The Variable Expansion Process — a New Cost Efficient Method for Cold Working Fastener Holes in Aluminium Aircraft Structures

Reese, Eggert D.; Dowson, A.L.; Jones, Timothy G. B.

doi:10.1007/978-90-481-2746-7_72

Cited by 4 publications

(3 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Cold expansion reduces the stress concentration locally by provoking a beneficial compressive residual stress zone around the hole [1][2][3][4]. Even though the current cold expansion processes increase overall life of the components, they suffer some drawbacks such as heterogeneous stress and strain distribution around the hole along the thickness, risk of crack initiation near ridges, sporadic tool holdup due to high levels of friction between the tool and the component, and for some specific processes high costs associated with disposing of tools [5].…”

Section: Introductionmentioning

confidence: 99%

A combined upper-bound and elastic-plastic finite element solution for a fastener hole subjected to internal torsion

Shamdani

Khoddam

2011

Arch Appl Mech

View full text Add to dashboard Cite

Fastener holes used in the mechanical joints are vulnerable to failure due to development of stress concentration at their edges. Inducing compressive residual stresses by different techniques has been the most common method to reinforce the holes to date. In this work, a new reinforcement technique called internal torsion, which can be classified as a localized severe plastic deformation process, is proposed as an alternative to the cold expansion pre-stressing. A special specimen is designed to represent the behavior of a typical fastener hole during the internal torsion process. The deformation of the specimen in the vicinity of its hole surface is studied by introducing a parametric kinematically admissible velocity field (PKAVF) within the deformation affected zone (DAZ). Calibration of the parameters in relation to the deformation of the material during the process is done by an elastic-plastic finite element solution that was performed in ABAQUS for a specimen made of interstitial free (IF) steel. Numerical analysis of the deformation is carried out to understand the process and to estimate the optimum process parameters. Subsequently, the calibrated model is used in an upper-bound solution of the problem to estimate the torque-twist response of the specimen during internal torsion. Finally, the results of upper-bound solution are compared with those of finite element analysis. There is a good agreement between the upper-bound solution and finite element results, which verifies validity of the calibrated velocity field model and the upper-bound solution based on the model for the internal torsion problem.

show abstract

Section: Introductionmentioning

confidence: 99%

A combined upper-bound and elastic-plastic finite element solution for a fastener hole subjected to internal torsion

Shamdani

Khoddam

2011

Arch Appl Mech

View full text Add to dashboard Cite

show abstract

“…al. (2008), Ayatollahi and Arian Nik (2009), Maximov et al (2009), Reese et al (2009) and Yan et al (2012). Gopalakrishna et al (2010) have considered the effect of two kinds of the cold working process at different expansion levels on the fatigue life.…”

Section: Introductionmentioning

confidence: 99%

Residual strains around cold worked holes from statistical view

Pooladi¹,

Farhangdoost²

2014

10.5267/j.esm

View full text Add to dashboard Cite

Cold working a hole decreases tendency of fatigue crack initiation and growth near the hole. It is due to creation of some compressive tangential residual stresses around the hole. But there are many uncertainties which affect the residual strain and residual stress field. In fact these uncertainties lead to have scatter in the test results and considering the residual strains and residual stresses as random variables. In this paper strains recorded by strain gages mounted around the hole during cold working process in seven pieces specimens, were analyzed by statistical tests and stochastic properties of mentioned random variables were obtained using SPSS software. The residual strains have been also distributed by normal probability distribution function.

show abstract

“…[1][2][3][4] However, there are some shortcomings associated with CE such as heterogeneous stress and strain distribution around the hole, possibility of crack initiation near ridges, sporadic tool holdup due to high levels of friction between the tool and the component and high costs associated with replacement of tools for some specific processes. 5 An alternative reinforcement method is severe plastic deformation (SPD) processing which refines grains and microstructural features through plastically deforming materials to very large strains. 6 SPD processes produce large and bulk components, but in general, they are not designed for local strengthening of the material.…”

Section: Introductionmentioning

confidence: 99%

A computer-aided specimen design to induce shearing strain around a hole

Shamdani

Khoddam

2012

Proceedings of the Institution of Mechanical Engineers, Part C:

View full text Add to dashboard Cite

The local torsion process which involves an axisymmetric torsional loading around the design position of a hole in a structure has recently found important applications for grain refinement in tubes and fastener holes. The specimen design is a pre-requisite for any experimental investigation of the local torsion process. The purpose of this study is to investigate a number of potential designs which enable the implementation of the local torsion. These designs include a mandrel to twist the specimen and a range of connection configurations between the mandrel and the specimen including threaded, hexagonal and spline bindings. In order to understand the process requirements and for estimating the effect of design parameters, a coupled numerical analysis of the specimen is utilized, involving a non-linear finite element analysis using Abaqus. A sequence of computational steps with different boundary conditions at the interface is devised to simulate the coupled problem. The proposed configurations are compared for their abilities to perform the local torsion and produce the shearing strain within an annular zone around the hole. This allows investigation of the effectiveness of each design for the implementation of the local torsion. The distribution of strain accumulated around the hole in the radial direction is studied after carrying out the process. Finally, a specimen–mandrel assembly design is recommended to ensure that the process can be successfully implemented.

show abstract

The Variable Expansion Process — a New Cost Efficient Method for Cold Working Fastener Holes in Aluminium Aircraft Structures

Cited by 4 publications

References 0 publications

A combined upper-bound and elastic-plastic finite element solution for a fastener hole subjected to internal torsion

A combined upper-bound and elastic-plastic finite element solution for a fastener hole subjected to internal torsion

Residual strains around cold worked holes from statistical view

A computer-aided specimen design to induce shearing strain around a hole

Contact Info

Product

Resources

About