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961.
Li Yan 《Acta Mechanica Solida Sinica》2005,18(4):334-339
In this study, the residual strength of sisal textile reinforced vinyl ester resin is studied using specimens with a central hole. Two kinds of chemicals, silane and permanganate, are used to treat sisal fibre surfaces. The effects of fibre surface treatments on the residual strength of sisal fibre reinforced composites with different central hole sizes are analysed. Optical microscopy (OM) surveys provide sound evidence for the relationship between residual strength properties and fracture morphologies of sisal textile reinforced vinyl ester. Several theoretical models used to predict the residual strength of laminated composites are briefly reviewed. Point stress criterion (PSC) and average stress criterion (ASC) models are used to analyze the mechanical properties of sisal textile reinforced polymers with a central hole in this research. Material constant, characteristic length (d0 or lc), is obtained and used to analyze the mechanical behavior of the composites. The residual strength of the composites predicted by PSC and ASC models is in good agreement with the experimental results.. 相似文献
962.
飞机复合材料层压板结构中的广义强度准则 总被引:1,自引:0,他引:1
通过对经典复合材料结构强度理论和准则在层压板上的适用性计算和试验对比研究,指出了在层压板上采用经典强度理论所得计算结果与试验结果的差异。并分析了产生这种差异的原因,主要是经典强度准则表达武中采用的无拉剪耦合假设和层与层之间理想粘接假设,只适用于单层板或正交各向异性板。本文提出了一种广义强度准则的思想,其核心是放松正交各向异性约束条件和通过试验测定强度参数,而在实际飞机结构中的准正交各向异性层压板结构设计上仍可使用经典层压板强度准则。 相似文献
963.
大多数结构用铝合金通常要经过热处理或加工硬化以得到更高的力学性能.这种合金焊接后,焊接热会使焊缝附近局部区域(称为热影响区HAZ)强度降低.这一特点使得焊接铝合金梁构件极限承载力的研究与焊接钢梁构件相比变得更为复杂.由于我国目前还没有关于铝合金结构的设计规范,为此本文对两种典型的纵向焊接工字型截面铝合金梁构件进行了试验研究,并在参考国外规范的基础上,提出了适用于静力设计的纵向焊接铝合金梁设计公式的建议.通过对试验构件进行数值分析,验证了有限元分析焊接梁的可靠性.在此基础上进行了大量的数值分析,并将试验结果及有限元计算结果与公式计算结果进行了比较,可以看出建议公式计算结果富有较大安全度,从而验证了其适用性,为我国《铝合金结构设计规范》的编制提供了依据和参考. 相似文献
964.
965.
966.
A. M. Kovrizhnykh V. D. Baryshnikov A. V. Manakov A. F. Nikitenko 《Journal of Applied Mechanics and Technical Physics》2007,48(6):871-877
It is proposed to construct long-term strength and creep relations for metals on the basis of the Coulomb-Mohr criterion.
The creep equations and the long-term strength criterion for plane stress are analyzed in detail. Results of long-term strength
calculations are compared with data of experiments with metallic materials. It is established that theoretical and experimental
results are in satisfactory agreement.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 6, pp. 115–123, November–December, 2007. 相似文献
967.
Yu. I. Meshcheryakov A. K. Divakov N. I. Zhigacheva M. M. Myshlyaev 《Journal of Applied Mechanics and Technical Physics》2007,48(6):887-896
Shock tests of two lots of a 1420 aluminum-lithium alloy are performed. The mean grain size is 24 μm in the first lot and
1.6 μm in the second lot obtained by the method of equal-channel angular pressing. Two characteristics of dynamic strength
of the material were determined in experiments on the high-velocity impact of flat samples: threshold of dynamic stability
with respect to compression on the fore front of the compression pulse and spall strength of the material. The materials of
both types have an identical threshold of dynamic stability with respect to compression, whereas the spall strength of the
microcrystalline alloy is 20% greater than the spall strength of the polycrystalline alloy. The reason is the consumption
of energy on structure formation in the coarse-grain material in passing to a larger-scale structural level (in the case with
a fine-grain material, such a structure is available in the initial state). The experiments reveal the presence of a second
plastic front whose amplitude is approximately 10% of the first plastic front.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 6, pp. 135–146, November–December, 2007. 相似文献
968.
变温下橡胶材料力学性能的实验分析 总被引:1,自引:0,他引:1
利用Zwick020材料试验机研究了天然橡胶材料在不同温度条件下单向拉伸的大变形力学行为。得到了不同温度和不同加载速率条件下材料的应力-应变关系曲线和材料的破坏条件,由此分析了高温和低温的温度变化条件及加载速率对材料力学性能的影响,得出天然橡胶材料在大变形条件下的温度和加载速率敏感特性。同时利用实验结果拟合出材料的应变能函数,并应用热超弹性模型对材料进行了理论分析。结果表明,理论分析结果与实验结果仅在一定温度范围内吻合得较好,因为材料软化或硬化,在很高或很低的温度情况下二者有一定差别。 相似文献
969.
Rebounding of a shaped-charge jet 总被引:1,自引:0,他引:1
E. V. Proskuryakov M. V. Sorokin V. M. Fomin 《Journal of Applied Mechanics and Technical Physics》2007,48(5):633-635
The phenomenon of rebounding of a shaped-charge jet from the armour surface with small angles between the jet axis and the
target surface is considered. Rebounding angles as a function of jet velocity are obtained in experiments for a copper shaped-charge
jet. An engineering calculation technique is developed. The results calculated with the use of this technique are in reasonable
agreement with experimental data.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 5, pp. 17–20, September–October, 2007. 相似文献
970.
A PREDICTIVE APPROACH TO THE IN-PLANE MECHANICAL PROPERTIES OF STITCHED COMPOSITE LAMINATES 总被引:1,自引:0,他引:1
Zhang Junqian Wei Yuqing 《Acta Mechanica Solida Sinica》2007,20(2):130-140
This contribution attempts to model the alteration of the in-plane elastic properties in laminates caused by stitching,and to predict the in-plane effective tensile strength of the stitched composite laminates.The distortion of in-plane fibers is considered to be the main cause that affects the in-plane mechanical properties.A fiber distortion model is proposed to characterize the fiber misalignment and the fiber content concentration due to stitching.The undistorted region,the fiber distortion region,the resin-rich pocket and the through-thickness reinforcement section are taken into account.The fiber misalignment and inhomogeneous fiber content due to stitching have been formulated by introducing two parameters,the distortion width and maximum misalignment.It has been found that the ply stress concentration in stitched laminates is influenced by the two concurrent factors,the stitch hole and inhomogeneous fiber content.The stitch hole brings about the stress concentration whereas the higher fiber content at the local region induced by stitching restrains the local deformation of the composite.The model is used to predict the tensile strength of the [0/45/0/-45/90/45/0/-45]_(2s) T300/QY9512 composite laminate stitched by Kevlar 29 yarn with different stitching configurations,showing an acceptable agreement with experimental data. 相似文献