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Article
Publication date: 1 April 1985

John W. Murray

This paper was delivered by the author at a conference on ‘Building Defects in Commercial Property’, organised by Henry Stewart Conference Studies on 7th February, 1985.

Abstract

This paper was delivered by the author at a conference on ‘Building Defects in Commercial Property’, organised by Henry Stewart Conference Studies on 7th February, 1985.

Details

Structural Survey, vol. 3 no. 4
Type: Research Article
ISSN: 0263-080X

Article
Publication date: 19 October 2022

Jiafeng Lai, Yuhan Wang, Yuwei Wei, Jinlu Liang and Xintian Liu

The purpose of the paper is to predict the residual life of liquid-storage tank to ensure safety and long-term service life of the structure.

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Abstract

Purpose

The purpose of the paper is to predict the residual life of liquid-storage tank to ensure safety and long-term service life of the structure.

Design/methodology/approach

The paper carried out the stress analysis of the wall plate and bottom plate of the liquid-storage tank, and the influence of circumferential stress on the tank is considered. On the other hand, considering the influence of the tank wall surface on the tank life, based on the Paris law, the surface processing coefficient and surface roughness coefficient are introduced to improve the Paris law.

Findings

The effectiveness of the improved model is verified by comparing with theoretical and experimental data, which provide a new method for the prediction of the remaining service life of the tank. Combined with the fatigue crack data in the test report and the calculated circumferential stress, the residual life of the storage tank is predicted.

Originality/value

The improved model provides a new method for the prediction of the remaining service life of the tank.

Details

International Journal of Structural Integrity, vol. 13 no. 6
Type: Research Article
ISSN: 1757-9864

Keywords

Article
Publication date: 31 May 2023

Songtao Qu and Qingyu Shi

In the electronic assembly industry, low-temperature soldering holds great potential to be used in surface mounting technology. Tin–bismuth (Sn–Bi) eutectic alloys are lead-free…

Abstract

Purpose

In the electronic assembly industry, low-temperature soldering holds great potential to be used in surface mounting technology. Tin–bismuth (Sn–Bi) eutectic alloys are lead-free solders applied in consumer electronics because of their low melting point, high strength and low cost. This paper aims to investigate how to address the problem of hot tear crack formation during Sn–Bi low-temperature solder (LTS) in the mass production of consumer electronics.

Design/methodology/approach

This paper explored the development of hot tear cracks during Sn–Bi soldering in the fabrication of flip chip ball grid arrays. Experiments were designed to simulate various conditions encountered in Sn–Bi soldering. Quantitative analysis was conducted on the number of hot tear cracks observed in different alloy compositions and solder volumes to explore the primary cause of hot tear cracks and possible methods to suppress crack formation.

Findings

Hot tear cracks existed in Sn–Bi solders with different bismuth (Bi) contents, but increasing the solder volume reduced the number of hot tear cracks. Experiments were designed to test the degree of chip transient thermal warpage with temperature change, and, according to the results, glue was dispensed in specific areas to reduce chip warpage deformation. Finally, the results of combined process experiments pointed to an effective method of low-temperature soldering to suppress hot tear cracks.

Research limitations/implications

The study focuses on Sn–Bi solders only without other solder pastes such as SAC305 or Sn–Zn series.

Practical implications

With the growing popularity of smart electronics, especially in intelligent terminals, new energy vehicles electronics, solar photovoltaic and other field, there will be more and more demand for low- temperature, energy-saving, lead-free solders. Therefore, this study will help the industry to roll out LTS (Sn–Bi) solutions rapidly.

Social implications

In the long term, lean and green manufacturing is expected to be essential for maintaining an advanced manufacturing industry across the world. Developing new LTSs and soldering processes is the most effective, direct solution for energy conservation and emission mitigation. With the growing popularity of smart electronics, especially in intelligent terminals, new energy vehicles and solar photovoltaics, there would be an increased demand for low-temperature, energy-saving, lead-free techniques.

Originality/value

Although there are many methods that can be used to suppress hot tear cracks, there is little research on how to control the hot tear cracks caused by the low-temperature soldering of Sn–Bi in laptop applications. The authors studied the hot tear cracks that developed during the world’s first mass production of 50 million personal laptops based on low-temperature Sn–Bi alloy solder pastes. By controlling the Bi content, redesigning the solder paste printing process (e.g. through a printer’s stencil) and adding dispensing processes, the authors obtained reliable and stable experimental data and conclusions.

