Finite Measurements Research Articles

Aerodynamic characteristics of a long-span cable-stayed bridge under construction

Aerodynamic characteristics or parameters such as pressure distributions, static force coefficients, and aerodynamic admittance of a long-span cable-stayed bridge girder during the erection stage have been investigated through field measurements. Buffeting response of the bridge girder at the longest single-cantilever stage was estimated via the field measurements and finite element analysis. Results of this study suggest that the drag- and lift-force coefficients, estimated from the field measurements, increase with an increase in the angle of attack. The Sears function and Davenport’s approximation function were found to overestimate corresponding aerodynamic admittances in the low frequency region. In the high frequency region, the Sears function tends to underestimate the lift force and moment aerodynamic admittances. Davenport’s approximation function were found to be smaller compared to those drag force aerodynamic admittance obtained via the field measurements. Lastly, the buffeting response of the bridge obtained via the finite element analysis and field measurements were found to agree well within a given range of wind speed.

Information Theory for Fields

AbstractA physical field has an infinite number of degrees of freedom since it has a field value at each location of a continuous space. Therefore, it is impossible to know a field from finite measurements alone and prior information on the field is essential for field inference. An information theory for fields is needed to join the measurement and prior information into probabilistic statements on field configurations. Such an information field theory (IFT) is built upon the language of mathematical physics, in particular, on field theory and statistical mechanics. IFT permits the mathematical derivation of optimal imaging algorithms, data analysis methods, and even computer simulation schemes. The application of IFT algorithms to astronomical datasets provides high fidelity images of the Universe and facilitates the search for subtle statistical signals from the Big Bang. The concepts of IFT may even pave the road to novel computer simulations that are aware of their own uncertainties.

Piezothermic Transduction of Functional Composite Materials.

Conveyances of physical energies (such as force, heat, and electricity) from one to another exist in nature and have initiated manifold useful applications. Piezothermic transduction refers to a change in the thermal conduction of a material when a mechanical strain is applied, which can be applied in high-performance pressure sensing and smart energy control. Here, we propose the piezothermic concept and investigate the mechanism of its transduction in three functional composite materials, that is, particle-reinforced composites, porous materials, and series-model materials. Theoretical models for analyzing relatedness effects of material properties (e.g., thermal conductivity, Young's modulus, and volume fraction) are established and validated by both finite element analyses and experimental measurements. The piezothermic transduction provides novel and promising strategies to implement high-performance mechanical sensing as well as energy control through optimizing composite materials. As a demonstration, a pressure sensor with a super high range-to-limit ratio of 50 000 that has a lower detection limit of 3.9 Pa and a large measurement range of 200 kPa is developed.

Electromagnetic-Thermal Analysis of Axial-Flux Permanent Magnet Eddy Current Couplers with Sub-loop Calculation Method

In this paper, a precise electromagnetic–thermal model of axial-flux permanent magnet (PM) eddy current couplers is proposed to calculate the eddy current loss and predict the copper plate node temperature. With subloop calculation method, the quasi 3-D electromagnetic field analytical model is established in cylindrical coordinate. Based on the electromagnetic field analytical model, magnetic field distribution, eddy current losses of PM, copper plate and copper back iron are analyzed under various loads. The eddy current loss of each loop in the copper plate is calculated, at the rated slip speed. Then, the thermal resistance network is carried out, in which the previously obtained eddy current losses are heat sources for calculating the copper plate node temperature. In the thermal study, the influence of various loads on copper plate node temperature rise is analyzed. Finally, the analytical predicted results are compared with the results of finite element method and measurement. The comparison results confirm the validity of the electromagnetic–thermal model.

Evaluation on Residual Stresses in Thick Titanium Welded Alloys

In this work, both Finite element simulated method and contour method experimental measurement are used to obtain residual stresses of different Titanium welded alloys, the results show that the maximum of the residual stress is mainly related to the internal restraint degree which formed inside of the thickness, the distribution of the residual stress depends primarily on the shape of weld shape. The heating stage plays a major role in relaxing the residual stress in this research. 95% of the residual stress is relieved in the temperature rising period, and about 75% of it is relieved in the temperature rising period when the temperature is above 500°C.

