Multi-axis Measurement Research Articles

Stochastic modeling and identification of a hyperelastic constitutive model for laminated composites

In this paper, we investigate the construction and identification of a new random field model for representing the constitutive behavior of laminated composites. Here, the material is modeled as a random hyperelastic medium characterized by a spatially dependent, stochastic and anisotropic strain energy function. The latter is parametrized by a set of material parameters, modeled as non-Gaussian random fields. From a probabilistic standpoint, the construction is first achieved by invoking information theory and the principle of maximum entropy. Constraints related to existence theorems in finite elasticity are, in particular, accounted for in the formulation. The identification of the parameters defining the random fields is subsequently addressed. This issue is attacked as a two-step problem where the mean model is calibrated in a first step, by imposing a match between the linearized model and nominal values proposed in the literature. The remaining parameters controlling the fluctuations are next estimated by solving an inverse problem in which principal component analysis and the maximum likelihood method are combined. The whole framework is illustrated considering an experimental database where multi-axial measurements are performed on a carbon-epoxy laminate. This work constitutes a first step towards the development of an integrated framework that will support decision making under uncertainty for the design, certification and qualification of composite materials and structures.

Effect of multi-axial stress on iron losses of electrical steel sheets

The effect of multi-axial stress on the iron losses of a non-oriented electrical steel sheet under alternating magnetization is analyzed. Multi-axial magneto-mechanical measurements on a M400-50A grade non-oriented electrical steel sheet are performed by using a custom made single sheet tester device. The measured losses are separated into hysteresis, classical and excess loss components by using statistical loss theory, and the effect of various stress configurations on the hysteresis and the excess loss components is analyzed. By utilizing the statistical loss theory, an equivalent stress model and a magneto-elastic invariant based model are derived. These models can be used to predict the iron loss evolution under multi-axial stress even if only uniaxial stress dependent measurements are available. The accuracy of both models to predict the multi-axial stress dependent iron losses is found to be satisfactory when they are identified only from uniaxial stress dependent measurements. The invariant based model is shown to be slightly more accurate for the studied material.

Isotropic differential phase contrast microscopy for quantitative phase bio-imaging.

Quantitative phase imaging (QPI) has been investigated to retrieve optical phase information of an object and applied to biological microscopy and related medical studies. In recent examples, differential phase contrast (DPC) microscopy can recover phase image of thin sample under multi-axis intensity measurements in wide-field scheme. Unlike conventional DPC, based on theoretical approach under partially coherent condition, we propose a new method to achieve isotropic differential phase contrast (iDPC) with high accuracy and stability for phase recovery in simple and high-speed fashion. The iDPC is simply implemented with a partially coherent microscopy and a programmable thin-film transistor (TFT) shield to digitally modulate structured illumination patterns for QPI. In this article, simulation results show consistency of our theoretical approach for iDPC under partial coherence. In addition, we further demonstrate experiments of quantitative phase images of a standard micro-lens array, as well as label-free live human cell samples.

A high bandwidth three-axis out-of-plane motion measurement system based on optical beam deflection.

Multi-axis measurement of motion is indispensable for characterization of dynamic systems and control of motion stages. This paper presents an optical beam deflection-based measurement system to simultaneously measure three-axis out-of-plane motion of both micro- and macro-scale targets. Novel strategies are proposed to calibrate the sensitivities of the measurement system. Subsequently the measurement system is experimentally realized and calibrated. The system is employed to characterize coupled linear and angular motion of a piezo-actuated stage. The measured motion is shown to be in agreement with theoretical expectation. Next, the high bandwidth of the measurement system has been showcased by utilizing it to measure coupled two-axis transient motion of a Radio Frequency Micro-Electro-Mechanical System switch with a rise time of about 60 μs. Finally, the ability of the system to measure out-of-plane angular motion about the second axis has been demonstrated by measuring the deformation of a micro-cantilever beam.

Multi-axis force measurements of polymer friction stir welding

In this study, high-molecular-weight-polyethylene sheets were welded in the butt-joint configuration in order to investigate the effect of welding parameters on the generated forces during welding. The welding procedure was performed using newly developed clamping device with the ability to measure and acquire the forces during welding in X, Y and Z directions (FX, FY and FZ). Using a welding tool with a stationary shoulder and position control, the applied force is kept approximately constant during the entire welding extension. The obtained results enabled the identification of the influence of each individual welding parameter on the applied forces. The axial force is the most influential force during this process, which is responsible for forging pressure and frictional heat, while traverse and rotational speeds have the main effect on the traversing and lateral forces. The developed sensitized clamping system was used in support of welding process optimization to produce quality welds without resourcing to costly force control sensors. Using this device, it was possible to use force as a welding parameter and produce strong welds with mechanical behavior close to the parent materials’.

