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Journal ArticleDOI

Small specimen techniques for estimation of tensile, fatigue, fracture and crack propagation material model parameters:

15 Jun 2021-Journal of Strain Analysis for Engineering Design (SAGE PublicationsSage UK: London, England)-pp 030932472110252
TL;DR: Small specimen mechanical testing is an exciting and rapidly developing field in which fundamental deformation behaviours can be observed from experiments performed on comparatively small amounts of data as discussed by the authors, which can be found in this paper.
Abstract: Small specimen mechanical testing is an exciting and rapidly developing field in which fundamental deformation behaviours can be observed from experiments performed on comparatively small amounts o...
Citations
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Journal ArticleDOI
TL;DR: In this paper , the authors revisited the existing methods to determine ultimate tensile strength (UTS) from small punch test and an improved method is proposed and validated through finite element analysis and experiments.

4 citations

01 Jan 1998
TL;DR: In this paper, small punch test techniques using miniature-sized specimens have been investigated on header components and linear relationships, obtained between mechanical characteristics determined from small punch tests and from Charpy tests, have been used to estimate the fracture appearance transition temperature.
Abstract: Accurate measurements of the fracture appearance transition temperature and fracture toughness KIC are greatly desired for engineering in steam power plant, especially from the standpoint of life extension. The current toughness of materials at critical locations is a key characteristic necessary for the remaining life analysis. For this purpose, small punch test techniques using miniature-sized specimens have been investigated on header components. Linear relationships, obtained between mechanical characteristics determined from small punch tests and from Charpy tests, have been used to estimate the fracture appearance transition temperature. Energy based and fracture stress formulations have been applied to estimate the fracture toughness in the upper- and lower-shelf regimes on a class of low alloy steels.

3 citations

Journal ArticleDOI
TL;DR: In this article , the relationship between crack propagation and electrical resistance change was investigated using single-edge notched specimens in a tensile tester using a digital image correlation (DIC) technique.
Abstract: This study investigated the crack propagation behavior of the graphene-reinforced synthetic rubber matrix nanocomposite materials. Graphene-filled rubber conductive nanocomposites developed within the scope of this study were obtained in two stages using mechanical mixers. The relationship between crack propagation and electrical resistance change was investigated using single-edge notched specimens in a tensile tester. Digital image correlation (DIC) technique was used to observe the crack resistance function depending on the local strain distribution. The results from the tests were evaluated to define the relationship between the crack length, the amount of conductive filler, and the change in electrical resistance. The sharp edges of the graphene nanoplatelets negatively affected the fracture resistance of the samples. In addition, it was observed that even at low strain values, gaps were formed in the areas close to the crack tip. The three-dimensional transmission network formed by graphene nanoplatelets dispersed in the matrix improved the electrical conductivity properties of the nanocomposites, so the relationship between crack propagation and electrical resistance change was determined.

1 citations

Journal ArticleDOI
TL;DR: In this paper , the authors investigated the tensile properties of a sea portal crane after a 33-year operation depending on the operational stresses and rolling direction in order to assess its serviceability.
Abstract: This paper presents the research results on the mechanical behavior of the low-carbon rolled steel of a sea portal crane after a 33-year operation depending on the operational stresses and rolling direction in order to assess its serviceability. The tensile properties of steels were investigated using rectangular cross-section specimens with different thicknesses and the same width. Strength indicators were slightly dependent on the considered factors (operational conditions, the cutting direction, and thickness of specimens). However, a clear trend of higher ultimate strength for thinner specimens was noticed, especially in the case of more brittle material due to its operational degradation. Plasticity of the tested steel specimens was more sensitive to the influence of the above-mentioned factors than strength but less sensitive than impact toughness. Uniform elongation was slightly less for thinner specimens regardless of the investigated steel state or the orientation of specimens relative to the rolling direction. The post-necking elongation was lower for transversal specimens compared with longitudinal ones, and the effect was more significant when testing steel with the lowest brittle fracture resistance. Among the tensile properties, non-uniform elongation was demonstrated to be the most effective for assessing the operational changes in the state of rolled steels.
References
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Journal ArticleDOI
TL;DR: In this paper, different expressions for estimating the tensile and fracture properties of metallic alloys by means of the small punch test were proposed and their applicability was assessed after experimental testing a wide range of metallic materials and the application of a numerical model developed to study the effect of specimen thickness on these proposals.

239 citations


"Small specimen techniques for estim..." refers background or methods in this paper

  • ...Due to plane strain state in the specimen a circular notch should allow to evaluate fracture toughness of brittle materials,(98) which was identified as impossible using a notch through thickness due to not uniform stress state.(37) An investigation was done into what effect the dimensions of the small punch testing setup have on the testing results....

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  • ...Tensile elongation was also evaluated using SPT data for a sintered material, good agreement with uniaxial results was achived,(34) however trying to evaluate it for a variety of unsintered steels via a correlation between it and displacement under maximum load was not successful.(37) It could be that SPT is only suitable for determining tensile elongation for brittle materials or perhaps different correlations are needed....

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Journal ArticleDOI
TL;DR: In this paper, a method for the identification of deformation, damage and fracture properties of ductile materials is presented. And the identified material parameters are validated by independent tests on notched tensile specimens.

