Rib Section Research Articles

Flow and heat transfer of supercritical hydrogen in a regenerative cooling channel with the arc ribs of a rocket engine

This paper reports on the heat transfer characteristics and flow performance of supercritical hydrogen in a regenerative cooling channel with arc-shaped ribs. A 3-D numerical model of hydrogen flowing inside the cooling channel has been established and the data are compared with experimental results. The effect of rib parameters such as the number of ribs n, rib angle θ, rib size (hr × e), and rib orientation (convex or concave) on the cooling channel performance has been explored. The results indicate that arc ribs effectively mitigate the heat transfer deterioration and thermal stratification phenomena by reducing the wall temperature; nevertheless, the pressure loss due to friction would considerably increase. In studied cases, the wall temperature significantly decreases when the rib angle θ increases from 0° to 90°. The results have also shown that increasing the size of square arc ribs while maintaining the same rib spacing p/hr and length of the ribbed section Lr is beneficial for the overall heat transfer performance. Compared to smooth channel, a channel with large 90° arc ribs oriented either convex or concave to the flow direction enhanced the thermohydraulic performance η by up to 45%. This enhancement in performance of channel due to arc ribs is 1.95 and 1.384 times higher than the previously known designs; V-ribs (23%) and cylindrical ribs (32.5%), respectively. The flow field has shown that the evolution and morphology of rib-induced streamwise vortex considerably improve the wall temperature reduction by intense fluid mixing. In addition, it has been shown that the direct impact of the coolant stream on the ribs, the reattachment of the separated shear layer, and the intermittent growth of the boundary layer helps to enhance heat transfer.

Histotaphonomy of a Pleistocene megamammal assemblage from Argentine Pampas

This work involves a multy-proxy approach of taphonomic features of the extinct giant ground sloth Lestodon armatus (Xenarthra, Mylodontidae). The study is based on paleohistological, mineralogical, and geochemical analyses from the Late Pleistocene Playa del Barco site (Buenos Aires Province, Argentina). Transverse thin sections of ribs and vertebrae were studied under light microscope, polarizing petrographic microscope, and scanning electron microscope (SEM), combined with chemical analysis using energy dispersive spectroscopy (EDS) and micro-X-ray diffraction (μXRD). The internal crystalline structure and mineral composition remains almost unaltered. The bone microstructure is well preserved in all the samples, although it was affected by different types of microfractures and infillings. Numerous radial microcracks were identified in the secondary osteons of all specimens evidencing wet depositional environment. The mineralogical and geochemical composition of the infillings and encrustations indicates that the enrichment with new elements was due to direct exchange with the sediments in which they were buried. Mineralogical evidence from the infillings allows to identify different diagenetic pathways; most of the skeletal elements were quickly buried in the vadose zone, while others were buried in the phreatic zone, directly or after some time immersed in a continental aquatic context. The fossildiagenetic information obtained from the Lestodon armatus fossils provides novel information to interpret and reconstruct the whole taphonomic history and the environmental and climatic conditions that favored the preservation of the Playa del Barco fossil assemblage during the end of the Last Glacial Maximum.

3D imaging assistance impact on atrial fibrillation cryoablation efficiency, a method validation study

Abstract Funding Acknowledgements Type of funding sources: Other. Main funding source(s): CGRA: CARD; CGRB: 31’297 Background Pulmonary vein isolation (PVI) by cryoballoon ablation is a well-known therapy for the treatment of atrial fibrillation (AF). Current 3D-navigation technologies usually used with RF ablation allow for a drastic reduction of intra-procedural X-ray exposure and imaging aided/guided methods allow for better anatomical characterization improving acute and long-term procedural results. 3D imaging fusion on real-time fluoroscopy is a well-known technology but the incremental value of 3D imaging fusion as a guiding tool on AF cryoballoon ablation therapy has not been studied yet. Purpose To increase procedural efficiency by integration of 3D imaging guidance in conventional cryoballoon PVI. Methods Using semi-automatic segmentation (Alphenix, Canon Medical Systems Corporation) obtained from pre-procedural cardiac computed tomography (CT); two anatomic volumes were fused on the real-time fluoroscopy display: left atrium (LA), including pulmonary veins (PV) and spine with proximal rib section (most radio-opaque body part in the thoracic area). The merging was performed by 3D registration of the bone segment with fluoroscopic acquisitions in three standard positions (AP, LAO, RAO), acquired at the beginning of the procedure. To standardize treatment workflow, the study was restricted to patients with paroxysmal atrial fibrillation. Results Twenty patients were included in the study: 10 in the control group (conventional fluoroscopy based cryoballoon ablation), and 10 in the 3D assisted group. Mean age was 59±15 SD years for the conventional group and 61.3±15.1 SD years for the 3D group with an 80% male population, in both groups. Acute PVI was achieved in all 20 patients. A decrease of both procedure time 86.8±16.1 SD in the control group Vs. 78.4±15.32 SD in the 3D group, and left sided dwelling time 69.7±14.31 SD in the control group Vs. 63.9±13.96 SD in the 3D group, although this trend did not reach statistical significance, while radiation time and cryo application time remained similar. Conclusions 3D imaging integration is feasible and safe and allows for an exact PV anatomy depiction on fluoroscopy. The assistance workflow might help increase AF cryoablation efficiency and safety (lower left sided dwelling time). Further research is needed to evaluate the incremental value of 3D imaging to assist fluoroscopy-based cryoballoon ablation. This could also impact long-term results since 3D Imaging assistance could reduce the likeability of missing intermediate PVs during AF ablation procedures.

