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Aluminum materials are popular materials for research in terms of lightweight construction. How cryogenic forming can be used to increase material utilization in terms of resource efficiency is one of the areas being investigated. Subject of this study are numerical and experimental investigations regarding the formability of the aluminum alloy AA6014-T4 with macro-structured deep drawing tools at cryogenic temperatures. The macro-structure of the deep drawing dies significantly reduces the heat flux between the dies and the blank due to the reduced contact area. For this reason, active cooling or heating of the dies is not required. The process of heat conduction between the tool and the blank, as well as the deep drawing process, is calculated using the FE-method and compared with the experimental investigations. In addition, the induced residual stresses are determined using the hole-drilling method and compared with the computational solution. The presented examination shows an improved deep drawing ratio of the aluminum alloy AA6014-T4 at cryogenic blank temperature without active tool cooling. Additionally, the influence of the blank temperature on the forming regarding the residual stresses in the cups is analyzed and discussed.

Thermomechanical ring rolling is an evolution of the process where deformation and heat treatment are combined to obtain a product with both the desired geometry and hardness or microstructure in a single step. However, the high sensitivity of the process to the initial condition and to various disturbances limits its repeatability and accuracy. In this paper, the authors implement a concept for hardness control of ring rolling in virtual experiments. A concept based on soft sensors and model predictive control is implemented on a digital twin. The operation of the different models needed for this control loop are detailed and the controller itself is illustrated.

Tangential profile ring rolling (Profiled Radial Ring Rolling, PRRR) enables the fast and compared to machining inexpensive production of bearing rings or similar ring-shaped parts with near net-shape geometry and advantageous material properties due to a high degree of work hardening at a high cadence. Conventionally, a specific heat treatment regime is required to achieve the desired microstructural and mechanical properties such as grain size, hardness or strength. Novel control strategies allow thermomechanical treatment during the forming operation itself. To monitor the evolution of properties during forming, a sensor system based on eddy current methods is presented and its ability to discriminate between various influences is demonstrated. It is shown that different process conditions result in different end-product microstructures, and that these differences both relate to application relevant properties and can be identified using non-destructive eddy current sensing, even in the presence of superposed disturbances such as local variations in electromagnetic properties.

To pursue better quality, there is a strong need for efficient and robust non-destructive testing methods for joining processes. A new approach has been proposed to detect loose bolted joints using acoustic waves. This method measures the dissipation of energy by recording the propagated waves on the surfaces of the joining partners next to the joint. The authors show a link between the torque moments applied to the bolt and the ability of the joint to transfer acoustic energy using both simulations and experiments. In this article, the method’s ability to detect variations of certain process parameters of the clinching process was investigated numerically. To this extent, results of FEM calculations of the joining process are used to simulate the non-destructive testing method. By varying parameters of the clinching model, their influence on the transmission of energy within the joint is studied.

Clinching is a cost-effective mechanical joining process used for metallic as well as nonmetallic materials. Destructive testing methods such as peel and tensile tests can be used for strength investigations of such joints. Additionally, by measuring the geometrical properties such as undercut, neck thickness, and final bottom thickness, the joint quality can be estimated. These methods are cumbersome and do not meet the time and cost efficiency requirements of industrial production. The harmonic analysis benefits from changes in vibration characteristics. In this paper, the structural response of a clinched joint, subjected to a dynamic displacement in order to introduce an acoustic wave testing method is studied. This is accomplished by using simulated joining processes. The approach of this paper is based on a transient dynamic finite element analysis, followed by a fast Fourier transform. The results are presented, together with an analysis of sensitivity to different process parameters.

The multi-material mix used nowadays requires several joints to establish a durable connection. It is necessary to test the joints without harming the parts to ensure the safety of the whole structure. Therefore, a new approach for a non-destructive testing method is presented and validated in this paper. The aim is to establish the testing routine as a fast and easy alternative to the few known non-destructive testing procedures. The approach measures the dissipation of energy by detecting the propagated waves on the surfaces of the joining partners next to the joint. After a short description and a theoretical insight in wave propagation, the experimental results will be substantiated by simulated findings. A bolted connection was chosen in the experiments due to the possibility to easily apply and check different torque moments. The simulation model was adapted and tested for different applied contact pressures. The general results show a detectable loss of energy that can be linked to different torque moments. Different effects are visible in the simulation and the experiments and will be described. The findings will be discussed and an short outlook will be given. The aim of proving the concept via experimental and simulated results was reached.