Multiple-Shot Impact Model for Vibration-Assisted SMAT Process

Surface mechanical attrition treatment enhances the mechanical properties of metallic materials by inducing high strength layer on the top surface. In this study, multiple-shot impact behavior was modeled for the 7075-T6 aluminum alloy to achieve maximum magnitudes of equivalent stress, plastic strain, residual stress depth, and residual stress. Finite element simulations have been carried out to investigate the effect of selected framework on stress and strains in constituent. The plastic deformation process during SMAT was analyzed using ANSYS/AUTODYN explicit dynamic solver according to shot velocity and diameter with a dynamic explicit finite element method (FEM). Deformation behavior was evaluated after multiple-shot impact.

A Theoretical Model For Predicting The Surface Topography of Inhomogeneous Materials After Shot Peening

Shot peening is widely used in engineering as a classical strengthening process. Although many studies on shot peening have been done, most have focused on homogeneous target materials. In this paper, a theoretical model is proposed for predicting the surface morphology of inhomogeneous target materials. The topography of target materials after single-shot impact is calculated on the basis of energy conservation and Hertz contact theory, and the final three-dimensional surface topography after multiple-shot impact is obtained through superposition. Single-shot and random multiple-shot finite element models are used to show the advantages of the proposed model over the existing theoretical model for homogeneous target materials. The roughness is found to increase with the shot velocity and shot radius.

Quality Assessment of 2.5D Prints Using 2D Image Quality Metrics

Quality assessment is an important aspect in a variety of application areas. In this work, the objective quality assessment of 2.5D prints was performed. The work is done on camera captures under both diffuse (single-shot) and directional (multiple-shot) illumination. Current state-of-the-art 2D full-reference image quality metrics were used to predict the quality of 2.5D prints. The results showed that the selected metrics can detect differences between the prints as well as between a print and its 2D reference image. Moreover, the metrics better detected differences in the multiple-shot set-up captures than in the single-shot set-up ones. Although the results are based on a limited number of images, they show existing metrics’ ability to work with 2.5D prints under limited conditions.

Multiple-shot and unambiguous discrimination of von Neumann measurements

We present an in-depth study of the problem of multiple-shot discrimination of von Neumann measurements in finite-dimensional Hilbert spaces. Specifically, we consider two scenarios: minimum error and unambiguous discrimination. In the case of minimum error discrimination, we focus on discrimination of measurements with the assistance of entanglement. We provide an alternative proof of the fact that all pairs of distinct von Neumann measurements can be distinguished perfectly (i.e. with the unit success probability) using only a finite number of queries. Moreover, we analytically find the minimal number of queries needed for perfect discrimination. We also show that in this scenario querying the measurements in parallel gives the optimal strategy, and hence any possible adaptive methods do not offer any advantage over the parallel scheme. In the unambiguous discrimination scenario, we give the general expressions for the optimal discrimination probabilities with and without the assistance of entanglement. Finally, we show that typical pairs of Haar-random von Neumann measurements can be perfectly distinguished with only two queries.

Dynamic nanoimaging of extended objects via hard X-ray multiple-shot coherent diffraction with projection illumination optics

The quest for understanding the structural mechanisms of material properties and biological cell functions has led to the active development of coherent diffraction imaging (CDI) and its variants in the hard X-ray regime. Herein, we propose multiple-shot CDI, a full-field CDI technique dedicated to the visualisation of local nanostructural dynamics in extended objects at a spatio-temporal resolution beyond that of current instrumentation limitations. Multiple-shot CDI reconstructs a “movie” of local dynamics from time-evolving diffraction patterns, which is compatible with a robust scanning variant, ptychography. We developed projection illumination optics to produce a probe with a well-defined illumination area and a phase retrieval algorithm, establishing a spatio-temporal smoothness constraint for the reliable reconstruction of dynamic images. The numerical simulations and proof-of-concept experiment using synchrotron hard X-rays demonstrated the capability of visualising a dynamic nanostructured object at a frame rate of 10 Hz or higher.

Discrimination of POVMs with rank-one effects

The main goal of this work is to provide an insight into the problem of discrimination of positive operator-valued measures with rank-one effects. It is our intention to study multiple-shot discrimination of such measurements, that is the case when we are able to use to unknown measurement a given number of times. Furthermore, we are interested in comparing two possible discrimination schemes: the parallel and adaptive ones. To this end, we construct a pair of symmetric informationally complete positive operator-valued measures which can be perfectly discriminated in a two-shot adaptive scheme but cannot be distinguished in the parallel scheme. On top of this, we provide an explicit algorithm which allows us to find this adaptive scheme.

3D Finite Element Simulation of Shot Peening Using a Sequential Model with Multiple-Shot Impacts

A sequential model of multiple-shot impacts has been established to investigate the shot peening process. Shot groups are proposed and designed with different patterns to obtain full surface coverage in the impacted region and a satisfactory computational efficiency. The sequential model was applied for the prediction of residual stress on a GH4169 alloy specimen. The results showed that uniform and saturated states of residual stress along the surface and depth profile were obtained in the impacted region when the numerical order of shot patterns reached 4. Furthermore, the numerical results of compressive residual stress in the subsurface were compared with the experimental results obtained using the X-ray diffraction (XRD) analysis and the incremental hole drilling method. The maximum relative error between the numerical results and XRD measurement was 11.6%. Furthermore, the stress profile measured using the incremental hole drilling method was consistent with the numerical results. The established finite element model demonstrated its robustness and effectiveness for the evaluation of residual stress in the shot-peened GH4169 alloy, and it may be applied to other metallic materials with simple modifications.

Adjustment of Surface Morphologies of Subwavelength-Rippled Structures on Titanium Using Femtosecond Lasers: The Role of Incubation

Laser-induced periodic surface structures have been extensively studied for various materials because of their promising applications. For these applications, uniform rippled structures with well-defined large areas are required. However, the efficient fabrication of uniform rippled structures is a challenge. Morphologies of rippled structures of multiple-shot-ablated regions considerably affect the processing efficiency of uniform rippled structures because incubation effects are crucial. In this study, the effects of a pulse number and irradiation modes on surface morphologies of rippled structures on the titanium surface are experimentally studied. The experimental results indicate the following: (1) Samples first irradiated using several shots and then using remaining shots by designing laser pulse irradiation modes exhibit improved surface morphologies, such as larger ablation areas and finer rippled structures. (2) When the pulse number in the first series is less than that in the second series, the rippled structures are characterized using larger areas and periods. (3) The ablated areas with rippled structures increase with the increasing number of pulses. (4) The periods of ripples reduce with the increasing number of pulses. Therefore, according to different requirements, uniform rippled structures can be efficiently fabricated and adjusted using the designed laser pulse modes and pulse number.