Die TRR 277-National-Summer-School-2021 in Digital-Realen-Hybridzeiten
Von 28. Juni bis zum 2. Juli 2020 fand die TRR 277-National-Summer-School im Haus der bayerischen Landwirtschaft am Ammersee statt. Dank der günstigen Pandemielage konnte das Treffen, vor einigen Monaten noch undenkbar, als hybrid kombinierte On- und Offline Veranstaltung stattfinden. Unter Einhaltung aller Schutz- und Hygienekonzepte und täglichen Tests, haben dabei wechselnd zwischen 40-60 Personen in Präsenz teilgenommen und ca. 20-40 Personen verfolgten die Vorträge online und nahmen digital an der Diskussion teil.
Den Auftakt der Summer-School am Montag machten die Sprecher des TRR 277 Harald Kloft und Christoph Gehlen mit inspirierenden Impulsvorträgen, denen noch insgesamt sechs spannende Impulsvorträge von Projektleitenden (PLs) am Dienstag und Donnerstag folgten.
Kerne der Summer-School waren die Vorträge der 20 Teilprojekte, in welchen die Doktorand*innen den Stand ihrer Forschungsarbeit vorstellten und zusammen mit den Projektleitenden wichtige Fragestellungen und die Zukunft ihrer Arbeit diskutierten.
Um neben seinem wissenschaftlichen auch seinen gesellschaftlichen Zielsetzungen gerecht zu werden, wurde am Mittwoche der Fokus bewusst auf das Thema „Gender & Diversity“ gelegt. Beginnend mit ihrem Vortrag über „Gender & Diversity - Kognitive Biases im Hochschulkontext“, stieß Frau Dr. Lisa Horvath (http://www.drlisahorvath.at) eine angeregte Diskussion an, welche im anschließenden von TRR 277 Vorstand geleitet Workshop auf die Gleichstellungsmaßnahmen im TRR277 bezogen werden konnte. Neben der Vermittlung und Verbesserung der bereits im TRR 277 implementierten Strukturen und Maßnahmen zur Gleichberechtigung, Familienfreundlichkeit und Karriereförderung, entstanden hier neue Ideen wie u.a. die Planung einer voll gendergerechten TRR277-Student-Spring-School im Jahr 2022.
Neben dem fachlichen Austausch stand natürlich nach fast 1,5 Jahren Pandemiebeschränkungen das persönliche Kennenlernen und die direkten „Face to Face“ Gespräche im Vordergrund. Begünstigt wurden diese durch viele kleine Sitzecken im Garten und das bunte Freizeitprogramm wie Baden im Ammersee, Spaziergänge zum Bayrischen Biergarten, ein wenig Disko und Liveübertragung der Fussball-EM auf der große Leinwand im Vortragssaal.
Auch wenn die Durchführung als hybride Veranstaltung eine neue technisch-organisatorische Herausforderung war, blicken wir (erschöpft vom gefüllten Wissensdurst und den Tücken der Technik) sehr zufrieden auf diese intensive und bereichernde Woche zurück. Es war ein großartiges Zusammentreffen und hat nicht nur die interdisziplinär vernetzte Forschung, sondern insbesondere den Teamgeist des TRR 277 beflügelt.
Vielen Dank an alle, die On- und Offline teilgenommen haben oder hybrid zwischen der digitalen und realen Welt hin und her gesprungen sind.
Research Summary Report - A 08
Structural Timber by Individual Layer Fabrication (ILF)
Henke, Klaudius; Project leader; Talke, Daniel; Doctoral researcher; Buschmann, Birger; Doctoral researcher; Technical University of Munich, Chair of Timber Structures and Building Construction
The main goal of the project ‘Structural Timber by Individual Layer Fabrication (ILF)’ is to find a way to additively manufacture large scale elements from wood composites with a minimum content of adhesive and strength values suited for applications in construction.
Similar to other particle bed binding technologies, in ILF, a thin layer of wood particles is bound by selectively applying adhesive according to the target geometry of the object. However, here each layer is manufactured individually with the added step of applying mechanical pressure. In doing so, the amount of required adhesive is drastically reduced while at the same time the mechanical properties of the panel as well as the finished product is increased. Preliminary tests have produced promising results with material strengths well above those of common particle boards. Current research is focused on automating the individual steps of the manufacturing process and exploring the process parameters and their influences.
Research Summary Report - A 07
Wire and Arc Additive Manufacturing (WAAM) of complex individualized steel components
Müller, Johanna; doctoral researcher, TU Braunschweig, Institute of Joining and Welding
The Wire Arc Additive Manufacturing (WAAM) of complex individualized steel parts presents different challenges. One of them is the thermal cycle during the fabrication of WAAM-parts and its effects on the material properties.
WAAM uses conventional gas metal arc welding for the layer-wise deposition of single weld beads. During this process, the deposited structure is frequently reheated. Especially for ferritic steel this may affect the mechanical properties since the material is exposed to high temperatures for a long period of time and undergoes several phase transformations.
