Abstract
A contactless temperature measurement system is presented based on a hyperspectral line camera that captures the spectra in the visible and near infrared (VNIR) region of a large set of closely spaced points. The measured spectra are used in a nonlinear least squares optimization routine to calculate a one-dimensional temperature profile with high spatial resolution. Measurements of a liquid melt pool of AISI 316L stainless steel show that the system is able to determine the absolute temperatures with an accuracy of 10%. The measurements are made with a spatial resolution of 12 µm/pixel, justifying its use in applications where high temperature measurements with high spatial detail are desired, such as in the laser material processing and additive manufacturing fields.
Highlights
A good knowledge of the temperature distribution in a part is important in many material processing applications
This paper presents a method for measuring the surface temperature distribution of a melt pool of AISI 316L stainless steel with high spatial resolution
The spectral radiance emitted by the melt pool surface is captured with a hyperspectral camera and used in a nonlinear least squares optimization routine for obtaining an estimated temperature value
Summary
A good knowledge of the temperature distribution in a part is important in many material processing applications This is especially true in the fields of laser-based additive manufacturing and laser material processing, including technologies such as laser welding, cutting, hardening and cladding. These techniques all have in common that a high power laser beam is focused onto a metallic part which results in strong local heating and potential melting of the surface. A lot of research is directed towards the design of effective melt pool monitoring methods which can acquire reliable temperature information, possibly to be used in automatic feedback control systems [3,4,5,6,7]. The melt pool properties themselves would be disturbed by the sensor, which is why a contactless measurement system is usually preferred
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