MODES OF FAILURE OF MATERIALS UNDER THE DYNAMIC LOADING

Tests are reported on sixteen pinjointed, triangulated steel frames, subjected to impulsive overload. The frames were statically determinate, consisting of a single strut, tie and connexion; the load was applied by a spring loading device. Records were taken of the transient force pulses and high-speed photographs showed the various modes of failure. The load on frames which failed by yielding at the tie exceeded the corresponding static value by a factor approximating closely to the proportional increase of yield stress under dynamic loading. In some experiments strut failure occurred under a transient load many times the corresponding static value. In many both members showed signs of failure with a change of mode during the course of deformation.

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Response of an HMX Based Explosive to Dynamic Loading by the Hopkinson Split Bar Technique

Физика горения и взрыва ◽

10.15372/fgv20160414 ◽

2016 ◽

Keyword(s):

Dynamic Loading

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Reverse torque values of abutment screws after dynamic loading: The effects of sealant agents and the taper of conical connections

Journal of Oral Implantology ◽

10.1563/aaid-joi-d-19-00228 ◽

2020 ◽

Author(s):

Arda Ozdiler ◽

suleyman dayan ◽

Burc Gencel ◽

Gulbahar Isık-Ozkol

Keyword(s):

Dynamic Loading ◽

Antibacterial Agent ◽

In Vitro Study ◽

Control Group ◽

Silicone Sealant ◽

Reverse Torque ◽

The Stability ◽

Torque Values ◽

Chlorhexidine Gel

This in vitro study evaluated the influence of taper angles on the internal conical connections of implant systems and of the application of chlorhexidine gel as an antibacterial agent or a polyvinyl siloxane (PVS) sealant on the reverse torque values of abutment screws after dynamic loading. The current study tested four implant systems with different taper angles (5.4°, 12°, 45°, and 60°). Specimens were divided into three groups: control (neither chlorhexidine gel filled nor silicone sealed), 2% chlorhexidine gel-filled or silicone-sealed group, and group subjected to a dynamic load of 50 N at 1 Hz for 500,000 cycles prior to reverse torque measurements. Quantitative positive correlation was observed between the taper angle degree and the percentage of tightening torque loss. However, this correlation was significant only for the 60° connection groups except in the group in which a sealant was applied ( p = 0.013 for the control group, p = 0.007 for the chlorhexidine group). Percentages of decrease in the torque values of the specimens with silicone sealant application were significantly higher compared with both the control and chlorhexidine groups ( p = 0.001, p = 0.002, p = 0.001, and p = 0.002, respectively, according to the increasing taper angles); the percentage of decrease in torque values due to chlorhexidine application was statistically insignificant when compared with the control group. The application of gel-form chlorhexidine as an antibacterial agent does not significantly affect the stability of the implant–abutment connection under dynamic loads. PVS sealants may cause screw loosening under functional loads.

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