scholarly journals In-SEM micro-machining reveals the origins of the size effect in the cutting energy

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Bentejui Medina-Clavijo ◽  
Gorka Ortiz-de-Zarate ◽  
Andres Sela ◽  
Iñaki M. Arrieta ◽  
Aleksandr Fedorets ◽  
...  
Keyword(s):  
Size Effect ◽  
Shear Zone ◽  
Metal Cutting ◽  
Force Measurement ◽  
Shear Zones ◽  
Deep Submicron ◽  
Orientation Measurement ◽  
Cutting Energy ◽  
In Operando ◽  
Geometrical Factors

AbstractHigh-precision metal cutting is increasingly relevant in advanced applications. Such precision normally requires a cutting feed in the micron or even sub-micron dimension scale, which raises questions about applicability of concepts developed in industrial scale machining. To address this challenge, we have developed a device to perform linear cutting with force measurement in the vacuum chamber of an electron microscope, which has been utilised to study the cutting process down to 200 nm of the feed and the tool tip radius. The machining experiments carried out in-operando in SEM have shown that the main classical deformation zones of metal cutting: primary, secondary and tertiary shear zones—were preserved even at sub-micron feeds. In-operando observations and subsequent structural analysis in FIB/SEM revealed a number of microstructural peculiarities, such as: a substantial increase of the cutting force related to the development of the primary shear zone; dependence of the ternary shear zone thickness on the underlaying grain crystal orientation. Measurement of the cutting forces at deep submicron feeds and cutting tool apex radii has been exploited to discriminate different sources for the size effect on the cutting energy (dependence of the energy on the feed and tool radius). It was observed that typical industrial values of feed and tool radius imposes a size effect determined primarily by geometrical factors, while in a sub-micrometre feed range the contribution of the strain hardening in the primary share zone becomes relevant.

Shear-Zone Size, Compressive Stress, and Shear Strain in Metal-Cutting and Their Effects on Mean Shear-Flow Stress

1960 ◽  
Vol 82 (1) ◽  
pp. 79-86 ◽  
Author(s):  
Dimitri Kececioglu
Keyword(s):  
Flow Stress ◽  
Shear Flow ◽  
Size Effect ◽  
Shear Strain ◽  
Shear Zone ◽  
Compressive Stress ◽  
Metal Cutting ◽  
Zone Size ◽  
Wide Range ◽  
Shear Flow Stress

A relationship for the calculation of the shear-zone size is given. The shear-zone size, when machining SAE 1015, 118-Bhn seamless steel tubing under a wide range of cutting conditions, is found to vary from 0.95 × 10−6 in.3 to 61.5 × 10−6 in.3 The mean shear-flow stress is found to increase significantly with a decrease in the shear-zone size and with an increase in the compressive stress in the shear zone. It is concluded that the only size effect in metal-cutting is the shear-zone size effect, and that no separate depth-of-cut size effect should be sought. An apparent decrease in the shear-flow stress with an increase in the true, mean shear strain in the shear zone is observed, and this behavior is explained.

Influence of Free Surface Environment on the Shear Zone in Metal Cutting

1966 ◽  
Vol 181 (1) ◽  
pp. 687-705 ◽  
Author(s):  
P. L. Barlow
Keyword(s):  
Free Surface ◽  
Carbon Tetrachloride ◽  
Strain Hardening ◽  
Shear Zone ◽  
Chemical Reaction ◽  
Cutting Forces ◽  
Metal Cutting ◽  
The Body ◽  
Surface Barrier ◽  
Rehbinder Effect

It has previously been suggested that the reduction in cutting forces obtained by the presence of fluids such as CCl4 on the backface or free surface of the forming chip was due to diffusion of the fluid into the body of the chip in the region of the shear zone. In the present work, experiments with carbon tetrachloride tagged with carbon-14 and with carbon tetrachloride tagged with chlorine-36 were performed with the object of assessing the extent of diffusion of lubricants into the chip when present on the free surface only. The results obtained disprove former hypotheses and suggest that the reduced cutting force is due solely to chemical reaction at the surface of the chip. Confirmation of the sensitivity of the surface of the deforming shear zone to change in surface condition was obtained by removing metal from this region by an electropolishing technique during slow speed cutting. By varying the electropolishing conditions increased or decreased cutting forces could be obtained. It is proposed that the result both of chemical reaction at the surface and of surface removal is to reduce the strain-hardening rate of the metal undergoing shear by reducing the surface barrier to the flow of dislocations out of the metal. The association of the surface reaction of carbon tetrachloride with a change in the strain-hardening characteristics of the metal in the shear zone leads to a classification of the backface phenomenon as a Rehbinder effect and enables this effect to be more closely defined than was hitherto possible. Evidence is also presented which indicates that the backface effect does not contribute to the reduction in cutting forces during rakeface lubrication and is therefore unimportant in practice where flood lubrication of the cutting region invariably occurs.

