scholarly journals Residual stress, distortion, and porosity analysis of LED heat sink printed by SLM process using machine learning

2021 ◽  
Author(s):  
Sumit Thakur ◽  
Gangadharudu Talla ◽  
Prakash Verma
Keyword(s):  
Machine Learning ◽  
Residual Stress ◽  
Residual Stresses ◽  
Heat Sink ◽  
Laser Power ◽  
Scanning Speed ◽  
Optimum Process ◽  
Light Emitting ◽  
Porosity Analysis ◽  
Hatch Spacing

Abstract In recent years, Light-emitting diodes (LEDs) are dominating the traditional lighting system. Besides mercury-free, they have small size, good break resistance and long life. Although LEDs are cool to touch, they generate a lot of unnecessary heat inside the gadgets. It is important to remove the heat using efficient thermal management component such as heat sink. Instead of using a conventional manufacturing process, selective laser melting (SLM) process is used to manufacture the heat sink. The quick solidification and various thermal regimes of the material during the SLM process led to the development of residual stresses that causes the part distortion and harm the mechanical properties of the component. The objective of the current study is to find the optimum value of laser power, scanning speed, and hatch spacing to bring down the residual stress and distortion in the SLM process to an acceptable range. Residual stress and distortion values of the heat sink are simulated using MSC Simufact additive and ANSYS Additive software. The conflicting nature between residual stress and porosity was observed. Hence, grey relation analysis was used to convert residual stress & porosity into a single objective. Optimum process parameters obtained were, laser power 80 (W), scanning speed 950 (mm/s), and hatch spacing of 70 (μm). The values of residual stress and porosity at optimum parameters were found to be 385.58 MPa and 12.21 %. Multiple regressions algorithm of machine learning was used to form a relationship between residual stresses and porosity. It was also observed that the magnitude of residual stress and distortion were low at lower energy densities and high at higher energy densities and the residual stress and porosities were high in the z-direction.

Simulation of Residual Stress in Lens Deposited H13 Tool Steel on Copper Substrate

2011 ◽  
Author(s):  
Tushar K. Talukdar ◽  
Liang Wang ◽  
Sergio D. Felicelli
Keyword(s):  
Residual Stress ◽  
Tool Steel ◽  
Laser Power ◽  
Copper Substrate ◽  
Scanning Speed ◽  
Temperature History ◽  
H13 Tool Steel ◽  
Scanning Strategies ◽  
Stress Accumulation ◽  
Free Edges

Solidification cracking represents a significant scientific and technical challenge in the rapid fabrication of bimetallic parts involving Cu and H13 tool steel. The main cause of the cracking formation is attributed to the residual stress accumulation, which depends on the thermal history and phase transformation during the deposition. In this research, a thermomechanical three-dimensional finite element model is developed to determine the temperature history and residual stress in Cu-H13 samples deposited by the Laser Engineered Net Shaping (LENS) process. The development of the model was carried out using the SYSWELD software package. The metallurgical transformations are taken into account using the temperature dependent material properties and the continuous cooling transformation diagram. Two different scanning strategies — alternative and unidirectional — are studied. The same model is also applied to a H13-H13 sample to compare the results. The input laser power is optimized for each layer and three different scanning speeds to maintain a steady molten pool size. It is observed that for a constant scanning speed the required laser power decreases with addition of more layers, and with the increase of scanning speed the laser power needs to be increased. The residual stress is found to be compressive near the center of the deposited wall and tensile at the free edges, which is consistent with the published experimental results in the literature. Similar stress distributions are obtained for both scanning strategies with higher stress concentration at the free edges of the interface between the substrate and the first layer. In these regions, the use of H13 substrate results in a higher stress accumulation than the Cu substrate.

scholarly journals Residual Stress Measurements in Mo/CuCrZr Tiles Using Neutron Diffraction

2008 ◽  
Vol 59 ◽  
pp. 299-303
Author(s):  
K. Mergia ◽  
Marco Grattarola ◽  
S. Messoloras ◽  
Carlo Gualco ◽  
Michael Hofmann
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Neutron Diffraction ◽  
Residual Stresses ◽  
Heat Sink ◽  
High Yield ◽  
Fusion Reactors ◽  
Plasma Facing Components ◽  
Induced Stresses ◽  
Compliant Layer

In plasma facing components (PFC) for nuclear fusion reactors tungsten or carbon based tiles need to be cooled through a heat sink. The joint between the PFC and the heat sink can be realized using a brazing process through the employment of compliant layer of either a low yield material, like copper, or a high yield material, like molybdenum. Experimental verification of the induced stresses during the brazing process is of vital importance. Strains and residual stresses have been measured in Mo/CuCrZr brazed tiles using neutron diffraction. The strains and stresses were measured in Mo tile along the weld direction and at different distances from it. The experimental results are compared with Finite Element Simulations.

