The Change of the Structure and Mechanical Properties of the Austenitic Steels after Exposure at the Critical Temperature

2017 ◽  
Vol 891 ◽  
pp. 330-334 ◽  
Author(s):  
Šárka Stejskalová ◽  
Ladislav Kander ◽  
Šárka Hermanová
Keyword(s):  
Mechanical Properties ◽  
Critical Temperature ◽  
Thermal Exposure ◽  
Tensile Tests ◽  
Austenitic Steels ◽  
Small Punch Test ◽  
Bend Radius ◽  
Small Punch ◽  
Σ Phase ◽  
Punch Test

The paper deals with the change of the structure and mechanical properties of the austenitic steels after the exposure at the critical temperature. The effects of the bend radius of tubes including effect of solution annealing on the mechanical properties and the structure were studied. The mechanical properties were studied using small punch test (SPT) and miniaturized tensile tests. From the results can be concluded that the mechanical properties and the structure have been influenced due to one year exposure at the working temperature significantly. Various amounts of σ-phase were found in the pulled part of the bend side of the tubes even after only thermal exposure without any loading. The effect of the heat treatment and the bend radius on the mechanical properties and the structure was also evident. Drop in fracture energy due to the presence of the σ-phase in the structure was clearly detected from force - displacement record of the small punch test. Keywords: Austenitic steels, bends, σ-phase, small punch test

scholarly journals Using the small punch test to analyse the influence of ultraviolet radiation on the mechanical behaviour of recycled polyethylene terephthalate

2019 ◽  
Vol 54 (7-8) ◽  
pp. 401-407 ◽  
Author(s):  
Tobias Abt ◽  
Guillermo Álvarez ◽  
Cristina Rodríguez ◽  
Maria Lluisa Maspoch
Keyword(s):  
Mechanical Properties ◽  
Ultraviolet Radiation ◽  
Polyethylene Terephthalate ◽  
Colour Change ◽  
Tensile Tests ◽  
Small Punch Test ◽  
Small Punch ◽  
Industrial Project ◽  
Punch Test ◽  
Recycled Polyethylene

The aim of this work is to evaluate the feasibility of small punch test as a tool for analysing the mechanical response of small plastic parts or specimens. Here, the small punch test was used to study the possible influence of ultraviolet radiation exposure on the mechanical properties of outdoor furniture made from recycled polyethylene terephthalate in the frame of an industrial project with participants from both industry and academia. The industrial project partners prepared four types of masterbatches in order to stabilize the recycled polyethylene terephthalate and to minimize photodegradation as well as colour change in the final product. The masterbatches contained red pigments, antioxidants and ultraviolet absorbers. Flat sample plates were injection moulded from recycled polyethylene terephthalate and these masterbatches. Some sample plates were used as-moulded, some samples received a thermal treatment in order to post-crystallize the bottle-grade recycled polyethylene terephthalate and some other samples were subjected to ultraviolet radiation for 900 h. In the frame of an industrial project, the ultraviolet ageing was performed superficially only on one side of the plates in order to evaluate the colour change. The three sets of samples were analysed by means of tensile tests, differential scanning calorimetry and intrinsic viscosity. However, the irradiated samples could not be tested with tensile tests due to their small size. Therefore, the small punch test was used to accurately characterize these small samples. The feasibility of the small punch test as a valid mechanical characterization method for these types of materials was demonstrated by comparing the small punch test results from the unradiated samples with the tensile test ones. The mechanical parameters obtained from both types of tests showed the same results. Although the used industrial ultraviolet ageing process produced a colour change in the studied recycled polyethylene terephthalate samples, it was possible to verify via small punch tests that the mechanical properties were not affected.

Application of Small Punch Test to Evaluate Tensile Properties of SA213T22 Grade Boiler Steel

2015 ◽  
Vol 830-831 ◽  
pp. 191-194
Author(s):  
M. Venkateswara Rao
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Tensile Properties ◽  
Test Methods ◽  
Uniaxial Tensile ◽  
Test Results ◽  
Small Punch Test ◽  
Small Punch ◽  
Punch Test ◽  
Aging Phenomena

Conventional tensile test methods are used for service exposed high temperature boiler tubes to evaluate the deterioration in mechanical properties such as tensile strength, yield strength and percentage elongation. The mechanical properties are required to be evaluated periodically as the boiler components undergo material degradation due to aging phenomena. The aging phenomena occurs due to continuous exposure of tubes to high temperature & pressure steam prevailing inside the tubes and high temperature exposure to corrosive combustible gases from the external surfaces within the boiler.A recent developed new technique called small punch testing has been used to evaluate the tensile properties of SA 213T22 grade steel predominantly exists in super-heater and re-heater sections of boiler. The small punch tests have been carried out on the miniature disk shaped specimens of diameter of 8.0 mm and 0.5 mm thickness extracted from both the new and service exposed tubes. Conventional uniaxial tensile tests on standard specimens from the same tube material have also been performed for comparison. The service exposed tubes showed considerable loss in mechanical properties in both the conventional and small punch test results. Correlations of tensile properties have been obtained based on the comparative analysis of both small punch and uniaxial tensile test results. Further, the study showed that an appropriate empirical relation could be generated for new and service exposed materials between both the techniques. Conventional test methods require large quantity of material removal for test samples from in-service components whereas small punch test method needs only a miniature sample extraction. This small punch test technique could also be extended to evaluate the thicker section boiler components such as pipelines and headers in the boiler as a part of remaining life assessment study. Also this technique could be a useful tool to any metallic component where large quantity of sample removal may be difficult or may not be feasible.