Within the scope of TP A07 the mechanical properties as well as the microstructure of WAAM wall structures manufactured with different energy inputs and interpass temperatures were analyzed and an active cooling device was used to shorten the manufacturing time and to reduce the effects of those thermal cycles.
The results showed a reduction of the tensile strength with increasing energy inputs whereas high interpass temperatures led to an increase of the tensile strength.
Regarding the yield strength, welding with high energy inputs and interpass temperatures leads to a decreased yield strength.
Especially at high energy input the active cooling had a positive effect as it led to a strong increase of the mechanical properties such as tensile strength and yield strength compared to cooling by free convection. When welding with higher interpass temperatures the active cooling showed no significant effect on the mechanical properties.
Research Summary Report - A 04
Integrated Additive Manufacturing Processes for Reinforced Shotcrete 3D Printing (SC3DP) Elements with Precise Surface Quality
Dörrie, Robin; doctoral researcher, Technische Universität Braunschweig, Institute of Structural Design
Based on the digital simulations and numerical analysis, coming from a FEM plugin (Karamba 3D), of different reinforcement layouts in beam elements, the research was continued with the production of these specimens as well as the testing.
The calculated forces and principal stress lines of the element were translated into a rebar reinforcement by using handmade templates to shape the rebar according to the visualized stress lines. The specimens were separated into two categories with different reinforcement layouts in each group. The first category contains the casted specimens with a non-reinforced beam, a standard reinforced beam and three optimised versions. All specimens from the second category were produced by SC3DP. In this category non-reinforced beams along with two optimised versions were produced.
The results of the 4-point bending tests showed the great potential of optimising reinforcement layouts. On the one hand a higher efficiency can be reached by keeping the amount of steel equal in both designs. On the other hand, a high amount of steel could be saved to reach the same flexural strength as a standard reinforced beam.
Online Symposium: Adaptive Envelopes and Structures - SFB 1244
Wire and Arc Additive Manufacturing (WAAM) of Reinforcement Bars & Pull-Out Tests
Fabrication and Testing of Wire and Arc Additively Manufactured reinforcement bars
Wire and Arc Additive Manufacturing (WAAM) opens up new possibilities for the fabrication of reinforcement bars/structures with optimized geometries and surface characteristics. By the variation of the wire feed and welding time per layer during the superimposition of single weld spots, bars with different surface topographies can be manufactured. For testing and characterizing the bond behavior between concrete and reinforcement bar, the bars are encased in concrete, stored in a controlled environment for 28 days and then are tested by pulling the bars out of the concrete while logging the force and the displacement.
This research was conducted as part of the networking of subprojects A07 "Wire and Arc Additive Manufacturing (WAAM) of Complex Individualized Steel Components " and A04 “Integrated Additive Manufacturing Processes for Reinforced Shotcrete 3D Printing (SC3DP) Elements with Precise Surface Quality” funded in TRR 277.
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Reinforced Concrete Components from the 3D Printer
Dr. Inka Dreßler on her research in the SFB "Additive Manufacturing in Construction"
How can reinforced concrete components be produced as geometrically precise and high-strength as possible using 3D printing? To this question, Dr. Inka Dreßler has now received support from experts from France during a TRR277-funded research stay in Brittany.
Modelling and Simulation of Shotcrete 3D Printing (SC3DP) Based on a Massively Parallel Multi-Phase, Multi-Component Coupled LBM-DEM Approach
K. Kutscher (PostDoc); TU Braunschweig, IRMB M. Geier (PI); TU Braunschweig, IRMB M. Krafczyk (PI); TU Braunschweig, IRMB
A new numerical model for Bingham fluids has been developed in this project . In this approach we made use of the fact that we found an analytical solution to the implicit problem of finding a relaxation rate for a given shear stress. Previous models relied on iterative solutions or smoothing functions . Differences between the new and the iterative method  are seen at higher resolution. It is observed that neither methods convincingly displays second-order convergence down to a resolution of 256 lattice nodes in the span. While both methods give nearly identical results for the lowest resolution, the approximate method levels off at higher resolutions. The next test is a planar Taylor-Couette flow. We investigate the flow between a rotating outer and a resting inner cylinder. Perpendicular to the plane periodic boundary conditions are used such that the setup is quasi two dimensional. Interpolated bounce back with and without velocity is used for the outer and the inner cylinder, respectively. In this test case, flow attached to the outer cylinder will be below the yield threshold and hence move as a solid with the same angular velocity as the outer cylinder. This plug flow domain attached to the outer cylinder is reduced in size with higher angular momentum.
