Assembly Configurations Research Articles

Prediction of flatness defects and of the stable configuration of thin multilayer assemblies due to chemical shrinkage

The manufacturing process of multimaterial and multilayer assemblies involving pre-impregnated laminates consist of heating the composite structure at high temperature, typically of the order of 200 °C, at which polymerization occurs. During the curing, a permanent deformation, called chemical shrinkage strain, is generated and may strongly influence the future flatness of the assembly. Moreover, the cooling generates additional thermal deformations, which also participate into the manifestation of flatness defects at room temperature. To predict warpage or flatness defects, the chemical shrinkage strain needs to be precisely determined.This work proposes an analytical approach dedicated to flatness prediction of multilayer composites taking into account shrinkage strain generated during processing. Our contribution also aims at predicting and analyzing stable and unstable solutions of flatness defects. The proposed analytical model, developed for any multilayer composite, is obtained from an extension of the classical laminate theory (CLT). Geometrical nonlinearities are also accounted for. The analytical approach relies on trial fields for strain and displacements, and on total potential energy minimization. The theory is applied to a bilayer laminate consisting of a cured layer made of epoxy/glass fiber composite and of a pre-impregnated one of the same material. Results obtained from the analytical modeling are validated by numerical simulations. Influence of material parameters is also analyzed for this configuration. Finally, from experimental measurements of curvatures on bilayer composite samples, an inverse method and a minimization procedure, the proposed analytical development provides an estimate of the effective shrinkage strain, which is responsible for the flatness defect. Illustration of this strategy is exemplified by considering a bilayer composite manufactured for this work.

Two-dimensional finite element network analysis: Formulation and static analysis of structural assemblies

Finite element network analysis (FENA) is a physics-informed, deep-learning-based framework for the simulation of physical systems. FENA combines the conceptual flexibility of classical finite element methods with the computational power of pre-trained neural networks. A remarkable characteristic of FENA is the ability to simulate assemblies of physical elements by concatenating pre-trained networks serving as models of classes of physical systems. This characteristic places FENA in a new category of network-based computational platforms because, unlike other techniques, it does not require ad hoc training for problem-specific conditions.The present study significantly expands the concept and functionalities of FENA by including 1D slender beams and 2D thin plates and by further extending its concatenation functionality. Concatenation, which is a key property to create multicomponent assemblies without requiring training, is reformulated following an energy-based variational approach that significantly enhances accuracy and speed of convergence. The approach is numerically validated against finite element solutions for different configurations of structural assemblies, loads, and boundary conditions. Although presented in the context of one- and two-dimensional structures, the present framework is extremely general and provides a foundation to potentially simulate a broad range of physical systems.

Chemically-Controlled Ultrafast Photothermal Response in Plasmonic Nanostructured Assemblies.

Plasmonic nanoparticles are renowned as efficient heaters due to their capability to resonantly absorb and concentrate electromagnetic radiation, trigger excitation of highly energetic (hot) carriers, and locally convert their excess energy into heat via ultrafast nonradiative relaxation processes. Furthermore, in assembly configurations (i.e., suprastructures), collective effects can even enhance the heating performance. Here, we report on the dynamics of photothermal conversion and the related nonlinear optical response from water-soluble nanoeggs consisting of a Au nanocrystal assembly trapped in a water-soluble shell of ferrite nanocrystals (also called colloidosome) of ∼250–300 nm in size. This nanoegg configuration of the plasmonic assembly enables control of the size of the gold suprastructure core by changing the Au concentration in the chemical synthesis. Different metal concentrations are analyzed by means of ultrafast pump–probe spectroscopy and semiclassical modeling of photothermal dynamics from the onset of hot-carrier photogeneration (few picosecond time scale) to the heating of the matrix ligands in the suprastructure core (hundreds of nanoseconds). Results show the possibility to design and tailor the photothermal properties of the nanoeggs by acting on the core size and indicate superior performances (both in terms of peak temperatures and thermalization speed) compared to conventional (unstructured) nanoheaters of comparable size and chemical composition.

