Mixed analysis of shell and solid elements using the overlaying mesh method

In the structural design of ship hull, the shell element is used for the analysis of the global model. However, the analysis using the solid elements is necessary for the analysis of the stress concentration zone or the crack vicinity. Generally, the zooming method is used to solve such problems. In this paper, the mixed method of the shell elements and the solid elements using the overlay method is presented. The present method is more advantageous than the zooming method in respect of the accuracy of the solution and the modeling of the finite element mesh. Some examples of the plate model with a crack are shown to demonstrate the effectiveness of the present method.

In this paper, the structure of cylindrical shell with a reinforced circular cutout using combination model of solid element and shell element was analyzed by Finite Element Method (FEM) simulations. Multipoint constraint (MPC) method is mainly used to solve the connection between solid element and shell element when considering the calculation accuracy and efficiency of the model. The combination model of solid and shell element is established in ANSYS, and has been compared to the model of shell element and the model of solid element. The result showed that in the aspects of the stress distribution of the pressure hull near the cutout, buckling behavior of the structure and its instability response, the combination model of solid and shell element was almost equal to the others, it is convincible as well as possessing merits of other models.

Prediction of plastic flow localization with shell element in thick AHSS sheets

In order to propose a simplified simulation method using finite element (FE) model for predicting deformation and residual stress generated by multi-pass butt welding, a series of experiments and numerical analyses were carried out. 3-pass butt welding of steel plates was simulated by the thermal elasto-plastic analysis with shell elements and with solid elements respectively. A heat input model for considering the temperature distribution in the thickness direction in shell elements was proposed. The validity of the heat input model was verified by comparing analytical results with experimental results or other analytical results using solid elements. Furthermore, the effectiveness for saving computing time by using shell elements was confirmed from the comparison with the case using solid elements. It was confirmed that the welding out-of-plane deformation and residual stress could be predicted with high accuracy by the proposed method. The computing time was around 14% of that by the precise model with solid elements.

A finite element post-processor for fatigue assessment of welded structures based on the Master S-N curve method

In recent years, with the increasing demand of reducing CO2 emissions, offshore pipeline found its new application in transporting CO2 offshore. Carbon capture and storage (CCS) is an effective method in the fight against climate change. This technology allows CO2 to be “captured” from large sources such as power plants and prevents release of greenhouse gas to the atmosphere. The captured CO2 has to be compressed and then transported to a safe and durable storage location, such as depleted subsea oil reservoirs. The captured CO2 is then locked away deeply under the sea floor so that it cannot escape into the atmosphere and contribute to global warming. To facilitate the connection between an offshore pipeline and an onshore plant, a robust landfall method must be adopted. The benefits of using horizontal direction drilling (HDD) for offshore pipeline landfall include longer durability, potentially lower project cost, less community and environmental disruption, and fewer authorization issues. In this paper, the analysis methods and the results of an HDD pull-in case study are presented. An analytical method for pull-in force is discussed first and then a global finite element (FE) model is developed. In the global model, a 10 km long pipeline is included. The pipeline, the pull wire and HDD borehole are simulated by using beam elements. The tube-to-tube elements are used to simulate the contact between the pipeline/wire and the borehole. The global model is used for both the pull-in and the hang-off analysis. To prevent corrosion of the pipeline in case of the coating damage, circular anodes are installed on the pipeline. In the HDD borehole, the anodes are installed for all the pipe joints. Since the anode pitch is small enough, the anodes are also used as centralisers during pull-in installation. To study of the effect of anodes on pull-in load, a local FE model is also developed. In the local model, a short pipe section and an anode with detailed geometry are included. The pipe and the HDD borehole are modelled using shell elements and the anode is modelled with solid elements. The additional pull-in load caused by the anode is predicted by using the local model. The loads acting on the hang-off structure in different phases are also obtained from the analysis, which are used as design input data for the hang-off structural design. The finite element analysis (FEA) results are compared with the results obtained from the simplified analytic calculation. It is concluded that the results obtained from the proposed FEA method are more accurate and more reliable than those from the simplified methods. In future, the proposed numerical analysis method can be used as reference or go-by for projects with HDD pull-in.

