
Wessel W. WitsRoyal NLR - Netherlands Aerospace Centre · Aerospace Vehicles Structures Technology (AVST)
Wessel W. Wits
Dr. Ir.
About
87
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Introduction
Working as R&D Engineer at Royal NLR - Netherlands Aerospace Centre.
Areas of interest and expertise: (metal) Additive Manufacturing
Publications
Publications (87)
Multi-material mixing in laser powder bed fusion is demonstrated by fabricating functionally graded structures in which Inconel and stainless steel are metallurgically bonded. Material mixing and elemental diffusion in the transition zone are studied for single scan tracks, hatch scans and multi-layer builds. An adapted recoater enabling powder dep...
Powder Bed Fusion (PBF) techniques constitute a family of Additive Manufacturing (AM) processes, which are characterised by high design flexibility and no tooling requirement. This makes PBF techniques attractive to many modern manufacturing sectors (e.g. aerospace, defence, energy and automotive) where some materials, such as Nickel-based superall...
Laser Powder Bed Fusion (LPBF), a promising additive manufacturing technique for composites of 2D materials and metals, requires knowledge of thermophysical properties, such as the thermal conductivity of powder, for process optimization. In this study, we measured the effective thermal conductivity of the most representative Cu-graphene composite...
Miniaturization and enhanced performance of microchips has resulted in powerful electronic devices with high heat flux components. For these advanced electronics, the current heat transfer method of single-phase forced convection is reaching its thermal limit and more effective cooling solutions are needed. A pumped two-phase loop, in which a pump...
The integrity of additively manufactured components is limited by the number, size, type and location of defects encapsulated in the build. Our ability to manufacture fatigue resistant components by the powder bed fusion process is still nascent as a result. The location of defects within a build volume is known to be of significance but efforts ar...
The geometrical design freedoms associated with additive manufacturing techniques are currently well exploited and finding commercial application. The capability of layer-based processes to allow modification of composition and microstructure in process to achieve functional grading is currently a growing topic. In this work, a method is demonstrat...
Conceptualizing a sound mechanical system exposed to dynamic loading conditions throughout its lifetime is a challenging task ill-supported by current design tooling. Current approaches typically use a Shock Response Spectrum (SRS) as design specification that describes the maximum dynamic response of a single subsystem component due to a given loa...
In this paper, the potential of selective laser melting (SLM) of stainless steel CL 20ES powder was investigated with a focus on controlled fabrication of porous structures with strongly reduced pore sizes, i.e. feature sizes significantly below conventional minimum SLM feature sizes. By controlling laser scan properties interacting with the powder...
Cold Spray(CS) is an emerging process, attracting much interest both as a coating and additive technique due to its solid-state nature and high deposition rates. The key element of any CS apparatus is the supersonic nozzle. The work presented here, for the first time, will explore in detail the relationship between particle flow, and its accelerati...
This study presents the phase change heat transfer characteristics of an additively manufactured wick for heat pipe applications. For this study, a flat heat pipe is considered that is made of stainless steel 316L utilizing a fabrication process that yields a wick structure with multi-scale features. Using laser powder bed fusion, relatively large...
This paper presents an appropriate method to significantly reduce the pore size of high porosity porous stainless steel 316L structures fabricated by laser powder-bed fusion (LPBF) utilizing pulse wave emission (PW). PW deliberately avoids full-melt and applies low energy conditions to achieve single layer sintered porous material with controlled c...
As one of the most important additive manufacturing (AM) techniques, laser metal deposition (LMD) has been extensively studied specially during the last few years. Similar to other AM techniques, the quality of LMD parts is highly dependent on the processing parameters that need to be optimized so as to obtain geometrically accurate parts as well a...
This paper presents a planar cooling strategy for rotating radar systems using heat pipe technology. The proposed design uses six 1 m long heat pipes in parallel oriented in an evaporator-down modus at an elevation angle of 85 deg. An analytical model based on conventional heat pipe limits is used to predict the performance taking into account both...
Lifetime prediction of polymer–polymer contacts is a major challenge. Current design methods stemming from metal contact surfaces lack accuracy because polymers behave differently, especially regarding temperature variations. Experiments were performed on a pin-on-disk setup alternating static and rotating elements. Common unfilled engineering poly...
