Material properties from small specimens using the punch and bulge test

Abstract

The punch and bulge test provides a technique for the determination of material properties from small specimens. Although the test has been in use for a number of years, the behaviour of the specimen is not fully understood. A finite element analysis of the test has thus been undertaken and validated by comparison with results from experiments, giving good agreement for the punch force for two differing specimen materials. The finite element analysis has enabled punch force±displacement curves, von Mises stresses, equivalent plastic strains and vertical deflections for the upper and lower surfaces of the disc to be obtained.The finite element model has also been used to determine the relationship between the specimen yield stress and the punch force for elastic±perfectly plastic specimens. It is shown that a linear law applies over a 6:1 range of yield stresses and thus the punch and bulge test represents an effective method of yield stress measurement from small specimens.The effect of experimental artefacts on the punch force has been investigated through finite element analysis and physical experiment. The punch force is shown to be effectively insensitive to small uncertainties in the test fixture and experimental conditions. Yield stress results are thus not significantly influenced by experimental uncertainties.

Factors Affecting the Mechanical Properties of Compact Bone and Miniature Specimen Test Techniques: A Review

“…• The modulus of elasticity E increased from 11 GPa in the new born to 35 GPa in the adults and drops to 23 GPa in the aged persons. Courtney et al [21] observed that the agerelated differences in post-yield behavior of human cortical bone were associated with increase in damage in the form of micro cracks.…”

“…However, the relation between fracture toughness and biaxial fracture strain contains the yield strength and work hardening coefficient terms. For the relationship of fracture toughness with the fracture strain of ductile materials, Bayoumi and Bassim [5] proposed empirical relation: (11) Here S is the shape factor characterizing the geometry of plastic zone which is approximated to be 1.0 and ρ * is the Neuber's micro support effect constant which is approximated to be 0.025mm. The L * ε is a characteristic distance which depends on the microstructure of the material, f (E, K, n ε y ) is a function determined from the stress vs. strain relationship of the material, σ f and E are fracture stress and elastic modulus respectively.Mao et al [54] estimated the biaxial fracture strain from small punch test based on the ductility of the material as:…”

Assessment of tensile strength using small punch test for transversely isotropic aluminum 2024 alloy produced by equal channel angular pressing

“…As the result of a European collaborative research program [21], an equation that predicts material tensile strength from load-displacement curves obtained by the SP test was formulated. The equation was derived through finite element analyses conducted under the assumption that the material showed elasticperfectly plastic behavior, which plastic deformation occurs under a constant flow stress that yield strength and tensile strength are equivalent.…”

“…The SP test method was originally developed for assessing the DBTTs (ductile-brittle transition temperatures) of small amounts of metallic material [19]. The scope of the SP test has recently been extended to assessing the tensile strength [8,20,21] and creep rupture life [22][23][24] of isotropic ductile materials. It was demonstrated that the SP test could be used for assessing tensile strengths along all axes of the ECAP materials that exhibit strength anisotropy [8].…”

“…The SP test data were obtained from a previous study [8] of an aluminum 2024 (Al 2024) alloy subjected to three ECAP passes at 150 • C. Section 2 of this work will detail the experiments conducted in the study. Previously proposed equations [20,21], which had been suggested to assess the tensile strength using the SP test for isotropic ductile materials, are tried for assessing the tensile strength of the Al 2024 alloy subjected to the ECAP process. A new strength assessment method is proposed in this study.…”