Vijay Vasudevan

• University of Cincinnati

An attempt is being made to develop novel Ni-Mo-W-Cr-Al-X alloys with ICME approach with critical experimental/simulations and processing/microstructural characterization/property evaluation and performance testing has been adopted. In this work, based on thermodynamic modeling five alloy compositions with varying Mo/W and two alloys with high tung...

Molten salts are being considered for use in a new generation of nuclear reactors. Therefore, any materials selection process necessarily involves corrosion studies to understand the compatibility between the salts of interest and the materials of construction. This project investigated the corrosion behavior of novel Ni-base superalloys in molten...

Aluminum 7075-T6 alloy was subjected to Laser Shock Peening without Coating (LSPwC) and Ultrasonic Nanocrystal Surface Modification (UNSM) to boost fatigue performance in both air and corrosive environment. Severe plastic deformation (SPD) caused by UNSM treatment induced significantly higher (~3.5 × ) surface compressive residual stress than LSPwC...

Many aviation accidents are caused by the failure of aircraft engine components, and engine blades are especially vulnerable to high‐cycle fatigue fracture in severe working environments as well as to impact damage caused by foreign objects. To address this problem, the United States took the lead and has been successful in implementing laser shock...

Molten Salt Reactors (MSRs) are a promising alternative to the current generation of light-water reactors. However, the corrosivity of molten salts is a significant issue that must be understood before MSRs become commercial. Ni-base superalloys are promising candidate materials that can provide corrosion resistance in molten salt environments and...

Low‐plasticity burnishing (LPB) has been widely used in various industries. In the LPB process, when the ball moves on the material surface, plastic deformation or cold working occurs in the burnished region. Through this process, not only can LPB improve the surface integrity of metallic material components by replacing polishing in some situation...

In this paper, an in situ integration of the laser-assisted powder-based directed energy deposition (DED) process with a post-processing surface engineering technique called an ultrasonic nanocrystal surface modification (UNSM) is presented and analyzed with a multiphysics computational approach. The goal of this integrated process is to improve th...

Image classification accuracy on the ImageNet dataset has been a barometer for progress in computer vision over the last decade. Several recent papers have questioned the degree to which the benchmark remains useful to the community, yet innovations continue to contribute gains to performance, with today's largest models achieving 90%+ top-1 accura...

The present study reports the formation of Laves phase in the Nb-Ti-Cr-Si-X-based alloys, which are being considered for high-temperature applications in aerospace engines. Depending upon the heat-treatment, various morphologies of the Laves phases could be induced. Aging at 1100 °C led to the dissolution of the Laves precipitates formed within mat...

Laser Shock Peening with (LSP) and without protective coating (LPwC) was applied to sensitized AA5083 followed by electrochemical analysis. Potentiodynamic tests indicated a region of increased passivity for the LPwC samples with lower corrosion current. Similarly, significantly reduced intergranular corrosion rate was observed during potentiostati...

In this research, ultrasonic nanocrystal surface modification (UNSM) was used to process a 7075-T651 aluminum alloy. After UNSM treatment, a work-hardened layer with compressive residual stress up to 500 MPa was generated on the near-surface region of the sample. The surface microhardness of the alloy was increased from 195 ± 4 to 225 ± 7 HV, and t...

Aluminium alloy 5083 was subjected to Laser Shock Peening both with (LSP) and without protective coating (LPwC) at multiple pulse densities. A second LPwC treatment was conducted fully submersed under water, in addition to the standard laminar water flow condition. The results show that compressive residual stresses were generated in all cases, alt...

The near-surface microstructure in an Al-Zn-Mg-Cu (7075-T6) alloy after Laser Shock Peening without Coating (LSPwC) was characterized by advanced electron microscopy methods. A remarkable microstructure composed of a ~2 μm wide newly solidified matrix recast surface layer embedded with O-rich Al nanoparticles (NPs) with the close-packed orientation...

Laser powder bed fusion (LPBF) has been increasingly used in the fabrication of dense metallic structures. However, the corrosion related properties of LPBF alloys, in particular environment-assisted cracking, such as corrosion fatigue properties, are not well understood. In this study, the corrosion and corrosion fatigue characteristics of LPBF 31...

3D object detection is vital for many robotics applications. For tasks where a 2D perspective range image exists, we propose to learn a 3D representation directly from this range image view. To this end, we designed a 2D convolutional network architecture that carries the 3D spherical coordinates of each pixel throughout the network. Its layers can...