A study of Fused Filament Fabrication process efficiency: ABS vs PLA materials

A study of the shape accuracy of pieces created using the Fused Filament Fabrication (FFF) process is presented. Accuracy of the parts coming from 3D Printing (3DP) technologies is an essential criterion, primarily when used in assembly configurations. Two polymers; PLA and ABS, three infill percentages; 20, 50, and 70 (%), three numbers for shells; 1, 2 and 3 and three different layer heights; 0.1, 0.2 and 0.3 (mm) were the variables and their corresponding levels. A benchmark specimen was designed whilst nine experiments were performed according to the Taguchi methodology. Dimensional accuracy readings then followed, and the results were analysed using descriptive statistical tools such as analysis of means (ANOM), analysis of variance (ANOVA) and contour plots. The presented results indicate that 3D printed parts of PLA material exhibited better dimensional accuracy than ABS ones.

A mechanism of origin licensing control through autoinhibition of S. cerevisiae ORC\xb7DNA\xb7Cdc6

The coordinated action of multiple replicative helicase loading factors is needed for the licensing of replication origins prior to DNA replication. Binding of the Origin Recognition Complex (ORC) to DNA initiates the ATP-dependent recruitment of Cdc6, Cdt1 and Mcm2-7 loading, but the structural details for timely ATPase site regulation and for how loading can be impeded by inhibitory signals, such as cyclin-dependent kinase phosphorylation, are unknown. Using cryo-electron microscopy, we have determined several structures of S. cerevisiae ORC·DNA·Cdc6 intermediates at 2.5–2.7 Å resolution. These structures reveal distinct ring conformations of the initiator·co-loader assembly and inactive ATPase site configurations for ORC and Cdc6. The Orc6 N-terminal domain laterally engages the ORC·Cdc6 ring in a manner that is incompatible with productive Mcm2-7 docking, while deletion of this Orc6 region alleviates the CDK-mediated inhibition of Mcm7 recruitment. Our findings support a model in which Orc6 promotes the assembly of an autoinhibited ORC·DNA·Cdc6 intermediate to block origin licensing in response to CDK phosphorylation and to avert DNA re-replication.

Assembly Configuration Representation and Kinematic Modeling for Modular Reconfigurable Robots Based on Graph Theory

A Modular Reconfigurable Robot (MRR) composed of standard joint and link modules has the advantages of rapid changeover of assembly configurations for a diversity of application requirements. To tackle the kinematics analysis issues for an MRR, it is essential to develop a generic method to mathematically represent all possible assembly configurations and automatically generate their kinematic models. In this paper, two types of robot modules, i.e., revolute joint modules and rigid link modules, are considered as the basic building blocks of an MRR. The topological structure of an MRR is represented by a graph, termed an Assembly Graph (AG), in which all robot modules, regardless of their types, are treated as vertices, while the connecting interfaces between any two robot modules are treated as edges. Based on graph theory, a modified adjacency matrix, termed an Assembly Adjacency Matrix (AAM), is proposed to represent the assembly configuration of an MRR, in which the three-dimensional assembly information is specified with connecting port vectors for the adjacent modules. A path matrix derived from the AAM of an MRR is employed to describe the connecting sequence of its constituting modules. The local frame representation of the Product-of-Exponentials (POE) formula is employed, which is configuration-independent. Therefore, for an MRR configuration represented with an AAM, its kinematic model will be automatically generated according to its path matrix. The proposed assembly configuration representation and kinematic modeling method are validated through a dual-branch MRR configuration.

The Impact of Assembly Configuration on Diaphragm-Embedded Fiber Bragg Gratings Pressure Sensors

