The Electromagnetic Testing: The Eddy Current Testing

The Electromagnetic Testing: The Eddy Current Testing In modern NDT methods electromagnetic testing plays an important role. Electromagnetism is a part of ndt process. It is a process based on inducing magnetic field. The process of inducing an electric current and magnetic field or both inside a test material. Then observe the magnetic flux induced in the material. This method is based on the electromagnetism. Electromagnetism is the property of a material to get magnetic effect while an electric field applied. The main factor of this test is that the material should be a conductor. These methods give more benefits and advantages than other tests. The major tests coming under the electromagnetic testing are, Eddy current testing Flux leakage testing Alternating current field testing Remote field testing Among these techniques my topics are Eddy current testing Flux leakage testing EDDY CURRENT TESTING Eddy current testing is relatively applicable in small materials. It gives good measurements on ferromagnetic materials. The basic principles of eddy current testing are electromagnetism and permeability. More details about eddy current testing is shown in the coming pages. FLUX LEAKAGE TESTING Flux leakage is another electromagnetic tesing.It is widely used. Electromagnetism is the basic principle of flux leakage testing. This method is most commonly used in pipe lines and storage tanks. After inducing magnetic field we are able to analyzing the defects through instruments. Other electromagnetic techniques are, ALTERNATING CURRENT FIELD MEASUREMENT ACFM methods are used to detect surface breaking cracks. This method can be applied to both magnetic and nonmagnetic materials.ACFM method is based on the electromagnetism and these entirely different from eddy current method.ACFM method gives us more benefit than other methods. It does not need the removal of paintings and coating.ACFM technique is more advanced testing than dye pentrant testing and magnetic particle testing. The main advantages of ACFM tastings are Able to work on coatings No need to cleaning more Does not require equipment shut down High speed inspection REMOTE FIELD SENSING METHOD RFT is the commonly used electromagnetic method in ndt. Remote field testing method also joined with eddy current testing is named as remote field eddy current testing. But in practically there are many difference shows between eddy current testing and remote field testing.RFT technique is mainly used to find out the thickness of the ferromagnetic material tube walls. Here RFT shows more sensitivity than eddy current testing. The main principle of RFT is the electromagnetism. In RFT, the probe contains transmitter zone and receiver zone. The remote field shows more coupling to the exciter coil and receiver coil. The main advantages of RFT are, High sensitivity Give accurate measurements from sheets and plates. Ability to inform internal defects Detect defects from the ferromagnetic tubes EDDY CURRENT TESTING Eddy current testing is used in a variety of industries to find defects and also measurements. Major use of eddy current testing is for defect detection when the nature of the defect is well understood. Naturally the method is used to test relatively small area and the probe design and test parameters must be established with a good understanding of the flaw that is to be detected. Eddy current testing only used to detect surface and near surface defects. In thin materials such as plates and sheets, eddy currents can be used to measure the thickness of the material. This shows eddy current is useful for detecting corrosion damage and other damage that causes a thinning of the material. The method is used to make corrosion thinning measurements on aircraft skins and in the walls of tubing used in assemblies such as heat exchangers. Eddy current method is also used to find the thickness of paints and other coatings. Eddy currents are varied with respect to the electrical conductivity and magnetic permeability of materials. So eddy current testing can be used to arrange materials and also find which heat treatment applied to the material. It is the main advantage and use of eddy current testing method. In Eddy current testing different probes or transducers are used. Compare to other testing methods eddy current testing shows many advantages and applications. Transducers used in eddy current testing is depend upon the properties and size of the material. PRINCIPLES In eddy current testing the major