Predicting the future motion of multiple agents is necessary for planning in dynamic environments. This task is challenging for autonomous driving since agents (e.g., vehicles and pedestrians) and their associated behaviors may be diverse and influence each other. Most prior work has focused on first predicting independent futures for each agent ba...

The effect of temperature over the range of ambient to 704 °C and strain rate from 10−4 to 10−2 s−1 on the tensile properties and fracture behavior of ATI 718Plus was investigated. The results showed that with increase in temperature at a strain rate 10−4 s−1, there is a small reduction in the yield strength, but a large drop in ductility at 704 °C...

As autonomous driving systems mature, motion forecasting has received increasing attention as a critical requirement for planning. Of particular importance are interactive situations such as merges, unprotected turns, etc., where predicting individual object motion is not sufficient. Joint predictions of multiple objects are required for effective...

To safely deploy autonomous vehicles, onboard perception systems must work reliably at high accuracy across a diverse set of environments and geographies. One of the most common techniques to improve the efficacy of such systems in new domains involves collecting large labeled datasets, but such datasets can be extremely costly to obtain, especiall...

Among metal additive manufacturing technologies, additive friction stir deposition stands out for its ability to create freeform and fully-dense structures without melting and solidification. Here, we employ a comparative approach to investigate the process-microstructure linkages in additive friction stir deposition, utilizing two materials with d...

Autonomous vehicles operate in a dynamic environment, where the speed with which a vehicle can perceive and react impacts the safety and efficacy of the system. LiDAR provides a prominent sensory modality that informs many existing perceptual systems including object detection, segmentation, motion estimation, and action recognition. The latency fo...

Data augmentation has been widely adopted for object detection in 3D point clouds. However, all previous related efforts have focused on manually designing specific data augmentation methods for individual architectures. In this work, we present the first attempt to automate the design of data augmentation policies for 3D object detection. We intro...

The tribological performance of AISI 52100 substrates subjected to several surface treatments have been evaluated in rolling, sliding, and mixed mode contact. The surface treatments include a boron-doped diamond-like carbon (B-DLC) coating deposited by plasma-assisted magnetron sputtering, an ultrasonic nanocrystal surface modification (UNSM) techn...

Autonomous vehicles operate in a dynamic environment, where the speed with which a vehicle can perceive and react impacts the safety and efficacy of the system. LiDAR provides a prominent sensory modality that informs many existing perceptual systems including object detection, segmentation, motion estimation, and action recognition. The latency fo...

In this study, the effects of ultrasonic nanocrystal surface modification (UNSM) treatment on the surface integrity, microstructures and wear resistance of 300 M ultra-high strength steel (300 M steel) were investigated. The results showed that surface roughness of 300 M steels after UNSM processing was significantly decreased with a lower scanning...

Data augmentation has been widely adopted for object detection in 3D point clouds. All previous efforts have focused on manually designing specific data augmentation methods for individual architectures, however no work has attempted to automate the design of data augmentation in 3D detection problems -- as is common in 2D image-based computer visi...

Additive Friction Stir (AFS), also called MELD, is a novel, high deposition, solid state additive manufacturing process developed that is receiving considerable interest and attention for additive manufacturing of metallic materials with refined microstructures and enhanced mechanical properties. In this study, alloy 600 claddings on 304L stainless...

The γ-FCC (face-centered cubic) to ε-HCP (hexagonal close packed) phase transformation in a laser additively fabricated Co-29Cr-5Mo alloy was investigated. The microstructure of the as-built material was γ-FCC featured with a sub-micron scale dislocation cell structure and stacking faults. Aging at 1073 K led to rapid transformation within 0.5 h to...

The research community has increasing interest in autonomous driving research, despite the resource intensity of obtaining representative real world data. Existing self-driving datasets are limited in the scale and variation of the environments they capture, even though generalization within and between operating regions is crucial to the overall v...

Recent work on 3D object detection advocates point cloud voxelization in birds-eye view, where objects preserve their physical dimensions and are naturally separable. When represented in this view, however, point clouds are sparse and have highly variable point density, which may cause detectors difficulties in detecting distant or small objects (p...

LiDAR sensor systems provide high resolution spatial information about the environment for self-driving cars. Therefore, detecting objects from point clouds derived from LiDAR represents a critical problem. Previous work on object detection from LiDAR has emphasized re-purposing convolutional approaches from traditional camera imagery. In this work...

