Tensile strength prediction of irregular fibres using diameter-dependent Weibull analysis

A modified Weibull model incorporating the within-fibre diameter variation is applied to examine the fibre diameter effect on the strength of single fibres. Australian Superfine Merino Wool (ASFW) and Inner Mongolia Cashmere (IMC) were used in the present work, since these animal fibres tend to have relatively large diameter variations. To determine single fibre strength, tensile measurements were carried out for fibres with diameters varying between 9 and 21?μm at a constant gauge length. It was found that an increase in the diameter disparity along the fibre reduces the strength of fibres. To validate this, the accuracy of predicting weak-link scaling was evaluated; the results showed that the application of modified Weibull distribution gives a better relationship with the empirical data than the standard Weibull model. The results suggest that the modified Weibull model is more accurate in predicting the size dependence and strength of single fibres with diameter variations.     

Tensile strength of spruce glulam

Comparative tests on spruce glulam members subject to tension and bending, respectively, were numerically simulated to determine the tensile-to-bending-strength ratio. Nine different grading methods were applied to cover a wide strength range. They are based on visual inspection and mechanical determination of density and MOE. The simulated tensile and bending strength values result in an almost constant tensile-to-bending-strength ratio of 0.88. The ratio is valid for fifth percentile values and for standardized tests with prescribed member sizes. It is independent of the grading method used. In addition the size effect in glulam tension members was numerically studied. The results show a strong dependence of the glulam tensile strength upon the length subject to tension in case of short members. The dependence slowly wears off in case of long members. The tensile strength for members 150 mm in length is 140 percent of the reference value. The limit strength for a quasi-infinite length is about 80 percent.     

角联锁织物的拉伸性能分析

介绍了角联锁织物的结构特点,采用小样箭杆织机织造了层数为2层、3层到9层的角联锁织物共8块,探讨了角联锁织物的拉伸性能与其结构层数之间的关系。结果表明,随着角联锁织物层数的增加,其断裂伸长率也会随之增加,但到一定层数时,断裂伸长率反而出现降低趋势。     

Tensile strength and the tenderness of beef sternomandibularis muscle

In their relationship to shortening, the tensile strength of cooked meat along the fibres and the shearing force measured across them are strikingly similar. Both increase to maximum values at 40% shortening before falling by a half with an approach to 60% shortening. A high correlation (r = 0·81) exists between the two sets of values, whether toughness is increased by cold shortening or reduced by ageing. The mechanical strength of meat along its fibres is therefore a simple measure of tenderness and a useful basis for relating muscle structure to stength.     

Tensile strength properties of particle boards at different temperatures and moisture contents

The equilibrium tensile properties of urea-formaldehyde (UF)- and phenol-formaldehyde (PF)-bonded particle boards have been studied at moisture contents between 1 and 33% and at temperatures between ?15°C and +45°C. These conditions may occur e.g. during exterior use of the boards. The tensile strength and the modulus of elasticity decrease slightly while the strain at rupture increases slightly between 1% and 7% moisture content. These effects are similar for UF- and PF-bonded boards. Above 7% moisture content the tensile strength and the modulus of elasticity decrease markedly while the stretch at rupture increases with increasing moisture content. These changes are more pronounced for UF-bonded boards. The bending stiffness is less affected than the modulus of elasticity since the board thickness increases with increasing moisture content. The tensile properties are not significantly affected by the temperature at low moisture contents, but at high moisture contents the combined effects are more pronounced. The effect of moisture is generally stronger than that of temperature, in the range studied.     

Heat-induced gelation of myosin in a low ionic strength solution containing L-histidine

Binding properties are important for meat products and are substantially derived from the heat-induced gelation of myosin. We have shown that myosin is solubilized in a low ionic strength solution containing l-histidine. To clarify its processing characteristics, we investigated properties and structures of heat-induced gels of myosin solubilized in a low ionic strength solution containing l-histidine. Myosin in a low ionic strength solution formed transparent gels at 40-50 °C, while myosin in a high ionic strength solution formed opaque gels at 60-70 °C. The gel of myosin in a low ionic strength solution with l-histidine showed a fine network consisting of thin strands and its viscosity was lower than that of myosin in a high ionic strength solution at 40-50 °C. The rheological properties of heat-induced gels of myosin at low ionic strength are different from those at high ionic strength. This difference might be caused by structural changes in the rod region of myosin in a low ionic strength solution containing l-histidine.     

