Undeformed Part Research Articles

Investigation of the unusual deformations of external tendons in concrete highway bridges

AbstractDuring a regular inspection of a multi‐span highway bridge, an unusual deformations of external post‐tensioned tendons were observed. These deformations were not noticed or recorded during the previous main inspections. A detailed visual inspection of the condition of external tendons was performed on all bridges with external tendons by mapping the location and extent of unusual deformation. Based on this, several non‐destructive tests were performed, where deformations were first noticed, from magnetic‐flux leakage to radiographic screening. Some local destructive investigations were subsequently carried out at several locations in two bridges, i.e. opening the tendons. The result of the tendons opening showed the presence of foreign objects and non‐tensioned strands, the latter being a possible cause for the deformations of that tendon. In both locations, the injection mass was compact with only hairy transverse cracks, both on the undeformed part as well as on the moderately deformed part of the tendon. In this paper, the latest results from this study are presented in detail.

Effects of multi-extensional tectonics in a cratonic area: 3D numerical modeling and implications for the Congo basin

Different hypotheses have attempted to explain the long-lasting subsidence of the intracratonic basins, characterized by prolonged intervals of low rate subsidence, alternating with episodic accelerations in subsidence rates. Among them, the Congo Basin (CB) occupies a large part of the Congo Craton, derived from the amalgamation of different cratons. Previous studies demonstrated that the CB formed from a rift phase, during the late Mesoproterozoic. This extensional phase could have been the effect of the action of a slow multi-directional extension on a cratonic lithosphere, which has induced the initial subsidence of the CB. We investigated this tectonic scenario with 3D numerical thermomechanical models, using bi-directional N-S/E-W intra-cratonic extension with uniform velocity applied for up to 200 Myr. We assumed that the amalgamation of several cratonic blocks left a rectangular region with warm and more fertile lithosphere in the model centre, having a size of 10 % or 20 % of the total model area. Numerical results show the formation of an almost circular subsided area in the central part of the model, due to the crustal and lithospheric thinning above the asthenosphere upwelling. We also observe series of topographic highs and lows inside the subsided area and significant uplift at the transition zones towards the almost undeformed cratonic parts. At a later stage (>100 Myr), the topographic depression becomes intersected by two nearly orthogonal, elongated rift structures (quadruple junction), which tend to raise their surface topography. These features well represent the first order heterogeneity characterizing the CB basement, considering that its depth has been further modified by tectonic and climatic events. The formed structures are input for static and dynamic forward gravity models and the outputs compared with the present-day gravity field. In this way, the consistency between the modelled and observed main structures of the CB is demonstrated.

Deformation and failure of thin spherical shells under dynamic impact loading: Experiment and analytical model

Thin curved shells are widely used in engineering. A shallow spherical shell is an effective representation of a curved shell affected by local impact loading. Therefore, the dynamic response of spherical shells under impact loading should be investigated to provide a design reference for curved shells applicable to engineering fields. In this study, the dynamic response and perforation of an aluminum spherical shell impacted by a cylindrical projectile were investigated theoretically. An isometric transformation was adopted to describe the major bending deformation of the spherical shell around the impact point. In addition, an edge region between the major bending part and an undeformed part was observed experimentally and described using a deformation mode. Hamilton's principle was adopted to derive the governing equations of the dynamic response of the impacted spherical shell. Furthermore, a viscoplastic strengthened model was introduced to describe the membrane force and bending moment of the perforation, whereas a rigid–plastic model was used to calculate the force and moment of the other parts of the spherical shell. The governing equations combined with the strengthened model were solved using the Runge–Kutta method. A comparison between the theoretical predictions and experimental results indicated a good agreement between them. Finally, the effects of the parameters set in the governing equations of the theoretical prediction were analyzed. We observed that the theoretical model predicted dimple radius more accurately than dimple depth. The dimple depth is linearly proportional to the impact velocity. In addition, the assumed sizes of the shear region of perforation only affect the ballistic limit and deformation generated by a velocity higher than the ballistic limit. The deformation and perforation of the impacted shell are almost independent of the initial width of the edge region of deformation. Additionally, we observed that the ballistic limit of the shell is linearly proportional to the shell thickness.

