Modelling and simulation of metal cutting by finite element method

Thesis (Master)--Izmir Institute of Technology, Mechanical Engineering, Izmir, 2009Includes bibliographical references (leaves: 70-73)Text in English; Abstract: Turkish and Englishxiii, 73 leavesMetal cutting is one of the most widely used manufacturing techniques in the industry and there are lots of studies to investigate this complex process in both academic and industrial world. Predictions of important process variables such as temperature, cutting forces and stress distributions play significant role on designing tool geometries and optimising cutting conditions. Researchers find these variables by using experimental techniques which makes the investigation very time consuming and expensive. At this point, finite element modelling and simulation becomes main tool. These important cutting variables can be predicted without doing any experiment with finite element method. This thesis covers a study on modelling and simulation of orthogonal metal cutting by finite element method. For this purpose, orthogonal cutting simulations of AISI 1045 steel are performed and model used in simulations is validated. At first step, effects of work piece flow stress and friction models on cutting variables such as cutting forces, chip geometry and temperature are investigated by comparing simulation results with experimental results available in the literature. Then, mechanical and thermal analyses are performed. Lastly, effects of rake angle and tool tip radius on strain, temperature and stress distributions are investigated

Experimental testing and full and homogenized numerical models of the low velocity and dynamic deformation of the trapezoidal aluminium corrugated core sandwich

The simulations of the low velocity and dynamic deformation of a multi-layer 1050-H14 Al trapezoidal zig-zag corrugated core sandwich were investigated using the homogenized models (solid models) of a single core layer (without face sheets). In the first part of the study, the LS-DYNA MAT-26 material model parameters of a single core layer were developed through experimental and numerical compression tests on the single core layer. In the second part, the fidelities of the developed numerical models were checked by the split-Hopkinson pressure bar direct impact, low velocity compression and indentation and projectile impact tests. The results indicated that the element size had a significant effect on the initial peak and post-peak stresses of the homogenized models of the direct impact testing of the single-layer corrugated sandwich. This was attributed to the lack of the inertial effects in the homogenized models, which resulted in reduced initial peak stresses as compared with the full model and experiment. However, the homogenized models based on the experimental stress–strain curve of the single core layer predicted the low velocity compression and indentation and projectile impact tests of the multi-layer corrugated sandwich with an acceptable accuracy and reduced the computational time of the models significantly

Cross wedge rolling of a Ti6Al4V (ELI) alloy: the experimental studies and the finite element simulation of the deformation and failure

The cross wedge rolling (CWR) deformation and fracture of a Ti6Al4Al (ELI) alloy were investigated experimentally and numerically using a coupled thermomechanical finite element model analysis. The experimentally determined flow stress and damage model parameters were verified by tension split Hopkinson pressure bar testing of notched samples. The simulation and experimental CWR forces showed well agreements except near the end of the stretching zone. The model analysis showed that the temperature distribution in the work piece was nonuniform during the CWR. When the initial temperature of the work piece was relatively low, the work piece temperature increased, a heating effect of the plastic deformation, while relatively high initial work piece temperatures resulted in cooling the work piece, caused by the work piece contact with the tools. The cracks were shown numerically to initiate in the midsections of the work piece during the guiding action and elongated in a direction normal to the maximum tensile stress triaxiality, resulting in cruciformshaped crack formation, which was well agreed with the previously observed crack shape

Modelling and simulation of metal cutting by finite element method

Thesis (Master)--Izmir Institute of Technology, Mechanical Engineering, Izmir, 2009Includes bibliographical references (leaves: 70-73)Text in English; Abstract: Turkish and Englishxiii, 73 leavesMetal cutting is one of the most widely used manufacturing techniques in the industry and there are lots of studies to investigate this complex process in both academic and industrial world. Predictions of important process variables such as temperature, cutting forces and stress distributions play significant role on designing tool geometries and optimising cutting conditions. Researchers find these variables by using experimental techniques which makes the investigation very time consuming and expensive. At this point, finite element modelling and simulation becomes main tool. These important cutting variables can be predicted without doing any experiment with finite element method. This thesis covers a study on modelling and simulation of orthogonal metal cutting by finite element method. For this purpose, orthogonal cutting simulations of AISI 1045 steel are performed and model used in simulations is validated. At first step, effects of work piece flow stress and friction models on cutting variables such as cutting forces, chip geometry and temperature are investigated by comparing simulation results with experimental results available in the literature. Then, mechanical and thermal analyses are performed. Lastly, effects of rake angle and tool tip radius on strain, temperature and stress distributions are investigated

Tek ve çok katmanlı zikzak 1050 H14 Al ikizkenar yamuk dalgalı göbekli sandviç yapıların yarı-statik ve dinamik gerinim hızlardaki ezilme davranışının deneysel ve nümerik incelenmesi

