Three-dimensional Deformation Measurement Research Articles

Laser welding of Ti–5Al–5V–5Mo–3Cr

Ti–5Al–5V–5Mo–3Cr butt joints were welded using a 4 kW continuous wave Nd:YAG laser. The effect of welding speed and defocusing distance on the weld quality was investigated. Welds with full penetration were achieved at a defocusing distance ranging from −1 to 0 mm and welding speeds from 2·25 to 6·0 m min−1. Underfill and porosity were the two main defects most frequently observed; however, within the optimum process window, these defects could be maintained to meet aerospace specification tolerances. The fusion zone consisted entirely of retained β with a refined dendritic morphology. Compared with the bimodal α+β microstructure of the base metal, dissolution of the α phase in the heat affected zone and the presence of entirely metastable/retained β phase in the fusion zone were observed, which led to a significant decrease in the HAZ and FZ hardness. To determine the tensile properties of the welds, an automated three-dimensional deformation measurement system was used to measure the local strain in the weld region. The yield strength and ultimate tensile strength increased with welding speed, achieving a maximum joint efficiency of 75%, albeit with a concomitant reduction in the ductility.On a soudé des joints de Ti-5553 bout à bout en utilisant un laser continu Nd:YAG de 4 kW. On a étudié l’effet de la vitesse de soudage et de la distance de défocalisation sur la qualité de la soudure. On a obtenu des soudures avec pénétration complète à une distance de défocalisation allant de −1 mm à 0 mm et à des vitesses de soudage de 2·25 à 6·0 m/min. Le manque de métal et la porosité étaient les deux principaux défauts les plus souvent observés, mais dans le cadre de la fenêtre optimale du procédé, on pourrait contenir ces défauts afin de satisfaire les tolérances de la spécification aérospatiale. La zone de fusion consistait entièrement de bêta résiduel à morphologie dendritique raffinée. Comparée à la microstructure bimodale a+b du métal de base, on a observé la dissolution de la phase a dans la zone affectée par la chaleur (HAZ) et la présence de la phase b entièrement métastable/résiduelle dans la zone de fusion (FZ), ce qui menait à une diminution significative de la dureté de la HAZ et de la FZ. Afin de déterminer les propriétés de traction des soudures, on a utilisé un système 3D automatisé de mesure de la déformation pour mesurer l’allongement local dans la région de la soudure. La limite d’élasticité et l’UTS augmentaient avec la vitesse de soudage, obtenant un rendement maximum du joint de 75%, quoique avec une réduction concomitante de la ductilité.

Quantitative Stereovision in a Scanning Electron Microscope

Accurate, 3D full-field measurements at the micron-level are of interest in a wide range of applications, including both facilitation of mechanical experiments at reduced length scales and accurate profiling of specimen surfaces. Scanning electron microscope systems (SEMs) are a natural platform for acquiring high magnification images for stereo-reconstruction. In this work, an integrated methodology for accurate three-dimensional metric reconstruction and deformation measurements using single column SEM imaging systems is described. In these studies, the specimen stage is rotated in order to obtain stereo views of the specimen as it undergoes mechanical or thermal loading. Simulations and preliminary experimental studies at 300× demonstrate that (a) spatially-varying image distortions can be removed from images using a non-parametric distortion model, (b) the system can be reliably calibrated using distortion-corrected images of a planar object and grid at various orientations and (c) specimen rotation variability during the measurement phase can be controlled so that baseline strain errors are within the range of ±150 µe. Benchmark rigid body motion experiments using calibrated SEM views demonstrate that all components of strain in the reconstructed object have a mean value around O(10−4) and a random spatial distribution with standard deviation ≈ 300 micro-strain.

