Prediction of mechanical properties of 3d printed lattice structures through machine learning

Lattice structures (LS) manufactured by 3D printing are widely applied in many areas, such as aerospace and tissue engineering, due to their lightweight and adjustable mechanical properties. It is necessary to reduce costs by predicting the mechanical properties of LS at the design stage since 3D printing is exorbitant at present. However, predicting mechanical properties quickly and accurately poses a challenge. To address this problem, this study proposes a novel method that is applied to different LS and materials to predict their mechanical properties through machine learning. First, this study voxelized 3D models of the LS units and then calculated the entropy vector of each model as the geometric feature of the LS units. Next, the porosity, material density, elastic modulus, and unit length of the lattice unit are combined with entropy as the inputs of the machine learning model. The sample set includes 57 samples collected from previous studies. Support vector regression (SVR) was used in this study to predict the mechanical properties. The results indicate that the proposed method can predict the mechanical properties of LS effectively and is suitable for different LS and materials. The significance of this work is that it provides a method with great potential to promote the design process of lattice structures by predicting their mechanical properties quickly and effectively

Predicting mechanical properties of 3D printed lattice structures

Lattice structures (LS) manufactured by 3D printing are widely applied in many areas, such as aerospace and tissue engineering, due to their lightweight and adjustable mechanical properties. It is necessary to reduce costs by predicting the mechanical properties of LS at the design stage since 3D printing is exorbitant at present. However, predicting mechanical properties quickly and accurately poses a challenge. To address this problem, this study proposes a novel method that is applied to different LS and materials to predict their mechanical properties through machine learning. First, this study voxelised 3D models of the LS units and then calculated the entropy vector of each model as the geometric feature of the LS units. Next, the porosity, material density, elastic modulus, and unit length of the lattice unit are combined with entropy as the inputs of the machine learning model. The sample set includes 57 samples collected from previous studies. Support vector regression was used in this study to predict the mechanical properties. The results indicate that the proposed method can predict the mechanical properties of LS effectively and is suitable for different LS and materials. The significance of this work is that it provides a method with great potential to promote the design process of lattice structures by predicting their mechanical properties quickly and effectively

ChatterBox: Multi-round Multimodal Referring and Grounding

In this study, we establish a baseline for a new task named multimodal multi-round referring and grounding (MRG), opening up a promising direction for instance-level multimodal dialogues. We present a new benchmark and an efficient vision-language model for this purpose. The new benchmark, named CB-300K, spans challenges including multi-round dialogue, complex spatial relationships among multiple instances, and consistent reasoning, which are beyond those shown in existing benchmarks. The proposed model, named ChatterBox, utilizes a two-branch architecture to collaboratively handle vision and language tasks. By tokenizing instance regions, the language branch acquires the ability to perceive referential information. Meanwhile, ChatterBox feeds a query embedding in the vision branch to a token receiver for visual grounding. A two-stage optimization strategy is devised, making use of both CB-300K and auxiliary external data to improve the model's stability and capacity for instance-level understanding. Experiments show that ChatterBox outperforms existing models in MRG both quantitatively and qualitatively, paving a new path towards multimodal dialogue scenarios with complicated and precise interactions. Code, data, and model are available at: https://github.com/sunsmarterjie/ChatterBox.Comment: 17 pages, 6 tables, 9 figurs. Code, data, and model are available at: https://github.com/sunsmarterjie/ChatterBo

Mechanical behaviours and mass transport properties of bone-mimicking scaffolds consisted of gyroid structures manufactured using selective laser melting

Bone scaffolds created in porous structures manufactured using selective laser melting (SLM) are widely used in tissue engineering, since the elastic moduli of the scaffolds are easily adjusted according to the moduli of the tissues, and the large surfaces the scaffolds provide are beneficial to cell growth. SLM-built gyroid structures composed of 316L stainless steel have demonstrated superior properties such as good corrosion resistance, strong biocompatibility, self-supported performance, and excellent mechanical properties. In this study, gyroid structures of different volume fraction were modelled and manufactured using SLM; the mechanical properties of the structures were then investigated under quasi-static compression loads. The elastic moduli and yield stresses of the structures were calculated from stress-strain diagrams, which were developed by conducting quasi-static compression tests. In order to estimate the discrepancies between the designed and as-produced gyroid structures, optical microscopy and micro-CT scanner were used to observe the structures’ micromorphology. Since good fluidness is conducive to the transport of nutrients, computational fluid dynamics (CFD) values were used to investigate the pressure and flow velocity of the channel of the three kinds of gyroid structures. The results show that the sizes of the as-produced structures were larger than their computer aided design (CAD) sizes, but the manufacturing errors are within a relatively stable range. The elastic moduli and yield stresses of the structures improved as their volume fractions increased. Gyroid structure can match the mechanical properties of human bone by changing the porosity of scaffold. The process of compression failure showed that 316L gyroid structures manufactured using SLM demonstrated high degrees of toughness. The results obtained from CFD simulation showed that gyroid structures have good fluidity, which has an accelerated effect on the fluid in the middle of the channel, and it is suitable for transport nutrients. Therefore, we could predict the scaffold's permeability by conducting CFD simulation to ensure an appropriate permeability before the scaffold being manufactured. SLM-built gyroid structures that composed of 316L stainless steel were suitable to be designed as bone scaffolds in terms of mechanical properties and mass-transport properties, and had significant promise

