Thick Cylinder Research Articles

Development of a unified constitutive model coupled with a continuum damage model for design and evaluation of high-temperature components

A unified constitutive model (UCM) coupled with a continuum damage model (CDM) is developed to design and evaluate high-temperature components in the energy, aerospace, and petrochemical industries. While different constitutive models can predict certain aspects of thermomechanical creep-fatigue responses, a generally applicable model for both short and long-term responses, including stress relaxation and tertiary creep/damage, and strain softening has not been available. Hence, this study unifies strain-focused viscoplastic and creep-rupture-focused damage models to predict fatigue, creep, and creep-fatigue interactions using a single set of model parameters. Two CDMs, Kachanov and isotropic damage, are evaluated by coupling these with a modified Chaboche UCM. The strengths and limitations of the original Kachanov and isotropic damage models in predicting a broad set of low-cycle fatigue and creep responses for a commercially important material, modified Grade 91 steel, are determined. Based on the evaluations, a modified isotropic damage model is proposed. The proposed UCM-CDM is experimentally validated against a large set of modified Grade 91 steel responses, including cyclic softening, rate-dependence, short-term stress relaxation, long-term creep, thermomechanical fatigue, and creep-fatigue interaction at temperatures 400 to 625 °C. The UCM is further validated by simulating a set of modified Grade 91 steel notch specimen creep responses. The modified UCM is demonstrated to simulate the influence of stress triaxiality and prior fatigue on creep rupture life. Finally, the proposed UCM is evaluated by analyzing a thick cylinder under thermal transient loading to demonstrate the modified UCM’s applicability for the design and evaluation of high-temperature components.

Cylinder Fatigue Design of Low-Speed, High-Torque Radial Piston Motor

Through the comparison of fatigue properties of components made of composite materials and high-strength structural steel materials, this study proves that composite materials can replace traditional steel materials used in the production of mechanical structural components. The focus of this study was a low-speed, high-torque radial piston motor mounted on a roadheader. According to different theories, the motor block was designed using a composite material made of carbon fiber, a classic high-strength structural steel, and an aluminum alloy. The thickness of the motor cylinder obtained by theoretical calculation was verified by finite-element numerical simulation technology, and the fatigue phenomenon caused by the time change of the piston cylinder pressure was considered. The results showed that the stress results of the numerical simulation verify the rationality of the theoretical calculation of the cylinder size. In terms of safety factors, the motor cylinder made of composite materials was close to the motor cylinder made of high-strength structural steel, and the difference between the static safety factor and fatigue safety factor was only 0.8 and 0.86. The weight of the motor cylinder made of composite material was reduced from 32 N to 7 N compared with steel material, which was about 78% lighter. This is of great significance for improving the use efficiency of equipment and reducing fuel costs.

Composite Overwrapped Pressure Vessel Design Optimization Using Numerical Method

Composite Overwrapped Pressure Vessels (COPVs) are widely used in fields including aeronautics and by companies such as SpaceX to hold high pressure fluids. They are favored for these applications because they are far lighter than all-metal vessels, although they demand special design, manufacturing, and testing requirements. In this study, finite element modeling was used to conducted stress and damage assessments on a composite overwrapped pressure vessel that has a 4 mm thick aluminum core cylinder. To develop the optimum COPV, the lamina sequences, thickness, and fiber winding angle were considered. The relationship between these variables and the composite-overwrapped structure’s maximum burst pressure bearing capacity was assessed. The ABAQUS composite modeler was used to design and generate 14 models of COPVs from carbon fiber/epoxy plies with a consistent thickness of 6.5 mm and various fiber angle orientations. The effects of the ply stacking order were analyzed by the finite element analysis approach for all designed models, which had 13 layers of uniform thickness but a varying fiber orientation. A ply stacking sequence of [55°, −55°] PP winding pattern had an optimum COPV design profile, with a burst pressure bearing capacity of 24 MPa. The stress–strain distribution along the geometry of the COPV was also obtained using the finite element method, and it was found that the distribution is uniform over the surface of the COPV and that its peak values are found towards the polar boss section of the COPV. Extreme stress gradients were noticed when the boss nears its geometrical transition to the dome phase. This factor is evident from the change in the ply thickness caused by the overlapped fiber orientation. The results obtained from this study are useful for the design and application of composite overwrapped pressure vessels.

