Abrasive Flow Machining Essay Example for Free

Abrasive Flow Machining Essay 1. Introduction Abrasive flow machining (AFM) was firstly developed fifty years ago by Extrude Hone Corporation, USA. By using the liquid viscoelastic material with easy flowability made of polymer and abrasive grains, AFM can be used to polish, deburr and radius for the workpiece. There are three kinds of AFM: one-way AFM, two-way AFM and orbital AFM [1]. In this case to manufacture the cylinder heads, consider of two-way AFM is much more widely used and its technology is more mature, we also choose the two-way AFM to do the surface finishing. Schematic of two-way flow shows in figure below. Figure 1 principle of material removal mechanism in two-way AFM process [1] Prior to machining, liquid abrasive will be put into the lower medium cylinder, the designed fixture which clamping the workpiece will be fixed between two cylinders. The upper medium, lower medium cylinder and fixture will form a confined space. After heat the whole system to working temperature, by forcing the lower piston (usually by hydraulic), the liquid abrasive will be pressed into the channel formed by clamp and workpiece, then flow into the upper medium cylinder. After the stroke of lower piston finished, the upper piston will force the liquid abrasive back into lower cylinder [2], an operating cycle will be finished. See more: Beowulf essay essay 2. Three key elements of AFM 1) Machine tool Use to fasten the workpiece and fixture, and control the pressure applied on the workpiece, to adjust the degree of abrasive accuracy. 2) Liquid Abrasive Liquid abrasive is abrasive tool in the AFM, it should has following properties, a) Non-corroding and don’t adhere to the workpiece and human skin. b) Good adhesive properties between different abrasive grains. c) Be able to maintain the viscoelasticity for a long time d) Non-volatile and non-deteriorate after a long time preservation. e) Strong cohesion. For these properties, the conventional liquid abrasive is made from Semi-solid carrier which has viscoelasticity, flexibility and cutting property mixed with abrasive grains. Different intrinsic viscosities of different carriers, different types and size of abrasive grains can affect the final tolerance and roughness [2]. The most frequently used abrasives are silicon carbide, carborundum, Cubic Boron Nitride(CBN), aluminum oxide, the size of grain vary from 0.005mm to 1.5mm. Abrasive with high viscosity is mainly used to polish the walls of workpiece and large through-hole while low viscosity abrasive is primarily for radiusing the edge and polishing the small through-hole. 3) Fixture The function of fixture, a) Positioning and fixing the workpiece. b) Bearing clamping force for some workpiece. c) Constitute a channel for liquid abrasive with some machined surface of workpiece in suitable size and section. d) Realizing simultaneous machine multiple workpiece in one device. 3. Advantage of AFM, Abrasive flow machining has accuracy, stability and flexibility. It uses liquid abrasive to remove the metal material infinitesimally, deburr and radius the internal intersections of workpiece. At present, AFM is widely used in automotive industry and other manufacturing. The fundamental advantage of AFM is the liquid abrasive can reach the positions which are not easily be machined by tradition surface finish methods since the complexity of workpiece, polished surface evenly and in integrity, batch processing has the same result. These characteristics improve the performance of part, extend the working life, avoid the multifarious manual labour, and lower the intensity of labor. For example, when polish the intake-tube of vehicle by traditional process, the tube need to be cut into half, then welding after polishing, but using the AFM, cut and welding can be avoided [3]. 4. Geometrical and thermal effects. Viscosity of liquid abrasive will decrease when the working temperature enhances [3], and working ability of abrasive depends on its viscosity as the figure 2 shown. Figure 2 the machining effects of different viscosity of abrasive materials [5] Since cutting force is proportional to viscosity, so higher viscosity means stronger grinding ability, as a result abrasive with higher viscosity will get a better surface. In conclusion, temperature is a very important factor during the process. While the abrasive grains polish the surface, it will generate heat, enhancing the temperature as the figure 3 shown. Figure 3 Variation of rise in temperature of workpiece with number of cycles [4] The rise of temperature will make the working ability reduce. So cooling system is need during the process to ensure the best machined surface. Geometry of cylinder head also affects the result of surface finishing. Many small through-holes exist in the cylinder head, flow rate of abrasive is much bigger in these through-holes according to fluid mechanics, even these accelerations enhance grinding ability, but due to shearing force generated by abrasive being extrusion at narrow pass, it is evident that temperature will rise rapidly, lower the grinding ability. So geometrical effect need to consider when design a cylinder head. 1. Rhoades L.J., Kohut T.A., Reversible Unidirectional AFM, US patent number 5,070,652, Dec 10th, 1991. 2 Szulczynski, Hubert, Uhlmann, Eckart, MATERIAL REMOVAL MECHANISMS IN ABRASIVE FLOW MACHINING 3 Guizhen Song, THEORETICAL ANALYSIS AND EXPERIMENTAL RESEARCH ON ABRASIVE FLOW MACHINING 4 Rajendra K. Jain, V. K. Jain. Specific energy and temperature determination in abrasive flow machining process[J]. International Journal of Machine Tools Manufacture, 2001(41):1689-1704 5 Tang Yong, Zhou De-ming, Yang Gang, Machinability of Abrasive Flowing Machining. Journal of south china university of technology, 2001-9