Determination of elastic parameters of Si3N4 thin films by means of a numerical approach and bulge tests

This paper describes and applies a methodology to determine the elastic properties of freestanding thin membranes by means of a bulge test and a numerical approach. The numerical procedure is based on the combination of two standard methods i.e. finite element analysis and classical analytical solutions to calculate elastic properties of thin films. Bulge tests were conducted on silicon nitride (Si3N4) monolayer of 2 × 2 mm (square) and 3.5 × 1.5mm (rectangular) membranes with the aim to determine elastics properties (Young's modulus (E) and Poison's ratio (v)) that define the load-deflection curves of both membranes. With this purpose, an error function was constructed for each membrane which involved finite element solutions, analytical solutions and experimental measurements. Error functions were found and minimized by mapping a set of elastic parameters for the two membranes (square and rectangular). A unique solution was determined in the intersection of both linear approximations, obtaining 236 GPa for E and 0.264 for v. It is well known that in a traditional bulge test analysis only one of both biaxial modulus can be determined and not a combination of E and v. Numerical results show that calculated load-deflection curves agree well with the measurements obtained for both square and rectangular membranes experimentally. The proposed methodology is only applicable in thin films with elastic behavior, however generalization for more complicated geometries is possible.

Statistical complexity of the quasiperiodical damped systems

Abstract We consider the concept of statistical complexity to write the quasiperiodical damped systems applying the snapshot attractors. This allows us to understand the behaviour of these dynamical systems by the probability distribution of the time series making a difference between the regular, random and structural complexity on finite measurements. We interpreted the statistical complexity on snapshot attractor and determined it on the quasiperiodical forced pendulum.

Quantum Zeno effect at finite measurement strength and frequency

Quantum Zeno effect at finite measurement strength and frequency

Quantifying the Partition Between Seismic and Aseismic Deformation Along Creeping and Locked Sections of the North Anatolian Fault, Turkey

Shallow aseismic creep is a key deformation component along plate boundaries that contributes to the energy budget during the seismic cycle. Several major active continental faults show spatial alternation of creeping and locked sections. The present study focuses on the evaluation of the aseismic part of the total displacement along the North Anatolian Fault in Turkey. Detailed microstructural analyses of finite strain were performed using various methods, based on change of length or angle, on six representative samples collected over 32 outcrops along locked and creeping sections of the fault. Chemical analyses were used to map mineral composition of fault rocks and to calculate relative volume changes associated with creep. The relationship between finite strain and volume change allowed quantifying the evolution of the penetrative pressure solution cleavage mechanism of creep. In volcanic and analogous creeping rocks, finite strain measurements revealed two spatial scales of strain that correspond to the alternation of two types of shear zones, with cleavages either oblique or sub-parallel to the fault displacement. Using geodetic and geologic data, cumulative aseismic displacement was calculated in the range 9–49% of the total 80-km displacement in the creping sections and was negligible in locked sections. The large uncertainty in the kilometer-width creeping sections was related to the difficulty of quantifying the high strain values associated with high shear displacement and for which measurement uncertainties are large. A promising way to improve such quantification would be to develop reliable statistical analysis of cleavage orientation in the field.

Effect of helix angle on residual stress in the spiral welded oil pipelines: Experimental and finite element modeling

This paper studied the distribution of weld residual stress in a spiral welded pipeline by finite element method (FEM) and experimental measurements, and the effect of helix angle on residual stress has also been investigated. Both the FEM and experiment results show that the residual stresses in HAZ are larger than those in weld. The error between FEM and experiment results is within 14%, proving that our FEM is correct. There is a peak-shape stress distribution through the weld thickness and the residual stresses in the inner surface are larger than those in the outer surface. Different helix angle has a different equivalent weld length along the hoop and axial directions, which generates different hoop and axial plastic strains, leading to different hoop and axial residual stresses. As the increase of the helix angle, both the radial and hoop residual stresses decrease, while the axial residual stresses increase. As the helix angle increases from 20° to 50°, the hoop stresses in HAZ decrease by 65%, while the axial stresses increase by 120%. The residual stresses are influenced by the pipe dimension (pipe diameter, thickness, weld profile), welding technology (heat input, welding speed) and material grade. When the helix angle is between 40° and 45°, both the hoop and axial residual stresses are reduced to the minimum. The most suitable helix angle is suggested to design around 40°–45°.

