Simulation of Thermoplastic Powder Cold Spraying

The work is devoted to the deposition of composite powder materials by cold spray method. As a spraying material, a thermoplastic compound «WAY» for marking the roadway was used. An asphalt concrete was used as a substrate. As a result of experimental studies, the dependence of the deposition efficiency on the stagnation temperature of the working air in the ejector nozzle was obtained. The ANSYS Fluent package was used for evaluative modeling of the cold spraying process. Gas flow patterns were obtained in the computational domain without particles and taking into account the interaction of the flow with particles. The trajectory of the particles was calculated for various spraying parameters

Fracture of Protective Structures from Heavy Reinforcing Cement During Interaction with High-velocity Impactor

In this work, the fracture of a reinforced concrete barrier made of heavy reinforced ce- ment is numerically simulated during normal interaction with a high-velocity titanium projectile. The projectile has the initial velocity 750 m/s. The problem of impact interaction is numerically solved by the finite element method in a three-dimensional formulation within a phenomenological framework of solid mechanics. Numerical modeling is carried out using an original EFES 2.0 software, which al- lows a straightforward parallelization of the numerical algorithm. Fracture of concrete is described by the Johnson-Holmquist model that includes the strain rate dependence of the compressive and tensile strengths of concrete. The computational algorithm takes into account the formation of discontinuities in the material and the fragmentation of bodies with the formation of new contact and free surfaces. The behavior of the projectile material is described by an elastoplastic medium. The limiting value of the plastic strain intensity is taken as a local fracture criterion for the projectile material. A detailed numerical analysis was performed to study the stress and strain dynamics of the reinforced concrete target and the effect of shock-wave processes on its fracture. The influence of reinforcement on the resistance of a heavy cement target to the penetration of a projectile has been investigated

Numerical Simulation of the Fused Deposition Modeling for the Manufacturing of Parts with both High Geometric Fidelity and Mechanical Quality

With increasing usage of additive manufacturing methods for mechanical parts the need for precise and reliable simulations of the manufacturing process increases as well. In this paper various com- putations suited for simulating the fused deposition modeling process are considered in two dimensions. In fused deposition modeling a molten polymer is laid down on a prescribed path before the cooling of the melt begins. The occuring flows are treated as multiphase flows. To model the deposition of the filament, methods of computational fluid dynamics are used in ANSYS-Fluent, namely the volume of fluid method (VOF). Different numerical experiments are simulated

Numerical Modelling of Compression Cure High-Filled Polimer Material

The article presents phenomenological constitutive relations for modeling the compression curing of a highly filled polymer medium, obtained in the framework of the mechanics of an almost incompressible viscoelastic solid using the modified Herrmann variational principle. The relations are based on the representation of the medium as a composition of a fluid and solidified material, taking into account the history of continuous nucleation and deformation of a new phase in the temperature range of phase transformations. During the manufacturing process, different mechanisms lead to process-induced deformations and stresses. These mechanisms depend on thermal expansion, shrinkage, nonlinear viscoelastic properties of the material, and variation in local temperatures. In critical cases, these residual stresses can lead to initial degradation and up to failure of the material. A stable numerical algorithm for the problem’s solution has been developed on the base of finite element method. Numerical investigation of the stress and deformation in system during the polymerization process has been carried out. The evolution of curing stresses in a singular zone of domain has been investigated

On the Parallel Kinematics of the FET Stretching Press in the Stretch Forming Operations in the Manufacture of Parts with Complex Spatial Geometry

The kinematics of a stretching press mechanism of a parallel structure are investigated. The kinematic dependences aimed at setting the spatial position of the working elements of a cross-stretching press of FET type, which allow positioning its jaws at any time during the technological operations, are obtained. The forward and inverse control kinematics problems of the jaw mechanism stretching press are solved

Thawing of Permafrost During the Operation of Wells of North-Mukerkamyl Oil and Gas Field

Thawing of ice-saturated rocks due to climate change or various technological impacts will be accompanied by subsidence of the earth’s surface and development of dangerous permafrost geological processes called thermokarst, leading to accidents, which may destruct the wells. Currently, the investment programs of the development of new northern oil and gas fields are restricted. In this regard, reducing the cost of developing the oil and gas fields is an urgent problem. For example, diminishing the area of well pads and maintaining efficiency in the northern oil and gas fields can significantly reduce the costs, in particular, during the design stage. A model of unsteady thermal fields propagation in frozen soil from new well construction for the North Mukerkamyl oil and gas field is developed, taking into account the construction features, the annulus, and the complex lithology of the soil surrounding the well. It is planned to take into account climatic and technological factors, in particular, an annual rest period of well operation, which held from several hours to two weeks. The paper discusses the computational features of the thermal fields calculating in frozen ground from wells and explores the influence of various parameters, which in the computations may lead to a significant increasing of thawing area in the well pads

Cyclic Behavior of Simple Models in Hypoplasticity and Plasticity with Nonlinear Kinematic Hardening

The paper gives insights into modeling and well-posedness analysis driven by cyclic behavior of particular rate-independent constitutive equations based on the framework of hypoplasticity and on the elastoplastic concept with nonlinear kinematic hardening. Compared to the classical concept of elastoplasticity, in hypoplasticity there is no need to decompose the deformation into elastic and plastic parts. The two different types of nonlinear approaches show some similarities in the structure of the constitutive relations, which are relevant for describing irreversible material properties. These models exhibit unlimited ratchetting under cyclic loading. In numerical simulation it will be demonstrated, how a shakedown behavior under cyclic loading can be achieved with a slightly enhanced simple hypoplastic equations proposed by Bauer

Construction of Nonsingular Stress Fields for Non-Euclidean Model in Planar Deformations

A material with a microstructure is considered. A material is described on the basis of a non-Euclidean model of a continuous medium. In equilibrium, the total stress field is represented as the sum of elastic and self-balanced stresses, the parameterization of which is given through the scalar curvature of the Ricci tensor. It is proposed to use the spectral biharmonic equation to calculate the scalar curvature. Using the example of a plane strain state of a material, it is shown that the amplitude coefficients of elastic and self-balanced fields can be chosen so that singularities of the same type compensate each other in the full stress field

Explicit-Implicit Schemes for Calculating the Dynamics of Layered Media with Nonlinear Conditions at Contact Boundaries

In this paper we consider the problem of dynamic loading of a deformable solid medium con- taining slip planes with nonlinear slip conditions on them. An explicit-implicit scheme was constructed for the numerical solution of the constitutive system of equations, which exactly reduces to correcting the stress tensor values after performing the elastic step. An implicit approximation of the constitutive relations containing a small parameter in the denominator of the nonlinear free term was used with the second order of the approximation. The correction procedure is applicable for those cases when the viscosity parameter of interlayers providing the sliding mode of the contact boundaries is not small. The solution of the problem of the seismic waves propagation in an inhomogeneous fractured geological massif in a two-dimensional case was obtained numerically

Molecular-dynamic Investigation of Silicon Carbide Fracture Under External Mechanical Loads

In this study, molecular dynamic simulations of quasi-static compression of silicon carbide nanorod, were performed. A longitudinal through defect in the form of a cylindrical channel was in- troduced into the central part of the nanorod. The influence of the cross sectional size of this internal channel on the strength properties was investigated