The testing application arising most frequently as part of quality assurance at Hydro’s rolling mill in Grevenbroich, Germany, is the tensile test on aluminium dumbbell specimens to ISO 68892-1 and other standards. It was at this plant that both systems were installed.
The first system consists of a Z020 materials testing machine and the roboTest L specimen feeding system. The testing machine has a nominal force of 20 kN and is equipped with symmetrically closing, pneumatically operated grips plus a makroXtens extensometer. The specimen magazines hold 40 specimens each and four of them can be accommodated on the mobile magazine table. The specimens are given a unique barcode, enabling error-free assignment of the specimen to the specification data.
The system is equipped with a 4-transducer cross-section measuring device for precise, standard-compliant testing. The pairs of transducers provide differential measurement of thickness and width, at one or three locations on the specimen as required. Alternatively, specimens can be weighed using integrated high-precision scales. Material thickness is determined from (the known) area and the density.
To ensure precise, reproducible alignment of the specimen in the test axis of the machine, the specimen is deposited in a centering tray and then picked up again immediately before being fed into the machine. To increase specimen throughput, the cross-section measurement / weighing is carried out at the same time as the tensile test and the broken halves are removed by gravity after the test. This enables around 20-25 specimens to be tested per hour.
The second system is designed for tensile tests on dumbbell specimens 165 mm long, 0.1 - 0.5 mm thick, also to ISO 6892-1. It consists of a Z005 materials testing machine and the roboTest L specimen feeding system. The testing machine has a nominal force of 5 kN and is equipped with symmetrically closing, pneumatically operated grips plus a makroXtens extensometer.
As some of the specimens undergo temperature conditioning before the test, special heat-resistant magazines each holding 30 specimens are used. While the tensile test is running the thickness of the next specimen is already being measured. This parallel operation allows results to be obtained for 35 - 40 specimens per hour.
Both systems are controlled by Zwick's autoEdition automation software. The systems are integrated into the customer's in-house network, where they receive specification data from the CAQ system and supply results in return.