Jesper Hattel

Jesper Hattel
Technical University of Denmark | DTU · Department of Mechanical Engineering

PhD Mech Eng

About

328
Publications
88,560
Reads
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7,273
Citations
Citations since 2016
163 Research Items
4709 Citations
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20162017201820192020202120220200400600800
20162017201820192020202120220200400600800
Introduction
Jesper Hattel currently is head of Section for Manufacturing Engineering at the Department of Mechanical Engineering, Technical University of Denmark. He does research in Numerical Modelling of Manufacturing Processes including Additive Manufacturing, Casting, Welding, and Composites Manufacturing. The research is interdisciplinary involving generic disciplines such as numerical heat transfer, computational fluid dynamics, computational solid mechanics as well as computational materials science.

Publications

Publications (328)
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...
Article
Full-text available
The electronics is protected using plastic or metallic enclosures. Although, the electronics is protected by the enclosures from the surrounding environment, the moisture can still enter the enclosure via gasket, plastic enclosure walls, cable feedthroughs. The moisture existing inside enclosure may condense on PCBA or components due to a temperatu...
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...
Conference Paper
Full-text available
Additively manufactured channels enable conformal cooling for applications such as injection molds or fuel injectors. Understanding the scalability of these channels for applications of different sizes is essential to pave the way for a more widespread adoption. This work uses a non-destructive testing approach to characterize and compare channels...
Article
Over the last 70 years, pultrusion has matured into an industry-leading process when it comes to providing high throughput and automated composite manufacture at a competitive price point. In this paper, we review recent innovations that have advanced pultrusion to a versatile manufacturing technology and thereby allowed composite materials to pene...
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
Laser-based powder bed fusion of 300-grade maraging steel allows the production of parts with a high hardness, which improves the service life and wear resistance of tooling or mould insert produced from this material. The material typically consists of a martensitic matrix material, with retained austenite and nano-precipitation. The transformatio...
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...
Article
This study presents a holistic segmentation procedure, which can be used to obtain individual fibre inclination angles from X-ray computed tomography. The segmentation approach is based on principal component analysis and was successfully applied for a unidirectional and an air-textured glass fibre–reinforced composite profile. The inclination resu...
Article
Full-text available
In spite of many years of research, the physical phenomena leading to the evolution of compacted graphite (CG) during solidification is still not fully understood. In particular, it is unknown how highly branched CG aggregates form and evolve in the semi-solid, and how local microstructural variations at micrometer length scale affect this growth p...
Article
Ductile cast irons (DCIs) are of increasing importance in the renewable energy and transportation sectors. The distribution and morphology of the graphite nodules, in particular the formation of degenerate features during solidification, dictate the mechanical performance of DCIs. In situ high-speed synchrotron X-ray tomography was used to capture...
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
Full-text available
Pultruded fiber-reinforced polymer composites are susceptible to microstructural nonuniformity such as variability in fiber volume fraction (Vf), which can have a profound effect on process-induced residual stress. Until now, this effect of non-uniform Vf distribution has been hardly addressed in the process models. In the present study, we charact...
Article
Full-text available
Channels manufactured by laser powder bed fusion have an inherent process-induced dross formation and surface texture that require proper characterization for design and process optimization. This work undertakes surface texture characterization of AlSi10Mg channels of nominal diameter sizes ranging from 1 mm to 9 mm using X-ray computed tomography...
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
Metal additive manufacturing is increasingly used as a complementary manufacturing technique in industrial settings and slowly moving from pure prototyping applications toward full production. In parallel, there is an emergence of Industry 4.0, where the applicability of concepts such as digital twins of manufacturing machines and components are be...
Article
This work concerns the accurate dimensional measurement of metal parts directly in a production environment. Applying an approach with the simultaneous measurement of part dimension and temperature over time (dynamically) followed by modeling of the thermo-mechanical effects, the corrected length at 20 °C and its measurement uncertainty can be pred...
