Transitional Arc Research Articles

Thermal mechanical fatigue cracking of a bladed disk in a turbo engine

After 1221 h of bench testing, linear fluorescent displays were observed on the transition arcs between the blade and the edge plate. Macroscopic and microscopic inspections revealed fatigue cracks originating from cracked grain boundaries on the surface. Metallographic examinations indicated severe oxidation of the crack flank and blunting tip. Finite element thermal stress analysis aligns with the crack distribution. The nature of the cracking is identified as thermal mechanical fatigue, and the elevated temperature gradient induced by the exhaust gas purification device is the main promoter for cracking. Comparative analysis suggests that the root cause lies in the low thermal impact resistance of the material, ultimately resulting in reduced thermal mechanical fatigue resistance. Corresponding remedial methods are proposed to enhance service life and safety.

Sediment Transport Mechanism and Provenance of Unconsolidated Sediments in Opak River Channel, Yogyakarta, Indonesia

This study focuses on the Opak River, which crosses administratively through two regencies, Sleman and Bantul. This research aims to reveal the sedimentation mechanism and provenance of Opak River sediment based on textural and sedimentary composition. Sediment samples were collected from ten points along the river channel, spanning from upstream to downstream. Granulometric and grain morphology analysis were conducted which the followed by QFL analysis wherein the presence of light detrital minerals (quartz, feldspar, lithic) was observed. The sediment texture of Opak River Channel generally consists of coarse-grained sand, poorly sorted, with varying degrees of roundness and sphericity, which are angular to sub-rounded and intermediate to sub-equant, respectively. Opak River sediment predominantly comprises Feldspar (20-48%), Quartz (4-17,9%) and Lithic (13,5-19,6%) which implies arkose-lithic arkose type. The sedimentation process in Opak River is mainly driven by the traction process, which is indicated by a 48-79% traction fraction on the probability log curve. Based on QFL analysis, it is inferred that the Opak River sediment originated tectonically derived from a magmatic arc setting, specifically a transitional arc subtype. The primary sediment source could have been derived from Mount Merapi with a potentially strong influence by the Oyo River, especially in the downstream of Opak River.

Life Assessment of Deep-Sea Observation Windows under Different Design Considerations

As a key component of deep-sea manned submersibles, the observation window is usually constructed with polymethyl methacrylate (PMMA) material. During the design of the observation windows, the consideration of actual lifespan and its influential factors is insufficient. There are no clear provisions in the widely applied specifications. In this paper, based on the continuum damage mechanics model, combined with the viscoelastic relationship of PMMA material, a series of calculations were performed on the PMMA observation window. The parametric analysis of the fatigue crack-initiation life of the observation window at various thickness-to-diameter ratios (1.6, 1.4, 1.2, and 1.0), different friction coefficients (0.1, 0.2, and 0.3), and different transition arc radii (4000 mm and 6000 mm) was carried out. The calculated crack positions in the numerical mode used for validation closely align with those in the tested window. And simulation results show that the fatigue life of the observation window gradually decreases with the decrease in the thickness–diameter ratio and the increase in the friction coefficient. However, the increase in the transition arc radius will prolong the fatigue life of the observation window, which is higher than that of the original structure.

Failure analysis of one main wheel hub bolt fracture of A320 aircraft

When an aircraft was performing flight tasks, it was found that one connecting bolt of No. 3 main wheel was missing during the short stop inspection. The bolt uses 148 ups and downs this time, and the use time is significantly lower than normal. It is inferred that the high probability of its fracture is not caused by long-term use, and it is speculated that the fracture reason is related to the quality of the bolt itself. Material analysis showed that there were no obvious abnormalities in the bolt material, and slight scratches were found near the bolt. The bolt is fatigue fracture and the fracture position is located at the transition arc position. Microscopic observation shows that there is a V-shaped groove on the side of the crack source area, but because the gasket is no longer in the installation position, it cannot directly determine the installation problem of the gasket. It is recommended to optimize the installation process and NDT (No Destructive Testing, NDT) detection process in the future.

