Tuesday, May 26, 2020
What Is the Shear Modulus Definition and Examples
The shear modulus is defined as the ratio of shear stress to shear strain. It is also known as the modulus of rigidity and may be denoted by G or less commonly by S orà à ¼. The SI unit of shear modulus is the Pascal (Pa), but values are usually expressed in gigapascals (GPa). In English units, shear modulus is given in terms of pounds per square inch (PSI) or kilo (thousands) pounds per square in (ksi). A large shear modulus value indicates a solid is highly rigid. In other words, a large force is required to produce deformation.A small shear modulus value indicates a solid is soft or flexible. Little force is needed to deform it.One definition of a fluid is a substance with a shear modulus of zero. Any force deforms its surface. Shear Modulus Equation The shear modulus is determined by measuring the deformation of a solid from applying a force parallel to one surface of a solid, while an opposing force acts on its opposite surface and holds the solid in place. Think of shear as pushing against one side of a block, with friction as the opposing force. Another example would be attempting to cut wire or hair with dull scissors. The equation for the shear modulus is: G Ãâxy / à ³xy F/A / Ãâx/l Fl / AÃâx Where: G is the shear modulus or modulus of rigidityÃâxy is the shear stressà ³xy is the shear strainA is the area over which the force actsÃâx is the transverse displacementl is the initial length Shear strain is Ãâx/l tan à ¸ or sometimes à ¸, where à ¸ is the angle formed by the deformation produced by the applied force. Example Calculation For example, find the shear modulus of a sample under a stress of 4x104 N/m2 experiencing a strain of 5x10-2. G Ãâ / à ³ (4x104 N/m2) / (5x10-2) 8x105 N/m2 or 8x105 Pa 800à KPa Isotropic and Anisotropic Materials Some materials are isotropic with respect to shear, meaning the deformation in response to a force is the same regardless of orientation. Other materials are anisotropic and respond differently to stress or strain depending on orientation. Anisotropic materials are much more susceptible to shear along one axis than another. For example, consider the behavior of a block of wood and how it might respond to a force applied parallel to the wood grain compared to its response to a force applied perpendicular to the grain. Considerà the way a diamond responds to an applied force. How readily the crystal shears depends on the orientation of the force with respect to the crystal lattice. Effect of Temperature and Pressure As you might expect, a materials response to an applied force changes with temperature and pressure. In metals, shear modulus typically decreases with increasing temperature. Rigidity decreases with increasing pressure. Three models used to predict the effects of temperature and pressure on shear modulus are the Mechanical Threshold Stress (MTS) plastic flow stress model, the Nadal and LePoac (NP) shear modulus model, and the Steinberg-Cochran-Guinan (SCG) shear modulus model. For metals, there tends to be a region of temperature and pressures over which change in shear modulus is linear. Outside of this range, modeling behavior is trickier. Table of Shear Modulus Values This is a table of sample shear modulus values at room temperature. Soft, flexible materials tend to have low shear modulus values. Alkaline earth and basic metals have intermediate values. Transition metals and alloys have high values. Diamond, a hard and stiff substance, has an extremely high shear modulus. Material Shear Modulus (GPa) Rubber 0.0006 Polyethylene 0.117 Plywood 0.62 Nylon 4.1 Lead (Pb) 13.1 Magnesium (Mg) 16.5 Cadmium (Cd) 19 Kevlar 19 Concrete 21 Aluminum (Al) 25.5 Glass 26.2 Brass 40 Titanium (Ti) 41.1 Copper (Cu) 44.7 Iron (Fe) 52.5 Steel 79.3 Diamond (C) 478.0 Note that the values for Youngs modulus follow a similar trend. Youngs modulus is a measure of a solids stiffness or linear resistance to deformation. Shear modulus, Youngs modulus, and bulk modulus are modulii of elasticity, all based on Hookes law andà connected to each other via equations. Sources Crandall, Dahl, Lardner (1959). An Introduction to the Mechanics of Solids. Boston: McGraw-Hill. ISBN 0-07-013441-3.Guinan, M; Steinberg, D (1974). Pressure and temperature derivatives of the isotropic polycrystalline shear modulus for 65 elements. Journal of Physics and Chemistry of Solids. 35 (11): 1501. doi:10.1016/S0022-3697(74)80278-7Landau L.D., Pitaevskii, L.P., Kosevich, A.M., Lifshitz E.M. (1970).à Theory of Elasticity, vol. 7. (Theoretical Physics).à 3rd Ed. Pergamon: Oxford. ISBN:978-0750626330Varshni, Y. (1981). Temperature Dependence of the Elastic Constants.à Physical Review B.à 2à (10): 3952.