scholarly journals The Dabie Extensional Tectonic System: Structural Framework

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Quanlin Hou ◽  
Hongyuan Zhang ◽  
Qing Liu ◽  
Jun Li ◽  
Yudong Wu
Keyword(s):  
Shear Zone ◽  
Shear Zones ◽  
Ultrahigh Pressure ◽  
Metamorphic Complex ◽  
The South ◽  
Magma Intrusion ◽  
The North ◽  
Extensional Tectonic ◽  
Mechanism Transition ◽  
Tectonic System

A previous study of the Dabie area has been supposed that a strong extensional event happened between the Yangtze and North China blocks. The entire extensional system is divided into the Northern Dabie metamorphic complex belt and the south extensional tectonic System according to geological and geochemical characteristics in our study. The Xiaotian-Mozitan shear zone in the north boundary of the north system is a thrust detachment, showing upper block sliding to the NNE, with a displacement of more than 56 km. However, in the south system, the shearing direction along the Shuihou-Wuhe and Taihu-Mamiao shear zones is tending towards SSE, whereas that along the Susong-Qingshuihe shear zone tending towards SW, with a displacement of about 12 km. Flinn index results of both the north and south extensional systems indicate that there is a shear mechanism transition from pure to simple, implying that the extensional event in the south tectonic system could be related to a magma intrusion in the Northern Dabie metamorphic complex belt. Two 40Ar-39Ar ages of mylonite rocks in the above mentioned shear zones yielded, separately, ~190 Ma and ~124 Ma, referring to a cooling age of ultrahigh-pressure rocks and an extensional era later.

Effect of kinematics of orogenic wedge on kinematic evolutionary paths and deformation profiles of major shear zones: An example from the eastern Himalaya 

2021 ◽  
Author(s):  
Pritam Ghosh ◽  
Kathakali Bhattacharyya
Keyword(s):  
Shear Zone ◽  
Strain Softening ◽  
Leading Edge ◽  
Shear Zones ◽  
Deformation History ◽  
Progressive Deformation ◽  
Trailing Edge ◽  
Orogenic Wedge ◽  
Transport Direction ◽  
Evolutionary Paths

<p>We examine how the deformation profile and kinematic evolutionary paths of two major shear zones with prolonged deformation history and large translations differ with varying structural positions along its transport direction in an orogenic wedge. We conduct this analysis on multiple exposures of the internal thrusts from the Sikkim Himalayan fold thrust belt, the Pelling-Munsiari thrust (PT), the roof thrust of the Lesser Himalayan duplex (LHD), and the overlying Main Central thrust (MCT). These two thrusts are regionally folded due to growth of the LHD and are exposed at different structural positions. The hinterlandmost exposures of the MCT and PT zones lie in the trailing parts of the duplex, while the foreland-most exposures of the same studied shear zones lie in the leading part of the duplex, and thus have recorded a greater connectivity with the duplex. The thicknesses of the shear zones progressively decrease toward the leading edge indicating variation in deformation conditions. Thickness-displacement plot reveals strain-softening from all the five studied MCT and the PT mylonite zones. However, the strain-softening mechanisms varied along its transport direction with the hinterland exposures recording dominantly dislocation-creep, while dissolution-creep and reaction-softening are dominant in the forelandmost exposures. Based on overburden estimation, the loss of overburden on the MCT and the PT zones is more in the leading edge (~26km and ~15km, respectively) than in the trailing edge (~10km and ~17km, respectively), during progressive deformation. Based on recalibrated recrystallized quartz grain thermometer (Law, 2014), the estimated deformation temperatures in the trailing edge are higher (~450-650°C) than in the leading edge (350-550°C) of the shear zones. This variation in the deformation conditions is also reflected in the shallow-crustal deformation structures with higher fracture intensity and lower spacing in the leading edge exposures of the shear zones as compared to the trailing edge exposures.</p><p>The proportion of mylonitic domains and micaceous minerals within the exposed shear zones increase and grain-size of the constituent minerals decreases progressively along the transport direction. This is also consistent with progressive increase in mean R<sub>s</sub>-values toward leading edge exposures of the same shear zones. Additionally, the α-value (stretch ratio) gradually increases toward the foreland-most exposures along with increasing angular shear strain. Vorticity estimates from multiple incremental strain markers indicate that the MCT and PT zones generally record a decelerating strain path. Therefore, the results from this study are counterintuitive to the general observation of a direct relationship between higher Rs-value and higher pure-shear component. We explain this observation in the context of the larger kinematics of the orogen, where the leading edge exposures have passed through the duplex structure, recording the greatest connectivity and most complete deformation history, resulting in the weakest shear zone that is also reflected in the deformation profiles and strain attributes. This study demonstrates that the same shear zone records varying deformation profile, strain and kinematic evolutionary paths due to varying deformation conditions and varying connectivity to the underlying footwall structures during progressive deformation of an orogenic wedge.</p>

