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Objective To compare the corneal biomechanical parameters identified from uniaxial tensile test under fast and slow loading. Methods The stress-strain and stress relaxation data were obtained from uniaxial tensile tests on corneal strips from 15 healthy adult rabbits at average loading rate of 0.16 mm/s and 0.02 mm/s, respectively. A visco-hyperelastic model was applied to analyze the loading and unloading data from the fast tensile tests, where the model parameter set was denoted by Gvh. The first-order Ogden model and second-order Prony series model were used to fit stress-strain and stress relaxation data from the slow tensile tests, respectively, in which the model parameter set was denoted by Gvh. Correlation analysis was used to compare the correlation of parameters between Gvh and GOP. Results All the goodness-of-fits to the three data sets were greater than 0.95. There were significant differences in 5 (μ, A1, A2, τ1, τ2,) of the 6 parameters between Gvh and GOP (P<0.05), and the Ogden model parameters was positively correlated between the two groups. Conclusions There are differences in corneal biomechanical parameters identified by data from uniaxial tensile tests under fast and slow loading. The results provide a preliminary research basis for further exploring the use of clinical data to identify corneal biomechanical properties.
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BACKGROUND: The three-dimensional printed titanium alloy porous structure has been developed rapidly in orthopedic implant design and clinical application due to its good mechanical properties and biocompatibility. Compared with coated prosthesis, the porous structure of titanium alloy trabecular bone has the advantages of fast and good bone growth. In order to ensure the safety of orthopedic implants, the tensile, shear and flexural fatigue strength of trabecular bone structures are determined by experimental methods. OBJECTIVE: To investigate the mechanical properties of trabecular bone porous structure by mechanical experiments and finite element numerical simulation. METHODS: (1) Tensile test of three-dimensional printed titanium alloy trabecular bone: three-dimensional printed titanium alloy trabecular bone was designed and fabricated. The wire diameter was 0.28-0.35 mm, the pore size was 0.71 mm, and the porosity was 73%. The tensile strength was detected, and the failure mechanism was analyzed. The effect of different printed parts on the tensile strength of trabecular bone was analyzed. (2) Numeric simulation test: a solid model of the tensile specimens including the theoretical structure of the trabecular bone was established to simulate the tensile failure process of trabecular bone specimens. RESULTS AND CONCLUSION: (1) The ultimate load of the three-dimensional printed titanium alloy trabecular bone was 39.55-47.11 kN, and an equivalent ultimate tensile stress was 62.79-74.53 MPa. The result of tensile failure was fracture of the network structure, suggesting that titanium alloy trabecular bone had higher tensile strength. (2) Results of tensile test and numeric simulation test showed that the failure location of trabecular bone was mainly on the wire diameter, but not on the interface between trabecular bone and titanium alloy solid. (3) The tensile failure load obtained by numerical simulation was lower than that of experimental results. The main reason is that the wire diameter of the three-dimensional printed trabecular bone (280-350 µm) was larger than that of the theoretical size (142 µm), and the pore size (75% porosity) was smaller than the theoretical value (96% porosity).
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Objective: To estimate resistance ability of improved anchor screw. Methods: The experiment consisted of two sections: tensile test and finite element analysis (FEA). In the first part, the traditional anchor screw and the improved anchor screw were implanted into the condylar cortical bone, respectively, tensile force was tested by tension machine. In the second part, the three-dimensional finite element model of mandibular condyle was established after the improved anchor screw was implanted, and the FEA was performed by the force applied from three different directions. Results: The FEA results revealed the minimum force of the traditional and improved anchor screws were 48.2 N and 200.0 N, respectively. The tensile strengths of the traditional and improved anchor screws with a 3-0 suture were significantly different (P=0.033). The difference between the traditional anchor screw (3-0 suture) and the improved anchor screw (2-0 suture) were significantly different (P=0.000). Conclusion: Compared with traditional screw, improved anchor screw has better resistance ability, especially combined with 2-0 suture.
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Abstract Introduction Ozonization is an alternative sterilization process for heat-sensitive medical devices. However, the side effects of this process on packaging materials should be verified. Methods Four types of commercial disposable packaging for medical devices were evaluated after undergoing ozone sterilization: crepe paper sheet, non-woven fabric sheet (SMS), medical grade paper-plastic pouch and Tyvec©-plastic pouch. For each material, the gas penetration through the microbiological barrier was measured. Other packaging properties, such as chemical composition, color, tactile and mechanical resistance, were also evaluated after sterilization, by using characterization techniques, namely microbiological indicators, infrared spectroscopy, tensile test and optical microscopy. Results All commercial disposable packaging showed good ozone penetration. Crepe paper and SMS were chemically and mechanically modified by ozone, while Tyvec© only suffered mechanical modification. Paper-plastic pouch was the packaging material which just experienced an acceptable reduction in tensile resistance, showing no variations on chemical or visual properties. Conclusion The results suggest that medical grade paper-plastic pouch is the most appropriate disposable medical device packaging to be sterilized by ozone when compared to other materials.
