Papers by Keyword: Bursting

Abstract: With the excavation depth increase，the bursting stabilization had become a major factor affecting the security of foundation pit. On the base of research situation about foundation pit stabilization and a large number engineering practices，the factors and the complexity that affected the stability of foundation pit were analyzed. The new ideas about mechanism and determining methods of bursting in foundation pit were proposed，that with the “hydraulic fracturing” to explain the mechanism of bursting and the factors that affect the stability of foundation pit as a system to analyze the anti-bursting stability and the factors that affect bursting stability could be divided into two types, system strength and system stiffness.

Abstract: In recent years, tube hydroforming has been considered by automobile and airplane industries, because it decreases weight and increases solidity of parts. For this reason, technical knowledge for manufacturing with better quality and accuracy has been developing. However, there are some probable defects in forming by hydroforming technique, which are bursting and wrinkling caused by improper loading paths. Therefore, it is very important to apply a proper path pressure proportional to axial feeding. In this research, firstly, tube hydroforming in a box-shaped die has been simulated by means of 3-D FEM in explicit dynamic software ABAQUSE 6.9-1. For prediction of these occurrences, different paths of pressure have been analyzed and then by comparison with obtained results from the simulation performed such as thickness distribution and final form of the tube, the range of pressure and axial feeding have been predicted. Accordingly, optimal range and loading path for hydroforming of box-shaped part without failure is determined. Considering the working conditions related to the same experimental tests and comparing these conditions with simulated results, efficiency and accuracy of the proposed method have been also investigated.

Abstract: Firstly, the geometry condition of useful wrinkles during the hydroforming of double-cone tube was given. Then the stress condition of useful wrinkles was given by formula between the parameters of wrinkles shape at the end of axial feeding and internal pressure, hoop stress and axial stress. The analytical results were compared with the FEM analysis and experiments results. The results show that the useful wrinkles must meet both the geometry condition and the stress condition. The geometry condition of useful wrinkles is that the area of arbitrary length of wrinkles is a little smaller than the area of corresponding die cavity. The stress condition of useful wrinkles is that shape parameter G is not smaller than the radius R at the top of middle wrinkle. That means the increment of thickness strain dεt is positive and no thickness thinning will occur during the calibration. When the wrinkles didn’t match geometry condition, the dead wrinkles or bursting will take place. And when the wrinkles didn’t match stress condition, the bursting at top of middle wrinkle will occur during the calibration.

Abstract: An ultra-precision instrument with concomitant micromanipulation techniques is designed and set up to measure the damage strength of a single biomimetic microcapsule. It can provide the capability of simultaneously measuring the applied force and resultant displacement of a single microcapsule, with maximum force range of 5mN, resolution of 0.1µN and ultimate traveling distance up to 12mm, resolution of 1nm, respectively. By armed high magnification side-view system, it can offer extra and withal valuable information for the supervened analyzing. The bursting force of urea-formaldehyde biomimetic microcapsules of diameter 65µm in glucose solution was measured by this technique. The microcapsule was burst when the deformation reached a value of 56.2% of its diameter and the corresponding resonant force is about 1700µN. The technique provides an effective means to characterize elastic properties of micro biomimetic capsules and compare mechanical strength of microcapsules made of different ingredients.