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Applications of Small Specimen Testing
Published in V. Karthik, K.V. Kasiviswanathan, Baldev Raj, Miniaturized Testing of ENGINEERING MATERIALS, 2016
V. Karthik, K.V. Kasiviswanathan, Baldev Raj
Shear punch testing has been put to use by Karthik et al. (2002) for evaluating the strength and ductility changes across the HAZs of 2.25Cr–1Mo steel weld joints, which consist of coarse-grained bainite, fine-grained bainite, and intercritical microstructures. By testing small specimens extracted from the individual regions of the HAZ in the weld joint (Figure 5.12), the tensile property gradients across the HAZ have been evaluated and related to their respective microstructural features. The methodology was based on tensile-shear correlations derived for the strength and ductility parameters using different microstructural conditions of the steel. Similar studies have been carried out by Stewart et al. (2006) for measuring the variation in mechanical properties of welded pipe line of 4130 steel at room temperature and over a range of potential service temperatures down to 213 K. The results showed that the shear punch technique could predict the properties with a resolution intermediate between those of tensile testing and hardness testing, with the advantage of both strength and ductility measurement unlike hardness tests.
Experiment and modified model for CFRP/steel hybrid tubes under the quasi-static transverse loading
Published in International Journal of Crashworthiness, 2021
Qihua Ma, Jiarui Sun, Xuehui Gan, Zeyu Sun
The model has not considered not only the elastic deformation but also the hardening behaviour of the pipe during plastic deformation. Therefore, in order to improve the prediction accuracy of tube bending, it is necessary to ensure that the material constitutive model reflects the elastic deformation behaviour of tube and the hardening characteristics of material. A piecewise non-linear stress-strain model is presented here, as shown in Eq. (4). In the elastic deformation region (σ ≤ σy), the classical Ramboerg-Osgood elastic–plastic σ–ε model is used to describe the plastic deformation behaviour of tubes; when the tubes enter the plastic deformation region (σ ≥ σy), the plastic deformation behaviour of pipes is described in the form of power exponential function. where σm is the true stress, σmy is the yield strength of metal, ε is the true strain, K is the strain strength coefficient, n is the strain hardening index. The yield strength and tensile strength of 4130 steel are 386 and 650 MPa, and the elongation rate after fracture is 0.11. The modified curves were got by bring formula (16) into formula (15).