Analysis of the waterjet contact/impact on target material

Numerical modeling via finite element analyses (FEA) and experimental measurements via moiré interferometry were applied to the investigation of abrasive waterjet (AWJ) drilling. Polycarbonate and alumina blocks with dimensions of 25.4 mm×19.5 mm×6.25 mm were subjected to concentrated static loads experimentally and numerically. The assumptions of the FEA model are verified by comparing the experimental results with the numerical solution. A closed-form solution confirmed the correlation between the two. It was concluded that the assumption of the FEA model (e.g. mesh, boundary conditions, pressure loading, etc.) represented the static conditions. This conclusion allowed the application of a hybrid numerical/experimental technique to understand the complex interaction of the target material and the AWJ slurry column during drilling.     

On the visualization of heterogeneous plastic strains by Moiré interferometry

Moiré interferometry is a valuable tool for investigations of the mechanics of materials. It is characterized by high-sensitivity and full-field capability. In this paper, the applicability of moiré interferometry and microscopic magnification to the visualization of the heterogeneous nature of the plastic strains in a polycrystalline material is considered. Plastic deformation of a coarse-grained aluminum is considered in detail.     

Whole-field analysis of uniaxial tensile tests by Moiré interferometry

Moiré interferometry—a high sensitivity whole-field optical technique—was used to follow the evolution of the deformation process of an aluminium sample subjected to a uniaxial tensile test. This technique allowed us to measure the two in-plane displacement components undergone by the sample, to evaluate the strain, stress and rotation fields, and to appreciate the trends in the deformation pattern that characterized the different stages of the test. Through a subtraction process between fields obtained at two different load levels, we were able to identify the area where strains began to localize and to observe the appearance of the diffuse neck.     

Analysis of CCD moiré pattern for micro-range measurements using the wavelet transform

A new approach based on the moiré theory and wavelet transform (WT) is proposed for measuring the micro-range distance between a charge-couple-device (CCD) camera and a two-dimensional reference grating. The micro-range distance is determined by measuring the pitch of the moiré pattern image, which is digitized by a CCD camera. A one-dimensional WT algorithm is applied to estimate the pitch of the moiré pattern. Experimental results prove that this technique is very efficient and highly accurate. The moiré range finder is an economic technique for measuring a micro-range distance.     

A simple method to unwrap the geometrically discontinuous phase map and its application in the measurement of IC package

Research on the techniques to unwrap the geometrically discontinuous phase map is an active area during the past decade, various algorithm are developed. Basically, these algorithms need a prior knowledge about the spatial extension of the discontinuity area in the sample for correct phase unwrapping, manual mask is often involved and negate the sense of automatic processing to fringe patterns. More ever, current phase unwrapping algorithms are either computationally complex or highly time consuming. In this paper, a refined method is proposed to deal with the geometrical discontinuity problem in an improved automation sense: suppression of background noise and recognition of discontinuity area in the phase map can be finished in the same time, and discontinuous phase map can be unwrapped in a simple way to avoid the effect of discontinuity area. An example of electronic package with complex shape and structure is used to verify the efficiency of this method.     

Monitoring/measurement of out-of-plane vibrations using shearing interferometry and interferometric grating

In this paper, an application of shear plate interferometry combined with moiré readout to monitor/measure out-of-plane vibrations is presented. Moiré fringes are produced between the fringe pattern from the shear plate and interferometric grating recorded by photographing the interference pattern generated from the shear plate. It is demonstrated that the method can be used to study periodic and non-periodic vibrations.     

Shadow Moiré method for the determination of the source position in three-dimensional shearography

Shearography is a full-field non-contact optical technique used for characterisation of surface strain. In a multi-component system, the displacement derivative components are measured using a number of illumination positions. These components are then transformed into a three-dimensional coordinate system, using a knowledge of the source positions. This process is highly sensitive to errors in the knowledge of the source position. Shadow Moiré, with either linear or circular gratings, can be used to measure angle of illumination, with the measurement sensitivity and accuracy variable by changing the grating pitch. Circular gratings have a measurement range determined by multiple fringe analysis and linear gratings have a different measurement range determined by sub-fringe analysis. In this paper vertical linear, horizontal linear and circular gratings are combined to extend the measurement range and the accuracy of the measurement of the source position in two directions. Using this method the source position was measured to an accuracy of ±3%.     

Experimental analysis of thermal displacement and strain distributions in a small outline J-leaded electronic package by using wedged-glass phase-shifting moiré interferometry

To evaluate the influence of a printed wiring board (PWB) with a high coefficients of thermal expansion (CTE) on the thermal deformation of a small outline J-leaded electronic package (SOJ), a newly developed phase-shifting method was applied to moiré interferometry. This phase-shifting moiré interferometry method uses a wedged glass plate as a phase shifter to obtain displacement fields with a sensitivity of 100 nm/line. This technique also enabled the quantitative determination of strain distributions in all observation areas. Thermal loading was applied from room temperature (25 °C) to an elevated temperature (100 °C), and then the thermal strains of SOJ with and without the PWB were compared. The results showed that the concentrations of the longitudinal strains ε_xx and ε_yy became increasingly prominent when mounted on the PWB, and the shear strains γ_xy were concentrated at the corners of the silicon chip. The values of these strains increased by about 50% when the SOJ was mounted on the PWB.     

Scanning moiré and spatial-offset phase-stepping for surface inspection of structures

In order to develop a high-speed and accurate surface inspection system of structures such as tunnels, a new surface profile measurement method using linear array sensors is studied. The sinusoidal grating is projected on a structure surface. Then, the deformed grating is scanned by linear array sensors that move together with the grating projector. The phase of the grating is analyzed by a spatial offset phase-stepping method to perform accurate measurement. The surface profile measurements of the wall with bricks and the concrete surface of a structure are demonstrated using the proposed method. The change of geometry or fabric of structures and the defects on structure surfaces can be detected by the proposed method. It is expected that the surface profile inspection system of tunnels measuring from a running train can be constructed based on the proposed method.     

Novel method for testing the long focal length lens of large aperture

In this paper, we present a novel method for testing the long focal length lens of large aperture, which is realized by calculating the angle of moiré fringe formed by Talbot image of two Ronchi gratings. A scanning method was developed to measure the focal length with the collimated lights projected on the different aperture position of the lens. Experiment data demonstrates that this method can be applied to the real-time long focal length measurement with high accuracy.