The Usefulness of Structuralism as an Analytical Tool for Uncovering Ho

In the words of Michael O’Shaughnessy, ‘narratives, or stories, are a basic way of making sense of our experience’ (1999: 266). As a society and a culture, we use stories to comprehend and share our experiences, typically by constructing them with a beginning, middle and an end. In fact, the order that a narrative is structured will directly impact the way it is understood, particularly across cultures. This idea originated through Claude LÃ ©vi-Strauss’s concept of structuralism in anthropology which ‘is concerned with uncovering the common structural principles underlying specific and historically variable cultures and myth’ in pre-industrial societies (Strinati 2003: 85). In terms of media studies, structuralism’s inherent objective is to dig beneath the surface of a media text to identify how the structure of a narrative contributes to it’s meaning. Structuralism encompasses a large range of analytical tools, however, this es say will examine Joseph Campbell’s monomyth and Claude LÃ ©vi-Strauss’s theory of binary oppositions. Through analysis of Victor Fleming’s film, The Wizard of Oz (1939), it will be shown that although the monomyth and binary oppositions are useful tools with which to unveil how meaning is generated in this text, structuralism can undermine the audience’s ability to engage with their own interpretations of the film. In the simplest form, there is a basic structural pattern to narratives, as expressed through Tzvetan Todorov’s explanation of narrative movement between two equilibriums. A narrative begins in a stable position until something causes disequilibrium, however, by the end of the story, the equilibrium is re-established, though it is different than the beginning (O’Shaughnessy 1999: 268). Joseph Cam... ...an adequate mechanism for unveiling the techniques used to create messages in a text. Works Cited Campbell, Joseph (1968), The Hero with a Thousand Faces, Princeton, N.J., Princeton University Press, pp. viii-97. Eco, Umberto (1979), ‘Narrative structures in Fleming’, in his, The Role of the Reader: Explorations in the Semiotics of Texts, Bloomington, Indiana University Press, pp. 144-172. Hartley, John (2002), Communication, Cultural and Media Studies: The Key Concepts, London, Routledge, pp. 19-21. O’Shaughnessy, Michael (1999), Media and Society: An Introduction, Melbourne, Oxford University Press, pp. 266-290. Strinati, Dominic (2003), ‘Structuralism, semiology and popular culture’ (extract), in his An Introduction to Theories of Popular Culture: 2nd Ed., London, Routledge, pp. 82-85. The Wizard of Oz (film), 1939, Director: Victor Fleming.

Final Descriptive Writing

Anton Meriwether When you are trying to write a descriptive piece then it is best to describe everything in a very visual way to that would make the reader use it's five senses. Using the five senses in a descriptive writing really elevates your piece and makes it stand out. I'm from a small city in northern Indiana where not many people visit even actually hardly at all. The city is off the coast of Lake Michigan which creates a slight cold breeze in middle of December and all of January. The city is called Michigan City, Indiana.Have you ever heard of The Blue Chip Casino? Of course you have I mean who haven't. The Blue Chip Casino is like a boat casino and it is also the tallest building in the whole city. The Casino sits at one end Of Michigan Blvd which is one of the main roads in the city and also one of the longest. Another thing about the city is a place called The Dunes. The Dunes is a big sand hill that depending on the weather will burn your feet. The Dunes is a great plac e to go if you're looking to have some fun walking n sand and also going to the beach.Hearing the beach at night just calms you down no matter what is going on because, hearing the breeze flow over the lake creates a sound that can't be mimicked by technology which is very rare nowadays. Michigan City is a good place to visit but of course every city has its down falls I mean Atlanta is too big like huge for no reason at all, no seriously, really dumb big and parking is expensive and can't even drive yet and I'm saying, it's just ridiculous, but back to the task at hand. One problem aboutMichigan City is the weather, if you are not used to cold weather or don't like it then it's not your place because it gets freezing, iceman, Antarctica, I'm staying inside the house cold. That is a descriptive writing that includes all five senses. When you use all the senses then you are truly writing a descriptive writing, because how can you describe something without using the senses, I mean, y ou not even describing anything all you are doing is just talking about it and that won't get my attention. I hope this helps you become a better descriptive writer.

