Transitional Arc Research Articles

Geochemistry and weathering history of the Balfour sandstone formation, Karoo basin, South Africa: Insight to provenance and tectonic setting

Geochemical analysis on sandstones from clastic sediments was carried out to understand the tectonic setting and subsequent post-depositional change in the Karoo basinal fill of the fluvial deposits of the Balfour Formation during the Late Permian to Early Triassic period. The major and trace element analysis reveal a relatively homogeneous provenance for the sandstones. The geochemical analysis shows that these rocks are first order mature sediments, derived from igneous and/or meta-igneous rocks of a felsic composition. The results show that the sandstone consists of SiO2 (71.58 wt. %), followed by Al2O3 (14.48 wt. %), but with low contents of Fe2O3+MgO (4.09 wt. %) and TiO2 (0.47 wt. %). These sandstones are classified as litharenites and arkoses based on the elements constituent ratio of various schemed adopted. The sandstone in the provenance discrimination diagram plots in the dissected and transitional arc fields suggesting an active margin and continental island arc provenance, preserving the signature of a recycled provenance. The Chemical Index of Alteration (CIA) ranging from 63.56 to 67.10% suggests recycling processes, and that the source area has undergone a moderate degree of chemical weathering. The geochemical characteristics of the sediment suggest the source area of uplifted terrane of folded and faulted strata with detritus of sedimentary and metasedimentary origin.

Failure analysis on premature fracture of boric acid recycle pump shaft in 1000 MW nuclear power plant

Abstract Boric acid recycling pump is used to maintain the circulation of boric acid solution for the need of nuclear safety protection. In a boric acid recycling pump, the pump shaft is an important component. As it is exposed to relatively harsh work environment, the pump shaft may encounter severe failures. In this paper, premature fracture of the pump shaft, happened after the pump serving only one year in a 1000 MW nuclear power plant, was carefully investigated. In order to find out the root cause of the failure, material identification, metallographic inspection, mechanical property test, wear and fractographic observation, micro-zone analysis and mechanism analysis were carried out. The obtained results indicated that triple stress concentration, caused by the small transition arc radius, surface defects and the aggregation of inclusions, was the primary reason. It resulted in the nucleation and coalescence of micro-cracks and consequently lead to the premature fracture. Countermeasures were then put forward to solve corresponding problems.

Zircon U-Pb ages and Hf isotopes of Paleozoic metasedimentary rocks from the Habahe Group in the Qinghe area, Chinese Altai and their tectonic implications

As one of the largest accretionary orogens in Earth's history, the Central Asian Orogenic Belt has attracted much attention in the past two decades, but there are still many unresolved issues regarding its tectonic nature and evolution. This is the case with the Chinese Altai whose tectonic provenance remains controversial, especially for the Paleozoic era. As the most widely exposed meta-sedimentary rocks in the Chinese Altai, the Habahe Group was previously considered as representing a component of Precambrian micro-continent, forming at a passive continental margin. Our new U-Pb data for detrital zircons from the Habahe Group in the Qinghe region of the eastern Chinese Altai indicate that the strata were deposited from the late Silurian to early Devonian (427–405 Ma) and experienced regional metamorphism in the middle Devonian (383 ± 9 Ma), as constrained by the age of youngest detrital zircons (427 ± 13 Ma), the age 405 ± 3 Ma of the tonalite that intrudes the Habahe Group, and the metamorphic age of 383 ± 9 Ma. Additionally, the majority of zircons from the Habahe Group have positive εHf(t) values (+0.22–+15.02). These data, combined with geochemical features and maturity of the sedimentary rocks, indicate an immature provenance for the Habahe Group, with the source materials mainly derived from a juvenile crust with some old continental components. The juvenile crust was most likely formed in a subduction zone, developing in the Chinese Altai during early-middle Paleozoic time. New geochemical data presented in this study suggest that the Chinese Altai was a transitional arc during early Paleozoic time, similar to the Japan-type arc with involvements of old continental components. Therefore, it is proposed that the Chinese Altai was likely rifted from the south margin of the Siberia Craton, probably related to the break-up of the Rodinia Supercontinent, and then experienced accretion and reworking with the subduction of the Paleo-Asian Ocean during early Paleozoic time.

