Aneurysms can be classified into two main types based on their shape: saccular (spherical) and fusiform (cylindrical). In order to clarify the formation of aneurysms, we analyzed and examined the relationship between ...Aneurysms can be classified into two main types based on their shape: saccular (spherical) and fusiform (cylindrical). In order to clarify the formation of aneurysms, we analyzed and examined the relationship between external force (internal pressure) and deformation (diameter change) of a spherical model using the Neo-Hookean model, which can be used for hyperelastic materials and is similar to Hooke’s law to predict the nonlinear stress-strain behavior of materials with large deformation. For a cylindrical model, we conducted an experiment using a rubber balloon. In the spherical model, the magnitude of the internal pressure Δp value is proportional to G (modulus of rigidity) and t (thickness), and inversely proportional to R (radius of the sphere). In addition, the maximum pressure Δp (max) is reached when λ (=expanded diameter/original diameter) is approximately 1.2, and the change in diameter becomes unstable (nonlinear change) thereafter. In the cylindrical model, localized expansion occurred at λ = 1.32 (λ = 1.98 when compared to the diameter at internal pressure Δp = 0) compared to the nearby uniform diameter, followed by a sudden rapid expansion (unstable expansion jump), forming a distinct bulge, and the radial and longitudinal deformations increased with increasing Δp, leading to the rupture of the balloon. Both models have a starting point where nonlinear deformation changes (rapid expansion) occur, so quantitative observation of the artery’s shape and size is important to prevent aneurysm formation.展开更多
文摘Aneurysms can be classified into two main types based on their shape: saccular (spherical) and fusiform (cylindrical). In order to clarify the formation of aneurysms, we analyzed and examined the relationship between external force (internal pressure) and deformation (diameter change) of a spherical model using the Neo-Hookean model, which can be used for hyperelastic materials and is similar to Hooke’s law to predict the nonlinear stress-strain behavior of materials with large deformation. For a cylindrical model, we conducted an experiment using a rubber balloon. In the spherical model, the magnitude of the internal pressure Δp value is proportional to G (modulus of rigidity) and t (thickness), and inversely proportional to R (radius of the sphere). In addition, the maximum pressure Δp (max) is reached when λ (=expanded diameter/original diameter) is approximately 1.2, and the change in diameter becomes unstable (nonlinear change) thereafter. In the cylindrical model, localized expansion occurred at λ = 1.32 (λ = 1.98 when compared to the diameter at internal pressure Δp = 0) compared to the nearby uniform diameter, followed by a sudden rapid expansion (unstable expansion jump), forming a distinct bulge, and the radial and longitudinal deformations increased with increasing Δp, leading to the rupture of the balloon. Both models have a starting point where nonlinear deformation changes (rapid expansion) occur, so quantitative observation of the artery’s shape and size is important to prevent aneurysm formation.
