Subsurface Deformation in Surface Mechanical Attrition Processes

2015 ◽  
Author(s):  
Zhiyu Wang ◽  
Saurabh Basu ◽  
Christopher Saldana
Keyword(s):  
Strain Hardening ◽  
Model Material ◽  
Process Models ◽  
Image Correlation ◽  
Analytical Models ◽  
Subsurface Deformation ◽  
Multi Stage ◽  
Mechanical Attrition ◽  
Dead Metal Zone ◽  
Plane Strain Deformation

A modified expanding cavity model (M-ECM) is developed to describe subsurface deformation for strain-hardening materials loaded in unit deformation configurations occurring in surface mechanical attrition. The predictive results of this model are validated by comparison with unit deformation experiments in a model material, oxygen free high conductivity copper, using a custom designed plane strain deformation setup. Subsurface displacement and strain fields are characterized using in-situ digital image correlation. It is shown that conventional analytical models used to describe plastic response in strain-hardening metals are not able to predict important characteristics of the morphology of the plastic zone, including evolution of the dead metal zone (DMZ), especially at large plastic depths. The M-ECM developed in the present study provides an accurate prediction of the strain distribution obtained in experiment and is of utility as a component in multi-stage process models of the final surface state in surface mechanical attrition.

On the Difference of Subsurface Deformation Obtained by Image Correlation Technique From That of Plane Strain Deformation in Orthogonal Metal Cutting

2016 ◽  
Author(s):  
Dong Zhang ◽  
Xiao-Ming Zhang ◽  
Han Ding
Keyword(s):  
Plane Strain ◽  
Inclination Angle ◽  
Metal Cutting ◽  
Side Surface ◽  
Image Correlation ◽  
Subsurface Deformation ◽  
Plane Strain Deformation ◽  
Orthogonal Metal Cutting ◽  
Angle Method ◽  
Side Flow

Subsurface deformation in orthogonal metal cutting process is nowadays widely determined by image correlation techniques. To get clearer images of the cutting process, two methods were usually adopted to reduce workpiece material side flow in the literature. One is inducing a weak inclination angle of the cutting tool; the other is to restrict material side flow by a piece of thick glass. However, the differences between the subsurface deformation determined by observing the side surfaces in these two methods and that of plane strain deformation has not been studied yet. Therefore, this paper aims to study the differences of subsurface deformation obtained by these two methods quantitatively through numerical methods. It is found that the restrict side flow method surpasses the inducing an inclination angle method; inducing an inclination angle method will produce larger discrepancy than the side surface of typical orthogonal cutting which stands for observing the side surface directly. Besides, restrict material side flow method surpasses inducing an inclination angle method in the aspect of strain distribution across the width direction. To reduce the differences further, a new method called split-workpiece method based on the bonded-interface technique is proposed in this paper. To validate the effectiveness of this method, numerical comparisons between the subsurface deformation produced by the proposed method and that of the plane strain deformation are made. The results show that the subsurface deformation produced by the proposed method is much closer to that of plane strain deformation than the previous two methods.

scholarly journals Deformation heterogeneity and texture in surface severe plastic deformation of copper

2016 ◽  
Vol 472 (2187) ◽  
pp. 20150486 ◽  
Author(s):  
Saurabh Basu ◽  
Zhiyu Wang ◽  
Christopher Saldana
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
High Speed ◽  
Surface Deformation ◽  
Image Correlation ◽  
Surface Mechanical Attrition Treatment ◽  
Model Parameters ◽  
Texture Model ◽  
Mechanical Attrition ◽  
Deformation Mechanics

Comprehensive understanding of thermomechanical response and microstructure evolution during surface severe plastic deformation (S 2 PD) is important towards establishing controllable processing frameworks. In this study, the evolution of crystallographic textures during directional surface mechanical attrition treatment on copper was studied and modelled using the visco-plastic self-consistent framework. In situ high-speed imaging and digital image correlation of surface deformation in circular indentation were employed to elucidate mechanics occurring in a unit process deformation and to calibrate texture model parameters. Material response during directional surface mechanical attrition was simulated using a finite-element model coupled with the calibrated texture model. The crystallographic textures developed during S 2 PD were observed to be similar to those resultant from uniaxial compression. The implications of these results towards facilitating a processing-based framework to predict deformation mechanics and resulting crystallographic texture in S 2 PD configurations are briefly discussed.

