Analysis of the mechanical properties of Q345R steel in deep-regulating units by the spherical indentation method

Abstract

The principles of testing the mechanical properties of metallic materials through the use of the spherical indentation test have been analysed and studied in this paper. The error between the representative indentation stress from spherical indentation and the theoretical stress of the power exponential equation was taken as the convergence condition using the optimization function in Matlab. The yield strength, strain hardening index and elastic modulus were optimized between the stress-strain curve from spherical indentation and the theoretical stress-strain curve of the power exponential equation. The smallest error that could be achieved between them was obtained and from this the mechanical properties of the material could then be calculated and analysed. Q345R steel, which is used for pressure vessels, was taken as an example and the mechanical properties were tested using the spherical indentation test, and the results were compared with the conventional tensile test. Comparative analysis of the mechanical properties of the steel between the results from the spherical indentation test and the conventional tensile test showed that the difference was small. The accuracy of the spherical indentation method when testing the mechanical properties of metallic materials is high. The results have shown that the spherical indentation test can be used as a replacement for the conventional tensile test and can be applied in the field of testing the mechanical properties of Q345R steel for pressure vessels.

Research on Determining Elastic–Plastic Constitutive Parameters of Materials from Load Depth Curves Based on Nanoindentation Technology

“…However, in the unloading section, the simulation curve was steeper than the experimental curve, which reflected that the elastic modulus calculated by simulation was slightly smaller than the value measured by experiment. The hardening exponent was close to the result of Sun et al (n = 0.142) (2019) [4] and the yield stress was larger than their research result (σ y = 381 MPa), which was basically consistent with the results obtained by Li et al (2020) [59] by cyclic loading indentation test with a spherical indenter (R = 500 µm, σ y = 424 MPa) and slightly larger than the yield stress obtained by the compression test (σ y = 392 MPa). From the comparations of the stress-strain curve in Figure 12b, it shows that the stress-strain curve of tensile experiment was lower than that of the indentation experiment in the study of Sun et al (2019), and the stress-strain curve obtained in this study was higher than both of them [4].…”

“…Characterization of the elastic–plastic properties of materials is of great significance for the structural design and engineering evaluation. Due to the incomparable advantages in the measurement of nondestructive and micro-mechanical properties [ 1 , 2 ], nanoindentation technology has been widely used in the research of mechanical properties of metals [ 3 , 4 , 5 , 6 ], films [ 7 , 8 , 9 ], and biomaterials [ 10 , 11 , 12 ], particularly in the elastic–plastic properties.…”

“…A spherical indenter can separate the elasticity and plasticity of materials [ 42 ], and it had been always used to solve multi-solution problems [ 42 , 43 , 44 ]. In recent years, cyclic loading with a spherical indenter has been gradually applied to obtain the solution of elastic–plastic properties of materials [ 3 , 4 , 45 , 46 , 47 , 48 , 49 ]. As far as this is concerned, only a few researchers have carried out the reverse engineering of elastic–plastic properties of materials based on the depth curve of cyclic loading [ 49 ], and the uniqueness of solutions has not been explained in their research.…”

Influence of temperature on the creep behaviour by macroindentation of Cocos nucifera shells and Canarium schweinfurthii cores (bio-shellnut wastes in Cameroon)

“…The determination of Young's modulus is based on the assumption that during the unloading curve the removal of the tip is accompanied by a spring back due to the elasticity of the material. Thus the slope of the unloading curve provides a measure Young's modulus [57][58][59]. The method is based on the recovery theory of Hertz [60].…”