Boundary element analysis of stiffened panels with repair patches

Abstract

In this paper a boundary element method for analysis of fractured stiffened panels repaired with riveted or adhesively bonded patches is presented. In order to achieve such a formulation, several boundary element formulations involving the membrane and bending of displacement, and, stress resultants are coupled together to analyse the model. The multi-region formulation is used to simulate the stiffeners, which are modelled as an assembly. They are then connected to the sheets to form the stiffened panels by means of a rivet formulation. The dual boundary element method is used to simulate the presence of cracks, and the patches, treated as independent plates, are joined to the panel either with rivets or adhesive. A boundary element formulation for adhesive bonding is implemented to model the adhesively bonded patches. The Crack Opening Displacements (COD) method and the Jintegral are implemented to evalute the required fracture parameters. Examples presented include a wing box with a three spar section, with fully stiffened skin, and, the skin is considered to have a crack and a repair patch is used on top of the crack to stop its growth.Response to Reviewers: Thank you for highlighting the missing references and figures numbers as well as certain typo's. We have corrected all the highlighted items.Thank you for highlighting the missing references and figures numbers as well as certain typo's. We have corrected all the highlighted items. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 Detailed Response to Reviewers AbstractIn this paper a boundary element method for analysis of fractured stiffened panels repaired with riveted or adhesively bonded patches is presented. In order to achieve such a formulation, several boundary element formulations involving the membrane and bending of displacement, and, stress resultants are coupled together to analyse the model. The multi-region formulation is used to simulate the stiffeners, which are modelled as an assembly. They are then connected to the sheets to form the stiffened panels by means of a rivet formulation. The dual boundary element method is used to simulate the presence of cracks, and the patches, treated as independent plates, are joined to the panel either with rivets or adhesive. A boundary element formulation for adhesive bonding is implemented to model the adhesively bonded patches. The Crack Opening Displacements (COD) method and the J-integral are implemented to evalute the required fracture parameters. Examples presented include a wing box with a three spar section, with fully stiffened skin, and, the skin is considered to have a crack and a repair patch is used on top of the crack to stop its growth.

Junctions in shell structures: A review

“…The procedure related the stress levels from FE software to the provisions of ASME codes. Di Pisa and Aliabadi [93] analysed the boundary element method (BEM) by the fractured stiffened panels repaired with riveted or adhesively bonded patches. The patches were joined to the panel either with rivets or adhesive.…”

The Frame Structure Analysis of the Structure with Repaired Part

“…Therefore, it is required to repair those aged infrastructure facilities to maintain the reliability of those structures. There are some repairing processes for these facilities such as the plate patch method [1] for closing the damaged part, the stop hole method [2] for restraining the propagation of a crack by a hole induced ahead of the crack tip, the overlay welding method [3] for covering damaged part and the thermal spraying method [4]. However, such a repairing treatment generates a large residual stress in the components, as well as distortion in the overall structure including the part to be repaired.…”

Analysis of cracked body repaired by adhesively bonded patches by bem-fem coupling

“…In addition, a parametric study was carried out to investigate the influence of the bond length, the bond width, the CFRP stiffness and the adhesive shear modulus on the stress intensity factors and concluding results were consistent with those of Liu et al (2009). Recently, Pisa and Aliabadi (2015) developed a technique based mainly on a boundary integral equation method to solve a problem associated with stiffened panels with repairing patches. In their study, the BEM formulation was enhanced to allow the treatment of complex structures including all the features of stiffeners and repairing patches.…”

“…In addition to their high stiffness and strength, the patches are structurally efficient and induce much less damages to the repaired structures. In the modeling point of view via a theory of linear elasticity and linear elastic fracture mechanics, the stress intensity factor along the crack front can be significantly reduced after the cracked body is repaired by attaching a patch over the cracked region (e.g., Alaimo et al, 2009;Jiann-Quo and Kam-Lun, 1991;Liu et al, 2009;Pisa and Aliabadi, 2015;Aliabadi, 1996, 1998;Sekine et al, 2005;Useche et al, 2008;Wen et al, 2000Wen et al, , 2002Wen et al, , 2003Widagdo and Aliabadi, 2001;Young et al, 1992;Yu et al, 2014). This is due to the fact that some of externally applied loads exerted to the cracked bodies are either shared by or transferred directly to the patch via the adhesive layer rendering the enhancement of stiffness near the patching region and the reduction of relative crack-face displacements.…”

“…As a direct consequence, the growth of the cracks can be delayed or even ceased if the repair is properly designed. Evidences from past studies have indicated that various parameters including the dimensions and material properties of the repaired structure, the patch, and the adhesive layer significantly affects the efficiency and effectiveness of the repair (e.g., Alaimo et al, 2009;Jiann-Quo and Kam-Lun, 1991;Liu et al, 2009;Pisa and Aliabadi, 2015;Aliabadi, 1996, 1998;Sekine et al, 2005;Useche et al, 2008;Wen et al, 2000Wen et al, , 2002Wen et al, , 2003Widagdo and Aliabadi, 2001;Young et al, 1992;Yu et al, 2014). The full investigation to understand the role of those parameters is considered essential and can assist designers/engineers in the optimization of their designs.…”