Cross-sectional properties of rib geometry from an adult population.

Introduction: Human body models (HBMs) play a key role in improving modern vehicle safety systems to protect broad populations. However, their geometry is commonly derived from single individuals chosen to meet global anthropometric targets, thus their internal anatomy may not fully represent the HBM's target demographic. Past studies show sixth rib cross-sectional geometry differences between HBM ribs and population-derived ribs, and corrections to HBM ribs based on these data have improved HBM's abilities to predict rib fracture locations. Methods: We measure and report average and standard deviations (SDs) in rib cross-sectional geometric properties derived from live subject CT scans of 240 adults aged 18-90. Male and female results are given as functions of rib number and rib lengthwise position for ribs 2 through 11. Population means/SDs are reported for measures of rib total area, rib cortical bone area, and rib endosteal area, as well as inertial moment properties of these rib sections. These population corridors are compared between males and females, and against the baseline rib geometries defined in six current HBMs. Results: Total cross-sectional area results found average males ribs to be larger than those of females by between approximately 1-2 SDs depending on rib number and position, and larger in cortical bone cross-sectional area by between 0-1 SDs. Inertial moment ratios showed female ribs being between approximately 0-1 SDs more elongated than male ribs, dependent again on rib number and position. Rib cross-sectional areas from 5 of the 6 HBMs were found to be overly large along substantial portions of most ribs when compared to average population corridors. Similarly, rib aspect ratios in HBMs deviated from average population data by up to 3 SDs in regions towards sternal rib ends. Discussion: Overall, while most HBMs capture overall trends such as reductions in cross-section along shaft lengths, many also exhibit local variation that deviates from population trends. This study's results provide the first reference values for assessing the cross-sectional geometry of human ribs across a wide range of rib levels. Results also further provide clear guidelines to improve rib geometry definitions present in current HBMs in order to better represent their target demographic.

Mechanism and Design Method of Load Transfer into Concrete-Filled Steel Tubular Arch Ribs through Perfobond-Rib-Shear Connectors

In terms of load transfer, the design of the joints in concrete-filled steel tubular (CFST) arch bridges is more critical than that in buildings due to the higher likelihood of steel–concrete-interface debonding. To improve the contact at the steel–concrete interface, a novel arch rib was manufactured by longitudinally welding perfobond-rib-shear connectors to the inner surface of a steel tube and then filling the tube with concrete. In this study, extensive numerical and analytical investigations on the mechanism of introducing loads into CFST arch ribs through perfobond-rib-shear connectors were carried out. A deck CFST arch bridge, namely, the Shuangbao Bridge in China, was selected as a typical application location. The design parameters, including the geometric dimensions of the perfobond-rib-shear connector and the arrangement of the perfobond rib along the cross-section and longitudinal section of the arch rib, were evaluated. The design flow for the joint with perfobond-rib-shear connectors between the vertical columns and the CFST arch ribs was proposed. To improve the load-transfer efficiency, the design scheme of the joint in the Shuangbao Bridge was optimized by replacing the weld studs with perfobond ribs. Significant increases of 1.84–4.02 in the shear resistance were found for the perfobond ribs compared to the welded studs. Additionally, the fabrication of the perfobond ribs was more convenient compared to that of the welded studs.

