Airframe Life Extension By Optimised Shape Reworking — Overview Of Dsto Developments

Heller, Manfred; Burchill, M.; Wescott, R.; Waldman, Witold; Kaye, R.; Evans, Richard M.; McDonald, Marcus

doi:10.1007/978-90-481-2746-7_17

Cited by 4 publications

(6 citation statements)

References 12 publications

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“…The present work involves edge-guided waves that impinge on a crack at the upper surface of a racecourse shaped hole. Cracking at fuel vent holes of that shape has occurred in practice [ 21 , 22 ], and presents a significant challenge for regular inspection. The scattered wave pattern, and amplitude for various crack lengths, will be reported on and compared to the previous findings for the simpler case of edge cracks along a straight or circular edge [ 3 , 4 , 20 ].…”

Section: Introductionmentioning

confidence: 99%

Experimental and Computational Studies on the Scattering of an Edge-Guided Wave by a Hidden Crack on a Racecourse Shaped Hole

2017

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Reliable and quantitative non-destructive evaluation for small fatigue cracks, in particular those in hard-to-inspect locations, is a challenging problem. Guided waves are advantageous for structural health monitoring due to their slow geometrical decay of amplitude with propagating distance, which is ideal for rapid wide-area inspection. This paper presents a 3D laser vibrometry experimental and finite element analysis of the interaction between an edge-guided wave and a small through-thickness hidden edge crack on a racecourse shaped hole that occurs, in practice, as a fuel vent hole. A piezoelectric transducer is bonded on the straight edge of the hole to generate the incident wave. The excitation signal consists of a 5.5 cycle Hann-windowed tone burst of centre frequency 220 kHz, which is below the cut-off frequency for the first order Lamb wave modes (SH1). Two-dimensional fast Fourier transformation (2D FFT) is applied to the incident and scattered wave field along radial lines emanating from the crack mouth, so as to identify the wave modes and determine their angular variation and amplitude. It is shown experimentally and computationally that mid-plane symmetric edge waves can travel around the hole’s edge to detect a hidden crack. Furthermore, the scattered wave field due to a small crack length, a, (compared to the wavelength λ of the incident wave) is shown to be equivalent to a point source consisting of a particular combination of body-force doublets. It is found that the amplitude of the scattered field increases quadratically as a function of a/λ, whereas the scattered wave pattern is independent of crack length for small cracks a << λ. This study of the forward scattering problem from a known crack size provides a useful guide for the inverse problem of hidden crack detection and sizing.

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Section: Introductionmentioning

confidence: 99%

Experimental and Computational Studies on the Scattering of an Edge-Guided Wave by a Hidden Crack on a Racecourse Shaped Hole

2017

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“…Then, many others dealt with similar problems. To name only a few of them: Francavilla et al 6 considered Tvergaard’s problem and solved it with use of FEM, and also searched for optimal shape of a connecting rod; Pedersen and Pedersen 7 considered optimisation of grooves in shafts and notches in flat bars; Burchill and Heller 8 investigated notch problem in plates, Heller et al 9,10 analysed problem of cavities in plates; Waldman et al 11 studied fillets in flat plates subjected to tension and bending. The state of the art in this matter is discussed and summarised in Pedersen.…”

Section: Introductionmentioning

confidence: 99%

“…Also, the alternative names such as gradientless method or moving boundary method are used. 10,11 One of the more recent implementations of the method is the gradientless multi-peak method, which successfully deals with problems including multiple stress peaks appearing along the boundary of stress concentrators. 9,10…”

Section: Introductionmentioning

confidence: 99%

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Parametric optimisation of stress relief groove shape in flat ends of boilers

Szybiński

Wroblewski

2011

The Journal of Strain Analysis for Engineering Design

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Flat ends of boilers with stress relief grooves have been used for many years. The existing standards set the value for the endplate thickness and admissible range of values for radius of the groove and the minimum thickness of the endplate under the relief groove. However, the codes do not specify the optimal parameters values for the endplate with stress relief groove. In this paper, the authors study the optimal choice of parameters for circular groove, and then propose its shape modification to elliptical, which considerably decreases stress concentration appearing in the zone of the groove. In the next step, the elliptical shape is replaced by the groove modelled by two spline functions, which results in further reduction of stress concentration. Finally, the groove with shape including several spline functions is proposed as an optimal one. In the performed study, the finite element modelling and the simple search method in optimisation procedures are used.

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“…In this approach, cracks are removed using an optimised rework shape that provides significantly reduced stress peaks. Details of the technology are given in [2,3]. As expected, reduced peak stresses typically lead to increased fatigue life, inspection intervals and airframe availability.…”

Section: Introductionmentioning

confidence: 99%

Life Extension of F/A-18 LAU-7 Missile Launcher Housings Using Rework Shape Optimisation

Heller

Calero

Wescott

et al. 2014

AMR

Self Cite

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LAU-7 missile launcher housings, which are fitted to most Royal Australian Air Force (RAAF) F/A-18A/B aircraft, can experience cracking in the guide rail. This paper covers the design, manufacture and validation of a life extension repair for cracked launcher housings. The repair development uses DSTO's rework shape optimisation technology and fatigue testing capabilities. The rework design reduces peak stresses by 33 %, resulting in significant fatigue life enhancements, as demonstrated by representative coupon testing. A special manufacturing jig has been designed and transitioned to the RAAF, which has used it to repair housings. These housings have performed well in flight tests, with no cracking detected.

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Airframe Life Extension By Optimised Shape Reworking — Overview Of Dsto Developments

Cited by 4 publications

References 12 publications

Experimental and Computational Studies on the Scattering of an Edge-Guided Wave by a Hidden Crack on a Racecourse Shaped Hole

Experimental and Computational Studies on the Scattering of an Edge-Guided Wave by a Hidden Crack on a Racecourse Shaped Hole

Parametric optimisation of stress relief groove shape in flat ends of boilers

Life Extension of F/A-18 LAU-7 Missile Launcher Housings Using Rework Shape Optimisation

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