Model-Based Coordination of Autonomous Vehicle Teams

2005 ◽  
Author(s):  
Cary Czichon ◽  
Robert W. Peterson ◽  
Erik Mettala ◽  
Jerry Speer ◽  
Jeff Stahl
Keyword(s):  
Autonomous Vehicle ◽  
Process Models ◽  
Behavior Modeling ◽  
Colored Petri Nets ◽  
Model Composition ◽  
Task List ◽  
Modeling Methodology ◽  
Multi Stage ◽  
Execution Environment ◽  
Robotic Vehicle

In order to coordinate autonomous robotic vehicle teams as they perform tactical tasks, a task formalism incorporating graphical (but mathematically rigorous) process models is being used. This extendable formalism, associated modeling methodology, and integrated modeling and execution environment are being developed by a U.S. Army funded SBIR project (RDECOM Contract N61339-04-C-0005). Colored Petri Nets (CPNs) provide the mathematical rigor needed for task and composite (ensemble) behavior modeling, while being conceptually elegant and easily displayed. Higher level task models can contain more fundamental models, allowing hierarchical model composition. Typed places within CPNs can hold tokens representing robotic equipment performing specific roles in a mission comprised of one or more tactical tasks. Army Tactical Tasks (ARTs) are defined within the Army Universal Task List (AUTL), FM 7-15. CPN mechanics support task synchronization and process simulation. CPN-based models can be enhanced to incorporate adaptive reasoning and dynamic/summative evaluation capabilities. In this SBIR project, executable task models are encapsulated by task agents operating within agent clusters. These clusters control virtual robotic vehicles (existing within constructive simulators like OneSAF) while multi-stage tactical missions are being performed.

Investigation of Size Effects on Process Models for Plane Strain Microbending

2006 ◽  
Author(s):  
Richard M. Onyancha ◽  
Brad L. Kinsey
Keyword(s):  
Size Effects ◽  
Strain Distribution ◽  
Past Research ◽  
Peak Force ◽  
Process Models ◽  
Analytical Models ◽  
Linear Strain ◽  
Bending Force ◽  
Bending Process ◽  
Individual Grains

Accurate process models provide vital information in the design of manufacturing processes. To characterize bending operations, analytical models have been developed and shown to predict the peak bending forces fairly accurately for sheets in the macro or mesoscale (i.e. sheets with a large number of grains through the thickness). However, whether these models also accurately predict bending forces for sheets in the microscale (i.e. sheets with approximately ten grains or less through the thickness) has not been evaluated. The present study is aimed at investigating the use of two such models from previous work with microscale bending data. In addition, using these previous models as a foundation, additional bending force models were developed to predict the bending force specifically for microscale bending operations. Data analysis showed that the process models from past research, which provide accurate results for macroscale bending, over predict the peak force required for bending microscale sheets. These process models assume a non-linear strain distribution through the thickness and a curved formed wall. The two models developed in this research provide accurate results for the microscale bending tests, however, they under predict the peak force for the macroscale bending operation. These developed process models assume a linear strain distribution through the thickness and a straight formed wall. The linear strain distribution is more appropriate for the microscale bending process as there are few grains through the thickness and the strain in individual grains varies linearly across the grain. The straight formed wall is more appropriate for the microscale bending process as there is not sufficient distance to warrant a curved formed wall assumption. These differences represent size effects for assumptions in the process models. The material used for these investigations was Brass (CuZn15). The sheets had between 2 and 50 grains through the thickness with grain sizes of between 10 μm and 71 μm.

THEORETICAL CARDIOLOGY: FROM MATHEMATICAL TO QUALITATIVE MODELS

1996 ◽  
Vol 04 (01) ◽  
pp. 131-150 ◽  
Author(s):  
P. SIREGAR
Keyword(s):  
Numerical Models ◽  
Analytical Models ◽  
Computational Framework ◽  
Cardiac Electrical Activity ◽  
Levels Of Detail ◽  
Multi Stage ◽  
Starting Point ◽  
Simplifying Assumptions ◽  
Qualitative Models ◽  
Predictive Role

A central concern in simulation studies is the adequation, or inadequation, of a designed model with respect to its intended goal. Models of cardiac electrical activity may differ in complexity, level of description and representation. Depending on the events to be be simulated, analytical, cellular automatas and qualitative models can be used. Their advantages and shortcomings can be put forth by comparing the space and time complexities, and if factors clinically relevant for studying arrhythmias and ischemias are taken into account in the respective models. In this paper, the factors under scrutiny are those characterizing impulse formation and conduction. If and how they are represented and computed constitutes a means of comparison between the models. The simplifying assumptions built into each can thus be put forth. Through illustrative examples, we then show that qualitative models can assume the explanatory and a predictive role usually devolved to numerical models. Such models can be used as a primer to quantification in a multi-stage process. A possibly useful development would be to integrate the analytical, cellular and qualitative models within a single computational framework. Central to this task is qualification. All piece of knowledge that is implicit in the mathematical or procedural representations has to be made explicit. Semantic links can thereafter be established between the models. This knowledge could be the starting point of a system emulating the reasoning of a theoretician working at different levels of detail. Its role would be to help researchers select, instantiate and interpret results of their most detailed cellular automata and/or analytical models.

