孔间超短延时台阶爆破干扰降振技术

为寻求台阶爆破降振效果最佳的孔间延时时间,借助ANSYS/LS-DYNA程序对台阶爆破在不同延时起爆时间条件下产生的爆破振动进行了数值模拟对比分析,并通过试验进行了验证。数值模拟和试验结果表明:在浅孔台阶爆破中,爆破降振效果最佳的孔间延时时间为5 ms;在深孔台阶爆破中,爆破降振最佳的孔间延时时间为7～10 ms。实际爆破施工中,不同的岩石条件下、不同的爆破参数时,数码雷管减振的最佳孔间延时应该在5～10 ms区间范围,应根据实际情况进行调整。研究成果解决了复杂环境下的爆破振动危害控制难题,研发的孔间超短延时台阶爆破干扰降振技术,为爆破振动控制要求严格的工程设计和施工提供参考和借鉴。     

Biomechanical response of the human foot when standing in a natural position while exposed to vertical vibration from 10–200 Hz

Exposure to foot-transmitted vibration (FTV) can lead to pain and numbness in the toes and feet, increased cold sensitivity, blanching in the toes, and joint pain. Prolonged exposure can result in a clinical diagnosis of vibration-induced white foot (VIWFt). Data on the biomechanical response of the feet to FTV is limited; therefore, this study seeks to identify resonant frequencies for different anatomical locations on the human foot, while standing in a natural position. A laser Doppler vibrometer was used to measure vertical (z-axis) vibration on 21 participants at 24 anatomical locations on the right foot during exposure to a sine sweep from 10–200?Hz with a peak vertical velocity of 30?mm/s. The most notable differences in the average peak frequency occur between the toes (range: 99–147?Hz), midfoot (range: 51–84?Hz) and ankle (range: 16–39?Hz).

Practitioner Summary: The biomechanical response of the human foot exposed to foot-transmitted vibration, when standing in a natural position, was measured for 21 participants. The foot does not respond uniformly; the toes, midfoot, and ankle regions need to be considered independently in future development of isolation strategies and protective measures.     

Microstructure evolution and mechanical properties of ultrasonic assisted laser clad yttria stabilized zirconia coating

Yttria stabilized zirconia (YSZ) coatings were fabricated on a titanium alloy substrate by ultrasonic assisted laser cladding technique and the effect of ultrasonic vibration on the microstructureevolution and mechanical properties was investigated. Experimental results indicated that with the increase of ultrasonic output power, the clad depth increased, the wettability between coating and substrate was improved, the size of equiaxed grains in the cladding zone decreased, and the band structures were broken up gradually. Simultaneously, the element content distribution along the thickness of coating in the transition region changed from exponential to linear distribution gradually, together with the increase of dilution rate. With the increase of ultrasonic output power, the microhardness distribution of fusion zone also converted from an exponential to a linear distribution. Additionally, the friction and wear tests showed that the wear mechanism of coatings both with and without ultrasonic vibration was abrasive wear while the friction coefficients of coating with ultrasonic vibration were lower than that without ultrasonic vibration, which was related to the refined microstructures within the YSZ coatings.     

Vibrations of an aramid anchor cable subjected to turbulent wind

The vibration response of an initially pre-stressed anchor cable made of parallel-lay aramid fibres excited by a measured and artificially simulated spatial turbulent wind field is presented in the paper. Results of the analyses of in situ measured wind records are described. For selected data set statistical characteristics and power spectral density functions of the measured wind velocity components are calculated. The wind stochastic velocity fluctuation is modelled as a one-variate bi-dimensional random field. Cross-power spectral density functions, at different point locations are introduced. The combination of the weighted amplitude wave superposition method (WAWS) with the Shinozuka–Deodatis method is used for the analyzed problem. A time-dependent behaviour of the synthetic cable is investigated which is subjected to turbulent wind with large expected oscillations that arise as a result of slackening due to the relaxation effects. A nonlinear transient dynamic analysis is used in conjunction with the finite element method to determine the dynamic response of the cable subjected to turbulent wind at its initially prestressed state and in the selected times after the relaxation effect. The constitutive equation of the relaxation of the aramid cable follows an experimentally obtained law of the logarithmic type. To monitor the dependences of the individual quantities of cable vibration in the phase space, attractors and Poincaré maps are created by sampling the cable’s displacement and velocity at periods of relevant frequencies. Interesting findings based on the response of the cable with rheological properties to turbulent wind are presented.     

