Calibration Specimens Research Articles

Determination of Elastic Constants of Composites with a Circular Disk Specimen

The in-plane elastic constants of orthotropic composite materials need to be determined in order to perform stress analysis and design of composite structures. Several specimen configurations have been proposed and the majority suffer from one of two drawbacks: either multiple specimens are required or the experimental method involves a scientific rather than an engineering approach. In the present investigation a simple procedure involving a single calibration specimen is suggested. The method utilises a theoretical solution available in the literature for an orthotropic circular disk under diametral compression, measured strains at specific locations on a circular disk specimen, and a least squares procedure that gives average rather than localised elastic constants.

Calibration of Testing Equipment for Reliable Small-Strain Deformation Measurements Using Synthetic Specimens

Abstract For reliable deformation measurements at small strains, calibration of the entire testing system in addition to routine transducer calibrations are very important. Seven synthetic specimens of varying stiffness (4.3 to 1500 MPa) were constructed and tested to measure the compliance of testing equipment and to improve the measurement setups. Testing equipment used in this study included resonant column device (RC), torsional shear device (TS), free-free resonant column device (FF-RC), cyclic resilient modulus testing device (MR) and the static compression testing device. Moduli of synthetic specimens determined by various testing equipment after improvement were almost identical if considered the effect of loading frequency, indicating that all of the testing devices were well calibrated over a wide stiffness range. To verify the effectiveness of calibration on soil testing, two subgrade soils were tested, and moduli determined by various tests compared well. Use of synthetic calibration specimens shows potential for calibrating testing equipment and determining its capability and limitation of small-strain deformation measurements.

Calibration specimens for measuring induced magnetic moments

One usually measures the differential magnetic moment dM/dH in examining the magnetic parameters of specimens of natural media. It is suggested that spheres of ferrites with high permeability μr should be used for these purposes. The self-demagnetization effect for a sphere means that any change in μ in response to temperature, mechanical loading, or ageing does not influence the susceptibility of it, and therefore such specimens need to be certified only as regards volume. Stable calibration specimens improve the measurement accuracy considerably and eliminate the need for periodic checking.

Photoelastic studies for composite dynamics

The orthotropic birefringent composites suitable for the study of dynamic photoelasticity are investigated and the determination of residual birefringence in the materials is briefly described. A stress-optic law for dynamic photoelastic analysis of orthotropic birefringent composites is postulated based on the static stress-optic law of Hyer and Liu. Subsequently, practical methods of calibrating dynamic mechanical constants and dynamic stress-fringe values are proposed. With dynamic strain measurements and time domain BEM for anisotropic media, three calibration specimens (0°, 90° and 45°) are used to verify the proposed stress-optic law in uniaxial-stress fields and a plate of unidirectional fiber-reinforced birefringent composite under impact loading, with the loading direction parallel, perpendicular and at 45° to the fiber direction, is analyzed to verify the proposed stress-optic law in biaxial-stress fields. Results show that the dynamic stress-optic law for orthotropic birefringent composites is valid in the two cases.

Calibration Specimens for Determining Energy-Dispersive X-ray k-Factors of Boron, Nitrogen, Oxygen, and Fluorine.

: We have fabricated amorphous thin-film specimens containing light elements (B, C, N, O, F, and Mg) in addition to silicon, and have measured their composition using electron energy-loss spectroscopy (EELS). The films appear to be stable during storage in air and during irradiation by an electron beam, for doses below 10(5) C/cm2. Used with a transmission electron microscope fitted with an energy-dispersive X-ray (EDX) detector, they provide a convenient means of determining light-element k-factors for X-ray microanalysis. For a TEM equipped with an electron energy-loss spectrometer, the specimens can also be used to check the EELS instrumentation and elemental-quantification procedures.

K-Factor Standards for Low-Z Quantification

Abstract Although elements of low atomic number (Z<11) are detectable in TEM specimens using a modem energy-dispersive (EDX) detector, quantification remains a challenge. Problems include the large absorption corrections needed for specimens of typical thickness and the need for calibration specimens which provide k-factors appropriate to a particular detector/window arrangement. We have addressed this second problem by fabricating thin films containing several light elements in combination with silicon, which typically acts as the reference element when specifying k-factors. Because the EDX peaks of adjacent light elements overlap considerably, it is preferable to have two specimens: one containing C, O and Si, the other B, N, F and Si. We have used both e-beam evaporation and sputtering techniques to deposit thin films on a substrate which can later be removed to leave a freestanding film mounted on a TEM grid.

