Analytical Algorithms for the Blend Ratios by Fibre-bundle Tensile Curves Part Ⅲ:The Definition Method and the Relationships between the Blend Ratio and Tensile Parameters Calculated from Different Ways

The algorithms of the strength, work, modulus and percentage methods have been introduced and discussed in Part Ⅰ and Part Ⅱ of the series papers. As the following, the percentage-function calculation and the frequency-function calculation of the definition method are defined and developed in detail. Meanwhile, the procedures to find the tensile parameters are analysed experimentally and involve "ED" being the average values of the corresponding tensile parameters of each bundle tensile curve measured; "EC" being the tensile parameters obtained from the averaged experimental tensile curve; and "TC" being the parameters of the theoretical tensile curve according to the corresponding nominal blend ratio. The theoretical and experimental results indicate that the blend ratio estimated by the definition method from wool/polyester blended fibre bundles has a high correlation with the actual blend ratio though the variables to be known in this method are the most of all the methods and there exist the difficulty to solve fibre bundle tensile behaviour without fibre broken in accuracy and that there are high correlations between the EC and TC data and the tensile parameters should be calculated using the EC method rather than the ED method with the exception of the bundle initial modulus. The relationships between blend ratios and the tensile properties of blended fibre bundles can be used to select the optimum blend ratio of blended tops or yarns.     

Analytical Algorithms for the Blend Ratios by Fibre-bundle Tensile Curves Part Ⅱ:Calculations of the Modulus Method and the Percentage Method

The principles for the modulus method and the percentage method are established and discussed in the part following Part Ⅰ of the series papers, in which we proposed the various algorithms of the strength method and the work method. The samples of Wool/PET blended fibre bundles,the method of fibre-bundle tensile tests and the typical specific stress-extension curves from the fibre bundles with different blend ratios are the same as in Part Ⅰ. Itcan be found that the theoretical results estimated by the modulus and percentage methods accord with the experimental values highly though the calculations of the two methods are slightly more complex than those of the strength and work methods. Especially, using the modulus method can not only avoid the influence of the error caused by the determination of the tensile curve of no fibre breaking in stretching, Y (e), but also need not to know the tensile curves of mono-component fibre bundles in certaincalculation. The latter advantage of the modulus method exists in the percentage method too, but it should adopt the improved calculation of ones.     

Estimation of Single-fibre Tensile Properties from the Bundle Tensile Curve of Polyester Fibres

Fibre bundle tensile curves can be used to characterise fibre processing properties and end-use performance directly and to predict single-fibre properties in theory. In this paper, the tensile behaviour of polyester fibre-bundles has been analysed in characteristic values and diagramming. The characteristic distributions which include the symmetry distribution on right part, SRBS‘(e), on left part, SLBS‘(e) and the curve on base-line modification, MBS‘(e),based on the modulus distribution, BS‘(e), as well as thefrequency density function of broken fibres, B‘(e), havebeen derived from the tail of bundle tensile curves. Thetheoretical and measured results show that the mostimportant curves are MRS‘(e) and B‘(e) and can be usedto estimate the breaking-extension distribution of singlefibres. Especially for MRS‘(e), the modulus distributioncan accurately characterize single-fibre tensile propertiesand is no limitation as the calculation of B‘(e) because thebundle specific stress Y(e) of no fibre breaking at extensione should be found at first.     

Relationships between the Tensile Properties and Tenacity-extension Behaviour of Fibre-bundles

Fibre bundle testing is different from single-fibre measurement, not only in testing methods and instruments, but in the results obtained. For wool fibres, Sirolan-TENSOR can supply fibre-bundle tenacity (BS) and bundle extension ( BE), but has some limitations on the analysis of the measured tensile curves of fibre bundles. It has not only raised new parameters, such as initial modulus (BM) and specific work of rupture (BW), as well as the specific work before or after the peak-point(WBP or WAP) and the ratios of WAP/WBP and WAP/BW, but also compared the tensile behaviour of different fibre-bundles, e.g. wool, polyester and viscose rayon fibre-bundles. The experimental results from 32 lots of wool tops show that there are correlations between bundle tensile properties, such as BS-BE, BS-BM, BS-BW, BE-BW and BM-BW. However, the variables of coefficients of variance (CV) are almost independent of each other and have no correlation with the average values of fibre bundle tensile parameters, except for BS-     

