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1 – 10 of 136
Article
Publication date: 1 February 1992

KEVIN M. O'CONNOR and CHARLES H. DOWDING

To simulate the kinematics associated with mining‐induced subsidence in a blocky rock mass, a hybrid rigid block model was developed by combining a small displacement code…

Abstract

To simulate the kinematics associated with mining‐induced subsidence in a blocky rock mass, a hybrid rigid block model was developed by combining a small displacement code with a large displacement code. Gravity was applied to a rigid block mesh using an implicit formulation and the equilibrium displacements are then used as initial conditions for an explicit analysis in which excavation of a longwall mine panel and subsequent subsidence was simulated. A parameter study was performed to evaluate the influence of rigid block contact stiffness, vertical joint density, and contact roughness on mining‐induced strata movements for comparison with previously obtained field measurements. The best agreement between measured and calculated displacements was obtained when a relatively low stiffness value was maintained constant for all contacts. A surprising result was that neither increasing the density of vertical joints nor reducing the rigid block contact roughness improved the agreement between measured and simulated displacements.

Details

Engineering Computations, vol. 9 no. 2
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 4 January 2022

Indrajit Pal, Subhajit Ghosh, Itesh Dash and Anirban Mukhopadhyay

This paper aims to provide a general overview of the international Tsunami warning system mandated by the United Nations, particularly on cataloging past studies and a…

Abstract

Purpose

This paper aims to provide a general overview of the international Tsunami warning system mandated by the United Nations, particularly on cataloging past studies and a strategic focus in the Indian Ocean, particularly on the Bay of Bengal region.

Design/methodology/approach

Present research assimilates the secondary non-classified data on the Tsunami warning system installed in the Indian Ocean. Qualitative review and exploratory research methodology have been followed to provide a holistic profile of the Tsunami rarly warning system (TEWS) and its role in coastal resilience.

Findings

The study finds the need for strategic focus to expand and interlink regional early warning cooperation mechanisms and partnerships to enhance capacities through cooperation and international assistance and mobilize resources necessary to maintain the TEWS in the Indian Ocean region. The enhanced capacity of the TEWS certainly improves the resilience of Indian Ocean coastal communities and infrastructures.

Originality/value

The study is original research and useful for policy planning and regional cooperation on data interlinkages for effective TEWS in the Indian Ocean region.

Details

International Journal of Disaster Resilience in the Built Environment, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1759-5908

Keywords

Article
Publication date: 1 June 1999

Mohamed S. Gadala and Andrew D.B. McCullough

This paper presents a numerical study of inverse parameter identification problems in fracture mechanics. Inverse methodology is applied to the detection of subsurface

1007

Abstract

This paper presents a numerical study of inverse parameter identification problems in fracture mechanics. Inverse methodology is applied to the detection of subsurface cracks and to the study of propagating cracks. The procedure for detecting subsurface cracks combines the finite element method with a sequential quadratic programming algorithm to solve for the unknown geometric parameters associated with the internal flaw. The procedure utilizes finite element substructuring capabilities in order to minimize the processing and solution time for practical problems. The finite element method and non‐linear optimization are also used in determining the direction a crack will propagate in a heterogeneous planar domain. This procedure involves determining the direction that produces the maximum strain energy release for a given increment of crack growth. The procedure is applied to several numerical examples. The results of these numerical studies coincide with theoretical predictions and experimentally observed crack behavior.

Details

Engineering Computations, vol. 16 no. 4
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 18 June 2019

Yuyan Zhang, Xiaoliang Yan, Xiaoqing Zhang, Juan Li and Fengna Cheng

This paper aims to investigate the effects of inhomogeneities on the rolling contact fatigue (RCF) life in elastohydrodynamically lubricated (EHL) point contacts.

87

Abstract

Purpose

This paper aims to investigate the effects of inhomogeneities on the rolling contact fatigue (RCF) life in elastohydrodynamically lubricated (EHL) point contacts.

Design/methodology/approach

A numerical model for predicting the RCF life of inhomogeneous materials in EHL contacts was established by combining the EHL model and the inclusion model through the eigen-displacement and then connecting to the RCF life model through the subsurface stresses. Effects of the type, size, location and orientation of a single inhomogeneity and the distribution of multiple inhomogeneities on the RCF life were investigated.

