欢迎来到麦多课文档分享! | 帮助中心 海量文档,免费浏览,给你所需,享你所想!
麦多课文档分享
全部分类
  • 标准规范>
  • 教学课件>
  • 考试资料>
  • 办公文档>
  • 学术论文>
  • 行业资料>
  • 易语言源码>
  • ImageVerifierCode 换一换
    首页 麦多课文档分享 > 资源分类 > PDF文档下载
    分享到微信 分享到微博 分享到QQ空间

    REG NASA-LLIS-0760-2000 Lessons Learned Eddy Current Testing of Aerospace Materials.pdf

    • 资源ID:1018406       资源大小:23.04KB        全文页数:6页
    • 资源格式: PDF        下载积分:10000积分
    快捷下载 游客一键下载
    账号登录下载
    微信登录下载
    二维码
    微信扫一扫登录
    下载资源需要10000积分(如需开发票,请勿充值!)
    邮箱/手机:
    温馨提示:
    如需开发票,请勿充值!快捷下载时,用户名和密码都是您填写的邮箱或者手机号,方便查询和重复下载(系统自动生成)。
    如需开发票,请勿充值!如填写123,账号就是123,密码也是123。
    支付方式: 支付宝扫码支付    微信扫码支付   
    验证码:   换一换

    加入VIP,交流精品资源
     
    账号:
    密码:
    验证码:   换一换
      忘记密码?
        
    友情提示
    2、PDF文件下载后,可能会被浏览器默认打开,此种情况可以点击浏览器菜单,保存网页到桌面,就可以正常下载了。
    3、本站不支持迅雷下载,请使用电脑自带的IE浏览器,或者360浏览器、谷歌浏览器下载即可。
    4、本站资源下载后的文档和图纸-无水印,预览文档经过压缩,下载后原文更清晰。
    5、试题试卷类文档,如果标题没有明确说明有答案则都视为没有答案,请知晓。

    REG NASA-LLIS-0760-2000 Lessons Learned Eddy Current Testing of Aerospace Materials.pdf

    1、Best Practices Entry: Best Practice Info:a71 Committee Approval Date: 2000-04-05a71 Center Point of Contact: MSFCa71 Submitted by: Wilson HarkinsSubject: Eddy Current Testing of Aerospace Materials Practice: Eddy Current Testing (ECT) can be used on electrically conductive material for detecting and

    2、 characterizing defects such as surface and near surface cracks, gouges, and voids. It can also be used to verify a materials heat treat condition. In addition, wall thickness of thin wall tubing, and thickness of conductive and nonconductive coating on materials can be determined using ECT.Programs

    3、 that Certify Usage: This practice has been used on Solid Rocket Motor (SRM) and Redesigned Solid Rocket Motor (RSRM).Center to Contact for Information: MSFCImplementation Method: This Lesson Learned is based on Reliability Practice number PT-TE-1421 from NASA Technical Memorandum 4322A, NASA Reliab

    4、ility Preferred Practices for Design and Test.Eddy Current Testing (ECT) is a fast, reliable, and cost effective nondestructive testing (NDT) method for inspecting round, flat, and irregularly shaped conductive materials. Specific processes have been developed to determine the usability and integrit

    5、y of threaded fasteners. In addition, ECT has the capability of being automated. With proper equipment and skilled test technicians readout is instantaneous.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Implementation:Alternating Current (AC) flowi

    6、ng through a coil produces an alternating magnetic field about the coil. When the coil is positioned near to, or placed on, material that is capable of conducting electrical current, the magnetic field passes into the material and circular (eddy) currents are induced in the material near the coil. T

    7、he flow of eddy currents in the material causes the excitation of a fluctuating magnetic field of its own. This magnetic field is always in opposition to the coils magnetic field as illustrated in Figure 1. When the coil is placed on conductive material, the strength of the coils magnetic field is r

    8、educed. This change in the magnetic field causes a change in the impedance of the coil, which causes a change in the current flowing through the coil. These changes are detected by an instrument placed in the circuit.refer to D descriptionD The flow of eddy current within the material is disrupted b

    9、y the presence of discontinuities, such as, cracks, porosity, or inclusions. Discontinuities cause a decrease in the flow of current in the material by increasing the length of the path along which the current must flow as shown in Figure 2. This results in a reduction of current flow which causes a

    10、 change in the impedance of the test probe coil.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-refer to D descriptionD There are three major factors that affect ECT. These are material conductivity, geometry, and permeability of the material being t

    11、ested. In addition, there are contributors that affect the three major factors. These are shown in Table 1.Table 1. Factors Affecting Eddy Current TestingConductivity Geometry PermeabilityAlloy Hardness Temperatur Residual stress CoatingsThickness Discontinuities Coil-to-Material Seperation (liftoff

    12、)Ferromagnetic* Material capable of being magnetized The ECT signal is strongly related to the geometrical shape of the coil, i.e., the size, shape, and positioning of the coil; the relationship between the coil windings and suspected discontinuities; the effect of changes in liftoff or fill factors

    13、; the depth of penetration; and the edge effect.Identifying the various factors causing impedance changes depends upon the knowledge and skill of the ECT technician. Thus, selecting the appropriate eddy current probe is an important part of eddy current testing.Various types of test instruments avai

    14、lable for ECT are: 1) conductivity testers, 2) crack detectors, 3) resistance and reactance measuring testers, 4) coating thickness testers, and 5) oscilloscopes and output devices such as strip chart recorders, printers, etc. when used as part of a test setup.A standard test specimen with known fla

