Fracture Evaluation of Low-Density Porous Materials by Reaction Force Analysis in Ball Indentation Test

An indentation test can easily measure the deformation characteristics of a material, because it does not require a test specimen to be cut from the material being examined. The applicability of this test is usually restricted to evaluating the fundamental characteristics of deformation, such as elasticity and plasticity; however, it is also useful if the test can be applied for the fracture evaluation of materials. Therefore, in this study, the fracture behavior of materials is discussed by performing indentation tests. The evaluation procedure depends on the variation in the indentation force owing to the differences in the deformation behavior. The observed variation is analyzed via the fractography of the material. A simple formulation is derived from the results for the development of a material evaluation method. Finally, the importance of the choice of the indenter diameter is explained in terms of the accuracy of the plateau stress of the porous material.

In-Elasticity Evaluation and its Design Technique for Soft Materials by Using Ball Indentation Test

In order to design the products made from soft materials, it is important to quantify the deformation characteristics of them for the quality and reliability of their design. But the quantification is ordinary difficult because of large deformation due to its softness even if the tensile test which is one of the fundamental technique is easily applied to the quantification for hard materials. Here, usefulness of indentation test is reported for soft materials by extending the Hertzian contact theory. Then the indentation technique based on the contact theory is adopted for quantification in this paper. This theory is commonly used to evaluate elastic materials, but it is found that inelastic behaviors of solid materials like viscosity and fracture can be quantified by the extension of the theory. In this paper, an evaluating equation is formulated and applied to quantify in-elasticity of various materials and it is known that an equation can analyze the variation of soft materials objectively, and the analyzed results has high compatibility to uniaxial test like the fundamental Hertzian contact theory.

A Study on the Ball Indentation Test for Linear Hardening Metals

In this work, a numerical analysis based on the linear hardening model and ball indentation test was proposed to determine the properties of materials such as austenitic stainless steels that obey linear hardening behavior. Experiments on 304 and 321 austenitic stainless steel showed that the numerical method provides yield and tensile strength values with a maximum error of less than 5% and the hardening behavior identical with uniaxial tensile tests, while the average error for yield strength was more than 30% with the empirical method. The reasons why the empirical method produces larger errors for non-power law materials were analyzed in detail. The elastic modulus calculation method was also re-investigated, and the model based on re-loading showed much bigger equivalent contact diameters and provided more accurate elastic modulus values in a simple way.

Comparison of Conventional Mechanical Testing with Innovative Techniques for Determination of Mechanical Properties of Nuclear Power Plant Components Materials

Within the nuclear power plant operational life management, components lifetime extension requires information on structural material degradation. Innovative testing methods of Small punch testing and Automated ball indentation test are based on the determination of material properties from sub-sized specimens. Present paper is focused on the employment of these techniques in the NPP irradiated materials testing and evaluation at the accredited hot cell testing laboratory of ÚJV Řež, a. s., Mechanical testing department. Comparison with the testing results from the conventional methods is depicted.