Comparative Characterization of Petrophysical and Mechanical Properties of Siliciclastic Reservoir Rocks within a compressional structure of the Teapot Dome Oilfield, Wyoming, USA

Abstract Working with subsurface engineering problems in Hydrocarbon exploration as regard rock elastic and petrophysical properties necessitate accurate determination of in-situ physical properties. Several techniques have been adopted in correlating log-derived parameters with petrophysical and mechanical behavior of the rocks. However, limited field applications show there are no particular parameters and correlations that are generally acceptable due to the regional variation in geologic features (i.e., degree of mineralogy, texture, etc.). This study presents a method that assesses the disparity in petrophysical properties of oil and gas reservoir rocks in relation to their elastic/mechanical properties from 10 well-logs and 3D migrated seismic data. Two distinct facies were identified from seismic data after computing attributes. Reflection strength attribute of 2.5 and above depicts Bright spots within the central section of the field as clearly revealed by Variance and Chaos attributes. Formation properties calculated from logs were conformally gridded in consonance with the reflection patterns from the seismic data. The average Brittleness index (BI) of 0.52 corresponds to Young’s modulus (E) values of between 8 and 16 for the dense portion. This portion is the laminated, reasonably parallel, and undeformed part, flanked by the unlaminated and chaotic zones. From cross plots, the distinguished lower portion on the plot is the segment with higher sand of more than 50 %. This segment corresponds to the reservoir in this study as confirmed from the genetic algorithm neural network Acoustic impedance inversion process result. Similarly, the plot of Compressional velocity (Vp ) and Poisson’s ratio (ν), reveals the laminated sand value of not less than 0.32 of ν, and Vp of about 4.2 km/s. The average porosity is about 16 %, average water saturation is about 16 %, and average permeability is approximately 25 md. Rock properties trends in a unique pattern and showing fluctuation that confirms the compressive nature of the structure with corresponding petrophysical properties. This trend is sustained in permeability computed and suggests a significant gravity-assisted compaction trend and fluid movement. It gives a reasonable idea of the fluid movement interplay and mechanical property variation within the sequence and across the dome. This part probably has been subjected to fair compressional deformational forces initiated from outside the survey.

Lateral variations of crustal structure beneath the Indochina Peninsula

Crustal thickness (H) and Vp/Vs (κ) measurements obtained by stacking P-to-S receiver functions recorded at 32 broadband seismic stations covering the Indochina Peninsula reveal systematic spatial variations in crustal properties. Mafic bulk crustal composition as indicated by high κ (>1.81) observations is found to exist along major strike-slip faults and the southern part of the Peninsula, where pervasive basaltic magmatism is found and is believed to be the results of lithospheric thinning associated with the indentation of the Indian into the Eurasian plates. In contrast, crust beneath the Khorat Plateau, which occupies the core of the Indochina Block, has relatively large H values with a mean of 36.9 ± 3km and small κ measurements with an average of 1.74 ± 0.04, which indicates an overall felsic bulk composition. Those observations for the Khorat Plateau are comparable to the undeformed part of the South China Block. The laterally heterogeneous distribution of crustal properties and its correspondence with indentation-related tectonic features suggest that the Indochina lithosphere is extruded as rigid blocks rather than as a viscous flow.