In this paper, the experimental analysis of different assembly configurations for diaphragm-embedded optical fiber sensors is proposed. A fiber Bragg grating (FBG) is embedded in a nitrile rubber diaphragm, which is positioned in different front and back supports. The difference between such supports is their contact angles with the diaphragm, which leads to differences in the strain applied in the FBG prior to the sensor application. This prestrain condition in the diaphragm influences the sensor’s performance in terms of sensitivity, linearity and hysteresis. To that extent, there are 8 different configuration angles, namely 0°, 1.5°, 3.8°, 6.8°, 9.0°, 11.3°, 13.5° and 15°. The diaphragm-embedded FBG is positioned at each configuration and pressure is transversely applied on the diaphragm region (which transmits strain to the optical fiber) at constant temperature conditions. Results show a relation between the configuration angle and the sensor performance, where sensitivity and linearity presented opposite behaviors, i.e., lower angles (especially the 0° angle) lead to high linearity with a coefficient of determination (R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) of 0.992, whereas higher angles resulted in higher sensitivity with the highest sensitivity value of 13.26 pm/kPa. In contrast, the sensor hysteresis showed a peak value of 6.7% at 9.0° angle with hysteresis decrease in angles higher and lower than 9.0°. The smallest hysteresis of 0.2% is obtained at 1.5°. The obtained results can be used as a guideline on the development of diaphragm-embedded sensors with the additional degree of freedom from the possibility of customizing the diaphragm assembly configuration to achieve predefined performance parameters.

A Developed Plasmatron Design to Enhance Production of Hydrogen in Synthesis Gas Produced by a Fuel Reformer System

Feeding IC engines with hydrogen-rich syngas as an admixture to hydrocarbon fuels can decrease pollutant emissions, particularly NOx. It offers a potential technique for low-environmental impact hydrocarbon fuel use in automotive applications. However, hydrogen-rich reformate gas (syngas) production via fuel reforming still needs more research and optimization. In this paper, we describe the effect of a plasma torch assembly design on syngas yield and composition during plasma-assisted reforming of gasoline. Additionally, erosion resistance of the cathode-emitting material under the conditions of gasoline reforming was studied, using hafnium metal and lanthanated tungsten alloy. The gasoline reforming was performed with a noncatalytic, nonthermal, low-current plasma system in the conditions of partial oxidation in an air and steam mixture. To find the most efficient plasma torch assembly configuration in terms of hydrogen production yield, four types of anode design were tested, i.e., two types of the swirl ring, and two cathode materials while varying the inlet air and fuel flow rates. The experimental results showed that hydrogen was the highest proportion of the produced syngas. The smooth funnel shape anode design in Ring 1 at air/fuel flow rates of 24/4, 27/4.5, and 30/5 g/min, respectively, was more effective than the edged funnel shape. Lanthanated tungsten alloy displayed higher erosion resistance than hafnium metal.

Fuel Performance Design Basis for the Versatile Test Reactor

The Fuel Performance Design Basis for the Versatile Test Reactor begins with requirements to maintain safe and efficient reactor operation. For the metal-fueled Versatile Test Reactor, this means a limited number of fuel rod breaches, no fuel melting under steady-state operation and anticipated transients, and continuity of the fuel rod and assembly configuration to avoid impacts to operations of safety systems, maintain expected coolant flow, and allow for efficient fuel handling. Using a large database gathered from previous testing, data were examined to identify and establish preliminary limits on fuel operating conditions. Fuel performance aspects important to fuel operating limits have been identified, including cladding creep, which is addressed with a cladding deformation limit to ensure a limited cladding breach. In addition, fuel-cladding chemical interaction is addressed through limits on cladding temperature and time-at-temperature for steady-state operation, transients, and accidents to mitigate effects leading to cladding breach or fuel melting. Through the implementation of these limits, cladding breach, fuel melting, and deleterious fuel rod and assembly dimensional changes will be prevented.

Mechanical strength of highly preloaded bolts affected by the ovalization of an aircraft wheel

This work presented in this paper concerns the modeling of the tensile and bending behavior of bolts in an airplane wheel. The design of a very rigid airplane tire means that the airplane wheel must be separated into two parts. In order not to have a separation between the two parts, several bolts with high preload are used. The main objective of this work is to predict the mechanical behavior of this assembly in a preliminary design phase with geometrical and global mechanical data. To achieve this objective, a simplified semi-numerical 1D model is developed. The complex geometry of the wheels is modeled by axisymmetric elements, while beam elements define the geometries and mechanical behavior of the bolts. The model is improved in non-axisymmetric cases to include the ring effect due to the wheel ovalization. Different cases are simulated (inflation and rolling). For each load case, the most stressed fastener is examined. Then, a comparison between its static and fatigue stress results and those of the 3D finite element reference model considered is analyzed for the validation of the developed tool. The semi-numerical model is used in the preliminary design phase and permits the geometric and mechanical properties of the aircraft wheel and fasteners to be defined so as to find the best assembly configuration that prevents separation.