Measurement of three-dimensional deformations using digital holography with radial sensitivity

A measurement system based on digital holography for the simultaneous measurement of out-of-plane and radial in-plane displacement fields for the assessment of residual stress is presented. Two holograms are recorded at the same time with a single image taken by a digital camera, allowing the separate evaluation of in-plane and out-of-plane movement. An axis-symmetrical diffractive optical element is used for the illumination of the object, which causes radial sensitivity vectors. By the addition and, respectively, the subtraction, of the four phase maps calculated from two camera frames, the in-plane and out-of-plane deformation of an object can be calculated separately. The device presented is suitable for high-speed, high-resolution measurement of residual stress. In addition to the setup, first measurement results and a short comparison to a mature digital speckle pattern interferometry setup are shown.

Modelling capacity of transparent soil

The modelling capacity of transparent soil was investigated by comparing boundary soil displacement fields under a model footing in a transparent soil model with those from a natural soil model. Transparent soil is made of either amorphous silica gels or powders and a pore fluid with a matching refractive index to model sand and clay. An optical system consisting of a laser light, camera, frame grabber, and computer was developed to optically slice a transparent soil model. A distinctive laser speckle pattern was generated by the interaction between the laser light and transparent soil. Two laser speckle images before and after a deformation were used to calculate the displacement field using an image processing technique called digital image correlation. The comparative study shows that transparent soil can be used to study natural soil with some limitations. Transparent soil and the developed optical system could be used to explore opportunities for more advanced nonintrusive three-dimensional deformation measurements for various soil–structure interaction problems.

Recent applications of optical and computer-vision methods to research for microelectronics assembly reliability

Material and structure evaluation for reliability is a key research area for advanced microelectronics and miniatures. This paper presents a new experimental mechanics-based approach devoted to the evaluation of critical failure conditions for solder materials and assembly structures. Several optical and computer-vision-based metrological techniques have been adapted and employed for three-dimensional (3D), multi-scale and real-time deformation measurement. Case studies are presented to illustrate how the approach accomplishes an evaluation with high efficiency and low cost. The paper raises the prospect for the in-situ deformation measurement to play a more extensive role in this area.

1309 圧縮負荷に対する肝臓の定量的損傷評価(OS13-3 生体材料力学の最前線-生体組織の損傷評価-)

A driver not wearing a seatbelt suffers fatal liver injury as the result of crash between a steering wheel and an abdomen in the traffic accident. In terms of automotive passive safety, it is essential to understand the mechanical properties of liver and establish the method of quantitative injury evaluation. We conducted the quasi-static compression tests using full-scale livers that were removed from fresh hogs slaughtered for meat packing. Three types of indenters (a plate, a quadratic-prism, and a cylinder) were developed, and specimens were compressed using them. After compression tests, specimens were extended formalin fixation in order to observe the intemal liver injuries in detail. The bulk injury scales in each specimen were calculated and evaluated the relationships with a maximum stress, a maximum compressive volume, and a maximum bulk strain. The compressive volume and bulk strain illustrated the linear correlations with the bulk injury scale while the stress showed no correlation. Therefore, it is considered that the liver injury scale can be predicted by measurement of three-dimensional deformation.

Fold-ray videometrics method for the deformation measurement of nonintervisible large structures

An optical measurement method, the fold-ray videometrics method, that is applicable to the deformation measurement of large structures is proposed. Through an illustration of ship deformation, the principle of fold-ray videometrics and the composition of the deformation measurement system are introduced. The fold-ray videometrics method is able to transfer or relay three-dimensional geometric information with a fold-ray optical path and thus is capable of real-time measurement of three-dimensional positions, attitudes, and deformations between nonintervisible objects and those of intervisible objects with a very large angle of view. The proposed method therefore has the potential to be applied in deformation measurement of large structures.

