A hybrid finite element analysis and evolutionary computation method for the design of lightweight lattice components with optimized strut diameter

Components incorporating lattice structures have become very popular lately due to their lightweight nature and the flexibility that additive manufacturing offers with respect to their fabrication. However, design optimization of lattice components has been addressed so far either with empirical approaches or with the use of topology optimization methodologies. An optimization approach utilizing multi-purpose optimization algorithms has not been proposed yet. This paper presents a novel user-friendly method for the design optimization of lattice components towards weight minimization, which combines finite element analysis and evolutionary computation. The proposed method utilizes the cell homogenization technique in order to reduce the computational cost of the finite element analysis and a genetic algorithm in order to search for the most lightweight lattice configuration. A bracket consisting of both solid and lattice regions is used as a case study in order to demonstrate the validity and effectiveness of the method, with the results showing that its weight is reduced by 13.5 % when using lattice structures. A discussion about the efficiency and the implications of the proposed approach is presented

Design optimization of hot stamping tooling produced by additive manufacturing

The design flexibility of Additive Manufacturing (AM) can be utilized to develop innovative and sustainable hot stamping tools with enhanced quenching capability compared to tools manufactured by conventional manufacturing processes. This study proposes a concept for hot stamping tools with integrated lattice structures that selectively substitute a die's solid areas. A lattice structure demonstrates reduced thermal mass and can affect the ability of the tool to absorb heat from the blank and the rate at which the tool is cooled between two consecutive stamping cycles. This study explores the design space of a hot stamping tool with integrated lattice structures. It presents the optimized design for an effective compromise between cooling performance, structural integrity, and several other design parameters shown in the study. The proposed method utilizes a 2D thermo-mechanical finite element analysis model of a single cooling channel combined with Design of Experiments (DoE) to reduce the computational cost. The results show that the integration of lattice structure cannot only deliver improved cooling performance with minimum change in the dimensions of the cooling system but also achieves a faster AM build time since less material is required to be printed

Boron difluorides with formazanate ligands:redox-switchable fluorescent dyes with large stokes shifts

The synthesis of a series of (formazanate)boron difluorides and their 1-electron reduction products is described. The neutral compounds are fluorescent with large Stokes shifts. DFT calculations suggest that a large structural reorganization accompanies photoexictation and accounts for the large Stokes shift. Reduction of the neutral boron difluorides occurs at the ligand and generates the corresponding radical anions. These complexes are non-fluorescent, allowing switching of the emission by changing the ligand oxidation state

Positioning variation modeling for aircraft panels assembly based on elastic deformation theory

Dimensional variation in aircraft panel assembly is one of the most critical issues that affects the aerodynamic performance of aircraft, due to elastic deformation of parts during the positioning and clamping process. This paper proposes an assembly deformation prediction model and a variation propagation model to predict the assembly variation of aircraft panels, and derives consecutive 3-D deformation expressions which explicitly describe the nonlinear behavior of physical interaction occurring in compliant components assembly. An assembly deformation prediction model is derived from equations of statics of elastic beam to calculate the elastic deformation of panel component resulted from positioning error and clamping force. A variation propagation model is used to describe the relationship between local variations and overall assembly variations. Assembly variations of aircraft panels due to positioning error are obtained by solving differential equations of statics and operating spatial transformations of the coordinate. The calculated results show a good prediction of variation in the experiment. The proposed method provides a better understanding of the panel assembly process and creates an analytical foundation for further work on variation control and tolerance optimization

Kallikrein-related peptidase 4 (KLK4) mRNA predicts short-term relapse in colorectal adenocarcinoma patients

The members of the kallikrein-related peptidase (KLK) family are aberrantly expressed in cancer, including colorectal adenocarcinoma. KLK4 is an endogenous activator of protease-activated receptor 1 (PAR1) in HT-29 colorectal adenocarcinoma cells, inducing PAR1 signaling and subsequent ERK1/2 activation. The aim of this study was to analyze . KLK4 mRNA expression in colorectal adenocarcinoma and to examine its prognostic value as a novel molecular tissue biomarker in this malignancy. Therefore, total RNA was isolated from primary tumors of 81 colorectal adenocarcinoma patients, cDNA was prepared, and . KLK4 mRNA expression analysis was performed using quantitative real-time PCR. . KLK4 mRNA was significantly associated with the Dukes stage, tumor invasion, size, and histological grade. Survival analysis demonstrated that . KLK4 mRNA expression constitutes an unfavorable prognostic biomarker in colorectal adenocarcinoma, predicting poor disease-free survival (DFS), independently of the nodal status and tumor size. Furthermore, . KLK4 mRNA predicts short-term relapse of lymph node-negative patients or those with tumors of early Dukes stage. In conclusion, . KLK4 mRNA expression can be regarded as a novel potential tissue biomarker in colorectal adenocarcinoma. © 2012 Elsevier Ireland Ltd

Design and evaluation of a real-time locating system for wireless sensor networks

