Key Engineering Materials Vols. 326-328

Abstract: The high-speed photography and the non-linear dynamics engineering program LS-DYNA are conducted to research on Al and Cu armatures expansion process under the drive of pressed composite B explosive with the charge method of several-section. A special experiment system with an equipment of blocking off armature fracture flashing light is built, and a thorough analysis of the “circular fracture” phenomena has been made: For the air gap existence, there is a difference between the axial movement velocity of the armature joint position wall and other positions wall. The upward wall forces the joint position wall and then the “circular fracture” appears. Some conclusions about Magnetic Flux Compression Generator design are obtained.

Abstract: Experimental and theoretical study of the non-planar response motions of a circular cantilever beam subject to base harmonic excitation has been presented in this paper work. Theoretical research is conducted using two non-linear coupled integral-differential equations of motion. These equations contain cubic linearities due do curvature term and inertial term. A combination of the Galerkin procedure and the method of multiple scales are used to construct a first-order uniform expansion for the case of one-to-one resonance. The results show that the nonlinear geometric terms are very important for the low-frequency modes of the first and second mode. The non-linear inertia terms are also important for the high-frequency modes. We present the quantitative and qualitative results for non-planar motions of the dynamic behavior.

Abstract: The variation process of radius and pressure of explosion products in borehole are analyzed in this paper, based on theory of damage and structural mechanics, the formative mechanism of blasting crater in reinforced concrete under internal blast loading is analyzed, the computation method of crater size has been proposed. The calculated results are identical with experimental results on the whole.

Abstract: The rail clamp is the device to prevent that a container crane slips along rails due to the wind blast as well as to locate the crane in the set position through loading and unloading containers on a vessel in the quay. In order to design the rail clamp, we need to determine the proper wedge angle to minimize the sliding distance of a roller and the proper clamping angle of a locker to generate the initial clamping force of a jaw pad. The researches for the proper wedge angle have conducted. So in this study we look into the relationship between the clamping angle of a locker and the initial clamping force in the rail clamp with wedge angle of 10
. The initial clamping force of the jaw pad was determined by the clamping angle of the locker. Therefore after we measured the locking force of a locker and the tensile stress of extension bar with respect to the clamping angle of a locker, such as 2.18, 3.05, 3.92, 4.80
, we compared the results with the FEA results.

Abstract: The dynamic compressive behavior of open-cell aluminum alloy foams with different length of specimens was investigated using the split Hopkinson pressure bar technique. Plastic strength was measured for aluminum alloy foam specimens having the three cell sizes but similar cell microstructure. Longer specimens exhibited lower mean strength and broader scattering of the strength values than the shorter ones. It can be observed that mechanical response of aluminum alloy foams appear to be dependent of the cell size for both the shorter and longer specimens.

Abstract: A 5x5 partial fuel assembly was used for a comparative design evaluation test of a newly developed spacer grid from a mechanical/hydraulic vibration aspect. Axial flow pattern along this rod bundle in the test was very complex due to the intermediate spacers and the mixing vane; Understanding of this flow field of a dynamic pressure is a preliminary step for a theoretical analysis of a vibratory behavior of a partial fuel assembly. Since a fluctuating pressure induced by the randomly-varying flow turbulence cannot be accurately predicted by an analysis alone, it has to be measured directly on the surface over the rod or in an accessible vicinity of the bundle. In this study, the fluctuating pressure acting on a partial fuel assembly with a spacer grid and a mixing vane was measured. The measured PSD showed different spectral features from the results of the literatures and had a series of periodic pulsations with sidebands over the specific frequency ranges; it is believed that the periodic components in the PSD have to do with the design of the spacer grid and the mixing vane. And, the exciting force function for the theoretical analysis of a partial fuel assembly with spacers and a mixing vane was estimated as a possible PSD form.

Abstract: Understanding the behavior of concrete under dynamic loading conditions is an issue of great significance in earthquake engineering. Moisture content has an important influence on the strain-rate effect of concrete. In this study, both tensile and compressive experiments were carried out to investigate the rate-dependent behavior of concrete. Tensile experiments of dumbbell-shaped specimens were conducted on a MTS810 testing machine and compressive tests of cubic specimens were performed on a servo-hydraulic testing machine designed and manufactured at Dalian University of Technology, China. The strain rate varied in a wide range. The analytical formulations between the dynamic strength and strain rate were proposed for both compressive tests and tensile tests. It was concluded from the results that with the increasing strain rate, strengths of specimens with both moisture contents tended to increase and the increase seemed to be more remarkable for the saturated specimens; based on the experimental observation, a better explanation for the dynamic behavior is presented.

Abstract: In order to investigate the mechanical behavior of newly developed materials such as bulk amorphous metals, it is essential to use small-size specimens. An instrumented impact testing apparatus was devised which could provide a load-displacement curve on subsize Charpy specimens under impact loading without oscillations. The impact fracture behaviors of Zr-based bulk amorphous metals (BAM) were investigated by using the instrumented impact tester using both V-notched and precracked subsize Charpy specimens. It was found that most of the fracture energy absorbed was used in the process of crack initiation through the development of shear bands.

Abstract: A hydraulic breaker for construction machinery generally used for the destroying and disassembling of buildings, crashing road pavement, breaking rocks at quarry and so on. So the measurement of the impact energy of a hydraulic breaker is very important thing to prove its capability to manufacturers and customers. In this study, the test system for measuring the impact energy of a hydraulic breaker was designed and constructed. The test system was consisted with hydraulic cylinders for mounting a breaker, impact absorbing base and frames, pressure and flow sensors, high speed and accurate data acquisition system
 diesel engine driven hydraulic power unit. The test process of the developed system was carried by measuring guide for tool energy rating for hydraulic breakers which was developed by the CIMA (Construction Industry Manufacturers Association) USA. The developed test system can be applied to measure the impact energy for various kinds of hydraulic breakers.

Abstract: MgAl2O4 layer with several decade nano-meter in thickness was coated uniformly on Al18B4O33 whisker by vapor-deposition of pure magnesium in vacuum and then heat-treated in atmosphere in order to prevent to the direct reaction between Al18B4O33 whisker and molten ZK60 (Mg-(4.8-6.2)%Zn-(0.45-0.8)%Zr) alloy in preparing the composites. By the coating, the composite have no interfacial reaction in whisker and matrix. As the consumption of Zn at the interface was not observed during preparation of the composites, the composites have good aging behavior, but showed the shortening of the time to reach the peak hardness. As the cooling speed of the composite after solution treatment is slow because of low thermal conductivity of the composites, some precipitation (MgZn2) was observed in the composites. Furthermore, the precipitation grew around the interface between whisker and matrix preferentially because of thermal stress around the interface. It seems these phenomena affect to the shortening of the time to reach the peak hardness.