碳纤维布胶接修复含裂纹钢管仿真分析

在胶接修复工艺中,裂纹的形式和不同的胶接方案影响结构的修复效果.以裂纹尖端应力强度因子(Stress Intensity Factor,SIF)为依据,分别对含有2种裂纹形式的钢管进行了仿真分析,探讨钢管的裂纹大小、碳纤维布的长度和层数对胶接修复强度的影响.分析结果表明,增加碳纤维布长度可以有效提高修复结构的强度,当长度超过有效胶接长度后,提高幅度不明显.裂纹面积所占比例越大,裂纹处应力集中程度越高,胶接碳纤维布的修复效果越显著.2层碳纤维布胶接修复对SIF的增长抑制效果比1层碳纤维布提高了10％以上,对于圆周裂纹损伤程度较小时,使用1层碳纤维布修复已能有效改善钢管的结构性能,对于圆弧裂纹和损伤程度较大的圆周裂纹,建议使用2层碳纤维布修复.     

L形碳纤维增强复合材料/铝合金胶接复合构件剥离应力建模与分析

针对承受剥离载荷的L形碳纤维增强复合材料(Carbon fiber reinforced plastic/polymer,CFRP)/铝合金胶接复合构件,以微元受力平衡方程为基础,建立胶层平均剥离应力的二维分布方程。在方程中引入基材的弯曲刚度系数,描述背材与基材均为刚性材料的情况下胶层剥离应力的分布规律。其应力分布曲线为拉压应力交替作用的阻尼调和函数,周期与峰值由胶接件构型尺寸与材料性能参数决定。通过CFRP/铝合金剥离试验及三维有限元模拟对理论模型进行对比验证,结果的总体趋势与数值吻合程度较好,并分析不同方法获得的剥离应力分布状态之间的差异及其产生的原因。基于胶接复合构件的理论模型与三维有限元模型,研究基材厚度改变对剥离应力分布的影响,发现伴随着CFRP板厚度的增加,剥离应力的峰值明显下降,在剥离前沿的应力集中现象得到改善。     

碳纤维管与铝合金的胶接强度试验研究

根据赛车轻量化设计的需要,对碳纤维管与铝合金接头的胶接工艺进行了试验研究。分析了胶接强度的影响因素,设计了因素水平;通过正交试验和分析,确定了胶层厚度、铝合金表面粗糙度和表面化学处理方式。试验结果为胶接工艺的实施提供了试验依据。     

复合材料胶接修复金属构件残余热应力研究进展

复合材料补片胶接技术是一种有效修复飞机受损构件的低成本方法.由于补片与金属材料热膨胀系数的显著差异,会在构件中引入残余热应力.归纳了复合材料修复技术中关于残余热应力的研究热点及成果,涉及常用的残余热应力分析模型、结构约束及固化制度对残余热应力的影响、减小残余热应力的途径等,并对今后的研究工作进行了展望.     

复合材料胶接强度分析

以Von Mises屈服准则为胶层失效判据及基于应力分布的三维Hashin失效准则为复合材料层合板失效判据,采用材料刚度退化的方法,在ANSYS中建立了考虑复合材料层合板和胶层失效的复合材料胶接强度分析模型;利用该模型对复合材料胶接强度进行了准确预测.重点研究了胶层厚度和胶接长度两个设计参数对复合材料胶接强度的影响,结果表明:胶接强度在一定范围内随着胶层厚度和胶接长度的增大而增大,呈非线性关系.     

含裂纹螺接件应力强度因子三维有限元分析

对飞机结构螺接件来说,最主要的强度问题之一,是在疲劳载荷下会产生裂纹并扩展。而目前对含裂纹螺接件的应力强度因子(Stress intensity factor,SIF)分析多以简化的二维有限元模型为主。为此,在考虑螺栓与孔壁间的非线性接触、摩擦和螺栓预紧力等因素影响的基础上,利用非线性有限元软件MSC.Marc构建含裂纹螺接件的三维有限元分析模型,通过分析得到不同损伤模式下的SIF与裂纹长度沿板厚度方向的变化曲线。结果表明,虽然螺接件孔边裂纹是复合型裂纹,但Ⅰ型SIF起主导作用,Ⅱ型和Ⅲ型SIF可忽略不计;在裂纹长度一定时,接触面处的SIF最大,外表面处最小,孔边双侧裂纹对称时的SIF大于孔边单侧裂纹情形;裂纹长度相同时,含沉孔螺接件接触面上的SIF大于直孔情形时相应的SIF,而外表面的SIF趋势则恰恰相反。     

