scholarly journals Simulation of thermal behaviours and powder flow for direct laser metal deposition process

2018 ◽  
Vol 190 ◽  
pp. 02001
Author(s):  
Quanren Zeng ◽  
Yankang Tian ◽  
Zhenhai Xu ◽  
Yi Qin
Keyword(s):  
Cfd Simulation ◽  
Effective Means ◽  
Flow Distribution ◽  
Fem Analysis ◽  
Deposition Process ◽  
Metal Deposition ◽  
Powder Flow ◽  
Laser Metal Deposition ◽  
Melt Pool ◽  
Direct Laser

Laser engineering net-shaping (LENS), based on directed energy deposition (DED), is one of the popular AM technologies for producing fully dense complex metal structural components directly from laser metal deposition without using dies or tooling and hence greatly reduces the lead-time and production cost. However, many factors, such as powder-related and laser-related manufacturing parameters, will affect the final quality of components produced by LENS process, especially the powder flow distribution and thermal history at the substrate. The powder concentration normally determines the density and strength of deposited components; while the thermal behaviours of melt pool mainly determines the cooling rate, residual stress and consequent cracks in deposited components. Trial and errors method is obviously too expensive to afford for diverse applications of different metal materials and various manufacturing input parameters. Numerical simulation of the LENS process will be an effective means to identify reasonable manufacturing parameter sets for producing high quality crack-free components. In this paper, the laser metal powder deposition process of LENS is reported. The gas-powder flow distribution below the deposition nozzle is obtained via CFD simulation. The thermal behaviours of substrate and as-deposited layer/track during the LENS process are investigated by using FEM analysis. Temperature field distributions caused by the moving laser beam and the resultant melt pool on the substrate, are simulated and compared. The research offers a more accurate and practical thermal behaviour model for LENS process, which could be applied to further investigation of the interactions between laser, melt pool and powder particles; it will be particularly useful for manufacturing key components which has more demanding requirement on the components’ functional performance.

Vision-based defect detection in laser metal deposition process

2014 ◽  
Vol 20 (1) ◽  
pp. 77-85 ◽  
Author(s):  
Shyam Barua ◽  
Frank Liou ◽  
Joseph Newkirk ◽  
Todd Sparks
Keyword(s):  
Defect Detection ◽  
Detection System ◽  
Vision System ◽  
Low Cost ◽  
Deposition Process ◽  
Metal Deposition ◽  
Cooling Curve ◽  
Laser Metal Deposition ◽  
Content Type ◽  
Melt Pool

Purpose – Laser metal deposition (LMD) is a type of additive manufacturing process in which the laser is used to create a melt pool on a substrate to which metal powder is added. The powder is melted within the melt pool and solidified to form a deposited track. These deposited tracks may contain porosities or cracks which affect the functionality of the part. When these defects go undetected, they may cause failure of the part or below par performance in their applications. An on demand vision system is required to detect defects in the track as and when they are formed. This is especially crucial in LMD applications as the part being repaired is typically expensive. Using a defect detection system, it is possible to complete the LMD process in one run, thus minimizing cost. The purpose of this paper is to summarize the research on a low-cost vision system to study the deposition process and detect any thermal abnormalities which might signify the presence of a defect. Design/methodology/approach – During the LMD process, the track of deposited material behind the laser is incandescent due to heating by the laser; also, there is radiant heat distribution and flow on the surfaces of the track. An SLR camera is used to obtain images of the deposited track behind the melt pool. Using calibrated RGB values and radiant surface temperature, it is possible to approximate the temperature of each pixel in the image. The deposited track loses heat gradually through conduction, convection and radiation. A defect-free deposit should show a gradual decrease in temperature which enables the authors to obtain a reference cooling curve using standard deposition parameters. A defect, such as a crack or porosity, leads to an increase in temperature around the defective region due to interruption of heat flow. This leads to deviation from the reference cooling curve which alerts the authors to the presence of a defect. Findings – The temperature gradient was obtained across the deposited track during LMD. Linear least squares curve fitting was performed and residual values were calculated between experimental temperature values and line of best fit. Porosity defects and cracks were simulated on the substrate during LMD and irregularities in the temperature gradients were used to develop a defect detection model. Originality/value – Previous approaches to defect detection in LMD typically concentrate on the melt pool temperature and dimensions. Due to the dynamic and violent nature of the melt pool, consistent and reliable defect detection is difficult. An alternative method of defect detection is discussed which does not involve the melt pool and therefore presents a novel method of detecting a defect in LMD.

