The tool-less additive manufacturing (AM) or 3D printing processes (3DP) use incremental consolidation of feed-stock materials to construct part. The layer by layer AM processes can achieve spatial material distribution and desired microstructure pattern with high resolution. This unique characteristics of AM can bring custom-made form and tailored functionality within the same object. However, incorporating form and functionality has their own challenge in both design and manufacturing domain. This research focuses on designing manufacturable topology by marrying form and functionality in additively manufactured part using infill structure. To realize the goal, this thesis presents a systematic design framework that focuses on reducing the gap between design and manufacturing of complex architecture. The objective is to develop a design methodology of lattice infill and thin shell structure suitable for additive manufacturing processes. Particularly, custom algorithmic approaches have been developed to adapt the existing porous structural patterns for both interior and exterior of objects considering application specific functionality requirements. The object segmentation and shell perforation methodology proposed in this work ensures manufacturability of large scale thin shell or hollowed objects and incorporates tailored part functionality. Furthermore, a computational design framework developed for tissue scaffold structures incorporates the actual structural heterogeneity of natural bones obtained from their medical images to facilitate the tissue regeneration process. The manufacturability is considered in the design process and the performances are measured after their fabrication. Thus, the present thesis demonstrates how the form of porous structures can be adapted to mingle with functionality requirements of the application as well as fabrication constraints. Also, this work bridges the design framework (virtual) and the manufacturing platform (realization) through intelligent data management which facilitates smooth transition of information between the two ends. / National Science Foundation #OIA-1355466 / National Science Foundation-DMR- MRI #1625704 / National Institute of Health - COBRE: CDTSPC; Grant # P20GM109024 / US-DOT # 693JK31850009CAAP / Dept. of Commerce Research-ND, Award # 17-08-G-191 / CSMS, NDEPSCoR / NDSU Grand Challenge and Development Foundation

Traditionally, the mechanical testing of ankle-foot orthoses (AFOs) has been performed with simple limb surrogates, typically with a single axis ankle joint and rigid foot and shank components. Since many current AFO designs allow 3D motion, a surrogate lower limb (SLL) that provides anatomically similar motion in all planes is needed to enable realistic load testing and cyclic testing in a controlled manner. The aim of this thesis was to design, fabricate and test a novel SLL that provides anatomically realistic 3D foot motion, based on a consensus of the passive lower limb range of motion (RoM) found in the literature. The SLL design was inspired by the Rizzoli model, sectioning the lower limb into five segments (shank, hindfoot, midfoot, forefoot, toes). Ball and socket joints were used for the shank-hindfoot, hindfoot-midfoot, and midfoot-forefoot. Forefoot-toes used a hinge-type joint. 3D printed flexible thermoplastic polyurethane (TPU) snap-fit connectors connected the 3D printed nylon foot blocks. A threaded ball stud connected the shank shaft and hindfoot. This shank shaft was surrounded by a 3D printed polylactic acid (PLA) shank cover. The foot was cast in silicone rubber to emulate soft tissue, with a PLA custom mould based on a Össur prosthetic foot cover model. The SLL was successfully designed for easy fabrication using readily available techniques, materials, and components. Only the metal shaft required additional machining. 3D printed components used an affordable 3D printer (Artillery Sidewinder X1), and readily available nylon, PLA, and TPU. Using motion capture testing, SLL foot rotation angles were found to be within standard deviation of mean foot passive rotation angle ranges found in the literature, showing that most joints were within 5° of target maximum rotation angles. With load testing, the SLL was shown to survive static loads representing 1.5 times body weight for a 100 kg individuals and cyclic loads representing normal gait loading for 500,000 cycles.

The presented diploma thesis deals with the control of the geometric accuracy of the parts produced by additive manufacturing technology selective laser melting. The paper first analyzed the work of the other authors dealing with this issue. Based on obtained informations from this analysis were developed benchmark test parts for quality control of production on a commercial machine SLM 280 HL supplied by SLM Solutions GmbH. The work was carried out several tests to determine the appropriate parameters of construction parts. These tests, their results and conclusions are fully described in this papper.

This diploma thesis deals with finding and verification of appropriate technological parameters of SLM technology for the processing of aluminum alloy 2618. In the theoretical part, an introduction to additive manufacturing of aluminum alloys and general description of processes occurring during SLM production is given. Based on general knowledge were designed different types of testing samples produced by sintering the metallurgical powder using 400 W ytterbium fiber laser, which so far in the literature for aluminum alloy 2618 were not described. As the result, the technological parameters dependence on relative density and the detailed overview of the 2618 alloy processing by SLM technology is determined.

