排序方式: 共有222条查询结果,搜索用时 15 毫秒
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采用试验研究的方法,探讨了不同结构参数出口侧向扩张孔的流量系数在不同工况下的变化规律。通过试验研究发现:出口侧向扩张孔圆柱段孔径为0.6 mm时的流量系数比孔径为0.8 mm时大3%;当孔倾角由30°减小至25°时,流量系数随之增大,当倾角继续减小至20°时,流量系数不变;当扩张角由20°增大至40°时,流量系数先增大后减小,且在扩张角为25°时最大;流量系数与次流通道雷诺数成正比,雷诺数越大,流量系数达到极限值所需的压降系数越小,且当压降系数大于0.9后,不同次流雷诺数下的流量系数差别在2%左右。 相似文献
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针对止口螺栓连接,论文从连接结构轴向拉压力学行为分析出发,提出了可模拟连接非线性刚度和阻尼耗散的扇区模型,基于此进一步构建了弯矩载荷下的非线性解析模型。通过与三维实体有限元模型计算结果的对比分析,验证了所提出模型的有效性,并揭示了连接的非线性刚度特性和迟滞阻尼特性。基于所提出模型研究了关键参数对止口螺栓的阻尼特性的影响规律,结果表明:连接的阻尼耗散能力随弯矩载荷幅值和摩擦因数的增加呈现先增加后降低趋势,而随止口紧度和法兰长度的增加单调增加;法兰长度除对连接的阻尼耗散存在一定影响外,还能显著降低连接结构的等效刚度。 相似文献
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通过DD6单晶薄壁管试样机械应变控制热机械疲劳(TMF)试验,获取温度交变、相位角以及载荷控制方式对单晶应力应变响应与疲劳寿命的影响规律。结果表明:温度交变会引起明显的应力不对称性并造成额外损伤,导致TMF寿命明显低于最高循环温度的等温疲劳(IF)寿命,并且反相(OP)循环寿命普遍要低于同等载荷的同相(IP)循环,这种寿命变化趋势与应力控制存在明显差异。采用Walker本构模型进行单晶材料在不同TMF循环下的滑移系黏塑性分析,构建单晶TMF损伤与滑移系细观应力应变参量的关联。在此基础上,选取最大Schmid应力、最大滑移剪应变率、滑移剪应变范围、循环Schmid应力比作为损伤参量,建立基于细观参量的TMF寿命模型,其对不同相位、不同载荷控制方式的TMF寿命预测精度均在2倍分散带内。 相似文献
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等增益比燃油计量活门型孔设计计算 总被引:1,自引:0,他引:1
为解决普通方形、圆形、三角形等燃油计量活门型孔流量增益比变化大的问题,提出了一种等流量增益比的燃油计量活门型孔设计思路。通过理论计算得到了等增益比活门型孔曲线函数的基本形式和详细设计计算方法,并进行了举例计算。流量增益比与计量活门开度扰动量的比值为定值,两者呈正比关系,活门开度扰动量越小,流量增益比越小,即计量精度越高。与方形型孔进行了对比分析,详细说明了等增益比型孔在小流量状态下,增益小抗干扰能力强的优点,并且通过组合型孔设计,避免了等增益比活门型孔大流量状态下的增益过大问题。 相似文献
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为了使高级波束成形中的函数波束成形、压缩感知波束成形、正交波束成形在旋转声源定位中获得广泛应用,对3种高级波束成形在旋转声源定位中的应用进行了研究,从声源空间分辨率,动态范围以及声源功率积分上与传统旋转波束成形和DAMAS(deconvolution approach for the mapping of acoustic sources)反卷积作对比。仿真与实验结果表明:3种高级波束成形均可以应用到旋转声源定位中,并且均能显著提升旋转声源空间分辨率和动态范围以及拥有较高的计算效率。函数波束成形在低频段的空间分辨率低于DAMAS并且容易产生较高的声源功率积分误差。压缩感知波束成形整体性能与DAMAS相近,并且在低频段的空间分辨率比DAMAS有优势。正交波束成形在低频段容易产生声源定位位置误差,抗干扰能力较弱,并且声源功率积分整体低于DAMAS。 相似文献
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《中国航空学报》2021,34(8):112-121
Uniaxial ratcheting behaviour and low cycle fatigue (LCF) failure mechanism of nickel-based single crystal superalloy DD6 with [001] orientation are investigated through the stress-controlled LCF tests with stress ratio of −1. Then the deformation behaviour during the whole-lifetime from the beginning of the experiment to the fracture of the specimen, as well as the fractographic/metallographic morphology, are compared with the strain-controlled LCF experimental results. Through the scanning electron microscope (SEM) observations, it is shown that the failure characteristics under stress-controlled LCF loading are similar with those under strain-controlled loading. Nevertheless, unlike strain-controlled LCF loading, even under fully reversed cycle loading for stress-controlled LCF, DD6 shows significant ratcheting behaviour due to the tension-compression asymmetry. In addition, the LCF lifetimes under stress control are significantly shorter than the LCF lifetimes under strain control, and the culprit might be the detrimental effect of ratcheting strain on LCF lifetime. Based on these phenomena, an improved crystal plasticity constitutive model on the basis of slip-based Walker constitutive model is developed through modifying the kinematic hardening rule in order to overcome the inaccurate prediction of decelerating stage and stable stage of ratcheting behaviour. Furthermore, combining the continuum damage mechanics, a damage-coupled crystal plasticity constitutive model is proposed to reflect the damage behaviour of DD6 and the accelerating stage of ratcheting behaviour. The simulation results for the stress-controlled LCF deformation behaviour including the whole-lifetime ratcheting behaviour show good agreement with the experimental data. 相似文献
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《Air & Space Europe》2001,3(1-2):45-49
Forecasts of air traffic growth and their interpretation in terms of the requirement for future airport and air traffic system capacity have an important part to play in guiding decisions about transport system design. The complex issues involved are illustrated in this paper, which analyses possible growth scenarios for the particular case of Germany. 相似文献
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