Main Plate Research Articles

Effect of location and dimensions of welded cover plate on stress intensity factors of cracked plates

Three dimensional finite element model was utilized to determine mode I stress intensity factor through the front of a single edge crack in main plate with welded cover plate. The numerical results showed that the ratio of the crack length to the position of the welded cover plate end is a crucial parameter for describing the efficiency of the cover plate location. When the crack tip just reached the cover plate end, the cover plate efficiency is only dependent on the cover plate dimensions regardless the location of the cover plate or the crack length. In the case of crack front not reached the cover plate end, the location of cover plate near the edge of the main plate, i.e., near the crack mouth, is less efficient than that faraway. However, the opposite trend was found for cracks pass beneath the cover plate.

The stratigraphic record of the Alì-Montagnareale Unit (Peloritani Mountains, NE Sicily, Italy)

Some Internal Units of the western Alpine peri-Mediterranean orogenic system (Betic Cordillera, Calabria-Peloritani Arc) point out to a complex Alpine tectono-metamorphic evolution followed by an exhumation phase. Before the onset of the Alpine compressive tectonics, the rocks of these units belonged to the margins of a microcontinent, the Mesomediterranean Microplate, originated, together with the main plates, following the break-up of Pangaea. To these units, characterized by similar tectono-sedimentary evolution, belongs the Ali-Montagnareale Unit of the Peloritani Mountains (NE Sicily), where the Internal Units of the Sicilian sector of the Maghrebian Chain crop out. The Ali-Montagnareale Unit appears within two small tectonic semi-windows, under the phyllites of the Mandanici-Piraino Unit, and it proves to be formed by three groups of anchimetamorphic formations.The Lower Group is made up of two Upper Permian?-Upper Triassic siliciclastic formations, which grade into each other and which were deposited in alluvial environments. This group is followed by the Intermediate Group, consisting of Middle?-Upper? Triassic formations, indicating deposition in an evaporitic coastal plain evolving to a marine carbonate platform. The Upper Group consists of a Pliensbachian formation, made up of pelagic calcilutites with added carbonate turbiditic beds, followed by a prevailingly marly formation with strata of silicified limestones and episodic calcareous re-sediments. In this latter formation, the finding of Jurassic fossils and Globuligerina oxfordiana, which occurs up to the Valanginian, indicate that the stratigraphic succession spans from the late Early Jurassic to the Late Jurassic and probably reaches the Early Cretaceous.The stratigraphic units are generally separated by tectonic contacts which act as preferential detachment surfaces during compressive and exhumation tectonic phases. The tectonic elision of more or less large intervals of the original stratigraphic succession is diffuse in both tectonic windows.The succession of the Ali-Montagnareale Unit testifies to extensional tectonics, which in Middle-Late Triassic determined the evolution of sedimentation from continental to evaporitic and neritic environments, and, since the Early Jurassic, to calcilutite and marly pelagic sediments with added calcareous re-sediments. This sedimentary evolution records the break-up of Pangaea and the successive opening of oceanic basins. A similar tectono-sedimentary history may be recognized in many other Internal Units of the Alpine peri-Mediterranean Chains.

Dicerapanorpa, a new genus of East Asian Panorpidae (Insecta: Mecoptera: Penorpidae) with descriptions of two new species

Dicerapanorpa gen. nov. is erected with Panorpa magna Chou as its type species. The genus is recognizable by the following characters: body yellowish with two blackish lateral longitudinal stripes on dorsum; tergum VI of males with two anal horns; abdominal segment VII of males much thinner at the basal half and abruptly thicker at apical half; parameres of males trifurcate; female genital plate with the axis not extending beyond the main plate. Six new combinations, Dicerapanorpa magna (Chou in Chou et al., 1981), D. diceras (MacLachlan, 1894), D. stotzneri (Esben-Petersen, 1934), D. tjederi (Carpenter, 1938), D. kimminsi (Carpenter, 1948) and D. triclada (Qian and Zhou, 2001) are transferred from Panorpa Linnaeus. Dicerapanorpa baiyunshana sp. nov. and Dicerapanorpa shennongensis sp. nov. are described and illustrated. A key to the genera of Panorpidae is updated to include the new genus. A key to the species of Dicerapanorpa gen. nov. is also presented.http://www.zoobank.org/urn:lsid:zoobank.org:pub:F50E44C3-7275-4EC8-B048-4C7B2C6D57EF

A synthesis of data from steel spot welded joints of reduced thickness by means of local SED