De nouvelles solutions basées sur la technologie de l'intégration hydraulique ont été introduites dans la mise en œuvre d'un système robotique humanoïde à actionnement hydraulique compact et léger. Pour ce faire, les chercheurs ont appliqué des méthodes et des technologies récentes basées sur des techniques d'usinage avancées et sur la fabrication additive de métaux. Malgré cela, ces méthodologies ont montré des limites liées non seulement au temps de réalisation, ce qui induit des coûts élevés, mais également au poids total du mécanisme obtenu. Ainsi, il important de développer des travaux de recherche sur de nouvelles méthodologies pour réaliser des mécanismes robotiques hydrauliques intégrés, compacts, légers et à faible coût économiques.C’est l’objet de travail développé dans cette thèse qui a pour objectif de proposer de nouvelles méthodologies pour la fabrication de composants mécaniques de robots humanoïdes à commande hydraulique. Cela concerne, en premier lieu, la fabrication additive de matériaux composites qui sera développée pour la réalisation des pièces structurelles classiques. En second lieu, deux nouvelles méthodologies sont proposées pour l’obtention de composants hydrauliques intégrés légers, avec une résistance élevée et un temps de réalisation et un coût réduits. La première méthodologie consiste à combiner la fabrication additive de polymères thermoplastiques et la simple formation de composites aléatoires en carbone. Tandis que la deuxième propose l'utilisation de tuyaux en silicone à la place des thermoplastiques imprimés tout en gardant le même matériau de renfort. Les deux méthodologies sont détaillées étape par étape et appliquées au bras du robot HYDROïD. Des gains importants sur le poids total du bras sont donnés. Par ailleurs, un nouvel vérin hydraulique composite léger est développé pour remplacer les vérins métalliques dont le poids est fatalement très élevé. Une procédure développée à partir du modèle de contraintes, passant par un processus d'optimisation et se terminant par la conception mécatronique est présentée. L’actionneur hydraulique est mis en œuvre et testé pour l'articulation du genou du robot HYDROïD et une proposition de généralisation à toutes les articulations est également avancée. Enfin, des perspectives à court et à moyen termes pour des développement ultérieur de nouvelles générations de systèmes robotiques à actionnement hydraulique intégré concluent cette thèse. / Modern researches have been inducted in the implementation of a compact and lightweight hydraulically actuated humanoid robotic systems, using the technology of hydraulic integration. In the a eld, researchers have applied recent technologies starting from advanced machining methodologies and ending with additive manufacturing of me-tals. Despite, these methodologies have shown inconvenient points related to cost, time and weight of the obtained mechanism. This motivates the research of new methodologies toward developing compact, cost effective and light-weight hydraulic integrated robotics mechanisms, which are discussed in this thesis.This thesis represents new methodologies toward fabricating mechanical components of the hydraulic actuated humanoid robots. This starts with the classical structural parts which will be fabricated using additive manufacturing of composite materials. Then, the hard task comes. Two new methodologies are proposed to obtain hydraulic integra-ted components with lightweight, high strength and with low time and cost. The rst methodology is by combining the additive manufacturing of thermoplastics polymers and the simple forming of random carbon ber composites. While, the second methodology proposes the usage of silicone pipes instead of the printed thermoplastics, keeping the same reinforcement material. The two methodologies are explained step by step and applied to the arm of HYDRO•D robot. Lately, a new lightweight composite hydraulic actuator is developed to replace the heavy weight metallic one. This is using a developed procedure starting from stress model, passing by an optimization process and ending with the mechatronic design. Then, this hydraulic actuator is implemented and tested. This is applied to the knee joint of the robot and generalized to all the robot joints. By the end of this thesis, an important conclusion will be drawn and the perspective of the research will be settled for further development.

La FA (Fabrication Additive) est un procédé de fabrication qui rend possible, en ajoutant de la matière couche après couche, la création de pièces en trois dimensions. Cette technologie a de nombreux intérêts car elle permet l’intégration de formes ou de structures complexes, la réduction des déchets, la fabrication sur demande et la réduction du temps de conception. Au cours de cette thèse, nous avons cherché à déterminer des orientations remarquables de pièces afin de les fabriquer par des procédés de FA. Au vu du grand nombre d’effets liés à l’orientation d’une pièce, nous avons choisi une approche multicritères prenant en compte la qualité de surface des pièces, le volume de support, le temps et le coût de fabrication. Afin d’avoir une bonne qualité de surface sur les faces fonctionnelles de la pièce et pour limiter le post-traitement, une orientation précise a été définie pour chacune d’elle. Cette méthodologie a été développée dans le cadre du projet Taal, projet de recherche et développement précurseur du logiciel 4D-Additive de Coretechnologie. Sur ce dernier, en plus de cette méthodologie, de nombreuses fonctions ont été développées pour préparer la fabrication d’une pièce par un procédé additif. L’orientation d’une pièce en FA est une étape à ne surtout pas négliger. Elle pourra permettre de trouver un compromis entre les spécificités liées aux procédés de FA ou entrainer un coût important de fabrication et une qualité de surface de la pièce médiocre. Des évolutions de la méthode sont possibles comme une étude mécanique de la pièce dans les différentes orientations testées car de nombreuses questions se posent sur la résistance des pièces imprimées. / AM (Additive Manufacturing) is a manufacturing process that makes possible, by adding layer-by-layer material, to create three-dimensional parts. This technology has many interests as it allows complex shapes or structures integration, waste reduction, on-demand fabrication and reduced conception time. During this thesis, we tried to determine remarkable orientations of parts in order to manufacture them by AM process. Considering the large number of effects related to part orientation, we chose a multi-criteria approach taking into account the surface quality of the parts, the volume of support, the manufacturing time and cost. In order to have a good surface quality on functional faces of the part and to limit the post-treatment, a precise orientation has been defined. This methodology was developed in the structure of the Taal project, a research and development project precursor of Coretechnologie's 4D-Additive software. On this last, in addition to this methodology, many functions have been developed to prepare the manufacture of a part by an additive process. The orientation of a part in AM is a step that can’t be overlooked. It may make it possible to find a compromise between the specificities related to the AM processes or generate a high manufacturing cost and a poor surface quality of the part. Evolutions of the method are possible as a mechanical study of the part in the different orientations tested because many questions arise on the strength of the printed parts.