It is necessary for nuclear power plant operation and spent fuel canisters to provide a sound technical basis for the safety and security of long-term operation and storage respectively. A new code case for mitigation of Primary Water Stress Corrosion Cracking (PWSCC) and Chloride Induced Stress Corrosion Cracking (CISCC) in Section III components...

This study investigates the effects of laser shock peening (LSP) on residual stress, near surface modification, and hardness of Inconel 718 (IN718) specimens manufactured by selective laser melting (SLM) technique. Optical microscope and electron backscattered diffraction (EBSD) is used to characterize the microstructures of both heat-treated and a...

We present the next generation of MobileNets based on a combination of complementary search techniques as well as a novel architecture design. MobileNetV3 is tuned to mobile phone CPUs through a combination of hardware aware network architecture search (NAS) complemented by the NetAdapt algorithm and then subsequently improved through novel archite...

The development of graded microstructure in Ni-base Alloy 602CA, processed through the new technique of high reduction (per pass) cold rolling (HRCR) and the severe surface plastic deformation technique of ultrasonic nanocrystal surface modification (UNSM) was investigated. Clear through-thickness gradients in residual stress, dislocation structure...

The objective of this study is to understand the influence of surface treatments, namely laser shock peening (LSP) and ultrasonic nanocrystal surface modification (UNSM), on the irradiation tolerance of a Ni-base alloy. Surface treatments such as LSP and UNSM have been shown to mitigate the potential for primary water stress corrosion cracking (PWS...

Hierarchical structures on metallic implants can enhance the interaction between cells and implants and thus increase their biocompatibility. However, it is difficult to directly fabricate hierarchical structures on metallic implants. In this study, we used a simple one-step method, ultrasonic nanocrystal surface modification (UNSM), to fabricate h...

Transfer learning is a widely used method to build high performing computer vision models. In this paper, we study the efficacy of transfer learning by examining how the choice of data impacts performance. We find that more pre-training data does not always help, and transfer performance depends on a judicious choice of pre-training data. These fin...

Designing convolutional neural networks (CNN) models for mobile devices is challenging because mobile models need to be small and fast, yet still accurate. Although significant effort has been dedicated to design and improve mobile models on all three dimensions, it is challenging to manually balance these trade-offs when there are so many architec...

LSPwC is an innovative surface enhancement technique  Warm LSPwC-dynamic aging integrates thermo-mechanical processing and aging treatment, the precipitation occurs during deformation simultaneously  Nd-YAG Laser with 10 ns pulse duration was used  The laser peak power density is 6 GW cm-2  Aluminium alloys are most versatile material for vario...

We present a simple and powerful algorithm for parallel black box optimization called Successive Halving and Classification (SHAC). The algorithm operates in $K$ stages of parallel function evaluations and trains a cascade of binary classifiers to iteratively cull the undesirable regions of the search space. SHAC is easy to implement, requires no t...

In this paper, we take a closer look at data augmentation for images, and describe a simple procedure called AutoAugment to search for improved data augmentation policies. Our key insight is to create a search space of data augmentation policies, evaluating the quality of a particular policy directly on the dataset of interest. In our implementatio...

The study proposes laser shock peening without a coating of high strength ultrafine bainitic steel to mitigating the fatigue failures for automotive and structural engineering applications. Laser pulse density of 2500 pulses/cm 2 (75% overlapping) was optimised based on the induced residual stresses for employing the wide range of characterisations...

The combination of interlocked lamellae grains is the primary feature of biological material “nacre” to constitute its highest strength. The mimic of this hierarchical assembly of biological material combinations remains the challenge for the future trending bioinspired engineering materials. In this study, the interlocked nanolaminated architectur...

In this study, the effects of applied tensile stress and temperature on laser shock peening (LSP) and cavitation shotless peening (CSP)-induced compressive residual stresses were investigated using neutron and x-ray diffraction. Residual stresses on the surface, measured in situ, were lower than the applied stress in LSP- and CSP-treated Alloy 600...

A multiscale simulation method is established to study the microstructural responses of near-surface grain boundary structures of copper subjected to ultrashort femtosecond laser pulse. By integrating a two-temperature model with molecular dynamics, the presented approach allows for incorporation of both laser processing parameters and microstructu...

