http://hdl.handle.net/10993/90 Search this channel search https://orbilu.uni.lu/simple-search http://hdl.handle.net/10993/55996 Title: Temperature effect on static and quasi-static bridge measurements <br/> <br/>Author, co-author: Dakhili, Khatereh; Kebig, Tanja; Schäfer, Markus; Maas, Stefan; Bender, Michél; Zürbes, Arno <br/> <br/>Abstract: The performance of bridge damage assessment based on model updating ap-proaches relies on correctly identifying the structural responses in the undamaged state. However, environmental uncertainties, such as temperature changes, influence structural responses in the same order of magnitude as damages. Therefore, a prestressed concrete bridge beam is studied in this paper. Temperature influences on static experiments in 2 test periods are minimized with physical temperature compensation technique. Displacement fluctuations decrease at least 60% after temperature compensation, making the summer and winter measurements comparable. Next, temperature-compensated Influence Lines (ILs), static flexibility and stiffness matrices are ob-tained. Comparing the results reveal the importance of performing measurements only on cloudy days. This paper contributes to differentiating between temperature effects and damages, which is crucial for a successful damage assessment. Sun, 17 Sep 2023 08:57:11 GMT http://hdl.handle.net/10993/55957 Title: Why Do Discrete Element Analysis? <br/> <br/>Author, co-author: Estupinan Donoso, Alvaro Antonio; Peters, Bernhard Wed, 13 Sep 2023 07:24:55 GMT http://hdl.handle.net/10993/55768 Title: Experimental and numerical assessment of two reconstructive techniques for the fragility fractures of the pelvis type Ia <br/> <br/>Author, co-author: Soliman, Ahmed Abdelsalam Mohamed; Kedziora, Slawomir; Kelm, Jens; Maas, Stefan; Gerich, Torsten <br/> <br/>Abstract: Anterior pelvic ring fractures are common in geriatric patients. The Supraacetabular External Fixator (SEF) is a relatively simple and effective surgical procedure. On the other hand, there is the option of a Subcutaneous Iliopubic Plate (SIP) osteosynthesis. Only limited comparative biomechanical data of these two devices are available. Therefore, this biomechanical study’s objective was to compare the stabilizing effect of the SEF versus the SIP in a model of Fragility Fractures of the Pelvis (FFP) type Ia. A test stand for pelvic biomechanics testing that emulates the gait loading cycle with physiological relevance was used. The osteotomy on the right pelvic ring was stabilized either with the SEF or the SIP. Strain gauges were used to measure strain in the pelvic ring. The osteotomy’s spatial interfragmentary displacement (SID) was monitored using a 3D digital image correlation system. The SEF stabilization reduced the SID by approximately 10%, whereas the locking SIP could reduce displacement by about 62%. Additionally, the SIP reduced the stress/strain levels by 67% in the posterior pelvic ring. We could demonstrate that the SIP is superior to SEF in treating FFP type Ia as it significantly reduced the osteotomy’s SID and the strain in the posterior pelvic ring. Thu, 10 Aug 2023 12:04:32 GMT http://hdl.handle.net/10993/55635 Title: Convolutional Neural Network for detection of fluid level in bores for assembly automation <br/> <br/>Author, co-author: Simeth, Alexej; Kumar, Atal Anil; Plapper, Peter Tue, 18 Jul 2023 10:50:23 GMT http://hdl.handle.net/10993/55634 Title: Artificial Intelligence Based Robotic Automation of Manual Assembly Tasks for Intelligent Manufacturing <br/> <br/>Author, co-author: Simeth, Alexej; Plapper, Peter <br/> <br/>Abstract: Increasing product customization and shortening product life cycles in an ever-changing world is challenging for automation. This is especially true for assembly tasks, requiring a high level of perception, skill, and adaptability. With the rise of smart manufacturing, intelligent manufacturing, and other aspects related to Industry 4.0, the hurdles for automation of the aforementioned tasks are getting reduced. Especially Artificial Intelligence (AI) is expected to enable smart and flexible automation since it is possible to deduct decisions from unknown multidimensional correlations in sensor data, which is critical for the assembly of highly customized products. In this research paper, three different conventional and AI-based glue detection models are proposed with the target to automate a gluing process in a manual assembly of highly customized products in a batch size one production scenario. A conventional, one-dimensional rule-based model, and two hybrid models using a support vector machine image classifier (SVM) and either Tamura features or convolutional neural network (CNN) feature extraction are presented and compared. The obtained results demonstrate the efficiency and robustness of AI-based algorithms, as the CNN and SVM hybrid model outperforms the other two approaches achieving a prediction accuracy of >99\% at the fastest classification speed. Tue, 18 Jul 2023 09:31:51 GMT http://hdl.handle.net/10993/55435 Title: Developing A Biomechanical Testing Setup Of The Pelvis, Part II - Experimental Testing <br/> <br/>Author, co-author: Soliman, Ahmed Abdelsalam