A COMPARATIVE EVALUATION OF EFFECTS OF DIFFERENT KINDS OF STERILIZATIONS ON LOAD DEFLECTION CHARACTERISTICS , TENSILE PROPERTIES OF COPPER NITI WIRES-AN INVITRO STUDY 1
Copper NiTi wires were introduced by Sachdeva R and Miyasaki S in 1994. This latest innovation in the evolutionary scale gives us the opportunity of choosing the force level by choosing the temperature at which the wires will deliver its optimum force level. With so many advantages and their ability to return to their original form coupled with the high cost of copper NiTi many clinicians started reusing the wire. This raises concern about disinfecting/sterilizing the wire before using in another patient for prevention of cross infection. Hence, various sterilization procedures like cold sterilization using 2% acidic glutaraldehyde, dry heat sterilization and autoclaving were used to prevent this cross infection..Aim: The main aim of this study is used to evaluate the effects of different kinds of sterilization on load characteristics and tensile properties of copper Ni Ti wire. Materials and Methods: In the present study, selected mechanical properties like load deflection characteristics, ultimate tensile strength of the 0.016 copper NiTi wires were studied before and after sterilization procedure. Three point bending test was performed to evaluate the load deflection characteristics and tensile test were evaluated to determine other mechanical properties. Pretreatment and post treatment values were statistically analyzed by one way ANOVA test. Results: On the load deflection characteristics, even though there was an increase in the loading and unloading forces, statistically significant changes in the forces are seen only when the wires were subjected to two cycles of sterilization with autoclave and dry heat. No detrimental changes were detected in tensile properties of copper NiTi were after single cycle of sterilization with any of the stated sterilants. Very minimal non significant changes occurred during the second cycle of sterilization procedure. Conclusion: Pronounced changes in load deflection characteristics have been found in the wires which have undergone two cycles of sterilization with either dry heat or autoclave implying that there was loss in pseudoplastic and pseudoelastic properties of wires and increase in stiffness of wires.
An evaluation of cobalt-substituted nitinol wire in orthodontics.
Abstract Eight distinct types of wires were compared for the property of each wire's working range. Specifically, the two types of cobalt nitinol wires were compared with three typical 18-8 stainless steel leveling wires (0.014, 0.016, and 0.018 inch) and three typical Twist-Flex leveling wires (0.0175, 0.0195, and 0.0215 inch). The parameter measured was per cent elastic return of the deflected wire back to an original undeflected undeformed parabolic preformed arch shape. Double determinations of 480 measurements by two independent observers, abstracted and statistically quantified, are reported in two tables in addition to being graphically illustrated. Ten replications of each of the eight wire types were made in order to determine and quantify the following four variables: 1. 1. Millimeter return of the wire after being deflected and tied into the bracket slot. 2. 2. Millimeter distance of the undeflected undeformed “standard” preformed arch wire form from the bracket slot. 3. 3. Standard deviation of the millimeter return after the wire was cut loose from the bracket slot and had some degree of permanent deformation remaining in the wire. 4. 4. Per cent return of the permanently deformed test wire expressed as a ratio of the “standard” undeformed preformed wire's distance to the deepest part of the bracket slot. Measurements were achieved by the investigators' use of vernier calipers (Helios) with a dial read out to 1 20 mm., on standardized photographs of each wire's deformation compared to its standard.
Numerical Simulation of Induction Heating Process of Continuous Casting Slab
Compared with traditional blazing furnace, the Continuous Casting-Direct Rolling is an advanced manufacturing steel technology, which can reduce energy waste, decrease pollution and enhance efficiency. The characteristics of steels during induction heating are complex, the change of material properties with temperature makes exact analysis methods very difficult to implement. Therefore, a powerful computer aided numerical tool (i.e., finite difference analysis) is selected to numerically model the induction heating process in this paper. The mathematic model coupling with electromagnetic field and thermal field was established, and it was solved by finite difference method (FDM), thus the slab temperature distribution and its variation with time were obtained, and the characteristics in whole induction heating process were studied. To validate the program feasible, the results were evaluated and compared with experiment results, which showed that the simulation results are reliable and effective. The skin effect in heating process from the two results was studied and demonstrated, the temperature change caused by different parameters such as the induced power intensity and the corner radian were also presented, which indicate that the slab temperature can be heated uniformly through adjusting these parameters, thus the continuous casting slab can meet the rolling requirement.