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Dissertation

Process Modeling of Micro-Cutting Including Strain Gradient Effects

15 Nov 2005-
About: The article was published on 2005-11-15 and is currently open access. It has received 27 citations till now. The article focuses on the topics: Process modeling & Finite element method.

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Citations
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Journal ArticleDOI
TL;DR: In this paper, a strain gradient plasticity-based finite element model of orthogonal micro-cutting of Al5083-H116 alloy developed recently is used to examine fundamentally the influence of tool edge radius on size effect.

172 citations

Journal ArticleDOI
TL;DR: In this paper, the authors examined the material strengthening effect where the material strength increases nonlinearly as the uncut chip thickness is reduced to a few microns and analyzed the contribution of the decrease in the secondary deformation zone cutting temperature and strain gradient strengthening, and their relative contributions to the increase in specific cutting energy.
Abstract: The specific cutting energy in machining is known to increase nonlinearly with decrease in uncut chip thickness. It has been reported in the literature that this phenomenon is dependent on several factors such as material strengthening, ploughing due to finite edge radius, and material separation effects. This paper examines the material strengthening effect where the material strength increases nonlinearly as the uncut chip thickness is reduced to a few microns. This increase in strength has been attributed in the past to various factors such as strain rate, strain gradient, and temperature effects. Given that the increase in material strength can occur due to many factors, it is important to understand the contributions of each factor to the increase in specific cutting energy and the conditions under which they are dominant. This paper analyzes two material strengthening factors, (i) the contribution of the decrease in the secondary deformation zone cutting temperature and (ii) strain gradient strengthening, and their relative contributions to the increase in specific cutting energy as the uncut chip thickness is reduced. Finite element (FE)-based orthogonal cutting simulations are performed with Aluminum 5083-H116, a work material with a small strain rate hardening exponent, thus minimizing strain rate effects. Suitable cutting conditions are identified under which the temperature and strain gradient effects are dominant. Orthogonal cutting experiments are used to validate the model in terms of cutting forces. The simulation results are then analyzed to identify the contributions of the material strengthening factors to the size effect in specific cutting energy.

100 citations

Journal ArticleDOI
TL;DR: Subbiah et al. as discussed by the authors investigated the effect of finite edge radius on ductile fracture by performing a series of experiments with inserts of different edge radii at various uncut chip thickness values ranging from 15 to 105μm.
Abstract: Evidence of ductile fracture leading to material separation has been reported recently in ductile metal cutting [S. Subbiah, S.N. Melkote, ASME J. Manuf. Sci. Eng. 28(3) (2006)]. This paper investigates the effect of finite edge radius on such ductile fracture. The basic question of whether such ductile fracture occurs in the presence of a finite edge radius is explored by performing a series of experiments with inserts of different edge radii at various uncut chip thickness values ranging from 15 to 105 μm. Chip–roots are obtained in these experiments using a quick-stop device and examined in a scanning electron microscope. Clear evidence of material separation is seen at the interface zone between the chip and machined surface even when the edge radius is large compared to the uncut chip thickness. Failure is seen to occur at the upper, middle, and/or the lower edges of the interface zone. Based on these observations, a hypothesis is presented for the events leading to the occurrence of this failure when cutting with an edge radius tool. Finite element simulations are performed to study the nature of stress state ahead of the tool edge with and without edge radius. Hydrostatic stress is seen to be tensile in front of the tool and hence favors the occurrence of ductile fracture leading to material separation. The stress components are, however lower than those seen with a sharp tool.

82 citations


Cites background from "Process Modeling of Micro-Cutting I..."

  • ...Other researchers have also used similar remeshing concepts to simulate chip flow around the tool edge [23, 24]....

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Journal ArticleDOI
TL;DR: In this article, a comprehensive review of literature on modeling and simulation that enhances the understanding of the process physics of the rapidly growing field of mechanical micro-machining is provided, focusing on a number of micro-scale machining issues such as size effect, minimum chip thickness effect, micro-structure effects and cutting tool dynamics which influence the underlying cutting mechanisms and the generated surface finish.
Abstract: This article provides a comprehensive review of literature on modeling and simulation that enhances the understanding of the process physics of the rapidly growing field of mechanical micro-machining. The article focuses on a number of micro-scale machining issues such as size effect, minimum chip thickness effect, micro-structure effects, and cutting tool dynamics which influence the underlying cutting mechanisms and the generated surface finish. We review the recent advances in modeling and simulation techniques, which include molecular dynamics simulation, finite element method, the newly emerging field of multi-scale simulation and mechanistic modeling. Some comments to emphasize the future requirements and directions of the modeling and simulation efforts in this field are also offered.

54 citations


Cites background or methods from "Process Modeling of Micro-Cutting I..."

