V. Oancea

• PhD
• Managing Director at Dassault Systèmes

Estimating 3D physics fields in structural mechanics is critical during early design phase but often computationally expensive, especially when using high-fidelity Finite Element Analysis. Although parametric surrogate modelling methods such as the one proposed in [1] provide faster inference alternatives, their applications are limited to cases w...

Advancements in modern technology necessitate batteries that can be safely charged and discharged at high rates with minimal aging. A promising strategy to achieve these ends is through optimization of porous microstructures of existing electrode materials to promote better electrical and ionic transport without compromising energy density, as has...

Several decades after the invention of the rechargeable Li‐ion battery, countless innovations from both the research and industry communities have led to placing the secondary battery at the heart of the electrification revolution in recent years. Mathematical and numerical models have been trusted companions in advancing the technology to help gui...

As composite structures are widely used across multiple industries to achieve advanced performance, multi-scale methods for design and engineering are required to fully capture their complex mechanisms. For instance, composite structures such as thin laminates might require modeling at multiple scales: the matrix made of resin and fibers at the mic...

As system controls and design exploration require a dramatic reduction in computing costs of high-fidelity multi-physics simulations, surrogate modeling technologies are today the most relevant solution. Due to the multiple directions that research is taking in the field, it is quite challenging today to implement general-purpose software. A possib...

The design exploration phase at the beginning of a product lifecycle determines to a large extent its full timeline and overall costs. During such phase, ideally a large number of simulations is run with parametric combinations of geometric shapes, material behaviors and operating condtions, in order to drive the selection of the optimal basic desi...

Physical simulations are performed at multiple scales covering diverse physical domains. Macro scale continuum simulations at the part and assembly level, usually employing traditional numerical techniques such as 3D Finite Elements or Finite Volumes, are widely used for physics-based product design because of their high predictive value. However,...

Lithium-ion battery safety and durability by nature are dependent on electrochemical and mechanical coupling. Interdisciplinary efforts are required to understand and quantify coupling behaviors. Here we design and conduct mechanically constrained charge and discharge characterizations with efforts supported by multiphysics modeling to unravel the...

Early design choices have a significant (and sometimes underestimated) impact on the overall costs in the entire life-cycle of a given product, as, for instance, external shape definitions, internal structural reinforcements, material assignments, engineering connections, to name just a few potential design choices, are all interconnected and possi...

In this paper, we present calculations of some of the key physical properties of microstructures of electrodes and separators present in lithium-ion batteries with porous electrode architectures. We analyze three-dimensional models of public domain real commercial porous anodes, cathodes and polyethylene (PE) separator, in order to characterize som...

As multiple industries are urged to address environmental and climate issues, the interest in electrification and energy storage is nowadays exponentially increasing, fostering the development of an interdisciplinary ecosystem spanning from material science to assemblies and systems engineering. Battery cell engineering constitutes a cardinal ingre...

Innovation has always been at the core of the aerospace industry. To attain the latest goals of passenger flights, a full digitalization of the aircraft has been systematized across multiple disciplines (such as structural mechanics, electro-magnetism, fluids dynamics, vibro-acoustics and multi-body dynamics) and multiple levels of abstraction (suc...

Hyperelasticity is characterized by a strain energy function. The strain energy functions fall primarily into two categories: one based on statistical thermodynamics, the other based on the phenomenological approach of treating the material as a continuum. This work is focused on the phenomenological approach. To determine the constants in the stra...

Constitutive modeling of elastoplastic materials usually requires expertise due to the challenges in constructing suitable mathematical formulas, and calibrating a large number of parameters to describe loading history dependent behavior. Established elastoplasticity models introduce different forms of state variables and their evolution laws to ca...

Metal Big Area Additive Manufacturing (MBAAM), an additive manufacturing based on wire-arc process, is progressively evolving from rapid prototyping to the industrial scale production. In MBAAM, the height of printed part can easily reach eight feet, and the printing can last for hours or days. For such large printed structures, distortion and resi...

Material discovery and development drives innovation and is a key component for almost all cutting edge technologies today. With progress in computing power and numerical methods, multiscale modeling has been a rapidly growing requirement in the science and engineering of materials. However, unresolved challenges in true multiscale modeling have th...

Proper Generalized Decomposition (PGD) has become a standard technique for the resolution of partial differential equations in high-dimensional spaces. The possibility to separate the overall calculation across multiple dimensions (e.g. multiple parameter spaces) is key ingredient for reduced order model-ing methods, the computing time gain general...