CLN 600MW汽轮机组轴系振动治理

文章通过对4号汽轮机组轴系实际振动测量数据以及TN8000机组振动在线监测分析故障诊断系统、生产实时监视系统图形数据的分析,找出了引起4号汽轮机组轴系振动的主要原因,并提出了解决的方法和措施。     

桩土耦合的桥梁管桩涡激振动数值模拟

采用有限元软件对跨海桥梁管桩涡激振动进行了数值模拟,分析了流速,土体刚度对管桩振动幅值的影响,结果表明:流速越大,桩体振动幅值越大,振动越剧烈,在相同流速下,土刚度对管桩振动幅值有着明显抑制作用,是一项不可忽略的参数。     

Vibration component separation by iteratively using stochastic resonance with different frequency-scale ratios

It is well-known that stochastic resonance (SR) is mainly used for signal denoising and weak signal detection. In this paper, we firstly find the frequency range selection characteristic (filtering characteristic) of re-scaling frequency SR (RFSR) caused by the driving frequency limitation of bistable SR. It then follows that a novel approach to separate vibration components with different frequencies by iteratively using SR is explored. The frequencies of most vibration signals exceed the driving frequency limitation, thus by use of different frequency-scale ratios, the vibration signals with different frequency range can be extracted by RFSR. Firstly, a small frequency-scale ratio is used to obtain the vibration signal with a narrow frequency range, i.e. low frequency vibration. As the output of SR may have a phase lag, a simple phase-shift correction method is proposed to improve the accuracy of signal component separation. The phase-shift corrected signal of RFSR output is separated from the original vibration signal and the residue is treated as the new vibration signal. Then, increasing the frequency-scale ratio according to a searching algorithm, the vibration signal with higher frequency can be obtained by RFSR. Through this iterative process, several harmonic vibration components can be separated from the original noisy vibration signal. The proposed method, empirical mode decomposition (EMD) and Hilbert vibration decomposition (HVD) are respectively applied to analyzing a simulated vibration signal and extracting the fault feature of a rotor system. The contrastive results show that this proposed method has good frequency resolution and can successfully separate monocomponent harmonic signals from a strongly noisy multicomponent harmonic vibration signal while EMD and HVD cannot.     

建筑物内振动源变频改造前后楼板振动测试与分析

针对采取简单减振措施后的设备振动仍然会引起楼板明显振感的情况,在进行原因分析后,通过改变振动源工作频率,并取得了良好的减振效果。     

基于小波分析的蜗轮蜗杆减速器故障诊断系统

随着蜗轮蜗杆减速器的广泛应用，其故障类型表现为复杂化和隐蔽化，这不仅会带来巨大的经济损失，甚至威胁工人的生命安全。为解决这一问题，提出了基于小波分析的蜗轮蜗杆减速器故障诊断系统，系统在模拟减速器真实工作情况的基础上，采用LabView编写故障诊断系统，实现对振动信号进行采集与显示、小波分析以及离线故障诊断，实验结果表明，文中提出基于小波分析的蜗轮蜗杆减速器故障诊断系统，能够较好地实现蜗轮蜗杆减速器故障的实时诊断，适用于蜗轮蜗杆减速器技术研究和安全应用等领域。     

Fest‐Flüssig‐Trennung von feindispersen Suspensionen durch Pressfiltration bei pulsierendem Überdruck

The productivity of filtration systems for dewatering of finely dispersed suspensions can be increased by pulsating overpressure. For suspensions of marine organic‐mineral sediments, press filtration processes were investigated under static and pulsating overpressure. The influence of the static pressure component, the pressure amplitude characteristic, the pressure vibration frequency, and the filtration time on the volume of filtrate were determined. Based on Darcy's law, a model of the filtration process under static overpressure was developed. For pulsating overpressure, the mathematical theory of experiment planning and the statistical data analysis method were used.