Spectral and electric diagnostics of low-current arc plasmas in CO2 with N2 and H2O admixtures

Plasma diagnostics is a key tool to support the further development of plasma-induced chemical conversion of greenhouse gases (such as CO2) into high-value chemicals. For this reason, spectroscopic and electric measurements of low current (below 1.7 A), stationary arc plasmas in CO2 at atmospheric pressure with addition of N2 or H2O are reported. High-speed photography, imaging emission spectroscopy and time-resolved electrical measurements are used to obtain time-space resolved gas temperatures as well as the electric-field current characteristics of the discharge. It is found that the lowest average electric field in a CO2 arc plasma at atmospheric pressure is ∼20 kV mm−1 at a current between 0.8 and 1 A. If the current decreases below this level, the arc remains in vibrational–translational (VT) equilibrium by increasing the electric field. However, VT equilibrium conditions can be only maintained until a threshold minimum current of 0.33 ± 0.05 A, at which the arc transitions into a non-equilibrium condition with further increasing electric fields (reaching 68 ± 15 V mm−1 at 0.03 A). The addition of N2 or H2O did not influence the electrical characteristics of the CO2 arc within to the tested mixtures. However, there is only a significant decrease in the electric field of the formed transition arcs and the threshold minimum current in the presence of N2. The spectra of the low-current CO2 arc is found to be dominated by emission from the C2 Swan band system and the O I 777 nm triplet peak. However, the CN band dominates the spectra even when small amounts (0.5 wt%) of N2 is present in the plasma. The gas temperature at the axis of the CO2 arc plasma decreased slightly with decreasing current, from an estimated 7000 K at 1 A down to 6300 K at 0.4 A. The thermal radius of the arc is estimated to be larger than 1.2 mm, more than two times larger than the optical radius obtained from the emitted radiation. The addition of N2 and H2O (up to 7 and 9 wt% respectively) lead to only to a 500 K decrease in the axial arc temperature.

Sedimentological Investigation of the Euphrates River from Babylon to Basrah, Iraq

The Euphrates River is considered a famous one among the rivers in the world. The current study is an attempt to give information about the bed sediments from Hilla to Shatt Al-Arab at Basrah, through sedimentological investigations. Forty-two samples were subjected to grain size analysis, representing twelve core sampling sites. The sand fractions (fine-very fine) decrease from Hilla to Basrah cities, beside the interval depths from top to bottom, whereas the silt fractions increase in the same direction and the depth interval, because the water current declined. The light minerals are examined by a polarized transmitted microscope as well as scanning electron microscopy and energy dispersive X-ray spectrometer techniques. The light minerals consist of 95.7%, and the heavy minerals of 4.3% among the total counted grains. The rock fragments, particularly carbonate and chert are the predominant constituents and increase from Hilla to Basrah cities, followed by quartz reduced in the same pattern. In addition, the lowest abundance of feldspar minerals where recognize in lower values also decreases to the southern orientation. Monocrystalline quartz is higher than polycrystalline. However, plagioclase is lesser in proportion than potash feldspar (orthoclase and microcline). The river bed sands are litharenite classification, and petrogenically, are transition recycled to transition arc referring to orogenic recycled derivation.

Design and deformation analysis of an inflatable metallic cylinder based on the Kresling origami pattern

Inflatable space capsules can be compactly folded to a small volume during launch and then deployed in space to create a large enclosed place for astronauts and equipment. Current inflatable space capsules are usually made of soft composite materials and need to be rigidized after deployment, but the rigidization techniques to date cannot meet the requirements of high stiffness and low thermal expansion simultaneously. The study on cylindrical transformable volume structures based on metals is also limited due to the large in-plane deformation during manufacturing and deployment. Here, we propose a novel inflatable metallic cylinder based on the Kresling origami pattern which has a large deployment ratio and high stiffness without rigidization. The folding and deployment process of the cylinder with varying geometric parameters and inflation rates are investigated through numerical simulation that is validated by experiments, from which the deformation process, maximum plastic strain, and the deployment ratio are unveiled. The results show that the maximum plastic strain reduces with the increase in the total number of creases in the cylinder and their transition arc radius, but a large number of creases will lead to a lower deployment ratio. To achieve a deployment ratio of 3.35 which is comparable with those of the state-of-the-art inflatable space capsules, the maximum plastic strain is kept below 0.18. This proposed metallic origami cylinder thus shows great potentials in the application of space capsules.

