兔眼角膜生物力学特性的年龄相关性

目的 利用兔眼角膜条的单轴拉伸实验数据,研究角膜生物力学特性与年龄的相关性。 方法 分别取3月龄和7~8月龄兔眼角膜条,实施单轴拉伸实验,获得实验数据;用指数模型和幂模型对应力 应变数据进行分析;用黏弹性力学模型对应力松弛数据进行分析。结果 兔眼角膜条呈现非线性黏弹性特征。在实验误差允许的范围内,不同月龄兔眼角膜条的非线性应力-应变关系差别不明显,7~8月龄兔眼角膜的切线模量略偏大,但其应力衰减得明显快。不同的拉伸速率对3月龄兔眼角膜条非线性应力-应变关系的影响不明显,但快速拉伸后的角膜条应力衰减明显变快。结论 兔眼角膜随月龄增加会轻微变硬,而角膜的松弛特性随月龄变化明显。     

膨胀试验测定猪眼角膜生物力学参数的研究

目的 通过膨胀试验测定猪眼角膜的非线性应力/应变关系,研究猪眼角膜弹性模量和眼内压之间的关系。方法 选取新鲜猪眼11只,剪下附带4~5mm宽度巩膜环的角膜,采取胶水黏附联合机械固定方式将猪眼角膜固定于自制的施压装置,缓慢逐步增加液压,液压范围：25mmH2O(1.8375mmHg) ~ 1000mmH2O (73.5mmHg),激光位移计记录角膜前表面顶点的前突位移量,根据板壳理论推导公式计算猪眼角膜的生物力学参数,包括应力、应变及弹性模量。结果 猪眼角膜前突位移量同眼内压的关系及应力/应变均呈指数函数关系,弹性模量与眼内压呈线性关系。结论 膨胀法测量猪眼角膜的弹性模量具有较好的重复性和精确性,此方法所测得的弹性模量可用于后期屈光手术模型的建立、人工角膜与角膜接触镜设计及其它方面的研究。     

基于快、慢速加载单轴拉伸数据识别的角膜生物力学特性比较

目的 比较基于快、慢速加载单轴拉伸数据确定的角膜生物力学特性参数。方法 选取15只健康成年兔的角膜进行平均加载速率为0.16、0.02 mm/s单轴拉伸实验,分别获得应力-应变以及应力松弛数据;分别利用黏超弹性模型、1阶Ogden模型和2阶Prony级数模型对加卸载迟滞环曲线、应力-应变曲线、应力松弛曲线进行分析。基于黏超弹性模型拟合快速加卸载迟滞环曲线确定的参数集记为G_vh。拟合慢速加载的应力-应变、应力松弛数据的材料参数集记为G_OP。利用相关性分析比较G_vh与G_OP之间参数的相关性。结果 对快速加卸载迟滞环数据、慢速加载的应力-应变数据与应力松弛数据的拟合优度R²都大于0.95。G_vh与G_OP中6个参数中5个(μ,A₁,A₂,τ₁,τ₂)差异明显(P<0.05),并且两参数组中Ogden模型参数呈正相关。结论 基于快、慢速加载的单轴拉伸数...     

脱细胞心血管组织的生物力学性能评价

目的比较心血管组织在脱细胞前后的生物力学性质。方法分别测试脱细胞处理前后肺动脉壁和瓣叶的强度、应力-应变、应力松弛等生物力学指标并进行比较。结果肺动脉壁在处理前后各指标无明显差异，瓣叶在脱细胞后其强度和应力-应变明显变化，应力-松弛无明显变化。结论脱细胞的心血管组织与天然组织的生物力学性能一致或接近。     

脱细胞猪主动脉瓣叶的生物力学特性和免疫反应性

目的：探讨脱细胞猪主动脉瓣叶构建组织工程心脏瓣膜支架的可行性。方法：经胰酶-EDTA、表面活性剂、核酸酶处理，去除瓣叶的细胞成分，测定脱细胞瓣叶的生物力学特性，同时行大鼠皮下包埋实验，观察其免疫反应性。结果：瓣叶中的细胞成分能完全去除，获得无细胞的纤维网状支架。脱细胞瓣叶与新鲜瓣叶有基本相同的应力-应变曲线及应力-松弛曲线，而弹性模量、面积比、松弛强度、断裂强度和断裂伸长率两者无显著差异。脱细胞瓣叶的免疫反应性明显降低。结论：猪主动脉瓣叶经脱细胞处理后可以作为组织工程心脏瓣膜的支架材料。     

