Tuesday, November 5, 2019
All About Mettre - Irregular French Verb
All About Mettre - Irregular French Verb Mettre, which means to put, is one of the most common French verbs. It is irregular in conjugation and is found in a number of idiomatic expressions.Using mettreMettre means to put:   Jai mis les livres sur la table.   I put the books on the table.   Il faut mettre sa famille avant son travail.   You have to put your family before your work.   Mettez les mains en lair.   Put your hands in the air.   Il veut mettre de largent dans votre affaire.   He wants to put money into your business.Mettre has various other meanings as well.1. to put on   Tu dois mettre un pull.   You need to put on a sweater.2. to spend time on   Jai mis deux semaines le faire.   I spent two weeks doing it.3. to turn on, activate   Peux-tu mettre la radio ?   Could you turn on the radio?4. to suppose   Mettons quil a raison....   Supposing / Lets just say that hes ri ght....Mettre noun infinitive means to put something up/out/on to do something:   Jai mis de leau bouillir.   I put some water on to boil.    Il doit mettre le linge sà ©cher.   He has to put (hang) the laundry up to dry.Se mettreSe mettre also has many different meanings.1. to put oneself   Mets-toi cà ´tà © de ton frà ¨re.   Put yourself next to your brother, Go sit/stand next to your brother.   Je dois me mettre lombre.   I have to get into the shade.(figurative)   Je ne sais pas oà ¹ me mettre.   I dont know where to look / what to do with myself.   se mettre dans une situation dà ©licate   to put/get oneself into a delicate situation2. to become (weather)   Il va se mettre au froid demain.   Its going to get/turn cold tomorrow.   Il sest mis au chaud.   It got hot.3. se mettre - to start, set to, take up   Il sest enfin mis au travail.   He finally started working.   Je vais me mettre la danse.   Im going to take up dancing.   Quand vas -tu te mettre à ©tudier ?   When are you going to start / set about studying?Expressions with mettre   mettre lessai - to put to the test   mettre en relief - to accentuate, bring out, emphasize   Il y a mis le temps ! - He took his sweet time about it!   se mettre au rà ©gime - to go on a diet   More expressions with mettreConjugationsPresent tense   je mets   tu mets   il met   nous mettons   vous mettez   ils mettentAll tenses
Saturday, November 2, 2019
Diversity in the United States Term Paper Example | Topics and Well Written Essays - 1000 words
Diversity in the United States - Term Paper Example Diversity in the United States I had always known about the settlers from Europe and their conflict with the Native Indians in the early days, but I had not realized just how many different national origins have made up the people of the modern United States. Looking at modern American culture, with such different styles as Hollywood films, rappers, classical orchestras and all kinds of local folk, country and rock music it is obvious that a creative mixture is going on. Learning about the different groups, such as Africans, British, Italians, Spanish, Japanese, Puerto Ricans, Mexicans etc, has opened my eyes to the rich cultural history that we all share. When I see this big range of cultures, this helps me to understand that immigration is a permanent and healthy tradition that America needs to manage well. People want to come here, because it is a great country to live in, but at the same time, we need to find ways to accept each other and get along peacefully together. My own background already combines two ve ry different cultures, since my parents are from the Philippines and Jordan. I grew up in a Muslim country, with a Muslim father and Christian mother. I can see that there are many differences between these two major religions, but what I have learned is that both of them have a belief in God, and both of them deserve our respect. I have seen how Muslims looked down on Christians (in Jordan) and Christians looked down on Muslims (in the United States) and this shows me that people are influenced by their own place of birth, rather than by any particular logic. I think my mother must have endured quite a lot of hardship to be married to my father and I think it took great courage for her to bring me to the United States and start a new life in a new country. She has been able to find a job, and I have been able to learn English, because this country welcomed us at a time when we needed a safe place to go to. Seeing this against the background of America’s history of diversity makes me very proud to have joined the many thousands who have brought their own culture into this country. I think that in the next thirty years or so there will be more immigrants to the US, including some from China, because of the attraction of the lifestyle and the freedom to think and speak what you want to. I hope that there will be a better agreement about immigrants from Mexico and the South American countries, because I believe that this has the potential to cause some tensions if it is not regulated properly. One big change that I see coming in the next thirty years is that there will be more people like myself who have a mixed heritage of more than one culture. Hispanic and Asian populations are growing faster, and so the proportion of these groups is likely to rise (Census Bureau, 2011). I think this is a good thing, and it will make people generally more tolerant. This is because second and third generation immigrants tend to marry outside of the narrow culture of thei r parents, and this will bring about more mixing of cultures, and more children who have the benefit of seeing things through different perspectives. A big challenge that the U.S. faces is the fact that different cultures have strong views about some issues, such as