Findings

The RCF life of a half-space containing manganese sulfide (MnS) inhomogeneity or the mixed inhomogeneity of aluminium oxide (Al2O3) and calcium oxide (CaO) was longer than that for the case of Al2O3 inhomogeneity. For a single ellipsoidal MnS inhomogeneity, increases of its semi-axis length and decreases of its horizontal distance between the inhomogeneity and the contact center shortened the RCF life. Furthermore, the relationship between the depth of a single MnS inhomogeneity and the RCF life was found. For the half-space containing multiple inhomogeneitites, the RCF life decreased remarkably compared with the homogeneous half-space and showed discreteness.

Originality/value

This paper implements the prediction of the RCF life of inhomogeneous materials under EHL condition.

Details

Industrial Lubrication and Tribology, vol. 71 no. 5
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 21 November 2018

Yong Yang, Wenguang Li, Jiaxu Wang and Qinghua Zhou

The purpose of this study is to investigate the tribological performance of helical gear pairs with consideration of the properties of non-Newtonian lubricant and the real…

Abstract

Purpose

The purpose of this study is to investigate the tribological performance of helical gear pairs with consideration of the properties of non-Newtonian lubricant and the real three-dimensional (3D) topography of tooth flanks.

Design/methodology/approach

Based on the mixed elastohydrodynamic lubrication (EHL) theory for infinite line contact, this paper proposes a complete model for involute helical gear pairs considering the real 3D topography of tooth flanks and the properties of non-Newtonian lubricant. Film thickness, contact load and contact area ratios at the mid-point of contact line are studied for each angular displacement of pinion. Both the total friction coefficient and surface flash temperature are calculated after obtaining the values of pressure and subsurface stress. Then, the influences of input parameters including rotational speed and power are investigated.

Findings

During the meshing process, contact load ratio and area ratio of the two rough surface cases first increase and then decrease; the maximum flash temperature rise (MFTR) on the gear is lower than that on the pinion first, but later the situation converses. For cylindrical gears, on the plane of action, there is a point or a line where the instantaneous friction reduces to a minimum value in a sudden, as the sliding–rolling ratio becomes zero. When rotational speed increases, film thickness becomes larger, and meanwhile, contact load ratio, coefficient of friction and MFTR gradually reduce.

Originality/value

A comprehensive analysis is conducted and a computer program is developed for meshing geometry, kinematics, tooth contact, mixed EHL characteristics, friction, FTR and subsurface stress of involute helical gear pairs. Besides, a numerical simulation model is developed, which can be used to analyze mixed lubrication with 3D machined roughness under a wide range of operating conditions.

Details

Industrial Lubrication and Tribology, vol. 71 no. 1
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 13 July 2021

Chen Li, Heng Wen, Kun Chen, Longxiao Zhang, Ting Xie, Yaru Shi and Junlong Zhang

This paper aims to develop a Mini-Tribometer for in-situ observation of subsurface.

Abstract

Purpose

This paper aims to develop a Mini-Tribometer for in-situ observation of subsurface.

Design/methodology/approach

To observe the change of the microstructure during wear in real time, an in-situ observation mini-tribometer was developed according to the requirements of the basic frictional experiments and carried out the verification experiments.

Findings

The subsurface images and the tribological data obtained from the mini-tribometer clearly show that the graphite in the matrix moves to the surface and takes part in lubrication mainly in the form of extrusion and peeling off, and the migration of graphite in the copper-based composite to the frictional interface to act as lubricant and to result in the decrease of the friction coefficient. The experimental results of the developed tribometer are accurate, which can provide important references for further research on the wear mechanism of materials.

Originality/value

The developed in-situ observation mini-tribometer can be used to observe the dynamic wear mechanism of the frictional pairs, which is very important for optimization of material design and tribological performances.

Details

Industrial Lubrication and Tribology, vol. 73 no. 5
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 1 June 2003

Neçar Merah

The electric potential techniques are of two types: the direct current potential drop method (DCPD) and the alternating current potential drop method (ACPD). While the…

1151

Abstract

The electric potential techniques are of two types: the direct current potential drop method (DCPD) and the alternating current potential drop method (ACPD). While the latter can be used mainly to detect surface defects, the first is more appropriate for detecting the initiation of cracks and monitoring their growth. One of the advantages of the ACPD is that it can be easily employed as a non‐destructive inspection tool. The DCPD has been used mainly in the laboratory environments under various conditions of loading including high gross inelastic deformations where subsurface flaws are present. Both these techniques have high accuracy and can be used as tools to detect defects in manufactured parts such as flaws in welds. Their findings are very useful in preventive maintenance; the inspectors and engineers use them to take decisions for scheduling maintenance. The present paper presents a review of the evolution in the design of ACPD and DCPD systems, with their advantages, disadvantages and fields of application. It is shown that ACPD and DCPD have comparable sensitivity and are widely used for surface crack measurement. The relatively new AC field measurement technique will be described. Its performance will be compared to that of ACPD. The use of DCPD in applications involving high temperature and gross inelastic strains will be stressed. The results obtained in low cycle fatigue conditions show that by including a special reference potential ratio, the DCPD yields a good estimation of the average surface and subsurface crack lengths. The method also allows an accurate detection of crack initiation in these conditions.