Research Summary Report - A 03
Extrusion of Near-Nozzle Mixed Concrete – Individually Graded in Density and in Rate of 3D Fibre Reinforcement
Hechtl, Christian Maximilian; TP editor, TUM, Chair of Materials Science and Testing (cbm) Matthäus, Carla; TP editor, TUM, Chair of Materials Science and Testing Dr.-Ing. Kränkel, Thomas; PL, TUM, cbm Prof. Dr.-Ing. Gehlen, Christoph; PL, TUM, Chair of Materials Science and Testing
The main goal of the A03 project is to design a new extrusion method for graded concrete. In contrast to conventional concrete extrusion, the Near-Nozzle Mixing System (NNMS), homogenizes the concrete components (both dry and liquid) in the mixing head and directly deposits the fresh material. This system has many advantages over the conventional approach. Figure 1 shows a rendering of the NNMS.
One of the essential advantages is the opportunity to immediately adjust the material properties during the printing process (gradation).This way, it is for example possible to switch between lightweight concrete structures with high thermal insulation properties and high-strength concrete, allowinghigh load transfer.Since the raw materials for this system can be selected relative freely after rheological adjustment, this system also offers to incorporate reinforcement into the printing process in the form of steel fibers or, as shown in Fig. 1, with the help of a second robot that inserts the steel reinforcement into the already printed layers.
Also, the conflict between pumpability and stiffness of the material is eliminated so that the focus can be on high processability and fast printing. More precisely, the green stability of the fresh material can be significantly increased, since the soft properties of the material are no longer needed for pumping.
Research Summary Report - C 01
Bridging Scales – From Geometric Part Details to Construction Elements
Additive Manufacturing (AM) offers unprecedented flexibility in design and production of geometrically complex components. This flexibility puts a strain on the conventional numerical analysis tools aiming to understand the physical behaviour of the components. As the geometry and material properties get more and more complex, the computing power needed by the numerical tools rapidly increase. The challenge is then to utilize the computing capabilities of the modern hardware to perform large-scale “virtual experiments” on AM components. Moreover, one needs not only an efficient implementation that can take advantage of the state-of-the-art compute nodes, but also a robust numerical approach that can handle such complex geometries with ease. The Finite Cell Method is one simulation approach that is well-suited to handle such geometric complexities, as it can avoid the time-intense task of mesh generation. To overcome the above challenges, we have extended our numerical analysis tool, an implementation of Finite Cell Method (FCM), to allow for solution of large-scale simulations of AM parts on massively parallel machines. The extension enables solution of problems with billions of unknowns where such problems have been close to impossible to tackle before.
Research Summary Report - A 02
Particle-Bed 3D Printing by Selective Cement Paste Intrusion (SPI) - Particle Surface Functionalisation, Particle Synthesis and Integration of WAAM Reinforcement
Straßer, Alexander, TP editor, TUM, Chair of Materials Science and Testing Matthäus, Carla, TP editor, TUM, Chair of Materials Science and Testing Kränkel, Thomas, TP editor, TUM, Chair of Materials Science and Testing Gehlen, Christoph, PL, TUM, Chair of Materials Science and Testing
The goal of A02 is the implementation of reinforcement with Wire and Arc Additive Manufacturing (WAAM) in concrete elements produced by Selective Paste Intrusion (SPI). Due to the application of cement paste in the SPI process onto the aggregates and the fact that the cement paste has to percolate into the aggregates by gravity alone, consistent and adjusted rheological properties are essential for a high layer bonding and a good print quality. The welding process with WAAM generates high temperatures – more than 1500°C at the welding point. Therefore, the first step is to verify which temperature loads affect on the cement paste through the WAAM process, what the temperature gradients are in the particle bed, and which temperatures the cement paste can withstand. According to preliminary results, the temperature load of WAAM exceeds the limiting temperature at which cement paste retains its rheological characteristics and can be processed accordingly. To prevent the cement paste used by SPI from dehydrating, the heat transfer and propagation into the particle-bed must be minimized, various parameters in the processes must be optimized, and different cooling strategies developed. Various cooling strategies can be considered to minimize the temperature in the particle bed. This includes varying the time needed to print a layer with the WAAM process. Furthermore, the distance between the welding point and the particle bed surface (in the z- direction) should be increased, and active cooling strategies implemented. Besides, the cement paste is to be optimized concerning temperature loads to retain consistent rheological properties even at higher temperatures. Another aspect is the optimization of the aggregates. As part of the research work, various coatings are to be tested so that the particle bed is more robust in case of a higher temperature load.
