PSI - Issue 66

Vladimír Chmelko et al. / Procedia Structural Integrity 66 (2024) 426–432

427

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Vladimír Chmelko at al ./ Structural Integrity Procedia 00 (2025) 000–000

- The first concept of cyclic testing derived from axle fatigue of railway carriages and locomotives, begun by August Wohler - The formulation of the power law for fatigue curves by Basquin - The observation of the first slip bands on the surface of cyclically loaded material, later the first intrusions and extrusions - Formulation of the first cumulative rule, still in use today and known as the Palmgren-Miner rule These and many other milestones along the path of progressively unraveling the mysteries of materials fatigue have led to the identification of key factors used in the engineering assessment of fatigue strength and durability of materials and structural elements: - The size factor - Surface roughness factor - Shape effects - Notch sensitivity of materials - Stress distribution gradient factor Virtually all factors have been experimentally documented and described using diagrams and prescriptions for evaluating the fatigue properties of structural parts [1-3]. At the end of the last century, efforts to describe fatigue under multiaxial stress state accelerated, and in the last 10 years, another challenge came - fatigue of additively manufactured metals [4-6]. Both topics of recent years have revealed additional factors in the already multifactorial field of materials fatigue that significantly affect the fatigue strength and service life of structural parts. It is the specifics in the fatigue assessment of additively manufactured materials that are the focus of this article. - Definition of an algorithm for extracting cycles from a time-random loading by Endo - Development of computer-controlled tension or torsion cyclic test puzzles by MTS

Nomenclature AM

additive manufacturing DLMS direct laser metal sintering

2. Materials description The most commonly used materials for additive manufacturing today are: light alloys AlSi10Mg and Ti6Al4V, stainless steels 316L and 17-4PH, tool steel MS1, Inconel 718 and 625, and more are being added all the time. In the laboratories of the Institute of Applied Mechanics and Mechatronics of the Slovak Technical University 3 additively manufactured materials have been subjected to cyclic tests: AlSi10Mg, 316L, MS1, while AlSi10Mg material was also tested on samples made from conventionally cast material. The printing technology was DLMS (Direct Laser Metal Sintering) on the EOS printer of the Regional Technological Institute Z Č U Pilsen. The chemical composition of the materials used is given in Table 1.

Table 1. Chemical composition of used materials.

Si (%)

Mg (%)

Fe (%)

Ti (%)

Mn (%)

Cu (%)

Zn (%)

Cr (%)

AlSi10Mg

Conventional metallurgy Additive manufacturing

10.20

0.346

0.112

0.121

0.046

0.0017

0.02

0.002

10.1

0.38

0.09

 0.03

 0.03

 0.03

 0.03

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