Comment on “Miocene to Quaternary tectonostratigraphic evolution of the middle section of the Burdur-Fethiye Shear Zone, south-western Turkey: Implications for the wide inter-plate shear zones. Tectonophysics 690, 336–354”

2018 ◽  
Vol 722 ◽  
pp. 595-600 ◽  
Author(s):  
M. Cihat Alçiçek ◽  
Lars W. van den Hoek Ostende ◽  
Gerçek Saraç ◽  
Alexey S. Tesakov ◽  
Alison M. Murray ◽  
...  
Keyword(s):  
Shear Zone ◽  
Shear Zones ◽  
Middle Section ◽  
Western Turkey

scholarly journals The internal structure and composition of a plate boundary-scale serpentinite shear zone: The Livingstone Fault, New Zealand

2019 ◽  
Author(s):  
Matthew S. Tarling ◽  
Steven A. F. Smith ◽  
James M. Scott ◽  
Jeremy S. Rooney ◽  
Cecilia Viti ◽  
...  
Keyword(s):  
New Zealand ◽  
Internal Structure ◽  
Shear Zone ◽  
Plate Boundary ◽  
Shear Zones ◽  
East Side ◽  
Local Dispersion ◽  
Fine Grained ◽  
Shear Sense ◽  
Tectonic Settings

Abstract. Deciphering the internal structural and composition of large serpentinite-dominated shear zones will lead to an improved understanding of the rheology of the lithosphere in a range of tectonic settings. The Livingstone Fault in New Zealand is a > 1000 km long terrane-bounding structure that separates the basal portions (peridotite; serpentinised peridotite; metagabbros) of the Dun Mountain Ophiolite Belt from quartzofeldspathic schists of the Caples or Aspiring Terranes. Field and microstructural observations from eleven localities along a strike length of c. 140 km show that the Livingstone Fault is a steeply-dipping, serpentinite-dominated shear zone tens to several hundreds of metres wide. The bulk shear zone has a pervasive scaly fabric that wraps around fractured and faulted pods of massive serpentinite, rodingite and partially metasomatised quartzofeldspathic schist up to a few tens of metres long. S-C fabrics and lineations in the shear zone consistently indicate a steep Caples-side-up (i.e. east-side-up) shear sense, with significant local dispersion in kinematics where the shear zone fabrics wrap around pods. The scaly fabric is dominated (> 98 vol %) by fine-grained (≪ 10 μm) fibrous chrysotile and lizardite/polygonal serpentine, but infrequent (

scholarly journals Kinematics and Timing Constraints in a Transpressive Tectonic Regime: The Example of the Posada-Asinara Shear Zone (NE Sardinia, Italy)

Geosciences ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 288
Author(s):  
Rodolfo Carosi ◽  
Alessandro Petroccia ◽  
Salvatore Iaccarino ◽  
Matteo Simonetti ◽  
Antonio Langone ◽  
...  
Keyword(s):  
Shear Zone ◽  
Finite Strain ◽  
Pure Shear ◽  
Deformation Gradient ◽  
Shear Zones ◽  
Temperature Deformation ◽  
Timing Constraints ◽  
Important Variation ◽  
Deformation Phase ◽  
First Time

Detailed geological field mapping, integrated with meso- and microstructural investigations, kinematic of the flow and finite strain analyses, combined with geochronology, are fundamental tools to obtain information on the temperature–deformation–timing path of crystalline rocks and shear zone. The Posada-Asinara shear zone (PASZ) in northern Sardinia (Italy) is a steeply dipping km-thick transpressive shear zone. In the study area, located in the Baronie region (NE Sardinia), the presence of mylonites within the PASZ, affecting high- and medium-grade metamorphic rocks, provides an opportunity to quantify finite strain and kinematic vorticity. The main structures of the study area are controlled by a D2 deformation phase, linked to the PASZ activity, in which the strain is partitioned into folds and shear zone domains. Applying two independent vorticity methods, we detected an important variation in the percentage of pure shear and simple shear along the deformation gradient, that increases from south to north. We constrained, for the first time in this sector, the timing of the transpressive deformation by U–(Th)–Pb analysis on monazite. Results indicate that the shear zone has been active at ~325–300 Ma in a transpressive setting, in agreement with the ages of the other dextral transpressive shear zones in the southern Variscan belt.

