Papers by Author: Bing Pan

Abstract: TiNi/Al-12%Si alloy is a kind of prospective material used as special energy absorbers for eliminating undesirable noise and mechanical vibration. The investigation on the mechanical properties of this composite alloy is of great importance. In this study, the surface deformation of TiNi/Al-12%Si composite alloy under external loading was measured experimentally by means of DSCM method. Some deformation characteristics of TiNi/AlSi composite alloy under the effect of the tensile load and the interaction between TiNi and AlSi are discussed. In addition, the elastic modulus and the poisson ' s ratio of this alloy were measured as well. The results agrees well with the theory predicts.

Abstract: In this study, focused gallium ion (Ga+) beam is utilised to fabricate micro/submicron spacing gratings on specimen surface. The grating types include: parallel, cross, and hybrid (grating with double-frequency). Several hybrid gratings with double frequency were produced in combination mode or superposition mode, which have a good potential to measure deformation within different range. Techniques for producing different type of gratings are discussed in detail. As an application, a 5000 lines/mm grating was fabricated on an amorphous SIC MEMS cantilever and was successfully used to measure its virtual strain with aid of digital moiré. The experimental results verify the feasibility of fabricating high frequency grating on metal or non-metal surface using the FIB milling and the resultant grating can be used to measure micro-deformation.

Abstract: The spider silk is considered as a new type of biomaterials with its excellent mechanical properties. The mechanical properties of the spider silk are crucial to their applications. In this study the mechanical properties of spider silk were studied with a micro-tensile system driven by magnet-coil force actuator, which is very effective to measure the properties of low dimensional materials. The Young’s modulus of the spider silk is obtained, the relationship between the mechanical properties of spider silk and time is also acquired.

Abstract: The school of aerospace of Tsinghua University has started a project to develop new kind of stratospheric balloons for earth observation. These balloons will be designed to stand in the same position during a few days at 20 kilometers of altitude. To reach this goal, the first step is to select adapted materials for the balloon envelope. The materials for stratospheric balloons application should have specific properties adapted to the environment such as mechanical, thermo-optical, and permeability properties. Thus, we have asked a material manufacture company to develop and manufacture a material adapted to our application. In this paper, we will present the first results concerning the mechanical properties of the material. Experimental facilities have been developed to test the mechanical behavior of the materials at room and low temperature. The future development of the project will be to identify behavior law adapted to our material that fits with the experimental results.

Abstract: In this study, the digital image correlation method(with Newton-Raphson iteration method) is used to measure the in-plane deformation of poly-crystal aluminum. When the specimen is exerted a tensile load, the strain distribution of the specimen surface will be inhomogeneous. The micro-deformation of the poly-crystal aluminum is studied under a SEM(scanning electron microscope), a series of images of the micro crystal are captured during the loading process. By using digital image correlation to analyze the images, the displacement and strain of a micro-crystal are obtained, which provide important data for further analysis of the inhomogeneous properties of the poly-crystal aluminum.

Abstract: Recently, many research works were concentrated on how to improve the accuracy of displacement fields in digital image correlation (DIC). However, the original displacement fields calculated at discrete locations using DIC are unavoidably contaminated by noises. If the strain fields are directly computed by differentiating the original displacement fields, the noises will be amplified even at a higher level and the resulting strain fields are untrustworthy. To acquire reliably estimation of strain fields, in this paper, Savitaky-Golay (SG) filters are introduced to obtain smoothed displacement fields and reasonable strain estimation. The principle of two-dimensional SG filters is described in detail first. Then images of uniaxial tensile and three-point bending experiments were used to verify the proposed approach. The resulting smoothed displacement fields and strain fields clearly show that the proposed method is simple and effective.