Three-dimensional numerical approach for geometrical prediction of multilayer laser solid freeform fabrication process

2007 ◽  
Vol 19 (1) ◽  
pp. 14-25 ◽  
Author(s):  
Masoud Alimardani ◽  
Ehsan Toyserkani ◽  
Jan P. Huissoon
Keyword(s):  
Solid Freeform Fabrication ◽  
Three Dimensional ◽  
Numerical Approach ◽  
Fabrication Process ◽  
Freeform Fabrication ◽  
Laser Solid Freeform Fabrication

Effect of Preheating on the Delamination and Crack Formation in Laser Solid Freeform Fabrication Process

2008 ◽  
Author(s):  
Masoud Alimardani ◽  
Ehsan Toyserkani ◽  
Jan Paul Huissoon
Keyword(s):  
Thermal Stresses ◽  
Crack Formation ◽  
Solid Freeform Fabrication ◽  
Fabrication Process ◽  
Experimental Results ◽  
Stress Fields ◽  
Thin Wall ◽  
Freeform Fabrication ◽  
Micro Cracks ◽  
Laser Solid Freeform Fabrication

This paper presents a numerical-experimental investigation on the effects of preheating the substrate on the potential delamination and crack formation across the parts fabricated using the Laser Solid Freeform Fabrication (LSFF) process. For this purpose, the temperature distributions and stress fields induced during the multilayer LSFF process, and their correlation with the delamination and crack formation are studied throughout the numerical analysis and the experimental fabrication of a four-layer thin wall of SS304L. A 3D time-dependent numerical approach is used to simulate the LSFF process, and also interpret the experimental results in terms of the temperature distribution and the thermal stress fields. The numerical results show that by preheating the substrate prior to the fabrication process, the thermal stresses throughout the process domain substantially reduce. Accordingly, this can result in the reduction of potential micro-cracks formation across the fabricated part. Preheating also decreases the transient time for the development of a proper melt pool which is an important factor to prevent poor bonding between deposited layers. The experimental results are used to verify the numerical findings as well as the feasibility of preheating on the reduction of the micro-cracks formed throughout the fabrication process.

Process Parameters Optimization in Multilayer Laser Solid Freeform Fabrication Process Using a 3D Transient Numerical Model

2007 ◽  
Author(s):  
Masoud Alimardani ◽  
Ehsan Toyserkani ◽  
Christ P. Paul
Keyword(s):  
Process Parameters ◽  
Solid Freeform Fabrication ◽  
Parameters Optimization ◽  
Fabrication Process ◽  
Main Process ◽  
Thin Wall ◽  
Aisi 304L ◽  
Freeform Fabrication ◽  
Modeling Approach ◽  
Laser Solid Freeform Fabrication

This paper presents a 3D transient numerical approach for thermal and strain/stress modeling of the multilayer laser solid freeform fabrication process, by which correlations between the main process parameters and their effects on the final build-up properties can be studied. This model can be used to optimize the process parameters to increase the controllability of the geometrical and metallurgical variations resulted from the thermal and stress fields. Using this modeling approach, the geometry of the material deposited as well as temperature and thermal stress distributions across the process domain can be predicted based on the process parameters such as powder feed rate, process speed and laser power, assuming the interaction between the laser beam and powder stream is decoupled. The main process parameters affected by a multilayer deposition due to the formation of non-planar surfaces such as powder catchment are also incorporated into the modeling approach. To verify the proposed method, fabrication of a four-layer thin wall of stainless steel AISI 304L on a low carbon steel substrate is modeled with the same process parameters throughout the build-up process. The results show that the temperature and stress slightly increase at the end-points of layers 2, 3, and 4 which cause over deposited materials and micro-crack formations at these regions. The results are then used to discuss optimum process parameters which can be used to have a buildup with better geometrical and physical qualities. The reliability and accuracy of the model are experimentally verified.

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