principles are, Electromagnetism Permeability ELECTROMAGNETISM The main principle of eddy current testing is the à ¢Ãƒ ¢Ã¢â‚¬Å¡Ã‚ ¬Ãƒâ€¹Ã…“electromagnetismà ¢Ãƒ ¢Ã¢â‚¬Å¡Ã‚ ¬Ãƒ ¢Ã¢â‚¬Å¾Ã‚ ¢. This states that à ¢Ãƒ ¢Ã¢â‚¬Å¡Ã‚ ¬Ãƒâ€¹Ã…“when an electron is passing through a conductor, a magnetic field induced on the conductor perpendicular to the axis. The same effect happens in a copper wire while alternating current passing through it. When the alternating current expands then the magnetic field also expands. The magnetic field obtained through electro magnetism is similar to the bar magnet. PERMEABILITY Permeability is also relating to the electromagnetism. It is also called as magnetic permeability. Permeability is ability to permeable. It is a constant of proportionality exists magnetic induction and magnetic field intensity. Permeability of some materials has been change according to the temperature changes and magnetic induction. PRINCIPLE OF EDDY CURRENT TESTING IMAGE-1 NB: COURTESY TO MARKTEC FROM MARKTCC.CO PRACTICAL METHOD Eddy current testing is used in different sectors for fin out the thickness and used to check the material losses in different materials. The cause of material loss is corrosion. It mainly used in thin sheets, plates and also in aircraft components. On the impedance plane, thickness variations exhibit on the eddy current signal response as a subsurface defect. Except that the signal represents a void of different size and depth. Due to this the phase rotation should be same and the amplitude should be greater. In the device the lift-off curves for different areas of taper wedge can be produced by nulling the probe in the air and touching it to the various surfaces at various locations of thee tapered wedge. A comma shaped curve is formed while a line is drawn between the end points of the lift-off curves. In the second stage the comma shaped curve path is traced on the screen when the probe is scanned down the length of the tapered wedge. So that the entire range of thickness values are measured. The important thing is that the depth of penetration of the eddy currents must cover the range of thickness being measured. Then a frequency is selected that produces standard depth of penetration at maximum thickness. Lower frequency is needed for getting high penetration. Due to the probe impedance is more sensitive to changes in electrical conductivity. So electrical conductivity cannot be phased out and is important to verify the conductivity of below the region of low level. If testing need more penetration single coil probe, reflection type probe and transformer probes are used based on configuration. Small diameter probe coils has the efficiencies to give very high sensitivity. EDDY CURRENT TESTING ON A BORE IMAGE-2 NB: COURTESY TO: BAM.DE TFROM BAM.DE EDDY CURRENT INSTRUMENTS In industries various eddy current instruments are used. Analog and digital display instruments are mainly used. Classification of eddy current instruments is based on the display used for presenting the data. The main display types are, Analog meter Digital readout Impedance plane Time vs. signal amplitude PROBES USED In eddy current testing a variety of probes or transducers are used. The probe classification is based on the configuration and mode of operation. The main probes are, Absolute probe Differential probes Reflection probes Hybrid probes Surface probes Bolt hole probes Bobbin probes Encircling coils WORKING OF A PROBE IMAGE-3 NB:COURTESY TO DAVISLABUS TO DAVISLABUS.COM CODES AND STANDARDS USED IN ECT BRITISH STANDARD BS 3683(PART 5) =Eddy current flaw detection glossary. BS 3889 (PART20) =Automatic eddy current testing of wrought steel tubes. BS 3889(PART213) =Eddy current testing of nonferrous tubes. BS 5411(PART3) =Eddy current method for measuring coating thickness of conductive coatings on nonmagnetic base materials. AMERICAN STANDARD ASTME 243=Eddy current testing of seamless copper and copper alloy tubes. ASTME 309=Eddy current examination of steel tubular products using magnetic saturation. ASTME 1033=Eddy current examination of type F continuously. The main advantages and disadvantages are, ADVANTAGES Ability to detect small cracks Find surface and near surface cracks High sensitivity Equipment is portable High accuracy Able to inspect on irregular shapes Economically adjustable DISADVANTAGES The material should be a conductor The Skilled and trained person needed Depth of penetration has some APPLICATIONS USES Eddy current testing is applicable in different sectors. The main