Mohamed; Ricci, Pierre-Louis; Kedziora, Slawomir; Kelm, Jens; Gerich, Torsten; Maas, Stefan <br/> <br/>Abstract: Biomechanical testbench emulating the physiological loading of the pelvis is crucial in developing reconstructive implants for fragility fractures of the pelvis. Additionally, it will help understand the influence of the common daily loading on the pelvic ring. However, most reported experimental studies were mainly comparative with simplified loading and boundary conditions. In (Part I - Computational Design of Experiments) of our study, we described the concept of the computational experiment design to design and construct a biomechanical testbench emulating the gait movement of the pelvis. The 57 muscles and joints' contact forces were reduced to four force actuators and one support, producing a similar stress distribution. The experimental setup is explained in this paper (Part II - Experimental Testing), and some experimental results are presented. In addition, a series of repeatability and reproducibility tests were conducted to assess the test stand capabilities of replicating the gait physiological loading. The calculated stresses and the experimentally recorded strains showed that the pelvic ring response to the loading always follows the loaded leg side during the gait cycle. Furthermore, the experimental results of the pelvis displacement and strain at selected locations match the numerical ones. The developed test stand and the concept of computational experiment design behind it provide guidelines on how to design biomechanical testing equipment with physiological relevance. Tue, 27 Jun 2023 17:40:15 GMT http://hdl.handle.net/10993/55434 Title: Developing a Biomechanical Testing Setup of the Pelvis, Part I - Computational Design of Experiments <br/> <br/>Author, co-author: Soliman, Ahmed Abdelsalam Mohamed; Ricci, Pierre-Louis; Kedziora, Slawomir; Kelm, Jens; Gerich, Torsten; Maas, Stefan <br/> <br/>Abstract: Biomechanics of the human pelvis and the associated implants are still a medical and engineering debated topic. Today, no biomechanical testing setup is dedicated to pelvis testing and associated reconstructive implants with accepted clinical relevance. This paper uses the Computational Experiment Design procedure to numerically design a biomechanical test stand that emulates the pelvis physiological gait loading. The numerically designed test stand reduces the 57 muscles and joints' contact forces iteratively to only four force actuators. Two hip joints' contact forces and two equivalent muscle forces with a maximum magnitude of 2.3 KN are applied in a bilateral reciprocating action. The stress distribution of the numerical model of the developed test stand is very similar to that of the numerical model of the pelvis with all 57 muscles and joint forces. For instance, at the right arcuate line, the state of stress is identical. However, at the location of superior rami, there is a deviation ranging from 2% to 20% between the two models. The boundary conditions and the nature of loading adopted in this study are more realistic regarding the clinical relevance than state-of-the-art. The numerically developed biomechanical testing setup of the pelvis in this numerical study (part I - Computational Design of Experiments) was found to be valid for the experimental testing of the pelvis. The construct of the testing setup and the experimental testing of an intact pelvis under gait loading is discussed in detail in part II - Experimental Testing. Tue, 27 Jun 2023 17:39:28 GMT http://hdl.handle.net/10993/55344 Title: A BIOMECHANICAL STUDY OF THE PELVIS WITH AND WITHOUT FRACTURES AND IMPLANTS: COMBINING COMPUTATIONAL DESIGN AND EXPERIMENTAL TESTING FOR TYPICAL DAILY MOVEMENTS <br/> <br/>Author, co-author: Soliman, Ahmed Abdelsalam Mohamed <br/> <br/>Abstract: This study fulfills the need for a dedicated pelvis testing setup that is widely accepted with physiological relevance. There is limited comparative biomechanical data available for the Supraacetabular External Fixator (SEF) and the Subcutaneous Iliopubic Plate (SIP) used in the treatment of anterior fragility fractures of the pelvis (FFP). Most experimental studies so far have relied on simplified loading and boundary conditions. There has been a growing interest in personalizing motion analysis to develop customized implants that can optimize implant performance and accelerate fractured bone recovery for individual patients. Therefore, the main objective of this study is to develop a biomechanical test bench that can emulate the physiological gait loading of the pelvis, experimentally evaluate the stabilizing effect of the SEF and the SIP in the treatment of FFP, expand the test stand's capability to emulate other common daily movements, investigate the impact of customized musculoskeletal (MS) models, and assess the potential benefits of using personalized 3D metallic printed subcutaneous plates for the treatment of FFP type Ia fractures. The study uses the Computational Experiment Design procedure to design a biomechanical test stand that realistically emulates the pelvis' physiological gait loading. The test stand is designed to iteratively reduce all muscles and joints' contact