In some previous works two fatigue scatterbands were given in terms of the local strain energy density (SED) for welded joints made of structural steel and aluminium alloy. The material-dependent radius R0 of the control volume was identified with reference to conventional arc welding processes. It resulted equal to 0.28mm for welded joints made of structural steel tested under prevailing mode I, with fatigue failures both at the weld root and the weld toe. The scatterband did not include data from thin welded joints, the main plate thickness being greater than 6mm. The SED approach is used here to summarise more than 400 fatigue data from steel spot welds in lap–shear joints, coach–peel specimens and cross–tension specimens of small thickness. Due to the typical crack initiation and propagation phases, an appropriate choice to summarise the data in a narrow scatterband seems to be the use of a toroidal control volume. The volume circumferentially encapsulates the slit tip along the weld spot nugget. The SED value at 2 million cycles is found to match that of the previous scatterband for welded joints of higher thicknesses.

Large deformation finite element analysis investigating the performance of anchor keying flap

Suction embedded plate anchors, as used in practice, include a hinged keying flap aligned with the main anchor plate (fluke). The flap was designed to rotate away from the shank during keying of the anchor, to minimise loss of anchor embedment and the associated reduction in pull-out resistance. However, it has been observed experimentally that the flap is activated only once keying is nearly completed, and thus does not assist in reducing embedment loss. In this paper, the performance of the keying flap is investigated using a large deformation finite element approach based on frequent mesh regeneration. The moment acting at the flap hinges, determined from the soil pressures and shear forces on the keying flap, is quantified. The moment controlling the flap activation depends mainly on the net soil pressure on the front or back face of the flap, and this prevents activation of the flap while the anchor is rotating significantly. The flap is only activated once the anchor motion becomes dominated by forward translation, normal to the plate. Various factors affecting flap activation and embedment loss are explored, including flap height, eccentricity of the padeye, soil strength profile, initial anchor depth and load inclination.

CFD Research and Investigation of 2011 P4/5 Competition Rear Wing

In order to analyze the influence of the rear wing of a competition race car on the aerodynamics of the whole vehicle, computational fluid dynamics simulations have been performed. Rear wing is set by two elements, a main plate and a flap. Their relative position and the angle of attack of these elements influence the aero- performances in terms of downforce and drag generated; 12 different configurations have been generated, modifying the angle of attack and the slot gap. 3D mesh has been generated from the geometrical model of the vehicle, and air flow around the vehicle and on the rear wing has been evaluated through a CFD commercial software. It has been proved that steeper angles of attack of the mainplate and of the flap contribute to generate more downforce until a certain point; when angle of attack reaches a critical value, the downforce no longer increases and the drag still keep high values.

Medial Mandibulotomies: Is there sufficient space in the midline to allow a mandibulotomy without compromising the dentition?

ObjectivesThe objective of this study was to determine the frequency of complications in median and paramedian mandibulotomies. In addition, the interdental space in the median and paramedian region was calculated.Study designRetrospective study.SettingTertiary care center.MethodsA retrospective chart review was performed for all cases where a mandibulotomy was performed from 2002 to 2010. 117 charts (61 paramedian and 56 median) were identified. We included data on complications, which fell in the following 2 categories: plate and dental complications. For our second objective, we evaluated 40 different patients with base of tongue or tonsillar cancer treated with intensity modulated radiation therapy (IMRT). The interdental space between the lateral incisors and the canines was electronically calculated on the digital Panorex images.Main outcome measuresDental and plate complications were evaluated. We also assessed interdental space.ResultsPatient characteristics were not significantly different. The median group had significantly more dental complications (p=0.0375, RD=0.19 and 95% CI (0.0139-0.3661)). The paramedian group had significantly more plate complications (p=0.0375, RD=0.082 and 95% CI (0.0131-0.1508). The distance between the central incisors was significantly less than the distance between the lateral incisors and canines both at the crestal and apical levels (p=0.0086 and p<0.001).ConclusionsThere are significantly more dental complications in the median approach. There were significantly more plate complications in the paramedian group. In addition, there is significantly less space in the between the median region as compared to the paramedian region. This is the first study that documents the advantage of the paramedian approach for dental complications.