Details

Soldering & Surface Mount Technology, vol. 35 no. 4
Type: Research Article
ISSN: 0954-0911

Keywords

Article
Publication date: 19 July 2021

Manoj Kumar, Gregory J. Gibbons, Amitabha Das, Indranil Manna, David Tanner and Hiren R. Kotadia

The purpose of this study is to investigate the microstructural evolution of high-strength 2024 Al alloy prepared by the laser powder bed fusion (L-PBF) additive manufacturing…

Abstract

Purpose

The purpose of this study is to investigate the microstructural evolution of high-strength 2024 Al alloy prepared by the laser powder bed fusion (L-PBF) additive manufacturing (AM) route. The high-strength wrought Al alloy has typically been unsuitable for AM due to its particular solidification characteristics such as hot cracking, porosity and columnar grain growth.

Design/methodology/approach

In this research work, samples were fabricated using L-PBF under various laser energy densities by varying laser power and scan speed. The microstructural features that developed during the solidification are correlated with operating laser parameters. In addition, finite element modelling (FEM) was performed to understand the experimentally observed results.

Findings

Microstructure evolution and defect formation have been assessed, quantified and correlated with operating laser parameters. Thermal behaviour of samples was predicted using FEM to support experimental observations. An optimised combination of intermediate laser power and scan speed produced the least defects. Higher energy density increased hot tearing along the columnar grain boundaries, while lower energy density promoted void formation. From the quantitative results, it is evident that with increasing energy density, both the top surface and side wall roughness initially reduced till a minimum and then increased. Hardness and compressive strength were found to decrease with increasing power density due to stress relaxation from hot tearing.

Originality/value

This research work examined how L-PBF processing conditions influence the microstructure, defects, surface roughness and mechanical properties. The results indicates that complete elimination of solidification cracks can be only achieved by combining process optimisation and possible grain refining strategies.

Article
Publication date: 19 October 2020

Elnaz Safari Gorjan, Nazanin Ezazshahabi and Fatemeh Mousazadegan

Occurrence of fabric rupture is a problem that can influence fabric performance during wear. In this regard, fabric tearing resistance is considered by manufacturers and consumers…

Abstract

Purpose

Occurrence of fabric rupture is a problem that can influence fabric performance during wear. In this regard, fabric tearing resistance is considered by manufacturers and consumers and enhancing tear resistance through optimization of related parameters is beneficial.

Design/methodology/approach

In this study, the tearing resistance of a series of shirting fabrics with various weave patterns and weft densities were investigated by both static and dynamic tear test methods. Moreover, the constituent yarn's frictional and tensile behaviour was evaluated and their relation with tear resistance was analysis.

Findings

According to the outcomes, the fabric firmness and density and friction of yarns affect the tear resistance, reversely. However an improvement in yarn's tenacity can raise the tear resistance.

Originality/value

In this study it was aimed to not only consider influence of both static and dynamic tear test approach on the tearing performance of fabrics regarding their structural parameters, the impact of the constituent's yarn properties include tensile behaviour and friction coefficient on the tearing performance of fabric considered, as well.

Details

International Journal of Clothing Science and Technology, vol. 33 no. 3
Type: Research Article
ISSN: 0955-6222

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 isotropic…

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 March 2012

Umar Ibrahim and Mohammad A. Irfan

The purpose of this paper is to find the response of micro‐layered rapid prototyping material under impact loading.

Abstract

Purpose

The purpose of this paper is to find the response of micro‐layered rapid prototyping material under impact loading.

Design/methodology/approach

A modified Hopkinson Bar was used to impart impact loading in velocities ranging from 2‐7 m/s. Strain gages and stress wave theory were employed to calculate the load‐point force and displacement. Hence the dynamic crack initiation and propagation energies were calculated.

Findings

It was found that the crack deflection and inter layer delamination mechanisms lead to greater absorption of crack propagation energy and hence offer better resistance to crack propagation as compared to monolithic acrylonitrile butadiene styrene (ABS).

Practical implications

The finding will lead to greater confidence for the use of rapid prototypes as direct‐use parts subjected to low velocity impact.

