Curvature Of Plate Research Articles

Experimental and numerical analysis of impact on curved nanocomposite panels

ABSTRACTIn this work nanopolyurea is used as reinforcement for curved steel plates under low velocity impact loading. Experimental and numerical analysis are used to study the effect of plate curvature and nano particle effects. A drop weight test apparatus is utilized to apply impact loading on bi-layer panels. Experiments show that maximum improvement in energy absorption capacity of nanopolyurea is about 5%. Numerical analysis is carried out using explicit LS-DYNA solver. The results show that by increasing panel radius of curvature, impact force increases; also comparison between numerical and experimental results shows a good agreement.

Nonuniform Jet Array Impingement on a Curved Surface

Experiments to investigate the effect of varying jet hole diameter and jet spacing on heat transfer and pressure loss from jet array impingement on a curved target surface are reported. The jet plate configurations studied have varying hole diameters and geometric spacing for spatial tuning of the heat transfer behavior. The configuration also includes a straight section downstream of the curved section, where the effect on heat transfer and pressure loss is also investigated. The jet plate holes are sharp-edged. A steady-state measurement technique utilizing temperature-sensitive paint (TSP) was used on the target surface to obtain local heat transfer coefficients. Pressure taps placed on the sidewall and jet plate of the channel were used to evaluate the flow distribution in the impingement channel. For all configurations, spent air is drawn out in a single direction which is tangential to the target plate curvature. First row jet Reynolds numbers ranging from 50,000 to 160,000 are reported. Further tests were performed to evaluate several modifications to the impingement array. These involve blocking several downstream rows of jets, measuring the subsequent shifts in the pressure and heat transfer data, and then applying different turbulator designs in an attempt to recover the loss in the heat transfer while retaining favorable pressure loss. It was found that by using W-shaped turbulators, the downstream surface average Nusselt number increases up to ∼13% as compared with a smooth case using the same amount of coolant. The results suggest that by properly combining impingement and turbulators (in the post impingement section), higher heat transfer, lower flow rate, and lower pressure drop are simultaneously obtained, thus providing an optimal scenario.

Triple Combination Therapy for Pincer Nail Deformity: Surgical Matricectomy, Thioglycolic Acid, and Anticonvex Sutures.

Pincer nail deformity (PND) is characterized by an excessive transverse curvature of the nail plate that increases along the longitudinal axis of the nail. Although many conservative and surgical techniques have been used in clinical practice, an established consensus for the correction of PND has not been present yet. Aim of the technique described in this article is to provide to restore the suitable nail-matrix system curvature by a simplified and quick approach, which could be seen as a synthesis of conservative and surgical treatments described in the literature. Nineteen cases of pincer nail of the great toe in 14 patients were analyzed. After softening nail plate with 5% thioglycolic acid solution for at least half an hour, surgical bilateral matricectomy and 2 anticonvex sutures with 1-0 polypropylene were performed to ensure proper nail plate shape. Besides demographic data, visual analog scale (VAS) score for pain, width index, height index, patient and surgeon satisfaction scores, operation time, and the day of painless return to the daily activities were investigated. A statistical significance was observed in VAS score for pain, width, and height indices between preoperative and postoperative values. This report gives acceptable outcomes with a combination of surgery and conservative treatments.

Asymmetric Intermixing and the Stress Buildup in Ni/Al-typed Nanomultilayer with Different Characteristic Scales

In order to detect scale-dependent interfacial evolution of metallic heterostructure during the deposition at room temperature, Ni/Al-typed nanomultilayers were prepared as a function of the periodicity and Ni:Al modulated ratio. Combined with X-ray diffraction, real-time plate curvature measurements by multi-beam optical stress sensor (MOSS) were employed to study the stress buildup so as to speculate interfacial characteristics during the growth process. Results show that with anisotropic nanocrystalline structure within the sub-layers, the multilayers possess asymmetrical interfaces, which is a result of dissymmetrical diffusion of Ni to Al lattice near the interface. Specially, for the smallest periodicity with the lowest Ni:Al ratio, above asymmetric intermixing behaviors turns to be aggravated by a promotion effect.

