Central Boss Research Articles

Design and Simulation of Digital Output MEMS Pressure Sensor

This paper presents the design and simulation of a MEMS pressure sensor with a digital output for measuring pressure in the range of 0–1 bar. The sensor uses the diaphragm deflection and a simple mechanical structure to convert the applied pressure to a logic digital output. Three different designs of the sensor have been proposed with square and circular diaphragms. The first design uses ten different sized square diaphragms on the same substrate to get a resolution of 0.1 bar. The second design uses a single square diaphragm instead of ten to get the same resolution. The third design also uses a single circular diaphragm with a central boss structure, which reduces the deflection nonlinearity at low pressures. Analytical analysis was carried out for all the diaphragm deflections, and the results are supported by numerical simulations carried out in COMSOL Multiphysics tool. The proposed sensor can operate on 5 V which suits well with conventional CMOS logic. The direct digital output from the pressure sensor makes its useful in wide variety of applications.

Lean manufacturing implementation using value stream mapping at excavator manufacturing company

Abstract The shop floor of each industry has several stations, working interdependent to carried out specified tasks, as per the schedule define to meet the production rate. The breakdown of machine, shortage of inventory, unavailability of tools causes delay to meet the demand. The excess inventory at workstation catches rust requires regrinding, fatigue to operator due to unnecessary movement, improper design of pallet, incorrect location of clamps are some of example consumes time at workstation and slower production rate. The fabrication line of global boom has considered for improvement and to increase production rate to satisfy the customer demand. This fabrication line is able to produce 12 global booms per day. This rate of production is inadequate to satisfy actual customer demand of 15 global booms per day. The efficiency of fabrication line has proposed to increases to meet actual demand. Value stream mapping is the only lean tool suggested in literatures, to eliminate Muda, bottlenecks across production line. The value stream mapping uses current state map to record current state of production line before implementation of techniques. The current state map plotted for globe boom fabrication line has identified several problems. The higher setup at welding station of center section due to improper clamping of center section, excess inventory at foot boss a center boss tacking station catches rust and requires regrinds, underutilized press station due to no provision of fixture are some of the problems identified across fabrication line. The lean implementation, kaizen are employed to solve above problems and future state map recorded. The lean implementation eliminates excessive inventory, reduces total cycle time and total setup time at various station. The future state map shows reduction of 156 min from value added activities which synchronously reduces 430 min of non-value added activities. This contributes reduction of 586 min from production lead time.

Multi-Conceptual Mechanical Design Optimization of Capacitive Pressure Sensors via Finite Element Analysis with use of Anisotropic Behavior of Silicon <111> Crystal: Summary of Design Optimization Approaches

In the world of micro-mechanical design of micro-sensors, up to date, there has not been substantial considerations given to the actual mechanical or structural aspect of the designs. Hence, most of the currently available designs are challenged to linearize the “non-linear” sensor’s output by utilization of electronic circuitry. In this research work, a micro-pressure diaphragm which possess linear pressure-deflection behaviour is designed via FEM optimization techniques. The diaphragm is modelled as a Silicon (111) plane, which possess plane isotropic properties. A circular centre boss section is added to the diaphragm and optimization is carried out, to achieve an optimum diaphragm geometry that would allow for flat or rigid deflection of this boss section under the applied surface pressure loading. The approximate closed−form deflection solutions are developed using the anisotropic thin plate theory and the diaphragm deflection behaviour of the FEM optimized design is compared with this thin plate theory model. This diaphragm design is proposed to be used as the top electrode plate of a capacitive pressure sensor, where linear pressure-capacitance change behaviour would become present. This pressure diaphragm has a pressure range of 0 to 206843 Pa (30 psi) with a pressure resolution of 689.5 Pa (0.1 psi).

Mechanical Structural Design of a Piezoresistive Pressure Sensor for Low-Pressure Measurement: A Computational Analysis by Increases in the Sensor Sensitivity.

This paper proposes a novel micro-electromechanical system (MEMS) piezoresistive pressure sensor with a four-petal membrane combined with narrow beams and a center boss (PMNBCB) for low-pressure measurements. The stresses induced in the piezoresistors and deflection of the membrane were calculated using the finite element method (FEM). The functions of the relationship between the dimension variables and mechanical performance were determined based on the curve fitting method, which can provide an approach for geometry optimization of the sensor. In addition, the values in the equations were varied to determine the optimal dimensions for the proposed membrane. Then, to further improve the sensitivity of the sensor, a series of rectangular grooves was created at the position of the piezoresistors. The proposed diaphragm was compared to existing diaphragms, and a considerable increase in the sensitivity and a considerable decrease in nonlinearity error could be achieved by using the proposed sensor. The simulation results suggest that the sensor with the PMNBCB structure obtained a high sensitivity of 34.67 mV/kPa and a low nonlinearity error of 0.23% full-scale span (FSS) for the pressure range of 0–5 kPa. The proposed sensor structure is a suitable selection for MEMS piezoresistive pressure sensors.