Evaluating target-tracking protocols for wireless sensor networks that can localise multiple mobile assets can be a very challenging task. Such protocols usually aim at the minimisation of communication overhead, data processing for the participating nodes and delivering adequate tracking information of the mobile assets in a timely manner. Simulations on such protocols are performed using theoretical models that are based on unrealistic assumptions like the unit disc graph communication model, ideal network localisation and perfect distance estimations. With these assumptions taken for granted, theoretical models claim various performance milestones that cannot be achieved in realistic conditions. In this paper, we design a new localisation protocol, where mobile assets can be tracked passively via software agents. Moreover, we address and mitigate issues that hinder performance over the wireless medium and provide a fully deployable protocol. The design, implementation and experimentation of this new protocol along with further optimisations were performed using the WISEBED framework. We apply our protocol in a real indoor wireless sensor testbed with multiple experimental scenarios to showcase scalability and trade-offs between network properties and configurable protocol parameters. By analysis of the real-world experimental output, we present results that depict a more realistic view of the target tracking problem, regarding power consumption and the quality of tracking information. Finally, we also conduct some much focused simulations to assess the scalability of our protocol in very large networks and multiple mobile assets

An Industrial Workflow to Minimise Part Distortion for Machining of Large Monolithic Components in Aerospace Industry

AbstractPart Distortion due to inherent residual stresses has resulted in recurring concession, rework and possibly scrap worth millions of Euro in the aircraft development and manufacturing life cycle. The paper presented here outlines an industrial solution based on years of fundamental research dated back to as early as mid-1990 to the development of a practical industrial solution to optimise part distortion in large monolithic components in the aerospace industry. The developed system was designed to empower manufacturing engineers at the shop floor level to help with their day to day activities from characterising residual stress profile in materials to numerical simulation to arrive at an optimised solution. The industrial technology suite includes the following technologies: (i) characterisation of inherent material residual stresses by adapting the established layer removal method for implementation on an industrial CNC machining centre; (ii) generation of residual stresses profiles using displacement measurements; and (iii) optimisation of part location in the materials through numerical modelling. The machine operator can characterise the bulk residual stresses in the materials on a standard CNC machining centre. The residual stresses profiles will subsequently be used as inputs via a user-friendly GUI, which will drive the numerical calculation to be performed remotely in supercomputers, in order to deliver an optimised solution

Design for additive manufacturing (DfAM) of hot stamping dies with improved cooling performance under cyclic loading conditions

Additive Manufacturing (AM) provides almost infinite design flexibility enabling the fabrication of intricate components. This study proposes a Design for AM (DfAM) method for hot stamping dies which exploits the benefit of lattice structures’ reduced thermal conductivity. The term effective cooling area of a cooling channel is introduced and is used for lattice structure integration into a hot stamping die. Four hot stamping dies with 4 different effective cooling areas were AMed using selective laser melting and subsequently tested in the hot stamping of AA7075 aluminum alloy blanks under cyclic loading conditions. Temperature evolutions, for both the blank and die, are presented with associated computed cooling rates. The analysis of the results shows that the proposed lattice structure AMed stamping dies significantly improve the cooling performance of a hot stamping die with printing times reduced by at least 12% compared to traditionally manufactured AM dies

Ab Initio Wave Function-Based Determination of Element Specific Shifts for the Efficient Calculation of X-ray Absorption Spectra of Main Group Elements and First Row Transition Metals

In this study, a detailed calibration of the performance of modern ab initio wave function methods in the domain of X-ray absorption spectroscopy (XAS) is presented. It has been known for some time that for a given level of approximation, for example, using time-dependent density functional theory (TD-DFT) in conjunction with a given basis set, there are systematic deviations of the calculated transition energies from their experimental values that depend on the functional, the basis set, and the chosen treatment of scalar relativistic effects. This necessitates a linear correlation for a given element/functional/basis set combination to be established before chemical applications can be performed. This is a laborious undertaking since it involves sourcing trustworthy experimental data, lengthy geometry optimizations, and detailed comparisons between theory and experiment. In this work, reference values for the element-specific shifts of all the first-row transition metal atoms and the main group elements C, N, O, F, Si, P, S, and Cl have been computed by using a protocol that is based on the complete active space configuration interaction in conjunction with second-order N-electron valence state perturbation theory (CASCI/NEVPT2). It is shown that by extrapolating the results to the basis set limit of the method and taking into account scalar relativistic effects via the second-order Douglas–Kroll–Hess (DKH2) corrections, the predicted element shifts are on average less than 0.75 eV across all the absorption edges and a very good agreement between theory and experiment in all the studied XAS cases is observed. The transferability of these errors to molecular systems is thoroughly investigated. The constructed CASCI/NEVPT2 database of element shifts is used to evaluate the performance and to automatically calibrate prior to comparison with the experiment two commonly used methods in X-ray spectroscopy, namely, DFT/Restricted open shell configuration interaction singles (DFT/ROCIS) and TD-DFT methods