Fibre orientation in an injection moulded specimen by ultrasonic backscattering

Ultrasonic polar backscattering (PBS) was used to determine the local fibre orientation in a short glass fibre reinforced injection moulded polypropylene specimen. The backscattered intensity as a function of fibre angle was determined from a specially prepared specimen. The information from two scans, 90° apart, was needed from the injection moulded specimen. A computer algorithm was developed to compare the backscattered intensity of the unknown fibre orientation to the calibration specimen's fibre orientation. The angle at which the difference between the functions was minimized was taken as the fibre orientation for that local region. The results were compared with the fibre orientations determined by classical methods. At regions close to the surface, a good correspondence between both methods has been obtained.

Assessment of local residual strain by electron backscatter patterns and nanoindentation

Nickel base superalloy and aluminium single crystal and polycrystalline specimens have been examined using mechanical property microprobe (MPM) measurements and electron backscatter patterns (EBSPs) as a function of applied strain. Grids of lines deposited on to the specimens before three point bending were used to determine the macroscopic strain. The MPM, or nanoindenter, has been used to produce arrays of five by three indents across the edge of the specimens, both before and after bending. Electron microscope film EBSPs have been produced from regions within the nanoindenter arrays. The effects of strain can be seen in the change in Kikuchi band profile and thus EBSP ‘image quality’ and in changes in the hardness of the sample. Software is being developed to quantify these differences. It has been found that when the nickel base superalloy calibration specimens were bent, stress relief occurred by the formation of slip bands. This caused problems with strain calibration, and alternative methods are being investigated.MST/3677

Assessment of local residual strain by electron backscatter patterns and nanoindentation

AbstractNickel base superalloy and aluminium single crystal and polycrystalline specimens have been examined using mechanical property microprobe (MPM) measurements and electron backscatter patterns (EBSPs) as a function of applied strain. Grids of lines deposited on to the specimens before three point bending were used to determine the macroscopic strain. The MPM, or nanoindenter, has been used to produce arrays of five by three indents across the edge of the specimens, both before and after bending. Electron microscope film EBSPs have been produced from regions within the nanoindenter arrays. The effects of strain can be seen in the change in Kikuchi band profile and thus EBSP ‘image quality’ and in changes in the hardness of the sample. Software is being developed to quantify these differences. It has been found that when the nickel base superalloy calibration specimens were bent, stress relief occurred by the formation of slip bands. This caused problems with strain calibration, and alternative method...

Development of a Method for Characterizing Joint Stiffness, Deadband, and Hysteresis

This article documents the development of a procedure for characterizing the stiffness, deadband, and hysteretic behavior of struts with pinned joints. A test setup utilized procedures recommended by other authors. The test results included a calibration specimen with linear stiffness and near zero hysteretic behavior that identified the capabilities and limitations of the procedure. Tension/compression pull tests of the truss joints were conducted. The load vs. displacement curves showed stiffness, deadband, and hysteresis loops consistent with theory. Vibration damping was inferred from the hysteresis loops and compared with measured data from a three bay truss.

Development of a Method for Characterizing Joint Stiffness, Deadband, and Hysteresis

This article documents the development of a procedure for characterizing the stiffness, deadband, and hysteretic behavior of struts with pinned joints. A test setup utilized procedures recommended by other authors. The test results included a calibration specimen with linear stiffness and near zero hysteretic behavior that identified the capabilities and limitations of the procedure. Tension/compression pull tests of the truss joints were conducted. The load vs. displacement curves showed stiffness, deadband, and hysteresis loops consistent with theory. Vibration damping was inferred from the hysteresis loops and compared with measured data from a three bay truss.