Due to rapid solidification of melted powders in metal additive manufacturing processes and high thermal gradients, large residual stresses are created in the build. This can lead to undesired distortions as well as crack initiation. The main aim of this work is to optimize the Additive Manufacturing (AM) process parameters by finite element modell...

The laser powder bed fusion (LPBF) process involves using a laser beam to selectively melt metal powder with a desired shape on a substrate to create a part layer-by-layer. As an Additive Manufacturing (AM) process, laser powder bed fusion (commonly referred to as selective laser melting—SLM) offers superior design freedom over conventional manufac...

Abstract: Reasonably accurate simulation of airbag deployment is an important part of a crash analysis. The different sizes, shapes, initial configurations and deployment methods for airbags demand a robust simulation approach. In almost all cases, the airbag is tightly folded, rolled-up or crumpled-up in a small space. When the inflator is fired,...

While significant progress has been made in the last few years, the reliability of Additively Manufactured (AM) parts is often less than desirable as they suffer from manufacturing defects and hence subpar strength and fatigue life. To address this challenge, numerical methods are sought to provide insight into the process and help accelerate progr...

In this paper, a highly performing model order reduction technique called Proper Generalized Decomposition (PGD) is applied to the numerical modeling of highly transient non-linear thermal phenomena associated with additive manufacturing (AM) powder bed fabrication (PBF) processes. The manufacturing process allows for unprecedented design freedom b...

While significant progress has been made in the last few years, the structural integrity and reliability of Additively Manufactured (AM) parts is often questionable and inconsistent due to manufacturing defects, subpar strength, and low fatigue lives. Parallel work by the authors presented a generic simulation framework to predict metallurgical pro...

Abaqus FEA simulations have been widely used across all product lines at HP, including PCs, tablets, laptops and printers. Last year, HP and Dassault Systèmes SIMULIA collaborated on developing process simulations for the Multi Jet Fusion (MJFTM) printers. It was presented how the Abaqus Additive Manufacturing simulation framework and functionaliti...

In the last decades, multiple industries have been embracing digitalization in engineering with the employment of numerical simulations for design and certification of structures and products. A multi-scale and multi-physics strategy is inevitable to cover all applications , making use of a growing number of specialized software. This is especially...

Powder Bed Fusion (PBF) is a category of Additive Manufacturing (AM) process in which a layer of metal powder is spread on the top and then a laser or electron beam melts areas where required and fuses the powder to the underlining part. After one layer is completed, the bed moves down and another layer of powder is spread on top. The material unde...

We implemented the Mean-Field Homogenization (MFH) method inside a general-purposed commercial Finite-Element (FE) program. An incremental formulation is used for nonlinear composites. The algorithmic tangent computed for each constituent is used in the homogenization. We also developed a software tool to build Finite Element Representative Volume...

The impetus of additive manufacturing (AM) technology in the last few years is significant. However, in many cases the reliability of the technology leads to parts that suffer from manufacturing defects and hence subpar strength and fatigue life when compared to parts manufactured with conventional technologies. Sustained experimentation is often r...

In this work a fully explicit partitioned method for the simulation of Fluid-Structure Interaction (FSI) problems is presented. The fluid domain is modelled with an explicit Particle Finite Element Method (PFEM) based on the hypothesis of weak compressibility. The Lagrangian description of the fluid is particularly effective in the simulation of FS...

1. Abstract Metal Big Area Additive Manufacturing (mBAAM) is a new additive manufacturing (AM) technology for printing large-scale 3D objects. mBAAM is based on the gas metal arc welding process and uses a continuous feed of welding wire to manufacture an object. An electric arc forms between the wire and the substrate, which melts the wire and dep...

Although additive manufacturing was first developed in the 1980’s, the technology is mainly applied for prototyping and tooling. The printing process is not well understood and controlled to be confidently used for printing of load bearing parts. Due to the complex geometry and the layer by layer printing process, parts as printed may show distorti...

Despite their interest, multi-scale methods based on domain decomposition are rarely used or even implemented within legacy codes. The reason is that their implementation is very demanding and that the robustness of their performance in industrial applications is questionable. In order to try to overcome these limitations, we recently adapted to th...

Most materials have some complexity of structure at the nano or micro scale that influences their behavior at the continuum level. To enable continuum models to be built that capture this complexity it is necessary to bridge the gap between molecular scale models and the continuum. The approach is likely to be particularly helpful for simulations o...

This paper presents new developments on a weakly intrusive approach for the simplified implementation of space and time multiscale methods within an explicit dynamics software. The ‘substitution’ method proposed in previous works allows to take advantage of a global coarse model, typically used in an industrial context, running separate, refined in...

