Experimental Study of Structure Shock Vibration in Soil Caused by Explosion of Conventional Weapons

When hitting underground structures directly or exploding in rock-soil media near underground structures, the conventional weapons with large charge weight will make underground structures be subjected to strong shock vibration and cause personal casualty and damage of precision electronic equipments. The shock vibration has become one of the cardinal killing means of weapons. However, the existing methods of predicting structure shock vibration are limited evidently. In this paper the coupling coefficient of acceleration in clayey soil is obtained firstly. Subsequently based on repeated experiments of chemical explosion, after dimension analysis and by using method of multivariate stepwise regression, the calculation formulae of shock vibration acceleration for the underground structure are obtained finally. The formulae consider top and side explosion respectively, taking into account the effects of penetration depth, charge weight, distance to explosion center, rock-soil media, size of structure and buried depth. They are easy to use with high practicability and degree of confidence, and can provide credible evidence for prediction of shock vibration and vibration isolating design of underground structure.     

Development of integrated precision vibration-assisted micro-engraving system

A novel precision vibration-assisted micro-engraving system was developed by the integration of fast tool servo and ultrasonic elliptical vibration system, in which the flexure hinge was designed to avoid backlash and PID control algorithm was established to guarantee specific precision. Apart from experimental validation of the performance of the system, various micro-V-grooves cutting experiments on aluminum alloy, ferrous material and hard cutting material were performed, in which Kistler force sensor was used to measure cutting force. Through experiments, it was clear that the vibration-assisted micro-engraving system can ensure good quality of micro-V-grooves and reduce cutting force by about 60% compared with traditional removal process without ultrasonic vibration.     

平板叶片的相关激励响应试验

为了研究不同频率的激振力叠加作用下平板叶片的位移响应变化,在平板叶片上选取激励点和多个响应点进行相关性激励试验。试验中,首先运用设计的加法器对频率为112、280和583 Hz的简谐力分别进行叠加,然后以压电陶瓷片作为激振器对平板叶片进行激励,同时以压电陶瓷片作为感应器采集位移响应,最后应用谱分析方法对位移响应进行分析。通过对比不同频率的激振力叠加作用下的位移响应自功率谱幅值,发现自功率谱幅值比单一频率激振力作用时有所降低,并且降低的程度和与其叠加的激振力频率的大小和个数有关,叠加的个数越多,降低的程度越大。     

液压轴表面裂纹成因分析

利用光电直读光谱、光学显微镜与显微硬度计对某厂表面开裂液压机械的液压主轴的成分、组织进行了分析。结果表明,液压轴的原材料符合中国GB标准45钢的成分要求;经高频淬火、磨削后的液压轴的组织为磨削热作用产生的不同程度的回火组织;表面裂纹产生的原因是液压轴材质、热处理工艺及磨削工艺不当三方面综合作用的结果。液压轴材质存在网状铁素体并且未经热处理消除,降低了材质表面的强度;磨削工艺不当使表层产生不同程度的回火带和应力集中;材质缺陷与工艺不当综合作用导致液压轴表面产生裂纹。     

电磁振动对金属粉末注射型坯结构均匀性的影响

把电磁振动技术引入到金属粉末注射成型中,在一定的工艺条件下,逐步调节振动频率和振幅,制备出不同振动条件的注射型坯,并通过SEM等实验手段对型坯的物料分散状态和微观结构进行研究,以探讨振动频率和振幅对型坯微观结构的影响。结果表明：施加振动后,型坯微观结构均散程度大大提高,且随着振动频率或振幅的不断增大,均散程度逐渐达到最好后,均匀和完善程度有所降低,但仍然好于稳态成型时的状态。     

