Application Of Small Punch Test Research Articles

Application of small punch test to estimate mechanical behaviour of SUS304 austenitic stainless steel

The small punch test with an application of a relatively small specimen has recently become a reliable material mechanics testing method. In this study, the small punch test is set up based on the conventional mechanical testing machine for SUS304 stainless steel to evaluate the mechanical properties of SUS304 steel at different displacement rates of the punch in quasi-static loading condition in the case of with and without heat treatment. Although heat treatment has an insignificant effect on the microstructure and hardness of the material, the mechanical properties of the material in the small punch test are greatly reduced after heat treatment. Both cases with and without heat treatment have a similar tendency for the rate - sensitivity of the applied force - displacement curve. A higher value of force is applied to obtain the same value of displacement at a low displacement rate in the stable plastic deformation zone. Meanwhile, the maximum value of applied force is higher at a higher displacement rate in the stage that initiation of crack might appear. In the examined range of displacement rate, a positive rate - sensitivity of displacement at the maximum force. Therefore, a correlation between equivalent fracture strain and fracture toughness of the material can be achieved.

Evaluating the tensile properties of high-strength stainless steels using small punch testing.

Accurately measuring the mechanical properties of high-strength stainless steels is of great significance for ensuring structural safety, predicting long-term performance and optimizing design. However, the standardized tensile test specimens used to obtain strength properties must be fabricated from bulk materials from an in-service structure or component, result in the loss of structural integrity or a reduction in remaining service life. Small punch tests require only miniscule material samples and are widely used to estimate in-service component material characteristics. This study performed small punch tests on three high-strength stainless steels-X17CrNi15-2, 15-5PH, and PH13-8Mo-to obtain the correlations between the small punch tests and the uniaxial tensile test results for each material. The estimated yield stresses obtained from the small punch tests were distributed within a factor of 1.5 on both sides of the unity line when compared with those obtained from the uniaxial tensile tests; the ultimate strength values estimated from the small punch tests correlated quite well with those obtained from the uniaxial tensile tests. An iterative finite element analysis was subsequently established to simulate the small punch tests and thereby obtain the coefficients for a Ludwik power law correlation representing the true stress-strain properties. The finite element predicted force-deflection curves agreed well with the small punch test results, which were also compared with the predictions obtained from empirical equations proposed in previous studies. Finally, the fracture mechanisms of the small punch test specimens were characterized through scanning electron microscopy, indicating that the dimple fracture mechanism dominated the failure mode. The results of this study are expected to inform the application of small punch test to evaluate in-service high-strength stainless steel materials.

Application of small punch test to lifetime prediction of plasticized polyvinyl chloride wire

In this study, it was investigated that the validity of small punch (SP) test for the lifetime prediction of polyvinyl chloride (PVC) resin used as an electric insulation material for the electric cable. The degradation behavior of PVC resin under the accelerated high-temperature condition was analyzed using Fourier transform-infrared spectroscopy (FT-IR), tensile testing, and SP testing. The activation energies and estimated lifetime obtained from the Arrhenius method were compared. The peak ratio of the carbonyl group obtained by FT-IR, the elastic modulus obtained by tensile testing, and the apparent elastic modulus obtained by SP testing were used as indicators for lifetime estimation, and the logarithm of these values showed a linear correlation with exposure time. The activation energy obtained from the apparent elastic modulus using SP testing was the smallest and the predicted lifetime was the shortest among all mechanical properties in this research. It indicates that SP testing is sensitive to the degradation. This is because the stress at the surface becomes maximum for SP testing, and the degradation occurs at the surface of the materials by priority degradation. SP testing is an excellent minimally destructive lifetime prediction method for detecting of early-stage degradation.

Application of small punch test to investigate mechanical behaviours and deformation characteristics of Incoloy800H

In this study, mechanical behaviours and deformation characteristics of Incoloy800H were investigated experimentally and analytically by small punch test at various temperatures. First, parameter sensitivity analysis was performed in order to estimate the influence of anisotropy, geometric dimensions, and temperature on material strengths. Then, the mechanical properties of Incoloy800H were investigated. A relatively simple yet reasonable relation between mechanical properties and specimen thickness was obtained. A new prediction model based on the deformation energy was established. Meanwhile, the inverse prediction model based on golden section search algorithm was proposed to estimate the yield strength and constitutive parameters on the basis of iterative calculations. On the other hand, a small punch deformation model was discussed. The hardness, strain, and stress triaxiality were analysed in order to estimate the evolution of plastic damage and deformation character. Finally, an economic, accurate mechanical behaviour evaluation system of Incoloy800H was established on the basis of the small punch test.