Influence of welding sequence on welding deformation and residual stress of a stiffened plate structure

The feasibility of implementing a thickness-stretch shell element in combination with a user-defined material model in LS-DYNA for completing the simulation of the thermoforming of a cross-ply thermoplastic is investigated. For fabric-reinforced sheets, the primary mode of deformation during the preforming phase of thermoforming manufacture is in-plane shearing of the fabric with varying degrees of shear to conform to the geometric variations over the surface of the preform tool. The decreases in areal coverage that occur with changes in the local shear angle will induce local changes in thickness. During the consolidation phase, multiple preform layers are compressed in a set of matched tools, and the compounding of the thickness variations through the plies can adversely affect the uniformity of the pressure distribution on the composite part in the matched die tooling. Pressure variations over the surface of the part can then lead to incomplete consolidation of the ply stack. Although solutions for implementing thickness changes and contact of the general shell elements have successfully been employed, the challenge of through-plane compressive properties cannot be addressed with that approach. The simulation must accurately capture the thickness changes not only from shear deformation, but also from compression between tooling and other laminate plies. New formulations of solid and shell elements in LS-DYNA may be able to handle the aspect ratios of a general shell element without any compromise in the fidelity of the solution and should be able to model the through-plane compressive properties as well as thickening from shear deformation. A user-defined material model is combined with thickness-stretch shell elements, and LS-DYNA simulations of tension and shear testing of Dyneema HB80 are performed.

The objective of this study was to construct a finite element model of a golf ball and an impact simulation model between the ball and a club, and to devise a method for the construction of simulation models by investigating the factors affecting the behaviour of the ball during and after impact. A ball model with hyperelasticity and viscoelasticity was constructed using solid elements, and the relationship between the material properties and the ball behaviour at impact was revealed by varying several material constants of the ball model. A finite element model of a club with elasticity was created from a computer-aided design surface model of a commercially available driver. The club head and shaft were modelled using solid and shell elements, respectively. The effects of initial conditions at impact on the rebound behaviour of the ball, that is, the velocity, angle and spin rate, were investigated from impact simulations by varying the impact points of the ball and the postures of the club. Then, methods for the construction of simulation models were proposed based on these relationships. Impact experiments were also conducted to obtain the ball behaviour. The results simulated using the models, constructed by the proposed methods, closely matched the experimental results.

Finite-Element Analysis (FEA) is a numerical method that facilitates designers to produce a part with the high degree of reliability. These advantages allow manufacturing engineer to produce a virtual tool prototype. This approach has eliminated the requirement to manufacture the prototype model from soft tool parts and soft tool press die. This research focuses on the numerical experiments for an advanced high-strength steel part in Body-in-White. The patchwork blank sheet of a structural body in white is modeled with three conditions - shell elements without spot welding nuggets, Shell elements with spot welding nuggets and Solid elements. Shell elements are usually the obvious choice in the blank in sheet metal forming simulation primarily due to the rapid and fairly accurate results generated. Solid elements of the other hand require extremely high computation time. The main objective of this study is to critically compare plastic deformation results obtained from three approaches on a B-Pillar part with 1.75mm thickness. The finite-element models are developed from the CAD data of production tool and blank material. The blank material is meshed with quad elements for optimized computing time and results. The input parameters for the simulation models are obtained from the current setup at Press Machine and Production Tool. The analyses of plastic deformation for all three blank material models are compared to the actual part thickness. Percentage of deviation from the actual part geometry will indicate the best approach in producing finite-element models for Hot forming process.

Modeling complex conditions involving extensive engineering structures with large numbers of beams and columns often requires a mixture of analytical modeling based on beam theory and numerical simulations involving finite element models composed of solid or shell elements. However, high levels of deformation in the planar configuration of cross-sections arising under extreme external loads, such as intensive earthquakes, explosions, and hurricanes, greatly complicates the task of fitting the numerical simulation results to the planar cross-sections required by beam theory. The present work addresses this issue by proposing a fitting method based on a least squares approximation method. The fitting problem is first transformed into a process of solving a cubic equation whose coefficients are integrals over the simulated cross-section. The solution of the cubic equation is defined using explicit formulae developed for calculating the integrals over the surfaces of single solid or shell elements lying within the cross-section by combining the shape functions and degree of freedom results of the elements. The proposed fitting method is then applied for analyzing the blast resistance of steel structures. The potential application of the proposed method is demonstrated by evaluating the rotations, shear deformations, and moment–curvature relationships of the fitted cross-sections.

