Numerical simulation of Rapid Additive Forging (RAF) process

The Rapid Additive Forging (RAF) process is a Direct Energy Deposition (DED) Additive Manufacturing (AM) process, based on the deposition of a Titanium alloy on a substrate plate. This process has been developed for the production of Titanium parts of aeronautic components. In this study, a Finite Element (FE) numerical simulation methodology has been established to perform a fast analysis of the RAF process, including full 3D-transient thermal-metallurgical and mechanical numerical simulations. Thus, residual stresses and distortions caused by the process can be estimated. Different modelling strategies have been compared in order to find a balance between computation time and accuracy. Analyses include the effects of phase transformations in the Titanium alloy. First analyses have been performed on a simple geometry of welding wall. The influences of the material activation modelling strategy on the thermal and mechanical results have been investigated. The effects of phase transformations on residual stresses and distortions are also discussed. Then a specimen with a more complex geometry has been considered in the analysis, including the effect of different deposition paths. A full 3D simulation of the whole deposition process has been compared with several simplified computation procedures, including a reduction of the number of layers considered in the simulation

SBR treatment of tank truck cleaning wastewater: sludge characteristics, chemical and ecotoxicological effluent quality

Abstract: A lab-scale activated sludge sequencing batch reactor (SBR) was used to treat tank truck cleaning (TTC) wastewater with different operational strategies (identified as different stages). The first stage was an adaptation period for the seed sludge that originated from a continuous fed industrial plant treating TTC wastewater. The first stage was followed by a dynamic reactor operation based on the oxygen uptake rate (OUR). Thirdly, dynamic SBR control based on OUR treated a daily changing influent. Lastly, the reactor was operated with a gradually shortened fixed cycle. During operation, sludge settling evolved from nearly no settling to good settling sludge in 16 days. The sludge volume index improved from 200 to 70\u2005mL gMLSS 121 in 16 days and remained stable during the whole reactor operation. The average soluble chemical oxygen demand (sCOD) removal varied from 87.0% to 91.3% in the different stages while significant differences in the food to mass ratio were observed, varying from 0.11 (stage I) to 0.37 kgCOD.(kgMLVSS day) 121 (stage III). Effluent toxicity measurements were performed with Aliivibrio fischeri, Daphnia magna and Pseudokirchneriella subcapitata. Low sensitivity of Aliivibrio was observed. A few samples were acutely toxic for Daphnia; 50% of the tested effluent samples showed an inhibition of 100% for Pseudokirchneriella