活性猪眼角膜的各向异性生物力学行为研究

以猪眼角膜为研究对象,应用实验分析和各向异性弹性理论,探讨动物角膜在双向载荷作用下的生物力学行为.在Zwick-Z010型小吨位双向电子万能试验机上,利用所开发的平口微型双轴夹具,分别对片状角膜进行单、双轴拉伸和循环加载实验,确定材料的弹性常数和强度、刚度等特性.研究表明,材料具有典型的各项异性生物力学行为,在角膜的长轴和短轴方向呈现出不同的应力和变形特征.沿短轴方向角膜具有更高的黏弹性和黏塑性,其延展率也要大于长轴方向,而沿长轴方向则有更高的弹性模量和拉伸极限强度,材料的破坏为多种变形相互作用所致.     

鼻骨膜和筋膜生物力学特性的比较

在隆鼻术中，假鼻体应埋于骨膜以下还是深筋膜以下一直是整形外科业内人士讨论的重要问题。本文着重研究了人鼻骨膜和深筋膜的生物力学特征。主要包括单轴拉伸下的强度，应力一应变及应力松弛，骨膜的强度较深筋膜大，且具有一定的弹性，但弹性不如深筋膜，在突加载荷下，骨膜的应力松弛较深筋膜少得多。因此，从生物力学的角度看，骨膜更厚，更坚韧，应力松弛更少，因此有更好的固定效果。     

成年离体猪气管生物力学特性的实验研究

目的对成年离体猪气管进行生物力学实验研究,评价其生物力学特性,为生物型人工气管支架的生物力学研究提供实验方法与依据。方法应用TY8000系列50-5000N伺服控制拉力试验机对成年离体猪气管作抗弯刚度、径向支撑、纵向拉伸以及残余应力、顶破强力的测试评价。结果数据显示离体猪气管环存在残余应力,50mm长气管直径压缩50%时径向支撑力约10N,气管顶破强力从咽部约180mmHg逐渐降低至隆突处约110mmHg,气管向前与左右弯曲50°时,应力分别为0.296～0.131N和0.254～0.150N。计算机描绘猪气管应力-应变曲线显示50%应变时应力很小。结论猪气管存在残余应力,内壁压力不断增高时气管膜部发生破裂。同时,猪气管具有良好的径向支撑、弯曲与拉伸性能。     

兔子宫壁组织力学特性的实验研究

目的 研究兔子宫壁组织的生物力学特性,并对分娩与未分娩组兔子宫壁力学特性进行比较.方法 以14只新西兰雌性大白兔为研究对象,取其子宫壁组织为拉伸试样,分娩与未分娩分组对照,用WDW4100微机控制电子万能实验机进行拉伸实验,测定其极限强度、应力应变关系;蠕变实验和应力松弛实验测定其黏弹性特征.结果 兔子宫壁组织表现出明显的黏弹性特征,应力应变呈指数关系;分娩组的平均极限应力为0.119MPa,未分娩组的平均极限应力为0.444MPa;分娩组的蠕变和松弛实验均明显比未分娩组低.结论 分娩与未分娩的兔子宫壁组织生物力学特性有明显的差别,对临床上研究人类子宫壁组织有一定的参考价值,有助于妇产科学的发展.     

小儿肠套叠肠管与人阑尾归一化应力松弛函数蠕变函数

本文对小儿肠管及套入部分肠管和人阑尾进行了生物力学实验研究。得出了单向拉伸破坏时的应力、应变、伸长比λ，还得出了小儿正常肠管及肠套叠肠管、人阑尾应力松弛、蠕变曲线还得出正常肠管、人阑尾应力松弛、蠕变函数及曲线。并对小儿肠套叠的发病机理以生物力学的观点进行分析讨论，对人阑尾和小儿肠管的力学性质进行比较     

人眼角膜黏弹性实验研究

对正常国人6具新鲜尸体8个眼角膜标本进行单向拉伸实验和拉伸应力松弛、蠕变实验。得出了人眼角膜拉伸最大载荷、伸长比、张应力、应变、拟弹性模量。还得出了人眼角膜的应力松弛、蠕变数据和曲线。对应力松弛、蠕变实验数据进行归一化处理,得出了归一化应力松弛函数、蠕变函数及曲线。对应力松弛、蠕变实验数据进行回归分析,得出了回归系数。对人眼角膜应力、应变数据以多项式,用最小二乘法进行拟合,得出了其应力应变关系公式及曲线,建立了人眼角膜的松弛函数k(λ,t)=G(t)T(e)λ的表达式,得出了一些重要结论。     

