| 摘要 |
<p>1442292 Applying predetermined tensions to fasteners A FISCHER 17 Feb 1975 [19 Feb 1974] 6534/75 Heading F2H [Also in Division G1] An element 9 to indicate the tension in a fastener 1 comprises a washer placed under the head 7 of the fastener and made of a material which changes colour in dependence on the compressive stress to which it is subjected. The washer is made of P.V.C. including a plasticizer, the colour change being due to a change in the structure of the plasticizer under compression. The colour change is a brightening of the original colour of the plastics, the amount of brightening indicating the loading, the limit being when the material is completely white. As shown, the fastener 1 comprises a longitudinally split expansible sleeve 2 on a bolt 4 having an expander head 3, the bolt being screwed into a threaded bore 6 of a rod 5. The head 7 may be integral with the rod 5, or may be a nut screw-threaded on to the rod. The washer 9 is arranged to reach its white colour at a load corresponding to the greatest force which can be applied safely to masonry 11 in which the fastener is anchored.</p> |
