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Article
Publication date: 1 June 2005

S.M.B. Afonso, J. Sienz and F. Belblidia

Shells are widely used structural systems in engineering practice. These structures have been used in the civil, automobile and aerospace industries. Many shells are designed…

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Abstract

Purpose

Shells are widely used structural systems in engineering practice. These structures have been used in the civil, automobile and aerospace industries. Many shells are designed using the finite element analysis through the conventional and costly trial and error scheme. As a more efficient alternative, optimization procedures can be used to design economic and safe structures.

Design/methodology/approach

This paper presents developments, integration and applications of reliable and efficient computational tools for the structural optimization of variable thickness plates and free‐form shells. Topology, sizing and shape optimization procedures are considered here. They are applied first as isolated subjects. Then these tools are combined to form a robust and reliable fully integrated design optimization tool to obtain optimum designs. The unique feature is the application of a flexible integrally stiffened plate and shell formulation to the design of stiffened plates and shells.

Findings

This work showed the use of different optimization strategies to obtain an optimal design for plates and shells. Both topology optimization (TO) and structural shape optimization procedures were considered. These two optimization applications, as separate procedures produce new designs with a great improvement when compared to the initial designs. However, the combination of stiffening TO and sizing optimization using integrally stiffened shells appears as a more attractive tool to be used. This was illustrated with several examples.

Originality/value

This work represents a novel approach to the design of optimally stiffened shells and overcomes the drawbacks of both topology optimization and structural shape optimization procedures when applied individually. Furthermore, the unique use of integrally stiffened shell elements for optimization, unlike conventional shell‐stiffening optimization techniques, provided a general and extremely flexible tool.

Details

Engineering Computations, vol. 22 no. 4
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 1 December 1999

F. Belblidia, S.M.B. Afonso, E. Hinton and G.C.R. Antonino

Topology optimization and conventional structural sizing optimization procedures are used together to obtain optimum designs for plate structures. A three‐layer, Mindlin‐Reissner…

893

Abstract

Topology optimization and conventional structural sizing optimization procedures are used together to obtain optimum designs for plate structures. A three‐layer, Mindlin‐Reissner plate model is first used with topology optimization to determine optimal stiffening zones. The central layer represents the unstiffened plate and the symmetrically located upper and lower layers are potential stiffening zones. A stiffening volume is specified and the objective is to minimize the strain energy. From these stiffening zones, a set of centre lines of equivalent stiffening Timoshenko beam elements is selected. A sizing optimization procedure is then used to optimize the stiffener dimensions. The objective of the design in the final sizing optimization stage is to minimise the strain energy keeping the total stiffened plate volume constant. The efficiency and accuracy of the proposed strategy is illustrated through several applications.

Details

Engineering Computations, vol. 16 no. 8
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 1 October 2004

M.F. Webster, I.J. Keshtiban and F. Belblidia

We introduce a second‐order accurate time‐marching pressure‐correction algorithm to accommodate weakly‐compressible highly‐viscous liquid flows at low Mach number. As the…

800

Abstract

We introduce a second‐order accurate time‐marching pressure‐correction algorithm to accommodate weakly‐compressible highly‐viscous liquid flows at low Mach number. As the incompressible limit is approached (Ma ≈ 0), the consistency of the compressible scheme is highlighted in recovering equivalent incompressible solutions. In the viscous‐dominated regime of low Reynolds number (zone of interest), the algorithm treats the viscous part of the equations in a semi‐implicit form. Two discrete representations are proposed to interpolate density: a piecewise‐constant form with gradient recovery and a linear interpolation form, akin to that on pressure. Numerical performance is considered on a number of classical benchmark problems for highly viscous liquid flows to highlight consistency, accuracy and stability properties. Validation bears out the high quality of performance of both compressible flow implementations, at low to vanishing Mach number. Neither linear nor constant density interpolations schemes degrade the second‐order accuracy of the original incompressible fractional‐staged pressure‐correction scheme. The piecewise‐constant interpolation scheme is advocated as a viable method of choice, with its advantages of order retention, yet efficiency in implementation.

Details

Engineering Computations, vol. 21 no. 7
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 1 January 2006

R. Balamurugan, C.V. Ramakrishnan and N. Swaminathan

The structural design problem can be viewed as an iterative design loop with each iteration involving two stages for topology and shape designs with genetic algorithm (GA) as the…

629

Abstract

Purpose

The structural design problem can be viewed as an iterative design loop with each iteration involving two stages for topology and shape designs with genetic algorithm (GA) as the optimization tool for both.