Thursday, October 31, 2019
Violence in Education Research Paper Example | Topics and Well Written Essays - 1750 words
Violence in Education - Research Paper Example This essay highlights that education is a very critical sector in the economy of any nation as it contributes too much in terms of expertise and professional knowledge which can be utilized in various fields for achievement of success and progress. It is also through education that many problems faced by the contemporary society are eradicated for instance poverty and ignorance. Despite its importance, education is faced with numerous challenges that hinder its success in one way or the other for example lack of adequate resources and facilities, poor management and violence among others. According to the report findings education is a very instrumental aspect to every individual, the society, a nation and the world at large. Every person should be entitled to education to the highest possible level with favorable conditions that allows for excellence. This is so because education is a significant building block in regard to the growth and development of human beings as it acts as a driving force towards improved living standards and also development through aspects like reduction of poverty, promotion of peace and stability, improvement of health, promotion of gender equality among other aspects. All this is made possible because people get enlightened when they go through various education systems which instill a lot of knowledge in a wide range of life issues hence helping them in general decision making and problem solving. Education sector is faced with a lot of challenges violence being one of them.
Tuesday, October 29, 2019
Impairments of intangible (including goodwill) Research Paper
Impairments of intangible (including goodwill) - Research Paper Example Under the USA GAAP principle, the methodology used for the determination of the impairment of long lived assets is based on the two step approach. In the two steps approach, the first step requires test of recoverability. In this test, the comparison of the carrying amount and future amount of discounted cash flows from the using and disposing. In case, the assets are determined to be not recoverable than impairment testing conduct becomes mandatory. Contrary to this, in the IFRS system one step approach is employed. Under this system, the existence of the impairment indicators makes it mandatory for the application of the impairment testing (EY, a). The second major difference in the treatment of intangible assets in US GAAP and IFRS exist in calculation of the loss in the impairment of long lived assets. Under the system of US GAAP using FAS 157 entitled Fair Value Measurement is employed and the loss calculation is difference between the carrying amounts to the fair value amount. On the other hand, the IFRS system of financial reporting, the calculation of the loss is conducted by measuring the difference between the carrying amount and the recoverable amount. The recoverable amount is measured as either the fair value net of cost of selling or value in use or value indicating future value of discounted cash flow including the amount received after disposal. ... Additionally, the reporting unit can also be accounted in the level under operating segment or the component. In the IFRS financial reporting of corporate accounts, the allocation of goodwill is conducted differently. Goodwill in the IFRS system is allocated either in the group of Cash Generation Unit (CGU) or CGU itself. Allocation of the Goodwill in the group of CGU represents lowest level from which the internal management monitors goodwill for internal assessment IAS 36.6. Importantly, this group, by law of IFRS 8 (Operating Segment) cannot larger than operating segments (EY, a). In addition to the goodwill allocation carrying differences in the two internationally followed systems of reporting of corporate accounts, methodology for the determination of impairment of goodwill also varies. Corporate accountants using US GAAP system of reporting has to imply the two step approach or methodology for the determining the requisite impairment. Under two-step approach requires performin g the recoverability test at the level of reporting unit in which the allocation of goodwill is conducted. In this initial test, the net amount of difference of the reporting unit’s carrying value to the reporting unit’s fair values is conducted. Positive difference between the carrying value and the fair value of the reporting unit makes it mandatory to perform the impairment test for the goodwill. Companies using IFRS system of developing the financial accounts apply the one step approach. Under the IFRS system it is simply mandated to conduct the impairment test. The impairment test of goodwill is conducted at CGU unit. Under this approach, the comparison of the carrying amount at CGU level with recoverable amount is conducted while carrying amount
Sunday, October 27, 2019
Teachers role in Facilitating Learning