INVESTIGATION OF LÜDERS DEFORMATION IN THE MILD STEEL

The features of macroscopic strain inhomogeneity in the form of Chernov–Luders bands development on elastic-plastic transition were investigated in the mild steel. The main regularities of nucleation and propagation of the bands are established. Particular attention was paid to the kinetics of moving boundaries (fronts) of bands, characteristic velocities were determined. It is shown that the rate of formation of nucleus of the Chernov–Luders band is more than an order of magnitude higher than the rate of its expansion. Situations are considered when more than one band develops simultaneously in the object and therefore several moving fronts are observed. It is established that in all cases the velocities of fronts of the Chernov–Luders bands are mutually consistent so that at any instant the generalized rate of expansion of the deformed zone is a constant value. The effect of the deformation rate on the kinetics of the Chernov–Luders fronts was analyzed. Both the generalized rate of expansion of the deformed zone and the speed of individual fronts increase with the increase of the loading rate. A nonlinear (power-law) character of this dependence is established. The fronts of the bands have a complex structure. Different parts of the front can move with unequal velocities, so that the front line is locally curved and split. Ahead of the front, in the undeformed part of the sample, the forerunners may appear, the configuration of which resembles the Chernov–Luders bands nuclei. When encountering the fronts of adjacent bands are annihilated. Annihilation of the fronts is a complex process, which is also characterized by the formation of a precursor and secondary diffusion Chernov–Luders bands. These facts demonstrate that a simplified view of the Chernov-Luders band as a deformed region in a loaded sample, and the front of the band as a boundary between deformed and undeformed zones, should be revised. The microscopic theory of Luders deformation is based on the avalanche growth of the density of mobile dislocations due to breaking from an obstacles and subsequent multiplication, which is realized simultaneously at the upper yield point within the crystallite (grain). At the same time, to form a mobile macroscopic deformation front it is necessary that plastic deformation should be transferred to neighboring grains without hardening, that is, grain-boundary accommodation is needed. The results obtained in the paper suggest that such a zone of accommodation is apparently the Chernov–Luders band front, and, therefore, it has a complex structure.

Microstructure characterization of 316L deformed at high strain rates using EBSD

Specimens from split Hopkinson pressure bar experiments, at strain rates between ~1000–9000s−1 at room temperature and 500°C, have been studied using electron backscatter diffraction. No significant differences in the microstructures were observed at different strain rates, but were observed for different strains and temperatures. Size distribution for subgrains with boundary misorientations >2° can be described as a bimodal lognormal area distribution. The distributions were found to change due to deformation. Part of the distribution describing the large subgrains decreased while the distribution for the small subgrains increased. This is in accordance with deformation being heterogeneous and successively spreading into the undeformed part of individual grains. The variation of the average size for the small subgrain distribution varies with strain but not with strain rate in the tested interval. The mean free distance for dislocation slip, interpreted here as the average size of the distribution of small subgrains, displays a variation with plastic strain which is in accordance with the different stages in the stress-strain curves. The rate of deformation hardening in the linear hardening range is accurately calculated using the variation of the small subgrain size with strain.

A microstrain measurement methodology applied to multiscale hydroforming of annealed ASTM 304 stainless steel sheet

Meso- and microscale sheet metal forming represents new and attractive solutions to many manufacturing problems for product miniaturization. Larger organizations are utilizing commercially available microscale digital image correlation systems to measure the strains on these scales. The cost of these systems is preventing smaller research and development organizations from entering this challenging area or they are sacrificing the ability to determine strains and evaluate material behavior at the microscale. However, microscale strain grid measurement has the advantage over digital image correlation when the researchers wish to avoid polishing and etching the surface of the sheet metal to make the grain structure visible for digital image correlation and where tooling interferes with obtaining images of the workpiece in real time. This article evaluates the strain measurement and strains resulting from multiscale sheet metal hydroforming operations for annealed 0.2-mm-thick ASTM 304 stainless steel using a simple method for producing microscale grids that has been previously described. The gridding methodology was shown to be accurate with high repeatability. In addition, a strain grid measurement method using an optical microscope and digital camera is described and an error analysis was performed. Provided reasonable care is taken, the inherent error in undeformed parts is 0.76% of true strain for samples with 127 µm grids using the strain measurement system described. The maximum variation in the mesoscale and microscale strain measurement static bulge testing was ±2.4% and more typically ±1.3% of true strain. With care, the errors were reduced to less than 1% of strain. Microscale strains from sheet bulge hydroforming experiments for 11, 5, and 1 mm diameter dies are used to show that the strains measured are reasonable and consistent.