基于单纤维断裂值分布特征的高性能纤维弱节的表征

纤维弱节是影响纤维性能和质量的决定性因素，虽弱节的理论和测量方法已有报道，但弱节的表征仍存在困难。本文并以PBO纤维和Nomex纤维为例，采用拉伸试验和形态观察相结合的方法，对纤堆的强力、应力、伸长率和断裂比功分布进行了讨论，得到了纤维的弱节率。这对纤维弱节形式的认识和纤维性能的改进具有参考价值。     

羊毛纤维的结构弱节及力学行为

纤维结构弱节决定纤维的力学性能。本文提出的断裂端特征的SEM观察及该纤维对应拉伸性质的组合分析方法，可获得羊毛纤维结构弱节及破坏的特征与证据。实验证明，依据拉伸曲线和断裂端形貌特征可知羊毛纤维的弱节结构主要表现为集中缺陷结构、细颈弱结构、机械损伤弱结构和散布缺陷结构，其与力学行为和形态弱节存在很好的相关。缺陷散布性弱节结构，应该引入曲线的抖动特征或临界断裂功判定依据。     

Effect of Testing Conditions on Fibre-Bundle Tensile Properties Part Ⅱ: the Gauge Length and Elongation Speed in Wool Fibre Bundle Measurement

The testing conditions of a fibre bundle tensile tester (TENSOR) are elongation speed (ES), gauge length (GL), pretension, jaw pressure, environmental temperature and relative humidity, instrument linearity and sensitivity. The effects on fibre-bundle tensile properties at different GL and ES have been discussed in detail and compared with Peirce's theories on the weaklinks and the breaking time effect. The experimental results indicate that the tensile properties of fibre bundles are strongly affected by GL and vary with different GL. The reasonable GL should be 5-15mm rather than 3.2mm for wool bundle measurements. The ES ranging from 20mm/min to 40mm/min is beneficial for obtaining comparatively stable and accurate tensile values, whereas 20 mm/min used in current testing for wool fibre bundles is at the lower limit of the suggested range. For bundle modulus measurement, the sampling interval must be selected appropriately. The new calculation of the sampling interval has been established.     

建筑PVC膜材双轴正交拉伸循环试验

通过对PVC膜材进行7种应力比下的双轴正交拉伸循环试验,经纬向应力比值分别为0∶1,1∶5,1∶2,1∶1,2∶1,5∶1和1∶0,对膜材在双轴拉伸作用下的拉伸特性进行了研究.试验表明,经过3次循环作用后,膜材的力学试验性能更接近工程实际情况,且材料具有非线性和正交各向异性.在循环荷载作用下,初次循环后残余应变较大.随着循环次数的增加（一般3次后）,残余应变趋于常数,滞回曲线形状趋于稳定.采用双轴拉伸试验方法测定了PVC膜材的广义泊松比,验证了广义泊松比的非线性特征.试验证明,当经纬向应力比C≥1时,经向应变为正值;当C≥0.5时,广义泊松比变为负值;当应力比C为1∶0或0∶1时,双轴变成单轴试验,广义泊松比测定变成常规泊松比试验.理论和试验均证明当C1时,膜材的经向和纬向同时具有最大的弹性模量.     

混煤燃烧特性及污染物形成规律的研究

采用热天平和滴管炉对几种单一煤及混煤的着火、燃烧、燃尽特性进行了测定,初步分析了挥发分含量及混合比对混煤燃烧性能的影响;同时对混煤的灰渣形成特性和NO_x形成规律进行了研究.根据试验结果,用模糊数学方法进行综合评判,确定了最佳混合比,为大型电站锅炉混煤燃烧的安全、经济和清洁运行提供了科学依据.     

