Interaction between laser-welded web-core sandwich deck plate and girder under bending loads

Present paper investigates the interaction between laser-welded web-core sandwich deck plate and supporting girder under bending loads. The study is based on two linear-elastic Finite Element (FE) approaches, i.e. one using beam elements to model the girder and shell elements to model the homogenized web-core sandwich plate. With this approach the obtained FE model is considerably smaller than in the case of modeling the full, periodic, 3D geometry with shell elements. The FE solution results in stress resultants for beam and shell elements. These stress resultants do not describe accurately the periodic stress response of the sandwich plate or shear stress distribution at girder web. Therefore, the paper utilizes analytical methods to calculate these stress components from the obtained Finite Element solution. The second computational approach is based on modeling the actual 3D topology with shell elements. The two approaches are shown to be in very good agreement. The investigation shows that the effective flange width of the sandwich is different for the top and bottom face plates indicating that the interaction is different for these face plates. The present study also shows that this difference between the two faces depends strongly on the orientation of the web plates of the sandwich with respect to girder axis and the stiffness of the girder. The investigation also shows that the normal stress response in bending is dominated by the interaction between the sandwich plate and the girder, but also by the shear-induced normal stresses at the outer surface of the plate.     

Experimental study on the effect of molecular weight and chemical composition distribution on the mechanical response of high-density polyethylene

This article aims to appraise the effect of microstructure comprising molecular weight distribution and chemical composition distribution on the mechanical properties of high-density polyethylene (HDPE). HDPE resins were synthesized using several titanium–magnesium-supported Ziegler–Natta catalysts in the industrial gas phase reactor under the same polymerization condition. Gel permeation chromatography and crystallization elution fractionation (CEF) were conducted on the resins to characterize the molecular weight and comonomer distribution. Crystallization, thermal and rheological behavior were evaluated following differential scanning calorimetry, polarization light microscopy, and rheometric mechanical spectrometry. The resins with higher soluble fraction in trichlorobenzene below 80°C (highly branched low molecular weight chains) exhibited longer crystallization time based on the crystallization kinetic obtained from the Avrami model. Rheological determination of the molecular weight between entanglements (M_e) and the average lamella thickness based on the Gibbs–Thomson equation revealed that the entanglement density and impact strength decreased, and the average lamella thickness increased with an increase in the ratio of CEF eluted fraction below 80°C to the crystallizable fraction in the range of 80–90°C.     

Batteries and flow batteries-life cycle assessment in Indian conditions

Clean Technologies and Environmental Policy - The intervention of renewable energy for curbing the supply demand mismatch in power grids has projected the added advantage of having lower greenhouse...     

Monitoring the fluidized bed reactor for polyethylene polymerization based on fibre optic acoustic emission sensor

This paper presents applications of a new class of fibre optic acoustic emission (FOAE) sensor to monitor the operation of fluidized bed reactors used in polyethylene production. Specifically, the sensor was implemented to detect undesired, abnormal phenomena related to particle agglomeration, wall sheeting, fine overflow, and variations in the superficial gas velocity. The experiments were executed using a fluidized bed cold model setup for polyethylene powders with average particle sizes of 250, 1000, and 2000 μm. The results demonstrated that the presence of agglomerated particles in the fluidized bed reactor increases the kurtosis of the acoustic emission (AE) signal. Furthermore, the overflow of small particles can be detected by mounting the FOAE sensor below the gas distributor plate and monitoring an increase in the root mean square (RMS) of the AE signal. The AE signal RMS increased with the rising superficial gas velocity. Besides, forming a sheet layer on the reactor wall decreased the AE signal RMS. The proposed sensor's main benefits are its simple design, rapid response to abnormal conditions in the fluidized bed reactor, immunity against electromagnetic noise, high-temperature resistance, and safety in hazardous areas.