Application of Small Punch Testing to Evaluate Elastic and Plastic parts of Fracture Energy of Cortical bone

Fracture mechanics approach provides useful information about failure behaviour of cortical bone. The understanding of failure mechanism of cortical bone is important for both medical and engineering researchers. Several toughening mechanisms associated with bone failure are responsible for significant amount of nonlinearity during bone deformation. The present study has been conducted to compare elastic and plastic parts of energy dissipated during bone fracture. Fracture toughness of cortical bone is determined in terms of J-toughness based of elastic-plastic fracture mechanics approach to determine energy dissipated during crack propagation. Total fracture energy is determined with the help of small punch testing in terms of area under curve values. It has been found during this study that elasticity plays an important role during crack propagation, however, plasticity has greater contribution during total fracture of bone staring from crack initiation to crack propagation. A significant linear relationship is obtained between plastic part of J-toughness and plastic part of fracture energy determined in terms of area under curve values. This relationship shows the contribution of various toughening mechanisms during crack initiation as well as its further propagation till fracture.

Application of the miniature small punch test for the mechanical characterization of polymer materials

The aim of this paper is to demonstrate the applicability of the Small Punch Test (SPT) in the mechanical characterization of polymers, following previous achievements in metallic materials. For this purpose, different polymers with a wide variation of tensile properties were examined. The applicability of this type of test to characterize polymeric materials is especially interesting when these products are in the form of films, as their greatly reduced thickness enables an easy preparation of the SPT specimens.All the polymer materials were characterized by means of small punch and tensile tests. The tensile stress-strain curves were compared with the load-displacement SPT curves and the representative SPT parameters were defined accordingly. A good correspondence was found between the tensile elastic modulus and the initial slope of the SPT plot (Slopeini/t), with t being the specimen thickness, and a good correlation was also observed between the tensile yield strength and the SPT Pym/t2 parameter. On the contrary, no corresponding relationship was found to predict the ultimate tensile strength or the failure elongation, since these properties depend greatly on the stress state of the test (uniaxial or biaxial).

Application of Small Punch Test in Predicting the Axial Fatigue Life of 304 Stainless Steel Sheets

Application of Small Punch Test in Predicting the Axial Fatigue Life of 304 Stainless Steel Sheets

Application of small punch testing on the mechanical and microstructural characterizations of P91 steel at room temperature

The use of small punch test (SPT) has emerged as a potential technique for mechanical characterization using miniaturized specimens. There is a strong interest in applying SPT for life prediction of power plant components operating at high temperatures. Another important application includes implementing surveillance programs for structural materials of nuclear plants where small volumes of irradiated samples are needed. In this work the small punch test was applied to study the mechanical behavior of P91 steel at room temperature. The selection criteria of the characteristic load PY in terms of two methods are discussed. Using this parameter the relationship with the yield stress is studied. The correlation factors were calculated from SPT curves. Microhardness was used to detect the most strained zones in a cross section of a punched specimen when reached its maximum load. The annular zone under the ball contact area, where the plastic thinning occurred up to maximum load, coincided with the highest microhardness values. Finally, transmission electron microscopy was employed to study the final microstructures after the deformation of the tensile and small punch tested samples. Refining of subgrains and considerable increasing of dislocation density was found with both, tensile and punch tested samples. By estimation of local strain and TEM observations it was confirmed the SPT produces higher deformation than that found with tensile test after rupture.

Application of Small Punch Test in Predicting the Axial Fatigue Life of 304 Stainless Steel Sheets

The application of small punch test (SPT) for predicting the axial fatigue life of 304 stainless steel is examined. The results of SPT on predamaged 304 stainless steel sheets show that the increase in fatigue damage decreases the maximum punch load. However, the change in the maximum punch load can be translated into the change in the ultimate strength of the specimen according to the literature. Using the Palmgren–Miner model then, a cyclic load history is estimated that is found to be in good agreement with the actual loading. Consequently, the SPT is suggested as a fatigue life estimating technique where the past loading history is not available. In other words, this study proposes an SPT-based assessment of the remaining fatigue life of used components.

Application of Small Punch Test to Evaluate Sigma-Phase Embrittlement of Pressure Vessel Cladding Material

The influence of σphase on mechanical properties in type ER309L stainless steel has been investigated by small punch test. The SA508 cl.3 reactor pressure vessel steel plates were overlay-cladded with the type ER309L welding consumable with different heat input rates. The microstructure of the clad was composed of fcc γ-austenite, a few percent of bcc δ-ferrite and bct σ-phase. Area fraction of σ-phase was ranging approximately 2–8% depending on the welding condition. Ductile to brittle transition behavior was observed in the clad, and it was strongly affected by the amount of brittle σ-phase. When the σ-phase content was about 8 percent, the transition behavior almost disappeared due to severe cracking. Fracture appearance gradually changed from circumferential to radial cracking not only as test temperature became low but as the volume fraction of σ-phase increased. The results are manifested in terms of fracture stress of σ-phase and δ-ferrite combined with the roles of radial and circumferential stress by means of the stress analysis of deformed specimen using finite element method.

Application of Small Punch Test to Evaluate Sigma-Phase Embrittlement of Pressure Vessel Cladding Material

Application of Small Punch Test to Evaluate Sigma-Phase Embrittlement of Pressure Vessel Cladding Material