Some of the tackle kit components included with the Structures & Materials Tester (Go Direct or LabQuest) can bend when excess force is applied. This includes the u-bolts, which will bend before the maximum rating of the force sensor/load cell (1000 N).
In one test on the small u-bolt, we noted elastic deflection occurred at approximately 200 N load and permanent deformation at approximately 500 N. With the large u-bolt, the permanent deformation set in at approximately 600 N. In both cases, the load was applied to a near single point by a thin rod suspended between the cross bars, which were positioned as close to each other as possible.
The effects of this can be minimized by purchasing a second plate for the u-bolt and doubling up this part, or by setting project limitations to avoid exceeding the strength of the hardware.
Additional hardware can be purchased from a local hardware store.