•A moderate NNBI system (H0 @ >2MW @ 400keV @ >100s) will be established in the framework of CRAFT. A gas neutralizer will be used in the CRAFT NNBI.•The final design of the neutralizer has been ...optimized to reduce the weight, to improve the maintenance and flexibility, to enhance the structural strength, and to increase the manufacturing availability and reliability.•All the machining processes of the neutralizer have been finished, including the deeply drilling channels of 1.7 m in length and 18 mm in diameter.•Assembly of the main body is designed to be implemented in a side-lying position and a trial assembly has been successfully carried out.
The Comprehensive Research Facility for Fusion Technology (CRAFT) is a highly integrated research and development base. It consists of 20 different demonstrating or testing facilities that address most of the critical technologies and systems for the fusion reactor in China. A negative ion-based neutral beam injector (NNBI) test facility is established in CRAFT. A gas neutralizer is applied to the CRAFT NNBI test facility for the neutralization of the negative hydrogen ion beam. The target of the neutralization efficiency is more than 50%. The length of the neutralizer is 3 m. The neutralizer is divided into two adjacent vertical channels and the total opening is 1.7 m × 0.32 m. The neutralizer is mainly composed of channel plate, support structure, beam scraper, cooling water pipes, and gas inlet pipes. Based on the design requirements of the neutralizer, the support structure and cooling water pipes were optimized, to reduce the total weight. The structural strength of all components was simulated and compared to the preliminary design. The manufacturing of the neutralizer is ongoing. Some manufacturing challenges have been overcome, such as deep hole drilling. Several 1.7 m long cooling channels were successfully drilled in a copper panel and the ratio of depth to diameter was 94.
This study examines 0.6 N and 1.2 N as the maximum orthodontic force for periodontal ligament (PDL) at multiple levels of periodontal breakdown, and the relationships with the ischemic, necrotic, and ...resorptive risks. Additionally, this study evaluates if Tresca failure criteria is more adequate for the PDL study. Eighty-one 3D models (from nine patients; nine models/patients) with the 2nd lower premolar and different degrees of bone loss (0-8 mm) where subjected to intrusion, extrusion, rotation, translation, and tipping movements. Tresca shear stress was assessed individually for each movement and bone loss level. Rotation and translation produced the highest PDL stresses, while intrusion and extrusion determined the lowest. Apical and middle third PDL stresses were lower than the cervical stress. In intact periodontium, the amount of shear stress produced by the two investigated forces was lower than the 16 KPa of the maximum physiological hydrostatic pressure (MHP). In reduced periodontium (1-8 mm tissue loss), the apical amount of PDL shear stress was lower than MHP for both applied forces, while cervically for rotation, translation and tipping movements exceeded 16 KPa. Additionally, 1.2 N could be used in intact periodontium (i.e., without risks) and for the reduced periodontium only in the apical and middle third of PDL up to 8 mm of bone loss. However, for avoiding any resorptive risks, in the cervical third of PDL, the rotation, translation, and tipping movements require less than 0.2-0.4 N of force after 4 mm of loss. Tresca seems to be more adequate for the study of PDL than other criteria.
•Bi2Te3-based n- and p-type legs with step-wise properties were developed.•Thermal stresses occurring in the converter at the cooling stage were estimated.•Numerical simulation results suggest the ...best metal contact layer for the junction.•The thermoelectric stepwise converter was fabricated via single-step sintering.•The developed converter shows the significant efficiency of energy conversion.
Due to industrial activity, an enormous amount of heat is wasted on the environment enabling energy loss and global warming. Thermoelectric (TE) technologies make possible the direct conversion of waste heat into electrical energy. The main bottlenecks of energy conversion by TE devices are low efficiency as well as the expensive and complex fabrication procedure of industrial converters. In this work, we fabricated a Bi2Te3-based TE converter with stepwise legs for highly efficient energy conversion using a single-step sintering method. Before the fabrication of the converter, we employed the numerical simulation and found that Co is the best choice among the other well-established metallic layers, that can be used for the highly conductive covering of the n- and p-type TE legs. The employment of this metal produces the lowest thermal stress that occurs in the stepwise converter at the cooling stage of a sintering process. The energy conversion efficiency of the designed converter estimated using the finite element method reaches 10.1% at a temperature difference of 375 K (Tc = 300 K). Moreover, the measured value of efficiency achieves 8.5%, which is 1.4 times higher than the commercial Bi2Te3-based converters and 9–14% higher than the other reported stepwise converters. The enhanced efficiency mainly originates from the effective stepwise design of the n- and p-type TE legs. This work offers a new path for the simple single-step fabrication of the Bi2Te3-based TE converters that should have great potential for energy harvesting.