Mapping the broadband circular dichroism of copolymer films with supramolecular chirality in time and space

Measurements of the electronic circular dichroism (CD) are highly sensitive to the absolute configuration and conformation of chiral molecules and supramolecular assemblies and have therefore found widespread application in the chemical and biological sciences. Here, we demonstrate an approach to simultaneously follow changes in the CD and absorption response of photoexcited systems over the ultraviolet−visible spectral range with 100 fs time resolution. We apply the concept to chiral polyfluorene copolymer thin films and track their electronic relaxation in detail. The transient CD signal stems from the supramolecular response of the system and provides information regarding the recovery of the electronic ground state. This allows for a quantification of singlet−singlet annihilation and charge-pair formation processes. Spatial mapping of chiral domains on femtosecond time scales with a resolution of 50 μm and diffraction-limited steady-state imaging of the circular dichroism and the circularly polarised luminescence (CPL) of the films is demonstrated.

A whole-core steady-state thermal-hydraulic model for annular fuel type fluoride-salt-cooled reactors

A whole-core, steady-state thermal-hydraulic model is developed for the fluoride-salt-cooled small modular advanced high-temperature reactor (SmAHTR) that employs an annular fuel configuration. This pre-conceptual reactor design by Oak Ridge National Laboratory (ORNL) has the annular fuel and moderator pins arranged in a hexagonal layout. The FLiBe coolant flows from the bottom to the top of the core, parallel to the hexagonal bundle. The fuel and moderator pins in the core are discretized into finite volumes and the 3-D heat conduction equation is solved to obtain the temperature profile. Inter-fuel assembly conduction is also addressed. For this fuel assembly configuration, the coolant flows through two distinct regions – the hexagonal pin bundle and the annulus between the fuel pin and the tie rod. The fluid flow through the hexagonal bundles is modeled using the subchannel approach, in which the coolant region is discretized into corner, edge and interior subchannels and the resulting conservation equations are systematically solved. The 1-D mass, momentum and energy equations are solved for the annulus channels between the fuel pin and the tie rod. Pertinent closure models from the literature are employed to close the system of equations. A preliminary code-to-code comparison between the present model and a CFD model is also performed. The resulting thermal-hydraulic model can provide temperature, flow rate and pressure drop profiles for the different solid and fluid regions throughout the entire core. Whole-core thermal-hydraulic results for a representative power profile are presented and discussed.

Assembly mechanism of surface-functionalized nanocubes.

Faceted nanoparticles can be used as building blocks to assemble nanomaterials with exceptional optical and catalytic properties. Recent studies have shown that surface functionalization of such nanoparticles with organic molecules, polymer chains, or DNA can be used to control the separation distance and orientation of particles within their assemblies. In this study, we computationally investigate the mechanism of assembly of nanocubes grafted with short-chain molecules. Our approach involves computing the interaction free energy landscape of a pair of such nanocubes via Monte Carlo simulations and using the Dijkstra algorithm to determine the minimum free energy pathway connecting key states in the landscape. We find that the assembly pathway of nanocubes is very rugged involving multiple energy barriers and metastable states. Analysis of nanocube configurations along the pathway reveals that the assembly mechanism is dominated by sliding motion of nanocubes relative to each other punctuated by their local dissociation at grafting points involving lineal separation and rolling motions. The height of energy barriers between metastable states depends on factors such as the interaction strength and surface roughness of the nanocubes and the steric repulsion from the grafts. These results imply that the observed assembly configuration of nanocubes depends not only on their globally stable minimum free energy state but also on the assembly pathway leading to this state. The free energy landscapes and assembly pathways presented in this study along with the proposed guidelines for engineering such pathways should be useful to researchers aiming to achieve uniform nanostructures from self-assembly of faceted nanoparticles.

