1. An approach to consider the arterial residual stresses in modelling of a patient-specific arteryJanez Urevc, Miroslav Halilovič, Milan Brumen, Boris Štok, 2016, original scientific article Abstract: In this work, the residual stress state of a human common carotid artery is predicted using the so-called thermomecha- nical analogy approach. The purpose of the approach is to enable consistent mapping of residual stresses and the respec- tive configuration from a circular arterial segment to a patient-specific arterial geometry. This is achieved by applying proper volumetric dilatations to the actual arterial stress-free in vivo geometry, which makes use of the analogy that states that the bending stresses can be obtained on an equivalent manner by applying proper thermal dilatations. The common carotid artery data are obtained in vivo from a healthy 28-year-old man using non-invasive methods. The pre- dicted residual stresses of the common carotid artery are in good quantitative agreement with the data from prior work in this field. The approach is validated by predicting the common carotid artery zero-stress state configuration, where a sector-like (cut-open) state is obtained. With this approach, it is thus possible to predict the residual stresses as well as the configuration of patient-specific arterial geometry without the need to model its cut-open zero-stress configuration.
Keywords: patient-specific artery, common carotid artery, residual stresses, arterial zero-stress state, thermomechanics, finite element method
Published in DKUM: 12.07.2017; Views: 1335; Downloads: 378
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2. Fatigue crack initiation from microstructurally small Vickers indentationsTomaž Vuherer, Andrej Godina, Zijah Burzić, Vladimir Gliha, 2007, original scientific article Abstract: The resistivity of coarse grain steel against crack initiation in the presence of micro defects is discussed. Samples of material with martensitic microstructure were prepared by adequate thermal treatment. Microstructurally small Vickers indentations were used as an artificial micro defect. The compressive residual stresses are due to the irreversibility of plastic deformation. The moment of indenting enables to prepare samples with and without effects of residual stresses. The stress level for crack initiation depends on the actual indentation size. The location of initiated cracks is affected by the presence and character of residual stresses.
Keywords: welded joints, micro defect, coarse grain HAZ, crack initiation, crack growth, stress concentration, fatigue limit, Vickers, residual stresses
Published in DKUM: 03.07.2017; Views: 1782; Downloads: 119
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3. Measurement of strain caused by residual stresses in a welded joint using neutron diffractionNenad Gubeljak, Jelena Vojvodič-Tuma, Hans-Georg Preismeyer, 1999, original scientific article Abstract: The distribution and amount of residual stresses can significantly contrubute to the fatigue fracture behaviour of welded joints in structures. Interior residual stresses, which interact with the plane strain state, are more dangerous than residual stresses at the surface of the welded joint. If the surface of the welded joint is mechanically treated (e.g. shapering), then significant differences between the stress stated at the surface and within the volume occur. Hence, different non-destructive methods (e.g. gamma radiation, neutron diffraction) have been developed to determine strains caused by residual stresses in the volume of polycrystalline materials. However, the measurement of strains caused by residual stresses becomes difficult for large samples. In this paper the measurement procedure on a sample taken from the weld joint is presented and the effecet of residual stresses on fatigue crack propagation is assessed for low and high cycle loading fatigue.
Keywords: zaostale napetosti, zvarni spoj, neutronski lom žarkov, utrujenostno širjenje razpoke, neutron diffraction method, residual stresses, fatigue crack propagation, weld joint
Published in DKUM: 10.07.2015; Views: 1308; Downloads: 35
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4. Role of residual stresses on fracture properties of under-matched butt weldInoslav Rak, Vladimir Gliha, 1999, original scientific article Abstract: Under-matched weld joints were adopted for producing a penstock of 47 mm wall thickness and 4200 mm diameter, to improve the weldability. The isothermal Robertson wide plate test on the under-matched weld joints, were the allowable stress level was 0.6 of the yield stress, proved that the longitudinal stresses caused the crack propagation alog the weld joint to deviate into tough base material where it was arrested. The arrest temperature was between -10 and -20°C. The behaviour of the crack propagation was the reason to omit the thermal stress relieving of the pipe section and on circumferential weld joints executed on this side. One can always take into consideration the role of axial residual stresses when assessing whether to use, or not, under-matched weld joints in severer loaded structures.
Keywords: strjeni zvar z nižjo mejo tečenja, zaostale napetosti, potek loma, lastnosti ujetja, lomna žilavost, under-matched weld joint, residual stresses, fracture path, arrest properties, fracture toughness
Published in DKUM: 10.07.2015; Views: 1582; Downloads: 46
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5. Effect of residual stresses on the fatigue crack propagation in welded jointsNenad Gubeljak, Jožef Predan, Reinhard Pippan, Maks Oblak, 2005, original scientific article Abstract: The effect of residual stress on the fatigue crack growth was investigated forcyclic tension. Three-point bend specimens were used with through thicknessnotches at the center line of the welded joint. The experiments were performed for different load amplitudes and load ratios under conditions of small-scale yielding. The influence of the residual stresses on fatigue crack growth was estimated by experimentally observed fatigue crack growth rate and measurement of residual stresses at the surface of specimen. This paper describes an approach taken in two models to estimate the residual stress effect on fatigue crack propagation and to predict remaining service life of awelded structure.
Keywords: fracture mechnaics, fatigue crack, crack growth, residual stresses, fatigue crack growh rate, X-ray
Published in DKUM: 01.06.2012; Views: 2029; Downloads: 93
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6. Effect of vibration on weld metal hardness and toughnessBogdan Pučko, Vladimir Gliha, 2005, original scientific article Abstract: Vibration of welded parts is usually applied to achieve effects similar to thermal stress relief. With vibration, it is not only residual stresses that are affected. Using two different welding processes, the influence of vibration on hardness and toughness of the weld was measured. For each weldingprocess, two series of Charpy specimens were made over the temperature range from -60 to +20°C. The only difference between the two series was in performing welding with or without vibration. Slight differences in weld metalhardness were observed. Toughness measurements show an increase in impacttoughness and a significant increase in fracture toughness in samples which were vibrated during welding.
Keywords: welding, welded joints, residual stresses, vibrational stress relief, hardness, toughness, steel
Published in DKUM: 01.06.2012; Views: 2601; Downloads: 97
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