Mohamad Bayat

Mohamad Bayat
Technical University of Denmark | DTU · Department of Mechanical Engineering

Multiphysics and multiscale simulation Metal additive manufacturing Thermal management devices Multiphase flow

About

39
Publications
16,645
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
585
Citations
Citations since 2017
39 Research Items
585 Citations
2017201820192020202120222023050100150200250
2017201820192020202120222023050100150200250
2017201820192020202120222023050100150200250
2017201820192020202120222023050100150200250
Introduction
I am currently working as a tenure-track assistant professor at DTU, Denmark and my main activities involve teaching fundamental courses like heat transfer at bachelor level as well as more advanced courses like thermo-mechanics at master level. My two main research areas are multiphysics simulation of advanced manufacturing processes and numerical/experimental analysis of single- and two-phase thermal management devices. My plan is to forma scientific group within advanced heat transfer.
Additional affiliations
October 2020 - present
Technical University of Denmark
Position
  • PostDoc Position
October 2017 - October 2020
Technical University of Denmark
Position
  • PhD Student
Description
  • Modelling the thermo-mechanical-metallurgical conditions during precision additive metal manufacturing (PAM^2) Marie-Curie-Skłodowska ITN
September 2015 - September 2017
Sharif University of Technology
Position
  • Master's Student
Description
  • In the thesis, I proposed a novel algorithm to extract the thermodynamic properties from the novel E-PPR 78 equation of state and subsequently solve the phase equilibrium problem in a cryogenic distillation column.