Details

Journal of Quality in Maintenance Engineering, vol. 9 no. 2
Type: Research Article
ISSN: 1355-2511

Keywords

Article
Publication date: 1 December 2003

Khaled Elleuch, Salah Mezlini, Siegfried Fouvry and Philippe Kapsa

Damage of aluminium alloy under contact loading is detected in different cases independent of contact configuration and operating conditions. An investigation of two…

Abstract

Damage of aluminium alloy under contact loading is detected in different cases independent of contact configuration and operating conditions. An investigation of two industrial cases is proposed to describe how it is possible to study the material degradation under friction. The experimental simulation of aluminium damage in laboratory conditions is carried out. Two contact configurations are studied in order to reproduce the industrial damage of aluminium alloys. Varying experimental conditions relative to a specific contact body for each test have demonstrated a realistic correlation between damage, test configuration and material properties. Independent of the tribological system, plastic deformation seems to be the major parameter controlling the wear of aluminium alloy under friction in the studied cases.

Details

Industrial Lubrication and Tribology, vol. 55 no. 6
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 3 February 2020

Hamed Arefizadeh and Hadi Shahir

Anchorage with concrete bearing pad is commonly used in Iran for stabilization of excavations because of the ease of construction, less costs and less time consumption…

Abstract

Purpose

Anchorage with concrete bearing pad is commonly used in Iran for stabilization of excavations because of the ease of construction, less costs and less time consumption than the soldier pile method. In this method, a wall facing which includes the concrete bearing pads at the location of the anchors and a shotcrete layer between the bearing pads is constructed parallel to the excavation operation similar to the nailing method.

Design/methodology/approach

In this paper, using the finite element software Abaqus, a three-dimensional model of the above-mentioned type of wall is constructed, and the effect of spacing and size of bearing pads on the wall behavior is discussed.

Findings

According to the obtained results, the size of the concrete bearing pads has little effect on wall deformations, but the internal forces and bending moments developed in the shotcrete layer between the bearing pads are greatly influenced by the bearing pads dimensions and spacing.

Originality/value

Owing to the discrete elements of the wall facing, the behavior of this system is completely three-dimensional.

Details

Journal of Engineering, Design and Technology , vol. 18 no. 6
Type: Research Article
ISSN: 1726-0531

Keywords

Article
Publication date: 11 November 2014

M. Grujicic, V. Chenna, R. Galgalikar, J.S. Snipes, S. Ramaswami and R. Yavari

A simple economic analysis has revealed that in order for wind energy to be a viable alternative, wind-turbines (convertors of wind energy into electrical energy) must be…

Abstract

Purpose

A simple economic analysis has revealed that in order for wind energy to be a viable alternative, wind-turbines (convertors of wind energy into electrical energy) must be able to operate for at least 20 years, with only regular maintenance. However, wind-turbines built nowadays do not generally possess this level of reliability and durability. Specifically, due to the malfunction and failure of drive-trains/gear-boxes, many wind-turbines require major repairs after only three to five years in service. The paper aims to discuss these issues.

Design/methodology/approach

The subject of the present work is the so-called white etch cracking, one of the key processes responsible for the premature failure of gear-box roller-bearings. To address this problem, a multi-physics computational methodology is developed and used to analyze the problem of wind-turbine gear-box roller-bearing premature-failure. The main components of the proposed methodology include the analyses of: first, hydrogen dissolution and the accompanying grain-boundary embrittlement phenomena; second, hydrogen diffusion from the crack-wake into the adjacent unfractured material; third, the inter-granular fracture processes; and fourth, the kinematic and structural response of the bearing under service-loading conditions.

Findings

The results obtained clearly revealed the operation of the white-etch cracking phenomenon in wind-turbine gear-box roller-bearings and its dependence on the attendant loading and environmental conditions.

Originality/value

The present work attempts to make a contribution to the resolution of an important problem related to premature-failure and inferior reliability of wind-turbine gearboxes.

Details

International Journal of Structural Integrity, vol. 5 no. 4
Type: Research Article
ISSN: 1757-9864

Keywords

1 – 10 of 136