Minimum Deflection Research Articles

Development of 3D Force Sensors for Nanopositioning and Nanomeasuring Machine

In this contribution, we report on different miniaturized bulk micro machined three-axes piezoresistive force sensors for nanopositioning and nanomeasuring machine (NPMM). Various boss membrane structures, such as one boss full/cross, five boss full/cross and swastika membranes, were used as a basic structure for the force sensors. All designs have 16 p-type diffused piezoresistors on the surface of the membrane. Sensitivities in x, y and z directions are measured. Simulated and measured stiffness ratio in horizontal to vertical direction is measured for each design. Effect of the length of the stylus on H:V stiffness ratio is studied. Minimum and maximum deflection and resonance frequency are measured for all designs. The sensors were placed in a nanopositioning and nanomeasuring machine and one point measurements were performed for all the designs. Lastly the application of the sensor is shown, where dimension of a cube is measured using the sensor.

Application of creep small punch testing in assessment of creep lifetime

In this contribution, the problem is investigated, whether the dependence of the time to rupture on the acting force in small punch tests can be analyzed in the same way as the dependence of time to rupture on the applied stress in conventional tensile creep tests. Two comparable sets of constant-force small punch tests and relevant conventional creep tests on P91 steel were performed at temperatures from 823 to 873 K. The experimental results were analyzed using various parametric approaches (Larsson–Miller, Fisher–Dorn, etc.) very well-known from conventional creep testing. It is shown that the methods based on time–temperature parameter can be used also for a description of small punch test data. The differences among various studied methods are negligible; the best description can be achieved with the Sud–Aviation parameter. The extrapolated data can be used for determination of empirical relationships between stress and minimum creep rate in the creep tests and force and minimum deflection rate in the small punch test.

In-plane photonic transduction of silicon-on-insulator microcantilevers

We demonstrate an in-plane photonic transduction method for microcantilevers, which have been widely investigated for sensor applications. In our approach the microcantilever is etched to form a single mode rib waveguide. Light propagates down the microcantilever and crosses a small gap at the free end of the microcantilever, some of which is captured by an asymmetrical multimode waveguide that terminates in a Y-branch. The Y-branch outputs are used to form a differential signal that is monotonically dependent on microcantilever deflection. The measured differential signal matches simulation when microcantilever rotation is properly accounted for. The measured differential signal sensitivity is 1.4 x 10(-4) nm(-1) and the minimum detectable deflection is 0.35 nm.

ESTIMATING THE STATIC STIFFNESS FOR A SPINDLE-TOOLHOLDER-TOOLING SYSTEM

This article focuses on static analysis to integrate the necessary components for the design of spindle-toolholder-tooling systems; the modeling and analysis of the systems is based on a mathematical model using a systematic approach for evaluating the static deflection at the cutting point. The analysis addresses the deflection of most of the components in the system including the spindle shaft, front and rear bearings, toolholder, cutting tool and their corresponding spindle-toolholder and toolholder-tool interfaces modeled with linear (radial) and rotational (tilting) springs. The effects of design parameters on the static performance of these systems are analyzed in order to assess the contribution and the influence of the individual system components. Computations and experimental results show that improvements can be made in the system by adjusting the aforementioned parameters. The proposed strategy is to iteratively predict the tool deflection at the tool tip using the analytical model based on the superposition appoach. The model is simple and it provides tremendous assistance to an engineer to select the proper toolholder and tool for minimum deflection.

An improved Schlieren method for the sensitive and spatially resolved measurement of the quality of optical crystals with small apertures

We present an improved Schlieren method to measure the optical quality of crystals, defined by it’s optical homogeneity and the surface roughness of it’s facets. The method is based on a combination of Schlieren, interferometric and tilting angle measurements. It is especially appropriate for the optical characterization of crystals with small clear apertures. The theory and an application of this improved technique on a BIBO crystal are given. Spatial resolution and sensitivity of the method are mainly defined by the Schlieren setup, which offers a spatial resolution as high as 27 μm and a minimum deflection angle as low as 2.3×10-6.

CONCEPT FOR THE DESIGN OF FLIGHT CONTROL ACTUATION AND LAWS FOR FUTURE ALL-ELECTRIC AIRCRAFT

This paper consolidates advanced techniques for flight control law design with the sizing issues of new technology electrical flight control actuators. An automatic optimisation tool is adapted to modify the control laws for minimum actuator deflection rates, which can be turned into weight savings for the overall aircraft. Thus, the paper outlines a new and up-to-date trade-off study, which is motivated by the recent trend towards the more-electric aircraft concept.

