The Experts below are selected from a list of 10491 Experts worldwide ranked by ideXlab platform
Daniele Rigon - One of the best experts on this subject based on the ideXlab platform.
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multiaxial fatigue strength assessment of welded joints using the peak stress method part i approach and application to aluminium joints
International Journal of Fatigue, 2017Co-Authors: Giovanni Meneghetti, Alberto Campagnolo, Daniele RigonAbstract:Abstract The notch stress intensity factor (NSIF) approach for the fatigue strength assessments of welded joints assumes the weld toe as a sharp V-notch with tip radius equal to zero and the weld root as a pre-crack. The Peak Stress Method (PSM) is an approximate, FE-oriented application of the NSIF-based approaches to fatigue design of welded joints and it is based on the singular linear elastic peak stresses calculated from FE analyses carried out by using a proper mesh pattern; more precisely, the Element type is fixed, the Average Element Size is kept uniform in the mesh pattern and before running the mesh generation algorithm the Size can be chosen arbitrarily within a given range. The PSM allows to adopt rather coarse FE meshes if compared to those required for the NSIFs evaluation from the local stress fields. While originally the PSM was validated for pure axial or bending loadings as well as pure torsion loadings, here the PSM is extended for the first time to analyse the fatigue strength of welded joints subjected to in-phase as well as out-of-phase multiaxial fatigue loadings. By adopting the Averaged Strain Energy Density (SED) as a fatigue strength criterion, a so-called equivalent peak stress is defined and it is adopted to assess either weld toe and weld root fatigue failures in conjunction with a properly defined design curve. Some multiaxial fatigue test data taken from the literature and relevant to welded joints made of aluminium alloys are analysed using the Peak Stress Method. The equivalent peak stress has shown to correlate with good approximation all the experimental data.
Giovanni Meneghetti - One of the best experts on this subject based on the ideXlab platform.
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multiaxial fatigue strength assessment of welded joints using the peak stress method part i approach and application to aluminium joints
International Journal of Fatigue, 2017Co-Authors: Giovanni Meneghetti, Alberto Campagnolo, Daniele RigonAbstract:Abstract The notch stress intensity factor (NSIF) approach for the fatigue strength assessments of welded joints assumes the weld toe as a sharp V-notch with tip radius equal to zero and the weld root as a pre-crack. The Peak Stress Method (PSM) is an approximate, FE-oriented application of the NSIF-based approaches to fatigue design of welded joints and it is based on the singular linear elastic peak stresses calculated from FE analyses carried out by using a proper mesh pattern; more precisely, the Element type is fixed, the Average Element Size is kept uniform in the mesh pattern and before running the mesh generation algorithm the Size can be chosen arbitrarily within a given range. The PSM allows to adopt rather coarse FE meshes if compared to those required for the NSIFs evaluation from the local stress fields. While originally the PSM was validated for pure axial or bending loadings as well as pure torsion loadings, here the PSM is extended for the first time to analyse the fatigue strength of welded joints subjected to in-phase as well as out-of-phase multiaxial fatigue loadings. By adopting the Averaged Strain Energy Density (SED) as a fatigue strength criterion, a so-called equivalent peak stress is defined and it is adopted to assess either weld toe and weld root fatigue failures in conjunction with a properly defined design curve. Some multiaxial fatigue test data taken from the literature and relevant to welded joints made of aluminium alloys are analysed using the Peak Stress Method. The equivalent peak stress has shown to correlate with good approximation all the experimental data.
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fatigue strength assessment of partial and full penetration steel and aluminium butt welded joints according to the peak stress method
Fatigue & Fracture of Engineering Materials & Structures, 2015Co-Authors: Giovanni Meneghetti, Alberto Campagnolo, Filippo BertoAbstract:In fatigue design of welded joints, the local approach based on the notch stress intensity factors (NSIFs) assumes that the weld toe profile is a sharp V-notch having a tip radius equal to zero, while the root side is a pre-crack in the structure. The peak stress method (PSM) is an engineering, FE-oriented application of the NSIF approach to fatigue design of welded joints, which takes advantage of the elastic peak stresses from FE analyses carried out by using a given mesh pattern, where the Element type is kept constant and the Average Element Size can be chosen arbitrarily within a given range. The meshes required for the PSM application are rather coarse if compared with those necessary to evaluate the NSIFs from the local stress distributions. In this paper, the PSM is extended for the first time to butt-welded joints in steel as well as in aluminium alloys, by comparing a number of experimental data taken from the literature with the design scatter bands previously calibrated on results relevant only to fillet-welded joints. A major problem in the case of butt-welded joints is to define the weld bead geometry with reasonable accuracy. Only in few cases such geometrical data were available, and this fact made the application of the local approaches more difficult. Provided the local geometry is defined, the PSM can be easily applied: a properly defined design stress, that is, the equivalent peak stress, is shown (i) to single out the crack initiation point in cases where competition between root and toe failure exists and (ii) to correlate with good approximation all analysed experimental data.
Alberto Campagnolo - One of the best experts on this subject based on the ideXlab platform.