Originality/value

Although the static properties of ABS material used in rapid prototyping are well documented, this paper is one of the first reported researches in measuring the impact response of the micro layered ABS.

Article
Publication date: 1 August 2001

R. Morgan, C.J. Sutcliffe and W. O’Neill

Describes the effects of the major process variables (Q‐switch pulse frequency, laser power, scan speed, scan spacing and scan length) on the production of single layer coupons…

2053

Abstract

Describes the effects of the major process variables (Q‐switch pulse frequency, laser power, scan speed, scan spacing and scan length) on the production of single layer coupons. Results are compiled as a list of qualitative effects on the samples, such as degree of melting, shock compression effects, thermal stress cracking, etc. The results show that at certain pulse frequencies, evaporation recoil forces overcome the surface tension forces acting on the melt, improving cohesion compared to continuous wave (CW) lasing regime. The advantages lie in greater scan spacing and scan speeds enabling faster processing times for metallic objects built in this manner. The results also show the effect of power, scan speed, scan spacing and scan length on the morphology of the samples.

Details

Rapid Prototyping Journal, vol. 7 no. 3
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 10 August 2015

Jirí Behal, Petr Homola and Roman Ružek

The prediction of fatigue crack growth behaviour is an important part of damage tolerance analyses. Recently, the author’s work has focused on evaluating the FASTRAN retardation…

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Abstract

Purpose

The prediction of fatigue crack growth behaviour is an important part of damage tolerance analyses. Recently, the author’s work has focused on evaluating the FASTRAN retardation model. This model is implemented in the AFGROW code, which allows different retardation models to be compared. The primary advantage of the model is that all input parameters, including those for an initial plane-strain state and its transition to a plane-stress-state, are objectively measured using standard middle-crack-tension M(T) specimens. The purpose of this paper is to evaluate the ability of the FASTRAN model to predict correct retardation effects due to high loading peaks that occur during variable amplitude loading in sequences representative of an aircraft service.

Design/methodology/approach

This paper addresses pre-setting of the fracture toughness K R (based on J-integral J Q according to ASTM1820) in the FASTRAN retardation model. A set of experiments were performed using specimens made from a 7475-T7351 aluminium alloy plate. Loading sequences with peaks ordered in ascending-descending blocks were used. The effect of truncating and clipping selected load levels on crack propagation behaviour was evaluated using both experimental data and numerical analyses. The findings were supported by the results of a fractographic analysis.

Findings

Fatigue crack propagation data defined using M(T) specimens made from Al 7475-T7351 alloy indicate the difficulty of evaluating the following two events simultaneously: fatigue crack increments after application of loads with maximum amplitudes that exceeded J Q and subcritical crack increments caused by loads at high stress intensity factors. An effect of overloading peaks with a maximum that exceeds J Q should be assessed using a special analysis beyond the scope of the FASTRAN retardation model.

Originality/value

Measurements of fatigue crack growth on specimens made from 7475 T7351 aluminium alloy were carried out. The results indicated that simultaneously evaluating fatigue crack increments after application of the load amplitude above J Q and subcritical increments caused by the loads at high stress intensity factors is difficult. Experiments demonstrated that if the fatigue crack reaches a specific length, the maximal amplitude load induces considerable crack growth retardation.

Details

International Journal of Structural Integrity, vol. 6 no. 4
Type: Research Article
ISSN: 1757-9864

Keywords

Article
Publication date: 1 April 1987

B. TOMKINS

THE Structural Integrity Centre (SIC) had its origins in the 1970s when major integrity issues arose on the UKAEA's plant in service, eg weld cracking in the prototype fast…

Abstract

THE Structural Integrity Centre (SIC) had its origins in the 1970s when major integrity issues arose on the UKAEA's plant in service, eg weld cracking in the prototype fast reactors (PFR) steam generator units, and safety concerns led to a rigorous assessment of the integrity of the civil pressurised water reactors (PWR) pressure vessel (the Marshall committee report). In both cases engineers and scientists from various disciplines throughout the authority were involved in the consideration and resolution of these issues, and it was demonstrated that assurance of plant integrity could no longer be provided by the plant designer or operator alone.

Details

Industrial Lubrication and Tribology, vol. 39 no. 4
Type: Research Article
ISSN: 0036-8792

1 – 10 of over 1000