27 research outputs found
Numerical modelling of dynamic ductile fracture propagation in different lab-scale experiments using GTN damage model
No full textsponsorship: The author gratefully acknowledges the support of the Research Foundation Flanders (FWO) via PhD fellowship grant 1SB6420N.. (Research Foundation Flanders (FWO) via PhD fellowship|1SB6420N)status: Published onlin
Mechanical joining of materials with limited ductility: Analysis of process-induced defects
No full textFailure Mechanisms of Mechanically and Thermally Produced Holes in High-Strength Low-Alloy Steel Plates Subjected to Fatigue Loading
No full textHigh-strength low-alloy steels (HSLA) are gaining popularity in structural applications in which weight reduction is of interest, such as heavy duty machinery, bridges, and offshore structures. Since the fatigue behavior of welds appears to be almost independent of the base material and displays little improvement when more resistant steel grades are employed, the use of bolted joints is an alternative joining technique which can lead to an increased fatigue performance of HSLA connections. Manufacturing a hole to allocate the fastener elements is an unavoidable step in bolted elements and it might induce defects and tensile residual stresses that could affect its fatigue behavior. This paper studies and compares several mechanical (punching, drilling, and waterjet-cut) and thermal (plasma and laser-cut) hole-making procedures in HSLA structural plates. A series of 63 uniaxial fatigue tests was completed, covering three HSLA grades produced by thermomechanically controlled process (TMCP) with yield strength ranging from 500 to 960 MPa. Samples were tested at single load level, which was considered representative in HSLA typical applications, according to the input received from end users. The manufactured holes were examined by means of optical and electron microscopy, 3D point measurement, micro hardness tests, X-ray diffraction, and electron backscatter diffraction (EBSD). The results give insight on cutting processes in HSLA and indicate how the fatigue failure is dominated by macro defects rather than by the steel grade. It was shown that the higher yield strength of the HSLA grades did not lead to a higher fatigue life. Best fatigue results were achieved with laser-cut specimens while punched samples withstood the lowest amount of cycles.(OLD) MSE-
On the strength of stainless steel fillet welds
No full textsponsorship: The first author is funded by a PhD fellowship from the Research Foundation Flanders. We would also like to thank Industeel for providing the duplex material for this research. (Research Foundation Flanders)status: Publishe
Experimental and numerical fatigue assessment of duplex welded transversal stiffeners
No full textFatigue is mostly the governing design criterion in girder steel bridges due to the presence of critical welded details. In this research, the hot spot stresses in welded cruciform duplex stainless steel joints are measured experimentally using digital image correlation as well as traditional strain gauges. They are also computed via FEM. The deduced fatigue lives are then compared to each other as well as to small-scale cyclic test results and to a series of literature data on similar welded details. The comparison highlights very consistent results and demonstrates applicability of the hot spot stress method to welded duplex details.sponsorship: The first author is funded by the Impulsfonds for the PhD project "3E160992" at KU Leuven. We would like to gratefully acknowledge Outokumpu for providing samples of EN 1.4162 for this research. (Impulsfonds at KU Leuven|3E160992)status: Published onlin
New zero-density estimates for the Beurling function
No full textIn two previous papers the second author proved some Carlson type density theorems for zeroes in the critical strip for Beurling zeta functions satisfying Axiom A of Knopfmacher. In the first of these invoking two additonal conditions were needed, while in the second an explicit, fully general result was obtained. Subsequently, Frederik Broucke and Gregory Debruyne obtained, via a different method, a general Carlson type density theorem with an even better exponent, and recently Frederik Broucke improved this further, getting with any . Broucke employed a new mean value estimate of the Beurling zeta function, while he did not use the method of Halász and Montgomery.
Here we elaborate a new approach of the first author, using the classical zero detecting sums coupled with a kernel function technique and Halász\u27 method, but otherwise arguing in an elementary way avoiding e.g. mean value estimates for Dirichlet polynomials. We will make essential use of the additional assumptions that the Beurling system of integers consists of natural numbers, and that the system satisfies the Ramanujan condition, too. This way we give a new variant of the Carlson type density estimate with similar strength as Turán\u27s 1954 result for the Riemann function, coming close even to the Density Hypothesis for close to 1
The shear behaviour of non-prismatic reinforced concrete beams determined using digital image correlation
No full textIt can be seen that when subject to a uniformly distributed load, a prismatic, steel reinforced concrete beam with constant longitudinal and transverse reinforcement percentages is inefficient. Following simple optimisation routines can result in beams whose flexural and shear capacities reflect the requirements of their loading envelope, and such elements tend to be non-prismatic. Structural research into the use of flexible formwork has developed simple methods for the creation of such elements to offer material and carbon emission savings of up to 40%.However, the shear behaviour of such variable section steel reinforced concrete beams has previously been an area of confusion for designers, who must often rely on empirical relationships derived from prismatic beam tests. This paper presents the results of new tests undertaken at the University of Bath on tapered concrete beams designed using BS EN 1992-1-1 [1], the compressive force path method and a strut and tie model, in which digital image correlation was used to analyse the specimens.Using the 'MatchID' program, strain distributions in each of the specimens during loading were determined, with the results allowing important comparisons to be drawn between the various design methods. A digital image correlation (DIC) technique was subsequently used to verify new proposals for the shear design of non-prismatic concrete beams, which aim to provide improved guidance for designers of optimised concrete structures.<br/
