Procedure of SPC data treatment for “uniaxial test correlation”

In order to determine creep properties from small punch creep (SPC) tests, several theoretical models and analytic methods are applied, such as the Chakrabarty’s membrane stretch model and reverse finite element method. However, because the problem is too complicated, differences are always found between the theoretical prediction and the uniaxial creep tests. In this paper, a concept of “Uniaxial test correlation” is proposed without any theoretical assumption and analytic calculation. By comparison of the rupture time in SPC with the uniaxial creep rupture data, the equivalent stres

The role of punch eccentricity in small punch testing

The small punch testing technique under quasi-static loading was examined in the view of punch eccentricity role. It might arise especially when the ball is used as the penetrating tool, instead of hemispherical-ended punch. The austenitic stainless steel AISI 316L was chosen to execute several various “large scale” tests in order to calibrate the multi-linear stress–strain relationship along with the ductile fracture criterion KHPS. All the calibration procedure was performed without using the small punch testing. Then, the model was applied to small punch tests to observe the prediction ability when compared to real small punch experiments. Consequently, a numerical study was conducted to see the role of eccentricity in the case of 2 and 2.5 mm ball diameters used as the penetrating tool. The magnitude of eccentricity up to 0.3 mm was numerically tested. The results showed negligible role of eccentricity for 2 mm ball diameter and minor role for 2.5 mm diameter and studied material

Determination of creep properties from small punch test using experimental correlation

The correlation of the small punch creep (SPC) test results with uniaxial creep test results is challenging due to several factors. The stress state is equibiaxial in the SPC test and the equivalent stress is not constant as the punch is advancing into the disc. The classical use of Chakrabarty membrane theory, with a constant F

Experimental and numerical analysis of initial plasticity in P91 steel small punch creep samples

To date, the complex behaviour of small punch creep test (SPCT) specimens has not been completely understood, making the test hard to numerically model and the data difficult to interpret. This paper presents a novel numerical model able to generate results that match the experimental findings. For the first time, pre-strained uniaxial creep test data of a P91 steel at 600 °C have been implemented in a conveniently modified Liu and Murakami creep damage model in order to simulate the effects of the initial localised plasticity on the subsequent creep response of a small punch creep test specimen. Finite element (FE) results, in terms of creep displacement rate and time to failure, obtained by the modified Liu and Murakami model are in good agreement with experimental small punch creep test data. The rupture times obtained by the FE calculations which make use of the non-modified creep damage model are one order of magnitude shorter than those obtained by using the modified constitutive model. Although further investigation is needed, this novel approach has confirmed that the effects of initial localised plasticity, taking place in the early stages of small punch creep test, cannot be neglected. The new results, obtained by using the modified constitutive model, show a significant improvement with respect to those obtained by a state of the art creep damage constitutive model (the Liu and Murakami constitutive model) both in terms of minimum load-line displacement rate and time to rupture. The new modelling method will potentially lead to improved capability for SPCT data interpretatio

An overview of using small punch testing for mechanical characterization of MCrAlY bond coats

Considerable work has been carried out on overlay bond coats in the past several decades because of its excellent oxidation resistance and good adhesion between the top coat and superalloy substrate in the thermal barrier coating systems. Previous studies mainly focus on oxidation and diffusion behavior of these coatings. However, the mechanical behavior and the dominant fracture and deformation mechanisms of the overlay bond coats at different temperatures are still under investigation. Direct comparison between individual studies has not yet been achieved due to the fragmentary data on deposition processes, microstructure and, more apparently, the difficulty in accurately measuring the mechanical properties of thin coatings. One of the miniaturized specimen testing methods, small punch testing, appears to have the potential to provide such mechanical property measurements for thin coatings. The purpose of this paper is to give an overview of using small punch testing to evaluate material properties and to summarize the available mechanical properties that include the ductile-to-brittle transition and creep of MCrAlY bond coat alloys, in an attempt to understand the mechanical behavior of MCrAlY coatings over a broad temperature range

Impact of residual elements on zinc quality in the production of zinc oxide

The paper is focused on zinc oxide manufacturing process. The present work deals with the character and morphology of the input material for the production of ZnO by the indirect pyrometallurgical process. Undesirable phases in the feedstock can be identified through profound recognition of the source material and the nature of its microstructure. If these compounds diffuse into the lining during thermal processes, they become the cause of stress in metallurgical ceramics. The emergence of these chemical reactions may subsequently affect the entire metallurgical zinc smelting process. The results obtained by analysis are used to minimize waste - zinc slag and to eliminate the conditions which enable the formation of the undesired product, thereby increasing the productivity of the ZnO production

Mechanisms of plastic deformation and fracture in coarse grained Fe–10Al–4Cr–4Y2O3 ODS nanocomposite at 20–1300°C

The coarse-grained Fe–10Al–4Cr–4Y2O3ODS nanocomposite (denoted as FeAlOY) has been developed by the authors and shows promising potential for high-temperature structural applications at 1000–1300 °C. Compared to classical ODS alloys, the FeAlOY contains ten times higher volume fraction of the stable Y2O3 nanodispersion, which gives the alloy its high-temperature strength. Furthermore, the high content of Al in the matrix guarantees excellent oxidation resistance. In practice, one can expect that the FeAlOY is loaded in the temperature range of 20–1300 °C due to intermittent device operation. To ensure a safe operation, it is necessary to determine the tensile strength and ductility of the FeAlOY in the whole temperature range and detect the dominant mechanisms of strengthening, plastic deformation, and fracture in the characteristic temperature ranges. Above 1100 °C the FeAlOY reaches ultimate tensile strength of ∼ 100 MPa and plasticity of ∼ 1%. However, in the temperature range of 400–600 °C, the plasticity can climb above 40%. The achieved results can also be utilized for the design of the FeAlOY pieces shaping by hot pressing