Engineering Computations: International Journal for Computer-Aided Engineering and Software

M. Vázquez; A. Dervieux; B. Koobus

doi: 10.1108/02644400610661145pmid: N/A

Purpose – To propose an integrated algorithm for aerodynamic shape optimization of aircraft wings under the effect of aeroelastic deformations at supersonic regime. Design/methodology/approach – A methodology is proposed in which a high‐fidelity aeroelastic analyser and an aerodynamic optimizer are loosely coupled. The shape optimizer is based on a “CAD‐free” approach and an exact gradient method with a single adjoint state. The global iterative process yields optimal shapes in the at‐rest condition (i.e. with the aeroelastic deformations substracted). Findings – The methodology was tested under different conditions, taking into account a combined optimization goal: to reduce the sonic boom production, while preserving the aerodynamic performances of flexible wings. The objective function model contains both aerodynamic parameters and an acoustic term based on the sonic boom downwards emission. Practical implications – This paper proposes a shape optimization methodology developed by researchers but aiming at the final strategic goal of creating tools that can be really integrated in design processes. Originality/value – The paper presents an original loosely coupled method for the shape optimization of flexible wings in which recent and modern techniques are used at different levels of the global algorithm: the aerodynamic optimizer, the aeroelastic analyser, the shape parametrization and the objective function model.

Minvydas Ragulskis; Liutauras Ragulskis

doi: 10.1108/02644400610661154pmid: N/A

Purpose – To develop order adaptive integration rule without limitation requiring that the number of equally spaced nodes must be a divisible numeral. Such integration technique could be of great practical value for different engineering applications where partition adaptability is impossible and use of standard high order integration techniques is unfeasible due to the fact that a significant number of nodes at the end of the sampling sequence must be deleted until the needed divisibility of the number of nodes is achieved. Design/methodology/approach – Finite element approximation is used for the subdivision of the domain of integration and the development of order adaptive integration rule. Findings – New integration rule is developed. It has a number of interesting features. Weights of the internal nodes are equivalent and equal to one. That makes the computational implementation of the integration rule very easy. Weights not equal to one are located only at the beginning and at the end of the sequence and are symmetric. For an m ‐th order rule the number of weights not equal to one is 2 m if m is odd. Originality/value – For different engineering applications where the integration order can be controlled without changing the number of nodes, especially for real time applications where the number of discrete samples is unknown before the experiment.

J. Pina‐Henriques; Paulo B. Lourenço

doi: 10.1108/02644400610661163pmid: N/A

Purpose – To contribute for a reliable estimation of the compressive strength of unreinforced masonry from the properties of the constituents (units and mortar). Design/methodology/approach – Sophisticated non‐linear continuum models, based on damage, plasticity, cracking or other formulation, are today standard in several finite element programs. The adequacy of such models to provide reliable estimates of masonry compressive strength, from the properties of the constituents, remains unresolved. The authors have shown recently that continuum models might significantly overestimate the prediction of the compressive strength. Hence, an alternative phenomenological approach developed in a discrete framework is proposed, based on attributing to masonry components a fictitious micro‐structure composed of linear elastic particles separated by non‐linear interface elements. The model is discussed in detail and a comparison with experimental results and numerical results using a standard continuum model is provided. Findings – Clear advantages in terms of compressive strength and peak strain prediction were found using the particle model when compared with standard continuum models. Moreover, compressive and tensile strength values provided by the model were found to be particle size‐ and particle distortion‐independent for practical purposes. It is also noted that size‐dependent responses were obtained and that shear parameters rather than tensile parameters were found to play a major role at the meso‐level of the phenomenological model. Originality/value – This paper provides further insight into the compressive behaviour of quasi‐brittle materials, with an emphasis on the strength prediction of masonry composites. Reliable prediction of masonry strength is of great use in the civil engineering field, allowing one to reduce experimental testing in expensive wallets and to avoid the usage of conservative empirical formulae.