MULTI-AGV SCHEDULING OPTIMIZATION BASED ON NEURO-ENDOCRINE COORDINATION MECHANISM

Ovaj se završni radi bavi mobilnim robotima koji su pokretani nogama. Rad se sastoji od dvije veće cjeline. Prvi dio rada donosi literaturni pregled mobilnih robota pokretanih nogama te daje njihovu podjelu. Mobilne robote pokretane nogama najčešće dijelimo prema broju nogu, ali i po ostalim fizičkim karakteristikama. U radu se govori o osnovnim prednostima i nedostacima pri konstruiranju i upravljanju ovakvih robota. Većina takvih robota izrađena je po uzoru na neku životinju ili čovjeka, odnosno imitirajući prirodu. Takav pristup proučavanja i preslikavanja životinjskih karakteristika u tehničke sustave naziva se biomimikrija. Biomimikrija je očita i u drugom dijelu rada koji se bavi adaptacijom već postojeće robotske platforme. U drugom dijelu rada se razrađuje prilagodba četveronožnog paukolikog robota za novoodabrano elektroničko sklopovlje. Nakon modeliranja konstrukcije u programskom paketu CATIA, izrađen je prototip na uređaju za brzu izradu prototipova. Posebnost ove platforme jest da se svi aktuatori nalaze unutar samog tijela robota, a ne u nogama. Na taj se način eliminira prekomjerna masa nogu. Svaka od ĉetiri noge se pokreće pomoću polužnog mehanizma koji se sastoji od četiri štapa. Zbog te karakteristike javlja se neuobičajena kinematika robota. Ovakvom konstrukcijom robot postaje izazovna platforma za proučavanje algoritama umjetne inteligencije koji se implemetiraju za ostvarivanje gibanja. Takvi algoritmi daju puno bolje rezultate od sekvencijalnog programiranja kod složenijih robotskih struktura.This final project addresses the issue of legged mobile robots. The paper consists of two major parts. First part of the paper brings literature review of legged mobile robots and classifies them. Legged mobile robots most commonly differ by the number of their legs, but they can be distinguished by many other physical characteristics. The paper tackles elementary advantages and disadvantages when designing and controlling this type of a robot. Most legged mobile robots are made by imitating animals and humans. This approach of implementing knowledge obtained form observing nature into technical systems is called biomimetics. Biomimetics is also obvious in the second part of this paper. The second part of the paper elaborates adaptation of already existing quadruped robotic platform for the new electronic circuitry. After 3D designing the model in the CATIA software, prototype is printed on the rapid prototyping printer. This platform is unique because all the actuators are located in the body of the robot, and none of them is in the robot's leggs. Specifically, each of the four legs is controlled by separete four-bar linkage mechanism. Consequently, robot's mass is reduced, however, complexity of control is increased. This design causes unconventional kinematics, thus providing challenging platform for gait-learning algorithms. These algorithms excel in complicated structures like this, where sequential programming tends to underperform

Manufacturability, mechanical properties, mass-transport properties and biocompatibility of Triply Periodic Minimal Surface (TPMS) scaffolds fabricated by selective laser melting

Selective laser melting is a promising additive manufacturing technology for manufacturing porous metallic bone scaffolds. Bone repair requires scaffolds that meet various mechanical and biological requirements. This paper addresses this challenge by comprehensively studying the performance of porous scaffolds. The main novelty is exploring scaffolds with different porosities, verifying various aspects of their performance and revealing the effect of their permeability on cell growth. This study evaluates the manufacturability, mechanical behaviour, permeability and biocompatibility of gyroid scaffolds. In simulations, mechanical behaviour and permeability exhibited up to 56% and 73% accuracy, respectively, compared to the experimental data. The compression and permeability experiments showed that the elastic modulus and the permeability of the scaffolds were both in the range of human bones. The morphological experiment showed that manufacturing accuracy increased with greater designed porosity, while the in vitro experiments revealed that permeability played the main role in cell proliferation. The significance of this work is improving the understanding of the effect of design parameters on the mechanical properties, permeability and cell growth of the scaffolds, which will enable the design of porous bone scaffolds with better bone-repair effects

