Homogenization of hardness distribution and distortion in high pressure gas quenching

Quenching with gases rather than oil or other liquid media has the advantages of reducing the risks concerning health and environment, while simultaneously homogenizing the quenching results and minimizing distortion due to a wide range of possible process parameter variations and the pure convective heat transfer. In this contribution, a coupled solution for increasing homogenization of quenching results within high pressure gas quenching will be presented. In the first stage, an experimental test facility was set up for flow investigations and in the second stage a numerical simulation model was generated. The numerical and experimental results of the flow through the chamber were compared for several boundary conditions. Finally, after complete verification of the simulation, the model may be used to assist in parameter variation for optimization of homogeneous high pressure gas quenching.     

Ermittlung von Verfahrensgrenzen für das Fügen durch Knickbauchen anhand des Werkstoffes E235+N

Through a systematic approach and the consistent comparison of the results between experimental and numerical investigations, a deep understanding of the bulging mechanisms has been first developed. From these investigations process limitations were derived and presented in the form of a working diagram for the material E235+N. With regard to a wide industrial use of upset bulging as a joining technology, a technologically, productively as well as economically appropriate method could be developed and validated by means of practical and numerical experiments.     

Model for thermodynamic point identification in laser cutting

In recent years, laser cutting has been introduced and developed to such an extent that it is now thought to be one of the leading and indispensable manufacturing tools. At the present time, dross‐free and accurately‐cut parts are basically regarded as the major targets to aim for, because the costs and efforts associated with dross removal by postprocessing cut parts are considerable. Therefore, control of dross formation during laser cutting is an important factor in maintaining edge quality. The initial aim of this paper is to describe the importance of physico‐mechanical material properties that need to be taken into account in modeling of laser material processing in order to control melting of the material.     

Ein Modell zur Berechnung des Verformungsverhaltens von horizontal hochzyklisch beanspruchten Pfählen

A model for the behavior of horizontally high‐cycle loaded piles For the prediction of the deformation for long or intermediate long piles under lateral high cycle load, embedded in non‐cohesive soil, a simplified engineering model for drained conditions is developed based on the high cycle accumulation (HCA) model of Niemunis , Wichtmann and Triantafyllidis [1]. The monotonic soil deformation under static load is approximated by elastic springs, placed around the pile, whereas the accumulation of soil deformations under cyclic loading is modelled by viscous dashpots (cyclic creep) according to the HCA model. In most instances this contemplation is physically validated by element tests. In conjunction with the pile the spring‐dashpot elements represent an elastically embedded beam system. Two versions of the model with a two‐sided arrangement of springs and dashpots on the Lee‐ and Luv‐side and a one‐sided arrangement only on the Lee‐side will be presented. The pile displacement prediction of the model is compared with the results obtained by existing engineering models already known in the literature and the solution of a 3‐D‐finite element simulation with the HCA model.     

Numerische Simulation disperser Gas/Flüssig‐Strömungen in Blasensäulen bei hohen Gasgehalten mit OpenFOAM®. Teil 2 – Numerische Simulation und Ergebnisse

The design of industrial gas/liquid reactors such as bubble columns requires detailed information with respect to the flow structure and characteristics of two‐ or multiphase systems in the reactor. The contribution is focused on the evaluation of the simulation results obtained by a selection of models. The results are further compared with those reported in literature. The simulations have been performed with the CFD software OpenFOAM®. The main focus of the numerical simulation was set on capturing the characteristic process and design parameters of bubble columns.     

Mathematical model of critical implant stress testing in the weld metal of API 5L X80 steel

In this paper the influence of heat input and preheat temperature on the critical implant stress was analyzed for the weld metal of API 5L X80. High strength steel marked as API 5L X80 is produced with a thermo – mechanical controlled process (TMCP), its chemical composition shows low carbon content due to which the steel has good weldability, but in the weld metal zone cold cracking can occure. The goal of this paper is to define optimal work conditions in form of flux cored arc welding (FCAW) welding parameters at which no cold cracks can be found. The experiment was conducted using central composite design (CCD) and design of experiments (DoE) with two independent variables (preheat temperature and heat input). Mathematical models were developed for all three different wire types that were used (two rutile, one basic flux cored wire). The samples in this paper which had cold cracks were further analyzed on the scanning electron microscope (SEM).