This paper describes the peculiarities encountered in the numerical modeling of non-circular spinning processes using motion-controlled roller tools and applying the Finite Element Method (FEM). This process is suitable for producing non-circular, hollow components in small to medium-sized production lots. Numerical simulation can be used to optimize the process. Therefore, it is necessary to make a realistic sheet thinning and wrinkling calculation by using the FEM. This can be achieved through the definition of the real kinematics, a suitable flow curve and an optimal sheet meshing strategy using solid elements. An optimal sheet meshing strategy is particularly necessary in order to realistically calculate the process within an acceptable computing time. Reference experiments with the rotationally non-symmetric mandrel types, the ''Tripode'' and ''Pagoda'', were carried out to compare simulations and experiments. A comparison of the reference experiments with the ''Tripode'' mandrel demonstrated that it is possible to simulate non-circular spinning with a deviation of less than 5% with respect to minimum sheet thickness. It is also possible to predict wrinkling in critical, non-circular spinning processes. This has been confirmed by comparing the ''Pagoda'' reference experiment with the FEM simulation.
High heat input during welding leads to transformations of the microstructure in the area subjected to welding, mostly resulting in an inhomogeneous microstructure and an overall deterioration of the mechanical properties. To restore these properties, post treatment processes which are typically separated from the welding process are state of the art. The present work focusses on recrystallization phenomena and shows the new methodology, WeldForming, which intends to eliminate subsequent treatment processes. The new inline process combination harnesses the synergies of a welding and a rolling process to ultimately prevent the typical zone formation of the heat affected zone. This is done by stimulating recrystallization and recovery processes. The development of the process is based on numerical simulations. A new aspect is the first time coupling of both processes in a single simulation model. The required material models were generated with the aid of thermophysical simulations. A novel approach is shown for creating a material model for the filler metal G4Si1 with the typical directed solidification microstructure. On the basis of the gained knowledge out of thermomechanical and numerical simulation, a process window was identified and a test setup was developed which gave the functional prove of the WeldForming process.
This paper examines how the initial austenite grain size in quench and partitioning (Q-P) processes influences the final mechanical properties of Q-P steels. Differences in austenite grain size distribution may result, for example, from uneven heating rates of semi-finished products prior to a forging process. In order to quantify this influence, a carefully defined heat treatment of a cylindrical specimen made of the Q-P-capable 42SiCr steel was performed in a dilatometer. Different austenite grain sizes were adjusted by a pre-treatment before the actual Q-P process. The resulting mechanical properties were determined using the upsetting test and the corresponding microstructures were analyzed by scanning electron microscopy (SEM). These investigations show that a larger austenite grain size prior to Q-P processing leads to a slightly lower strength as well as to a coarser martensitic microstructure in the Q-P-treated material.
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