Strong behavioral similarities in timed-arc Petri nets

The concept of process similarity has attracted the attention of many researchers in the recent literature, since it measures the degree of proximity of processes. Similarities are therefore useful for the efficient management of large repositories, since they allow us to find the appropriate process models among hundreds or thousands of possible candidates. However, time constraints are usually omitted when these similarity measures are defined, so in this paper two similarity measures are defined over a timed extension of Petri nets, the so-called timed-arc Petri nets, in which tokens are assigned an age indicating the time elapsed from creation, and PT-arcs (place to transition arcs) are labeled with time intervals that are used to restrict the age of the tokens that can be used to fire the adjacent transition.

Peri-Laurentian, Pinwarian-age oceanic arc crust preserved in the Grenville Province: Insights from the Escoumins supracrustal belt

The remnants of an island arc system of Pinwarian age, the Escoumins supracrustal belt (ESB), are exposed for over 100 km in the Low-pressure belt of the Central Grenville Province (Canada), and are part of the Quebecia terrane. The ESB mainly consists of amphibolite-facies supracrustal rocks with well preserved primary textures (Saint-Siméon Group; SSG), and their plutonic counterpart (Tadoussac Intrusive Suite; TIS) that provide a record of the evolution of a Mesoproterozoic arc system. Granodiorite (1502 ± 6 Ma) and tonalite of the TIS have calc-alkalic oceanic arc signatures, positive εNd (+2.66) with old model age (1672 Ma) consistent with remelting of previously formed juvenile mafic crust and interaction with an older crustal component, and are crosscut by younger within-plate granitoids. Tectonically above the TIS, the lowest formation of the SSG (Saint-Paul-du-Nord) consists of sedimentary, and minor basalt, intruded by syn-volcanic juvenile (εNd = +5.21) tholeiitic gabbro and is interpreted to represent the remnants of an oceanic basin adjacent to an arc. The middle formation (Moulin-à-Baude) records an evolution from: (a) subalkaline tholeiitic to transitional arc basaltic andesite, basalt, and minor calc-alkalic volcanic arc 1492 ± 3 Ma dacite with crustal-derived signature (εNd = −0.77, model age of 1936 Ma), to (b) transitional to tholeiitic dacite–rhyodacite and 1464 + 38/−32 Ma rhyolite, and (c) subalkaline juvenile (εNd = +3.91–+4.92) tholeiitic basalts and FeTi basalts of arc rift and back-arc affinities. This formation is interpreted to represent an oceanic arc undergoing rifting. Finally, the upper formation (Port-aux-Quilles) is composed of epiclastic sedimentary rocks with detrital zircon of Laurentian affinities, indicating proximity of the arc to Laurentia, but dominated by 1.5–1.47 Ga ages, showing a maximum age of deposition of 1476 ± 10 Ma. The εNd and Nd-model ages indicate an association of mixed crustal and mantle-derived signatures typical of Quebecia crust combined with younger depleted mantle-derived basaltic magma. The data provide new insights on the organisation of Quebecia, and show that crust formed in an oceanic arc setting during late Geon 15 to Geon 14 constitutes a significant component of the central Grenville Province.

A prediction method for fatigue life of large moving components as function of scale factor: A case of motor‐generator rotor

AbstractWith the development of science and technology, more and more large moving components have been used in industry, and their service lives have become an important issue. After analysis of the previous results, considering the scale factor, a prediction method for fatigue life of large moving components based on the Basquin relation was proposed at first, and then the magnet pole part of motor‐generator rotor was chosen to make simulation parts with different scale factors mainly in terms of their S‐N curves and fractographies. It was found that with the change of specimen scale factor, the stress concentration factor at transition arc is almost unchanged as well as the fatigue strength exponent, and the fatigue strength coefficient changes linearly. Based on those results, a life prediction method was validated, and the results show that this method is a simple but more precise relation. After fatigue fracture surface and crack growth angle observations and quantitative analyses, the fatigue damage mechanisms associated with the relation among fatigue strength exponent and coefficient and scale factors were explained well. Those studies will provide a new clue to the prediction of the service life for those large moving components.

