Wyniki wyszukiwania - BazTech

1

Investigations on an influence of the material properties on vibrations of active rocker-bogie suspension

Sokół Krzysztof, Pierzgalski Maciej

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2022

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Vol. 70, nr 1

art. no. e138239

EN

Unmanned vehicles are often used in everyday life, mostly by rescue teams or scientists exploring new terrains. In those constructions, the suspension has constant dimensions, which leads to many disadvantages and limits the application area. The solution to these problems can be creating a six-wheeled mobile platform that can dynamically change the wheelbase in relation to the area of action or terrain inclination angle. The active change in location of the center of gravity gives a possibility to access sloppy obstacles not available with classical suspensions. The main scope of this study is to investigate the influence of material properties on vibration frequency at different lengths of suspension members. The obtained results will allow finding the optimum material for producing a prototype unit.

2

Application of computational mechanics approaches for increasing of tribosystem operational parameters by using plasma hardening method

Kopylov Viacheslav, Kuzin Oleg, Kuzin Nickolai

Journal of Applied Mathematics and Computational Mechanics

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2021

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Vol. 20, nr 1

61--70

EN

On the basis of the mathematical model of the continual description of functionalgradient metal systems, taking into account their structure, a computational computer scheme has been developed that makes it possible to assess the stress-strain state of local volumes of parts taking into account their spatial inhomogeneity. With the use of modern software components of computational mechanics - FEniCS finite element analysis package and its implementation in Python, the optimal structural characteristics of wheelsets of railway locomotive tires after plasma treatment have been established. It is shown that, depending on the value of the load, hardening of products must be carried out to a depth of 4.5 mm; with a further increase in thickness, the parameters of operational strength do not change.

3

Application of numerical methods for solving the non-Fourier equations. A review of our own and collaborators’ works

Majchrzak E., Mochnacki B.

Journal of Applied Mathematics and Computational Mechanics

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2018

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Vol. 17, nr 2

43--50

EN

Thermal processes occuring in the solid bodies are, as a rule, described by the well-known Fourier equation (or the system of these equations) supplemented by the appropriate boundary and initial conditions. Such a mathematical model is sufficiently exact to describe the heat transfer processes in the macro scale for the typical materials. It turned out that the energy equation based on the Fourier law has the limitations and it should not be used in the case of the microscale heat transfer and also in the case of materials with a special inner structure (e.g. biological tissue). The better approximation of the real thermal processes assure the modifications of the energy equation, in particular the models in which the so-called lag times are introduced. The article presented is devoted to the numerical aspects of solving these types of equations (in the scope of the microscale heat transfer). The results published by the other authors can be found in the references posted in the works cited below.

4

Modeling of mechanical phenomena in the platinum-chromium coronary stents

Idziak-Jabłońska A., Karczewska K., Kuberska O.

Journal of Applied Mathematics and Computational Mechanics

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2017

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Vol. 16, nr 4

29--36

EN

This study discusses the geometrical model of a coronary stent with known design and strength analysis using the finite element method. The coronary stent model was made of platinum and chromium alloy. Static analysis based on compression of the coronary stent was also performed. The aim of the analysis was to examine the strength of the stent structure. The study analyzed stresses, plastic strains and displacements after applying a constant load to the stent walls. The mechanical phenomena such as percentage degree of shortening (foreshortening), relative narrowing and area of stent covering were also determined.

5

Errors of stress numerical integration for cross-sections with straight and curved boundaries

Matuszak A.

Computer Assisted Methods in Engineering and Science

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2015

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Vol. 22, no. 2

153--176

EN

Internal forces are integrals of stress in a section area. Integrating the stress for an arbitrary cross-section shape and for the nonlinear stress-strain law σ(ε) is tedious and the use of the boundary integral approach can simplify computations. Numerical integration when applied to the computations of such integrals introduces errors in many cases. Errors of numerical integration depend on the adopted integration scheme, the type of σ(ε) and the shape of the cross-section boundary. In the case of adaptive numerical integration what is very important are the properties of the sequence of errors produced by a given integration scheme in the increasing order of the numerical quadrature or the increasing number of subdivisions. This paper analyses errors caused by different integration schemes for the typical σ(ε) either for a straight or curved boundary. Special attention is paid to the properties of the error sequence in each case. The outcome of this paper is important from the viewpoint of the reliability and robustness of the software developed for nonlinear simulations of bar structures.

