主承力缠绕管件轴压强度实验研究

缠绕复合材料管件已经在航空航天上用于大载荷主承力构件,为进一步提高这类管件的轴压强度,本文对影响缠绕管件轴压强度的一系列因素进行了实验研究,系统地探讨了提高缠绕管件轴压强的途径.研究表明,除了一般文献研究较多的缠绕角对管件轴压强度具有很大影响以外,一般文献很少涉及的环向缠绕层含量和端面边缘效应等因素也对缠绕管件的轴压强度有重要影响.在材料用量和缠绕角相同的前提下,把20%的角度缠绕层改为环向缠绕层后,轴压强度最大能够提高77%;采用缠绕方式对管件受压端头进行加强以后,可以有效地消除受压端面边缘效应的负面影响,亦可提明显高管件轴压强度.     

钛内衬复合材料环形气瓶结构设计与优化EI北大核心CSCD

根据微分几何,推导环形气瓶测地线缠绕轨迹以及缠绕角应满足的稳定缠绕条件,并针对不同切点数进行线型轨迹仿真。基于有限元分析,针对钛合金内衬环形气瓶的初始缠绕角及缠绕层数进行优化设计,并评估对比有、无环向补强层的环形气瓶承载能力。结果表明:本文设计的测地线轨迹精确可靠,很好地满足环形气瓶的缠绕工艺性。优化设计的缠绕参数既满足工艺可缠性,又能提高环形气瓶的结构性能。此外,有环向补强层的气瓶爆破强度提高了14%,钛合金内衬屈服强度提高了24.8%。因此,采用环向补强层有利于进一步提高环形气瓶的承载性能。水压实验结果表明本文设计方法预测的变形和爆破压力与实验值吻合良好。     

基于爆破试验的CFRP固体火箭发动机壳体的可靠性设计

根据GJB 1878-94制备了8个碳纤维缠绕复合材料压力容器，通过试验获得壳体的纤维强度、缠绕角、几何尺寸、爆破压强等随机变量特征值，利用这些实验数据对固体火箭发动机壳体进行可靠性设计，并与传统的安全系数法设计进行比较。结果表明，使用可靠性安全系数法设计可以实现安全性和经济性的统一。分析了材料的力学性能参数及壳体的几何参数等随机变量的变异系数对CFRP固体火箭发动机壳体爆破压强分散程度的影响。纤维应力、壳体纤维层厚度和壳体半径的变异系数的大小直接影响了爆破压强的分散程度；而纤维缠绕角除其变异系数的大小直接影响爆破压强的分散程度外，其参数均值也对爆破压强的分散程度有影响。     

多角度交替缠绕复合圆筒的剩余应力算法及水压试验

针对含薄壁钢内衬碳纤维增强聚合物基复合材料（CFRP）多角度交替缠绕复合圆筒的剩余应力计算问题,基于正交各向异性材料的厚壁圆筒理论和弹性叠加理论,提出了考虑卸去芯模影响的多角度交替缠绕下CFRP各层和钢内衬剩余应力的逐层叠加算法,研究了恒缠绕张力下,芯模厚度和螺旋层缠绕角对CFRP各层和钢内衬剩余应力的影响。计算表明：芯模厚度越大则CFRP层剩余应力越低,但芯模厚度过大将减弱缠绕张力对钢内衬的强化效应;螺旋层缠绕角约65°时,环向层剩余应力出现极小值,螺旋层剩余应力和内衬剩余应力均出现极大值。针对缠绕张力对钢内衬的强化效应,通过水压试验加载过程中钢内衬声发射特征与复合圆筒外壁应变测试,测得的钢内衬屈服载荷与理论预测值一致,基本证实了算法的有效性。为提高CFRP层缠绕质量,基于等剩余应力假设,提出了多角度交替缠绕张力制度优化设计思路,适用于内压管的张力制度优化。     

210m高钢筋陶泥混凝土内衬结构烟囱的爆破拆除

介绍了210m高、内衬为钢筋陶泥混凝土结构的钢筋混凝土烟囱的爆破拆除,该结构韧性好、强度高,预拆除及钻爆施工难度大。重点介绍了烟囱高位切口爆破时,在内衬钻孔施工困难的条件下,采用在筒壁与内衬的保温层上掏水平孔,用水平装药爆破内衬的方法,解决了高位切口内衬钻孔难的问题。爆破取得了良好效果,可为类似工程提供参考。     

