Development Of Deformation Bands Research Articles

How pressure-solution enables the development of deformation bands in low-porosity rocks

Occurrence of deformation bands developing with various orientations in a low-porosity bioclastic calcarenite in the Cotiella Massif (Spanish Pyrenees), questions about the mechanism responsible for their generation in low-porosity carbonates. Our work is based on the combination of a 2D and 3D petrographic and microstructural study, using electron backscattering diffraction microscopy and X-ray microtomography, with a diagenetic study, using cathodoluminescence microscopy and scanning electron microscopy images. Diagenetic and petrographic observations indicate early cementation, which led to significant porosity reduction prior to a sequence of deformation processes comprising the development of tectonic stylolites around which deformation bands eventually formed. Along the latter, quartz grains appear fractured with high strain patterns, showing a different appearance compared to the quartz along the stylolite. Moreover, the ratio of carbonate matrix versus quartz grains shows distinctive variations throughout the different stages of deformation. Based on these observations, we propose a conceptual model for the genesis of deformation bands in low-porosity rocks, accounting for the preferential dissolution of calcite with respect to quartz grains along the stylolite plane that resulted in local porosity development in between quartz grains. Consequently, quartz aggregation led to the classical deformation band mechanism of strain accumulation and breakage.

Development of Deformation Bands and Deformation Induced Weathering in a Forearc Coal-Bearing Paleogene Fold Belt, Northern Japan

We conducted microstructural and microchemical analyses of deformation bands in a forearc fold belt consisting of the Eocene Urahoro Group located in northern Japan. In the study area, there was one flexure (or monocline) developed where deformation bands pervasively occurred in arkosic sandstone intercalated with mudstone and coal layers. Deformation bands formed at the maximum burial depth of c. 1.5–2.5 km; this was inferred from both the thickness of the overlying strata and vitrinite reflectance values (%RO) of the coal layers (c. 0.5). These bands were inferred to have originated as phyllosilicate bands, which developed into cataclastic bands with increasing strain on sandstones with up to c. 10% volume of phyllosilicate. In the cataclastic bands, the detrital grains in the host parts were crushed into sizes less than one-half to one-fifth of the original ones, and the long axis of the fractured grains tended to align parallel to the deformation bands. It was found that the deformation bands became a site of intense weathering at later stages, where not only detrital biotite grains were altered to vermiculite and kaolinite, but also authigenic clay minerals such as smectite grew in pore spaces created by the fracturing of detrital grains.

Factors affecting the development of deformation bands in the Nubian Sandstone, Central Eastern Desert, Egypt

Reservoir quality prediction is a key element in petroleum exploration and investigation of reservoir potential. The Nubian Sandstone reservoir in Egypt has excellent potential for hydrocarbon production. However, many deformation bands of different scales were rerecorded regionally and have a substantial influence on the porosity and permeability of the Nubian Sandstone Unit. Therefore, the effects of these deformation bands need to be quantified. Samples from the Cretaceous succession along the Qift-El-Qusier road were petrographically and petrophysically studied. Three sets of deformation bands trending in a NE-SW direction were identified during mapping. The host sandstone unit is quartz arenite where is composed mainly of quartz. A significant petrographic difference in grain size was noticed, where deformation bands have smaller grain sizes. Two lithological facies were recognized based on the mineralogy, grain size, sorting, and porosity. Facies 1 is coarse-grained, well sorted and with high porosity characteristics, where deformation bands dominated.On the other hand, Facies 2 with fine grains, well sorting and low porosity possesses deformation bands with a lower degree of cataclasis. The deformation bands have negatively impacted the porosity and permeability of the sandstone. The porosity in the Nubian Sandstone ranges from 24.3 to 29.7%, which is reduced from 9.6 to 17.1% in plugs containing the deformation bands. A similar trend for permeability was also found, where permeability is tremendously reduced from 1200 to 8400 mD in the host sandstone to 0.08–0.3 mD in deformation bands.

Mechanical stratigraphy influences deformation band pattern in arkosic sandstones, Rio do Peixe Basin, Brazil

This study shows how mechanical stratigraphy influences deformation bands' structural attributes in faulted, heterolithic arkosic sandstones in the Rio do Peixe Basin, northeastern Brazil. We combined the analyses of sedimentary units with rock properties (porosity, permeability, Young's modulus, Poisson's ratio, and uniaxial compressive strength) and structural data to characterize the mechanical units and related deformation band pattern. Our results show that deformation bands have differences in frequency, geometry, thickness, and dip in different mechanical units. In addition, sedimentary parameters as grain size, layer thickness, stratification, cementation, and mineral composition impact the vertical propagation of deformation bands. In each layer, deformation bands frequency increases approaching a normal fault, and the dip of the deformation bands varies when passing through layers. In the studied mechanical units, deformation band density increases with increasing host rock porosity and decreasing Young's modulus. Finally, we document that the development of deformation bands increases the overall cohesion of the fault zone, particularly in units with coarser grain sizes. Our results have implications for mechanical stratigraphy in faulted siliciclastic reservoirs.

