Shape Components Research Articles

Cold Metal Transfer (CMT) Based Wire and Arc Additive Manufacture (WAAM) System

The forming system of wire and arc additive manufacture (WAAM) based on cold metal transfer (CMT) is a high build rate system for production of near-net shape components layer by layer, which is composed of industrial robot operation system and 3D path simulation software. In the 3D path simulation software, the working layout of the off-line virtual robot is carried for the imported three-dimensional model to screen the model wall thickness, correct process library, set process parameters, slice, layer, plan deposition path, form simulation and upload program to execution system. Among the whole system, the 3D path simulation software provides essential database for process control and an innovative planning path to coordinate industrial robot platform to build parts layer by layer. Furthermore, the experiment is also performed to study the stability of aluminum alloy forming using the WAAM-CMT system by establishing different experimental models and changing process parameters and process modes of industrial robot and Fronius digital welding machine embedded on robot operation platform.

Joining of elements fabricated by a robotized laser/wire directed energy deposition process by using an autogenous laser welding

A robotized laser/wire directed energy deposition (RLW-DED) process has been employed, specifically in applications where higher deposition rates or larger buildup envelopes are needed. However, this process might have limitations in printing certain complex shape parts. Fabricating parts with overhang sections, depending on the geometry, might cause a collision between the laser head and the buildup. Part segmentation and joining the elements back together has been presented to overcome those limitations. In this study, the welding of additively manufactured parts by RLW-DED has been proposed. Autogenous laser welding, performed at the same setup used for RLW-DED, was utilized to join the thin-walled 316LSi DED parts. Mechanical and microstructural testing were then performed on the welded samples. The results showed that the mechanical properties of welded DED parts are comparable with those of DED parts. Furthermore, a component of complex shape was fabricated to show the capability of the developed process. Therefore, the welding of RLW-DED parts can expand the application of 3D-printed parts in industry.

What makes a landmark effective in adolescent and adult rats? Sex and age differences in a navigation task.

In three experiments, rats of different ages were trained in a circular pool to find a hidden platform whose location was defined in terms of a single landmark, a cylinder outside the pool. Following training, two main components of the landmark, its shape and pattern, were tested individually. Experiment 1 was performed by adolescent and adult rats (Exp. 1a, males; Exp. 1b, females). Adult rats always learned faster than the adolescent animals. On test trials, interesting tendencies were found-mainly, one favoring males on the shape test trial, and another favoring females on the pattern test trial. Experiment 2 was conducted only with adolescent rats, and these males and females did not differ when learning the task. However, on test trials the males learned more about the landmark shape component than about the landmark pattern component, while the females learned equally about the two components of the landmark. Finally, Experiment 3 was conducted only with adult rats, and again the males and females did not differ when learning the task. However, on test trials the males learned equally about the two components of the landmark (shape and pattern), but the females learned more about the landmark pattern component than about the landmark shape component. This set of experiments supports the claim that male and female rats can learn rather different things about a landmark that signals the location of the platform, with age being a critical variable.

Numerical Analysis of Influence of Mechanical Processing Conditions on Stress-Deformed State of Large-Size Thin-Wall Complex Parts

Многие предприятия приборостроительной, машиностроительной, авиакосмической отрасли сталкиваются с трудностями механической обработки крупногабаритных тонкостенных деталей сложной формы из алюминиевых сплавов, отвечающих за работоспособность всего изделия. К рассматриваемой группе деталей предъявляются повышенные требования по точности и качеству изготовления, к ним относятся несущие элементы конструкции летательных аппаратов, корпуса, волноводы, радиаторы. Зачастую допуск формы на поверхностях данных деталей не превышают 0,01 мм при площади поверхности 1-2 м2. Для обеспечения выпуска качественной продукции без увеличения производственного цикла и затрат на отработку технологии необходимо применение численного инженерного анализа для моделирования сложных технологических процессов. Статья содержит обоснование актуальности исследования взаимосвязи режимов механической обработки, схемы и усилия закрепления с технологическими остаточными напряжениями и деформациями детали. Представлены результаты анализа напряженно-деформированного состояния (НДС), возникающего в процессе фрезерования под воздействием силы и температуры резания, методом конечных элементов (МКЭ). На основе расчетов методом МКЭ показано, что в процессе фрезерования под действием силы резания в детали формируются сжимающие остаточные напряжения, приводящие к короблению поверхностей деталей. Разработана имитационная модель механического воздействия концевой фрезы на обрабатываемую деталь. Полученные результаты в дальнейшем планируется применить для формирования управляющих воздействий на параметры технологического процесса с целью повышения качества обработки и минимизации цикла производства деталей.

