Closed-loop control of microstructure and mechanical properties in additive manufacturing by directed energy deposition

DMLS İLE EKLEMELİ İMALATTA DENGESİZ SICAKLIK DAĞILIMI ve PARÇAYA ETKİLERİNİN ARAŞTIRILMASI

“…Bu çalışma kapsamında sıcaklık değişimleri, şekil hataları, kalıntı gerilmeler ve boyutsal toleranslar konularına irdelenecektir. Kalıntı gerilmeler ve boyutsal değişimler, sıcaklık dağılımının doğrudan bir sonucu olarak gözlenecektir [19,22,33,[35][36][37][38][39][40][41]. Şekil 6.…”

Calibrated Closed-Loop Control to Reduce the Effect of Geometry on Mechanical Behaviour in Directed Energy Deposition

“…Camera-based monitoring provides much more information about the melt pool than photodiodes, including the shape and distribution of intensity across the image. Hofman et al (2012) used an optical camera (400-1000 nm wavelength, 200 Hz) to monitor a laser cladding process, while for monitoring DED, Akbari and Kovacevic (2019) used a near-infrared camera (700+ nm wavelength, 200 Hz) and Farshidianfar et al (2021) used a thermal infrared camera (7.5-14 µm wavelength, 30 Hz).…”

“…Using the width allows the virtual measurement to be calibrated to a physical measurement from a built component, as demonstrated by Akbari and Kovacevic (2019), adding a link in the chain of process qualification. Melt pool images have also been used with pixel tracking to calculate live cooling rates (Farshidianfar et al, 2021).…”

“…DED has a large number of build parameters including power, speed, hatch spacing, layer thickness, scan strategy and powder flow rate. Commonly, the adjusted parameter is either the laser power (Akbari and Kovacevic, 2019) or travel speed (Farshidianfar et al, 2021), but studies have also considered live modifications to the scan strategy to avoid localised heat build-up (Nassar et al, 2015). Comprehensive parameter studies have demonstrated that laser power is the most significant factor affecting melt pool width (Qi et al, 2010).…”

Laser metal deposition materials-process-performance characterization studies

“…Future work should also include a parametric study on the number, size, and type of defects that occur at the interface. Farshidianfar et al applied a pre-solidification pre-heating to define the primary solidification heat cycle's initial temperature before deposition that achieves a more consistent microstructural grain growth and minimise defect formation [208]. Apart from applying a pre-solidification pre-heating, additional localised control was used to regulate the cooling rate to a uniform rate at all deposited layers.…”