Finite-element analysis of an overturned fold using a viscous-fluid model

In order to employ the classical Rayleigh-Rite and the popular finite element methods to model different structural regions so that each is used to its fullest advantage, a coupled Rayleigh-Rite and finite element formulation using the penalty function method is presented. The formulation is based on a constrained variational principle. Along the interface of two different regions, deformations obtained from the Rayleigh-Ritz method are set equal to deformations obtained from the finite element method. The potential energy of the Rayleigh-Rite and finite element regions with these deformation constraints is used to derive a coupled stiffness matrix. This coupled stiffness matrix contains stiffness contributions from each region and an interface stiffness contribution from the constraints. The derivation is given for one dimensional coupling of a beam and two dimensional coupling of an equivalent plate with membrane finite elements to model a wing-like structure with box beam and leadingltrailing edges. Displacements and stresses using the coupled analysis are compared with those of using a single finite element analysis. Results indicate that using the coupled RayleighRite and finite element analysis produces results with a level of accuracy approaching that of a finite element analysis, while providing enhanced modeling flexibility.

Use of partial least-squares analysis and fractionated X-ray computed tomography images in the investigation of density distribution of round tablets

This paper presents an efficient inverse analysis technique for the identification of an unknown boundary condition in a finite element method (FEM) on a small memory capacity machine such as a personal computer. The author has previously presented the FEM of inverse analysis introducing an inverse compliance matrix that uses an influence function into the stiffness matrix for the unknown boundary. Since the stiffness matrix of the FEM becomes singular, following two calculation processes are adopted: (1) a calculation process which obtains an approximate solution by decreasing the effect of the inverse compliance in the stiffness, and (2) an iterative calculation process computing a correct solution from the approximation using (1). First, a penalty function method is used to decrease the rank of a singular stiffness matrix in (1). Then, the number for computing LDU decomposed matrix becomes twice in comparison with fourth times in the previous paper. Next, an efficient calculation method is presented using an attack technique based on both accelerative moving lower and upper bounds in (2). Moreover, a zooming identification method is developed, owing to an improvement of node displacements on and near the edges. Therefore, this technique makes it possible to establish an efficient inverse analysis for the identification of the unknown boundary. Finally, the validity of the inverse analysis technique is confirmed from the numerical solution of a three-dimensional inverse finite element analysis model, as an example of an elastic structure with reinforced members under tension, carried out on a small memory capacity machine.

Performance and operating costs are the most important factors in internal combustion engines. It is one of the most commonly used methods to coat pistons with advanced technological ceramic materials in order to improve performance and fatigue life in internal combustion engines. In this study, changes in temperature and heat flux were investigated in various thickness coatings made on a 2500 cc turbo diesel engine piston. As bonding coat, NiCrAl was used in a thickness of 0.2 mm, while ZrO2 (zirconium dioxide) was used in thicknesses of 0.2-0.4-0.6 and 0.8 mm as thermal barrier coating material. The piston was modeled in PTC Creo parametric software and then transferred to ANSYS Workbench environment to create a mathematical model. Engineering calculations were also done using the finite element method. After the calculation, the temperatures at the depth of 5 mm from the combustion chamber upper surface, the binder layer upper surface, the thermal coating upper surface and the combustion chamber upper surface were compared. As a result, it was observed that the combustion chamber and the section at the depth of 5 mm from the combustion chamber had a temperature decrease of 13%.

