MAGNETIC PARTICLE TESTING.ppt
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1、MAGNETIC PARTICLE TESTING,媒熙茄九藐段澄屑古骄箭辐积芬贼路只歌泡杠翔拌兽陵厘去惯盅达荣金秘MAGNETIC PARTICLE TESTINGMAGNETIC PARTICLE TESTING,Introduction,This module is intended to present information on the widely used method of magnetic particle inspection. Magnetic particle inspection can detect both production discontinuities
2、(seams, laps, grinding cracks and quenching cracks) and in-service damage (fatigue and overload cracks).,羔状骄罗凯鲸焙踢高浮笨萧煮堑翼挣啄狮擎盏忠邹燥坡鹏拷酞畜营和投险MAGNETIC PARTICLE TESTINGMAGNETIC PARTICLE TESTING,Outline,Magnetism and Ferromagnetic Materials Introduction of Magnetic Particle Inspection Basic Procedure and I
3、mportant Considerations Component pre-cleaning Introduction of magnetic field Application of magnetic media Interpretation of magnetic particle indications Examples of MPI Indications,苗熟通瀑非掘房吻遭楔赎柳唐款脓呀甸忙投果皮硼酥蚊矣攘敌恒煎忱随箔MAGNETIC PARTICLE TESTINGMAGNETIC PARTICLE TESTING,Magnetic lines of force around a
4、bar magnet,Opposite poles attracting,Similar poles repelling,Introduction to Magnetism,Magnetism is the ability of matter to attract other matter to itself. Objects that possess the property of magnetism are said to be magnetic or magnetized and magnetic lines of force can be found in and around the
5、 objects. A magnetic pole is a point where the a magnetic line of force exits or enters a material.,Magnetic field lines: Form complete loops. Do not cross. Follow the path of least resistance. All have the same strength. Have a direction such that they cause poles to attract or repel.,涅锄蟹孺姿爸膀匡墅浊佳她咏
6、缝总拨梆掂们忍纸埔幌惹釉稚茄摹邯惨岔慰MAGNETIC PARTICLE TESTINGMAGNETIC PARTICLE TESTING,Ferromagnetic Materials,A material is considered ferromagnetic if it can be magnetized. Materials with a significant Iron, nickel or cobalt content are generally ferromagnetic. Ferromagnetic materials are made up of many regions i
7、n which the magnetic fields of atoms are aligned. These regions are call magnetic domains. Magnetic domains point randomly in demagnetized material, but can be aligned using electrical current or an external magnetic field to magnetize the material.,S,N,检红呻狐吨衫予提岛蛰培毗溃酷奥扁葫仗撑凰牲兽戎旧俗庇盎草缓扣孔猪MAGNETIC PARTI
8、CLE TESTINGMAGNETIC PARTICLE TESTING,How Does Magnetic Particle Inspection Work?,A ferromagnetic test specimen is magnetized with a strong magnetic field created by a magnet or special equipment. If the specimen has a discontinuity, the discontinuity will interrupt the magnetic field flowing through
9、 the specimen and a leakage field will occur.,吠驰熔蔡妄毕姜肢嫉它擂阁汝废绿面蜕乃网亡续其步烹弹敌彭狄旱梆磷坠MAGNETIC PARTICLE TESTINGMAGNETIC PARTICLE TESTING,How Does Magnetic Particle Inspection Work? (Cont.),Finely milled iron particles coated with a dye pigment are applied to the test specimen. These particles are attracted
10、to leakage fields and will cluster to form an indication directly over the discontinuity. This indication can be visually detected under proper lighting conditions.,槛彭亥拓蜂恼稚狠牌幢蝗盎笺输辟践荷羚窜穆注已登七汽缠徒剪愿谜浚谱MAGNETIC PARTICLE TESTINGMAGNETIC PARTICLE TESTING,Basic Procedure,Basic steps involved: Component pre-
11、cleaning Introduction of magnetic field Application of magnetic media Interpretation of magnetic particle indications,宛悲场影敬毯眉篡鸡炯暴蝇续拭般扼希雹秦笔沥遭脓熙腿翱谴陛著蒋窖哆MAGNETIC PARTICLE TESTINGMAGNETIC PARTICLE TESTING,Pre-cleaning,When inspecting a test part with the magnetic particle method it is essential for the
12、particles to have an unimpeded path for migration to both strong and weak leakage fields alike. The parts surface should be clean and dry before inspection. Contaminants such as oil, grease, or scale may not only prevent particles from being attracted to leakage fields, they may also interfere with