applications are, Crack detection Material thickness measurement Coating thickness measurement Conductivity measurement Material identification Hest damage detection 2. ELECTROMAGNETIC FLUX LEAKAGE TESTING Magnetic flux leakage is an important method in NDT process. Magnetic flux leakage method can be used to detect the circumferential cracks on the stainless steel and metal losses in ferromagnetic materials. It is widely used in tubes and heat exchangers for find out the discontinuities. The major principle of magnetic flux leakage testing is the electromagnetism. During MFL inspection a magnetic field induced on the material. This property of material is termed as electromagnetism. MFL tools consist of two or more bodies while inspecting tubes and complicated material models. The main body is named as magnetizer with magnets and others are batteries and electronics.MFL tool is able to find sensor readings based on either the distance of tool travelled or on increment time. In flux leakage examination of tubular parts three types of defects can be detected. They are longitudinally oriented, transversely oriented, silvers. Magnetic flux leakage testing has some limitations in sizing the capacity of defects. In compare with eddy current testing magnetic flux leakage testing shows more sensitivity and advantages. In magnetic flux leakage testing method of tubular products both outside and inside diameter defects can be detected but generally they cannot be distinguished. WORKING PRINCIPLE The main principles of electromagnetic flux leakage are, ELECTROMAGNETISM The main principle of MFL is that electro magnetism. This states that when electron is passing through a material a magnetic flux induced on the conductor. The magnetic field should be perpendicular to the axis. An electromagnet is an object, which acts like a magnet and its magnetic effect created and controlled by electricity. HALL EFFECT Some Hall Effect sensors are used in electromagnetic flux leakage testing. Hall Effect is the production of a voltage difference across an electrical conductor, transverse to an electric current in the conductor and a magnetic field perpendicular to the current. PERMEABILITY Permeability is also related to the electromagnetic field. It is the ability to become permeable. Permeability changes occur in some material with temperature changes and magnetic induction. PRACTICAL METHOD Magnetic flux leakage testing was used earlier because eddy current cannot detect subsurface defects in ferromagnetic test material. In such a situation a common technique using encircling coils but them sometimes inconvenient while using in internal coils. Flux leakage testing is used at steel mills and fuel mills for getting correct measurements without errors. When ferromagnetic material that is free from defects is magnetized, then an unbroken flux field flows through the object material. The magnetic flux flows through between its poles. Next the flux density decreases towards the outer material surfaces and a detector of flux leakage testing would pick up a very weak signal from the surfaces. However, if the surface is interrupted by a discontinuity, poles are formed at opposite sides of the resulting gap. Then the flux lines flow externally from the north to South Pole. The flux leakage lines are detected by a transducer or probe passing over the discontinuity and signal is displayed. Disturbance of the materials original flux lines also extends under the discontinuity and if the material wall is thin itself, a discontinuity on wall surface may be detected from the opposite wall. After getting the signals from the detector we have to find out the length, thickness and measurement about the defect through monitoring.MFL gives us to the ability to detect the surface and subsurface defects. FLAW DETECTION USING FLUX LEAKAGE IMAGE-4 NB: COURTESY TO FARREL.CO FROM FARREL.CO.ID CODES AND STANDARDS USED IN MFL BRITISH STANDARD BS 6072 =Magnetic particle flaw detection. BS 4489 =Automatic black light measurement. BS 5044 (PART) =Forged and stamped crank shafts. AMERICAN STANDARD ASTME 709=Magnetic particle inspection practice. ASTME 1251=Indications in ferrous castings. ASTME 570=Flux leakage examination of ferromagnetic steel tubular products ADVANTAGES OF MFL 1. Able to detect surface and subsurface defects 2. It is a simple method 3. High sensitivity 4. Easy measurement 5. No need to remove the coatings DISADVANTAGES OF MFL 1. Surface contamination not detectable. 2. Works only with ferromagnetic materials. 3. Difficult to measure deep depts. 