Influence of welding parameters on diffusible hydrogen content in high-strength steel welds using modified spray arc process

In order to satisfy the growing requirements towards lightweight design and resource efficiency in modern steel constructions, e.g., mobile cranes and bridges, high-strength steels with typical yield strength ≥ 690 MPa are coming into use to an increasing extent. However, these steels require special treatment in welding. The susceptibility for degradation of the mechanical properties in the presence of hydrogen increases significantly with increasing yield strength. In case of missing knowledge about how and the amount of hydrogen that is uptaken during welding, hydrogen-assisted cracking (HAC) can be a negative consequence. Moreover, modern weld technology like the modified spray arc process enables welding of narrower weld seams. In this context, a reduced number of weld beads, volume, and total heat input are technical and economical benefits. This work presents the influence of welding parameters on the diffusible hydrogen content in both (1) single-pass and (2) multi-layer welds. Different hydrogen concentrations were detected by varied contact tube distance, wire feed speed, arc length, and varied arc type (transitional arc and modified spray arc). The results show that all welding parameters have significant influence on the diffusible hydrogen concentration in the single-pass welds. By increasing the number of weld beads in case of multi-layer welding, the hydrogen concentration has been reduced. Whereby, differences in hydrogen concentrations between both arc types are present.

Tectonic evolution of the Juvenile Tonian Serra da Prata magmatic arc in the Ribeira belt, SE Brazil: Implications for early west Gondwana amalgamation

The evolution of the Ribeira belt resulted from the progressive amalgamation of several terranes against the eastern margin of the São Francisco Craton between ca. 620 and 580Ma. This work brings new field, U-Pb geochronology, geochemistry and isotopic (Sm-Nd and Sr) data on the evolution primitive rocks from the Serra da Prata magmatic arc and their relationships with the previously described Rio Negro arc. The new U-Pb data allow the distinction of two episodes of arc generation: the Serra da Prata Arc (856–838Ma) and the Rio Negro Arc (790–620Ma). Rocks from the oldest stage are composed of metaluminous calc-alkaline diorites, tonalites and granodiorites, and geochemical signatures compatible with magmatic arc scenarios. Their rocks are associated to a metamorphosed volcano-sedimentary of intra or back-arc basin setting platform carbonates, amphibolites (basaltic lavas) and psammitic rocks of the Italva group. Whole-rock Nd and Sr isotope data indicate more primitive contribution than earliest stage: initial εNd=−3.7 to +5.2, TDM=1.68–0.92Ga and 87Sr/86Sr initial ratios between 0.7061 and 0.7113. The second stage – Rio Negro arc – yielded more mature arc signatures: initial εNd=−8.4 to −2.5, TDM=1.93–1.33Ga and 87Sr/86Sr initial ratios between 0.7098 and 0.7211. The new data have been interpreted as an evolution of a Tonian primitive intra-oceanic stage of the magmatic arc generation, followed by more continental or transitional arcs during the Rio Negro stage. The data from both arc stages contrast with the younger Serra da Bolívia and Rio Doce continental arcs (570–590Ma) developed in a proximal location. The data are similar to other Tonian-Ediacaran magmatic arcs: the Goiás arc in the Brasília Belt (ca. 862–630Ma) and the São Gabriel arc (ca. 840–690Ma), located respectively along the western margin of the São Francisco and Rio de La Plata cratons. In a Western Gondwana scenario, the juvenile signature indicates intra-oceanic tectonic settings. The combination of the older Tonian arcs with the more evolved Cryogenian to Ediacaran arcs within the Neoproterozoic belts, suggests more than 200m.y. of subduction around the older cratonic blocks that made up Western Gondwana.

Fretting fatigue fracture of the supporting shaft in a rotary kiln

Abstract The fracture failure of the supporting shaft in a rotary kiln was analyzed to determine the failure mechanism. The rotary kiln was used to heating and mixing nickel ores and was supported by four group riding wheels with two wheels in each group. One of the supporting shafts was found fractured after it was used for about two years. The fracture was located at the interface between the supporting shaft and the sleeve. This location was 100–120 mm far from the transition arc of the supporting shaft where high stress concentration usually occur. A failure analysis was carried out, using characterization techniques such as scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and so on. Obvious fatigue propagation zone caused by multi-initial cracks were observed at the circle edge of the fracture surface. Adhesive wear and some circumferential cracks were found on the outside surface of the supporting shaft. It was considered that fatigue due to the fretting wear between the shaft and sleeve was the most probable mechanism.