2D longitudinal modeling of heat transfer and fluid flow during multilayered direct laser metal deposition process

2012 ◽  
Vol 24 (3) ◽  
pp. 032008 ◽  
Author(s):  
Simon Morville ◽  
Muriel Carin ◽  
Patrice Peyre ◽  
Myriam Gharbi ◽  
Denis Carron ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Deposition Process ◽  
Metal Deposition ◽  
Longitudinal Modeling ◽  
Laser Metal Deposition ◽  
Direct Laser ◽  
Direct Laser Metal Deposition

scholarly journals Ultrasonic Characterization of Components Manufactured by Direct Laser Metal Deposition

Materials ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2658
Author(s):  
Anna Castellano ◽  
Marco Mazzarisi ◽  
Sabina Luisa Campanelli ◽  
Andrea Angelastro ◽  
Aguinaldo Fraddosio ◽  
...  
Keyword(s):  
Microstructural Analysis ◽  
Deposition Process ◽  
Metal Deposition ◽  
Laser Metal Deposition ◽  
Nickel Based Superalloy ◽  
Ultrasonic Characterization ◽  
Direct Laser ◽  
New Material ◽  
Direct Laser Metal Deposition

Direct laser metal deposition (DLMD) is an innovative additive technology becoming of key importance in the field of repairing applications for industrial and aeronautical components. The performance of the repaired components is highly related to the intrinsic presence of defects, such as cracks, porosity, excess of dilution or debonding between clad and substrate. Usually, the quality of depositions is evaluated through destructive tests and microstructural analysis. Clearly, such methodologies are inapplicable in-process or on repaired components. The proposed work aims to evaluate the capability of ultrasonic techniques to perform the mechanical characterization of additive manufactured (AM) components. The tested specimens were manufactured by DLMD using a nickel-based superalloy deposited on an AISI 304 substrate. Ultrasonic goniometric immersion tests were performed in order to mechanical characterize the substrate and the new material obtained by AM process, consisting of the substrate and the deposition. Furthermore, the relationship was evaluated between the acoustic and the mechanical properties of the AM components and the deposition process parameters and the geometrical characteristics of multiclad depositions, respectively. Finally, the effectiveness of the proposed non-destructive experimental approach for the characterization of the created deposition anomalies has been investigated.

A Methodology for Optimization of the Direct Laser Metal Deposition Process

2011 ◽  
Vol 473 ◽  
pp. 75-82 ◽  
Author(s):  
Andrea Angelastro ◽  
Sabina L. Campanelli ◽  
Giuseppe Casalino ◽  
Antonio D. Ludovico ◽  
Simone Ferrara
Keyword(s):  
Optimization Procedure ◽  
Deposition Process ◽  
Metal Deposition ◽  
Hard Coatings ◽  
Full Density ◽  
Laser Metal Deposition ◽  
Scanning Velocity ◽  
3D Cad ◽  
Direct Laser ◽  
Direct Laser Metal Deposition

Direct Laser Metal Deposition (DLMD) is actually one of the most attractive techniques in the group of Material Accretion Manufacturing (MAM) processes. In fact, the DLMD technology is able to realize, to repair and restore, objects, moulds and tools, directly from the 3D CAD model in a rapid and economic way. A great variety of metals, including those very difficult to work with the conventional techniques, can be shaped in a large number of complex geometries. This technique is also well suited to produce very hard coatings. The metallic parts, which are obtained through melting coaxially fed powders with a laser, present very good mechanical properties, with minimum porosity and good adhesion to the substrate. The objective of this work was to optimise the scanning velocity of the laser beam in order to maximize the density of DLMD parts. The optimization procedure was worked out with a mathematical model together with an experimental analysis to study the shape of the track clad generated melting coaxially fed powders with a laser. The material tested was Colmonoy 227-F, a nickel alloy specially designed for manufacturing moulds. The presented methodology has permitted to select the better combination of parameters that produce almost full density parts, free of cracks and well bonded to the substrate sintered parts.

Molten Pool Tracking Using a Superpixel-Based Approach in a Laser Metal Deposition Process

2021 ◽  
Vol 143 (10) ◽  
Author(s):  
Angel-Iván García-Moreno ◽  
Juan-Manuel Alvarado-Orozco ◽  
Juansethi Ibarra-Medina ◽  
Enrique Martínez-Franco
Keyword(s):  
Molten Pool ◽  
Infrared Camera ◽  
Ground Truth ◽  
Deposition Process ◽  
Metal Deposition ◽  
Laser Metal Deposition ◽  
Detector Resolution ◽  
Direct Laser ◽  
Color Similarity ◽  
Manufacturing Technologies

Abstract Nowadays, additive manufacturing technologies (AM) suffer from insufficient or lacking methodologies/techniques for quality control. This fact represents a key technological barrier preventing broader industrial adoption of AM, particularly in high-value applications where component failure cannot be accepted. This article presents a real-time melt pool segmentation and monitoring technique applicable to the direct laser metal deposition (LMD) process. An infrared camera with an InSb detector (resolution of 640 × 480, spectral range between 3 and 5 μm) was used. An algorithm, called gravitational superpixels, is presented. This algorithm can group pixels and generate superpixels based on a block generation technique that compares color similarity and temperature in infrared images. Besides, a color similarity correction is applied to reduce uncertainty in segmentation, as well as for eliminating the image background. The task of extracting edges is based on the law of universal gravitation. A quantitative and qualitative algorithm performance analysis, which uses standard metrics, is presented. The analysis demonstrates better versatility than reduction/feature extraction or image segmentation approaches by high-/low-pass filtering. The experimental validation was carried out, extracting and measuring the molten pool geometry and its thermal signature. Then, measures were compared against ground truth and against results obtained by other similar methods. The proposed gravitational superpixel method has higher precision and performance. Our proposal has a significant potential for monitoring industrial AM processes since it requires minimal modifications of commercially available industrial machines.

Sign in / Sign up

Export Citation Format

Share Document