Search results

1 – 10 of over 9000
To view the access options for this content please click here
Article
Publication date: 1 May 1978

Thomas W. Crooker

Corrosion‐fatigue testing using precracked specimens has, in recent years, become an important means of evaluating structural alloys for service in corrosive environments…

Abstract

Corrosion‐fatigue testing using precracked specimens has, in recent years, become an important means of evaluating structural alloys for service in corrosive environments. The recent emphasis towards the use of precracked specimens for corrosion‐fatigue testing is based upon several factors. First, there is the general recognition that metallic structures of all types are prone to contain cracks and that the growth of such cracks can play a crucial role in overall structural performance; and secondly, a fracture mechanics technology basis has been developed for quantitatively assessing crack growth phenomena. The coexistence of a visible problem area and a means of attacking the problem has stimulated considerable activity in this field of endeavour.

Details

Anti-Corrosion Methods and Materials, vol. 25 no. 5
Type: Research Article
ISSN: 0003-5599

To view the access options for this content please click here
Article
Publication date: 1 March 1988

R.N. Wild

This paper reviews some continuing IBM study efforts conducted on surface mounted Leadless Chip Carrier (LCC) packaging for use in high density, high thermal stress…

Abstract

This paper reviews some continuing IBM study efforts conducted on surface mounted Leadless Chip Carrier (LCC) packaging for use in high density, high thermal stress military environments. The paper presents some designs, materials and solder joint processing considerations that can affect solder joint fatigue life. Also discussed are some thermal cycling test limitations, important properties of solder failure mechanisms and finally some technical concerns with both WS 6536E and DoD 2000 specifications as to their limitations with future surface mounted technologies.

Details

Circuit World, vol. 14 no. 4
Type: Research Article
ISSN: 0305-6120

To view the access options for this content please click here
Article
Publication date: 2 October 2017

Sergio Baragetti, Riccardo Gerosa and Francesco Villa

7075-T6 is the most widespread structural aluminium alloy due to its high mechanical strength. However, use of this alloy in critical aeronautic, maritime, and automotive…

Abstract

Purpose

7075-T6 is the most widespread structural aluminium alloy due to its high mechanical strength. However, use of this alloy in critical aeronautic, maritime, and automotive sectors is limited by the susceptibility of T6 treatment to cracking and pitting corrosion. To improve fatigue behaviour in aggressive environments, several authors have proposed the use of different coatings to protect the substrate. Studies have investigated the application of thin hard coatings on light alloys by physical vapour deposition (PVD). Different contributions of residual stresses, thermal modification of the substrate, and mechanical interaction between the coating and aluminium substrate were investigated. The purpose of this paper is to investigate the rotating bending fatigue behaviour (R=−1) of 7075-T6 PVD diamond-like carbon (DLC)-coated specimens in air and in a corrosive environment. Tests were conducted at different applied stresses. Scanning electron micrographs of the fracture surface are provided to investigate the influences of mechanical and environmental driving forces on the failure mechanism.

Design/methodology/approach

The paper conducted an experimental study of the fatigue resistance of DLC coatings on a 7075-T6 substrate for corrosion protection at long and short fatigue lives, which includes rotating bending fatigue tests, step-loading fatigue test procedure, tests in aggressive environment (methanol), tests at high and low fatigue lives, analysis of the fracture surface, and analysis of the driving forces.

Findings

Tests performed in air showed that the coating anticipates crack nucleation for high applied loads, whereas for lower loads, the difference among fatigue curves decreases. This result is very interesting from an industrial standpoint because the obtained material shows improved corrosion and wear resistance, without the fatigue resistance loss generally associated with hard coatings. The methanol environment accelerates crack nucleation and propagation, resulting in a sensible deterioration of the fatigue behaviour. A minimum soaking time seems to be necessary before the damaging effect of the environment begins. The coating has a certain protective effect against the environment, but this protection is insufficient for the specimen to achieve fatigue limits beyond those of the uncoated specimens. This deficiency can be related to small pores or defects in the coating, which allow contact between the substrate and the environment. Further tests are necessary to verify whether there exists a load under which the fatigue behaviour of the coated specimens is better than that of the uncoated specimens. Crack nucleation due to fatigue occurs close to the outer surface for all observed samples. For coated samples tested at the lowest stress level, crack nucleation seems to be located below the surface. This observation means that premature coating cracking, which characterises the nucleation mechanism at higher loads, did not occur at lower stress levels. The fracture surface of uncoated samples was clearly damaged by the aggressive solution, justifying the poor fatigue resistance.

