Innovative Stainless Steel Applications in transport ... - Euro Inox

2400 N. Thus, the specified fatigue load was 3000 N ± 600 N applied to an area of
100 × 100 mm 2 for 10 7 cycles at a maximum frequency of 100 Hz.
5.2.1 Four-point bend testing of full-size panels
The bending tests were carried out in a customisable load frame, using two separate
loading cylinders and displacement control. The forces were measured directly from the
hydraulic cylinders and the displacements from both the top and bottom panel surfaces.
The bending tests were carried out using displacement control at a speed of
~ 3 mm/min. Details of the test arrangements can be found in Figure 59.
Figure 59. Details of panels in the four-point bending test, showing a) top-sheet wrinkling
under compressive load and b) failure caused by local buckling of the core element.
Altogether, 18 full-size panels were tested by four-point bending. Apart from the
maximum loading force and the corresponding displacements, an effort was also made
to evaluate the yielding behaviour of the panels. Determining a reliable and common
yield criterion for all the panels proved too difficult, however, mainly because the
scatter originating from the distortion of the panels after welding was too great. Instead,
the slope of the elastic region of each force-displacement curve was defined, to gain at
least a rough estimate of the elastic behaviour of various panel types under loading.
An effort was made to evaluate the elastic behaviour of the panels, by determining the
slope of the load-displacement curve of each panel at the elastic region. Both panel
types show – within reasonable scatter – approximately the same slope, which depends
mainly on the thickness of the bottom sheet. Increasing the thickness from 1.2 mm to
1.5 mm results in a 15 - 20 % higher slope value. It is also noteworthy that the scatter is
less for the thicker, bottom-sheet panels. In the theoretical panel-optimisation
calculations, the decrease in displacement caused by the change of bottom-sheet
thickness from 1.0 mm to 1.5 mm is 17.5 % and 18.4 % respectively for the O- and Vfpanels
(i.e. comparable to the experimental results).
97