Comparative Three-Dimensional Morphology of Baleen: Cross-Sectional Profiles and Volume Measurements Using CT Images.

ABSTRACTBaleen whales are obligate filter feeders, straining prey‐laden seawater through racks of keratinized baleen plates. Despite the importance of baleen to the ecology and natural history of these animals, relatively little work has been done on baleen morphology, particularly with regard to the three‐dimensional morphology and structure of baleen. We used computed tomography (CT) scanning to take 3D images of six baleen specimens representing five species, including three complete racks. With these images, we described the three‐dimensional shape of the baleen plates using cross‐sectional profiles from within the gum tissue to the tip of the plates. We also measured the percentage of each specimen that was composed of either keratinized plate material or was void space between baleen plates, and thus available for seawater flow. Baleen plates have a complex three‐dimensional structure with curvature that varies across the anterior‐posterior, proximal‐distal, and medial‐lateral (lingual‐labial) axes. These curvatures also vary with location along the baleen rack, and between species. Cross‐sectional profiles resemble backwards‐facing airfoils, and some specimens display S‐shaped, or reflexed, camber. Within a baleen specimen, the intra‐baleen void volume correlates with the average bristle diameter for a species, suggesting that essentially, thinner plates (with more space between them for flow) have thinner bristles. Both plate curvature and the relative proportions of plate and void volumes are likely to have implications for the mechanics of mysticete filtration, and future studies are needed to determine the particular functions of these morphological characters. Anat Rec, 300:1942–1952, 2017. © 2017 The Authors The Anatomical Record published by Wiley Periodicals, Inc. on behalf of American Association of Anatomists

Mixed mode fracture analysis of multiple cracks in flat and curved stiffened panels of aircraft fuselage structures

In real time, aircraft panels are mainly subjected to fatigue loading induced by the pressurization cycle. When two cracks approach one another, their stress fields influence each other and produce enhancing or shielding effect depending on the position of the cracks. In the present work, an attempt has been made to determine the effect of plate curvature on mixed mode stress intensity factor (SIF) of multiple cracks in a riveted joint using numerical and experimental methods. Diametrically opposite surface cracks of various crack depth ratios [(a / t); ‘a’ crack length and ‘t’ thickness of the plate] were considered for a typical longitudinal splice joint. ‘Frictional contact interaction’ was defined between rivet hole, rivet head-sheet, between sheet surfaces and stringer to sheet interfaces in order to simulate the service conditions. At lower crack depths, [\(({a}/{t}) =2\)] higher SIF was observed for biaxial loading compared to uniaxial loading. Marginal influence of loading condition was observed for deep cracks [\(({a}/{t})=5\)]. SIF values of curved panels were observed to be higher than that of flat panel irrespective of the crack depths considered the present work. This is mainly due to ‘flattening’ of curved plate when loading. It was also noticed that, the presence of stiffener reduces the in plane (mode-II) and out of plane (mode-III) shear fracture considerably for curved panel as it exerts compressive force on the joint. To validate the numerical observations, experiments were conducted on a Al 2024-T3 specimens to determine the fatigue crack growth rate and it showed a good correlation with numerical methods. The experimental results also indicated a higher crack growth rate for curved panel compared to flat panel which is mainly due to additional bending stress at the rivet hole region caused by eccentric loading.

Detection of earthquake swarms at subduction zones globally: Insights into tectonic controls on swarm activity