Petrogenesis and tectonic implications of Late Devonian arc volcanic rocks in southern Beishan orogen, NW China: Geochemical and Nd–Sr–Hf isotopic constraints

Late Devonian (ca. 370Ma) volcanic rocks provide important information about the nature of magmatism during the tectonic transition between the Early and Late Paleozoic in the Beishan orogen, southern Central Asian Orogenic Belt. They are predominantly an andesitic–dacitic–rhyolitic assemblage, characterized by alkali contents ranging from slightly calcic to slightly alkaline. The rhyolitic rocks are generally ferroan, whereas the andesitic rocks are magnesian. These volcanic rocks exhibit similar trace element characteristics to those of continental arcs. Strongly negative εNd(t) values (−2.8 to −3.6) and high Sr isotopic compositions (initial 87Sr/86Sr=0.7036–0.7108) suggest that they are mainly derived from an ancient crust. However, the positive zircon εHf(t) values (+1.4 to +16.4) support the role of juvenile components in their genesis, indicating the significant input of new mantle-derived magmas. These characteristics imply a hybrid derivation, from an ancient crustal source with the addition of juvenile materials during magma genesis, or perhaps heterogeneous contamination or hybridization during magma emplacement. Combined with the regional geology, our results indicate that the Late Devonian magmatism resulted from a southward retreat of the subduction zone, which records significant continental crustal growth in a transitional arc or an accretionary arc setting. The distinct geochemical compositions, especially the Nd–Hf isotope decoupling of the Dundunshan volcanic rocks, imply a significant change in the geodynamic setting in the Late Paleozoic.

Two-Way Bounded Dynamic Programming Approach for Operations Planning in Transshipment Yards

We propose a two-way bounded dynamic programming (TBDP) approach to deal with situations, when it takes a long time to evaluate the value function in the state graph of dynamic programming. TBDP provides sharp bounds early in the solution process and identifies critical subproblems, i.e., states and transition arcs, for which the value function has to be estimated. Based on the TBDP framework, we develop a heuristic and an exact algorithm for the static crane scheduling problem (SCSP). The SCSP refers to simultaneous yard partitioning into single-crane areas and job sequencing at railway container transshipment yards, where both rail-rail and rail-road transshipments are present and rail-rail moves are short. The designed exact solution algorithm solves instances of practically relevant size within acceptable time limits. The proposed heuristic finds optimal solutions in 90% of the cases. We recommend using the heuristic algorithm for planning very large transshipment yards, with more than five tracks and a large number of container moves per crane.

Sedimentology, provenance and geochronology of the Miocene Qiuwu Formation: Implication for the uplift history of Southern Tibet

Located on the south of the Gangdese, the Qiuwu Formation has traditionally been considered as Eocene coal-bearing clastic sediments consisting of sandstone, mudstone and conglomerate, unconformably on top of Gangdese batholith. However, its precise age and depositional environment remain ambiguous. Here, we present a newly measured stratigraphic section near the Ngamring County, western Xigaze. Detrital zircon U–Pb ages were also applied to trace the provenance of sediments and to constrain the maximum depositional age of the Qiuwu Formation. Sedimentary facies analyses indicate subaqueous fan and alluvial fan depositional environments. Clast composition of the conglomerate is dominated by magmatic rocks at the lower part, while chert and mafic detritus occur in the upper part, suggesting a southern source. Sandstone modal analyses indicate that the compositions of quartz, feldspar and lithic grains changed from transitional arc to dissected arc, implying the unroofing of the Gangdese arc. Detrital zircon U–Pb ages of the Qiuwu Formation are compared with those from Gangdese magmatic rocks and Yarlung-Zangbo ophiolites, suggesting that the Gangdese arc is a main source of the Qiuwu detritus and that the southern source played a role during the later stage. The major peak of detrital zircon ages is at 45–55 Ma, which corresponds to Linzizong volcanic rocks in southern Gangdese arc. The weighted mean age of the five youngest zircons from the lower part of the section is 21.0 ± 2.2 Ma, suggesting that the Qiuwu Formation was deposited in early Miocene, coeval with other conglomerates exposed along the southern margin of Gangdese. Combining new observations with previously published data, we propose that the provenance of the Qiuwu Formation had shifted from a single northern source to double sources from both the north and the south. Activities of Great Counter Thrust were primarily responsible for the shift by making the south area a high elevation to provide sediments for the Qiuwu Formation.

