A fundamental investigation on rotating tool cold expansion: numerical and experimental perspectives

Kumar, B M; Panaskar, Nitin; Sharma, Abhay

doi:10.1007/s00170-014-5888-2

Cited by 14 publications

(6 citation statements)

References 20 publications

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“…Thus, their method produces three beneficial effects: hole cold expansion, burnishing, and surface microstructure modification (friction stir and torsion due to tool rotation). Finally, Kumar et al [9] proposed a novel technique for cold expansion using a rotating tapered mandrel, which combines cold expansion and friction processing.…”

Section: Introductionmentioning

confidence: 99%

Modified Split Mandrel Method and Equipment to Improve the Fatigue Performance of Structural Components with Fastener Holes

Maximov,

Duncheva,

Anchev

et al. 2024

Metals

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Fastener holes are among the most common natural stress concentrators in metal structures. The life cycles of various structural elements, such as those in aircraft structures, automobiles, and rail-end bolt joints, are limited by fatigue damage around the holes. An effective approach to delay the formation and growth of fatigue macrocracks is to introduce residual hoop compressive stresses around the holes. Two methods have become established in the prestressing of fastener holes in aircraft components, split sleeve and split mandrel, which implement one-sided processes. The common disadvantage of both methods is the complex procedure due to the need for high accuracy of the initial holes. This article presents a new modified split mandrel method providing the same tightness (interference fit) with a wide tolerance of the pre-drilled hole diameters, reducing the number of technological cycle steps and production costs. То implement the new method, a functionally connected tool and a device with a hydraulic drive were developed. An extensive experimental study of 2024-T3 AA specimens was carried out to evaluate the effectiveness of the method under a high scattering of the pre-drilled holes. The new method provided a deep zone of residual hoop compressive stresses on both faces of the specimens after cold working and after hole final reaming. The removal of a plastically deformed layer around the hole of suitable thickness during the final reaming decreased the axial gradient of residual hoop stress distribution. Fatigue tests on a tensile pulsating cycle verified the effectiveness of the modified split mandrel method to significantly increase the fatigue life by 6.6 times based on 106 cycle fatigue strength compared to the conventional case of machining the holes. The obtained S-N curves for three groups of samples with initial hole diameters of 8.0, 8.1, and 8.2 mm, which were cold worked with the same tightness of 0.32 mm and final reamed, aligned well, indicating that the new method can provide constant fatigue strength for a given stress amplitude.

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Section: Introductionmentioning

confidence: 99%

Modified Split Mandrel Method and Equipment to Improve the Fatigue Performance of Structural Components with Fastener Holes

Maximov,

Duncheva,

Anchev

et al. 2024

Metals

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“…To improve the service life and reliability of the devices, it's important to extend the fatigue life of these fastener holes. Conventional hole strengthening methods, named cold working, such as direct cold expansion [2], split sleeve cold expansion [3][4][5][6] and shot peening [7], have already been developed. The principle of these methods is to push the hole wall radially outward, then the elastic/plastic deformation is occurred.…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation on the effects of circuit parameters on the plastic deformation of fastener holes in thin aluminum alloy via electromagnetic expansion process

Geng

Cao

et al. 2021

Int J Adv Manuf Technol

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The size of plastic deformation zone during fastener hole strengthening is a critical indicator of the strengthening effect. In this study, a considerable plastic deformation zone in 1.5 mm aluminum alloy plate with a hole was produced via electromagnetic strengthening. The finite element analysis results showed that the electromagnetic strengthening process could achieve high compressive hoop residual stress around the fastener hole in thin plate without serious axial deformation compared with conventional cold hole expansion process. The simulation results were experimentally validated by the grid method. Furthermore, for the same discharge energy, the size of plastic deformation zone varies with the discharge capacitance, and there was an optimal combination of the discharge capacitance and discharge voltage.What's more, even the plastic deformation zone was the same at the maxed load, different unloading process during the electromagnetic hole expansion process also had a great influence on the strengthening effect.

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“…Unfortunately, there are no known reports concerning experimental verification of the effectiveness of slide burnishing on the fatigue life of a structural component with a slide burnished hole. Another surface modification technique is rotating tool cold expansion . The method is similar to that, proposed by Northrop Grumman Corporation, but the contact of the tool with the treated hole is continuous in cross section, and the interference fit is larger.…”

Section: Introductionmentioning

confidence: 99%

“…Another surface modification technique is rotating tool cold expansion. 20 The method is similar to that, proposed by Northrop Grumman Corporation, 19 but the contact of the tool with the treated hole is continuous in cross section, and the interference fit is larger. This method combines the effect of mandrel cold working (as a result of the presence of interference fit) with the 'local torsion' effect 18 (which effect is made possible by the insured interference fit and the friction between the tool and the hole surface).…”

Section: Introductionmentioning

confidence: 99%

“…Essentially, this method is a type of friction stir processing (FSP) because it is targeted at a micro‐structural modification of the hole surface. That is why in a subsequent publication of the same authors, the FSP concept is already used. An object of their study is the surface modification and nanocomposite layering of a fastener hole in commercial aluminium grade 1200.…”

Section: Introductionmentioning

confidence: 99%

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A new conception for enhancement of fatigue life of large number of fastener holes in aircraft structures

Duncheva

Maximov

Ganev

2016

Fatigue Fract Eng Mat Struct

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A B S T R A C T A new conception for increasing fatigue life of large number of fastener holes in aircraftstructures is developed. It is accomplished by a new method, called friction stir hole expansion (FSHE). This method not only reduces labour and time consumption, but it also decreases the overall cost for processing a large number of holes in structures made of aerospace grade 2024-T3 aluminium alloy. FSHE combines the advantages of friction stir processing with these of mandrel cold working methods in two ways: a micro effect, expressed in hole surface modification, and a macro effect, expressed by the introduction of beneficial compressive residual macro stresses. The effectiveness of the method has been assessed by fatigue tests. Finite element simulations have been carried out. It has been proven that the greater fatigue life of fastener holes, processed by FSHE, is a consequence of the obtained micro effect.Keywords aircraft failures; cold working; fatigue life; finite element analysis; residual stress. N O M E N C L A T U R Ef = feed rate h = hole length ℓ i = working part tool length n = rotating frequency q = heat flow density C = initial kinematic hardening modulus E = Young's modulus F i = area of ith portion from the hole surface M = rotating moment magnitude R = load ratio α ij = back-stress tensor (micro-stress tensor, kinematic shift) γ = coefficient determines the rate of decreasing the kinematic modulus γ ij = angular strain φ sp = coefficient taking into account how much of the generated heat passes into the specimen ε p = equivalent plastic strain ν = Poisson's ratio σ 0 = size of yield surface σ| 0 = size of yield surface at zero plastic strain τ ij = shear stress ω = tool angular velocity Correspondence: J. T. Maximov.

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A fundamental investigation on rotating tool cold expansion: numerical and experimental perspectives

Cited by 14 publications

References 20 publications

Modified Split Mandrel Method and Equipment to Improve the Fatigue Performance of Structural Components with Fastener Holes

Modified Split Mandrel Method and Equipment to Improve the Fatigue Performance of Structural Components with Fastener Holes

Numerical investigation on the effects of circuit parameters on the plastic deformation of fastener holes in thin aluminum alloy via electromagnetic expansion process

A new conception for enhancement of fatigue life of large number of fastener holes in aircraft structures

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