Experimental Mechanics in Nano and Biotechnology

Abstract: As the application technique for glass bottle’s recycling system, a new “Cullet” generation method by using underwater shock wave was proposed. This small fragmentation technique of glass bottles has a lot of excellent advantages such as the simplification of process by simultaneous cleaning and crushing operation, the high collect rate of “Cullet” and so on. In this study, the relation between of the explosive conditions and “Cullet” sizes were clarified and the high speed fracture process of glass bottle was observed by framing photograph of high speed image converter.

Abstract: The spacer grid assembly, which is an interconnected array of slotted grid straps and welded at the intersections to form an egg crate structure, is one of the main structural components of the nuclear fuel assembly of a Pressurized light Water Reactor (PWR). The spacer grid assembly supports and aligns the fuel rods, guides the fuel assemblies past each other during handling and, if needed, sustains lateral seismic loads. The ability of the spacer grid assembly to resist the lateral loads is usually characterized in terms of its dynamic and static crush strengths, which are acquired from tests. In this study, dynamic buckling tests and finite element analyses on spacer grid assembly specimens are carried out. Comparisons show that the analysis results are in good agreement with the test results to within an 8 % difference range. Therefore, we could predict the crush strength of a spacer grid assembly in advance before performing the dynamic buckling test.

Abstract: Present investigation were carried out to study photoelastically the stress distributions in a simply supported beam with over- hangs subjected to a low velocity central- and quarter- spanimpact loadings by light strikers keeping beam/ striker weight ratio constant (2.675), and then comparing the results so obtained with those in similar simply supported beams made of other materials subjected to central- impact loadings from an analysis of dynamic strain gauge data. Interesting new findings were obtained from the results of the present investigation and also from results reported in the literature in this respect. Introduction. In modern times dynamic stress analysis is becoming increasingly important for various engineering applications. Although significant amount of insight in these respects have been developed, the subject being rather intricate would continue to attract of more research workers in future. A beam is a common structural element, and in several applications, simply supported beams with over- hang are employed in practice. Transverse and longitudinal bridge girders and chassis of rails- and road- wagons are some of the typical applications of the same. Here, photoelastic technique was employed to determine dynamic stress distributions in a model simply supported beam with over- hang.

Abstract: Structural failure of fibre-reinforced polymers (FRP) caused by impact is an important factor in product development for the aircraft industry. Therefore it is necessary to obtain knowledge of the mechanisms and of the material loading during and shortly after an impact load. On account of this a Finite-Element-Model was developed with the goal to deduce design rules for impact tolerant composite materials. To verify and validate the Finite-Element-Model it is essential to have information of the state of stress on the surface of the FRP shortly after the impact. An impact test device was developed at the University of Bremen. The time variable, stress and strain conditions in composite plates are measured using photoelastic technique, strain gauges and holographic interferometry.

Abstract: Attempts have been made to improve the impact resistance
of biodegradable thermoplastic polymer, PLA. A ductile biodegradable polymer, PCL, has been used to improve such property of PLA by using blending technique. Details of the impact fracture properties and mechanisms of PLA/PCL blends, however, have not fully been understood yet. Recently, it was also found that LTI can improve the immiscibility between PLA and PCL. In this study, PLA/PCL and PLA/PCL/LTI blends were prepared, and their impact fracture toughness values were measured
to assess the effect of PCL content and LTI addition on the impact resistance. Fracture mechanisms of the polymer blends were also characterized by scanning electron microscopy.

Abstract: Dynamic response and fracture of high strength boride/alumina ceramic composite were investigated by split Hopkinson pressure bar (SHPB) experiment in this paper. The compressive stress–strain curves and dynamic compression strength of the composites were tested. The surface’s microstructure of fractured composites were examined by using scanning electron microscope (SEM) to investigate the fracture mechanism. The results show that boride/alumina has high dynamic compressive strength and high Young’s modulus. The main fracture mode of the material is the fracture of the ceramic grains. The micro-voids and flaws, generated during the sintering and manufacturing of material and mechanical process of specimen, decrease the strength of the material because they provide the source of crack expansion when the material undergoes the dynamic loadings.

Abstract: This paper presents a modified Split Hopkinson Pressure Bar(SHPB) technique to obtain compressive stress-strain data for a rubber material. An experimental technique with a modified the conventional SHPB has been developed for measuring the compressive stress strain responses of materials with low mechanical impedance and low compressive strengths such as a rubber. This paper uses an aluminum pressure bar to achieve a closer impedance match between the pressure bar and the specimen materials. In addition, a pulse shaper is utilized to lengthen the rising time of the incident pulse to ensure stress equilibrium and homogeneous deformation of a rubber. It is found that the modified technique can determine the dynamic deformation behavior of rubbers under various conditions such as high strain rate and low temperature effects.

Abstract: Results of tests using two kinds of nylon reinforced concrete samples are described . In order to deal with the heterogeneous effects of samples resulted from large particles which range from7mm to10mm in diameters, a SPH bar which is 74mm in diameter is used. There seems something new and difficult in the method of testing the concrete’s dynamic compressive responses. The results show that there are obvious strain rate effects in both the two kinds of samples , and the failure strength increases with the increasing of the strain rate.

Abstract: Hard disk drives (HDD) are now the most important means of information storage, and they continue to be made smaller in size, higher in capacity, and lower in cost. The dynamic performance of an HDD has been an increasingly important consideration for its design, as we move forward toward its consumer applications. The dynamic properties of the head arm assembly (HAA) of a micro-drive were investigated using both experimental and numerical techniques. A finite element model for studying the dynamic property of the HAA was created and modified according to the experimental results. Good correlation between the experimental results and those by finite element simulation was achieved.

Abstract: Optical disk drive (ODD) technology has been rapidly improved to treat the gradually increasing data storage and data transfer rate. The rotational velocity of the disk must be increased to deal with huge data. However the increased rotational velocity can inherently cause unwanted phenomena such as noise and vibration. The major noise sources of the ODD system are mechanical vibration which generated inside ODD and turbulent aerodynamic noise which generated by the viscous flow rotation. In this study, practical experimental tests of driving noise for various optical disk drives have been performed using 1/2” microphone noise measurement system. Sound insulation case with absorbing materials for the present experimental tests is designed and constructed in order to minimize the effects of disturbance. Several commercial ODD models by different manufacturers are practically considered in the present experiments and compared for realistic driving conditions. It is shown that sound noise level, average data transfer rate and operating RPM seems to be somewhat different for the ODD models with same proposed speed by different manufacturers. Moreover, driving sound noise level can be largely affected by both tray shape and driving speed even for the same apparent data transfer rate.