16,428 research outputs found
Marriage record of Pla, Antonio and Baldi, Nunzia
No full textMarriage license for Antonio Pla and Nunzia Baldi. T.L. James was the Justice of the Peace
Far-Field Boundary Conditions for Calculation of Hole-Drilling Residual Stress Calibration Coefficients
No full textThe Hole-Drilling method for residual stress measurement, both in its standard version based on strain gauge rosettes (ASTM E837-08e1 2008) and its derivative using optical methods for estimating the displacement field around the hole (Baldi (2005) J Eng Mater Technol 127(2):165–169; Schajer and Steinzig (2005) Exp Mech 45(6):526–532; Schajer (2010) Exp Mech 50(2):159–168), relies on numerical calibrated coefficients (A and B) to correlate the experimentally acquired strains (displacements) with residual stress components. To estimate the A and B coefficients, two FEM (Finite Element Method) computations are required, the former related to a hydrostatic stress state, the latter to a pure shear case. Both can be implemented using either a semi-analytical approach (i.e. an axis-symmetric mesh expanded in the tangential direction using a Fourier series) or a tri-dimensional mesh, usually exploiting the double symmetry of the problem. Whatever the approach selected, the definition of constraints to be applied to the outer boundary is critical because the hole-drilling method assumes an infinite plate, thus both the usual solutions—fully constrained or free boundaries—are unable to correctly describe the theoretical situation. In the following, the problem of correct simulation of the infinite domain will be discussed and two simple and effective solutions will be proposed
A Spatio-temporal Approach for iDIC-Residual Stress Measurement
No full textRecently, the Integrated-Digital Image Correlation (iDIC) has been proposed as a simple and effective approach for residual stress measurement. iDIC is a variant of the classical Digital Image Correlation where the “standard” displacement functions are replaced by problem-specific ones. By this simple modification, stress components become the unknowns of the problem, thus allowing a single-pass analysis. However, implementation of the Integral Method for estimation of depth-dependent Residual Stress components is difficult. In particular, the Least Squares approach is not possible.
This work suggests a two-pass approach: in the former the direct solution of the triangular linear system is solved. In the latter, the previous estimates are used as starting point for a global minimization involving all the acquired images
Experimental image dataset for validation of the noise-induced bias that affects Digital Image Correlation
No full textThe present article shares with the scientific community several image sets used for experimentally validating the noise-induced bias on different Digital Image Correlation (DIC) formulations, as reported in Baldi et al. [1]. These sets are provided with a description of the experimental setup used for image acquisition. The basic idea is to acquire a series of images obtained by rigidly translating the target, where incremental displacement is of the order of a small fraction of a pixel. This condition requires a high-precision control of the target position through the tests. Moreover, the noise content of each image set is modulated using a statistical approach that uncouples the intensity field from the standard deviation. Lastly, the images are acquired with different exposure conditions to analyze the gray tone gradient effect on noise-induced bias
Digital Image Correlation and Color Cameras
No full textDigital Image Correlation (DIC) is a well-known experimental technique. It works by
constructing a (surjective) mapping of pixel intensity from reference to target image,
where the mapping parameters are identified using a Least Squares approach.
Because it makes use of the luminance component of the image, Digital Image
Correlation is usually implemented by assuming monochrome cameras. In this work,
we will discuss its implementation when color cameras are used, focusing on pitfalls
and potential advantages of this solution. Since most cameras implement color
acquisition using a Color Filter Array (CFA), much of the article will focus on this
technology. However, we will not limit ourselves to this aspect and will show that
Three-CCD cameras can provide significant advantages over both CFA and
monochrome cameras
On the Gyroscopic Stabilisation of a Single-Track Vehicle: Experimental Results
No full textThis paper analyses the experimental behaviour of a 2 degrees of freedom vehicle model stabilised by
a gyroscopic device. After a brief review of the system and the governing equations of motion, the
experimental device is presented in detail and its performance discussed. The response in the cases of
absence of control, constant external moment and sinusoidal external solicitations is examined,
showing the agreement between experimental behaviour and numerical simulation
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