Procedia Engineering最新文献

HNBR (Hydrogenated Nitrile Butadiene Rubber) is a synthetic rubber with good resistance to heat and oil products; due its properties, HNBR is utilized in high-demanding applications in oil exploration, aerospace, automotive, and other industries. However, compared to other industrial rubbers, there are only few published studies on the fatigue behavior of HNBR. Moreover, it is important to understand how fatigue resistance is affected by the formulation of HNBR, specifically by the content of acrylonitrile (ACN) monomers and percentage of hydrogenation (number of saturated bonds). First, fatigue experiments are carried out for unaged samples at 120°C, which is the median operating temperature for these HNBR blends. Five HNBR blends are tested with various contents of acrylonitrile and various percentages of hydrogenation. Afterwards, testing is carried out one of the blend, i.e. HNBR with 36% ACN and 96% hydrogenation at 150°C for simultaneous ageing and fatigue conditions. For fatigue life experiments, the Wöhler curve is built according to a novel experimental approach of true stress control for four loading levels and R=0 loading ratio. Preliminary results with thermal ageing are subsequently presented.

This paper presents a newly developed mesoscopic model with grid-based structure for building evacuation simulation. The evacuation space in this model is discretized into cells with larger size than that of the microscopic models. This mesoscopic model directly computes the density flow between the cells governed by the density flow algorithm. The computation speed is higher than the traditional cellular automata model in which the movements of all pedestrians should be tracked for calculating the crowd density. To test the feasibility of this model, we applied it to a typical scenario in which pedestrians evacuate from a square room with single exit and conducted parameter sensitivity study on the length of the time step δ. The simulation results show that, within a valid range, changing δ only has minor influence on the evacuation process. We can directly identify area with high density as bottleneck from dynamically changed density map even the relatively large time step is adopted. In addition, the commercial package AnyLogic was used to benchmark the performance of this model. The results show that the mesoscopic model discerns evacuation patterns in more details compared to the macroscopic models and with higher efficiently computational speed than the microscopic models.

This paper presents numerical studies of smoke movement in the double skin facades type of Shaft-box. The room size is constructed with the reference of ISO9705 while the cavity width is selected to be 1m as the maximum fire hazard width. It turns out that when the smoke in the shaft is steady, the temperature in the shaft will change exponentially along with the height. Once the smoke enters the cavity, the toxicity hazard of smoke on the roof floor is the largest, under the action of "Stack Effect" and buoyancy created by the fire. And the room on the roof floor near the shaft towards the fire room is the most dangerous. The CO concentration of Room 3 on the roof floor reaches 200ppm within 4.5 min after the internal panes break.

Bangladesh has often been considered as the land of extremes in terms of natural processes. The statement is justified by the presence of world’s largest delta, one of the largest river systems carrying a huge amount of water and sediment discharge as well as prevalence of a number of natural hazards. These characteristics make the region very dynamic and sensitive to changes. Bangladesh is one of the most densely populated countries in the world and human development activities to accommodate the large population have caused major disruptions to the dynamics of the natural system. The study focuses on such a case where anthropogenic activities, such as polderization, dam construction etc. have disrupted the natural land building process and have caused persistent waterlogging in the southwest region of Bangladesh. The rivers in the region are naturally characterized by active deposition of sediment in riverbed causing reduced drainage capacity. Moreover, construction of coastal polders that de-linked the flood plains from the rivers, and diminished upstream flow during the dry season deteriorated the sedimentation problem in the region. The study delineates different hydrological parameters and characteristics of the deposited sediments along with identification of social vulnerabilities. The investigated hydrological and sedimentological characteristics refer to the existing sediment management as well as provide a framework for the future development works in the pre-identified TRM sites. Based on the findings, the suitability of Inclusive and Adaptive Tidal River Management (TRM++) technique was assessed.

In casting, molding, or additive manufacturing processes, there are some typical issues that can change the geometry of a part and cause porosity or other defects. With the aid of X-ray computed tomography (CT), internal discontinuities and geometry deviations can be accurately detected and visualized. However, the question remains in how far a given defect affects mechanical failure. We aim at bridging this gap by structural mechanics simulations based on CT images. In this study, we describe a method to predict the tensile strength and the location of crack initiation from the simulated stress distributions on the basis of local stress concentrations. We validate the method for tensile rods and real-life aeronautic parts which were additively manufactured from an AlSi10Mg aluminum alloy. Thirty-six specimens were manufactured in total, where different porosity patterns were deliberately inserted. The specimens were CT-scanned in high resolution. Structural mechanics simulations were carried out on basis of the CT images. An immersed-boundary finite elements code is used. The generation of a conforming simulation mesh is not required, making the code suitable especially for complex geometries like porous objects. The same test specimens were subjected to destructive physical tensile tests. We show that there is a very good correlation between the predicted and measured tensile strengths, and that the location of the first crack occurrence can be forecasted accurately.

This study has demonstrated the preparation of NaOH-FBC and investigated its potential application as an adsorbent to remove MB from aqueous solution. Adsorption Experiments of MB removal were carried out based on the parameters of initial pH, initial MB concentration, temperature and contact time. Results showed that the specific surface area of the NaOH-FBC reached up to 61.13m²/g. The experimental adsorption data were analyzed with Langmuir and Freundlich isotherm models. The kinetic adsorption models were also studied. By fitting the Langmuir adsorption isotherm model, the q_max of the NaOH-FBC was highly achieved as 605.82±9.09 mg/g, compared to 70.42±1.34 mg/g produced by the untreated FBC. The MB adsorption process using the untreated FBC was a non-spontaneous and endothermic process, which was well fitted with the pseudo-first-order kinetic model and Freundlich adsorption isotherm model. However, the MB adsorption process of the NaOH-FBC was a spontaneous and endothermic process, which was in accordance with the pseudo-second-order kinetic model and Freundlich adsorption isotherm model. Furthermore, with the increase of pH, temperature and contact time, the adsorption capacity of MB onto the FBC and NaOH-FBC were both increased. The adsorption results suggest the efficiency and potential of NaOH-FBC as a MB adsorbent.

Based on the fire safety of cotton, five groups of test samples were selected in the combustion experiment. Experiments were carried out under different wind speed conditions. The experimental results show that, as the wind speed increases, the phenomenon of flame combustion becomes more obvious and the mass loss rate is accelerated. According to the analysis of the same wind speed at different temperatures, it can be seen that the larger the wind speed is, the faster the combustion will spread from the surface of the specimen to the interior.