Thermal deformation behavior and processing maps of 7075 aluminum alloy sheet based on isothermal uniaxial tensile tests

Manufacturing of advanced smart tooling for metal forming

Hybrid fitting-numerical method for determining strain-hardening behavior of sheet metals

A feasibility study on warm forming of an as-quenched 22MnB5 boron steel

Functional optimization of hot-stamped components by local carburization

Within the last decades, stringent regulations on fuel consumption, CO2 emissions and product recyclability forced the automotive sector to implement new strategies within the field of car body manufacturing. Due to their low density and good corrosion resistance, aluminum became one of the most relevant lightweight materials. Recently, especially high- strength aluminum alloys for structural components gained importance. Since the low formability of these alloys limits their application, there is a need for novel process strategies in order to enhance the forming behavior. One promising approach is the hot stamping of aluminum alloys. The combination of quenching and forming in one step after solution heat treatment leads to a significant improvement of the formability. Furthermore, higher manufacturing accuracy can be achieved due to reduced spring back. Within this contribution, the influence of forming temperature on the subsequent material behavior and the heat transfer during quenching will be analyzed. Therefore, the mechanical and thermal material characteristics such as flow behavior and heat transfer coefficient during hot stamping are investigated.

https://iopscience.iop.org/article/10.1088/1742-6596/896/1/012055/pdf

Experimental study on the warm forming and quenching behavior for hot stamping of high-strength aluminum alloys

Improvement in accuracy of the predicted results from numerical simulation results into a reduction of cost and time involved in tool design and experimental trials. However, the predicted results from finite element simulations are significantly affected by the chosen yield criterion and work hardening law. The selection of yield criterion and work hardening law depends on the characterization methods used for defining the material behavior. In this work, the mechanical behavior of AA5083-O aluminum alloy sheet is modeled by performing biaxial tensile tests using cruciform specimen and hydraulic bulging experiments in addition to uniaxial tensile tests. Biaxial to uniaxial yield stress ratios are determined using the equal plastic work principle from the flow curves obtained from these tests. The obtained ratios are used to find the coefficients of Yld2000-2d and Hill48 yield criteria which is then used in the numerical simulations of cylindrical cup deep drawing. Numerical simulations are also carried out using uniaxial and biaxial flow curves fitted with different isotropic hardening laws. Thickness distributions and the load-displacement curves are predicted and validated by performing cylindrical cup deep drawing experiments.

Modeling material behavior of AA5083 aluminum alloy sheet using biaxial tensile tests and its application in numerical simulation of deep drawing

Today, manufacturing of structural car body parts faces several challenges, like forming accuracy, passenger safety and lightweight design One possibility to fulfill these partially rivalling demands is the application of hot stamped components The combination of hot forming and in-die quenching reduces not only springback, but also results in tensile strengths of more than 1500 MPa Besides conventional hot stamping, the process can be adapted to manufacture parts with tailored properties One of the biggest issues of these state-of-the-art processes is the formation of extensive transition zones due to heat transfer A promising approach to adjust the mechanical properties with a minimized transition zone is tailored carburization of sheet metal Therefore, the parts are locally coated with graphite, heat treated and subsequently quenched In this work, the time variant process of carbon diffusion is investigated Sheets with two different thicknesses are carburized and quenched The resulting mechanical properties are analyzed using uniaxial tensile tests and microhardness measurements On this basis, a process window is identified Furthermore, the applicability of EDX and WDX analysis for the measurement of carbon concentration is investigated within this work

/pdf/investigation-of-diffusion-behavior-of-carburized-sheet-2p4xr16c5j.pdf

Investigation of diffusion behavior of carburized sheet metal in hot stamping

Hot stamping of boron manganese steel is a state of the art process for manufacturing safety-relevant automotive components with regard to lightweight design. In terms of the mechanical properties, the microstructural evolution is of particular interest. Besides conventional hot stamping processes, this is especially apparent for the manufacture of hot stamped parts with tailored properties. To reduce costs and scrap parts, numerical process design requires appropriate material models considering transformation kinetics during in-die quenching. The phase transformation behavior can be characterized through experiments on various testing facilities, which can lead to discrepancies in the results and therefore in the predicted mechanical properties. In this paper, the results from two testing facilities are compared to each other through dilatometry experiments on the boron-manganese steel 22MnB5. For further characterization of the differences, secondary samples are taken to analyze the hardness as well as the microstructure by optical microscopy.

Alexander Horn

Papers

Experimental study on the warm forming and quenching behavior for hot stamping of high-strength aluminum alloys

Functional optimization of hot-stamped components by local carburization

Modeling material behavior of AA5083 aluminum alloy sheet using biaxial tensile tests and its application in numerical simulation of deep drawing

Investigation of diffusion behavior of carburized sheet metal in hot stamping

Investigation of the Phase Transformation in Hot Stamping Processes with Regard to the Testing Facility