3种离子强度下pH值对罗非鱼肌球蛋白溶解度及分子构象的影响

研究了3种离子强度下,不同pH值(2.0~12.0)对罗非鱼(Oreochromis niloticus)肌球蛋白溶解性、表面疏水性、SDS-PAGE及α-螺旋含量的影响。结果表明,在实验范围内,离子强度增大使肌球蛋白等电点向酸性方向偏移,在低离子强度(1 mmol/L KCl)、生理离子强度(150 mmol/L KCl)及高离子强度(600 mmol/L KCl)条件下,其溶解度最小的pH值分别为5.5、5.0和4.5,极端酸性(pH 2.0)和碱性(pH 11.0~12.0)条件下,肌球蛋白溶解度较高(80%);在中性和高离子强度条件下,分子表面疏水性低,α-螺旋含量高,稳定性较好;酸诱导去折叠过程中,在等电点附近表面疏水性较低,在偏离等电点的酸性条件下,表面疏水性增加,而极端酸性条件下展开的肌球蛋白分子可能会发生折叠,分子降解及静电相互作用导致溶解度增大;碱诱导去折叠过程中,表面疏水性随pH值的升高而增加,肌球蛋白重链通过二硫键形成聚合物;在中性、碱性和极端酸性条件下,α-螺旋含量随着盐浓度的增加而增大,高盐对肌球蛋白的二级结构有保护作用。总体分析,在高盐浓度和极端碱性条件下,肌球蛋白呈现"熔球态"构象。     

不同离子强度下罗非鱼肌球蛋白热变性聚集研究

以罗非鱼肉为原料,提取肌球蛋白,分析不同离子强度(1、50、150、300、600 mmol/L KCl)下热处理(40~80℃,1℃/min)对其浊度、溶解度、表面疏水性、α-螺旋含量及聚集体粒径的影响。结果显示,离子强度及热处理温度明显影响肌球蛋白的热变性聚集。在低离子强度(1~150 mmol/L KCl)下,肌球蛋白聚集成纤丝,溶解性差,热处理后分子聚集沉淀,溶解度和α-螺旋含量减小(p0.05),体系热稳定性差;在高离子强度(300~600 mmol/L KCl)下,肌球蛋白分子解离成单体,溶液澄清,当热处理温度高于50℃时,肌球蛋白溶解度下降,表面疏水性增加,α-螺旋含量显著减小(p0.05),但分子聚集不明显。总体分析,高盐离子的静电屏蔽作用导致肌球蛋白纤丝解离,由此也会对肌球蛋白分子结构有一定的保护作用,热稳定性相对较好。     

拉伸速率对经编土工格栅拉伸特性的影响研究

文章通过对4种不同强度的经编聚酯土工格栅开展室内单轴拉伸试验,研究了拉伸速率对其拉伸性能的影响。试验结果表明:在单轴拉伸过程中,拉伸速率对不同标称抗拉强度土工格栅的影响不同,但4种土工格栅的拉伸曲线具有相似性,说明土工格栅经纬向纱线的拉伸失效机制具有相似性,破坏时应变均在10%以上。随着拉伸速率的增大,土工格栅的拉伸强度增加,峰值应变减小,割线拉伸模量增大。试验结果对加筋结构内部力学机制的分析具有重要的参考价值。     

样品长度和拉伸速度对生丝拉伸试验结果的影响

通过采用不同的丝样品固定方式、丝样长度、拉伸速度进行生丝拉伸试验,比较分析测得的主要性能指标,探索了一种正确评价生丝机械性能的拉伸试验方法.结果表明:不牢固的丝样品固定方式下测得的强度和初始模量偏低,伸长率和断裂功不稳定,用速干胶水固定的效果最好.当试验丝样品长度增加时,测得的初始模量变化不大,强度和伸长率下降.随丝样品长度的增加按比例提高拉伸试验速度,可以减小不同的丝样长度间的断裂强度、断裂伸长率、初始模量的差异.在4种评价指标中,初始模量的波动最小.     