AbstractEarthquake swarms are characterized by an increase in seismicity rate that lacks a distinguished main shock and does not obey Omori's law. At subduction zones, they are thought to be related to slow‐slip events (SSEs) on the plate interface. Earthquake swarms in subduction zones can therefore be used as potential indicators of slow‐slip events. However, the global distribution of earthquake swarms at subduction zones remains unclear. Here we present a method for detecting such earthquake sequences using the space‐time epidemic‐type aftershock‐sequence model. We applied this method to seismicity (M ≥ 4.5) recorded in the Advanced National Seismic System catalog at subduction zones during the period of 1995–2009. We detected 453 swarms, which is about 6.7 times the number observed in a previous catalog. Foreshocks of some large earthquakes are also detected as earthquake swarms. In some subduction zones, such as at Ibaraki‐Oki, Japan, swarm‐like foreshocks and ordinary swarms repeatedly occur at the same location. Given that both foreshocks and swarms are related to SSEs on the plate interface, these regions may have experienced recurring SSEs. We then compare the swarm activity and tectonic properties of subduction zones, finding that swarm activity is positively correlated with curvature of the incoming plate before subduction. This result implies that swarm activity is controlled either by hydration of the incoming plate or by heterogeneity on the plate interface due to fracturing related to slab bending.

Automated local line rolling forming and simplified deformation simulation method for complex curvature plate of ships

Abstract. Local line rolling forming is a common forming approach for the complex curvature plate of ships. However, the processing mode based on artificial experience is still applied at present, because it is difficult to integrally determine relational data for the forming shape, processing path, and process parameters used to drive automation equipment. Numerical simulation is currently the major approach for generating such complex relational data. Therefore, a highly precise and effective numerical computation method becomes crucial in the development of the automated local line rolling forming system for producing complex curvature plates used in ships. In this study, a three-dimensional elastoplastic finite element method was first employed to perform numerical computations for local line rolling forming, and the corresponding deformation and strain distribution features were acquired. In addition, according to the characteristics of strain distributions, a simplified deformation simulation method, based on the deformation obtained by applying strain was presented. Compared to the results of the three-dimensional elastoplastic finite element method, this simplified deformation simulation method was verified to provide high computational accuracy, and this could result in a substantial reduction in calculation time. Thus, the application of the simplified deformation simulation method was further explored in the case of multiple rolling loading paths. Moreover, it was also utilized to calculate the local line rolling forming for the typical complex curvature plate of ships. Research findings indicated that the simplified deformation simulation method was an effective tool for rapidly obtaining relationships between the forming shape, processing path, and process parameters.

Elastic flexure controls magma trajectories and explains the offset of primary volcanic activity upstream of mantle plume axis at la Réunion and Hawaii hotspot islands

Surface volcanism at la Réunion and Hawaii occurs with an offset of 150–180 km upstream to the plume axis with respect to the plate motion. This striking observation raises questions about the forcing of plume-lithosphere thermo-mechanical interactions on melt trajectories beneath these islands. Based on visco-elasto-plastic numerical models handled at kilometric resolution, we propose to explain this offset by the development of compressional stresses at the base of the lithosphere, that result from elastic plate bending above the upward load exerted by the plume head. This horizontal compression adopts a disc shape centered around the plume axis: (i) it is 20 km thick, (ii) it has a 150 km radius, (iii) it lays at the base of the elastic part of the lithosphere, i.e., around ∼50–70 km depth where the temperature varies from ∼600 °C to ∼750 °C, (iv) it lasts for 5 to 10 My in an oceanic plate of age greater than 70 My, and (vi) it is controlled by the visco-elastic relaxation time at ∼50–70 km depth. This period of time exceeds the time during which both the Somalian/East-African and Pacific plates drift over the Reunion and Hawaii plumes, respectively. This indicates that this basal compression is actually a persistent feature. It is inferred that the buoyant melts percolating in the plume head pond below this zone of compression and eventually spread laterally until the most compressive principal elastic stresses reverse to the vertical, i.e., ∼150 km away from the plume head. There, melts propagate through dikes upwards to ∼35 km depth, where the plate curvature reverses and ambient compression diminishes. This 30–35 km depth may thus host a magmatic reservoir where melts transported by dykes pond. Only after further magmatic differentiation can dykes resume their ascension up to the surface and begin forming a volcanic edifice. As the volcano grows because of melt accumulation at the top of the plate, the lithosphere is flexed downwards, inducing extra tensile stress at 30–35 km depth and compression at ∼15 km depth (induced by the edifice load). It implies that now the melts pond at ∼15 km and form another magmatic reservoir lying just underneath the crust. These processes explain the ponding of primary (shield) melts at ∼35 km and ∼15 km depths as recorded below La Reunion, Mauritius or Hawaii volcanoes, all shifted by ∼150 km with respect to the plume axis.

