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Article
Publication date: 1 May 2000

D.S. Liyanapathirana, A.J. Deeks and M.F. Randolph

In finite element analysis of pile driving, the nodes of the finite element mesh are the most important locations for output stresses. Especially at the pile‐soil…

Abstract

In finite element analysis of pile driving, the nodes of the finite element mesh are the most important locations for output stresses. Especially at the pile‐soil interface, it is essential to obtain accurate nodal stresses. Several global and local stress smoothing methods available in the literature were reviewed and examined. Global methods are found to be computationally expensive, so results obtained from several local stress smoothing methods are compared. It is shown that accurate nodal stresses can be obtained by approximating the stress distribution inside four‐element patches by a polynomial with order equal to the order of the shape functions. Equally good results can be obtained by approximating the stress distribution inside each element by a bilinear surface. When a method taking into account both equilibrium and boundary conditions was applied, a set of ill‐conditioned matrices was produced for the four‐element patches. Such methods are therefore not recommended.

Details

Engineering Computations, vol. 17 no. 3
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 30 September 2019

Rong Li and Jun Xiong

An accurate prediction of process-induced residual stress is necessary to prevent large distortion and cracks in gas metal arc (GMA)-based additive manufactured parts…

Abstract

Purpose

An accurate prediction of process-induced residual stress is necessary to prevent large distortion and cracks in gas metal arc (GMA)-based additive manufactured parts, especially thin-walled parts. The purpose of this study is to present an investigation into predicting the residual stress distributions of a thin-walled component with geometrical features.

Design/methodology/approach

A coupled thermo-mechanical finite element model considering a general Goldak double ellipsoidal heat source is built for a thin-walled component with geometrical features. To confirm the accuracy of the model, corresponding experiments are performed using a positional deposition method in which the torch is tilted from the normal direction of the substrate. During the experiment, the thermal cycle curves of locations on the substrate are obtained by thermocouples. The residual stresses on the substrate and part are measured using X-ray diffraction. The validated model is used to investigate the thermal stress evolution and residual stress distributions of the substrate and part.

Findings

Decent agreements are achieved after comparing the experimental and simulated results. It is shown that the geometrical feature of the part gives rise to an asymmetrical transversal residual stress distribution on the substrate surface, while it has a minimal influence on the longitudinal residual stress distribution. The residual stress distributions of the part are spatially uneven. The longitudinal tensile residual stress is the prominent residual stress in the central area of the component. Large wall-growth tensile residual stresses, which may cause delamination, appear at both ends of the component and the substrate–component interfaces.

Originality/value

The predicted residual stress distributions of the thin-walled part with geometrical features are helpful to understand the influence of geometry on the thermo-mechanical behavior in GMA-based additive manufacturing.

Details

Rapid Prototyping Journal, vol. 26 no. 2
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 1 February 1998

Claudio Ruggieri and Robert H. Dodds

Describes a probabilistic methodology for fracture assessments of flawed structures constructed of ferritic steels using the research code WSTRESS. The probabilistic…

Abstract

Describes a probabilistic methodology for fracture assessments of flawed structures constructed of ferritic steels using the research code WSTRESS. The probabilistic formulation for cleavage fracture implements a multiaxial form of the weakest link model which couples the macroscopic fracture behavior with a micromechanics model based on the statistics of microcracks. The Weibull stress, σw, emerges as a suitable near‐tip parameter to provide a connection between the microregime of failure and remote loading (J). WSTRESS builds on an iterative procedure to incorporate a 3‐D finite element description of the crack‐tip stress field and measured values of fracture toughness to calibrate the Weibull modulus, m, and the scale parameter, σu. Specific features of the code include statistical inference of Weibull parameters based on uncensored and censored models (with maximum likelihood method), construction of confidence intervals, several definitions for the near‐tip fracture process zone and other general facilities such as spatial integration of the stress field (to incorporate the random orientation of microcracks) and stochastic simulation of fracture data using the Monte Carlo method. The code also includes a convenient free‐form command language and a seamless interface with finite element results files stored in Patran binary or ASCII format.

Details

Engineering Computations, vol. 15 no. 1
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 1 November 1962

K.B. Ayers

Thermal stresses due to arbitrary temperature distributions are calculated for beams of I‐section or of multicell sections which can be considered to be built up from…

Abstract

Thermal stresses due to arbitrary temperature distributions are calculated for beams of I‐section or of multicell sections which can be considered to be built up from I‐section units. Stress distributions are presented graphically for a wide range of the parameters involved. It is shown that for a high‐speed aircraft the thermal stresses alone could produce plasticity in a homogeneous structure.

