摘要:
利用生物材料试验机和套管式高聚物霍普金森拉杆装置,试验得到了猪后腿肌肉在宽应变率范围
(0.02~2100s-1)内沿纤维方向和垂直纤维方向的拉伸应力应变曲线。编写程序对动态试验中高聚物杆波
的弥散和衰减效应进行了修正。对试验结果采用了1维方差统计分析,结果发现:应变率从0.02s-1上升到
2100s-1,肌肉在2个加载方向上流动应力都显著提高,即具有明显的应变率效应;低应变率下,纤维方向的
极限强度比垂直纤维方向的大,而破坏应变无显著不同,准静态应力应变曲线的形状与其他软组织类似,开始
为足趾区,后进入线性区,接着又有1段非线性区,最后达到极限强度,试样逐渐破坏;高应变率下,应力应
变曲线无足趾区,这是因为组织中的螺旋结构来不及伸直所致。垂直纤维方向比纤维方向有更高的初始模
量,但随应变增加,两者流动应力无显著差别,且纤维方向流动应力有逐渐高于垂直纤维方向的趋势。
Abstract:
Thetensilestress-straincurvesofporcineham musclealongthelongitudinalandtransverse
directionsofthemusclefibrewereobtainedoverawiderangeofstrainrates(0.02~2100s-1).The
experimentswereperformedbyusingthebiomechanicaltestingsystemandthepolymericsplitHopkinsontensilebar(
SHTB)inthetubes.Aprogram wascompiledtomodifytheeffectofdispersion
andattenuationofwavesintheviscoelasticpolymericbarusedasthetransmissionbarinthedynamic
experiments.Statisticalanalysesweredonebyusingone-wayANOVA (p0.05).Theresultsshow
thattheflowstressoftheporcineham muscleatthehighstrainrateof2100s-1isbothapparently
higherthanthatatthelowstrainrateof0.02s-1alongthetwoloadingdirections,illustratingthe
strainratesensitivitiesoftheporcineham muscle.Atthelowstrainrates,theultimatestrengthsalongthelongitudinaldirectionarehigherthanthosealongthetransversedirection,
whereasthereare
nosignificantdifferencesbetweentheirfailurestrainvalues.Thequasi-staticstress-straincurvesbehaveastheothersofttissues,
exhibitinganinitialnon-lineartoeregion,followedbyalinearregion
andsubsequentlyanonlinearregionpriortothegradualfailure.Atthehighstrainrates,thetoeregionvanishesbecauseithasnoenoughtimetopermitthestraighteningofthehelicalstructure.
The
initialmodulusinthetransversedirectionismuchhigherthanthatinthelongitudinaldirection.However,
whenthestrainincreases,theflowstressesinthetwodirectionshavenosignificantdifference
andtheflowstressinthelongitudinaldirectiongraduallyinclinestohigherthanthatinthetransverse
direction.
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