Effect of Target Wall Curvature on Heat Transfer and Pressure Loss From Jet Array Impingement

Experiments to investigate the effect of target wall curvature on heat transfer and pressure loss from jet array impingement are performed. A jet plate configuration is studied with constant hole diameters and spacings. The geometry of the jet plate has streamwise jet spacings of 5.79 jet diameters, spanwise jet spacings of 4.49 jet diameters, and a jet-to-target plate distance of 3 jet diameters. For the curved case, the radius of the target plate is r/D = 31.57. A flat target wall setup with identical geometric spacing is also tested for direct comparison. Jet spacings were chosen such that validation and comparison can be made with open literature. For all configurations, spent air is drawn out in a single direction, which is tangential to the target plate curvature. Average jet Reynolds numbers ranging from 55,000 to 125,000 are tested. A steady-state measurement technique utilizing temperature-sensitive paint (TSP) is used on the target surface to obtain Nusselt number distributions. Pressure taps placed on the sidewall of the channel are used to evaluate the flow distribution in the impingement channel. Alongside the experimental work, CFD was performed utilizing the v2 − f turbulence model to better understand the relationship between the flow field and the heat transfer on the target surface. The main target of the current study is to quantify the impact of target wall radius and the decay of heat transfer after the impingement section, and to check the open literature correlations. It was found that the target wall curvature did not cause any significant changes in either the flow distribution or the heat transfer level. Comparisons with established correlations show similar level but different trends in heat transfer, potentially caused by differences in L/D. CFD results were able to show agreement in streamwise pitch-averaged Nusselt number levels with experimental results for the curved target plate at higher Re numbers.

Forming Information Calculation Algorithm of 3-D Template for Evaluation of Curved Hull Plates

Curved hull plates are essential to the construction of a ship. Moreover, curved hull evaluation is significant during the curved hull plate forming process. Most shipyards use 2D- and 3D-type wooden template to estimate curvature of plates by placing the template on specific positions of curved hull plates. Only the 3-D template can be utilized to evaluate plates that are relatively thick with large radius of curvature. In general, forming plans of the 3-D template, based on the given information, are drawn manually by workers, and the information is only given for plates that may require 3-D templates. These plates are predicted empirically by the designers in the detailed design phase, resulting in the presence of unpredicted plates. For unpredicted plates, workers used to request additional information for manufacturing, and during the process, there exists a complex information exchange between related departments, which is a time-consuming process. To solve the above-mentioned problems, in this paper, a 3-D template forming information calculation algorithm, based on the surface geometric information, was proposed. Moreover, the proposed algorithm was implemented as a computer program in which forming information of 3-D template can be calculated automatically.

Feasibility of Multipoint Press with Continuously Divisional Forming for Double Curvature Plates in Shipbuilding

Feasibility of Multipoint Press with Continuously Divisional Forming for Double Curvature Plates in Shipbuilding

Experimental study on reflection coefficient of curved perforated plate

A set of experiments is carried out in a towing tank to study the effects of the curvature of perforated plates on the wave reflection coefficient (Cr). The curvature of a perforated plate can be changed by rotating a reference perforated plate aboutits origin according to the parabolic equation y=−x2. A plunger-type wave maker is used to generate regular waves. The reflection coefficients are calculated using Goda and Suzuki’s (1976) method. The results are compared with those of vertical or sloped passive wave absorbers. The comparison shows that a perforated plate with a curved profile is highly efficient in terms of reducing the wave reflection coefficient. A correlation is established to estimate the reflection coefficient of curved perforated plates as a function of both flow and geometry characteristics.