Research Summary Report - A 01
Particle-bed 3D printing by selective cement activation: Particle surface functionalization, particle bed compaction and reinforcement
Herding, Friedrich; Researcher, TU Braunschweig, Institute of Building Materials and Concrete Construction and Fire Safety (iBMB) Dreßler, Inka; Leading researcher, TU Braunschweig, Institute of Building Materials and Concrete Construction and Fire Safety (iBMB) Lowke, Dirk; Project leader, TU Braunschweig, Institute of Building Materials and Concrete Construction and Fire Safety (iBMB)
The main objective of our research is to understand the material-process interaction in particle bed 3D printing in order to produce concrete elements with high mechanical performance and geometric precision. The research focuses on the effect of fluid application on the mechanical performance of printed objects from a material (w/c-ratio) and process (fluid discharge rate from the nozzle) point of view. A positive correlation between increasing water to cement ratio and compressive strength is observed. This is in contrast to common concrete technology and is the result of a better bonding between the layers. Additionally, the compressive strength of 3D printed specimens with constant w/c-ratio is increasing with increasing fluid discharge rates from the nozzle. One reason may be the fact that a higher injection depth of the fluid into the particle-bed is achieved. Moreover a rearrangement in particles may take place and a mechanical interlocking of the layers may be prevalent.
Research Summary Report - C 05
Jointing Principles for Combination of Concrete Elements Produced by Different Additive Manufacturing Processes
Baghdadi, Abtin; Research Assistent, Institut für Tragwerksentwurf (ITE)
This project aims to investigate the execution process and load-bearing capacity of the concrete-dry joints, considering different printed concrete material to be utilized in the construction of segmental beams. Accordingly, C05 (ITE) is mainly working on the application of the post-processinggrinding technique (milling and cutting) for making pre-selected types of dry joints and on developing innovative connection geometries, which can be produced by the robotic CNC method. These studies will be followed by experimental tests applied to the concrete specimens prepared by different printing technics (AM).
Through the first working package (2020), ITE prepared appropriate clamping systems, software and milling tools, which can be adaptively applied to a wide range of geometries. Then, for the first CNC applications, multi joint-geometries were selected (10x10x10cm). Their parametric CAD models(Rhino-Grasshopper) were prepared and exported to the CNC software (EasyStone) to simulate and make the G-codes. Finally, these dry joints in DBFL were produced, and the geometries scanned to once entirely complete and evaluate the process.
Research Summary Report - C 04
Integrating Digital Design and Additive Manufacturing through BIM-Based Decision Support and Digital Twin Methods
Li, Chao; Doctoral researcher, TU Munich, Chair of Architectural Informatics Slepicka, Martin; Doctoral researcher, TU Munich, Chair of Computational Modeling and Simulation
In the context of AMC, C04 workgroups attempt to cohesively integrate AM and BIM-based early design, through the design decision support and fabrication- enhanced multi-LOD BIM models.
Knowledge Base Formalization
Domain-specific knowledge base usually serves as a backbone in a Knowledge-Based System (KBS). Furthermore, the knowledge base of proposed DDSS has to be formalized in an extensible, reusable and interoperable manner. In the first stage of work, C04 workgroups have conducted semi-structured interviews between other sub-projects (A01-A05, C01- C06). From the interviews, four groups of knowledge have been initiated while need to be updated iteratively. Accordingly, Semantic Web technology stack has been chosen by WP1 to approach the formal description of AMC-specific knowledge, for its capability, over the individual Knowledge Representation (KR) techniques, to holistically embody rules, ontology, knowledge querying and reasoning. To prove the workability of integrating Semantic Web based knowledge into BIM authoring system, a Revit add-in has been developed to query the preliminary AMC-related ontology through the dotNetRDF. Up to now, basic queries from code-behind to the knowledge base turned out a success, which paves the road of upcoming milestones. As inspired from Design for Additive Manufacturing (DFAM) ontologies, adaptations of the initialized knowledge base is under work. Basically, the new ontology aims to loosely couple manufacturability of a building component from its form and function while intermediating those using parameters, manufacturing features and design rules.
Automatic derivation of fabrication information from a BIM model
Both BIM-based design and additive manufacturing processes describe the same object once it has been manufactured, but design focuses more on the final form and function of the component and AM processes focus more on the manufacturing process itself. In the construction industry, the two disciplines are currently handled separately, even though a common database and mutual integration would be beneficial in create a continuous digital chain from design to the finished product . In the field of mechanical engineering, this is realized by linking Computer Aided Design (CAD) and Computer Aided Manufacturing (CAM) processes in uniform software solutions and further improved with the extension of the exchange data format STEP to STEP-NC, to contain a database for the numerical control of machine tools . This makes it possible, for example, to be informed about possible conflicts or obstacles caused by manufacturing processes directly during the design phase .
To integrate design decision support and an automated system to derive fabrication information into the BIM-workflow we propose a new methodology, the Fabrication Information Modeling (FIM). As an iterative workflow (shown in Fig. 1), it enables an efficient integration of AM information and workflows into BIM, starting from the early design phase.