Details

Aircraft Engineering and Aerospace Technology, vol. 34 no. 11
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 24 June 2019

Jan Karthaus, Silas Elfgen and Kay Hameyer

Magnetic properties of electrical steel are affected by mechanical stress. In electrical machines, influences because of manufacturing and assembling and because of…

Abstract

Purpose

Magnetic properties of electrical steel are affected by mechanical stress. In electrical machines, influences because of manufacturing and assembling and because of operation cause a mechanical stress distribution inside the steel lamination. The purpose of this study is to analyse the local mechanical stress distribution and its consequences for the magnetic properties which must be considered when designing electrical machines.

Design/methodology/approach

In this paper, an approach for modelling stress-dependent magnetic material properties such as magnetic flux density using a continuous local material model is presented.

Findings

The presented model shows a good approximation to measurement results for mechanical tensile stress up to 100 MPa for the studied material.

Originality/value

The presented model allows a simple determination of model parameters by using stress-dependent magnetic material measurements. The model can also be used to determine a scalar mechanical stress distribution by using a known magnetic flux density distribution.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 38 no. 4
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 1 February 2016

Miguel Abambres and Wai-Meng Quach

Although the actual residual stress distribution in any structural steel member can be only obtained by experimental measurements, it is known to be a difficult, tedious…

Abstract

Purpose

Although the actual residual stress distribution in any structural steel member can be only obtained by experimental measurements, it is known to be a difficult, tedious and inefficient piece of work with limited accuracy. Thus, besides aiming at clarifying structural designers and researchers about the possible ways of modelling residual stresses when performing finite element analysis (FEA), the purpose of this paper is to provide an effective literature review of the longitudinal membrane residual stress analytical expressions for carbon steel non-heavy sections, covering a vast range of structural shapes (plates, I, H, L, T, cruciform, SHS, RHS and LSB) and fabrication processes (hot-rolling, welding and cold-forming).

Design/methodology/approach

This is a literature review.

Findings

Those residual stresses are those often required as input of numerical analyses, since the other types are approximately accounted for through the s-e curves of coupons cut from member walls.

Practical implications

One of the most challenging aspects in FEA aimed to simulate the real behaviour of steel members, is the modelling of residual stresses.

Originality/value

Besides aiming at clarifying structural designers and researchers about the possible ways of modelling residual stresses when performing FEA, this paper also provides an effective literature review of the longitudinal membrane residual stress analytical expressions for carbon steel non-heavy sections, covering a vast range of structural shapes (plates, I, H, L, T, cruciform, SHS, RHS and LSB) and fabrication processes (hot-rolling, welding and cold-forming).

Details

International Journal of Structural Integrity, vol. 7 no. 1
Type: Research Article
ISSN: 1757-9864

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Article
Publication date: 16 November 2012

Khalil Farhangdoost and Abbas Hosseini

The bodies of aircraft structures have a lot of fastener holes and under different situations these holes bear external forces, which cause a tensile stress on the surface…

Abstract

Purpose

The bodies of aircraft structures have a lot of fastener holes and under different situations these holes bear external forces, which cause a tensile stress on the surface that leads to the failure of materials. Cold expansion process is one of the widely‐used methods to improve the fatigue behavior of materials used in aerospace industry, and such improvement is due to the compressive residual stress around cold expanded hole. The induced residual stress distribution around cold expanded hole is affected by several parameters such as, diametrical interfaces, surface finish of fastener holes, temperature, mandrel speed, i.e. the speed of inserting mandrel into the hole, and so on. In previous studies, most of effective parameters were investigated, whereas, the effect of mandrel speed on the residual stress distribution has not been considered. The present study, seeks to simulate cold expansion process on aluminum alloy 2A12TA using ABAQUS finite element (FE) package and to consider the effect of different mandrel speeds on residual stress distribution around cold expanded hole. It aims to verify the results of FE simulation by experimental data.

Design/methodology/approach

There are two kinds of data in this paper; experimental and FE results. The experimental results for cold expansion process have been extracted from the literature and ABAQUS finite element package was employed in order to simulate the above‐mentioned process. Moreover, FE results were validated by the experiments.

