Numerical uncertainty due to discretization on the Arbitrary Lagrangian-Eulerian (ale) Finite Element method is investigated in the study. The paper quantifies uncertainty using two ITTC recommended methods, and also ...
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Numerical uncertainty due to discretization on the Arbitrary Lagrangian-Eulerian (ale) Finite Element method is investigated in the study. The paper quantifies uncertainty using two ITTC recommended methods, and also applies a constant Courant-Friedrichs-Lewy (CFL) number based discretization approach, instead of performing the independent grid and time-based discretization recommended by ITTC. As a case study, water entry of a flat bottom rigid and flexible plate is simulated considering various entry velocities. The total slamming loads and structural responses on both the rigid and elastic bottom plates are predicted and validated against available experimental data. Results indicate that numerical errors due to discretization differ in the various parameters and from case to case. They do affect the analysis of slamming loads and associated structural responses, and the hydroelasticity analysis as well. The hydroelasticity effects on the slamming force generally increase as the entry velocity increases, however, the quantitative results differ much for models with different grids. For example, when the hydroelasticity effect is estimated using the finer model, the deviation of the total slamming force on the elastic plate relative to the one on the rigid body are 56%, 57%, and 63% respectively for the three constant entry velocities, whereas the estimations are -27%, -4% and 3% with the coarser model. The study concludes that the uncertainty due to discretization in ale is not just case-specific, but also parameter specific. The uncertainty quantification procedures with a constant CFL number based refinement are recommended to investigate the uncertainty comparing to the individual grid and time step study, in particular for the ale solution where the time step is adjusted automatically as the grid changes. Thus, consideration should be given to updating the ITTC guidelines to incorporate the constant CFL based discretization approach.
In the process of developing oil and gas resources in the Arctic,the impact of icebergs can pose a considerable threat to the structural safety of semi-submersible mooring platforms in ice *** the basis of the arbitra...
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In the process of developing oil and gas resources in the Arctic,the impact of icebergs can pose a considerable threat to the structural safety of semi-submersible mooring platforms in ice *** the basis of the arbitrary Lagrangian Eulerian(ale)algorithm,a numerical model for the interaction between an iceberg and a semi-submersible mooring platform is built in this ***,a mooring system with a link element is designed and *** ice material model for the target iceberg is built and validated.A numerical model for the interaction between an iceberg and a semi-submersible mooring platform is then built.A parametric study(cable angle,tension angle and number of cables)is carried out to study the performance of the mooring *** collision process between the semi-submersible mooring platform and the iceberg in the polar marine environment can be predicted by the present numerical model,and then the optimal mooring arrangement scheme can be *** research results in this work can provide a reference for the design of mooring systems.
The focus of this paper is to investigate the damage characteristics and protective structure design of pontoons as an important barrier for the protection of ports. Two types of protective measures of pontoons are in...
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The focus of this paper is to investigate the damage characteristics and protective structure design of pontoons as an important barrier for the protection of ports. Two types of protective measures of pontoons are investigated:filling tanks with water and installing springs in tanks. In this paper, the damage characteristics of two types of pontoon side structures under the action of near-field explosion loads are simulated by using LS-DYNA explicit dynamic analysis software and the ale algorithm. According to the numerical experiment results for filling different volumes of water in the side tanks, the volume of water for the minimum deformation of the shell plate is 100%, and for the first longitudinal bulkhead, it is 30-40%. Moreover, by applying weights to their deformations based on the actual explosion-proof performance requirements of the shell plate and the first longitudinal bulkhead, the pontoon side structure with the best explosion-proof performance can be obtained. The plastic deformation of the pontoon structure equipped with different types of springs is an order of magnitude smaller than that of the ordinary structure and of the pontoon structure filled with a water medium in the positive tanks. The explosive shock wave energy absorbed by the pontoon is effectively reduced by the addition of water or springs to the protective tanks. The minimum energy absorbed by the pontoon structure with water added in the protective tanks is 18.31% of the energy absorbed by the ordinary structure, and the corresponding volume ratio of water added in the protective tanks is 100%. The pontoon structure with springs in the side protection tanks absorbs only 7.2% of the energy absorbed by the ordinary structure. Both new side protection structures have demonstrated excellent explosion-proof performance.
