Search

The paper aims to numerically reflect mineral-asphalt mixture structure by a standard FEM software. Laboratory test results are presented due to bending tests of circular notched elements. The result scatter is relatively high. An attempt was made to form a random aggregate distribution in order to obtain various results corresponding to laboratory tests. The material structure calibration, its homogenization and finite element dimensioning are the issues decisive for the objective mixture description. The representative volume element (RVE) is investigated here, while it does not precisely reflect the material structure it displays relevant global material parameters. The simulation procedure applied here makes it possible to introduce the name of Monte Carlo simulation-based constitutive model. [ABSTRACT FROM AUTHOR]

One of the main problems in control is that the overwhelming number of physical quantities cannot be measured directly. Hence, there arise so-called inverse problems on the determination of physical quantities from the results of their manifestations. In the mechanics of a deformable solid there is a problem of obtaining material properties at all stages of deformation and especially at the overcritical stage. In this paper, we formulate and solve the inverse problem of finding the tensile diagram of a material element from the diagram of the dependence of the bending moment on the curvature of a rectangular beam under pure bending. [ABSTRACT FROM AUTHOR]

This paper deals with the development and approbation of a computational model of damage accumulation in a vertical steel tank at the non-uniform foundation subsidence. The object of research is structure behavior at the survivability stage, namely, the character and sequence of damage initiation and accumulation (elastic-plastic strain, bottom and wall buckling) in the tank structure. [ABSTRACT FROM AUTHOR]

A parallel computational environment for modeling the resin transfer molding manufacturing process has been developed at the U.S. Army Research Laboratory. This environment utilizes an implicit numerical method for modeling resin flow, a thermal model for analyzing convection and conduction, and a resin kinetics model to compute the heat generated and degree of resin cure during the curing process. The computing environment also includes a multiscale thermal residual stress model for computing the distortions and residual stresses in the composite component caused by the manufacturing process. All of these models have been tied together within a parallel object-oriented programming framework. This paper will discuss the computing environment in detail and its utility to real world applications. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

The machining of FRP composites has posed a serious challenge to industry and academia alike as far as the sub-surface damage is concerned caused by fiber-matrix debonding. Proper prediction of sub-surface damage is thus essential for different fiber orientations and fiber-matrix bonding. A Cohesive Zone Modeling (CZM) of the fiber-matrix debonding leading to interfacial separation is presented in this paper. The cohesive bonding strength existing between the fiber and matrix increases with increased separation, reaches a maximum value before causing permanent debonding when the cohesive strength between the interfaces vanishes. An effort is made to implement the Cohesive Zone Model (CZM) and to ascertain the extent of debonding below the trim plane at fiber failure. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Usually, in the finite element analysis of metal forming processes tools are assumed to be rigid. However, processes like flat rolling clearly show the necessity of taking into account elastic effects. The distribution of strip tension influences the shape of the rolling gap and vice versa. Considering all elastic effects in one finite element model of the rolling process leads to a very large model that is difficult to manage and suffers from severe numerical problems due to the multiple contact situations. Therefore, a concept is being developed that very efficiently meets the above demands. Elastic effects are computed separately and coupled with the simulation of the actual rolling process via data interchange. In this paper, experience with this iterative concept is shown concentrating on run-time, reliability of the results, and the convergence of the coupled elastic models and the conventional rolling process model. All algorithms have been implemented in the commercial nonlinear finite element code LARSTRAN/SHAPE. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