Primary surface ruptures of the great Himalayan earthquakes in 1934 and 1255

It is unclear where plate boundary thrusts generate giant rather than great earthquakes. Along the Himalayas, the source sizes and recurrence times of large seismic events are particularly uncertain, since no surface signatures were found for those that shook the range in the twentieth century. Here we challenge the consensus that these events remained blind and did not rupture the surface. We use geomorphological mapping of fluvial deposits, palaeo-seismological logging of river-cut cliffs and trench walls, and modelling of calibrated 14C ages, to show that the Mw 8.2 Bihar–Nepal earthquake on 15 January 1934 did break the surface: traces of the rupture are clear along at least 150 km of the Main Frontal Thrust fault in Nepal, between 85° 50′ and 87° 20′ E. Furthermore, we date collapse wedges in the Sir Valley and find that the 7 June AD 1255 earthquake, an event that devastated Kathmandu and mortally wounded the Nepalese King Abhaya Malla, also ruptured the surface along this stretch of the mega-thrust. Thus, in the past 1,000 years, two great earthquakes, 679 years apart, rather than one giant eleventh-century AD event, contributed to the frontal uplift of young river terraces in eastern Nepal. The rare surface expression of these earthquakes implies that surface ruptures of other reputedly blind great Himalayan events might exist. The recurrence times of great Himalayan earthquakes are difficult to assess because they rarely rupture the surface. Field mapping and 14C dating of offset fluvial deposits are used to identify two great Himalayan quakes that ruptured the surface along the main plate boundary fault in AD 1255 and 1934.

Transmission and reflection of the fundamental Lamb modes in a metallic plate with a semi-infinite horizontal crack

Numerical simulations were carried out to quantify the reflection and transmission characteristics of the fundamental Lamb modes propagating in aluminium sub-plates, which are formed due to a semi-infinite horizontal crack. It was observed that, a Lamb mode propagating in a sub-plate when incident at the edge of a crack, undergoes reflection and transmits through the main plate, as well as the other sub-plate. The mode transmitted through the sub-plate has been termed the ‘Turning Lamb Mode’ (TLM). Furthermore, a mode converted mode also propagates along with the TLM. This mode has been termed the ‘Mode Converted Turning Lamb Mode’ (MCTLM). Reflection and transmission characteristics of the fundamental Lamb modes in aluminium sub-plates were studied at frequencies 150kHz, 175kHz, and 200kHz. Experiments conducted to validate the observations made in numerical simulations, confirmed that the transmission and reflection characteristics depend on the thickness ratio. From this study it is surmised that when a Lamb mode propagates through a plate containing horizontal crack, the TLM and the MCTLM start propagating from one sub-plate to the other at the rear edge of the crack and amplitude of these modes depends on the location of the crack across the plate thickness.

Predicting the fatigue strength of small thickness welded joints using the implicit gradient method

This paper discusses the problem of the fatigue behaviour of small thickness welded joints using the implicit gradient method. Welds have been designed using 3D CAD and then subjected to finite element analysis, using the same computational procedure developed in the past for large thickness welded joints. In order to determine the Woehler curves for the various test series described in the literature, reference shall be made to either a monoaxial strength criterion or a multiaxial strength criterion capable of more efficiently evaluating the effect of a complex stress state while maintaining linear elastic behaviour for the material. The fatigue fault initiation zone is automatically evaluated by the computational procedure which indirectly returns the Woehler curve for the particular test. Application of the computational procedure to several test series taken from the literature has been performed for 2 mm thick sheets, predicting that the implicit gradient method may be applied to assess welded joints independently of the dimensions of the main plate and the shape of the weld bead.

Comparison of Visual Estimation Methods for Regular and Modified Textures: Real-Time vs Digital Imaging

A variety of methods are available for assessing diet; however, many are impractical for large research studies in an institutional environment. Technology, specifically digital imaging, can make diet estimations more feasible for research. Our goal was to compare a digital imaging method of estimating regular and modified-texture main plate food waste with traditional on-site visual estimations, in a continuing and long-term care setting using a meal-tray delivery service. Food waste was estimated for participants on regular (n=36) and modified-texture (n=42) diets. A tracking system to ensure collection and digital imaging of all main meal plates was developed. Four observers used a modified Comstock method to assess food waste for vegetables, starches, and main courses on 551 main meal plates. Intermodal, inter-rater, and intra-rater reliability were calculated using intraclass correlation for absolute agreement. Intermodal reliability was based on one rater's assessments. The digital imaging method results were in high agreement with the real-time visual method for both regular and modified-texture food (intraclass correlation=0.90 and 0.88, respectively). Agreements between observers for regular diets were higher than those for modified-texture food (range=0.91 to 0.94; 0.82 to 0.91, respectively). Intra-rater agreements were very high for both regular and modified-texture food (range=0.93 to 0.99; 0.91 to 0.98). The digital imaging method is a reliable alternative to estimating regular and modified-texture food waste for main meal plates when compared with real-time visual estimation. Color, shape, reheating, mixing, and use of sauces made modified-texture food waste slightly more difficult to estimate, regardless of estimation method.