  • ...With recent advances in hardware and software, an arbitrary Lagrangian–Eulerian formulation, which is a finite element formulation that lies between the pure Eulerian formulation and the pure Lagrangian formulation, is used by most of the major software packages such as ABAQUS R ©, DEFORM R © for modeling material removal processes (Liu, 2005)....

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  • ...…an arbitrary Lagrangian–Eulerian formulation, which is a finite element formulation that lies between the pure Eulerian formulation and the pure Lagrangian formulation, is used by most of the major software packages such as ABAQUS R©, DEFORM R© for modeling material removal processes (Liu, 2005)....

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  • ...Liu et al. (2004) described that many commonly used materials such as steels do not behave in a homogeneous manner when considered at the micro-scales used in the micromachining processes....

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Journal ArticleDOI
TL;DR: The literature is filled with works done by researchers working in this domain this paper, and a significant contribution comes from the works which have been published during the period 1998-2014, which have primarily been on conventional and non-conventional micromachining techniques.
Abstract: The concept of miniaturizing machine tools has received a strong interest in the research community due to their ability to fabricate intricate components. Lower power consumption, higher productivity rate, and smaller sizes of work stations have enabled microscale machining operations to acquire an edge over other fabrication techniques in various applications such as aerospace, instrumentation, automotive, biomedical, etc. The literature is filled with works done by researchers working in this domain. A significant contribution comes from the works which have been published during the period 1998–2014. The focus of these studies has primarily been on conventional and nonconventional micromachining techniques. Since nonconventional machining operations such as microelectrical discharge machining, laser machining, etc., are not compatible with traditional workpiece materials, conventional micromachining techniques such as micromilling and microdrilling are generally used. However, as of today, the...

50 citations


Cites methods from "Process Modeling of Micro-Cutting I..."

  • ...Since this technique makes use of the interatomic forces arising between atoms at the boundary, MD simulations necessitate the use of software with high computational accuracy [180]....

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  • ...However, certain software such as ABAQUS(1) makes use of mixed models like Lagrangian–Eulerian formulation for modeling material removal rate [180]....

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References
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Journal ArticleDOI
TL;DR: In this article, the indentation size effect for crystalline materials can be accurately modeled using the concept of geometrically necessary dislocations, which leads to the following characteristic form for the depth dependence of the hardness: H H 0 1+ h ∗ h where H is the hardness for a given depth of indentation, h, H 0 is a characteristic length that depends on the shape of the indenter, the shear modulus and H 0.
Abstract: We show that the indentation size effect for crystalline materials can be accurately modeled using the concept of geometrically necessary dislocations. The model leads to the following characteristic form for the depth dependence of the hardness: H H 0 1+ h ∗ h where H is the hardness for a given depth of indentation, h, H0 is the hardness in the limit of infinite depth and h ∗ is a characteristic length that depends on the shape of the indenter, the shear modulus and H0. Indentation experiments on annealed (111) copper single crystals and cold worked polycrystalline copper show that this relation is well-obeyed. We also show that this relation describes the indentation size effect observed for single crystals of silver. We use this model to derive the following law for strain gradient plasticity: ( σ σ 0 ) 2 = 1 + l χ , where σ is the effective flow stress in the presence of a gradient, σ0 is the flow stress in the absence of a gradient, χ is the effective strain gradient and l a characteristic material length scale, which is, in turn, related to the flow stress of the material in the absence of a strain gradient, l ≈ b( μ σ 0 ) 2 . For materials characterized by the power law σ 0 = σ ref e 1 n , the above law can be recast in a form with a strain-independent material length scale l. ( builtσ σ ref ) 2 = e 2 n + l χ l = b( μ σ ref ) 2 = l ( σ 0 σ ref ) 2 . This law resembles the phenomenological law developed by Fleck and Hutchinson, with their phenomenological length scale interpreted in terms of measurable material parametersbl].

3,655 citations

Journal ArticleDOI
TL;DR: In this paper, a deformation theory of plasticity is introduced to represent in a phenomenological manner the relative roles of strain hardening and strain gradient hardening, which is a non-linear generalization of Cosserat couple stress theory.
Abstract: Dislocation theory is used to invoke a strain gradient theory of rate independent plasticity. Hardening is assumed to result from the accumulation of both randomly stored and geometrically necessary dislocation. The density of the geometrically necessary dislocations scales with the gradient of plastic strain. A deformation theory of plasticity is introduced to represent in a phenomenological manner the relative roles of strain hardening and strain gradient hardening. The theory is a non-linear generalization of Cosserat couple stress theory. Tension and torsion experiments on thin copper wires confirm the presence of strain gradient hardening. The experiments are interpreted in the light of the new theory.

3,266 citations

Journal ArticleDOI
TL;DR: HAL as discussed by the authors is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not, which may come from teaching and research institutions in France or abroad, or from public or private research centers.
Abstract: HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Elastic materials with couple-stresses R. Toupin

2,574 citations