In this study, Inconel 718 (IN718SPF) samples were treated with three surface modification techniques: laser shock peening (LSP), cavitation shotless peening (CSP) and ultrasonic nanocrystalline surface modification (UNSM). Subsequently, these samples were exposed to temperatures between 550 °C–650 °C for different time intervals. Residual stresses...

Ultrasonic Nanocrystal Surface Modification (UNSM) is a mechanical surface treatment that induces large compressive residual stresses and near-surface microstructural changes in the material using repetitive impacts at ultrasonic frequencies with a WC tip. In this study, we investigate the use of UNSM to improve the fatigue life of ATI 718 Plus (71...

In this study, ultrasonic nanocrystal surface modification (UNSM) of 304 stainless steel welds was carried out. UNSM effectively eliminates the tensile stress generated during welding and imparts beneficial compressive residual stresses. In addition, UNSM can effectively refine the grains and increase hardness in the near-surface region. Corrosion...

Rubbery materials are widely used in industrial applications and are often exposed to cyclic stress and strain conditions while in service. To ensure safety and reliability, quantifying the effect of loads on the life of rubbery material is an important but challenging task, due to the combination of geometric/material nonlinearities and loading co...

We present an approach to automate the process of discovering optimization methods, with a focus on deep learning architectures. We train a Recurrent Neural Network controller to generate a string in a domain specific language that describes a mathematical update equation based on a list of primitive functions, such as the gradient, running average...

Low energy laser shock peening without coating (LSPwC) was conducted on AISI 304 austenitic stainless steel specimens with varying pulse densities or overlapping. Highest magnitude of compressive residual stress (CRS) was achieved for an optimized pulse density of 2500 pulses/cm2 (75% overlapping). The 2-D and 3-D topographical analysis were indica...

Developing state-of-the-art image classification models often requires significant architecture engineering and tuning. In this paper, we attempt to reduce the amount of architecture engineering by using Neural Architecture Search to learn an architectural building block on a small dataset that can be transferred to a large dataset. This approach i...

In this study, we investigate the effect of thermo-mechanical processing (TMP) on the evolution of low coincident site lattice (CSL) grain boundaries (3 ≤ Σ ≤ 27) and thence on the precipitation behavior of carbides at various types of grain boundaries in Alloy 600. Detailed analysis of the microstructure using Electron Back-scattered Diffraction (...

Many architects believe that major improvements in cost-energy-performance must now come from domain-specific hardware. This paper evaluates a custom ASIC---called a Tensor Processing Unit (TPU) --- deployed in datacenters since 2015 that accelerates the inference phase of neural networks (NN). The heart of the TPU is a 65,536 8-bit MAC matrix mult...

Many architects believe that major improvements in cost-energy-performance must now come from domain-specific hardware. This paper evaluates a custom ASIC---called a Tensor Processing Unit (TPU) --- deployed in datacenters since 2015 that accelerates the inference phase of neural networks (NN). The heart of the TPU is a 65,536 8-bit MAC matrix mult...

Inconel 718 (IN718) is a nickel based Ni-Cr-Fe super alloy. It has a unique set of properties such as good workability, corrosion resistance, high temperature strength, favorable weldability and excellent manufacturability. Due to its wide range of applications, IN718 is an alloy of great interest for many industries. Meanwhile, additive manufactur...

Enhancing the strength of materials is of great concern in that the failures such as wear, corrosion and fatigue occur on the surface. A tantalum (Ta), which is a refractory metal, was subjected to severe plastic deformation induced by ultrasonic nanocrystalline surface modification (UNSM) technique at room- and high-temperatures of 200°C and 800°C...

3D-printed metals have great potential for application in the biomedical and the aerospace industries. Unfortunately, they suffer from poor surface finish, high porosity, and high tensile residual stresses, leading to inferior mechanical properties as compared with traditional cast or wrought metals. In this study, we introduce an innovative method...

Many architects believe that major improvements in cost-energy-performance must now come from domain-specific hardware. This paper evaluates a custom ASIC---called a Tensor Processing Unit (TPU)---deployed in datacenters since 2015 that accelerates the inference phase of neural networks (NN). The heart of the TPU is a 65,536 8-bit MAC matrix multip...

The effects of laser shock peening (LSP) on the microstructure, residual stress, hardness, strength, and fatigue life of ATI 718 Plus (718Plus) alloy was investigated and the results are reported. Microstructure before and after LSP and after mechanical testing was characterized using scanning electron microscopy (SEM), electron backscatter diffrac...

