Thin Ribs Research Articles

Study on rotary bending fatigue performance of TC4 lattice structure fabricated by selective laser melting

Prediction of the fatigue performance of lattice structures in additive manufacturing still lacks widely applicable methods. To address this issue, we investigated the effect of a BCC lattice structure combined with thin walls and ribs on the fatigue performance of TC4 alloy samples. The lattice-structured samples were fabricated by selective laser melting. In addition, we proposed a prediction model of fatigue performance that combined ABAQUS finite element analysis with FE-safe fatigue analysis. The simulation and experimental results verified the reliability of the model. Based on this method, the effects of lattice and ribbed plate structures on the bending fatigue performance were investigated. The experimental results showed that the stress concentration generated by lattice structures weakened the fatigue performance. On the contrary, ribbed plates can enhance fatigue performance, which also depends on the orientation of the rib structure. The simulation results showed that increasing the volume fraction of unit cells can mitigate the stress concentration, leading to improved fatigue performance. The lattice structure combined with the rib structure exhibited superior fatigue performance. In addition, the proposed models can also be applied to other metallic materials. The findings in this study can provide a theoretical basis for the design of lattice structures with better fatigue performance.

Radial envelope forming mechanism and process design method for cylindrical rings with thin wall and high web ribs

Cylindrical rings with thin wall and high web ribs (CRTWHWR) are widely used as the key load bearing structures such as rocket body and space station cabin in aerospace field. However, it is still difficult to efficiently manufacture CRTWHWR with high performance because of their extreme geometry with thin-walled skins, high web ribs and large size. In this paper, a novel radial envelope forming process is put forward to efficiently achieve the plastic forming of CRTWHWR with high performance. Firstly, the principle of radial envelope forming process is clarified. Then, an efficient design method for the tool motion and geometry is proposed based on the reverse envelope principle, i.e., CRTWHWR is adopted to reversely envelope the tool and thus the tool which does not interfere with CRTWHWR can be efficiently obtained in a single operation. Finally, a reasonable 3D FE model of the radial envelope forming process of CRTWHWR is established and the radial envelope forming mechanism of CRTWHWR is comprehensively revealed. Through the FE simulation and experiments with material of plastic mud, a typical CRTWHWR with diameter of 300 mm, axial height of 192 mm, the maximum rib height of 25 mm, the minimum rib thickness of 3 mm and skin thickness of 5 mm is radial envelope formed, i.e., the ratio of the maximum rib height to the minimum rib thickness reaches 8.33, the ratio of the maximum rib height to skin thickness reaches 5 and the ratio of diameter to the minimum rib thickness reaches 100. The above results verify that the proposed radial envelope forming process has great potentials in efficiently manufacturing CRTWHWR with extreme geometry.

NEW SPECIES OF COILED NAUTILOIDS FROM THE PENNSYLVANIAN OF THE DONETS BASIN, UKRAINE

Two new species of coiled nautiloids, Gzheloceras poletaevi sp. nov. and Celox oliphanti sp. nov., are described from the Late Bashkirian and Early Moscovian of the Central Donets Basin, Ukraine. Gzheloceras poletaevi sp. nov. differs from Gzheloceras aisenvergi in absence of a longitudinal ridge on the ventolateral shoulder and more compressed whorl profile; Gzheloceras poletaevi differs from Gzheloceras striatum in absence of a spiral lateral ribs and less compressed whorl. Gzheloceras poletaevi is distinguished from Gzheloceras memorandum by more compressed whorl profile and thinly discoidal conch. Gzheloceras poletaevi differs from Gzheloceras pulcher in the absence of a thin transverse lateral ribs and longitudinal ridge on the ventolateral shoulder. Celox oliphanti sp. nov. differs from Celox erratica by delicate growth lines on the conch surface and more rapid whorl’s increase in width and height.