forces of the pelvis to only four force actuators while still producing a similar stress distribution in the pelvis. The study conducts repeatability and reproducibility tests to ensure the test stand's capabilities. Next, the FFP type Ia is created on a synthetic pelvis for biomechanical testing under gait loading. The osteotomy on the right pelvic ring is then stabilized with the SEF or the nonlocking/locking SIP, and the stability provided by both implants is assessed numerically and experimentally under physiological loading. Motion analysis is conducted to calculate joint and muscle force envelopes for the common daily movement of interest. Stress, strain and displacement of the pelvis under these loads are assessed numerically and then implemented in the biomechanical test stand to emulate each movement following the computational experiment design concept. A metallic 3D-printed SIP is developed to match the anatomical landmarks of the insertion points on the pelvis used in the experiments. This 3D printed plate is assessed numerically and experimentally under physiological load to evaluate its performance compared to conventional plates. Personalization of the MS model is conducted for the pelvis by matching the anatomical landmarks of the pelvis in the generic MS model and the model of the pelvis used in the actual experiments. The developed test stand and the concept of computational experiment design behind it provide guidelines on how to design biomechanical testing equipment with physiological relevance. The boundary conditions and the nature of loading adopted in this study are more realistic regarding physiological relevance compared to the state-of-the-art. The numerically developed biomechanical testing setup of the pelvis in this study is a significant step forward in developing a physiologically relevant pelvis testing setup. Tue, 13 Jun 2023 13:18:26 GMT http://hdl.handle.net/10993/54858 Title: Prediction of the biomass particles through the physics informed neural network. <br/> <br/>Author, co-author: Darlik, Fateme; Adhav, Prasad; Peters, Bernhard <br/> <br/>Abstract: Woody biomass energy is a kind of renewable energy that contributes to the reduction of greenhouse gas emissions, the creation of healthier forests, and the reduction of wildfire danger. Simulations of biomass combustion, in general, are time-consuming simulations with a large number of input particles. We use a deep hidden physics-based neural network model to predict the behavior of particles throughout the simulation based on the equations of motion to achieve an efficient simulation and reduce the processing effort. We replace discrete element methods with inverse methods, which have the advantage of simulating velocity fields without knowing the simulation's boundary and initial conditions. Reconstruction of the velocity fields is done using a recurrent neural network in conjunction with a physics-based loss function. The proposed model is suitable for modeling problems that involve moving particles in a fixed bed. The number of neurons and activation functions in the artificial neural network are optimized, and the effect of the sampling method and the number of outputs are studied. Sun, 16 Apr 2023 03:30:19 GMT http://hdl.handle.net/10993/54583 Title: Reconstruct the biomass particles fields in the particle-fluid problem using continuum methods by applying the physics-informed neural network <br/> <br/>Author, co-author: Darlik, Fateme; Peters, Bernhard <br/> <br/>Abstract: The motion of particles in the moving grate combustion chamber is used as the case study. These problems are categorized as particle-fluid problems. They are typically solved using Lagrangian-Eulerian methods, one of which is the coupling between the discrete element method (DEM, which is applied to the particles phase) and the computational fluid dynamics method (CFD, which is applied to the fluid phase). The current study's objective is to avoid coupling and instead, focusing on using the CFD method only. There are dense piles of particles moving on the grates in the biomass combustion chamber. We assumed the dense particles' behaviors similar to the fluid, and then, applied the fluid governing equations to the particles phase. The virtual fields of the velocities, pressure and density are specified for the particles' phase. Afterward, the physics-informed neural network (PINN) is used to reconstruct particles' fields and additionally to investigate the capability of the predicted fields to satisfy the fluid governing equations. This model has the benefit of reconstructing the particles' fields without the need for boundaries and initial conditions. The precision of the model is assessed by comparing the test data set with the exact data obtained from the eXtended discrete element method (XDEM is an in-house software). It is demonstrated that the trained neural network delivered high accuracy and is capable of predicting all outputs with an error value of less than 2 percent. Additionally, to choose the optimum architecture for the neural network, the effect of the number of hidden layers and neurons is studied. Thu, 16 Mar 2023 09:31:47 GMT http://hdl.handle.net/10993/54577 Title: Developing the AM G-code based thermomechanical finite element platform for the analysis of thermal deformation and stress in metal additive manufacturing process <br/> <br/>Author, co-author: Mashhood, Muhammad; Peters, Bernhard; Zilian, Andreas; Baroli, Davide; Wyart, Eric <br/> <br/>Abstract: The 3D printing process known as SLM involves the melting of the metal powder, which results in a melt-pool. When this melt-pool solidifies, the solidified metal undergoes cooling and reheating in the presence of air and multiple laser passes for continuous material consolidation. As a result of such thermal cycles, the manufactured part develops permanent thermal deformation and residual stresses. The current work proposes the FEM and AM G-code based numerical strategy to qualitatively analyze the formation of such deformations and stresses at part scale. A multi-physics model was developed by coupling of transient thermal heat equation with non-linear structural solver. To mimic the consolidation of material with laser motion, the finite elements were activated as per the pattern of metal deposition under the influence of AM G-code. A numerical experiment was conducted to virtually manufacture the part with mechanical properties of 15--5PH stainless steel [1]. We found that the thermomechanical FEM model interfaced with the AM G-code translated data helps to evaluate the comparable trends of thermal deformation and residual stress results with already established studies. This demonstrates that with a given set of operational instructions, how the thermal conduction, convection and radiation drive the AM process by thermally loading the deposited material. Furthermore, the AM G-code interfacing facilitated the communication of laser scanning path with numerical FEM solver. We anticipate that such development may enable the manufacturing and simulation engineers to early estimate the possible final deformation of the AM fabricated part. Additionally, the developed strategy may also be the initial step for the physically informed neural networks to optimize the laser scan path for precise manufacturing of the metal parts. Mon, 13 Mar 2023 18:08:45 GMT http://hdl.handle.net/10993/54573 Title: DEVELOPMENT OF RESIDUAL STRESS DURING PART BUILD IN METAL ADDITIVE MANUFACTURING <br/> <br/>Author, co-author: Mashhood, Muhammad <br/> <br/>Abstract: The Additive Manufacturing (AM) process is the scale-able, flexible and prospective way of fabricating the parts. It forms the product of desired design by depositing layer upon layer of material to print the object in 3D. It has a vast field of applications from forming prototypes to the manufacturing of sophisticated parts for space and aeronautical industry. It has even found its way into the domain of biological research and the development of implants and artificial organs. Depending upon the form of the raw material and the mechanism of printing it layer upon layer, there are different techniques of AM in metal parts production. One of them is Selective Laser Melting (SLM). This process involves the raw material in the form of metal powder. To manufacture the product, this powder first undergoes melting through a moving laser. Afterwards, it solidifies and joins with the already solidified structure in the layer below. The movement of the laser is carried out in the shape of a 2D cross-section design which has to be consolidated at the corresponding height. This process involves the repetitive heating and cooling of the material which causes sharp thermal gradients in the object. Because of such gradients, the material during manufacturing consistently undergoes thermal loading. Such thermal loading, therefore, induces the residual stress and permanent distortion in the manufactured part. These residual stress and thermally induced distortions affect the quality of the part and cause the mismatch in dimensions between the final product and the required design. To reduce the waste of raw material and energy, therefore it is important to predict such problems beforehand. This research work presents the modelling of a numerical simulation platform which simulates the part-scale AM SLM part manufacturing process and its cooling down in a virtual environment. The objective of establishing this platform was to evaluate the residual stress and thermal distortion. It included the modelling of thermal & structural analysis and their coupling to establish the multi-physics simulation tool. The transient thermal analysis with the elastoplastic non-linearity of the material model was implemented to capture the permanent deformation behaviour of a material under thermal loading. The modelling was done on the Finite Elements Method (FEM) based open source numerical analysis tools to incorporate the flexibility of numerical modelling in the project. The modelling strategy of solidified material deposition was incorporated via the elements activation technique. To synchronize the activation of the elements in the multi-physics FEM solver with the laser movement, the interfacing with AM G-code based data was performed. With this modelling strategy, the simulation experiments were conducted to analyse the evolution of thermal