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1 – 10 of 285
Article
Publication date: 4 April 2008

T.Y. Qin, B.J. Zhu and N.A. Noda

This paper aims to calculate the mixed‐mode stress intensity factors (SIFs) of a 3D crack meeting the interface in a bimaterial under shear loading by a hypersingular…

Abstract

Purpose

This paper aims to calculate the mixed‐mode stress intensity factors (SIFs) of a 3D crack meeting the interface in a bimaterial under shear loading by a hypersingular integral equation (HIE) method, And further to assess the accuracy of numerical solutions for the mixed mode SIFs along the crack front.

Design/methodology/approach

A 3D crack modeling is reduced to solving a set of HIEs. Based on the analytical solutions of the singular stress field around the crack front, a numerical method for the HIEs is proposed by a finite‐part integral method, where the displacement discontinuities of the crack surface are approximated by the product of basic density functions and polynomials. Using FORTRAN program, numerical solutions of the mixed‐mode SIFs of some examples are presented.

Findings

The numerical method is proved to be an effective construction technique. The numerical results show that this numerical technique is successful, and the solution precision is satisfied.

Research limitations/implications

This work takes further steps to improve the fundamental systems of HIE for its application in the fields of arbitrary shape crack problems. Propose several techniques for numerical implementation, which could increase the efficiency and accuracy of computation.

Practical implications

Whenever there is a structure containing the 3D crack, the analysis method described in this paper can be utilized to find the critical configurations under which the structure may be most vulnerable. In such cases, the strength predictions would be safer if the crack could be taken into account.

Originality/value

This paper is the first to apply HIE method to analyzing the mixed‐mode crack meeting the interface in 3D dissimilar materials. Numerical solutions of the mixed‐mode SIFs can give the satisfied solution precision.

Details

Engineering Computations, vol. 25 no. 3
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 16 November 2012

Kazuhiro Oda, Xin Lan, Nao‐Aki Noda and Kengo Michinaka

The purpose of this paper is to compute the stress intensity factors (SIFs) of single edge interface crack for arbitrary material combinations and various relative crack…

Abstract

Purpose

The purpose of this paper is to compute the stress intensity factors (SIFs) of single edge interface crack for arbitrary material combinations and various relative crack lengths, and compare with those for the bonded plates subjected to tensile loading conditions. It aims to discuss the results of the shallow edge interface crack on the basis of the singular stress near the free‐edge corner without the crack.

Design/methodology/approach

In this study, the SIFs of interface crack in dissimilar bonded plates subjected to bending loading conditions are analyzed by the finite element method and a post‐processing technique. The use of post‐processing technique of extrapolation reduces the computational cost and improves the accuracy of the obtained result.

Findings

The empirical expressions are proposed for evaluating the SIFs of arbitrary material combinations.

Originality/value

Empirical functions can be used to obtain the SIFs for arbitrary material combinations for the bending loading conditions easily. It is very convenient for engineering application.

Details

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

Keywords

Open Access
Article
Publication date: 6 July 2018

Ayaka Noda, Angela Yung Chi Hou, Susumu Shibui and Hua-Chi Chou

The purpose of this paper is to examine how the Japanese and Taiwanese national quality assurance (QA) agencies, National Institution for Academic Degrees and Quality…

3346

Abstract

Purpose

The purpose of this paper is to examine how the Japanese and Taiwanese national quality assurance (QA) agencies, National Institution for Academic Degrees and Quality Enhancement (NIAD-QE) and Higher Education Evaluation and Accreditation Council of Taiwan (HEEACT), transform their respective frameworks in response to social demands, and analyze and compare the respective approaches for the key concepts of autonomy, accountability, improvement and transparency.

Design/methodology/approach

Using a qualitative document analysis approach, this paper initially examines the higher education system, major policies and QA developments, after which the methods associated with the QA restructuring transformations are outlined in terms of motivations, expectations and challenges. Finally, the NIAD-QE and HEEACT evaluation policies and frameworks are compared to assess how each has prepared to respond to emerging challenges.

