Papers by Keyword: Impact Effect

Abstract: Ultrasonic-assisted metal forming have been studied numerously in conventional macro scale. However, ultrasonic dynamic impact effect, occurring in micro scale, has never been studied thoroughly, which makes the characteristics of material deformation more unpredictable in ultrasonic-assisted micro forming. The purpose of this study is to confirm the critical condition for occurrence of ultrasonic dynamic impact effect and to investigate the dimensional height dependency of ultrasonic dynamic impact effect on material deformation. In this paper, commercially pure aluminum 1100 with varying height (φ2×2mm, φ2×1.5mm, φ2×1mm) were selected for conventional static (without ultrasonic vibration) and ultrasonic-assisted compression tests. Ultrasonic-induced stress reduction was evaluated and the contour shape of deformed specimens was compared to investigate the ultrasonic dynamic impact effect on material deformation. The results showed that, as dimensional height of specimen decreased, ultrasonic vibration can reduce forming stress more effectively. In addition, a surprising anti-barreling shape and a significant contact surface area expansion were observed near contact surfaces in every specimen compressed with ultrasonic-assistance, indicating that additional plastic deformation can be produced by ultrasonic dynamic impact effect. An ultrasonic dynamic impact factor (y) is proposed and estimated by an exponential type trend line as y = 2.42e^-1.48x for different dimensional specimen height (x) to quantify the ultrasonic dynamic impact effect. The promising prospect of ultrasonic vibration in micro-forming was demonstrated by the findings above, which helped to provide a basis to understand the underlying mechanism of ultrasonic-assisted micro forming and design the process in the future.

Abstract: The essence of the axle coupling vibration in case of random bridge deck is random vibration, therefore, it is quite necessary to research the effect of vehicle impact on basis of statistic analysis. With some large concrete-filled steel tube arch bridge as the object, by applying a self-made analysis program on axle coupling vibration that was demonstrated by a dynamic test, a dynamic response analysis on axle was implemented for many groups of random roughness swatches. On basis of the analysis result, a statistic analysis was conducted for the dynamic impact effect of bridge under the conditions of different deck status and vehicle speeds, in the determination of vehicle speed and roughness, the impact factor obeys the normal distribution. The analysis result shows that, the level of deck status may apparently affect the mean value and the MSD(mean square deviation), the differences of vehicle impact factors in case of different assurance rates are large. It will effectively improve the reasonableness and scientificalness of the value of a vehicle impact factor to determine the impact factor according to the level of bridge importance and a statistic analysis method.

Abstract: The simulation models concrete filled steel tubular arch was constructed by using a finite element software, the 1/4 vehicle model and vehicle vibration equilibrium equation were derived by D Alemberts principle, samples of each bridge roughness were created by using the discrete Fourier transform method, the effect of bridge roughness and vehicles speed on the impact coefficient of the suspenders. The results showed that the bridge roughness had a strong influence on the impact coefficient of the suspenders; the impact coefficient fluctuated with a raise of vehicles speed; the dynamic internal force of the suspenders obviously increased with the shortening length under the vehicle load. Theory basis can be provided for the fatigue fracture inclination of the middle and short suspender in the half-through and through bridge, and a reference can be provide for the bridge design, maintenance, management, survey and evaluation.

Abstract: As a new structure type, arch bridge of concrete filled steel tube (CFST) has many merits and unique dynamic characteristics. Some present researches indicate that the CFST arch bridge has obvious impact effect, but the research on its dynamic performance due to vehicle is relative backward. In this paper, power spectral density function is selected to simulate the roughness of pavement, the dynamic equation of vehicle-bridge is built with seven degrees of freedom vehicle model. Based on separated iterative method, the parameters’ influence of CFST arch bridge on dynamic performance due to vehicle is carried out systematically. The analysis results are useful and helpful for the design theory of impact effect of CFST arch bridge.

Abstract: Euler beam dynamic analysis model under moving loads and wheels plus spring-damper-sprung mass action were established respectively. The simply-supported beam motion control equations were derived and the corresponding simulation analysis procedures were worked out. The vertical dynamic responses of simply-supported bridge under typical vehicles at different speeds were studied systematically. Impact factors calculated from the two analysis model were compared with the values of the current bridge specifications. It is shown that vehicle inertia force has little effect on the vertical deflection and vertical vibration acceleration of the bridge, the vehicle impact effect on bridge gradually go up with the passing speed increasing, vehicle weight has great influence on the vertical vibration of the bridge. The problem of passing overloaded vehicles must be considered seriously in bridge design and use.

Abstract: To investigate the seismic response of long-span rigid frame bridges with high-pier, the shaking table test of a 1/10 scaled rigid frame bridge model is introduced in this paper. Details about test equipment, model design, test arrangement, input ground motion waves and test principle are provided. The response of bridge model under the seismic excitation included the uniform excitation and the multi-support excitation is observed. The influence of the soil-structure interaction on the bridge is considered through the real-time dynamic hybrid testing method. The impact effect for different ground motion input during the test is discussed. The influence of multi-support excitation, soil-structure interaction and impact effect on structural seismic responses are studied based on the test results. The isolation effectiveness and the damping effect are discussed as well.

Abstract: It is well-known that in modern through arch bridges the suspenders are important components since they connect the bridge deck and the arch ribs. When the suspender break happens, the other components of the through arch bridge will be impacted successively. Sometimes, the collapse of bridge deck may be induced by the possible suspender break. In this paper, the impact effect on the remaining components of the through arch bridge due to the suspender break is studied and obtained by appropriate simulation and time-history analysis using the comprehensive commercial software ANSYS, which is based on a real through arch bridge. The study in this paper will be helpful to carry out the reasonable design of the through arch bridge.

Abstract: Based on the finite strip thought and displacement interpolation function of Bernoulli-Euler beam element, using the transformation relationship between skew coordinate and Cartesian coordinate system, a new kind of thin parallel slab element was established, element stiffness matrix and consistent mass matrix were derived. The vibrating frequency of simply supported skewed slab was calculated. Computing results were compared with theoretical results and Ansys results. The maximum error was 2.68%. Changing the mesh density of skew slab, the convergence of present element was tested. Examples show that this element has the features of high precision and strong convergence. At last, the vibrating frequency coefficients of skew slab bridge with different ratios of span to width were provided, which can be adopted to compute the vehicle’s impact factor of skew slab bridge by specification method.