Transmission of vibration from a vibrating plate to the head of standing people

Little is known about the transmission of vibration to the head when using whole-body vibration (WBV) training machines. This paper investigates the effect of frequency and posture on the transmission of vibration from a vibrating plate to the head of standing people. Nine male participants were exposed to vertical vibration at nine frequencies in the range of 17–46 Hz and vibration acceleration in the range of 7.85–18.64 m/s² (peak). The participants adopted four standing postures described as standing with locked knee (LK), bent knee (BK), one leg (OL), and one foot to the front and the other to the back (FB). The transmissibility to the head differed among postures (t-test, p < 0.05) and was greatest with the FB posture and smallest with the BK posture. The transmissibility to the head decreased with increasing the frequency (t-test, p < 0.05) but the extent of the decrease depended on the adopted posture. This frequency-posture interaction effect on the transmissibility should be considered when designing a training program. The data will be useful for developing standards/protocols that govern the use of WBV machines as well as for building human body models that can predict potential risks arising from using WBV machines.     

用经验模式分解和重标极差分析法进行摩擦振动信号分析

为提取和表征摩擦振动的特征信号,在摩擦磨损试验机上进行以船用柴油机缸套和活塞环为材质的摩擦副摩擦磨损试验.应用经验模式分解(Empirical Mode Decomposition, EMD)对非线性、非平稳的摩擦振动信号进行分解,获得若干个本征模式函数(Intrinsic Mode Function, IMF).从中选择反映摩擦振动特征的IMF重新合成摩擦振动特征信号,应用重标极差分析法对摩擦振动特征信号进行分析,得到线性回归谱和Hurst指数.结果表明,EMD能够实现摩擦振动特征信号的提取,重标极差分析法可以分析摩擦振动信号的渐变过程,提取摩擦振动信号的特征.该方法可为基于摩擦振动信号的机械摩擦副摩擦磨损行为的研究提供新的途径.     

振动训练的生理基础与应用研究进展

采用文献资料法,分析了振动训练影响运动能力及其提高肌肉力量可能的生理学机制,综述了振动训练的研究进展,旨在为教练员和运动员及体育健身者认识和合理利用振动训练方法提供理论依据。     

不同频率全身振动刺激对运动员下肢肌群力量训练效果的对比研究

采用PHYSIO PLATE振动训练台,对北京优秀垒球、女子游泳及女子跳水运动员进行同振幅下不同频率振动刺激力量训练,并采用MERAC等速肌力测试系统,对实验前后以及实验中运动员下肢肌力变化情况进行对比研究。研究发现,抗负荷力量训练附加振动刺激可以有效地提高力量训练的效果,能够以相对较小的负荷有效地提高肌肉的最大力量、爆发力以及肌肉耐力;同振幅下,次高频(35Hz～50Hz)振动刺激对肌肉最大力量、快速力量、爆发力以及肌肉耐力的训练效果显著高于中低频(25Hz～35Hz)振动刺激。     

全身振动介入抗阻力训练对能量消耗的影响研究

探讨全身性振动介入抗阻力训练对能量消耗的影响,为体重控制及健身减肥者制定有效的运动处方提供依据。方法：以我院体育教育专业健康男性为对象,利用气体代谢分析仪及心率表对"振动介入+抗阻力训练"（实验组,Resistance exercise+Vibration,REV）及单纯"抗阻力训练"（对照组,Resistance exercise, RE）模式下的摄氧及能量消耗等指标进行监测,并运用SPSS17.0对相关指标进行统计分析。结果：1）REV组在训练中及训练后0-25分、25-50分的总每分钟能量消耗及每分钟最大摄氧显著高于RE组;2）抗阻力训练结束后相当长的时间内以脂肪消耗供能为主,表现为REV组脂肪供能比例明显高于RE组;3）抗阻力训练能显著提升训练中呼吸交换率及换气量,表现为REV组提升率高于RE组。结论：全身性振动介入抗阻力训练可比单纯抗阻力增加更多能量消耗,且在训练后恢复期能提升脂肪供能比例,故控体重运动员及健身减肥者将振动作为辅助训练手段是非常有效的。