Page 307 - 00. Complete Version - Progress Report IPEN 2014-2016

Materials and Nanotechnology | Progress Report 307

joints were made through welding by using crucial for the performance of an implant. Den-
the GTAW process at the root and the SMAW tal implants are a class in itself due to its size,
process in the subsequent welding layers. The chemical and biological environment. This
welded joints were subjected to PWHT with paper presents a study on the electric signals
different tempering times (1h, 4h e 8h) and from a strain gage used in a custom-made lab-
their mechanical properties were evaluated by oratory micro torque meter specially developed
performing conventional tensile, elevated-tem- to evaluate the influence of the bone-implant
perature tensile (540ºC), Charpy V-notch im- and implant-abutment screwed interfaces on
pact toughness, Vickers hardness testing and the micro torque signals. The original electric
microstructural characterization (Figure 28). signals were acquired via National Instru-
Results indicated that mechanical properties of ments (NI) hardware and real time processed
Grade 91 steel change with increasing temper- with the Labview® software for the evaluation
ing time, and a better combination of strength of noise and its relation to the physical val-
and toughness can be reached with more than ues of interest and equipment precision (Fig-
4 hours of PWHT, under certain conditions. ure 29). The results indicate the need of care-
ful attention to the noise pickup, noise source
Study of the strain gage signals for controls and mechanical amplification of the
the control of a micro torque meter original signal in order to obtain higher accu-
racy of the equipment and automated control
on the equipment (Figure 30).

Figure 29: Image showing the inner and main
parts of a prototype micro torquemeter.

The controls of the stresses on the bone-im-
Figure 30: Experimental torque against microstrain
plant and implant-abutment interfaces are calibration curve for the torquemeter.