Hyperspectral imaging and chemometrics assessment of intramuscular fat in pork Longissimus thoracic et lumborum primal cut

To assess the intramuscular fat (IMF) of Longissimus thoracis et lumborum (LTL) primal cut excised from an animal carcass, rib sections are dissected for chemical or subjective evaluation. Dissection destroys the integrity of the LTL. This study examined the feasibility of developing a method based on hyperspectral imaging to predict the IMF of pork LTL using hyperspectral imaging. Spectral information from different tissues was collected at the cranial (Serratus ventralis, Spinalis dorsi, longissimus , backfat), and the caudal ( Gluteus medius, Psoas major ) ends of the LTL. The spectral information and the IMF content chemically extracted from the mid-loin (3rd and 4th last rib of the LTL) were used to develop regression models for the prediction of the IMF content in the 3rd and 4th. The individual results of the analysis from the various tissues at both the cranial and caudal ends show that models exhibited performances for IMF prediction with root-mean-square-error (RMSEP) ranging from 0.36 to 0.92% and coefficient of determination in prediction ranging from 0.43 to 0.81. Gluteus medius showed the highest accuracy. This study has demonstrated that hyperspectral imaging could be used to accurately predict the IMF content in the mid-loin by using spectral data from Gluteus medius . The result could be useful in segregating pork LTL based on IMF content. • Intramuscular fat in whole pork Longissimus thoracic et lumborum was evaluated. • Muscles from the cranial and caudal of the Longissimus thoracic et lumborum were scanned. • PLSR was used to develop models between tissues and intramuscular fat at 3rd/4th last ribs. • The Gluteus medius muscle predicted intramuscular fat accurately.

Analysis of thermal stresses synergy in surface layer of carburised creep-resistant casts during rapid cooling processes

ABSTRACT During the carburising processes, treated elements are transported on a specially designed technological equipment of the furnaces. This equipment works in particularly hard conditions. This is because in each work cycle, apart from the load carried by the charge, it is subjected to harmful effect of many other factors such as the highly carburising technical atmosphere of the furnace and high and rapidly changing temperature. These factors influence fatigue changes in the equipment’s parts, the observable effect of which may be cracks on the surface, propagating deeper into the material in subsequent cycles. A pivotal factor influencing the kinetics of fatigue processes in the carburising furnaces equipment are thermal stresses appearing in each operating cycle, with each temperature change. The thermal stresses in this equipment are caused by the temperature gradient across the section of the heated or cooled element and different thermal expansion of the structural components of the carburised alloy. In the paper, on the developed FEM model of the subsurface layer of a carburised rib of a pallet for transporting the charge in the furnace, analyses of stress distributions during rapid cooling were carried out. These analyses were performed with taking into account the separate impact of the above-mentioned sources of thermal stresses and their simultaneous action. In the analyses which consider the influence of the temperature gradient, the main load factor was the temperature distribution determined on the basis of the heat flow analyses carried out for the analysed section of pallets rib. The conducted analyses made it possible to assess the impact of local stresses caused by different thermal expansion of structural components of the carburised alloy on the change in the distribution of global stresses caused by the temperature gradient formed during rapid cooling. Based on the obtained results, it was assessed how the increased concentration of carbide precipitates, characteristic for the grain boundary of the carburised alloy, favours the formation of cracks observed in real castings, and whether the analysed stress sources have a significant impact on the kinetics of fatigue processes.

Design and Analysis of Aircraft Wing Rib with Different Configuration for A380 model

The wing rib of an aircraft is a very critical part. It provides airfoil contour to the wing. Its principal role in wing structure is that to transfer load from skin to stringers or other parts of wing. Cut-outs in aircraft structural components such as wing spars and ribs are commonly encountered in practice. Cut-outs are often necessary for lightening holes, passages for wire bundles, hydraulic and fuel pipes, control linkages, accessibility for final assembly and maintenance inspections. The shape of the cutout is a important parameter where depends on the cutout shape the structural parameters may get varied. The main objective in here is to study about the influence of cutout in rib section with different cutout shapes. The Airbus A380 model is considered and the rib section for the model is modeled using Solidworksmodeling package and the model is analyzed for different cutout shapes. The model has the cutout shapes such as circle, ellipse and rectangle, where the circular hole is a most practiced method in recent models. The numerical analysis is carried out in ANSYS static structural analysis to find the structural parameters such as stress, strain, deformation and weight.