210m高钢筋陶泥混凝土内衬结构烟囱的爆破拆除

介绍了210m高、内衬为钢筋陶泥混凝土结构的钢筋混凝土烟囱的爆破拆除,该结构韧性好、强度高,预拆除及钻爆施工难度大。重点介绍了烟囱高位切口爆破时,在内衬钻孔施工困难的条件下,采用在筒壁与内衬的保温层上掏水平孔,用水平装药爆破内衬的方法,解决了高位切口内衬钻孔难的问题。爆破取得了良好效果,可为类似工程提供参考。     

炭纤维复合材料及与钢内衬复合管状件轴向压缩性能研究

研究了不同材料体系、不同工艺条件制备的炭纤维复合材料管状件轴向压缩性能以及钢内衬外加炭纤维复合材料复合管状件的动态和静态压缩性能对比,结果表明,采用单向预浸料纵向(或轴向)铺层与纤维缠绕相结合的成型工艺较纤维缠绕工艺制备的管状件轴向压缩强度更高;钢内衬外加复合材料复合管状件的动态轴向压缩强度明显高于静态压缩强度,钢内衬...     

聚酰亚胺纤维与碳纤维缠绕复合气瓶性能对比研究

本文主要研究高性能国产聚酰亚胺纤维在复合材料气瓶上的应用,并表征其与进口碳纤维的性能差距.采用国产聚酰亚胺纤维进行缠绕成型工艺优化与复合材料性能测试分析,在测试数据及工艺优化基础上针对其进行了复合材料气瓶的强度设计.分别采用聚酰亚胺纤维、进口T300、T700以及T800碳纤维缠绕成型复合材料气瓶,进行水压爆破压强的测试,并引进声发射检测技术对其在水压过程中的损伤信号进行监测分析.结果表明聚酰亚胺纤维缠绕工艺性良好,与树脂界面结合优异,适用于湿法缠绕成型工艺.复合材料拉伸强度达到1 708 MPa,纤维的强度发挥率高达80%,相比于碳纤维复合材料其呈现出较好的断裂韧性,有利于减少复合材料气瓶在水压下的应力损伤.缠绕成型的聚酰亚胺纤维复合材料气瓶容器特征系数(PV/W)高达32.2 km,其在航空航天、医用、汽车、核工业等领域具有广阔的应用前景.     

专利技术

一种轻金属内衬玄武岩纤维全缠绕复合气瓶及其制造工艺,包括：一轻金属内衬;复合有环氧树脂材料的玄武岩纤维缠绕层,该玄武岩纤维缠绕层形成于所述轻金属内衬外表面上,且通过该玄武岩纤维缠绕层中的环氧树脂材料使其与轻金属内衬紧密地粘结成一体;以及涂覆于所述玄武岩纤维缠绕层外表面的保护胶层。本复合气瓶满足合理的应力场分布,保证复合气瓶在使用最小的纤维用量条件下能承受最大的爆破压力,具有持久的良好气密性能和最佳的安全性能。     

钙塑瓦楞复合纸板性能的实验研究

钙塑瓦楞纸板是将普通瓦楞纸板的芯纸替换为钙塑材料而成,该材料除普通瓦楞纸板的优点外,还具有强度高、防潮等性能。通过实验方法,对3层钙塑瓦楞复合纸板平压强度、边压强度和戳穿强度进行了测试分析,同时将钙塑瓦楞复合纸板与普通5层瓦楞纸板性能进行了对比。结果表明,3层钙塑瓦楞复合纸板的边压强度为0.650 kN,平压强度为1.274 kN,戳穿强度为7.5 J;5层瓦楞纸板的边压强度为0.378 kN,平压强度为0.437 kN,戳穿强度为6.75 J。为该新材料的推广使用提供了依据。     

Prediction of bending strength of long corrugated boxes

Long corrugated boxes were supported at both ends and bent by a concentrated force applied at the middle. Boxes with different lengths, cross‐sectional shapes, flute directions and board strengths were tested, using a standard compression tester with a fixed platen in accordance with ASTM D‐642. An equation was developed to relate compression strength to the various properties of the box. The correlation coefficient R² for the fit to actual data was about 0.4. Boxes having the flutes run around the box had a 20% higher compression strength than with horizontal flutes. The most significant factor was found to be the board edge crush strength. The results suggest that failure of boxes in bending is due to localized crushing at the point of application of the load, rather than whole‐box collapse. Copyright © 2001 John Wiley & Sons, Ltd.     