Further Results on the Friction of Ploughing in the Presence of Bulk Straining

1991 ◽  
Vol 113 (4) ◽  
pp. 789-794 ◽  
Author(s):  
A. Azarkhin ◽  
O. Richmond
Keyword(s):  
Plane Strain ◽  
Frictional Stress ◽  
Subsurface Deformation ◽  
Plane Strain Deformation ◽  
The Mean

Algorithms developed by the authors in previous work (Azarkhin and Richmond, 1990; Azarkhin and Richmond, 1991) have been used here to model friction due to ploughing of rigid, adhesionless, fully embedded asperities through the surface of a material undergoing bulk plane strain deformation. It is shown that the mean frictional stress is influenced by the intensity of the subsurface deformation and by the size of the contacting area relative to asperity dimensions.

scholarly journals A new look at multi-stage models of cancer incidence

2018 ◽  
Author(s):  
Tyler Lian ◽  
Rick Durrett
Keyword(s):  
Branching Process ◽  
Probabilistic Approach ◽  
Process Models ◽  
Hyperbolic Partial Differential Equations ◽  
Main Method ◽  
Stage Models ◽  
Multi Stage ◽  
Cancer Initiation ◽  
Seer Data ◽  
The One

AbstractMulti-stage models have long been used in combination with SEER data to make inferences about the mechanisms underlying cancer initiation. The main method for studying these models mathematically has been the computation of generating functions by solving hyperbolic partial differential equations. Here, we analyze these models using a probabilistic approach similar to the one Durrett and Moseley [7] used to study branching process models of cancer. This more intuitive approach leads to simpler formulas and new insights into the behavior of these models. Unfortunately, the examples we consider suggest that fitting multi-stage models has very little power to make inferences about the number of stages unless parameters are constrained to take on realistic values.

scholarly journals Effect of Discontinuous Yielding on the Strain Hardening Behavior of Fine-Grained Twinning-Induced Plasticity Steel

2021 ◽  
Vol 8 ◽  
Author(s):  
Singon Kang ◽  
Sujin Jeong ◽  
Yeon-Sang Ahn
Keyword(s):  
Strain Hardening ◽  
Tensile Deformation ◽  
Early Stage ◽  
Image Correlation ◽  
Localized Deformation ◽  
Fine Grained ◽  
Cooling Conditions ◽  
Strain Hardening Behavior ◽  
Strain Hardening Rate

The yielding of a high Mn twinning-induced plasticity steel was examined in three fine-grained specimens recrystallized at 700°C for 5 min with different cooling conditions. While the stress-strain curves of furnace-cooled and air-cooled specimens exhibit a stress drop at yielding, the drop was not observed in the water-quenched specimen. A simple analysis of the displacement data indicates the occurrence of localized deformation at the beginning of the plastic deformation in the three tensile specimens with different cooling conditions. The localized deformation of all three specimens was confirmed as Lüders strain by digital image correlation (DIC) analysis. Based on this observation, the role of yielding behavior on the strain hardening rate evolution at an early stage of the tensile deformation was discussed.

A full-range stress-strain model for metallic materials depicting non-linear strain-hardening behavior

2020 ◽  
pp. 030932472095779
Author(s):  
Digendranath Swain ◽  
S Karthigai Selvan ◽  
Binu P Thomas ◽  
Ahmedul K Asraff ◽  
Jeby Philip
Keyword(s):  
Constitutive Model ◽  
Strain Hardening ◽  
Image Correlation ◽  
Linear Strain ◽  
Stress Strain ◽  
Material Parameters ◽  
Hardening Behavior ◽  
Non Linear ◽  
Strain Hardening Behavior ◽  
Strain Model

Ramberg-Osgood (R-O) type stress-strain models are commonly employed during elasto-plastic analysis of metals. Recently, 2-stage and 3-stage R-O variant models have been proposed to replicate stress-strain behavior under large plastic deformation. The complexity of these models increases with the addition of each stage. Moreover, these models have considered deformation till necking only. In this paper, a simplistic multi-stage constitutive model is proposed to capture the strain-hardening non-linearity shown by metals including its post necking behavior. The constitutive parameters of the proposed stress-strain model can be determined using only elastic modulus and yield strength. 3-D digital image correlation was used as an experimental tool for measuring full-field strains on the specimens, which were subsequently utilized to obtain the material parameters. Our constitutive model is demonstrated with an aerospace-grade stainless steel AISI 321 wherein deformation response averaged over the gauge length (GL) and at a local necking zone are compared. The resulting averaged and local material parameters obtained from the proposed model provide interesting insights into the pre and post necking deformation behavior. Our constitutive model would be useful for characterizing highly ductile metals which may or may not depict non-linear strain hardening behavior including their post necking deformations.

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