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Nondestructive ultrasonic evaluation of formability of metallic sheets

Nondestructive ultrasonic evaluation of formability of metallic sheets

noncontacting electromagnetic acoustic transducers, calculating an ultrasonic correlation parameter from the measurements, destroying the specimens in tensile tests to measure a formability index, and then correlating the ultrasonic correlation parameter with the formability index. Once this relationship is established, the formability index of a working sample, which is not to be destroyed, is found by making the same types of ultrasonic property measurements on the working sample, calculating the ultrasonic correlation parameter for the working sample, and then employing the previously established correlation to ascertain the formability index for the working sample.
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A Comparative Study on the Formability Prediction of Two-Layer Metallic Sheets

A Comparative Study on the Formability Prediction of Two-Layer Metallic Sheets

In order to do the numerical study of the formability of two-layer metallic sheets, all the consumed geometries in experimental study were simulated using commercially available finite element code ABAQUS/ Standard. In other word, experimental conditions were duplicated in numerical simulation. Punch, die and blank holder were rigid bodies, while two-layer metallic sheets were deformable. Sheets were modeled using four-node shell elements S4R with two integrations. One-quarter of the geometry was modeled due to symmetry condition. A default surface to surface contact explicit used to specify the interfaces between the surfaces of the tooling and the blank. The tie constraint was used between two layers by assuming there is no slipping among layers.
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Equal Channel Angular Pressing as a New Processing to Control the Microstructure and Texture of Metallic Sheets

Equal Channel Angular Pressing as a New Processing to Control the Microstructure and Texture of Metallic Sheets

The extended band structures of as-cold-rolled high Cr steel sheets are recrystallisation-resistant, and tend to become aggregates of the so-called grain colonies as a partially recovered state after final annealing. Such band structures di- minish formability and become origin of the so-called ridging. A novel processing will be shown here, which involves strain-path change by introducing one-pass ECAP prior to cold-rolling, and facilitates recrystallisation. Indeed, the recrys- tallisation temperature was reduced by 100˚C, compared with cold-rolling alone imposing an equivalent strain. Grain- scale microshear bands introduced during one-pass ECAP perturbed the banded structures in post-ECAP cold-rolling and enhanced the recrystallisation at the final annealing.
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Design and Development of a Contactless Laser-based Automated Nondestructive Evaluation (CLANDE) System for Metallic and Composite Structures.

Design and Development of a Contactless Laser-based Automated Nondestructive Evaluation (CLANDE) System for Metallic and Composite Structures.

When modelling Lamb waves propagating in finite plate structures, reflections at the boundaries can complicate the study of the ultrasonic wavefield. To avoid this inconvenience two approaches are possible: (1) make the model large enough to delay the reflections at the boundaries. This approach however leads to a considerable increase of the model size. (2) Use absorbing boundary conditions. Unfortunately ABAQUS does not offer absorbing boundary conditions in Explicit. To overcome this limitation, Drozdz (Drozdz, 2008) suggested the use of absorbing layers that use increasing damping. The work of Drozd showed that Lamb waves can be totally absorbed when propagating through a finite layer with mass proportional damping, 𝐶 𝑀 , that increases according to the power law:
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Nondestructive Detection of Cold Flakes in Aluminum Alloy Die Cast Plate with Ultrasonic Measurement

Nondestructive Detection of Cold Flakes in Aluminum Alloy Die Cast Plate with Ultrasonic Measurement

0.5 ns and a sampling number of 10020, and then subjected to the Wavelet analysis with the Gabor function as the wavelet function to obtain an intensity distribution of the ultrasonic wave in a time-frequency domain. Figure 3 shows a typical ultrasonic wave and mapping of wavelet analysis. In the bottom figure, left and right echoes are those reflected from the specimen surface and a boundary between the cold flake and the matrix, respectively. A traveling time from the specimen surface to the cold flake was converted into a distance from the surface with the ultrasonic velocity of 6440 m/s determined by the preliminary measurement.
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Nondestructive Evaluation of Iowa Pavements Phase I

Nondestructive Evaluation of Iowa Pavements Phase I

Evaluating structural condition of existing, in-service pavements is a part of the routine maintenance and rehabilitation activities undertaken by the most DOTs. In the field, the pavement deflection profiles (or basins) gathered from the nondestructive FWD test data are typically used to evaluate pavement structural conditions. This kind of evaluation requires the use of a backcalculation-type structural analysis to determine pavement layer stiffness and, as a result, estimate a pavement’s remaining life. Over the past decade, there has been an increased interest in a new class of computational intelligence system, ANNs, for use in geomechanical and pavement systems applications. ANNs have been found to be powerful and versatile computational tools for organizing and correlating information in ways that have proved useful for solving certain types of problems too complex, too poorly understood, or too resource- intensive to tackle using more traditional computational methods.
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Concentric coplanar capacitive sensor for nondestructive evaluation