This paper presents an approach of direct die shape compensation implemented in a forging optimization system in order to achieve net-shape forging production for aeroengine blade components. This approach is based on the modification of die shape in relation to the dimensional errors of forged aerofoil shape due to the die and press deflections during forging and the thermal distortion upon cooling. In hot forging of a Ni-based alloy, the forging errors due to die elastic deformation, thermal distortion and press elasticity were quantified and further minimized by up to 95% of the original errors prior to the die shape compensation. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Over the past two decades, various finite element formulations and solution techniques for metal forming analysis have been developed. Most finite element codes for bulk metal forming used in the industry today are based on static implicit solution schemes wherein a non-linear system of equations is solved iteratively for each time increment. For simple 2D problems, static implicit analysis models are generally known to be more accurate and efficient than dynamic explicit analysis models. However, for complex 3D forming problems, the static implicit procedures encounter a number of inherent difficulties especially in incremental forming processes such as ring rolling in which several surface nodes repeatedly make contact with and separate from the dies. Static implicit finite element formulations require a very long computational time for the analysis of ring rolling. Several solution techniques have been developed to reduce the computational time of static implicit finite element analysis, namely the dual mesh technique, Arbitrary Lagrangian Eulerian (ALE) technique, etc. The dynamic explicit method on the other hand appears to be very effective in analyzing complex incremental forming problems. In this paper, a comparison of the analysis results obtained using dynamic explicit finite element method and static implicit method using a dual mesh approach is presented. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

The hot rolling of thin strip can result in several problems in hot rolling, for instance, the control of strip steering, strip shape and flatness and surface roughness etc. Therefore, the hot rolling of thin strip brings out a requirement of innovative technologies such as the extended control of shape and flatness, steering control and reduction of load by roll gap lubrication. In this paper, the authors focus on the analysis of thin strip snaking movement, as well as solve the related problems such as the shape and flatness due to a larger reduction applied when the strip is thinner. A finite element method was used to simulate this nonsymmetricity rolling considering the non-uniform reduction along the strip width. The calculated spread is compared with the measured values obtained from the rolling mill in laboratory and the friction effect is also discussed. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

A helical skew rolling process is a continuous hot forming process that produces near net-shape parts from tubing for hard turning or machining to the finished parts. The process can challenge forging processes in a number of applications by its high production rate and ability of forming intricate geometry. Because of its technical complexity, a number of tests have to be performed to improve and validate the design before a part can be put into production. To reduce the design lead-time and cost as well as improving the production quality, developing and implementing the finite element analysis procedures in design is an inevitable step. In literature, it has not been seen that the numerical simulation is applied to the skew rolling process so far. Simulation of the skew rolling is in a complicated three-dimensional metal large-deformation category, characterized by its severe mesh distortion and consistent contact and separation between the workpiece and dies. This paper describes the new development in finite element modeling of the skew rolling process and demonstrates the application of finite element modeling to aid the design of tooling and process parameters. By the use of the DEFORM-3D finite element program, the simulations can predict the geometry and some defects in parts reasonably well agreed with the actual products. However, one of the key issues is simulation time due to the nature of the nonlinear finite element method and the Lagrangian formulation adopted in the DEFORM-3D program. Solving nonlinear algebraic equations in each time step combined with iterative procedures is very computationally demanding and time consuming. Repeatedly reduction in time step size to satisfy the contact criterion prolongs the simulation significantly. Therefore, the improvement in the finite element theories and solving methods is necessary before the simulation can achieve reasonable timing. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

For many years, metal cutting simulations have been performed using two dimensional approximations of the actual process. Factors such as chip morphology, cutting force, temperature, and tool wear can all be predicted on the computer. However, two dimensional simulation is limited to processes which are orthogonal, or which can be closely approximated as orthogonal. Advances in finite element technology, coupled with continuing improvement in the availability of low cost, high performance computer hardware, have made the three dimensional simulation of a large variety of metal cutting processes practical. Specific improvements include efficient FEM solvers, and robust adaptive remeshing. As researchers continue to gain an improved understanding of wear, material representation, tool coatings, fracture, and other such phenomena, the machining simulation system also must adapt to incorporate these evolving models. To demonstrate the capabilities of the 3D simulation system, a variety of drilling, milling, and turning processes have been simulated and will be presented in this paper. Issues related to computation time and simulation accuracy will also be addressed. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