Understanding the process of the sugarcane milling is important for improving sugar extraction. The Arbitrary Lagrangian-Eulerian algorithm within LS-DYNA was successfully used for the first time to simulate the dynam...
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Understanding the process of the sugarcane milling is important for improving sugar extraction. The Arbitrary Lagrangian-Eulerian algorithm within LS-DYNA was successfully used for the first time to simulate the dynamic process of milling. The predictions of the numerical model were validated using experimental crushing data from a previous study and dynamic process of milling was examined in detail. The draining performance during milling needs to be carefully considered. It was found that the deformation of the sugar-cane in the XY cross-section under loads consisted of two main phases;compression and expansion with reabsorption mostly occurring during the expansion phase. The feeding side of the nip is the main area for the draining of juice. A sensitivity analysis of param-eters influencing load and pressure was conducted. This research method could be applicable to similar engineering problems where there is contact, collision, extrusion, large displacement, and large deformation. (c) 2021 IAgrE. Published by Elsevier Ltd. All rights reserved.
In order to ensure the safety of horseshoe-shaped pipeline during tunnel blasting excavation, the vibration test and dynamic response of horseshoe-shaped pipeline were investigated. The velocity and frequency of tunne...
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In order to ensure the safety of horseshoe-shaped pipeline during tunnel blasting excavation, the vibration test and dynamic response of horseshoe-shaped pipeline were investigated. The velocity and frequency of tunnel blasting vibration were analyzed. Sodev's empirical formula was used for regression analysis of the velocity of blasting vibration. 3D numerical model of a horseshoe-shaped pipelines was established with ale algorithm using ANSYS/LS-DYNA. The propagation law of a blasting seismic wave was analyzed, and the transverse and longitudinal vibration response characteristics of pipelines under tunnel blasting vibration were studied. The velocity of the pipeline increases gradually and the frequency tends to decrease with the decrease of the distance away from the explosion source center under the same charge. The principal frequency of vibration in the Z direction is mainly distributed from 50 to 80 Hz, which is difficult to generate resonance with the pipelines. The maximum relative error between the simulated and measured velocity of X, Y and Z directions was 8.2%. It was reliable to study the dynamic response of pipelines under blasting vibration based on this numerical model. The blasting seismic wave first reached the bottom of the pipeline right above the explosive. Subsequently, seismic waves propagated along the transverse and the longitudinal axes of the pipeline, and the pressure on the pipeline increased gradually. And when it attenuated completely in the soil, the pipeline stopped its response. The peak value of tensile stress of each element of the vault is the largest. However, the velocity of the bottom plate and the arch roof of pipeline are the largest. The peak values of velocity and tensile stress exist in 0 to 4 m away from the explosion source, and gradually decrease as the distance away from the explosion source increases.
The entrance shape of spread die plays a crucial role in the quality control of large-scale aluminum panel production. The conventional design of spread die is generally based on the experience and expertise of the di...
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The entrance shape of spread die plays a crucial role in the quality control of large-scale aluminum panel production. The conventional design of spread die is generally based on the experience and expertise of the die designers or costly plant trials. Thus, it is difficult to guarantee the material flow through subsequent feeder die with the same velocity and ensure the die strength. In this work, the extrusion processes of three spread dies with different entrance shapes used generally in the real extrusion production for large-scale aluminum panel were investigated by FE simulations. Firstly, 3D-FE models for simulating the extrusion processes of the three spread dies were established by using HyperXtrude software based on ale algorithm. Then, the effects of different die designs on the material flow behavior, extrusion load, temperature, residual stress distribution, and die deflection were synthetically studied by analyzing and comparing the simulated results. Finally, the optimal die was manufactured and corresponding extrusion experiment was carried out on a 2600-t extrusion press. The simulation and experimental results show that the die 2 with fan-shaped entrance was the optimum one among the three spread dies, where the minimum required extrusion load, uniform flow velocity at the die exit, minimum residual stress in extruded profile, and minimum die deflection were obtained. This study could provide effective guidance on the entrance shape design of spread extrusion die for the large-scale aluminum panel.
Numerical Wave Tank (NWT) becomes more and more prominent in the corresponding scientific research. On the basis of the Navier-Stokes (N-S) equation, the early application be adopted for discretising and calculating t...