The Cretaceous Sedimentary Environments and Tectonic Setting of the Southern East China Sea Shelf Basin

Although the amount of oil and gas reserves and the reservoir properties in the East China Sea Shelf Basin (ECSSB) indicate good prospects for oil and gas exploration in the Mesozoic strata, there has not yet been a significant breakthrough in oil and gas production. An important reason is that there are few detailed studies on the sedimentary paleogeography of the ECSSB which make it difficult to predict the distribution of sand bodies. In this paper, well-core observations, thin-section identifications, electron probe microanalysis, trace elements analysis and seismic interpretations were synthetically applied to study the sedimentary environments and the tectonic setting of the Upper Cretaceous in the southern ECSSB. In the Oujiang Sag, red mudstones and pyroclastic rocks were deposited, accompanied by wedged, chaotic pro-grading reflections in the seismic profile, indicating a volcano-alluvial fan sedimentary system. Abundant sedimentary structures including double-mud drapes, asymmetric herringbone cross-beddings and burrows, such as Planolites and Skolithos, were developed in the Minjiang Sag, typically indicating a high-energy tidal environment. The autogenetic glauconites in situ and the fossil Tintinnid also indicate a shallow marine environment. The resulting sedimentary characteristics are in accordance with the littoral facies revealed by the seismic reflections in the Minjiang Sag. Moreover, volcanic conduit facies, effusive facies, and pyroclastic facies were also recognized in the seismic profile in the Minjiang Sag. Therefore, it was presumed that subaqueous volcanic eruptions occurred in the Minjiang Sag. In the Keelung Sag, the littoral facies were dominant. The tectonic setting of the Upper Cretaceous in the southern ECSSB is the transitional arc accompanied by large-scale volcanic activities. In conclusion, the volcano-alluvial fan sedimentary system was developed in the Oujiang Sag and volcano-littoral sedimentary system was developed from the Minjiang Sag to the Keelung Sag. This study is intended to promote the understanding of the sedimentary paleogeography of the Upper Cretaceous in the southern ECSSB and to provide help in oil and gas exploration.

Studi Batuan Asal (Provenance) Batupasir Formasi Simpangaur Daerah Way Krui, Lampung

Bengkulu basin is the one of fore arc basin which formed in Sumatra island. The basin formation is inseparable from tectonic activity of the Sumatra Island from the Pre-Tertiary era to present day. The relationship between tectonic activities and the basin filling can be identified by conducting a provenance study on the sedimentary rocks. The Simpangaur Formation is a Tertiary sedimentary rock that has filled the Bengkulu Basin in the southern Sumatra. The aim of this research is determining the provenance of Simpangaur Formation existed in Way Krui area, Lampung, and its tectonic environment. The observations of thin section were carried out on eleven sedimentary rock samples obtained from field. The provenance of these rocks is analyzed by quantifying the mineral composition microscopically. The result analysis show that the grains originated from a magmatic arc environment, specifically the transitional arc and undissected arc. Based on the presence of polycrystalline quartz in eleven rock samples, it is interpreted as originating from the Orogen Arc. In addition, it is also interpreted that the provenance for sandstone samples of the Simpangaur Formation are plutonic and metamorphic rocks in a semi-arid climate, based on ancient climate.

