RECONSTRUCTION ON THE VOLTAGE OF THE PRE-SLIDING STATE OF THE TRAGICHOUS MOUNTAIN SLOPE LANDSCAPE «AK KAIN»

The method of reconstruction and investigation of the pre-landslide condition of the tragic landslide «Ak-Kain» of the Northern Tien Shan is proposed. A model and a finite element algorithm for studying the stress-strain state (VAT) of soil sediments of an obliquely layered structure are briefly presented. The established zones and places of accumulation of dangerous stress concentrations along the inclined layer that led to the tragedy are shown. The plots show the found other areas of hazardous stress concentrations prone to destruction.

Sports Injury Modeling of the Anterior Cruciate Ligament Based on the Intelligent Finite Element Algorithm

In order to solve the problem of sports injury modeling of the anterior cruciate ligament, a method based on the intelligent finite element algorithm is proposed. Considering the transverse isotropy of the ligament, this paper constructs a 3D finite element model of the knee joint based on medical image data. The same ligament constitutive equation was used to fit the parameters of stress-strain mechanical experimental curves of three different anterior cruciate ligaments, and the effects of different anterior cruciate ligament mechanical parameters on kinematics and biomechanical properties of the knee joint were compared. The experimental results show that, in models 1, 2, and 3, the maximum stress values appear in the posterolateral of the femoral attachment area of the ligament, which are 16.24 MPa, 16.36 MPa, and 22.05 MPa, respectively. However, the stress values at the tibial attachment area are 9.80, 13.8, and 13.93 MPa, respectively, and the stress values at the anterolateral part of the middle ligament are 6.36, 11.89, and 12.26 MPa, respectively, which are all smaller than those at the femoral attachment area, which also quantitatively explains the clinical phenomenon that ACL fracture often occurs in the femoral attachment area in practice. Thus, the three-dimensional finite element model of the knee joint highly simulates the structure and material properties of the knee joint. This method proves that the intelligent finite element algorithm can effectively solve the modeling problem of sports injury of the anterior cruciate ligament.

Medical Imaging Diagnosis of Anterior Cruciate Ligament Injury Based on Intelligent Finite-Element Algorithm

A medical imaging method based on an intelligent finite-element algorithm was proposed to diagnose anterior cruciate ligament injury modeling better. CT three-dimensional finite-element modeling was used to predict the fixation points of the anterior cruciate ligament (ACL) femoral tunnel. In this study, 19 subjects were selected, including 11 males and 8 females. There were seven cases of the left knee and 12 cases of the right knee; all patients had sports injuries. The anatomical structure of a patient’s knee was transformed into a three-dimensional model using finite-element analysis software for segmentation. The models of the tibial plateau and lateral femoral condyle were retained. The results showed that the Lysholm score difference (D) between 6 months after surgery and 1 day before surgery was used as the dependent variable in the three-dimensional finite-element model of knee joint established by the software. Pearson’s correlation analysis was performed, and the difference P < 0.05 was statistically significant. The original image of the Dicom format obtained through CT scan is preprocessed in Mimics without any format conversion, which avoids the loss of information, saves more time, and reduces the workload. The definition of “threshold” is used to complete the extraction of bone contour and realize automation. The speed and accuracy of modeling are improved.

A Finite Element Algorithm for Large Deformation Biphasic Frictional Contact Between Porous-Permeable Hydrated Soft Tissues

The frictional response of porous and permeable hydrated biological tissues such as articular cartilage is significantly dependent on interstitial fluid pressurization. To model this response, it is common to represent such tissues as biphasic materials, consisting of a binary mixture of a porous solid matrix and an interstitial fluid. However, no computational algorithms currently exist in either commercial or open-source software that can model frictional contact between such materials. Therefore, this study formulates and implements a finite element algorithm for large deformation biphasic frictional contact in the open-source finite element software FEBio. This algorithm relies on a local form of a biphasic friction model that has been previously validated against experiments, and implements the model into our recently-developed surface-to-surface contact algorithm. Contact constraints, including those specific to pressurized porous media, are enforced with the penalty method regularized with an active-passive augmented Lagrangian scheme. Numerical difficulties specific to challenging finite deformation biphasic contact problems are overcome with novel smoothing schemes for fluid pressures and Lagrange multipliers. Implementation accuracy is verified against semi-analytical solutions for biphasic frictional contact, with extensive validation performed using canonical cartilage friction experiments from prior literature. Essential details of the formulation are provided in this paper, and the source code of this biphasic frictional contact algorithm is made available to the general public.