无损检测是指检测与零件或材料的可用性或质量相关的因素而不限制其用途的检测。可以检测到材料缺陷，如表面裂纹、搭接、凹坑、内部夹杂物、爆裂、收缩、接缝、热裂和成分分析。有时可以确定它们的尺寸和确切位置。这种测试通常可以快速进行。加工结果，如硬度、涂层深度、壁厚、延展性、脱碳、裂纹、表观抗拉强度、晶粒尺寸以及焊缝未焊透或未熔合，可能是可检测和可测量的。 腐蚀和疲劳裂纹等使用结果可通过无损检测方法进行检测和测量。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。SAE手册描述了以下无损检测方法:SAE J359–红外线SAE J420–磁性颗粒SAE J425–涡流SAE J426–液体渗透SAE J427–穿透辐射SAE J428–超声波SAE J1242–声发射SAE J1267–泄漏检测表1总结了大多数这些检测的主要特征。 除上述试验外，还存在其他非破坏性试验，这些试验不太成熟，但其用途正在扩大。其中包括微波测试、全息测试和声波测试。微波用于定位非金属物质中的缺陷，并确定这些材料的某些物理特性。光学全息利用激光束的相干光，通过三维成像和干涉测量技术检测材料中的应变和缺陷。声全息术使用超声波成像固体内部的不连续性。 最近对声波测试的改进使铸铁的物理性能得到了更客观的测定。有关每项无损检测的完整信息可从上述报告的参考书目中列出的书籍中获得。消费者对合理成本的产品质量的需求不断增加，导致了可应用于材料和制造零件的无损检测技术的发展。尽管有多种互补的无损检测方法可用，但应用于特定材料或产品通常需要开发时间。 零件轮廓、表面状况、热处理、成分变化和其他变量的影响可能会限制某些测试以所需精度检测缺陷的能力。对基本材料进行适当的无损检测可以为设计强度的性能增加更大的保证，从而影响材料和制造经济性。此外，每个基本操作后都可以对零件进行测试，这对成品零件的使用性能至关重要。过程中无损检测也可以作为反馈过程控制系统的基本组成部分，因为所有检测都基于不会损坏被检测材料或零件的测量。

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.