Research Summary Report - A 02
Particle-bed 3D printing by Selective Cement Paste Intrusion: Particle Surface Functionalisation, Particle Synthesis and Integration of WAAM Reinforcement
Hamilton, Leigh Duncan; Researcher, TU Braunschweig, Institute for Particle Technology (iPAT) Breitung-Faes, Sandra; Leading Researcher, TU Braunschweig, Institute for Particle Technology (iPAT) Kwade, Arno; PL, TU Braunschweig, Institute for Particle Technology (iPAT)
Selective cement paste intrusion (SPI) is an additive manufacturing method where aggregate particles are spread in small layers, followed by the local intrusion of the cement paste into the aggregate layers. These steps are repeated layer-by-layer and the consequent hardening forms the structure. In comparison to other AM processes, the necessity of support structures for cantilevers is redundant for SPI. In addition, research to date has shown that SPI-made components closely acquire isotropic compressive strength (>70 MPa), reliable shape accuracy as well as high durability.
Whilst the aforementioned advantages are promising for future industrial implementation, the SPI process is in need of a reinforcement mechanism in order to perform a scale-up, and thus, produce structural concrete elements. Hence, the goal of the project A02 is the implementation of Wire and Arc Additive Manufacturing (WAAM) as a means of simultaneously printing the reinforcement during SPI. A successful implementation of WAAM would provide the production of reinforced concrete structures in accordance with the principle of “form follows force”, leading to economically and ecologically viable components.
The combination of SPI and WAAM is accompanied by obstacles that must be overcome in order to ensure the collaborated functionality. One major challenge occurs from the propagated thermal load of WAAM (approx. 1600 °C), which has negative effects on the paste rheology and resulting concrete strength. Therefore, the overall goal is to minimise heat propagation into the particle bed.
Research Summary Report - A 05
Integration of Individualized Prefabricated Fibre Reinforcement in Additive Manufacturing with Concrete
Rothe, Tom; Doctoral researcher, TU Braunschweig, Institute of Mechanics and Adaptronics (IMA) Hühne, Christian; Project leader, TU Braunschweig, Institute of Mechanics and Adaptronics (IMA)
One of the biggest challenges in 3D printing with cementitious materials is the integration of reinforcement. The project aims to develop textile-based reinforcement strategies for additive manufacturing with concrete and to utilize the advantages of textile reinforcement (e.g. corrosion resistance and material flexibility) for the production of material-efficient, individualized structures. These structures should be produced by a robotic winding process, which provides a high degree of freedom in shaping in combination with a minimal amount of tooling and formwork. To be able to do so, a highly autonomous production process is required. Therefore an in situ fiber preparation is integrated. Within this process, fiber rovings are formed to strands. Furthermore, the fiber preparation includes the resin impregnation and the application of a helix surface structuring by wrapping a secondary yarn around the preformed strands to increase the interlocking between the reinforcement structure and the concrete.
Besides their structural task, the winded reinforcement meshes serve as a base for additively applied concrete. Different methods for applying the concrete can be used.
First experiments to produce reinforcement structures by the winding of glass fiber strands have successfully been conducted. Fig. 1 shows the used robot while winding fiber strands around pins on a rectangular frame. The preparation of the fibers occurred in situ with an end-effector, which has been developed for this purpose within this project. After the winding, concrete was applied on the winded frame by shotcreting.
Further investigations on the winding process and the use of different additive manufacturing techniques to apply the concrete are planned for the near future.
Research Summary Report - A 06
Laser Powder-Bed Fusion (PBF-LB/M) of Steel Elements for Construction – Basics of Design and Mechanical Resilience
Diller, Johannes; Doctoral researcher, TU Munich Dorina Siebert; Doctoral researcher, TU Munich, Chair of Metal Structures Wenzler, David; Doctoral researcher, TU Munich Kolb, Cara; Doctoral researcher, TU Munich, Institute for Machine Tools and Industrial Management
The reproducibility of the mechanical properties of PBF-LB/M parts needs to be increased. This requires a more detailed understanding of the correlation between the process parameters and the mechanical and metallurgical properties of the manufactured parts. In project A06 a first step towards this goal has been taken:
With a thermography camera, the cooling rates during the fabrication of fatigue test specimens were measured. Two process parameter sets with different scanning speed and laser power were used for the manufacturing. Afterwards, strain-controlled fatigue testing was performed to investigate the plastic deformation behaviour resulting from the different processing conditions. The first results show significant correlations between the manufacturing conditions, cooling rates, and mechanical properties.
Currently, the thermography set-up is being optimised by a high-speed camera to increase the spatial and temporal resolution. In the next step, the process parameter space will be extended and comprehensive tensile and fatigue testing will be conducted.
1st aaec network member symposia:
“research insides in Additive Manufacturing Construction”
The CRC/Transregio TRR 277 - Additive Manufacturing in Construction based in Braunschweig and München has organised the 1st research insides on 1st of february 2021 within the Research Network for Advancing Architecture, Engineering and Construction" (AdvanceAEC) (https://www.advanceaec.net). The Video of the Symposia shows different Presentations adressing Additive Manufacturing Construction.