Damage in carbon fibers/Epoxy laminate composites containing carbon nanotubes (CNTs) is described. This investigation presents the third part of paper series on composite materials based CNTs. ...Experimental characterization and numerical homogenizations were published in order to obtain effective elastic orthotropic properties. Therefore, the homogenized properties are used as input data for investigation of damage initiation and propagations in the specimens for Open Hole tensile tests. The numerical intralaminar damage model is created under ABAQUS software with Hashin's criteria. The model is formulated according to damage mechanics. The prediction of ply delamination in laminated composites containing CNTs is modeled by using interface elements. The numerical approach is based on the cohesive zone model, provides an efficient description of the delamination growth. The numerical study is performed in the quasi-static regime and an implicit finite element scheme is used. The force-displacement curves obtained numerically shows a good agreement with the experimental.
Figure: Numerical simulation of damage progressive in composites with carbon nanotubes. Display omitted
•Damage modeling in laminate composites based carbon nanotubes is proposed.•Numerical intralaminar damage model is created and confronted to experimental results.•Numerical approach is based on the cohesive zone model.•The effect of carbon nanotubes on matrix and fiber damages is studied.
Mass customisation (MC) can provide significant benefits to the customers. For example, custom-fit design approaches can improve the users’ perceived comfort of products where the fit is an important ...feature. MC can also bring major value to the producers, where for instance, premium prices can be implemented to the products. Research show that MC can bring competitive advantages especially when the system is new. It is therefore surprising that MC of helmets has not been studied more extensively, especially given the advances in 3D scanning, computational analyses, parametric design, and additive manufacturing techniques. The purpose of this study was to present a novel MC framework for the design of custom-fit bicycle helmet models.
In the proposed design framework, we first categorized a subset of the Australian population into four groups of individuals based on their similar head shapes. New customers were then classified inside one of these groups. The customisation took place inside these groups to ensure that only small variations of the helmet liner were implemented. During the design process, the inside surfaces of a generic helmet model was modified to match the customer's head shape. We demonstrated that all the customized models created complied with the relevant drop impact test standard if their liner thickness was between the worst and best case helmets of each group. Fit accuracy was verified using an objective evaluation method. Future work should include detailed description of the manufacturing methods engaged in our MC framework.
•A Mass Customisation framework for the design of custom-fit helmets is presented.•The studied population was first split into clusters based on shape similarity.•New customers were then classified inside one of the four computed groups.•The customisation process took place within each group for automatic certification.•The fit accuracy of the custom-fit models was then tested with the Helmet Fit Index.
Objective
To compare the stress distribution and initial displacements during traction of palatally impacted canine between Kilroy and nickel‐titanium (NiTi) closed‐coil springs by means of the ...finite element analysis.
Setting and Sample Population
A finite element method analysis of two traction methods for a maxillary impacted canine.
Materials and Methods
The corresponding periodontal ligaments (PDLs), brackets, molar tubes and a 0.019 × 0.025‐in base stainless‐steel (SS) wire were modelled and imported to ANSYS SpaceClaim version 2020 R1. Traction was simulated under two different set‐ups with equal force magnitude (60 g); (1) the Kilroy spring, which is made of 0.016‐inch SS, and (2) the NiTi closed ‐coil spring. Von Mises stress distributions and initial displacements of the maxillary teeth were analysed.
Results
In both mechanics, while the highest stress was seen on the impacted canine (Kilroy, 10.41 kPa; NiTi closed‐coil, 5.27 kPa), the stress distribution decreased as the distance from the impacted canine increased. The Kilroy spring showed a greater total displacement (465.60 μm) on the impacted canine. The higher stresses on the adjacent lateral (5.29 kPa) and premolar (6.41 kPa) occurred with the Kilroy spring.
Conclusions
The Kilroy spring yielded higher stresses than the NiTi closed‐coil spring on the impacted canine and the adjacent teeth. The difference between distribution of the stresses over the impacted canine induced greater displacement with the Kilroy spring, particularly in the vertical direction.