154 citations


"Small specimen techniques for estim..." refers methods in this paper

  • ...Neural networks were used for identifying plastic behaviour from SPT data after having been trained with FEA simulations, with good results.(16,17) As the model is sensitive to stress triaxiality, at least two experiments at different triaxialities need to be done....

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  • ...A very indirect method was the usage of neural networks to get parameters for a damage model from small punch testing results, then using those parameters to simulate a CT test and using that to get fracture toughness, with a reasonably good agreement to standard test data.(17,56) Other observations related to small punch fracture toughness testing were that the pre-cracking method did not have a significant effect on the evaluated fracture toughness....

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  • ...Damage model parameters were exclusively evaluated for steels16,17,31,57,86,88 using small punch testing, one of the small punch specimens used had a notch through length (Figure 23).86 Two models were considered: Gurson-Tvergaard88 and Gurson-Tvergaard-Needleman.16,17,57,86 Two methods were used to obtain the material model parameters: neural networks trained on a database of systematically varied material parameters16,17 and FEA simulation fitting the model parameters.57,86,88 Two approaches to the neural network method were attempted: neural network approximated the inverse problem to the FEA solution and gave the material parameters as an answer or neural network approximated the FEA solution directly and damage model parameters were identified by conjugate directions finding algorithm....

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  • ...Two models were considered: Gurson-Tvergaard(88) and Gurson-Tvergaard-Needleman.(16,17,57,86) Two methods were used to obtain the material model parameters: neural networks trained on a database of systematically varied material parameters(16,17) and FEA simulation fitting the model parameters....

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  • ...This method was further validated with additional testing.(17) FEA simulation method was validated by simulating small punch tests and comparing the resulting forcedisplacement curves to experimentally obtained forcedisplacement curves....

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Journal ArticleDOI
TL;DR: In this paper, the elastic bending, plastic bending and membrane stretching regimes of small punch load-deflection curves have been used to estimate the uniaxial tensile stress-strain behavior of ferritic 2.25Cr-1Mo and AISI 403 steels.

145 citations


"Small specimen techniques for estim..." refers methods in this paper

  • ...Therefore various correlations based on limit load (Ps in Figure 29) were used, with different ones being applicable to different materials.(21,32,35,66) In general the results after applying the correlations matched standard testing results well, apart from when the material did not exhibit a limit load,(50) sometimes the results were too scattered to be used for anything other than ranking(33) or when the thickness to grain size ratio was too low (less than 19), making the results not representative of bulk material....

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Journal ArticleDOI
TL;DR: In this article, the use of microstructural features of the material, the effect of constraint and the actual region of the specimen that is undergoing deformation, and finally statistical approaches.
Abstract: The review is concerned with the use of miniature specimens to identify the mechanical/creep properties of metals and alloys. It is not intended to consider the nanoscales, which have been reviewed elsewhere, but focus on the size ranges and forms that are of use to areas such as alloy development, surveillance monitoring, effects of irradiation, properties of weld structures and remaining life. For many of these cases, there are technical advantages in the use of small specimens. Where possible, available reviews in this area are used and identified. The needs for small specimen sizes are considered, and the wide range of sizes of both conventional and more unusual specimen designs is reviewed. The potential effects of specimen size are considered: the microstructural features of the material, the effect of constraint and the actual region of the specimen that is undergoing deformation, and finally statistical approaches. The results of published studies are considered under the general groupings of yield/deformation behaviour, creep properties, toughness and fatigue, with an examination of the current state of interpretation of data from mini-specimens because interpretation is one of the key areas of interest. Finally, the current status of each area is considered, as certain designs of specimen will be better suited to answering specific technical questions. The need for standards for specific designs is also examined.

115 citations


"Small specimen techniques for estim..." refers background or methods in this paper

  • ...As the most commonly investigated small specimen application recently is creep testing, reviews on creep have been written by Dyson et al.1 and by Hyde et al.2 The use of small punch specimens for creep properties has been reviewed by Rouse et al.3 A review on tests performed exclusively on irradiated materials in the size range of tens of nanometers to tens of micrometres has been written by Hosemann et al.4 and a review on fatigue testing of microfabricated materials and micro-electromechanical systems has been written by Connolley et al.,5 they focus specifically on the small scale material behaviour, as opposed to bulk material behaviour....

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  • ...and by Hyde et al.(2) The use of small punch specimens for creep properties has been reviewed by Rouse et al....

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  • ...More detail about these specimens, their dimensions and testing considerations can be found in review by Dyson et al.1 and Hyde et al.2 Examples from all subcategories can be found when tensile properties are of interest....

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  • ...and Hyde et al.(2) Examples from all subcategories can be found when tensile properties are of interest....

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Journal ArticleDOI
TL;DR: In this article, the authors used a focused ion beam instrument to introduce small notches in selected grains to study the evolution of fatigue cracks from these notches during interrupted in situ fatigue cycling.

114 citations


"Small specimen techniques for estim..." refers methods in this paper

  • ...An interesting testing method was developed in order to study short stage 1 cracks in situ, based on diffraction contrast tomography and synchrotron tomography.(153) Kim used a load separation method to measure the crack propagation and d-c potential drop method to verify it....

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