Friday, May 15, 2020
Education Differences Have Made A Child s Education
There doesnââ¬â¢t go a day where thinking about education differences have made a childââ¬â¢s education much different than what is expected. Todayââ¬â¢s society are suffering from the same injustice that our ancestors have gone through. I personally have experienced a type of segregation of education because of being middle class and because of my race. There is a need for equal education systems that can help children of this generation better understand the curriculum and not have to put behind because of who they are and where they come from. Children suffer the most when they are not taught well enough to their abilities that can be shown. There are ways teachers can help advance the knowledge of students by expanding their abilities and explain things better than they believe is best. When one teacher believes their way of teaching is better than other teachers it is hard to tell when you canââ¬â¢t see it personally. Ones abilities are too limited to what wiser peop le can give to you. ââ¬Å"In Math, when two-digit division was introduced, the teacher in one school gave a four-minute lecture on what the terms are called. The children were to copy these names in their notebooksâ⬠¦ the math teacher in the other working-class school followed similar procedures regarding two-digit division and at one point her class seemed confused. She said, ââ¬ËYouââ¬â¢re confusing yourselves. Youââ¬â¢re tensing up. Remember, when you do this, itââ¬â¢s the same steps over and over again- and thatââ¬â¢s the way division alwaysShow MoreRelatedA Child s Education Is Vital991 Words à |à 4 Pagescharacter of a childââ¬â¢s life and education, especially those children of poverty? These questions are important to consider for educators and all involved in the goal for children to have greater achievement. It s even more important to note that forty percent of the poor, in the United States, are children (Stevenson, 1997). Knowing this is the re ason that finding solutions and studying the effects of parent involvement, both at school and at home, can have on a childââ¬â¢s education is vital. This paper willRead MoreHomeless Child Education : Homeless Children1678 Words à |à 7 PagesHomeless Children Education Several factors severely compromise the ability of homeless children to succeed in school, as I discovered in interviews with 277 homeless families in New York City in 1988. Barriers to the success of these children include health problems, hunger, transportation obstacles, and difficulty obtaining school clothes and suppliesà ¢Ã¢â ¬Ã¢â¬ all of which are linked to low attendance rates (Rafferty and Rollins 1989). 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Wednesday, May 6, 2020
The Effects Of Outdoor Play On Children - 1120 Words
Outdoor Play In todayââ¬â¢s society, we have increasing numbers of obesity in children. Researchers are trying to find the answer as to why this is happening. The sad part is, no one has looked at the numbers of how much time a child spends outside has decreased over the last decade. We have increasing numbers of technology being produced on the market and fail to look at how technology has harmed humans in a biological sense. There has been evidence of blue-violet light, produced from smart phones, is related to macular degeneration, where a macula sits in front of the ocular nerve prohibit loss of central vision (Newsbeat, 2014). Why should our world fall into the trap of smartphones and devices and forget about the outdoors? Playing outdoors stimulates many things for children, along with keeping them healthy. One blog promotes playing outdoors and explains the enhancement of development that happens when a child is outside. Itââ¬â¢s time our children step away from technolo gy and learn the greatness of the outdoors. Laurie Hollman (2016), a psychoanalyst, wrote an article on Huffington post explaining the positive effects of playing outdoors has on children. When a child is able to play outside, they are first learning to coordinate their body with their surroundings. This can either be through playing with a ball, using a swing, playing on a jungle gym, or even playing hop-scotch. When a child is playing with parent outside they are building a relationship. This relationshipShow MoreRelatedThe Effects Of Outdoor Play On Children1860 Words à |à 8 PagesOutdoor Play In todayââ¬â¢s society, we have increasing numbers of obesity in children. Researchers are trying to find the answer as to why this is happening. The sad part is, no one has looked at the numbers of how much time a child spends outside has decreased over the last decade. 