Design of a thin circular sawblade for natural stone sawing process

The existing crisis has accentuated problems related to the energetic perspective which forces the industrial framework to take actions. Natural stone companies are those more deteriorated by the crisis since they depend on the construction sector. While it is true that embedded energy in the natural stone industry includes extraction, transport and processing stages, the abrasive effect of sawing and polishing activities is responsible for the most energy consumption in stone manufacture. For this reason, improving sawing processes could have a major impact on the natural stone sector. This article presents a design of a new thinner diamond segmented circular sawblade for marble sawing, which reduces energy consumption during the sawing process. First of all, a multi-axis force measurement system was employed to determine the cutting conditions of a conventional diamond segmented circular sawblade under a pre-set configuration. Then, the research team defined a digital prototype of a commercial diamond segmented circular sawblade, and the data extracted from experimental measurements were used to configure the simulation. The simulation provided information about the mechanical performance experienced by the circular sawblade (such as stresses, displacements and eigenfrequencies). Subsequently, the geometry of that commercial circular sawblade was optimised seeking to reduce the moment of inertia while keeping the mechanical performance within safe and functional limits. At the end of the research, it was experimentally demonstrated that the new thinner circular sawblade designed reduces energy consumption during a sawing operation compared to the commercial circular sawblade.

Investigating the challenges of measuring combination mechanics in textile fabrics

Measurements of the mechanical behavior of fabrics started during the Zeppelin era in the 1900s, where tensile, shear and biaxial behavior of the airship’s envelope fabric were measured. More measurement methods were developed later when there was a need to measure fabric handle and behavior. Although measurements of tensile, shear, buckling and bending have been established and are being used, their combinations, which represent a more realistic approach, are still being developed. However, these multi-axial measurements pose challenges not only in apparatus design but also in determining the measurement parameters. Here these challenges are being put forward and further research requirements are identified and discussed.

Application of an atomic force microscope piezocantilever for dilatometry under extreme conditions

We report on the development of a sensitive dilatometer based upon an atomic force microscope piezocantilever. This dilatometer is designed to measure the elastic properties of bulk materials in extreme conditions, such as temperatures down to 25 mK and magnetic fields up to 16 T. The layered heavy fermion superconductor and its non-magnetic analog are measured to demonstrate their use in detecting phase transitions and quantum oscillations. In addition, using this dilatometer, a simultaneous multi-axis dilation measurement is performed. This compact dilatometer has many advantages, such as its ability to measure very small samples with sub-mm lengths at low temperature and small field dependence, and its ability to rotate, while it works well irrespective of whether it is in a changing liquid or gas environment (i.e. within a flow cryostat or mixing chamber).

Laser source for dimensional metrology: investigation of an iodine stabilized system based on narrow linewidth 633 nm DBR diode

We demonstrated that an iodine stabilized distributed Bragg reflector (DBR) diode based laser system lasing at a wavelength in close proximity to nm could be used as an alternative laser source to the helium-neon lasers in both scientific and industrial metrology. This yields additional advantages besides the optical frequency stability and coherence: inherent traceability, wider optical frequency tuning range, higher output power and high frequency modulation capability. We experimentally investigated the characteristics of the laser source in two major steps: first using a wavelength meter referenced to a frequency comb controlled with a hydrogen maser and then on an interferometric optical bench testbed where we compared the performance of the laser system with that of a traditional frequency stabilized He–Ne laser. The results indicate that DBR diode laser system provides a good laser source for applications in dimensional (nano)metrology, especially in conjunction with novel interferometric detection methods exploiting high frequency modulation or multiaxis measurement systems.

Investigating the nitrogen dioxide concentrations in the boundary layer by using multi-axis spectroscopic measurements and comparison with satellite observations.

