http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Fricke, Wolfgang,Zacke, Sonja The Society of Naval Architects of Korea 2014 International Journal of Naval Architecture and Oc Vol.6 No.2
During ship design, welding-induced distortions are roughly estimated as a function of the size of the component as well as the welding process and residual stresses are assumed to be locally in the range of the yield stress. Existing welding simulation methods are very complex and time-consuming and therefore not applicable to large structures like ships. Simplified methods for the estimation of welding effects were and still are subject of several research projects, but mostly concerning smaller structures. The main goal of this paper is the application of a multi-layer welding simulation to the block joint of a ship structure. When welding block joints, high constraints occur due to the ship structure which are assumed to result in accordingly high residual stresses. Constraints measured during construction were realized in a test plant for small-scale welding specimens in order to investigate their and other effects on the residual stresses. Associated welding simulations were successfully performed with fine-mesh finite element models. Further analyses showed that a courser mesh was also able to reproduce the welding-induced reaction forces and hence the residual stresses after some calibration. Based on the coarse modeling it was possible to perform the welding simulation at a block joint in order to investigate the influence of the resulting residual stresses on the behavior of the real structure, showing quite interesting stress distributions. Finally it is discussed whether smaller and idealized models of definite areas of the block joint can be used to achieve the same results offering possibilities to consider residual stresses in the design process.
Assessment of WELD ROOT Fatigue of Fillet-welded Strucrtures Based on Local Stresses
Wolfgang Fricke 한국강구조학회 2006 International Journal of Steel Structures Vol.6 No.4
Stel structures are frequently subjected to high cyclic loads and therefore prone to fatigue failures. Typical examples arecularfrom the notch at the weld toe or from the weld root in case of incomplete weld penetration. The later is applied to anincreasing extent for fabrication reasons. It requires, however, careful fatigue assesment for cyclic loaded structures as non-fused root faces may act like initial cracks. On the other hand, well-established approaches exist for the fatigue assessment ofsuch weld roots, for instance the nominal stress approach, which simplifies the problem to a great extent, and the crackwhich require less effort but consider the main effects on fatigue behaviour. This is ofered by aproaches based on localnominal, structural or notch stresses, which are outlined in this paper. They can consider the locally increased load transfer inwelds occurring at filet-welded ends of attachments with additional stress concentrations, or pronounced bending of the weldthroat due to lateral loading of the attachment and/or the ecentricity of one-sided welds. The approaches are aplied to diferent
Wolfgang Fricke,Sonja Zacke 대한조선학회 2014 International Journal of Naval Architecture and Oc Vol.6 No.2
During ship design, welding-induced distortions are roughly estimated as a function of the size of the component as well as the welding process and residual stresses are assumed to be locally in the range of the yield stress. Existing welding simulation methods are very complex and time-consuming and therefore not applicable to large struc-tures like ships. Simplified methods for the estimation of welding effects were and still are subject of several research projects, but mostly concerning smaller structures. The main goal of this paper is the application of a multi-layer weld-ing simulation to the block joint of a ship structure. When welding block joints, high constraints occur due to the ship structure which are assumed to result in accordingly high residual stresses. Constraints measured during construction were realized in a test plant for small-scale welding specimens in order to investigate their and other effects on the residual stresses. Associated welding simulations were successfully performed with fine-mesh finite element models. Further analyses showed that a courser mesh was also able to reproduce the welding-induced reaction forces and hence the residual stresses after some calibration. Based on the coarse modeling it was possible to perform the welding simulation at a block joint in order to investigate the influence of the resulting residual stresses on the behavior of the real structure, showing quite interesting stress distributions. Finally it is discussed whether smaller and idealized models of definite areas of the block joint can be used to achieve the same results offering possibilities to consider residual stresses in the design process.
The impact of air contaminants on humidifier membrane performance
Daniel Ilk,Viktoria Frick,Christopher Hänel,Thomas Schiestel,Michael Schoemaker,Holger Kraus,Harry E. Hoster 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.126 No.-
Membrane humidifiers are often used to increase the performance and lifetime of polymer electrolytemembrane fuel cells (PEMFC). In order to avoid possible problems and consequential costs in later fuelcell applications due to the degradation of humidifier membranes, in this work five industrial humidifiermembranes (hollow fiber and flat sheet membranes in various material combinations) are tested againstfive pollutant gases from the environment (NO, NO2, NH3, SO2, O3). Herefor the water transfer capabilitiesbefore and after exposure to the pollutant gases is quantified. The results show that polyimides and fluoropolymersare degraded by ozone so that mechanical stability drastically decreases, so that they disintegrate. When polysulfone membranes are tested with pollutants a clear decline in water transfer can beseen over time. The decline of water transfer does not always seem to be due to the presence of harmfulgases but could also reflect physical degradation of the polymer. Perfluorinated sulfonic acid-based(PFSA) membranes are particularly sensitive to ammonia.