Research Summary Report - A 07
Wire and Arc Additive Manufacturing (WAAM) of Complex Individualized Steel Components
29.01.2021 Unglaub, Julian; Associate Researcher,TU Braunschweig, Institute of Steel Structures Jahns, Hendrik; PhD Researcher, TU Braunschweig, Institute of Steel Structures Thiele, Klaus; Project Leader; TU Braunschweig, Institute of Steel Structures
Project A07 investigates structural design, WAAM methods and component testing of complex, large-scale, individualized steel components. The objective is to connect conventionally manufactured steel components and semi-finished products with additively manufactured, complex steel components The Institute of Steel Structures develops a novel test method based on fill field strain data.
This test method considers potentially anisotropic component behaviour, surface topographies, geometric irregularities and residual stresses in addition to the relevant material properties.
Research Summary Report - A 08
Structural Timber by Individual Layer Fabrication (ILF)
22.01.2021 Bunzel, Frauke; Project leader; Fraunhofer Institute for Wood Research, Wilhelm-Klauditz-Institut WKI Asshoff, Carsten; Doctoral researcher; Fraunhofer Institute for Wood Research, Wilhelm-Klauditz-Institut WKI
In order to produce future-oriented timber structures in the building industry that meet the requirements of ecological and economic sustainability, an additive manufacturing process with wood chips is being developed using the new approach of individual layer fabrication (ILF). In first steps,established wood chip fractions and adhesive systems from the wood-based materials industry are used e. g. for particleboards or oriented strand boards.
For an acceptable adhesive-wood-chips ratio the amount of adhesive must be as low as possible, which is one of the challenges in developing ILF, see Fig. 1. In addition to the distribution of the adhesive over the wood chips surface, the intrusion behavior into the bulk is decisive. On the adhesive side, approaches such as reducing the viscosity by emulsifying with water or reducing the surface tension can lead to better processing results. In first steps, the wood chips should remain untreated. However, it is necessary to determine whether one wood chip fraction can be processed better than others. It is known that higher stiffness and strength can be produced by coarser wood chips fractions, which is also considered. The structural performance of the final component is not only determined by the strength and stiffness of the material but also significantly by the geometry of the part.
For the repeatable and automatable application of the adhesive from above onto the wood chips, a pre-selection of potential valves was made. First, the pressure-time, spray- and jet-valves are investigated. Each of the mentioned valves has advantages and disadvantages in the general application technique of liquids. Experiments will be conducted to determine which of the valves offers the best potential for the ILF process by varying materials and application parameters.
Research Summary Report - B 04
Process Control and Adaptive Path Planning for Additive Manufacturing Processes Based on Industrial Robots with an Extended Degree of Freedom
14.01.2021 Ekanayaka, Virama; Doctoral researcher, TU Braunschweig, Institute of Machine Tools and Production Technology (IWF)
The integration of robot-guided additive manufacturing in the construction industry increases the degree of automation and can thus lead to an increased productivity and increased component quality. In shotcrete 3D printing (SC3DP), reproducible manufacturing results and ensuring component qualities are a major challenge, as the properties of shotcrete depend on many different parameters (e.g. temperature, pressure, water-cement ratio, hardening accelerator).
The goal of this research project is to develop a reproducible, robot-guided shotcrete process based on multi-model adaptive path planning for the production of high-quality large and complex components. The core of this multi-model based path planning is the combination of geometric data and a physical material model into an application process model.
Within the scope of this research, a MATLAB framework is created which enables the coupling of the path planning to a Finite Element model. The STL data of the CAD Model to be printed represents the input used in the MATLAB framework.
Based on the printing path, a novel finite element approach was implemented which builds the mesh independently from the printed component’s ideal CAD geometry. This has the clear advantage that the actual printed structure is simulated instead of the ideal target geometry. In this way, it is possible to directly simulate the material behavior during application and thus, to determine deviations from the CAD model.
By achieving better results from detailed FEA, the information on the obtained loads and deformations as seen in Figure 1, can be used within an additional feedback loop to adapt the printing path and printing parameters. Using those optimized paths will finally lead to better component quality, reduced test effort, and fewer buildability failures.
Research Summary Report - C 06
Integration of Additive Manufacturing in the Construction Process
08.01.2021 Mawas, Karam; Doctoral researcher, TU Braunschweig, Institute of Geodesy and Photogrammetry (IGP) Gerke, Markus; Project leader, TU Braunschweig, Institute ofGeodesy and Photogrammetry (IGP) Maboudi, Mehdi; Associated scientist, TU Braunschweig, Institute of Geodesy and Photogrammetry (IGP) Riedel, Björn; Associated scientist, TU Braunschweig, Institute of Geodesy and Photogrammetry (IGP)
Additive Manufacturing (AM) allows us to print objects in unprecedented and novel ways, pushing the boundaries of what was previously possible in construction. By seamlessly embedding the process of the design directly into the printing process, ever more complex and free form objects can now be realized. Nonetheless, AM remains a challenging and involved process that is influenced by a variety of factors. To ensure that a robust process is followed and that the printed object adheres to the model of the original, continuous monitoring and inspection of the process is required.