In order to grasp the force performance and stress distribution of shaped pylon steel anchor box under the action of the cable tension, with a main span of 555m length of three towers cable-stayed and self-anchored suspension combined system bridge as the engineering background, through the APDL command stream parametric programming, the different finite element models of pylon steel anchor box is established by the spatial solid element and shell element, the mechanical properties of cable-pylon anchorage zone were studied under the most unfavorable load combination, considering the stress state and distribution characteristics of steel anchor box under different orthodontic force. The results showed that: under the most unfavorable combination of loads, the stress was concentrated at the position of the anchor plate and pressure plate using the initial strain mode; the calculation results of solid element and shell element were consistent by uniform loading mode, which could reflect the real stress state of steel anchor box, but the shell element corner contact area prone to stress calculation distortion.

This paper presents three different numerical models for the evaluation of the stresses in corrugated sheets under bending. Regarding the numerical simulations different approaches can be considered, i.e., a elastic linear analysis or a physical nonlinear analysis, that considers criteria to fail for the sheet material. Moreover, the construction of the finite element mesh can be used shell elements or solid elements. The choice of each finite element must be made from the consideration of their representativity before behavior to be simulated. Thus, the numerical modelling in this manuscript was performed from the three-dimensional models using the SAP2000Nonlinear software, version 7.42, which has as base the finite elements method (FEM). It was considered shell elements in the build the mesh of finite elements and an analysis of type elastic linear in this case. Five mm thick sheets were evaluated considering three different longitudinal dimensions (spans), i.e., 1100 mm, 1530 mm and 1830 mm. The applied load to the models was 2500 N/m and it was verified that the spans of support of sheets have a significant influence on the results of stresses. The sheets with larger spans present larger stresses for the same applied load. The most intense values of tension occur in the troughs (low waves) of the sheets, on the lower surface, while the most intense values of compression occur in the crests (high waves), on the upper surface of the sheet. The flanks, which are the parts among the troughs and crests of the sheets, are submitted to low levels of stresses. The numeric results of the stresses showed a good agreement with the results obtained from other researchers 3 and these results can be used to predict the behavior of corrugated sheets under bending.

Creep Age Forming (CAF) is an effective forming technique combined forming and heat treatment, based on creep and age hardening characteristics of some aluminum alloys. It has been widely used to manufacture large integral panels with airfoil sections and complex curvatures of high strength aluminum alloy. The aim of this paper is to study the influence of element types on springback prediction of creep age forming of aluminum alloy integral panel. Firstly, the finite element models are built by 3D-solid elements and Shell elements separately. And then a set of creep aging constitutive equations of 7055 aluminum alloy are implemented into the commercial FE solver MSC.MARC through user defined subroutine. Finally, springback values predicted by 3D-solid elements model and Shell elements model respectively are compared under different height to width ratios. Some important conclusions were drawn. For the reinforcing panel with the height to width ratio is more than 5:1, shell elements should be used to get more accurate springback prediction result. If the height to width ratio is less than 5:1, solids elements should be used. Above conclusions provide theoretical basis for the study of CAF of the aluminum alloy integral panel by finite element simulation method.

Tied-arch bridges have being widely used in railway for their beautiful shape and rigidity. Current analysis software Midas civil is applied in the overall analysis of many bridges, including the bridge in the article. However, there is huge amount of concrete in the arch foot of the arch bridge, which means that this part cannot be accurately calculated with the model of skeletal structures. Based on the principal of finite element method, Midas FEA plays an important role in the detailed analysis of complicated structure. As a result, it is applied in the local stress analysis of this arch foot. Introduction and Finite Element Division The tied-arch bridge has a span of 120m, whose girder is a trough girder. The height of the channel section at the middle of the span is 2.5m and 3.0m at the support. The arch rib has a shape of dumbbell whose height is 3.0m. Arch foot is a structure of large amount of concrete, in which buried the arch rib with other reinforced steel bar. Longitudinal and lateral pre-stressed tendons also lie in the arch foot, which makes it the most important and complicated part of an arch bridge and can only be analyzed with solid element. In respect of the model in FEA, part of the collar beam right before the first suspender are taken out along with the similar part of arch rib for detailed analysis. Concrete is simulated with solid element and steel plate of the arch rib is simulated with shell element while the lateral tendon is simulated with steel bar element. As longitudinal tendons are continuous in the bridge, they are not simulated in the model.