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Objective To determine the hyperelastic parameters shear modulus (μ) and curvature parameter (α) of extraocular muscles (EOMs) in Ogden hyperelastic model, so as to provide theoretical basis for clinical EOM surgery by numerical modeling. Methods The passive behavior of fox EOMs in vitro was determined by the uniaxial tensile test, and the hyperelastic analysis was conducted by the first-order Ogden model and ABAQUS software. Results The experimental result showed that the passive behavior of fox EOMs was nonlinear. The corresponding hyperelastic parameters μ =(6.57±3.76) kPa and α=8.16±1.63 were obtained. When the strain of EOMs was larger than 6%, there were no statistical differences between the experimental result and the calculation result of the first-order Ogden hyperelastic model (P>0.05). Both the calculation result and the simulation result well fitted to the experimental result. Conclusions The hyperelastic parameters identified in this study can be used as the input for the corresponding numerical modeling of fox EOMs.
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Objective To determine the hyperelastic parameters of shear modulus (μ) and curvature parameter (α) of extraocular muscles (EOMs) in Ogden hyperelastic model,so as to provide theoretical basis for clinical EOM surgery by numerical modeling.Methods The passive behavior of fox EOMs in vitro was determined by the uniaxial tensile test,and the hyperelastic analysis was conducted using the first-order Ogden model and ABAQUS software.Results The experimental result showed that the passive behavior of fox EOMs was nonlinear.The corresponding hyperelastic parameters μ =(6.57 ± 3.76) kPa and oα =8.16 ± 1.63 were obtained.When the strain of EOMs was larger than 6％,there were no statistical differences between the experimental result and the calculation result of the first-order Ogden hyperelastic model (P ＞ 0.05).Both the calculation result and the simulation result well fitted to the experimental result.Conclusions The hyperelastic parameters identified in this study can be used as the input for the corresponding numerical modeling of fox EOMs.
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Objective To determine the hyperelastic parameters of shear modulus (μ) and curvature parameter (α) of extraocular muscles (EOMs) in Ogden hyperelastic model,so as to provide theoretical basis for clinical EOM surgery by numerical modeling.Methods The passive behavior of fox EOMs in vitro was determined by the uniaxial tensile test,and the hyperelastic analysis was conducted using the first-order Ogden model and ABAQUS software.Results The experimental result showed that the passive behavior of fox EOMs was nonlinear.The corresponding hyperelastic parameters μ =(6.57 ± 3.76) kPa and oα =8.16 ± 1.63 were obtained.When the strain of EOMs was larger than 6％,there were no statistical differences between the experimental result and the calculation result of the first-order Ogden hyperelastic model (P ＞ 0.05).Both the calculation result and the simulation result well fitted to the experimental result.Conclusions The hyperelastic parameters identified in this study can be used as the input for the corresponding numerical modeling of fox EOMs.
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Objective To determine the hyperelastic parameters of shear modulus (μ) and curvature parameter (α) of extraocular muscles (EOMs) in Ogden hyperelastic model,so as to provide theoretical basis for clinical EOM surgery by numerical modeling.Methods The passive behavior of fox EOMs in vitro was determined by the uniaxial tensile test,and the hyperelastic analysis was conducted using the first-order Ogden model and ABAQUS software.Results The experimental result showed that the passive behavior of fox EOMs was nonlinear.The corresponding hyperelastic parameters μ =(6.57 ± 3.76) kPa and oα =8.16 ± 1.63 were obtained.When the strain of EOMs was larger than 6％,there were no statistical differences between the experimental result and the calculation result of the first-order Ogden hyperelastic model (P ＞ 0.05).Both the calculation result and the simulation result well fitted to the experimental result.Conclusions The hyperelastic parameters identified in this study can be used as the input for the corresponding numerical modeling of fox EOMs.
