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An inertial micro-switch with multi-threshold acceleration detection capability has been proposed, taking advantage of electromechanical coupling behavior. A mathematical model of electromechanical coupling behavior was established to display the dependence of highly sensitivity on pull-in characteristic and show the ability to detect threshold acceleration by controlling the voltage applied to the inertial micro-switch. The capability of sensitivity and detection that was described in mathematical model was implemented to occur at the inertial switch and showed agreement with that of a simulation. Inertia switches that were comprised of various microstructures with dimensions ranging 3.5 µm from 180 µm were manufactured by means of the micro-electro-mechanical system (MEMS) manufacturing process, and their functions were evaluated by a dropping system. The control method related to the manufacturing of inertial switches was obtained by analyzing the effect of the structural parameters of the inertial switch on threshold voltage and threshold acceleration, resulting in a relatively small error between simulation and experiment. The inertial micro-switch showed high sensitivity to achieving the pull-in effect at 30 V, sense multi-threshold acceleration ranging from 500 g to 2000 g in 2.46 ms and provided enough time for outputting the acceleration signal. Furthermore, the multi-threshold acceleration can be adjusted by controlling the voltage applied to inertial micro-switches. In addition, other functions of inertial micro-switches, such as lower residual stress, high recoverability, and repeatability, have been displayed.

Acceleration switch can trigger switches according to the variation of external acceleration without complex control system and circuit. With the excellent characteristics of integration of sensor and actuator, zero power consumption and high reliability, multi-threshold acceleration switch has great application value in the fields of vehicle safety, aerospace and industrial equipment. In order to reduce the complexity of the measurement system and improve the reliability, we realized the design of a multi-threshold and anti-overloading acceleration switch which can distinguish specific pulse width. Additionally, the magnetic elastic contact is designed to prevent the rebound phenomenon when switch is overloaded. Considering the coupling force of spring, magnetic elastic contact and magnetic, we built the dynamic model and analysed the influence of the acceleration threshold and the pulse width on the switch actuation. The numerical simulation shows that the proposed switch has accurate sensitivity of acceleration excitation with specific threshold and certain pulse width, and it also has the ability of anti-overload. Consequently, the proposed method provides a new method for designing acceleration switch.

The occurred earthquakes in recent years have proved that in some parts of the world, they possess more duration and cause further damage to structures. Due to the fact that major cities of Iran are located in the high seismic areas and also a significant part of existing buildings are concrete structures, it is necessary to study their vulnerability under long duration earthquakes. In this study, the performance of concrete structures affected by earthquakes with different durations (from low to high) has been investigated. In order to investigate the duration of the earthquake, a new index is defined, which is the number of accelerated cycles where their period is close to the structure predominant periods (with 10% difference) and their corresponding acceleration is also higher than the plastic acceleration threshold of the structure. For this purpose, three concrete structures with, 3, 6, and 9 stories were designed with optimal sections and the predominant period and the threshold acceleration for entering nonlinear behavior were calculated. Subsequently, all three buildings were investigated in two-dimensional SeismoStruct software and nonlinear analysis was carried out considering the stiffness deterioration and strength reduction (Takeda model). Each of the 3, 6 and 9 story structures was subjected to 119 earthquake records, durations, distances, magnitudes, and different soil types. Seismic performance of structures such as relative maximum displacement and number of plastic joints were investigated. The results of the analysis show that the use of the index introduced in this study is much more efficient than other definitions of duration for damage to concrete structures. In other words, duration of an earthquake, as defined by the number of cycles whose period is near the predominant period of the structure and accelerated beyond the plastic acceleration threshold of the structure, is very consistent with the rate of damage to the concrete structure. In continuation, the effects of the height and plastic acceleration threshold on various models are discussed in detail.

This paper presents a tunable multi-threshold micro-electromechanical inertial switch with adjustable threshold capability. The demonstrated device combines the advantages of accelerometers in providing quantitative acceleration measurements and g-threshold switches in saving power when in the inactive state upon experiencing acceleration below the thresholds. The designed proof-of-concept device with two thresholds consists of a cantilever microbeam and two stationary electrodes placed at different positions in the sensing direction. The adjustable threshold capability and the effect of the shock duration on the threshold acceleration are analytically investigated using a nonlinear beam model. Results are shown for the relationships among the applied bias voltage, the duration of shock impact, and the tunable threshold. The fabricated prototypes are tested using a shock-table system. The analytical results agree with the experimental results. The designed device concept is very promising for the classification of the shock and impact loads in transportation and healthcare applications. [ABSTRACT FROM AUTHOR]

