Search results

1 – 10 of over 18000
Article
Publication date: 30 March 2022

Farzad Shafiei Dizaji and Mehrdad Shafiei Dizaji

The purpose is to reduce round-off errors in numerical simulations. In the numerical simulation, different kinds of errors may be created during analysis. Round-off error is one…

Abstract

Purpose

The purpose is to reduce round-off errors in numerical simulations. In the numerical simulation, different kinds of errors may be created during analysis. Round-off error is one of the sources of errors. In numerical analysis, sometimes handling numerical errors is challenging. However, by applying appropriate algorithms, these errors are manageable and can be reduced. In this study, five novel topological algorithms were proposed in setting up a structural flexibility matrix, and five different examples were used in applying the proposed algorithms. In doing so round-off errors were reduced remarkably.

Design/methodology/approach

Five new algorithms were proposed in order to optimize the conditioning of structural matrices. Along with decreasing the size and duration of analyses, minimizing analytical errors is a critical factor in the optimal computer analysis of skeletal structures. Appropriate matrices with a greater number of zeros (sparse), a well structure and a well condition are advantageous for this objective. As a result, a problem of optimization with various goals will be addressed. This study seeks to minimize analytical errors such as rounding errors in skeletal structural flexibility matrixes via the use of more consistent and appropriate mathematical methods. These errors become more pronounced in particular designs with ill-suited flexibility matrixes; structures with varying stiffness are a frequent example of this. Due to the usage of weak elements, the flexibility matrix has a large number of non-diagonal terms, resulting in analytical errors. In numerical analysis, the ill-condition of a matrix may be resolved by moving or substituting rows; this study examined the definition and execution of these modifications prior to creating the flexibility matrix. Simple topological and algebraic features have been mostly utilized in this study to find fundamental cycle bases with particular characteristics. In conclusion, appropriately conditioned flexibility matrices are obtained, and analytical errors are reduced accordingly.

Findings

(1) Five new algorithms were proposed in order to optimize the conditioning of structural flexibility matrices. (2) A JAVA programming language was written for all five algorithms and a friendly GUI software tool is developed to visualize sub-optimal cycle bases. (3) Topological and algebraic features of the structures were utilized in this study.

Research limitations/implications

This is a multi-objective optimization problem which means that sparsity and well conditioning of a matrix cannot be optimized simultaneously. In conclusion, well-conditioned flexibility matrices are obtained, and analytical errors are reduced accordingly.

Practical implications

Engineers always finding mathematical modeling of real-world problems and make them as simple as possible. In doing so, lots of errors will be created and these errors could cause the mathematical models useless. Applying decent algorithms could make the mathematical model as precise as possible.

Social implications

Errors in numerical simulations should reduce due to the fact that they are toxic for real-world applications and problems.

Originality/value

This is an original research. This paper proposes five novel topological mathematical algorithms in order to optimize the structural flexibility matrix.

Details

Engineering Computations, vol. 39 no. 6
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 1 February 1955

J.H. Argyris

THE general theorems given in Sections 4 and 6 include, from the fundamental point of view, all that is required for the analysis of redundant structures. However, to facilitate…

Abstract

THE general theorems given in Sections 4 and 6 include, from the fundamental point of view, all that is required for the analysis of redundant structures. However, to facilitate practical calculations it is helpful to develop more explicit methods and formulae. To find these is the purpose of this Section.

Details

Aircraft Engineering and Aerospace Technology, vol. 27 no. 2
Type: Research Article
ISSN: 0002-2667

Article
Publication date: 1 May 1959

J.H. Argyris and S. Kelsey

The flexibility matrices for the unassembled structural elements are discussed and a more concise form developed appropriate to the fuselage structure. A general method is given…

33

Abstract

The flexibility matrices for the unassembled structural elements are discussed and a more concise form developed appropriate to the fuselage structure. A general method is given for obtaining self‐equilibrating flange load and shear flow systems in a single‐cell fuselage, the primary redundancies being defined by a simple transformation matrix. The particular matrix based on the orthogonal stress systems for a circular section is especially convenient. A slight extension of the equations leads also to alternative statically equivalent stress systems in the cover.

Details

Aircraft Engineering and Aerospace Technology, vol. 31 no. 5
Type: Research Article
ISSN: 0002-2667

Article
Publication date: 10 August 2015

Maryam Daei and S. Hamid Mirmohammadi

The interest in the ability to detect damage at the earliest possible stage is pervasive throughout the civil engineering over the last two decades. In general, the experimental…

Abstract

Purpose

The interest in the ability to detect damage at the earliest possible stage is pervasive throughout the civil engineering over the last two decades. In general, the experimental techniques for damage detection are expensive and require that the vicinity of the damage is known and readily accessible; therefore several methods intend to detect damage based on numerical model and by means of minimum experimental data about dynamic properties or response of damaged structures. The paper aims to discuss these issues.