A Non-Structural Representation Scheme for Articulated Shapes

Articulated shapes are successfully represented by structural representations which are organized in the form of graphs of shape components. We present an alternative representation scheme which is equally powerful but does not require explicit modeling or discovery of structural relations. The key element in our scheme is a novel multi scale pixel-based distinctness measure which implicitly quantifies how rare a particular pixel is in terms of its geometry with respect to all pixels of the shape. The spatial distribution of the distinctness yields a partitioning of the shape into a set of regions. The proposed representation is a collection of size normalized probability distribution of the distinctness over regions over shape dependent scales. We test the proposed representation on a clustering task.

Default mode network is mechanism for semantic color-emotional interdomain integration

Progressing toward more accurate and more efficient numerical codes for the simulation of transport and turbulence in the edge plasma of tokamaks, we propose in this work a new hybrid discontinuous Galerkin solver. Based on 2D advection–diffusion conservation equations for the ion density and the particle flux in the direction parallel to the magnetic field, the code simulates plasma transport in the poloidal section of tokamaks, including the open field lines of the Scrape-off Layer (SOL) and the closed field lines of the core region. The spatial discretization is based on a high-order hybrid DG scheme on unstructured meshes, which provides an arbitrary high-order accuracy while reducing considerably the number of coupled degrees of freedom with a local condensation process. A discontinuity sensor is employed to identify critical elements and regularize the solution with the introduction of artificial diffusion. Based on a finite-element discretization, not constrained by a flux-aligned mesh, the code is able to describe plasma facing components of any complex shape using Bohm boundary conditions and to simulate the plasma in versatile magnetic equilibria, possibly extended up to the center. Numerical tests using a manufactured solution show appropriate convergence orders when varying independently the number of elements or the degree of interpolation. Validation is performed by benchmarking the code with the well-referenced edge transport code SOLEDGE2D (Bufferand et al., 2013, 2015 [1], [2]) in the WEST geometry. Final numerical experiments show the capacity of the code to deal with low-diffusion solutions.

Using geometric morphometrics for the genetics analysis of shape and size of lactation curves in Israeli first-parity Holstein cattle

Our objective was to combine the methods of geometric morphometrics and multivariate quantitative genetics to genetic evaluation of the size and shape of lactation curves of milk of 3,492 Israeli first-parity Holstein cattle. Lactation records were treated as morphological data, for which 2 different lactation shape functions were evaluated, one depicted by a line graph and the other by an orbital graph. The lactation curves from both shape functions were represented by 2-dimensional Cartesian landmark coordinates. The 2 sets of landmarks were then analyzed individually for each shape function with geometric morphometrics to separate variation into components of size and shape. The analysis yielded 2 size measures and 2 sets of shape variables, and they were the inputs to estimate variance components using the MTC REML individual animal model program. Variance components were also estimated for the 305-d lactation production as a reference. Shape variables showed negligible correlation with 305-d production, providing evidence of size and shape of lactation curve as separate characters. The size measure derived from the orbital-depicted lactation curve had equal heritability (0.39 ± 0.01; ± standard error) and complete genetic and environmental correlations with 305-d production, whereas the size measure derived from the line-depicted lactation curve showed low heritability (0.09 ± 0.01) and environmental correlation (0.02 ± 0.004) and relative high genetic correlation with 305-d production (0.48 ± 0.04). This may validate both the orbital graph to depict lactation records and the use of geometric morphometrics to split variation of lactation curve into size and shape components. The maximal heritability for shape of lactation curve was 0.55 for orbital- and 0.56 for line-depicted lactation curves. The respective patterns of variations were visualized as shape changes from the mean shape in the data set. Geometric morphometrics are well grounded within the theory of shape analysis and can be paired with conventional methods in the field to characterize the patterns of phenotypic and genetic variation of shape and size of lactation curve in dairy cattle.

The Use of Matrix Training to Teach Color-Shape Tacts to Children with Autism.

Matrix training consists of preplanning instruction by arranging components of desired skills across a minimum of two axes. In the current study, three matrices were developed for each participant (e.g., Matrix 1, Generalization Matrix 1, and Generalization Matrix 2) with known color and shape components. Following baseline, nonoverlapping (i.e., diagonal) training was conducted with Matrix 1. Results of posttests were used to determine the extent of emergence of untrained color-shape combinations across all matrices. Results from all six participants indicated that mastery criteria were eventually met for Matrix 1. For five participants, mastery criteria were also eventually met for generalization matrices. Results replicate findings from prior studies and offer a simple approach for both testing emergence of untrained skills and remediating responding.