Intensity range extension method for three-dimensional shape measurement in phase-measuring profilometry using a digital micromirror device camera

Phase-measuring profilometry is an accurate and effective technique for performing three-dimensional (3D) shape and deformation measurements of diffuse objects by fringe projection. However, phase analysis cannot be performed in underexposed or overexposed areas of the detector when an object with wide reflectance is measured. A novel intensity range extension method using a digital micromirror device (DMD) camera is proposed. In the optics of the DMD camera, each pixel of the CCD corresponds exactly to each mirror of the DMD. The phase-shifted fringe patterns with high contrast can be easily captured by programming an inverse intensity pattern that depends on the reflectance of the object. Our method can provide a wider intensity range and higher accuracy for 3D shape measurement than other conventional methods in both underexposed and overexposed areas. The measurements of a replica of a metallic art object and a flat plane are analyzed experimentally to verify the effectiveness of our method. In the experiment, the percentage of invalid points due to underexposure and overexposure can be reduced from 20% to 1%.

Three-wavelength electronic speckle pattern interferometry with the Fourier-transform method for simultaneous measurement of microstructure-scale deformations in three dimensions

We present the simultaneous measurement of three-dimensional deformations by electronic speckle pattern interferometry using five object beams and three colors. Each color, corresponding to an orthogonal direction of displacement, is separated through dichroic filtering before being recorded by a separate CCD camera. Carrier fringes are introduced by tilting the beam path in one arm of each of the three interferometers. The measured deformation modulates these carrier fringes and is extracted using the Fourier-transform method to achieve high displacement sensitivity. The field of view is on the order of a millimeter, making the system suitable for study of microstructural deformations. We compare experimental results with calculated values to validate out-of-plane and in-plane deformation measurements and demonstrate sensitivity on the order of 10 nm.

Three-dimensional deformation measurement from the combination of in-plane and out-of-plane electronic speckle pattern interferometers.

An optical setup that can be switched to produce in-plane and out-of-plane sensitivity interferometers was designed for three-dimensional deformation measuring by electronic speckle pattern interferometry. Divergent illumination is considered in the evaluation of sensitivity vectors to measure both in-plane and out-of-plane displacement components. The combination of these interferometers presents the advantage of greater sensitivity in directions u, v, and w than a typical interferometer with three illumination beams provides. The system and its basic operation are described, and results with an elastic target that is exposed to a mechanical load are reported.

PZT polarization voltage effects on off-centered PZT patch actuating silicon membrane

Abstract We have investigated the static and dynamic behavior of piezoelectric (PZT) actuated SiO2/Si membranes with an off-centered PZT patch. Three-dimensional wide-field interferometer has been used to achieve measurement of membrane topography and bending. It is demonstrated that the piezoelectric coefficient d31 can be extracted directly from these three-dimensional static deformation measurements. We have also shown that polarization voltage of an off-centered PZT patch influences in a different manner the resonant frequency shift of the first and the second vibration modes. Degenerated modes can be also discriminated thanks to the positioning of the PZT patch.

Deformations in wide, center-notched, thin panels, part I: three-dimensional shape and deformation measurements by computer vision

The response of wide, thin, center-notched, 2024-T3 aluminum panels undergoing far-field tensile load is investigated. Three panels with a notch length to panel width of 0.33 and widths of 305, 610, and 1016 mm were subjected to far-field tensile loading. As part of the experimental program, two pairs of cameras were configured into separate stereovision systems and used to simultaneously capture both the global response of the sheet and the local response near a notch tip. Global areas, ranging in size from 250x 250 mm to 550x 550 mm, were imaged for each panel. A second stereovison system recorded images of a small area, 10×20 mm, ahead of one notch tip. Postprocessing of the stereovision measurement data from global and local systems using three-dimensional digital image correlation was used to obtain the complete displacement field at each point in the region of interest. In general, results demonstrate that the combination of stereovision and three-dimensional digital image correlation is capable of accurately measuring true, three-dimensional structural deformations in regions undergoing both large out-of-plane displacements and large displacement gradients. Furthermore, 3-D measurements on the panel specimen near the grip location are shown to provide an independent assessment of the true boundary conditions, with specimen slippage clearly noted in the 1016-mm specimen. Results from the extensive notched, wide panel experimental program demonstrate that (a) each panel has an initial shape that deviates up to 3 mm from planarity, with the greatest deviations occurring at the center of the notch, (b) the global load-displacement response is essentially linear for load levels that are well beyond the onset of large, out-of-plane displacements in the notch region, and (c) increasing the size of the notched, thin panel specimen results in distinctly different surface deformations and deformed shapes, with three separate maxima/minima in the out-of-plane component of the largest panel. The region where tensile opening strains are above 2% extends several millimeters ahead of the hole, while compressive strains parallel to the notch direction are contained within a few millimeters of the hole. The in-plane shear strains are concentrated along circular lobes at +/-45 deg from the horizontal direction, a trend which is generally consistent with plane stress conditions.