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multiaxial fatigue strength assessment of welded joints using the peak stress method part i approach and application to aluminium joints
International Journal of Fatigue, 2017Co-Authors: Giovanni Meneghetti, Alberto Campagnolo, Daniele RigonAbstract:Abstract The notch stress intensity factor (NSIF) approach for the fatigue strength assessments of welded joints assumes the weld toe as a sharp V-notch with tip radius equal to zero and the weld root as a pre-crack. The Peak Stress Method (PSM) is an approximate, FE-oriented application of the NSIF-based approaches to fatigue design of welded joints and it is based on the singular linear elastic peak stresses calculated from FE analyses carried out by using a proper mesh pattern; more precisely, the Element type is fixed, the Average Element Size is kept uniform in the mesh pattern and before running the mesh generation algorithm the Size can be chosen arbitrarily within a given range. The PSM allows to adopt rather coarse FE meshes if compared to those required for the NSIFs evaluation from the local stress fields. While originally the PSM was validated for pure axial or bending loadings as well as pure torsion loadings, here the PSM is extended for the first time to analyse the fatigue strength of welded joints subjected to in-phase as well as out-of-phase multiaxial fatigue loadings. By adopting the Averaged Strain Energy Density (SED) as a fatigue strength criterion, a so-called equivalent peak stress is defined and it is adopted to assess either weld toe and weld root fatigue failures in conjunction with a properly defined design curve. Some multiaxial fatigue test data taken from the literature and relevant to welded joints made of aluminium alloys are analysed using the Peak Stress Method. The equivalent peak stress has shown to correlate with good approximation all the experimental data.
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fatigue strength assessment of partial and full penetration steel and aluminium butt welded joints according to the peak stress method
Fatigue & Fracture of Engineering Materials & Structures, 2015Co-Authors: Giovanni Meneghetti, Alberto Campagnolo, Filippo BertoAbstract:In fatigue design of welded joints, the local approach based on the notch stress intensity factors (NSIFs) assumes that the weld toe profile is a sharp V-notch having a tip radius equal to zero, while the root side is a pre-crack in the structure. The peak stress method (PSM) is an engineering, FE-oriented application of the NSIF approach to fatigue design of welded joints, which takes advantage of the elastic peak stresses from FE analyses carried out by using a given mesh pattern, where the Element type is kept constant and the Average Element Size can be chosen arbitrarily within a given range. The meshes required for the PSM application are rather coarse if compared with those necessary to evaluate the NSIFs from the local stress distributions. In this paper, the PSM is extended for the first time to butt-welded joints in steel as well as in aluminium alloys, by comparing a number of experimental data taken from the literature with the design scatter bands previously calibrated on results relevant only to fillet-welded joints. A major problem in the case of butt-welded joints is to define the weld bead geometry with reasonable accuracy. Only in few cases such geometrical data were available, and this fact made the application of the local approaches more difficult. Provided the local geometry is defined, the PSM can be easily applied: a properly defined design stress, that is, the equivalent peak stress, is shown (i) to single out the crack initiation point in cases where competition between root and toe failure exists and (ii) to correlate with good approximation all analysed experimental data.
Meneghetti G. - One of the best experts on this subject based on the ideXlab platform.
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Multiaxial fatigue assessment of a structural steel joint according to the peak stress method
2018Co-Authors: Meneghetti G., Campagnolo A., Menegalli A.Abstract:In fatigue design of welded joints, the local approach based on the notch stress intensity factor (NSIF) assumes that the weld toe profile is a sharp V-notch having a tip radius equal to zero, while the root side is a pre-crack in the structure. The Peak Stress Method (PSM) is an approximate, FE-oriented application of the NSIF approach to fatigue design of welded joints, which is based on the singular linear elastic peak stresses calculated from FE analyses carried out by using a proper mesh pattern. The Element type is kept constant while the Average Element Size can be chosen arbitrarily within a given range of applicability. The PSM allows rather coarse FE meshes to be adopted if compared to those required for the NSIFs evaluation from the local stress fields. The PSM was originally validated for pure axial or bending loadings as well as pure torsion loadings. Recently, the PSM has been extended to analyse the fatigue strength of welded joints subjected to multiaxial fatigue loadings. By adopting the Averaged Strain Energy Density (SED) as a fatigue strength criterion, a design stress, the so-called equivalent peak stress, can be defined and adopted in conjunction with a reference design fatigue curve to assess multiaxial fatigue failures. In the present contribution, new fatigue test results relevant to weld toe failures have been generated by testing full-penetration welded steel joints under in-phase bending-torsion fatigue loadings, generated by an external fatigue axial loading (F in the figure). Joints, having the geometry reported in the figure, have been tested under both as-welded and stress relieved conditions. First, the experimental fatigue test results have been compared with the theoretical estimations based on the nominal stress approach as proposed in International Standards and Recommendations. Then, experimental data have been re-analysed using the equivalent peak stress in conjunction with the multiaxial design scatter band according to PSM. All experimental data fall definitely in the safe side as compared to the design scatter band. To better explain this result further investigations have been carried out by analyzing in more detail both the root radius and the residual stress field at the weld toe. It has been shown that the notch tip radius at the weld toe is about equal to 4.5 mm, so that the sharp V-notch hypothesis was not consistent. Moreover, high values of compressive residual stresses have been measured close to the weld toe of both as-welded and stress-relieved joints by means of X-ray diffraction technique. Finally, by considering a blunt V-notch at the weld toe, the deviation between experimental results, re-converted in terms of equivalent peak stress, and the PSM-based design curve has been significantly reduced, even if results fall slightly on the safe side. However, this could be explained on the basis of the compressive residual stress state, which allows to protect the weld toe against fatigue crack initiation and propagation, increasing the fatigue life