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Numerical Wave Tank (NWT) becomes more and more prominent in the corresponding scientific research. On the basis of the Navier-Stokes (N-S) equation, the early application be adopted for discretising and calculating the specific region is by Volume of Fluid (VOF) and Finite Volume Method (FVM) method. But with the non-linear increasing size of calculation quantity, it becomes difficult to meet the requirements for engineering. However, ale algorithm and SPH algorithm developed in recent years have the tendency to be mature enough to meet the engineering requirements. The calculation model of three-dimensional NWT is built by ale algorithm as an example in this paper, and the results are compared with theoretical solution and experiment. The comparison has proved that ale algorithm matches with the theoretical solution and experiment, and is suitable for engineering use.
This paper establishes a finite element model of pyrotechnic separation nuts and simulates the whole separation process based on the explicit dynamic codes LS-dyna with Arbitrary Lagrange-Euler (ale) algorithm. The se...
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This paper establishes a finite element model of pyrotechnic separation nuts and simulates the whole separation process based on the explicit dynamic codes LS-dyna with Arbitrary Lagrange-Euler (ale) algorithm. The separation shock generated in the unlocking process is analyzed in detail and the results reveal that the pyrotechnic explosion shock and strain energy shock are two sources for the whole separation shock. Besides that, the influence of prestress on the separation shock and its two shock sources is also researched. The results show that the prestress could strengthen all three shocks, especially the strain energy release shock. This paper also compares the shock response spectrum (SRS) of the three shocks and finds that the SRS of separation shock is equal to the envelope of the SRS of pyrotechnic explosion shock and strain energy release shock. In the model of this paper, the pyrotechnic explosion shock plays a dominant role in the frequency range of 100 Hz to 10 KHz. The conclusions got in this work are helpful to insight the mechanism of separation shock and can provide a reference for the design of separation nuts.
Ensuring the safe operation of large LNG storage tank projects under blast loads is very important. First, using LS-DYNA software, numerical simulations of air blast wave propagation are studied with the ale algorithm...
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Ensuring the safe operation of large LNG storage tank projects under blast loads is very important. First, using LS-DYNA software, numerical simulations of air blast wave propagation are studied with the ale algorithm and fluid-solid coupling theory. A new corrected formula for the peak overpressure is proposed based on the numerical results, and its accuracy is verified by comparing the numerical results with the empirical formula and test results. Then, a finite element model of a large LNG storage tank is built, assuming that the explosion source is located 10 m away from both the ground and the tank wall. This model is used to analyse the overpressure and dynamic response of the outer concrete tank and to predict the TNT equivalent quantity that the tank can withstand. The results show that the tank wall facing the burst loads is in a more dangerous state and that the principal tensile stress increases approximately linearly with increasing TNT equivalent quantity. When the TNT equivalent quantity reaches 2.5 t, concrete element failure occurs on the centre facing the explosions, and the outer tank structure is damaged. The conclusions can provide a reference for the blast-resistant design of large LNG storage tanks.
Single-side- steel-concrete (SSSC) panel and center steel-concrete (CSC) panel, which consists of concrete infill, steel plate, and shear studs, are usually applied as protective structures in the industrial structure...
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Single-side- steel-concrete (SSSC) panel and center steel-concrete (CSC) panel, which consists of concrete infill, steel plate, and shear studs, are usually applied as protective structures in the industrial structures, commercial buildings, and nuclear power plant. In the past, limited research about these types of slabs under blast loads has been studied. In this study, three small-scale RC, SSSC and CSC slabs under contact detonation were tested to obtain the failure modes, mid-span deflection, and dynamic response. Nonlinear 3D finite element models of RC, SSSC, and CSC panels consisting steel plate, concrete infill, and shear connectors were established to assess the blast behaviors using Arbitrary-Lagrange-Eulerian (ale) coupled with Fluid-structure interaction (FSI) algorithm. The accurateness of the numerical models was verified with the experiments by comparison of damage modes and deflection. The results indicated that the failure modes of these slabs were summarized as three types such as type I, type II and type III from both experimental and numerical results. The damaged areas of concrete in SSSC and CSC slabs were larger than that of RC slab. However, the RC slab suffered severe penetration damage with the loss in loading bearing capacity. The experimental and the numerical results demonstrated that the steel plate plays an important role in the blast resistance of SSSC, and CSC slabs under contact explosion, which had better blast resistances compared with the RC slab.
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