Simultaneous three-dimensional dynamic deformation measurements with pulsed digital holography

The three deformation components x, y, z of a vibrating object are measured simultaneously by use of digital holography with a double-pulse ruby laser source. The object is illuminated from three different directions, each optically path matched with three reference beams such that three independent digital holograms are formed and added incoherently in one single CCD image. The optical phase difference between the two recordings taken for each hologram is quantitatively evaluated by the Fourier-transform method so that a set of three phase maps is obtained, representing the deformation along three sensitivity vectors. The total object deformation is obtained as a vector resultant from the data of the three phase maps. To give the full three-dimensional (3-D) description, the shape of the object is measured by the two-wavelength contouring method. Experiments are performed with a cylinder as the test object, transiently and harmonically excited. The 3-D deformation and shape measurement results are presented graphically.

Noninvasive measurement of three-dimensional myocardial deformation with tagged magnetic resonance imaging during graded local ischemia.

The purpose of this study was to investigate the relationship between three-dimensional (3D) deformation patterns in the canine left ventricle and localized graded reductions in perfusion. Magnetic resonance (MR) tissue tagging in a clinical scanner was used to determine systolic 3D deformation throughout the left ventricle with 32-msec time resolution. Six dogs were studied at normal and reduced left anterior descending coronary artery flow levels, for a total of 14 studies. Deformation was calculated by fitting a 3D displacement field to tag displacement data from three orthogonal sets of tags and taking spatial derivatives. A novel index of 3D radial mechanical function, calculated from the 3D strain tensor components and the tissue incompressibility constraint, had a higher correlation (R = 0.94) with perfusion (colored microspheres) than any of the 3D Lagrangian finite strain tensor components or wall thickening. As a function of the fraction of baseline perfusion, it was well fit by a linear relationship for subnormal perfusion with a slope of 0.46 +/- 0.05 and an intercept of -0.156 +/- 0.026. Longitudinal strain was lost first with decreasing perfusion (48%), followed by circumferential (40%) and finally radial function (35%). The strain method detected perfusion drops as small as 20%, and early paradoxical strain transients lasting 100 msec were seen only with ischemia. 3D strain changes can be noninvasively measured throughout the left ventricle with MR tissue tagging. MR imaging-derived strain indices, unique to 3D analysis, correlate most sensitively with regional perfusion in the canine left ventricle.

Grating holographic interferometry

A holographic interferometric technique, combining an image hologram with a grating approach, is proposed for three-dimensional deformation measurements on opaque planar object surfaces. In this technique, the holographic plate is brought close to the object surface, onto which a high-frequency crossed-line diffraction grating has been replicated. The grating surface produces multiple object waves rather than the usual diffusely reflected object waves. The double-exposed single holograms can be reconstructed at multiple off-axis angles. Four independent high-contrast fringe patterns are extracted simultaneously. Displacement vectors over the entire measurement area are separated in three orthogonal directions. The resultant displacements are presented as three-dimensional meshed plots and topographic contour maps. The optical system for both recording and reconstruction of the holograms has been simplified compared to conventional holographic interferometry. Experimental errors associated with fringe readout and system geometry are reduced because of the sharp images and the well-defined spatial orientation in the reconstruction system.