Findings

The results presented here show the influence of mandrel speed on residual stress distribution around cold expanded hole using a new analytical‐numerical method. The results gained by FE simulation show relative differences between the diagrams of residual stress distribution corresponding different mandrel speeds. It is shown in the paper; the residual stress around cold expanded hole rises by the increase of mandrel speed and consequently the improvement of fatigue life will be achieved.

Originality/value

The present study is part of Abbas Hosseini's MSc. dissertation, an original research work.

Details

International Journal of Structural Integrity, vol. 3 no. 4
Type: Research Article
ISSN: 1757-9864

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Article
Publication date: 19 April 2011

S. Samar Ali and S. Kannan

The objective of the paper is to consider the problem of the strength of a manufactured item against stress, when the component follows Weibull failure law. Different…

Abstract

Purpose

The objective of the paper is to consider the problem of the strength of a manufactured item against stress, when the component follows Weibull failure law. Different cases of stress and strength with varying parameters are discussed for the Weibull‐Weibull stress‐strength model considered in this paper. The application of the proposed technique will help in understanding the design methodology of the system and addressing the risks involved in perceived quality and reliability levels by eliminating or at least reducing the risk impact at the design phase.

Design/methodology/approach

Generalised Weibull‐Weibull stress‐strength models have been analysed for different cases of shape parameters for stress and strength to estimate the reliability of the system. The model is generalized using semi‐regenerative stochastic processes with the help of a state space approach to include a repair facility.

Findings

Different cases of stress and strength with varying parameters have been discussed for the Weibull‐Weibull stress‐strength models considered in this paper. The results show how the stress‐strength reliability model is affected by changes in the parameters of stress and strength. The application of the proposed technique will help in understanding the design methodology of the system, and also lead to the problem of addressing the risks involved in perceived quality and reliability levels by eliminating or at least reducing the risk impact in the design phase.

Research limitations/implications

The present study is limited to a few special cases of Weibull‐Weibull stress‐strength models. The authors propose to continue to study the behaviour of general Weibull strength against exponential stress in particular and to identify the shape parameter that maximises the strength reliability.

Practical implications

The application of the proposed technique will help in understanding the design methodology of the system, and also lead to the problem of addressing the risks involved in perceived quality and reliability levels by eliminating or at least reducing the risk impact at the design phase. The model has been extended and generalized to include a repair facility under the assumption that all the random variables involved in the analysis are arbitrarily distributed (i.e. general).

Originality/value

In the Weibull‐Weibull stress‐strength model of reliability, different cases have been considered. In the first case, both parameters of stress‐strength have the same values and are independent of the distribution. In the second case, if the shape parameter of the strength is twice that of the stress, the probability will have a normal distribution with different parameter values. In the third case, if the shape parameter of the stress is twice that of the strength, then probability distribution is a parabolic cylindrical function. The study shows how to proceed in all cases. The model is generalized to include a repair facility, with all the random variables involved in the analysis being arbitrarily distributed using semi‐regenerative stochastic processes.

Details

International Journal of Quality & Reliability Management, vol. 28 no. 4
Type: Research Article
ISSN: 0265-671X

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Article
Publication date: 1 April 1992

JAROSLAV MACKERLE

This bibliography is offered as a practical guide to published papers, conference proceedings papers and theses/dissertations on the finite element (FE) and boundary…

Abstract

This bibliography is offered as a practical guide to published papers, conference proceedings papers and theses/dissertations on the finite element (FE) and boundary element (BE) applications in different fields of biomechanics between 1976 and 1991. The aim of this paper is to help the users of FE and BE techniques to get better value from a large collection of papers on the subjects. Categories in biomechanics included in this survey are: orthopaedic mechanics, dental mechanics, cardiovascular mechanics, soft tissue mechanics, biological flow, impact injury, and other fields of applications. More than 900 references are listed.

Details

Engineering Computations, vol. 9 no. 4
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 1 June 1956

A.E. Johnson

TURBINE disks of jet propulsion units operate under conditions of considerable complexity for which steam turbine practice and experience afford little assistance in…

Abstract

TURBINE disks of jet propulsion units operate under conditions of considerable complexity for which steam turbine practice and experience afford little assistance in matters of calculation and design.

Details

Aircraft Engineering and Aerospace Technology, vol. 28 no. 6
Type: Research Article
ISSN: 0002-2667

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