Publications

Publications (39)
Chapter
Additive Manufacturing (AM) technologies, also known as 3D Printing technologies are one of the main driving technologies of the fourth industrial revolution. The main benefits they offer to academic as well as industrial adopters include, increased design complexity freedom, decreased lead times and enhanced functionalities. Additionally, due to A...
Article
Full-text available
Porous inserts and nanofluids are among the conventional methods for the amelioration of heat transfer in industrial systems. The heat transfer rate could also be improved by utilizing porous substances with a higher thermal conductivity in these systems. This research work presents a two-dimensional (2D) numerical examination of the laminar forced...
Preprint
Full-text available
Spatter and denudation are two very well-known phenomena occurring mainly during the laser powder bed fusion process and are defined as ejection and displacement of powder particles, respectively. The main driver of this phenomenon is the formation of a vapor plume jet that is caused by the vaporization of the melt pool which is subjected to the la...
Preprint
Full-text available
Laser Powder Bed Fusion (L-PBF) is a Metal Additive Manufacturing (MAM) technology which offers several advantages to industries such as part design freedom, consolidation of assemblies, part customization and low tooling cost over conventional manufacturing processes. Electric coils and thermal management devices are generally manufactured from pu...
Article
Full-text available
Additive manufacturing (AM) creates digitally designed parts by successive addition of material. However, owing to intrinsic thermal cycling, metallic parts produced by AM almost inevitably suffer from spatially dependent heterogeneities in phases and mechanical properties, which may cause unpredictable service failures. Here, we demonstrate a syne...
Article
Full-text available
The laser energy density was believed to control microstructure and mechanical properties of additive-manufactured Inconel 718 (IN718) alloy. However, in this study, remarkable differences were found in the microstructures, tensile mechanical properties, and fracture surfaces of industrial IN718 alloy (with densities higher than 99.75%), which were...
Article
Full-text available
In laser powder bed fusion (LPBF), defects such as pores or cracks can seriously affect the final part quality and lifetime. Keyhole porosity, being one type of porosity defects in LPBF, results from excessive energy density which may be due to changes in process parameters (namely, laser power and scan speed) and/or result from the part’s geometry...
Conference Paper
Full-text available
Laser Powder Bed Fusion (L-PBF) is a Metal Additive Manufacturing (MAM) technology where a complex 3D metal part is built from powder layers, which are selectively consolidated using a laser heat source. The processing zone is in the order of a few tenths of micrometer, making L-PBF a multi-scale manufacturing process. The formation and growth of g...
Conference Paper
Full-text available
Laser Powder Bed Fusion (L-PBF) has attracted a lot of attention from various industrial sectors and mainly thanks to its well-proven well-known capacity of realizing complex topology-optimized components that have so far been impossible to make using conventional manufacturing techniques. In Pulsed L-PBF (PL-PBF), the laser's temporal profile can...
Article
Full-text available
Dross formation is a phenomenon that is observed while printing metallic components using Laser Powder Bed Fusion (L-PBF) and occurring primarily at down-facing surfaces that are unsupported and suffer inadequate heat removal. Naturally, dross formation causes dimensional inaccuracy, high surface roughness and also adversely affects the mechanical...
Preprint
Full-text available
In laser powder bed fusion (LPBF), defects such as pores or cracks can seriously affect the final part quality and lifetime. Keyhole porosity, being one type of porosity defects in LPBF, results from excessive energy density which may be due to changes in process parameters (laser power and scan speed) and/or result from the part’s geometry and/or...
Article
Full-text available
Numerical simulations have recently shown their potential as a robust, cheap and reliable tool for predicting the quality of components produced by metal additive manufacturing (MAM) processes. Despite the advantages of the MAM processes over conventional manufacturing methods, there is still a lack of thorough understanding on how different defect...
Article
The Directed Energy Deposition (DED) process of metals, has a broad range of applications in several industrial sectors. Surface modification, component repairing, production of functionally graded materials and more importantly, manufacturing of complex geometries are major DED’s applications. In this work, a multi-physics numerical model of the D...
Article
Full-text available
Modeling the metal additive manufacturing process can be done on different length scales depending on the field of interest. However, due to the moving heat source and the narrow heat affected zone, a fine mesh and fine time resolution are required to analyze detailed information on various length scales. In this paper, the focus is on macro-scale...
Article
Full-text available
Numerical models, especially when validated against experimental findings, are valuable tools that can be used as a cheap and reliable alternative to the expensive and time-consuming experimental investigations. In the current work, a multiphysics model of laser powder bed fusion (L-PBF) has been developed for stainless steel SS 316-L and validated...
Article
Full-text available
Several different interfacial forces affect the free surface of liquid metals during metal additive manufacturing processes. One of these is thermo-capillarity or the so-called Marangoni effect. In this work, a novel framework is introduced for unraveling the effects of thermo-capillarity on the melt pool morpholoogy/size and its thermo-fluid condi...
Article
Grain refinement of additively manufactured titanium and titanium alloys can be promoted via adding foreign elements or particles, but it may lead to a reduction in ductility due to the formation of brittle intermetallic compounds. The present study shows that in-situ grain refinement of commercially pure ti- tanium (CP-Ti) can be achieved through...
Article
Full-text available
Laser-based powder bed fusion, due to its layer-by-layer nature, results in a unique stress profile in a part after the primary production process. The residual stresses are typically tensile near the top, while they are compressive near the bottom of the part. When it is removed without proper precautions, the part will bend excessively. In order...