Thermal performance analysis of artificially roughened solar air heater under turbulent pulsating flow with various wave shapes

This paper presents a numerical investigation of the operation of a solar air heater (SAH) with cylindrical shape ribs under turbulent pulsating flow based on thermal and frictional considerations. Turbulence and thermal natures of flow physics are modeled by taking the relevant governing equations into the account using RNG k−ε turbulence model and transient state Reynolds-Averaged Navier-Stokes (RANS) equations. The pulsating flow is modeled with four different wave shapes including rectangular, sinusoidal, triangular, and sawtooth functions. The influence of various factors such as wave shape, Reynolds number (Re), frequency, and amplitude of pulsating flow on the thermal and hydraulic performance of SAH has been evaluated. Results indicated that the SAH with ribbed absorber section under pulsed flow has a larger Nu number compared to the air heater with smooth duct under steady flow. Moreover, the pulsating flow with a sawtooth velocity profile leads to the greatest value of the thermo-hydraulic performance parameter (THPP). The growth of pulsation frequency up to 200 enhances the heat transfer coefficient of the air heater while for frequencies larger than 200, the thermal performance declines. In addition, the increase in pulsation amplitude has a negative effect on the THPP. It was proved that the increment of the Re number enhances the THPP. Up to 53.3% improvement of THPP can be achieved by applying pulsed flow with sawtooth wave shape and ribbed absorber section compared to air heat with smooth duct under steady flow.

Early postmortem muscle proteome and metabolome of beef longissimus thoracis muscle classified by pH at 6 hours postmortem

The objective was to identify metabolome and proteome differences at 1 h and 1 d postmortem between longissimus thoracis (LT) muscle classified based on 6 h pH values. Twenty beef LT rib sections were sorted based on 6 h postmortem pH values into low (LpH; pH < 5.55; n = 9) and high (HpH; pH > 5.84; n = 8) pH classifications. Warner-Bratzler shear force (WBSF), desmin degradation, and calpain-1 autolysis were measured. Two-dimensional difference in gel electrophoresis (3–10, 4–7, and 6–9 pH range) and Tandem mass tagging (TMT) protein analyses were employed to determine how the sarcoplasmic protein profile varied across pH classification. Non-targeted metabolomic analyses were conducted on extracts prepared at 1 h and 1 d postmortem. The LpH classification had a lower WBSF value at 1 d postmortem, which was explained by greater calpain-1 autolysis and desmin degradation at 1 d postmortem. Proteome and metabolome analysis revealed a phenotype that promotes more rapid energy metabolism in the LpH group. Proteome and metabolome analyses identified energy production, apoptotic, calcium homeostasis, and proteasome systems influencing pH classifications that could explain the observed pH, proteolysis, and beef tenderness differences. SignificanceThis study is the first to identify proteomic and metabolomic variations early (1 h and 1 day) postmortem that are linked to differences in early (6 h) postmortem pH values and to tenderness differences at 1 day postmortem. This study integrates postmortem biochemical features (protein degradation, proteome, and metabolome variations) to postmortem pH decline and eating quality of beef steaks. Potential biomarkers of more rapid postmortem metabolism linked to earlier tenderization in beef are suggested. Identification of these biochemical features will assist in predicting the eating quality of beef products.

PSIII-A-18 The Effects of Feeding Finishing Cattle Benzoic Acid and/or Live Active Yeast (Saccharomyces Cerevisiae) on Meat Quality

Abstract In a randomized complete block design, 59 Angus-cross finishing steers were used to evaluate the effects of benzoic acid, active dry Saccharomyces cerevisiae, or a combination of both when supplemented in a high-grain finishing diet on meat quality and sensory evaluation of longissimus steaks. Steers were fed a high-moisture corn-based finishing diet for 106 d containing: no supplementation (CON), 0.5% benzoic acid (ACD), 3 g/head/d active dry S. cerevisiae (YST), or both (0.5% benzoic acid and 3 g/head/d S. cerevisiae (AY)). Cattle were humanely slaughtered at a commercial facility where 54 rib sections (CON; n=15, ACD; n=14, YST; n=15, and AY; n=11) were retrieved and used for evaluation of meat quality and trained sensory parameters. Statistical analysis was completed using PROC GLIMMIX of SAS. Longissimus pH, proximate composition, shear force, and cooking loss did not differ between treatments (P ≥ 0.10). Although no differences in lipid oxidation was detected at the beginning of the retail display (d 0), lipid oxidation levels were greater (P = 0.02) in CON vs. AY steaks following 12 days of retail display. Some colour parameters differed (P ≤ 0.04) among treatments on days 11 (L*) and 12 (a*, L*, and discolouration) of the retail display. Although dietary treatment did not impact fatty acid profiles for longissimus muscle, n-6:n-3 polyunsaturated fatty acids ratios were greater in CON and YST than in ACD longissimus (P = 0.007). Steaks from Combination (AY) supplemented steers were chewier than steaks from steers only supplemented with benzoic acid, while juiciness, tenderness, and flavour were not impacted by supplementation. These results suggest that supplementation with benzoic acid and(or) yeast does not have a substantial impact on meat quality or sensory traits.