When Did Apartheid End and How

Apartheid, from an Afrikaans word meaning â€Å"apart-hood,† refers to a set of laws enacted in South Africa in 1948 intended to ensure the strict racial segregation of South African society and the dominance of the Afrikaans-speaking white minority. In practice, apartheid was enforced in the form of â€Å"petty apartheid,† which required racial segregation of public facilities and social gatherings, and â€Å"grand apartheid,† requiring racial segregation in government, housing, and employment. While some official and traditional segregationist policies and practices had existed in South Africa since the start of the twentieth century, it was the election of the white-ruled Nationalist Party in 1948 that allowed the legal enforcement of pure racism in the form of apartheid. The first apartheid laws were the Prohibition of Mixed Marriages Act of 1949, followed by the Immorality Act of 1950, which worked together to prohibit most South Africans from marrying or having sexual relationships with persons of a different race. The first grand apartheid law, the Population Registration Act of 1950 classified all South Africans into one of four racial groups: black, white, Colored, and Indian. Every citizen over age 18 was required to carry an identity card showing their racial group. If a person’s exact race was unclear, it was assigned by a government board. In many cases, members of the same family were assigned different races when their exact race was unclear. Apartheid was then further implemented through the Group Areas Act of 1950, which required people to live in specifically-assigned geographic areas according to their race. Under the Prevention of Illegal Squatting Act of 1951, the government was empowered to demolish black â€Å"shanty† towns and to force white employers to pay for houses needed for their black workers to live in areas reserved for whites. Between 1960 and 1983, over 3.5 million nonwhite South Africans removed from their homes and forcibly relocated into racially segregated neighborhoods. Especially among the â€Å"Colored† and â€Å"Indian† mixed-race groups many family members were forced to live in widely separated neighborhoods. The Beginnings of Resistance to Apartheid   Early resistance to the apartheid laws resulted in the enactment of further restrictions, including the banning of the influential African National Congress (the ANC), a political party known for spearheading the anti-apartheid movement. After years of often violent protest, the end of apartheid began in the early 1990s, culminating with the formation of a democratic South African government in 1994. The end of apartheid can be credited to the combined efforts of the South African people and governments of the world community, including the United States. Inside South Africa From the inception of the independent white rule in 1910, black South Africans protested against racial segregation with boycotts, riots, and other means of organized resistance. Black African opposition to apartheid intensified after the white minority-ruled Nationalist Party assumed power in 1948 and enacted the apartheid laws. The laws effectively banned all legal and non-violent forms of protest by non-white South Africans. In 1960, the Nationalist Party outlawed both the African National Congress (ANC) and the Pan Africanist Congress (PAC), both of which advocated for a national government controlled by the black majority. Many leaders of the ANC and PAC were imprisoned, including ANC leader Nelson Mandela, who had become a symbol of the anti-apartheid movement. With Mandela in prison, other anti-apartheid leaders fled South Africa and mustered followers in neighboring Mozambique and other supportive African countries, including Guinea, Tanzania, and Zambia. Within South Africa, resistance to apartheid and apartheid laws continued. The Treason Trial, Sharpeville Massacre, and Soweto Student Uprising are just three of the best-known events in a worldwide fight against apartheid that grew increasingly fierce in the 1980s as more and more people around the world spoke out and took action against white minority rule and the racial restrictions that left many non-whites in dire poverty. The United States and the End of Apartheid U.S. foreign policy, which had a first helped apartheid flourish, underwent a total transformation and eventually played an important part in its downfall. With the Cold War just heating up and the American people in the mood for isolationism, President Harry Truman’s main foreign policy goal was to limit the expansion of Soviet Union’s influence. While Truman’s domestic policy supported the advancement of the civil rights of black people in the United States, his administration chose not to protest the anti-communist South African white-ruled government’s system of apartheid. Truman’s efforts to maintain an ally against the Soviet Union in southern Africa set the stage for future presidents to lend subtle support to the apartheid regime, rather than risk the spread of communism. Influenced to an extent by the growing U.S. civil rights movement and the