Fig. 1 shows a freeform doubly-curved reinforced wall. A laser scanner was used to scan the object as it was constructed, after which it was compared directly to the 3D design model. The resultant model was then colorized based on Cloud to Cloud distance.
As we have stated, while 3D construction printing affords unprecedented freedom, it also poses new challenges for quality control. These challenges include collecting adequate data while ensuring the optimal time for data capturing, the size of the object, and its material properties, all while utilizing the proper type of sensor needed to control the structure's progress as it is being built. It is worth noting that many of these challenges are interrelated and interdependent. For instance, data capture must return reasonably rapid data within a predetermined time window so that the data acquisition of the object is in the range of the predefined time window. However, the type of sensor needed for a project is also dependent upon the size and material properties of the object in question.
One of the defined objectives of the Institute of Geodesy and Photogrammetry of TU is to continuously and effectively monitor the quality of 3d printed construction objects with the use of several different methods of data capturing. This includes the use of quality control during the printing process, as well as data capturing to inspect the object after printing is completed. For this process to be effective, several types of sensors are needed to be investigated, allowing for enhanced data capture, enhanced accuracy, and ongoing comparison with the designed model. Also, the challenges related to each step-in quality inspection process has to be considered.
Research Summary Report - A 07
Wire and Arc Additive Manufacturing (WAAM) of complex individualized steel components
01.01.2021 Christoph Müller, doctoral researcher, TU Braunschweig, Institute for Structural Design (ITE)
This sub-project of the SFB 277 deals with the design process of components for additive manufacturing by Wire and Arc Additive Manufacturing (WAAM). In contrast to large industrial sectors such as mechanical engineering, aeronautical engineering or medical technology, components in the construction industry have to be designed under different general conditions.
If no building system is used to create a structure, the components are usually individual. These components are usually used in the building as a single part or in small quantities. With the implementation of additive manufacturing processes, these components are usually free-form geometries that result from the fulfilment of a wide range of boundary conditions.
This includes improvements in material utilization through topology or shape optimization, geometries suitable for production and architectural design requirements.
Due to the frequently small number of identical components, the effort required to create the geometry must also be kept low, as otherwise the economic advantages of additive manufacturing are outweighed by the effort required in the design process.
The approach in this research project is to automate as many work steps as possible. As a further guideline, the respective effort per work step should be kept as low as possible. Topology optimization serves as an example here. Up to now, this has often been a decisive part of the design process. However, since geometry suitable for production is also required, time and resources can be saved by reducing the precision of topology optimization in favor of design speed.
For this purpose, a basic geometry is created that represents the design space. This geometry is transferred into a spatial framework and calculated by FEM for the corresponding load. Subsequently, the connection points are moved depending on the beam forces of the spatial beam system. In this process step, the points are considered as cellular automata and are all subject to the same set of rules.
AAEC Network Member Symposia
The TRR 277 is pleased to inform, that on Monday, 1st of February 2021, the first AAEC network member symposia will take place:
Organisation: sfb/trr 277
Agenda: 1. Guest Keynotes by Ena Lloret-Fritschi and Fabian Meyer-Brötz 2. TRR 277 selected project insides 3. Discussion
Architektur und Bau: Mehr Dialog zwischen Forschungsverbünden
Fünf Forschungsverbünde, unter anderem der TRR 277, haben das „Research Network for Advancing Architecture, Engineering and Construction“ ins Leben gerufen. Das Netzwerk bringt internationale Wissenschaftlerinnen und Wissenschaftler zusammen, die danach streben, Architektur, Ingenieur- und Bauwesen durch digitale Technologien und einen interdisziplinären Ansatz voranzubringen. Es zielt darauf ab, die vielfältigen ökologischen, wirtschaftlichen und soziokulturellen Herausforderungen anzugehen, mit denen die Bauwelt konfrontiert ist.
Der vollständige Text ist unter folgendem Link zu finden:
16 Meter lang, neun Meter breit und ein Arbeitsraum von 370 Kubikmetern: Das Digital Building Fabrication Laboratory (DBFL) des Instituts für Tragwerksentwurf (ITE) der Technischen Universität Braunschweig ist ein echtes Großgerät. Es schlicht 3D-Betondrucker zu nennen, greift zu kurz. Für Dr. Jeldrik Mainka vom ITE ist es das „größte Schweizer Taschenmesser“, das er kennt. Warum das so ist, hat das DBFL unserer Redakteurin Bianca Loschinsky selbst erzählt.