Research on Warpage of Polystyrene in Selective Laser Sintering

2010 ◽  
Vol 43 ◽  
pp. 578-582 ◽  
Author(s):  
C.Y. Wang ◽  
Q. Dong ◽  
X.X. Shen
Keyword(s):  
Layer Thickness ◽  
Process Parameters ◽  
Laser Power ◽  
Selective Laser Sintering ◽  
Scanning Speed ◽  
Laser Sintering ◽  
Main Process ◽  
Influence Of Process Parameters ◽  
Temperature Changes ◽  
Hatch Spacing

Warpage is a crucial factor to accuracy of sintering part in selective laser sintering (SLS) process. In this paper, The influence of process parameters on warpage when sintering polystyrene(PS) materials in SLS are investigated. The laser power, scanning speed, hatch spacing, layer thickness as well as temperature of powder are considered as the main process parameters. The results showed that warpage increases with the increase of hatch space. Contary to it, warpage decreases with the increase of laser power. Warpage decreases with the increase of layer thickness between 0.16~0.18mm and changes little with increase of the thickness. Warpage increases along with the increase of scanning speed but decreases when the speed is over about 2000mm/s. When the temperature changes between 82°C-86°C, warpage decreases little with the increase of temperature. But further increase of temperature leads to warpage decreasing sharply when the temperature changes between 86°C-90°C.

An Analysis of Residual Stress Improvement for a Dissimilar Metal Nozzle-to-Pipe Weld by Using the Heat Sink Method

2008 ◽  
Author(s):  
J.-S. Park ◽  
J.-M. Kim ◽  
G.-H. Sohn ◽  
Y.-H. Kim
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Heat Sink ◽  
Nuclear Power ◽  
Power Plants ◽  
Base Alloy ◽  
Fatigue Cracking ◽  
Hole Drilling ◽  
Fe Model ◽  
Dissimilar Metal

This study is concerned with the mechanics analysis of residual stress improvement by the heat sink method applied to a dissimilar metal weld (DMW) for the use in nuclear power plants. The DMW joint considered here is composed of ferritic low-alloy steel nozzle, austenitic stainless steel safe-end, and nickel-base alloy A52 weld metal. To prepare the DMW joint with a narrow-gap, the gas tungsten arc welding (GTAW) process is utilized, and the heat sink method is employed to control thermal gradients developed in the critical region of work pieces during welding. Weld residual stresses are computed by the non-linear thermal elasto-plastic analysis using the axisymmetric finite element (FE) model, for which temperature-dependent thermal and mechanical properties of the materials are considered. A full-scale mock-up test is conducted to validate analytical solution for the DMW joint, and residual stresses are measured by using the hole-drilling method. Results of the FE modeling and mock-up test for the DMW joint are compared and effects of the heat sink method are discussed. It is found that a significant amount of residual compressive stresses can be developed on the inner surface of the DMW joint by using the heat sink method, which can effectively reduce the susceptibility of the welded materials to stress corrosion or fatigue cracking.

Residual Stresses Prediction for CO2 Laser Butt-Welding of 304-Stainless Steel

2006 ◽  
Vol 3-4 ◽  
pp. 125-130 ◽  
Author(s):  
Khaled Y. Benyounis ◽  
Abdul Ghani Olabi ◽  
M.S.J. Hashmi
Keyword(s):  
Residual Stress ◽  
Stainless Steel ◽  
Residual Stresses ◽  
Laser Power ◽  
Travel Speed ◽  
304 Stainless Steel ◽  
Hole Drilling ◽  
Design Matrix ◽  
Butt Welding ◽  
Input Variables