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Rapid calculation of Residual Notch Stress Intensity Factors (R-NSIFs) by means of the Peak Stress Method
country:HRV, 2018Co-Authors: Colussi M., Ferro P., Berto F., Meneghetti G.Abstract:Recently the residual stress fields near the weld toe of welded joints have been investigated according either to the theoretical linear elastic solution obtained by Williams in 1952 or to the elasto-plastic solution obtained by Hutchinson, Rice and Rosengren in 1968, depending on the process parameters and boundary conditions. These approaches are appropriate if the weld toe region is modelled as a pointed V-notch having a zero notch root radius, according to a \u201cworst case\u201d geometrical hypothesis. Accordingly, the intensity of the residual singular stress distribution can be quantified by the residual notch stress intensity factor (R-NSIF), which might be a useful stress parameter to include in local approaches for fatigue strength assessments of welded joints, though its use has not yet been validated. In order to calculate the residual stress fields by means of welding process simulations, the mesh adopted in numerical models has necessarily to be very fine, the smallest Element Size being of the order of 10-5 mm. Unfortunately, the non-linear and transient behaviour of the welding simulation makes numerical analyses extremely demanding in terms of computational time, particularly if large welded structures and/or multi-pass welds have to be simulated. In this scenario, the use of methods aimed at reducing the computational effort to estimate local stresses and strains in welded structures can be effective. Among these, the peak stress method has been proposed to estimate the NSIFs at sharp V-notches, using coarse finite Element patterns, characterized by a uniform Average Element Size and by a mesh density within a proper range of applicability. In this work, the PSM has been used to calculate the R-NSIF of a full penetration welded T-joint. It has been shown that the PSM can successfully be used to estimate R-NSIFs values, provided that the stress redistribution induced by plasticity in the zone very close to the notch tip is negligible
Menegalli A. - One of the best experts on this subject based on the ideXlab platform.
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Multiaxial fatigue assessment of a structural steel joint according to the peak stress method
2018Co-Authors: Meneghetti G., Campagnolo A., Menegalli A.Abstract:In fatigue design of welded joints, the local approach based on the notch stress intensity factor (NSIF) assumes that the weld toe profile is a sharp V-notch having a tip radius equal to zero, while the root side is a pre-crack in the structure. The Peak Stress Method (PSM) is an approximate, FE-oriented application of the NSIF approach to fatigue design of welded joints, which is based on the singular linear elastic peak stresses calculated from FE analyses carried out by using a proper mesh pattern. The Element type is kept constant while the Average Element Size can be chosen arbitrarily within a given range of applicability. The PSM allows rather coarse FE meshes to be adopted if compared to those required for the NSIFs evaluation from the local stress fields. The PSM was originally validated for pure axial or bending loadings as well as pure torsion loadings. Recently, the PSM has been extended to analyse the fatigue strength of welded joints subjected to multiaxial fatigue loadings. By adopting the Averaged Strain Energy Density (SED) as a fatigue strength criterion, a design stress, the so-called equivalent peak stress, can be defined and adopted in conjunction with a reference design fatigue curve to assess multiaxial fatigue failures. In the present contribution, new fatigue test results relevant to weld toe failures have been generated by testing full-penetration welded steel joints under in-phase bending-torsion fatigue loadings, generated by an external fatigue axial loading (F in the figure). Joints, having the geometry reported in the figure, have been tested under both as-welded and stress relieved conditions. First, the experimental fatigue test results have been compared with the theoretical estimations based on the nominal stress approach as proposed in International Standards and Recommendations. Then, experimental data have been re-analysed using the equivalent peak stress in conjunction with the multiaxial design scatter band according to PSM. All experimental data fall definitely in the safe side as compared to the design scatter band. To better explain this result further investigations have been carried out by analyzing in more detail both the root radius and the residual stress field at the weld toe. It has been shown that the notch tip radius at the weld toe is about equal to 4.5 mm, so that the sharp V-notch hypothesis was not consistent. Moreover, high values of compressive residual stresses have been measured close to the weld toe of both as-welded and stress-relieved joints by means of X-ray diffraction technique. Finally, by considering a blunt V-notch at the weld toe, the deviation between experimental results, re-converted in terms of equivalent peak stress, and the PSM-based design curve has been significantly reduced, even if results fall slightly on the safe side. However, this could be explained on the basis of the compressive residual stress state, which allows to protect the weld toe against fatigue crack initiation and propagation, increasing the fatigue life
