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As one of the key techniques for manufacturing three-dimensional metal microstructure, micro-electroforming processing technology plays an important role in MEMS. Mechanical properties of micro-electroforming Ni have become a new research hotspot. This paper gives a brief overview of micro-electroforming Ni material’s mechanical properties. Due to the complexity and lack of standardization during micro-electroforming process, mechanical properties are found to be dependent on micro-electroforming process parameters and conditions. It is essential to reveal the essence of mechanical properties from microcosmic aspect. This paper briefly summarizes observation tools of microstructure and reviews the relationship of mechanical properties and microstructure. This work lays theoretical foundation for dynamic analysis and calculation of micro-electroforming Ni devices.

The variable stiffness micro-springs’ load and deformation have nonlinear relationship, thus they can be used in special occasions. MEMS processing technology can manufacture any complex structures in a plane, using this feature, a variable stiffness design idea for the planar micro-spring is proposed. That is, using one type of structure named contact pairs to achieve stiffness change during the micro-spring’s stretching process. Using contact pairs, two types of variable stiffness springs are designed: stiffness increase spring and stiffness convexity spring. Because of the influence of processing precision, the contact pairs’ sizes of the first type of variable stiffness spring are different each other, the machining error makes the test results and simulation results various. In order to avoid the above problem of above spring, this paper designs another two variable stiffness micro-springs, test results indicate that the improved variable stiffness springs can realize the variable stiffness’ tendency.

As one of the significant structural materials used in safe and arming system of MEMS fuze, the research on micro-electroforming process technologies and micro-electroforming nickel's properties have been a popular field for MEMS area. This paper surveys present domestic and overseas research status of mechanical characterization of electroformed nickel, summarizes and analyzes that changes of the microstructure led by parameters of micro-electroforming process and the external environment make great effects. © (2015) Trans Tech Publications, Switzerland.

A FPEG (flexible piezoelectric generator) composed of PVDF (polyvinylidene fluoride) piezoelectric film, conducting resin and titanium alloy substrate, which occupies less room and produces electrical energy while the axial wind flows through the oscillator surface. When the axial wind flows through the generator surface, generator begins to vibrate and produce electrical energy, as the wind speed reaches a critical value, generator yields resonance phenomenon. In this paper, more work was placed on how the substrate structure parameters such as length, width and thickness affected the power generation capacity in resonance mode.

MEMS processing technology can manufacture any complex structures in a plane, using this point, a variable stiffness design idea for the planar micro-spring is proposed. That is, using one type of structure named contact pairs to achieve stiffness change during the micro-spring’s stretching process. Using contact pairs, three types of variable stiffness springs are designed: stiffness increase spring, stiffness decrease spring and stiffness hump spring. Finally, the variable stiffness springs’ application for fuze setback arming device is discussed. When the three types of springs are used in setback arming device, the stiffness decrease spring is better than the other two springs from security analysis. Kinematic analysis shows that, if the variable stiffness spring’s design is reasonable, the setback arming device not only can effectively solve the safety and reliability issues for rocket fuze, but also applies in small caliber grenade fuze’s working environment without changing the setback arming device’s size and structure. Analysis result indicate that the setback arming device based on MEMS variable stiffness spring is universal for rocket fuze and small caliber grenade fuze.

Micro springs are often served in the fuzes MEMS-based safe and arm systems as force and energy transmission elements, which are critical to guarantee the fuze safe and arm systems' safety in normal time and proper function after launching. While the micro springs are easy to get buckled under pressure thus influence the normal function, to avoid that, the relationships between the critical buckling pressure and the structural parameters were taken into consideration in the design process. Taking the S-shaped micro spring as example, models were built using modeling software Inventor and eigenvalue buckling analysis was performed with the FEM (finite-element method) software ANSYS, hence the relationships between the critical buckling pressure and the structural parameters of the micro spring in certain conditions were obtained.

In disc magneto electric generator, the output voltage is proportional to the coil surrounding area. Establish the sectorial coil model, trapezoidal coil model and rectangular coil model and build simplified calculation formulaused for calculation of coil surrounding area. The maximum error between simplified and the precisecalculation formula is 6% that can meet the needs of engineering design. It can be used to guide structural design and optimization of this type of generator.

Maxwell 3D software of finite-element analysis in electromagnetic fields is used to model and simulate the micro disc magneto electric generator. Distribution characteristics of magnetic induction are required and theoretical analysis and calculation is presented. Error between the simulation result and experimental result is about 6% which verify the rationality and accuracy of finite-element simulation. It can be used to guide the structural design and optimization of this type of generator.

For the existing symmetry Z-tooth MEMS delay mechanisms can not play sports in place under the influence of centrifugal force, this paper presents an asymmetric Z-tooth delay mechanism which can works reliably by weak environmental forces. Working principle and the stress condition of the mechanism are analyzed. Based on the dynamic model, this paper makes a computational analysis and simulation about the kinetic characteristics of the asymmetric Z-tooth delay mechanism, and the results show that the improved mechanism can works reliably and meets the requirements.