Effect of processing parameters on the size of molten pool in GH3536 alloy during selective laser melting

A combination of the finite element simulation and experimental measurement is proposed to study the influence of laser power and scanning velocity on the molten pool size in the selective laser melting (SLM) of GH3536 alloy. The results show that line energy density and molten pool size exhibit linear growth relationship within the scope of the study parameters. In addition, several GH3536 alloy samples are fabricated by SLM technology with different parameters. All SLM samples are used for metallographic experiment to measure the molten pool size. The result shows that experimental measurements are in good agreement with the simulation predictions.

The Research of Low-profile Load Cell Design Sensitivity

This low profile load cells are referred to the current injection molding machine manufacturers commonly used specifications. This study is about the low-profile load cell design by the finite element analysis and experimental strain measurement verification. In the study, two low-profile load cell were designed and analyzed. The A-type cross-section of the sensor is a generally designed cross-section and has sufficient reliability for commercial use. The B-type curve cross-section load cell from the previous study found that can carry a more significant load. In the study, compare the finite element analysis results with the actual strain measurements to verify the correctness of the analysis. In the experimental verification, the two type sections loadcells were calibrated. The load cells were loading from 0kN to 60kN to measure strain values. The strain values were recorded in experiment processes. When the two types of load cell under loading, the loading force, and strain values regression linearity was 99.99 %. The measured values of the A-type and B-type load cells at 60 kN were 298 με and 170 με, and the results matched finite element analysis strain values. It was shown that the setup of boundary conditions and loading method in finite element analysis were acceptable.

A comprehensive kinematic model of single-manifold Cosserat beam structures with application to a finite strain measurement model for strain gauges

In this paper, we investigate the coupling of Poisson’s and warping effect for a general asymmetric cross-section of Cosserat beam. We present the challenges and inconsistencies observed as a result of our attempt to couple the two effects. The fully-coupled Poisson’s transformation is then developed to describe the in-plane deformation for the prismatic beam. A comprehensive kinematic treatment of geometrically exact and nonlinear Cosserat beam subjected to large deformation and finite strain is finally obtained that extensively captures the deformation due to multiple curvatures, torsion, shear, axial deformation, warping and a fully-coupled Poisson’s effect in the cross-section, all while maintaining the single manifold nature of the problem. The contributions to the strain vector and the deformation gradient tensor due to various deformation effects are interpreted and explained in detail. In the final part of the paper, we use the kinematics developed to establish a measurement model of discrete and finite length strain gauges attached to the surface of the beam (or embedded into the beam). We investigate the relationship between the scalar strain measurement of the strain gauge and the local finite strain parameters of the beam.

A combined numerical and experimental approach for determining the contact temperature in an industrial ironing operation

Tribological conditions in forming operations depend on several parameters such as tool-workpiece interface pressure, surface expansion, sliding length, sliding speed, tool and workpiece materials and the roughness of the parts. Among indirect parameters, the most influential one is the tool-workpiece interface temperature, which directly influences the lubricant performance. Prior to testing new tribo-systems to determine their limits of lubrication, it is therefore important to find the interface temperature. However, measurement of the interface temperature in metal forming is difficult. The present work investigates the determination of the interface temperature in an industrial ironing operation, where severe process parameters lead to lubricant film breakdown and galling after several strokes. The methodology combines finite element simulations and experimental measurements. The overall procedure is based on a steady-state thermal analysis to determine the temperature distribution within the tool and a transient thermo-mechanical analysis of the ironing process when steady-state conditions are achieved. Results show that the proposed methodology applied to a single stroke can effectively and accurately predict the interface temperature in the test tool, thus avoiding the otherwise required thermo-mechanical FEM analyses of hundreds of strokes to reach steady-state. Furthermore, the influence of parameters, such as the predicted steady-state tool temperature, the friction coefficient and the heat transfer coefficient on the contact temperature, is analysed. It is concluded that the frictional heating is the primary cause for the peak temperature. By calibration of the friction coefficient and the heat transfer coefficient to ensure matching of the numerical results and the experimental measurements, a maximum tool-workpiece interface temperature of 158 °C was determined during the forward stroke and 150 °C during the backward stroke.