Objective To explore the establishment of 3D thoracic model by finite element methods, and study the mechanical mechanism of minimally invasive surgery for correcting the chest wall deformity, and provide personalized surgery solution in the future. Methods According to admission and exclusion criteria, we selected 10 cases of pectus carinatum that received chest CT scan. The finite element model of pectus carinatum was established and analyzed by Mimics, ABAQUS, etc. The validity of finite element method for chest wall was verified by comparing the sternal displacement between the simulated values and actual values with the same force. Results The 3D finite element model of pectus carinatum was successfully established and analyzed. The stress distribution of the 10 cases in the posterior ribs was mainly in the 1-6 ribs on both sides, mostly concentrated in the 4th to 6th ribs, and the stress was symmetrical on both sides. Statistical analysis showed that the displacement value of the sternum was correlated, and the validity of the model was verified. Conclusion Mimics, ABAQUS and other finite element modeling and analysis software can effectively establish the thoracic 3D finite element model and mechanical analysis, which can help the further development of personalized minimally invasive surgery for correcting chest wall deformities. Key words: Pectus carinatum; Chest wall deformity; Finite element analysis

The damage behavior of soda-lime glass was studied due to a steel ball of 1mm and 2mm at oblique impact test. The thickness of glass specimen were 3mm and 5mm and oblique degrees of impact were 90,70 and 50. After the steel ball impact test, the crack patterns were investigated using a stereo-microscope. In addition, the finite element method was performed to analyze the stresses distribution and variation in the oblique impacted glass by steel ball. As a result of the impact test, the crack length of 90impacted glass was the largest and that of 50impacted glass was the smallest. In particular, as the impact velocity and diameter of the steel ball increased, the difference of crack length was prominent. The finite element analysis showed the maximum principle stresses distribution in contact area of glass specimen. The result of analysis was accorded with the crack growth behavior by the oblique impact test.

In order to study the temperature distribution of aluminum alloy thick plate during snake hot rolling, several coupled thermo-mechanical models using finite element method (FEM) were established. Effects of different factors on temperature distribution of the plate and the bending behavior due to temperature difference were analyzed. Temperature asymmetry coefficient was defined in this study. The results show that the temperature distribution of plate is asymmetrical and the temperature of the lower surface is higher than the upper surface during snake hot rolling, in which the maximum α can gd reach 58 °C/m. The asymmetric coefficient was increased with the increase of rolling velocity and speed ratio. Different ways of heat exchange play different roles in the temperature distribution. Friction heat and deformation heat play dominant role in hot rolling process and pass interval time and their weight influences were 47 and 69 %, respectively. The bending curvature is increased with the increase of temperature difference and pass reduction and decreased dramatically with the increase of initial thickness. The FEM results agree well with experimental results.

Real-world groundwater modeling deals with heterogeneous and anisotropic aquifer systems. Numerical models, particularly the finite difference and finite element methods, are extensively used for modeling such a complex aquifer system. The finite difference method is an age-old straightforward approach, whereas the finite element method is more idealistic, relatively new, and has emerged as a popular approach. The unique advantages with the finite element method are (i) an irregular-shaped domain can be discretized into elements with a matching boundary, (ii) a node can be connected with the neighboring nodes in any direction. Thus, the finite element analysis allows water/solute to flow more freely toward the surrounding nodes along nodal links. On the other hand, the mathematical formulation of the finite element technique follows a set of rules step by step. Conventionally, this idealistic approach uses shape functions and integration techniques to develop element matrices, which, in turn, are assembled to form the global matrix. This conventional global matrix was found to be inconsistent with the basic partial differential equation representing the mass balance in a nodal domain as a control volume. As a result, the matrix solution, particularly for nonlinear problems (e.g., vadose zone flow, density dependent flow, and so forth) becomes unstable and computationally burdensome. To overcome the limitations of the conventional finite element method for real-world groundwater modeling, a new approach, called the direct-formulation finite element (DFFE) method, has been developed. In this approach, a two-dimensional model domain is discretized into triangular elements. Element matrices are formed directly based on flow principles and material properties of elements without using shape functions and integration process. The DFFE method is robust. The global matrix is consistent, and the solution is stable and efficient. The results obtained from this approach were found in a good agreement with that obtained from analytical and other widely used models.