Teachers role in Facilitating Learning To fully understand, appreciate and reflect on this title, I will have to study three, very different, yet at the same time inherently linked facets of the education spectrum. Firstly, the role of the teacher will have to be explored and the functions and responsibilities this position entails. Are teachers just lecturing child-minders, or are they fundamental, not only to a childs learning in school, but to their social and moral development and education? Secondly, what children learn, how children learn, and how we, as educators, learn with them, are crucial aspects which cannot be ignored. And thirdly, I will refer to the aforementioned areas of teaching within the context of key stage 3 and 4 English. The precise role of the teacher varies, but educator and role-model are two essential parts. Teachers have a responsibility and a moral duty (and are legally contracted), to assist the development of a pupils learning throughout their school life, whether they are in a lesson or during any other scholastic situation. Teachers and pupils have to co-exist, live and work within the confines of a school, and the reasons why many children just cannot cope with this set-up are many. To minimize these potential problems, the teacher therefore has to cater for every pupils different needs, (race, gender, SEN etc). A teacher can do this by researching particular pupils asking previous teachers, seeing SAT scores and literacy and numeracy levels. Consulting the Senco can be beneficial if there are concerns over teaching somebody with special educational needs. Understanding and accepting pupils differences, whether they are educational, religious or cultural have to be, not tackled, but worked through with all parties present. A working relationship has to develop where the teacher can initiate and then assist learning and the pupil can respond in their own way. Knowing the pupils individually is of vital importance in knocking down walls and building bridges. The pupils knowing the teacher and the teache rs consistencies of discipline, standards and expectations, can benefit the two-way relationship. Both parties know each others likes, dislikes and boundaries etc. Children are constantly underestimated, they frequently gauge and assess the teacher, acting and reacting in different situations with different teachers, so its important to assert yourself and get that relationship right. This is a key target for me; because I worked as a teaching assistant at The Woodroffe, I had to create a formality between myself and a few of the pupils, whereas before it was beneficial to have a more relaxed approach to get the job done. In English, the teacher has several key tasks which help children to get the most out of the subject: giving the pupils confidence to try when reading and when writing and to give them the relevant skills. Encouraging them to share opinions and interact with their peers through discussion speaking and listening. Introduce literature and language variation. Help them to understand the authors craft reading for meaning. They should be given access to our literary heritage and texts from different cultures and traditions. Recognise where a pupil may benefit from drama and ICT related lessons and then differentiate accordingly. Teachers should consolidate this information with media topics and theories to expand knowledge and understanding. The ability to fuse these areas is a teachers aim. The teacher constantly has to push the boundaries, challenge the pupils to get them out of their comfort-zone. There is an element of risk involved for the teacher in attempting a balanced but chall enging lesson. There is also risk for many pupils in different ways: Some of us are risk tolerant and some of us are risk averse with all points equally represented. If you are in a learning situation and anxiety tips into stress, then what happens next is predictable. There are four categories of survival response available to you. A teacher or anyone is involved in formally educating others will be familiar with them. They are fight, flight, freeze and flock. You show resistance or fight the source of stress, you flee from it, you freeze in the face of it or you hang out with others like you or flock from it. If you have an accumulation of stressors that leave you feeling out of control, then the four Fs are what is left for you. [1] The teacher regularly reviews the boundaries to reduce the usage of these defence mechanisms. These four Fs are prevalent in English where in ascertaining whether the students have understood, the teacher will direct questions to random pupils, which in their eyes might be thought of as picking on. Speaking and listening tasks can offer problems to some students who may be good in other areas and some pupils respond by using one of these defence mechanisms because they lack the basic skills needed. What the teacher can do to alleviate this problem is to fore-warn the class that questions will be asked, nominate a table, group or pairs for an answer and say what type of questions you are going to ask, building up from easy questions to harder questions. A quieter student could be asked before the lesson if they felt okay with answering a question/performing a poem etc. A certain degree of sensitivity and common sense is needed when considering this question. Because English is such a varied subject that encompasses many different teaching and learning styles, it can be difficult to teach and consider the different and necessary approaches. Key stage 3 can be problematic at The Woodroffe as the classes are of mixed ability with a vast range of skills and needs. Key stage 4 are put into sets which, although can help with differentiation, means