Abstract
Although there are methods for testing the stress-strain relation and strength, which are the most fundamental and important properties of metallic materials, their application to small-volume materials and tube components is limited. In this study, based on energy density equivalence, a new dimensionless elastoplastic load-displacement model for compressed metal rings with isotropy and constitutive power law is proposed to describe the relations among the geometric dimensions, Hollomon law parameters, load, and displacement. Furthermore, a novel test method was developed to determine the elastic modulus, stress-strain relation, yield and tensile strength via ring compression test. The universality and accuracy of the method were verified within a wide range of imaginary materials using finite element analysis (FEA), and the results show that the stress-strain curves obtained by this method are consistent with those inputted in the FEA program. Additionally, a series of ring compression tests were performed for seven metallic materials. It was found that the stress-strain curves and mechanical properties predicted by the method agreed with the uniaxial tensile results. With its low material consumption, the ring compression test has the potential to be as an alternative to traditional tensile test when direct tension method is limited.
Highlights
Various tubular structures are widely applied in engineering due to their high strength and stiffness to weight ratios, and high energy absorption to weight ratios, such as the fuel-cladding tubes in nuclear reactor [1, 2] and energy absorbers [3, 4]
2.1 Energy Density Equivalence Method For an unidirectionally loaded ring specimen, as shown in Figure 1, assuming that a geometric point M exists in the effective deformation region Ω and that the energy density of the representative volume element (RVE) at M is equal to the average energy density of all RVEs in Ω, we have εij - M
The k0 versus 1−ρ curve was obtained via finite element analysis (FEA) with Ep fixed at 400 GPa, as shown in Figure 6(a); the relation between k0 and 1-ρ can be described by the following power law equation: k0 = a1(1− ρ) a2, where a1 and a2 are the fitting coefficient and exponent, respectively
Summary
Various tubular structures are widely applied in engineering due to their high strength and stiffness to weight ratios, and high energy absorption to weight ratios, such as the fuel-cladding tubes in nuclear reactor [1, 2] and energy absorbers [3, 4]. Wang et al [5] proposed a ring hoop tension test method to acquire the hoop σ–ε relations of nuclear fuel cladding tubes. Chen and Cai [11,12,13,14] proposed a theoretical model for compressed rings under plane-stress conditions based on energy density equivalence This model can predict the σ–ε curves of metallic materials with constitutive power law; it does not give details about the elastic modulus test method, and the thickness effect of ring specimen is not considered. A dimensionless elastoplastic load-displacement model for compressed rings (EPLD– Ring) is proposed based on energy density equivalence Solving this model using the information contained in the P–h curves yielded the elastic modulus, σ–ε relation, and strength of the tested material. The model is verified via FEA with a wide range of imaginary materials and through experiments with seven metallic materials
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