As a typical type of MEMS acceleration sensor, the inertial switch can alter its on-off state while the environmental accelerations satisfy threshold value. An exhaustive summary of the design concept, performance aspects, and fabrication methods of the micro electromechanical system (MEMS) inertial switch is provided. Different MEMS inertial switch studies were reviewed that emphasized acceleration directional and threshold sensitivity, contact characteristics, and their superiorities and disadvantages. Furthermore, the specific fabrication methods offer an applicability reference for the preparation process for the designed inertial switch, including non-silicon surface micromachining technology, standard silicon micromachining technology, and the special fabrication method for the liquid inertial switch. At the end, the main conclusions of the current challenges and prospects about MEMS inertial switches are drawn to assist with the development of research in the field of future engineering applications.

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Squeeze-film damping and acceleration load are two major issues in the design of inertial micro-switches. In order to deeply and systematically study these two issues, this paper proposes a typical vertically-driven inertial micro-switch, wherein the air and electrode gaps were chosen to design the required damping ratio and threshold value, respectively. The switch was modeled by ANSYS Workbench, and the simulation program was optimized for computational accuracy and speed. Transient analysis was employed to investigate the relationship between the damping ratio, acceleration load, and the natural frequency, and the dynamic properties (including contact bounce, contact time, response time, and threshold acceleration) of the switch. The results can be used as a guide in the design of inertial micro-switches to meet various application requirements. For example, increasing the damping ratio can prolong the contact time of the switch activated by short acceleration duration or reduce the contact bounce of the switch activated by long acceleration duration; the threshold value is immune to variations in the damping effect and acceleration duration when the switch is quasi-statically operated; the anti-jamming capability of the switch can be improved by designing the sensing frequency of the switch to be higher than the acceleration duration but much lower than the other order frequencies of the switch.

This paper reports an analysis on the relationship between the tilt of the proof mass in MEMS switch and the chattering phenomena. Low-g MEMS acceleration switch developed by Kim’s group was modelled in 2D and displacements of each end of the proof mass were analysed using RK 4th method. Some elementary assumptions were made to ease the modelling and analysis. The chattering time of the MEMS switch gets longer as the tilt of the proof mass increases. The reason is that the elongated travel distance of one end of proof mass increases the impact velocity and lengthens the bouncing back time. From the results, we found that the chattering phenomena can last very long even if the tilt of the proof mass is very small.

Shaking table tests were performed on reduced-scale models of integrated and two-tiered mechanically stabilized earth walls (TMSEWs) to evaluate the effect of a tiered configuration on the dynamic behavior of geogrid-reinforced soil walls. The results of particle image velocimetry and instrumentation indicate that preventing the development of a slip surface in the lower half of the wall, improving the seismic stability by increasing the failure threshold acceleration, mitigating acceleration amplification and decreasing the reinforcement load were the main advantages of a tiered configuration. It was found that the use of an insufficient offset distance in TMSEWs not only eliminated the advantage of the tiered configuration for reducing wall deformations, but also increased the lateral displacement at the wall crest. In this regard, 0.22H was identified as the minimum offset distance required when constructing MSE walls in a tiered configuration. Moreover, comparison of integrated and tiered MSE walls showed that the effect of a tiered configuration on reducing the force of the reinforcements in the lower tier was approximately 2.2 times that for the upper tier reinforcements. It was also found that Mononobe-Okabe method can be used to find the upper bound for estimating the load of reinforcements in TMSEWs. [ABSTRACT FROM AUTHOR]

A pseudostatic coefficient is required for pseudostatic analysis of mechanically stabilized earth (MSE) walls, but there are no clear criteria for its selection. The current study assessed the horizontal pseudostatic coefficient (kh) for MSE walls by considering the effects of a tiered configuration and reinforcement type. A series of shaking table tests were performed on reduced-scale models of integrated and two-tiered MSE walls reinforced by metal strips and geogrids to determine the failure threshold acceleration, axial force distribution along the reinforcements at the failure stage, and geometry of the slip surfaces. Physical models were simulated using the limit equilibrium horizontal slice method to estimate the value of kh required to establish slip surfaces and reinforcement forces similar to those observed in shaking table tests. Based on the results, the horizontal pseudostatic coefficient was introduced as a function of the maximum horizontal acceleration, offset distance, and reinforcement type. [ABSTRACT FROM AUTHOR]

