5000kN双梁式复合材料液压机结构设计与有限元仿真

为解决复合材料三梁四柱液压机结构轻量化与成形工艺零件厚度不均匀问题,设计一台5000kN新型双梁双抗偏载结构的液压机。使用SolidWorks建立机身初始结构模型,采用ANSYS Workbench对液压机模型进行静态有限元分析,得到机身主要部件的应力和位移的分布情况,确保机架的刚度和强度以及整体性指标达到使用要求。同时,在中心载荷和两种极限偏载工况下,对液压机结构进行强度和刚度校核,获得满足工程要求的新型双梁液压机结构。

复合材料液压机偏载工况下滑块变形规律的研究

偏载是影响复合材料制品精度的关键因素,特别是在成形较薄的复合材料制件时,因为薄制件固化时间短,倘若滑块发生偏载,成形出来的制件壁厚将不均匀。利用ANSYS有限元分析软件,针对YT71S-2400复合材料液压机在不同偏载工况下进行模拟,得出不同偏载工况下复合材料液压机滑块的刚度变化规律,可为压机机身设计及四角调平技术研究提供理论基础,从而减小偏载所造成的复合材料制件的质量问题。

复合材料液压机偏载预应力下的模态分析

液压机模态分析是整个液压机结构动态设计的核心.通过对YT71S-2400复合材料液压机的模态分析,得到液压机-模具耦合结构在偏载预应力状态下的固有频率和振型,并对该状态下的前10阶模态进行振动特性分析,得出该耦合结构的有害振型及其位置,为液压机整体设计提供动态特性参考.同时,通过该研究还得出了该液压机-模具耦合模型在偏载预应力状态下的最小频率远大于其工作频率,不会产生共振,但处于次声波范围内,需要注意防护可能产生的噪声污染.

复合材料液压机四角调平缸支撑结构的优化

四角调平的设计对整个压机的精度具有决定性的影响,本文对调平系统进行可行性分析,文中对复合材料液压机的四角调机构进行了数值模拟,对四角调平支架结构进行有限元分析,并对四角调平的支撑机构进行了结构优化。对改进后的调平支架结构进行模拟分析,模拟结果表明该调平缸支架结构可以可靠保证系统的准确调平。

热塑性PP蜂窝夹层结构复合材料制备和性能

采用双钢带环带压机制备了连续玻璃纤维增强热塑性聚丙烯(CFRTP)片材复合聚丙烯(PP)蜂窝夹芯板(CFRTP-PP蜂窝夹芯板),研究了CFRTP-PP蜂窝夹芯板在–40~80℃温度下的力学性能变化。随着温度升高,CFRTP-PP蜂窝夹芯板的平压性能呈下降趋势,相对于常温(25℃),在–40℃时,平压强度、平压弹性模量分别提高38.8%,39.3%;在80℃时,平压强度、平压弹性模量分别下降23.1%,23.8%。CFRTP-PP蜂窝夹芯板的弯曲强度、弯曲刚度总体上随着温度的降低而升高,相对于常温(25℃),在–40℃时,弯曲强度和弯曲刚度分别增加33.7%,38.6%;在80℃时,弯曲强度和弯曲刚度有所下降,但保持率分别为68.1%,70.7%,具有良好的抵抗弯曲变形的能力。在25~80℃范围内,蜂窝夹芯板的滚筒剥离强度随着温度升高而逐渐降低,在–40~25℃范围内,随着温度降低而逐渐降低。在80℃时,滚筒剥离强度比常温降低了19.6%;在–40℃时,滚筒剥离强度比常温下降了27.5%。但滚筒剥离强度大于120(N·mm)/mm,仍表现出优异的性能,可以满足不同温度环境下的应用。

基于双阀并联控制的压机四角调平系统研究

针对热塑性复合材料压机压制精度低、模具磨损严重等问题,在压机四角调平系统中采用双闭环控制策略,此时,内环的压力控制误差直接影响外环的位置同步控制精度。在大流量工况下,调平系统控制阀的阀口开度增加会导致压力控制误差增大,为进一步改善其综合控制性能,提出双阀并联压力控制方案。使用大通径流量补偿阀与小通径压力控制阀并联替换原有单个控制阀,分别对调平缸无杆腔的流量和压力进行控制,满足大流量工况的同时提高压力控制精度,进而提高位置同步控制精度,并搭建调平缸压力台架进行试验以验证双阀并联控制的有效性。结果表明,双阀控制下的压力误差比单阀减少0.5 MPa以上,且压制速度越大其性能优势更突出,为压机调平系统实现高速高精度同步控制提供有效参考。

Fabrication and mechanical properties of Ti_(2)AlC/TiAl composites with co-continuous network structure

Ti_(2)AlC/TiAl composites with different volume fractions were prepared by hot pressing technology,and their reinforced structural characteristics and mechanical properties were evaluated.The results showed that when the reinforced phase volume fraction of Ti_(2)AlC was 20%,three-dimensional interpenetrating network structures were formed in the composites.Above 20%,Ti_(2)AlC phase in the composites accumulated and grew to form thick skeletal networks.The microplastic deformation behavior of Ti_(2)AlC phase,such as kink band and delamination,improved the fracture toughness of the composites.Comparative analysis indicated that the uniform and small interconnecting network structures could further reinforce the composites.The bending strengths of composites prepared with 20 vol.%Ti_(2)AlC reached(900.9±45.0)MPa,which was 25.5% higher than that of TiAl matrix.In general,the co-continuous Ti_(2)AlC/TiAl composite with excellent mechanical properties can be prepared by powder metallurgy method.

