PSI - Issue 59

Yaroslav Shved et al. / Procedia Structural Integrity 59 (2024) 664–671 Yaroslav Shved et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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To determine the parameters of the structure's SSS and to model its limit state, it is necessary to know the mechanical properties of the truss material and its welds. Information on the mechanical properties of A570-36 steel is publicly available in standards DSTU 4484:2005 and quality certificates for batches of rolled profiles made of this material. However, these documents reveal a significant dispersion of mechanical property values, and it is not advisable to use them for research, as this will immediately transfer the corresponding dispersion to the value of the limit state of the construction, reducing the reliability of the results. There is no information on the mechanical properties of A570-36 steel determined on welded samples. According to the research objectives, the mechanical properties of the A570-36 steel, of which the welded truss is made, were determined through experiments. For the study, samples of a standard configuration were made, which were obtained from a rolled angle profile (Fig. 3).

Fig. 3. Samples for experimental determination of the strength properties of A570-36 steel in static tension: (a) cutout scheme; (b) main material; (c) welded material; (d, e) – photos of the samples.

The mechanical properties of A570-36 steel were determined on a certified electrohydraulic testing complex STM-100 for five solid and five welded samples according to a standardized method. Welding was a semi-automatic electric arc in the CO 2 environment. The results were statistically analyzed. 3. Results and Discussion The results of the mechanical properties studies of A570-36 steel are with main material tensile strength average value at 380 MPa, yield strength at 273 MPa and 36% elongation. Sample average quadratic deviation at S σ v = 8.16 MPa, S σт = 8.45 MPa, S δ =0.012. Dispersion at D σ v = 66.6 MPa 2 , D σт =71.4 MPa 2 , D δ =1.44x10 - 4 . Results with welded joint are: strength limit at 283 MPa, sample average quadratic deviation S σ v = 14.2 MPa and dispersion D σ v =202 MPa 2 Comparison of the tensile strength and the yield strength for A570-36 steel obtained from different sources and as a result of the experiment (Fig. 4) shows a significant discrepancy between these indicators (the difference is 1.5...2.5 times), which explains the expediency of experimentally determining the actual values of these parameters.

Fig. 4. Distribution of tensile strength (a) and yield strength (b) values for A570-36 steel: 1 – according to standard; 2 – according to the manufacturer's quality certificates; 3 – according to the results of the experiment. A physical model of the 600x120 mm studied truss was designed and manufactured in compliance with the classical principles of small-scale experiments (Fig. 5).