A Short Review on the Microstructure, Transformation Behavior and Functional Properties of NiTi Shape Memory Alloys Fabricated by Selective Laser Melting.

Due to unique functional and mechanical properties, NiTi shape memory alloys are one of the most promising metallic functional materials. However, the poor workability limits the extensive utilization of NiTi alloys as components of complex shapes. The emerging additive manufacturing techniques provide high degrees of freedom to fabricate complex structures. A freeform fabrication of complex structures by additive manufacturing combined with the unique functional properties (e.g., shape memory effect and superelasticity) provide great potential for material and structure design, and thus should lead to numerous applications. In this review, the unique microstructure that is generated by selective laser melting (SLM) is discussed first. Afterwards, the previously reported transformation behavior and mechanical properties of NiTi alloys produced under various SLM conditions are summarized.

Experimental Investigation on the Geometrical Accuracy of the CNC Multi-Pass Sheet Metal Spinning Process

The geometrical accuracy of multi-pass sheet metal spinning products is crucial in many applications. Aerospace, petroleum, and chemical industries motivated the development of modern spun components of complicated shapes with special functionality, but a substantial research lag exists behind this progress. Due to the localized plastic deformation involved, careful control of dimensions and form is required in spinning procedures. In this study, two sets of experiments were implemented for cup manufacturing using a retrofitted computer numerically controlled (CNC) spinning machine to identify the critical factors affecting product geometry and reveal their influence on the shape accuracy of the spun cups. The first set is a screening experiment to determine the most significant parameters and the second provides the optimum processing conditions affecting cup quality. The feed ratio, number of spin-forming passes, spinning ratio, and lubrication were found to have the most important effect on the geometry of the spun cups. Optimum quality with a higher processing speed (productivity) was achieved under a lubricated condition using a larger number of spin-forming passes at a high feed ratio, diminishing the commonly adopted rule of slow spinning for accurate products and reflecting a significance for state-of-the-art spinning practice. The findings of this paper introduce a basis for a spinning quality database.

Experimental investigation and optimization of surface roughness in negative incremental forming

Single Point Incremental Forming (SPIF) allows the possibility of forming components of various shapes and sizes with the use of simple and economical tooling. Investigation of surface quality of the formed components becomes necessary for selecting the optimal process parameters in order to ensure precision and safe forming of the components. Moreover, lack of available knowledge regarding the process parameters makes the process limited for industrial applications. In this paper, various input factors have been investigated on the surface roughness of formed components. The process has been optimized to obtain the optimal levels of input factors for producing better surface quality using Taguchi Method (TM) as Design of Experiment (DOE) and analysis of variance (ANOVA). Results showed that the optimal experimental condition for average roughness has been determined as tool diameter (15.66 mm), tool shape (hemispherical), the viscosity of the forming oil (320 cSt), sheet thickness (0.8 mm), wall angle (60°), step size (0.2 mm), tool rotation (1000 rpm), and feed rate (1500 mm/min). The tool diameter has been found the most dominating factor for average surface roughness of the conical frustums. Tool shape and the viscosity of forming oil have also been significant factors for average roughness. The results obtained from confirmatory experiments showed that predictive model obtained from TM is efficient and effective for estimating optimal levels of input parameters for producing the better surface quality during the SPIF process.

Effect of Impact Hydroforming Loads on the Formability of AA5A06 Sheet Metal

Recently, aluminium (Al) alloys are increasingly used in the automobile and aerospace industries because of their light weight and corrosion resistance properties. However, the applications of these materials are limited due to their poor formability especially at room temperature. Although hydroforming technology is one of the approaches used to improve the formability of Al alloys, it still cannot fulfil the requirements of designers and manufacturers to form high-quality complex shaped components. It has been found that high-speed forming is able to improve the formability of low plasticity metals at room temperature. Thus, impact hydroforming (IHF) technology is proposed by combining the advantages of high-speed forming and hydroforming, and it was used to address the issues of quasi-static hydroforming. Accordingly, the aim of this study is to investigate the effect of IHF on the formability of AA5A06 sheet metal. An IHF bulge experiment setup was developed by making use of a light gas gun which can accelerate the projectile up to 300m/s. The results show that the formability of the AA5A06 increased under most of the impact velocities, and the equi-biaxial strain before failure of the IHF is 50% higher than that of quasi-static hydroforming at strain rate of 2 × 103 s−1. It is concluded that the IHF technology is an appropriate method to improve the formability of Al alloys and form complex shape components.