胶接技术在工程中的应用

简要介绍了胶接剂的组成及其在工程中的选用原则。对实际应用中通常采用的胶接原理作了定量的说明,在此基础上对胶接前构件的表面处理工艺及表面涂胶方式进行了叙述;同时对胶接技术的使用场合及性能特点也作了说明。     

损伤复合材料层板胶接修理强度分析

对于飞行器复合材料结构在制造和服役中产生的缺陷损伤,一种常用的外场临时修理方法是在受损结构的外表面胶接复合材料补片来进行补强。本文采用“双板—弹簧元”和“三板—弹簧元”修正有限元模型分别对层合板的穿透型损伤和半穿透型损伤的临时修理进行强度分析,并进行了相关的强度试验验证。根据计算和试验结果对补片直径、厚度等修理参数对修理效果的影响进行了分析,并提出了合理选择修理参数的一般原则。     

复合材料层合板胶接修理的粘弹性有限元分析

基于修补结构的本构关系,对一受损层合板的双面胶接修理问题进行分析。采用粘弹性和弹性有限元两种分析方法,并用相应的试验来验证两种方法所得的计算结果。通过分析得到了胶接参数对修补后的结构强度及胶层应力的影响,同时对比计算结果和试验结果,可以发现粘弹性分析比弹性分析更为准确。     

复材双搭胶接结构应力分析与试验研究

飞机复材结构连接的趋势是向着无紧固件方向发展,常采用双搭胶接连接,该连接接头处的胶层剪应力分布是分析双搭胶接连接强度和预测整体复材结构失效的关键问题。建立了基于经典弹性理论的复材双搭胶接结构应力分析理论模型,得到了胶层剪应力分布的解析解,并与根据所测得应变提出的基于经典弹性理论和基于经典层压板理论的应力计算方法得出的胶层剪应力分布结果相比较。结果表明:胶层剪应力分布曲线吻合度较高,峰值相差不超过10.9%。     

铸造起重机T型钢裂纹的计算与修复

铸造起重机在起重量较大的情况下（额定起重量在100t以上）,其主梁形式通常都采用偏轨箱型梁的形式,即将主小车的轨道置于主腹板的正上方。目前一般都采用T型钢的主梁形式,就是在轨道的下方选用合适的T型钢,T型钢的翼缘板与起重机的翼缘板对接,T型钢的腹板与起重机的主腹板对接。这也是目前大吨位铸造起重机最常用的主梁截面形式。     

基于SolidWorks Simulation的管端定径机的研究与分析

钢管厂生产的钢管,单根长度通常小于14m,而在地质钻探和石油钻采中,钻井深度通常1000m以上,最深7000m,用于输送石油、天然气、水、矿物等的管线长达数公里甚至数百公里,为此,需在钢管端部车螺纹,利用相应接箍将钢管连接起来.管端定径的目的是减小钢管椭圆度,保证加工精度,提高成材率,相应管端定径机难点在于定径液压缸顶...     

钢结硬质合金ELID磨削表面的AFM分析

研究了采用ELID磨削技术磨削钢结硬质合金,使其表面粗糙度Ra≤0.02μm。并通过原子力显微镜(AFM)对其微观表面形貌、表面缺陷及钢结硬质合金难加工机理进行分析。     

预制钢筋泥凝土楼板板缝开裂原因分析

分析钢筋混凝土空心板在民用住宅应用中,楼板板缝开裂问题,提出了预防措施及处理办法.     