the need to further challenge pupils becomes more apparent. Pupils know every trick in the book, every survival technique that will help them to stay alive in the jungle that is their classroom. The teacher has to remain one step ahead of them, using their motivational techniques along with a good lesson, to keep the class participating. Knowing each pupil and their needs is of vital importance to the teacher. The balance of praise and criticism in teaching is an ongoing debate and an issue of common sense. Educational psychologists, writers, theorists, parents and teachers have all added their ideas to the following questions: Is it three ticks to one cross? Do you give out fewer ticks as the pupils get older? Do you mark in green or red pen? These are just some of the basic questions that are trying to be answered. At my school there is an Assessment For Learning initiative set up where a group of teachers have volunteered to try many of these schemes. They meet up quarterly to share results. From attending one of these meetings and by witnessing them in class, I am now aiming to use one or two of the ideas in my lessons. For instance, the question of how to mark effectively: Within this context it is very difficult to state what type of marking is needed and where. One possible rule offered is that you dont highlight every spelling mistake, especially for the lower ability groups. This issue splits teachers. As previously mentioned, I feel that this is an issue of common sense depending on the context of the situation. There is also the question of summative vs. formative marking, but does there have to be verses, they can co-exist together. Sometimes a comment is more beneficial to the student than a grade. Some students may prefer to see a mark or grade so that they can easily see improvement. There is ongoing research into this area. Choosing which type of marking to use is a matter for each individual teacher and their individual students. Again, it is your knowledge of the pupils as individuals, building on your expectations for them, what they are achieving and what they should be achieving and getting the pupil to recognise these expectations. Just as two pupils are never the same, the marking, comments and grades reflect this. Teachers have to regulate and differentiate and only by knowing the pupils, (SEN, background, social problems etc) will this occur. I have realised that some pupils benefit from formative marking and that some crave a grade or number so that they see if they are progressing. It appears to me that higher ability students like to see the grades. I was asked recently by a higher ability year 12 student to give a grade for a piece of homework where I had just put a constructive comment. Putting crosses in red, underlining incorrect spelling and putting see me! at the end of the work, are all methods which we are familiar with, but how many teachers actually appreciate and celebrate pupils work? At every level pupils like to see their work appreciated by the teacher and the class. They like to know that they understood the question or showed a great deal of effort. They like to be rewarded appropriately and consistently. For some pupils just to finish a piece of work is a cause for celebration. This celebration should be differentiated by the teacher in accordance with individual expectations. Linked with praise and criticism is target-setting. A current theme in schools is for the student and teacher to work together to set the pupils targets for the term/year etc. The theory behind this idea is to involve the pupil as much as possible so they can create manageable targets. Also, they are more likely to resist completely if a teacher were to set their targets and force-feed them to the student. In English, setting targets, no matter how small and achieving them is the basis for progression in learning. Targets could include spelling certain words, taking part more in class discussions, not calling out or handwriting. Again, this target setting is heavily differentiated and that is why I feel it is a good idea to involve the student, they know probably better than the teacher where they need to improve. I have worked with students and other teachers setting literacy targets and behavioural targets in other schools and at The Woodroffe. We adjusted the targets by looking at levels and listening to comments from other teachers, not just in English. This idea attempts to motivate students by shifting the responsibility, from the teacher to the pupil, involving them more in their learning. This is just one facet of an interactive movement within education today; self-marking and self-evaluation are important tools in the classroom for all key stages. Just recently I asked a year 10 group to mark their own work as if they were a teacher. The comments and grades that I were shown were very interesting, the amount of constructive reflection was very surprising. This allows the students to see their work from a teachers perspective what they will be marked on and how the teacher allocates marks for spelling and handwriting, for example. The idea is to create reflective pupils. Pupil responsibility is the current catchphrase, although some students understand the reasoning behind the idea more than others. In my year 9 lessons, preparing for their SATS, I ma ke very explicit what they will be marked on for each type of question. They are given the mark scheme to mark their own mock papers. This seems to help them a great deal and they