The purpose of this thesis is to prove that the use of compliant mechanisms in gearbox applications is viable. Compliant mechanisms are developed for their implementation in Scania’s hybrid asynchronous gearboxes. These mechanisms are presented as a replacement for the latch assembly currently in use to hold the position of the gear-shifting elements. The objective is to implement a compliant mechanism in order to avoid wear and increase the life cycle within the given constraints, as well as to have a better understanding of this kind of mechanisms. The presented literature study shows that bistable and tristable compliant mechanisms are the most suitable ones for this application. Titanium alloys, tool steels, and bulk metallic glasses are discussed as the best material options for compliant mechanism manufacturing. A mechanism idea generation and selection process is conducted. Finite Element Analysis (FEA) is developed with the chosen bistable and tristable compliant mechanism ideas. The tristable concept results on being inappropriate for this application, as it does not fulfil the volume and positioning constraints. The bistable device is proven to be suitable, and further analysis is carried out to study its fatigue resistance and show that it fulfils all the requirements, solving the weaknesses of the latch and absorbing the impact in the shaft. Additive manufacturing methods and injection moulding are found to be incompatible with the designed mechanisms. That is why the chosen bistable mechanism is designed to be made out of different parts. Future work is presented to strengthen the weaker points of this project.

Additive manufacturing brings versatility and new degree of freedom for part design and manufacturing possibilities. Binder jetting is powder bed printing technique that does not require direct energy transfer rather binding powder metal particles through mechanical entanglement by use of the organic binder. The polymer chains in the solution hardens when heated thus creating a green part. Green parts are sintered in high temperature to adhere metal powder particles together creating a solid body. Binder jetting still developing to its full potential in scalability and material portfolio. This thesis aims to contribute know how in process and material development of H13 tool steel in very fine particle size distributions from -16 µm to -10µm. Process parameters as well as sintering cycle developed specifically for H13 fine powders. With 52 samples printed, sintered in four different temperatures and analyzed material properties such as density and hardness to evaluate how particle size distributions affect printing process, densification and shrinkage in the sintering. Density of the green body has been evaluated through measurements of dimensions and weight, sintered density was analyzed by Archimedes method and light optical metallography. Trials for the processing and evaluation of the powders concluded that it is possible to use ultra-fine PSDs in binder jetting process with good results, this opens up opportunity for increased sustainability and profitability for powder manufacturing industry. Particle size distribution of -10 µm has outperformed the -16 µm in areas of relative density of the green body, sintered density and hardness. Although superior performance, the -10 µm requires higher ultrasonic intensity and lower spreading speed to achieve homogeneous powder bed. For the -16 µm powder it is worth noting that it is possible to bring up green density with further process development. Although materials presented high hardness in as printed state compared to that of PIM manufactured parts, achieved hardness is not satisfactory for the applications of the alloy and requires heat treatment corresponding to customer requirements.