Laser Powder Bed Fusion (LPBF) is a commercially available technology to industry for a selected range of materials only. Opportune to the next stage of LPBF will be the development of multi-material capabilities alongside methods for rapid formulation of new materials. To this end the present work compares two viable material preparation technique...
The thermal performance and operating modi of a flat-plate closed-loop pulsating heat pipe (PHP) are experimentally observed. The PHP is manufactured through computer numerical controlled milling and vacuum brazing of stainless steel 316 L. Next to a plain closed-loop PHP, also one that promotes fluid circulation through passive Tesla-type valves w...
This paper examines the so-called capillary performance of a freeform porous structure fabricated by advanced 3D metal printing technology. The fabricated structure is intended as wick for two-phase heat transfer devices, in which it contributes to the transport of a liquid working fluid through capillary forces. A stainless steel porous structure...
This paper reviews advanced heat transfer devices utilizing
advanced manufacturing technologies, including well-established thermal
management applications. Several factors have recently contributed to
developing novel heat transfer devices. One of the potential technologies
revolutionizing the field of energy conversion is additive manufacturing
(...
Evaporation rates of working fluid from porous structures are of great importance to heat pipe applications. This study presents the evaluation of the evaporation/boiling process of water from a stainless steel 316L wick structure fabricated through 3D-printing technology. The fabrication process that is employed to provide the test sample, yields...
The thermal performance and operating modi of a flat-plate closed-loop Pulsating Heat Pipe (PHP) are experimentally observed. The PHP is manufactured through CNC milling and vacuum brazing of stainless steel 316L. Next to a plain closed-loop PHP also one that promotes fluid circulation through passive Tesla-type valves was developed. Each channel h...
This paper presents a planar cooling strategy for rotating radar systems using heat pipe technology. The principle idea is to use an array of heat pipes. The proposed design uses six 1 m long heat pipes in parallel and top cooling through a fan-based heat sink. The heat pipes are oriented in an evaporator-down modus at an elevation angle of 85°. An...
U-shaped assembly lines (U-SALs) are cellular manufacturing systems that, among other things, provide a remarkable feature for industrial cost efficiency: their effectiveness in space utilization. While the challenge of machine placement for labour productivity optimization is widely studied in the literature, surface productivity optimization has...
Due to the ongoing component miniaturization and integration in the electronics industry, there is a need for asymmetric lay-ups for printed circuit boards (PCBs), especially in the case of complex boards that house both analog and digital circuits. This paper focuses on the contribution of the constituent layers that make up the PCB to the board’s...
As today's markets are more susceptible to rapid changes and involve global players, a short time to market is required to keep a competitive edge. Concurrently, products are integrating an increasing number of functions and technologies, thus becoming progressively complex. Therefore, efficient and effective product development is essential. For e...
This paper presents a planar cooling strategy for advanced electronic applications using heat pipe technology. The principle idea is to use an array of relatively long heat pipes, whereby heat is disposed to a long section of the pipes. The proposed design uses 1 m long heat pipes and top cooling through a fan-based heat sink. Successful heat pipe...
Specific properties of porous media such as thermal conductivity and wicking of liquid into the porous structure are of great importance to many applications. Typically, such porous structures are found in two-phase devices, such as heat pipes (HPs). In this study, we have experimentally analysed the effective thermal conductivity and the wicking o...
This paper explores the pumping characteristics and behaviour of a thermally driven self-oscillating pump. The pump consists of a single wickless capillary tube with a circular cross-section. The tube is closed at one end and has a T-section with two check valves at the other end to provide for a one directional flow. An experimental setup was buil...
This paper projects how Maintenance, Repair and Overhaul (MRO) strategies can be optimized to the specific needs of end-users using Additive Manufacturing (AM) technologies. AM can significantly reduce the design and production times for customized parts. This leads to key advantages for MRO strategies from the end-user perspective, as well as envi...
Additive manufacturing, or 3D printing, is an emerging type of production technology that is seen as the core technology for future high-value engineered products. Due to the additive nature of stacking and unifying individual layers, the part and process design is substantially different from conventional production methods. This paper addresses o...
This study focuses on the comparison of porosity testing methods for the quality assessment of selective laser melted parts. Porosity is regarded as important quality indicator in metal additive manufacturing. Various destructive and non-destructive testing methods are compared, ranging from global to local observation techniques and from quick low...