Monoclinic-celsian ceramics formation: Through thermal treatment of ion-exchanged 3D printing geopolymer precursor

Based on conventional ion exchange method from zeolite materials, we herein report a facile synthetic procedure to prepare monoclinic celsian ceramics through thermal treatment of ion-exchanged 3D printing geopolymer precursors. In this contribution, both ion exchange process and thermal evolution of celsian precursors were systematically investigated. The results proved 3D printing Na- and K- based geopolymer were ideal precursors with low residual Na+ content (0.10 meq/g) and K+ content (0.05 meq/g) and translated into monoclinic celsian after being heated at 1400 °C. With increasing Sr2+ doping concentration from 20% (mole ratio) to 30% (mole ratio), more significant phase transition results (hexagonal → monoclinic) were observed. All 3D printing geopolymer precursors kept fine integrity and stable 3D structure upon ion exchange process and heating, indicating the combination of geopolymer technique and 3D printing opens up a versatile and robust way to yield monoclinic celsian ceramics and related components of complex shapes.

Microstructure and mechanical properties of gel casted Ti3AlC2

Dense Ti3AlC2 components with a complex shape were fabricated using gel casting followed by pressure-less sintering. Low viscosity slurry was prepared using an aqueous based acrylamide (AM) monomer with a 50% solid loading. Homogeneous and crack free Ti3AlC2 green bodies were obtained. The sintering temperatures were set at 1500, 1550 and 1600 °C, highest relative density of 93% was achieved at 1550 °C. Surprisingly, samples sintered at 1600 °C resulted in a drop of relative density because of the abnormal grain growth and entrapped porosity. The pressure-less sintered samples had mechanical properties comparable to hot pressed counterparts with Vickers hardness of 3.1 ± 0.2 GPa, fracture toughness of 4.2 ± 0.2 MPa m1/2 and flexural strength of 302.3 ± 25.0 MPa. Final machining was still required to obtain a net shape components free from surface defects.

Machining of GTAW additively manufactured Ti-6Al-4V structures

Titanium components such as spars, brackets and landing gear assemblies, containing deep pockets, thin walls and fixturing holes are used in almost all aircraft. The traditional method of fabricating these parts involves significant amount of machining resulting in unsustainably high buy-to-fly ratios. For this reason, additive manufacturing (AM) processes are being considered for making near-net shape components. Gas tungsten arc welding (GTAW) is an economical AM process with higher deposition rates which has been employed to fabricate these titanium components. However, the GTAW-fabricated parts require post-finish machining to meet the strict dimensional tolerances as per design. On the other hand, it is well known that titanium is a difficult-to-machine material. Therefore, the primary objective of this study was to evaluate the machinability of Ti-6Al-4V thin wall and pad structures produced using GTAW additive manufacturing in terms of cutting forces, surface roughness and tool wear during milling and drilling operations. The cutting forces were found to be lower by about 13–21% during milling owing to the lower hardness of the additively manufactured wall in comparison to the wrought T-fillet structure. In contrast, the normal drilling force was higher by about 10–15% for the additively manufactured pad due to its higher hardness as compared to the wrought Ti-6Al-4V billet, though the tool wear was noticed to be higher when drilling the wrought billet. Nevertheless, it was concluded that the machinability of the GTAW-fabricated Ti-6Al-4V was better than the wrought counterpart.

A hybrid discontinuous Galerkin method for tokamak edge plasma simulations in global realistic geometry

Progressing toward more accurate and more efficient numerical codes for the simulation of transport and turbulence in the edge plasma of tokamaks, we propose in this work a new hybrid discontinuous Galerkin solver. Based on 2D advection–diffusion conservation equations for the ion density and the particle flux in the direction parallel to the magnetic field, the code simulates plasma transport in the poloidal section of tokamaks, including the open field lines of the Scrape-off Layer (SOL) and the closed field lines of the core region. The spatial discretization is based on a high-order hybrid DG scheme on unstructured meshes, which provides an arbitrary high-order accuracy while reducing considerably the number of coupled degrees of freedom with a local condensation process. A discontinuity sensor is employed to identify critical elements and regularize the solution with the introduction of artificial diffusion. Based on a finite-element discretization, not constrained by a flux-aligned mesh, the code is able to describe plasma facing components of any complex shape using Bohm boundary conditions and to simulate the plasma in versatile magnetic equilibria, possibly extended up to the center. Numerical tests using a manufactured solution show appropriate convergence orders when varying independently the number of elements or the degree of interpolation. Validation is performed by benchmarking the code with the well-referenced edge transport code SOLEDGE2D (Bufferand et al., 2013, 2015 [1,2]) in the WEST geometry. Final numerical experiments show the capacity of the code to deal with low-diffusion solutions.

