Shear localization in molecular crystal cyclotetramethylene-tetranitramine (β-HMX): Constitutive behavior of the shear band

The formation of shear localized chips in orthogonal machining of Ti-6Al-4V was investigated. The chips in different cutting velocities were collected and the structure of the adiabatic shear localization was examined by optical microscope and SEM after polishing and eroding. The serrated coefficient, serrated frequency and fibred coefficient were proposed in this paper to characterize the degree of serration and plastic shear flow of the chip quantitatively. Experimental results show that the width of the shear band decreased and the fibred coefficient of the shear band increased as cutting speed increased. The serrated and frequency, the serrated coefficient increased with the increase of cutting speed in the experimental range of cutting speeds.

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Analytical Modeling of Shear Localization in Orthogonal Cutting Processes

Journal of Manufacturing Science and Engineering ◽

10.1115/1.4051605 ◽

2021 ◽

pp. 1-45

Author(s):

Mohammadreza Fazlali ◽

Mauricio Ponga ◽

Xiaoliang Jin

Keyword(s):

Shear Band ◽

Orthogonal Cutting ◽

Shear Bands ◽

Chip Morphology ◽

High Strength ◽

Shear Localization ◽

Shear Band Formation ◽

Workpiece Material ◽

Band Formation ◽

Cutting Processes

Abstract This paper presents an analytical thermo-mechanical model of shear localization and shear band formation in orthogonal cutting of high-strength metallic alloys. The deformation process of the workpiece material includes three stages: homogeneous deformation, shear localization, and chip segmentation. A boundary layer analysis is used to analytically predict the temperature, stress, and strain rate variations in the primary shear zone associated with the shear localization. The predictions of shear band spacing and width from the proposed model are verified by experimental characterization of the chip morphology. The rolling of shear bands on the tool rake face is discussed from the experimental observations. The cutting tool temperature, which is influenced by the heat generated during the shear band formation, is simulated and compared with the finite element simulations. The proposed analytical model reveals the fundamental mechanism of the complete shear localization process in orthogonal cutting, and predicts the stress and temperature variations with high computational efficiency.

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Analysis of Shear Band Development in a Viscoplastic Double Slip, Single Crystal in Tension

Journal of Applied Mechanics ◽

10.1115/1.2896007 ◽

1995 ◽

Vol 62 (4) ◽

pp. 827-833 ◽

Cited By ~ 1

Author(s):

S. Yang ◽

C. Rey

Keyword(s):

Shear Band ◽

Single Crystal ◽

Shear Banding ◽

Rate Sensitivity ◽

Shear Localization ◽

Rigid Plastic ◽

Band Formation ◽

Linearized Stability ◽

Slow Progression ◽

Crystal Model

Using an idealized planar single crystal model undergoing symmetrical double slip in tension, the effect of rate sensitivity on shear band initiation and on shear band development is analysed. The behavior of the crystal is assumed to be rigid-viscoplastic. By analysing the kinematics and statics of shear banding, the deformation modes involving shear banding pattern are formulated. By a linearized stability analysis, the critical condition for shear band initiation is obtained. To study shear band development, the formulated constitutive equations are numerically solved, and the maximum value of the localized shear is predicted. The results show three different stages of shear band development. The first corresponds to a slow progression of shear localization in the band, the second to a rapid shear localization accompanied with an unloading of surrounding material, and the third to a resumption of deformation in the surrounding material and to a progressive saturation of the shear band. All three stages depend strongly on rate sensitivity, especially the first stage which does not exist in the rigid-plastic case. Even very small rate sensitivity can delay significantly or even preclude the shear band formation. Finally a discussion of the results illustrates how a macroscopic shear band forms and propagates.

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Adiabatic Shear Localization in High Speed Cutting of Hardened Steel

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.55-57.983 ◽

2011 ◽

Vol 55-57 ◽

pp. 983-987 ◽

Cited By ~ 1

Author(s):

Chun Zheng Duan ◽

Wei Sen Kong ◽

Zhao Xi Wang ◽

Min Jie Wang

Keyword(s):

Shear Band ◽

High Speed ◽

Adiabatic Shear Band ◽

Shear Bands ◽

Cutting Speed ◽

Shear Localization ◽

Adiabatic Shear ◽

Adiabatic Shear Bands ◽

High Speed Cutting ◽

Serrated Chips

The formation and development of adiabatic shear localization in serrated chips have great significance to study of mechanism of high speed cutting. This paper investigates the theory prediction and experimental verification of the critical cutting speed of adiabatic shear localization, distribution of adiabatic shear band in serrated chip and the geometry of adiabatic shear band during high speed cutting of hardened steel. The results indicated that the theoretical prediction of critical cutting speed is consistent with the experimental results.With the increase of cutting speed, the width and spacing of adiabatic shear bands in the serrated chips decrease linearly. There are two types of adiabatic shear bands during the formation and development of adiabatic shear localization, i.e. the deformation shear band and the transformed shear band.

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Advancing the use of Voronoi–Dirichlet polyhedra to describe interactions in organic molecular crystal structures by the example of galunisertib polymorphs

CrystEngComm ◽

10.1039/d0ce01535k ◽

2021 ◽

Author(s):

Viktor N. Serezhkin ◽

Anton V. Savchenkov

Keyword(s):

Crystal Structures ◽

Molecular Crystal ◽

Noncovalent Interactions ◽

Organic Molecular Crystal ◽

Universal Approach ◽

Structure Properties

The universal approach for studying structure/properties relationships shows that every polymorph of galunisertib is characterized with unique noncovalent interactions.

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