Cold expansion technology of connection holes in aircraft structures: A review and prospect

Modeling of strain hardening and creep behaviour of 2024T3 aluminium alloy at room and high temperatures

This review paper is devoted to the slide burnishing (SB) of metal components—state-of-the-art, achievements and perspectives. SB belongs to the group of static methods for mechanical surface treatment used largely in aerospace, automotive and other industries. By means of the plastic deformation of the surface layers, the surface integrity (SI) of the respective component is improved greatly in terms of minimum roughness, micro-hardness and introduced residual compressive stresses. As a result, fatigue crack resistance, crack corrosion resistance, wear resistance and corrosion resistance increase dramatically. The main feature of SB is the sliding friction contact between the deforming element and the surface being treated. Using the differential-morphological method, an integrated classification of the static methods is created and the area of SB is outlined. The proposed morphological matrix, which can be expanded and supplemented contains existing burnishing methods as well as combinations of elements and interactions that can be used to synthesize new burnishing methods and tools. In addition, a literature review of the publications devoted to SB has been conducted. Further, an analysis of the published studies on different criteria has been carried out and graphic visualizations of the statistical results have been made. On this basis, relevant conclusions have been made and the directions for future investigations of SB have been outlined.

Slide burnishing—review and prospects

Experimental and numerical investigations on the influence of cold expansion on low cycle fatigue life of bolt holes in aeroengine superalloy disk at elevated temperature

Effect of hole cold expansion on fatigue performance of corroded 7B04-T6 aluminium alloy

Chromium–nickel steels are widely used in various fields of the engineering practice because of their increased corrosion resistance. One of the most used chromium–nickel steel is AISI 316Ti. It is known from the engineering practice that processing this steel by cutting creates difficulties and problems. However, there is no information regarding the effectiveness of the slide burnishing (SB) method in terms of quality of the processed surface of this chromium–nickel steel. A comprehensive experimental and FEM study of the surface integrity of slide burnished specimens made of AISI 316Ti austenitic stainless steel has been carried out. The effect of the SB parameters on the obtained roughness, microhardness, residual stress, fatigue strength (life) and wear resistance has been studied. A fully coupled thermal-stress FEM analysis has been conducted to be appreciated the effect of the generated temperature in SB process on the residual stress formation. The SB of AISI 316Ti steel achieves: roughness of Ra = 0.055 μm; micro-hardness increased by more than 32%; significant wear resistance; introduced residual stress with a maximum absolute value, which significantly exceeds the yield limit of the bulk material; increased fatigue strength by 38.9%; fatigue life increasing more than 385 times. The obtained experimental outcomes for the main characteristics of the surface integrity prove that SB can be successfully applied as a mixed burnishing for finishing symmetrical rotational components made of chromium–nickel steels.

Effect of slide burnishing method on the surface integrity of AISI 316Ti chromium–nickel steel

A novel method and tool which enhance the fatigue life of structural components with fastener holes

Bolted joint railroad is the subject matter of this paper Rail joint elements are subjected to cyclic and impact loads as a result of the passage of trains, which causes the origination and growth of fatigue cracks occurring, in most cases, around the bolt holes Fatigue failure around rail-end-bolt holes is particularly dangerous because it leads to derailment of trains and, consequently, to inevitable accidents Moreover, the cracking at rail-ends, which starts from bolt hole surface, causes premature rails replacement The presence of residual compressive hoop stresses around the bolted holes, which is achieved by prestressing of these holes, extends the fatigue life of bolted joint railroads This article presents an innovative technology for pre-stressing of rail-end-bolt holes, implemented on a vertical machining centre of Revolver vertical (RV) type Two consecutive operations are involved in the manufacturing technology process: formation of the hole by drilling, reaming and making of a chamfer t

A new approach for pre-stressing of rail-end-bolt holes

The fatigue failure around fastener holes in metal structures is particularly dangerous, since it leads to inevitable accidents. The presence of residual compressive hoop stresses around these holes, imparted by means of mandrel cold working methods closes the existing cracks and impedes the formation of new ones and thereby extends the fatigue life of corresponding component. Although this type of pre-stressing of fastener holes has been of great advantage over recent years it has some disadvantages: significant and nonsymmetrical with respect to the plate middle plane axial gradient of the residual hoop stresses due to axial force flow passing through the plate, considerable surface upset, etc. The article presents a patented method and a tool ensuring symmetric cold hole expansion—introducing near-uniform residual hoop stresses around the hole along its axis having minimized and symmetric gradient with respect to the plate middle plane. Finite element (FE) simulations of the new process have been carried out. The residual stresses and out-of-plane deformations (surface upset) have been analyzed and compared with those obtained by mandrel cold working method and thus the advantages of the patented method have been shown. The symmetric cold expansion process has been realized experimentally and modeling of residual stress distribution around cold expanded holes in carbon steel specimens has been made. The residual hoop stresses have been measured by means of X-ray diffraction technique. The obtained generalized empirical mathematical model of the residual hoop stress distribution is polynomial with respect to the distance from the hole edge and has “coefficients” that are functions of the governing factors. On the basis of the information obtained from FE simulations, suitable fractional factorial experimental design has been synthesized and used for obtaining the polynomial “coefficients”. The verifications of the generalized model prove its authenticity.

Modeling of residual stress distribution around fastener holes in thin plates after symmetric cold expansion

Article history: Received June 6, 2014 Accepted 17 June 2014 Available online 19 July 2014 The fatigue failure around rail-end-bolt holes is particularly dangerous since it leads to derailment of trains and consequently to inevitable accidents. It is well-known that the fatigue life of structural holed components, subjected to cyclic load, can be increased by generating compressive hoop stresses around the holes. These beneficial residual compressive stresses significantly reduce the maximum values of the operating tensile stresses arising at the critical points of the components and thus impede the formation of first mode cracks. A new approach to enhancement of fatigue life of rail-end-bolt holes has been developed. The approach involves sequential drilling and reaming through a new combined tool and then slide diamond burnishing by a new device. The technology implementation was carried out on machine tool. The process of creating residual stresses has been studied both experimentally and numerically. The experimental study was conducted by means of a modified split ring method. A reliable finite element modeling approach to the slide diamond burnishing process was developed. On this basis, the process was optimized by means of a genetic algorithm. As a result, the optimal combination of the governing process parameters is established, which ensures both maximum depth of the compressive zone and maximum absolute values of the residual stresses. © 2014 Growing Science Ltd. All rights reserved.

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I. M. Amudjev

Papers

Effect of slide burnishing method on the surface integrity of AISI 316Ti chromium–nickel steel

A novel method and tool which enhance the fatigue life of structural components with fastener holes

A new approach for pre-stressing of rail-end-bolt holes

Modeling of residual stress distribution around fastener holes in thin plates after symmetric cold expansion

Enhancement of fatigue life of rail-end-bolt holes by slide diamond burnishing