无损检测-缺陷分析

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1、Chapter2DefectAnalysis本章提要：缺陷分析是无损检测的技术基础。主要解决两方面的问题：一是弄清defects’classification、propertyandharmfulness；二是分析thecausesofdefects，以便有效地Identifydefectsandeliminatedefects，提高工艺质量。本章重点讲授defects’classificationandharmfulness。缺陷的产生原因应结合《材料成型原理》课程内容深入理解与总结。最后，对Commonlyuseddetectionmetho

2、ds作简要介绍。2.1Conceptandclassificationofprocessdefects2.1.1Conceptofprocessdefects（1）Whataretheprocessdefects？在材料加工成型过程中，经常会出现某种或某些不合乎质量要求的appearancedefect,propertydefectandorganizationdefect和更为严重的internalgeometricdefect（如cracks、pores、inclusions等）。我们把这些“metallurgicalfactors、stru

3、cturalfactorsandtechnologicalfactors”导致的产品质量不符合相关参考标准的各类缺陷统称为工艺缺陷。（2）Dialecticalanalysisofprocessdefects①Theabsolutenessofdefectgeneration——Inactualproduction,theacquirementoftheproductswithoutanydefectsisquitedifficult；Itisnoteconomicalorevenimpossibletomaketheproductsproduc

4、edinbatcheswithoutanydefects.②Therelativityofdefectevaluationstandards——Therelativityofwastestandards.Asforthesameofvariousparts,thequalityrequirementsaredifferentduetothedifferentworkingconditions.Therefore,thewastestandardsarealsodifferent.③Formulationprincipleofwastestanda

5、rds：Generallyspeaking,thehighertheproductqualitylevelis,thegreatertheriskafterfailurewillbe,andthecontrolofdefectsshouldbemorestrict.Therefore,Itisnecessarytopayattentiontotheimplementationandreferencetotherelevantstandards,whichisalsocalledtheprincipleoffitnessforpurpose.④Re

6、pairofprocessdefects：Minordefectthatdonotaffecttheapplicationcanbetolerated.Seriousdefectthatdonotmeettherequirementsmustbetreated.Somedefectscanberepairedintime,andsomedefectsmaynotberepairedwhichmustbesentencedtowaste.Examples比如：Excessivereinforcement，属于焊缝形状不良，严重时可以Grinding

7、；必要时grindedthereinforcementsmooth。再如：sandinclusiononthesurfaceofcasting，可以通过repairwelding来修复。特别指出，考虑到焊接接头组织和性能的恶化，某些产品的weldingrepair不允许超过2次！所以，应该注意formulatearigorousrepairprocess，否则就会造成Economicloss！2.1.2Classificationofprocessdefects工艺缺陷种类繁多，产生原因也相当复杂。为了便于分析和处理工艺缺陷、制定检验工艺、方便技

8、术交流，有必要对其进行分类。(1)按technicalconnotation大体分为：①Manufacturingandassembly