Effect of dynamic loading conditions on the dynamic performance of MP1 energy-absorbing rockbolts:Insight from laboratory drop test

Energy-absorbing rockbolts have been widely adopted in burst-prone excavation support, and their serviceability is closely related to the frequency and magnitude of seismic events. In this research, the splittube drop test with varying impact energy was conducted to reproduce the dynamic performance of MP1rockbolts under a wide range of seismic event magnitudes. The test results showed that the impact process could be subdivided into four distinct stages, i.e. mobilization, strain hardening, plastic flow(ductile), and rebound stage, of which strain hardening and plastic flow are the primary energy absorbing stages. As the impact energy per drop increases from 8.1 to 46.7 k J, the strain rate of the shank varies between 1.20 and 2.70 s^(-1), and the average impact load is between 240 and 270kN, which may be considered as constant. The MP1 rockbolt has a cumulative maximum energy absorption(CMEA) of 31.9–40.0 k J/m, with an average of 35.0 k J/m, and the elongation rate is 11.4%–14.7%, with an average of 12.7%, both of which are negatively correlated with the impact energy per drop. Regression analysis shows that energy absorption and shank elongation, as well as momentum input and impact duration,conform to the linear relationship. The complete dynamic capacity envelope of MP1 rockbolts is proposed, which reflects the dynamic bearing capacity, elongation, and distinct stages. This study is helpful to better understand the dynamic characteristics of energy-absorbing rockbolts and assist design engineers in robust reinforcement systems design to mitigate rockburst damage in seismically active underground excavations.

TEST AND CONTROL SYSTEM DEVELOPMENT AND APPLICATION OF LANDING GEAR DROP TEST RIG

A control and test system of a landing gear drop test rig is developed considering the drop test specifica- tions for the ＂Seagull 300＂ multi-functional amphibious airplane. In order to realize the automation of drop test process, a servo system is proposed and programmable logic controller（PLC） technology is used. Several key technologies for measuring the horizontal load, the vertical load and the transient rotational speed are studied. According to the requirements of CCAR-23-R3, the drop test of landing gears of the ＂Seagull 300＂ airplane is accomplished. Test results show that the system has a high accuracy of data collection. The system is stable and reliable. The drop test satisfies the requirements of the drop test specifications and the results can be used as the certification of airworthiness for this kind of airplane.

Drop test and crash simulation of a civil airplane fuselage section

Crashworthiness of a civil airplane fuselage section was studied in this paper. Firstly, the failure criterion of a rivet was studied by test, showing that the ultimate tension and shear failure loads were obviously affected by the loading speed. The relations between the loading speed and the average ultimate shear, tension loads were expressed by two logarithmic functions, Then, a vertical drop test of a civil airplane fuselage section was conducted with an actual impact velocity of 6.85 m/s, meanwhile the deformation of cabin frame and the accelerations at typical locations were measured. The finite element model of a main fuselage structure was developed and validated by modal test, and the error between the calculated frequencies and the test ones of the first four modes were less than 5%. Numerical simulation of the drop test was performed by using the LS-DYNA code and the simulation results show a good agreement with that of drop test. Deforming mode of the analysis was the same as the drop test; the maximum average rigid acceleration in test was 8.8 l g while the calculated one was 9.17g, with an error of 4.1%; average maximum test deformation at four points on the front cabin floor was 420 mm, while the calculated one was 406 mm, with an error of 3.2%; the peak value of the calculated acceleration at a typical location was 14.72g, which is lower than the test result by 5.46%; the calculated rebound velocity result was greater than the test result 17.8% and energy absorption duration was longer than the test result by 5.73%.

Separation occurring during the drop weight tear test of thick-walled X80 pipeline steels

A separation phenomenon occurring during the drop weight tear test of commercial thick-walled API （American Petroleum Institute） X80 strip steel was investigated in this work. Microstructural analysis showed that the band structure of bainite elongated along the rolling direction works as the initiation sites of separation. The propagation of separation can be promoted not only by the occurrence of the band structure of martensite/austenite constituent, prior austenite grain boundaries, and elongated bainite, but also by fine acicular ferrite and bainite. Wide separation formed in the former case, while the narrow one appeared in the latter case. acicular ferrite in thick-walled X80 pipeline steel in order Some methods were proposed to obtain fine and homogeneous to minimize the occurrence of separation.