Moman's Secret Agenda

Moman's Secret Agenda

Real-time pulse shape discrimination for neutron scattering science using EJ-270

A detector for neutron scattering applications utilizing the 6Li loaded pulse shape discrimination scintillator EJ-270 was developed. The detector utilises a pulse shape discrimination algorithm developed for high-count rate applications implemented in FPGA to enable real time operation. The implemented algorithm we call Tail Sum was specifically developed for high-rate thermal neutron detection and implemented into a 2 channel 500 MSps 14-bit ADC with a Xilinx Kintex 7 K325T FPGA. The detector consisted of a 48 mm diameter × 15 mm thick cylinder of EJ-270 mounted on a Hamamatsu R6231-100 PMT and an E1198-2 base at -1000 V. The performance of the system was evaluated using a moderated 241Am-Be mixed radionuclide source, a figure of merit of 1.605 ± 0.007 was measured. The γ-ray sensitivity of the system was measured using a 60Co source and found to be 3.23 × 10-6 ± 7 × 10-8. The high neutron count rate capability of the system was tested on the Emma instrument at the ISIS pulsed neutron and muon source based at the Rutherford Appleton Laboratory, a peak count rate of 5 × 105 neutrons per second was measured on a single channel and was found to have no statistically significant deviation from the expected count-rate.

An efficient, safe, and energy-saving saddle for pressure vessel based on electro-permanent magnet technology

In this paper, a novel magnetic transport saddle based on the electro-permanent magnet (EPM) technology is proposed. A strong and stable magnetic force can be generated by passing only a momentary current during loading and unloading since the magnetic force is provided by the internal permanent magnet, not the electromagnet. The EPM system is convenient to control and has low energy consumption. This research commenced with a preliminary design of the magnetic circuit structure and circuit structure. The feasibility of this magnetic circuit structure is verified by theoretical derivation and magnetic field simulation, and the factors influencing the magnetic force are further investigated. Subsequently, transient thermal analysis was performed for the extreme case of continuous magnetization and demagnetization. Then, a series of experiments such as electrical circuit, magnetic field, and tensile test were performed for the EPM chuck. Based on the magnetic element, the magnetic transport saddle is designed and the magnetic field simulation is performed for the magnetization state. In addition, when the wall thickness of the transport cylinder is too thin and the magnetic force is insufficient, this paper proposes a solution to increase the cushions inside the transported equipment. Finally, the energy-saving performance of the magnetic transport saddle based on the EPM technology is calculated.

(Invited) Raman Scattering By Exciton-Polaritons in Carbon Nanotubes

Resonant Raman scattering has been used for decades to study single walled carbon nanotubes (CNTs), but lacks a consistent theory that simultaneously explains all characteristic signatures. We argue that a proper description requires introducing exciton polaritons as couples excitonic and photonic states. We describe the polaritons by waveguided theory for a nanometre thick cylinder with modified dielectric function. During their propagation along the tube, the polaritons scatter with phonons and are re-emitted as photons with smaller energy (Stokes scattering event). This approach consistently explains the energetic positions of the Raman resonances for the radial-breathing mode (RBM), the G and the 2D line as well as the asymmetry in the scattering intensity of the incoming and outgoing resonances without resorting to higher-order scattering events. We measured the Raman effect on chirality-sorted nanotubes over the first and second exciton resonance and excellently predict its behaviour, which has not been achieved before. The formation of polaritonic states will affect other optical processes in CNTs. Furthermore, exciton-polariton effects appear inevitable in all one-dimensional excitonic systems, similar to our observations in single walled carbon nanotubes.

Practical level-of-detail aggregation of fur appearance

Fur appearance rendering is crucial for the realism of computer generated imagery, but is also a challenge in computer graphics for many years. Much effort has been made to accurately simulate the multiple-scattered light transport among fur fibers, but the computation cost is still very high, since the number of fur fibers is usually extremely large. In this paper, we aim at reducing the number of fur fibers while preserving realistic fur appearance. We present an aggregated fur appearance model, using one thick cylinder to accurately describe the aggregated optical behavior of a bunch of fur fibers, including the multiple scattering of light among them. Then, to acquire the parameters of our aggregated model, we use a lightweight neural network to map individual fur fiber's optical properties to those in our aggregated model. Finally, we come up with a practical heuristic that guides the simplification process of fur dynamically at different bounces of the light, leading to a practical level-of-detail rendering scheme. Our method achieves nearly the same results as the ground truth, but performs 3.8×-13.5× faster.