gradients, residual stress and deformation in part manufacturing. The study also highlights the challenges of the applied elements activation technique and its limitations. It was also studied how the prediction of simulation results vary with the different material deposition methods. Moreover, the resulting numerical analysis of the established simulation platform was also compared with the experimental and validated simulation data to ensure its reliability. In this comparative study, the current numerical strategy replicated the trends of stress and deformation from physical experimental data and represented the expected material behaviour in the manufactured part. Additionally, during this study, the skill gained for results handling and their validation was also applied in the other field of numerical modelling e.g. in the numerical analysis conducted for a blast furnace with Computational Fluid Dynamics - Discrete Element Method (CFD-DEM) coupled multi-physics platform of eXtended Discrete Element Method (XDEM). The current working simulation platform, via its AM G-code machine data interface with numerical solver, can facilitate the manufacturing engineers to predict earlier the possible thermally caused residual stress and deformation in their AM SLM produced product via simulation. On the other hand with the identified challenges in the virtual depiction of material deposition, the simulation developers may also be able to expect such limitations and make relevant decisions in the choice of material deposition technique in their AM SLM process modelling. Moreover, with the potential of this simulation tool being the basic building block, it may also provide the opportunity to build upon it the multi-scale numerical techniques and add them to the multidisciplinary research work of Artificial Intelligence based digital twins. Sun, 12 Mar 2023 13:33:05 GMT http://hdl.handle.net/10993/54571 Title: A mechanical model for compaction of strands in wire ropes <br/> <br/>Author, co-author: Chen, Li; Magliulo, Marco; Beex, Lars <br/> <br/>Abstract: Steel wire ropes are used for numerous industrial applications such as ships, elevators, cranes and bridges. A wire rope consists of numerous thin, steel wires and its geometrical construction can be explained in two steps. First, several wires are wrapped together in a helical shape called a strand. Second, several strands are wrapped together in a helical shape to form the final wire rope. In most cases, each strand is compacted before they are wrapped together to form the final wire rope. Compaction generally reduces contact stresses and thereby, extends ropes’ service life. Not many models have been proposed to predict the compaction process and its influence on the strand’s mechanical behavior during service. This contribution proposes a computationally efficient approach that consists of two elastoplastic mechanical models. The first model, describing the compaction process, is of a 2D plane strain nature and is therefore fast. Subsequently, the 2D geometry and plastic variables predicted by the compaction model are used to generate the initial geometry and initial plastic state of a 3D model, that is subsequently used to describe the strand’s mechanical behavior during service (we limit ourselves to tension). The results of the approach, with and without the mapping of the plastic variables, are compared to experimental measurements and the results without compaction. This is investigated for two real world strands. Sat, 11 Mar 2023 06:44:36 GMT http://hdl.handle.net/10993/54536 Title: InSAR for climate change <br/> <br/>Author, co-author: Salehian Ghamsari, Sona <br/> <br/>Abstract: Did you know that 50% of our drinking and irrigation water comes from underneath the earth? Understanding and managing these water resources is critically important as we prepare to tackle challenges such as population growth and man-made climate change in the 21st century. The goal of my research is to combine data from satellites with computer models to help us understand more about the groundwater on our planet. The surface of the earth moves all of the time, for example, when two tectonic plates move during an earthquake. But did you know that the surface of the earth also moves up and down all of the time depending on how wet it is? You can think of the earth as being a bit like a sponge. It is elastic, meaning that when it is loaded it deforms, and when it is unloaded it returns to the same position. It is also porous, so water can flow and be stored in small spaces inside the rock. Elasticity and porosity are coupled, so when we squeeze the rock, water flows out of it. The mathematical theory of poroelasticity gives us a model that can help us predict this movement. By using this theory we can build a model of the flow of water in the Earth and underground deformation on a computer. But to make this model useful we need real data about the earth as input. Incredibly, modern satellite systems can give us data about how the surface of the earth moves to centimetre or even millimetre accuracy. Every six days a satellite from the Sentinel-1 mission passes over Belval, and every other place on the planet. The satellite sends