Validation for Microbial Limit Test Method of Compound Yu E Nose Drops

[Objectives] This study was conducted to establish a method for microbial limit test of Compound Yu E Nose Drops.[Methods] According to the Chinese Pharmacopoei (General Rules in the fourth part of the 2015 edition),the microbial limit test method for Compound Yu E Nose Drops was verified.[Results] Compound Yu E Nose Drops has a strong inhibitory effect on Staphylococcus aureus and Bacillus subtilis,and the inhibitory activity was significantly eliminated after increasing the diluent (1∶ 20).The recoveries were all in the range of 0.5-2.0 when the total quantities of aerobic microbes were determined by the dilution method (1∶ 20).When the total quantities of mould and yeast were determined by the conventional method,the recoveries were both in the range of 0.5-2.0.When examining control bacteria,Escherichia coli,S.aureus and Pseudomonas aeruginosa can all be detected in the test groups by the test liquid dilution method.[Conclusions] For Compound Yu E Nose Drops,the total quantities of aerobic microbe can be counted by the dilution method;the quantities of mould and yeast can be examined by the conventional plate method;and the conventional method can be used for control microbe examination.

舰载机前起落架缓冲性能参数敏感性研究

为了同时满足缓冲和突伸性能,舰载机前起落架常采用双腔缓冲器设计。以某型机前起落架为研究对象,建立前起落架缓冲性能分析动力学模型,并将仿真计算结果与试验结果进行验证对比,验证理论模型的有效性和正确性。对缓冲器高、低压腔初始压力以及体积占比进行参数敏感性分析。结果表明,高、低压腔初始充填压力和体积占比对起落架缓冲性能的影响有别于它们对突伸性能的影响,所以对舰载机前起落架缓冲器的设计需不断优化,同时兼顾缓冲和突伸性能。

内埋武器机弹分离动态风洞投放试验研究

基于动力学相似的动态风洞投放试验研究了尖拱圆柱体从空腔中分离的气动及运动特性,并创新性地采用快响应压敏漆技术对动态运动模型表面上的压力分布测量进行初步探索研究,试验中探究了不同空腔模型攻角(α=0°,-1.5°,-3°)及弹体在空腔内的不同位置(L_(0)=25 mm,39 mm)对内埋武器机弹分离特性的影响。结果表明:弹体在空腔内的位置对机弹分离运动特性的影响最大,当L_(0)=25 mm时,弹体模型头部区域压力明显高于后部区域压力,产生抬头俯仰力矩,导致弹体模型俯仰角逐渐增大,最终碰撞空腔模型,降低载机攻角并未改变弹体模型碰撞空腔模型的效果。当L_(0)=39 mm时,弹体模型在给定的攻角下均能安全地从空腔中分离。

Wettability,reactivity,and interface structure in Mg/Ni system

The sessile drop method was applied to the experimental investigation of the wetting and spreading behaviors of liquid Mg drops on pure Ni substrates.For comparison,the experiments were performed in two variants:(1)using the Capillary Purification(CP)procedure,which allows the non-contact heating and squeezing of a pure oxide-free Mg drop;(2)by classical Contact Heating(CH)procedure.The high-temperature tests were performed under isothermal conditions(CP:760℃for 30 s;CH:715℃for 300 s)using Ar+5 wt%H_(2) atmosphere.During the sessile drop tests,images of the Mg/Ni couples were recorded by CCD cameras(57 fps),which were then applied to calculate the contact angles of metal/substrate couples.Scanning and transmission electron microscopy analyses,both coupled with energy-dispersive X-ray spectroscopy,were used for detailed structural characterization of the solidified couples.It was found that an oxide-free Mg drop obtained by the CP procedure showed a wetting phenomenon on the Ni substrate(an average contact angleθ<90°in<1 s),followed by fast spreading and good wetting over the Ni substrate(θ_((CP))~20°in 5 s)to form a final contact angle ofθ_(f(CP))~18°.In contrast,a different wetting behavior was observed for the CH procedure,where the unavoidable primary oxide film on the Mg surface blocked the spreading of liquid Mg showing apparently non-wetting behavior after 300 s contact at the test temperature.However,in both cases,the deep craters formed in the Ni substrates under the Mg drops and significant change in the structure of initially pure Mg drops to Mg-Ni alloys suggest a strong dissolution of Ni in liquid Mg and apparent values of the final contact angles measured for the Mg/Ni system.