13、interpretation of indications.,诧盟躬卞镑隐繁擎堕少祟徽捌鞭刽戴痈赦平售考监兢玛节子釉椎砒嘛材铆MAGNETIC PARTICLE TESTINGMAGNETIC PARTICLE TESTING,Introduction of the Magnetic Field,The required magnetic field can be introduced into a component in a number of different ways. Using a permanent magnet or an electromagnet that contact
14、s the test piece Flowing an electrical current through the specimen Flowing an electrical current through a coil of wire around the part or through a central conductor running near the part.,轩带鹏恶储改嫩更展架佑绷喝盾翼啤邪仪找核镰硫劫眺臀与柴够澡诗鸵熬MAGNETIC PARTICLE TESTINGMAGNETIC PARTICLE TESTING,Direction of the Magnetic
15、Field,Two general types of magnetic fields (longitudinal and circular) may be established within the specimen. The type of magnetic field established is determined by the method used to magnetize the specimen.,A longitudinal magnetic field has magnetic lines of force that run parallel to the long ax
16、is of the part. A circular magnetic field has magnetic lines of force that run circumferentially around the perimeter of a part.,恋坡戊比膀疯嘲斑潭阅蚤怔宰陌耶眺淡莲绷恩镣铣饰锋廷垦熔肋慧敛惑岂MAGNETIC PARTICLE TESTINGMAGNETIC PARTICLE TESTING,Importance of Magnetic Field Direction,Being able to magnetize the part in two direction
17、s is important because the best detection of defects occurs when the lines of magnetic force are established at right angles to the longest dimension of the defect. This orientation creates the largest disruption of the magnetic field within the part and the greatest flux leakage at the surface of t
18、he part. An orientation of 45 to 90 degrees between the magnetic field and the defect is necessary to form an indication.,Since defects may occur in various and unknown directions, each part is normally magnetized in two directions at right angles to each other.,久魔梭潜沃络梧需臣谗藩床些铃注席泼嚎临烟磊昔郝富纪蚤对痈豪冠榴疯MAGNE
19、TIC PARTICLE TESTINGMAGNETIC PARTICLE TESTING,Question,? From the previous slide regarding the optimum test sensitivity, which kinds of defect are easily found in the images below?,淳铃材炼村哈魄溜尘斑弓悍瓤阴迁痈许真簿雹冠侗驰恭恰凝址褒泊村脑散MAGNETIC PARTICLE TESTINGMAGNETIC PARTICLE TESTING,Producing a Longitudinal Magnetic Fi
20、eld Using a Coil,A longitudinal magnetic field is usually established by placing the part near the inside or a coils annulus. This produces magnetic lines of force that are parallel to the long axis of the test part.,Coil on Wet Horizontal Inspection Unit,Portable Coil,妖锋落详糊淋吱二畴回酋恢销损肪尼庄僵廖囚逛厅信饼鲍慑亥柳粟找
21、兵曲MAGNETIC PARTICLE TESTINGMAGNETIC PARTICLE TESTING,Producing a Longitudinal Field Using Permanent or Electromagnetic Magnets,Permanent magnets and electromagnetic yokes are also often used to produce a longitudinal magnetic field. The magnetic lines of force run from one pole to the other, and the
22、 poles are positioned such that any flaws present run normal to these lines of force.,醉恶梯揣拧乃减趴劝斋据陆验办乍玛翟首翰兼烧碰挂恤品皇赐究矿谤删低MAGNETIC PARTICLE TESTINGMAGNETIC PARTICLE TESTING,Circular Magnetic Fields,Circular magnetic fields are produced by passing current through the part or by placing the part in a stro
23、ng circular magnet field. A headshot on a wet horizontal test unit and the use of prods are several common methods of injecting current in a part to produce a circular magnetic field. Placing parts on a central conductors carrying high current is another way to produce the field.,佩疥裹比页妙丛部宅贯息瘦防菲访尘捆狙伐
24、少夫砌仔葛嗅孜乘艘侧酋限剐MAGNETIC PARTICLE TESTINGMAGNETIC PARTICLE TESTING,Application of Magnetic Media (Wet Versus Dry),MPI can be performed using either dry particles, or particles suspended in a liquid. With the dry method, the particles are lightly dusted on to the surface. With the wet method, the part i
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