An innovative design of a counter-current two-phase thermosyphon is investigated for the in-plane cooling of flat product structures. The thermosyphon features multiple pools staggered along the entire evaporator section, in which liquid flowing toward the bottom of the thermosyphon can be stored. The pools are used to cascade the working fluid to...
In this paper the joinability of titanium Additive Manufactured (AM) parts is explored. Keyhole welding, using a pulsed laser beam, of conventionally produced parts is compared to AM parts. Metal AM parts are notorious for having remaining porosities and other non-isotropic properties due to the layered manufacturing process. This study shows that...
In 2011, a round robin test was initiated within the group of CIRP Research Affiliates. The aim was to establish a platform for linking interdisciplinary research in order to share the expertise and experiences of participants all over the world. This paper introduces a testpart which has been designed to allow an analysis of different manufacturin...
This paper explores the application of Computer Aided Synthesis (CAS) to support the implementation of Set-Based Concurrent Engineering (SBCE) and Just In Time Decision Making (JIT-DM), which are considered as two of the cornerstones of the Lean Design method. Computer Aided Synthesis refers to a next generation computational tools that automates t...
TRIZ based Function Analysis models existing products based on functional interactions between product parts. Such a function model description is the ideal starting point for product innovation. Design engineers can apply (TRIZ) methods such as trimming and function ranking to this function model to improve their products. This paper describes the...
This paper proposes guidelines for a systematic patent circumvention strategy utilizing innovation and TRIZ tools. It focuses on starting from a landscape of patents and claims of an existing patent to create solutions that circumvent this existing patent. Information gathered from various sources is used to create the landscape of patents and clai...
New idea generation is imperative for successful product innovation and technology development. This paper presents the development of a novel type of invention support software. The support tool integrates both function modeling and mathematical modeling, thereby enabling quantitative analyses on a relative high level of abstraction. The function...
Additive manufacturing (AM) is emerging as an important manufacturing sector, due to its almost unlimited design freedom, the capability to produce personalized parts and the efficient material use. A reliable knowledge about material porosity of manufactured parts is crucial for optimizing AM process parameters. Indeed, internal pores can be somet...
ATLAS, the Academy of Technology and Liberal Arts & Sciences, is an interdisciplinary three-year Bachelor of Science honours programme for selected students that started in September 2013 at the University of Twente, the Netherlands. It aims to educate the so-called ‘new engineer’: a generalist who can combine technological and societal approaches...
This paper proposes a design method to seek potential product innovation fully exploiting in-house capabilities. The method triggers scientists, designers and engineers in discovering both new instantiations of physical principles and new physical phenomena that may appear by modifying the embodiment of existing technologies. The embodiment modific...
Foreword
DESIGN EDUCATION &
HUMAN TECHNOLOGY RELATIONS
The 16th International Conference on Engineering and Design Education (E&PDE) was held at the University of Twente on the 4th and 5th September 2014.
The conference was hosted by the Faculty of Engineering Technology of the University of Twente in Enschede, the Netherlands, in close collaborati...
Electronic circuitry includes a circuit board and at least one component mounted on the circuit board, with the at least one component generating heat while in use. The circuit board includes one or more apertures aligned with one or more respective components, and the electronic circuitry is configured to provide, while in use, a path for coolant...
This paper presents an investigation into the development of an information model to support the Product Development Process (PDP) of shaving devices at PHILIPS. Firstly, challenges of the PDP were identified by carrying out interviews with several systems engineers and product architects. It was found that an increase in product functions combined...
This paper presents an analytical method to predict deformations of Printed Circuit Boards (PCBs) in relation to their manufacturing process steps. Classical Lamination Theory (CLT) is used as a basis. The model tracks internal stresses and includes the results of subsequent production steps, such as bonding, multilayer press cycles and patterning...
For the thermal control of future space applications pumped two-phase loops are an essential part to handle the increasing thermal power densities. This study investigates the design of a reliable, leak tight, low-weight and high-pressure micro-pump for small satellite applications. The developed micro-pump uses a piezoelectric disk to create a pre...
Design for eXcellence (DfX) entails a wide range of goal specific design methods targeting different phases of a product’s lifecycle. These methods are often not standardized and sometimes even have contradicting rules among them. As a consequence, design processes experience an increase in organizational entropy. This paper presents a template for...