Compressive failure modes and parameter optimization of the trabecular structure of biomimetic fully integrated honeycomb plates

To develop lightweight biomimetic composite structures, the compressive failure and mechanical properties of fully integrated honeycomb plates were investigated experimentally and through the finite element method. The results indicated that: fracturing of the fully integrated honeycomb plates primarily occurred in the core layer, including the sealing edge structure. The morphological failures can be classified into two types, namely dislocations and compactions, and were caused primarily by the stress concentrations at the interfaces between the core layer and the upper and lower laminations and secondarily by the disordered short-fiber distribution in the material; although the fully integrated honeycomb plates manufactured in this experiment were imperfect, their mass-specific compressive strength was superior to that of similar biomimetic samples. Therefore, the proposed bio-inspired structure possesses good overall mechanical properties, and a range of parameters, such as the diameter of the transition arc, was defined for enhancing the design of fully integrated honeycomb plates and improving their compressive mechanical properties.

A new method for high speed and smooth transfer of robot motion trajectory

In the process of the robot practical working, the change of motion direction of trajectory is inevitable. When the direction changes dramatically, the sharp angle between adjacent trajectories, which can generate the vibration of robot, affects the service life of the robot. In order to deal with the sharp angle between adjacent trajectories, we propose a method which can deal with the sharp angle transferring by inserting transition arc, which is called position level, to solve the trajectory speed control problem. We analyze three basic analytic trajectories—space line, space arc, and space parabola—and present the formula for calculating the parameters of circular-arc-related parameters and propose the implementation process of algorithm of robot system. Through the simulation and experiment, this method can solve the sharp angle trajectory transfer problem effectively, increase the transfer speed dramatically, and reduce the vibration of robot’s mechanical structure.

Minimum Clearance Offsets for Providing Desired Stopping Sight Distances at Simple Curves with Variable Operating Speeds

Lateral clearance on the inside of horizontal curves is required by all geometric design guidelines in order to provide at least stopping sight distance. There already exist graphical models, analytical models, and design charts for determining minimum clearance offsets to meet the requirement. Some of these models determine the offsets based on constant design sight distance values on the assumption that drivers negotiate horizontal curves at constant speed. Therefore, those models are suitable for sites where there is no difference in speeds between tangent and curved sections. Past studies have reported that there are sites where drivers decelerate on entering horizontal curves and accelerate on departing from the curves. At those sites stopping sight distance for a given driver varies with driver location due to variable speed. This paper presents an analytical model and a chart for determining minimum offsets needed to provide desired sight distances at horizontal curves with variable operating speeds. At those sites the offsets yield roadside clearance boundaries that have transition arcs with performances that are similar to those of elliptical arcs. Therefore, practitioners may choose to use elliptical equations or equations and the chart developed herein. Results of this study will be of value to practitioners in the area of roadside design.

Evaluation of the ongoing rifting and subduction processes in the geochemistry of magmas from the western part of the Mexican Volcanic Belt

