Ehsan Toyserkani

University of Waterloo | UWaterloo · Department of Mechanical and Mechatronics Engineering

Although structural design complexities do not potentially pose challenges to many additive manufacturing technologies, several manufacturing constraints should be considered in the design process. One critical constraint is a structure's unsupported or overhanging features. If these features are not reduced or eliminated, they can cause a decline...

Laser directed energy deposition (LDED), a class of additive manufacturing (AM) processes, has immense potential to be used for various engineering applications to build components with medium to high complexity. However, dimensional deviations from intended values and inadequate surface quality of the built parts limit its wide deployment. The pre...

Laser-directed energy deposition (LDED) is a promising technology for coating, repairing, and building near-net-shape 3D structures. However, the processing of copper alloys, specifically, has presented a significant challenge due to their low laser absorptivity at the 1060 nm laser wavelength and high thermal conductivity. This study undertook a m...

Laser powder bed fusion (LPBF) is one class of metal additive manufacturing (AM) used to fabricate high-quality complex-shape components. This technology has significantly progressed over the last several years allowing the fabrication of high-value components for a broad range of applications, normally unmatched by other metal AM processes. Howeve...

This article aims to highlight the development of an intermittent controller designed to compensate and rectify the lack of fusion (LoF) zones that induce during the LPBF process. The initial step involved the utilization of the Self-Organizing Map (SOM) algorithm to identify the location of LoF defects. Subsequently, the identified defects undergo...

Although structural design complexities do not potentially pose challenges to many additive manufacturing technologies, several manufacturing constraints should be considered in the design process. One critical constraint is the structure's unsupported or overhanging features. If these features are not reduced or eliminated, they can cause a declin...

Magnetic levitation and additive manufacturing (AM) are two fields of significant interest in academic research. The use of non-contact forces for magnetic levitation techniques provides opportunities for adoption within the AM environment. The key goal of this article is to experimentally validate the implementation of a magnetic levitation system...

Ti6Al4V has been used widely as a biomedical alloy and is increasingly manufactured by additive manufacturing due to customized shapes. As implant material, it is frequently exposed to both friction and corrosive environments. This study investigates the effect of the fabrication process (laser powder bed fusion and forging) on the tribocorrosion b...

Compliant mechanisms are useful in microelectromechanical (MEM) and robotic systems. While several methodologies have been devised to optimize their performances, this study presents a new approach that improves their output displacements by introducing infill-like features through a local volume-constrained topology optimization framework. This fr...

Laser-directed energy deposition (LDED) is a suitable manufacturing technology for processing CuCrZr alloy that has recently gained interest to be used in high heat flux applications due to its unique thermal properties. Despite its promising properties, the successful deposition of CuCrZr alloy through LDED processing is impeded by its low laser-m...

The geometric stability of thin-wall structures built by Laser Directed Energy Deposition (LDED) depends on the process parameters. This paper presents the interrelation between combined LDED process parameters and geometrical deviations of thin-walls. The thin-walls are built at different combinations of laser energy per unit length (LEL) and powd...

Metal additive manufacturing is gaining immense research attention. Some of these research efforts are associated with physics, statistical, or artificial intelligence-driven process modelling and optimisation, structure–property characterisation, structural design optimisation, or equipment enhancements for cost reduction and faster throughputs. I...

In the present investigation, a NiCr–Cr3C2 powder mixture was deposited on titanium aluminide substrate by laser cladding. The kinetics and mechanism of oxidation of the substrate and coating were studied at 800–1100 °C using XRD, SEM, ToF–SIMS and XPS characterization techniques. The results demonstrated that the Ni–Cr–C coating had improved oxida...

In this article, an innovative 3-dimensional (3D) heat-transfer finite element parallel-computing model with adaptive mesh capability, named LPBFSim, for Laser Powder Bed Fusion (LPBF) additive manufacturing is introduced for high precision prediction of melt pool dimensions and single-layer part-level process simulations. Numerical modeling can si...

Ti-5553, a metastable beta Ti alloy is a promising upgrade for existing aircraft landing gear parts and additive manufacturing offers manufacturing supremacy. However, directional solidification leads to anisotropy, which is often regarded as a disadvantage. In this article, the anisotropy effect is engineered to result in improving the as-printed...