织物起球与纤维力学性能的关系

在影响织物起球性能的各种纤维性能中，除纤维的几何形态（线密度、截面形状、长度等）之外，经过测试研究分析筛选出来的主要影响因素是纤维的重复弯曲疲劳强度、重复扭转疲劳强度、拉伸断裂相对强度、拉伸断裂伸长率和拉伸初始模量．后者与织物的手感也有很密切的关系．本文研制了学纤维重复弯曲疲劳测试仪、单纤维重复扭转疲劳测试仪，优选了它们的测试条件参数，先后测试了绵羊毛，山羊绒、马海毛等纤维和２０余种化学纤维的性能，并经过优选工艺，对由１３种纤维纯纺或混纺生产的７种毛型梭织物进行了起球规律的测试、试穿和研究，发现在研究中织物的穿着起球效果与客观测试中随摩擦次数球粒数变化的曲线下积分值相关最密切．最后对纤维五种力学性能与织物起球曲线下积分值进行了主成分析和多元回归分析，获得了由纤维力学性能评价织物起球性能的预测方程式．     

羊毛单纤维性质对束纤维强伸性的影响

对21种澳大利亚羊毛进行单纤维性质测量,其包括纤维的直径及其离散、纤维卷曲性质和纤维强伸性质.同时采用SIROLAN-TENSOR对此类羊毛做束纤维力学性质测量.通过实验结果的对比分析得到,单纤维强伸性与束纤维强伸性存在线性相关,纤维直径和卷曲也与束纤维强度和伸长有较好的相关.因此采用束纤维力学指标表征单纤维性质,在理论和实用上都是可行的.     

超塑性薄壁圆筒拉扭作用下应力分析

超塑性材料具有延伸率非常高,可以形成复杂结构件等优点,已得到广泛应用．用塑性增量理论研究了超塑性材料薄壁圆筒受拉扭作用下的应力和应变率之间的关系．导出拉扭问题中,拉应力与切应力之比,等于它们相应的应变率比值K的3倍．讨论了在拉扭等比例应变率加载情况下,正应力和切应力的变化规律;讨论了当应变率相同的情况下,拉扭正应力与单向拉伸正应力之比,拉扭切应力与纯扭转切应力之比的变化规律．计算结果表明：应变率s：越大,以应力值越大．随着应变速率敏感性指数m的增加,az应力值减小,较大的m值使应力σz变化趋缓,较大的应变率εz使σz应力值变化较大;     

混煤燃烧特性的热重实验

将洞口和平煤分别与邵阳岩头岭、武冈龙坪老矿煤在不同配比下得到的混煤在STA449F3型热重分析仪中进行热重实验,利用热重分析法对两种不同掺烧方式下的混煤进行燃烧特性实验研究,分析两种掺混方式下混煤的着火温度和可燃性,并对其燃尽特性和综合燃烧特性进行研究,研究结果表明,各混煤的着火特性、燃烧特性和综合燃烧特性都是随着易着火煤种比例的增加而有所改善,通过对各项性能的分析,确定了混煤的最佳掺配比。     

Effect of Testing Conditions on Fibre-Bundle Tensile Properties Part Ⅰ: Sample Preparation, Bundle Mass and Fibre Alignment of Wool Bundles

Due to the effects of samples and testing conditions on fibre-bundle tensile behaviour, it is necessary to investigate the relationships between experimental factors and tensile properties for the fibre-bumdle tensile tester (TENSOR). The effects of bundle sample preparation, fibre bundle mass and fibre alignment have been tested. The experimental results indicated that (1) the low damage in combing and no free-end fibres in the cut bundle are most important for the sample preparation; (2) the reasonable bundle mass is 400- 700tex, but the tensile properties measured should bemodified with the bundle mass because a small amount of bundle mass causes the scatter results, while the larger is the bundle mass, the more difficult to comb fibres parallel and to clamp fibre evenly; and (3) the fibre irregular arrangement forms a slack bundle resulting in interaction between fibres, which will affect the reproducibility and accuracy of the tensile testing.     

毛竹纤维鞘的拉伸力学性能

以成熟毛竹为研究对象,在显微镜下从竹纤维鞘中成功切割出竹纤维束拉伸试样,并应用微拉伸技术测量其纵向拉伸强度和模量。通过对机械剥离的单根维管束以及竹片小试样进行拉伸对比,获得竹纤维鞘拉伸弹性模量和强度的间接测量值和计算值。结果显示,竹纤维束的拉伸弹性模量和强度平均值分别为42.72 GPa和729.25 MPa,介于竹纤维鞘的间接测量值和计算值之间,并与已有的研究结果也吻合得较好,表明竹纤维束试样的测试结果可以代表竹纤维鞘的整体力学性能。同时,笔者提出了在细观尺度下研究竹子力学特性的关键实验技术。     