6

Pyramidal ceramic armor ability to defeat projectile threat by changing its trajectory

Stanislawek S., Morka A., Niezgoda T.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2015

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Vol. 63, nr 4

843--849

EN

This paper presents a numerical study of a multilayer composite panel impacted by an AP (Armor Piercing) 14.5×114 mm B32 projectile. The composite consists of alternating layers of hard ceramic and a ductile aluminum alloy. While the alloy layer consists of typical plate, ceramics confront projectiles in the form of ceramic pyramids. The studied models are compared with a reference structure, which is a standard double layer panel. The problem has been solved with the usage of modeling and simulation methods as well as a finite elements method implemented in LS-DYNA software. Space discretization for each option was built with three dimensional elements ensuring satisfying accuracy of the calculations. For material behavior simulation, specific models including the influence of the strain rate and temperature changes were considered. A steel projectile and aluminum plate material were described by the Johnson-Cook model and a ceramic target by the Johnson-Holmquist model. The obtained results indicate that examined structures can be utilized as a lightweight ballistic armor in certain conditions. However, panels consisting of sets of ceramic prisms are a little easier to penetrate. Despite this fact, a ceramic layer is much less susceptible to overall destruction, making it more applicable for the armor usage. What is most important in this study is that significant projectile trajectory deviation is detected, depending on the impact point. Such an effect may be utilized in solutions, where a target is situated relatively far from an armor.

7

The identification of degenerated systems in the impact energy dissipation process

Bocian M., Jamroziak K.

Journal of Achievements in Materials and Manufacturing Engineering

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2013

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Vol. 57, nr 1

23--30

EN

Purpose: The article presents an analysis of impact energy dissipation process with selected non-classical dynamic models. Design/methodology/approach: Identification of impact energy dissipation phenomena in mechanical systems with a layered structure (eg. composite ballistic shields) is quite a challenge, because on the one hand it is sought to the model, whose parameters are as much as possible responsible for the energy dissipation, on the other hand, the number of parameters should be optimized. Searched model should be reduced to a simple description of the whole phenomenon and completely imitate entire mechanical system. Description of the impact energy dissipation was modeled with selected degenerated systems in this case. Models were subjected to hammer extortion the specified impulse of force. The mathematical description of pulsed extortion was carried out by using the energy and balance equation of power. Verification of mathematical identification equations for selected model parameters was performed by computer simulation technique. Findings: This is original analytical method, which uses the degenerated systems in various configurations. It involves the use of specially derived identification equations, which are described by the decrease of potential energy of the system during the vibrations induced by a single impulse load. Research limitations/implications: Method of identification requires the use of appropriate input function. Input function could be a periodic type or a type of step function. Practical implications: Estimation of the energy consumption objects in terms of method of identifying the parameters of the model. Originality/value: Presented work includes the identification of piercing the ballistic shield, and it is a part of work on the implementation of the degenerated models to describe these phenomena.

8

Thermo-viscoelastic-plastic deformation of huge products in thermal process

Cho C., Kwahk S.-Y., Kim W.-J., Choi J.-K.

Journal of Achievements in Materials and Manufacturing Engineering

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2006

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Vol. 17, nr 1-2

233--236

EN

Purpose: This paper is to numerically predict thermo-elastic-plastic deformation during thermal process. Decreasing material strength in thermal processes causes severer deformation at elevated temperature even under self-weight of huge and heavy products. Design/methodology/approach: A hybrid method is proposed and applied, in this study, to analyse thermomechanically coupled problems such as heat treatment. The finite difference method (FDM) and the finite element method (FEM) are prefered. In general, FDM is favored for heat/fluid flow, FEM for structure analysis. Findings: The solution of heat treatment processing is conducted by using the proposed hybrid method that we developed the numerical program for calculating the deflection induced due to its own weight and the creep. The code is verified by the analytic solution of a simple plate model. Research limitations/implications: There have been developed peculiar computational methods fitted in each single field problem. Recent problems necessitate total solutions not only in a major relating science but also in adjacent engineering parts. To keep the efficiency of respective methods even in coupled field problems, it is very desirable to combine advantages of respective methods as hybrid technique. This study suggests and applies a hybrid method of FEM and FDM for simulating heat treatments. Further improvement to convert different types of computational models to each other is one of important issues. Practical implications: In the past half century, there have been developed numerous computational techniques in various fields in separate ways. Hybrid method of combining existing computational techniques rather than further extending the techniques may have significant implication whenever practical problems necessitate total solutions coupled over multiple physics. Originality/value: The concept of a hybrid technique between FEM and FDM was implemented in this study and applied to simulate a heat treatment case as a multiphysical problem.

9

Shell element simulation of the push method of tube bending

Zhang Y., Redekop D.