Modeling analysis and fabrication of MEMS capacitive differential pressure sensor for altimeter application

This paper proposes the modeling analysis of MEMS highly sensitive Capacitive Differential Pressure Sensor (CDPS) and also the development of a fabrication process for CDPS structures for aircraft altimeter applications. Highly sensitive CDPS structure models using circular and square sandwich polyimide diaphragm membranes, with and without center boss, were adopted, whereas other studies report on silicon diaphragms. CDPS characterization was carried out to analyze the deflection sensitivity, capacitive sensitivity, stress on diaphragm membrane and the effect of temperature on capacitive sensitivity. Simulation results of square diaphragm without center boss show better characteristics than other proposed diaphragm structures. This design yields 145.8 nm/mbar and 0.574 fF/mbar of deflection and capacitive sensitivity, respectively. The maximum stress developed on the diaphragm at maximum working pressure is less than the yield stress of polyimide material by a factor of 1.77 and capacitive sensitivity deviates at ±0.00195%/°C. From the modeling analysis, square diaphragm CDPS structure yields better characteristics and hence the fabrication process for CDPS has been developed, and its fabrication process flow verified using Intellisuit virtual fab tool.

Drill hole convergence and a quantitative analysis of drill holes in mollusks and brachiopods from the Triassic of Italy and Poland

The history of predation is recorded primarily from drilling in Cenozoic invertebrates. Quantitative data are uncommon from the Triassic, a period before the appearance and radiation of many known drill hole producers such as various gastropod families and octopods. We present quantitative evidence of drilling from the Late Triassic (Carnian) Cassian Formation of Italy and the Middle Triassic (Anisian) Lower Muschelkalk of Poland, documenting the first drill holes in Triassic brachiopods. A single brachiopod with a cylindrical, complete drill hole was found in a brachiopod sample from of Poland (drilling percentage=0.3%, n=365). The Cassian Formation yielded drill holes in gastropods, bivalves, and brachiopods, indicating that more species are drilled than was known previously. The minimum drilling percentage exclusive of incomplete drill holes of a sample from the Stuores Wiesen (Cassian Formation) is 1.7% (n=116.5). Prey selectivity is evident: complete drill holes are primarily present in one gastropod species, Polygyrina lommeli (11.8% of specimens with a complete drill hole), whereas other common species were not drilled. Single drill holes in brachiopods are cylindrical and complete and may be predatory in origin. Multiple drill holes in mollusks are common, and drill holes are parabolic and often incomplete with a central boss, resembling the shape of drill holes produced by extant naticid gastropods. A survey of the Paleozoic literature showed that such drill holes are also present in Devonian and Carboniferous brachiopods. However, naticids did not evolve until the Cretaceous so we propose the term “drill hole convergence” for similar-shaped drill holes produced by different organisms. The Triassic parabolic drill holes are not caused by domicile-seeking or boring organisms. Instead, we favor a predatory origin of these drill holes, but we cannot entirely rule out parasitism. Surveying other Triassic invertebrate assemblages should yield more evidence of drilling.

Traces (ichnospecies Oichnus paraboloides) of predatory gastropods on bivalve shells from the Seogwipo Formation, Jejudo, Korea

Circular to subcircular drill holes were identified on the bivalve shells collected from the Seogwipo Formation, Jejudo, Korea. A great majority of the drill holes (>70%) were found on the surfaces of a bivalve species Glycymeris rotunda. They are characterized by a beveled sharp edge and paraboloid in cross section with larger outer borehole diameter (OBD; mean 4.21 mm) and smaller inner borehole diameter (mean 2.94 mm). Walls of the drill holes are generally smooth, and walls ornamented with etched relief-like structures were also recognized. A slightly raised central boss observed in an incomplete specimen may indicate a failure of predator’s attack. All drill holes collected are classified as a single ichnospecies Oichnus paraboloides Bromley, 1981. They are interpreted as boring traces produced by predatory gastropods, particularly naticid gastropods. Most O. paraboloides boreholes are observed in the central area of shell surfaces; a few boreholes lie marginally, which may reflect a borehole-site selectivity. No correlation between size of prey (shell height) and size of predator (OBD) is recognized. It is likely, however, that drilled shells of about 30 mm in height represent optimal prey size for naticid predators that lived in a benthic Seogwipo community.