Study on Algorithms for the Virtual Assembly and Best Combinations of In-line Measured Injection-Molded Parts

Geometrical deviations of manufactured parts affect the quality of the resulting product. In an assembly, deviations accumulate so that the functional requirements may no longer be met. Therefore, the compliance of geometrical interfaces is of great importance in order to achieve a high-quality product. Modern 3D sensors capture dense point clouds of manufactured parts and thus enable creating a part’s geometrical digital twin. However, there are no suitable registration techniques that allow computing the assembly of the measured parts. With the knowledge of the assembly configuration, the geometrical accumulation can be determined, ultimately allowing the prediction of the quality of the final product. In the authors preceding work, the virtual assembly registration technique was presented methodologically. This paper focusses on the implementation of a dedicated use case. As real-world problem, the assembly of injection-molded covers and housings is examined. The data acquisition is fully integrated into an in-line measurement process. Therefore, a fringe projection system is used for capturing 3D data. Specific segmentation approaches are presented in order to detect the part and to segment assembly-relevant geometries in the measurement data. Due to possible artefacts in the point clouds, strategies for increasing the robustness are discussed. Finally, the developed quality prediction is embedded in the production context. In order to achieve time, cost, and quality benefits, a selective assembly strategy is applied that reduces the number of scrap parts by a factor of two and more.

Experimental and numerical investigation of Cross-Flow nebulizer for developing optimized suction pressure

A pneumatic nebulizer, a device that supplies the spray of the mist of liquid using pressurized air. A cross-flow nebulizer is a very popular pneumatic nebulizer due to its robust design. It consists of a partially filled liquid vessel and an orifice-capillary assembly through which pressurized gas is supplied. When air passes through the orifice, low pressure develops in the capillary, leading to the free aspiration of liquid in the nebulizer. It is expected that nebulizers must have controllable and reproducible output performance. In this paper, an experimental and numerical investigation of the orifice-capillary assembly of a nebulizer is presented. A cross-flow nebulizer is fabricated using 3D printing. In the experimental study, the vacuum pressure and the gas velocity developed in the cross-flow nebulizer are recorded. The steady-state numerical analysis of the three-dimensional nebulizer using Ansys Fluent R19 software and gas–liquid interaction inside the nebulizer is studied. The effect of supply inlet pressure on the performance of the nebulizer, i.e. generating the vacuum at capillary, is presented. It has been observed that for a certain range, with an increase in supply inlet air pressure till 2 bar, the vacuum developed inside the nebulizer, i.e. in the liquid capillary of the nebulizer increase. But with a further increase in supply inlet air pressure, a negative relationship is seen. Hence for a given geometry, there exists an optimized orifice-capillary assembly configuration.

Understanding the Impacts of Li Stripping Overpotentials at the Counter Electrode by Three-Electrode Coin Cell Measurements.

The evaluation of new materials, interfaces, and architectures for battery applications are routinely conducted in two-electrode coin cell experiments, which although convenient, can lead to misrepresentations of the processes occurring in the cell. Few three-electrode coin cell designs have been reported, but those which have involve complex cell assembly, specialized equipment, and/or cell configurations which vary drastically from the standard coin cell environment. Herein, we present a novel, facile three-electrode coin cell design which can be easily assembled with existing coin cell parts and which accurately reproduces the environment of traditional coin cells. Using this design, we systematically investigated the inaccuracies incurred in two-electrode measurements in both symmetric/asymmetric cells and half-cell experiments by galvanostatic charge/discharge, galvanostatic intermittent titration technique (GITT), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry. From our investigation, we reveal that lithium metal stripping contributes larger overpotentials than its nucleation/plating processes, a phenomenon which is often misinterpreted in two-electrode cell measurements.

A modified cut-set method for mechanical subassembly identification

PurposeThe purpose of this paper is to perform a comparative assessment on working of the existed subassembly identification (SI) methods, which are widely practiced during the product development stage and to propose an improved method for solving the SI problem in assembly sequence planning (ASP).Design/methodology/approachThe cut-set method is found as a suitable method among various knowledge-based methods such as the theory of loops, theory of connectors and theory of clusters for the workability enhancement to meet the current requirements. Necessary product information is represented in the matrix format by replacing the traditional AND/OR graphs and the advanced predicates are included in the evaluation criteria.FindingsThe prominent methods in SI are followed a few of the predicates to avoid complexity in solution generation. The predicate consideration is found as the most influencing factor in eliminating the infeasible part combinations at SI. However, the quality of identified subassemblies without advanced predicates is not influencing the solution generation phase but practical applicability is affecting adversely.Originality/valueThe capability of performing SI by the cut-set method is improved to deal with the complex assembly configurations. The improved method is tested by applying on different assembly configurations and the effectiveness is compared with other existent methods of ASP along with the conventional method.