Design/methodology/approach

In this paper, the damage detection problem is formulated as an optimization problem such as to obtain the minimum difference between the numerical and experimental variables, and then a modified ant colony optimization (ACO) algorithm is proposed for solving this optimization problem. In the proposed algorithm, the structural damage is detected by using dynamically measured flexibility matrix, since the flexibility matrix of the structure can be estimated from only the first few modes. The continuous version of ACO is employed as a probabilistic technique for solving this computational problem.

Findings

Compared to classical methods, one of the main strengths of this meta-heuristic method is the generally better robustness in achieving global optimum. The efficiency of the proposed algorithm is illustrated by numerical examples. The proposed method enables the deduction of the extent and location of structural damage, while using short computational time and resulting good accuracy.

Originality/value

Finding accurate results by means of minimum experimental data, while using short computational time is the final goal of all researches in the structural damage detection methods. In this paper, it gains by applying flexibility matrix in the definition of objective function, and also via using continuous ant colony algorithm as a powerful meta-heuristic techniques in the constrained nonlinear optimization problem.

Details

Multidiscipline Modeling in Materials and Structures, vol. 11 no. 2
Type: Research Article
ISSN: 1573-6105

Keywords

Article
Publication date: 1 March 1955

J.H. Argyris

HAVING discussed in the standard longhand notation the main ideas and methods for the calculation of redundant structures on the basis of forces as unknowns we now turn our…

Abstract

HAVING discussed in the standard longhand notation the main ideas and methods for the calculation of redundant structures on the basis of forces as unknowns we now turn our attention to the matrix formulation of the analysis. Consider a system consisting of s structural elements with a total number n of redundancies which may be forces (stresses), moments or any generalized forces. We select a basic system by ‘cutting’ a number r of redundancies where r<n. Thus, the simple idea of a statically determinate basic system (r=n) is but a particular case of our investigations.

Details

Aircraft Engineering and Aerospace Technology, vol. 27 no. 3
Type: Research Article
ISSN: 0002-2667

Article
Publication date: 6 December 2017

Ruchi Mishra and Onkar Nath Mishra

The purpose of this paper is to propose a novel hybrid approach to assess marketing-based flexibility with respect to its source factors, enablers and attributes.

Abstract

Purpose

The purpose of this paper is to propose a novel hybrid approach to assess marketing-based flexibility with respect to its source factors, enablers and attributes.

Design/methodology/approach

The study demonstrates an application of a hybrid principal component analysis (PCA)-analytical hierarchical process (AHP)-multi-grade fuzzy approach (MFA) to measure marketing-based flexibility. Using PCA method, attributes, enablers and source factors of marketing-based flexibility were identified and a conceptual model was developed. AHP and MFA were used to compute marketing-based flexibility index.

Findings

The proposed approach measures existing level of marketing-based flexibility and therefore it identifies weak areas that should be taken care to improve flexibility.

Research limitations/implications

The scope of the study is limited to plant level. The validity of the proposed approach is shown using a case study. For generalisation point of view, the application of this proposed approach should be investigated in a large number of firms in different industrial settings.

Practical implications

The study gives a reliable and valid method, which combines both statistical and MCDM techniques to measure existing level of flexibility and identify weak areas for flexibility improvement.

Originality/value

The findings provide insight into factors that should be worked upon to improve flexibility.

Details

Marketing Intelligence & Planning, vol. 36 no. 2
Type: Research Article
ISSN: 0263-4503

Keywords

Article
Publication date: 1 August 1959

J.H. Argyris and S. Kelsey

The derived data matrices established for the basic system in the previous issues are assembled to give the compatibility equations from whose solution the redundancies are…

Abstract

The derived data matrices established for the basic system in the previous issues are assembled to give the compatibility equations from whose solution the redundancies are obtained. The assembly is presented in detail to show the necessary submatrix operations required in the computer. The general solution of the compatibility equations leads to the complete stress distribution and deformation of the regularized fuselage due to external loads, wing or tail interaction redundancies and to thermal strains. From these wc obtain, by use of the cut‐out and modification technique, the corresponding results for the actual fuselage as an independent structure. The interaction redundancies at the wing and tail unit attachments are determined on the assumption that these components are also analysed by the Force Method. Hence the final stress distribution is obtained for the fuselage as an integral part of the complete aircraft structure.

Details

Aircraft Engineering and Aerospace Technology, vol. 31 no. 8
Type: Research Article
ISSN: 0002-2667

Article
Publication date: 25 September 2019

Rajesh Kumar Singh and Pravin Kumar

In complex business environment of today, organizations are trying to be flexible and agile for meeting dynamic demands of customers in terms of product variety, cost cutting and…

Abstract

Purpose

In complex business environment of today, organizations are trying to be flexible and agile for meeting dynamic demands of customers in terms of product variety, cost cutting and decreasing product life cycle. The main purpose of this paper is to identify different attributes of flexibility and to propose an approach for evaluating flexibility index of a supply chain.