Carbide evolution and service life of simulated post weld heat treated 2.25Cr–1Mo steel

Abstract To estimate the service life of the reactor internals made of 2.25Cr–1Mo steel in the high temperature gas-cooled reactor pebble-bed module demonstration plant, creep rupture test was performed on the simulated post weld heat treated steel at 773 K over a range of stress levels 300–200 MPa. It has been shown that the rupture time is 126–5532 h, correspondingly. Then, the service life under stress of 161.2 MPa at 648 K was calculated to be so long as 210,374,853 h (≈24,015 years). Four types of carbides M 3 C, M 2 C, M 7 C 3 and M 23 C 6 existed in both the steel plate and the post-rupture specimens. As the rupture time increases, the weight percentages of M 23 C 6 and M 2 C that are stable in thermodynamics in the post-rupture specimens increase while those of metastable M 3 C and M 7 C 3 decrease on the whole. During the long term creep exposure, the deformation promotes the precipitation of M 3 C, M 2 C and M 23 C 6 , according to the experimental results with the deformed and undeformed parts of the post-rupture specimens, but its influence on the weight percentage of M 7 C 3 seems rather complicated.

Emplacement and fabric-forming conditions of plutons from structural and magnetic fabric analysis: A case study of the Plana pluton (Central Bulgaria)

The relationship between intensity parameters, such as the corrected anisotropy degree P′ and mean susceptibility Km for plutons with similar magnetic mineralogy, yields a criterion to determine the origin of their magnetic fabric: for a same mineralogy, the higher the P′ values for the same mean susceptibility Km (irrespective of its absolute value) the higher tectonic effect was possible. Using this criterion, comparison of the magnetic fabric of the Upper Cretaceous mid- to shallow crustal level Plana pluton with that of other small Upper Cretaceous plutonic bodies in Sredna Gora Zone (Central and Southeast Bulgaria) highlights the structural evolution of the Plana pluton. The central part of Plana pluton and its southwest, west and east margins have preserved their emplacement fabric. Along its northern contact the pluton is affected by the last movements within the Okol Shear Zone where high-temperature S/L mylonites developed. The fabric of the pluton at its southeastern border was disturbed during the intrusion of the neighboring Gutsal pluton. The similarity in the orientation of magmatic and magnetic structures preserved in the central and southern parts of the Plana pluton and the transition from magmatic to high-temperature superimposed foliations and lineations at its north contact point to a composite superimposed shear-induced and emplacement-related magmatic magnetic fabric. Nearly vertical orientation of magnetic and magmatic foliations and lineations from the undeformed parts of the pluton shows a process of vertical magma rising and emplacement. The sub-vertical high-temperature solid-state mylonitic foliation and dip-parallel stretching lineation in the pluton along its northern contact reveals the transpression nature of the deformation in the vicinity of Okol Shear Zone with a strong pure shear component. The smooth transition between the deformed and undeformed parts of Plana pluton reveals the syn-kinematic character of the emplacement.

Interplay of deformation and magmatism in the Pangong Transpression Zone, eastern Ladakh, India: Implications for remobilization of the trans-Himalayan magmatic arc and initiation of the Karakoram Fault

In the eastern part of Ladakh, the right-lateral Karakoram Fault Zone (KFZ) bifurcates into two strands called the Pangong Strand and the Tangtse Strand. These two strands bound a region called the Pangong Transpression Zone (PTZ), which consists of migmatitic dioritic gneiss, calc-silicates and the Durbuk Pluton; a pluton of two-mica leucogranite. Outcrop scale observations suggest pervasive migration of leucogranitic melt through the existing tectonic structures of the gneiss. Magnetic fabric from both the tectonized and undeformed parts of the Durbuk Pluton show parallelism with the tectonic fabric of the host gneiss, which, along with pervasive melt migration, indicates syn-kinematic relationship between deformation along the KFZ, leucogranite magmatism and emplacement of the Durbuk Pluton. U–Pb geochronology of zircons from the dioritic gneiss yields a crystallization age of 63.6 ± 1.5 Ma and also shows younger zircon growth down to ∼13 Ma, which suggest arc magmatism at ∼65 Ma followed by partial melting and leucogranite magmatism in the KFZ till ∼13 Ma. One two-mica leucogranite sample from the Durbuk Pluton gives a crystallization age of 22.7 ± 0.5 Ma. As the Durbuk Pluton is syn-tectonic with deformation along KFZ, it is inferred that the KFZ initiated at least ∼23 Ma ago.

