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1.
Modeling of impact toughness of cold formed material by genetic programming
Leo Gusel, Miran Brezočnik, 2006, original scientific article

Abstract: In the paper, an approach completely different from the conventional methods for determination of accurate models for the change of properties of cold formed material, is presented. This approach is genetic programming (GP) method which is based on imitation of natural evolution of living organisms. The main characteristic of GP is its non-deterministic way of computing. No assumptions about the form and size of expressions were made in advance, but they were left to the self organization and intelligence of evolutionary process. First, copper alloy rods were cold drawn under different conditions and then impact toughness of cold drawn specimens was determined by Charpy tests. The values of independent variables (effective strain, coefficient of friction) influence the value of the dependent variable, impact toughness. On the basis of training data, different prediction models for impact toughness were developed by GP. Only the best models, gained by genetic programming were presented in the paper. Accuracy of the best models was proved with the testing data set. The comparison between deviation of genetic model results and regression model results concerning the experimental results has showed that genetic models are more precise and more varied then regression models.
Keywords: metal forming, genetic programming, evolutionary computing, impact toughness, copper alloy, modelling
Published: 30.05.2012; Views: 1332; Downloads: 65
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2.
In-service damage of railway steel axles
O. Jasnìî, Tomaž Vuherer, Ju. I. Pindus, Andriy Sorochak, Ivan Samardžić, 2011, short scientific article

Abstract: The influence of temperature and specimens undercut place on impact toughness of railway axle material in service is investigated. The obtained results show inversely proportional dependence of impact toughness on undercut radius of specimens. The decrease of test temperature from +20 to –40 ºC decreases significantly the impact toughness and portion of ductile fracture.
Keywords: impact toughness, in-serice damage, railway axle, undercut
Published: 01.06.2012; Views: 591; Downloads: 43
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3.
The fracture behaviour of global/local mis-matched weld joints provided on HSLA steels
Inoslav Rak, Nenad Gubeljak, Zdravko Praunseis, 2001, original scientific article

Abstract: The fracture behaviour of thick section high strength steel weldments, that contain soft root passes, has been studied. Two different weld consumables with different strength mismatch (1>M>1) and fracture toughness properties in the WM have significantly increased the complexity of the mis-match effect and failure behaviour of weld joints, depending on the crack location and the thickness of the soft root layer. The aim was to explain the effect of strength heterogeneity between BM and WM and between different regions in WM (global/local mismatching). R-curves of WM and HAZ regions were also discussed. The conclusion is that the application of a welding procedure with a two-pass soft root layer, introduced for the purpose of reducing or even omitting preheating, can be recommended in mis-matched weld joints on steel grade HT80. Nevertheless, the alloying from BM, and the tempering effect of subsequent weld passes, have to be taken into account. They can cause reduction of the root region ductility and affect the local mismatch in WM and HAZ. The deterioration by providing a soft root layer can probably be reduced by a selected consumable and proper welding procedure. The final conclusion is that the application of a mismatched weld joint with a soft root layer can be recommended only if high root toughness can be provided.
Keywords: welding, welded joints, strength mismatching, fracture toughness, CTOD, hardness, impact toughness, HSLA steels
Published: 01.06.2012; Views: 1184; Downloads: 58
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Low temperature impact toughness of the main gas pipeline steel after long-term degradation
P. O. Maruščak, Irina Danyliuk, R.T. Biščak, Tomaž Vuherer, 2014, original scientific article

Abstract: The correlation of microstructure, temperature and Charpy V-notch impact properties of a steel 17G1S pipeline steel was investigated in this study. Within the concept of physical mesomechanics, the dynamic failure of specimens is represented as a successive process of the loss of shear stability, which takes place at different structural/scale levels of the material. Characteristic stages are analyzed for various modes of failure, moreover, typical levels of loading and oscillation periods, etc. are determined. Relations between low temperature derived through this test, microstructures and Charpy (V-notch) toughness test results are also discussed in this paper.
Keywords: impact toughness, fracture, damage, gas pipeline, steel, degradation
Published: 03.04.2017; Views: 388; Downloads: 186
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6.
Charpy toughness of vibrated microstructures
Bogdan Pučko, Vladimir Gliha, 2005, original scientific article

Abstract: The aim of this study was to investigate the influence of vibration on impact toughness of weld metal. Studies were carried out on two welds, of which one had been welded with applying vibration during welding. From test plates samples were made to simulate heat affect in combination with or without vibration after solidification. In this way conditions at multi-pass welding were simulated. According to different conditions Charpy toughness on non standard specimens and fracture appearance were observed. Vibration during welding benefits impact energy of weld metal, especially if weld metal undergoes further heatb treatment.
Keywords: welded joints, impact toughness, vibration, Charpy toughness, SAW
Published: 03.07.2017; Views: 232; Downloads: 54
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7.
The influence of simulated thermal cycle on the formation of microstructures of multi-pass weld metal
Danilo Rojko, Vladimir Gliha, 2005, original scientific article

Abstract: The influence of weld thermal cycle on the micrstructural changes in weld metal by use of the simulated microstructures. We examined the kinetics of the formation of austenite from the starting microstructure. The simulated microstructures were prepared by the application of simulated thermal cycles with different peak temperatures on a sample of real single-pass weld metal. The reproduction of thermal cycles were carried out by the SMITWELD simulator. Special attention was dedicated to the influence of thermal cycle on the formation of microstructures, which can be potential triggers of brittle fracture (local brittle zones).
Keywords: welding, welded joints, multi-pass weld metal, simulated microstructure, impact toughness
Published: 03.07.2017; Views: 1212; Downloads: 50
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8.
Deformation and energy parameters of fracture of steel of the main gas pipeline
P. O. Maruščak, Sergey Panin, Ulyana Polyvana, Tomaž Vuherer, Anna Guzanová, Janette Brezinová, 2015, original scientific article

Abstract: By example of steel 17G1S, the regularities in the impact fracture of Charpy specimens at normal and low temperatures are described. The relationship between the energy parameters of fracture (impact toughness) and the deformation response of the material (the height of shear lips) of the specimens from the pipe steel is established. The micromechanisms of impact fracture of the material are described. At 20 °C and –30 °C, focal splitting of the material was observed on the fracture surface of specimens; at –60 °C, the material failed in a brittle manner by the mechanism of cleavage.
Keywords: impact toughness, main gas pipeline, failure analysis
Published: 08.08.2017; Views: 340; Downloads: 201
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