Concentric coplanar capacitive sensor for nondestructive evaluation

A capacitive nondestructive evaluation system for evaluating a dielectric test piece, the system comprising: a concentric coplanar capacitive sensor, comprising a a charged central disc [r]

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FATIGUE DAMAGE AND ITS NONDESTRUCTIVE EVALUATION: AN OVERVIEW

FATIGUE DAMAGE AND ITS NONDESTRUCTIVE EVALUATION: AN OVERVIEW

An interesting study of the crack size distribution in stage I as a function of fatigue cycles applied has been performed by Ma and Laird [12] who made their observations on a large numb[r]

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New Method for Nondestructive Evaluation of Concrete Strength

New Method for Nondestructive Evaluation of Concrete Strength

Compared with water immersion curing, concretes that were steam cured for the period prior to testing, where the average ambient daily temperature varied in the range of 20 to 45ºF, res[r]

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Development of an Ultrasonic Motor That Uses an Inchworm Shaped Deformation of a Metallic Plate

Development of an Ultrasonic Motor That Uses an Inchworm Shaped Deformation of a Metallic Plate

Figure 4 shows the result of finite element method (FEM) analysis when the thick- ness of piezoelectric elements is increased by 5.0 μm. From this figure, it can be seen that the metallic plate is deformed into an inchworm shape with a maximum displace- ment of 6.144 μm. Therefore, the ratio of the displacement expansion is 1.23 times big- ger than the displacement of the piezoelectric element.

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A multi-step assembly process: drawing, flanging and hemming of metallic sheets

A multi-step assembly process: drawing, flanging and hemming of metallic sheets

shows a roll-in 400 % less than the classical hemming, since the descent of the roller during pre-hemming causes more roll-in on the edge of the sample. For both configurations, the curv[r]

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Accurate descriptions of the ansiotropic plastic yielding behaviour of various metallic sheets

Accurate descriptions of the ansiotropic plastic yielding behaviour of various metallic sheets

Researchers realised that the description of the anisotropic behaviour of the metallic sheets can be improved further. Therefore, different complex yield criteria were proposed such as BBC2008 introduced by researchers in [20] with 16 experimental values. Another example of complex yield criteria is the function proposed by Barlat et al. [36], denoted as Yld2004-18. This yield function requires 18 and 13 experimental values for 3-D and 2-D cases, respectively. Some of these values are calculated using polycrystalline plasticity model. A further example is the Vegter model [53] which is based on interpolation by second-order Bezier curves. The anisotropy coefficients of this model are derived from four mechanical tests (uniaxial tension, biaxial tension, plane strain, and pure shearing). Some of these tests must be repeated for various directions. This number of parameters leads to a far more accurate description of the yield loci than other yield functions. However, the accuracy of these complex models is achieved at the expense of cost. Most of the anisotropic yield functions mentioned here are implemented in the commercial finite element software dedicated to numerical modelling of sheet metal forming. These kinds of complex criteria are recommended only when accuracy is desired (for example, when dealing with highly textured materials such as 2090-T3).
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Impact dynamics of metallic nano particles in collision with graphene nano sheets

Impact dynamics of metallic nano particles in collision with graphene nano sheets

It should be noted that normal coecient of restitution must be associated with a pair of contacting bodies. The normal coecient of restitution is fre- quently considered as a constant for given geometries and a given combination of contacting materials [13]. Actually, it depends on the impact velocity and ap- proaches unity as the impact velocity approaches zero with increasing relative impact velocity [14]. However, such behavior is not valid in the case of collision of nanoparticles with graphene sheets. This will be discussed in the following sections. For collision

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Nondestructive detection of an undesirable metallic phase, T1, during processing of aluminum lithium alloys

Nondestructive detection of an undesirable metallic phase, T1, during processing of aluminum-lithium alloys

In employing eddy current to measure conductivity, when the eddy current decreases with aging of the alloy, while the hardness of the material continues to increase, the presence of the [r]

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Nondestructive Evaluation of Steel Bridges: Methods and Applications