The effect of adding nano-SiO2 and nano-Al2O3 on properties of high calcium fly ash geopolymer cured at ambient temperature

This article presents the effect of adding nano-SiO₂ and nano-Al₂O₃ on the properties of high calcium fly ash geopolymer pastes. Nano-particles were added to fly ash at the dosages of 0%, 1%, 2%, and 3% by weight. The sodium hydroxide concentration of 10 molars, sodium silicate to sodium hydroxide weight ratio of 2.0, the alkaline liquid/binder ratio of 0.60 and curing at ambient temperature of 23 °C were used in all mixtures. The results showed that the use of nano-SiO₂ as additive to fly ash results in the decrease of the setting time, while the addition of nano-Al₂O₃ results in only a slight reduction in setting time. Adding 1–2% nano-particles could improve compressive strength, flexural strength, and elastic modulus of pastes due to the formation of additional calcium silicate hydrate (CSH) or calcium aluminosilicate hydrate (CASH) and sodium aluminosilicate hydrate (NASH) or geopolymer gel in geopolymer matrix. In addition, the additions of both nano-SiO₂ and nano-Al₂O₃ enhances the shear bond strength between concrete substrate and geopolymer.     

新型4层瓦楞纸板的性能分析

研究了一种新型的4层瓦楞纸板结构,并将4层瓦楞纸板和3层、5层瓦楞纸板的平压强度、边压强度、戳穿强度和耐破度性能进行比较,最后得到新型4层瓦楞纸板的主要优点是:厚度比5层瓦楞纸板要薄,节省了夹芯纸的用量,降低瓦楞纸板的成本,而且强度高,在一定情况下可以代替5层瓦楞纸板达到抗压、防震、缓冲的目的。     

The role of 0–2 mm fine recycled concrete aggregate on the compressive and splitting tensile strengths of recycled concrete aggregate concrete

The aim of this study is to investigate the role of 0–2 mm fine aggregate on the compressive and splitting tensile strengths of recycled concrete aggregate (RCA) concrete with normal and high strengths. Normal coarse and fine aggregates were substituted with the same grading of RCAs in two normal and high strength concrete mixtures. In addition, to keep the same slump value for all mixes, additional water or superplasticizer were used in the RCA concretes. The compressive and splitting tensile strengths were measured at 3, 7 and 28 days. Test results show that coarse and fine RCAs, which were achieved from a parent concrete with 30 MPa compressive strength, have about 11.5 and 3.5 times higher water absorption than normal coarse and fine aggregates, respectively. The density of RCAs was about 20% less than normal aggregates, and, hence, the density of RCA concrete was about 8–13.5% less than normal aggregate concrete. The use of RCA instead of normal aggregates reduced the compressive and splitting tensile strengths in both normal and high strength concrete. The reduction in the splitting tensile strength was more pronounced than for the compressive strength. However, both strengths could be improved by incorporating silica fume and/or normal fine aggregates of 0–2 mm size in the RCA concrete mixture. The positive effect of the contribution of normal sand of 0–2 mm in RCA concrete is more pronounced in the compressive strength of a normal strength concrete and in the splitting tensile strength of high strength concrete. In addition, some equation predictions of the splitting tensile strength from compressive strength are recommended for both normal and RCA concretes.     

