The bending testing machine has been specifically built for the 180x30x30 mm size specimens that will be analyzed in our tests. This device allows to determine the bending resistance under constant bending moment in accordance with UNE-EN 12372: 2007, which in turn allows us to obtain the fracture toughness of the material based also on CEN / TS 14425-1 : 2003. The gadget is composed of a base for the test specimens and an independent upper head. The base is formed by a fixed structure containing two rollers of 10 mm of diameter and whose axes are separated by 150 mm. One of these lower rollers is completely fixed, while the other allows tilting for a better adjustment of the supports.
The upper head, in contrast, has two more rollers with the same dimensions as the previous ones but separated 50 mm from each other. They both allow tilting for adjustment. In addition, this piece has a spherical ball joint that offers greater movement and rotation freedom, ensuring a correct support of the rollers at any time and making sure that the axis of load application remains always centered.
Finally, it is important to guarantee correct alignment of the base and upper head at the time that the device is attached to the hydraulic press, so that the upper rollers are located at a distance of 50 mm from the nearest lower roller. In short, prior to the execution of the tests, it is essential to ensure that both parts of the device are correctly aligned both longitudinally and transversely, as shown below:
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