Effect of Testing Conditions on Fibre-Bundle Tensile Properties-Part Ⅱ: the Gauge Length and Elongation Speed in Wool Fibre Bundle Measurement

ＩｎｔｒｏｄｕｃｔｉｏｎＩｎＰａｒｔⅠｏｎｔｈｉｓｔｏｐｉｃ ,ｗｅｈａｖｅｍｅｎｔｉｏｎｅｄｔｈｒｅｅｓｏｒｔｓｏｆｔｈｅｆａｃｔｏｒｓｗｈｉｃｈａｆｆｅｃｔｔｈｅｒｅｓｕｌｔｓｏｆｆｉｂｒｅｂｕｎｄｌｅｔｅｎｓｉｌｅｔｅｓｔｉｎｇａｎｄａｎａｌｙｓｅｄｔｈｅｅｆｆｅｃｔｏｆｔｈｅｆｉｒｓｔｓｏｒｔｏｆｔｈｅｆａｃｔｏｒｓ,ｎａｍｅｌｙｆｉｂｒｅ ｂｕｎｄｌｅｍａｓｓ,ｆｉｂｒｅａｌｉｇｎｍｅｎｔｉｎａｂｕｎｄｌｅａｎｄｃｌａｍｐｉｎｇｐｒｅｓｓｕｒｅｏｆｊａｗｓ[1] ,ａｓｗｅｌｌａｓｔｈｅｂｕｎｄ…     

TENSILE BEHAVIOUR OF ROTOR SPUN YARNS

This paper deals with the tensile behaviour of rotor spun yarns. Having regard to the spe-cial construction of rotor spun yarn, some modifications for Hearle's theory have been made inorder to apply Hearle' s theory to rotor spun yarn. The paper then goes into calculating thetensile curve and investigating the effect of main parameters and spinning conditions on thetensile behaviour of rotor spun yarn. It was found that the following facts are noteworthy forimproving the mechanical properties of rotor spun yarn: (1) Selecting suitable navel so as tocontrol the P. T. E. length within a reasonable range. (2) Improving the design of single fibresupply device to decrease the amount of spoiled fibre and hence increase the effective fibrelength. (3) Increasing spinning yarn tension without yarn break to enhance the fibre migrationratio. (4) For the rotor spun yarn of industrial use, it is the way to increase the yarn strengththat the rotor groove should be designed with the groove angle beneficial to decrease the yarnspecific volume.     

纤维弱节的力学特征与判定

纤维弱节是造成纤维力学性能退化和纤维品质下降的主要原因。这里采用单纤维拉伸和形态轮廓观察结合的方法，对羊电纤维弱节的力学行为进行表征。提出了用纤维细节处的平均断裂应力σ^-和断裂应变ε^-，作为纤维弱节的判断的依据。并对羊电的细节断裂、弱节断裂，非弱节(正常)断裂的概率作了实到和理论计算，其结果分别为印％、奶％和印％。这征明作者采用的单纤维性能分析仪(SIFAN)法和显微图像加单纤维强力仪(OM XQ)法的实用性与有效性。     

飞艇用层压织物膜材料在双向应力作用下的弹性参数分析

为揭示双向应力作用下飞艇用层压织物膜材料弹性参数的响应特征,针对高性能蒙皮材料Uretek3216LV~进行了一系列双轴拉伸试验,获得了9种应力比例条件下的应力-应变关系数据,并分析了其非线性及正交异性特征;采用膜材料试验标准计算了膜材料的弹性参数,分析了应力比及应力比组合对弹性参数的影响规律;运用Matlab软件进行数值分析,得出应力空间的弹性参数响应曲面特征,并提出应力空间弹性参数加权平均值的计算方法,研究了在不同应力水平及应力比下弹性参数的变化规律.结果表明:层压膜材料的弹性参数之间无耦合关系,正交互补性质在其本构关系上的适用性不足;膜材料的变形特征及弹性参数受应力比及应力比组合的影响显著,且均呈现出明显的非线性及正交异性特征;在飞艇结构设计中,宜根据膜材料所属结构部件的应力比分布特征,选取包含相应应力比的组合项来求取弹性参数,以提高弹性参数计算的稳定性和可靠性.