Thermographic testing of spot welds

Schlichting, J.; Brauser, Stephan; Pepke, Lutz-Alexander; Maierhofer, Ch.; Rethmeier, Michael; Kreutzbruck, Marc

doi:10.1016/j.ndteint.2012.02.003

Cited by 44 publications

(17 citation statements)

References 7 publications

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“…The other effect was due to varying surface emissivity of the sample due to discolorations and contaminations of the surface and to surface scratches. In [3] and [4], the solution for this problem was to coat the sample with a material of high emissivity, which homogenizes the emissivity. However, this is not a viable solution for industrial testing.…”

Section: Resultsmentioning

confidence: 99%

“…Therein, it was proposed to conduct the thermographic testing in reflection geometry or transmission geometry. In [3] thermographic testing procedure in transmission geometry was carried out. In order to compensate for the varying surface emissivity and to raise the signal intensity, the samples were coated with a material of high emissivity.…”

Section: Introductionmentioning

confidence: 99%

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Laser based spot weld characterization

Jonietz¹,

Myrach²,

Rethmeier³

et al. 2016

AIP Conference Proceedings

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Abstract. Spot welding is one of the most important joining technologies, especially in the automotive industry. Hitherto, the quality of spot welded joints is tested mainly by random destructive tests. A nondestructive testing technique offers the benefit of cost reduction of the testing procedure and optimization of the fabrication process, because every joint could be examined. This would lead to a reduced number of spot welded joints, as redundancies could be avoided. In the procedure described here, the spot welded joint between two zinc-coated steel sheets (HX340LAD+Z100MB or HC340LA+ZE 50/50) is heated optically on one side. Laser radiation and flash light are used as heat sources. The melted zone, the so called "weld nugget" provides the mechanical stability of the connection, but also constitutes a thermal bridge between the sheets. Due to the better thermal contact, the spot welded joint reveals a thermal behavior different from the surrounding material, where the heat transfer between the two sheets is much lower. The difference in the transient thermal behavior is measured with time resolved thermography. Hence, the size of the thermal contact between the two sheets is determined, which is directly correlated to the size of the weld nugget, indicating the quality of the spot weld. The method performs well in transmission with laser radiation and flash light. With laser radiation, it works even in reflection geometry, thus offering the possibility of testing with just one-sided accessibility. By using heating with collimated laser radiation, not only contactfree, but also remote testing is feasible. A further convenience compared to similar thermographic approaches is the applicability on bare steel sheets without any optical coating for emissivity correction. For this purpose, a proper way of emissivity correction was established.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Laser based spot weld characterization

Jonietz¹,

Myrach²,

Rethmeier³

et al. 2016

AIP Conference Proceedings

View full text Add to dashboard Cite

show abstract

“…Thus, the defect turns into the heat source and can be directly detected on the thermal image. The active thermographic monitoring methods are used for the detection of cracks in ceramic (Kurita et al 2009), metallic (Kordatos et al 2012) and composite materials (Fernandes et al 2015;Mendioroz et al 2017), delamination failure in composite materials (Fernandes et al 2015), welding inspection (Schlichting et al 2012). …”

Section: Acoustic Emission Monitoringmentioning

confidence: 99%

Computational monitoring in real time: review of methods and applications

Dyskin

Başarır

Doherty

et al. 2018

Geomech. Geophys. Geo-energ. Geo-resour.

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Continuous monitoring of mechanical parameters determining the state of natural and manmade systems is essential in a wide range of engineering disciplines from mechanical to civil and geotechnical engineering. To be effective, the monitoring response time needs to be commensurate with the characteristic time of variation of the processes being monitored e.g. from seconds as for example in some machinery, to weeks and months for mining excavations and years in the case of structures. The methods of measurement can therefore differ significantly for different applications. In spite of this, the methods of information processing-the computational monitoring-have considerable commonality. This review focuses on the methods of computational monitoring in solid and structural mechanics problems in different engineering applications. The traditional methods of monitoring are reviewed along with the corresponding computational and measurement methods. The basic principles of the computational monitoring in real time are established.

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“…All experiments were conducted with a transmission set-up, double sided. Both Schlichting et al [7] and Shpartko et al [8] used a flash lamp for heating a spot weld area and determined the spot weld position and size in a transmission setup. Lee et al [6] used lock-in thermography to measure the nugget size of a spot weld.…”

Section: Related Workmentioning

confidence: 99%

Automatic Inspection of Spot Welds by Thermography

et al. 2014

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The interest for thermography as a method for spot weld inspection has increased during the last years since it is a full-field method suitable for automatic inspection. Thermography systems can be developed in different ways, with different physical setups, excitation sources, and image analysis algorithms. In this paper we suggest a single-sided setup of a thermography system using a flash lamp as excitation source. The analysis algorithm aims to find the spatial region in the acquired images corresponding to the successfully welded area, i.e., the nugget size. Experiments show that the system is able to detect spot welds, measure the nugget diameter, and based on the information also separate a spot weld from a stick weld. The system is capable to inspect more than four spot welds per minute, and has potential for an automatic non-destructive system for spot weld inspection. The development opportunities are significant, since the algorithm used in the initial analysis is rather simplified. Moreover, further evaluation of alternative excitation sources can potentially improve the performance.

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Thermographic testing of spot welds

Cited by 44 publications

References 7 publications

Laser based spot weld characterization

Laser based spot weld characterization

Computational monitoring in real time: review of methods and applications

Automatic Inspection of Spot Welds by Thermography

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