down a burst of radar that reflects off the Earth’s surface, and the satellite receives this information back. By comparing two radar signals, we can precisely measure the distance by which the ground has risen, or sunk. So we can produce data describing the surface displacement everywhere and every time. By combining the data from the satellite with the computer model, we will be able to reveal the hidden world of water under our feet. Mon, 06 Mar 2023 16:03:38 GMT http://hdl.handle.net/10993/54425 Title: Implementing a hybrid immersed boundary/fictitious domain (HFD-IB) method coupled with the Discrete Element Method (DEM) to consider lubrication effects between the particles in the fluid domain <br/> <br/>Author, co-author: Hassanzadeh Saraei, Sina; Peters, Bernhard <br/> <br/>Abstract: Suspensions of particles in a fluid domain could be seen in different natural and industrial applications, ranging from food production to blood flow. For this reason, many researchers studied this topic to get a better insight into the physics of the problem. One of the main topics in this field is to understand the inter-particle forces. In which, particles in the fluid domain face three main forces, which are hydrodynamic long-range interaction, a collision between particles, and lubrication forces. [1] Treatment of first and second forces is straightforward because they could be modeled accurately with the computational fluid dynamics (CFD) method coupled with the Discrete Element Method (CFD-DEM). However, this strategy becomes less accurate for calculating lubrication force when two particles approach each other in a gap distance smaller than the grid size. This is because the grid resolution is not fine enough to capture the correct hydrodynamic interaction. Among different CFD methods that could be implemented to consider the physics of the suspensions of particles, Immersed Boundary (IB) method has provided a better description of the nature of the topic since it could be used to provide fully resolved CFD simulation. However, the results of the previous researchers also have shown the IB methods also face difficulty in correctly capturing the lubrication effects. Although some researchers have proposed to add a corrective force term in the IB method, this strategy faces a stability problem when there are many particles inside the simulation domain. For this reason, Naoki Hori et al [2] proposed a new strategy to use IB without considering any correction term. In their work, the C dt parameter is defined as a function of time step size, fluid viscosity, and mesh resolution. By keeping this parameter in a specific range, IB could simulate lubrication force with high accuracy, meaning that the grid resolution and time step size are the key parameters in determining the lubrication force. [2] In the present work, a variant of the IB method named the hybrid immersed-boundary/fictitious domain (HFD-IB) method was selected as the CFD solver. [3] Then, it was coupled with the XDEM code to consider the collision forces between the particles. After successful validation of this CFD-DEM solver, the problem of falling two inline spherical particles in the fluid domain is considered. Our solver could get the interaction forces between two-particle correctly by keeping the C dt in a specific range mentioned by the reference articles. As seen in Figure 1, drafting, kissing, and tumbling of particles are illustrated. References [1] Kroupa, M., Vonka, M., Soos, M. and Kosek, J., 2016. Utilizing the discrete element method for the modeling of viscosity in concentrated suspensions. Langmuir, 32(33), pp.8451-8460. [2]Hori, N., Rosti, M.E. and Takagi, S., 2022. An Eulerian-based immersed boundary method for particle suspensions with implicit lubrica [3] Municchi, F. and Radl, S., 2017. Consistent closures for Euler-Lagrange models of bi-disperse gas-particle suspensions derived from particle-resolved direct numerical simulations. International Journal of Heat and Mass Transfer, 111, pp.171-190. Sun, 19 Feb 2023 04:30:23 GMT http://hdl.handle.net/10993/54424 Title: first_page settings Order Article Reprints Open AccessArticle Pore-Level Multiphase Simulations of Realistic Distillation Membranes for Water Desalination <br/> <br/>Author, co-author: Jäger, Tobias; Mokos, Athanasios; Prasianakis, Nikolaos I.; Leyer, Stephan Sat, 18 Feb 2023 04:30:32 GMT http://hdl.handle.net/10993/54165 Title: Mobile robots path planning and mobile multirobots control: A review <br/> <br/>Author, co-author: Hichri, Bassem; Gallala, Abir; Giovannini, Francesco; Kedziora, Slawomir <br/> <br/>Abstract: Mobile robots and multimobile robotic system usage for task achievement have been an emerging research area since the last decades. This article presents a review about mobile robot navigation problem and multimobile robotic systems control. The main focus is made on path planning strategies and algorithms in static and dynamic environments. A classification on mobile robots path planning has been defined in the literature and divided to classical and heuristic approaches. Each of them has its own advantages and drawbacks. On the other hand, the control of multimobile robots is presented and the