Papers by Keyword: FE Modeling

Abstract: Aluminum alloy sheets are widely considered for manufacturing lightweight thin-walled structural components in the automotive and aerospace industries. However, the poor formability of the material at room temperature is still a technical challenge. Warm forming evolved as a promising technology where the sheet metal is deformed at elevated temperatures below the recrystallization temperature. Numerical modeling is vital in the modern scenario to better understand formability and to improve the designing of tooling for complex sheet components during warm forming. Hence, it is imperative to understand the accuracy of material models on formability predictions at elevated temperatures. This work presents the effect of three yield criteria, namely, von Mises, Hill-48, and Barlat-89, on the formability predictions of AA6082-O sheet at elevated temperature, say, 200 °C. Analytical necking-based Marciniak-Kuczynski forming limit diagrams (MK-FLD) at the elevated temperature were predicted by incorporating these yield models. The accuracy of predicted MK-FLDs was validated with experimental data. Furthermore, finite element (FE) modeling of limiting dome height (LDH) tests was performed using sample sizes that developed deformation modes towards biaxial, plane strain, and uniaxial modes. The effect of different yield models on the forming behavior was studied in terms of part depths and major surface strain distributions. The compatibility of yield criteria on accuracy in prediction was assessed by overlapping with the experimental data. It was demonstrated that Barlat-89 was best suited compared to Hill48 and von Mises yield models.

Abstract: Steel structures are commonly used in seismic regions of the world because of its strength and ductility. However, these structures are still prone to damage during an earthquake. With this risk of seismic damage, the strengthening of steel structures is a major concern in order to resist the dynamic loads resulted from earthquakes. This report investigates the potential for the use of Carbon Fibre Reinforced Polymer (CFRP) to strengthen the rigid steel frame under a real earthquake load. This research will be undertaken using Strand7, a finite element (FE) analysis software. To validate the accuracy of this research, the finite analysis results have been compared to the available experimental study by the Authors. First, both FE models of a five-story bare steel frame and CFRP strengthened steel frame has been developed. Then the predicted numerical results of bare steel frame and CFRP strengthened steel frame under earthquake excitation are compared. The results indicated an increase in the seismic performance of the steel structure due to the strengthened with CFRP. The CFRP strengthened steel frame showed 15% less tip deflection compared to bare steel frame. Further analysis on the strengthening capabilities of higher thickness CFRP was performed to assess the effect of the thickness of CFRP and the higher thickness CFRP showed better seismic performance compare to normal thickness CFRP by reducing 34.38% of tip deflection.

Abstract: In this article we perform comparative analysis of the criteria of fracture during blade machining simulation, characterized by high intensity of the strain rate (about 10^-6 s^-1). For each 3D virtual experiment a milling processing model has been developed in DEFORM software package. The character of chip segmentation during the simulation was determined the accepted failure criterion. The adequacy of the model was evaluated by full-scale experiment based on geometry of real chips.

Abstract: Uncertainty in the properties of semi-finished parts can cause fluctuations in the product properties, especially if they have a strong effect on the process and cannot be compensated by process adjustments. Incremental forming processes have the potential to react to changing conditions by adapting the tool movement during the process. This paper analyzes the feasibility of controlling material flow in an orbital forming process in order to selectively fill those geometric elements which were specified with narrow tolerances by the designer. The effect of different process parameters on the mushroom effect and the degree of mold filling are analyzed by FEM simulations and experiments. In order to realize online monitoring and control, an estimation model is introduced, which maps signals from sensors and the process control to the geometric target values.

Abstract: Bone cutting is a well know procedure in orthopedics. Large cutting force causes overstressing of the bone which may result in trauma. Control penetration of the cutting tool into bone tissue is important to avoid unnecessary damage to the bone tissue. The purpose of this study was to measure and predict cutting force using experiments and Finite Element (FE) analysis when a plane cutter passes over the bone surface in the presence of irrigation. The effect of cutting speed, tool rake angle, depth of cut and width of the cutting face on the cutting force was found. The force was found to decrease with increase in rake angle and significantly rise with increase in depth of cut and width of cutting face. The cutting force was found unaffected by the range of cutting speed used in experiment as well as in simulations. The results obtained from this study strongly recommend the use of irrigation to minimize plane cutting force or force arising from similar cutting action for safe and efficient surgical incision in bone.

Abstract: Ring Rolling is a complex hot forming process where different rolls are involved in the production of seamless rings characterized by extreme dimensions (i.e. external diameter higher more than 1m). Because each roll can be independently controlled from the other ones different speed laws must be set; usually, in the industrial environment, a milling curve is introduced to monitor the shape of the workpiece during the deformation in order to ensure a correct ring production. In former works the authors focused their attention on the influence of different milling curves for an industrial case and the results underlined that a ring produced with a good quality and lower loads and energy could be obtained imposing a linearly descending trend to the Idle roll speed law. However different approaches could be used in order to evaluate the mentioned speed law.In this work the authors enhanced the knowledge about the optimization of the Idle roll speed law: different Idle roll speed laws were designed and simulated and the results were compared in order to identify the best speed law that guarantees a good quality ring with lower loads and energy required for manufacturing.

Abstract: This research work was focused on the application of powder metallurgy technology to the production of high-quality products from Ti10V2Fe3Al alloy. For the purpose of investigations hot compaction and hot closed-die forging processes were used. As an initial material a mixture of elemental powders was applied. As a result of hot densification, fully densified semi-products were obtained (99.4 % relative density). Numerical modelling of forging of a selected forging was performed using finite element method. Various options of forging process conditions were applied. The designed parameters of forging technology were verified by means of trials performed in industrial conditions. The quality of the product was estimated by microstructure observations. It was found that hot forging of compacted mixture of elemental powders resulted in obtaining defect-free gear wheel showing the relative density of 99.8 ±0.2 %.

Abstract: The ring-core method allows the determination of residual stresses at high depth from the surface. The numerical calculation integral method, commonly used for the hole-drilling, can also be applied to the ring-core. The integral method coefficients were obtained for several depth steps after axial-symmetric FE simulations with harmonic load. These coefficients were then validated with a 3D finite element model. Finally, an application was reported, showing the performance of the Tikhonov regularization on experimental data.

Abstract: The paper describes a summary of the complex approach to evaluation of quasi-brittle structures/structural members made of (advanced) cement based composites. It reviews chosen aspects and results of nonlinear stochastic analysis of structural members made of these composites and inserts them into the complex methodology. Application example illustrates the methodology.

Abstract: The paper deals with the mechanical response of a pre-stressed railway sleeper during a standardized static loading test estimations of the variability of the sleepers response and especially the probabilities of the occurrence of cracks of specific widths at specific load levels (as a consequence of random concrete parameters) based on the results of (3D) numerical models are presented. The paper follows on from and extends previous results obtained by the authors research team in cooperation with specialists from the sleeper manufacturing company ZPSV a. s.