Ichnology and palaeobiology of Phoebichnus trochoides from the Middle Jurassic of north‐east England

AbstractPhoebichnus trochoides is a large, radiating trace fossil most commonly found in shallow marine siliciclastic deposits. The structure consists of a central boss from which extend numerous, lined, radiating burrows which have an active fill. Serial grinding and modelling techniques allow the full three‐dimensional morphology of Phoebichnus trochoides to be constructed for the first time. Three‐dimensional models of the trace fossil demonstrate that the central zone is composed of stacked disc‐shaped layers. The structure is inferred to result from collapse of sediment below a surficial cone created by the trace‐maker from excavated sediment produced during burrowing. The fill of the radial burrows is herein determined to be composed of angle of repose laminae that are inclined towards the central zone rather than the meniscate backfill documented in the ichnogeneric diagnosis and all subsequent descriptions. The structure of the fill resulted from the trace‐making organism filling its burrows from a dwelling position close to the central boss, probably with material excavated from other parts of the burrow system. This study also reports for the first time subtle conical structures above the radial galleries that are inferred to result from collapse cone feeding. The new fully three‐dimensional data set created of the burrow and the near‐burrow environment allows for a new palaeobiological understanding of the burrow, which suggests that a crustacean trace‐maker is most likely.

Simulation of Lateral Extrusion of Spline Form Based on the Software DEFORM-3D

Lateral extrusion, sometimes called injection upsetting, offers a product with central boss section having complete or segmented protrusions. Collar flanges, spur gear forms, spline or taper with shaft are examples of the products of produce by lateral extrusion. The aim of this study is to investigate the lateral extrusion of gear-like spline form in terms of forming load and load die filling ratio and comparison the results with those results obtained from a commercially FEM based programme named DEFORM-3D. A series of experiment has been carried out using solid lead billets with two different billet diameters and two different billet heights. Experiments were carried out by using a hydraulic press of which capacity 150 metric tons. Load-stroke relations and die filling ratios are obtained both theoretically and experimentally. It is obviously shown that the results obtained from the DEFORM-3D could be used for simulating of the deformation process.

Cold Forging Die Design and Process Simulation of a Disk with Inner Ring Gear

Cold forging die design and process simulation were studied in this paper for a disk with center boss and outer ring gear. The complexity of part geometry results in defects of under-filling and folding. The material flow interference in the radial and the axial directions at the corner areas is the main reason of the occurrence of defects. A multi-stage cold forging process was proposed to control the material flow and volume distribution simultaneously. FEM simulations were carried out to evaluate the designs of process and die. The proposed preform and web geometry designs were able to decrease the forging load and control the material flow. The simulation results showed the proposed methods were able to make this forged part without defects.

Structured diaphragm with a centre boss and four peninsulas for high sensitivity and high linearity pressure sensors

Using the structured diaphragm with a centre boss and four peninsulas (CBP structure), a high sensitivity and high linearity pressure sensor for low pressure ranges was demonstrated. The finite element analysis indicated that the CBP structure could achieve a far better performance than other typical structures for low pressure applications. In accordance with the simulation, the fabricated pressure sensor showed a sensitivity of 21.0 mV/V full-scale output and a nonlinearity error of 0.15% full-scale span in the pressure range of 0–5 kPa. The sensors with the CBP structure are potentially a better choice for measuring low pressures.

A high sensitivity and high linearity pressure sensor based on a peninsula-structured diaphragm for low-pressure ranges

The trade-off between sensitivity and linearity has been the major problem in designing the piezoresistive pressure sensors for low pressure ranges. To resolve the problem, a novel peninsula-structured diaphragm with specially designed piezoresistors was proposed. Finite element method (FEM) was adopted for analyzing the sensor performance as well as comparisons with other sensor structures. In comparison to flat diaphragm, the proposed sensor design could achieve a sensitivity increase by 11.4%, nonlinearity reduction of 60% and resonance frequency increase of 41.8%. In addition, the modified peninsula-structured diaphragms featuring a center boss have been optimized to achieve ultra-low nonlinearities of 0.018%FFS and 0.07%FFS for the 5kPa and 3kPa pressure ranges respectively with higher sensitivities as compared to the CBM (cross beam membrane) and hollow stiffening structures. In accordance with the FEM results, the fabricated pressure sensor with the peninsula-structured diaphragm showed a sensitivity of 18.4mV/V full-scale output and a nonlinearity error of 0.36%FSS in the pressure range 0–5kPa. The proposed sensor structure is potentially a better choice for designing low pressure sensors.