Constructing minimum deflection fixture arrangements using frame invariant norms

This paper describes a fixture planning method that minimizes object deflection under external loads. The method takes into account the natural compliance of the contacting bodies and applies to two-dimensional and three-dimensional quasirigid bodies. The fixturing method is based on a quality measure that characterizes the deflection of a fixtured object in response to unit magnitude wrenches. The object deflection measure is defined in terms of frame-invariant rigid body velocity and wrench norms and is therefore frame invariant. The object deflection measure is applied to the planning of optimal fixture arrangements of polygonal objects. We describe minimum-deflection fixturing algorithms for these objects, and make qualitative observations on the optimal arrangements generated by the algorithms. Concrete examples illustrate the minimum deflection fixturing method. Note to Practitioners-During fixturing, a workpiece needs to not only be stable against external perturbations, but must also stay within a specified tolerance in response to machining or assembly forces. This paper describes a fixture planning approach that minimizes object deflection under applied work loads. The paper describes how to take local material deformation effects into account, using a generic quasirigid contact model. Practical algorithms that compute the optimal fixturing arrangements of polygonal workpieces are described and examples are then presented.

Development of a low temperature MEMS process with a PECVD amorphous silicon structural layer

Amorphous silicon (a-Si:H) deposited at 150 °C by plasma-enhanced chemical vapor deposition (PECVD) is investigated as a structural layer for low temperature microelectromechanical system (MEMS) fabrication. The process development of depositing thick a-Si:H films and the material characterization of the film stress and hydrogen content is presented. To demonstrate a MEMS application, bimorph thermal actuators incorporating a-Si:H and aluminum were designed and fabricated resulting in tip deflection of hundreds of microns. The PECVD film coverage of various sidewall structures was also studied by scanning electron microscopy. Our a-Si:H films formed a sidewall coverage angle of 80° with the substrate. Mechanical simulations relate this angle within the range of minimum stress and maximum deflection of the actuator. Our results indicate that amorphous silicon is as an attractive structural material offering a low thermal budget for post-processing and integration of MEMS devices with complementary metal-oxide–semiconductor technology.

Toolpath selection based on the minimum deflection cutting forces in the programming of complex surfaces milling

In this paper, a new methodology for the selection of the milling toolpaths on complex surfaces that minimize dimensional errors due to tool defection is presented. In this way, an improvement on the accuracy of milled surfaces is achieved. The methodology can be applied to both three and five axes milling. In the three axes case, it is based on the calculation of the minimum cutting force component that is related with the tool deflection. This component has been previously defined as that perpendicular to the tool axis and contained on the plane defined by the tool axis and the normal vector to the workpiece surface. Cutting forces are calculated for each 15° sense on the tangent plane to the milled surface, in a grid of control points defined by the user, both for dowmilling and upmilling. With this information there are two possibilities. First, select a general toolpath direction that minimizes the mean value of the tool deflection force on the surface, and bearing this in mind, the CAM operator can produce a CNC program which leads to an accuracy improvement. The second option is the selection of different milling directions at each control point. Joining these points, the minimum force lines are defined on the workpiece surface. These can be used as the master guides for the toolpath programming of a complete surface. In the case of five axes milling, the approach is different, because in this case the tool-axis orientation with respect to the workpiece surface may be changed using the two rotary axes. Therefore, for each workpiece area both tool-axis orientation and machining direction can be selected to keep tool deflection force below a threshold value. Some case studies of both techniques and in-deep discussion of results are presented. Applying this approach, in three axes milling dimensional errors fall down from 30 μm to below 4 μm. In five axes milling errors can be kept below 15 μm in most of the cases.

Development of liquid-environment frequency modulation atomic force microscope with low noise deflection sensor for cantilevers of various dimensions

We have developed a liquid-environment frequency modulation atomic force microscope (FM-AFM) with a low noise deflection sensor for a wide range of cantilevers with different dimensions. A simple yet accurate equation describing the theoretical limit of the optical beam deflection method in air and liquid is presented. Based on the equation, we have designed a low noise deflection sensor. Replaceable microscope objective lenses are utilized for providing a high magnification optical view (resolution: <3μm) as well as for focusing a laser beam (laser spot size: ∼10μm). Even for a broad range of cantilevers with lengths from 35to125μm, the sensor provides deflection noise densities of less than 11fm∕Hz in air and 16fm∕Hz in water. In particular, a cantilever with a length of 50μm gives the minimum deflection noise density of 5.7fm∕Hz in air and 7.3fm∕Hz in water. True atomic resolution of the developed FM-AFM is demonstrated by imaging mica in water.