Design/methodology/approach

Total 33 factors are identified from the literature and further clustered into six major groups. They are top management commitment, organizational factors, mutual understanding, flow of information, relationship and decision-making and responsiveness. On the basis of these factors, an index has been developed by using graph theory matrix approach to evaluate the flexibility intensity of the supply chain for the firm in consideration.

Findings

The proposed approach has been illustrated in context to an Indian automobile organization, and value of the flexibility index has been evaluated. Framework proposed will help the supply chain managers to evaluate the flexibility index of their respective organizations.

Research limitations/implications

As values taken for different flexibility sub-factors are based on inputs given by managers of case organization, chances of bias may be there. Therefore, a study may be validated with more case studies to validate the proposed framework. Based on the flexibility index, organizations can find their strong and weak areas for strategy development.

Originality/value

A firm can also compare the flexibility index of its own supply chain with other’s supply chain or with the best in the industry for benchmarking purpose. Benchmarking of flexibility will help organizations in developing strategies to compete in dynamic market scenario.

Details

Journal of Global Operations and Strategic Sourcing, vol. 13 no. 1
Type: Research Article
ISSN: 2398-5364

Keywords

Article
Publication date: 1 March 1959

J.H. Argyris and S. Kelsey

A DSIR Sponsored Research Programme on the Development and Application of the Matrix Force Method and the Digital Computer. This work presents a rational method for the structural…

Abstract

A DSIR Sponsored Research Programme on the Development and Application of the Matrix Force Method and the Digital Computer. This work presents a rational method for the structural analysis of stressed skin fuselages for application in conjunction with the digital computer. The theory is a development of the matrix force method which permits a close integration of the analysis and the programming for a computer operating with a matrix interpretive scheme. The structural geometry covered by the analysis is sufficiently arbitrary to include most cases encountered in practice, and allows for non‐conical taper, double‐cell cross‐sections and doubly connected rings. An attempt has been made to produce a highly standardized procedure requiring as input information only the simplest geometrical and elastic data. An essential feature is the use of the elimination and modification technique subsequent to the main analysis of the regularized structure in which all cutouts have been filled in. Current Summary A critical historical appraisal of previous work in the Western World on fuselage analysis is given in the present issue together with an outline of the ideas underlying the new theory.

Details

Aircraft Engineering and Aerospace Technology, vol. 31 no. 3
Type: Research Article
ISSN: 0002-2667

Article
Publication date: 14 June 2019

I St Doltsinis

The employment of spring cell substitutes for the numerical analysis of solids and structures in place of finite elements has occasioned research on the subject with regard to…

Abstract

Purpose

The employment of spring cell substitutes for the numerical analysis of solids and structures in place of finite elements has occasioned research on the subject with regard to both, the applicability of existing approaches and the advancement of concepts. This paper aims to explore in the context of linear elasticity the substitution of the simplex tetrahedral element in space and the triangle in the plane by corresponding spring cells deduced on a flexibility basis using the natural formalism.

Design/methodology/approach

The natural formalism is characterized by the homogeneous definition of strain and stress along the lines connecting nodes of the simplex tetrahedron and the triangle. The elastic compliance involves quantities along the prospective spring directions and offers itself for the transition to the spring cell. The diagonal entities are interpreted immediately as spring flexibilities, the off-diagonal terms account for the completeness of the substitution. In addition to the isotropic elastic material, the concept is discussed for anisotropic elasticity in the plane.

Findings

The natural point of view establishes the spring cell as part of the continuum element. The simplest configuration of pin-joined bars discards all geometrical and physical cross effects. The approach is attracting by its transparent simplicity, revealing deficiencies of the spring cell and identifying directly conditions for the complete substitution of the finite element.

Research limitations/implications

The spring cell counterparts of the tetrahedral- and the triangular finite elements allow employment in problems in three and two dimensions. However, the deficient nature of the approximation requires attention in the design of the discretization lattice such that the conditions of complete finite element substitution are approached as close as possible.

Practical implications

Apart from plane geometries, triangular spring cells have been assembled to lattice models of space structures such as membrane shells and similar. Tetrahedral cells have been used, in modelling plates and shell structures exhibiting bending stiffness.

Originality/value

The natural formalism of simplex finite elements in three and two dimensions is used for defining spring cells on a flexibility basis and exploring their properties. This is a novel approach to spring cells and an original employment of the natural concept in isotropic and anisotropic elasticity.

Details

Engineering Computations, vol. 36 no. 5
Type: Research Article
ISSN: 0264-4401

Keywords

1 – 10 of over 18000