The advent of additive manufacturing has opened up new frontiers in developing metal structures that can have complex geometries, composite structures made of dissimilar metals, and metal structures with embedded sensing and actuation capabilities. These types of structures are possible with ultrasonic additive manufacturing (UAM); a novel manufacturing technology that combines additive manufacturing through the ultrasonic welding of thin metal foils with computer numerical control (CNC) milling. However, the process suffers from a critical limitation, i.e., a range of build heights within which bonding between a foil and the substrate cannot be originated. <br>This work has two research objectives, the first is a fundamental understanding of the complex dynamic interaction between the substrate and ultrasonic horn, or sonotrode. Specifically, it focuses on the effects that specific modes of vibration have on the dynamic response of the substrate. The second objective is to utilize the UAM process to create metal structures with an embedded sensor that can detect contact or impact. In addressing the first objective, a semi-analytical model was developed to determine the response to three forcing descriptions that approximate the interfacial friction between the foil and substrate induced by sonotrode compression and excitation. Several observations can be seen in the results: as the height increases the dominant modes of vibration change, the modes of vibration excited also change during a single weld cycle as the sonotrode travels across the length of the substrate, and finally the three forcing models do not have a significant impact on the substrate response trends with height and during the weld cycle. <br>In addressing the second objective, three prototypes were created by embedding a triboelectric nanogenerator (TENG) sensor within an AL3003 metal-matrix. TENGs utilize contact electrification between surfaces of dissimilar materials, typically polymers, combined with electrostatic induction to generate electrical energy from a mechanical excitation. The sensors demonstrate a discernible response over a 1-5 Hz frequency range. In addition, the sensors have a linear relationship between output voltage and a mechanically applied load, and have the ability to sense contact through both touch and due to an impacting object.

<p>There has been increasing demand for 3D printed metals from aerospace & defense and automotive end-use industries, due to their low manufacturing cost, and reduction in lead times. Although the significant advancement in metal 3D printing promises to revolutionize industry, it is constrained by a widespread problem: the cracks and other defects in the metal 3D printed parts. In this work, two major causes of defects in the laser power bed fusion (L-PBF) process are focused: keyhole mode and spattering phenomena. Both defect sources are highly dependent to the processing parameters. Although extensive efforts have been made on experiments and computational models to improve the quality of printed parts, the high experimental costs and large computational intensity still limit their effect on the optimization of the processing parameters. In addition, the uncertainty in the design process further limits the accuracy of these models.</p><p>The aim of this thesis is to develop a probabilistic design framework for reliability-based design in the L-PBF process. The modeling framework spans physical models, machine learning models, and probabilistic models. First, the keyhole mode and spattering phenomena are simulated by physical models including computational fluid dynamics (CFD) and smoothed particle hydrodynamics (SPH) methods, respectively. Then, the data acquired by the physical models serve as the training data for machine learning models, which are used as surrogates to alleviate the high computational cost of physical models. Finally, the feasible design region is computed by probabilistic models such as Monte Carlo simulation (MCS) and the first order reliability method (FORM). The feasible design region can be used assessing a satisfactory reliability not lower than the specified reliability level.</p><p>The developed Gaussian process (GP) based machine learning model is capable of predicting the remelted depth of single tracks, as a function of combined laser power and laser scan speed in the L-PBF process. The GP model is trained by both simulation and experimental data from the literature. The mean absolute prediction error magnified by the GP model is only 0.6 μm for a powder bed with layer thickness of 30 μm, suggesting the adequacy of the GP model. Then, the process design maps of two metals, 316L and 17-4 PH stainless steel, are developed using the trained model. The normalized enthalpy criterion of identifying keyhole mode is evaluated for both stainless steels. For 316L, the result suggests that the criterion should be related to the powder layer thickness. For 17-4 PH, the criterion should be revised to .</p><p>Moreover, a new and efficient probabilistic method for the reliability analysis is developed in this work. It provides a solution to address quality inconsistency due to uncertainty in the L-PBF process. The method determines a feasible region of the design space for given design requirements at specified reliability levels. If a design point falls into the feasible region, the design requirement will be satisfied with a probability higher or equal to the specified reliability. Since the problem involves the inverse reliability analysis that requires calling the direct reliability analysis repeatedly, directly using MCS is computationally intractable, especially for a high reliability requirement. In this work, a new algorithm is developed to integrate MCS and FORM. The algorithm finds the initial feasible region quickly by FORM and then updates it with higher accuracy by MCS. The method is applied to several case studies, where the normalized enthalpy criterion is used as a design requirement. The feasible regions of the normalized enthalpy criterion are obtained as contours with respect to the laser power and laser scan speed at different reliability levels, accounting for uncertainty in seven processing and material parameters. The results show that the proposed method dramatically alleviates the computational cost while maintaining high accuracy. This work provides a guidance for the process design with required reliability.</p><p>The developed SPH model is used to simulate the spattering phenomenon in the L-PBF process, to overcome the limitation of commercial CFD packages, including their incapability of phase change and particle sticking phenomena, which are however commonly seen in the spattering process. The SPH model is capable to couple heat transfer, particle motion and phase change. The sticking phenomenon observed in the experiment is successfully reproduced by the SPH model using a similar scenario.</p><p>In summary, the modeling framework developed in this thesis can serve as a comprehensive tool for reliability-based design in the L-PBF process. The work is helpful for applying machine learning models in the additive manufacturing field.</p><p> </p><p><br></p><p> </p><p> </p><p></p>