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Effects of plate stiffness on the fatigue resistance and failure location of pipe-to-plate welded joints under bending
Get PDFA series of tests have been carried out using specimens made of a tube, having a thickness of t=10 mm, joined to a plate by fillet welding. Two different kinds of specimen were employed, differing in the plate geometry (stiffness). Both kinds of specimen were tested under bending (prevalent load) and shear loading in as welded conditions. Different initiation regions for the fatigue cracks were found and significantly different fatigue resistances were obtained for the two geometries in terms of the nominal stress approach (or in terms of applied load vs cycles to failure). Two local methods for the fatigue life assessment were then applied to independently analyse the experimental results: the fictitious notch rounding approach proposed by Radaj, which is also recommended by some international standards and the more recently proposed peak stress method, which is based on the NSIF concept. It is shown that the nominal stress method, which is by far the simplest method among those recommended in standards for analysing the joint under study, fails to explain the observed different endurances. On the other side, the methods based on local stresses account for the different joint stiffness and provide a reduced scatter in the results. However, even if local approaches, accounts for differences in the structural behaviour of the joint, the knowledge of the actual geometry of the weld need to be accounted for, in order to be able to identify the fatigue crack initiation region. For a design purpose, a safe prediction of the fatigue endurance of the joint can be obtained by all the analysed methods, if the corresponding recommended design curve is used
Fatigue life assessment of welded joints by local stress methods
No full textmethod in the analysis of the fatigue endurances of welded joints. Said methods are applied
to a collection of experimental data from three different geometries of welded joints, which
are characterized by different geometric parameters and, in particular, by a wide range of the
element thickness. The performance of the two methods is discussed in terms of the width of
the scatter band in the S-N plane and on the basis of some practical aspects related to the
implementation of the two methods
Fatigue strength assessment of laser welded thin-walled joints made of mild and high strength steel
No full textA database of fatigue tests taken from literature on thin-walled laser welded joints was created. Fatigue tests related to specimens made of different steel grades were considered, i.e. conventional and high strength steel, which is becoming of more concern in the automotive industry. For each specimen geometry in the database, the stress field in the notch ligament was obtained by means of finite element analysis, where the reference radius of ρf=0.05 mm was modelled. The fatigue assessment was performed by using three representative stresses: the maximum notch stress as well as the stress according to the critical distance and the stress averaging approach. For each assessment approach a regression S–N curve with a dedicated scatter band (Tσ) was obtained. The scatter was taken as measure of the assessment reliability. In addition to the assessment approach, also the effect of the base material on the fatigue strength is discussed
Fatigue assessment of a FSAE car rear upright by a closed form solution of the critical plane method
Get PDFMaterial fatigue is extensively discussed and researched within scientific and industrial communities. Fatigue damage poses a significant challenge for both metallic and non-metallic components, often resulting in unexpected failures of in-service parts. Within multiaxial fatigue assessment, critical plane methods have gained importance due to their ability to characterize a component's critical location and detect early crack propagation. However, the conventional approach to calculate critical plane factors is time-consuming, making it primarily suitable for research purposes or when critical regions are already known. In many real-world scenarios, identifying the critical area of a component is difficult due to complex geometries, varying loads, or time limitations. This challenge becomes particularly crucial after topological optimization of components and in the context of lightweight design. Recently, the authors proposed an efficient method for evaluating critical plane factors in closed form, applicable to all cases that necessitate the maximization of specific parameters based on stress and strain components or their combination. This paper presents and validates the proposed methodology, with reference to a rear upright of a FSAE car, which is characterized by a complex geometry and is subjected to non-proportional loading conditions. The efficient algorithm demonstrated a substantial reduction in computation time compared to the standard plane scanning method, while maintaining solution accuracy
Fatigue life assessment of welded joints by two local stress approaches: The notch stress approach and the peak stress method
Get PDFThis paper presents a comparison between two local methods that can be used for the fatigue life assessment of welded joints: the notch stress approach and the peak stress method. Even if they have been derived starting from entirely different theoretical backgrounds, both methods are based on the evaluation of a local stress acting at the notch tip of the seam weld, which is usually obtained through a finite element simulation. Said methods are applied to a collection of experimental data from three kinds of welded joints, which are characterized by different geometric parameters and, in particular, by a wide range of the element thickness. A total of 177 experimental tests are evaluated in this investigation, 31 of which are taken from literature while the other 152 are published here for the first time. The performance of the two methods is discussed in terms of the statistical dispersion in the analysed data. This is accomplished comparing the scatter bands obtained from a regression procedure in the S-N plot. In addition, some practical aspects related to the implementation of both methods are discussed, with particular attention to the ease of use offered, considering that this may represent a relevant aspect for the method's diffusion in practical applications
Fatigue endurance of welded joints subjected to different blocks of bending and torsion loading
Get PDFThe fatigue strength of pipe-to-plate welded joints under bending, torsion and combined (in-phase and out-of-phase) bending and torsion has been already investigated in previous works by the authors. The specimen consisted of a pipe joined by seam welding to a plate. Both the pipe and the plate were made of S355JR steel. The test apparatus allows to apply any combination of proportional and non-proportional bending and torsion loads to the specimen.
For the analysed specimens failure originated mainly from the weld root, where a severe notch is present, even if some failure from the weld toe was observed in case of bending loading. However, the crack propagation and fracture surface under bending and under torsion were significantly different. For this reason, in order to investigate any possible influence of the loading order on the fatigue endurance, the effect of different loading blocks was analysed in this work. This subject has not been widely investigated in the technical literature about welded joints.
In a first series of tests, specimens were loaded in bending for a given fraction of the estimated endurance and then were loaded in torsion till failure. A similar series of tests was then conducted by varying the loading order: specimens were loaded in torsion for a given fraction of the estimated endurance, followed by a block of bending loading till failure. The whole test campaign was repeated for two different fractions of the estimated life, i.e. 0.3 and 0.45, respectively. The failure was intended as the presence of a through the thickness crack, whose presence was monitored by a drop in the internal pressure of the pipe. Results are discussed in terms of the Miner’s rule based on nominal stresses and to the cumulative damage suggested by Eurocode and IIW
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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