Mile R. Vujičić

doi: 10.1108/02644400610661172pmid: N/A

Purpose – To provide an analysis of transient heat conduction, which is solved using different iterative solvers for graduate and postgraduate students (researchers) which can help them develop their own research. Design/methodology/approach – Three‐dimensional transient heat conduction in homogeneous materials using different time‐stepping methods such as finite difference (Θ explicit, implicit and Crank‐Nicolson) and finite element (weighted residual and least squared) methods. Iterative solvers used in the paper are conjugate gradient (CG), preconditioned gradient, least square CG, conjugate gradient squared (CGS), preconditioned CGS, bi‐conjugate gradient (BCG), preconditioned BCG, bi‐conjugate gradient stabilized (BCGSTAB), reconditioned BCGSTAB and Gaussian elimination with incomplete Cholesky factorization. Findings – Provides information on which time‐stepping method is the most accurate, which solver is the fastest to solve a symmetric and positive system of linear matrix equations of all those considered. Practical implications – Fortran 90 code given as an abstract can be very useful for graduate and postgraduate students to develop their own code. Originality/value – This paper offers practical help to an individual starting his/her research in the finite element technique and numerical methods.

Grant Steven

doi: 10.1108/02644400610661181pmid: N/A

Purpose – To describe the mathematics, mechanics and computer code that are involved in deriving the mechanical properties of a 3D composite material with a complicated internal architecture. To inform the reader how an application programming interface (API) can be used with a commercial FEA code to undertake the task. Finally to validate the process an demonstrate the versatility of the process. Design/methodology/approach – The complex architecture of the composite is imported to an FEA environment and meshed. The special code is written in Pascal that applies six sets of constraints to simulate unit strain vectors on a cell of the composite. After six separate analyses are undertaken, the forces necessary to achieve the boundary constraints are summed to provide stresses and hence the necessary coefficients in the stress to strain relationship for the composite. After global FEA the strains in the homogenized material are used as input to the inverse homogenizer so that stress and strain levels in the individual ingredients of the composite can be calculated for the purposes of assessing failure. Findings – The process of writing separate code to operate in conjunction with a commercial FEA code was found to be very reliable, time‐effective and can be of great benefit to engineers researching with composites. Research limitations/implications – At this state all the materials can only be stressed within their elastic limit. There is no logical impediment to extending the algorithm to increase stresses into the non‐linear range. Practical implications – The use of the API environment allows third parties to develop application‐specific code that overcomes the increasing generality of commercial FEA codes. The author can easily make the research available to the whole engineering and materials community without losing any intellectual property. Originality/value – The practical results of this research are now freely available to the whole community and the work demonstrates in a general way how researchers can make their work available without having to write any FEA code, only the things they have researched.

Murat Tunç; Ünal Çamdali; Cem Parmaksizoğlu; Sermet Çikrikçi

doi: 10.1108/02644400610661190pmid: N/A

Purpose – Cancer is the foremost disease that causes death. The objective of hyperthermia in cancer therapy is to raise the temperature of cancerous tissue above a therapeutic value while maintaining the surrounding normal tissue at sublethal temperature values in cases where surgical intervention is dangerous or impossible. The malignant tissue is heated up to 42°C in the treatment. In this method, the unaffected tissues are aimed to have minimum damage, while the affected ones are destroyed. Therefore, it is very important for the optimization of the method to know the temperature profiles in both tissues. Accurately estimating the tissue temperatures has been a very important issue for tumor hyperthermia treatment planning. This paper, proposes to theoretically predict the temperature response of the biological tissues subject to external EM heating by using the space‐dependent blood perfusion term in Pennes bio‐heat equation. Design/methodology/approach – The bio‐heat transfer equation is parabolic partial differential equation. Grid points including independent variables are initially formed in solution of partial differential equation by finite element method. In this study, one dimensional bio‐heat transfer equation is solved by flex‐PDE finite element method. Findings – In this study, the bio‐heat transfer equation is solved for variable blood perfusion values and the temperature field resulting after a hyperthermia treatment is obtained. Homogeneous, non‐homogeneous tissue and constant, variable blood perfusion rates are considered in this study to display the temperature fields in the biological material exposed to externally induced electromagnetic irradiation. Originality/value – Temperature‐dependent tissue thermophysical properties have been used and the Pennes equation is solved by FEM analysis. Variable blood perfusion and heat generation values have been used in calculations for healthy tissue and tissue with tumor.