Findings

During the QA framework restructuring, both the NIAD-QE and HEEACT struggled to achieve autonomy, accountability, improvements and transparency. While the new internal Japanese QA policy is assured through the external QA, the Taiwanese internal QA, which has a self-accreditation policy, is internally embedded with university autonomy emphasized. The QA policies in both the NIAD-QE and HEEACT have moved from general compliance to overall improvement, and both emphasize that accountability should be achieved through improvements. Finally, both agencies sought transparency through the disclosure of the QA process and/or results to the public and the enhancement of public communication.

Originality/value

This study gives valuable insights into the QA framework in Asian higher education institutions and how QA has been transformed to respond to social needs.

Details

Higher Education Evaluation and Development, vol. 12 no. 1
Type: Research Article
ISSN: 2514-5789

Keywords

Article
Publication date: 1 April 2020

Qingchao Sun, Qingyuan Lin, Bin Yang, Xianlian Zhang and Lintao Wang

Bolted joints are the most common type of mechanical connections, and improving the anti-loosening performance of bolts for the reliable performance of mechanical and…

Abstract

Purpose

Bolted joints are the most common type of mechanical connections, and improving the anti-loosening performance of bolts for the reliable performance of mechanical and building structures is highly significant.

Design/methodology/approach

Because of the lack of sufficient theoretical basis for the evaluation and design of anti-loosening bolts, a quantitative evaluation model exhibiting the following two evaluation criteria for anti-loosening bolts is introduced: bolt rotation angular acceleration criterion and critical transverse load criterion. Based on the relationship among bolt tension, transverse load and bolt rotation angular acceleration, a critical transverse load calculation model is put forward, and the mechanism by which the critical transverse load increases with the increase of bolt tension is revealed.

Findings

Based on the above model, a new type of anti-loosening bolt is designed, which generates additional bolt tension when the transverse load increases, and then improves the critical transverse load of the bolt. The effectiveness of the new type of anti-loosening bolt is verified by theoretical calculations and experiments.

Originality/value

The proposed model and method set a preliminary theoretical foundation for the evaluation of bolt anti-loosening performance and the design of a new anti-loosening bolt.

Details

Assembly Automation, vol. 40 no. 4
Type: Research Article
ISSN: 0144-5154

Keywords

Article
Publication date: 24 August 2010

Z.C. Zhang, J.H. Lin, Y.H. Zhang, W.P. Howson and F.W. Williams

Purpose — The purpose of this paper is to present a new nonstationary, random vibration method for the analysis of coupled vehicle‐bridge systems with vertical track…

Abstract

Purpose — The purpose of this paper is to present a new nonstationary, random vibration method for the analysis of coupled vehicle‐bridge systems with vertical track irregularity. Design/methodology/approach — The vehicle is modeled using a two‐layer suspension system and hence possesses ten degrees of freedom. The bridge is simulated using a Bernoulli‐Euler beam and the longitudinal track irregularity is taken as a uniformly modulated, evolutionary random process that includes phase lags between successive wheels. The pseudo‐excitation method (PEM) is extended to include time‐dependent systems for the first time, thus making it possible to compute the nonstationary random vibration of coupled vehicle‐bridge systems. Additionally, the precise integration method (PIM) is adapted to simulate continuous vehicle force variations in both time and space. Findings — The accuracy and effectiveness of the proposed PEM‐PIM method are confirmed by comparisons with Monte Carlo simulations. The influence of vehicle speed and track irregularity on system random responses are evaluated, and it is shown that the first and second derivatives of the track irregularity should not be arbitrarily ignored, as is usually the case. Originality/value — PEM and PIM are relatively new tools for the numerical solution of complicated random vibration problems and direct dynamic analyses. Until now, they have only been applied to time‐independent systems. However, it is shown herein that the proposed PEM‐PIM method performs nonstationary random vibration analysis of time‐dependent coupled vehicle‐bridge systems efficiently and accurately.

Details

Engineering Computations, vol. 27 no. 6
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 13 June 2016

Hemant Krishnarao Wagh, Girish R. Desale and Kartikeya Tripathi

The purpose of this paper is to give a brief introduction of helical spring locked washer along with extensive literatures survey on role of helical spring locked washer…

Abstract

Purpose

The purpose of this paper is to give a brief introduction of helical spring locked washer along with extensive literatures survey on role of helical spring locked washer in bolted joint analysis. It is very small component of bolted joint assembly, but it play vital role in holding the assembly components together. Helical shape of it produces spring effect in the assembly which is used for keeping the assembly in tension and that is lock the assembly under dynamic loading due to vibrations to avoid the accident.