Splay fault slip in a subduction margin, a new model of evolution

In subduction zones, major thrusts called splay faults are thought to slip coseismically during large earthquakes affecting the main plate interface. We propose an analytical condition for the activation of a splay fault based on force balance calculations and suggest thrusting along the splay fault is generally conditioned by the growth of the accretionary wedge, or by the erosion of the hanging wall. In theory, normal slip on the splay fault may occur when the décollement has a very low friction coefficient seaward. Such a low friction also implies an unstable extensional state within the outer wedge. Finite element elasto-plastic calculations with a geometry based on the Nankai Kumano section were performed and confirm that this analytical condition is a valid approximation. Furthermore, localized extension at a shallow level in the splay hanging wall is observed in models for a wide range of friction coefficients (from ∼0 to the value of internal friction coefficient of the rock, here equals to 0.4). The timing of slip established for the splay fault branch drilled on Nankai Kumano transect suggests a phase of concurrent splay and accretionary wedge growth ≈2Ma to ≈1.5Ma, followed by a locking of the splay ≈1.3Ma. Active extension is observed in the hanging wall. This evolution can be explained by the activation of a deeper and weaker décollement, followed by an interruption of accretion. Activation of a splay as a normal fault, as hypothesized in the case of the Tohoku 2011 earthquake, can be achieved only if the friction coefficient on the décollement drops to near zero. We conclude that the tectonic stress state largely determines long-term variations of tightly related splay fault and outer décollement activity and thus influences where and how coseismic rupture ends, but that occurrence of normal slip on a splay fault requires coseismic friction reduction.

Measuring yield stress: a new, practical, and precise technique derived from detailed penetrometry analysis

The displacement of an object through a yield stress is a complex process which involves the continuous deformation and transition of new regions from the solid to the liquid regime. We studied the force vs depth variations during the progressive penetration of a plate or a cylinder in a bath of simple yield stress fluids with negligible thixotropic character (Carbopol solutions, emulsions, and foams). Three regimes could be distinguished: elastic deformation, penetration (partially immersed object), and displacement through the fluid (fully immersed object). A detailed analysis of the force vs depth curves makes it possible to show that in the partially immersed regime the force is the sum of the critical force before penetration and a term associated with a uniform shear stress along the main plate surface, which is independent on the object geometry (plate dimensions and cylinder radius). This understanding can be used to precisely determine the yield stress as the critical shear stress along the plate at vanishing velocities. We also show that it is possible to measure accurately the yield stress from relaxation tests (stress vs time curve for motion stoppage): it indeed appears that the additional force term associated with penetration is negligible in that case so that the asymptotic average shear stress after stoppage is equal to the yield stress.

Considerations on the Design of Keying Flap of Plate Anchors

AbstractOne of the critical issues associated with plate anchor performance and design relates to the reduction of the loss of embedment during the keying process. As deep water offshore sediments typically exhibit an increasing soil strength with depth, the loss of embedment results in a reduction in anchor bearing capacity. A keying flap hinged to the main plate has been developed and adopted by industry with the aim to reduce the loss of embedment by limiting the vertical motion of the anchor. However, uncertainties remain regarding the behavior and the performance of the keying flap. This paper presents a series of numerical analyses performed to investigate the flap rotation mechanism and the condition of activation of the flap. They are compared with existing centrifuge modeling. The numerical results validate the centrifuge observations and demonstrate the nonactivation of the keying flap for typical anchor pull-out conditions.

선체 블록의 판접 위치 획득을 위한 센서 모듈 시제품 개발

Alignment of the main plates during the tack welding is essential to block assembly since most of the curved blocks and outfitting parts are assembled on the jigs and fixtures. Tact welding of main plates is the initial process of the curved hull block assembly. Due to the heavy weight of the main plates it is difficult to locate the plate on the accurate position of the jig and fixtures before welding. The conventional masonry process requires much time and manual work in order to achieve the accurate alignment. This labour-intensive process results in relatively high errors and correction works. Due to their larger dimensions and heavier weights, these hull blocks are not ergonomically desirable and, therefore, various mechanical devices such as hydraulic balancers or hydraulic jigs are used for the plate alignment. In this study, the position-sensing scheme implemented by sensors is presented in order to align the main plates on the accurate position during the hull block assembly. Integrating the Infrared photo sensors and micro processor unit, a small scaled prototype of the position-sensing module is developed to determine the alignment of main plates.