The design of spine implants requires a good understanding of spine kinematics and loading conditions. Realistic simulation of each functional spinal unit (FSU) requires capturing complicated contact and deformation of biological tissues in a computationally efficient manner. Specifically, the complexities include contacts in intervertebral and fac...

Due to the increasing usage of complex materials in lightweight design the development of proper material models for the prediction of damage and failure within Finite Element simulations has become an extensive task. Other fields of application already have shown that the introduction of Soft Computing and Machine Learning methods can be very bene...

This paper describes the modeling and validation of the new WorldSID 50th percentile male dummy (WorldSID50) model for the Abaqus finite element (FE) software suite [1]. The Abaqus WorldSID50 model has been developed by Dassault Systèmes Simulia Corp. in cooperation with the Partnership for Dummy Technology and Biomechanics (PDB), a consortium that...

The envelope theory provides a solid mathematical tool for accurate computations and design of milling tools that generate helical surfaces such as disk or end mill tools. Given an analytical description of the helical surface to be generated, and considering that the machined surface and milling tools are reciprocally enwrapping during the generat...

This paper presents a simplified algorithm for the profiling of the rack gear tool to generate the active profile associated with rolling centrodes. The algorithm is based on the enveloping surfaces principles and reduces the computational problem by proposing an approximate representation of tool’s profile using only three or four points on the pr...

Accurate simulation of anti-lock braking systems (ABS) requires detailed models of several subsystems in different physical domains. The most important subsystems are the hydraulic brake system, the tire and the control algorithm. The creation of detailed models of each subsystem in a single modeling tool may be difficult if not impossible. To over...

This paper describes how the Biofidelic Rear Impact Dummy (BioRID-II) has been developed as a testing tool to measure automotive seat and head restraint system performance in low-speed, rear-end crashes and to help with understanding of whiplash neck injuries. The paper focuses on the current Abaqus BioRID-II model which has been developed by Dassa...

Most of the existing methods for profile calculation of cutting tools that work by wrapping are based on the envelope theory (Litvin, 1989). The method requires cumbersome analytical formulations associated with the solution of equations not always easy to resolve. More recently, alternative methods for surface tool generation have been proposed in...

Dry frictional contact between two steel surfaces in a harmonically forced spring–mass system is investigated both experimentally and numerically. The experimental set-up is somewhat novel in that the spring–mass system is excited through the frictional interface, facilitating detailed study of interactions between the system's dynamic characterist...

In this work, a combined theoretical and numerical approach is taken to consider the dynamic behaviour and the thermomechanical interactions of systems in which friction has an important role. Emphasis is placed on the proper numerical description of fully coupled thermomechanical response on frictional interfaces. From a theoretical standpoint, th...

A number of methods exist for determining profiles of cutting tools that work by wrapping. Most of these methods are based on the envelope theory and almost inevitably require cumbersome analytical formulations not always easy to resolve. This work presents a new method for studying conjugated surfaces associated with rolling axodes. Originally dev...

Friction induced vibrations are often encountered both in everyday life (e.g., squealing brakes or doors) and in technological applications of interest (e.g., machine tool feed drives, bearings). Prediction of such effects in general circumstances requires rate dependence of the underlying friction model, as has been recognized by many researchers....

Machining of helical surfaces of constant pitch with tools bounded by surfaces of revolution is accompanied by generation errors due to imperfections of the effective cutting edge, relative positioning errors or kinematics of the machine tool. Therefore, the development of algorithms for the geometrical modelling of helical surfaces could be very u...

This paper proposes a rate-dependent constitutive model for the kinetic sliding of frictional interfaces. The model is presented in the context of a convected reference frame, which preserves frame indifference and is highly amenable to numerical implementation. The model features a state variable approach to the quantification of steady state slid...

This paper discusses a state- and rate-dependent frictional model and its implementation in large deformation finite elements. The model features a state variable to describe fading memory of slip history and a Perzyna viscoplastic regularization to quantify the frictional response to rapid slip changes. Some results in nonlinear dynamics for a sim...

In recent work, the augmented Lagrangian approach to large deformation frictional contact problems has been advocated for finite element calculations. The resulting algorithms have been shown to facilitate accurate constraint enforcement in a robust manner, while providing an effective technique for removal of the nonsymmetry associated with most f...

Typescript. Thesis (Ph. D.)--Duke University, 1996. Vita. Includes bibliographical references (leaves 173-181).