    15、w sizes must be fabricated for use in adjusting the sensitivity setting of the test instrument for accurate interpretation of the test results. The standard Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-test sample should be sound and of the same a

    16、lloy, temper, and geometry as the part to be tested. Flaws may be produced in the standard test specimen by drilling, electrical discharge machining, milling, or any other means that will not distort the standard. Any flaw size outside the predetermined acceptable flaw size for the object being test

    17、ed shall be a noted defect for corrective action or rejection.Table 2 lists advantages and disadvantages to be considered when selecting ECT. The most important elements required to maximize successful eddy current operations are dedicated personnel, training, proper equipment, and adequate standard

    18、s. Also, at reasonable time intervals during ECT, routine checks should be made with the standard test specimen to insure equipment is operating properly.Table 2. Advantages and Limitations of Eddy Current Testing (ECT)Advantages Limitations1. High speed testing (can be automated) 2. Accurate measur

    19、ing of conductivity 3. Discontinuities at or near surface can be reliably detected 4. High-sensitivity to small discontinuities 5. Accurate coating thickness measurements 6. Direct Go/No Go answers can be quickly obtained 7. No physical contact required 8. Low cost 9. Portable1. Limited penetration

    20、into test article 2. Several variables simultaneously affect output indication 3. Discontinuities are qualitative not quantitative indications 4. Material must be conductive 5. Requires skill when many variables are involved 6. False indications can result from edge effects and parts geometryECT is

    21、useful in the areas of material heat treat determination, coating thickness measurements, and flaw detection. A list of typical applications is shown in Table 3.Table 3. Typical Applications of Eddy Current TestingProvided by IHSNot for ResaleNo reproduction or networking permitted without license f

    22、rom IHS-,-,-Material Property DeterminationsThickness Measurements Flaw DetectionHeat treatment evaluations Hardness Fire damage Impurities Chemical compositions Corrosion damage Conductivity of ionized gasThin sheet metal Foil Paints Anodic coatings Lacquers Thin insulation Rocket motor liningsShee

    23、t metal Foil Wire Bars Tubes Bolt holes Fasteners Welds Ball bearingsTechnical Rationale:For the past ten years, eddy current testing has been a necessary tool at MSFC for the inspection of bolts, (heads, grip length, and threads), nuts, and holes for defects. Standards are fabricated as required an

    24、d special adapters have been fabricated which allows the probe (coil) to be positioned at the correct angle and distance from surface. ECT is a fast, accurate, and highly reliable method for determining defects in surface and near surface areas of aerospace materials.References1. MIL-HDBK-728/2: “Mi

    25、litary Handbook Eddy Current Testing,“ December 1985.2. MIL-HDBK-727/1: “Military Handbook Nondestructive Testing,“ December 1985.3. Bray, Don E., and Don McBride: “Nondestructive Testing Techniques,“ John Wiley & Sons, Inc., 1992.4. CT-6-5: “Nondestructive Testing Eddy Current,“ Classroom Training

    26、Handbook, Second Edition, Convair Division of General Dynamics, 1979.5. PT-4-5: “Nondestructive Testing, Eddy Current Testing,“ Programmed Instruction Handbook, Convair Division of General Dynamics, San Diego, CA, 1967.6. Bray, Don E., and Roderick Stanley: “Nondestructive Evaluation,“ McGraw-Hill,

    27、Inc., 1989.7. Kutz, Myer: “Mechanical Engineers Handbook,“ John Wiley & Sons, Inc., 1986.8. ASTM E426-92: “Standard Practice for Electromagnetic (Eddy Current) Examination of Seamless and Welded Tubular Products, Austenitic Stainless Steel and Similar Alloys.“9. Birnbaum, George, and George Free: “E

    28、ddy Current Characterization of Materials and Structures,“ ASTM Special Technical Publication 722, American Society for Testing and Materials, 1916 Race Street, Philadelphia, PA, 19103, September 1979.10. McMaster, R.C., P. McIntire, and M. L. Mester: “Nondestructive Testing Handbook,“ Second Editio

    29、n, American Society for Nondestructive Testing, Inc., 1986.11. Metals Handbook, Volume 1: “Nondestructive Inspection and Quality Control“ ASM International Metals, Park, OH, 1989.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Impact of Non-Practice:

    30、 Failure to detect flaws in the surface or near surface areas of components could result in failure of the components and possibly failure of the mission. Failure to use ECT when applicable to aerospace materials could result in the use of a slower, less cost effective, and less reliable method for

    31、detecting surface and near surface flaws in aerospace materials.Related Practices: N/AAdditional Info: Approval Info: a71 Approval Date: 2000-04-05a71 Approval Name: Eric Raynora71 Approval Organization: QSa71 Approval Phone Number: 202-358-4738Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-


    注意事项

    本文(REG NASA-LLIS-0760-2000 Lessons Learned Eddy Current Testing of Aerospace Materials.pdf)为本站会员(terrorscript155)主动上传,麦多课文档分享仅提供信息存储空间,仅对用户上传内容的表现方式做保护处理,对上载内容本身不做任何修改或编辑。 若此文所含内容侵犯了您的版权或隐私,请立即通知麦多课文档分享(点击联系客服),我们立即给予删除!




    关于我们 - 网站声明 - 网站地图 - 资源地图 - 友情链接 - 网站客服 - 联系我们

    copyright@ 2008-2019 麦多课文库(www.mydoc123.com)网站版权所有
    备案/许可证编号:苏ICP备17064731号-1 

    收起
    展开