Design and Analysis of MataMorph-3: A Fully Morphing UAV with Camber-Morphing Wings and Tail Stabilizers

Conventional aircraft use discrete flight control surfaces to maneuver during flight. The gaps and discontinuities of these control surfaces generate drag, which degrades aerodynamic and power efficiencies. Morphing technology aims to replace conventional wings with advanced wings that can change their shape to control the aircraft with the minimum possible induced drag. This paper presents MataMorph-3, a fully morphing unmanned aerial vehicle (UAV) with camber-morphing wings and tail stabilizers. Although previous research has presented successful designs for camber-morphing wing core mechanisms, skin designs suffered from wrinkling, warping, or sagging problems that result in reduced reliability and aerodynamic efficiency. The wing and tail stabilizers of MataMorph-3 feature hybrid ribs with solid leading-edge sections that house servomotors, and compliant trailing-edge sections with integrated flexible ribbons that are connected to the servomotors to camber-morph the ribs. Thin laminated carbon fiber composite skin slides smoothly over the compliant rib sections upon morphing, guided by innovative trailing-edge sliders and skin-supporting linkage mechanisms strategically located between the ribs. Sample prototypes were built and tested to show the effectiveness of the proposed design solutions in enabling smooth camber-morphing. The proposed design provides a better alternative to stretchable skins in morphing airplane designs through the concept of skin sliding.

Analysis of axial compression performance of steel - foamed ceramsite concrete composite structure wallboard

Through the finite element analysis of the vertical axial load test of 9 self bearing and self insulation precast walls, the effects of the thickness of section steel, the strength of section steel, the strength of foamed ceramsite concrete, the layout of section steel and the thickness of foamed ceramsite plate on the failure mode, bearing capacity and overall stress of the wall plate are studied. The research shows that the strength of foamed ceramsite concrete is the main factor affecting the wall stress-strain curve, the layout form of section steel and wall thickness are important factors, and the change of section steel thickness and section steel strength has little effect on the stress-strain curve. The strength of foamed ceramsite concrete decreases by 30%, the wall bearing capacity decreases by 15%, and the wall deformation increases by three times. Therefore, quality management should be strengthened in the production process of foamed ceramsite concrete to prevent the strength decline of foamed ceramsite concrete due to production reasons; Foamed ceramsite concrete and section steel frame are constrained to form a stressed whole, and the ribbed section steel frame bears the main load, which provides a basis for subsequent experimental research and engineering design.

Study on the forming limit of rectangular-ribbed profile (日-shaped section) in rotary bending with flexible core die

The profile with rectangular ribbed (日-shaped) section is applied to the anti-collision beam of commercial vehicles, which not only improves the anti-collision performance but also improves the lightweight of the car. With the gradual decrease of the bending radius of the profile, the profile is prone to defects such as wrinkling of the inner wall or fracture of the outer wall. In this paper, the ABAQUS, a finite element simulation software, is used to establish the simulation model of the profile with rectangular ribbed section during the process of rotary draw bending, and the stress and strain laws are analyzed. The bending forming limit of the profile with rectangular ribbed section is studied by choosing the fracture of the outer wall as the evaluation standard. And the influences of bending speed, friction coefficient, and thickness on the forming limit are obtained. The minimum bending radius decreases as the bending speed increases and increases with increasing of friction coefficient and thickness.

