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Abstract

Purpose

Traditional gas tungsten arc welding (GTAW) and GTAW-based wire and arc additive manufacturing (WAAM) are notably different. These differences are crucial to the process stability and surface quality in GTAW WAAM. This paper addresses special characteristics and the process control method of GTAW WAAM. The purpose of this paper is to improve the process stability with sensor information fusion in omnidirectional GTAW WAAM process.

Design/methodology/approach

A wire feed strategy is proposed to achieve an omnidirectional GTAW WAAM process. Thus, a model of welding voltage with welding current and arc length is established. An automatic control system fit to the entire GTAW WAAM process is established using both welding voltage and welding current. The effect of several types of commonly used controllers is examined. To assess the validity of this system, an arc length step experiment, various wire feed speed experiments and a square sample experiment were performed.

Findings

The research findings show that the resented wire feed strategy and arc length control system can effectively guarantee the stability of the GTAW WAAM process.

Originality/value

This paper tries to make a foundation work to achieve omnidirectional welding and process stability of GTAW WAAM through wire feed geometry analysis and sensor information fusion control model. The proposed wire feed strategy is implementable and practical, and a novel sensor fusion control method has been developed in the study for varying current GTAW WAAM process.

Details

Rapid Prototyping Journal, vol. 25 no. 5
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 7 March 2016

Stefan May, Julien Vignollet and René de Borst

– The purpose of this paper is to introduce a new arc-length control method for physically non-linear problems based on the rates of the internal and the dissipated energy.

Abstract

Purpose

The purpose of this paper is to introduce a new arc-length control method for physically non-linear problems based on the rates of the internal and the dissipated energy.

Design/methodology/approach

In this paper, the authors derive from the second law of thermodynamics the arc-length method based on the rate of the dissipated energy and from the time derivative of the energy density the arc-length method based on the rate of the internal energy.

Findings

The method requires only two parameters and can automatically trace equilibrium paths which display multiple snap-through and/or snap-back phenomena.

Originality/value

A fully energy-based control procedure is developed, which facilitates switching between dissipative and non-dissipative arc-length control equations in a natural way. The method is applied to a plate with an eccentric hole using the phase field model for brittle fracture and to a perforated beam using interface elements with decohesion.

Details

Engineering Computations, vol. 33 no. 1
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 1 July 2006

M. Rezaiee‐Pajand and H.R. Vejdani‐Noghreiyan

The aim of this paper is to develop a new method for finding multiple bifurcation points in structures.

Abstract

Purpose

The aim of this paper is to develop a new method for finding multiple bifurcation points in structures.

Design/methodology/approach

A brief review of nonlinear analysis is presented. A powerful method (called arc‐length) for tracing nonlinear equilibrium path is described. Techniques for monitoring critical points are discussed to find the rank deficiency of the stiffness matrix. Finally, by using eigenvalue perturbation of tangent stiffness matrix, load parameter associated with multiple bifurcation points is obtained.

Findings

Since other methods of finding simple bifurcation points diverge in the neighborhood of critical points, this paper introduces a new method to find multiple bifurcation points. It should be remembered that a simple bifurcation point is a multiple bifurcation point with rank deficiency equal to one. Therefore, the method is applicable to simple critical points as well.

Practical implications

Global buckling of the structures should be considered in design. Many structures (specially symmetric space structures) have multiple bifurcation points, therefore, analyst and designer should be aware of these points and should control them (for example, by changing the geometry or other related factors) for obtaining a safe and optimum design.

Originality/value

In this paper a robust method to find multiple bifurcation points is introduced. By using this method, engineers can be aware of critical load of multiple bifurcation points to control global buckling of related structures.

Details

Engineering Computations, vol. 23 no. 5
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 1 January 1990

M. Papadrakakis and N. Nomikos

The application of the preconditioned Lanczos method is proposed for the solution of the linearized equations resulting from a non‐linear solution routine based on Newton…

Abstract

The application of the preconditioned Lanczos method is proposed for the solution of the linearized equations resulting from a non‐linear solution routine based on Newton methods. A path‐following solution algorithm with an arc length method is employed for tracing all types of post‐critical branches of a load‐displacement curve. The proposed methodology retains all characteristics of an iterative method by avoiding the complete factorization of the current stiffness matrix. The necessary eigenvalue information is retained in the tridiagonal matrix of the Lanczos approach.

Details

Engineering Computations, vol. 7 no. 1
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 1 January 1978

J.J. Hunter

Welding is becoming increasingly unacceptable as a manual job and this is causing an acceleration in the trend towards automation. This paper briefly reviews some recent…

Abstract

Welding is becoming increasingly unacceptable as a manual job and this is causing an acceleration in the trend towards automation. This paper briefly reviews some recent efforts at automating welding processes, including a program in the UK by the National Engineering Laboratory and the Welding Institute, and considers the future progress and effects of automation in this field.

Details

Industrial Robot: An International Journal, vol. 5 no. 1
Type: Research Article
ISSN: 0143-991X

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Article
Publication date: 1 August 1999

D.P. Mok, W.A. Wall, M. Bischoff and E. Ramm

The present study focusses on algorithmic aspects related to deformation dependent loads in non‐linear static finite element analysis. If the deformation dependency is…

Abstract

The present study focusses on algorithmic aspects related to deformation dependent loads in non‐linear static finite element analysis. If the deformation dependency is considered only on the right hand side, a considerable increase in the number of iterations follows. It may also cause failure of convergence in the proximity of critical points. If in turn the deformation dependent loading is included within the consistent linearization, an additional left hand side term emerges, the so‐called load stiffness matrix. In this paper several numerical test cases are used to show and quantify the influence of the two different approaches on the iteration process. Consideration of the complete load stiffness matrix may result in a cumbersome coding effort, different for each load case, and in certain cases its derivation is even not practicable at all. Therefore also several formulations for approximated load stiffness matrices are presented. It is shown that these simplifications not only reduce the additional effort for linearization and implementation, but also keep the iterative costs relatively small and still allow the calculation of the entire equilibrium path.

