无损检测

[中文适用范围]： 无损检测是在不限制其有用性的情况下检测与零件或材料的适用性或质量相关的因素的测试。可检测表面裂纹、搭接、凹坑、内部夹杂物、爆裂、收缩、接缝、热撕裂等材料缺陷，并进行成分分析。有时可以确定它们的尺寸和确切位置。此类测试通常可以快速进行。诸如硬度、渗层深度、壁厚、延展性、脱碳、裂纹、表观抗拉强度、晶粒尺寸以及焊缝熔深或熔合缺失等加工结果是可检测和可测量的。腐蚀和疲劳裂纹等使用结果可以通过无损检测方法检测和测量。在许多情况下，可以自动检测缺陷，以便对零件或材料进行分类。 [外文原描述]： Nondestructive tests are those tests which detect factors related to the serviceability or quality of a part or material without limiting its usefulness. Material defects such as surface cracks, laps, pits, internal inclusions, bursts, shrink, seam, hot tears, and composition analysis can be detected. Sometimes their dimensions and exact location can be determined. Such tests can usually be made rapidly. Processing results such as hardness, case depth, wall thickness, ductility, decarburization, cracks, apparent tensile strength, grain size, and lack of weld penetration or fusion may be detectable and measurable. Service results such as corrosion and fatigue cracking may be detected and measured by nondestructive test methods. In many cases, imperfections can be automatically detected so that parts or materials can be classified.The SAE Handbook describes the following nondestructive test methods:SAE J359—InfraredSAE J420—Magnetic ParticleSAE J425—Eddy CurrentSAE J426—Liquid PenetrantSAE J427—Penetrating RadiationSAE J428—UltrasonicSAE J1242—Acoustic EmissionSAE J1267—Leakage TestingTable 1 summarizes the principal features of most of these tests. In addition to the tests described, other nondestructive tests exist which are less well established, but whose use is expanding. Among these are microwave tests, holography, and sonic tests. Microwaves are used to locate defects in nonmetallic substances and to determine some physical characteristics of those materials. Optical holography uses coherent light from a laser beam to detect strains and defects in materials by means of three-dimensional imaging and interferometry techniques. Acoustical holography uses ultrasonic waves to image discontinuities in the interior of solids. Recent refinements in sonic testing permit more objective determination of the physical properties of cast iron. Complete information concerning each nondestructive test can be obtained from books listed in the bibliographies of the aforementioned reports.Increasing consumer demand for product quality at reasonable cost has resulted in development of nondestructive tests which can be applied to materials and manufactured parts. Although a variety of complementary nondestructive methods is available, development time is generally required for application to specific materials or products. The effect of part contour, surface condition, heat treatment, composition variation, and other variables may limit the ability of certain tests to detect imperfections with desired accuracy.Nondestructive tests properly applied to basic material can add greater assurance of performance to design strengths, thereby affecting material and manufacturing economy. In addition, parts can be tested after each basic operation which is critical to service performance of the finished part. In-process nondestructive tests can also serve as basic components of feedback process control systems since all tests are based upon measurements which do not damage the material or part being inspected.Cross Reference: J1242_201801,J1267_201801,J359_201801,J420_201801,J425_201801,J426_201801,J427_201801,J428_201801