Direct numerical simulation of different finite cylinders rolling on a horizontal surface: The thickness effects on the aerodynamics

The flow around a cylinder rolling along a horizontal ground plane is investigated using direct numerical simulation for a Reynolds number based on the cylinder diameter, D, of ReD=3×104. Three cylinder thicknesses, T/D=0.040, 0.126, and 0.400, are considered. The time-averaged drag coefficients are found to be 0.87, 0.69, and 0.97 for the three cylinders, respectively. The non-monotonic variation in drag coefficient with thickness suggests a transition in the proportion of contributions of friction and pressure drag to the total drag which changes about 30% with thickness increase. Indeed, the ratio of friction drag to pressure drag varies from 0.333 to 0.085 and finally to 0.013 for the three cylinders. The pressure coefficient become more negative in the aft of the thicker cylinders, because the cylinder become more bluff body which suggests more pronounced pressure drag. Temporal fluctuations in the drag coefficient associated with vortex shedding events increase monotonically with thickness, though the root-mean-square of the drag coefficient follows the same trend as the mean drag coefficient. The lift coefficients are −0.057, 0.066, and 0.64 for the three respective cylinders. The negative value for the thinnest cylinder indicates down force. The transition from negative lift on the thin cylinder to positive lift on the thick cylinder is associated with elevated surface pressure just upstream of the ground contact point as thickness increases. As the flow is more detached from the cylinder sides, the friction lift is less significant with thickness increase. Furthermore, the pressure coefficient is negative spatially larger in the top of the thicker cylinders which the expansion offers a more significant upward pressure lift.

A study on the effect of biconvex compact shape factors on prediction of dilution potential from tensile strength–compaction force data of coprocessed diluents

BackgroundThe purpose of this research was to compare the effect of shape factors of biconvex compacts on prediction of dilution potential from polynomial regression models of area ratio-mass fraction data of novel α-lactose monohydrate-starch orodispersible diluent (α-LSOD) and StarLac®. Ibuprofen-diluent blends were compacted between 4.98 and 29.89 kN. Given the biconvex round compact dimensions (t = axial thickness, w = central cylinder thickness, and d = diameter), tensile strength was computed as sigma_{{{text{biconvex}}}} = Phi frac{F}{{pi {text{d}}t}}, where F is the breaking force. The shape factor (Φ) was defined as left[ frac{t}{2d} right]^{ - 1} ,left[ {frac{0.14t}{d} + frac{0.36w}{d}} right]^{ - 1} ,left[ {10/left[ {left( {frac{2.84t}{d}} right) - left( {frac{0.126t}{w}} right) + left( {frac{3.15w}{d}} right) + 0.01} right]} right] for Podczeck (ΦPz), Shang (ΦSh), and Pitt (ΦPt) models, respectively. Area under the curve (AUC) was obtained by second-order polynomial fitting of the tensile strength–compaction force curve followed by integration of the quadratic regression equation between the two compaction force limits. The AUC of each powder system was normalised with the AUC of ibuprofen-free powder to obtain area ratio (AR). The AR was plotted against mass fraction of ibuprofen, and the curvilinear data was fitted by third-order polynomial fitting. Dilution potential was obtained from the regression equation by back extrapolation to zero area ratio.ResultsTukey’s multiple comparison test indicated statistically significant differences between the three shape factors (p < 0.001). The shape factors ΦSh and ΦPt were higher than ΦPz by a factor of 2.4 and 1.2, respectively. The quadratic regression model sufficiently explained the observed relationship between tensile strength and compaction force as indicated by the coefficient of determination whose values ranged between 0.9344 and 0.99843 and 0.93725 and 0.99812 for α-LSOD and Starlac®, respectively. Dilution potential was predicted as AR = B_{3} x^{3} + B_{2} x^{2} + B_{1} x + c, where x and its coefficients are ibuprofen mass fraction and regression constants, respectively. The predicted dilution potential of the three tensile strength models were within a close range of approx 110.93 pm 1.02 and approx 116.02 pm 0.62 for both α-LSOD and StarLac®.ConclusionsThis study suggests the adoption of the simplest Podczeck model given a biconvex round punch tooling and highlights the suitability of polynomial regression to predict dilution capacity from nonlinear area ratio-mass fraction data.