scholarly journals A New Prediction Method for the Ultimate Tensile Strength of Steel Alloys with Small Punch Test

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1491 ◽  
Author(s):  
Jose Calaf Chica ◽  
Pedro Bravo Díez ◽  
Mónica Preciado Calzada
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Yield Strength ◽  
Correlation Method ◽  
Small Punch Test ◽  
Steel Alloys ◽  
Small Punch ◽  
Punch Test ◽  
Hardening Coefficient

The load–deflection curve acquired from the Small Punch Test (SPT) is used to obtain the mechanical properties of materials using different correlation methods. The scattering level of these regressions tends to be high when a wide set of materials is analyzed. In this study, a correlation method based on a specific slope of the SPT curve was proposed to reduce scattering. Assuming the Ramberg–Osgood hardening law, the dependence of the SPT curve slope on the yield strength and the hardening coefficient is demonstrated by numerical simulations (FEM). Considering that the ultimate tensile strength could be obtained from the hardening coefficient, a response surface of the ultimate tensile strength with the yield strength and SPT curve slope, along with its equation, is presented for steel alloys. A summary of steel mechanical properties, based on the Boiler and Pressure Vessel Code (BPVC) and limited to yield strengths lower than 1300 MPa, is shown to select a set of experimental tests (tensile tests and SPTs) for which the range is completely covered. This experimental analysis validates the previous FEM analyses and the validity of the proposed correlation method, which shows more accurate correlations compared to the current methods.

Influence of the Residual Stress on Mechanical Properties of Ductile Materials by Simulating Small Punch Test

2015 ◽  
Vol 750 ◽  
pp. 285-291
Author(s):  
He Hui Wang ◽  
Shao Jie Zhang ◽  
Yao Gang Wang ◽  
Kai Shu Guan
Keyword(s):  
Mechanical Properties ◽  
Residual Stress ◽  
Material Behavior ◽  
Small Punch Test ◽  
Small Punch ◽  
Ductile Materials ◽  
Punch Test ◽  
Original Specimen ◽  
Loading And Unloading ◽  
Simulated Material

This paper describes an approach to identify the influence of mechanical properties of the materials under the condition of containing residual stress. The numerical method of simulating small punch test (SPT) is used to determine the material response under loading. The simulated material behavior of the specimen is based on the ductile elastoplastic damage theory of Gurson, Tvergaard and Needleman (GTN). The residual stress can be prefabricated on the specimen by loading and unloading. By comparing the original specimen with the specimen contains residual stress, the change of the mechanical properties of the materials can be studied. The results of simulation indicate that the material properties decrease with the increase of the residual stress.

Use of small punch test to estimate the mechanical properties of sintered products and application to synchronizer hubs

2017 ◽  
Vol 72 (5) ◽  
pp. 355-360 ◽  
Author(s):  
M. Fernández ◽  
C. Rodríguez ◽  
F.J. Belzunce ◽  
T.E. García
Keyword(s):  
Mechanical Properties ◽  
Small Punch Test ◽  
Small Punch ◽  
Punch Test

Validation of the Incremental Step Loading Technique Application to Small Punch Tests in Aggressive Environments in X80 Steel

2020 ◽  
Author(s):  
B. Arroyo ◽  
L. Andrea ◽  
P. González ◽  
J. A. Álvarez ◽  
S. Cicero ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Hydrogen Embrittlement ◽  
Threshold Stress ◽  
High Strength ◽  
Constant Load ◽  
Small Punch Test ◽  
Small Punch ◽  
Punch Test ◽  
Step Loading ◽  
Incremental Step

Abstract The Small punch test, which consists on punching a small plane specimen up to failure, is a technique to be taken into account for the estimation of mechanical properties when there is shortage of material. In recent works it has been applied to the estimation of mechanical properties steels in aggressive environments. In aggressive environments, tests under a constant load are usually employed for the threshold stress determination, but this a slow and sometimes inaccurate technique. The standard ASTM F1624 solves these issues; it consists on applying steps of constant loads subsequently increased up to the specimen’s failure. In a previous work, it was indicated how to implement this technique for Small Punch testing of steels in hydrogen embrittlement scenarios, adapting the steps duration. This proposal allows to obtain a threshold load by using at least 3 specimens in a total time of around a week. In the present work, the incremental step loading technique from ASTM F1624 standard is applied to the Small Punch test in order to estimate tensile threshold stress of a X80 high strength steel in hydrogen embrittlement environments by cathodic polarization in an acid electrolyte. Regular standard tests on cylindrical tensile specimens were carried out following the ASTM F1624 standard, in order to validate the methodology proposed.

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