Microstructure of axial bones of lithostrotian titanosaurs (Neosauropoda: Sauropodomorpha) shows extended fast-growing phase

Titanosaurs reached extremes in size and diversity, but many paleobiological aspects of these sauropod dinosaurs are still unknown. Here we infer life history traits based on the microstructure of axial bones of three lithostrotian titanosaur species: Austroposeidon magnificus, Gondwanatitan faustoi and Maxakalisaurus topai — Campanian–Maastrichtian of Bauru Group, Brazil. The present study is the first wide characterization of the microstructure of axial bones comparing distinct lithostrotian lineages with different body sizes. We analyzed the cross sections of cervical ribs, dorsal ribs and haemal arches. The medullary cavity in samples of A. magnificus are pneumatic, with the primary bone rich in fibrolamellar bone, with scarce growth marks, which is different from the Lines of Arrested Growth (LAGs)-dominated pattern of G. faustoi and M. topai, with parallel fibered bone. In general, the inner cortex exhibits fibrolamellar bone with longitudinal canals. The outer cortex is rich in parallel fibered bone rows of longitudinal canals and growth marks. Based on dense remodeling, decrease of LAGs distances and presence of an External Fundamental System in some samples; we concluded that all individuals reached at least the sexual maturity. These titanosaurs shared with basal neosauropods two main growth phases: modular (inner cortex) and LAG-dominated (outer cortex). Distinct from basal neosauropods, titanosaurs presented extended fast modular period (rather than LAG-dominated). This pattern supported that titanosaurs adopted a distinct strategy of bone mass gain in dorsal ribs, alternating the timing in rib growth.

A computational approach for modelling composite slabs in fire within OpenSees framework

Modelling tall buildings responding to fires, especially multi-floor fires, requires the consideration of composite slabs as the composite action can significantly affect the structure fire response. Modelling composite slabs in fire is tedious and complex due to the existence of ribs and complicated thermal action. In view of the complexity of the existing modelling approaches, this paper aims to propose a computational approach for modelling composite slabs in fire in the open-source program of ‘OpenSees for fire’. The proposed approach adopts a unified reference plane in the shell element discretization along with built-in approximation of the ribbed section and temperature loading. The modelling approach is incorporated into a new version of layered shell thermal section with a vision of enabling efficient modelling of tall buildings in fire. Benchmark tests are performed using T-shaped plain concrete beams to verify the approach. A collection of tests on composite slabs or composite floor systems are then modelled to extensively validate the approach with respect to the ambient loading and fire tests. Validation results demonstrate good performance of the modelling approach even without extra calibration. The work implemented in OpenSees will be made open source and can significantly simplify the modelling efforts of including multiple floors of composite slabs in a tall building model when investigating its fire performance.

Multifidelity Heating Prediction of Adaptable, Deployable Entry Placement Technology Vehicles

The objective of this work was to investigate a multifidelity modeling approach to accurately and efficiently predict the laminar convective, turbulent convective, and radiative heating on adaptable, deployable entry placement technology vehicles in Mars entry. A previously developed cokriging-based multifidelity modeling approach was used to model the heat fluxes at several surface locations along the vehicle, including the rib sections. The laminar convective heat flux multifidelity model was found to have a mean convective heat rate error of approximately 3% when compared with high-fidelity computational fluid dynamics (CFD) simulations. The turbulent convective heat flux multifidelity model was found to have a mean convective heat rate error of approximately 8% when compared with high-fidelity CFD simulations. The radiative heat flux multifidelity model was found to have a mean convective heat rate error of approximately 10% when compared with high-fidelity CFD simulations. Compared with a single-fidelity model, the multifidelity model required, at most, one-third the number of high-fidelity model evaluations to obtain the same accuracy level. The computational cost of evaluating the multifidelity model was approximately six orders of magnitude less than one high-fidelity model simulation.

Seismic Response Analysis of Multidimensional and Multiangle Long‐Span Top‐Supported CFST Arch Bridge