Topology optimization-driven design of added rib architecture system for enhanced free vibration response of thin-wall plastic components used in the automotive industry

A relentless paradigm switch in the automotive industry is being witnessed, where traditional combustion engines are progressively replacing with electric counterparts. In order to compensate for heavy electric engine technology, plastic components used in the interior parts of electric vehicles seems to be a reasonable strategy aligned with the lightweight trend as the automotive industry’s top priority. Extremely thin plastic components (ultra-lightweight) attached to ribs-based architectures have been identified as an adequate solution offering a good balance between lightweight and structural/vibrational response of the overall composition. Still, they may yield detrimental features regarding thermal-induced deformations (i.e., warpage and shrinkage) associated with the typical mold injection process for their manufacturing. This paper uses topology optimization to determine the precise location of the added rib architecture system for enhanced vibration response of the overall plastic component (thin original plastic part and ribs architecture). Following a constant mass criterion, the topology optimization-driven design of the additional material is replaced with a more convenient ribs-based architecture component, showing a reasonable similarity from a vibration standpoint. The component in its initial state (without some ribs-based architecture) shows a vibration response of 16.69 Hz. Once the topology optimization is applied, a significant improvement is observed since a value of 26.05 Hz is obtained. At a postprocessing stage, the design is analyzed and subjected to typical static loading cases to verify its stiffness properties, getting a significant displacement reduction from 7.68 to 3.51 mm. Finally, the design implementation of a warpage and shrinkage analysis confirmed that the final design was not adversely affected according to standard considerations.

A Numerical Study of the Effect of Rectangular Shaped Ribs Organized in Different Patterns on the Thermal Performance of a Solar Air Heater

Abstracts: A solar air heater is a useful device that can be used to raise the temperature of a roomby capturing heat from solar energy This paper is about a two-dimensional numerical study that was done to predict the influence of transverse rectangular cross-sectioned ribs on the convective heat transfer properties of a solar air heater. It is a rectangular duct with an absorber plate on top, and heat only falls on the top of the absorber plate. The thermal performance of air flowing through the rectangular duct is significantly altered when different shapes and orientations of ribs/baffles are introduced just beneath the absorber plate. A comparison was made between the results of thin (high aspect ratio) and square ribs arranged in three patterns, namely, single wall arrangement ,staggered arrangement and in-line arrangement on two opposite walls. The Nusselt number variation with Reynolds number range 4000-25000 was checked at a fixed rib pitch (p) and height (e) values. Computational fluid dynamics (CFD) simulations were performed using commercially available software ANSYS FLUENT v15.0..The results revealed that the thin ribs yielded better performance than the squared ones. Out of the three arrangements, the best thermal performance was given by thin inline ribs whose convective heat transfer coefficient was 1.93 times smooth duct’s convective heat transfer coefficient.