Effect of remelting processes on the microstructure and mechanical behaviours of 18Ni-300 maraging steel manufactured by selective laser melting

Selective laser melting (SLM) is an established metal additive manufacturing technology extensively used in the automotive domain to manufacture metallic components with complex structures from 18Ni-300 maraging steel. However, achieving high-performance 18Ni-300 maraging steel using SLM still presents a challenge in terms of formulation of the processing parameters. The remelting process has the potential to address this challenge during SLM before post-treatments. This paper systematically investigated the effect of remelting on the microstructure and mechanical behaviours of the SLM-built 18Ni-300 maraging steel. The experimental results suggest that increases in the relative density of the as-built samples from 99.12% to 99.93% are achieved by a specific combination of remelting parameters (laser power 200 W, scan speed 750 mm/s, remelting rotation 90° and hatch spacing 0.11 mm) that eliminate large-sized pores. Compared with the as-built condition, remelting can slightly coarsen the average grain sizes and increased the fraction of low-angle grain boundaries (2°–15°). The tensile strength showed no remelting dependence, whereas both the ductility and microhardness increased. Elongation of the as-built sample increased from 10.5 ± 0.8% to 13 ± 3.5% after remelting under the #28 condition. These findings provide a fundamentally new understanding of how a combination of SLM and remelting can aid in the manufacture of high-performing 18Ni-300 maraging steel

Laser powder bed fusion-built Ti6Al4V bone scaffolds composed of sheet and strut-based porous structures: Morphology, mechanical properties, and biocompatibility

Laser powder bed fusion (L-PBF)-built triply periodic minimal surface (TPMS) structures are designed by implicit functions and are endowed with superior characteristics, such as adjustable mechanical properties and light-weight features for bone repairing; thus, they are considered as potential candidates for bone scaffolds. Unfortunately, previous studies have mainly focused on different TPMS structures. The fundamental understanding of the differences between strut and sheet-based structures remains exclusive, where both were designed by one formula. This consequently hinders their practical applications. Herein, we compared the morphology, mechanical properties, and biocompatibility of sheet and strut-based structures. In particular, the different properties and in vivo bone repair effects of the two structures are uncovered. First, the morphology characteristics demonstrate that the manufacturing errors of sheet-based structures with diverse porosities are comparable, and semi-melting powders as well as the ball phenomenon are observed; in comparison, strut-based samples exhibit cracks and thickness shrinking. Second, the mechanical properties indicate that the sheet-based structures have a greater elastic modulus, energy absorption, and better repeatability compared to strut-based structures. Furthermore, layer-by-layer fracturing and diagonal shear failure modes are observed in strut-based and sheet-based structures, respectively. The in vivo experiment demonstrates enhanced bone tissues in the strut-based scaffold. This study significantly enriches our understanding of TPMS structures and provides significant insights in the design of bone scaffolds under various bone damaging conditions

Effect of heat treatment on microstructure and mechanical behaviours of 18Ni-300 maraging steel manufactured by selective laser melting

Selective laser melting (SLM) of 18Ni-300 maraging steel is an important research area in view of its numerous applications in the automotive domain. Heat treatment plays a significant role in the microstructure and mechanical behaviour of maraging steels and is a major area of interest. This paper investigated the effect of heat treatment on microstructure and mechanical behaviour of SLM-built 18Ni-300 maraging steel. The experimental results showed that the densest parts with the smallest number of defects were fabricated at optimum laser energy density of 70 J/mm3 and laser power of 275 W. When the laser power was fixed at 275 W, lower laser energy density resulted in the formation of balling and irregular pores, while higher laser energy density induced spherical pores and microcracks. The as-built samples consisted of cellular and columnar microstructures due to the fast cooling and solidification rates during SLM. However, solution treatment led to changes in the typical microstructure and massive lath martensite phase. The tensile strength and microhardness decreased slightly due to grain growth and residual stress relief upon solution treatment; an opposite effect was observed when the samples were subjected to solution treatment followed by aging at 490 °C for 2 h. With regard to the tensile anisotropy, yield strength and ultimate tensile strength of the horizontally-built samples slightly exceeded those vertically-built. These findings are significant as they allow an informed prediction about the effect of various heat treatments on the microstructure and mechanical behaviour of components manufactured from 18Ni-300 maraging steel using the SLM process