Improved design of roller linear guide for heavy load based on finite element method and measurement

Roller linear guides are key components in machine tool. The accuracy and efficiency of a machine toll are determined by the stiffness and friction torque of roller guide. This study proposes an improved design method for roller guide. The influences of the rollers profile on stiffness, stress distribution of roller linear guide are analyzed using finite element simulation. In this work, the design of the roller, slider, and the overall structure is modified. Moreover, experimental investigations on noise and sliding friction of roller linear guide are compared to validate the proposed design method. It seems that the proposed design can improve the dynamical performance of the roller linear guide.

Hybrid multilevel modelling of axial permanent magnet drivers

A five-layered analytical model of axial permanent magnet drivers that considers the permanent magnet back iron, the permanent magnet array, the air gap, the copper, and the copper back iron is presented. The multilayer boundary value problem is solved and a simple torque expression represented by the Fourier series is derived. A permanent magnet array optimisation method is proposed based on this novel idea. The results achieved are compared with the results of the finite element method and measurements which confirms that our proposed analytical method is more effective.

$H_2$ Output-Feedback Control With Finite Multiple Measurement Information

This paper proposes a new $H_2$ output-feedback control with finite multiple measurement information for discrete-time systems with disturbances. This control is called an $H_2$ finite multiple measurement output-feedback control (H2FMMOFC). The new control ascertains the $H_2$ performance for disturbances and the equivalence to the $H_2$ state-feedback control without disturbances on a finite measurement horizon. The boundedness and exponential stability of the proposed H2FMMOFC are also investigated. The gain matrices of the H2FMMOFC are obtained by solving a convex problem utilizing the linear matrix inequality tool. Via a numerical example, the H2FMMOFC is shown to ensure the $H_2$ performance as well as the excellent robustness property against unexpected temporary model uncertainty although the uncertainty is not considered in its design.

Adaptive Gradient-Based Iterative Algorithm for Multivariable Controlled Autoregressive Moving Average Systems Using the Data Filtering Technique

The identification problem of multivariable controlled autoregressive systems with measurement noise in the form of the moving average process is considered in this paper. The key is to filter the input–output data using the data filtering technique and to decompose the identification model into two subidentification models. By using the negative gradient search, an adaptive data filtering-based gradient iterative (F-GI) algorithm and an F-GI with finite measurement data are proposed for identifying the parameters of multivariable controlled autoregressive moving average systems. In the numerical example, we illustrate the effectiveness of the proposed identification methods.

Estimation of element‐by‐element demand‐to‐capacity ratios in instrumented SMRF buildings using measured seismic response

SummaryThis paper presents a methodology to estimate element‐by‐element demand‐to‐capacity ratios in instrumented steel moment‐resisting frames subject to earthquakes. The methodology combines a finite element model and acceleration measurements at various points throughout the building to estimate time history of displacements and internal force demands in all members. The estimated demands and their uncertainty are compared with code‐based capacity from which probabilistic bounds of demand‐to‐capacity ratios are obtained. The proposed methodology is verified using a simulated six‐story building and validated using acceleration data from California Strong Motion Instrumentation Programstation 24370 during the Northridge and Sierra Madre earthquakes.

Determination of the hyper-viscoelastic model parameters of open-cell polymer foams and rubber-like materials with high accuracy

This paper focuses on a newly-developed method for the extraction of the accurate hyper-viscoelastic model parameters of open-cell polymer foams and rubber-like materials. Although the parameter identification method is developed for strain-controlled uniaxial tension/compression, the finite time increment-based approach used can be extended to other experimental loading modes, such as simple and pure shear, biaxial tension/compression, and confined compression. Furthermore, the method makes it possible to use any hyperelastic material model and to extract the constitutive model parameters of both compressible and incompressible hyper-viscoelastic solids subjected to arbitrary strain (stretch) history. The applicability of the method and the reliability of the constitutive model parameters determined from the numerical prediction of the stress response are proved through the comparison of finite element and measurement results. Finally, the material model parameters of an incompressible isoprene rubber and a compressible polyurethane foam extracted with the proposed method and those determined with the two-step and the direct (closed-form) method are used to compare the accuracy of the predicted behaviours. It clearly revealed that the constitutive constants extracted using the proposed direct (numerical) method result in the best agreement between the measurement and the simulation.