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The history of children s programming shows an increase in quality programming and new content for children is constantly being made with networks like Nickelodeon announcing more than 650Read MoreThe Crucible - Comparing Play and Movie1004 Words à |à 5 Pages#9;Arthur Miller s play, The Crucible, and the movie with the same name have many differences and similarities, all of which contribute to the individual effectiveness of each in conveying their central message. #9;There are several additions and variances in the movie. First of all, the scene where the children and Tituba are dancing in the forest is never seen in the forest; we simply learn of it from dialogue. This scene was most probably added in the movie for a dramatic effect: foreshadowingRead MoreThe Health Of A Landscape1282 Words à |à 6 Pagesphysical surroundings can have an impact on their overall health. With a contemporary cultural emphasis on healthy living, land planners including urban designers and landscape architects have unique opportunities to integrate health into our everyday outdoor spaces. In a publication written by Landscape Institute, a Royal Chartered Institute for Landscape Architects and land planners, there are 5 essential principles that contribute to the success of a ââ¬Ëhealthy landscapeââ¬â¢. Principle 1 ââ¬Å"Healthy places
Tuesday, May 5, 2020
Renaissance Art Essay Example For Students
Renaissance Art Essay As we move into the Renaissance period, artists of the fifteenth-century represented a variety of textures, shapes, and spaces that they experienced around them in their lives. They developed a style of painting called linear perspective which would allow them to reflect simulations of three-dimensional forms arranged in space. This would give the painting a depth and realism not seen until now in the different eras. There was a heavy emphasis placed on the realistic portrait-like paintings giving a life-like sense to the images. This Humanist style of painting placed retreat value on science reason, and the individual while keeping an unwavering religious faith style. One of the techniques developed in Northern Europe was oil painting, unlike the Italian artist, the northern artists painted in oil on canvas. Oil paint takes much longer to dry allowing the painter time to easily make changes. The long drying process would allow the paint to dry smooth erasing the brush strokes. More importantly, oil paint is translucent when applied in thin layers, known as glazes. This method of built up glazes would let the light penetrate to the lower areas and then reflect back which would create the appearance of an interior glow, giving viewers the illusion that they were looking at real objects rather than painted imitations. Italian artists favored tempera, the method of suspending powered pigments in oils like linseed or sometimes walnut. One large difference from the Northern oils was that tempera had to be precisely applied as it dried almost immediately. Also, tempera has an opaque finish which did not allow light to penetrate to the lower layers not allowing the reflections, this resulted in a matte or dull finish unless a layer f varnish is applied to give the painting a sheen. As we notice in figure 12-4 below, we see that the artists stay with some of the Christian features so well known in the Gothic and Romanesque periods except for a much more real or life-like detail. The patrons who funded this pious donation appear on the outside of the polyphonys shutters, much brighter than the rest of the images in the otherwise sober painting, which is only visible when in the closed position. When in the open position however, the upper seven panels are vibrant and colorful depicting God, Mary, John the Baptist, angelic musical ensembles, and ending tit Adam and Eve shown in startlingly lifelike nudes. The lower five panels are shown in almost amazing realistic images of meadows, woods cities and a diverse mixture of apostles, saints, confessors, virgins, martyrs, hermits, pilgrims Assemble to adore the Lamb of God as described in the book of Revelation. Fig. 12-4 (Closed) Fig. 12-4 (open) Italian painters and artists aimed at achieving lifelike figures like their counterparts in the north but focusing on idealized figures in three-dimensional forms set within a rationally organized space using linear perspective. If we look at fugue 12-7, we see the lifeli ke images of Mary, Joseph adoring the newborn Jesus with a host of angels sympathetic expressions on the faces of the on lookers. Fig. 12-7 During this time in the Renaissance era, southern Europe rebirths the nude in the artworks as was a normal in early Greek art. Figure 13-11 below, Michelangelo David, the fugue embodies the antique ideal of the athletic male, the facial expression on the other hand is a stark difference from the earlier arts showing emotional power and a concentrated glaze. Looking at figure 13-12, The Creation of Adam, Michelangelo captures the instance when god tasks him with the spark of life. The facial expressions and the body interaction are extremely evolved from the earlier Greek works and exhibits a more humanistic appearance. Figure 13-10, Interior, Sistine Chapel, Michelangelo painted images depicting the sincere empathetic expressions so well known to the Italian Classicism of Southern Europe. Fig. 13-9 Fig. 13-10 Fig. 13-12 The relationship between the artist and patron appears to have been somewhat comparable to what [the relationship between a ball player and his/her agent. The patron more often than not would be the subject of the painting.
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