14 research outputs found
Fat classes of welded steel details derived from the master design curve of the peak stress method
In this paper, the peak stress method (PSM) is adopted to analyse the fatigue strength of steel welded joints.
According to this method, a single design curve is expressed in terms of a properly defined equivalent peak stress
and it is valid for fatigue design of arc-welded steel joints. Private companies often need simple finite element beam
models for fatigue strength assessments, because of the large dimensions of the structures. However, beam elements
provide nominal stresses (and not local stresses) that must be compared with appropriate fatigue strength values (the
FAT classes) available in design standards. Due to the limited number of FAT classes available, finding the
appropriate one is frequently troublesome, particularly when complex geometries are considered. The objective of
this work is to define FAT classes in terms of nominal stress for a number of geometrically complex structural
details, starting from the design curve of the PSM. FAT classes have also been determined using the hot spot stress
approach. Then the results obtained with the two methods are compared. The structural details analysed in the
present paper are typically adopted in amusement park structures and are not classified in common design standards
definition of nominal stress based fat classes of complex welded steel structures using the peak stress method
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Fatigue assessment of weld toe and weld root failures in steel welded joints according to the peak stress method
The peak stress method is an engineering, finite
element (FE)-oriented application of the local approach
based on the notch-stress intensity factors
(NSIFs), which quantify the intensity of the local, linear
elastic stress field at the potential crack initiation points
(either the weld toe or the weld root). All effects due to
plate thickness, joint shape and loading mode (axial or
bending) are fully included in the NSIFs, such that a
single design curve is sufficient to assess the fatigue
strength of arc-welded joints in structural steels, tested
in the as-welded conditions. The design stresses to analyse
the fatigue strength are the peak stresses evaluated
by FEM at the weld toe or the weld root, which are
modelled as sharp notches with a tip radius equal to
zero. The mean value of the FE size adopted to calculate
the singular peak stresses can be chosen within a
range of applicability, while the FE pattern of elements
to use is the free mesh generated automatically by the
Ansys\u2122 numerical code. Due to the rather coarse
meshes required to apply the PSM and its suitability
to be used directly with results of 3D FE analyses, the
method is rather useful in everyday design practice
FATIGUE ASSESSMENT OF WELD TOE AND WELD ROOT FAILURES IN STEEL WELDED JOINTS ACCORDING TO THE PEAK STRESS METHOD
The Peak Stress Method is an engineering, FE-oriented application of the local approach based on the Notch-Stress Intensity Factors (N-SIFs), which quantify the intensity of the local, linear elastic stress field at the potential crack initiation points (either the weld toe or the weld root). All effects due to plate thickness, joint shape and loading mode (axial or bending) are fully included in the N-SIFs, such that a single design curve is sufficient to assess the fatigue strength of arc-welded joints in structural steels, tested in the as-welded conditions. The design stresses to analyse the fatigue strength are the peak stresses evaluated by FEM at the weld toe or the weld root, which are modelled as sharp notches with a tip radius equal to zero. The mean value of the FE size adopted to calculate the singular peak stresses can be chosen within a range of applicability, while the FE pattern of elements to use is the free mesh generated automatically by Ansys\uf0d4 numerical code. Due to the rather coarse meshes required to apply the PSM and its suitability to be used directly with results of three-dimensional FE analyses, it seems that the method is rather useful in the everyday design practise
Comportamento a fatica di giunti saldati tubo-su-flangia con nervature di rinforzo soggetti a carichi multiassiali ad ampiezza costante secondo il Peak Stress Method
Multiaxial fatigue assessment of welded steel details according to the peak stress method: Industrial case studies
In fatigue design of welded joints, the Peak Stress Method (PSM) is an engineering, rapid, finite element-based
tool to apply the notch stress intensity factor (NSIF) approach. The PSM presents some advantages, such as: (i)
coarse meshes can be adopted, the required FE size being some orders of magnitude larger than that necessary to
evaluate the NSIFs from the local stress distributions; (ii) only a single stress value is sufficient to estimate the
NSIFs; (iii) 2D as well as 3D FE models can be used and (iv) the design engineer is able to determine the crack
initiation point when competition between weld root and weld toe failure exists. Therefore the PSM may be a
convenient design tool to adopt in the industry. In the present paper, new fatigue results have been generated by
testing plate-to-tube welded steel details taken from industrial case studies under in-phase bending-torsion fatigue
loadings. In particular, full-penetration joints adopted in the structure of a roundabout-type carousel and
fillet-welded joints for quarter-turn scotch-yoke valve actuators have been tested. Experimental fatigue results
have been analysed using the PSM, which proved to identify correctly the fatigue crack initiation location.
