In-Situ Calibrated Modeling of Residual Stresses Induced in Machining under Various Cooling and Lubricating Environments

Abstract

Although many functional characteristics, such as fatigue life and damage resistance depend on residual stresses, there are currently no industrially viable ‘Digital Process Twin’ models (DPTs) capable of efficiently and quickly predicting machining-induced stresses. By leveraging advances in ultra-high-speed in-situ experimental characterization of machining and finishing processes under plane strain (orthogonal/2D) conditions, we have developed a set of physics-based semi-analytical models to predict residual stress evolution in light of the extreme gradients of stress, strain and temperature, which are unique to these thermo-mechanical processes. Initial validation trials of this novel paradigm were carried out in Ti-6Al4V and AISI 4340 alloy steel. A variety dry, cryogenically cooled and oil lubricated conditions were evaluated to determine the model’s ability to capture the tribological changes induced due to lubrication and cooling. The preliminarily calibrated and validated model exhibited an average correlation of better than 20% between the predicted stresses and experimental data, with calculation times of less than a second. Based on such fast-acting DPTs, the authors envision future capabilities in pro-active surface engineering of advanced structural components (e.g., turbine blades).

Determination of the Cutting-Edge Microgeometry Based on Process Forces during Peripheral Milling of Ti-6Al-4V Using Machine Learning

“…For the second series of experiments (Table 2), eight different tools (No. [4][5][6][7][8][9][10][11] were prepared, with cutting edge radii ranging from 5 ± 1 µm (new tool) to 60 ± 1 µm. The cutting speed v c and the radial depth of cut a e were kept constant and the feed per tooth was varied from 0.04 to 0.08 mm in steps of 0.2 mm.…”

“…The change in residual stresses can therefore be used to assess the overall structural strength of the component and its propensity to fatigue failure in service [7]. Mechanical loads tend to cause compressive stresses, while thermal effects generally cause residual stresses in the tensile range [8,9]. Compressive residual stresses have been found to positively affect the fatigue life, creep behavior and crack propagation resistance, while tensile residual stresses are usually detrimental [1,10].…”

Hydrogen Cooling of Turbo Aggregates and the Problem of Rotor Shafts Materials Degradation Evaluation

“…Rotor shafts are periodically machined using LCLs. It is known that the use of various LCLs can significantly affect a number of processes in the surface and subsurface layers, for example, the stress-strain state and the course of destructive processes [85][86][87][88][89][90][91][92][93].…”