Taking a concrete‐filled steel tube (CFST) arch bridge with a clear span of 400 m as an example, the in‐depth analysis of its natural vibration characteristics is carried out by establishing a finite element model. Then, the three‐dimensional El Centro recorded wave after amplitude modulation is taken as the excitation wave; the structural response under three kinds of single dimension and four kinds of multidimensional combined excitation and 0∼90° transformation X(longitudinal) + Y(transverse) orthogonal combined excitation is evaluated. The results show that the structure of long‐span top‐supported arch bridge extends in the longitudinal and vertical dimensions at the same time, and the mode shape density and mass distribution have multidirection and multiangle coupling. With the increase of excitation dimensions, the value and relative ratio of chord axial force increase. The maximum axial force ratio of X + Y to X and Y is 2.1, the maximum axial force ratio of X + Y + Z (longitudinal) to X + Y, X + Z, and Y + Z is 1.4, 1.8, and 1.8; the displacement in X and Y direction under combined excitation is independent and the displacement in Z direction is its coupling term, but the displacement under X + Y + Z combined excitation is only 10% larger than that under X + Z and Y + Z combined excitation. Under the combined excitation of X + Y with a changing angle of 0°∼90°, the axial force variation of the chord at different positions and on the same section of the arch rib has spatial characteristics. The variation range of upper and lower rod axial force varies from 0.63 to 1.35 and from 0.81 to 1.51, respectively, the change trend of displacement in the X and Y directions is relatively consistent, the change of displacement in the Z direction is asynchronous, and the displacement of vault section increases by one time. The seismic response of this bridge type under multidimensional and multiangle excitation shows obvious superposition.

Математический расчет и значение коэффициента восстановления формы грудной клетки при планировании торакопластики врожденной воронкообразной деформации грудной клетки

Актуальность. Врожденная воронкообразная деформация грудной клетки характеризуется разным по глубине и ширине западением грудины и передних отделов ребер. Формообразование, его прогнозирование, расчет деформированного состояния грудной клетки и их изучение при планировании торакопластики по D. Nuss по поводу этой патологии является важной проблемой ортопедии и торакальной хирургии. Цель работы — расчет коэффициента восстановления формы грудной клетки путем соотношения глубины воронкообразной деформации и размера грудной клетки во фронтальной плоскости до и после математического моделирования торакопластики по D. Nuss. Материалы и методы. Для оценки перемещений ребер в зависимости от глубины деформации грудной клетки h были построены две модели. Первая модель представляет собой плоскую раму на опорах, элементы которой состоят из хрящевых частей ребер и грудины. Для данной модели определялась зависимость усилия F, которое необходимо для исправления глубины деформации грудной клетки. Вторая модель представляет собой изогнутый стержень, моделирующий ребро, к одному из концов которого приложена опорная нагрузка, вычисленная при анализе первой модели. Для данной модели определялось перемещение точки фиксации пластины под действием заданного усилия. Для получения более точных результатов были проведены исследования методом конечных элементов на модели грудной клетки. Результаты. Моделировалась коррекция глубины воронкообразной деформации без фиксации пластины к ребрам. Была проведена оценка перемещений участков ребер в месте фиксации пластины при разной глубине воронкообразной деформации грудной клетки: h = 2–5 см. Анализ результатов расчета показал, что после коррекции глубины деформации грудной клетки происходит уменьшение ее размера во фронтальной плоскости. Так, при максимальной глубине деформации h = 5 см отклонение участков ребер в месте фиксации пластины произошло на 2,4 см. Выводы. Установлена зависимость между глубиной воронкообразной деформации и размером грудной клетки во фронтальной плоскости при моделировании новообразованной формы грудной клетки при торакопластике по D. Nuss. Математически рассчитан коэффициент восстановления формы грудной клетки, который составляет 2 (2∆=h), где h — глубина воронкообразной деформации. Практическое значение коэффициента заключается в том, что при планировании торакопластики и придании формы пластине расстояние между ее латеральными концами, которые соответствуют форме грудной клетки и прилегают к ребрам, перед коррекцией воронкообразной деформации необходимо уменьшить на 1/2 h, где h — глубина воронкообразной деформации, для полноценного прилегания к ребрам в послеоперационном периоде.

Stresses in the cap of a connecting rod

In this practically oriented paper, representative examples of cap failures in a connecting rod are discussed, and deeply dissimilar geometries of the cap cross section are presented. An analytical model of the stresses within a connecting rod cap is developed and satisfactorily validated versus FE (Finite Elements). This model accounts for the effect of the initial clearance between the crankpin surface and the cap intrados, and it realistically mimics the crankpin-cap progressive contact. A load parameter that accounts for the combined effects of several leading variables is analytically derived, on which the following variables depend: a) the contact angular extent between the crankpin and the cap; b) the ratio between the normal and bending stress. This model indicates that the cap bending stress depends on the initial gap between the crankpin and the cap, and not on the applied load. The normal stress within the cap is found to be considerably higher than its bending counterpart. The mechanical response of cap rectangular and ribbed cross sections is compared, and it is found that ribbed sections undesirably increase the cap bending stress. Consequently, the employment of ribs appears to be unjustified from a purely stress related viewpoint.