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.
In order to do the numerical study of the formability of two-layer metallicsheets, 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 metallicsheets 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.
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.
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:
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.
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.
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.
Researchers realised that the description of the anisotropic behaviour of the metallicsheets can be improved further. Therefore, different complex yield criteria were proposed such as BBC2008 introduced by researchers in  with 16 experimental values. Another example of complex yield criteria is the function proposed by Barlat et al. , 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  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).
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 . Actually, it depends on the impact velocity and ap- proaches unity as the impact velocity approaches zero with increasing relative impact velocity . 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
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.
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
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.
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 . Methods based on neural networks and feature selection are able to handle with high data dimensionality maintaining good generalization level [13, 14].
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.