American Journal of Mechanical Engineering, 2017, Vol. 5, No. 6, 274-279 Available online at http://pubs.sciepub.com/ajme/5/6/8 ©Science and Education Publishing DOI:10.12691/ajme-5-6-8 Determination of the Fatigue Life of the Vehicle Construction Based on Strength Calculations Michal Kicko * , Peter Frankovský, Róbert Huňady, Adam Kaľavský, Ján Kostka Department of Applied Mechanics and Mechanical Engineering, Faculty of Mechanical Engineering, Technical University, Košice, Slovakia *Corresponding author: michal.kicko@tuke.sk Abstract The article is divided into three parts. Except the foundations of theoretical knowledges about the fatigue life, the design of the breakdown truck body construction for a particular vehicle is also described in initials. In the second part the stress analysis of this construction is analyzed by finite element method (FEM). Based on this, at the end of the thesis, the fatigue life time is evaluated and compared with the experimental. Keywords: fatigue service lifetime, breakdown truck body construction, Rule EEC 55, Abaqus CAE, finite element method (FEM) Cite This Article: Michal Kicko, Peter Frankovský, Róbert Huňady, Adam Kaľavský, and Ján Kostka, “Determination of the Fatigue Life of the Vehicle Construction Based on Strength Calculations.” American Journal of Mechanical Engineering, vol. 5, no. 6 (2017): 274-279. doi: 10.12691/ajme-5-6-8. 1. Introduction With an increasing number of vehicles on the roads, the demand for breakdown trucks is rising. This article deals with the design of the breakdown truck body construction and its subsequent strength analysis, with a lifetime evaluation for piece or small-lot production. For the use in practice of such a breakdown truck, it is necessary to experimentally verify the fatigue life of the critical part of the body construction according to the EEC 55 standard. This must be done before the joining assembly. As a result, the idea of life prediction rises and she was based on numerical calculations, and critical design nodes could be optimized before a real fatigue test in the event of a negative result. 2. Basics of the Fatigue Life Time The dependence of the stress amplitude on the number of cycles to the break is determined by the SN - curve constructed on the basis of a series of fatigue tests on samples of the same material, dimensions, shape and quality of the surface, subjected to cyclical loads with zero value of mean stress up to break. The individual samples are loaded descending from the highest load amplitude, with the observed parameter being the number of cycles to the fraction, to obtain a set of points corresponding to the number of loaded samples, which after the translation by curve will characterize the fatigue characteristic shown in Figure 1. From the Figure 1 it is possible to reveal the dependence of the stress amplitude on the number of cycles to the fracture for which . , B a AN σ = (1) one is more often written in shape ' .(2 ) , B a f N σ σ = (2) where ' f σ is a coefficient of fatigue strength which is generally equal to the actual fracture stress f σ which is higher than the ultimate strength itself. Figure 1. SN - curve construction for ussual low carbon steel Low carbon steels are characterized by the fact that from the number of cycles 10 6 upwards, the amplitude of the stress does not decreasses, and therefore, under such a load, the component withstand theoretically an infinite number of cycles, without causing fatigue damage. From this assumption, a material property σ c , which is called the material fatigue limit, was created. [1] 2.2. Prediction of Fatigue Lifetime The first step is to determine the amplitude of the symmetric cycle σ ar , which can be determined from each