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11 – 20 of over 2000GREAT progress has been made in recent years in both fields of aircraft design and manufacture. No longer is the designer completely in the dark regarding the operational loads…
Abstract
GREAT progress has been made in recent years in both fields of aircraft design and manufacture. No longer is the designer completely in the dark regarding the operational loads his aircraft will have to sustain, nor completely ignorant of the capabilities of its structure. Progress has brought knowledge of the sort of operational load likely to be encountered in both flight and landing operations as well as powerful methods of analysis of aircraft structures. Even that, however, is not enough, for without a thorough understanding of the possibilities and properties of the materials at the designer's command, he cannot hope to utilize such knowledge to the full.
Costas A. Charitidis and Dimitrios A. Dragatogiannis
The purpose of this paper is to investigate the use of nanoindentation with a Berkovich indenter as a method of extracting equivalent stress‐strain curves for the base metal and…
Abstract
Purpose
The purpose of this paper is to investigate the use of nanoindentation with a Berkovich indenter as a method of extracting equivalent stress‐strain curves for the base metal and the welded zone of a friction stir welded aluminum alloy.
Design/methodology/approach
Friction stir welding is a solid‐state joining process, which emerged as an alternative technique to be used in high strength alloys that were difficult to join with conventional joining techniques. This technique has a significant effect on the local microstructure and residual stresses combined with deformation. Nano‐ and micro‐indentation are the most commonly used techniques to obtain local mechanical properties of engineering materials. In order to test the reliability of nanoindentation technique and to connect nanoscale with macroscale, the indentation hardness‐depth relation established by Nix and Gao was applied on the experimental values.
Findings
The predictions of this model were found to be in good agreement with classical hardness measurements on AA 6082‐T6 aluminum alloy. Also, finite element method provides a numerical tool to calculate complex nanoindentation problems and in correlation with gradients theories forms a well‐seried tool in order to take into account size effects.
Originality/value
By studying this alloy, the paper reviews fundamental principles such as stress‐strain distribution, size effects rise during nanoindentation and the applicability of finite element method, in order to take into account these issues.
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This paper presents the generalized theory of the most important energy principles in structural analysis. All derive from two basic complementary theorems denoted as the…
Abstract
This paper presents the generalized theory of the most important energy principles in structural analysis. All derive from two basic complementary theorems denoted as the principles of virtual displacements and virtual forces. Both exact and approximate methods are discussed and particular attention is paid to the derivation of upper and lower limits. The theory is not restricted to linearly elastic bodies but includes ab initio the effect of non‐linear stress‐strain laws and thermal strains. Finally the basic principles are illustrated on a number of simple examples in preparation for the more complex ones to appear in Parts II and III.
A FEATURE of many of the light alloys now in common use is that the stress and strain curve often does not evidence any well defined region in which the elastic strain becomes…
Abstract
A FEATURE of many of the light alloys now in common use is that the stress and strain curve often does not evidence any well defined region in which the elastic strain becomes plastic strain, and a linear portion of the diagram from the origin, which in the case of so many metals represents a region of proportionality, is sometimes almost non‐existent, the diagram being curved right from the origin so that it is not possible to define any region or limit of proportionality, and the proof stress; by standard definition, has accordingly a relatively low value compared with the ultimate tensile stress of the alloy concerned. (Fig. 1).
The purpose of this study is to (re-)evaluate the explanatory power of the stressor–stress–strain model and its' current operationalization by examining the influence of general…
Abstract
Purpose
The purpose of this study is to (re-)evaluate the explanatory power of the stressor–stress–strain model and its' current operationalization by examining the influence of general and interaction adjustment and the mediating effect of general satisfaction on expatriates' and spouses' intention to prematurely return from an assignment or overseas location. Though expatriates' premature return intention has been well examined in prior literature, this is the first study to focus on spouses' premature return intention from the expatriate's assignment.
Design/methodology/approach
To evaluate the hypotheses, a sample of 104 expatriates and a sample of 64 spouses were collected and analysed utilizing structural equation modeling.
Findings
The results show that adjustment, as the opposite of distress, is not a direct negative driver of expatriates' nor spouses' premature return intention. Instead, the findings underscore the relevance of the general satisfaction with the international assignment (IA) as a mediator for both expatriates and spouses, which emphasizes the importance of attitudinal factors in the model. Overall, the results indicate that adjustment, in particular interaction adjustment, might not be a timely measure of distress anymore.
Practical implications
In order to reduce expatriates' and spouses' premature return intention multinational corporations should aim at maximizing satisfaction levels during the IA. To achieve this, both should be included in the selection process prior to the IA to tailor support mechanisms to satisfy their expectations.
Originality/value
This study is the first to investigate the premature return intention from the expatriates' and spouses' perspectives, while (re-)evaluating the explanatory power of the stressor–stress–strain model at present.
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This paper aims to study the residual test results under uni-axial compression of tie confined pre-damaged normal strength concrete short columns subjected to elevated…
Abstract
Purpose
This paper aims to study the residual test results under uni-axial compression of tie confined pre-damaged normal strength concrete short columns subjected to elevated temperatures.
Design/methodology/approach
The test variables included temperature of exposure, spacing of transverse confining reinforcement and pre-damage level. An experimental program was designed and carried out involving testing of hoop confined concrete cylindrical specimens exposed to elevated temperatures ranging from room temperature to 900 °C.