舰载飞机着舰撞击载荷实测技术研究

针对国内飞机起落架载荷测量中普遍存在的静标动测问题,从理论和机理上分析了静标定的应变法实测动态载荷存在问题的原因。同时,考虑到舰载飞机因定点着舰方式遭受严重的动态载荷,重点研究了舰载飞机着舰撞击载荷的静标动测问题。通过动态落震试验模拟飞机着舰过程,根据测力平台的实测载荷分析,获取了应变法实测载荷精度受动态影响的程度,提出一种改进的惯性修正方法,即:通过落震试验数据辨识质量矩阵,通过辨识的质量矩阵和实测加速度修正应变法的实测载荷。试验结果表明,改进的惯性修正方法进一步提高了垂向载荷的测量精度,显著提高了航向和侧向载荷的实测精度。

基于停泵压降曲线的压裂窜扰效果定量评价--以吉木萨尔页岩油平台井为例

针对目前缺乏压裂窜扰效果定量评价方法的难题,创新提出一套基于停泵压降曲线的压裂窜扰效果诊断分析方法。结合井组拉链式压裂工艺,提出了4种典型窜扰模式下的停泵压降曲线,用以诊断压裂窜扰类型。选取吉木萨尔页岩油A平台6个典型压裂窜扰段开展实例应用,通过与微地震监测结果对比,验证了方法的有效性。在此基础上,利用压降试井解释方法对吉木萨尔“新井组内部压窜”和“新老井间压窜”两种典型的停泵压降曲线开展拟合分析,反演解释缝网参数。解释结果表明,新井组内部压窜使主次裂缝的改造效果均受到影响,具体影响效果因窜扰类型的不同而存在差异;新老井间压窜主要影响主裂缝的改造效果,导致缝网由“长宽”向“短窄”转变,有效体积降低28%,整体改造效果变差。

不同钢纤维掺量全轻混凝土梁落锤冲击试验研究

由于全轻混凝土结构抗剪承载力较低,因此有必要探究钢纤维的加入对全轻混凝土梁动力性能的影响。设计钢纤维体积掺量为0%、1%、2%共3根适筋梁,对其跨中区域进行落锤冲击试验,并利用LS-dyna有限元软件进行数值模拟,对比分析各试件破坏形态、冲击力时程曲线、跨中位移时程曲线。试验结果表明:在相同冲击荷载作用下随着钢纤维体积掺量的增加抑制裂缝产生和发展的现象越显著,并且裂缝相对更加集中于梁跨中区域,支座处裂缝相对减少。钢纤维的加入不影响试件冲击力最大值,但随着钢纤维体积掺量的增加,各试件冲击力第二峰值与最大值之比增加14%和26%,跨中位移最大值与残余位移分别降低3、8mm与3、7mm。经研究得出钢纤维的加入显著提高全轻混凝土梁抗冲击性能。

减蛋综合征病毒抗体胶体金免疫层析试纸条的研制及初步应用

为建立快速检测减蛋综合征病毒(EDSV)抗体的方法,基于EDSV的Fiber蛋白,制备快速检测EDSV抗体的免疫层析试纸条,为养禽业提供针对病原微生物的感染预警及免疫评估。利用胶体金标记EDSV Fiber蛋白抗原为探针,将羊抗鸡IgG和抗Fiber蛋白的抗体包被到硝酸纤维膜上,分别作为质控线和检测线,对家禽EDSV抗体水平进行监测。结果表明,制备的EDSV免疫层析试纸条具有高度特异性,与其他家禽病毒抗体无交叉反应,仅与EDSV抗体反应,在试纸条上产生可见的检测线;并且制备的试纸条具有高度稳定性,在室温条件下可至少保存6个月。应用制备的检测EDSV抗体的免疫层析试纸条对从河南、安徽、山东等地养鸡场采集的576份鸡血清样本检测,与血凝抑制试验(HI)结果进行平行比较,二者的Kappa值为0.878,具有良好一致性。综上,制备的检测ESDV抗体的免疫层析试纸条具有高度的特异性、敏感性、稳定性和易操作性,对EDSV抗体的临床检测具有实际应用价值。