are beginning to realise that teachers dont just give a random grade with could do better on the bottom. A teacher has to consider the use of the different learning styles: visual, auditory and kinaesthetic. Visual learners like to see what they learn, auditory learners like to hear what they learn and kinaesthetic learners like to be physically involved in what they learn. They should be used together and this cross-over is of vital importance in an inclusive learning environment. In English, skills are needed that incorporate different styles of teaching (reading, writing, watching, speaking, listening, performing). When planning, teachers have to accommodate all the methods to make sure they appeal to all the different types of learners in their class. Across both key stages I have aimed to deliver a varied programme within the lesson; when I am explaining something I try to express it clearly and concisely, have what I am saying on the board, sometimes with a picture and by giving out helpful handouts. By demonstrating something as I am explaining it, especially in drama and speakin g and listening, helps to address all the different types of learners. Also, I prefer to set work involving a mixture doing tasks, reading tasks, written tasks, whilst incorporating drama and ICT. Flexibility within a lesson structure is a key theme. Recognising where to be flexible is a trait of a good teacher: (Is this too easy for them shall I move on to something more challenging? Did they get all that shall I go over it again?) Because of the wide range of topics in English, a well-structured lesson should be planned, although digression in a lesson, especially when instigated by a pupils question, can be beneficial to develop. It is beneficial if a teacher is enthusiastic and is able to enthuse students. This enthusiasm should be considered a valuable resource, just like the teachers subject knowledge. The knowledge of, understanding and using resources are essential for enhancing the learning experience. Resources can be varied and obviously differ between subjects, classrooms and teachers. Resources can include such things as: Teacher knowledge Student knowledge Teaching Assistants I.C.T. computers, O.H.P.s, digital cameras, video cameras etc Research Homework A brilliant and effective lesson is very hard to achieve. A well-structured lesson is a must as long as there is flexibility allowed, as previously mentioned. Presentation and delivery are also important aspects to consider whilst not forgetting the power of the teacher to inspire: Use rich language and lots of repetition. Encourage learning behaviours noticing, naming, describing, speculating, questioning. Encourage physical exploration and robust play. (Smith, p.46) Other things that are found in a good lesson vary from subject to subject, factors that I consider crucial in English are: 1) Good planning and preparation. A well planned and prepared lesson is more likely to be a good one. Each learning objective and task to meet that objective is carefully considered to be beneficial to the students. This is an ongoing target, which I feel I have met to a basic level. 2) Knowing the pupils well. By knowing the pupils well you can cater for all their weaknesses and abilities, set achievable targets, expectations and boundaries. Again, I know the majority of my students and some of their weaknesses and strengths but I realise more background research on the pupils is needed. 3) Differentiation/learning styles. This is to benefit each student with their own needs and learning styles tailoring the lesson so that it is accessible to thirty or more students. This is a key aim of mine and although I feel I understand what is needed, I need to spend a great deal of time on this area. 4) Check understanding continually (also from assessment). I check at regular intervals by asking questions, checking books and work in lesson. This is important because it is vital to realise if you are going too fast or too slow. Students that dont understand will switch off. Also, knowing when you are going too fast is crucial and leads on to: 5) Consolidation building on prior knowledge/looking to future lessons. This can be added to the start of a lesson to refresh memories and to let the students know the content of the lesson. I feel I do consolidate consistently but it is an ongoing, rolling target of mine. 6) Appropriate working relationship with students. As previously mentioned, to benefit the student and the teacher, getting the correct balance has to be achieved. This is an area where I realised I needed to focus myself. I think I am gradually achieving that balance. A critical aspect of the facilitation of learning is the actual environment where the learning takes place, usually the classroom. Children are learning all the time, whether they know about it or not: There is a great deal of learning that goes on outside of conscious attention. The brain processes information that is neither attended to nor noticed and this process is pervasive and ongoing. Children can, in some situations, be learning without the involvement of the teacher! (Smith, p.161) There are other ways to make the classroom an enriched learning place and accessible to all. Behaviour is a major factor, if you have bad behaviour constantly and from different students, you may well question your choice of lesson for them. A lesson that is too easy for students is just as bad as a lesson that is too hard for them. Better behaviour means better learning. Classrooms become better places in which to study and more enjoyable to work in. [2] It is also beneficial to students and teachers alike, to be consistent when setting and enforcing rules and boundaries. By talking to staff and from my own experiences, I have realised this is an important aspect. Clarification, explanation and the displaying of rules and guidelines are essential as pupils learn best in ordered environments where boundaries are clear.