低温液体火箭发动机氢主阀动态特性仿真分析

低温液体火箭发动机阀门多采用气控菌阀,阀门开关动态特性对发动机启动和关机性能存在重要影响。因此,在设计阶段获取准确的阀门开关动态特性至关重要。针对某型低温膨胀循环发动机氢主阀,采用AMESim仿真软件对其工作过程进行动态特性仿真,以获得阀门启闭动作时间与启闭过程中出口压力变化情况,并将仿真结果与试车数据进行对比,结果表明:仿真结果与试车数据变化趋势基本一致,低温下阀门打开时间变长,关闭时间不变。同时对影响阀门启闭动作时间的参数进行分析,结果显示阀门动作时间随开关作动力增大而减少,随控制腔容积增大而增加。因此,提出的气控菌阀动态特性仿真方法具有较高的可行性和准确性,可用于各类气控菌阀动态特性分析,为气控菌阀设计提供了参考依据,有助于缩短产品研制周期,降低生产成本。

Microstructure and Mechanical Properties of Al-5Cu-4.5Mg-2.5Zn Squeeze Cast Alloy

Al-5Cu-4.5Mg-2.5Zn alloy was prepared and the alloy ingots were fabricated by squeeze casting in this work.Considering these negative effects of composition segregation and coarse second phases,some heat treatments were adopted in this research.Microstructures,element distribution,phase constitutions and mechanical properties of Al-5Cu-4.5Mg-2.5Zn alloy ingots before and after heat treatments were investigated.It was discovered that these heat treatments would influence and extremely optimize the microstructures and properties of Al-5Cu-4.5Mg-2.5Zn alloy.Except some residual S (Al_(2)CuMg) phase and a few of η phase,the precipitate free zone (PFZ) and the Guinier Preston zone (GPZ) formed in the alloy.It was also found that θ′′ (Al_(2)Cu) and η′′ (MgZn_(2)) phases formed and kept a consistent relationship with the aluminum matrix.As the result,these properties of ultimate tensile strength (UTS),percentage of elongation and Brinell hardness (HB) were greatly elevated.The UTS,percent of elongation and HB were 469 MPa,8.1% and 208 N/mm^(2),respectively.

Sc和Zr对挤压铸造ZL205A合金组织与性能的影响

研究了Sc和Zr含量对挤压铸造ZL205A铝合金微观组织和力学性能的影响。结果表明,随着Sc含量增加,合金基体晶粒组织细化,抗拉强度先升高后降低,当Sc含量为0.40%(质量分数,下同)时,铝合金的抗拉强度、伸长率和硬度(HV)分别为389.5 MPa、14.8%和122.9。同时添加Sc和Zr对合金组织的细化和力学性能的提升效果更显著,当添加0.40%的Sc和0.15%的Zr时,合金在室温下的抗拉强度和伸长率分别达到398.3 MPa和15.7%;经过T5热处理后,合金在150℃下的抗拉强度为345.1 MPa,伸长率为15.8%。对Sc和Zr元素改性的ZL205A铝合金采用挤压铸造制造了连杆构件,表面质量良好,构件最高抗拉强度和伸长率分别为468.6 MPa和15.2%,硬度(HV)最高为146.6。

SiC泡沫陶瓷增强ZL205A铝合金复合材料的制备与性能

通过挤压浸渗工艺成功制备了SiC泡沫陶瓷增强ZL205A铝合金复合材料,并研究了不同孔隙率的泡沫陶瓷增强相对复合材料性能的影响。通过微观结构分析,制备的复合材料两相间结合紧密,没有裂纹及其他缺陷产生。多孔陶瓷作为增强相可以有效地细化ZL205A合金的晶粒,多孔陶瓷孔隙率降低,孔结构越小,合金晶粒越细小。对制备的复合材料进行力学性能测试,复合材料的硬度(HV)和抗弯强度最高能够达到1276 MPa和415 MPa。对制备的复合材料进行摩擦磨损测试。结果表明,连续陶瓷相的存在将铝基体严重的粘着磨损和剥落磨损转变为较轻的磨粒磨损,极大提升了复合材料的摩擦磨损性能,为其用于耐磨领域提供了理论依据。