Tensile Characteristics of Squid Mantle

The mechanical properties of cooked and uncooked mantles of Loligo pealei and Illex illecebrosus in uniaxial tension were characterized by strength, strain at failure, overall stiffness and curvature of corrected stress vs strain relationships which is associated with degree of strain hardening. All four parameters differed at different orientations to the squid's principal axis. Uncooked mantle was considerably stronger and stiffer in the longitudinal direction, showed a higher degree of strain hardening, but sustained a smaller prefailure strain. Cooking at 60°C and 100°C had a much more drastic effect on the mechanical behavior of longitudinal specimens than on the transverse. These anisotropic mechanical features are attributed to the orientation of the collagen fibers of squid.     

Dynamic rheological measurements on heat-induced myosin gels: Effect of ionic strength,protein concentration and addition of adenosine triphosphate or pyrophosphate

Myosin solutions and suspensions have been monitored during heating at pH 6.0 by using dynamic rheological measurements. The storage modulus (G′), the loss modulus (G) and the phase angle (δ) all showed a marked dependence on ionic strength in the temperature range 25–75°C. The filamentous gels (ionic strength <0.34) displayed a temporary reduction in G′ at temperatures between 50 and 60°C, presumably due to denaturation in parts of the rod portion of the myosin molecule. In the same temperature region the concentration dependence of G′ changed by a power of 2. The loss modulus also showed a marked concentration dependence, while the phase angle varied with concentration primarily at low (<50°C) temperatures. For the final gels, heated to 75°C, only G′ indicated marked differences due to different protein concentrations and ionic strengths; all gels were almost completely elastic (δ?1°). Adenosine triphosphate was shown to have a pronounced temporary effect on the filamentous gel formed at low temperatures, i.e. on the gel with the highest concentration dependence, while pyrophosphate had no such effect. However, both adenosine triphosphate (or rather its hydrolysis product: adenosine diphosphate) and pyrophosphate appeared to have a small, lasting effect on the heat-gelling ability of myosin: the former a detrimental effect, the latter an improvement.     

原纱抗拉强度的讨论

通过ＴＥＮＳＯＪＥＴ单纱强力仪试验、对原纱细节与断裂强力弱环（断裂点）之间的相关关系以及因细节造成强力弱环对喷气织机停台的影响进行了分析。指出：在织造过程中,细节是引起原纱断裂的主要因素;当原纱强力弱环的强度为４．０ｃＮ／ｔｅｘ及以下时,原纱发生断裂;当原纱伸长率弱环处的伸长率等或小于２％时,原纱也必须断裂。为喷气织机用纱提供了参考指标。并对在纺纱生产中如何减少细节疵点进行了讨论。     

Interaction of cationic starch derivatives and cellulose fibres in the wet end and its correlation to paper strength with a statistical evaluation

The adsorption onto a softwood pulp of cationic modified starches with a degree of substitution (DS) ranging from 0.015 to 0.130 and native potato starch was investigated using a method based on size exclusion chromatography‐multi angle laser light scattering (SEC‐MALLS). This technique provides information about the amount and molecular composition of the adsorbed starch product such as the AP–AM‐ratio, the average MW and molar mass distribution. Factors influencing adsorption, like the electrolyte content in the suspension and the initial starch polysaccharide concentration, were investigated. Furthermore, hand sheets were made and the resulting mechanical paper strength was tested. Results were analysed statistically using analysis of variance. Representative results were discussed in detail. In general, low‐substituted cationic starch (DS 0.030) exhibited a higher degree of adsorption and resulted in high paper strength when there was a low electrolyte content in the starch–pulp‐suspension. However, high amounts of electrolytes impeded electrostatic interaction of the charged groups of the starch polysaccharides and cellulose fibre due to partial screening and therefore strongly limited adsorption. This resulted in lowered mechanical paper strength. The water quality of the suspensions had little impact on the polyelectrolyte adsorption of the highly substituted cationic starch (DS 0.100). However, paper strength was markedly higher in the case of starch adsorption where there was a high ionic content and when both starch polysaccharides–AP and AM– were adsorbed. The initial starch concentration determined starch adsorption both quantitatively and qualitatively and subsequently paper strength as well. The relation between adsorption behaviour and paper strength was discussed, particularly in the case of 6% initial starch concentration. In deionised water (DW), the low‐substituted starch (DS 0.03) adsorbed onto the pulp to a greater extent with an AP–AM‐ratio similar to that of the initial starch. Moreover, this achieved the best strength properties in contrast to 36 dGH, where less starch adsorbed and that being almost exclusively AP. In water with 36 dGH, the highly substituted starch (DS 0.100) with both the AP and AM was absorbed and this resulted in higher paper strength. In contrast, AM was almost exclusively adsorbed in DW. Increasing the initial starch concentration increased the amount adsorbed while subsequently changing the AP–AM‐ratio towards increased AM adsorption and decreased AP adsorption in the case of DS 0.100 in DW. Exclusive adsorption of AM markedly lowered the development of the paper strength.     

