6 Finite element analysis of anti-stress shielding internal fixed steel plate 1 An 2 Xin Jingyi 1 Qiong Yijian. Tianjin Institute of Integrated Traditional and Western Medicine, Tianjin 3002; 2 Tianjin University. Tianjin analysis. Method In the finite element analysis, 1223 nodes, 764 nodes, hexahedral isoparametric elements, and 3564 degrees of freedom were used. Results Compared with the original internally fixed steel plate, the improved internally fixed steel plate has a flexibility of 60130.861.2. . In line with biomechanics, internal fixation plate biomechanics internal fixation plate is a common method for the treatment of fractures. A researcher in trauma of Tianjin Hospital. The heart sets the plate of Neguding to the shape of the center and achieves a good clinical effect. In this paper, we use the dimensional finite element method to analyze the stress and deformation.
1 Materials and methods ii The shape and material of the internal fixed steel plate are improved. The material of the internal fixed steel plate before and after the Shishi is stainless steel. Its mechanical parameters are as follows. If the force boundary and displacement boundary conditions of the structure are also symmetrical, half or part of the structure can be intercepted for analysis. It completely substitutes the force situation of the entire structure, but for the sake of being more intuitive, we have not specifically used its symmetry, and An overall analysis was carried out.
The main improvement of the internal fixed steel plate is in the middle of the steel plate. According to the analysis, the middle section is selected for finite element analysis to improve the amount of work before and after the improvement. In order to reduce the influence of the load acting area on the calculation results, the analysis section is at the same time as the color center 2. It also extends on both sides. Within the boundary conditions of the internal fixed steel plate of 1.2, the force of the fixed steel plate is mainly the force of the two parts of the broken bone. The force of the broken bone is mainly transmitted by the positive force. Pressing, bending distance and 1% 1. Cheng, praying for score points for this. Analyze and compare the stress conditions of internally fixed steel plates before and after improvement. The above-mentioned stress 1 condition, stress; about the surface is paid 1.2.1 Force boundary conditions According to the above analysis, in the calculation, the tension is selected to be 2.4 continents, the bending distance and, respectively, 1.6 1 and 4.81 are reducing nodes The effect of the superset force on the calculation results. In the analysis, the relationship between stress and concentration in installation mechanics is specifically converted into a surface force applied to the unit surface, and the force is accurate. Judging from the results, there is indeed no effect of concentration, which is consistent with the pre-effect.
1.2.2 Constraint conditions As mentioned above, the geometry and stress of the internally fixed steel plate can be considered to be symmetrical about 2 sides, so its stress, strain and displacement should also be> 7 blood symmetrical. The flash is displacement is a relative scene change, and the stress and strain are absolute quantities, so the displacement constraint of the finite element model can not produce rigid body displacement, nor can it produce additional force. At the same time, it should also satisfy at least stress and strain. According to the above restrictions, in the analysis, = 3, on the cross section. Freedom is unconstrained, and after all, it is afterburning.
The division of 3 units is complicated due to the fixing holes in the internal fixing steel plate. It is also necessary to use more elements to simulate its shape, so high-precision dimension node hexahedron isoparametric elements are used in the analysis. There are 95 unmodified structural nodes, 752 units, and 3480 degrees of freedom. The improved structure node has 1223 units, 764 units, and 3564 degrees of freedom.
Results For the numerical analysis of the stress and strength of the complex structure, the finite element is currently the most effective and mature and the least expensive numerical method. The calculation data is formed according to the aforementioned boundary conditions and lattices. The middle part of the internally fixed steel plate with the largest difference is analyzed. At the ends of the two sections of steel plates, apply the same amount of tensile force to the positive bend, side, and compare their deformation ratio and stress ratio. Thus, the size of the bearing replacement effect is determined. 1.
Forced positive force forward displacement 10 bending moment bending moment, bending moment bending moment is not improved structure improvement structure increase percentage 3 discussion Insufficiency such as breakage. After the compression steel plate is fixed, the rigidity of the steel plate used is about 10 times greater than that of the cortical bone, and the steel plate replaces the load that the bone should bear. The bone within the fixed part of the steel plate is subjected to stress stimulation for a long time. That is, stress shielding is generated, which affects the bone reconstruction, causing osteoporosis and atrophy, and the steel plate is removed, and there is a possibility of re-fracture. From the point of view of treatment of fractures with integrated Chinese and Western medicine. After folding, internal fixation of the steel plate hinders the physiological mechanism of tendons and bones. The muscle contraction under functional exercise and activity is not so much exercise as bone exercise, but exercise plate.
In order to avoid the disadvantages in the use of steel plates, many scholars have proposed improvement measures and research in recent years to come up with new internal fixation materials with anti-torsion and anti-torque properties. For example, the Hongyicheng alloy has a stiffness smaller than that of ordinary steel plates or close to the stiffness of the bone. The centrally designed stainless steel has a shaft compression stiffness similar to bone. The torsional and bending stiffness is stronger than bone, which is beneficial to fracture fixation. A consensus was reached on the use of internal fixation plates to treat fractures. In order to avoid stress shielding, the fracture plates should be removed as soon as possible, so that the affected limbs can gradually bear the load in the daily activities of control, so that the bones are shaped and reconstructed according to the normal functional state. It is worth noting that after removing the steel plate, some parts should be properly protected.
In order to prevent the occurrence of eccentric stress, pre-bent steel plates are sometimes used. The middle of the steel plate is equivalent to the bulge of the fracture site, and the bulge of the steel plate is away from the bone surface by 12. High pressure makes the fracture end more evenly stressed, thus avoiding the opening of the opposite side of the steel plate. 3. Clinical practice shows that this type of steel plate designed by the Orthopedics Department of Tianjin Hospital has the characteristics of anti-stress shielding and the other Biomechanical advantages of bent steel plates.
According to our calculation results, after the improved design, the internally fixed pre-bent steel plate has a positive force bending distance and 1 in other words, the stiffness decreases by a corresponding proportion compared to the original internally fixed steel plate. Therefore, in clinical treatment, the improved internal fixation plate will bear a relatively small load under the premise of maintaining the necessary fixation, which reduces the stress replacement effect on the bone. In clinical practice, the types of trauma fractures are complex. Accurate analysis of the stress substitution relationship between internal fixation plates and bones needs to be done a lot of biomechanics. The use of dimensional finite element methods for stress and deformation analysis of internal fixation will play an important role. Make â‘´.
Xie Yiquan, He Fubao. Finite element method in elastic and plastic mechanics. Beijing mechanics Wang Xiaotong, Wang Zhibin, Shi Yijian, etc. Calcaneal finite element calculation and analysis. Biomedical engineering Meng He, editor in chief of Gu Zhiqu. Bone injury biomechanics. Beijing People's Medical Publishing House, 1991.296.
Received 19905 editor Li Weinong reader Bian editor.
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