PSI - Issue 66

0LORVODY .HSND -U et al. / Procedia Structural Integrity 66 (2024) 135–141 Miloslav Kepka Jr. et al / Structural Integrity Procedia 00 (2025) 000 – 000

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Experimental research on the fatigue strength of weldments with the application of HFMI at the Regional Technological Institute (RTI), a research center of the Faculty of Mechanical Engineering of the University of West Bohemia in Pilsen, was motivated by the aforementioned recommendation [1]. A wide range of fatigue tests of weldments of various configurations was carried out not only as part of internal research and student qualification works but mainly as part of R&D projects financed by the Technology Agency of the Czech Republic (TREND and TRANSPORT 2020+ programs). Subsequently, findings from these experimental activities are presented. 2. Research in cooperation with ŠKODA TRANSPORTATION In cooperation with ŠKODA TRANSPORTATION, an ambitious test program is being completed, the o utput of which will be about 90 S-N curves for 3 structural steels used in the construction of rolling stock, 7 different configurations of welds in the state without and with the application of HFMI made from sheets of 3 different thicknesses (4, 8 and 15 mm). Part of the test matrix is shown in the photos of the test samples in Fig. 4.

Fig. 4. Photos of test samples.

The aim of the test program is to prepare arguments for the national railway authority (this authority, which approves the commissioning of rolling stock, does not yet accept the use of methods such as hammering to improve the fatigue strength of welds). An example of the experimental results presented in the literature [2] is in Fig. 5. From the results shown, the beneficial effect of the application of HFMI and a more significant improvement in fatigue strength for steel of higher strength is evident.

Fig. 5. Examples of S-N curves of the same test specimens without and with HFMI application made from different steels.