This paper proposes a new approach based on knowledge structures for building simulation models. The target are products to be redesigned integrating new technologies. The main idea of the approach is to limit the development of an analysis model to that of the new technology and merge it into the existing prototype using the connection parameters...
This paper highlights the imperative need for innovation and characterizes a promising support tool to stimulate this process. The importance of innovation for both a global economy and specifically for engineering education is discussed. Additionally, the urgency for multidisciplinary skills for inventors is rationalized. Our ongoing research deve...
High-performance electronics cooling moves from utilizing modular heat pipes to fully integrated heat pipes. Filling and sealing of these nontubular embedded heat pipes is a challenge, since traditional methods such as evacuate, fill, and pinch do not suffice. This paper presents a charging station that is able to fill and seal embedded heat pipes...
Product designers typically use existing concept solutions in their day-to-day business and development generally takes place via incremental improvements leaving little room for innovation. This study aims to improve system performance by an integrated design approach. The approach encompasses three phases: technology assimilation, technology inse...
In product development, the chosen product architecture often possesses characteristics of both modular and integral design. Within a modular architecture, a Function-Behavior-Structure (FBS) model has been applied to describe modules and their interfaces. To resolve emerging interface conflicts, several strategies based on both modular and integra...
A novel, integrated approach in thermal management of electronic products, based on two-phase cooling, is presented. A flat miniature heat pipe, integrated inside the laminated structure of a printed circuit board (PCB), has been developed, based on mainstream PCB multilayer technology. To accurately predict the thermal performance of this two-phas...
Best practice for collaborative design demands good interaction between its collaborators. The capacity to share common knowledge about design models at hand is a basic requirement. With current advancing technologies gathering collective knowledge is more straightforward, as the dialog between experts can be supported better. The potential for 3D...
This paper presents two novel approaches for the thermal management of electronic components. Electronics cooling is currently receiving more and more attention, since the power densities have increased significantly. Interesting cooling technologies thermally surpassing traditional applications are among others: jet impingement cooling and two-pha...
This paper presents an integrated design strategy for chip layout optimization. The strategy couples both electric and thermal aspects during the conceptual design phase to improve chip performances; thermal management being one of the major topics. The layout of the chip circuitry is optimized according to the proposed design rules. This offers ch...
This paper proposes a model to structure routine design problems as well as a model of its design complexity. The idea is that having a proper model of the structure of such problems enables understanding its complexity, and likewise, a proper understanding of its complexity enables the development of systematic approaches to solve them. The end go...
Competitive product development faces the challenge of including novel technologies often requiring a new understanding of physical phenomena. Industry must assimilate interesting applicable technologies and implement them into their current product design processes, in a rapid and efficient manner.
Technical products are formed by integration of m...
Design Engineering is a discipline that bridges the gap between the inventor and the manufacturer. The task of a design engineer is to make sure that the envisioned product functions are realized while minimizing the usage of resources. In recent decades, the development of Computer Aided Design (CAD) and Computer Aided Manufacturing (CAM) systems...
Designing thermal control systems for electronic products has become very challenging
due to the continuous miniaturization and increasing performance demands. Two-phase
cooling solutions, such as heat pipes or vapor chambers, are increasingly used as they offer
higher thermal coefficients for heat transfer. Following a multidisciplinary and integr...
A novel, integrated approach in thermal management of electronic products, based on two-phase cooling, is presented. A flat miniature heat pipe, integrated inside the laminated structure of a printed circuit board (PCB) has been developed, based on mainstream PCB fabrication processes. Hot spots on the PCB, caused by heat dissipating components, ca...
To broaden the scope of inkjet printing, this paper focuses on printing of an organic silver complex ink on glass substrates towards the fabrication of metallic 3D microstructures. The droplet formation sequence of the inkjet printer is optimised to print continuous layers of metal. A brief discussion on orientation trials, aimed at optimising the...
Within the University of Twente, the Netherlands, TRIZ is seen as a powerful methodology that stimulates students in investigating innovative solutions during the product development process. The TRIZ methodology has been part of the Twente curriculum for many years, mainly as small parts of courses and projects. In 2009, TRIZ was presented as an 8...