A Control Method of Space Manipulator for Peg-in-Hole Assembly Task Considering Equivalent Stiffness Optimization

To meet the control requirements of high precision and high robustness for peg-in-hole assembly tasks, an optimized control method for a peg-in-hole assembly task of a space manipulator is proposed to reduce the system disturbance caused by the change contact status during the assembly process. The first step is to build an equivalent stiffness model, which considers the structure and control characteristics of the space manipulator. Flexibility indices along the assembly direction are then created. On completion of the flexibility indices, the assembly configuration of the manipulator is optimized with the gain of the joint controller. After that, based on the sliding mode impedance control law, the disturbance of contact force is compensated using a zero-sum optimal control compensation strategy. Finally, the correctness and effectiveness of the control method are verified through simulation experiments. The results of the simulation experiments show that the contact force of the space manipulator can be precisely controlled by the method proposed in this paper. Compared with existing methods, the sudden change of contact force and the disturbing force of the base are reduced by 90% and 54%, respectively. A control method of the space manipulator for a peg-in-hole assembly task considering the equivalent stiffness optimization is proposed, which effectively reduces the influence of disturbance caused by contact collision and improves the control robustness of peg-in-hole assembly tasks.

Numerical and experimental evaluation of the general performance in a modular electrochemical reactor and its feasibility for electro-chlorination purposes: Effect of the different electrode assembly configurations

Evaluation of electrochemical reactors consisting of different electrode assemblies, stacks, or modular units, by the employing of computational techniques and its comparison with experimental data is desirable for its applications and scaling up for electrochemical processes like the mediated electro-chlorination. This work aimed to evaluate the effect of three different electrode configurations (flat, interspersed, and C-stack assemblies) on the general performance of a homemade modular reactor, based on former ElectroSyn design with an improved inlet-outlet system, through studies of hydrodynamics, electrical characteristics, and mass transfer. Additionally, a secondary potential-current distribution study was carried out to evaluate the feasibility of different electrode configurations tested for the electro-chlorination process, that can be applied mainly for environmental purposes like mediated oxidation of organic pollutants and disinfection by the production of active chlorine species.From the hydrodynamic study, velocity profiles and RTD curves obtained in all electrode configurations tested, suggest that the flat electrode configuration exposes a low fluid dispersion and resistance than the other configurations, because of the diminishing of the high-velocity zones and by its higher cross-sectional area, which was confirmed by the pressure drop measurements. On the other hand, calculation of primary and secondary current distribution suggests that the presence and modification of edge effect in the different configurations tested generate strong non-uniformities in the electrode corners and the reactor walls, which could affect the distribution of reaction rate during the mass transport evaluations. Also, the secondary potential-current distribution study indicates that the flat and C-stack configurations are the more electrical feasible configurations (since the effect of the flow field and mass transfer was not taken into account) to be applied in the electro-chlorination process.

Dissipative particle dynamics simulations of H-shaped diblock copolymer self-assembly in solvent

We examine the self-assembly of H-shaped block-copolymers as the function of the middle block to branch length ratio and interaction between the middle and branch blocks differing in their solvophobicity. The work shows that the examined H-shaped polymers readily transition from uniform mixing of the polymer species to domain formation and a variety of advanced assembly configurations including vesicles, onion-like, and multicompartment aggregates. We identify the polymer conformational and packing changes involved to extract governing interactions and molecule features giving rise to the different assembly structures. The findings are discussed in terms of the H-shaped polymer architecture and polymer assemblies. We conclude that the assembly structure is governed by the molecular level local curvature induced by the varying conformations of the polymers. The findings highlight that for H-shaped polymers the degree of polymerization and polymer chemistries in terms of solvation and mixing characteristics of the blocks are keys to controlling the assembling structures.