Research limitations/implications

The obtained data do not represent actual S-N curves, which would necessitate a larger number of tests with proper statistics. Nevertheless, some indications of the DLC effects on 7075-T6 specimens in air and methanol environments can be deduced. The step-loading technique seems to be critical for tests in corrosive environments, probably because the total soaking time in the corrosive environment is generally higher than it is for the single-run test.

Originality/value

The originality of the paper lies in the application of the step-loading test procedure to quickly detect the mechanical and chemical driving forces that control the damage and structural integrity of light alloys components in very aggressive environments.

Details

International Journal of Structural Integrity, vol. 8 no. 5
Type: Research Article
ISSN: 1757-9864

Keywords

To view the access options for this content please click here
Article
Publication date: 1 February 1979

R.J. PARKER and R.S. HODDER

ROLLING‐element bearings for aircraft turbine engine mainshaft applications are generally specified to be made of AISI M‐50 steel. Current aircraft turbine engine…

Abstract

ROLLING‐element bearings for aircraft turbine engine mainshaft applications are generally specified to be made of AISI M‐50 steel. Current aircraft turbine engine manufacturers' material specifications require a double vacuum melted (VIM‐VAR, for vacuum induction melt, vacuum arc smelt) AISI M‐50 steel for mainshaft bearings. With this material, ball bearing fatigue lives of nearly 100 times AFBMA predicted life have been obtained. Reduction in inclusion content, trace elements, and interstitial gas content is considered responsible for a major portion of this life advancement. AISI M‐50 also has the hot hardness and hardness retention ability for long‐life rolling‐element bearing operation at temperatures up to 588 K (600°F).

Details

Industrial Lubrication and Tribology, vol. 31 no. 2
Type: Research Article
ISSN: 0036-8792

To view the access options for this content please click here
Article
Publication date: 4 December 2017

António A.M.A. Campos, Abílio M.P. de Jesus, José A.F.O. Correia and José J.L. Morais

Adhesively bonded joints are gaining importance in the structural joining processes competing against welding and bolting processes. However, long-term behaviour of…

Abstract

Purpose

Adhesively bonded joints are gaining importance in the structural joining processes competing against welding and bolting processes. However, long-term behaviour of adhesively bonded joints is still an open question. Due to the increasing interest in adhesively bonded joints, mainly in the transports industry, there is a need to deep the knowledge about the fatigue behaviour of adhesive joints with metallic substrates allowing the development of reliable joints to resist cyclic loadings. The paper aims to discuss these issues.

Design/methodology/approach

An experimental research aiming at characterizing the fatigue behaviour of adhesively bonded aluminium substrates is presented in this paper, covering both fatigue crack propagation and global S-N behaviours. Double cantilever beam (DCB), end notch flexure (ENF) and double lap joints (DLJ) specimens built using the AA6061T651 substrate and epoxy adhesive were used to evaluate the pure modes I and II fatigue crack propagation rates and the S-N fatigue behaviours.

Findings

DCB and ENF specimens allowed the formulation of pure modes I and II fatigue crack propagation laws including the propagation thresholds. DLJs showed higher static shear strength than recommended by the manufacturer for aluminium substrates, but fatigue resistance of the DLJs was lower than suggested by the manufacturer. The fatigue damage process in the DLJs was dominated by a fatigue crack initiation process.

Originality/value

A consistent fatigue research on adhesively bonded aluminium substrates is presented covering in the same study aspects of fatigue crack propagation and fatigue crack initiation. Data reduction schemes involving both numerical and analytical procedures were followed. Proposed work constitutes a rigorous basis for future fatigue prediction models developments.

Details

International Journal of Structural Integrity, vol. 8 no. 6
Type: Research Article
ISSN: 1757-9864

Keywords

To view the access options for this content please click here
Article
Publication date: 1 April 1956

SEVENTEEN papers were presented during the three days of the conference on a variety of topics affecting fatigue in aircraft structures. The conference was organized under…

Abstract

SEVENTEEN papers were presented during the three days of the conference on a variety of topics affecting fatigue in aircraft structures. The conference was organized under the joint auspices of the Department of Civil Engineering and Engineering Mechanics, Columbia University, and the Air Research and Development Centre, U.S.A.F., Baltimore.