Constraining ring rolling of thin-walled conical rings with transverse ribs

As critical load-bearing components of aerospace equipment, thin-walled conical rings with inner transverse ribs (TWCRITR) are widely used for manufacturing rocket body, aircraft fuselage and space station shell et al., due to light weight, high strength and high load-bearing capacity. However, TWCRITR cannot be manufactured by traditional ring rolling (TRR), due to thin skin and high ribs. Aimed at this problem, a novel constraining ring rolling method (CRR) is proposed in this work to achieve the near-net-shape manufacturing of TWCRITR with high performance and efficiency. CRR innovatively uses a constraint roll and two baffles to fully constrain the diameter and height enlargement of ring, which ensures that the CRR process is still stable and the metal is enforced to flow axially to form high and wide ribs. Owing to the extreme geometry of TWCRITR and the complicated constraints of rolls in CRR of TWCRITR, the inherent relation between geometric and process parameters, stress state and metal flow is complicated, and it cannot be quantitatively determined by the FE simulation or experiment. Hence, the mechanical model which can determine the quantitative relation between geometric and process parameters, stress state and metal flow in CRR of TWCRITR is firstly established by using the slab method and upper bound method. Secondly, three new metal flow modes related with rib width in CRR of TWCRITR are found based on the established mechanical model. The first one is that the real-time height difference of two ribs slightly fluctuates and the two ribs almost grow synchronously when the width of two ribs is almost identical. The second one is that the rib with small width at the small end grows much faster than the rib with large width at the large end when the width difference of two ribs exceeds a critical value. The third one is that the rib with small width at the large end grows much faster than the rib with large width at the small end when the width difference of two ribs exceeds a critical value. Further, the quantitative relations between the metal flow resistance, divided-flow plane and rib growth under three metal flow modes are revealed theoretically, and consequently the mechanisms behind three metal flow modes in CRR of TWCRITR are clarified theoretically. Finally, the simulation and experiment for CRR of TWCRITR are conducted, and TWCRITR with 3 mm in skin thickness, 7 mm in rib width and 12.5 mm in rib height (the ratio of rib height to skin thickness is 4.16 and the ratio of rib width to skin thickness is 2.33) are stably rolled. Moreover, the roundness of rolled TWCRITR is good (it nearly approaches the inner surface roundness of constraint roll). The predicted values of rib height using the established mechanical model are in good accordance with the simulated and experimental ones, which validates the established mechanical model. Through analyzing the novel CRR process and complicated metal flow mechanisms, it is demonstrated that CRR is promising for manufacturing TWCRITR with high performance and efficiency.

Thin Ribs on Chest X-Ray-a Sign Pointing the Way to the Diagnosis of Congenital Myotonic Dystrophy.

Thin Ribs on Chest X-Ray-a Sign Pointing the Way to the Diagnosis of Congenital Myotonic Dystrophy.

An innovative constraining ring rolling process for manufacturing conical rings with thin sterna and high ribs

Conical rings with thin sterna and high ribs (CRTSHR) are key bearing-load parts of aerospace equipment, which are required to be manufactured with high performance and efficiency. Traditional ring rolling is the most preferred method for manufacturing high-performance ring parts, but it can hardly achieve the forming of CRTSHR due to the extreme geometry of CRTSHR. To solve this difficulty, an innovative constraining ring rolling process (CRR) is proposed in this paper to manufacture CRTSHR. To evaluate the proposed CRR and reveal its deformation behaviors, a thermomechanical coupled FE model for CRR of CRTSHR is established. Then, the experiment for CRR of CRTSHR is performed on a modified ring rolling machine, which proves that CRR of CRTSHR is feasible and the established FE model is reliable. Based on the reliable FE model, the metal flow mode in deformed CRTSHR is analyzed, and the deformation characteristics such as the stress state, strain distribution and the evolution of power parameters in CRR of CRTSHR are revealed. Finally, the influences of key parameters such as the friction factor between ring and molds, the diameter of idle roll and the feed velocity of idle roll on CRR of CRTSHR are investigated by FE simulation.

A NEW COELACANTH SPECIMEN WITH ELONGATE RIBS FROM THE MIDDLE TRIASSIC (LADINIAN) KALKSCHIEFERZONE OF MONTE SAN GIORGIO (CANTON TICINO, SWITZERLAND)

A new finding of a coelacanth from the upper Ladinian upper Kalkschieferzone of the Meride Limestone Formation of Monte San Giorgio (UNESCO World Heritage area) is described. It represents the first known coelacanth from the Middle Triassic that undoubtedly bears elongate thin ribs. The incompleteness of the specimen prevents a reliable taxonomic assignment or the erection of a new species, however some characters, mainly scale morphology, are very similar to those of the holotype of Heptanema paradoxum Bellotti, 1857 from the roughly coeval Perledo Formation of Northern Italy. Elongate ribs are not reported in original descriptions of H. paradoxum, however small portion of ribs are visible among the scales of the holotype. Accordingly, the new specimen is tentatively ascribed to Heptanema as Heptanema cf H. paradoxum.