Design/methodology/approach

The topology optimization problem, which is ill posed, is regularized using a constraint on perimeter and solved using GA. The problem is formulated as one of compliance minimization subject to volume constraint for the single loading case. A dual formulation of this has been used for the multiple loading cases resulting in as many behavioral constraints as there are loading cases. The tentative topology given by the topology optimization module is taken and the domain boundary is approximated using straight lines, B‐splines and cubic spline curves and design variables are selected among the boundary defining points. Optimum boundary shape of the problem has been obtained using GA in two different ways: without stress constraints; and with stress constraints.

Findings

The proposed two stage strategy has been tested on benchmark structural optimization problems and its performance is found to be extremely good.

Practical implications

The strategy appears to be eminently suitable for implementation in a general purpose FE software as an add‐on module for structural design optimization.

Originality/value

It has been observed that the integrated topology and shape design method is robust and easy to implement in comparison with other techniques. The computing time requirements for the GA does not appear daunting in the present scenario of high performance parallel computing and improved GA techniques.

Details

Engineering Computations, vol. 23 no. 1
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 1 May 2001

J.E. Akin and Javier Arjona‐Baez

The goal of structural optimization is to find the best possible configuration that minimizes the objective function and satisfies a set of constraints. Here we present a method…

801

Abstract

The goal of structural optimization is to find the best possible configuration that minimizes the objective function and satisfies a set of constraints. Here we present a method based on the evolutionary structural optimization method, where the quality of the solution is improved by avoiding the chain‐like sets of elements which are sources of potential kinematic instabilities, and by including local error estimators. Both of these enhancements are employed to activate refining the mesh so as to obtain accurate and stable solutions as the volume removal proceeds. Several related contributions of Professor E. Hinton are cited.

Details

Engineering Computations, vol. 18 no. 3/4
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 23 October 2018

Jingfu Liu, Behrooz Jalalahmadi, Y.B. Guo, Michael P. Sealy and Nathan Bolander

Additive manufacturing (AM) is revolutionizing the manufacturing industry due to several advantages and capabilities, including use of rapid prototyping, fabrication of complex…

1156

Abstract

Purpose

Additive manufacturing (AM) is revolutionizing the manufacturing industry due to several advantages and capabilities, including use of rapid prototyping, fabrication of complex geometries, reduction of product development cycles and minimization of material waste. As metal AM becomes increasingly popular for aerospace and defense original equipment manufacturers (OEMs), a major barrier that remains is rapid qualification of components. Several potential defects (such as porosity, residual stress and microstructural inhomogeneity) occur during layer-by-layer processing. Current methods to qualify AM parts heavily rely on experimental testing, which is economically inefficient and technically insufficient to comprehensively evaluate components. Approaches for high fidelity qualification of AM parts are necessary.

Design/methodology/approach

This review summarizes the existing powder-based fusion computational models and their feasibility in AM processes through discrete aspects, including process and microstructure modeling.

Findings

Current progresses and challenges in high fidelity modeling of AM processes are presented.

Originality/value

Potential opportunities are discussed toward high-level assurance of AM component quality through a comprehensive computational tool.

Details

Rapid Prototyping Journal, vol. 24 no. 8
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 12 September 2024

Tunay Turk, Cesar E. Dominguez, Austin T. Sutton, John D. Bernardin, Jonghyun Park and Ming C. Leu

This paper aims to present spot pattern welding (SPW) as a scanning strategy for laser-foil-printing (LFP) additive manufacturing (AM) in place of the previously used continuous…

62

Abstract

Purpose

This paper aims to present spot pattern welding (SPW) as a scanning strategy for laser-foil-printing (LFP) additive manufacturing (AM) in place of the previously used continuous pattern welding (CPW) (line-raster scanning). The SPW strategy involves generating a sequence of overlapping spot welds on the metal foil, allowing the laser to form dense and uniform weld beads. This in turn reduces thermal gradients, promotes material consolidation and helps mitigate process-related risks such as thermal cracking, porosity, keyholing and Marangoni effects.