Laser directed energy deposition (LDED) can be deployed for depositing high-performance materials for various engineering applications. Alumina-forming steel is a high-performance material that possesses excellent corrosion and oxidation resistance, finding application in the power generation sector. In the present work, LDED using powder feeding (...

Alloy 718 is a Ni-Fe-based superalloy, which has been successfully adapted to powder bed fusion (PBF) additive manufacturing because of the alloy’s adaptability with such emerging technology in achieving enhanced mechanical properties. Despite a promising perspective for PBF-built Alloy 718 in different industries, a few factors, including microstr...

The present work reports on an adaptive trajectory planning to build tubular components with variable overhang angles using a robotic Laser Directed Energy Deposition (LDED) based Additive Manufacturing process without utilizing support structures. The proposed technique uses a non-parallel slicing methodology to build complex components (e.g., ben...

The contact lens (CL) industry has made great strides in improving CL‐wearing experiences. However, a large amount of CL wearers continue to experience ocular dryness, known as contact lens‐induced dry eye (CLIDE), stemming from the reduction in tear volume, tear film instability, increased tear osmolarity followed by inflammation and resulting in...

Flexible piezoresistive strain sensors have promising applications in wearables and soft robotics. For sensing dynamic strains, such as a runner’s gait or a slipping object held by a robotic gripper, the sensor must be capable of vibration strain sensing for a range of amplitudes and frequencies. This article presents the characterization and desig...

In-situ microstructure control is an important feature of laser powder-bed fusion (LPBF) that enables the tailoring of the mechanical behaviour of additively manufactured metallic parts. In this research, a novel method is introduced to control the formation of microstructure by laser post-exposure (PE) treatment during the LPBF process. Laser post...

The powder stream from a side feed nozzle, or part of the powder stream in some coaxial nozzles, in a directed energy deposition via powder feeding (DED-PF) machine, can be modeled using a particle velocity field that has a constant downward component and a linearly increasing outward component, in proportion to the powder stream's center line dist...

The powder stream from a side feed nozzle, or part of the powder stream in some coaxial nozzles, in a directed energy deposition via powder feeding (DED-PF) machine, can be modeled using a particle velocity field that has a constant downward component and a linearly increasing outward component, in proportion to the powder stream’s center line dist...

One of the challenges in directed energy deposition via powder feeding (DED-PF) is the powder stream divergence that results in low catchment efficiency (i.e., the fraction of particles added to the melt pool). This article introduces a new ultrasound-based powder focusing method referred to as ultrasound particle lensing (UPL), tailored for powder...

In this study, different eddy-current based probe designs (absolute and commercial reflection) are used to detect artificial defects with different sizes and at different depths in parts composed of stainless-steel (316) and titanium (TI-64) made by Laser Additive Manufacturing (LAM). The measured defect signal value using the probes is in the rang...

This research studies the development of a machine-learning algorithm to detect porosity induced during laser powder bed fusion (LPBF) due to the lack of fusion (LoF) phenomenon. The detection algorithm is based on analyzing in-situ light intensity data emitted from the melt pool during LPBF. A Self-Organizing Map (SOM), an unsupervised machine lea...

Scanning strategies can significantly affect temperature distribution and location-specific variation of solidification microstructure in laser-directed energy deposition by powder-feeding (LDED-PF). In this paper, a physics-based analytical model of multi-track LDED-PF is developed to rapidly predict the temperature field of cuboidal geometries un...

Magnetism and magnetic levitation has found significant interest within the field of micromanipulation of objects. Additive manufacturing (AM), which is the computer-controlled process for creating 3D objects through the deposition of materials, has also been relevant within the academic environment. Despite the research conducted individually with...

3D Bioprinting Vascularization is key to the prolonged functionality of the organs. Template‐assisted bioprinting enables biofabrication of stand‐alone thick tissues with complex vascularized networks. In article number 2102123 by Ehsan Toyserkani, Ali Khademhosseini, and co‐workers, an indirect printing strategy not only eliminates the need for co...

Laser Powder-bed Fusion (LPBF) is a common technique categorized as one of the Additive Manufacturing (AM) processes to efficiently fabricate complex geometries. The involvement of complex phenomena relating to laser and metal powder requires a thorough investigation to understand the complex multi-physics behind this process. Modeling and simulati...

