Scientific production

In this page you will be able to find the scientific publications related to Fatigue4Light project published by partners

Effect of Cutting Clearance and Sandblasting on Fatigue of Thick CP800 Steel Sheets for Heavy-Duty Vehicles

Proceedings of the 8th International Conference “Hot Sheet Metal Forming of High-Performance Steel (CHS2), Barcelona, Spain, 30th May 2022 – 2nd June 2022

by D. Gustafsson (Luleå University of Technology); S. Parareda (Eurecat, CIEFMA, EEBE, Universitat Politècnica de Catalunya-BarcelonaTech); P. Jonsén; J. Kajberg and E. Olsson (Luleå University of Technology)

Effect from manufacturing processes on fatigue properties of high-strength thick steel sheets have gained increased attention the recent years, due to new demands on the heavy-duty vehicle (HDV) industry to reduce the carbon footprint. The aim of this study is to add knowledge of the effect of shear cutting clearance on the fatigue behaviour of complex phase CP800 thick steel sheets. In ad-dition, sandblasting and its effect on the fatigue properties are studied. Service loads are fluctuating loads acting on chassis component making fatigue an important failure mode. The fatigue strength usually follows the yield strength of the material and hence weight could in theory be saved by using steels of higher strength. However, in the presence of edge defects this relation does not necessarily hold, this leads to large safety factors of the design and under-utilization of the high-strength mate-rial. Thus, an increased knowledge about the effect from manufacturing processes on fatigue prop-erties is important for the quest to achieve weight reduction. This is particularly true for thick sheets which, to the best of our knowledge, are less investigated than their thinner counterparts, but of high importance for the HDV development.

In this paper, empirical results from fatigue testing of complex phase steel CP800, subjected to punching and trimming, are presented. Results for different cutting clearances are compared as well as the effect of sandblasting. A fast fatigue testing method called Rapid fatigue test based on stiffness evolution is utilized. The results show the improvement obtained by using sandblasting as well as illustrating the effect of different cutting clearances. These results can be used as a guidance for design and production of HDV components, where cutting clearance is set. Furthermore, the results can be used as an input for discussions whether the extra costs associated with sandblasting is mo-tivated or not for components made from high strength, thick steel sheets.

Fatigue resistance evaluation of high Mn-TWIP steel through damage mechanics: a new method based on stiffness evolution

International Journal of Fatigue (2021)

by S. Parareda; A. Lara (Eurecat); D. Casellas (Eurecat, Luleå University of Technology); A. Mateo (Universitat Politècnica de Catalunya).

The work presented here deals with the implementation of a new methodology that allows fast and reliable determination of the fatigue strength. It is based on monitoring the specimen stiffness changes at different stress levels, as an indicator of the evolution of fatigue damage. This new rapid fatigue test uses techniques available in many laboratories, as the DIC (Digital Image Correlation) technique and common extensometers. Moreover, the obtained data are easier to handle than infrared cameras or acoustic emission systems data, and the experimental procedure to determine the fatigue limit is more evident than in the self-heating method.

Experiments have been conducted in TWIP (Twinning Induced Plasticity) steel, a material used for lightweighting the structural parts of vehicles. With their excellent energy absorption capacity, TWIP steels can satisfy the part requirements in terms of crash performance, while their high tensile strength can deal with the cyclic loads acting on chassis parts. Therefore, many efforts focus on improving the fatigue strength of TWIP steels through pre-straining and/or surface treatments. However, finding the best way to improve the fatigue resistance requires time and resources that often hinder the development of the material. For this reason, a TWIP steel has been selected to check the new rapid fatigue test. The prediction made using the proposed approach is validated by comparison with conventional staircase results and fatigue crack growth standardised tests. The good agreement allows proposing the new method as a fast and efficient way to determine the fatigue resistance in metals.

Statistical models for estimating the fatigue life, the stress-life relation, and the P-S-N curves of metallic materials in Very High Cycle Fatigue: A review

Fatigue & Fracture of Engineering Materials & Structures (2021)

by A. Tridello; C. Boursier Niutta; M. Rossetto; D.S. Paolino (POLITO) F. Berto (NTNU).

The research on the Very High Cycle Fatigue (VHCF) response of materials isfundamental to guarantee a safe design of structural components. Researchersdevelop models for the fatigue life in VHCF, aiming at assessing the stress–liferelation and, accordingly, the probabilistic S–N (P-S–N) curves. In the paper,the models for the stress–life relation in VHCF are comprehensively reviewed.The models are classified according to the approach followed for defining thestress–life dependency, that is, power law, probabilistic, fracture mechanics, orParis law-based approach. The number of failure modes that can be modeled,the statistical distribution for the fatigue life, and the characteristics of the esti-mated P-S–N curves are also reviewed by analyzing the fitting capability ofexperimental datasets for each model. This review is supposed to highlight thestrengths and weaknesses of the currently available models and guide thefuture research.

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