Papers by Keyword: Meso-Scale

Abstract: Manufacture of piezoelectric energy harvesters typically assumes bulk piezoelectric material for the transducer until the reduction in size of the device prevents this. However when designing piezoelectric harvesters, the complete system must be taken into account including the transducer, power circuit, and battery, as these will impose restrictions on what can be achieved. Therefore a comparison between MEMS and meso-scale piezoelectric energy harvesting systems using a fully parametrised model is required. The comparison was restricted to a piezoelectric beam with a mass at the end connected to a single supply pre-biasing circuit to provide the optimal damping force and rectification. A buck converter was used to transfer extracted energy to a 1.5V battery. The results indicate that for devices with a volume side length less than 16.25 mm, no device using meso-scale properties can be made to resonant at 100 Hz or less due to the length and stiffness of the beam. Whereas above this limit, the voltage required to damp devices with MEMS scale properties causes a breakdown in the dielectric. We present a comparison of the theoretical limits of MEMS and meso-scale piezoelectric harvesters to provide design insight for future devices to maximise power generation.

Abstract: Multi-scale theory and framework in research of fatigue crack is described, and then in meso-scale the simulation model of polycrystalline material grains is established using Voronoi algorithm, and the feasibility of this algorithm is verified at the same time; cohesive zone method is introduced and cohesive strength on the interface along grain boundaries is discussed, then Young´s modulus is tried to define in meso-scale according to cohesive zone method, which prepares the calculation of the finite element model.

Abstract: This paper proposes a vision detection algorithm to acquire LIGA part’s edges based on an in-house multi-DOF manipulator for LIGA part assembly. Feature recognition based on maximum information entropy is proposed to solve the problem that high precision edge recognition under backlight source. In order to further improve vision recognition accuracy, edge feature recognition algorithm based on symmetrical edge is proposed to recognize the center line of the symmetrical parts when the quality of the image is poor.

Abstract: Currently machine tools and strategies researched in micro-milling field universally cannot be applied to 3D meso-scale parts machining directly, so great importance should be attached to the research on 5-axis machine tools and the suitable strategies for 3D meso-scale machining. This paper introduced a self-made 5-axis machine tool and several micro-milling strategies which were applicable to 3D meso-scale parts machining. Using these strategies, a mini impeller was successfully machined on the 5-axis machine tool developed independently. The experiment result showed the machine tool and the strategies were suitable for machining meso-scale 3D parts.

Abstract: Conventional machining is generally preferred in manufacturing metal components with 2½D features and/or 3D silhouettes. With the ever increasing demand for reduced sizes and increased accuracy, however, traditional machine tools have become ineffective for cutting miniature components. A typical example is gear manufacturing. It is known that gears are machined using the gear hobbing process in which the cutter axis and the workpiece axis are required to be synchronized to an accurate constant ratio. According to a market survey, only a few machine tools can make gears with the size of φ1.0 mm. This paper presents our effort in developing a PC-based millimeter scale CNC turning centre with gear hobbing capability to machine miniature gears. In this machine, the synchronization required by the gear hobbing process was achieved directly by controlling the AC servomotors. Experiment results show that the machine is able to machine high quality components with diameter as small as 0.075 mm and hob gears with module as small as 0.09.

Abstract: This paper presents a new meso-mechanical analysis method of rock failure. The actual inhomogeneity of rock at meso-scale level is represented by processing the image of rock section and incorporated into Realistic Failure Process Analysis code (abbreviated as RFPA2D). Here, this numerical tool is employed to study the fracture phenomena of granite sample considering the interface strength between mineral grains. Numerical results show that interface strength has significant influence on the strength of sample and its failure mode. The larger the interface strength is, the more brittle rock samples become and the strength is bigger. With the interface strength increasing, failure mode gradually varies from intergranular frature to transgranular fracture.

Abstract: The mechanical properties of polymers are strongly influenced by meso-scale structure such as entanglement, orientation, folded chain, etc. However, the relationship between the meso-scale structure and macro-scale mechanical properties of polymers has not been clarified. In this paper, network models of polymer chains are introduced to simulate the meso-scale interactions. From the FEM analysis of this model, the effects of interactions on macro-scale mechanical properties are investigated.