Response time is one of the core attributes for threshold acceleration switches for determining the impact severity. Different from single function inertial switches for only converting circuit states, a wireless inertial microswitch incorporating the bistable flexible mechanism was designed and fabricated using multilayered microelectroforming technology, which can be used for remote detection of both the threshold acceleration and the corresponding response time in severe environments. The threshold snap-through characteristic of the nonlinear bistable mechanism has been introduced to achieve the threshold acceleration sensing capability. The switch mainly consists of one wireless module, one proof mass supported by two pairs of ultralong V-shaped slender beams with the dimension of \(28.0~\mu \) m \(\times 25.0 \mu \) m \(\times 5150.0 \mu \) m, and two contact points for recording triggering times through the high speed sending and receiving wireless module. Then, an accurate design model for analyzing the threshold acceleration and the dynamic response time was established. The 20 repeated experimental results are in good agreement under the same triggering threshold acceleration of 32.38 g, in which, the response time with the traveling distance of \(530.0~\mu \) m is 179.80 ± 0.20 ms. [ABSTRACT FROM AUTHOR]

Recent experiments by Shao et al. ["Surface wave pattern formation in a cylindrical container," J. Fluid Mech. 915, A19 (2021)] have revealed complex wave dynamics on the surface of a liquid bath in a vertically vibrated cylindrical container that are related to the presence of a meniscus on the container sidewall. We develop a corresponding theoretical model for this system by detuning the driving acceleration of the container, which results in an inhomogeneous Mathieu equation that governs the wave dynamics whose spatial structure is defined by the mode number pair (n , m) , with n and m the radial and azimuthal mode numbers, respectively. Asymmetric m ≠ 0 modes are unaffected by the detuning parameter, which is related to the meniscus shape and satisfy a homogeneous Mathieu equation with the shape of the instability tongues computed by the Floquet theory. The Poincaré–Lindstedt method is used to compute the instability tongues for the axisymmetric m = 0 modes, which have a lower threshold acceleration and larger bandwidth that depend upon the detuning parameter. Our model results explicitly show how the shape of the meniscus and spatial structure of the wave determine the temporal response and are in good agreement with prior experimental observations for both pure modes and mixed modes. [ABSTRACT FROM AUTHOR]

Shake table tests on two-tiered metal-strip MSE walls showed that the prevention of slip surface development in the lower half of the wall, improving seismic stability by increasing failure threshold acceleration, and mitigating acceleration amplification were the main advantages of using a two-tiered configuration in constructing MSE walls. This was also found that the use of an insufficient offset distance not only eliminated the advantage of the tiered configuration for reducing wall deformations, but also increased the wall crest displacement. Hence, 0.22 H was found to be as the minimum offset distance required when constructing MSE walls in a two-tiered configuration. [ABSTRACT FROM AUTHOR]

S-net is a large-scale seafloor observation network for earthquakes and tsunamis around the Japan Trench, consisting of 150 observatories equipped with seismometers and pressure gauges. The sensors have been set up inside cylindrical pressure vessels, which have been buried in the shallow-water regions (water depth <1,500 m), while the vessels have been laid freely on the seafloor in the deeper-water regions. Previous studies showed that the cylindrical pressure vessels rotate during strong shakings due to poor coupling with the seabed sediments, thus making it difficult to retrieve the actual ground motions. We investigated the static changes in the orientations of S-net accelerometers due to shakings from 1,878 earthquakes of Mj greater than 4 that occurred around the network, and found that rotations as large values as 16° were observed during the 2022,Mj 7.4, off-Fukushima Prefecture earthquake. We estimated the threshold acceleration levels after which the sensors are likely to rotate at all S-net stations separately and found that the threshold values lie mostly between 5 and 50 cm/s². Finally, we discussed the observed peak accelerations and velocities at the S-net stations with those recorded on land, where high-quality records were obtained, during the 2022, Mj 7.4 earthquake, which was also the largest magnitude earthquake to occur in the region after the network commenced operation. The results presented herein complement several previous studies and form the basis for more comprehensive future investigations. [ABSTRACT FROM AUTHOR]

The nonlinearity of the soil may considerably affect the response of structures subjected to seismic events. This paper aims to show under which circumstances geometry, soil, and earthquake-type; the nonlinearity is important. A simple model based on a 1D shear column was developed to calculate the maximum shear strain (γ) in the soil subjected to earthquake excitation. It was found that Δ is a function of peak ground acceleration PGA and the maximum horizontal ground displacement (Δ). EC8 provides an expression for calculating Δ that is independent of the soil thickness. It was found that this expression is conservative for shallow layers and underestimates γ for thick ones, as a result, improvements have been suggested. By performing several time history analyses, simple formulas are developed which enable the designer to assess when nonlinearity must be taken into account. Four curves based on soil thickness and peak ground acceleration have been introduced for different soil types (A, B, C, and D) using a limit value of γ = 10-4. These curves show that depending on the soil depth, the threshold acceleration of nonlinear soil behavior is around 0.48, 0.36, 0.29, and 0.10 m/s2 for soil types A, B, C, and D, respectively. Obviously, nonlinear analysis must be performed for shallow soil layers under moderate seismicity. [ABSTRACT FROM AUTHOR]

