In-situ monitoring of a laser metal deposition (LMD) process: comparison of MWIR, SWIR and high-speed NIR thermography

Altenburg, Simon J.; Straße, Anne; Gumenyuk, Andrey; Maierhofer, Christiane

doi:10.1080/17686733.2020.1829889

Cited by 49 publications

(23 citation statements)

References 19 publications

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“…This was in good agreement with the visually noticeable tempering colors and the literature review. For example, apparent emissivity values of 0.58 were determined using the same camera in the laser metal deposition of AISI 316L, where stronger oxidation is expected to occur due to a less efficient shielding of oxygen by a local shielding gas flow in surrounding air conditions [34].…”

Section: Oxidation Effects On the Apparent Emissivity Of The 316l L-pbf Surfacementioning

confidence: 99%

Experimental Determination of the Emissivity of Powder Layers and Bulk Material in Laser Powder Bed Fusion Using Infrared Thermography and Thermocouples

Mohr

Nowakowski

Altenburg

et al. 2020

Metals

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Recording the temperature distribution of the layer under construction during laser powder bed fusion (L-PBF) is of utmost interest for a deep process understanding as well as for quality assurance and in situ monitoring means. While having a notable number of thermal monitoring approaches in additive manufacturing (AM), attempts at temperature calibration and emissivity determination are relatively rare. This study aims for the experimental temperature adjustment of an off-axis infrared (IR) thermography setup used for in situ thermal data acquisition in L-PBF processes. The temperature adjustment was conducted by means of the so-called contact method using thermocouples at two different surface conditions and two different materials: AISI 316L L-PBF bulk surface, AISI 316L powder surface, and IN718 powder surface. The apparent emissivity values for the particular setup were determined. For the first time, also corrected, closer to real emissivity values of the bulk or powder surface condition are published. In the temperature region from approximately 150 °C to 580 °C, the corrected emissivity was determined in a range from 0.2 to 0.25 for a 316L L-PBF bulk surface, in a range from 0.37 to 0.45 for 316L powder layer, and in a range from 0.37 to 0.4 for IN718 powder layer.

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Section: Oxidation Effects On the Apparent Emissivity Of The 316l L-pbf Surfacementioning

confidence: 99%

Experimental Determination of the Emissivity of Powder Layers and Bulk Material in Laser Powder Bed Fusion Using Infrared Thermography and Thermocouples

Mohr

Nowakowski

Altenburg

et al. 2020

Metals

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“…The accuracy of determining the surface temperature is limited by the unknown emissivity ε . In addition, emissivity can change during additive manufacturing (AM), as it depends on material, temperature, viewing angle, surface roughness, and presence of oxide films [ 17 , 18 ]. As a consequence, the instrument-calibration process is extremely difficult.…”

Section: Introductionmentioning

confidence: 99%

Analytical Solution of the Non-Stationary Heat Conduction Problem in Thin-Walled Products during the Additive Manufacturing Process

2021

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The work is devoted to the development of a model for calculating transient quasiperiodic temperature fields arising in the direct deposition process of thin walls with various configurations. The model allows calculating the temperature field, thermal cycles, temperature gradients, and the cooling rate in the wall during the direct deposition process at any time. The temperature field in the deposited wall is determined based on the analytical solution of the non-stationary heat conduction equation for a moving heat source, taking into account heat transfer to the environment. Heat accumulation and temperature change are calculated based on the superposition principle of transient temperature fields resulting from the heat source action at each pass. The proposed method for calculating temperature fields describes the heat-transfer process and heat accumulation in the wall with satisfactory accuracy. This was confirmed by comparisons with experimental thermocouple data. It takes into account the size of the wall and the substrate, the change in power from layer to layer, the pause time between passes, and the heat-source trajectory. In addition, this calculation method is easy to adapt to various additive manufacturing processes that use both laser and arc heat sources.

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“…In order to correctly assess temperature distribution on the housing of electronic components, it is necessary to take into account all factors that can influence the measurement [ 6 , 7 , 8 ]. The most important of them include the value of the emissivity coefficient ε [ 9 ], the reflected temperature ϑ r [ 10 ], the distance between the lens and the observed object d [ 11 ], the ambient temperature ϑ a [ 12 ], the temperature of the external optical system [ 13 ], the transmittance of the external optical system [ 14 , 15 ], the relative humidity ω [ 16 ], the viewing angle β [ 7 ], and the sharpness of the recorded thermogram [ 17 , 18 , 19 ]. An assessment of the influence of the abovementioned factors on the accuracy of the thermographic temperature measurement of small-sized electronic components is possible thanks to the use of a microscopic thermography stand.…”

Section: Introductionmentioning

confidence: 99%

The Solution for the Thermographic Measurement of the Temperature of a Small Object

Hulewicz

Dziarski

Dombek

2021

Sensors

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This article describes the measuring system and the influence of selected factors on the accuracy of thermographic temperature measurement using a macrolens. This method enables thermographic measurement of the temperature of a small object with an area of square millimeters as, e.g., electronic elements. Damage to electronic components is often preceded by a rise in temperature, and an effective way to diagnose such components is the use of a thermographic camera. The ability to diagnose a device under full load makes thermography a very practical method that allows us to assess the condition of the device during operation. The accuracy of such a measurement depends on the conditions in which it is carried out. The incorrect selection of at least one parameter compensating the influence of the factor occurring during the measurement may cause the indicated value to differ from the correct value. This paper presents the basic issues linked to thermographic measurements and highlights the sources of errors. A measuring stand which enables the assessment of the influence of selected factors on the accuracy of thermographic measurement of electronic elements with the use of a macrolens is presented.

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In-situ monitoring of a laser metal deposition (LMD) process: comparison of MWIR, SWIR and high-speed NIR thermography

Cited by 49 publications

References 19 publications

Experimental Determination of the Emissivity of Powder Layers and Bulk Material in Laser Powder Bed Fusion Using Infrared Thermography and Thermocouples

Experimental Determination of the Emissivity of Powder Layers and Bulk Material in Laser Powder Bed Fusion Using Infrared Thermography and Thermocouples

Analytical Solution of the Non-Stationary Heat Conduction Problem in Thin-Walled Products during the Additive Manufacturing Process

The Solution for the Thermographic Measurement of the Temperature of a Small Object

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