture - human factors and human reliability - resilience engineering - structural reliability - natural hazards - security - economic analysis in risk managemen

Use, Operation and Maintenance of Renewable Energy Systems:Experiences and Future Approaches

The aim of this book is to put the reader in contact with real experiences, current and future trends in the context of the use, exploitation and maintenance of renewable energy systems around the world. Today the constant increase of production plants of renewable energy is guided by important social, economical, environmental and technical considerations. The substitution of traditional methods of energy production is a challenge in the current context. New strategies of exploitation, new uses of energy and new maintenance procedures are emerging naturally as isolated actions for solving the integration of these new aspects in the current systems of energy production. This book puts together different experiences in order to be a valuable instrument of reference to take into account when a system of renewable energy production is in operation

Writing Science Through Critical Thinking

Written and extensively class tested with NSF/NIH support, this timely and useful text addresses a crucial need which is acknowledged in most universities and colleges. It is the need for students to learn to write in the context of their field of study; in this case science. Although numerous how to writing books have been published, few, if any, address the central pedagogical issues underlying the process of learning to think and write scientifically. The direct connection between this writing skill and that of critical thinking is developed with engaging style by the author, an English professor. Moriarty\u27s book is an invaluable guide for both undergraduate and graduate science students. In the process of learning the specific requirements of organization demanded by scientific writing, students will develop strategies for thinking through their scientific research, well before they sit down to write. This instructive text will be useful to students who need to satisfy a science writing proficiency requirement in the context of a science course, a course in technical writing, advanced composition, or writing for the profession.https://digitalcommons.hollins.edu/facbooks/1047/thumbnail.jp

Plant Physiology, Development and Metabolism

Water is one of the most important constituents of life. Chemically, water is the hydride of oxygen. Oxygen, being more electronegative, exerts a strong attractive pull on its electrons. This unequal attraction results in small positive charge on twohydrogenmoleculesandasmallnegativechargeontheoxygenmolecule.The two lone pairs of electrons of the oxygen molecule result in bending of water molecule. The partial charges on oxygen and hydrogen molecules result in high electric dipole moment and polarity of water molecule