This paper presents a study on microstructural deformation of a ferritic–pearlitic ductile iron, utilizing in-situ tensile testing, digital image correlation (DIC) and finite element analysis (FEA). ...For this purpose, the in-situ tensile test and DIC were used to measure local strain fields in the deformed microstructure. Furthermore, a continuum finite element (FE) model was used to predict the strain maps in the microstructure. Ferrite and pearlite parameters for the FE-model were optimized based on the Ramberg–Osgood relation. The DIC and simulation strain maps were compared qualitatively and quantitatively. Similar strain patterns containing shear bands in identical locations were observed in both strain maps. The average and localized strain values of the DIC and simulation conformed to a large extent. It was found that the Ramberg–Osgood model can be used to capture the main trends of strain localization. The discrepancies between the simulated and DIC results were explained based on the; (i) subsurface effect of the microstructure; (ii) differences in the strain spatial resolutions of the DIC and simulation and (iii) abrupt changes in strain prediction of the continuum FE-model in the interface of the phases due to the sudden changes in the elastic modulus.
The Cathedral of Santa Maria del Fiore was constructed in 1420 and features one of the largest masonry domes constructed without the use of reinforcement. The city of Florence is situated between two ...zones of seismic activity, namely Mugello and Chianti, and has been affected by earthquakes in recent years. The objective of the present work is to develop a non-linear numerical analysis of the seismic behavior of the Cathedral using the finite element method, with the aim of allowing the perpetuation of historical constructions. The seismic analysis was developed with geological database comprising seven natural accelerograms, with five return times (50, 75, 101, 201, and 475 years). This analysis entailed the detailed examination of the accelerations, tensions and deformations resulting from the application of seismic events in the Cathedral’s structure and indicate the failure zones. The greatest accelerations were observed for the seismic event with a magnitude of 6.93 Mw, a return time of 475 years, and were indicative of the most fractures in the Dome region.
•Numerical model calibrated by experimental dynamic characteristics.•Seismic response in terms of stresses, accelerations and deformations•The maximum horizontal displacement was on average 12.86 mm.
Abstract
In this study, a new flexible hybrid shape memory alloy composites (SMAHCs) with a polydimethylsiloxane (PDMS) matrix containing a shape memory alloy (SMA) of a hybrid Basalt/Kevlar fiber 3D ...woven composite is developed. The SMAHC is implanted into a glass fiber/PDMS composite laminate in a modular manner to study the stiffness of composite plates in response to temperature. The variable stiffness theory of the SMAHC is derived, and the influence of SMA parameters on the stiffness of the SMAHC is analyzed. A three-point bending test is performed to determine the stiffness of the composite plates at multiple temperature points in the form of Joule heat driving the composite plates. The stress and temperature distributions of the composite plate are analyzed in Abaqus under a temperature-displacement coupling setting. The results shows that the SMAHC stiffness is negatively correlated with SMA fiber diameter and positively correlated with SMA fiber volume fraction. With an increase in driving temperature, the stiffness of the composite plates tends to decrease. When the end temperature of the austenitic phase transformation is reached, the high-modulus austenitic SMA slightly increase the stiffness of the composite plate. The stiffness improvement is more significant when the SMAHC is placed in the middle area of the laminate and the SMA is located in the tension area. This study may provide a reference for the design of variable stiffness SMAHC for plate composite structures.
•Analysed masonry walls under hydrodynamic and hydrostatic loads.•Correlated rise of water level against the wall to its damage during the flood.•Correlated submerged surface area of the wall to its ...slenderness ratio.•Element deletion technique used to simulate opening of micro-cracks in masonry wall under flash flood.•Water rise after the first impulsive hit can cause early collapse of the wall due to stiffness reduction.
Damage surveys from past flash flood events show that the combined hydrodynamic impulsive loading and the subsequent hydrostatic loading due to rising water levels caused the failure of masonry walls/buildings. However, limited studies have been conducted to understand the responses of masonry walls to these loading states. To bridge this knowledge gap, an explicit 3D shell element based finite element modelling method that incorporates a homogenised anisotropic masonry material model was developed and applied to analyse the out-of-plane collapse behaviour of masonry walls under flash flooding conditions. The developed modelling method was validated with an available experimental study of masonry wall subjected to hydrostatic loading conditions. It was then extended to comprehend the behaviour of masonry walls under hydrodynamic impulsive water pressures. Results reveal that the effect of hydrodynamic impulsive loading generated by the first hit of the flash flood water is significant in reducing the stiffness of the masonry. This reduction in stiffness can result in an early collapse of the wall, even with a gradual rise of hydrostatic water level. This study has also evaluated the behaviour and damage patterns of masonry walls with two different slenderness ratios (single brick/24.5 and double brick/11.7) under flash flooding and prescribed the maximum percentage of surface area of inundation that the walls can resist. The importance of considering hydrodynamic impulsive loading in designing masonry buildings vulnerable to flash flooding and the capability of the modelling technique developed in this research for evaluating their vulnerability under these flooding scenarios are highlighted.