Evolution of deformation bands, insights from structural diagenesis

The vast majority of deformation bands (Dbs) studies focus on structural analysis only and neglect chemical/diagenetic effects. Here we report the structural diagenesis of Dbs occurring in the Tucano Basin (NE-Brazil). Although the occurrence of these structures in this basin has been well registered in literature, none of the researches related to them addressed the linking between structural and diagenetic processes. To fill this gap, we performed a multiscale (macro, meso and microscopic) analysis. Some key outcrops were selected and sampled for microscopic studies in order to investigate the deformational mechanisms active during Dbs formation and the coeval diagenetic processes. The diagenetic analysis reveals that the sandstones attained a minimum burial depth around 3 km and a temperature ≥100 °C, which means they reached the deep mesodiagenesis field. The nucleation of Dbs in these rocks started in the transition between the late eodiagenesis and initial (shallow) mesodiagenesis. In such conditions, the active deformational regime was the hydroductile flow, expressed by the dragging (bending) of rocks’ bedding (S0) by the Dbs. In the syn-lithification stage, transitional bands (hydroductile-cataclastic) developed exhibiting SC-type patterns and sigmoidal fractures. During deep mesodiagenesis, the cataclastic bands were formed by the cataclastic flow. These types of Dbs developed after mesodiagenetic quartz overgrowth and before (or synchronically) to chemical dissolution processes. The formation of tectonic matrix at this stage, along with the siliceous/ferruginous cementations, enhanced the strength of these structures.

Autowaves of Localized Deformation Induced by Phase Transformation

An approach and a model of the birth and development of deformation bands and their fronts under plastic deformation due to phase transformation are proposed. A solid body is considered as an open nonequilibrium system the relaxation of which is determined both by vibrational and by electronic degrees of freedom. Electron transitions between different states of the system of nuclei and electrons under deformation initiate excitation of the unstable vibrational mode of atomic displacements into positions peculiar to the martensitic phase.

Автоволны локализованной деформации, индуцированной фазовым превращением

An approach and a model for the nucleation and development of deformation bands and their fronts during plastic deformation due to phase transformation are proposed. A solid is considered as an open nonequilibrium system, the relaxation of which is determined by both vibrational and electronic degrees of freedom. Electronic transitions between different states of a system of nuclei and electrons upon deformation initiate the excitation of an unstable vibrational mode of atomic displacement to positions characteristic of the martensite phase.

MULTIAXIAL INVESTIGATION OF PVC FOAMS AND ANALYSIS OF THE DEFORMATION MECHANISM BY 3D-DIC

Closed-cell polyvinylchloride (PVC) foams are widely used as core for sandwich composites for applications, in which multiaxial loads are involved. In the present work a wide range of uniaxial (tension, compression and torsion) and multiaxial experiments (both simultaneous tension-torsion and compression-torsion) were conducted on a high performance PVC foam. Failure data for each experiment were collected and depicted in the invariants plane. The whole cylindrical surface of the specimen was monitored by means of an 8-camera-system, strain fields were obtained by 3D-DIC. Hence, the occurrence and the evolution of deformation bands were inspected. The usage of an 8-camera system was essential for the observation of the deformation mechanism, especially for pure compression, pure torsion and combined axial load-torsion, in which the arising of deformation bands is affected by the occurrence of buckling and the orthotropy of the foam.

How Porosity Controls Macroscopic Failure via Propagating Fractures and Percolating Force Chains in Porous Granular Rocks

AbstractThis contribution aims to illuminate the micromechanisms that control the macroscopic failure of porous, granular, and cohesive rocks. With discrete element method simulations, we triaxially compress cohesive granular models composed of interlocking breakable grains, similar to sandstone and oolitic limestone. We track the morphology of the force network and the resulting spatiotemporal fracture distribution. To shed light on the varying applicability of the pore‐emanated and Hertzian fracture models, we focus on differences in the micromechanics that develop between and within grains. For 5–20% porosity rocks, the cement between grains develops 10–50% higher mean forces than material within grains. Force chains that support the highest system‐spanning forces are more localized prior to failure in 20% porosity rocks and are more diffusely spread in 5% porosity rocks. Confining stress reduces this localization, similar to the impact of confining stress on the macroscopic expression of brittle failure. The magnitude and rate of fracture development relative to the axial strain or axial stress increase toward failure, consistent with experimental observations. In contrast, the rate of fracture development relative to the amount of external work done on the system, Wext, is approximately constant. Higher porosity rocks require lower inputs of Wext to produce the same degree of fracturing. Decreasing the cement strength promotes fracture development within the cement, revealing the dominance of intergranular, pore‐emanated fractures. These simulations provide predictions about how porosity controls the persistence of the stress field, with implications on the sequential development of deformation bands, and other deformational processes that modify porosity.