(DfES 2003) It is easy to overlook the actual classroom space. This is an integral part to the students lessons. Is it light and airy? Is it overcrowded or badly set out? Are the wall displays overbearing, too busy? Or, are the displays subtly aiding learning by just being visible? Students are proud to see their own work on the walls and this sense of well-being can only help create a positive atmosphere. It is good for the students to know where everything is in a classroom. Are the dictionaries and other resources easily accessible? Are the tables and chairs set out in rows or in groups? Which way would suit the task you are about to set? I have always thought that this is an area that could easily be overlooked by teachers and although I aim to consider this factor, I find it difficult when I use twelve different rooms, some of them art and science rooms which are not conducive for teaching English. Differentiation is a major consideration in the classroom. Recognising, understanding and catering for every childs individual needs are essential; knowing the pupils, planning for them appropriately and setting achievable learning outcomes. Getting the balance between challenging content and achievement can be difficult, even for experienced teachers. That is why it is so important to know your pupils well, as previously discussed. What special educational needs do they have? What can you do to help them progress in their learning? In English, recognising reading and writing problems, are they dyslexic? Also, speaking and listening problems, autism and understanding these problems is necessary. How can you make your lessons more accessible for them? You can try to understand their problems and talk to the Senco about how to facilitate learning better. Have they any background or social problems? Teachers have to differentiate for the gifted and talented in their classes, with extens ion tasks combined with rewards, whilst not forgetting all the pupils in between. It is also a key aim for teachers to be reflective, recognising the good aspects of their teaching and developing them in order to facilitate progression in pupils learning. It is also necessary for them to realise where their teaching techniques and methods can be improved to achieve their full potential as an educator, which in turn, will improve the student. Although I have only limited experience, one example is fresh in my mind: Whilst beginning to take a year 11 GCSE prep. group, I realised that because of their lack of motivation, they werent really benefiting from my lessons. I discussed the issue with my mentor and approached from a different angle, changing my lesson plans, tasks and delivery to get their attention and to offer the skills they needed to learn. I think that the role of the teacher is an indefinable idea. As times change, so do the responsibilities and duties for a teacher. One thing remains constant however, the main drive of teacher as educator. Although teachers wear many different hats, their actual teaching hat is never taken off, that is the one thing that takes precedence. As previously mentioned, teachers have to be flexible nowadays, and it is this pliability that has helped to make teaching such a demanding but rewarding career. Teaching has evolved and the roles are many and varied across the entire spectrum. There is a shift in telling the children what they need to know, to telling the children how to find out what they need to know, giving them the responsibility for their learning and development. In English, there is a drive towards prioritising what the child needs to progress on, students are marked and evaluated as individuals not as a whole class. Getting the balance between consolidation and moving the class on is a constant consideration and through teaching, teachers are learning how to adapt and improve so they can benefit the students to their full potential.
Friday, October 25, 2019
Teenage Alcohol Abuse Essay -- essays research papers
Is there ever going to be an end of teenagers drinking before they are allowed to according to law? In today’s society teenagers walk around as if they know exactly what is good for them, as if they are invincible. Take a look at the number of crashes caused every year by teenage under-aged drinkers and how alcohol effects their future and see how bold of a word invincibility is. Issues that need to be considered when it comes to alcohol are the medical conditions it gives people, how alcohol effects each teenagers future, and who the people are that are inspiring teenagers to drink. People have the right to drink but because of law teenagers are not legally allowed to. There is a reason for everything and this is to keep everyone safe. Alcohol has a major effect on people medically, especially teenagers. Between the years 1988-1996, there was between 130-150 deaths each year caused medically by the use of alcohol. Believe it or not but alcohol is the most commonly consumed drug in New Zealand. It causes cancer, high blood pressure, haemorrhagic strokes, cardiac conditions...