Article
Full-text available
Residual stresses and deflections are two major issues in laser-based powder bed fusion (L-PBF) parts. One of the most efficient and reliable ways for predicting residual stresses and final distortions is via a calibrated numerical model. In this work, a part-scale finite element thermo-mechanical model for Ti6Al4V is developed in the commercial so...
Conference Paper
Full-text available
Additive Manufacturing (AM) offers unprecedented design freedom that allows for manufacturing highly complex and efficient engineering structures. However, parts produced using AM still suffer from certain defects. For example, in the context of metal parts, local accumulation of heat leads to inferior surface quality [1]. Also, high thermal gradie...
Article
Full-text available
Due to its nature as a layer-by-layer production technique, the stresses and subsequent deformation from laser-based powder bed fusion are different from the ones observed in other manufacturing techniques. Additionally, because of the cyclic heating and cooling, the material undergoes significant microstructural changes during the process. Especia...
Article
Full-text available
Laser polishing of metals consists of irradiating the part's surface with a laser beam, thus generating a molten layer that is redistributed and resolidified to create a surface with reduced roughness. However, the process is also characterized by an instantaneous formation of heat-affected zones with consequent microstructural changes that influen...
Article
Laser polishing of metals consists of irradiating the part’s surface with a laser beam, thus generating a molten layer that is redistributed and resolidified to create a surface with reduced roughness. However, the process is also characterized by an instantaneously formation of heat-affected zones with consequent microstructural changes that influ...
Conference Paper
Full-text available
Extrusion process has been used for many decades as a transformation and shaping technology in the plastic processing industry. In this study the die deformation, critical for the extrudate product quality, was investigated in the plastic extrusion process by numerical modelling and compared with the experimental results. Dies with various thicknes...
Article
Full-text available
Metal additive manufacturing, despite of offering unique capabilities e.g. unlimited design freedom, short manufacturing time, etc., suffers from raft of intrinsic defects. Porosity is of the defects which can badly deteriorate a part’s performance. In this respect, enabling one to observe and predict the porosity during this process is of high imp...
Article
Full-text available
Additive manufacturing (AM) of metals faces a growing number of applications in different industries e.g. aerospace, medical, automotive, etc. Although metal AM outweighs current conventional production methods in some certain areas, the exact effect of processing conditions on the final quality and microstructure of the parts is still not well und...
Article
Full-text available
Laser-based powder bed fusion (L-PBF) is a branch of additive manufacturing technology which is considered to be a superior process due to its capability of producing complex designs with low material waste. Despite L-PBFs various unique characteristics, manufactured parts still suffer from a wide variety of defects, among which porosity is one of...
Article
Full-text available
There is a growing interest for integrating additive manufacturing (AM) technology in different manufacturing processes such as injection moulding (IM) due to the possibility of achieving shorter manufacturing times and increased cost effectiveness. This paper evaluates IM inserts fabricated by the AM vat photopolymerisation method. The inserts are...
Article
In this study, a cryogenic distillation column has been designed and simulated via a computer code based on the theta method of convergence. The required thermodynamic properties are determined from the enhanced predictive Peng-Robinson (E-PPR 78) equation of state which has a good accuracy in predicting the corresponding thermodynamic properties o...
Preprint
Full-text available
The presented numerical model in this preprint is the third generation model (out of total four) I developed during my PhD. An elongated version including a comprehensive parametric study is about to be submitted to an international journal very soon.
Preprint
Full-text available
In this paper, a multi-physics numerical model for multi-track-multi-layer laser powder bed fusion (L-PBF) process is developed and used for analysing the formation and evolution of porosities caused by lack of fusion and improper melting. The simulations are divided into two categories: first and foremost, a multi-physics thermo-fluid model in mes...
Conference Paper
Full-text available
PAM^2, which stands for Precision Additive Metal Manufacturing, is a European MSCA project in which 10 beneficiaries and 2 partners collaborate on improving the precision of metal Additive Manufacturing. Within this project, research is done for each process stage of AM, going from the design stage to modelling, fabricating, measuring and assessmen...
Preprint
Full-text available
In this paper, a transient 3-dimensional thermal model for the selective laser melting process, based on the finite volume method, has been developed, which takes into account the phase change and powder to bulk material transition. A parametric study has been performed for the temperature field as well as the melt pool dimensions, and the results...
Article
Full-text available
The entire process chain of selective laser melting of Ti-6Al-4V is analysed. First, a thermo-fluid dynamical model is used to investigate the temperature profile during the process and estimate the size and shape of the melt pool. The inclusion of the Marangoni effect improves upon previous work by showing the liquid velocity in the melt pool. Nex...

Network

Cited By

Projects

Projects (2)
Project
Producing dense pure copper parts by L-PBF is difficult due to low optical absorptivity to infrared radiation and high thermal conductivity. To produce dense copper parts in a conventional L-PBF system either the power of the infrared laser must be increased above 500W, or a green laser should be used for which copper has a high optical absorptivity. In this project a complete investigation from experiments to numerical modelling of the L-PBF process is conducted.