The plastic and creep characteristics of silicon microstructure at elevated temperature

As the basic process, elevated temperature annealing is widely used in silicon MEMS device fabrication. This paper studies plastic and creep characteristics of single crystal silicon (SCS) microstructure which would take place during high temperature fabrication processes. The widely used microstructure in MEMS design, which consists of a square diaphragm with a center boss and a vacuum cavity, is adopted in this work. During high temperature process, because of atmospheric pressure outside the vacuum cavity, maximum Von Mises stress of SCS microstructure will exceed the yield stress of SCS, and plastic deformation of the SCS microstructure will occur. An empirical formula for plastic deformation is derived from measurement results in order to predict the plastic deformation in the SCS microstructure design. The plastic deformation is in inverse ratio to the cube of the diaphragm thickness and is not continuous at the yield point. The creep of the microstructure is also investigated by measuring the deformation as a function of annealing time. The obvious creep was observed at 1,100 °C. Due to the non-uniform stress distribution, the creep curve of SCS microstructure is found to be different from that of SCS by tension tests. For SCS microstructure, the creep rate decreases with annealing time in the primary creep and becomes nearly zero in the secondary creep.

Modeling of Electrodynamic Zero-Net Mass-Flux Actuators

electrodynamic zero-net mass-flux (ZNMF) actuator for flow control applications. The electrodynamic actuation schemeemploysamagneticassemblytoestablisharadialmagnetic fieldpatternwithanimbeddedcurrent-carrying coil winding. The coil is attached to a composite diaphragm having a rigid center boss and compliant outer annular region. The magnetic field acting on the coil assembly is modeled using a one-dimensional magnetic circuit. The composite diaphragm is modeled as a transversely isotropic, annular clamped plate. An overall lumped-element electromechanical system model is obtained by combining previously developed lumped models of the cavity/neck structures with lumped models for the composite diaphragm and electrodynamic actuation. The complete lumpedelement model is used to provide insight regarding performance characteristics and design limitations. The model is validated over a frequency range of 10–1000 Hz with hotwire anemometry measurements for both slot and orifice configurations for the jet. The model is useful as a design tool for electrodynamic ZNMF actuators. Nomenclature Amagnet = cross-sectional area of the permanent magnet, m 2 a = outer radius of the diaphragm, m aorif = axisymmetric orifice radius, m Bavg = average magnetic flux density acting on the coil placed in the magnetic assembly, T Bgap = magnetic flux density in the magnet gap predicted by magnetic circuit, T Br = remnant magnetic flux density of the permanent magnet, T b = inner radius of the compliant part of the diaphragm or the radius of the center boss, m CaC = acoustic compliance of the cavity, m 5 =N CaD = acoustic compliance of the diaphragm, m 5 =N CmD = mechanical compliance of the diaphragm, m=N c0 = speed of sound in air, m=s dC = diameter of the cavity, m dslot = diameter of the rectangular slot, m dT = overall diameter of the ZNMF actuator, m Ememb = Young’s modulus of the material of the compliant region of the diaphragm, Pa fN = undamped natural frequency of the diaphragm, Hz fr = steady-state resonant frequency of the diaphragm, Hz f1 = lower 3 dB cutoff frequency, Hz

Nonlinear Analysis of Large Deflection of Elastically-Bossed Sensor Plate under Initial Tension

The nonlinear problem of large deflection of an elastically-bossed layered plate under pretension due to lateral load is studied. The approach follows von Karman plate theory for large deflection for a symmetrically layered isotropic case. The thus derived nonlinear governing equations are solved using a numerical finite difference method with the aid of an iteration scheme. For a nearly monolithic plate with a thin boss, the obtained solutions correlate well with those available in literature for a single-layered flat plate, thus validates the presented approach. For three layered symmetric plates made of typical silicon based materials, various initial tension and lateral pressure are implemented. The results indicate that, edge behavior may appear at both the boss edge and the clamped end of the plate, thereby revealing severe variations for the structural responses. Varying the central boss size and relative thickness may have a sensible influence upon the behavior of the bossed layered plate. Furthermore, lateral pressure appears to have a sensible effect upon the nonlinear behavior of the bossed layered plate. For a relatively large initial tension, however, the pretension effect dominates, yielding a total membrane behavior for the bossed plate, regardless of the size of the center boss, except in the vicinity of the clamped edge.