A multiscale space–time finite element method based on time-discontinuous Galerkin and enrichment approach is presented in this work with a focus on improving the computational efficiencies for high cycle fatigue simulations. While the robustness of the TDG-based space–time method has been extensively demonstrated, a critical barrier for the extens...

The effects of thermomechanical processing (TMP) with iterative cycles of 10% cold work and strain annealing, on corrosion and stress corrosion cracking (SCC) behavior of alloy 600 was studied. The associated microstructural and cracking mechanisms were elucidated using transmission (TEM) and scanning electron microscopy (SEM), coupled with precess...

TensorFlow is a machine learning system that operates at large scale and in heterogeneous environments. TensorFlow uses dataflow graphs to represent computation, shared state, and the operations that mutate that state. It maps the nodes of a dataflow graph across many machines in a cluster, and within a machine across multiple computational devices...

TensorFlow is an interface for expressing machine learning algorithms, and an implementation for executing such algorithms. A computation expressed using TensorFlow can be executed with little or no change on a wide variety of heterogeneous systems, ranging from mobile devices such as phones and tablets up to large-scale distributed systems of hund...

The presence and interaction of nanotwins, geometrically necessary dislocations, and grain boundaries play a key role in the mechanical properties of nanostructured crystalline materials. Therefore, it is vital to determine the orientation, width and distance of nanotwins, the angle and axis of grain boundary misorientations as well as the type and...

In this paper, the results of a study on microstructural influences on mechanical behavior of the high-strength alloy steel Tenax™ 310 are presented and discussed. Under the influence of fully reversed strain cycling, the stress response of this alloy steel revealed softening from the onset of deformation. Cyclic strain resistance exhibited a linea...

We report herein the effects of Ultrasonic Nano-crystal Surface Modification (UNSM), a severe surface plastic deformation process, on the microstructure, mechanical (hardness, wear), wettability and biocompatibility properties of NiTi shape memory alloy. Complete surface amorphization of NiTi was achieved by this process, which was confirmed by X-r...

In this paper, we demonstrate a novel method for grain boundary engineering in Alloy 600 using iterative cycles of ultrasonic nanocrystal surface modification (UNSM) and strain annealing to modify the near surface microstructure (~250. μm) for improved stress corrosion cracking (SCC) resistance. These iterative cycles resulted in increased fraction...

TensorFlow [1] is an interface for expressing machine learning algorithms, and an implementation for executing such algorithms. A computation expressed using TensorFlow can be executed with little or no change on a wide variety of heterogeneous systems, ranging from mobile devices such as phones and tablets up to large-scale distributed systems of...

In this paper, the results of a study on microstructural influences on cyclic strain response, deformation and fracture behavior of an alloy steel is presented Cyclic strain resistance exhibited a linear trend for the variation of both elastic strain amplitude with reversals-to-failure, and plastic strain amplitude with reversals-to-failure. Fractu...

In this study, the effects of laser shock peening (LSP) on stress corrosion cracking (SCC) behavior of nickel based Alloy 600 in tetrathionate solution were investigated. The LSP induced compressive residual stresses and changes in the near surface microstructure, hardness were characterized. The effects of LSP on SCC susceptibility of Alloy 600 in...

An integrated experimental and modeling/simulation approach was developed to investigate and secure a quantified knowledge of the impact of high temperature exposures on the stability of residual stresses in a laser shock peened (LSP) high temperature aero-engine alloy, IN718 SPF (super-plastically formed). Single dimple LSP and overlap LSP treatme...

In this study, the effects of Ultrasonic Nano-crystal Surface Modification (UNSM) on the microstructure changes and the mechanical properties of austenitic stainless steel 304 were studied. Due to the dynamic impacts induced by the multiple strikes during UNSM, surface nanocrystallization and transformation to martensite has been achieved. The work...

In this paper, the results of a recent study aimed at understanding the role of microstructure on cyclic stress response, cyclic strain resistance, deformation, fatigue life, and fracture behavior of the high strength alloy steel PremoMet 290 is presented and discussed. The cyclic strain amplitude-controlled fatigue properties, deformation, and res...

In this paper, the results of a study aimed at understanding the specific role of microstructure on cyclic stress response, cyclic strain resistance, and cyclic stress versus strain response, deformation and fracture behavior of high strength alloy steel AerMet® 100 is presented and discussed. The cyclic strain amplitude-controlled fatigue properti...