The UMT is a versatile and modular mechanical tester that can simulate a wide range of real-life industrial applications. This article presents the application of the UMT to simulate the hot rolling of aluminum. Similar to a bench top simulator, the full-scale mechanical mechanism should be understood in-depth before scaling down the sample geometries.
Aluminium samples with approximate dimensions of 35 x 10 x 10 mm were placed inside a 1000°C reciprocating stage provided in a UMT system. A passively rolling sample with a diameter of 12 mm was utilized as the upper sample (Figure 1).
Figure 1. Passive roller system used for simulation of hot rolling.
Three lower aluminum samples were heated to different temperatures ranging from 450°C to 550°C in an atmosphere of inert gas. Of the three samples, two were run first in a forward direction and then in a reversed direction so that the same path was passed over. The third sample was run only in a single direction. Lowering the passively rotating upper roller was carried out either to a displacement of interest or to a load of interest.
The UMT can be operated either in the displacement-control mode or in the load-control (maximum of 2000 N) mode. Immediately after applying a lubricant and water mixture to the lower sample, it is moved under the roller to cause a specific deformation path. Figure 2 depicts the deformed sample.
Figure 2. Lower sample after deformation.
The deformed region was examined by using a Bruker white light interferometry (WLI) instrument. Figure 3 illustrates the profile of the deformed region. A number of parameters such as normal load, sample temperature, frictional force (resistance to rolling), and Z position of the roller within 2 µm were monitored throughout the simulated rolling step. The channels can be obtained at the rate of several kHz per channel, and can be plotted in the UMT viewer software. Figure 4 illustrates a typical plot of the experiments.
Figure 3. Profile along rolling direction of aluminium sample.
Figure 4. UMT viewer software plotting all critical parameters of one step of simulated hot rolling of aluminium.
Due to the deeper penetration of the roller, the resistance to rolling (COF) increases with an increase in temperature. To obtain a lower COF, reverse-stroke passes were viewed. Under the condition of force control, the pause at the beginning and end of the stroke caused deeper ‘indentations’, probably due to material creep.
The UMT is an exceptional system that enables hot rolling processes to be understood in a laboratory setting. It enables highly precise setting and control of all the parameters. The UMT allows the control of the sample temperature to ±1°C, the control of the load to microNewtons, and the adujustment of the position to within 1 µm. It also allows the control of the flow rate of inert gas. The parameters mentioned above can be easily managed and set using the UMT software.
The following companies may benefit from this system:
- Roll makers
- Rolling lubricant manufacturers
- Metal rolling companies
This information has been sourced, reviewed and adapted from materials provided by Bruker Nano Surfaces.
For more information on this source, please visit Bruker Nano Surfaces.