Steel plate curvatures of soil-steel structures during construction and exploitation

The paper analyses the deformation of cir- cumferential bands of shells made of corrugated metal sheets in soil-steel structures. A change of curvature in the crown of a shell is assumed as a measure of deformation. In the upper part of analysed objects, regardless of their cross-sectional geometry, e.g. arched or elliptical shaped, a section of shell with a constant radius of curvature R is nowadays designed. As a result of earth pressure, moving loads and the self-weight of metal sheets, the shape of this part is subjected to deformation with a noticeable deviation from the circular shape. The change of curvature radius is determined in the paper on the basis of three coordinates of measuring points that form a triangle inscribed in a circle. Every (asymmetrical) position of the measuring points is taken into account. A system of three such points is transformed into a form of an equilateral triangle, and thus the radius of curvature is determined. Based on the change of curvature formulated during the construction and exploitation of soil-steel structures, the bending moments and normal stresses in the shell crown can be estimated and therefore a safety evaluation of the objects is possible.

Complete solutions at or near the boundary nodes of boundary elements for coupled stretching-bending analysis

In boundary element analysis if the field point is located at or near the boundary nodes, its associated integrals may become singular. Although in the literature the displacements and tractions at the boundary nodes have been well solved for the coupled stretching-bending analysis, their related strains and stresses still remain unsolved due to the coincidence of field points and boundary nodes. In this paper to avoid the singular problem, at the boundary nodes the components of stress resultants, bending moments, in-plane strains and plate curvatures in the tangential direction are approximated by finite difference method, whereas the components in normal direction are evaluated with the aid of constitutive laws for the tangential-normal coordinate. After getting the complete solutions at the boundary nodes, the solutions for the points near the boundary are interpolated by the moving least square method. To verify the correctness of the proposed method, examples of the laminated plates with or without holes subjected to in-plane tension, or out-of-plane bending, or transverse loading are illustrated and compared with the solutions obtained by the other methods.

A new cervical artificial disc prosthesis based on physiological curvature of end plate: a finite element analysis

Study DesignThe study aimed to build a new cervical artificial disc C3–C7 segment prosthesis, and perform a biomechanical comparison between the new prosthesis and the Prestige LP prosthesis using a three-dimensional non-linear finite element (FE) model. PurposeThe study compared the biomechanical differences between the new cervical artificial disc prosthesis based on the physiological curvature of the end plate and the Prestige LP prosthesis after artificial disc replacement. Background ContextThere has been no prior research on artificial disc prostheses based on the physiological curvature of the end plate; studies of biomechanical changes after cervical disc arthroplasty (CDR) are few. MethodsAn FE model of the C3–C7 segments was developed and validated. A new cervical artificial disc prosthesis based on the physiological curvature of the end plate and the Prestige LP prosthesis were integrated at the C5–C6 segment into the validated FE model. All models were subjected to a follower load of 73.6 N and a 1 Nm in flexion-extension, lateral bending, and axial torsion. The segmental range of motion (ROM) and stress on the prostheses were analyzed. ResultsThe ROM in most segments after CDR with new cervical artificial disc prosthesis was more similar to that of the normal cervical spine than the Prestige LP prosthesis. However, there was no significant difference between the two prostheses. The stress on the new artificial disc was significantly less than that in the Prestige LP prosthesis. ConclusionsThere was no significant difference in ROM in all segments after CDR for the two prostheses. The stress on the new cervical artificial disc prosthesis based on the physiological curvature of the end plate was significantly less than that in the Prestige LP prosthesis. The new artificial disc prosthesis is feasible and effective, and can reduce the implant-bone interface stress on the end plate, which may be one of the causes of prosthesis subsidence.