The influence of α precipitate morphology on the mechanical properties of additively manufactured Ti-5Al-5V-5Mo-3Cr (Ti-5553) is evaluated. Initially, Archimedes density measurements on cylindrical Ti-5553 samples printed using laser powder-bed fusion process were employed to determine the influence of parameters on the conduction melting band. The...

Quasi-static and fatigue behavior of laser powder-bed fusion Hastelloy X (LPBF-HX) specimens were studied. Tension–compression asymmetry was evaluated through a wide range of plastic strains. LPBF-HX specimens are not showing loading direction dependency during monotonic tension and compression tests at low plastic strains. LPBF-HX showed primary h...

In this study, for the first time, hexagonal structured molybdenum aluminosilicide Mo(Si,Al)2 has been successfully in-situ produced with the help of laser powder bed fusion (LPBF) of a blended powder mixture of 90 wt% MoSi2-10 wt.%AlSi10Mg feedstock. Applying triple scanning for upskin changed the top surface morphology, suggesting that applicatio...

Interconnected pathways in three-dimensional (3D) bioartificial organs are essential to retaining cell activity in thick functional 3D tissues. Three-dimensional bioprinting methods have been widely explored in biofabrication of functionally patterned tissues; however, these methods are costly and confined to thin tissue layers due to poor control...

Metal additive manufacturing (AM) has led to an evolution in the design and fabrication of hard tissue substitutes, enabling personalized implants to address each patient's specific needs. In addition, internal pore architectures integrated within additively manufactured scaffolds, have provided an opportunity to further develop and engineer functi...

Additive manufacturing (AM), also known as 3D printing, is one of the most promising digital manufacturing technologies, thanks to its potential to produce highly complex geometries rapidly. AM has been promoted from a prototyping methodology to a serial production platform for which precise process monitoring and control strategies to guarantee th...

This chapter covers a brief description of the fundamental principles governing laser/electron beam material interaction and absorption. It focuses on physics, and governing equations of laser directed energy deposition (LDED) and electron beam directed energy deposition (EDED). Lasers and electron beams provide many advantages when it comes to the...

This chapter helps the students to understand the main additive manufacturing (AM) technologies used for metal fabrication and advantages and limitations of each technology. It introduces the main metal AM technologies: powder bed fusion, directed energy deposition, and binder jetting, and sheds some light on sheet lamination, material extrusion, a...

Additive manufacturing (AM) is becoming a major research target for industrialized countries as they seek to regain leadership in manufacturing through innovation. AM has been considered a platform to convert digital models to physical parts in a short chain of processes, a platform facilitating a rapid move from “Art” to “Part” in a fancy analogy....

This chapter helps the students to gain a clear understanding of the physics behind the powder bed fusion (PBF) processes. It identifies the main governing equations for heat transfer by conduction and fluid flow in the melt pool. The chapter also helps to gain an understanding of the numerical models and techniques employed in the description of t...

The application of additive manufacturing (AM) techniques can bring evolution in conventional manufacturing systems, with some additional precautions for industrialists and their workers. These precautions involve possible safety hazards connected with AM fabrication processes, equipment, and materials. The most common hazards related to metal AM c...

This chapter explores some design frameworks proposed by researchers for additive manufacturing (AM). AM has experienced contextual inconsistencies in establishing standard design rules and guidelines, which is not far‐fetched from the inability to represent design criteria and compare it with AM processes and system performance. The chapter focuse...

This chapter helps the students to understand the concept of Metal Matrix Composites (MMCs), and to learn about applications of additive manufacturing (AM) technology in the fabrication of MMCs and possible challenges. There is a wide variety of manufacturing techniques available for MMCs. Based on the processing temperature of the matrix material,...

This chapter helps the students to gain a clear understanding of main modules used in additive manufacturing (AM) systems and gain knowledge on the physics behind the laser functioning. In metal AM processes, the 3D object is built through the selective solidification/joining of powder materials in a layer‐by‐layer fashion. The chapter discusses th...