Nondestructive Evaluation of Steel Bridges: Methods and Applications

Another factor to consider is the potential impact of a flaw on structure. This is addressed in terms of the nature of the flaw, the component where it is located and the potential impact of that component’s fracture on structural integrity of the bridge. Cracks transverse to principal tensile stresses in fracture-critical members that are growing by fatigue are probably the most common critical circumstances encountered on steel bridges. Determining the criticality of a flaw can be a challenging task for bridge engineers especially when they are required to make quick decisions. The potential threat of a flaw to a bridge’s structural integrity generally depends on its type, size, disposition in a structural component, type of steel involved, the impacted structural details and the magnitude and nature of the loading (both live and dead loads). Usually, flaw severity can be ranked from worst to least as cracks, lack of fusion, lack of penetration, arc strikes (welding), slag stringers and porosity (neglecting stress concentrators resulting from fabrication, corrosion or construction/service damage). Typically, the severity of non-crack flaws in steel bridges is related to their propensity to generate cracks in a fatigue environment. Characterization of flaws by type can be done readily for surface-breaking flaws (typically cracks). Subsurface flaws can be best characterized by type using radiography. It is generally easier to characterize flaw severity by size than by type. Ultrasonic testing has been used by KYTC to determine whether a surface indication detected by magnetic particle cracking is an actual crack.
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Geometrical Feature Extraction from Ultrasonic Time Frequency Responses: An Application to Nondestructive Testing of Materials

Geometrical Feature Extraction from Ultrasonic Time Frequency Responses: An Application to Nondestructive Testing of Materials

In this paper we show that parameters extracted from the TFR of ultrasonic A-scans can be used for material characterization/classification. The novelty of this work is based on the use of TFRs as input information in 2D-shape analysis algorithms, specifically geometrical descriptors. This technique compliments traditional classification parameters (attenuation, longitudinal ultrasonic velocity, etc.) with shape-related parameters. Additionally, for some parameters, the new technique allows to obtain lower variance estimators. When binarized TFRs are processed and 2-D geometrical modeling, inherent in our approach, is used, a new set of estimators can be derived. The proposed geometrical estimators can provide better estimates and moreover, they are less sensitive to noise than conventional estimators. Thanks to this superior performance, in terms of bias
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Interfacial Microstructure and Thermal Stability of Zr55Cu30Ni5Al10 Metallic Glass Joints Formed by Ultrasonic Bonding

Interfacial Microstructure and Thermal Stability of Zr55Cu30Ni5Al10 Metallic Glass Joints Formed by Ultrasonic Bonding

Numerous metallic glasses have been developed in the last decade owing to the alloy-design technology invented by Inoue. 1) The constituent atoms in these metallic glasses are arranged eliminating free spaces. Such arrangement of the atoms is effective for suppression of self-diffusion and long- range ordering, i.e. stabilization of the amorphous state. The stability allows production of massive components under considerably low cooling rates, which had been the most critical problem for the production of amorphous alloys.

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On the Evaluation of Texture and Color Features for Nondestructive Corrosion Detection

On the Evaluation of Texture and Color Features for Nondestructive Corrosion Detection

A wide variety of literature works [6, 8, 10, 11] have reported that texture features are proper to characterize corroded surfaces. In addition, typical color changes of metallic surfaces are often related to corrosion. Thus, color attributes carry out relevant information to design corrosion detection systems. Moreover, some works have reported that feature combination carries more discriminant power to applications designed on small database image samples [12]. Methods based on neural networks and feature selection are able to handle with high data dimensionality maintaining good generalization level [13, 14].
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Nondestructive Evaluation of Damage in Beams Using Displacement Curvature

Nondestructive Evaluation of Damage in Beams Using Displacement Curvature

In this paper, damage identification in beams using displacement curvature extracted from a static analysis has been investigated. The effects of many parameters may affect the effic[r]

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Evaluation of formability and fracture of pure titanium in incremental sheet forming

Evaluation of formability and fracture of pure titanium in incremental sheet forming

diagram of the hyperbolic truncated cone shape that there is a big change on one axis of the circular grid, whereas the change in the other one is small, meaning there is an increase in major strain, while the minor strain remains unchanged (plain strain).It is also observed with the hyperbolic truncated pyra- mid shape that there is uniform distortion in the grid at fracture and that the ratio is close to 1 (equi-biaxial strain). Based on these ratios of strain, the hyperbolic truncated cone is de- formed under plain strain conditions and the corner of the hyperbolic truncated pyramid part is deformed under equi- biaxial strain. Therefore, two points can be recorded in the first quadrant of FLD; these points are used to validate the capability of the Nakajima test to describe the formability of SPIF process.
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