A deep learning approach based on the physics-informed neural networks for Gaussian thermal shock-induced thermoelastic wave propagation analysis in a thick hollow cylinder with energy dissipation

This paper proposes a novel approach based on the physics-informed neural networks (PINNs) as an efficient deep learning approach to solve a broad range of the coupled partial differential equations (PDEs). For the first time, the PINN methodology is successfully applied to the thermoelastic wave propagation analysis with energy dissipation in a thick hollow cylinder based on the Green-Naghdi (GN) theory of coupled thermoelasticity. The assumed thick hollow cylinder is subjected to Gaussian thermal shock loading applied on the inner bounding surface. This research presents a PINN architecture with self-adaptive weights, which does not suffer from the curse of dimensionality as opposed to the numerical methods. An in-depth discussion is provided on the method and its capabilities to address PDE-related issues. Moreover, the PINN-based parametric studies are performed to show the effects of the materials coefficients on the thermoelastic wave propagation and dynamic behaviors of the fields’ variables. Numerous examples of thermoelastic wave propagation analysis with and without energy dissipation are solved via this approach. The framework generates satisfactory results in terms of accuracy and stability, as summarized in the paper.

Thermally nonlinear generalized thermoelasticity investigation of a functionally graded thick hollow cylinder based on the finite difference method

In the present paper, the propagation and reflection of the transient displacement, temperature, and stress waves are numerically explored in a functionally graded thick-walled hollow cylinder, based on the Lord–Shulman generalized thermoelectricity theory and using the finite difference method. The motion and thermoelastic energy balance equations are first established based on the dimensionless radial displacement and temperature fields. It is assumed that the elasticity modulus, Poisson’s ratio, mass density, thermal expansion coefficient, thermal conductivity coefficient, and specific heat follow power functions of the dimensionless radius while the relaxation time is assumed to be constant within the FGM cylinder. Unlike many previous studies in which the energy balance equation was linearized by assuming small temperature rises, the present research accounts for the significant temperature variations and employs a nonlinear energy balance equation. Nondimensional forms of energy balance and motion equations are derived by introducing dimensionless quantities and discretized via the finite difference method. The Newmark method with constant average acceleration was employed to solve the highly nonlinear equations found from the finite difference method. Two different boundary conditions were used to investigate the propagation and reflection of the displacement, temperature, and stress transient waves in the radial direction of the cylinder. The results revealed the variable speed of the displacement wave and the significant role of the changes in the properties along the radius of the cylinder and the boundary conditions in altering the results.

Forced convection flow over a moving porous and non-uniform cylinder of variable thickness

Forced convection flow of viscous fluid over a moving, porous, and heated cylinder of variable thickness is studied in this paper. The non-uniform cylinder is placed vertically in a quiescent fluid. All the field quantities (the normal and axial velocities and temperature), defined at the wall or surface of cylinder, are variable and may have non-linear form. An appropriate set of transformations is developed on the analogies of systematic classical symmetries for a system of partial differential equations (PDE’s), whereas, they are equipped with the representative of each velocity component, temperature function, and similarity variable. However, the PDE’s along with the boundary conditions (BC’s) are reduced into a system of boundary value problem (BVP) of ordinary differential equations (ODE’s) by using these new and unseen similarity variables. The system of non-linear coupled ODE’s, combined with the BC’s is solved, whereas, the numerical results are obtained for different values of the existing governing parameters. All the field quantities, skin friction, rate of heat transfer at the surface of the cylinder are evaluated with the help of [Formula: see text] package of MATLAB and the results are shown in different graphs. The present simulation generalizes all types of forced convection flow problems, over a porous and heated cylinder of variable (uniform) radius, when it is stretched (shrunk) with linear and non-linear (uniform) velocity. However, the simulated problem gives rise to a new set of problems and that they are valid for non-linear (linear and uniform) injection (suction) velocity.