4. Skilled and trained person needed. APPLICATIONS OF MFL 1. Bars transverse and tilted effects. 2. Tubes longitudinal defects. 3. Pressure vessels 4. Heat exchangers 5. Power plants CONCLUSION EDDY CURRENT TESTING In this project contains an explanation of eddy current testing. The main concept is the understanding of basic theories and working methods of eddy current testing. The second thing is to describe the advantages and disadvantages and also describe the applications. This method is used in different industry sectors for getting accurate measurements and to find out the discontinuities for increasing the safety and production. So eddy current testing is a method which gives good sensitivity and accurate measurements. ELECTROMAGNETIC MFLUX MLEAKAGE the performance of MFL testings.MFL testing can be carried out only in ferromagnetic materials. It can be applicable in coated and non coated ferromagnetic materials.MFL is used in the inspection of tube and piping to find unwelded areas of longitudinal joints. It also a most useful method in plate materials, storage tanks and also to find other forms of degradation In this project also describes the magnetic flux leakage testing in NDT.This study is used to understand. REFERENCE 1. GOOGLE 2. NDT.NET 3. WWW.MARKTEC.CO.JP 4. WWW.BAM.DE 5. DAVISLABS.COM 5. FARREL.CO.ID

Capital Budgeing Case Study Essay

There are at least six capital budgeting tools a firm can use in analyzing a capital expenditure. They are: net present value (NPV), internal rate of return (IRR), profitability index (PI), payback period (PB), discounted payback period (DRP), and modified internal rate of return (MIRR). This case study will focus mainly on NPV and IRR, in addition to the remaining four capital budgeting tools. Net Present Value (NPV) The NPV of an investment proposal for a project is the same as the† present value of its annual free cash flows less the investment’s initial outlay† (Keown, Martin & Petty, p. 310, 2014). Before calculating the NPV you must first forecast the projected revenue for the life of the project to obtain the net cash flow figures. This involves accountants and analysts crunching numbers based on many factors such as the economy, supply and demand, competition, and how the company plans on carrying out the project (University of Phoenix, 2013). NPV looks at the present value of the benefits minus the present value of the costs. You also need a discount rate; it is normally the cost of capital. The cost of capital is used because a firm wants the project to at a minimum make more than what capital is now costing the firm to run its business. The rule for NPV is if the value is greater than or equal to zero the project is accepted (Keown, Martin & Petty, p. 310, 2014). After completing a five year projected income statement and a five year projected cash flow from the capital budgeting case study for corporation A and B, this information was used to calculate the NPV for each corporation. Corporation A’s NPV= $2,025 and B’s is NPV= $3,293. Both NPV’s are equal or greater than zero so both projects are a go, but corporation B has a greater NPV, making it a better choice if based on NPV alone (University of Phoenix, 2013). Internal Rate of Return (IRR)

Mt. Rushmore

Katie Gerard English Comp I Mrs. Hynek Descriptive Research 5 October 2012 Mount Rushmore: the History Ever since Mount Rushmore was created it has been and iconic symbol because of its beauty, magnificent and especially its history. Mount Rushmore is a shrine of democracy, a monument and memorial to the birth of America. Mount Rushmore is a symbol of the nation through the greatness of its leaders. The magnificent sculpture depicts the faces of four American presidents who symbolize this nation’s history, rugged determination and long-lasting achievements.According to an episode of Modern Marvels: Mount Rushmore, Doane Robinson, South Dakota’s state historian, wanted a way to attract tourism to the Black Hills in the early 1920s. Robinson came up with the idea to sculpt â€Å"the Needles. † â€Å"The Needles† were ancient stone structures, made of granite, almost impossible to carve, but Robinson was not turned away. The needles were not an option so he c hoose Mount Rushmore, which were near â€Å"The Needles. † All he knew was that he needed to recruit an artist who loved a challenge.He recruited Gutzon Borglum, world renowned stone sculpture, who, according to Howard Shaff, co-writer of his biography Six Wars at a Time, â€Å"was always looking for new worlds to conquer† (Modern