Finally, a fairly good agreement has been obtained between the experimental results and the relevant PSM-based
design curves
Multiaxial fatigue assessment of welded steel details according to the peak stress method based on tetra elements
The Peak Stress Method (PSM) is an engineering, FE-oriented application of the notch stress intensity factor (NSIF) approach to fatigue design of welded joints, which takes advantage of the singular linear elastic peak stresses from FE analyses with coarse meshes. Originally, the PSM was calibrated by using 3D, eight-node brick elements, taking advantage of the submodeling technique. Recently, the PSM has been calibrated by using ten-node tetra elements, which are able to directly discretize complex 3D geometries without the need for submodels. The PSM was validated for pure axial or bending loadings as well as pure torsion loadings; recently it has been extended to multiaxial loadings by adopting a design stress, the so-called equivalent peak stress, in conjunction with a reference design fatigue curve. After having briefly recalled the calibration of the PSM with tetra elements, the paper presents some applications of the PSM relevant to steel plate-to-tube welded details of industrial interest under in-phase bending-torsion fatigue loadings. Experimental data have been re-analysed using the PSM based on tetra elements. Eventually a good agreement between experimental and theoretical results has been obtained in terms of fatigue crack initiation location as well as total fatigue life
Pasta Consumption and Connected Dietary Habits: Associations with Glucose Control, Adiposity Measures, and Cardiovascular Risk Factors in People with Type 2 Diabetes-TOSCA.IT Study
Pasta is a refined carbohydrate with a low glycemic index. Whether pasta shares the metabolic advantages of other low glycemic index foods has not really been investigated. The aim of this study is to document, in people with type-2 diabetes, the consumption of pasta, the connected dietary habits, and the association with glucose control, measures of adiposity, and major cardiovascular risk factors
Pasta Consumption and Connected Dietary Habits: Associations with Glucose Control, Adiposity Measures, and Cardiovascular Risk Factors in People with Type2 Diabetes-TOSCA.IT Study.
Background: Pasta is a refined carbohydrate with a low glycemic index. Whether pasta shares the metabolic advantages of other low glycemic index foods has not really been investigated. The aim of this study is to document, in people with type-2 diabetes, the consumption of pasta, the connected dietary habits, and the association with glucose control, measures of adiposity, and major cardiovascular risk factors.
Methods: We studied 2562 participants. The dietary habits were assessed with the European Prospective Investigation into Cancer and Nutrition (EPIC) questionnaire. Sex-specific quartiles of pasta consumption were created in order to explore the study aims.
Results: A higher pasta consumption was associated with a lower intake of proteins, total and saturated fat, cholesterol, added sugar, and fiber. Glucose control, body mass index, prevalence of obesity, and visceral obesity were not significantly different across the quartiles of pasta intake. No relation was found with LDL cholesterol and triglycerides, but there was an inverse relation with HDL-cholesterol. Systolic blood pressure increased with pasta consumption; but this relation was not confirmed after correction for confounders.
Conclusions: In people with type-2 diabetes, the consumption of pasta, within the limits recommended for total carbohydrates intake, is not associated with worsening of glucose control, measures of adiposity, and major cardiovascular risk factors.
Keywords: body mass index; cardiovascular risk factors; dietary habits; glucose control; pasta consumption; type 2 diabetes