One of the most practical methods for simulation of steady state thermal processing is the Arbitrary Lagrangian-Eulerian method. Each calculation step is split into two phases. In the first phase, the Lagrangian phase, the element mesh remains attached to the material. The evolution of the state variables is monitored and the state at the end of the phase is calculated. In the second phase, the Eulerian phase, the mesh is, broadly speaking, restored to its original position with respect to a window attached to the moving heat source. The mesh is not restored to its exact original position, but some allowance is made perpendicular to the flow direction in order to capture movement of the free surfaces. In this paper a finite element model for Lagrangian simulation of thermo-mechanical processes with phase transformations is combined with a second order discontinuous Galerkin method for modeling of Eulerian advection. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

The aluminum can industry in the United States and Canada manufactures over 100 billion cans per year. Two-piece aluminum cans are commonly used to seal and deliver foodstuffs such as soft drinks, beer, pet food, and other perishable items. In order to ensure product safety and performance, the double seam between the can body and lid is a critical component of the package. Double-seaming is a method by which the flange of the can body and the curl of the end are folded over together such that the final joint is composed of five metal thicknesses. There are a number of design challenges involved with the art of double seaming, especially with the push to lightweight. Although the requirements vary by product, the typical beer package must be able to hold pressures in excess of 90psi. In addition, in production, double seaming is a high-speed operation with speeds as high as 3000 cans/minute on an 18-spindle seamer. For this high volume, low cost industry, understanding and optimizing the seaming process can advance the industry as well as help prevent various manufacturing problems that produce a poor seal between the two pieces of the can. To aid in understanding the mechanics of the can parts during double-seaming, a simulation procedure was developed and carried out on a 202 diameter beverage can and lid. Simulations were run with the explicit dynamics solver ABAQUS/Explicit using the continuum shell element technology available in the ABAQUS general purpose FEA program. The continuum shell is a shear-deformable shell element with the topology of an eight node brick. The element’s formulation allows continuously varying, solution-dependent shell thickness and through-thickness pinching stress. One important advantage of using the continuum shell as opposed to a traditional shell element is that true contact interactions at the top and bottom surfaces of the can body and lid can be accurately modeled. With a conventional shell element, contact is performed at the shell mid-surface or at an offset point representing where the top or bottom surface is expected to be. This paper discusses this new simulation technique and provides an example of its use. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Crystallographic homogenization procedure is implemented in the piezoelectric and elastic-crystalline plastic finite element (FE) code to assess its macro-continuum properties of piezoelectric ceramics and BCC and FCC sheet metals. Triple scale hierarchical structure consists of an atom cluster, a crystal aggregation and a macro- continuum. In this paper, we focus to discuss a triple scale numerical analysis for piezoelectric material, and apply to assess a macro-continuum material property. At first, we calculate material properties of Perovskite crystal of piezoelectric material, XYO3 (such as BaTiO3 and PbTiO3) by employing ab-initio molecular analysis code CASTEP. Next, measured results of SEM and EBSD observations of crystal orientation distributions, shapes and boundaries of a real material (BaTiO3) are employed to define an inhomogeneity of crystal aggregation, which corresponds to a unit cell of micro-structure, and satisfies the periodicity condition. This procedure is featured as a first scaling up from the molecular to the crystal aggregation. Finally, the conventional homogenization procedure is implemented in FE code to evaluate a macro-continuum property. This final procedure is featured as a second scaling up from the crystal aggregation (unit cell) to macro-continuum. This triple scale analysis is applied to design piezoelectric ceramic and finds an optimum crystal orientation distribution, in which a macroscopic piezoelectric constant d33 has a maximum value. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

In this paper a Voronoi Cell Finite Element (VCFEM) scheme is presented to model ductile damage in metal matrix composites (MMCs). Particle fracture and matrix cracking are used to model failure of the composite. Numerical examples for simple microstructures are used to validate the model. An example of an actual morphological description of a MMC is used illustrate the potential of the method. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

This paper summarizes the results of an experimental and analytical study conducted to investigate the effect of mixed-mode ratio on the cryogenic interlaminar fracture toughness of woven fabric glass/epoxy laminates. Interlaminar fracture tests were performed and a three-dimensional finite element analysis was carried out to obtain critical strain energy release rates. The cryogenic interlaminar fracture toughness increased upon the introduction of the mode II component. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]