Marvels). At this time Borglum was carving â€Å"Stone Mountain† in Atlanta, GA, but the project was stopped, because of his temper, and he needed a new project to restore his reputation. In 1925 Borglum and his son, Lincoln, explored the Black Hills for a carving site.This is where he stumbled upon Mount Rushmore and â€Å"envisioned the ultimate American monument† (Modern Marvels). Mount Rushmore was solid granite, like â€Å"the Needles† and riddled with cracks, but this did not turn Borglum away. He stated â€Å"American history shall march along this skyline† (Modern Marvels). Borglum convinced Robison not to sculpt western folk heroes and to instead sculpt four American presidents, George Washington, Thomas Jefferson, Abraham Lincoln, and Theodore Roosevelt, who all â€Å"symbolized the evolution of American spirit† (Modern Marvels).He choose Washington because he was the father of our country and led the fight for freedom; Jefferson because he wrote the Declaration of Independence and had the vision of a growing nation, which inspired the Louisiana Purchase; Lincoln, the great emancipator, who served â€Å"the union of states in its darkest hour;† and choose Roosevelt because he was a spirited individualist who defined 20th century America and was an old friend of Borglum (Modern Marvels). It took Borglum two years, the funds, and a president to get the project started.In 1927 President Calvin Coolidge took a trip to South Dakota; this was Borglum’s opportunity to secure official federal recognition and raise the much needed funds. To impress Coolidge, South Dakota Governor William Bulow made a hunting lodge available and named it Summer White House. He also renamed a local stream, â€Å"Grace Coolidge Creek,† and stocked it with prize winning fish. It all worked, Coolidge loosened up and â€Å"Borglum gave Coolidge Mount Rushmore Fever† (Modern Marvels). 1000 people showed up to watch Coolidge and the Secret Service declare work on Mount Rushmore; this event took place August 10 1927.Work began that October. In 1929, during the last days of Coolidge’s presidency, he signed the legislation which granted the Mount Rushmore project $250,000 in federal funds (Modern Marvels). Borglum first started with miniature models of each president, which he held in the sun to see how they would reflect. Then he made a 1:12 model of Mount Rushmore out of plaster. He used the 1:12 ratio so the measurement could be converted to feet easily. This model was then carried up to the mountain and he and his 400 workers used the pointing techniq ue, an ancient Greek method, to transfer the model onto the mountain.Pointing consisted of an angle and two measurements, one measurement on the top of the studio model and the other on the actual carving, and then he placed a vertical axis. It was like a giant propeller on each head. They took the measurement of each angle, distance from the axis, and distance from the top the workers who were called â€Å"pointers,† (which was Borglum son in this case), found the spot where drilling or blasting happened (People & Events: Carving the Mountain). Over the years, Mount Rushmore began to take shape.Borglum had to constantly change his design due to the shape of the granite. To extract the rock, workers used the â€Å"Honey Combing† technique, which involved making small holes in the rock where dynamite could fit to remove up to six inches of rock (People & Events: Carving the Mountain). Workers also used channel irons, jack hammers with a four star bit, and pneumatic devi ces to shape and smooth the faces. According to Glen Bradford, a Mount Rushmore worker, â€Å"you had to be one tough person to hold that jackhammer all day, while dangling in the air† (Modern Marvels).The workers had a hard time visualizing what they were making while working so close to it so Borglum made five foot models of each head and hung them below the workers so they could see and feel what they were doing. According to Orville Worman, another Mount Rushmore worker, Lincoln Borglum, Borglum’s son, didn’t get any credit for all the work he did. He hired all the workers and most of the time was the project manager because his father was gone for months at a time (Modern Marvels). When the depression hit, it caused the work to slow down.Shaff said that Borglum â€Å"could not understand how money could put a limit on his dream,† (Modern Marvels) and with the dwindling funds and the depression, Borglum’s temper was uncontrollable. But Borglum was not giving up; he used Roosevelt’s plan of bringing America back as a