Tethered particle motion method for studying transcript elongation by a single RNA polymerase molecule

Schafer et al. (Nature 352:444-448 (1991)) devised the tethered particle motion (TPM) method to detect directly the movement of single, isolated molecules of a processive nucleic acid polymerase along a template DNA molecule. In TPM studies, the polymerase molecule is immobilized on a glass surface, and a particle (e.g., a 0.23 microns diameter polystyrene bead) is attached to one end of the enzyme-bound DNA molecule. Time-resolved measurements of the DNA contour length between the particle and the immobilized enzyme (the "tether length") are made by determining the magnitude of the Brownian motion of the DNA-tethered particle using light microscopy and digital image processing. We report here improved sample preparation methods that permit TPM data collection on transcript elongation by the Escherichia coli RNA polymerase at rates (approximately 10(2)-fold higher than those previously obtained) sufficient for practical use of microscopic kinetics techniques to analyze polymerase reaction mechanisms. In earlier TPM experiments, calculation of tether length from the observed Brownian motion was based on an untested numerical simulation of tethered bead Brownian motion. Using the improved methods, we have now empirically validated the TPM technique for tether lengths of 308-1915 base pairs (bp) using calibration specimens containing particles tethered by individual DNA molecules of known lengths. TPM analysis of such specimens yielded a linear calibration curve relating observed Brownian motion to tether length and allowed determination of the accuracy of the technique and measurement of how temporal bandwidth, tether length, and other experimental variables affect measurement precision. Under a standard set of experimental conditions (0.23 microns diameter bead, 0.23 Hz bandwidth, 23 degrees), accuracy is 108 and 258 bp r.m.s. at tether lengths of 308 and 1915 bp, respectively. Precision improves linearly with decreasing tether length to an extrapolated instrumentation limit of 10 bp r.m.s. and improves proportionally to the inverse square root of measurement bandwidth (1.9 x 10(2) bp Hz-1/2 for 1090-bp tethers). Measurements on large numbers of individual polymerase molecules reveal that time-averaged single-molecule elongation rates are more variable than is predicted from the random error in TPM measurements, demonstrating that the surface-immobilized RNA polymerase molecules are kinetically heterogeneous.

A differential interferometer for scanning force microscopy

A magnetic force instrument is described which makes use of a differential interferometer which can be used with a very short length cantilever in the force detection assembly. Conventional methods work with cantilevers of a few millimetres in length, but are not suitable for the very much smaller commercial cantilevers which are now available. The instrument described contains novel features which enable it to be used with such cantilevers. Topographical images of calibration specimens and magnetic images of hard disk samples obtained using this instrument are presented.

Quantification of matrix collagen architecture in murine cortical bone to assess the effect of a type I collagen mutation on bone mechanical properties

Internal three-dimensional (3D) “fit” of prostheses to prepared teeth is likely more important clinically than “fit” judged only at the level of the margin (i.e. marginal “opening”). This work evaluates two techniques for quantitatively defining 3D “fit”, both using pre-cementation space impressions: X-ray microcomputed tomography (micro-CT) and quantitative optical analysis. Both techniques are of interest for comparison of CAD/CAM system capabilities and for documenting “fit” as part of clinical studies.Pre-cementation space impressions were taken of a single zirconia coping on its die using a low viscosity poly(vinyl siloxane) impression material. Calibration specimens of this material were fabricated between the measuring platens of a micrometre. Both calibration curves and pre-cementation space impression data sets were obtained by examination using micro-CT and quantitative optical analysis. Regression analysis was used to compare calibration curves with calibration sets.Micro-CT calibration data showed tighter 95% confidence intervals and was able to measure over a wider thickness range than for the optical technique. Regions of interest (e.g., lingual, cervical) were more easily analysed with optical image analysis and this technique was more suitable for extremely thin impression walls (<10–15 μm). Specimen preparation is easier for micro-CT and segmentation parameters appeared to capture dimensions accurately.Both micro-CT and the optical method can be used to quantify the thickness of pre-cementation space impressions. Each has advantages and limitations but either technique has the potential for use as part of clinical studies or CAD/CAM protocol optimization.

New Products

Agar Scientific will be exhibiting its extensive range of accessories for electron and light microscopy. Products include calibration specimens, filaments, tweezers, magnifiers, specimen preparation equipment, a range of EM film and photographic items together with books relevant to light and electron microscopy.

Comparison between precision roughness master specimens and their electroformed replicas

Two random profile precision roughness calibration specimens with R a = 0.028 and 0.043 μm are compared with their electroformed replicas. Measurements of surface texture and roughness parameter values show very good agreement. Fluctuations in the R a values across the replicas track those across the masters to within 1.8 nm. However, the form errors of the replicas, approximately 0.6 μm over a 3.2 × 2.6 mm 2 area, are much bigger than those of the masters, and their hardness ( HV = 243) is not as good as the master specimens' ( HV = 852).