Design/methodology/approach

The critical literatures survey identifies role of helical spring locked washer in different areas such as design optimization, mechanism of loosening-resistant components, bolted joint analysis, finite element-based modeling, analysis and simulation. The related literatures show contribution of helical spring washers in evaluation of anti-loosening performance of assemblies as compare to other types of washers.

Findings

It proposed that design optimization of helical spring locked washer is needed as it improves the performance in the form of load-deflection characteristics, load bearing capacity and provides the best locking force for optimize functionality.

Originality/value

The originality or value of this paper is to finding research gaps in literatures by dividing literatures into seven different research areas and concentrating the only on role of helical spring locked washer in bolted joint analysis.

Details

International Journal of Structural Integrity, vol. 7 no. 3
Type: Research Article
ISSN: 1757-9864

Keywords

Article
Publication date: 13 November 2009

Chia‐Hau Chen, Chao‐Shi Chen, Ernian Pan, Han‐Chou Tseng and Pao‐Shan Yu

The purpose of this paper is to present special nine‐node quadrilateral elements to discretize the un‐cracked boundary and the inclined surface crack in a transversely…

Abstract

Purpose

The purpose of this paper is to present special nine‐node quadrilateral elements to discretize the un‐cracked boundary and the inclined surface crack in a transversely isotropic cuboid under a uniform vertical traction along its top and bottom surfaces by a three‐dimensional (3D) boundary element method (BEM) formulation. The mixed‐mode stress intensity factors (SIFs), KI, KII and KIII, are calculated.

Design/methodology/approach

A 3D dual‐BEM or single‐domain BEM is employed to solve the fracture problems in a linear anisotropic elastic cuboid. The transversely isotropic plane has an arbitrary orientation, and the crack surface is along an inclined plane. The mixed 3D SIFs are evaluated by using the asymptotical relation between the SIFs and the relative crack opening displacements.

Findings

Numerical results show clearly the influence of the material and crack orientations on the mixed‐mode SIFs. For comparison, the mode‐I SIF when a horizontal rectangular crack is embedded entirely within the cuboid is calculated also. It is observed that the SIF values along the crack front are larger when the crack is closer to the surface of the cuboid than those when the crack is far away from the surface.

Research limitations/implications

The FORTRAN program developed is limited to regular surface cracks which can be discretized by the quadrilateral shape function; it is not very efficient and suitable for irregular crack shapes.

Practical implications

The evaluation of the 3D mixed‐mode SIFs in the transversely isotropic material may have direct practical applications. The SIFs have been used in engineering design to obtain the safety factor of the elastic structures.

Originality/value

This is the first time that the special nine‐node quadrilateral shape function has been applied to the boundary containing the crack mouth. The numerical method developed can be applied to the SIF calculation in a finite transversely isotropic cuboid within an inclined surface crack. The computational approach and the results of SIFs are of great value for the modeling and design of anisotropic elastic structures.

Details

Engineering Computations, vol. 26 no. 8
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 2 September 2019

Arash Tavakoli, M. Pourseifi and Sara Rezaei

The purpose of this paper is to provide a theoretical analysis of the fracture behavior of multiple axisymmetric interface cracks between a homogeneous isotropic layer and…

Abstract

Purpose

The purpose of this paper is to provide a theoretical analysis of the fracture behavior of multiple axisymmetric interface cracks between a homogeneous isotropic layer and its functionally graded material (FGM) coating under torsional loading.

Design/methodology/approach

In this paper, the authors employ the distributed dislocation technique to the stress analysis, an FGM coating-substrate system under torsional loading with multiple axisymmetric cracks consist of annular and penny-shaped cracks. First, with the aid of the Hankel transform, the stress fields in the homogeneous layer and its FGM coating are obtained. The problem is then reduced to a set of singular integral equations with a Cauchy-type singularity. Unknown dislocation density is achieved by numerical solution of these integral equations which are employed to calculate the SIFs.