A compilation of new and published geochemical data for 1512 samples of volcanic rocks from the western part of the Mexican Volcanic Belt was first subdivided according to the age group (136 samples of Miocene and 1376 samples of Pliocene-Holocene). Rocks of the younger group were then subdivided as Rift (1014 samples from the triple-rift system) and No Rift (362 samples outside of the triple-rift system) or Near Trench (937 samples) and Far Trench (439 samples) magmas. These subdivisions were considered separately as basic, intermediate, and acid magmatic rocks. The application of the conventional and multidimensional techniques confirmed the great tectonic and geochemical complexity of this region. The presence of oceanic-type basalts suggested to result from a mantle plume was not confirmed from the tectonomagmatic multidimensional diagrams. The Miocene rocks, which are present at the surface far from the Middle-America Trench, showed a likely continental rift setting in most diagrams for basic rocks and a continental arc setting for intermediate rocks. These differences can be explained in terms of the petrogenetic origin of the magmas. Unlike the current thinking, the triple-rift system seems to have influenced the chemistry of Pliocene-Holocene basic rocks, which indicated a continental rift setting. The Pliocene-Holocene intermediate and acid rocks, however, did not show such an influence. The Pliocene-Holocene basic rocks indicated a continental rift setting, irrespective of the Near Trench and Far Trench subdivision because numerous Near Trench rocks also lie in the triple-rift and graben systems. However, the intermediate rocks having a crustal component in their genesis indicated a continental arc (Near Trench) or a transitional arc to within-plate setting (Far Trench). The acid rocks having a crustal component also suggested a continental arc (Near Trench) or a transitional setting (Far Trench). The application of the tectonomagmatic multidimensional diagrams to the data from the three rifts (Tepic-Zacoalco Rift, Colima Rift, and Chapala Rift) also revealed similarities and differences among them. The application of significance tests to log-transformed ratios further clarified the similarities and differences among the chemical characteristics of the Rift – No Rift and Near Trench – Far Trench subdivisions.

Major, trace and platinum group element (PGE) geochemistry of Archean Iron Ore Group and Proterozoic Malangtoli metavolcanic rocks of Singhbhum Craton, Eastern India: Inferences on mantle melting and sulphur saturation history

The geological and metallogenic history of the Singhbhum Craton of eastern India is marked by several episodes of volcanism, plutonism, sedimentation and mineralization spanning from Paleoarchean to Mesoproterozoic in a dynamic tectonic milieu. Distinct signatures of this Archean-Proterozoic geodynamic process are preserved in discrete crustal provinces that constitute the Singhbhum Craton. Here we report new major, trace and PGE geochemical data from the ~3.4Ga Iron Ore Group (IOG) volcanic rocks of the Jamda-Koira basin, a part of the BIF-bearing volcano-sedimentary sequences of the Noamundi-Jamda-Koira iron ore basin in the western part of Singhbhum Granite (SBG), and ~2.25Ga metavolcanic rocks of Malangtoli. The IOG and Malangtoli volcanic rocks are porphyritic basalts and despite belonging to different ages, they exhibit similar mineralogical composition marked by clinopyroxene, plagioclase (present as both phenocryst and groundmass), opaques and volcanic glass (restricted to groundmass). The igneous mineralogy of these rocks has been overprinted by greenschist to lower amphibolite grade of metamorphism. The Malangtoli samples show low and high MgO compositional varieties. Immobile trace element compositions classify the IOG samples as andesite having a calc-alkaline composition, whereas the Malangtoli rocks correspond to basalt and andesite displaying a tholeiitic to calc-alkaline trend. The IOG basalts show low to moderate PGE contents marked by 26.23–68.35ppb of ΣPGE, whereas the Malangtoli basalts display a moderate to high concentration of PGE (ΣPGE=43.01–190.43ppb). The studied samples have relatively enriched ΣPPGE ranging from 24.1–63.3ppb (IOG) and 34–227.3ppb (Malangtoli) against 2.2–4.1ppb and 1.9–8.9ppb ΣIPGE contents respectively. PPGE/IPGE ratios for IOG and Malangtoli samples range from 7.7–17.6 and 4.8–59.9. HFSE, REE and PGE compositions suggest a low degree (<1 to 1%) of partial melting in the garnet lherzolite domain for the generation of IOG volcanic rocks. The parental magma of the Malangtoli basalts were generated by lower to higher degrees (3–<10%) of mantle melting at depths corresponding to spinel to garnet lherzolite regime. Trace element (Zr/Nb, Th/Ta, Th/Nb, Ni/Cu) and PGE (Pd/Ir, Pd/Pt, Cu/Pd, Ni/Pd, Cu/Ir) ratios corroborate a sulphide saturated and PGE depleted character of IOG volcanic rocks that underwent crustal assimilation. In contrast, the high MgO Malangtoli basalts exhibit sulphide undersaturated, PGE undepleted nature devoid of crustal contamination whereas the low MgO Malangtoli basalts are sulphide saturated, PGE depleted and crustally contaminated. The IOG volcanic rocks correspond to intraoceanic arc with polygenetic crustal signatures, and show affinity towards arc-generated calc-alkaline basalts. The low- and high MgO basalts of Malangtoli are affiliated to transitional arc to rift-controlled back arc tectonic setting in a basinal environment that developed proximal to an active convergent margin.