Multielement analysis of biological reference materials by total-reflection X-ray fluorescence and inductively coupled plasma mass spectrometry in the semiquant mode

Total-reflection X-ray fluorescence (TXRF) and inductively coupled plasma mass spectrometry (ICP-MS) were used for the analysis of two biological reference materials. The quantifications were carried out after addition of one single standard element which serves as an internal standard in both cases. The results of TXRF analysis were good to satisfactory. The method is therefore suitable for fast multielement analysis, because it needs no special calibration specimens. The results of ICP-MS analysis are at least in the order of magnitude of the certified values. In some cases recoveries fit very well. For quantitative analysis, however, the use of the standard addition method or the calibration with external standards is required.

Standard Reference Specimens in Quality Control of Engineering Surfaces.

In the quality control of engineering surfaces, we aim to understand and maintain a good relationship between the manufacturing process and surface function. This is achieved by controlling the surface texture. The control process involves: 1) learning the functional parameters and their control values through controlled experiments or through a long history of production and use; 2) maintaining high accuracy and reproducibility with measurements not only of roughness calibration specimens but also of real engineering parts. In this paper, the characteristics, utilizations, and limitations of different classes of precision roughness calibration specimens are described. A measuring procedure of engineering surfaces, based on the calibration procedure of roughness specimens at NIST, is proposed. This procedure involves utilization of check specimens with waveform, wavelength, and other roughness parameters similar to functioning engineering surfaces. These check specimens would be certified under standardized reference measuring conditions, or by a reference instrument, and could be used for overall checking of the measuring procedure and for maintaining accuracy and agreement in engineering surface measurement. The concept of “surface texture design” is also suggested, which involves designing the engineering surface texture, the manufacturing process, and the quality control procedure to meet the optimal functional needs.

A method to test the accuracy of critical dimension measurement systems (CDMS)

As already shown in previous articles different combinations of SEM's with PC-based measurement systems are available to determine the linewidth in the submicron area. One common problem for all these measurement tools is a missing test for measuring the accuracy of these systems. This investigation presents a method describing how the measuring accuracy of these systems can be checked. For this purpose different calibration specimens for light microscopy were tested for usability in low-voltage SEM imaging. Chrome on glass micrometer specimens proved to be especially useful. In comparison with specimens manufactured by photographic methods they combine good imaging qualities with thin high contrast lines with sharp edges. The test for consistant linewidths was done using quantitative Image Analysis, allowing the measurement of a high volume of data quickly and accurately. The resulting value was used as the absolute value for the determination of the accuracy of the CDMS. As such a comparison value was not available before, the accuracy of measurements could only be given within certain confidence limits. This latest method can now prove how accurate the resulting values really are. Initial tests using an AMRAY 1830 SEM and Critical Dimension Measurement System showed a distortion of the measuring results of 0.3% or 0.5% compared with the true value. This means a difference of 0.6 or 0.8 pixels. This result is better than the theoretical accuracy of a CDMS. Using these values, the error of linewidth measurements in the 1 micron range is only about 0.005 μm.

Standard Specimens for Stain Calibration: Application to Romanowsky-Giemsa Staining

Standardized specimens with reproducible staining properties were fabricated from extracts of biological objects (bovine liver, nucleoprotamine and defatted muscle). The standard specimens were stained with two formulations of the Romanowsky-Giemsa stain (RG), using the same azure B and eosin Y. One formulation used methanol and Sorensen's buffer and the other DMSO and Hepes buffer as solvents. The standard specimens were stained either in the composite stain or in the individual dyes dissolved in the same solvents and at the same concentration as the composite stain. Solution spectroscopy demonstrated different spectra for the two formulations with some wavelength regions varying by more than an order of magnitude. The RG spectra were also very different from those of the individual dyes dissolved at the RG concentration in the respective solvents. The stained standard specimens were analyzed by microspectrophotometry and were found to have spectra similar to those of cell smears. Furthermore, the standard specimens were shown to be a repeatable substrate for stain uptake. The transmitted light intensity from random fields of the same standardized specimen varied +/- 5%. When specimens were stained at the same time, the specimen-to-specimen variation depended on preparation conditions and the measurement wavelength, but was as good as +/- 5% for some conditions. The quantitative stain performance of both formulations was studied and compared. The standardized specimens provide a tool for the quantitative study of staining processes and specimen preparation procedures and for stain calibration.