Thursday, October 24, 2019
Lab Test: Tensile Testing
The mechanical properties of materials are determined by performing carefully designed laboratory experiments that replicate as nearly as possible the service conditions. In real life, there are many factors involved in the nature in which loads are applied on a material. The following are some common examples of modes in which loads might be applied: tensile, compressive, and shear. These properties are important In materials selections for mechanical design. Other factors that often complicate the design process Include temperature and time factors.The topic of this lab is confined to the tensile property of polymers. Figure 1 shows a tensile testing machine similar to the one used in this lab. This test is a destructive method, in which a specimen of a standard shape and dimensions (prepared according to ASTM D 638: standard test method for tensile properties of plastics) is subjected to an axial load. During a typical tensile experiment, a dog-bone shaped specimen Is gripped at I ts two ends and Is pulled to elongate at a determined rate to Its breakpoint; a highly ductile polymer may not reach its breakpoint.The tensile tester seed in this lab is manufactured by Insertion (model 5569). It has a maximum load of 2 or 50 ink and a variable pulling rate. The setup of the experiment could be changed to accommodate different types of mechanical testing, according to the ASTM standard (e. G. Compression test, etc). For analytical purposes, a plot of stress (o) versus strain (E) Is constructed during a tensile test experiment, which can be done automatically on the software provided by the instrument manufacturer. Stress, in the metric system, is usually measured in N/ mm or Pa, such that 1 N/mm = 1 Pa.From the experiment, the value of stress is lactated by dividing the amount of force (F) applied by the machine in the axial direction by its cross-sectional area (A), which is measured prior to running the experiment. Mathematically, It Is expressed In Equation 1. T he strain values, which have no units, can be calculated using Equation 2, where L Is the Instantaneous length of the specimen and LO Is the initial length. (Equation 1) (Equation 2) A typical stress-strain curve would look like Figure 2. The stress-strain curve shown In Figure 2 Is a textbook example of a stress-strain curve.In reality, not all stress-strain curves perfectly resemble the one shown In Figure 2. This stress-strain curve Is typical for ductile metallic elements. Another thing to take note is that Figure 2 shows an â€Å"engineering stress-strain†curve. When a material reaches its ultimate stress strength of the stress-strain curve, its cross-sectional area reduces dramatically, a term known as necking. When the computer software plots the stress-strain curve, it assumes that the cross sectional area stays constant throughout the experiment, even during necking, therefore causing the curve to slope down.The â€Å"true†stress- change in the cross section al area of the specimen throughout the experiment. Theoretically, even without measuring the cross-sectional area of the specimen during the tensile experiment, the â€Å"true†stress-strain curve could still be constructed by assuming that the volume of the material stays the same. Using this concept, both the true stress (UT) and the true strain (ET) could be calculated using Equations 3 and 4, respectively. The derivation of these equations is beyond the scope of this lab report. Consult any standard mechanics textbook to learn more about these equations.In these equations, LO refers to the initial length of the specimen, L refers o the instantaneous length and o refers to the instantaneous stress. (Equation 3) (Equation 4) Figure 2 also shows that a stress-strain curve is divided into four regions: elastic, yielding, strain hardening (commonly occurs in metallic materials), and necking. The area under the curve represents the amount of energy needed to accomplish each of these â€Å"events. †The total area under the curve (up to the point of fracture) is also known as the modulus of toughness.This represents the amount of energy needed to break the sample, which could be compared to the impact energy of the sample, determined from impact tests. The area under the linear region of the curve is known as the modulus of resilience. This represents the minimum amount of energy needed to deform the sample. The linear region of the curve of Figure 2, which is called the elastic region (past this region, is called the plastic region), is the region where a material behaves elastically. The material will return to its original shape when a force is released while the material is in its elastic region.The slope of the curve, which can be calculated using Equation 5, is a constant and is an intrinsic property of material known as the elastic modulus, E. In metric units, it is usually expressed in Pascal (Pa). (Equation 5) Figure 3(a) shows typical stre ss-strain curves of polymers. The figure shows that materials that are hard and brittle do not deform very much before breaking and have very steep elastic modulo. The mechanical property of polymers generally depends on their degree of crystalline, molecular weights and glass transition temperature, Tug.Highly crystalline polymeric materials with a Tug above the room temperature are usually brittle, and vice versa. When a semi-crystalline polymer undergoes a tensile test, the amorphous chains, will become aligned. This is usually evident for transparent and translucent materials, which become opaque upon turning crystalline. Figure 3(b) shows a diagram showing the mechanical property of some common polymers. Important! Make sure you wear safety glasses before starting any operation. Your eyes could be hurt by a broken piece of polymer. Also wear gloves to protect against any residue on the machine and samples. . 