Residual stresses are an integral part of the total stress acting on any component in service. It is important to determine and/or predict the magnitude, nature and direction of the residual stress to estimate the life of important engineering parts, particularly welded components. This work aims to introduce experimental models to predict residual stresses in the heat-affected zone (HAZ). These models specify the effect of laser welding input parameters on maximum residual stress and its direction. The process input variables considered in this study are laser power (1.03 - 1.368 kW), travel speed (26.48 – 68.52 cm/min) and focal point position (- 1 to 0 mm). Laser butt-welding of 304 stainless steel plates of 3 mm thick were investigated using a 1.5 kW CW CO2 Rofin laser as a welding source. Hole-drilling method was employed to measure the magnitude, and direction of the maximum principal stress in and around the HAZ, using a CEA-06- 062UM-120 strain gauge rosette, which allows measurement of the residual stresses close to the weld bead. The experiment was designed based on Response Surface Methodology (RSM). Fifteen different welding conditions plus 5 repeat tests were carried out based on the design matrix. Maximum principal residual stresses and their directions were calculated for the twenty samples. The stepwise regression method was selected using Design-expert software to fit the experimental responses to a second order polynomial. Sequential F test and other adequacy measures were then used to check the models adequacy. The experimental results indicate that the proposed mathematical models could adequately describe the residual stress within the limits of the factors being studied. Using the models developed, the main and interaction effect of the process input variables on the two responses were determined quantitatively and presented graphically. It is observed that the travel speed and laser power are the main factors affecting the behavior of the residual stress. It is recommended to use the models to find the optimal combination of welding conditions that lead to minimum distortion.

Machine Learning Approach for Estimating Residual Stresses in Girth Welds of Topside Piping

2020 ◽  
Author(s):  
Sachin Bhardwaj ◽  
R. M. Chandima Ratnayake ◽  
Arvind Keprate ◽  
Xavier Ficquet
Keyword(s):  
Machine Learning ◽  
Residual Stress ◽  
Residual Stresses ◽  
Gradient Boosting ◽  
Support Vector ◽  
Welding Parameters ◽  
Learning Approach ◽  
Machine Learning Approach ◽  
Boosting Algorithm ◽  
Girth Welds

Abstract Residual stresses are internal self-equilibrating stresses that remain in the component even after the removal of external load. The aforementioned stress when superimposed by the operating stresses on the offshore piping, enhance the chances of fracture failure of the components. Thus, it is vital to accurately estimate the residual stresses in topside piping while performing their fitness for service (FFS) evaluation. In the present work, residual stress profiles of girth welded topside sections of P91 pipes piping are estimate using a machine learning approach. The training and testing data for machine learning is acquired from experimental measurements database by Veqter, UK. Twelve different machine learning algorithms, namely, multi-linear regression (MLR), Random Forest (RF), Gaussian process regression (GPR), support vector regression (SVR), Gradient boosting (GB) etc. have been trained and tested. In order to compare the accuracy of the algorithms, four metrics, namely, Root Mean Square Error (RMSE), Estimated Variance Score (EVS), Maximum Absolute Error (AAE), and Coefficient of Determination (R^2) are used. Gradient boosting algorithm gives the best prediction of the residual stress, which is then used to estimate the residual stress for the simulated input parameter space. In the future work authors shall utilize the residual stress predictions from Gradient boosting algorithm to train the Bayesian Network, which can then be used for estimating less conservative through-thickness residual stresses distribution over a wide range of pipe geometries (radius to thickness ratio) and welding parameters (based on heat input). Furthermore, besides topside piping, the proposed approach finds its potential applications in structural integrity assessment of offshore structures, and pressure equipment’s girth welds.

scholarly journals Study on residual stresses caused by underwater friction stir welding: FE modeling and ultrasonic measurement

2018 ◽  
Vol 233 (1) ◽  
pp. 118-137
Author(s):  
Solaleh Salimi ◽  
Pouya Bahemmat ◽  
Mohammad Haghpanahi
Keyword(s):  
Residual Stress ◽  
Friction Stir Welding ◽  
Residual Stresses ◽  
Ultrasonic Method ◽  
Stress Fields ◽  
Optimum Process ◽  
Friction Stir ◽  
Mechanical Deformations ◽  
Underwater Friction Stir Welding ◽  
Precipitation Phenomena

Predicting residual stresses arising from the thermal and mechanical loading history during engineering processes including welding would be a viable tool to reach the optimum process parameters. In the present article, an elasto-thermo-visco-plastic model has been employed to estimate the residual stress caused by the underwater friction stir welding, which are resulted by large thermo-mechanical deformations on one hand and rapid cooling arising from the enormous non-uniform boiling heat convention of water on the other hand. Finally, the numerical results are compared with experimental data acquired by the ultrasonic method to evaluate the accuracy of the simulation process. Regarding the low temperature during underwater friction stir welding, the employed constitutive equations result in acceptable residual stress fields, while for in-air case, the amount of error increases significantly due to experience of high temperatures and intensification in hardening precipitation phenomena.

scholarly journals Optimization of Process Parameters, Microstructure, and Properties of Laser Cladding Fe-Based Alloy on 42CrMo Steel Roller

