Finite element analysis of industrial steel elbows under strong cyclic loading

Steel elbows are used in petrochemical facilities and power plants. In the case of an earthquake event, in addition to other service loads, they are subjected to strong repeated cyclic structural loading that may lead to failure due to cyclic accumulation of plastic strain or collapse. Furthermore, due to their flexibility, significant non-linearities occur and the elbow cross-section shape distorts as cyclic loading takes place resulting at an oval or flatten shape at the end of the loading sequence. Accumulation of plastic strains takes place at the most stressed parts of the elbow, associated with extensive bulging of the cross-section which is more pronounced in the presence of internal pressure. The present study is numerical, based on a finite element simulation of the elbow, and examines elbow behavior subjected to strong cyclic bending in the presence of internal pressure. The material constitutive model has a dominant effect on describing the elbow response, and this is shown through the employment of three different classical plasticity models. [26]. Copyright © 2011 by ASME

Simulation of industrial elbow response under strong cyclic loading

Elbow components are widely used in industrial facilities as parts of piping/tubing systems. Their performance under severe loading conditions may be critical for the structural integrity of an industrial facility In the case of an earthquake event in addition to other ser-vice loads, such as internal pressure, they are subjected to strong repeated cyclic structural loading. When these elements are subjected to strong repeated loading, they present failure modes associated with cyclic plasticity phenomena (material degradation or cyclic creep). Furthermore, due to their flexibility, significant non-linearities occur and the elbow cross-section shape distorts as cyclic loading takes place resulting at an oval or flatten shape at the end of the loading sequence. Accumulation of plastic strains (cyclic creep or ratcheting) also takes place at the most stressed parts of the element, associated with extensive bulging of the cross-section which is more pronounced in the presence of internal pressure. The present study is numerical, based on a finite element simulation of the elbow, and investigates the el-bow component behavior subjected to strong cyclic bending of various amplitudes in the presence of different levels of internal pressure. The material constitutive model has a domi-nant effect on the elbow response, and this is shown trough the use of 3 different plasticity models. The capabilities and drawbacks of each plasticity model regarding the simulation of cyclic plasticity phenomena are discussed in detail

Structural performance of TS590 high-strength steel welded tubular joints under extreme bending loading

The present work examines the behavior of welded tubular connections made of high-strength steel and subjected to extreme loading conditions focusing on their low-cycle fatigue performance and highlighting the benefits of using high strength steel in structural tube applications. An experimental investigation of tubular X-joints made of high-strength steel is presented first. Experimental testing has been designed in order to examine the joint's behavior under out-of-plane monotonic and cyclic loads in loading levels exceeding the elastic limit of the joint. The second part of the work is numerical aimed at simulating numerically the experiments through a detailed finite element model in ABAQUS. The overall joint behavior and local phenomena at the weld toe are simulated and the numerical results are compared with the experimental measurements. Special attention is given on the evaluation of stress and strain fields at the connection & quot;hot-spot & quot; locations, which are compared with the values found in the literature. The results of this research effort are aimed at proposing static and low-cycle fatigue design methodologies for welded tubular connections made of high-strength steel. © 2012 Taylor & Francis Group, London

Low cycle fatigue tests and simulations on steel elbows

In this paper the low cycle fatigue behaviour of steel elbows under strong cyclic loading conditions (in-plane and out-of-plane) is examined. The investigation is conducted through advanced finite element analysis tools, supported by real-scale test data for in-plane bending. The numerical results are successfully compared with the experimental measurements. In addition, a parametric study is conducted, which is aimed at investigating the effects of the diameter-to-thickness ratio on the low-cycle fatigue of elbows, focusing on the stress and strain variations. Strain gauge measurements are compared with finite element models. Upon calculation of local strain variation at the critical location, the number of cycles to fracture can be estimated. Copyright © 2013 by ASME

Fate of ochratoxin A during vinification of Semillon and Shiraz grapes

Semillon and Shiraz grapes containing ochratoxin A (OA) were obtained by inoculation of bunches on the vine with Aspergillus carbonarius. Citric acid content was greater in the inoculated grapes than in healthy grapes. Samples were collected throughout vinification of these grapes and the OA content was quantified using a stable isotope dilution liquid chromatographic-tandem mass spectrometric method. The mass of processed and waste streams during vinification was also noted. Reduction in the amount of OA in juice and wine occurred at every solid-liquid separation stage. The OA concentration (μg/kg) in white and red wine after racking was 4% and 9%, respectively, of that in crushed grapes. This corresponds to 1% and 6% of the total OA content that was initially present in the inoculated grapes. The OA content was divided between solid and liquid phases at each stage of vinification. OA did not appear to be transformed either chemically or biologically by yeast during fermentation, rather was discarded with the marc, juice lees, and gross lees.Su-lin L. Leong, Ailsa D. Hocking, Peter Varelis, Georgina Giannikopoulos, and Eileen S. Scot