Multiaxial failure surface of PVC foams and monitoring of deformation bands by three-dimensional digital image correlation

Closed-cell polyvinylchlorid foams are among the most used core materials for sandwich composites. Therefore, a deep knowledge of their multiaxial behaviour is fundamental. More precisely, a literature review proves the lack of investigations concerning combined tensile-torsional loadings. In the present work simple tests, namely tension, compression and torsion have been performed for determining failure loads. Afterwards, multiaxial tests have been executed by applying different percentages of the previously calculated failure loads as preload and subsequent superposition of torsion, keeping simultaneously the axial load constant. For each multiaxial test, failure data have been collected in order to construct the failure surface for the foam material. The whole specimen surface has been inspected by means of the three-dimensional digital image correlation, in order to detect the failure of the specimen, as well as the onset and the development of deformation bands. Monitoring of the specimen has been performed for each main loading case. Afterwards, the analysis of deformation bands has been coupled with stress-strain diagrams and linked with the arising of buckling or fracture and the instrinsic orthotropy of the foam.

Development of Deformation Bands During Cyclic Deformation of Multiple Slip Oriented Copper Single Crystals with multiple slip orientation

Development of Deformation Bands During Cyclic Deformation of Multiple Slip Oriented Copper Single Crystals with multiple slip orientation

Fault baffle to conduit developments: reactivation and calcite cementation of deformation band fault in aeolian sandstone

The damage zone of three small faults in the Navajo and Page formations, located on the NE side of San Rafael Swell, Utah, USA, are studied. Scanlines and microstructural analyses are used to document three distinct deformation events: (1) an early phase creating cataclastic deformation bands, during which most of the displacement on the fault took place; (2) a fracturing event with opening and shearing along fractures; and (3) fluid flow and local calcite precipitation along the NW-trending faults. Microstructural characterization of deformation structures shows complex interaction between deformation bands, fractures and the calcite precipitation. Calcite cement is observed as veins in the host rock and along cataclastic bands, with varying amount of cataclastic material floating within the veins. In addition to patchy calcite cement in the host rock, extensive poikilotopic cementation is observed to extend into cataclastic bands with a low degree of cataclasis. However, some cataclastic bands with a high degree of cataclasis show almost no cementation. Development of deformation bands and their link to fracturing affected the flow field, from a fault baffle to a conduit. Calcite cementation reveals the flow paths, before cementation recreated the fault baffle.

AZ31B 마그네슘 합금에서 압연방향이 미세조직 및 기계적 특성에 미치는 영향

In this study, AZ31B Mg alloy samples were rolled in two different routes. One sample was normally rolled by maintaining the rolling direction (RD) and the other one was cross rolled by rotating the RD once by 90 around the normal direction (ND). Deformed bands, similar to shear, were observed in response to increasing deformation in the sheets. The texture was split by approximately 10-15 from the ND toward the RD in both sheets. The degree of the split texture rotation depended on the direction of the deformed bands. The grains in the deformed bands had a weak texture owing to the rotated c-axis of the hexagonal close-packed (hcp) structure. The texture affected the mechanical properties because of the easy basal slip for the observed split basal texture. Cross rolling definitely lowered the total elongation which was attributed to the frequent development of deformation bands in the cross rolled sample. It turned out that occurrence of a large number of compression twins in the cross rolled sample accelerated hardening of the AZ31B Mg alloy during the tensile deformation. The r-value of the cross-rolled sample was higher than that of the normal-rolled sample. †(Received November 4, 2013)

Microstructural evolution in the bonding zones of co-extruded aluminium/titanium

In the present study, the interfacial microstructure of dissimilar Al/Ti joints formed by a co-extrusion process has been investigated. The material combinations used for the experiments were commercially pure aluminium and titanium, respectively, in the alloys EN AW-6082 and TiAl6V4. X-ray diffraction, energy-dispersive X-ray spectroscopy, electron microscopy and electron backscatter diffraction revealed titanium aluminide formation in the interface, the development of deformation bands in the sleeve material, and the occurrence of grain size refinement and twinning in the core material. The results are discussed with respect to the concept of a hard core–soft sleeve co-extrusion comprising plastic deformation to promote solid-state diffusion. The study shows the phase distribution and the microstructural evolution in the bonding zone with the aim to improve the quality of the bonding by adequately adjusting the process parameters.