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2061 ◽  
Author(s):  
Jiang Ju ◽  
Yang Zhou ◽  
Maodong Kang ◽  
Jun Wang
Keyword(s):  
Laser Cladding ◽  
Process Parameters ◽  
Laser Power ◽  
Salt Spray ◽  
Continuous Casting Machine ◽  
Scanning Speed ◽  
Optimum Process ◽  
Chemical Compositions ◽  
Cladding Layer ◽  
42Crmo Steel

The mould foot roller is a key component of a continuous casting machine. In order to investigate the possibility of using laser cladding to repair mould foot roller, Fe-based powders and 42CrMo steel are used in this work. The laser cladding process parameters were optimized by orthogonal experiments. The chemical compositions, microstructure, properties of the cladding layer under the optimum process parameters, and substrate were systematically investigated by using optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), microhardness test, wear test, and salt spray corrosion test. The results indicate that the primary factor affecting the width and depth of the cladding layer is laser power. The scanning speed also has a significant effect on the height of the cladding layer. The optimum process parameters for repairing the mould foot roller are 2 kW laser power, 4 mm/s scanning speed, and 15 g/min feeding rate of powder. Along the depth direction of the cladding layer, the microstructure of the coating gradually transforms from plane crystal, cell grains, or dendrites to equiaxed grains. The matrix is mainly martensite with retained austenite; the eutectic phase is composed of netlike M2B, particulate M23(C,B)6, and M7(C,B)3 phase. The hardness of the cladding layer is significantly improved, about three times that of the substrate. The weight loss of the cladding layer is just half that of the substrate. Its wear resistance and corrosion resistance have been significantly improved. The work period of the laser cladding-repaired foot roller is much longer than for the surfacing welding-repaired one. In summary, laser cladding technology can increase the life of mould foot rollers.

scholarly journals Modeling of Residual Stress Distribution for Components Manufactured by Selective Laser Melting

2019 ◽  
Vol 224 ◽  
pp. 05006
Author(s):  
Tong Ye ◽  
Xiaohui Jiang ◽  
Miaoxian Guo ◽  
Vladimir Kuptsov ◽  
Sergey Fedorov
Keyword(s):  
Residual Stress ◽  
Stress Distribution ◽  
Selective Laser Melting ◽  
Laser Power ◽  
Laser Scanning ◽  
Scanning Speed ◽  
Residual Stress Distribution ◽  
Laser Melting ◽  
Laser Scanning Speed ◽  
Formed Part

In this paper, the selective laser melting (SLM) simulation analysis of components is carried out. The residual stress distribution of the formed part was predicted, and the influence of process parameters such as exposure time, laser power and laser scanning speed on the residual stress of the SLM formed part was analyzed. It was found that the residual stress concentration of the formed part was in the middle of the upper surface or the bottom surface. In addition, the laser power and the laser scanning speed have a great influence on the residual stress of the formed part. The results of this study lay a theoretical and experimental basis for the optimization of residual stress and quality control of SLM components.

scholarly journals Laser Powder Bed Fusion of Pure Tungsten: Effects of Process Parameters on Morphology, Densification, Microstructure

Materials ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 165
Author(s):  
Junfeng Li ◽  
Yunxiao Wu ◽  
Bokang Zhou ◽  
Zhengying Wei
Keyword(s):  
Relative Density ◽  
Laser Power ◽  
Grain Morphology ◽  
Scanning Speed ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
High Laser ◽  
Columnar Grains ◽  
Hatch Spacing

Tungsten has been widely used in many industrial fields due to its excellent properties. However, owing to its characteristics of inherent brittleness at room temperature and high melting point, it is difficult to prepare tungsten parts with high complexity via traditional methods. In the present work, tungsten samples were prepared by laser powder bed fusion. The influence of each process parameter including laser power, scanning speed, and hatch spacing on the surface morphology, densification, and microstructure of tungsten samples was systematically investigated. The results showed that the use of the appropriate parameters, especially high laser power, can effectively improve the surface quality and obtain a dense surface. The tungsten samples with a relative density of 98.31% were obtained with optimized parameter combinations: a laser power of 300 W, scanning speed of 400 mm/s, and hatch spacing of 0.08 mm. Compared with scanning speed and hatch spacing, the laser power had a more obvious influence on the relative density. Additionally, for the grain morphology by microstructure inspection, elongated curved grains gradually transformed into fine straight columnar grains as the scanning speed increased. The hatch spacing would change the grain morphology slightly but had no significant effect on the grain size.

Sign in / Sign up

Export Citation Format

Share Document