Numerical study of nozzle erosion in a hybrid rocket motor with wagon wheel fuel grain

Nozzle erosion directly affects the design quality of hybrid rocket motors, and it is a critical issue that restricts the practical application of hybrid rocket motors. In this paper, coupled numerical simulations of combustion flow field and thermochemical erosion of a graphite nozzle in a hybrid rocket motor with multi-port wagon wheel fuel grain are carried out. The results indicate that distributions of temperature, species and erosion rate in the flow field of hybrid rocket motor with wagon wheel grain show symmetrical characteristics related to the grain shape. The erosion rate decreases at first and then increases at the convergent section of throat insert, and it reaches the maximum value at the transition arc between convergent section and straight section of the throat. The maximum erosion rates at the central hole (position A) and outer edge of wheel holes (position B) are 0.0625 mm/s and 0.0902 mm/s, respectively. The erosion rate increases slowly in the straight section of the throat and it decreases gradually in the divergent section. Circumferentially inhomogeneous ablation occurs in the throat, and the erosion rate at the front end of throat straight section varies from 0.0484 mm/s to 0.0809 mm/s. The main oxidizing species causing thermochemical erosion are H2O and OH. At position A in the front end of throat straight section, erosion rates caused by H2O and OH are 66.50% and 30.48%, respectively. With the increase of oxidizer mass flow rate, the combustion chamber pressure increases linearly, and the erosion rate at position A in the front end of throat straight section gradually increases, but the growth rate decreases.

Mineralogy and Geochemistry of Sandstones from the Tanjero Formation, Bekhme Gorge Northeastern Iraq: Implications for Paleoweathering and Provenance

The Tanjero Formation is exposed on the Northern flank of the Perat anticline near the Northern entrance to the Bakhme gorge through which the waters of the Upper Zab flow. As for tectonics, it is located within the High Folded Zone of the Unstable Shelf. The Tanjero Formation is about 80 m. thick, it is bounded from the bottom by the Shiranish Formation. The formation consists of gray sandstone that contains gravel at the bottom followed by beds of marl, hard sandstone, and black claystone containing cushioning structures and small-scale cross-bedding are present. According to the Williams classification, theTanjero sandstones drop at the lithic wacke field. The provenance of these sandstones was investigated based on their minerals and geochemical composition. The geochemical analyses showed low silica, a negative correlation of silica with the most major oxides due to recycling sedimentary sources or weathering of silicates. The index of compositional variability indicates that the sandstones of the Tanjero Formation are immature clastic sediments and the high index of compositional variability values confirm that the clastic sediments occurred in the tectonically-active-settings area. Moderate chemical weathering has dominated in the studied area, which was inferred from the chemical index of alteration, the chemical index of weathering and the plagioclase index of alteration. Based on the tectonic discrimination diagrams, the Tanjero sandstones are quartzose sedimentary provenance, felsic igneous rocks source, transitional arc–lithic recycled setting, and located in the collision zone between the passive Arab margin and the effective Iranian-Turkish margin that formed the orogeny belt along the collision zone.

Radially loading rotary extrusion for manufacturing large-size conical cylinders with inner transverse high ribs

The Large-size Conical Cylinders with Inner Transverse High Ribs (LCCWITHR) can reduce the weight of the parts while maintaining high rigidity and strength. Radially Loading Rotary Extrusion (RLRE) forming technology can achieve integral forming of LCCWITHR through the synergy of radial and rotary movements of dies. The flow law of the material during the forming process is the key to forming large-size inner ribs. At present, there is no unified understanding of the metal flow law of RLRE forming technology. An analytical expression was derived to predict the Radial Direction (RD) deformation loads. The FE simulation and process experiment were carried out to investigate the effects of the inclination angle, thickness factor and transition arc radius of the split top dies on the spacing of the metal diversion plane, the metal flow velocity of the rib area and the final radius of the inner rib. The influence of the split top dies loading distance and the bottom die rotation angle of each pass on the inner radius of the inner rib was verified. And the optimal combination of dies shape parameters and loading paths which can make the metal flow orderly was obtained: the inclination angle is 140°, the thickness factor is 3.64, the transition arc radius is 16 mm; the top dies loading distance is 15 mm, the bottom die rotation angle is 45°. The FE simulation results have been found to be in close agreement with physics experiment. The research results reveal the metal flow law of rib growth in the RLRE of LCCWITHR, which lays a theoretical foundation for subsequent thorough research and process optimization.