Tests and analysis of mechanical behaviours of rock bolt components for China's coal mine roadways

A series of laboratory tests were performed to study the mechanical behaviours of newly developed high strength rock bolt components, including rebar, thread, plate, and domed washer. The characteristics of deformation and damage of each component were presented. The stress distribution of plate and domed washer was investigated through finite element modelling. The numerical results show that the yield and tensile strengths of the developed high strength rebar are 33.6%–58.3% and 17.2%–28.7% greater than those of the conventional rebar, respectively. The increase in yield strength was higher than that in tensile strength, suggesting an increase in yield to tensile strength ratio and a decrease in elongation. It is well-known that the thread processing may not be of high precision and accuracy as expected, which is characterised as rough thread surface, non-identical tooth height, toe stripping, and cracks in the surface. Hardening during thread processing tends to increase the thread yield and tensile strengths. In this paper, the typical deformation process of arch-shaped plate is classified into five stages. The tested plates exhibited distinct deformation characteristics and bearing capacities due to variations in shape, size, material and presence of washer. It was observed that uneven bottom surface, low bearing arch and large radius of the transitional arc connecting bearing arch and bottom surface were the major reasons accounting for low load-bearing capacity of plates. The performance of domed washer has a close relation with the shape, size, strength, and deformation compatibility with plate. Stress concentration was observed on the periphery of the contact surface between domed washer and plate, which is significantly influenced by the strength of domed washer and is considered to be 20%–30% higher than that of plate. Finally, a case study in the Datong coal mining district was presented, and the support pattern and effect of the developed rock bolt were described.

Geochemical and Geophysical Characteristics of the Balud Ophiolitic Complex (BOC), Masbate Island, Philippines: Implications for its Generation, Evolution and Emplacement

This paper presents the first field, geochemical and geophysical information on the recently recognized Early Cretaceous Balud Ophiolitic Complex (BOC) in the island of Masbate in the Central Philippines. Mapping of the western limb of the island revealed that only the upper crustal section of the BOC is exposed in this area. Geochemically, the pillow basalts are characterized by transitional mid-oceanic ridge basalt-island arc tholeiitic compositions. Gravity surveys yielded low Bouguer anomaly values that are consistent with the highly dismembered nature of the BOC. Short wavelength, high amplitude magnetic anomalies registered across the study area are attributed to shallow magnetic sources. This is taken to support the model that the ophiolitic complex occurs as thin crustal slivers that are not deeply-rooted in the mantle. Comparing BOC with other ophiolites in the Central Philippines, such as those in the islands of Sibuyan, Leyte and Bohol, suggests the possibility of a common or contiguous source for similarly-aged and geochemically composed crust-mantle sequences in the region.

Finite Element Calculation about Stress Concentration Coefficient of Welded Butt Joints of Magnesium Alloy

Geometrical parameters of welded joint affect the stress concentration coefficient seriously. In order to increase the fatigue property of welded structure, it has great significance to reduce stress concentration coefficient of welded structures by researching and improving the geometry of welded joints. In this paper, the effects of weld toe inclination angle θ and weld edge transition arc radius r on the stress concentration coefficient of welded butt joints of magnesium alloy were analyzed by using ABAQUS finite element program, and the change rule of stress concentration coefficient with the variation of the two parameters was also researched. The calculation results indicate that reducing weld toe inclination angle or increasing transition arc radius can effectively decrease the stress concentration coefficient of welded butt joints, so as to improve the fatigue property of welded structures. For the safe use of welded structures, the true weld edge transition arc radius r should be greater than 3mm, and weld toe inclination angle θ should be smaller than 30°.