مطالعه تجربي و مدل سازي رفتار رهايي از تنش بانداژ

چكيده انگليسي :

65Experimental study and modeling of bandage relaxtion of stress behavior Date of Submission 2018 8 26 Department of textile Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language PersianSupervisor Prof M GhaneAbstractA wound cloth or in other words bandage is a fabric of various types used to coverinjured surfaces or to protect a damaged position Applying stress to bandage inducepressure on a damaged position This pressure is related to the type of injury On the otherhand when a wound bandage is stretched to a certain level the stress starts to relax inaccordance to the time due to the viscoelastic properties The stress relaxation of thebandage leads to decrease of radial pressure onto the position which may cause problems issome wound injuries The main aim of this study is to investigate into the stress relaxation and recovery of thebandage Two cases of Elastic and non elastic bandage were studied For tensile testing Zwick tensile tester was used The samples were stretched to a certain level of extension Four different levels of initial stretch were applied i e 5 10 15 20 percent for the non elastic bandage and 50 100 150 and 200 percent for the elastic bandage The stressrelaxation values versus the time were then recorded and plotted The stress relaxation wasstudied in short time of 20 minutes The data was then used for viscoelastic modeling ofthe relaxation process Linear standard model was used to model the relaxation behavior ofthe bandage To verify the model curve fitting based on Least Square mothed was used The results showed that the stress relaxation starts with a high rate speed at the beginning zero time and tends to slow down to a nearly constant value at the end 20 minutes Theresults also revealed the value of the relaxed force at the end was highly proportional tothe applied initial level of extension The correlation between the relaxed force and thelevel of the initial extension was also studied Both elastic and non elastic bandage showedsimilar trend The results of curve fitting revealed that the linear stand model can justifythe relaxation of the bandage fabrics with a high correlation constant i e R square Theratio of the dashpot constant to the spring consent in the Maxwell part of the linearstandard model is define as the relaxation time or relaxation constant This wascalculated for all cases The results of the modeling showed that the model constant aredifferent in different cases of initial extensions However the relaxation constants arenearly close to each other The relaxation time or relaxation constant is higher in the caseof non elastic bandage showing that the speed of relaxation is lower in the case of non elastic bandage in comparison to the elastic bandage Keywords Bandage Stress relaxation Recovery Mechanical model Curve Fitting Relaxation constant

اميني، فرزانه

مطالعه تجربي و مدل سازي رفتار رهايي از تنش بانداژ

بانداژ , افت تنش , مدل مكانيكي , ريلكس , ويسكوالاستيك