Fracture failure of the multi-throw crankshaft in a sport utility vehicle

A sport utility vehicle crankshaft was premature failure after a short service life of about 3 years. The fracture took place at the transition arc between the crankpin and the journal. The fracture surface has an angle of 45° inclination with the axial direction of the crankshaft, which is in accordance with the maximum primary stress plane caused by the torsion. A fractographic study indicates that the fracture surface exhibits a brittle fracture morphology reflective of a low toughness of the material. Macro beach marks and micro striations indicate that the failure mechanism of the crankshaft is fatigue failure. Metallographic analysis shows that flake pearlite and reticular ferrite are the characteristics of the microstructure near the fracture surface, which may lead to the lower plasticity of the material. Reticular ferrite is induced by the heterogeneous inclusion with a chemical structure of CaO-MnS complex. The weaker ferrite destroys the continuous matrix material and reduces the plasticity of the material, resulting in a brittle fracture. Collected evidence reveal that a series of manganese sulfide inclusions are distributed near the crack initiation. According to the quantification analysis of inclusion distribution, the density of inclusions is great enough to act as the initiation of cracks. Moreover, finite element analysis indicates the stress concentration induced by the geometry structure is less than the inclusion. Given all of that, the failed crankshaft is supposed to be initiated by the harmful inclusions. Therefore, it is recommended that rigorous testing of the inclusions and improving the heat treatment quality of crankshafts are effective ways to solve the problem.

Experimental study on dressing concave trapezoidal diamond grinding wheel by electrical discharge grinding method

Electrical discharge grinding (EDG) method is proposed for dressing bronze bonded diamond grinding wheel for the first time. The advantage of this dressing method is that it can realize the discharge removal of non-conductive diamond abrasive particles and greatly improve the dressing efficiency. It is suitable for dressing coarse-grained complex forming grinding wheel. The material removal mechanism in EDG dressing is deeply analyzed, and a three-dimensional heat conduction model in the discharge process is established. The temperature field distribution in bronze and diamond under corresponding discharge parameters is obtained by numerical simulation, and the grinding depth is optimized based on the softening depth of diamond. The dressing scheme of quickly removing the rectangular block area first and then approaching layer by layer according to the design profile is formulated. The high-precision concave isosceles trapezoidal grinding wheel is dressed by using the optimized machining parameters. Finally, the dressing accuracy is evaluated by grinding the graphite plate. The detection results show that the dimensional errors of the upper and lower lines are all within 5 μm, the dimensional error of the height is 9 μm. The maximum error of the angle between the two waist is 0.33°. The minimum transition arc radius between waist and lower line is 202 μm. The straightness errors of the lower line and the two waist oblique lines are less than 7 μm. The profile error at the transition between waist and lower line is less than 62 μm.

Petrogenesis of the East Hoerba harzburgites, SW Tibet: Implications for melt stagnation in the lithospheric mantle of Neo-Tethys

In this study we present petrographic and compositional data for harzburgites from the eastern parts of the Hoerba Massif of the Yarlung-Zangbo Suture Zone (YZSZ), SW Tibet. These harzburgites are cross cut by semi-ductile mylonitic zones. The investigated rock samples contain aggregates of unstrained clinopyroxene with tapered edges. They also contain olivine with a high forsterite [Fo# = Mg/(Mg + Fe) × 100] content (89.3–91.8), orthopyroxene with a low Al 2 O 3 content (2.0–5.6 wt%), and clinopyroxene porphyroclasts with Cr 2 O 3 contents between 0.2 and 1.0 wt% and low lanthanide contents. Chromian spinel (Cr-spinel) in the East Hoerba harzburgites has low Cr# [100 × Cr/(Cr + Al)] and high Mg# [100 × Mg/(Mg + Fe)] values (23.7–39.2 and 62.2–76.3, respectively). These harzburgites have chondrite-normalized rare earth element (REE) patterns characterized by enrichments in the light (L-)REE and positive slopes from the middle to the heavy REE. Semi-quantitative geochemical modeling demonstrates that the bulk-rock compositions of the East Hoerba harzburgites differ from those of typical abyssal and forearc peridotites. Clinopyroxene trace element modeling suggests that the East Hoerba harzburgites initially underwent melting below a mature spreading center, followed by melting in the mantle wedge above a Cretaceous Neo-Tethyan subduction system. Enrichment of the harzburgite samples in LREE is interpreted as due to post-melting entrapment of small volumes of a LREE-rich melt in the lithospheric mantle. We suggest that the East Hoerba harzburgites are sub-oceanic peridotites that underwent melt depletion events and melt stagnation before their exhumation at the Neo-Tethyan seafloor. • The East Hoerba Massif is composed of variably depleted harzburgites. • They were formed from mantle depletion events and post-melting magma stagnation. • They were generated beneath a transitional arc–back-arc setting. • They do not represent fragments of old sub-continental lithospheric mantle.