Yield strength in submicrovolumes of single crystals

The specificity of the transition from elastic to elastoplastic deformation in defect-free single crystals during the localization of the deformation in a submicron region has been studied by nanoindentation. A sharp transition from elastic to elastoplastic deformation has been observed in tested single crystals at depths of about 20–50 nm. To define the yield strength using the nanoindentation data, the stressed-strained state in the contact region has been analyzed. It has been shown that the yield strength in submicrovolumes of single crystals is tens-hundreds times higher than that at the macroscopic level and approaches the value of the theoretical shear strength. A mechanism of the transition from elastic to elastoplastic deformation has been discussed in the framework of the phenomenological model of the nucleation of dislocations. The transition has been induced by the homogeneous nucleation of dislocations in a contact.     

Concrete with ceramic waste aggregate

Use of hazardous industrial wastes in concrete-making will lead to greener environment. In ceramic industry about 30% production goes as waste, which is not recycled at present. In this study an attempt has been made to find the suitability of the ceramic industrial wastes as a possible substitute for conventional crushed stone coarse aggregate. Experiments were carried out to determine the compressive, splitting tensile and flexural strengths and the modulus of elasticity of concrete with ceramic waste coarse aggregate and to compare them with those of conventional concrete made with crushed stone coarse aggregate. The properties of the aggregates were also compared. Test results indicate that the workability of ceramic waste coarse aggregate concrete is good and the strength characteristics are comparable to those of the conventional concrete.     

A practical model for efficient anti-fatigue design and selection of metallic materials:Ⅰ.Model building and fatigue strength prediction

The high cost and low efficiency of fatigue tests are bottleneck problem for the anti-fatigue design of metallic materials.For this problem,a theoretical fatigue model is proposed in this study,the possible applications have also been discussed.Specific results would be introduced in two serial papers,in which the first paper focuses on the model building and the applications on fatigue strength prediction;the second paper put emphasis on the influencing factors of the model parameters and the applications on fatigue strength improvement.In this first paper,a theoretical model is proposed considering both the strength and plastic restrictions of fatigue strength.As the model builds up a brief relationship among yield strength(Y),tensile strength(T)and fatigue strength(F),it is named as the Y-T-F model.Through the verification with fatigue strength data covering various kinds of metallic materials and loading condi-tions,this Y-T-F model exhibits both generality and accuracy.With the Y-T-F model,the efficient fatigue strength prediction could be conducted by brief linear fitting and calculation,just through yield strength,tensile strength and several known fatigue strength data.Moreover,through its deduced Y-F model,the analytical formula of fatigue strength continuously changing with materials strengthening can be obtained,as well as the maximum value of fatigue strength and corresponding critical yield strength.In summary,the Y-T-F model would be useful for reducing the fatigue tests,thus providing new possibilities on the efficient anti-fatigue design and selection of metallic materials.     

碳/铝复合材料界面结合强度对拉伸性能的影响

本文主要研究C/Al复合材料先驱丝的界面结合强度的表征方法以及界面结合状态对复合材料拉伸性能的影响.用自行研制的小型剪切试验机测定复合材料先驱丝的纵向剪切强度,通过计算得到复合材料界面处的剪切强度以此作为界面结合强度的定量表征方法.实验证明,不同界面结合强度的复合丝在宏观上表现出有不同纵向剪切强度值,复合材料的界面结合强度可以用界面剪切强度值定量描述.复合材料拉伸强度随界面强度提高而减少,在满足复合材料横向强度要求前提下,降低复合材料界面结合有利于提高拉伸强度.     

High-Cycle Fatigue of Materials and Parts of Gas-Turbine Engines

We present a historical survey of the development of the scientific direction called “Structural Strength” at the Central Institute of Airplane Engine Manufacturing (CIAEM) for the last 30 years in connection with the 100th birthday of Academician S. V. Serensen, founder of this direction in the USSR, and the 75th anniversary of foundation of the CIAEM. We present the principal results obtained by the scientific staff of the Sector of Fatigue Strength of Materials of Gas-Turbine Engines at the CIAEM.__________Translated from Problemy Prochnosti, No. 3, pp. 5 – 21, May – June, 2005.     

Enhancement on Fatigue Property of Aluminum Alloy Welded Joint by Utilizing Trailing Peening

The fatigue properties of 2024T3 aluminum alloy welded joint treated by different peening methods were examined. The different effects on fatigue performance of high strength aluminum welded joints were compared with each other by carry out a series tests