Probability Assessment of the Mechanical and Low-Cycle Properties of Structural Steels and Aluminium

Abstract

Key mechanical properties used in low-cycle strength and durability calculations are the strength (proportional limit stress, σpr; relative yield strength, σ0.2; and ultimate tensile stress, σu) and strain properties (proportional limit strain, epr; percent area reduction, ψ; and percent area reduction at failure, ψu). When selecting the key mechanical properties provided in the specifications, an error may be made due to the failure to account for a series of random factors that determine the distribution of properties. The majority of research papers dealing with statistical descriptions of the low-cycle strain properties do not look deeper into the distribution of mechanical properties and the diagram parameters of strain characteristics. This paper provides a description of the distribution patterns of mechanical properties, statistical parameters, and low-cycle fatigue curves. Log-normal distribution generated the lowest values for the coefficient of variation of one of the key statistical indicators, suggesting that log-normal distribution is superior to normal or Weibull distribution in this respect. The distribution of low-cycle strain parameters exceeded the distribution of mechanical properties considerably. Minimum coefficients of variation of the parameters were generated at normal distribution. The statistical analysis showed the lower distribution of the durability parameters compared to the distribution of parameters of the strain diagrams. The findings of the paper enable a revision of the durability and life of the structural elements of in-service facilities subject to elastoplastic loading by assessing the distribution of mechanical characteristics and low-cycle strain parameters as well as the permissible distribution limits.

Statistical Estimation of Resistance to Cyclic Deformation of Structural Steels and Aluminum Alloy

“…As follows of the equations from the previous paragraph, the values of parameters A 1 , A 1 f , A 2 , A 2 f , β, c, S T and α are necessary in the analytical description of the cyclic deformation curves. According to the methodology provided in [34], the histograms for the cyclic deformation parameters mentioned above were defined (Figures 4 and A1-A3). The histograms of parameter A 1 for 15Cr2MoVA steel indicate a significant scatter of the parameter, and with an increase in the volume of the statistical series (the level of loading σ 0 = 1.00-20 samples and σ 0 = 1.14-40 samples), their form approaches the normal distribution.…”