Numerical Study of Vertical Slot Fishway Flow with Supplementary Cylinders

The vertical slot fishway (VSF) is one of the most common types of fishway facilitating migratory fish movement past obstacles in rivers, such as dams. The uniform vertical distribution of velocity is friendly to fishes with different depth preferences, but unfriendly to fishes with different swimming capacities. For an established VSF, the insertion of an additional structure is a more convenient and effective way to change the flow field rather than altering the original elements. Numerical experiments were carried out using large-eddy simulation (LES) to optimize a typical VSF with supplementary cylinders for fishes with low swimming capacity. The computational domain of the original design is idealized as a box including two pairs of baffles with the periodic boundary condition used in the streamwise direction. The numerical model is well validated by comparison of time-averaged velocity and turbulence kinetic energy with the ADV measurements at gauging points and lines. Two arrangements of cylinders with different numbers and diameters were investigated and compared with the original design based on the first and second-order hydrodynamic statistics at the half height of the VSF. The insertion of cylinders significantly alters the flow field by introducing a branch path of relatively low-speed current. The arrangement of four slim cylinders slightly outperformed that of one thick cylinder against velocity homogeneity along the minor migration path. Although the turbulence intensity is enhanced due to the additional cylinders, the perturbation on fishes is not significant due to the small size of these vortices.

Increase of Trigonelline in Trigonella persica Plant under Drought Stress

Trigonella persica is a valuable medicinal plant which comprises trigonelline that is secondary metabolite and important component in cosmetic and medicine. This research was conducted in order to evaluation the drought stress effect on growth parameters, root anatomical changes and trigonelline content in T. persica. Plants were grown under soil moisture corresponding to 100%, 75%, 50% and 25% field capacity for two weeks. The data showed that drought stress was significantly decreased fresh weight and dry weight of shoot and root. In addition, leaf area was declined due to drought stress. Interestingly, root length was enhanced by drought stress. Root microscopic study demonstrated that drought stress increased thickness of epidermal, endodermal, vascular bundle, central cylinder and parenchyma in T. persica. Drought stress caused a significant increment in alkaloid and trigonelline content in aerial parts and roots of T. persica. These results revealed that T. persica responded to drought stress by increasing the alkaloid and trigonelline, as well as the anatomical changes in root. Considering the importance of trigonline and alkaloids, this work may open prospects for production of the pharmaceutically valuable secondary metabolites thereby drought stress.

Simulative analysis on large local deformation features of single-shell and double-shell cylinders subjected to underwater explosion

Simulative studies on a series of the cylinders subjected to underwater explosion were presented using coupled acoustic-structural analysis in ABAQUS in order to analyze the large local deformation feature and the influence of the outer water tank. The results revealed that large inward local deformation occurs on the front side of the cylinder, and the plastic hinge locates near the boundary of the spherical projection of the explosion to the cylinder with an approximate elliptic type. The inner water and the outer shell’s thickness of double-shell cylinders have great influence on the large local deformation feature of the inner shell, and with the increase of the outer shell’s thickness, large local inward deformation occurs on the back side of the cylinder, which is caused by the local jet effect of the inner water. The research can provide reference to the design and assessment of underwater anti-explosion structures.

Free vibration analysis of a circular cylindrical shell using a new four-variable refined shell theory

A theory is proposed to study the vibrations of homogenous isotropic circular cylindrical shells based on a developed plate vibration theory. By proposing a novel distribution of the shear stress and strain across the thickness of the shell, the arguments are adjusted such that the transverse shear strains and stresses equal zero at the shell surfaces. Due to the existing curvature in the circumferential direction, the defined shear stress and strain distributions consider a change in the position of the neutral plane toward the center of curvature. In the presented Two-Separated Lateral Displacement (TSLD) theory, the lateral displacement is defined by two bending and shear parts to provide an analytical model, referred to as the four-variable refined plate theory. The similarity to classical theory and involving only four unknowns are significant features of the introduced theory. The TSLD theory is verified against the available data in the literature. It is shown that the provided stress and stress distributions lead to more accurate results, especially in moderately thick cylinders. The proposed theory is remarkably more precise than classical shell theory and First-order Shear Deformation Theory (FSDT). Results of the TSLD theory are as accurate as the Higher-Order Shear Deformation Theory (HOST12) for the higher frequency parameters and more thick shells, while the TSLD theory implementation is much simpler than the HOST12.