张力减径内六方成因分析及解决方法

分析了无缝钢管在张力减径时内六方产生的原因及影响因素,重点分析了温度不均匀对内六方的影响,并结合现有工艺条件提出多种减少直至消除内多边形的措施。     

Dynamic mixed mode crack propagation behavior of structural bonded joints

The stress field around the dynamically propagating interface crack tip under a remote mixed mode loading condition has been studied with the aid of dynamic photoelastic method. The variation of stress field around the dynamic interface crack tip is photographed by using the Cranz-Shardin type camera having 10⁶ fps rate. The dynamically propagating crack velocities and the shapes of isochromatic fringe loops are characterized for varying mixed load conditions in double cantilever beam (DCB) specimens. The dynamic interface crack tip complex stress intensity factors,K ₁ andK ₂, determined by a hybrid-experimental method are found to increase as the load mixture ratio of y/x (vertical/horizontal) values. Furthermore, it is found that the dynamically propagating interface crack velocities are highly dependent upon the varying mixed mode loading conditions and that the velocities are significantly small compared to those under the mode I impact loading conditions obtained by Shukla (Singh & Shukla, 1996a, b) and Rosakis (Rosakis et al., 1998) in the USA.     

Reliability analysis of stainless steel/carbon steel double-layered tube on the basis of thermal deformation behavior

The thermal expansion of pipes depends on both the temperature of the pipe and the expansion coefficient of the piping material at the operating temperature. In the case of a double-layered tube consisting of two different tube materials, the thermal deformation behaviors are dependent on the relative tube sizes, thermal expansion coefficients, and the mechanical properties of the inner and outer tubes. For the safe and reliable application of double-layered tubes that are fabricated by hydroforming, the thermal stress in circumferential direction and the gap between the inner and outer tubes need to be analyzed over a wide range of temperatures (?50°C～200°C). As it is difficult to measure the thermal stress and the gap between tubes at operating temperature, this study has analytically investigated the thermal deformation behavior of a double-layered tube. From the analytical model, the effect of hydraulic pressure, residual stress, and the relative sizes of the inner and outer tubes on the resultant thermal deformation, such as the circumferential thermal stress and the gap between inner and outer tubes, has been analyzed. The analytical results provide a theoretical basis for determining the reliable operating temperature of double-layered tubes.     

Wear characteristics of a diffusion bonded sintered steel with short term surface treatments

A pin on disc machine was used to investigate the tribological behavior of a diffusion bonded sintered steel, with and without surface treatments of steam oxidation and manganese phosphating, over a wide range of speed (0.2–4 m/s) and applied load (4–500 N) in conditions of dry sliding and starved lubrication by oil impregnation of the porous structure of the materials. Besides the calculated wear rates, the wear mechanisms were determined by examination of the components of the rubbing system (sintered pin, disc and generated debris). A transition from a mild to a severe wear regime was identified, denoted by sharp changes of the wear rate. A transient wear regime, interposed between the mild and severe wear regimes, was detected. The rubbing surface quality degradation was in terms of material displacement around the pin circumference due to a delamination wear mechanism. Such regime was detected for the base sintered steel in dry sliding at 1 m/s for the load range 60–80 N and for both surface treatments in oil impregnated sliding at 0.5 m/s for the load range 200–300 N. Oil impregnation of the base sintered steel expanded the mild wear regime towards higher loads throughout the whole sliding speed range compared to dry sliding. For the lower speeds of 0.2 and 0.5 m/s, manganese phosphated samples in dry sliding exhibited higher transition loads compared to the base sintered steel. The lower oil impregnability of the surface treated samples, due to the sealing of porosity by steam oxidation, led to slightly lower transition loads in oil impregnated sliding, compared to the base sintered steel.     

Surface crack susceptibility of electrodischarge-machined steel surfaces

This study investigates the correlation between the surface cracking susceptibility of seven common engineering steels (JIS SKS93, SNCM439, SCM440, SKS2, SK2, SKH51, and SKD11) and the major electrodischarge machining processing parameters, namely the pulse current and the pulse-on duration. The results reveal that the susceptibility of the working materials to surface cracking can be reduced by increasing the pulse current or shortening the pulse-on duration. Furthermore, it is shown that steels with a lower carbon equivalent index or a higher thermal conductivity are more resistant to crack formation. Overall, the steels considered in this study can be ranked in terms of an increasing surface cracking susceptibility as follows: low alloy steel, carbon tool steel, high speed steel, and cold working steel.