Materials science is concerned with properties of solid materials, and the study of those properties and the way they are linked to material compositions and structures. Properties of materials are correlated with the microstructure, which can be modified by changing the microconstituents’ relative magnitude, known as phases. Additive manufacturing...

This chapter helps the students to learn different classes of in‐situ sensing devices used for metal additive manufacturing (AM) processes and theories of some sensors used in metal AM. The AM process parameters can be categorized into two groups: intrinsic, and extrinsic. There are a variety of sensors used in metal AM processes. In‐situ sensors c...

This chapter helps the students to understand the basic governing physics of droplet formation in binder jetting (BJ) and material jetting (MJ). It also helps the students to understand the basic governing physics of droplet–surface and droplet–powder bed interaction in material jetting and binder jetting processes, respectively. The impact of drop...

This chapter reviews the physics and modeling of the material extrusion (ME) additive manufacturing process. It also reviews available analytical and numerical models to provide a base for a better understanding of ME with this fact in mind that none of these models have been customized for highly filled composite filaments. In addition to the anal...

Laser Powder-Bed Fusions (LPBF), a class of additive manufacturing (AM), is a promising technique for producing components with complex geometry design. However, parts fabricated by LPBF suffer from residual stresses arising due to substantial temperature gradients inherent to the process. Numerical models are unable to provide a comprehensive ther...

Ni-based superalloys can withstand a temperature of around 1400 K, while the gas turbine can endure a temperature of around 1800 K thanks to thermal barrier coatings such as Yttria stabilized zirconia (YSZ). The present work attempts to introduce a method for modifying commercial Inconel 625 metal powder to enhance the properties of the additively...

Additive manufacturing (AM) is a promising method for fabricating customized and anatomically correct surgical implants. Advancement in design and the AM of joint replacement implants has mainly targeted implants for large joint replacement while progress in small joint replacements has been limited. This study describes a method for fabrication of...

Mo(Si,Al)2-based composites are promising candidates to be used as heating elements, high temperature coatings and structural materials. In this work, powders mixture of 90 wt.% MoSi2 and 10 wt.% AlSi10Mg was subjected to a laser powder-bed fusion (LPBF) to produce Mo(Si,Al)2-based composites. The effect of process parameters on morphological featu...

Additive manufacturing (AM) has changed the entire manufacturing enterprise by offering unique features for the fabrication of complex-shapes with superior mechanical properties. In the last decades, through an exponential advancement, AM has been promoted from a prototyping to a series and mass production platform. Like all conventional techniques...

This study presents a unique melting strategy in electron beam-powder bed fusion of Alloy 718 to tailor the grain morphology from the typical columnar to equiaxed morphology. For this transition, a specific combination of certain process parameters, including low scanning speeds (400–800 mm/s), wide line offsets (300–500 μm) and a high number of li...

In this work, a two-dimensional (2D) and three-dimensional (3D) integrated topology optimization (TO) parallel-computing framework, named TopADD (TOPology optimization for Arbitrary Design Domains), is developed to deal with topology optimization problems with arbitrary design domains. The parallel-computing framework is an extended work of the ini...

The present paper aims to develop an effective analytical solution for laser directed energy deposition through powder feeding (LDED-PF). Three heat source models are introduced and compared to analytically describe the transient temperature field in the process. These models are known as point (1D) heat source, circular (2D) heat source, and semi-...

This work presents a framework to initialize structural problems for 2D topology optimization while offering capabilities to post-process the optimized results into STL models that can be produced directly by additive manufacturing technologies. Conveniently named Image-based Initialization and Post-Processing (IbIPP) for topology optimization, it...

Columnar grain structure typically formed along the build direction in the electron beam-powder bed fusion (EB-PBF) technique leads to anisotropic physical and mechanical properties. In this study, casting solidification condition was mimicked, and in situ recrystallization was promoted in EB-PBF to facilitate columnar-to-equiaxed grain structure t...

Near full dense C40 hexagonal structured Mo(Si 1-x Al x ) 2 -based composite coupons with 7 mm diameter by 7 mm height were prepared by selective laser melting (SLM) of MoSi 2 -30 wt.% AlSi10Mg powder mixture and subjected to isothermal oxidation. As a reference, MoSi 2 bulk sample was prepared by spark plasma sintering (SPS) technique. The quantit...