social equality laws enacted as part of President Lyndon Johnson’s â€Å"Great Society† platform, U.S. government leaders began to warm up to and ultimately support the anti-apartheid cause. Finally, in 1986, the U.S. Congress, overriding President Ronald Reagan’s veto, enacted the Comprehensive Anti-Apartheid Act imposing the first substantial economic sanctions to be levied against South Africa for its practice of racial apartheid. Among other provisions, the Anti-Apartheid Act: Outlawed the importation of many South African products such as steel, iron, uranium, coal, textiles, and agricultural commodities into the United States;prohibited the South African government from holding U.S. bank accounts;banned South African Airways from landing at U.S. airports;blocked any form of U.S. foreign aid or assistance to the then pro-apartheid South African government; andbanned all new U.S. investments and loans in South Africa. The act also established conditions of cooperation under which the sanctions would be lifted. President Reagan vetoed the bill, calling it â€Å"economic warfare† and arguing that the sanctions would only lead to more civil strife in South Africa and mainly hurt the already impoverished black majority. Reagan offered to impose similar sanctions through more flexible executive orders. Feeling Reagan’s proposed sanctions were too weak, the House of Representatives, including 81 Republicans, voted to override the veto. Several days later, on October 2, 1986, the Senate joined the House in overriding the veto and the Comprehensive Anti-Apartheid Act was enacted into law. In 1988, the General Accounting Office – now the Government Accountability Office – reported that the Reagan administration had failed to fully enforce the sanctions against South Africa. In 1989, President George H.W. Bush declared his full commitment to full enforcement of the Anti-Apartheid Act. The International Community and the End of Apartheid The rest of the world began to object to the brutality of the South African apartheid regime in 1960 after white South African police opened fire on unarmed black protesters in the town of Sharpeville, killing 69 people and wounding 186 others. The United Nations proposed economic sanctions against the white-ruled South African government. Not wanting to lose allies in Africa, several powerful members of the U.N. Security Council, including Great Britain, France, and the United States, succeeded in watering down the sanctions. However, during the 1970s, anti-apartheid and civil rights movements in Europe and the United States several governments to impose their own sanctions on the de Klerk government. The sanctions imposed by the Comprehensive Anti-Apartheid Act, passed by the U.S. Congress in 1986, drove many large multinational companies – along with their money and jobs – out of South Africa. As a result, holding on to apartheid brought the white-controlled South African state significant losses in revenue, security, and international reputation. Supporters of apartheid, both inside South Africa and in many Western countries had touted it as a defense against communism. That defense lost steam when the Cold War ended in 1991. At the end of World War II, South Africa illegally occupied neighboring Namibia and continued to use the country as a base to fight communist party rule in nearby Angola. In 1974-1975, the United States supported South the African Defense Force’s efforts in Angola with aid and military training. President Gerald Ford asked Congress for funds to expand U.S. operations in Angola. But Congress, fearing another Vietnam-like situation, refused. As Cold War tensions eased in the late 1980s, and South Africa withdrew from Namibia, anti-communists in the United States lost their justification for continued support of the Apartheid regime. The Last Days of Apartheid Facing a rising tide of protest within his own country and international condemnation of apartheid, South African Prime Minister P.W. Botha lost the support of the ruling National Party and resigned in 1989. Botha’s successor F. W. de Klerk, amazed observers by lifting the ban on the African National Congress and other black liberation parties, restoring freedom of the press, and releasing political prisoners. On February 11, 1990, Nelson Mandela walked free after 27 years in prison. With growing worldwide support, Mandela continued the struggle to end apartheid but urged peaceful change. When popular activist Martin Thembisile (Chris) Hani was assassinated in 1993, anti-apartheid sentiment grew stronger than ever. On July 2, 1993, Prime Minister de Klerk agreed to hold South Africa’s first all-race, democratic election. After de Klerk’s announcement, the United States lifted all sanctions of the Anti-Apartheid Act and increased foreign aid to South Africa. On May 9, 1994, the newly elected, and now racially mixed, South African parliament elected Nelson Mandela as the first president of the nation’s post-apartheid era. A new South African Government of National Unity was formed, with Mandela as president and F. W. de Klerk and Thabo Mbeki as deputy presidents.