Design/methodology/approach

304L stainless steel (SS) feedstock is used to fabricate test specimens using the LFP system. Imaging techniques are used to examine the melt pool dimensions and layer bonding. In addition, the parts are evaluated for residual stresses, mechanical strength and grain size.

Findings

Compared to CPW, SPW provides a more reliable heating/cooling relationship that is less dependent on part geometry. The overlapping spot welds distribute heat more evenly, minimizing the risk of elevated temperatures during the AM process. In addition, the resulting dense and uniform weld beads contribute to lower residual stresses in the printed part.

Originality/value

To the best of the authors’ knowledge, this is the first study to thoroughly investigate SPW as a scanning strategy using the LFP process. In general, SPW presents a promising strategy for securing embedded sensors into LFP parts while minimizing residual stresses.

Details

Rapid Prototyping Journal, vol. 31 no. 1
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 14 October 2021

Boppana V. Chowdary and Deepak Jaglal

This paper aims to present a reverse engineering (RE) approach for three-dimensional (3D) model reconstruction and fast prototyping (FP) of broken chess pieces.

321

Abstract

Purpose

This paper aims to present a reverse engineering (RE) approach for three-dimensional (3D) model reconstruction and fast prototyping (FP) of broken chess pieces.

Design/methodology/approach

A case study involving a broken chess piece was selected to demonstrate the effectiveness of the proposed unconventional RE approach. Initially, a laser 3D scanner was used to acquire a (non-uniform rational B-spline) surface model of the object, which was then processed to develop a parametric computer aided design (CAD) model combined with geometric design and tolerancing (GD&T) technique for evaluation and then for FP of the part using a computer numerical controlled (CNC) machine.

Findings

The effectiveness of the proposed approach for reconstruction and FP of rotational parts was ascertained through a sample part. The study demonstrates non-contact data acquisition technologies such as 3D laser scanners together with RE systems can support to capture the entire part geometry that was broken/worn and developed quickly through the application of computer aided manufacturing principles and a CNC machine. The results indicate that design communication, customer involvement and FP can be efficiently accomplished by means of an integrated RE workflow combined with rapid product development tools and techniques.

Originality/value

This research established a RE approach for the acquisition of broken/worn part data and the development of parametric CAD models. Then, the developed 3D CAD model was inspected for accuracy by means of the GD&T approach and rapidly developed using a CNC machine. Further, the proposed RE led FP approach can provide solutions to similar industrial situations wherein agility in the product design and development process is necessary to produce physical samples and functional replacement parts for aging systems in a short turnaround time.

Details

Journal of Engineering, Design and Technology, vol. 21 no. 5
Type: Research Article
ISSN: 1726-0531

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Book part
Publication date: 26 January 2022

Miriam Belblidia and Chenier Kliebert

As communities grappled with a slew of concurrent disasters in 2020, grassroots mutual aid regained prominence, providing lessons for a more equitable approach to emergency…

Abstract

As communities grappled with a slew of concurrent disasters in 2020, grassroots mutual aid regained prominence, providing lessons for a more equitable approach to emergency management. Within emergency management, “mutual aid” has come to mean the specific legal mechanisms by which governments, non-governmental organizations, and private sector entities share resources. However, the term “mutual aid” has a much longer history of functioning outside of government and emergency management circles. With a recorded history in Black and Creole communities dating back to the mid-1700s, it has been widely used within communities of color for centuries. To see grassroots mutual aid in practice, the authors present a case study of Imagine Water Works’ Mutual Aid Response Network (MARN) in New Orleans, which was developed in 2019 and responded to the COVID-19 pandemic and a record-breaking Gulf Coast hurricane season in 2020. Utilizing Facebook as a platform, the MARN’s “Imagine Mutual Aid (New Orleans)” group saw its membership grow by 5,000 members from March 2020 to March 2021. Within the first week of Hurricane Laura’s landfall, the group welcomed evacuated individuals from Southwest Louisiana and quickly facilitated thousands of requests for support, providing food, housing, clothing, medical devices, emotional support, emergency cash, laundry services, and personalized care for those in non-congregate shelters, as well as locally informed flood and hurricane preparedness information for subsequent storms. Grassroots mutual aid sheds light on root causes and existing gaps within emergency management and provides a model for autonomous community care.

Details

Justice, Equity, and Emergency Management
Type: Book
ISBN: 978-1-83982-332-9

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