人体颞下颌关节外侧壁囊-韧带复合结构生物力学研究

用软组织拉伸力学方法对８个８－１５岁新鲜尸体颞下颌关节外侧壁试件共３１个进行纵向应力松驰和拉伸破坏实验。结果表明：关节外侧壁是囊和韧带结构的复合体,抗拉伸和抗变形能力较弱,应力松驰方式在缓冲外力载荷可可能起主要作用。     

An Indentation Technique to Characterize the Mechanical and Viscoelastic Properties of Human and Porcine Corneas

Cornea is a load-bearing tissue whose mechanical and viscoelastic characteristics are not well understood, due to the challenge associated with most of the measurements. A novel indentation technique has been developed for mechanical characterization of human and porcine corneal tissue, using a tailored depth-sensing microindentation instrument. During indentation, the corneas were suspended by clamping the edges of the cornea, thus allowing depth-sensing measurement free from the complication of the backing substrate. The deformation displacement and the amount of force applied by the indenter were used to obtain hysteresis and stress relaxation data for both human and porcine corneas. Optical coherence tomography was used to measure the thickness of the cornea. Simple theoretical analyses have been undertaken to explain the loading–unloading and the stress relaxation data. The effect of swelling on the mechanical properties of the cornea was also examined. Porcine corneas appeared to be less stiff and to demonstrate more linear response than human corneas under loading. More importantly, it is shown that swelling reduced the strength of the corneas. Our results demonstrate that this new indentation system can be used to characterize the mechanical and viscoelastic properties of corneas.     

大白鼠周围神经的生物力学性质研究

目前对神经的生物力学性能找不到定量的依据，而受损神经的再生及功能恢复过程需要有客观的指标给予评价。本文用生物力学的理论和方法测定了大白鼠周围神经的力学性质。其中包括应力－应变关系，抗张强度，滞后，应力松驰与蠕变现象。结果表明大白鼠周围神经的力学性质与其他生物软组织相似，但定量上有较大区别。大白鼠周围神经的抗张强度高于血管，肌肉等生物软组织，其拉伸时组织破坏前的应变范围宽于血管、肌肉、肌腱。为神经损伤桥接术的研究提供了有益的参考。     

An experimental study on the biomechanical properties of the cancellous bones of distal femur

OBJECTIVES: To study the comprehensive biomechanical properties of the cancellous bone of distal femur through a series of mechanical tests, and provide relevant subjects with the basic technical data. BACKGROUNDS: The study on bone mechanics is a commonly used approach to evaluate the biomechanical competency of bone. The biomechanical properties of bone have come to be the precondition of the further research of these relevant clinical subjects. METHODS: In this paper, comprehensive items of mechanical properties of the cancellous bones of distal femur were conducted, and many valuable test results were obtained through a series of mechanical tests, which comprised tensile test, compression test, torsion test, shear test, bending test and impact test. The specimens were extracted from the normal corpses of Chinese donors died from acute head injury. As another key problem in this kind of experiment, the sampling and fixing method of cancellous bones specimens was developed and optimized in this research. RESULTS: A series of the experimental data of mechanical properties of cancellous bones were obtained in the tests, these experimental data include tensile strength, compression strength, yield tensile strength, modulus of elasticity, torsion strength, shear strength, torsion modulus, bending strength, yield shear limit and impact toughness, which can reflect the complex mechanical competency of bone, being of great value and practice in clinic and further research on cancellous bones. The mechanical properties of the cancellous bones of distal femur were analyzed and discussed. CONCLUSIONS: The biomechanical properties of the cancellous bones have a close relationship with individual difference. Comprehensive items of the mechanical properties of the bone can evaluate the mechanical performance of the bone better, and can provide more valuable data to relevant research.     

