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 R a = 0.055 lm; 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.

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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.

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 through a new combined cutting tool; cold hole working by spherical motion cold working through a new tool equipment, which minimizes the axial force on the reverse stroke. The new technology introduces beneficial residual compressive stresses around the bolted holes thereby preventing the fatigue cracks growth and increasing the fatigue life of these openings.

A new method and tool for processing a large number of small fastener holes in high-strength Al alloy structures through cold plastic deformation have been developed in order to decrease labor and operational time by following the high fatigue resistance requirement. The deforming portion of the tool has been specifically profiled in cross section so that the contact with the hole surface is disrupted. The diameter of the circumference around the deforming portion is greater than the diameter of a preliminary drilled and reamed hole. The tool and hole have a common axis around which the tool is rotating and, at the same time, moving along the same axis while passing through the hole. Thus, this method produces three main beneficial effects: hole cold expansion, surface plastic deformation (mixed burnishing) and microstructure modification (friction stir and torsion). These three effects have been studied and proven through an experiment and 3D FEM simulations. An integral evaluation of the proposed method and tool has been made through fatigue tests of cyclic tension. The obtained S-N curves prove that the fatigue life increases significantly in comparison with the case of only drilled and reamed holes. Based on the conducted studies, a super-combined tool that consequently performs drilling, reaming and cold plastic deformation has been designed and manufactured. This tool significantly increases the productivity of processing a large number of fastener holes in aluminum structures.