1 Specimen Preparation The polymer specimens were injection-molded int o dog-bone shapes. Their dimensions were determined according to the ASTM D 638 standard mentioned earlier in the introduction. (1) Measure the thickness, width and gage length of polymer samples in mm. These dimensions should be approximately the same for each sample. (2) Also make note of any sample defects (e. G. Impurities, air bubbles, etc. ). The following samples will be tested: 1) Polypropylene (UP), polystyrene (AS), polycyclic acid (polymer), high density polyethylene (HIDE), and Dentally for analysis of mechanical properties. ) Polystyrene: to compare effects of feeding direction on mechanical properties. 3) Polypropylene: to analyze effects of strain rate on mechanical properties. . 2 Bluebill Software Setup 1) Turn on the tensile test machine. The switch is located on the right side of the machine. Also turn on the video extensors. (2)Go to the desktop and double-click on the â€Å"Bluebill†icon. (3) On the main page, select Test to start a new sample. Name your test and click Browse to select the folder you would like to save it in. Click next. (4) Choose which method you would like to use.Create and save a new method if needed. (5) Method set up: Save after any changes are made. General: used for display purposes Specimen: specifies sample dimensions and parameters. A doggone sample is used for tensile testing. Select rectangular, and specify the width, thickness and gauge length of the sample. The gauge length is the distance between the clamps before starting the test. Control: describes the actual test. Select extension for mode of displacement, then specify the rate of extension. Most use 5 mm/min or 50 min/mm, depending on if you want a slow or fast test.End of Test: identifies the criteria for the end of the test. A large load drop is experienced when sample failure occurs. For this test, when the sample load drops by a certain percentage of the peak load, he machine will stop. Data: specifies if the data is acquired manually or au tomatically, while the strain tab recognizes whether the strain is measured from the video exterminates or the extension. Results and Graphs: select what data is shown and how it is displayed. (1) Make sure the proper load cell is installed, either 2 ink or 50 ink depending on the load range and sensitivity of the sample.To switch load cells, make sure the machine is off. Unscrew the bolts and remove using the handle. Make sure to plug the new load cell into the port behind the machine. (2) Calibrate the load cell by licking on the button in the upper right hand corner. Make sure all loads are removed from the load cell and click calibrate. (3) Install the correct type of clamps for the testing. For tensile testing, non or ink samples can be used. Install the clamps using the pins. Also install height brackets if needed. Zero the load once the clamps are installed. 4) Press the up and down arrows on the controller until the clamps are Just touching. Press the reset gauge length butt on at the top of the screen to zero the position of the clamps. (5) Use the up and down arrows until the clamps are about 100 mm apart. This is a typical gauge length for the dog bone samples. (6) Place the polymer sample between the grips of both the tensile test machine. While holding the sample vertically with one hand, use another hand to turn the handle of the top grip in the closing direction as tightly as possible. The specimen should be gripped such that the two ends of the specimen are covered by the grip, approximately 3 mm away from its gage-length. It is important that the specimens are tightly gripped onto the specimen grips to prevent slipping, which will otherwise result in experimental errors. ) (8) Make sure that the specimen s vertically aligned, if not a torsion's force, rather than axial force, will result. (9) Turn the bottom handle in the â€Å"close†direction as tightly as possible. Visually verify that the sample is gripped symmetrically at its two en ds. 10)Zero the extension by pushing zero extension button at the top of the screen. Also zero the load if needed. Wait for a few seconds to let the computer return its value to zero. 2. 4 Tensile Test (1) Enter geometry of the sample before starting. (2) Click on the Start button. Both the upper and bottom grips will start moving in opposite directions according to the specified pulling rate. Observe the experiment at a safe distance (about 1. 5 meters away) at an angle and take note of the failure mode when the specimen fails. (NOTE: Be sure to wear safety glasses.Do not come close to equipment when the tensile test is running). (3) A plot of tensile stress (Amp) versus tensile strain (mm/mm) will be generated in real-time during the experiment. 2. 6 End of Test (1) The machine will stop automatically when the sample is broken. (2) Press the â€Å"Return†button on the digital controller. Both the upper and lower grips will be returned to their original positions automatica lly. 3) Turn the two handles in the open directions to remove the sample (4) Repeat the previous steps for any additional tests. 5) When finished, save your file and click Finish. This will export your data into a PDF and individual data files. (6) Clean up any broken fragments from the specimens. (7) Turn off the machine and exit the program when finished. Graph UP (50 mm/mm extension), AS (2 feed inputs), PLAN, HIDE and Dentally results using raw data files. There should be two tests for each polymer, but Just pick one to graph. Construct the true stress-strain curves for each polymer (hint: use Equations 3) and (4) provided in the Introduction section).Calculate Young Modulus for each material and testing condition and compare experimental values with literature values. Discuss any differences in mechanical behavior between the polymers (use pictures! ) Analyze the fracture modes of each sample (ductile fracture, brittle fracture, or intermediate fracture mode). Using the data fo r polypropylene, discuss the effects of strain rate on the mechanical behavior of the polymers. Using the data for polystyrene, compare effects of feed direction on the mechanical behavior. Explain any unexpected results.
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