Macro- and microstructural analysis of the Zhujiafang ductile shear zone, Hengshan Complex: Tectonic nature and geodynamic implications of the evolution of Trans−North China orogen

2020 ◽  
Author(s):  
Lingchao He ◽  
Jian Zhang ◽  
Guochun Zhao ◽  
Changqing Yin ◽  
Jiahui Qian ◽  
...  
Keyword(s):  
Shear Zone ◽  
North China ◽  
Shear Zones ◽  
Crustal Thickening ◽  
Slip Systems ◽  
High Grade ◽  
Ductile Shear Zone ◽  
Crustal Rocks ◽  
Ductile Shear ◽  
Lower Crustal

In worldwide orogenic belts, crustal-scale ductile shear zones are important tectonic channels along which the orogenic root (i.e., high-grade metamorphic lower-crustal rocks) commonly experienced a relatively quick exhumation or uplift process. However, their tectonic nature and geodynamic processes are poorly constrained. In the Trans−North China orogen, the crustal-scale Zhujiafang ductile shear zone represents a major tectonic boundary separating the upper and lower crusts of the orogen. Its tectonic nature, structural features, and timing provide vital information into understanding this issue. Detailed field observations showed that the Zhujiafang ductile shear zone experienced polyphase deformation. Variable macro- and microscopic kinematic indicators are extensively preserved in the highly sheared tonalite-trondhjemite-granodiorite (TTG) and supracrustal rock assemblages and indicate an obvious dextral strike-slip and dip-slip sense of shear. Electron backscattered diffraction (EBSD) was utilized to further determine the crystallographic preferred orientation (CPO) of typical rock-forming minerals, including hornblende, quartz, and feldspar. EBSD results indicate that the hornblendes are characterized by (100) <001> and (110) <001> slip systems, whereas quartz grains are dominated by prism <a> and prism <c> slip systems, suggesting an approximate shear condition of 650−700 °C. This result is consistent with traditional thermobarometry pressure-temperature calculations implemented on the same mineral assemblages. Combined with previously reported metamorphic data in the Trans−North China orogen, we suggest that the Zhujiafang supracrustal rocks were initially buried down to ∼30 km depth, where high differential stress triggered the large-scale ductile shear between the upper and lower crusts. The high-grade lower-crustal rocks were consequently exhumed upwards along the shear zone, synchronous with extensive isothermal decompression metamorphism. The timing of peak collision-related crustal thickening was further constrained by the ca. 1930 Ma metamorphic zircon ages, whereas a subsequent exhumation event was manifested by ca. 1860 Ma syntectonic granitic veins and the available Ar-Ar ages of the region. The Zhujiafang ductile shear zone thus essentially record an integrated geodynamic process of initial collision, crustal thickening, and exhumation involved in formation of the Trans−North China orogen at 1.9−1.8 Ga.

scholarly journals Eburnean deformation pattern of Burkina Faso and the tectonic significance of shear zones in the West African craton

2020 ◽  
Vol 191 ◽  
pp. 2 ◽  
Author(s):  
Dominique Chardon ◽  
Ousmane Bamba ◽  
Kalidou Traoré
Keyword(s):  
Burkina Faso ◽  
Shear Zone ◽  
Regional Scale ◽  
Kinematic Model ◽  
Shear Zones ◽  
West African ◽  
Deformation Pattern ◽  
The West ◽  
West African Craton ◽  
Regional Flow

Shear zones of the Paleoproterozoic Eburnean accretionary Orogen (West African craton) are investigated by means of large-scale structural mapping. Regional scale (10-100 km) mapping was based on the aeromagnetic survey of Burkina Faso and craton-scale (1000 km) mapping on a compilation of fabric data. At both scales, shear zones are arranged as an anastomosed transpressional network that accommodated distributed shortening and lateral flow of the orogenic lithosphere between the converging Kénéma-Man and Congo Archean provinces. Structural interference patterns at both scales were due to three-dimensional partitioning of progressive transpressional deformation and interactions among shear zones that absorbed heterogeneities in the regional flow patterns while maintaining the connectivity of the shear zone network. Such orogen-scale kinematic patterns call for caution in using the deformation phase approach without considering the “bigger structural picture” and interpreting displacement history of individual shear zones in terms of plate kinematics. The West African shear zone pattern is linked to that of the Guiana shield through a new transatlantic correlation to produce an integrated kinematic model of the Eburnean-Transamazonian orogen.

Sign in / Sign up

Export Citation Format

Share Document