Papers by Keyword: Finite Element Method (FEM)

Abstract: Tire mobility with low compaction for off-road tires is considered necessary. In this regard, it is imperative to investigate the tire/ground interaction and finite element method has the capability to perform the fundamental analyses and simulations to present the results accordingly. A two-dimensional (2D) low-fidelity model pertaining to an off-road tire for a relatively light autonomous vehicle rolling on ground with consideration of different values of slipping percentages was simulated using a finite element (FE) software ABAQUS. A comprehensive parametric study was conducted to understand the essential effects on the tire/ground interaction specifically, the vertical stress distribution in the ground right beneath the tire after travelling a specific amount of time. The effect of several parameters including the autonomous vehicle weight, friction coefficient between the tire and the ground, Young’s modulus of tire as well as various types of ground such as natural soil, sand and soft soil (clay) were scrutinized and are discussed in detail. Keywords: Tire/ground interaction; Tire slipping; Soil compaction; Vertical stress distribution; Finite element method (FEM).

Abstract: In the present study the notched fatigue behavior of two multi-phase medium entropy alloys (MEAs) AlCrFe₂Ni₂ and AlCrFe₂Ni₂Mo_0.1 was characterized by three-point-bending (3-PB), along with a super-duplex steel 1.4517 as a reference material. An analytical approach for characterizing the fatigue notch factor (k_f), based on grain size analysis in combination with finite element modelling (FEM) was used, relating the theory of critical distances (TCD) to the grain size of the material. To validate the approach, for the reference steel, the fatigue notch factor was also determined experimentally by comparing the fatigue behavior of notched and smooth specimens, resulting in an experimentally determined fatigue notch factor (k_f) ~ 1.07. The numerically and analytically estimated notch effects increase with decreasing average grain size and vary between ~ 1.07 for the coarse-grained reference material – in very good agreement with the experimental results – and ~ 1.35 for the much more fine-grained AlCrFe₂Ni₂Mo_0.1 medium entropy alloy. Note that these values are significantly lower than the stress concentration factor (k_t) ~ 1.58, associated with the notch geometry. Fatigue endurance limits were measured at a fatigue stress ratio R ~ 0.1 (unidirectional stress), but were converted to fatigue amplitudes at R = -1 (σ_{a, R-1}, fully reversed stress), to be able to make due comparisons with available literature data, by using the elliptical relationship. The resulting fatigue endurance limit amplitudes for specimens surviving at least 2E+06 cycles for a minimum of three tested samples and including notch effects are σ_{a, R-1} ~ 508 MPa for the AlCrFe₂Ni₂ alloy, σ_{a, R-1} ~ 540 MPa for the AlCrFe₂Ni₂Mo_0.1 alloy modification and σ_{a, R-1} ~ 400 MPa for the reference super-duplex steel, putting the analyzed MEAs into a very competitive position compared to Cobalt containing multi-phase high or medium entropy alloys as well as commercially available steels.

Abstract: Today environmental aspects are of great importance in the sustainability of the planet, in this aspect anti-corrosive treatments facilitate the durability of metal structures. Among the most widely used anticorrosive metals is Zinc and its alloys. In the deep galvanizing process of large steel structures, tanks containing Zinc in a molten state at a temperature of 460 °C are necessary. Then, to protect elements that are too large or that need to be treated "in situ", metallization is used, which consists of projecting molten zinc wire on the metal surface that has previously been subjected to a process sandblasting (mechanical abrasion). The two main methods of metalizing are electric arc and flame. In the present work an industrial wiredrawing draft has been studied, determining the drawing force and the power required in each stage. For this purpose, linear strain hardening model vs non-linear strain hardening model that takes strain rate hardening into account has been proposed for its implementation in the analytical model of the process and finite element model (FEM) has been developed too. The use of Hall Petch equation has been allowed to get a prediction of the evolution of the grain size during the wiredrawing sequence.

Abstract: In the present work, a finite element model of the first stage, plunge, of friction stir welding is considered. The welded parts are flat aluminum 1050 plates. The arbitrary Lagrangian-Eulerian formulation implemented in ABAQUS/Explicit is used. The material model of the welded parts is the Johnson-Cook law, and Coulomb’s law describes the friction between the tool and the weldment. Temperature field during the process is obtained, and the influence of the parameters concerning the algorithmic implementation of the finite element method is established. The simulation results are compared with experimental results obtained for this purpose.