This study emphasizes on near surface observation of chemically active trace gases such as nitrogen dioxide (NO2) over Islamabad on a regular basis. Absorption spectroscopy using backscattered extraterrestrial light source technique was used to retrieve NO2 differential slant column densities (dSCDs). Mini multi-axis-differential optical absorption spectroscopy (MAX-DOAS) instrument was used to perform ground-based measurements at Institute of Environmental Sciences and Engineering (IESE), National University of Sciences and Technology (NUST) Islamabad, Pakistan. Tropospheric vertical column densities (VCDs) of NO2 were derived from measured dSCDs by using geometric air mass factor approach. A case study was conducted to identify the impact of different materials (glass, tinted glass, and acrylic sheet of various thicknesses used to cover the instrument) on the retrieval of dSCDs. Acrylic sheet of thickness 5mm was found most viable option for casing material as it exhibited negligible impact in the visible wavelength range. Tropospheric NO2 VCD derived from ground-based mini MAX-DOAS measurements exceeded two times the Pak-NEQS levels and showed a reasonable comparison (r 2=0.65, r=0.81) with satellite observations (root mean square bias of 39%) over Islamabad, Pakistan.

Development and validation of a set-up to measure the transferred multi-axial impact momentum of a bird strike on a booster vane

Reaction force has always been one of the main characterization parameters for impact events. Today, a set of force transducers are a common and valuable tool to measure reaction forces. But the force signals are often influenced by vibrations of the supporting structures. Many other attempts were already taken in the past to use other methods to measure force, such as ballistic pendulums, Hopkinson bars, etc., all having their advantages and disadvantages. In this work, a multi-axial force measurement tool is developed to serve in a test campaign of bird strike experiments on booster vanes. The idea is to give some well-chosen mass three rotational degrees of freedom and acquire the transferred rotational momentum from an optical measurement, which is a direct measure for the impact force. The tool is validated experimentally and numerically using a simplified steel vane.

Study on signal characteristic analysis of multi-axis load measurement sensors

This study suggested a tactile sensor with piezoelectric sensors in a fibrous shape to detect multi-axial loads (vertical load and horizontal load) simultaneously for the skins of unmanned robots. The sensor was designed by finite element analyses. A simple detecting scheme of the multi-axial loads was constructed by lab-scale experiments. Verification tests of the developed tactile sensor confirmed that applied vertical and horizontal loads could be detected with less than 4% error.

Multi-axial response of idealized cermets

The yield response of two idealized cermets comprising mono and bi-disperse steel spheres in a Sn/Pb solder matrix has been investigated for a range of axisymmetric stress states. Proportional stress path experiments are reported, from which are extracted the initial yield surfaces and their evolution with increasing plastic strain. The initial yield strength is nearly independent of the hydrostatic pressure but the strain hardening rate increases with stress triaxiality up to a critical value. For higher triaxialities, the responses are independent of hydrostatic pressure. Multi-axial measurements along with X-ray tomography were used to demonstrate that the deformation of these idealized cermets occurs by two competing mechanisms: (i) a granular flow mechanism that operates at low levels of triaxiality, where volumetric dilation occurs under compressive stress states, and (ii) a plastically incompressible mechanism that operates at high stress triaxialities. A phenomenological viscoplastic constitutive model that incorporates both deformation mechanisms is presented. While such multi-axial measurements are difficult for commercial cermets with yield strengths on the order of a few GPa, the form of their constitutive relation is expected to be similar to that of the idealized cermets presented here.

The Compressive Response of Idealized Cermetlike Materials

Metals reinforced with a high volume fraction of hard particles, e.g., cermets, have properties that are more akin to those of granular media than conventional composites. Here, the mechanical properties and deformation mechanisms of this class of materials are investigated through the fabrication and testing of idealized cermets, comprising steel spheres in a Sn/Pb solder matrix. These materials have a similar contrast in the properties of constituent phases compared to commercial cermets; however, the simpler microstructure allows an easier interpretation of their properties. A combination of X-ray tomography and multiaxial strain measurements revealed that deformation at large strains occurs by the development of shear bands similar to granular media, with the material dilating under hydrostatic pressure within these shear bands. Predictions of finite element models with a random arrangement of inclusions were in excellent agreement with the experimental results of idealized cermets. These calculations showed that at large inclusion volume fractions, composites with a random arrangement of inclusions are significantly stronger compared to their periodic counterparts, due to the development of a network of force chains through the percolated particles.