Preservation Technology of Underground Space -Three-Dimensional Deformation Measurement of Rock Joint-

Preservation Technology of Underground Space -Three-Dimensional Deformation Measurement of Rock Joint-

Accurate measurement of three-dimensional deformations in deformable and rigid bodies using computer vision

Recently, digital-image-correlation techniques have been used to accurately determine two-dimensional in-plane displacements and strains. An extension of the two-dimensional method to the acquisition of accurate, three-dimensional surfacedisplacement data from a stereo pair of CCD cameras is presented in this paper. A pin-hole camera model is used to express the transformation relating three-dimensional world coordinates to two-dimensional computer-image coordinates by the use of camera extrinsic and intrinsic parameters. Accurate camera model parameters are obtained for each camera independently by (a) using several points which have three-dimensional world coordinates that are accurate within 0.001 mm and (b) using two-dimensional image-correlation methods that are accurate to within 0.05 pixels to obtain the computer-image coordinates of various object positions. A nonlinear, least-squares method is used to select the optimal camera parameters such that the deviations between the measured and estimated image positions are minimized. Using multiple orientations of the cameras, the accuracy of the methodology is tested by performing translation tests. Using theoretical error estimates, error analyses are presented. To verify the methodology for actual tests both the displacement field for a cantilever beam and also the surface, three-dimensional displacement and strain fields for a 304L stainless-steel compact-tension specimen were experimentally obtained using stereo vision. Results indicate that the three-dimensional measurement methodology, when combined with two-dimensional digital correlation for subpixel accuracy, is a viable tool for the accurate measurement of surface displacements and strains.

部分床義歯における印象採得条件の相違が欠損部顎堤粘膜の微小形態変化に及ぼす影響について

In the impression-taking procedure for the distal extension removable partial denture, the pressure produced at the interface of the soft mucosal tissue and the impression material is the most important factor for the stability of the saddle under functional load. However, a review of the literature revealed little information about the displacement of the soft tissue caused by the impression pressure. In the present study, to investigate the influence of various impression procedures on the magnitude of the soft tissue displacement more precisely, a new three-dimensional deformation measurement system was devised. Compared to the previous studies, the greatest advantage of the system is that the hardened impression material can be surveyed directly without substituting a dental stone. It was found that, in the investigation using a partially edentulous simulated model, the amount of the subsidence in the soft tissue was increased as the thickness of the spacer of the impression tray was reduced or the seating speed of the tray was fast. Especially in the buccal area, a large amount of vertical displacement was present compared to the midridge and lingual area. Thus it was suggested that many factors are associated with the form of soft tissue under impression loading.

Measurement of three-dimensional deformation of an interfacial crack in a bimaterial

An interfacially cracked bimaterial beam made of two different types of polyester resins was studied under loading of four-point bending. Three layers of random speckle patterns were seeded in the specimen. The white light speckle method was used to obtain the surface displacements and the interior displacements along the crack faces. The results revealed that there existed a mixed-mode field near the crack-tip but it was dominated by an opening-mode, and the opening displacement of the crack measured in the free surface was approximately twice as large as that in the interior. The experimental results imply that the effect of the free surface is more significant than that in a homogeneous material.

Three-dimensional surface deformation measurement by a grating method applied to crack tips

The three-dimensional coordinates of a cross grating fixed on a slightly curved surface are determined by stereo imaging using polynomial imaging functions. These functions transform each spatial point within a limited flat volume into adjoined points in the images of two stereo cameras. The same functions also solve the inverse problem: finding the spatial coordinates when the related image coordinates are given, provided the points were placed within the above mentioned volume when taking the photograph. The method is applied to crack tip propagation. The out-of-plane displacement of the surface and the plane strain tensor are determined for the 3-D coordinates of the grating in different load stages.