The effect of interference-fit on fretting fatigue crack initiation and ΔK of a single pinned plate in 7075 Al-alloy

The effect of interference-fit on fretting fatigue crack initiation and ΔK was studied numerically for available experimental results in a single pinned plate in Al-alloy 7075-T6. The role of interference ratio was investigated alongside friction coefficient through finite element. Cyclic stress distributions in the plate ligament and fretting stresses on the contact interface were evaluated using 3-D elastic-plastic finite element models. Additionally a 3-D elastic finite element model was utilized to discuss ΔK of cracks emanating from interference fitted holes. Results demonstrate that fretting was the main reason for crack nucleation, and furthermore, the location was precisely predicted and fatigue life enhancement was explained. © 2011 Elsevier Ltd

Effect of hole lubrication on the fretting fatigue life of double shear lap joints: An experimental and numerical study

In this research the affect that lubrication at a hole and pin connection has on the fatigue life of a double shear lap joint is studied both experimentally and numerically. The study focuses on the joint middle plate item, which is connected via a central hole to the outer plates by means of a clearance fitting pin, thereby placing the hole in double shear. In the experimental work three identical batches of fatigue specimens, which are made from aluminum alloy 2024-T3, were fatigue tested. In the first batch the surface of the fastener hole was not lubricated whilst the hole in the other two batches was lubricated - each batch using a different lubricant. The three batches of double shear lap joint specimens were fatigue tested and their S-N curves established. The results show that the specimens in which the holes were lubricated have better fatigue lives than the non-lubricated hole specimens. In the numerical study, FE simulations were performed to include hole lubrication effect on the stress distribution by using different friction coefficient at the interface of the hole and its fastener (pin). The FE results have helped to gain an understanding of the reasons for fatigue life improvement and also have helped to quantify the level of improvement. © 2009 Elsevier Ltd. All rights reserved

Experimental and numerical investigations into the effect of an interference fit on the fatigue life of double shear lap joints

In this research the effect of bolt interference fit on the fatigue life of lap joints in double shear was investigated by conducting experimental fatigue tests and also analytically by FE simulation. In the experimental part, fatigue tests were carried out on specimens made from aluminium alloy 2024-T3 plates joined together as double lap joints and secured using bolts having fits ranging from zero clearance to different levels of interference. The results demonstrate how the failure is affected using different levels of interference fit. In the numerical study, 3-D FE models were used to simulate the different pin in hole fits considered and the results have been used to help explain the trends which were observed in the experimentally obtained S-N curve behaviour. © 2009 Elsevier Ltd. All rights reserved

Fatigue crack growth and life prediction of a single interference fitted holed plate

To understand the different aspects of fatigue behaviour of complex structural joints it will be much helpful if the effects of different parameters are studied separately. In this article, to study the isolated effect of interference fit on fatigue life a pined hole specimen is investigated. This specimen is a single-holed plate with an oversized pin which force fitted to the hole. The investigation was carried out both experimentally and numerically. In the experimental part, interference fitted specimens along with open hole specimens were fatigue tested to study the experimental effect of the interference fit. In the numerical part, three-dimensional finite element (FE) simulations have been performed in order to obtain the created stresses due to interference fit and subsequent applied longitudinal load at the holed plate. The stress distribution obtained from FE simulation around the hole was used to predict crack initiation life using Smith-Watson-Topper method and fatigue crack growth life using the NASGRO equation with applying the AFGROW computer code. The predicted fatigue life obtained from the numerical methods show a good agreement with the experimental fatigue life. © 2010 Blackwell Publishing Ltd

On the prediction of fatigue life in double shear lap joints including interference fitted pin

In this paper, the fatigue life of double shear lap joints involving interference fitted pin is predicted considering both the initiation and propagation fatigue lives without a prior definition of an initial crack length. Finite element analyses were employed to predict fatigue crack initiation life using different multiaxial fatigue criteria. Pre-stress fields resulting from interference fit and also the longitudinal loading effect were introduced to the AFGROW code to obtain the effective stress intensity factor for the estimation of fatigue crack growth life using β-modification in pre-stress field method (β-MPFM). The predictions demonstrate a good agreement with experimental data. © 2012 Elsevier Ltd

An investigation about interference fit effect on improving fatigue life of a holed single plate in joints

In this article, the effect of interference fit on fatigue life of holed plate of mechanical joints was investigated both experimentally and numerically. In the experimental part, fatigue tests were carried out on the holed specimens of Al 7075-T6 alloy in which oversized steel pins were force fitted to them. These fatigue tests were conducted on open hole specimen and specimens with 1, 1.5, 2 and 4% nominal interference fit sizes at different cyclic longitudinal loads. From these tests the stress-life (S-N) data for different interference fit sizes were obtained. The results show that interference fit increases fatigue life compared to open hole specimens. In the numerical part of the investigation, 3D finite element simulations have been performed to obtain stress (or strain) histories and distributions around the hole due to interference fit and subsequent cyclic longitudinal loading using FEM package. The stress history from finite element (FE) simulation was used to explain the reason for fatigue life improvement in the interference fitted specimens. © 2010 Elsevier Masson SAS. All rights reserved

Investigation of the fatigue life and crack growth in torque tightened bolted joints

The fatigue crack initiation and fatigue crack growth life estimations have been numerically investigated and the total estimated fatigue lives have been compared with available experimental fatigue test results for a single plate of aluminum 7075-T6 bolted with different applied torques. To do so, pre-stresses around the hole due to the torque tightened bolt and stress concentration factor of the combined longitudinally applied load and bolt clamping force were determined using 3D finite element simulations results. The calculated pre-stresses and stress concentration factors for different bolt clamping forces were employed in AFGROW computer package to predict fatigue crack initiation and fatigue crack growth lives. The results show that there is good agreement between the numerically predicted total fatigue lives and available experimental fatigue test results. The numerical results also show that bolt clamping force increases both fatigue crack initiation and fatigue crack growth lives individually. © 2010 Elsevier Masson SAS. All rights reserved