Finite Element Analysis of Split Sleeve Cold Expansion Process on Multiple Hole Aluminum Alloy

Yuan, Le; Dong, Meng’en; Zhang, Teng; Wang, Changkai; Hou, Bo; Li, Changfan

doi:10.3390/ma16031109

Cited by 6 publications

(3 citation statements)

References 38 publications

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“…Nevertheless, apart from the residual stresses and fatigue performance, studies of the microstructure around the holes after the split sleeve cold expansion process for AZ31B magnesium alloy sheet [26] and 7075-Т6 aluminum alloy [27] are of interest. Furthermore, Lv et al [28] used finite element analysis to investigate the distribution and variation of residual stresses along the hole edges of 7075 aluminum alloy single-hole and multi-hole split sleeve cold expansion specimens.…”

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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show abstract

“…The domestic academic system has invested a great deal of research in order to clarify the cold expansion strengthening mechanism. Lv et al improved the fatigue life of fasteners by applying compressive residual stresses around their holes [16]. They used the finite element method (FEM) to study the distribution and variation of residual stresses around the hole.…”

Section: Introductionmentioning

confidence: 99%

Research on the Residual Stress Field of a Compression Bushing-Lug Plate in Cold Expansion Strengthening

Lin,

Bai,

Wang

et al. 2023

Applied Sciences

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The accurate acquisition of the residual stress field is the key to clarifying the cold expansion strengthening mechanism of compression bushings, optimizing the extrusion process parameters, and improving the structural fatigue life. In the actual cold expansion strengthening process, the resultant distribution of residual stresses is influenced by the relative extrusion amount, mandrel structure, material properties, and extrusion speed. In this article, the distribution patterns of residual stress after cold extrusion are investigated through a combination of finite element simulation and experimental measurements using a micro-region stress tester. To examine the redistribution law of the stress field of cold expansion reinforcement under external load, the compression bushing-lug-plate-reinforced structure is loaded and unloaded. The results show that large circumferential residual compressive stresses are distributed in the hole wall of the compression bushing after cold expansion. Radial residual stresses are also compressive stresses, although the values are small. In addition, the reinforced structure after cold extrusion presents a large difference in the stress redistribution rules compared with cold extrusion after the load is applied and removed.

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“…Nevertheless, apart from the residual stresses and fatigue performance, the studies of the microstructure around the holes after the split sleeve cold expansion process of AZ31B magnesium alloy sheet [24] and 7075-Т6 aluminum alloy [25] are of interest. Furthermore Lv et al [26] Used finite element analysis to investigate the distribution and variation of residual stresses along the hole edges of 7075 aluminum alloy single-hole and multi-hole split sleeve cold expansion specimens.…”

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. 2023

Preprint

View full text Add to dashboard Cite

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 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.

show abstract

Finite Element Analysis of Split Sleeve Cold Expansion Process on Multiple Hole Aluminum Alloy

Cited by 6 publications

References 38 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

Research on the Residual Stress Field of a Compression Bushing-Lug Plate in Cold Expansion Strengthening

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

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