control approaches for a fleet of robots are presented. Scientists found that using more than one robot as opposed to a single one presents many advantages when considering redundant task, dangerous tasks, or a task that scales up or down in time or that requires flexibility. They have defined three main approaches of multiple robots control: behavior-based approach, leader–follower approach, and virtual structure approach. This article addresses these approaches and provides examples from the literature. Thu, 26 Jan 2023 06:56:44 GMT http://hdl.handle.net/10993/54164 Title: Influence of UV Ageing on Properties of Printed PLA Containing Graphene Nanopowder <br/> <br/>Author, co-author: Czechowski, Leszek; Kedziora, Slawomir; Museyibov, Elvin; Schlienz, Markus; Szatkowski, Piotr; Szatkowska, Martyna; Gralewski, Jacek <br/> <br/>Abstract: The present paper analyses the properties of printed polylactic acid (PLA) samples with admixtures of graphene nanopowder (GNP) at wt. 1%, 2% and 4%. The pure polylactide and admixed polylactide printed samples were examined to determine their chemical-physical properties, stiffness, and strength parameters. The tests of tensile, dynamic mechanical analysis (DMA), difference thermogravimetric (TG), and differential scanning calorimetry (DSC) were executed before and after UV (ultraviolet) treatment. The first part of the paper shows the process of manufacturing granulates and filaments mixed with graphene. The second part of the paper concerns the results of the tests made on printed samples. The analysed samples were printed using a Prusa i3 MK3 printer. It transpired that the content of graphene at 1% improved the mechanical parameters of the printed composite by organising its structure. Increasing the amount of graphene caused the values of the measured parameters to drop. This research indicates how important it is to determine the optimal values of nanoadditives in biopolymers. Thu, 26 Jan 2023 06:55:25 GMT http://hdl.handle.net/10993/54163 Title: Strength Properties of 316L and 17-4 PH Stainless Steel Produced with Additive Manufacturing <br/> <br/>Author, co-author: Kedziora, Slawomir; Decker, Thierry; Museyibov, Elvin; Morbach, Julian; Hohmann, Steven; Huwer, Adrian; Wahl, Michael <br/> <br/>Abstract: The number of additive manufacturing methods and materials is growing rapidly, leaving gaps in the knowledge of specific material properties. A relatively recent addition is the metal-filled filament to be printed similarly to the fused filament fabrication (FFF) technology used for plastic materials, but with additional debinding and sintering steps. While tensile, bending, and shear properties of metals manufactured this way have been studied thoroughly, their fatigue properties remain unexplored. Thus, the paper aims to determine the tensile, fatigue, and impact strengths of Markforged 17-4 PH and BASF Ultrafuse 316L stainless steel to answer whether the metal FFF can be used for structural parts safely with the current state of technology. They are compared to two 316L variants manufactured via selective laser melting (SLM) and literature results. For extrusion-based additive manufacturing methods, a significant decrease in tensile and fatigue strength is observed compared to specimens manufactured via SLM. Defects created during the extrusion and by the pathing scheme, causing a rough surface and internal voids to act as local stress risers, handle the strength decrease. The findings cast doubt on whether the metal FFF technique can be safely used for structural components; therefore, further developments are needed to reduce internal material defects. Thu, 26 Jan 2023 06:53:52 GMT http://hdl.handle.net/10993/54162 Title: Biocomposites with Epoxy Resin Matrix Modified with Ingredients of Natural Origin <br/> <br/>Author, co-author: Szatkowski, Piotr; Szatkowska, Martyna; Gralewski, Jacek; Czechowski, Leszek; Kedziora, Slawomir <br/> <br/>Abstract: This study aims to present various forms of cellulose, whose shape depends on the source of origin, and to demonstrate the differences in the influence on the properties of materials produced with its participation. For this purpose, composites with various plant additives have been designed and obtained. Some of them have undergone chemical and pyrolytic modifications. The results of the mechanical, physicochemical and microscopic tests showed differences in cellulose structure, even in the case of very similar sources, and its diversified influence on the characteristics of the obtained materials. The research shows the effect of the use of natural additives and their modified versions on the mechanical properties of the composite based on epoxy resin. It turns out that cellulose modifiers are not only fillers that reduce the price of the final product but can also increase some mechanical properties, e.g., compressive strength, which is an additional advantage and a reason for wider use. The potential of natural resources is not yet fully understood. Relatively recently, people have started to be interested in cellulose on a nanometric scale, as it turns out that it can exist in several different forms with interesting properties. Thu, 26 Jan 2023 06:52:07 GMT