Search results

Being the key sensitive elements of the micro-electromechanical systems (MEMS) resonant sensors, performance of the double-ended tuning fork (DETF) will affect precision of the whole sensor greatly. Currently, most of the research on DETF is concentrated on ideal theory or simply mentioned as part of the sensor. But, in most engineering occasions, there exists many factors such as the additional mass, air damping and fabrication process, etc. However, few references are individually aimed at the mechanical characters of DETF. To choose the suitable DETF, it is important to solely research and measure the performance of this element.

In this paper, the authors combine the practical engineering applications and deduce the calculation method of sensitive element’s resonant frequency under various circumstances. The authors also design a force-generating system to make the loading simulation and verify the correctness of theory.

On the basis of Euler–Bernoulli theory and Rayleigh’s equation, frequency theories of DETF under four different situations have been deduced. A force-generating device is designed and fabricated to measure the mechanical characters of the DETF. The experiments using force-generating system, DETF, the high performance laser vibrometer and oscillograph are carried out. It verifies the correctness of theory.

Currently, most of the research on DETF is concentrated on ideal theory or simply mentioned as part of the sensor, and few references are individually aimed at the mechanical characters of DETF. Combining the practical engineering applications, the authors deduced the frequency theories of DETF. A force-generating system is designed and fabricated to measure the mechanical characters of the DETF, and the experiment results match the theoretical results very well.

Direct additive manufacturing of ceramics (DAMC) is a highly promising ceramics preparation technology because of its simple process and rapid response capability, but the cracking issue prevents its industrial application. The purpose of this paper is to propose aluminum titanate (Al₂TiO₅) with low coefficient of thermal expansion (CTE) to suppress cracks during the DAMC.

Al₂O₃/Al₂TiO₅ (A/AT) composite ceramic samples with different compositions were in-situ synthesized from Al₂O₃/TiO₂ (A/T) powder in a directed laser deposition (DLD) process. The relationship between the content of TiO₂ and cracking characteristics of fabricated sample was discussed. Phase composition, microstructure and properties of the fabricated samples were also investigated.

The results of this paper show that the doping of TiO₂ can obtain Al₂TiO₅ synthesized in situ by reaction with Al₂O₃ and effectively suppress cracks during DAMC. When the content of TiO₂ reaches 30 wt.per cent, cracks hardly occur even under conditions of slow deposition. Crack-free structures such as vane, cone and pyramid were successfully prepared, with a maximum cross-sectional dimension of 30 mm and maximum length of 150 mm. A continuous matrix phase formed of the low CTE of Al₂TiO₅ is the major cause of crack suppression. The dispersed distribution of a-Al₂O₃ columnar dendrites has the effect of increasing the strength of the matrix. Under current process conditions, the prepared sample with 10 wt.per cent TiO₂ has micro-hardness of 21.05 GPa and flexural strength of 170 MPa.

This paper provides a new method and inspiration for direct additive manufacturing of large-sized crack-free ceramics, which has the potential to promote practical application of the technology.