Modelling and experiment for grinding forces of gear form grinding considering complete tooth depth engagement

Grinding is an essential gear finishing method. Grinding force analysis and prediction are critical to understand grinding mechanisms. By using a geometry model for gear form grinding and surface grinding mechanisms, a theoretical model was established to calculate the gear form grinding force. By considering the complete tooth depth engagement between tooth grooves and wheel profiles during form grinding, three segments of the involute, transition arc and tooth bottom line, which were included in complete tooth groove profiles, were analysed using the model. Contact relations among the normal grinding depth, wheel equivalent radius, wheel linear velocity and wheel profile were obtained. In addition, grinding experiments were outperformed on the basis of the single tooth, and the unknown coefficients of the form grinding force calculation model were acquired. The effects of the grinding depth, feed speed and grinding speed on grinding force were analysed using the grinding force model. The comparison of the predicted values of the form grinding force model with the experimental results, indicated that the relative errors of tangential and normal grinding forces are within ±10% and ±12%, respectively. The results confirmed the accuracy of gear form grinding force calculation model. These findings play a key role in parameter optimisation during gear form grinding.

Provenance evolution of the San Juan Precordillera Silurian-Devonian basin (Argentina): Linking with other depocentres in Cuyania terrane

This paper explores the sedimentary provenance of the Silurian to Devonian siliciclastic successions in the Central region of the San Juan Precordillera, in central-western Argentina. The comprehensive provenance analysis of the Tambolar Formation (upper Silurian), Talacasto Formation (Lower Devonian) and Punta Negra Formation (Lower-Middle Devonian) from the San Juan River section is based on petrography, detrital zircon analyses and combined U–Pb and Lu–Hf isotopic data. Modal composition of the three units here studied shows an evolution trend from quartzose recycled, mixed, to transitional arc. Detrital zircon morphologies indicate derivation from dominantly plutonic and metamorphic sources with little evidence of transportation. The most representative detrital zircon U–Pb age populations are Famatinian (middle Cambrian - Devonian), Pampean–Brazilian (Tonian - lower Cambrian), and Grenvillian (Ectasian - Stenian) cycles derived rocks. Hf isotopes determined mainly in Mesoproterozoic detrital zircons reflect a juvenile mantle source during crystallization, with less significant inputs from those with a crustal and recycled crust origin. Results from this work are compared to data from outcrops of the same units developed in the North-Central region of the Precordillera, presented in previous works. Provenance proxies provide insights regarding the correlation of probably equivalent units deposited in other foreland basins within the Cuyania terrane, such as the Villavicencio Formation (Mendoza Precordillera), Río Seco de los Castaños and La Horqueta Formations (San Rafael Block). The K–S test suggests a low correlation between the units studied at the San Juan River and the equivalent outcrops exposed towards the central and northern parts of the San Juan Precordillera, as well as with the known records of the Río Seco de los Castaños and La Horqueta Formations of the San Rafael Block. In contrast, the samples from the Villavicencio Formation show a high correlation with the sample from the Punta Negra Formation, indicating a possible common sediment source. The broad variations of U–Pb detrital age pattern distributions observed between Silurian and Devonian successions throughout the Precordillera and the San Rafael Block point to provenance shifts linked to variability in east-to-west sediment dispersal patterns within an axial peripheral foreland basin. Fluctuations in the sedimentary composition are ascribed to the differential exhumation rate of source rocks and a progression from a convergent tectonic setting in the San Rafael block towards a coeval collisional environment in the Precordillera. The Silurian - Early Devonian foreland basin is tectonically linked to the Ocloyic Orogen that resulted from the collision of Cuyania terrane to the Western margin of Gondwana. Source rocks were most likely located within the Mesoproterozoic basement of Cuyania, exhumed during the Middle Devonian as a response to the approximation of Chilenia.