Sequential growth of deformation bands in a multilayer sequence

[1] The outstanding exposure of deformation bands in a multilayer sequence of the Orange quarry, Provence, France, motivates a study investigating the development and controls of deformation band geometries by field mapping combined with finite element modeling. Field mapping yields new insights into angular relations between, and evolution of, the deformation bands as well as provides input parameters for the setup and boundary conditions of the numerical simulations using ADELI 2D. In particular, reverse-sense deformation bands are found to have developed within three of the four exposed layers of the multilayer stack with similar orientations to bedding, indicating layer-parallel contraction. Numerical simulations, carried out as a parametric study to investigate the influence on deformation band development and geometry, successfully reproduce the sequential development of deformation bands in the three layers as seen in the field as well as recreate the observed angular geometries of ∼39° to the maximum compression. This angular relationship is put into context with observations from other field studies and theoretical values to explore controls of deformation band orientations. Furthermore, band localization is impeded in the model by increased layer cohesive strength, demonstrating the importance of host-rock property variations on localization of bands within the multilayer sequence. Results from both field investigation and numerical simulations are consistent with regional tectonics, where the strata underwent gentle folding due to thrust faulting at depth, and bring further insight into the development and geometry of deformation bands in both extensional and contractional tectonic regimes.

The EBSD Investigation on Microstructure Evolution in Fe-32%Ni Alloy during Multi-Axial Forging

The microstructure evolution taking place in Fe-32%Ni alloy during multi-axial forging was investigated by electron backscattered diffraction (EBSD). The samples were compressed with loading direction changed through 90º from pass to pass at temperature of 650°C and a strain rate of 10-1/s. The results show the microstructure evolution is characterized by continuous grain subdivision process, i.e. the multi-axial forging promotes the development of deformation bands in various direction followed by their frequent intersection in grain interiors with changing of strain path, which results in continuous fragmentation of coarse grains into subgrains. Concurrently the misorientations of subgrain boundaries rise gradually with repetitive deformation followed by their progressive transformation into high angle boundaries. The ultra-fine grains are concluded to evolve by continuous dynamic recrystallization (CDRX).

Orientation splitting and its contribution to grain refinement during equal channel angular extrusion

The early stage mechanisms of grain refinement during ECAE of a single-phase aluminium alloy have been studied using the EBSD technique. It was found that, in addition to the formation of shear-plane cell bands and shear bands by “simple shear”, the development of deformation bands due to orientation splitting contributed significantly to the refinement of microstructure. “Regular” slab-like deformation bands and “irregular” transitional bands were observed after the first pass; both developed boundaries of high misorientations. In the second pass, moderate orientation splitting took place within the deformation bands, although new deformation bands were not detected. With increased strains, fine scale orientation splitting tended to occur in local bands, generating high densities of new high misorientation boundaries. The crystallographic features of the different types of orientation splitting are examined.

Digital Image Correlation investigation of Portevin–Le Chatelier effect in an aluminium alloy

The Portevin–Le Chatelier (PLC) effect in an Al–4.5 Mg–0.7Mn alloy was studied using the Digital Image Correlation technique. The results provide a new insight into the development of deformation bands related with the stress oscillations observed during the tensile testing of the alloy.

大ひずみ多軸鍛造による結晶粒微細化プロセスと機構

The evolution processes of new high-angle boundaries as well as ultrafine grains processed by severe multidirectional forging (MDF) are studied in ferritic, austenitic steels and copper at low temperatures below 0.5Tm (Tm is the melting point), and aluminum and magnesium alloys at high temperatures above 0.5Tm, where dynamic recovery operates mainly as a restoration process. The structural changes can be characterized by the evolution of deformation bands such as microshear or kink bands at moderate strains. MDF promotes the multiple shearing, which results in the formation of spatial net of mutually crossed bands subdividing the original grains. This is a mechanical induced event and so an athermal process. On the other hand, in large strain the fast operation of recovery processes accelerates the kinetics of ultrafine grain evolution with increasing temperature at low temperatures below 0.5Tm. In contrast, the volume fraction of new grains decreases in large strain through hard development of deformation bands with increasing temperature at elevated temperatures above 0.5Tm. The misorientations between (sub)grains evolved gradually increase with increase in strain, finally leading to the development of a new fine-grained structure. Temperature effect and the mechanism of strain-induced grain formation are discussed in detail.

Structural features hindering deformation-band formation in thermally hardened carbon steels

Deformation-band nucleation is analyzed to explain the causes that hinder the development of deformation bands in thermally hardened carbon steels.