Details

Aircraft Engineering and Aerospace Technology, vol. 28 no. 4
Type: Research Article
ISSN: 0002-2667

To view the access options for this content please click here
Article
Publication date: 1 March 1990

E.E. de Kluizenaar

In Part 1, background information on mechanical properties and metallurgy of solder alloys and soldered joints has been presented. In Part 2, mechanisms of damage and…

Abstract

In Part 1, background information on mechanical properties and metallurgy of solder alloys and soldered joints has been presented. In Part 2, mechanisms of damage and degradation of components and soldered joints during soldering, transport and field life have been discussed, the most important mechanism being low cycle fatigue of the solder metal. In this third part, the determination of the fatigue life expectancy of soldered joints is discussed. Accelerated testing of fatigue is needed, as the possibilities of calculations are strongly limited. A temperature cycle test under specified conditions is proposed as a standard. A model is worked out for the determination of the acceleration factor of this test. A compilation of a number of solder fatigue test results, generated in the author's company, is presented.

Details

Soldering & Surface Mount Technology, vol. 2 no. 3
Type: Research Article
ISSN: 0954-0911

To view the access options for this content please click here
Article
Publication date: 4 July 2016

Ronald I. Powell and Alex G. Copping

This research was founded on the premise that more can be done to help improve safety in the global construction industry. Worker fatigue-impairment may be an underlying…

Abstract

Purpose

This research was founded on the premise that more can be done to help improve safety in the global construction industry. Worker fatigue-impairment may be an underlying cause or major contributor to accidents. Fatigue-impairment is believed to be pervasive in construction, and research has shown it can be as concerning as alcohol-impairment. When fatigue-impairment is acknowledged as existing, there is poor understanding of its severity or how it contributes to performance and accidents. The purpose of this research was to attempt to measure fatigue-impairment in real time.

Design/methodology/approach

This research expanded on actual measurements of fatigue-related impairment from workers on a large construction project displaying significant fatigue-related impairment. The research identified and tested possible techniques for real-time measurement solutions to assist with this safety-related issue. 100 participants had their sleep/wake cycles monitored for a month with an actigraph to derive their on-going mental effectiveness levels by the minute. The same participants took cognitive tests over the month to compare mental performance results to the modelled mental effectiveness levels.

Findings

Performance results from cognitive tests were compared with modelled mental effectiveness from actigraph-monitored sleep of 100 participants for a month each and showed significant correlation for all cognitive tests used.

Practical implications

This research showed that real-time surrogate measurements for fatigue-impairment in the workplace exist to assist organizations manage an important workplace hazard.

Originality/value

Derived from operational settings, this research developed predictive models based on simple, quick and inexpensive cognitive tests as screening techniques for workplace impairment and confirmed the need for and found a solution for fatigue monitoring in the workplace.

Details

Journal of Engineering, Design and Technology, vol. 14 no. 3
Type: Research Article
ISSN: 1726-0531

Keywords

To view the access options for this content please click here
Article
Publication date: 1 October 1975

A.D. Hall

This article outlines the procedures being used at Westland Helicopters Limited to establish the fatigue lives of the dynamic and structural components of the Lynx and to…

Abstract

This article outlines the procedures being used at Westland Helicopters Limited to establish the fatigue lives of the dynamic and structural components of the Lynx and to demonstrate how an adequate safety level is achieved under the loading sustained by the aircraft. For the newcomer to the fatigue problem a brief introduction to the phenomenon of fatigue will be provided and it will be shown how it is applicable to a helicopter. A philosophical outline of the fatigue procedures in current use at Westlands follows and then a description of the Lynx is given. The article will then describe the fatigue testing, flight testing and substantiation procedures used with the Lynx and it will be shown how the eventual fatigue lives are estimated. Finally some thoughts are put forward about the future of fatigue substantiation.

Details

Aircraft Engineering and Aerospace Technology, vol. 47 no. 10
Type: Research Article
ISSN: 0002-2667

To view the access options for this content please click here
Article
Publication date: 1 November 1957

J.R. Linge

THE application of cemented wires to determine the location of initial failure in static tests on large specimens has been investigated, among others, by R. W. Powell in 1946.

Abstract

THE application of cemented wires to determine the location of initial failure in static tests on large specimens has been investigated, among others, by R. W. Powell in 1946.

Details

Aircraft Engineering and Aerospace Technology, vol. 29 no. 11
Type: Research Article
ISSN: 0002-2667

1 – 10 of over 9000