電磁檢測(cè)是無損檢測(cè)中的一種，用于查找物體中的缺陷。每種測(cè)試都有不同的應(yīng)用和方法。所有測(cè)試都使用電場(chǎng)或磁場(chǎng)，有些測(cè)試同時(shí)使用電場(chǎng)或磁場(chǎng)。根據(jù)所使用的測(cè)試類型，電流或磁場(chǎng)的變化，當(dāng)它通過或圍繞被測(cè)試的物體發(fā)生電磁轉(zhuǎn)化時(shí)，則信號(hào)指向可能存在的缺陷或缺陷。

渦流檢測(cè)技術(shù)是利用電磁感應(yīng)原理，通過測(cè)定被檢工件內(nèi)感生渦流的變化來無損評(píng)定導(dǎo)電材料及其工件的某些性能，或發(fā)現(xiàn)缺陷的無損檢測(cè)。

與渦流伴生的感應(yīng)磁場(chǎng)與原磁場(chǎng)疊加，使得檢測(cè)線圈的復(fù)阻抗發(fā)生變化。導(dǎo)體內(nèi)感生渦流的幅值、相位、流動(dòng)形式及其伴生磁場(chǎng)受導(dǎo)體的物理特性影響，因此通過監(jiān)測(cè)檢測(cè)線圈的阻抗變化即可非破壞地評(píng)價(jià)導(dǎo)體的物理和工藝性能，此即渦流檢測(cè)的基本原理。

常規(guī)渦流檢測(cè)是一種表面或近表面的無損檢測(cè)方法。由于渦流因電磁感應(yīng)而生，因此進(jìn)行渦流檢測(cè)時(shí)，檢測(cè)線圈不必與被檢材料或工件緊密接觸，不需用耦合劑，檢測(cè)過程不影響被檢材料或工件的性能。

與其它無損檢測(cè)方法比較,渦流檢測(cè)的主要特點(diǎn)有：

對(duì)導(dǎo)電材料表面和近表面缺陷的檢測(cè)靈敏度較高；應(yīng)用范圍廣，對(duì)影響感生渦流特性的各種物理和工藝因素均能實(shí)施監(jiān)測(cè)；不需用耦合劑，易于實(shí)現(xiàn)管、棒、線材的高速、高效、自動(dòng)化檢測(cè)；在一定條件下,能反映有關(guān)裂紋深度的信息；可在高溫、薄壁管、細(xì)線、零件內(nèi)孔表面等其它檢測(cè)方法不適用的場(chǎng)合實(shí)施監(jiān)測(cè)。渦流檢測(cè)的缺點(diǎn)是檢測(cè)效率相對(duì)較低;另外，僅依靠渦流檢測(cè)通常也難以區(qū)分缺陷的種類和形狀。

An electromagnetic test is a class of non-destructive testing used to find defects in an object. Each type of test has a different application and methodology. All tests use electricity or magnetic fields, with some using both. Depending on the specific type of testing used, the amount of electrical current that is reflected, refracted or otherwise conducted through the piece is measured. Changes in the current or magnetic field, as it moves through or around an object being tested, point to possible flaws or defects.

In the past, the term “electromagnetic test” typically referred to eddy-current testing. Eddy-current testing finds defects close to the surface of metal objects. Improvements in testing capabilities, however, have resulted in an ever-expanding number of electromagnetic test options. Other tests such as remote field testing, magnetic flux leakage testing, wire-rope testing and magnetic particle inspection allow users to test for defects in a variety materials, shapes and locations. Using electricity and magnetic fields, each type of electromagnetic test produces a response that points to cracks, heat damage, corrosion or other flaws in a broad range of materials and environments.

Aside from detecting defects, the use of electricity in magnetic fields can also help determine the other unseen properties of metal, earth and soft tissue. Results indicate material thickness, electrical conductivity, the presence of foreign objects and other information. The purpose of any electromagnetic test is to provide the ability to gather information before embarking on expensive or unnecessary digging, dissembling or surgery or to ensure the safety of a manufactured component.

Examples of the many uses of various types of electromagnetic testing can be found in commercial construction and the medical field. For example, pulsed eddy-current testing is used on pipes to determine metal loss without the need to expose the actual pipe. This type of electromagnetic testing can be done from a considerable distance when direct access to the pipe in question is not practical.

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