Lamb wave band gaps in locally resonant phononic crystal strip waveguides

Using finite element method, we have made a theoretically study of the band structure of Lamb wave in a locally resonant phononic crystal strip waveguide with periodic soft rubber attached on the two sides of epoxy main plate. The numerical results show that the Lamb wave band gap based on local resonant mechanism can be opened up in the stub strip waveguides, and the width of the local resonant band gap is narrower than that based on the Bragg scattering mechanism. The results also show that the stub shape and width have influence on the frequency and width of the Lamb wave band gap.

Compression–Sliding approach: Dependence of transitional displacement of a driving element on its size and load

Every element of a pulling traction device (e.g. track shoe with grouser or tire section with lug) exhibits increasing rearward displacement during its engagement with soft ground. Compression–Sliding (CS) approach states in agreement with experimental evidence that on common soft ground this displacement starts due to longitudinal soil compression by the grouser or lug, which steadily increases up to the transitional displacement when the soil segment beneath a driving element fails in shear. Further displacement of a driving element is marked by forced slide of a sheared off soil block, which may eventually collapse. There was justified reasoning that the transitional displacement depends not only on the grouser (lug) contact pressure but also on the area and load of the respective traction element. The presented article reports on experiments designed to test this premise. The measurements applying the novel double plate (DP) meter technique were carried out in a laboratory soil bin containing loam charge of uniform bulk density and moisture content. Three sizes (proportions 1:2:4) and two mean vertical contact pressures (ratio1:2) of DP meter main plate were tested. The analysis of performed experiments confirmed the existence of dimensional and loading relationship “main plate – transitional displacement”, which bears upon the evaluation of thrust–slip relationship of any traction device by the CS approach or by any other method observing the existence of displacement.

Fatigue behaviour of T welded joints rehabilitated by tungsten inert gas and plasma dressing

This paper concerns a fatigue study on the effect of tungsten inert gas (TIG) and plasma dressing in non-load-carrying fillet welds of structural steel with medium strength. The fatigue tests were performed in three point bending at the main plate under constant amplitude loading, with a stress ratio of R = 0.05 and a frequency of 7 Hz. Fatigue results are presented in the form of nominal stress range versus fatigue life ( S– N) curves obtained from the as welded joints and the TIG dressing joints at the welded toe. These results were compared with the ones obtained in repaired joints, where TIG and plasma dressing were applied at the welded toes, containing fatigue cracks with a depth of 3–5 mm in the main plate and through the plate thickness. A deficient repair was obtained by TIG dressing, caused by the excessive depth of the crack. A reasonable fatigue life benefits were obtained with plasma dressing. Good results were obtained with the TIG dressing technique for specimens with shallower initial defects (depth lesser than 2.5 mm). The fatigue life benefits were presented in terms of a gain parameter assessed using both experimental data and life predictions based on the fatigue crack propagation law.

Study of Fatigue Tests on the Structural Details of Welding Joints of Integral Bridge Deck and Main Girder Gusset Plates

Under the action of both dead and live loads, the welding joints of the integral bridge deck and the main truss gusset plates of a steel truss bridge in the transverse and longitudinal directions are all subjected to tensile force, the fatigue performance of which greatly influence the safety and durability of the bridge during operation. Fatigue tests were carried out on a full-scale model designed and made in accordance with the structural details of the welding joints of the integral bridge deck and the main truss gusset plates of Dashengguan Changjiang River Bridge. On the basis of the results of the fatigue tests, the stress distribution of the welding joints was analyzed, the fatigue life of the welding joints under load cycles with constant amplitude was discussed and the fatigue performance of the welding joints under the condition of two-way tensile forces was studied. It is concluded that under the effect of fatigue loading with given amplitude, the fatigue life of the welding joints is more than 200 million numbers of load cycles, the structural details of welding joints have ample fatigue resistant ability under the condition of two-way tensile forces, and the maximum main stress value of the fatigue tests is lower than the allowable fatigue stress value given in various codes and relevant references and the fatigue strength meets requirement.

선박블록 탑재용 러그구조의 파라메트릭 설계 고찰

In view of the importance of material reduction because of the jump in oil and steel prices, structural design studies for lifting lugs were performed. Hundreds of thousands of such lifting lug structures are needed every year for ship construction. A direct design study was reviewed using the developed design system to increase the design efficiency and provide a way of directly inserting a designer's decisions into the design system process. In order to understand the design efficiency and convenience of a lug structure, parametric studies for prototype lug shapes were performed using the developed design system. From these design studies, various patterns of design parameters for the lug structure according to changes in the main plate length were examined. Based on these parametric study results, design guides were developed for more efficiently suggesting structural data for enormous lug structures. Additionally, a more detailed structural analysis through local strength evaluations will be performed to verify the efficiency of the optimum structural design for a lug structure.