Processing, characterization, room temperature mechanical properties and fracture behavior of hot extruded multi-scale B_4C reinforced 5083 aluminum alloy based composites

Microstructural characteristics and mechanical behavior of hot extruded Al5083/B4C nanocomposites were studied.Al5083and Al5083/B4C powders were milled for50h under argon atmosphere in attrition mill with rotational speed of400r/min.For increasing the elongation,milled powders were mixed with30%and50%unmilled aluminum powder(mass fraction)with meanparticle size of>100μm and<100μm and then consolidated by hot pressing and hot extrusion with9:1extrusion ratio.Hot extrudedsamples were studied by optical microscopy,scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),transmission electron microscopy(TEM),tensile and hardness tests.The results showed that mechanical milling process andpresence of B4C particles increase the yield strength of Al5083alloy from130to566MPa but strongly decrease elongation(from11.3%to0.49%).Adding<100μm unmilled particles enhanced the ductility and reduced tensile strength and hardness,but usingthe>100μm unmilled particles reduced the tensile strength and ductility at the same time.By increasing the content of unmilledparticles failure mechanism changed from brittle to ductile.

Optimizing consolidation behavior of Al 7068-TiC nanocomposites using Taguchi statistical analysis

The fabrication of high strength Al 7068？5%TiC （mass fraction） nanocomposite was studied by mechanical alloying and hot pressing routes. Considering densification importance and grain growth effects, hot pressing process conditions for producing bulk nanocomposite were optimized using statistical Taguchi method based on compressive strength achievement. The Taguchi results indicate that 30 min hot pressing under pressure of 500 MPa at 385 °C provides high compressive strength and hardness of 938 MPa and HV 265, respectively. More interestingly, analysis of variance proves that the applied pressure is the most influential factor for hot pressing of the nanocomposite. The contribution percentages of factors in hot pressing terms are as follows： applied pressure （61.3%）, exposed temperature （29.53%） and dwelling hot pressing time （4.49%）.

Mechanical properties of 3D carbon/carbon composites by nanoindentation technique

Nanoindentation tests were conducted to investigate the near-surface mechanical properties of the individual components(fiber and matrix) for three-dimensional reinforced carbon/carbon composites(3D C/C).Optical microscope and polarizing light microscope were used to characterize the microstructure of 3D C/C.The microscopy results show that large number of pores and cracks exist at both bundle/matrix interface and pitch carbon matrix.These defects have important effect on the mechanical behavior of 3D C/C.The in situ properties for components of 3D C/C were acquired by nanoindentation technique.Relative to the matrix sample,the fiber samples have more larger values for modulus,stiffness and hardness.However,there is no significant difference of modulus and stiffness among fiber samples with different directions.

Processing and mechanical properties of network ceramic/steel composites by pressureless infiltration

A new style Ni-containing alumina ceramic foam based continuous three-dimensional interconnected skeleton was prepared by impregnating a polymeric sponge with aqueous ceramic slurry.Subsequently,alumina ceramic foam/steel metal matrix composites(MMCs) were prepared successfully by sand mold casting technique.The microstructure and mechanical properties of MMCs were investigated by SEM,EDS and compressive test.The results show that the depth of infiltration is about 40 μm to the bonding interface of ceramic/steel and the fracture strength σmax and plastic strain limit εp of composite are 520 MPa and 11.2%,respectively.The fretting wear mechanism of MMCs is mainly performed at the oxidative wear mode with lower load/friction frequency and the predominant oxidation wear together with slight adhesive wear and abrasive wear multiple mode with higher load/ friction frequency.Moreover,the infiltration bonding and continuous three-dimensional interconnected ceramic skeleton play a vital role in the stability of the bonding interface and excellent mechanical properties.

Resin Matrix/Fiber Reinforced Composite Material, Ⅱ: Method of Solution and Computer Code

According to a mathematical model which describes the curing process of composites constructed from continuous fiber-reinforced, thermosetting resin matrix prepreg materials, and the consolidation of the composites, the solution method to the model is made and a computer code is developed, which for flat-plate composites cured by a specified cure cycle, provides the variation of temperature distribution, the cure reaction process in the resin, the resin flow and fibers stress inside the composite, the void variation and the residual stress distribution.

Mechanical analysis and reasonable design for Ti-Al alloy liner wound with carbon fiber resin composite high pressure vessel

To consider the internal pressure loaded by both the cylindrical Ti-Al alloy liner and the carbon fiber resin composite (CFRC) wound layers, two models are built. The first one is a cylinder loaded with the internal pressure in the hoop direction only. In this model, the total hoop direction load is distributed over all layers under the internal pressure. The second one is a cylinder loaded with the internal pressure in the axial direction only. In this model, the total axial load is distributed over all cylinders under the internal pressure. Taking the boundary conditions of the continuous displacement between layers into account, a group of equations are built. From these equations, we get the solutions of stresses in both hoop direction and axial direction loaded by every layer under internal pressures. After the stresses are obtained, a reasonable design can be done. An example is given in the final section of this study.