Abstract

In order to design components that are safe and durable, material-efficient lightweight construction methods have become established in many areas of mechanical engineering. But lightweight construction methods have not yet been widely used in the design of chemical process equipment. The design goal here is dimensioning against failure and fatigue of the apparatus. Established guidelines are used, which often lead to safe but rather over-dimensioned and thus material-inefficient solutions. To analyze possible advantages of lightweight design in apparatus engineering flat and dished pressure vessel heads are designed by bionic principles, and achieved mass and resulting stresses are compared with conventional design. The sandwich comb design of diatoms is applied to pressure vessel heads as a bionic principle. The good mechanical properties of diatoms were already shown by several groups [1]. However, no technical application in the fields of apparatus engineering can be found in literature. Therefore, the concentric comb construction of diatoms was converted in a parametric CAD-Script. The essential parameters of this script influence both number and distribution of combs over the circle radius. Thus, it is possible to create models with clear different geometrical properties only with a small set of parameters. The flat pressure vessel heads are designed with a diameter of 1 m and a wall thickness of 2 mm. In linear-elastic FEM-simulations the pressure vessel heads are loaded with pressure of 1 bar and the resulting Von-Mises equivalent stresses and masses are evaluated. Subsequently a multi objective optimization takes place, which optimizes both mass and stresses using methods of artificial intelligence. For the optimization, the TSEMO algorithm was used which uses Gaussian process surrogates and genetic algorithms to evaluate the pareto front [1]. In comparison to pressure vessel heads designed by conventional guidelines, flat heads with comb sandwich structures only need 50% of mass. The results of the flat pressure vessel heads are transferred to dished components. In the high loaded knuckle region of widely used Klöpper heads a sandwich structure is inserted and a parametric CAD-Model is scripted. As in the case of the flat pressure vessel heads, optimization takes place in terms of strength and weight, for which linear-elastic simulations are performed. Compared to conventional dished heads, designed according to the AD2000 guideline [3], the equivalent stresses were reduced by 30% for the same mass. Both in flat and in curved construction, pressure vessel heads can be designed more material-economically and safely by sandwich construction methods. The use of artificial intelligence methods can significantly reduce the effort of multi-objective optimization. [1] C.E. Hamm (2005) The evolution of advanced mechanical defenses and potential technological applications of diatom shells. J Nanosci Nanotechnol 5:108–119. https://doi.org/10.1166/jnn.2005.023 [2] E. Bradford, A.M. Schweidtmann, & A. Lapkin. Efficient multiobjective optimization employing Gaussian processes, spectral sampling and a genetic algorithm. J Glob Optim 71, 407–438 (2018). https://doi.org/10.1007/s10898-018-0609-2 [3] AD 2000-Merkblatt B3, Gewölbte Böden unter innerem und äußerem Überdruck, Verband der Technischen Überwachungs-Vereine e.V. Essen (2000)