纸巾纸湿抗张强度的测定

对GB/T20808-2006中5.6.1纸面巾、纸餐巾、纸手帕、纸香巾纵向湿抗张强度的测定方法中热处理的必要性进行了比对试验,以找出内中的联系.     

棉纱拉伸性能的评价

本文研究了延伸速率对棉纱拉伸性能的影响 ,阐明了用 Uster Tensorapid-3和 Uster Ten-sojet测得的棉纱不同强力伸长指标间的关系。据观察 ,从这两种纱线强力伸长测试仪得到的结果有很好的相关性。不同支数棉纱的强力—时间系数和断裂伸长—时间系数平均值可由 Meredith提出的公式导出。超过 50英支的高支纱 ,强力—时间系数和断裂伸长—时间系数的绝对值随纱线细度的提高而减少。1　引　言　　在纱线可测量的机械性质中 ,拉伸强力和断裂伸长值受到相当重视 ,因为短纤纱的这些性质会影响织机和针织机械的效率及其织物的质量。但纱线的拉伸…     

芳纶织物-树脂复合材料的动态拉伸实验研究

利用三段直拉式Ｈｏｐｋｉｎｓｏｎ杆,获得了弹道防护用芳纶织物复合材料高应变率下力学性能的数据,讨论了应变率对芳纶织物复合材料力学性能的影响。     

经编间隔织物的拉伸特征

为探讨经编间隔织物的拉伸特征,选取4种不同结构的织物进行拉伸试验,分析了各织物及其上下表面层的断裂强力、断裂伸长和拉伸曲线特征,解释了经编间隔织物的拉伸机制和三维尺寸变化规律,并从织物层角度讨论对拉伸强力和断裂伸长的影响。实验结果表明:间隔织物三维尺寸的变化在拉伸过程中呈现出不同的规律;断裂伸长较小的间隔织物表面在拉伸过程中会率先发生断裂;间隔层对间隔织物的拉伸强力和断裂伸长影响较小,但会延长间隔织物拉伸断裂过程;上下表面层的强力和伸长数值及其大小关系共同决定着间隔织物的断裂强力和断裂伸长。     

Anisotropy in Tensile Properties of Mozzarella Cheese

Effects of sampling direction (parallel or perpendicular to protein fiber orientation), cheese type (low-moisture, part-skim, LMPS and reduced fat, RF) and deformation rate (5 and 25 cm/min) on fracture properties of Mozzarella cheese were determined with tensile tests. The fracture toughness, stress, and strain in the parallel direction were, respectively, 2.8, 2.1 and 1.4 times greater than those in the perpendicular direction. This verified that the Mozzarella cheese had anisotropic tensile properties. A composite-material approach was used to explain the direction-dependent properties. The toughness, stress, and strain values for RF cheese were, respectively, 5.9, 5.4, and 1.3 times those of LMPS cheese. The tensile properties of Mozzarella were also affected by deformation rate.     

精干罗布麻纤维的拉伸性能

探讨了常态下和热处理后精干罗布麻单纤维的拉伸性能。着重探讨了处理温度、处理时间对纤维断裂强度、断裂伸长率以及断裂功的影响。随着处理温度的升高和处理时间的延长,纤维的断裂强度、断裂伸长率以及断裂功在整体上呈现下降趋势;与常态相比,120℃处理后纤维拉伸性能有明显下降;在180℃以上,纤维的以上指标下降程度增大;时间对纤维拉伸性能的影响小于温度,且在210℃时,纤维的各指标随时间变化明显。试验表明:精干罗布麻纤维的拉伸属高强高模低伸长类型,且纤维具有较好的拉伸性和较好的耐热性。