基于角膜生物力学对小切口角膜基质透镜取出手术优化及联合角膜胶原交联手术的效果分析

目的 建立小切口角膜基质透镜取出(small incision lenticule extraction, SMILE)手术的有限元模拟体系,模拟术后角膜生物力学性能变化,为SMILE手术的优化设计提供依据,并探讨角膜胶原交联(corneal collagen cross-linking, CXL)手术对SMILE术后角膜生物力学性能的影响。方法 采用交联强度梯度分布的超弹性本构关系描述角膜的生物力学性能,建立SMILE手术的压痕有限元模型,设置不同的切口位置、切口弧度、侧切口角度和角膜帽厚度,分析SMILE术后角膜生物力学性能的变化;对SMILE术后角膜进行CXL手术的有限元模拟,分析不同辐射能量对角膜生物力学性能的影响。结果 随着切口位置角度变小、切口弧度增加、侧切口角度从90°增大到135°或减小到45°、角膜帽厚度减小,SMILE术后角膜最大von Mises应力不断增大;随着辐射能量增加,CXL术后最大von Mises应力不断增加。结论 构建的有限元模型可有效表征SMILE术后角膜的生物力学响应,为SMILE手术的优化设计提供模拟依据;CXL手术有助于提高SMILE术后角膜...     

A New Method to Determine Rate-dependent Material Parameters of Corneal Extracellular Matrix

The cornea protects internal ocular contents against external insults while refracting and transmitting the incoming light onto the lens. The biomechanical properties of the cornea are largely governed by the composition and structure of the stromal layer which is an extracellular matrix composed of collagen fibrils embedded in a hydrated soft matrix. The mechanical behavior of the corneal stroma has commonly been characterized using uniaxial tensile tests and inflation experiments. In the present study, unconfined compression experiments were used to investigate the influence of loading rates on compressive behavior of nineteen porcine corneal specimens. The experiments were performed at ramp displacement rates 0.15 μm/s (eight samples), 0.5 μm/s (six samples), and 1.0 μm/s (five samples). For all tests, a maximum compressive strain of 50% (five strain increments of 4% followed by three strain increments of 10%) was selected. The experimental data was analyzed by a transversely isotropic biphasic model and material parameters, i.e., the in-plane Young’s modulus, the out-of-plane Young’s modulus, and the permeability coefficient were calculated. It was observed that while the permeability coefficient decreased exponentially with increasing compressive strain, the in-plane and out-of-plane Young’s moduli increased exponentially with increasing strain. Furthermore, it was found that the equilibrium stress was almost rate independent.     

Viscoelastic Properties of Human Tympanic Membrane

The tympanic membrane or eardrum of human ear transfers sound waves into mechanical vibration from the external ear canal into the middle ear and cochlea. Mechanical properties of the tympanic membrane (TM) play an important role in sound transmission through the ear. Although limited resources about linear elastic properties of the TM are available in literature, there is a lack of measurement or modeling of viscoelastic properties of the TM at low stress levels. In this study, the uniaxial tensile, stress relaxation, and failure tests were conducted on fresh human cadaver TM specimens to explore mechanical properties of the TM. The experimental results were analyzed using the hyperelastic Ogden model and digital image correlation method. The constitutive equation and non-linear elastic properties of the TM were presented by functions of the stress and strain at the stress range from 0 to 1 MPa. Viscoelastic properties of the TM were described by the stress relaxation function and hysteresis. The results show that the uniaxial tensile test with the aid of digital image correlation analysis is a reliable and useful approach for measuring mechanical properties of ear tissues. The data presented in this paper contribute to ear biomechanics in both experimental measurement and theoretical analysis of ear tissues.     

Mechanical behavior of human cortical bone in cycles of advancing tensile strain for two age groups

The capacity of bone for post-yield energy dissipation decreases with age. To gain information on the causes of such a change, we examined age-related changes in the mechanical behavior of human cadaveric bone as a function of progressive deformation. In this study, tensile specimens from tibiae of nine middle aged and eight elderly donors were loaded till failure in an incremental and cyclic (load-dwell-unload-dwell-reload) scheme. The elastic modulus, maximum stress, permanent strain, stress relaxation, permanent strain energy, elastic release strain energy, and hysteresis energy were determined in each loading cycle at incremental strains. Similar with previous work, the results of the present study also indicated that elderly bone failed at much lower strains compared to middle aged bone. However, no significant differences in the mechanical behavior of bone were observed between the two age groups except for the premature failure of elderly bone. After yielding, the energy dissipation and permanent strain of bone appeared to linearly increase with increasing strain applied, while nonlinear changes occurred in the modulus loss and stress relaxation with increasing strain. Moreover, stress relaxation tended to peak at 1% strain beyond which few elderly bone specimens survived. This study suggests that damaging mechanisms in bone vary with deformation, and aging affects the post-yield mechanisms, thus giving rise to the age-related differences in the mechanical properties of bone, especially the capacity of the tissue for energy dissipation.