跨域飞行器惯导装置设计及抗冲击测量方法

跨域飞行器由于工作环境复杂多变,在飞行过程中运动参数受瞬态冲击影响较大,导致导航精度降低且难以稳定控制。针对瞬态冲击导致跨域飞行器难以获取准确运动参数的问题,本文研制了一种基于大小量程加速度计组合的惯性导航装置,并提出了一种大小量程加速度计切换策略,利用巴特沃斯滤波器对采集的数据进行滤波处理,通过预设阈值的累计和控制图算法和自主可变滑动窗口实现对冲击点的检测,并采用分段式线性插值方法保证了数据的同步性,最后通过模拟仿真和跌落台试验对本文所提出的切换策略进行试验验证,试验结果表明,分段式线性插值方法的估计误差不超过0.6 g,并在小量程加速计测量值饱和后,切换至大量程加速计的测量值,满足了实时切换的要求,进一步证明该惯性导航装置及大小量程切换策略可应用于飞行器进行跨域试验。

基于Fluent的球形托卡马克装置磁体的水冷结构设计

应用Fluent软件对SUNIST-2球形托卡马克磁体内部流动与传热进行了数值模拟,对磁体的水冷结构设计进行了优化。依据SUNIST-2特定的工作状态,分别对磁体水冷系统在多种流速及不同进口温度条件下的性能进行了仿真分析,对比了各条件下的冷却效能与压力降。模拟研究表明,基于数值模拟优化的磁体水冷结构方案,显著增强了磁体在实际运行状态下的稳定性与安全性。加工后的磁体水冷结构的压力降测试的实验结果验证了数值模拟的结论。

二氧化铀粉末运输容器假想跌落事故下的安全设计与试验验证

目的设计易裂变二氧化铀粉末运输容器,证明容器在最危险姿态下,可以满足9 m跌落的核临界、屏蔽安全和放射性物质包容相关设计准则。方法设计外柔内刚的三层密封容器,内外壳之间填充聚氨酯减振吸能材料,建模分析容器多种姿态下的结构与功能材料动态响应,确定最危险跌落姿态。针对最危险工况开展实际跌落测试试验,证明容器在假想事故下的安全性。结果容器在最危险跌落工况下,聚氨酯材料减振吸能效果与设计计算相符,中子吸收板、中子慢化板等功能材料位置和缺损量符合要求。二氧化铀粉末的密封性得以保障。结论以有限元分析为基础的容器仿真分析与样机试验结果匹配度较高,试验样机通过了相关跌落试验,证明了容器在危险姿态下的9 m跌落安全性能。

350 km/h高速铁路隧道行车振动的波阻板隔振特性研究

地下铁路行车速度的提高对车致环境振动的控制提出了更高的要求。围绕350 km/h高速铁路隧道行车诱发的振动问题开展研究。基于车辆—轨道耦合动力学理论和有限元方法,构建了地下铁路车致振动预测模型,并通过现场振动试验验证其准确性。通过数值计算详细探讨了波阻板(wave impeding block,WIB)宽度、埋深和材料属性对隔振性能的影响。研究表明,隧道上方土体中设置水平WIB可显著降低行车引发的地面振动。特别地,当WIB布设位置靠近振源较近时,对5 Hz以上的振动成分呈现出显著的隔振效果。同时,WIB宽度、埋深与其隔振性能直接相关,但过大的宽度和埋深可能导致远场地面振动增强;多孔聚苯乙烯波阻块相较于橡胶、细砂及C30混凝土展现出最佳的隔振性能,特别是在5~200 Hz的振动频率范围内有较好隔振效果。