Theoretical strength assessment of unstiffened bilge shell plating and some considerations on rule prescriptions

In ship hull structures, bilge part is often composed of unstiffened radiused plating, for which the harmonized CSR stipulates required scantlings, locations of the longitudinals adjacent to the bilge radius, and so on. In recent years, under the increased demand for rational structural design, larger radius than ever is sought, expecting reduction of hull steel weight and welding lengths, thus contributing to the reduction of production cost of structures. However, structural problems arising from the larger bilge radius and associated structural arrangement around the bilge shell are not yet sufficiently identified. In these circumstances, the authors developed theoretical formulae, assuming radiused plating connected to continuous stiffened flat plating with regular stiffener spacing. The results of the theoretical calculations are compared with the results of finite element analysis, and it was found that the derived theoretical formulae well explain the complicated phenomena of the curved shell plating connected to the flat stiffened panels. Utilizing the derived theoretical formulae, parametric studies were carried out with regard to the radius of the bilge shell plating, the distance between the position where the curvature of the bilge plate starts and the adjacent longitudinal, and so on. As a result of the calculations, it was found that large bilge radius exceeding current usual practice is feasible, on the condition that the location of the longitudinals is well controlled to reduce bending stresses on the shell plate, and the buckling strength is satisfied. In such case, the stipulation in the harmonized CSR is not always rational, and the authors propose modified structural design methodologies around the unstiffened bilge shell plating.

Ultrasonic high-frequency guided waves for the inspection of shell weld in core support structure of fast breeder reactors

This article reports an ultrasonic high-frequency guided wave based methodology for inspection of shell weld of core support structure of the main vessel in 500-MWe sodium-cooled prototype fast breeder reactor. The high-frequency guided waves are generated in 30-mm-thick plate of core support structure at 2 MHz (frequency–thickness product of ∼60 MHz-mm). These wave modes are fairly nondispersive over considerable distance of propagation through the material. In order to understand the generation and propagation characteristics of these high-frequency guided waves, a series of two-dimensional plane strain finite element models are developed using explicit scheme. The optimum transducer placement for generating efficient high-frequency guided wave is achieved by sweeping the transducer position along the curvature of the main vessel plate with respect to the centerline of the vertical shell support plate. The generated high-frequency guided waves are analyzed and identified with the help of dispersion curves and time–frequency analysis. The simulation results are found to capture the features observed in the experimental measurements rather well, and the time of flight of the reflected waves in the simulation is found to be in excellent agreement with the experimental results. The optimum transducer locations for inspection of a general T-joint configuration with different angles between the web and the base have been studied in detail using finite element simulations. With optimum transducer position, the high-frequency guided waves are also used to inspect the artificially introduced defects in the connecting weld of shell support plate. It has been demonstrated that the high-frequency guided wave could detect defects of 20% wall thickness (6 mm) in the connecting shell weld.

Effect of pulse duration and shape on dynamic buckling of stiffened panels

Dynamic buckling of stiffened panels under axial compression loading having the form of finite duration pulse was analyzed by finite element modeling. Welding induced defects modifying the skin plate curvature were incorporated. Material degradation in the heat-affected zone was also taken into account. The Budiansky and Roth criterion was employed to predict the collapse load. Various pulse shapes were investigated. The obtained results have shown that the pulse period and profile have severe effects on the buckling strength. For the considered boundary conditions and load pulses up to 56% reduction of the strength was observed in comparison with static buckling.

Nail changes in patients with inflammatory bowel diseases.

Inflammatory bowel disease (IBD) is a group of inflammatory conditions of the colon and small intestine. To our knowledge, no studies to date pertain to the profile of nail changes in IBD, except for onychomycosis. We aimed to study the frequency and pattern of nail changes among patients with IBD and evaluate their potential relationships with several parameters in IBD. The study included 73 patients with IBD and 51 healthy control subjects. Nails of both groups were examined for changes with regard to color, striations, texture, curvature of nail plates, dystrophy of nail plates, and pigmentation. Mycological examinations were performed when onychomycosis was suspected. Nail changes were statistically higher in patients with IBD than in the control group (P = 0.001). The presence of onychomycosis was significantly more common in patients with IBD (P = 0.041). Subungual hyperkeratosis and brownish discoloration of the nail were the most common findings in patients with IBD. Our study is the first report showing all nail changes in IBD. Further studies with more subjects are needed to reveal more detailed information about nail changes in IBD.