ATOMIZATION AND DISPERSION MEASUREMENTS IN FIRE SPRINKLER SPRAYS

Water sprays are commonly used in fire suppression applications for cooling the fire environment. This cooling is achieved through the evaporation of droplets (dispersed in the fire gases) and through the wetting of surfaces (from hot or burning materials), inhibiting both the growth and spread of the fire. The suppression performance of these sprays is determined by their ability to penetrate the fire (i.e., the induced flow) to reach burning surfaces below, while dispersing water throughout the hot environment. Spray penetration and dispersion are governed by the initial drop size and velocity characteristics of the spray, which depend on the injection conditions and nozzle configuration. In many fire suppression devices, such as sprinklers, a jet is injected onto a deflector to generate the water spray. Although there are many variations on this basic concept, most sprinklers include a central boss surrounded by a deflector having both tines and spaces. To study the essential physics of the atomization process, discharge characteristics from simplified nozzles were measured. These measurements were compared with those from a more realistic sprinkler configuration. Flow visualization experiments revealed that the canonical impinging jet configuration produces a radially expanding sheet. While similar atomization mechanisms were observed, the realistic sprinkler configuration produces a three-dimensional sheet with two distinct flow streams generated by the tines and spaces of the nozzle. Comprehensive experiments were conducted to describe atomization (e.g., sheet breakup locations and initial drop sizes) and dispersion (e.g., volume density and local drop size profiles) in these sprays.

Sensitivity in Large Deflection of Bossed and Pre-Tensioned Layered Plate under Lateral Load

Mechanical sensitivity of a bossed and clamped layered isotropic circular plate with pretension in large deflection is evaluated. The approach extends Von-Karman’s plate theory for large deflection to a symmetrically layered plate with a center boss. The derived nonlinear governing equations are solved using a finite difference method incorporating a numerical iteration scheme in finding the lateral slope and radial force resultant. The obtained geometrical responses are further manipulated to calculate the associated mechanical sensitivity. For a 3-layered plate with nearly the same layer moduli, the results correlate well with those following available formulation for a single-layer isotropic plate. The developed approach is then implemented for various initial tensions, lateral pressures as well as different boss sizes and ratios between the layer moduli. The obtained numerical results show that, initial tension appears to have the strongest influence upon the radial variation of mechanical sensitivity over the top surface of the bossed layered plate. While both the size of center boss and magnitude of lateral pressure can still have a significant effect, the mechanical sensitivity seems to be insensitive to the change of the ratio between layer moduli for a bossed and symmetrically layered plate.

Optimization of inelastic conical shells with cracks

Inelastic conical shells loaded by the central rigid boss with vertical load are studied. The thickness of the conical part of the structure is piecewise constant. The connection between the shell and the boss is weakened with a stable crack. The designs with the maximal load-carrying capacity are established under a given material consumption of the shell. Material of the shell wall obeys the von Mises yield condition.

Use of SLFET for design of flash gap with V-notched lands in a closed-die forging

The article concerns an influence of the geometrical flash gap parameters on the closed-die forging process. It is focused on the analysis of die forging process where used two kinds of flash gaps with V-notched lands (which have not applied in industries yet). The theoretical calculations were carried out using an authors method of sequential analysis, called slip line fields elemental technique (SLFET). Additionally, in order to determine the best shape of flash gap (depending on forming load and degree of cavity filling by metal) the poly-optimisation was made. The special geometrical model of forging process, which is assumed a forming by extrusion of parts with a central boss (in plane-strain conditions) was assumed in these analyses. Beside, the experimental verification of worked out forging model and obtained selected numerical results was done. That research was realized in laboratory conditions with the use of commercially pure lead workpieces and the special designed tools-set (which assures a forming in conditions similar to plane-strain state). Generally, the obtained experimental results confirm a satisfactory agreement with theoretical results.

감도특성 향상을 위한 국부적 표면식각 다이아프램 구조 연구

In the pressure sensor, about below 20 kPa, the center boss diaphragm structure is generally used, but it is hard to obtain the high sensitivity because the center boss structure is limited at the thickness and size of diaphragm with chip size. Therefore, this paper suggests that the Center boss structure has surface etched diaphragm using a stress concentration to improve the sensitivity. We carried out the simulation and fabrication applied new diaphragm design. In the result, the sensitivity is improved to 60% without the change of non-linearity (0.14%FS). So, the Center boss of surface etched diaphragm can be applied for the high sensitivity in the low-pressure sensor.