Findings
The test results indicate that the residual strength, strain corresponding to the peak stress and the post-peak strains of confined concrete are not affected significantly up to an exposure temperature of 300 °C. However, the peak confined stress falls and the corresponding strain increase considerably in the temperature range of 600 to 900 °C. It is shown that an increase in the degree of confinement reinforcement results in an increased residual strength and deformability of pre-damaged confined concrete.
Research limitations/implications
It is applicable in finding the residual strength and strain of the pre-damaged confined concrete in uni-axial compression after exposure to elevated temperature.
Practical implications
The practical implications is that the test result is applicable in finding the residual strengths of pre-damaged confined concrete under uni-axial compression after exposure to elevated temperature.
Social implications
The main aim of the present investigation is to provide experimental data on the residual behaviour of pre-damaged confined concrete subjected to high temperatures.
Originality/value
The results of this study may be useful for developing the guidelines for designing the confinement reinforcement of reinforced concrete columns against the combined actions of earthquake and fire, as well as for designing the retrofitting schemes after these sequential disasters.
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Qing Xie, Yucai Hu, Yexin Zhou and Wanshui Han
Poor bending response is a major shortcoming of lower-order elements due to excessive representation of shear stress/strain field. Advanced finite element (FE) formulations for…
Abstract
Purpose
Poor bending response is a major shortcoming of lower-order elements due to excessive representation of shear stress/strain field. Advanced finite element (FE) formulations for classical elasticity enhance the bending response by either nullifying or filtering some of the symmetric shear stress/strain modes. Nevertheless, the stress/strain field in Cosserat elasticity is asymmetric; consequently any attempt to nullify or filter the anti-symmetric shear stress/strain modes may lead to failure in the constant couple-stress patch test where the anti-symmetric shear stress/strain field is linear. This paper aims at enhancing the bending response of lower-order elements for Cosserat elasticity problems.
Design/methodology/approach
A four-node quadrilateral and an eight-node hexahedron are formulated by hybrid-stress approach. The symmetric stress is assumed as those of Pian and Sumihara and Pian and Tong. The anti-symmetric stress components are first assumed to be completely linear in order to pass the constant couple-stress patch test. The linear modes are then constrained with respect to the prescribed body-couple via the equilibrium conditions.
Findings
Numerical tests show that the hybrid elements can strictly pass the constant couple-stress patch test and are markedly more accurate than the conventional elements as well as the incompatible elements for bending problems in Cosserat elasticity.
Originality/value
This paper proposes a hybrid FE formulation to improve the bending response of four-node quadrilateral and eight-node hexahedral elements for Cosserat elasticity problems without compromising the constant couple-stress patch test.
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Qing-Yun Deng, Shun-Peng Zhu, Jin-Chao He, Xue-Kang Li and Andrea Carpinteri
Engineering components/structures with geometric discontinuities normally bear complex and variable loads, which lead to a multiaxial and random/variable amplitude stress/strain…
Abstract
Purpose
Engineering components/structures with geometric discontinuities normally bear complex and variable loads, which lead to a multiaxial and random/variable amplitude stress/strain state. Hence, this study aims how to effectively evaluate the multiaxial random/variable amplitude fatigue life.
Design/methodology/approach
Recent studies on critical plane method under multiaxial random/variable amplitude loading are reviewed, and the computational framework is clearly presented in this paper.
Findings
Some basic concepts and latest achievements in multiaxial random/variable amplitude fatigue analysis are introduced. This review summarizes the research status of four main aspects of multiaxial fatigue under random/variable amplitude loadings, namely multiaxial fatigue criterion, method for critical plane determination, cycle counting method and damage accumulation criterion. Particularly, the latest achievements of multiaxial random/variable amplitude fatigue using critical plane methods are classified and highlighted.
Originality/value
This review attempts to provide references for further research on multiaxial random/variable amplitude fatigue and to promote the development of multiaxial fatigue from experimental research to practical engineering application.
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Umesh Sharma, Kaleem Zaidi and Navratan Bhandari
This study attempts to investigate the post-fire residual stress-strain behaviour of unconfined plain and fibrous concretes under axial compression. The experimental variables of…
Abstract
This study attempts to investigate the post-fire residual stress-strain behaviour of unconfined plain and fibrous concretes under axial compression. The experimental variables of the study were concrete strength levels, volume fractions of flat crimped steel fibres and polypropylene fibres, inclusion of hybrid fibres and temperature of exposure. A total of 147 cylindrical specimens (150 x 450 mm) were cast and tested under this study. The specimens were first exposed to temperatures ranging from room temperature to 800°C and then tested under uni-axial compression after cooling to obtain complete residual stress-strain response. Based on the test data obtained, a simple empirical model is proposed to describe the complete residual stress-strain relationships of plain and fibre reinforced concrete after exposure at elevated temperatures. Important observations have been made in the paper about the influence of temperature on various mechanical properties namely strength, stress-strain curves, compressive toughness and modulus of elasticity of both plain and fibrous concretes.
IN modern structural design the maximum carrying capacity of a member under non‐uniform static stress at normal temperatures is not necessarily the load which gives a maximum…
Abstract
IN modern structural design the maximum carrying capacity of a member under non‐uniform static stress at normal temperatures is not necessarily the load which gives a maximum stress equal to that at the limit of proportionality. All experiments have shown the ultimate strength of beams to exceed the value predicted on the basis of the elastic theory. This applies to simply supported and redundant beams made of steel and wrought iron, as well as to beams constructed from other metals such as cast iron, aluminium, magnesium, etc. Investigators differ, however, in the interpretation of this increased strength and in their methods of a more advantageous use of the material. These are usually based on specific experiments and apply to certain conditions only, without embracing all materials and all possible load distributions and types of structures.