The Suwannee suture: Significance for Gondwana-Laurentia terrane transfer and formation of Pangaea

In southeastern Laurentia the Suwannee suture separates the undeformed part of the Gondwanan Suwannee terrane (SWT) from crust of Laurentia and previously accreted Gondwanan terranes that were deformed during the Alleghanian orogeny. Undeformed early Paleozoic sedimentary rocks of the SWT are considered of Gondwanan-African derivation on the basis of various considerations, including a lack of Mesoproterozoic (Grenville) detrital zircons. The cratonic heritage of Suwannee lithosphere is complicated, however, because Sm–Nd depleted mantle model ages from both Neoproterozoic and Alleghanian (Carboniferous–Permian) granites north and south of the suture zone are Mesoproterozoic. Mesoproterozoic lithosphere has not been reported in conjugate West Africa, but is present in Amazonia, suggesting that the SWT: 1) may be a composite terrane, containing both African upper crust and Amazonian lower crust/lithosphere, 2) was separated from Gondwana during Atlantic Ocean rifting along a Mesoproterozoic–Neoproterozoic suture, and/or 3) contains Laurentian Grenville-age lower crust and lithosphere that must also underlie other accreted proximal Gondwanan terranes (e.g., Uchee terrane). In addition, the ~300Ma, syn- to post-tectonic granitoids emplaced across the Suwannee suture zone are the product of crustal anatexis, not supra-subduction magmatism, on the basis of Mesoproterozoic Sm–Nd Tdm and zircon xenocrysts. The lack of documented ~300Ma, supra-subduction magmatism in both Laurentian and Gondwanan components in southern Laurentia (e.g., southernmost Appalachian and Ouachita orogens) strongly suggests that accretion of the SWT and related Gondwanan terranes occurred during dextral transpressional convergence between Laurentia and a combined African-Amazonian craton, a characteristic shared with conjugate crust in southwestern Europe. In this interpretation, intervening oceanic lithosphere and contemporary volcanic arcs (if any) were largely removed by disaggregation and dispersion along the transpressional boundary possibly combined with highly oblique overthrusting and/or partly subducted at the leading edge(s) of other blocks of Gondwanan lithosphere that were accreted to southern Laurentia in the late Paleozoic (e.g., Wiggins, Sabine, Coahuila, Maya, etc.). Mesozoic opening of the Gulf of Mexico has subsequently and variably altered the original configuration of these terranes.

Deformation analysis of short glass fiber-reinforced polypropylene injection-molded plastic parts

The warpage of injection-molded plastic parts is a complex problem being affected by different technological parameters, material properties, and mold design. Hence, the description of the deformation is difficult as well. This article presents the effect of fiber content and mold temperature difference on the deformation of polypropylene parts. Based on the measurement results, a linear approximation and a calculation method are shown, which can be used to jointly determine the ideal fiber content and mold temperature difference to produce undeformed plastic parts.

가상 트라이아웃을 이용한 소음기 케이스 성형에 관한 연구

Forming of a silencer case was studied using a virtual tryout method. First, the appropriate blank shape was determined by cutting off the undeformed part of the rectangular blank. Then drawbeads were designed such that the formation of wrinkles on the shoulders and pipe connection can be prevented. Finally, the shape bead was designed such that fracture and formation of wrinkles around the pipe connection can be avoided. The prototype of the silencer case was manufactured in accordance with the conditions of the virtual tryout process. By comparing the formability of the prototype with the results of finite element analysis, it was found that the forming of the prototype agreed well with the results of analysis.

Large-scale sedimentary recycling of tectonic melange in a forearc setting: The Ionian basin (Oligocene-Quaternary, southern Italy)