Bending and optimisation of an inflated braided beam

Two braided inflatable beams have been made that differ in the number of axial fibres that are placed parallel to the length, and in the angle at which the bias fibres are placed. Each beam consists of a silicone rubber bladder, two end caps and a dry carbon fibre braid placed over the silicone bladder. Experimental and theoretical analysis of the beams have been revealed that due to bending, the beams initially deflect in a linear manner like the Euler–Bernoulli beam model predicts. Once the stress in the axial fibres becomes zero, wrinkling occurs resulting in a significant loss of bending stiffness. The two beams that were tested were optimised for minimum deflection at a constant volume of fibres. The stiffest design has the maximum possible amount of fibres in parallel to the beam.

Structural Analysis of Directional Deflection Beams

Parallel leaf springs are often used for precise linear motion because of their simplicity and freedom from static friction in cases where elasticity and high deformation are required. Using a parallel beam in force sensing requires minimum deflection and limited stress concentration. We previously proposed a unidirectional force sensor based on the H-slit parallel beam structure – an extension of conventional parallel beam. In this paper, we use finite element analysis (FEA) to investigate parallel beam structures that deflect easily in one direction, and evaluate the optimum profile for the notch in the H-slit beam and applications of the parallel beam structure.

Establishment of BMD reference curves at different skeletal sites in women, using a Cartesian coordinate numeration system

The BMD reference curve is the reference value used for diagnosing osteoporosis and assessing bone mass changes. Its accuracy would affect the correctness of T-score and Z-score values and thus the reliability of diagnostic results. In this paper, we report the use of a new method, a Cartesian coordinate numeration system, to establish BMD reference curves at different skeletal sites in women. In a reference population of 3,919 women ranging in age from 5-85 years, we used the dual X-ray absorptiometry (DXA) bone densitometer to measure BMD at the posteroanterior spine (PA; vertebrae L1-L4), followed by a paired PA/lateral spine scan of the vertebral bodies of L2-L4, expressed in g/cm2 and g/cm3, and of the hip and forearm. We chose the cubic regression model to best fit BMD curves that varied with age at different skeletal sites. We then referred the BMD of the fitting curves established by the method of the coordinate numeration system as reference curves, compared them to BMD reference curves derived from the fitting curve equation or age cross-section, and calculated the deflection degrees of the BMD reference curves acquired from the fitting curve equation. At the PA spine, lateral spine (expressed in g/cm3), femoral neck, Ward's triangle and radius + ulna ultradistal, the reference curves calculated from the equation were significantly lower than those confirmed by the method of the coordinate numeration system; whereas, at the lateral spine (expressed in g/cm2), total hip, and radius + ulna 1/3 sites, the reference curves derived from the equation were markedly higher than those acquired from the coordinate numeration system. The differences in the two kinds of reference curves calculated by these two different methods gradually increased along with the increment in ages of the women. At the peak value of the reference curves, the BMD calculated from the equation deflected from 2.02% to -10.0% from the BMD acquired from the coordinate numeration system at different skeletal sites, and from 21.5% to -121.8% until the age of 85 years. The highest positive deflection of 65.2% existed at the lateral spine (expressed in g/cm2) and the lowest positive deflection of 21.5% at the total hip. The maximum negative deflection of -121.8% was at the radius + ulna ultradistal, and the minimum negative deflection of -32.6% at the PA spine. The BMD curve acquired from age cross-section was highly positive compared with the one derived from the coordinate numeration system (r=0.955-0.985 p=0.000) with no significant difference between them. Various analysts used such a method to obtain the coefficient of variance (CV) in BMD precision on each curve that was from 0.05-0.19%. Our study shows that the Cartesian coordinate numeration system is an accurate, precise and reliable method and can serve to reveal the serious drawbacks of using the fitting curve equation to calculate BMD. The BMD reference curves established by this coordinate numeration system maintained the authenticity of the fitting curve, whereas, using the fitting curve equation to obtain BMD reference curves at different skeletal sites led to distortion, and resulted in false increases or decreases in T-score and Z-score values.

Optimising a shaft’s geometry by applying genetic algorithms

Many engineering design tasks involve optimizing several conflicting goals; these types of problem are known as Multiobjective Optimization Problems (MOPs). Evolutionary techniques have proved to be an effective tool for finding solutions to these MOPs during the last decade. Variations on the basic genetic algorithm have been particularly proposed by different researchers for finding rapid optimal solutions to MOPs. The NSGA (Non-dominated Sorting Genetic Algorithm) has been implemented in this paper for finding an optimal design for a shaft subjected to cyclic loads, the conflicting goals being minimum weight and minimum lateral deflection.