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
Process-induced stress and deformation are critical factors when ensuring product quality and structural integrity of composite profiles manufactured using thermoset pultrusion processes. In this paper, we present a new steady-state 3D-Eulerian numerical framework that enables 9–35 times faster computations compared to the current state-of-the-art...
Article
Additive Manufacturing (AM) enables the design of complex part geometries for high-temperature applications. Laser Powder Bed Fusion or Direct Energy Deposition of the nickel-based superalloy MAR-M247 poses a challenge in additive manufacturing due to its poor weldability. Binder Jetting does not utilize a heat source and interaction with a liquid...
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
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The feasibility of butt friction stir welding (FSW) of a metal matrix composite (MMC) with a very high SiC particle content to a monolithic aluminum alloy is tested in this work. It is demonstrated for the first time that sound FSW joints can be obtained between an AA6061 aluminum plate and a thick MMC plate consisting of AA6061 reinforced with 40...
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
This study presents a detailed material characterization study of a pultrusion specific polyurethane resin system. Firstly, the chemical behaviour was characterized by utilizing differential scanning calorimetry. The cure kinetics was fitted well to an autocatalytic cure kinetics model with Arrhenius temperature dependency. The resin system did not...
Article
This paper concerns non-isothermal flow in a thermoset resin-injection pultrusion process. Supported by temperature measurements from an industrial pultrusion line and a material characterisation study (curing kinetics, chemorheology, and permeability), the material flow was analysed for the manufacture of a thick glass-fibre profile saturated with...
Article
Full-text available
Through various examples, this short review presents the main X-ray based techniques that are available to characterize nodular cast iron at the microstructural level. Emphasis is placed on the enormous potential offered by the recent developments in X-ray tomography, X-ray diffraction and digital volume correlation, which allow collecting microstr...
Article
Full-text available
This is a literature review of the published scientific results by the authors on numerical modelling and experimental characterization of composites processing with a focus on the resin injection pultrusion (RIP) process. Differential scanning calorimetry is used to obtain cure kinetic parameters for an epoxy resin system. The cure kinetic paramet...
Article
The present work focuses on comparing the ability of different constitutive formulations to model the deformation of fresh pork bellies during handling operations. A computed tomography (CT) scan is initially performed when the belly is lying on a curved substrate, in order to obtain its 3D geometry. Then, based on the assumption of homogenous mate...
Article
Conformal cooling channels, made by the laser powder bed fusion process, are a promising design strategy for optimising cooling and process control of manufacturing tools and injections moulds. The addition of internal features such as corrugations and ribs are becoming an interesting addition to the cooling channel designs. Internal surfaces of la...
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...
Article
Full-text available
The mechanistic understanding of the processing-structure-property relations in ductile iron is still far from complete. One reason is that the impact on the mechanical properties of some of the microstructural features arising from the casting process can be hard or even impossible to investigate using experimental methods alone. The present work...
Article
Full-text available
The distribution of Si content in tensile deformed ductile cast iron has been characterized using electron microscopy and correlated to the strain distribution determined based on 3D tomography data collected before and after tensile deformation and digital volume correlation analysis. The results show that the high plastic strain regions localize...
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
Air-texturisation is a process that adds bulkiness to bundles of fibres. In this study, the permeability and compaction behaviour of air-texturised glass fibre rovings are experimentally characterised and compared to conventional unidirectional rovings. Based on radial impregnation experiments and single-step compaction/decompaction tests, the foll...
Article
Full-text available
Due to the layer-by-layer nature of the process, parts produced by laser-based powder bed fusion (LPBF) have high residual stresses, causing excessive deformations. To avoid this, parts are often post-processed by subjecting them to specially designed heat treatment cycles before or after their removal from the base plate. In order to investigate t...
Article
A method to construct 3D representative volume element (RVE) models of the nodular cast iron microstructure that accounts for the presence of heterogeneities in the matrix is proposed. The main advantage is the possibility to generate a wide spectrum of realistic distributions of the matrix heterogeneities in a simple and fast way. The method takes...