Research Article| November 01, 2010 Large-scale sedimentary recycling of tectonic mélange in a forearc setting: The Ionian basin (Oligocene–Quaternary, southern Italy) William Cavazza; William Cavazza † 1Dipartimento di Scienze della Terra e Geologico-ambientali, Università di Bologna, Piazza di Porta San Donato 1, 40126 Bologna, Italy †E-mail: william.cavazza@unibo.it Search for other works by this author on: GSW Google Scholar Mirko Barone Mirko Barone 2Fugro Robertson B.V., P.O. Box 141, 2260 AC Leidschendam, The Netherlands Search for other works by this author on: GSW Google Scholar Author and Article Information William Cavazza † 1Dipartimento di Scienze della Terra e Geologico-ambientali, Università di Bologna, Piazza di Porta San Donato 1, 40126 Bologna, Italy Mirko Barone 2Fugro Robertson B.V., P.O. Box 141, 2260 AC Leidschendam, The Netherlands †E-mail: william.cavazza@unibo.it Publisher: Geological Society of America Received: 18 Sep 2009 Revision Received: 05 Dec 2009 Accepted: 07 Dec 2009 First Online: 08 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 © 2010 Geological Society of America GSA Bulletin (2010) 122 (11-12): 1932–1949. https://doi.org/10.1130/B30177.1 Article history Received: 18 Sep 2009 Revision Received: 05 Dec 2009 Accepted: 07 Dec 2009 First Online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation William Cavazza, Mirko Barone; Large-scale sedimentary recycling of tectonic mélange in a forearc setting: The Ionian basin (Oligocene–Quaternary, southern Italy). GSA Bulletin 2010;; 122 (11-12): 1932–1949. doi: https://doi.org/10.1130/B30177.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Distinctive horizons of mélange—ranging in maximum thickness from a few tens to several hundreds of meters—are conformably interbedded with the regularly stratified, Oligocene-to-Quaternary, predominantly marine deposits of the Ionian forearc basin along the leading edge of the Calabria-Peloritani microplate of southern Italy. These mélange horizons were emplaced from the late-early to the late Miocene during collision of the southern and northern margins of the microplate with the passive margins of northern Africa and the Apulian Platform, respectively. Collisional deformation induced uplift of parts of the accretionary prism and ensuing sedimentary recycling of mélange into the adjacent Ionian forearc basin. The thickest mélange horizon can be traced for a distance >80 km with a consistent stratigraphic position within the forearc basin fill, and ranges in thickness from ∼1 km near the collision zone to zero away from it. It was emplaced in the late Burdigalian and records oblique collision of the Calabria-Peloritani microplate with the northern continental margin of Africa. In this context, portions of the mélange of the accretionary prism were extruded tectonically and gravitationally mobilized from southwest to northeast in the remaining, undeformed parts of the forearc basin. This interpretation is supported by (1) the overall geometry of the mélange horizon pinching out away from the collision zone, (2) its conformable contacts and chronostratigraphic relationships with the underlying and overlying stratigraphic units, (3) its composition, and (4) the absence of tectonic deformation at base and top of the horizon. Younger and thinner mélange horizons are interbedded within the latest Tortonian–Messinian succession and resulted from the erosion of thrust tip areas within the inner portion of the accretionary prism following incipient collision of the northern end of the microplate with the Apulian Platform. Integration of the results of this and other studies indicate that sedimentary recycling of large volumes of mélange from accretionary prisms into forearc basins is an important process along both collisional and noncollisional active plate margins. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Anomalous dissolution of microindentation deformed zone of ITO/Si coated system

AbstractThe joint effect of a film and a substrate on the modification of the mechanical properties of an ITO/Si coated system (CS), a promising material for solar cells, and its response to an external load in comparison with the Si substrate were considered. An unusual combination of a pronounced crack formation and a plastic character of indenter–sample contact zone was revealed. This feature was accounted for a high brittleness of the Si substrate and the enhanced plasticity of the ITO film that improves the mechanical characteristics of the whole ITO/Si structure, which is useful for its operation. Another unexpected result, the anomalous etching (dissolution) of the ITO film near the indentations, was found out when the ITO/Si CS was subjected to an aggressive medium. A preferable dissolution of the ITO film was detected in the deformed zone near the indentation (Df), commensurable with the dimension of the substrate elastic/plastic dislocation free zone which was two or three times larger than the indentation diagonal (d) and approximately ten times larger than the dislocation rosette around indentation on the Si support. An assumption was made that the effect is basically determined by high internal stresses in this zone and, hence, by weaker atomic bonds as compared with the undeformed part of the material. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Thermal Structure of the Ionian Slab