Heat transfer in solar air duct with multi-V-ribbed absorber and grooved back-plate

The article presents an experimental study on heat transfer and friction behaviors in a solar air duct fitted with multiple V-shaped ribs on the absorber and delta-grooves on the back plate. Measurements were carried out in the test duct having a cross-section of width, W=300mm and height, H=27mm. The air flow rate inside the duct was varied to have Reynolds numbers based on the duct hydraulic diameter from about 7000 to 30,000. Two vortex flow devices: rib and groove turbulators, were introduced to generate the vortex flows along the duct. In the test duct, the upper/absorber plate having a constant heat-flux was mounted repeatedly by multiple V-shaped thin ribs with an attack angle (α) of 45° relative to main flow direction while the lower/back plate was grooved periodically in the delta/triangular shape with an attack angle (θ) of 60°. In the present investigation, the geometrical parameters of the ribs included three different rib- to duct-height ratios (e/H=BR=0.108, 0.162 and 0.217) and three rib-pitch to duct-height ratio (P/H=PR=1.0, 1.5 and 2.0). The experimental results have shown that the duct with the V-ribbed absorber at BR=0.217, PR=1 in conjunction with the delta-grooved back plate has the greatest heat transfer and pressure loss. However, the use of the combined devices with PR=1, BR=0.108 leads to the highest thermal performance and also provides greater heat transfer and thermal performance than employing the V-rib or the delta-groove alone.

Molecular basis of a new ovine model for human 3M syndrome-2

BackgroundBrachygnathia, cardiomegaly and renal hypoplasia syndrome (BCRHS, OMIA 001595–9940) is a previously reported recessively inherited disorder in Australian Poll Merino/Merino sheep. Affected lambs are stillborn with various congenital defects as reflected in the name of the disease, as well as short stature, a short and broad cranium, a small thoracic cavity, thin ribs and brachysternum. The BCRHS phenotype shows similarity to certain human short stature syndromes, in particular the human 3M syndrome-2. Here we report the identification of a likely disease-causing variant and propose an ovine model for human 3M syndrome-2.ResultsEight positional candidate genes were identified among the 39 genes in the approximately 1 Mb interval to which the disease was mapped previously. Obscurin like cytoskeletal adaptor 1 (OBSL1) was selected as a strong positional candidate gene based on gene function and the resulting phenotypes observed in humans with mutations in this gene. Whole genome sequencing of an affected lamb (BCRHS3) identified a likely causal variant ENSOARG00000020239:g.220472248delC within OBSL1. Sanger sequencing of seven affected, six obligate carrier, two phenotypically unaffected animals from the original flock and one unrelated control animal validated the variant. A genotyping assay was developed to genotype 583 animals from the original flock, giving an estimated allele frequency of 5%.ConclusionsThe identification of a likely disease-causing variant resulting in a frameshift (p.(Val573Trpfs*119)) in the OBSL1 protein has enabled improved breeding management of the implicated flock. The opportunity for an ovine model for human 3M syndrome and ensuing therapeutic research is promising given the availability of carrier ram semen for BCRHS.

Single-channel properties of skeletal muscle ryanodine receptor pore Δ4923FF4924 in two brothers with a lethal form of fetal akinesia