Microwave sintering of complex shapes: From multiphysics simulation to improvements of process scalability

AbstractThe microwave sintering homogeneity of large and complex shape specimens is analyzed. A new approach enabling the fabrication of complex shapes ceramics via 3D printing and microwave sintering is presented. The use of a dental microwave cavity is shown to enable a substantial level of densification of complex shape components while restricting the grain growth. The homogeneity of the processed samples during microwave sintering is studied by an electromagnetic‐thermal‐mechanical simulation. The realistic densification behavior, that phenomenologically takes into account the microwave effect, is included in the modeling framework. The simulation indicates the sharp correlation between the microwave field distribution in the cavity, the temperature profile, and the specimen's shape distortion.

The guidance of visual search by shape features and shape configurations.

Representations of target features (attentional templates) guide attentional object selection during visual search. In many search tasks, targets objects are defined not by a single feature but by the spatial configuration of their component shapes. We used electrophysiological markers of attentional selection processes to determine whether the guidance of shape configuration search is entirely part-based or sensitive to the spatial relationship between shape features. Participants searched for targets defined by the spatial arrangement of two shape components (e.g., hourglass above circle). N2pc components were triggered not only by targets but also by partially matching distractors with one target shape (e.g., hourglass above hexagon) and by distractors that contained both target shapes in the reverse arrangement (e.g., circle above hourglass), in line with part-based attentional control. Target N2pc components were delayed when a reverse distractor was present on the opposite side of the same display, suggesting that early shape-specific attentional guidance processes could not distinguish between targets and reverse distractors. The control of attention then became sensitive to spatial configuration, which resulted in a stronger attentional bias for target objects relative to reverse and partially matching distractors. Results demonstrate that search for target objects defined by the spatial arrangement of their component shapes is initially controlled in a feature-based fashion but can later be guided by templates for spatial configurations. (PsycINFO Database Record

Savanna chimpanzees adjust sleeping nest architecture in response to local weather conditions.

Great ape nests are hypothesized to aid safe, secure sleep via providing thermoregulation or protection from predators and vectors. We aimed to describe and investigate variation in chimpanzee nest architecture across two populations in response to local weather conditions. We experimentally tested whether nests provide insulation by measuring heat loss within and outside nests, and took detailed measurements of the number, size, and type of materials used in nest building across two dry-habitat research sites (Fongoli, Senegal, and Issa, Tanzania). We tested application of principal components analysis (PCA) to extract composite quantitative measures of the key components of shape and architecture, before testing how PCs vary across populations with overnight weather conditions that reflect hypothesized thermoregulatory function. Heat loss is greater and occurs faster outside of nests. PCA allowed meaningful comparison of nests within and between sites. Nest variation at both sites revealed chimpanzees built thicker nests in cooler conditions and used more broken branches and support in moister conditions. Chimpanzees in Fongoli used more lining and mattress material in colder conditions, whilst in Issa nest depth and support branch size were larger in windier conditions. Shape and architectural measures reflected insulation and stability of nest structure. Chimpanzees in Fongoli and Issa may achieve the same functional goals by adjusting nest shape and architecture in different ways. These results suggest that wild chimpanzees show flexible building techniques in response to local, overnight weather conditions in making an insulating and stable, supportive platform for sleep.

Bayesian variable selection logistic regression with paired proteomic measurements.

We explore the problem of variable selection in a case‐control setting with mass spectrometry proteomic data consisting of paired measurements. Each pair corresponds to a distinct isotope cluster and each component within pair represents a summary of isotopic expression based on either the intensity or the shape of the cluster. Our objective is to identify a collection of isotope clusters associated with the disease outcome and at the same time assess the predictive added‐value of shape beyond intensity while maintaining predictive performance. We propose a Bayesian model that exploits the paired structure of our data and utilizes prior information on the relative predictive power of each source by introducing multiple layers of selection. This allows us to make simultaneous inference on which are the most informative pairs and for which—and to what extent—shape has a complementary value in separating the two groups. We evaluate the Bayesian model on pancreatic cancer data. Results from the fitted model show that most predictive potential is achieved with a subset of just six (out of 1289) pairs while the contribution of the intensity components is much higher than the shape components. To demonstrate how the method behaves under a controlled setting we consider a simulation study. Results from this study indicate that the proposed approach can successfully select the truly predictive pairs and accurately estimate the effects of both components although, in some cases, the model tends to overestimate the inclusion probability of the second component.