Thesis (Doctoral)--Izmir Institute of Technology, Mechanical Engineering, Izmir, 2014Includes bibliographical references (leaves: 163-173)Text in English; Abstract: Turkish and Englishxxii, 173 leavesThe quasi-static and dynamic crushing behavior of single, double and multi-layer zig-zag 1050 H14 Al trapezoidal corrugated core sandwich structures in 0°/0° and 0°/90° core orientations and with and without interlayer sheets were investigated both experimentally and numerically at varying impact velocities. The numerical simulations were conducted using the finite element code of LS-DYNA. The effect of fin wall imperfection was assessed through the fin wall bending and bulging. The numerical homogenization of the single layer corrugated structure was performed using MAT26 honeycomb material model. The buckling stress of single- and double-layer corrugated sandwich structures increased when the strain rate increased. The increased buckling stresses were ascribed to the micro inertial effects. The initial buckling stress at quasi-static and high strain rate was numerically shown to be imperfection sensitive. Increasing the number of core layers decreased the buckling stress and increased the densification strain. The panels tested with spherical and flat striker tips were not penetrated and experienced slightly higher deformation forces and energy absorptions in 0°/90° corrugated layer orientation than in 0°/0° orientation. However, the panels tested using a conical striker tip were penetrated/perforated and showed comparably smaller deformation forces and energy absorptions, especially in 0°/90° layer orientation. The homogenized models predicted the low velocity compression /indentation and projectile impact tests of the multi-layer corrugated sandwich with an acceptable accuracy with reduced computational time

Single- and double-layer aluminum corrugated core sandwiches under quasi-static and dynamic loadings

The crushing of single- and double-layer zig-zag trapezoidal corrugated core sandwiches was investigated experimentally and numerically at quasi-static and dynamic rates. The buckling stress of sandwiches increased when the rate increased from quasi-static to dynamic. The increased buckling stresses were ascribed to the micro-inertial effects, which altered the buckling mode of the core from three plastic hinges to higher number of plastic hinge formations. The initial buckling stress was numerically shown to be imperfection sensitive when the imperfection size was comparable with the buckling length. The numerical buckling stresses of zig-zag and straight corrugated cores were similar, while higher inertial effects were found in triangular corrugated core

The impact responses and the finite element modeling of layered trapezoidal corrugated aluminum core and aluminum sheet interlayer sandwich structures

The impact responses of brazed and adhesively bonded layered 1050 H14 trapezoidal corrugated aluminum core and aluminum sheet interlayer sandwich panels with 3003 and 1050 H14 aluminum alloy face sheets were investigated in a drop weight tower using spherical, flat and conical end striker tips. The full geometrical models of the tests were implemented using the LS-DYNA. The panels tested with spherical and flat striker tips were not penetrated and experienced slightly higher deformation forces and energy absorptions in 0°/90° corrugated layer orientation than in 0°/0° orientation. However, the panels impacted using a conical striker tip were penetrated/perforated and showed comparably smaller deformation forces and energy absorptions, especially in 0°/90° layer orientation. The simulation and experimental force values were shown to reasonably agree with each other at the large extent of deformation and revealed the progressive fin folding of corrugated core layers and bending of interlayer sheets as the main deformation mechanisms. The experimentally and numerically determined impact velocity sensitivity of the tested panels was attributed to the micro inertial effects which increased the critical buckling loads of fin layers at increasingly high loading rates

Cross wedge rolling process of complex geometries: Die design with finite element simulations

Çapraz Kama Haddeleme (ÇKH), düz plakalar ya da merdaneler üzerine oluşturulmuş kamalar ile iş parçalarının deforme edildiği ve genellikle yüksek sıcaklıarda gerçekleştirilen bir metal şekil verme işlemidir. Ancak işlemde meydana gelen hasar yapısının karmaşık olması ve özellikle karmaşık geometriye sahip parçalar için kalıp tasarımının zor olması bu yöntem için dezavantaj sağlamaktadır. Bu çalışmada içi boş ve karmaşık dış geometriye sahip iş parçasının sonlu elemanlar simülasyonları ile ÇKH kalıbı tasarımı ele alınmıştır. Tasarlanan kalıplar ile gerçekleştirile sonlu elemanlar analizleri, iş parçasının tam olarak şekillenip şekillenmediğini belirlemiş ve sonuca göre mevcut kalıp tasarımı en iyilenmiştir. Simülasyonlarda büyük genişletme açısının içi boş iş parçasında eğilmeye sebep olduğu görülmüştür. Ayrıca iş parçası ile kalıp arasında sürtünmenin yetersiz olduğu bölgelerde çentiklerin kullanılması gerektiği belirlenmiştir.Cross Wedge Rolling (CWR) is a metal forming process in which work pieces are deformed by wedges located on flat plates or rolls and it is generally conducted at elevated temperatures. However, CWR method has disadvantages such as damage evolution during process and difficult tool design for complex parts. In this study, CWR tool design supported with finite element simulations for a hollow complex part is given. Finite element analyses are carried out with designed tools and tool geometry is optimised according to FE results. Simulations show that high stretching angles result in bending of hollow work pieces. It is also seen that serrations should be used in tool-work piece contact areas which have low friction