Journal of Achievements in Materials and Manufacturing Engineering

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2006

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Vol. 17, nr 1-2

301--304

EN

Purpose: In this paper the new push bending process for the forming of curved tubes is simulated using the finite element method. It is demonstrated that the results obtained using shell elements compare closely with those obtained earlier using three-dimensional elements. A parametric study is carried out which gives on indication of the effect of changes in geometry and material properties on results. Design/methodology/approach: A non-linear finite element analysis is carried out using the program LS-DYNA. A bilinear elastic plastic material is assumed, and both aluminum and steel are modelled. Findings: It is found that the radius of the bend is significant with respect to potential wrinkling. The inner pressure can be increased to suppress possible wrinkling. Lubrication is shown to be significant with regard to final results for wall thickness. Research limitations/implications: The present work is restricted to quasi-static behavior, and thermal effects are not considered. Practical implications: Some limitation on thickness variation in the finished product is possible through choice of lubricant. Originality/value: This paper gives original simulated results for tube push bending relating to new geometries and different materials.

10

Optimization of the blank holder force in cup drawing

Gharib H., Wifi A. S., Younan M., Nassef A.

Journal of Achievements in Materials and Manufacturing Engineering

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2006

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Vol. 18, nr 1-2

291--294

EN

Purpose: Develop an optimization strategy for the cup drawing process in order to produce a defect free deep drawn cup. Design/methodology/approach: An optimization strategy for the blank holder force (BHF) scheme is proposed which searches for the BHF scheme that minimizes the maximum punch force and avoids process limits. This strategy is applied to the linearly varying BHF scheme and compared to the constant BHF. Findings: The optimized linear BHF scheme resulted in an improved cup forming when compared to that produced by the constant BHF scheme. The BHF scheme is optimized for different cases of drawing ratios and die coefficients of friction in order to analyze the nature of the optimum linear BHF scheme. It was found that the slope of the linear BHF scheme increases with the increase in the drawing ratio in a linear manner. Also, the intercept of the function showed a nearly linear variation with the drawing ratio. A general equation is deduced for the optimum blank holder force at any drawing ratio for the cup under study. Research limitations/implications: The proposed optimization strategy can be applied to BHF schemes other than the linear one, and with different objectives. In this scheme, the objective has been the minimization of the maximum punch load. Other objectives like minimum punch work may be implemented. Practical implications: The proposed optimization strategy can be applied to any deep drawn part if an analytical or numerical model is available for this part. Originality/value: The research presented in this paper offers a new optimization strategy which can be useful in controlling the process parameters to produce a defect free deep drawn part using optimum process conditions.

11

Comparison of experimental and simulation results of 2D-draw-bend springback

Da Sisva Botelho T., Bayraktar E., Inglebert G.

Journal of Achievements in Materials and Manufacturing Engineering

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2006

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Vol. 18, nr 1-2

275--278

EN

Purpose: This paper presents the results of experimental, analytical and numerical studies of draw-bend springback on the response of steel blank strips. Design/methodology/approach: Springback, the elastically-driven change of shape of a part after forming, has been simulated with 2-D plane strain finite elements model (ABAQUS). Springback simulations compared with experimental test results under some test conditions and also sidewall curls were further discussed in this paper. Findings: The results validate the finite element approach as a trustworthy tool for predicting the springback parameters for a given set of stamping conditions and material properties. Research limitations/implications: This model is a simple and an efficient way to take apart the responsibilities of the steel maker for the selection of steel to be used and sheet stamping designer for the selection of the forming conditions to work in a safety zone in order to increase the reliability of the stamped structures. Originality/value: Experimental and finite element analyses have been conducted on blank strips of Hadfield steel (high strength steel) and Mild steel with similar operational conditions.

12

An analytical incremental model for the analysis of the cup drawing

Gharib H., Wifi A. S., Younan M., Nassef A.

Journal of Achievements in Materials and Manufacturing Engineering

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2006

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Vol. 17, nr 1-2

245--248

EN

Purpose: of this paper Develop an analytical model for the cup drawing process to solve for the induced stresses and strains over the deforming sheet at any stage of deformation until a full cup is formed. Design/methodology/approach: An analytical model is developed for the cup drawing process by determining the variation of stresses and strains over the deforming sheet. The model uses finite difference approach and numerical procedures to solve for equilibrium, continuity, and plasticity equations in an incremental fashion. Findings: The developed analytical model results showed good correlation with experimental ones from the literature. Also, the analytical model was found to be useful in conducting parametric studies in order to determine how the different process parameters can affect the deforming cup. Research limitations/implications: This paper includes the development of an analytical model to analyze the deep drawing of axisymmetric cups. This model is then used as the solution engine for the optimization of the blank holder force for such cups avoiding failure by wrinkling or tearing. This model also gives an insight of the modes of deformation in the deep drawing process. Practical implications: This paper is part of a procedure that leads to the optimization of the blank holder loading scheme. The full procedure as presented in the two parts of the work may be applied in industry to minimize the maximum punch load or the work done during deep drawing process by modifying the blank holder force and at the same time avoid failures by wrinkling or tearing. Originality/value: Developing a predictive/corrective technique for solving the unknown boundaries of the deforming sheet.