Article
The increasingly complex shapes and geometries being produced using additive manufacturing necessitate new characterization techniques that can address the corresponding challenges. Standard techniques for roughness and texture measurements are inept at characterizing the internal surfaces in freeform geometries. Hence, this work presents a new met...
Article
Full-text available
A heat treatment is an essential part of the metal additive manufacturing process chain. If an additively manufactured part, made of Ti-6Al-4 V, is heated above its β transus temperature, the columnar prior-β grains will become equiaxed β grains. This work quantitatively models this transition and the subsequent cooling down to room temperature by...
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...
Chapter
This chapter concerns numerical modeling of the mechanics of pultrusion processes, with a focus on the physics that takes place inside the pultrusion die. The following topics are covered: (1) impregnation mechanisms of saturated and unsaturated flow to predict the resin impregnation and pressure rise in straight and tapered impregnation chambers;...
Article
Full-text available
Strain partitioning between first-to-solidify (FTS) and last-to-solidify (LTS) regions upon tensile loading of ductile iron was investigated by combining in-situ X-ray tomography with digital volume correlation and post-mortem metallographic examinations. The results indicate that the plastic shear bands form mainly by linking graphite particles co...
Article
Full-text available
In this paper we describe metal additive manufacturing (AM) processes in general, and laser bed fusion processes in particular. The process characteristics are described, and the various modelling approaches demonstrated. The open AM architecture developed at DTU Mechanical Engineering is introduced, as well as an alternative process chain based on...
Article
A multi-physics thermo-chemical-mechanical 1-dimensional implicit finite difference model is presented to simulate the evolution of composition and residual stress profiles over the expanded austenite case developing during low temperature nitriding of austenitic stainless steels. The model combines 1-dimensional diffusion of nitrogen in the depth...
Conference Paper
Full-text available
Increasingly advanced shapes and geometries are being manufactured using additive manufacturing and new characterization techniques must emerge in order to fully utilize the new possibilities given by freeform design. Cooling channels produced by the laser powder bed fusion process has been shown to have high roughness at overhanging areas due to p...
Conference Paper
Full-text available
Metal additive manufacturing has the potential to enhance the performance of engineering applications by utilizing its inherent design freedom to create complex geometries such as required for conformal cooling. However, additively manufactured channels show significant form deviations when made by laser powder bed fusion. Thereby, not only process...
Article
The discrete element method (DEM) has great advantages in expressing the deformation and fracture of materials at large scale compared to the molecular dynamics (MD) and the finite element method (FEM). However, its application is constrained by the fact that most of the existing models are limited to elastic-brittle homogeneous materials. In this...
Article
Molded pulp products are experiencing increased importance due to their environment-friendly characteristics with regards to both production and disposal. In this study, the thermoforming process for the production of molded pulp products was examined by means of two experimental campaigns, with the scope of distinguishing between the water removal...
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
In this paper, a first-order projection method is used to solve the Navier–Stokes equations numerically for a time-dependent incompressible fluid inside a three-dimensional (3-D) lid-driven cavity. The flow structure in a cavity of aspect ratio δ = 1 and Reynolds numbers ( 100 , 400 , 1000 ) is compared with existing results to validate the code. W...
Conference Paper
Full-text available
In this paper has a numerical framework for multiphysical simulation of resin-impregnation, heat-transfer and cure in a resin-injection pultrusion process been developed. Using the framework, the material flow through the pultrusion die was studied for the manufacture of a 100 mm thick glass fibre reinforced polyurethane (thermoset) composite profi...
Article
Temperature and relative humidity are crucially important for the reliability of electronic devices in outdoor applications. For small enclosures, thermal control by a heat sink that is cooled by natural convection is the most widely used method. In this work, the functionality of a heat sink as a thermal mass for partially storing the heat that is...
Article
In this paper, a 2D numerical framework for the simulation of flows in porous media that are characterised by a sharp transition between the saturated and unsaturated zone is presented. Using a finite volume scheme and the level-set method, the framework is derived based on a conventional, implicit solution of Darcys law for the pressure field, whi...