We propose a thermal model of the subducting Ionian microplate. The slab sinks in an isothermal mantle, and for the boundary conditions we take into account the relation between the maximum depth of seismicity and the “thermal parameter” Lth of the slab, which is a product of the age of the subducted lithosphere and the vertical component of the convergence rate. The surface heat-flux dataset of the Ionian Sea is reviewed, and a convective geotherm is calculated in its undeformed part for a surface heat flux of 42 mW m−2, an adiabatic gradient of 0.6 mK m−1, a mantle kinematic viscosity of 1017 m2 s−1 and an asthenosphere potential temperature of 1300°C. The calculated temperature-depth distribution compared to the mantle melting temperature indicates the decoupling limit between lithosphere and asthenosphere occurs at a depth of 105 km and a temperature of 1260°C. A 70–km thick mechanical boundary layer is found. By considering that the maximum depth of the seismic events within the slab is 600 km, a Lth of 4725 km is inferred. For a subduction rate equal to the spreading rate, the corresponding assimilation and cooling times of the microplate are about 7 and 90 Myr, respectively. The thermal model assumes that the mantle flow above the slab is parallel and equal to the subducting plate velocity of 6 cm yr−1, and ignores the heat conduction down the slab dip. The critical temperature, above which the subduced lithosphere cannot sustain the stress necessary to produce seismicity, is determined from the thermal conditions governing the rheology of the plate. The minimum potential temperature at the depth of the deepest earthquake in the slab is 730°C.

A contribution to the understanding of chip formation mechanism in high-speed cutting of hardened steel

High-speed machining processes are characterized by their high productivity, good surface finish quality and higher dimensional tolerances. Additionally, these technologies make it possible to execute final machining operations without consequent grinding or similar finishing operations. The newest investigations in the segment of high-speed machining are focused on four characteristic directions: mechanisms of tool wear, quality of surface finish, mechanisms of chip formation, and problems of machining of materials in their hardened state (hard machining). The chip-formation mechanism analysis is an effective tool for deeper understanding of cutting process. During conventional and high-speed milling of the hardened tool steel (X 63CrMoV 51), with cutting speed range from 50 to 1500 m/min, different mechanisms of chip-formation appear. The analysis covered the chip segmentation frequency, chip shape and dimensions, and also the size of deformed and un-deformed parts of chip segments. The results show that there exists a close relationship among these chip parameters, especially in the region of high-speed machining.

Formation of saucer-shaped sills

Abstract We have developed a coupled model for sill emplacement in sedimentary basins. The intruded sedimentary strata are approximated as an elastic material modelled using a discrete element method. A non-viscous fluid is used to approximate the intruding magmatic sill. The model has been used to study quasi-static sill emplacement in simple basin geometries. The simulations show that saucer-shaped sill complexes are formed in the simplest basin configurations defined as having homogeneous infill and initial isotropic stress conditions. Anisotropic stress fields are formed around the sill tips during the emplacement due to uplift of the overburden. The introduction of this stress asymmetry leads to the formation of transgressive sill segments when the length of the horizontal segment exceeds two to three times the overburden thickness. New field and seismic observations corroborate the results obtained from the modelling. Recent fieldwork in undeformed parts of the Karoo Basin, South Africa, shows that saucer-shaped sills are common in the middle and upper parts of the basin. Similar saucer shaped sill complexes are also mapped on new two- and three-dimensional seismic data offshore of Mid-Norway and on the NW Australian shelf, whereas planar and segmented sheet intrusions are more common in structured and deep basin provinces.

Experiments on vertical basement fault reactivation below volcanoes

Scaled modeling has been conducted to study the role played by the reactivation of vertical basement faults in the destabilization process of overlying volcanoes. Results show that basement fault reactivation induces the formation of faults within the volcanic edifice. These faults delimite a central block which is extruded from between the two undeformed lateral parts of the edifice. Collapse of this central block can occur when heterogeneous cones are used in experiments, revealing that mechanical interfaces are of paramount importance in triggering rockslide avalanches. Collapse structures may display horseshoe shapes in map view and are then surprisingly similar to avalanche scars resulting from failure created by magmatic intrusions in natural volcanoes. Large‐scale destabilisation of half the surface of the cone may also occur in a single event depending on the position of the reactivated basement fault below the edifice. It is emphasized that the process under consideration may occur on a dormant volcano as well, provided that a fault is reactivated below it.