Ryanodine receptor ion channels (RyR1s) release Ca2+ ions from the sarcoplasmic reticulum to regulate skeletal muscle contraction. By whole-exome sequencing, we identified the heterozygous RYR1 variant c.14767_14772del resulting in the in-frame deletion p.(Phe4923_Phe4924del) in two brothers with a lethal form of the fetal akinesia deformation syndrome (FADS). The two deleted phenylalanines (RyR1-Δ4923FF4924) are located in the S6 pore-lining helix of RyR1. Clinical features in one of the two siblings included severe hypotonia, thin ribs, swallowing inability, and respiratory insufficiency that caused early death. Functional consequences of the RyR1-Δ4923FF4924 variant were determined using recombinant 2,200-kDa homotetrameric and heterotetrameric RyR1 channel complexes that were expressed in HEK293 cells and characterized by cellular, electrophysiological, and computational methods. Cellular Ca2+ release in response to caffeine indicated that the homotetrameric variant formed caffeine-sensitive Ca2+ conducting channels in HEK293 cells. In contrast, the homotetrameric channel complex was not activated by Ca2+ and did not conduct Ca2+ based on single-channel measurements. The computational analysis suggested decreased protein stability and loss of salt bridge interactions between RyR1-R4944 and RyR1-D4938, increasing the electrostatic interaction energy of Ca2+ in a region 20 Å from the mutant site. Co-expression of wild-type and mutant RyR1s resulted in Ca2+-dependent channel activities that displayed intermediate Ca2+ conductances and suggested maintenance of a reduced Ca2+ release in the two patients. Our findings reveal that the RYR1 pore variant p.(Phe4923_Phe4924del) attenuates the flow of Ca2+ through heterotetrameric channels, but alone was not sufficient to cause FADS, indicating additional genetic factors to be involved.

Investigation of chatter stability in high speed milling on thin ribs

Chatter is a self-excited vibration that occurs during high speed machining of parts which is an undesirable phenomenon that affects work piece and also the tool. Chatter mainly depends upon the stiffness, the damping ratio of the material, the force applied and the clamped area. As the machined area continuously changes, the chatter stability of the work piece also changes continuously. The change in natural frequency of Aluminium 7010 T7651 thin rib during milling is calculated by using Modal analysis in ANSYS Workbench. The model is validated with published journal results and experimentally. Also, the scaled-down model of thin rib for same geometry is analysed for any change in natural frequency. The polynomial fit equation for finding instantaneous frequency of thin rib has been found which is applicable for same geometry irrespective of its scale. Using the equation, Stiffness is found and 2D Stability Lobe Diagram has been plotted and chatter free machining has been carried out experimentally in both stable and unstable regions to prove chatter zones. Also it was found that varying spindle speed is easier approach to avoid chatter during milling.

Electrodynamic Analysis of a Circular Waveguide with Thin Metal Ribs

We solve the problem of electrodynamic analysis of the mode composition of radiation in a circular waveguide with thin radial metal ribs. Algorithms for calculation of cutoff wave numbers and components of the electromagnetic fields of the H and E modes have been developed with allowance for the singularity of the field behavior near a thin metal rib. Spectral characteristics of the waveguide are studied. Structures of the electromagnetic fields of the fundamental mode and the higher modes are determined.

Compensation of frequency response function measurements by inverse RCSA

This paper describes an analytical approach for compensating accelerometer-based (contact-type) modal testing results for both mass loading and cable energy dissipation (damping). The inverse Receptance Coupling Substructure Analysis (RCSA) approach is implemented, where a lumped parameter model of the accelerometer-cable is decoupled from the measured receptance (or frequency response function) to isolate the structure's receptance. Experimental results are presented for a 12.7mm diameter cantilever rod, a 6.35mm diameter cantilever rod, and clamped-clamped-clamped-free boundary condition thin ribs.

Experimental and numerical investigation of forced convective heat transfer in solar air heater with thin ribs

Ribs on the underside of the absorber plate of solar air heater enhance the convective heat transfer rate of the air flowing through it. Several experimental and numerical investigations, with different rib geometry and flow conditions, have been carried out. This paper is one such effort of experimental and numerical investigations of solar air heater. It presents the effect of rib arrangements on the heat transfer and frictional loss characteristics of a rib roughened solar air heater. The geometrical and flow conditions of the present work circumscribe with aspect ratio (W/H) of 10 for the duct, blockage ratio (e/H) is 0.1, relative roughness height (e/Dh) of 0.055, relative roughness pitch (P/e) of 10, angle of attack (α) of 90° and Reynolds number (Re) from 4000 to 16000. Two thin transverse continuous and two truncated ribs are used for one pitch length. Four different rib arrangements are considered for the heat transfer, friction factor and thermo hydraulic performance parameter (THPP) investigations. A three dimensional (3D) numerical simulation is carried out with the commercial CFD code ANSYS FLUENT ver. 16.2 and RNG k–ε turbulence model. The enhanced wall treatment as wall function is used, keeping the Y+ criteria<1. The numerical results are in good agreement with the experimental results. Three important outcomes are observed in the present investigation. Rib arrangement 1, with mid ribs placed at 3.3% and 6.67% truncation from the sidewalls gives the highest heat transfer enhancement. Arrangement 3, with mid ribs placed at 5% truncation from the side walls gives the best overall THPP results and arrangement 4, with two transverse continuous ribs in between the truncated ribs shows the highest average friction factor.