Findings

From the numerical results, the following key points were observed: first, for two types of the axisymmetric interface cracks, the SIFs decrease with growing in the values of the non-homogeneity. Second, the SIFs increase with increases in interface crack length. Third, the magnitude of the SIFs decreases with increases in the FGM coating thickness. Fourth, the interaction between cracks is an important factor affecting the SIFs of crack tips.

Originality/value

New analytical dislocation solution in an FGM coating-substrate system is developed.

Details

Multidiscipline Modeling in Materials and Structures, vol. 15 no. 6
Type: Research Article
ISSN: 1573-6105

Keywords

Article
Publication date: 27 July 2018

V.R. Manthena, G.D. Kedar and K.C. Deshmukh

The purpose of this paper is to determine the temperature distribution of a thin rectangular plate made of thermosensitive functionally graded (FG) material. By finding…

Abstract

Purpose

The purpose of this paper is to determine the temperature distribution of a thin rectangular plate made of thermosensitive functionally graded (FG) material. By finding out thermal deflection and stress resultants, the thermal stresses have been obtained and analyzed.

Design/methodology/approach

Initially, the rectangular plate is kept at the surrounding temperature. The upper, lower and two parallel sides (y=0, b and z=0, c) are thermally insulated, while other parallel sides (x=0, a) are given convective-type heating, that is, the rate of change of the temperature of the rectangular plate is proportional to the difference between its own temperature and the surrounding temperature. The non-linear heat conduction equation has been converted to linear form by introducing Kirchhoff’s variable transformation and the resultant heat conduction equation is solved by integral transform technique with hyperbolic varying point heat source.

Findings

A mathematical model is prepared for FG ceramic–metal-based material, in which alumina is selected as the ceramic and nickel as the metal. The thermal deflection and thermal stresses have been obtained for the homogeneous and nonhomogeneous materials. The results are illustrated numerically and depicted graphically for comparison. During this study, one observed that variations are seen in the stresses, due to the variation in the inhomogeneity parameters.

Research limitations/implications

The paper is constructed purely on theoretical mathematical modeling by considering various parameters and functions.

Practical implications

This type of theoretical analysis may be useful in high-temperature environments like nuclear components, spacecraft structural members, thermal barrier coatings, etc., as the effect of temperature and evaluation of temperature-dependent and nonhomogeneous material properties plays a vital role for accurate and reliable structural analysis.

Originality/value

In this paper, the authors have used thermal deflection and resultant stresses to determine the thermal stresses of a thin rectangular plate with temperature- and spatial variable-dependent material properties which is a new and novel contribution to the field.

Details

Multidiscipline Modeling in Materials and Structures, vol. 14 no. 5
Type: Research Article
ISSN: 1573-6105

Keywords

Article
Publication date: 1 December 2002

Shin‐ichi Satake and Tomoaki Kunugi

A direct numerical simulation with turbulent transport of a scalar quantity has been carried out to grasp and understand a laminarization phenomena caused by a pipe…

Abstract

A direct numerical simulation with turbulent transport of a scalar quantity has been carried out to grasp and understand a laminarization phenomena caused by a pipe rotation. In this study, the Reynolds number, which is based on a bulk velocity and a pipe diameter, was set to be constant; Reb=5283, and the rotating ratios of a wall velocity to a bulk velocity were set to be 0.5, 1.0, 2.0 and 3.0. A uniform heat‐flux was applied to the wall as a thermal boundary condition. Prandtl number of the working fluid was assumed to be 0.71. The number of computational grids used in this study was 256×128×128 in the z‐, r‐ and ϕ‐ directions, respectively. The turbulent quantities such as the mean flow, temperature fluctuations, turbulent stresses and pressure distribution and the turbulent statistics were obtained. Moreover, the Reynolds stress and the scalar flux budgets were also obtained for each rotating ratio. The turbulent drag decreases with the rotating ratio increase. The reason of this drag reduction can be considered that the additional rotational production terms appear in the azimuthal turbulence component. The contributions of convection and production terms to the radial scalar flux budget and also to the balance with temperature‐pressure gradient term are significant. The dissipation and viscous diffusion terms are negligible in higher rotating ratio.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 12 no. 8
Type: Research Article
ISSN: 0961-5539

Keywords

1 – 10 of 285