Dynamic Testing Technology Research Articles

Experimental Mode and Vibration Comfort Analysis of High-Rise Glulam Building Floor Structure

In order to better meet the objective requirements of the use safety of the high-rise glulam building floor structure and the living comfort of the residents, the transient excitation, environmental excitation and frequency spectrum identification methods were used to carry out experimental modal test in-site on the three rooms numbered A, B and C of the same glulam structural building. The three rooms have different functions, different floor sizes and different floor supporting structures. The research results have shown that the first-order bending frequency of the floor structure of Room A is 27.50 Hz, the transverse second-order bending frequency is 34.75 Hz, the longitudinal second-order bending frequency is 53.25 Hz, and the first-order torsional frequency is 56.25 Hz. The reinforced wooden beam at the bottom of the floor of Room A increases the transverse stiffness of the floor structure, but does not offset the anisotropy caused by the longitudinally installed glulam floors. The fundamental frequency values of the floor structures of the three rooms numbered A, B, and C are 27.5, 13 and 18 Hz, respectively. This has a relatively high innovation and reference significance for integrating the theory of structural dynamic characteristics with the dynamic testing technology, improving the design level of high-rise glulam structure buildings, and improving the living comfort of residents.

Numerical and experimental studies on dynamic gas emission characteristics of boreholes.

The gas emission rate of boreholes is one of the most important indices for coal and gas outburst prediction. In this work, instantaneous gas emission velocity and environmental effects on borehole gas emission were studied. Through theoretical analysis, the mechanism of crack propagation in the coal borehole was clarified, and the effect of soft and hard coal on gas desorption and gas emission. The results of numerical simulations also indicated that the initial gas emission has a function relationship to the drilling distance and the physical characteristics of the coal seam. A novel dynamic testing technology was proposed to obtain gas emission velocity. Laboratory experiments under adsorption and desorption of CO2 and N2 were performed using coal samples from Xuehu, Fenghui, Weishe, and Wuzhong coal mines. The data of initial gas emission under different coal samples were recorded, and the fitting curves were obtained. The results show a positive correlation between initial gas emission and drilling depth. However, abnormal would occur when the drill pipe enters the soft stratification, and the maximum value of the initial gas emission of the abnormal part is 3.8 times the normal value, which indicates a high degree of sensibility to soft stratification. The results were revealed the dynamic gas emission law of boreholes.

The mechanical behaviours of the Ti-10V-2Fe-3Al alloy under the high-temperature and dynamic loading conditions

In this work, we develop a high-temperature dynamic testing technology for characterizing the properties of Ti-1023 alloy. The modified Hopkinson torsion bar system includes a high-temperature furnace subsystem and a water cooling subsystem. High-temperature dynamic tests of the alloy are performed. The dependence of the yield stress on the temperature and the shear strain rate is studied. The scanning electron microscopy observations show that the microstructural evolution makes up of two steps: the first one is caused by thermal loading and the second one by the mechanical loading. The high-temperature dynamic constitutive model is established based on the experimental results.

Research of the Snatch and Holding up Safety Automatic Control System for the Farm Grasping Grass Machine

This paper introduced tilting accident phenomenon of the farm grasping grass machine in the practical application. Through to analyze overturn accident of instantaneous critical stress state at work, this paper put forward a basic idea that can control and prevent the overturn accident, designed the snatch and holding up safety automatic control system. It can detect the pressure changes of lifting hydraulic by installed pressure sensor in the lifting oil cylinder, and with the aid of weight-pressure mathematical model, cooperate with dynamic testing technology measures and corresponding measures of hardware, to realize the dynamic real-time monitoring of snatch and holding up weight. That the function of accumulated and recorded load, the early warning of overweight and accident prevention about falling down are realized by the system overall structure and software design.

SVD-based MEMS Dynamic Testing Technology

To obtain the MEMS micro structure's high resolution measurement dynamic parameters ,this paper ,by obtaining stroboscopic imaging technology of micro structure of moving image sequence, proposed one kind based on the phase correlation technique and singular value decomposition technique combining sub-pixel measurement method. By the method of phase correlation, image space coordinate can transform into the frequency domain to the coordinates of the parameter space. And then through the singular value decomposition technique to obtain the correlation matrix, using the least-squares fitting, get the sub-pixel level displacement measurement results. The experimental results show that, with this method of measuring MEMS micro structure plane motion amplitude can reach sub-pixel accuracy, and can be effectively reduced by uneven illumination effect on the measuring result, thereby increasing the measurement results of stability and reduces the measuring error. DOI: http://dx.doi.org/10.11591/telkomnika.v11i1.1870

Experimental Study of Pile Foundation Dynamic Testing Used in the Anchor Rod Nondestructive Testing

The dynamic testing of stress wave reflection method is an easy, economical, rapid and reliable nondestructive testing technology and has been perfected used in the pile foundation dynamic testing. Anchor rod is more in line with the wave theory of one-dimensional elastic rod than pile foundation whether to theory or the geometric solid, material, stress state and other factors. The quality of anchor rod is determined by using small strain method (hammering method) of pile foundation dynamic measurement. Four testing anchor rods with different length and integrity were made in project of "China Marine Sport School", stress wave time domain curve of anchor rod was obtained by ZK-7E portable intelligent testing of piles instrument, defect location, length of anchor rod and integrity reflected by measured waveform are consistent with the actual situation, the method using pile foundation dynamic testing technology for anchor rod nondestructive testing is proved feasible and reliable.

Research on the Sensitivity Damage Identification Method Based on Closed-Loop Feedback Control

The structural mode parameters are identified by dynamic test technology, the system mode sensitivity(the structure parameter changes with characteristic parameter) is defined. At the same time, the controlled target is constructed according to feekback way, then the damage identification sensitivity is improved by feekbace force and its place. Finally, a simulant example is given to show the effective aspects of the method.