A deflection yoke for projection TV with reduced geometrical distortion

— We have succeeded in coping with raster-distortion and deflection-defocusing problems in CRT projection TV by utilizing a longer horizontal coil and uniquely shaped windings. The field distribution along the tube axis was also modified and optimized to achieve minimum raster distortion and deflection defocusing simultaneously. The position of the centering magnet was shifted towards the screen side to minimize the defocusing of the spot.

Decomposition-Based Assembly Synthesis of a Three-Dimensional Body-in-White Model for Structural Stiffness

This paper presents an extension of our previous work on decomposition-based assembly synthesis for structural stiffness, where the three-dimensional finite element model of a vehicle body-in-white (BIW) is optimally decomposed into a set of components considering (1) stiffness of the assembled structure under given loading conditions, (2) manufacturability, and (3) assembleability of components. Two case studies, each focusing on the decomposition of a different portion of a BIW, are discussed. In the first case study, the side frame is decomposed for the minimum distortion of front door frame geometry under global bending. In the second case study, the side/floor frame and floor panels are decomposed for the minimum floor deflections under global bending. In each case study, multiobjective genetic algorithm with graph-based crossover, combined with finite element methods analyses, is used to obtain Pareto optimal solutions. Representative designs are selected from the Pareto front and trade-offs among stiffness, manufacturability, and assembleability are discussed.

ＦＥＭと結合した積層板の層別最適化（ＬＯ）法の提案

A concept of a layerwise optimization (LO) approach, previously proposed by the author, is extended to be combined with the finite element method (FEM) and this combined approach for structural optimization, named LO-FEM approach, is demonstrated to obtain the optimum performance of symmetrically laminated composite plates. Design variables are taken to be the fiber orientation angles in all K layers. This usually causes a rapid increase in computation time due to the search for optimum solutions in the K dimensional space. The LO makes it possible, however, that this multi-dimensional optimization problem reduces into only K times repetition of onedimensional search. In the FEM formulation, the stiffness matrix is modified to be suited for the LO procedure. The numerical examples show that the LO-FEM approach is a quite effective tool to obtain the minimum deflection in the bending problem and the maximum frequency in the vibration problem.

Small punch creep in Fe28Al3Cr0.02Ce alloy

Small punch testing of Fe3Al-based intermetallic alloy with Cr, Mn and Ce additions was performed in temperature range 773–873 K. It is shown that the testing procedure enables to study the creep properties of the alloy. The time dependence of the central deflection resembles creep curves observed in conventional uniaxial creep testing and the minimum deflection rate can be determined. Similarly as in conventional creep tests, the deflection process is then analyzed in terms of the activation energy and force exponent. In accordance with the phase structure of the alloy, two distinct areas can be observed. In the B2 range, the activation energy equals 181 kJ/mol; the force exponent is about 4.6. In the DO3 range, the activation energy equals 82 kJ/mol and the stress exponent is about 44. The transformation temperature DO3⇔B2 is close to 812 K. The technique can be used for an estimation of creep resistance.

A study of U-shaped micromachined cantilever array

In order to increase the resolution and realize the versatility of cantilever, U-shaped piezoresistive cantilever array has been designed and fabricated in this research. The optimized geometries of cantilever and piezoresistor were determined by analyzing the stress, noise and sensitivity of piezoresistive cantilever from theory. Based on silicon micromachining technology, the piezoresistive cantilevers were fabricated by using polysilicon as the piezoresistive materials. With the measurement results of noise and sensitivity, the Hooge factor was calculated to be 3×10-3, the gauge factor is 27, and the minimum detectable deflection of piezoresistive cantilever was calculated to be 0.5nm at a 6V bias voltage and a 1000Hz measurement bandwidth. The noise sources of polysilicon pizeoresistor are also discussed in this paper.

Analysis of ShuffleNets with limited number of wavelength converters employing deflection routing

Optical node performance analysis in terms of number of wavelength converters for a multihop optical ShuffleNet under deflection routing is presented. From the computed results for a given number of wavelengths, it is found that in order to achieve the minimum deflection probability at full load, the number of wavelength converters required is at most 60% of the number of wavelengths. Any additional wavelength converters would not be necessary in reducing the overall deflection probability. These upper-bound findings are indeed helpful for network engineers designing a cost-effective network node.