Parameter optimization of rubber cylinder of expansion liner hanger based on numerical simulation

The expansion liner hanger has great advantages over the traditional slip liner hanger. Therefore, scholars at home and abroad have carried out extensive research on the expansion liner hanger, but there are few researches on the optimization design of the rubber cylinder of the expansion liner hanger. How to select the size and material of the rubber cylinder is very important to the suspension performance of the expansion liner hanger. Based on the Ø245 mm × Ø178 mm expansion liner hanger as the research object, the condition of the changes under the wall thickness and friction coefficient, using the finite element analysis software of rubber cylinder elongation rate, stress conditions are numerically simulated. The results show that when the wall thickness of the rubber cylinder is t = 1.5 mm, the elongation rate of the rubber cylinder is 2.14 mm, and then the elongation rate of the rubber cylinder increases rapidly with the increase of the wall thickness, and the growth of elongation rate slows down when the wall thickness is t ≥ 3.0 mm. The contact stress of the inner and outer walls of the rubber cylinder increases with the increase of the wall thickness, and the contact stress of the inner wall of the rubber cylinder fluctuates, and the fluctuation tends to be gentle when t ≥ 2.5 mm, and the residual stress of the rubber cylinder is uniformly distributed when t ≥ 2.5 mm. When different friction coefficients (0.05, 0.1, 0.15, 0.2, 0.25, 0.3) were taken between the rubber cylinder and the outer casing, the elongation rate of the rubber cylinder was negatively correlated with the friction coefficient, and the average contact stress on the wall was positively correlated with the friction coefficient. The results of this paper provide guidance for the design and material optimization of the rubber cylinder in the expansion liner hanger.

Bounded Elastic Moduli Multiplier Technique for Limit Loads: Part 2—Case Studies

Abstract Part 1 of the article provides the theoretical underpinnings of a new method to determine statically admissible stress distributions in a structure, called bounded elastic moduli multiplier technique (BEMMT). It is shown that this method offers statically admissible stress distributions better than the power law and closer to elastic-plastic solutions for textbook cases such as thick cylinder, beam, etc. This part of the article offers several numerical examples to demonstrate the robustness of the method. Upper and lower bound limit loads are calculated using iterative elastic analyses using both power law and BEMMT. These results are compared with the ones obtained from elastic-plastic FEA. Consistently BEMMT has outperformed power law when it comes to estimating lower bound limit loads.

Numerical investigation of hemodynamic pattern in carotid artery dynamic aneurysm on bifurcation region for early clinical decision making

AbstractIn this paper, a numerical estimation of wall shear stress (WSS) and study on hemodynamic pattern in carotid artery (CA) near the bifurcation region with dynamic growth of aneurysm using computational fluid dynamics (CFD) for making early clinical decision is presented. Aneurysm in the carotid artery affects the blood supply to brain and if it is untreated at early stage may lead to sudden death. Computed tomography images of four different cases of stroke subjects scanned of 600 slices with 1 mm resolution with neighbouring layers from neck to head are considered for this study. Numerically a CA with bifurcation region is developed from these images and aneurysm is and allowed to grow dynamically from 10 to 20 mm. WSS and hemodynamic pattern is estimated numerically using Ansys platform at various region of interest in both rigid and compliant wall conditions. The arterial wall thinning was analytically estimated using thick cylinder theory to estimate the increase in aneurysm under various stress conditions (rest and exercise conditions). The findings show that WSS is found to reduce at the aneurysm region with a corresponding strong vortex pattern. Thus, the vortex pattern could be the cause of tissue damage and thinning rather than WSS. The corresponding increase in velocity gradient at the bifurcation region is also captured. This high gradient is the cause for higher WSS at the bifurcation region which is a possible cause for the formation of plaque and arteriosclerosis. It is interesting to note that the WSS did not change drastically for 10 and 15 mm aneurysm but a large change was seen from normal to 10 and 15–20 mm respectively. This study provides a better clinical insight on the effect of aneurysm in CA bifurcation region using a systematic approach to numerical modelling compared to traditional imaging modalities. It can be used as an adjunct tool for physicians and surgeons for planning necessary clinical interventions.