Details

Engineering Computations, vol. 16 no. 5
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 30 September 2014

Pedro Miguel de Almeida Areias, Timon Rabczuk and Joaquim Infante Barbosa

– The purpose of this paper is to discuss the linear solution of equality constrained problems by using the Frontal solution method without explicit assembling.

Abstract

Purpose

The purpose of this paper is to discuss the linear solution of equality constrained problems by using the Frontal solution method without explicit assembling.

Design/methodology/approach

Re-written frontal solution method with a priori pivot and front sequence. OpenMP parallelization, nearly linear (in elimination and substitution) up to 40 threads. Constraints enforced at the local assembling stage.

Findings

When compared with both standard sparse solvers and classical frontal implementations, memory requirements and code size are significantly reduced.

Research limitations/implications

Large, non-linear problems with constraints typically make use of the Newton method with Lagrange multipliers. In the context of the solution of problems with large number of constraints, the matrix transformation methods (MTM) are often more cost-effective. The paper presents a complete solution, with topological ordering, for this problem.

Practical implications

A complete software package in Fortran 2003 is described. Examples of clique-based problems are shown with large systems solved in core.

Social implications

More realistic non-linear problems can be solved with this Frontal code at the core of the Newton method.

Originality/value

Use of topological ordering of constraints. A-priori pivot and front sequences. No need for symbolic assembling. Constraints treated at the core of the Frontal solver. Use of OpenMP in the main Frontal loop, now quantified. Availability of Software.

Details

Engineering Computations, vol. 31 no. 7
Type: Research Article
ISSN: 0264-4401

Keywords

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Article
Publication date: 1 February 1997

Amit Dutta and Donald W. White

In the inelastic stability analysis of plated structures, incremental‐iterative finite element methods sometimes encounter prohibitive solution difficulties in the…

Abstract

In the inelastic stability analysis of plated structures, incremental‐iterative finite element methods sometimes encounter prohibitive solution difficulties in the vicinity of sharp limit points, branch points and other regions of abrupt non‐linearity. Presents an analysis system that attempts to trace the non‐linear response associated with these types of problems at minor computational cost. Proposes a semi‐heuristic method for automatic load incrementation, termed the adaptive arc‐length procedure. This procedure is capable of detecting abrupt non‐linearities and reducing the increment size prior to encountering iterative convergence difficulties. The adaptive arc‐length method is also capable of increasing the increment size rapidly in regions of near linear response. This strategy, combined with consistent linearization to obtain the updated tangent stiffness matrix in all iterative steps, and with the use of a “minimum residual displacement” constraint on the iterations, is found to be effective in avoiding solution difficulties in many types of severe non‐linear problems. However, additional procedures are necessary to negotiate branch points within the solution path, as well as to ameliorate convergence difficulties in certain situations. Presents a special algorithm, termed the bifurcation processor, which is effective for solving many of these types of problems. Discusses several example solutions to illustrate the performance of the resulting analysis system.

Details

Engineering Computations, vol. 14 no. 1
Type: Research Article
ISSN: 0264-4401

Keywords

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Article
Publication date: 1 March 1998

Alberto Cardona and Alfredo Huespe

Presents an implementation of continuation methods in the context of a code for flexible multibody systems analysis. These systems are characterized by the simultaneous…

Abstract

Presents an implementation of continuation methods in the context of a code for flexible multibody systems analysis. These systems are characterized by the simultaneous presence of elastic deformation terms and rigid constraints. In our formulation, the latter terms are introduced by an augmented Lagrangian technique, resulting in the presence of Lagrange multipliers in the set of unknowns, together with displacement and rotation associated terms. Essential aspects for a successful implementation are discussed: e.g. the selection of an appropriate metric for computing the path following constraint, a flexible description of control parameters which accounts for conservative and nonconservative loads, imposed displacements and imposed temperatures (dilatation effects), and the inclusion of second order derivatives of rigid constraints in the Jacobian. A large set of examples is presented, with the objective of evaluating the numerical effectiveness of the implemented schemes.

Details

Engineering Computations, vol. 15 no. 2
Type: Research Article
ISSN: 0264-4401

Keywords

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Article
Publication date: 26 June 2009

J.F. Wang, B. Chen, H.B. Chen and S.B. Chen

The purpose of this paper is to analyze the characteristics of sound during gas tungsten argon welding (GTAW), which is very important to effectively monitor the welding…

Abstract

Purpose

The purpose of this paper is to analyze the characteristics of sound during gas tungsten argon welding (GTAW), which is very important to effectively monitor the welding quality in future by using the information extracted from sound.

Design/methodology/approach

The hardware used in the experiment is described. Then the paper researches the influence of welding techniques (gas flow, welding speed, welding current, and arc length) on arc sound and the distribution of the welding sound field. Finally, the relation between welding power and sound are studied based on Fourier transforms and recursive least square methods.

Findings

The sound pressure is affected greatly by gas flow, arc length, and current; welding sound source obeys the dipole model; the sound can be better predicted when the three orders derivative of the welding power are combined together.

Originality/value

This paper provides a new insight into welding sound resource model and a detailed analysis of the influence of the welding sound caused by welding techniques.

Details

Sensor Review, vol. 29 no. 3
Type: Research Article
ISSN: 0260-2288

Keywords

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