A novel contact-enhanced low-g inertial microswitch has been proposed and fabricated by surface micromachining technology in this paper. A novel segmental circle spring has been designed in the low-g inertial switch, which can decrease its stiffness compared with traditional semicircle spring. The dynamic response of the microswitch is simulated by ANSYS software, which has estimated its threshold acceleration and holding time. The vibrations of proof mass under the applied overload acceleration in the sensitive direction and the opposite direction are both simulated and analyzed, which demonstrates that the rebound of proof mass can be restrained effectively by the introduced limit blocks. The fabricated prototype has been tested by a dropping hammer system. The test results indicate that the threshold acceleration of fabricated inertial switch is ∼25g with holding time ∼650 μs. The overload acceleration of 80g, 120g have been applied on the fabricated prototype, and the test results indicate that the spurious trigger have been eliminated due to the limit blocks, which is in agreement with the simulation results. The acceleration of 100g is applied to the tested inertial microswitch with and without limit block in the opposite sensitive directions, respectively. The test result verifies the function of limit blocks. [ABSTRACT FROM PUBLISHER]

Shaking table tests were performed on reduced-scale models of integrated and two-tiered mechanically stabilised earth (MSE) walls to evaluate the effect of a tiered configuration on the seismic behaviour of metal-strip and geogrid reinforced soil walls. The results showed that, although inextensible reinforcements could reduce the fundamental period, acceleration amplification and lateral deflection and improve wall stability, these benefits declined with the use of a tiered configuration and gradually faded with an increase in the offset distance. This made changing the degree of extensibility a low-impact factor in two-tiered MSE walls with a sufficiently large offset distance (D > (0.4–0.5)H). In order to benefit from the advantage of a tiered configuration, it was found that 0.22H should be considered as the minimum offset distance. The findings indicated that preventing the development of a slip surface in the lower half of the wall, improving the seismic stability by increasing the failure threshold acceleration, mitigating acceleration amplification and decreasing the reinforcement load were the main advantages of a tiered configuration. Moreover, it was concluded that the Mononobe–Okabe method could be used to find the upper bound for estimating the reinforcement forces in two-tiered MSE walls. [ABSTRACT FROM AUTHOR]

Raised strips were introduced into the micromachined acceleration switch to avoid the stiction between the mass and the substrate. The system spring constant of the switch with serpentine springs was calculated. The influence of the introduced anti-stiction raised strips on squeeze-film damping of the switch was analyzed closed-form using reasonable boundary conditions. Based on the calculated systems parameters, a Simulink model was constructed to simulate the dynamic properties of the switch under different types of shock acceleration. It is indicated that the dynamic responses (threshold acceleration and response time) were almost not affected by those raised strips which are instead beneficial to reduce the oscillation of the moving mass and improve the yield of the switch. Dependence of dynamic properties on the distance between two electrodes, thickness of the mass and spring constant has also been simulated. The drop hammer experiment was conducted to characterize dynamic properties of the fabricated and packaged acceleration switch. Test threshold acceleration and response time are, respectively, about 41 g and 0.7 ms when the half-sine wave shock was applied, which are in accordance with simulated ones. The package strength of the switch was also evaluated and corresponding critical shear stress for failure is about 22 MPa. [ABSTRACT FROM PUBLISHER]

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, we propose a modified frequency up-conversion mechanism to lower the operational acceleration level for energy harvesting devices using a snap-through buckling phenomenon. The proposed device consists of a buckled bridge beam clamped on flexible sidewalls with a proof mass and cantilever beams attached to the bridge. When subject to a vibration, the buckled bridge beam snaps through between two stable states, inducing impulsive acceleration on the attached piezoelectric cantilevers. During the snap-through transition, the flexible sidewalls deflect outward, thus lowering the threshold acceleration value for the state transition. Various sidewall materials with different flexibilities were tested to determine the maximum output power, bandwidth, and output characteristics for various input acceleration values. The minimum acceleration value for snap-through transition was 0.5 g ( g = 9.8 m/s) when using latex sidewalls. A maximum output power of 0.4 mW Hz/cm-that is 10 μW for test sample at an excitation frequency of 15 Hz-was generated by using the proposed device with latex sidewalls. [ABSTRACT FROM AUTHOR]