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Objective To study the anisotropic mechanical properties of the thoracic aorta in porcine. Methods Twenty-one porcine thoracic aortas were collected and categorized into three groups. The aortas were then cut through in their axial directions and expanded into two dimensional planes. Then, by setting the length direction of the planar aortas (i.e., axial directions of the aortas) as 0°, each planar aorta was counterclockwisely cut into 8 samples with orientation of 30°, 45°, 60°, 90°, 120°, 135°, 150° and 180°, respectively. Finally, the uniaxial tensile tests were applied on three groups of samples at the loading rates of 1, 5 and 10 mm/min, respectively, to obtain the elastic modulus and ultimate stress of the aorta in different directions and at different loading rates. Results The stress-strain curves exhibited different viscoelastic behaviors. With the increase of sample orientations, the elastic modulus gradually increased from 30°, reached the maximum value at 90°, and then gradually decreased till 180°. The variation trend of ultimate stress was similar to that of elastic modulus. Moreover, different loading rates showed a significant influence on the results of elastic modulus and ultimate stress, but a weak influence on the anisotropic degree. Conclusions The porcine thoracic aorta is highly anisotropic. This research finding provides parameter references for assignment of material properties in finite element modeling, and is significant for understanding biomechanical properties of the arteries.
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Objective:To introduce a new fixation set-up for micro-tensile test.Methods:Dentin-composite were bonded with AdperTM Single Bond 2 (SB2)and sectioned into stick-shaped specimens.Specimens from each tooth(n =6)were equally divided into Ciucchi's jig and the designed set-up(Control and experimental)groups for micro-tensile bond test according to the utilized fixa-tion set-up.The bonding interface failure mode was examined with field-emission scanning electron microscope (FESEM).Three-dimensional models of the two set-ups and the specimen were developed,stress distribution was analyzed by finite element analysis (FEA).Results:The bond strength(MPa)of experimental and control group was 32.76 ±7.43 and 43.58 ±4.72(P <0.05),the ratio of mixed failure was 28 /36 and 20 /36(P <0.05)respectively.FEA showed that the designed set-up for fixing the sticks pro-vided a uniform stress distribution along the long axis of the specimen.FEA and failure mode analysis confirmed such uniform distri-bution was also concentrated at the bonding interface.Conclusion:The new set-up is feasible for micro-tensile test.
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Objective To observe the effect of cervical rotatory manipulation on tensile mechanical properties of atherosclerotic carotid artery in rabbits, so as to provide safety references for such manipulation. Methods Twenty male New Zealand rabbits were randomly divided into control group (n=10) and experimental group (n=10), then all fed with high-cholesterol diet for 12 weeks. The rabbits in experimental group were then applied with cervical rotatory manipulation (rotating on each side once a day during a total of 4 weeks), while no manipulation for rabbits in control group. The bilateral carotid arteries were obtained after all the rabbits were executed, and measured for the maximum load, the maximum displacement, the average load, the elastic modulus, elongation at break and stress-strain by the material testing machine. Results The maximum tension, the maximum displacement, the average tension, the elastic modulus and elongation at break in experimental group were (1.36±0.35) N, (6.84±2.08) mm, (0.44±0.30) N, (4.30±2.66) MPa and (83.08±51.32)%, respectively, while the corresponding data in control group were (2.92±0.65) N, (9.23±2.62) mm, (1.17±0.63) N, (3.71±0.60) MPa and (154.19±34.32)%. The maximum load, the average load and elongation at break in experimental group were obviously smaller than those in control group (P0.05). Conclusions The tensile mechanical properties of atherosclerotic carotid artery after cervical rotatory manipulation were declined; thus, intensity and magnitude of cervical rotatory manipulation should be proper so as to avoid harm to carotid artery.
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Injuries of the posterior cruciate ligament have almost universally been treated nonoperatively in the past due to indignity of this complex structure. Recent studies have shown new informations on the anantomical, histological, biomechanical characteristics of the Posterior cruciate ligament PCL), and thereby interest of reconstruction surgery is increasing. But intraarticular PCL reconstruction still remains one of the most challenging problems in knee surgery. Although, various types of graft and surgical techniques have been used for reconstruction, results of surgery has been variable. In this study, three different methods of graft fixation for PCL reconstruction are evaluated biomechanically to determine the effect on mechanical property of reconstructed PCL using 30 porcine knees. Grafts used in this study were bone-patellar tendon-bone fixed with interference screw and Achilles tendon tied with suture. Additionally, five original PCLs were also tested by Instron universal testing instrument to determine its mechanical proprety. Tensile test was performed at extended knee position. It was demonstrated that mechanical strength of bone-patellar tendon-bone graft is superior to that of Achilles tendon graft. All of the failures of bone-patellar tendon-bone graft and Achilles tendon graft occurred at tibial fixation site whereas original PCLs which failed at proximal midsubstance of ligament. In conclusion, tensile strength of Bone-patellar tendon-bone graft used for PCL reconstruction is higher than that of Achilles tendon but latter can be used in terms of as clinical meanings.