曳引摇枝式板栗落果装置设计与试验

针对当前丘陵山地板栗采摘困难、人工收获工作强度大、采收效率低等问题,设计了一种由柔性钢丝绳曳引振动的小型摇枝式板栗落果装置。建立板栗果实-果枝单摆动力学模型,分析果实脱落条件,得到板栗果实振动脱落切向加速度为285.36 m/s~2,得出影响板栗果实脱落的主要因素为果枝振动频率、振幅、振动时间;进行板栗果枝振动特性试验,用Default Shaker液压振动台以0~30 Hz扫频方式确定垂直方向上板栗果枝共振频率,并在频率7~15 Hz段进行驻频试验,得出振动落果较优频率为10~12 Hz。根据果枝振动试验结果,利用ADAMS软件对摇振机构进行仿真,结果表明,摇杆振幅大于95 mm时,果枝末端加速度可满足板栗果振动脱落的加速度条件,确定了落果装置参数设计的合理性。设计了三因素三水平正交试验,试验结果表明,板栗落果最佳作业参数组合为摇振频率11 Hz、振幅135 mm、摇振时间30 s,此时板栗落果率为91.9%,树皮损伤率为8.8%,满足农业机械推广鉴定标准中树皮损伤标准。

粗骨料纤维充填体的力学特性与能量损伤演变规律

为提升充填体的抗拉性能、抗裂性能和韧性,通过抗压、巴西劈裂和落锤冲击试验研究了聚丙烯纤维对充填体强度特征、变形特征、抗冲击性能和能量演变的影响。结果表明:随着纤维掺量增加,充填体强度先增大后减小,弹性模量逐渐降低;掺入纤维后,充填体总耗能增加,达到峰值后释放动能减小,摩擦内能增加,可促进弹性应变能转变为耗散应变能;随着纤维掺量增加,充填体冲击耗能、延性比和韧性系数先增大后减小,终裂形态由“开裂即碎”演变为“裂而不碎”;掺入0.10%纤维的充填体抗拉强度、韧性和抗冲击等性能最优。强化机制主要是充填体内纤维“筋网结构”延缓裂纹产生、抑制裂纹扩展和提升能量吸收上限。研究成果有助于提升采场充填体顶板的稳定性,保障矿山生产作业安全。

应用于低速冲击的新型力学超材料

目的针对低速碰撞场景下的吸能缓冲需求,设计一种具有准零刚度特性的新型力学超材料。方法首先对力学超材料的几何结构进行参数化建模,超材料主要组成包括薄壁结构与格栅结构。薄壁结构为正弦构型的曲梁,格栅结构由圆杆组成,将薄壁曲梁连接成整体。为了缩短不同应用场景下缓冲结构的设计周期,提出了一种结构力学响应的计算方法。首先建立基于欧拉-伯努利梁原理的薄壁结构运动微分方程,随后提出了一种基于四阶龙格库塔法以及打靶法的数值求解方法,最后基于叠加原理,提出了缓冲结构的力学响应预测方法并进行了相应的线性补偿。结果提出的数值算法可以准确地计算大柔度薄壁结构的力学响应,从而减少设计迭代的次数,大幅缩短设计周期。结论准静态试验结果表明,提出的超材料构型具有准零刚度的特点,并且压缩率超过70%。落锤冲击场景下缓冲结构无明显的初始峰值,响应载荷得到抑制。这说明这种超材料在缓冲领域具有很大的应用潜力,尤其适用于体积受限场景下的冲击防护。

一种组合式二级缓冲吸能装置的吸能特性研究

基于胀管和泡沫铝的缓冲吸能特性,以能量吸收值为设计目标,提出了一种新型二级缓冲吸能装置设计方法,并通过准静态压缩试验和落锤冲击试验验证了该方法的有效性。试验结果表明:该二级装置可实现预期的多级梯度应力平台。建立了二级缓冲吸能装置的有限元模型,通过仿真分析其在不同冲击工况下的动态响应和能量变化特征,该装置泡沫铝和胀管部分吸能占比可达80%,且更换主要耗能部分后其余构件可实现重复使用,并针对其失效模式提出优化方法,有效增加耗能材料的利用率和装置的整体稳定性。