Das vollständige Interview ist unter vollgendem Link zu finden:
Der Beitrag "Studying the Bond Properties of Vertical Integrated Short Reinforcement in the Shotcrete 3D Printing Process" von Niklas Freund, Inka Dreßler und Dirk Lowke wurde auf der Digital Concrete 2020 mit dem Best Presentation Award ausgezeichnet. Die Digital Concrete ist eine internationale Konferenz, dessen Fokus auf der digitalen Fertigung zementgebundener Baustoffe liegt. Aufgrund der aktuellen Covid-19-Situation musste die diesjährige Konferenz auf ein vollständiges Onlineformat umgestellt werden.
Niklas Freund präsentierte die Ergebnisse experimenteller Untersuchungen, in denen das Verbundverhalten von Bewehrungsstäben untersucht wurde, die in den Shotcrete-3D-Printing-Prozess integriert wurden. Die Ergebnisse sind im Beitrag „Freund, N.; Dreßler, I.; Lowke, D.: Studying the Bond Properties of Vertical Integrated Short Reinforcement in the Shotcrete 3D Printing Process.“ veröffentlicht (https://www.researchgate.net/publication).
Die Integration von Bewehrungselementen in die bestehenden Beton-3D-Druckprozesse stellt ein sehr aktuelles und wichtiges Forschungsthema dar, welches durch Niklas Freund im Teilprojekt A04 des TRR 277 - „Additive Manufacturing in Construction (AMC)“ untersucht wird. Mehr Informationen erhalten Sie unter www.tu-braunschweig.de/trr277/projects/amc-structure/a-projects/a04
Bauteile aus Stampflehm effizient herstellen
Das Institut für Tragwerksentwurf (ITE) der Technischen Universität Braunschweig ist beim diesjährigen Wettbewerb der Deutschen Gesellschaft für Nachhaltiges Bauen (DGNB) unter den drei Finalisten in der Kategorie „Forschung“. Der Beitrag des ITE befasst sich mit robotischer Fabrikation von Bauteilen aus Stampflehm.
Bis zum 13. September 2020 kann für das Projekt abgestimmt werden.
Professor Dr.-Ing. Dirk Lowke, head of the institute of building materials, concrete construction and fire protection and head of the projects A01 and A04 within the TRR 277 was Keynote Speaker at this year's Digital Concrete 2020 conference.
The whole presentation can be heard in full at the following links
20./21.04.2020 | Erstes TRR 277-Quartalstreffen als Online-Konferenz
Der SFB/ TRR 277 - Additive Manufacturing in Construction - The Challenge of Large Scale hat situationsbedingt sein erstes Quartalstreffen aller Teilprojekte als virtuelle zweitägige Online-Konferenz am 20. und 21.04.2020 durchgeführt. Die 22 interessanten Vorträge, die von über 70 Teilnehmenden interaktiv gesehen und gehört wurden, zeigen dabei, dass der TRR 277 trotz mobiler Arbeit seine Ziele kontinuierlich weiterverfolgt.
Die eingesparte Reisezeit der Teilnehmenden aus Braunschweig, München und Hannover wurde beim Online-Quartalstreffen dazu genutzt, den wissenschaftlichen Präsentationen und Diskussionen mehr Raum zu ermöglichen. Zudem wurden großzügige und teilweise mit Livemusik untermalte Pausen eingefügt, um den gesteigerten Konzentrationsanforderungen der Online-Präsentationen Rechnung zu tragen. Obwohl Online-Konferenzen den persönlichen Austausch nicht ersetzen, hat dieses Quartalstreffen gezeigt, dass auch über digitale Medien die Wissenschaftlerinnen und Wissenschaftler des TRR 277 weiter in Kontakt bleiben und sich aktiv über den aktuellen Stand in der Forschungs- und Zusammenarbeit der Teilprojekte austauschen können.
In den Teilprojekten selbst werden die theoretischen Arbeiten wie Modellbildung, Simulation, analytische Verfahren vornehmlich bearbeitet und zum Teil vorgezogen und experimentelle Arbeiten und Versuche nur in absolut notwendiger Teamgröße durchgeführt.Zudem wird der virtuelle Austausch der Doktorandinnen und Doktoranden dazu genutzt, große Versuche für die Zukunft zu planen und zusammen mit den Teilprojektleitenden an gemeinsamen Veröffentlichungen in Journalen oder an Beiträgen für Online-Konferenzen zu arbeiten. Alle TRR 277-Projektteilnehmenden hoffen, dass die Wissenschaft Lösungen für die Covid-19-Pandemie finden wird und reale Treffen mit einem persönlichen Austausch bald wieder möglich sein werden.
Virtuelles Gruppenfoto der TRR 277-Projektbeteiligten beim 1. Quartalstreffen 2020
New Youtube Channel of the TRR 277
The TRR 277 has it's own Youtube Channel "AMC - Additive Manufacturing in Construction" presenting currently the preliminary work of the AMC project partners. The channel will be updated with new videos created within the AMC research project.