Measurement technologies for precision positioning

Precision positioning of an object relative to a reference point is a common task in many activities of production engineering. Sensor technologies for single axis measurement, either linear or rotary, which form the fundamentals of measurement technologies for precision positioning, are reviewed. Multi-axis coordinate measurement methods such as triangulation and multilateration, as well as Cartesian and polar systems for specifying the position in a plane or three-dimensional (3D) space are then presented, followed by a discussion on traceability and standards. Some advanced applications of measurement technologies for precision positioning in manufacturing industries are also demonstrated.

Scanning and mobile multi-axis DOAS measurements of SO2 and NO2 emissions from an electric power plant in Montevideo, Uruguay

In March 2012 the emissions of NO2 and SO2 from a power station located on the east side of Montevideo Bay (34° 53′ 10″ S, 56° 11′ 49″ W) were quantified by simultaneously using mobile and scanning multi-axis differential optical absorption spectroscopy (in the following mobile DOAS and scanning DOAS, respectively). The facility produces electricity by means of two technologies: internal combustion motors and steam generators. The motors are powered with centrifuged heavy oil and produce a maximum power of 80 MW approximately. The steam generators produce approximately 305 MW and are powered with heavy fuel oil. We compare the emissions obtained from the measured slant column densities (mobile DOAS and scanning DOAS) with the emissions estimated from fuel mass balance. On one occasion it was possible to distinguish between the two types of sources, observing two plumes with different SO2 and NO2 emission rates.During the period of the campaign the mean SO2 emission flux was determined to be 0.36 (±0.12) kg s−1 and 0.26 (±0.09) kg s−1 retrieved from mobile and scanning DOAS respectively, while the calculated SO2 flux from the sulphur content of the fuel was 0.34 (±0.03) kg s−1. The average NO2 flux calculated from mobile DOAS was determined to be 11 (±3) × 10−3 kg s−1. Using the scanning DOAS approach a mean NO2 flux of 5.4 (±1.7) × 10−3 kg s−1 was obtained, which is significantly lower than by the mobile measurements. The differences between the results of mobile MAX-DOAS measurements and scanning DOAS measurements are most probably caused by the variability and the limited knowledge of the wind speed and direction.

VISAR 'cross-hairs': Simultaneous perpendicular line-imaging VISAR

Often the velocity measured at the rear surface of a dynamic compression target varies spatially, caused for instance by the tilt/curvature of a gas gun flyer, asymmetries in the magnetic field on a pulsed power driven experiment, or meso-scale heterogeneous targets. One way to monitor this in an experiment is to employ multiple point velocimetry techniques, but even with multiplexing this can become expensive in terms of hardware, in particular high speed sensors and scope channels. We report on the initial development of a multi-axis line-imaging VISAR system, which will record the spatial velocity along two orthogonal directions. Cylindrical optics are used to project a set of cross-hairs onto the target, maximising the use of input laser light; we then describe the image relay, interferometer configuration and alignment. This 'quasi' two dimensional system will become one of the principal diagnostics on the MACH (Mega Ampere Compression and Hydrodynamics) facility at Imperial College London, where the multi-axis measurement will help optimise strip-line design to achieve uniform ramp compression of targets.

Analysis of Volumetric Geometric Accuracy in Multi-Axis Measurement and Technological Systems based on Laser Measurements

Design principles of a system for automatic correction of the volumetric geometric accuracy of multi-axis systems (control measurement machines or programmed numerically controlled machine tools) based on laser interferometry are set forth. Control of geometric accuracy and the process of increasing this accuracy by means of correction are demonstrated using as an example three-axis machining centers.

Design of Precise Synchrone Mechanism in Multiaxial Laser Measurement

Precision measurement is the premise of precision motion control. When a worktable is operating, the synchronization of multiaxial sampling will directly affect the precision of table position conversion. In this paper, a precise synchrone mechanism for multiaxial laser measurement was proposed. Tests showed that the maximum synchronous sampling time error from 6 laser axes was 0.404 ns. When the table was moving at 1 m/s, the induced maximum displacement conversion error was 0.202 nm, which satisfied the strict nanometer-scale requirement imposed by ultra-precise motion control for position measurement.

Active Touch Sensing by Multi-axial Force Measurement Using High-Resolution Tactile Sensor with Microcantilevers

Active Touch Sensing by Multi-axial Force Measurement Using High-Resolution Tactile Sensor with Microcantilevers