Abstract: Stress concentration is a complex problem in material mechanics, especially in Aeronautics and Astronautics applications, the concentrated stress will do great harm to the safe operation of the launch vehicle. Therefore, it is a common practice to simulate and verify the structural design or manufacturing process in the use of materials and dynamics. This paper first introduces the problem of stress concentration in aerospace, demonstrates the necessity and importance of studying this problem, at the same time, puts forward a stress concentration solution based on finite element method, which simplifies the geometric model by using symmetrical characte-ristics, so as to reduce the batch data of analysis. Compared with the conventional analysis using Patran and NASTRAN, its geometric model has a higher degree of discretization, The superiority and reliability of this method are verified by two examples. The results show that this finite element method is more accurate and effective in dealing with stress concentration problems, especially complex geometric models, and has high value for engineering practice.

Abstract: In this paper, two numerical models of friction stir welding of two aluminum plates are considered. The coupled mechanical-temperature problem is solved with explicit integration over the time. The two models are based on the finite elements method (FEM) and have different complexity and number of participating parameters. The aim of the development is to highlight the weaknesses and strengths of the models of different complexity. The first model is simpler and it is based on the free penetration of the tool into the parts. The second model is based on the arbitrary Lagrange-Euler method and take in to the account the instrument penetration that allows to take into account the movement of the material in the process area. Convective and radiative heat transfers are accounted in the two models. The results for the temperature, stress and strain in the welded joint are studied and compared. The calculation time is given for each model. A parametric analysis was performed for the influence of the rotational speed of the pin, welding velocity and the pressing force. The influence of the temperature dependent physical properties of the welded plates is determined and compared for the both finite element models.

Abstract: This paper presents a finite element model of submerged arc welding. The modeling of the filler material has been performed by applying the technique for deactivation and subsequent activation of the finite elements involved in the welding seams. The nonlinear material properties are taken into account. The description of the peaks in the specific heat capacity in the phase changes has been done by introducing latent heat. The welding arc is modeled as a heat source with a constant heat flux density. Experiments have been conducted to validate and verify the numerical model. The influence of the ratio between surface and volume of the set heat sources has been studied. Tack welds have been taken into account. Data on the relationship between the accuracy of the obtained results and the number of passages has been presented.

Abstract: Joining and local forming processes for fibre-reinforced thermoplastics (FRTP) like hole-forming or variations of the clinching process require an in-depth understanding of the process induced effects on meso-scale. For numerical modelling with a geometrical description of a woven fabric, adequate material models for a representative unit cell are identified. Model calibration is achieved employing a mesoscopic finite-element-approach using the embedded element method based on tensile tests of the consolidated organo-sheets and a phenomenological evaluation of photomicrographs. The model takes temperature dependent stiffness and fibre tension failure into account.

Abstract: Corrosion is a major cause for the failure of metallic components in various branches of the industry. Depending on the corrosion severity, the time until failure of the component varies. On the contrary, a study has shown that certain riveted metal joints, exposed to a short period of mechanical loading and corrosion, have greater fatigue limits. This study gives rise to the question how different corrosion exposure times affect joint metallic components. In the present research, a theoretical approach is developed in order to evaluate the influence of galvanic corrosion on joint integrity of clinched metal joints. At first, the framework for modeling galvanic corrosion is introduced. Furthermore, a simulative investigation of a clinching point is carried out based on the assumption that corrosion leads to a reduction of the contact area which leads to a local increase in contact pressure. For this purpose, the stiffness values of individual elements in a finite element model are reduced locally in the contact area of the undercut and the contact stress along a path is evaluated. Summarizing, a modeling approach is introduced to investigate corrosion effects on load-bearing behavior of clinched joints.

Abstract: The mechanical properties of joined structures are determined considerably by the chosen joining technology. With the aim of providing a method that enables a faster and more profound decision-making in the spatial distribution of joining points during product development, a new method for the load path analysis of joining points is presented. For an exemplary car body, the load type in the joining elements, i.e. pure tensile, shear and combined tensile-shear loads, is determined using finite element analysis (FEA). Based on the evaluated loads, the resulting load paths in selected joining points are analyzed using a 2D FE-model of a clinching point. State of the art methods for load path analysis are dependent on the selected coordinate system or the existing stress state. Thus, a general statement about the load transmission path is not possible at this time. Here, a novel method for the analysis of load paths is used, which is independent of the alignment of the analyzed geometry. The basic assumption of the new load path analysis method was confirmed by using a simple specimen with a square hole in different orientations. The results presented here show a possibility to display the load transmission path invariantly. In further steps, the method will be extended for 3D analysis and the investigation of more complex assemblies. The primary goal of this methodical approach is an even load distribution over the joining elements and the component. This will provide a basis for future design approaches aimed at reducing the number of joining elements in joined structures.