Prediction of Stability of Thin Wall Ribs in High Speed Machining

Prediction of Stability of Thin Wall Ribs in High Speed Machining

Computational study on effects of rib height and thickness on heat transfer enhancement in a rib roughened square channel

A computational study was carried out for the heat transfer augmentation in a three-dimensional square channel fitted with different types of ribs. The standard k–ε model and its two variants (RNG and realizable) were used for turbulence modeling. The predictions were compared with available experimental and computational results. Three rib configurations were used in the present study: 90° continuous attached ribs, 60° V-shaped broken attached thick and thin ribs. It was observed that the maximum heat transfer occurs at the normalized rib spacing (p/e) = 10 in the case of 90° attached ribs. The effects of the blockage ratio and rib thickness were investigated for 60° V-shaped broken ribs with Re = 10,000–30,000 and p/e = 10. It was observed that the average Nusselt number decreases with an increase in the Reynolds number for almost all configurations studied in the present study. For the 60° V-shaped broken ribs, increasing the blockage ratio had an adverse effect on the heat transfer. It was also observed that thin ribs perform better than thick ribs.

Effects of rib size and arrangement on forced convective heat transfer in a solar air heater channel

The article presents an experimental investigation on turbulent heat transfer and friction loss behaviors of airflow through a constant heat-fluxed solar air heater channel fitted with rib turbulators. The experiment was conducted for the airflow rate in terms of Reynolds numbers based on the hydraulic diameter of the channel in a range of 5000–24,000. In the present work, a comparative study between square and thin ribs (90°-rib) with three rib arrangements, namely, one ribbed wall (or single rib), in-line and staggered ribs on two opposite walls was first introduced. The study shows a significant effect of the presence of the ribs on the heat transfer rate and friction loss over the smooth wall channel. The comparison made at a single rib pitch and height also revealed that the thin rib performs better than the corresponding square one. Among the three arrangements, the in-line rib array provides higher heat transfer and friction loss than the staggered and the single one. However, the staggered thin rib provides the highest thermal performance. With this reason, only the staggered thin ribs at four different relative heights (BR = 0.1, 0.2, 0.3 and 0.4) and three relative pitches (PR = 0.5, 0.75 and 1.33) are investigated further. It is found that the staggered rib at BR = 0.4 and PR = 0.5 yields the highest heat transfer and friction factor but the maximum thermal performance is at BR = 0.2 and PR = 0.75.

Design and Simulation of Long Slender end Mill Embedded with Passive Damper

Milling operations associated with chatter vibrations usually result in poor surface quality, tool wearing and low efficiency. For some high speed cutting processes, such as the milling of aerospace products, long slender end milling tools are applied for the parts with deep pockets and thin ribs. Cutting tool with large length-diameter ratio is a significant factor leading to chatter, and damping cutter embedded with single degree of freedom (SDOF) passive damper is investigated. Finite element model of the damping cutter is established by ANSYS, and modal analysis and harmonic response analysis are performed to verify the damping effect of the tool. Simulation results show that the amplitude of the frequency response of function (FRF) is decreased 80%and critical depth of cut is increased by 2.7 times for the proposed damping tool compared to the common solid tool with the same length-diameter ratio, which therefore cause the enhancement of machining stability.