This paper focus on the treating the multi freedom constraints in geometrically nonlinear buckling and post buckling analysis of truss structure using finite element method. The solution of geometrically nonlinear buckling problem of truss structure having multi freedom constraints is required to incorporate the boundary constraints to the nonlinear master stiffness equation. This work proposes approach to impose the multi freedom constraints and construct stiffness equation for solving the nonlinear buckling problems of truss structures using Penalty function method. The nonlinear balanced equations for buckling analysis of truss structures are developed by minimization of the augmented potential energy function of system by incorporating the multi freedom constraints and changing the constrained problem to the non-constrained problem using Penalty objective function. Using the arc length method, this research proposes the incremental-iterative algorithm for solving the nonlinear balanced equations. Based on proposed algorithm, the calculation program for determining equilibrium paths is written. The numerical test results show the efficiency of proposed method in analysing buckling and post buckling behaviour of truss structures.

In this paper, we propose an effective finite element method (FEM) on the basis of domain decomposition method. In the domain decomposition method, the domain of structure is decomposed into subdomains, which are connected each other with an independent interface using a penalty function method. Using this FEM, the analysis of the whole structure can be carried out by analyzing the individual subdomain. As a numerical example, the stress analysis of an aircraft structural panel repaired with bonded composite patches is made, and the efficiency and the accuracy of the FEM are verified. The FEM is also used to carry out several parametric studies to examine the effects of patch shape and size on the stress fields in the repaired structural panel and composite patches. Finally, we determine the optimum shape and size of a composite patch to endure the maximum tensile applied stress by a mathematical programming.

This paper concerns with the finite element analysis of reactor internals with structural faults. For investigating the influence of hold-down spring faults on dynamic characteristics of CSB (core support barrel), reactor internals of Ulchin-1 nuclear power plant are modeled using finite element method and simulated with artificial defects on the hold-down springs. To prove the validity of the finite element models, the calculated natural frequencies of CSB in normal state are compared with those from the measurement results, which shows good agreement. According to results of finite element analysis, CSB beam mode natural frequency decreases by 4.5% in the case of 10% partial relaxation of hold-down springs, and decreases by 18.4% in the case of 20%. The range of shell mode natural frequency change is within 5.3%.

Because of the huge lifting weight and complex structure of large-tonnage gantry crane and in order to effectively design and review it, this paper aims to carry out a research on its structural performance based on the method of theoretical calculation and finite element analysis. During the early period of design, the method of theoretical calculations is adopted, and after specific design it comes the finite element analysis, so as to get the results of analysis under a variety of operating conditions, which illustrates that the structural design and review of large-tonnage gantry crane based on theoretical calculations and finite element are feasible, and also verifies that the method of finite element is an effective way to find a real dangerous cross-section, thus providing the basis for the design and manufacture of the crane structure.

Recently, materials used to construct house or building wall are considered not only in the physical material behaviour but also energy conscious and economic factor. The possibility of utilization of the sludge waste obtained from the natural rubber manufacturing process as a raw material for producing composite brick was investigated. It has been widely known that the finite element method (FEM) is a tool used for finding accurate solutions of the heat transfer equation of materials including the composite bricks. In this work, study of the heat transfer of a composite brick containing rubber sludge waste (RSW) was showed and compared to results of finite element analysis (FEA) simulation. To determine the effect of rubber sludge waste to the heat transfer behaviour of composite brick with different volume fractions are varied by 10, 20, 30, 40 and 50%. It appeared that a FEA prediction showed good correspondence with the experimental results.

A new symmetric contact element stiffness matrix for frictional contact problems

The study presented in this work deals with analytical methods for an axisymmetric problem of an elastic layer partially reposing on a rigid circular base, and is indented along the upper surface with a rigid punch. The contact between the medium and the base is smooth. This boundary value problem is transformed into a system of dual integral equations. In contrast to the classical approach consisting in resolving the corresponding Fredholm equation of the second kind, the latter equations are obtained from an infinite algebraic system of simultaneous equations, where the particular case [Formula: see text] is verified. The results of this system are also obtained numerically. The normal displacement, normal stress, and the stress singularity factor are given analytically and shown graphically with discussion. By comparison with those predicted by the finite element method, the accuracy of the numerical method is approved.