Papers by Keyword: Stress Wave

Abstract: Stress wave test technique has broad prospects because of the long distance, large scale and relatively low cost. This paper studies the stress wave propagation characteristics in the butt weld joints in the case of external symmetrical impact. The stress wave propagating before and after the joints is measured by dynamic strain gauge. Then model analysis and simulation is applied to research stress wave. The results show the loss of stress wave is small. After spectrum analysis, the change of propagating stress wave can be detected.

Abstract: The properties of the SW and its transmission law in the low-speed rolling bearing were studied in this paper. Firstly, the three-dimension contact model of the bearing was set up. The defects which occurred on the outer race were simulated in the model. According to the model, the stress, the strain and the contact stress distribution was computed. Then, the stress and strain distribution law and the contact stress distribution law of the interface on good and fault bearing were compared. In the real-world testing, fault signals were acquired using stress wave transducer. Fault characteristic parameters were extracted and the background noise was reduced using wavelet analysis. Both simulation and real-world testing result obtained indicate that SW and wavelet transform can be the effective method in the fault diagnosis of low-speed bearing.

Abstract: The procedure of beam subjected to transverse impact by bar is simulated using numerical method. The method considers the propagation of the expansion wave and shear wave in beam. The effect of beam height on elastic impact loads with different bar lengths and beam heights are investigated. With condition that the length of beam is longer than or equal to that of bar, the numerical solution shows that: when the bar length is constant, if the length of bar is shorter than the height of beam, the longer the bar, the bigger the peak value of impact force; the impact load curve consists of ascending and descending part basically; When the bar length is longer than or equal to beam height, the peak value of impact force is not related to the bar length and equal to that of bar with the same length as the beam height; the impact load curve is trapezium. The contact time is proportional to bar length and equal to the duration time of stress wave propagation in the bar for once return. If the bar length is constant, when bar length is shorter than beam height, the impact load is not related to beam height; when bar length longer than or equal to beam height, the peak value of impact force increases along with the beam height and approach to that of bar with the same length as the beam height.

Abstract: High velocity compaction technology was used to press 316L stainless powders. Effects of impact times on stress wave, green density and ejection force were analyzed. It was found that under the same total impact energy, the first loading time and the actuation duration of the second impact in double impact process were longer when compared with single impact process, while the first delay time was shorter. Furthermore, the green density of compacts prepared by double impact was greater than that prepared by single impact, but no obvious variation in maximum ejection force can be observed between single impact and double impact process.

Abstract: The dynamic pile driving process is so complex that till now the analysis on the process had been focusing on the filed test or laboratory test. However, the past study about the dynamic process is a time consuming one; with the computational method development, the numerical simulation on this process is possible. In this paper, explicit dynamical analysis method is adopted, the pile is simulated using the elastic solid element, two computational cases are considered and finally the pile driving process dynamical stress is studied.

Abstract: The dynamic modulus of elasticity (MOE) of forty one small Acer mono clear wood specimens was tested via stress wave, ultrasonic wave, edgewise vibration and flatwise vibration method respectively in laboratory. Then the static MOE of these specimens was measured with static bending test. The correlations between dynamic and static MOE were analyzed using linear regression method, and the difference of various methods was discussed using paired t test. The results show that the dynamic MOE of wood measured by four methods described above are higher than the static MOE, but their linear correlation is significantly strong. Thus, it is feasible to estimate static MOE using these four methods. Additionally, the mean of paired difference between static MOE and dynamic MOE tested by flatwise vibration method is least, and the correlation highest. Therefore, it is better to use flatwise vibration method to estimate static MOE of wood.

Abstract: This paper presented a new propagation time estimation method based on ICA-domain filter. The technique consists of two steps. Firstly, denoising in ICA domain by sparse code shrinkage was applied to each received signal to recover the original waveform. In the process, a new shrinkage function was designed to make the filter more adaptive. Then, the propagation time was found by locating the peak of the cross-correlation function. The propagation time estimations under several conditions were simulated to evaluate the performance of the method. The experiment results show that the proposed method performs better than classic correlation methods, which makes it an efficient method in wood nondestructive evaluation.

Abstract: The specification of the vibration cutting loading is a decision factor for the generation of stress wave and the stress wave propagation has a significant impact on its micro-mechanism. Making the stress waves’ generation in the cutting area of vibration cutting for entry point, the analysis of internal inflection wave, inflection fracture and dynamic stress intensity factor has been carried out, the simulation of vibration cutting has also been done by finite element method, the essential of energy concentrated role, shear angle increment and cutting quality improvement has been explained.

Abstract: Reviewed the achievements and advances in the vibratory metal machining, analyzed the features and mechanics in microstructure with SEM. The dynamic stress intensity factor is derived on the basis of fracture mechanics and stress-wave theory with the Griffith- II type sliding-open crack.. Comparison between the vibratory machining and the conventional machining has been made with brass on lathe CW6150B, with computer controlled piezoelectric ceramic micro-drive system and cutting forces and surface texture of the specimen were observed. The dynamic stress intensity factor was discussed and it was found that the value of dynamic stress intensity factor may be high with response to the Heaviside impulsive loading, indicating the reason why vibratory machining has better comprehensive results than the conventional one does.

Abstract: Due to the special heating mode of High Current Pulsed Electron Beam (HCPEB) irradiation, intense stresses such as thermoelastic stress, quasi-static stress, and shock wave stress can be generated by a dynamic thermal field. A dynamic thermo-stress is the origins of these stresses. The simulations for non-melting and melting modes are respectively compared with related phenomena such as bending, surface plastic deformation, and residual stress (non-melting mode, quasi-static stress-related), crater formation, depth distribution of microhardness, fragmentation of pearlites (melting mode, shock-stress wave-related).