Determination of Nonlinear Behavior of the Human Ureter Wall by the Uniaxial and Biaxial Experimental Tests

The mechanical properties of the ureter altered by different diseases. So having the properties of the healthy ureter to detect tissue abnormalities is necessary.Wall tension alterations of the ureter can occur, leading to some abnormalities such as reflex mechanisms. Numerical analysis of urine flow in the ureter can help advance our understanding of the reflux phenomenon. To that end, a constitutive model that can predict the mechanical response of ureteral tissue under complex mechanical loading is required.Therefore, in this study the twenty-six human ureter samples were taken and uniaxial and biaxial tension tests were performed by loading in longitudinal and circumferential directions. Then the stress-strain curves achieved from the uniaxial tests were modeled with a mathematical function and the Young modulus was obtained. The biaxial stress-stretch curve was plotted and fitted to a hyperelastic four-parameter Choi-Vito type model. The specimens showed some degree of anisotropy. The specimens were stiffer in the longitudinal than in the circumferential direction.