مشخصه يابي قرنيه انسان با بكار بردن مدل ناهمسانگرد تقويت شده با فيبر توسط روش اجزاءمحدود معكوس

Characterization of Human Cornea Using an Anisotropic Fiber Reinforced Model and Inverse Finite Element Analysis

ﻫﺪف از اﯾﻦ ﻣﻄﺎﻟﻌﻪ، ﭘﯿﺶﺑﯿﻨﯽ ﭘﺎﺳﺦ ﮔﺬار ﺑﺎﻓﺖ ﻗﺮﻧﯿﻪ اﻧﺴﺎﻧﯽ ﺑﺎ اﺳﺘﻔﺎده از ﻣﺪل ﺳﺎﺧﺘﺎري ﻣﺘﻨﺎﺳﺐ ﺑﺎ رﻓﺘﺎر ﺑﯿﻮﻣﮑﺎﻧﯿﮑﯽ آن ﺑﻮد. ﺑﺮاي اﯾﻦ ﻣﻨﻈﻮر ﺗﻐﯿﯿﺮ ﺷﮑﻞ ﺑﺎﻓﺖ ﻗﺮﻧﯿﻪ اﻧﺴﺎن ﺗﻮﺳﻂ آزﻣﻮن ﮐﺸﺶ ﺗﮏﻣﺤﻮره، ﺑﻪ ازاي ﺳﻪ ﻧﺮخ ﮐﺮﻧﺶ ﻣﺘﻔﺎوت )ﺳﺮﻋﺖﻫﺎي ﺑﺎرﮔﺬاري 5 ،1 و 10 ﻣﯿﻠﯽﻣﺘﺮ ﺑﺮ دﻗﯿﻘﻪ(، ﺑﺮرﺳﯽ ﺷﺪ. در اﯾﻦ ﻣﻄﺎﻟﻌﻪ، ﺗﻌﺪاد 8 ﭘﺎراﻣﺘﺮ ﻣﻮاد ﻣﺪل ﺳﺎﺧﺘﺎري ﻧﺎﻫﻤﺴﺎنﮔﺮد ﺗﻘﻮﯾﺖ ﺷﺪه ﺑﺎ ﻓﯿﺒﺮ ﻫﺎﯾﭙﺮوﯾﺴﮑﻮاﻻﺳﺘﯿﮏ، ﺑﺎ زواﯾﺎي ﻣﺨﺘﻠﻒ ﻓﯿﺒﺮﻫﺎ ﺑﺎ اﺳﺘﻔﺎده از ﮐﻮﭘﻞ اﺟﺰاء ﻣﺤﺪود-ﺑﻬﯿﻨﻪﺳﺎزي و دادهﻫﺎي آزﻣﺎﯾﺸﮕﺎﻫﯽ ﺑﻪ دﺳﺖ آﻣﺪ. اﯾﻦ ﻣﺪل ﭘﺮاﮐﻨﺪﮔﯽ ﻓﯿﺒﺮﻫﺎ را ﺑﻪ ﻫﻤﺮاه ﺗﻐﯿﯿﺮ ﺟﻬﺖ آنﻫﺎ در ﻃﻮل ﻣﺪت ﺑﺎرﮔﺬاري و ﻫﻤﭽﻨﯿﻦ رﻓﺘﺎر ﻏﯿﺮﺧﻄﯽ ﺗﻐﯿﯿﺮ ﺷﮑﻞ ﻣﺤﺪود ﺑﺎﻓﺖ را ﺑﻪ ﻫﻤﺮاه ﺧﺎﺻﯿﺖ وﯾﺴﮑﻮاﻻﺳﺘﯿﮏ ذاﺗﯽ ﻣﺎﺗﺮﯾﺲ زﻣﯿﻨﻪ در ﻧﻈﺮ ﮔﺮﻓﺘﻪ اﺳﺖ. ﺑﺎ اﻓﺰاﯾﺶ و ﮐﺎﻫﺶ ﭘﺎراﻣﺘﺮﻫﺎي ﻣﻮاد ﺑﻬﯿﻨﻪ ﺷﺪه، ﺗﺄﺛﯿﺮ ﻫﺮ ﭘﺎراﻣﺘﺮ ﺑﺮ روي ﭘﺎﺳﺦ ﻧﻤﻮﻧﻪﻫﺎ در ﺷﺒﯿﻪﺳﺎزي ﺗﺴﺖ ﮐﺸﺶ ﺑﺮرﺳﯽ ﺷﺪ. اﻓﺰاﯾﺶ ﻧﺮخ ﮐﺮﻧﺶ ﺑﺎﻋﺚ اﻓﺰاﯾﺶ ﺳﻔﺘﯽ ﻧﻤﻮﻧﻪﻫﺎي ﺗﺤﺖ آزﻣﺎﯾﺶ ﺷﺪه ﮐﻪ اﯾﻦ ﺳﻔﺖ ﺷﺪن در ﻗﺴﻤﺖ اﻧﺘﻬﺎﯾﯽ ﭘﺎﺳﺦ ﺑﺎﻓﺖ در ﻧﺮخ ﮐﺸﺶ آﻫﺴﺘﻪﺗﺮ )1 ﻣﯿﻠﯽﻣﺘﺮ ﺑﺮ دﻗﯿﻘﻪ(، ﻗﺎﺑﻞ ﺗﻮﺟﻪ ﺑﻮده و ﺑﺎ اﻓﺰاﯾﺶ ﻧﺮخ ﮐﺮﻧﺶ )5 و 10 ﻣﯿﻠﯽﻣﺘﺮ ﺑﺮ دﻗﯿﻘﻪ(، اﯾﻦ اﻓﺰاﯾﺶ ﺳﻔﺘﯽ ﺑﻪ ﻣﯿﺰان ﻗﺎﺑﻞ ﺗﻮﺟﻬﯽ ﮐﺎﻫﺶ ﯾﺎﻓﺘﻪ اﺳﺖ. در ﭘﺎﯾﺎن رﻓﺘﺎر ﻣﺪل و ارﺗﺒﺎط آن ﺑﺎ رﯾﺰﺳﺎﺧﺘﺎرﺷﺎن، از ﻗﺒﯿﻞ ﻓﯿﺒﺮﻫﺎي ﮐﻼژﻧﯽ، ﻣﻮرد ﺑﺮرﺳﯽ ﻗﺮار ﮔﺮﻓﺖ. ﺑﺮرﺳﯽ ﻧﺘﺎﯾﺞ ﻧﺸﺎن داد ﮐﻪ ﺷﺒﯿﻪﺳﺎزي ﻋﺪدي اﻧﺠﺎم ﺷﺪه ﺑﺮاي ﭘﯿﺶﺑﯿﻨﯽ رﻓﺘﺎر ﺑﺎﻓﺖ ﻗﺮﻧﯿﻪ در ﻣﻘﺎﯾﺴﻪ ﺑﺎ ﻧﺘﺎﯾﺞ ﺗﺠﺮﺑﯽ ﺗﻘﺮﯾﺒﺎً ﺑﺮ ﻫﻢ ﻣﻨﻄﺒﻖ و از دﻗﺖ ﺧﻮﺑﯽ ﺑﺮﺧﻮردار ﺑﻮده و ﻣﺪل داراي ﭘﺎﯾﺪاري ﻗﺎﺑﻞ ﻗﺒﻮﻟﯽ اﺳﺖ.

The purpose of the present study is to predict the transient response of the human cornea via a structural model appropriately representing its biomechanical behavior. Load bearing characteristics of the cornea remain poorly understood due to the complexity of its constitutive model. A constitutive model that captures the response of cornea over the whole experimental time and incorporates all included nonlinearities is necessary. In the current study, parameters of the structural anisotropic fiber-reinforced hyper-viscoelastic model have been obtained using coupled finite element-optimization analysis and the uniaxial tensile test for three different strain rates. The utilized model accounts for the dispersion of the fibers along with their reorientation during loading, the nonlinear behavior of finite tissue deformation, and the intrinsic viscoelastic property of the matrix. Results show that the higher the strain rate the higher the stiffness of tested samples. Samples showed stiffening behavior specially at the end section of the tissue response for slower tensile rates. Eventually, the model behavior and its connection with its micro structures such as the collagen fibers, have been investigated. Examining the results shows that the numerical simulations performed for the prediction of the cornea tissue behavior are in agreement with the experimental results.