Early Eocene high-Sr/Y magmas from the Urumieh-Dokhtar paleo-arc, Iran: Implications for the origin of high-flux events in magmatic arcs

High-flux magmatic events, or flare-ups, are seen in many continental and transitional arcs but the underlying cause is not fully understood. Throughout Iran, voluminous calc-alkaline rocks emplaced between ~53 Ma and ~37 Ma are manifestations of a high-flux event. This high-flux event has been attributed to extension in the upper plate of one or more Neo-Tethyan subduction zones. Here, we present new findings in the Urumieh-Dokhtar paleo-arc, Iran where emplacement of Early Eocene granitic intrusions (ca. 55–52 Ma) immediately preceded the high-flux event. Geochemically, the studied rocks display high-K calc-alkaline compositions, continental crust-like trace element patterns, variable depletion of Y and heavy rare-earth elements, and SrNd isotopes that are close to or slightly more enriched than the Bulk Silicate Earth. The SrNd isotopic compositions indicate that the intrusions derived from upper plate materials. Relatively high Sr/Y and La/Yb of the studied rocks indicate that the residue of melt extraction, the crystalline assemblage that was left behind during magma differentiation, or both, to have existed in the deep arc crust. Following a ~ 20 Myr magmatic lull, the Early Eocene crustal thickening was most likely related to underthrusting of rear-arc crust towards the main arc, a process that not only promoted rapid root growth but also triggered the Eocene high-flux event. In the Iranian case example in particular, magmas formed during the high-flux event do not display elevated Sr/Y, implying that dense, locally thickened root might have foundered from the base of the arc lithosphere to the convecting mantle soon after their formation.

An Innovative Method for Designing Smooth Catenary Well Trajectories in Extended-Reach Drilling

A catenary well trajectory is known for its reduced drag and torque during drilling. Modern deflection tools have made it possible to drill catenary well trajectories efficiently, thanks to tool’s capacity of dynamic build rate that creates wellbore profile of varying curvature. However a method to design well trajectory with smooth transition from the kick-out point to the catenary section to reduce “dog-leg” and thus friction is still lacking. This paper presents a 2D mathematical solution to fill the gap. The solution uses equations of closed-form rather than numerical computations. The complete well trajectory profile involves a vertical section, a transitional arc section, a catenary section, and a horizontal/slant section. A case study is presented to compare the friction forces on the drill string in a catenary trajectory profile and a conventional trajectory profile of arc type. The calculation procedure of catenary trajectory design was realized in an MS Excel spreadsheet with direct inputs, which provides an excellent flexibility to meet well trajectory design requirement. The presented mathematical model is an easy-to-use and reliable tool for designing catenary well trajectories in extended-reach wells to minimize wellbore friction and thus increase well depth.

Is the cubic parabola really the best railway transition curve?

Abstract In the current study, the authors tested two railway transition curves in terms of their usefulness for railway practice. The first curve was a cubic parabola – the curve most popular in railway engineering. The second curve was a polynomial of ninth degree, and this curve was chosen due to the fact that this curve satisfies advanced geometrical demands. In this study, the model of a two-axle vehicle was applied. The study relied on the passage of the vehicle model through the route consisted of straight track, railway transition, and circular arc. Three different circular arc radii were used. The value – 0.6 m/s2 – of maximum lateral acceleration in the circular arc was applied. Three different vehicle velocities were also used. In this study, the authors simulated vehicle dynamics for different curves and ten lengths of the curves. As the main criterion, lateral acceleration of the vehicle body was applied. The results for these two mentioned curves were compared.