springboard to keep the project going. He used films to show the nation each stage and keep the public and politicians informed. Borglum had many other dreams for the monument like a timeline of American events and a â€Å"Hall of Fame† behind Lincoln’s head. Congress wanted it done and the hall project cancelled when Borglum passed away in 1941.The partial tunnel is still there and it shows the hard work of everyone (Modern Marvels). After Borglum’s death, there was no chief for the project World War II was declared, and Congress wanted all work to stop on Mount Rushmore. His son closed up shop. After 14 years of work, Mount Rushmore was an unfinished dream of one man’s conception and beliefs of America’s evolution. It was a piece of art done by the â€Å"Work of a dreamer, inspired by dreamers, [which included] the sacrifice of many, and celebrated the promise for A merica† (Modern Marvels).The shrine of democracy is visited by 2. 5 million people every year (Mount Rushmore National Memorial). Some people visit to relive the memory of watching it being carved and some visit on a patriotic adventure of America, and when leaving people cannot forget the beauty, magnificence, and history of Mount Rushmore. It â€Å"has become one of the most iconic images of America and an international tourist attraction† (Mount Rushmore). Bibliography Modern Marvels: Mount Rushmore. Dir. Jeff Scheftel. Perf. Harlan Saperstein, William O. Farber, James Popovich, Howard Shaff, and Dan Wenk.History Channel, 1996. TV â€Å"Mount Rushmore. † History. com. A&E Television Networks, n. d. Web. 01 Oct. 2012. . â€Å"People & Events: Carving the Mountain. † PBS. PBS, 1999. Web. 01 Oct. 2012. . â€Å"Mount Rushmore National Memorial. † Mount Rushmore Info, Directory Information for Vacationers at Mt. Rushmore. SD Web Traveler, Inc. , 12 Ju ne 2012. Web. 01 Oct. 2012. .

Hazelwood vs. Kuhlmeier, An essay. - 1047 Words

Should a school be able to censor their students? This question has reached the supreme court multiple times, such as in this case, or in Tinker vs. Des Moines. While restricting a freedom may be annoying, it can be necessary, but when is it dictatorship, and when is it necessary? That is what is questioned in this court case. The U.S. Supreme Court had a difficult decision in the court case of Hazelwood vs. Kuhlmeier, and they were right in their ruling, because even though censorship is often overused, in the classroom, it is often needed, and though the fear of a dictatorship in any place is often scary, it is needed in a classroom full of rowdy minors, even in my experience many of my classmates have inappropriate outbursts. In this case, the Principal of Hazelwood east high, Principal Reynolds, reviewed the school paper before it was published. He thought two articles were inappropriate for school, one on some of the student’s pregnancies and experiences while pregnant, and one person’s experiences through her parent’s divorce. (Facts and Case Summary: Hazelwood v. Kuhlmeier.1 ) Even though all of the names were changed, the principal was worried that the students may be identified. Also, the father in the divorce article was not reached for comment, so the article had not been unbiased, as should be expected in a newspaper.(Landmark Cases of the U.S. Supreme Court: Hazelwood v. Kuhlmeier1) The principal removed these articles, causing the paper to miss aShow MoreRelatedThe Amendment Of The United States Constitution833 Words   |  4 Pagespetitioning for a governmental redress of grievances. Post this amendment, there have been several cases where the Supreme Court has been re quired to interpret or make a decision to uphold its provisions. One of such landmark cases is the Hazelwood School District vs Kuhlmeier. The case involved two articles that were refused publication by a principal in a student newspaper. One of the articles dealt with the experience of students whose parents are divorce and the other with teenage pregnancy. In myRead MoreEssay on Implementing Uniforms In School is The Right Thing To Do1563 Words   |  7 Pageshave name brand clothing would decrease drastically. However others are worried that this policy would infringe on students First Amendment rights. Yet there are other parents that all worried that the uniforms will cost too much. In the following essay these issues will be addressed. Proponents of uniforms argue that the widespread violence in schools is due largely to the gangs. They believe that the distinctive gang colors and symbols are used to intimidate non-gang members and reinforce gang