A novel piezoelectric accelerometer with switch characteristic was introduced. The accelerometer is composed of top head, cross elastic beam, base core, insulation cylinder, mass block, piezoelectric elements, and the base etc. The accelerometers structure and operating principle were presented and its mathematic model was established. Test results show that the accelerometer can filter out high frequency vibration signal, which the out signal is smooth compared with the conventional piezoelectric accelerometer, furthermore with good linearity. It can be used in the smart fuze to take the place of conventional piezoelectric accelerometer in order to recognize the target accurately.

First of all, this paper analyzes the piezoresistive accelerometers’ research achievements at home and abroad. Then, design, manufacturing and testing method of the accelerometer array is presented. According to the detection requirements of fuze’s environmental forces, this paper provides an array accelerometers structure. In this way, each independent chip has 2*2 accelerometers, and every two accelerometers have the same structure sizes. So, the accelerometer array has two different measurement ranges. In order to reduce the influence of cross sensitivity, the accelerometer uses criss-cross beams. Every single accelerometer comprises sensing unit, signal processing circuit and self-test unit. According to the characteristics of processing plant, an entire series of independent processes for micro-mechanical piezoresistive fabrication is designed, and also given the layouts. The accelerometer is fabricated and its sensitivity and self-test performances are tested in this paper, finally this paper gives the reasons which cause test errors.

Micro electro mechanical system (MEMS) has been increasingly used in military application. For the reliability and specialty of military requirements, the material of the MEMS device is supposed to be metal and the device is moveable. Lithographic, Galvanoforming, Abformung (LIGA) technology capable of producing high aspect ratio structures in metals like nickel is one of the important fabrication technologies in military MEMS. There are many moveable MEMS device like micro-gear and micro-slider producing by LIGA technology. But the moveable devices cannot behave well because of the friction effect. In this paper, an improved elastic-plastic model including roughness effects and an experimental procedure that predict the static friction prosperity of LIGA-processed nickel is proposed. Firstly, we use the 3D optical profilometer to research the surface roughness of LIGA-processed nickel, the surface heights distribution was found to be nearly Gaussian distribution. Secondly, the static friction model, the Kogut-Etsion (KE) model is adopted to obtain the static friction coefficient. Finally, a special designed static friction coefficient measurement apparatus is used to conduct the friction experiments. The results indicate that the surface roughness affects the friction and the smoother surface leads to a higher friction coefficient. Also good agreement was found between simulations and experimental results.

This paper presents the design, simulation and fabrication of an mm-scale air-driven microturbomachine. The circumferential-flow turbomachine has a plain-shaped structure with an overall size of 8×8×3mm3. The predicted formulas for driving torque and driving power are deduced by analyzing the working condition of the model. Finite element simulation is carried out to determine the driving torque and driving power. Turbine and stator are fabricated using UV-LIGA technique, while other components using pension micromachining. Test results of assembled prototype show that under the air-flow speed of 80m/s, no-load and load rotation speed are 10kr/min and 9.5kr/min respectively, and the output power is 326.57µW. The results indicate micro turbomachine is potential power source for the micro system.

As a device for time-delay, clock mechanism is widely used in fuze safety and arming device, whose core component is the runaway escapement. With the development of artillery systems, the dynamic environment during the projectile becomes more and more complicated. Recently, some shots misfire or premature explode during shooting process because runaway escapements’ miswork. This paper utilizes gear system’s research results applied in other fields, discusses clock mechanism’s dynamics problem, and uses ADAMS to analyze runaway escapement’s rigid-flexible coupling model. From comparing the simulation results of multi-rigid model and rigid-flexible coupling model, we find that elastic deformation will affect runaway escapement’s movement, even can cause the whole device to work abnormally.

To recognize the boundary of wireless networks to meet some specific needs, relative azimuth angles of nodes distributed in the 1-hop neighborhood of each node in one network were used to recognize the boundary of the network. A novel recognition algorithm based on local generalized convex hull was proposed for one node to decide if it self is a boundary node. The flexibility, efficiency and consistency of the algorithm are shown in its performance by extensive simulations.

Because of magnetorheological (MR) dampers’ mechanical simplicity, high dynamic range, low power requirements, large force capacity and robustness, they are the most promising devices for structural vibration control. But this paper uses MR dampers’ damp characteristics to complete a function of short time delay, and the damper’s volume is smaller than the other dampers that have been applied for commercial uses. This paper discusses two types of structures for time delay, gap structure time delay device and holes structure time delay device. In order to estimate the two kinds of devices’ delay time, mathematical modeling and experimental testing are built in this paper. From the test results, we know that holes structure does not always implement theoretical delay time, but the gap structure can complete the time delay function satisfactory. For judging whether the time delay device can work normally under different circumstance, the time delay device with gap structure is tested in a change temperature field from -40 °C to 55 °C.

In this paper, the explicit finite element dynamic software LS-DYNA was utilized to investigate the process of projectile penetrating targets. The finite element model of projectile is simplified as two parts, warhead and balance part. In the finite element model, the threaded connection between warhead and balance part was set appropriately as contact. Projectile penetrated two or three target plates with different thicknesses, which are made of different materials. The results show that the contact between warhead and balance part fails in the penetration. After penetration, petal shaped crevasse appears on the target plate. While projectile penetrate the second or the last target plate, balance part may impact warhead after the failure of contact. Keywordsfinite element analysis; penetration; projectile; threaded connection; dynamic characteristics