In today’s car manufacturing industry, sheet metal forming is a important process that takes preparation, which is time consuming and complex when new processes are made. When new metal grades and alloys are provided to the industry, tests are conducted to determine it’s behaviour and strengths. This gives the data for complex material models that can approximate the metal behaviour in an accurate way in a simulation environment. One of the unknown factors from tests is the friction coefficient on the sheet metal. The software Triboform is able to provide an adaptable friction coefficient model that depends on multiple simulation and user input conditions. The problems that occur when acquiring data for the material model is that testing is time consuming and the friction model has to be adjusted to give accurate results. At Volvo Cars there are two material models used with their different advantages, BBC 2005 and Vegter 2017.The purpose with this work is to compare the two material models using the Triboform friction models implemented to see if any combination provides accurate simulation results and then create recommendations for which model is best suited for different cases. Some side studies is also done with an older Vegter model, a strain rate sensitive BBC 2005 model and a Triboform model on all simulation parts.The purpose is achieved by implementing the Triboform model in Autoform and run a simulation of a Limiting Dome Height (LDH) test with both material models and compare the results with experimental data for several different materials. The data that is directly compared from the LDH test is the major and minor strain from two perpendicular sections at four different stages and also the force from the punch tool. The material models will be evaluated by how it manages to mimic the strain behaviour of the metals and how it estimates the punch force.The results point towards an improvement of the accuracy for most of the metals tested and BBC 2005 is the better model if there’s available biaxial data from tests, Vegter 2017 is decent if there’s not. However Vegter 2017 is not a good option for aluminum alloys simulations when the punch force is compared. Side study also shows that Vegter 2017 is bit of a downgrade when it comes to strain values, compared to the old Vegter.The work, in summary shows a dynamic friction model can improve the accuracy for strain predictions in the simulation process. If there’s biaxial yield data available for the metal or if it’s an aluminum alloy, BBC 2005 is the superior choice, but if only tensile tests are available for metals, Vegter 2017 is a decent choice for some cases. / I dagens bilindustri är plåtmetalformning en viktig process som kräver förberedelser som är tidskonsumerande och komplex när nya processer tillkommer. När nya metallslag kommer in till industrin, så utförs tester för att avgöra dess egenskaper och styrka. Denna testdata används till materialmodeller som kan approximera metallens beteende på ett noggrant sätt i en simuleringsmiljö. Den okända faktorn från dessa test är friktionskoefficienten på plåten. Programvaran Triboform är kapabel att göra en dynamisk friktionsmodel som beror på användar- och simuleringsdata. Problemen som uppstår vid framtagning av data är att det är tidskonsumerande och flera simuleringar måste göras för att bestämma friktionen. Volvo Cars använder sig av två modeller med olika fördelar, BBC 2005 och Vegter 2017.Syftet med detta arbete är att jämföra de två materialmodellerna med Triboform modeller implementerat för att se om de påverkar noggrannheten i simuleringar och sedan förse rekommendationer för vilken modell passar bäst för olika fall. Några sidojobb i studien som görs är en jämförelse med gamla Vegter modellen, ett test med en modell som är känslig för töjningshastighet och test med att implementera Triboform modellen på alla pressverktyg.Detta utförs med att implementera Triboform modellerna i Autoform och köra en simulering på ett LDH-test med båda materialmodeller och jämföra resultaten med experimentell data för flera olika metaller. Data som skall jämföras från LDH-testet är första och andra huvudtöjningen i två vinkelräta sektioner i fyra processsteg och stämpelkraften genom hela processen. Modellerna kommer evalueras genom hur de lyckas imitera töjningens beteende och hur den estimerar stämpelkraften.Resultaten pekar mot en förbättring när Triboform är implementerat i simuleringar för de flesta metaller som ingår i testen och BBC 2005 är den model som föredras om det finns tillgänglig biaxiel spänning data från tester, Vegter 2017 är en duglig modell om dessa data inte finns. Vegter 2017 är dock inte ett bra alternativ när det kommer till jämförelse av töjning och stämpelkraften för aluminium. Sidojobb med gamla Vegter visar att den nya Vegter 2017 inte är en direkt förbättring med hänsyn till noggrannheter av krafter och töjningar.Arbetet visar att en dynamisk friktionsmodel kan förbättra prediktering av töjningar i simuleringar. Om det finns biaxiel data för metallen eller om det gäller att simulera aluminium är BBC 2005 det bättre altermativet, om det endast finns dragprovsdata för metallen så är Vegter 2017 duglig för vissa fall.

In this work, the Bauschinger effect is shown to be intimately tied not only to plasticity but to damage as well. The plasticity-damage effect on the Bauschinger effect is demonstrated by employing different definitions (Bauschinger Stress Parameter, Bauschinger Effect Parameter, the Ratio of Forward-to-Reverse Yield, and the Ratio of Kinematic-to-Isotropic Hardening) for two differently processed aluminum alloys (rolled and cast) in which specimens were tested to different prestrain levels under tension and compression. Damage progression from second phase particles and inclusions that were generally equiaxed for the cast A356-T6 aluminum alloy and elongated for the rolled 7075 aluminum alloy was quantified from interrupted experiments. Observations showed that the Bauschinger effect had larger values for compression prestrains when compared to tension. The Bauschinger effect was also found to be a function of damage to particles/inclusions, dislocation/particle interaction, the work hardening rate, and the Bauschinger effect definition.

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This master's thesis is focused on the structural response due to blast loading, where the geometry used was arbitrary but heavily inspired by Siemens Energy. The aim of the thesis is to gain a better understanding on how to model the blast load and how it affects the structure, as well as to study the modeling of bolts with both pre-tension and a damage criteria in an explicit analysis. Lastly, the importance of strain rate dependent material models was studied. Other aspects such as mass scaling and Rayleigh damping were also investigated. The software used to solve these tasks were Hypermesh, Abaqus and Python. To conclude, the conclusions drawn from this thesis was that bolts should be modeled using connector elements, and including pre-tension is more conservative than not using it for the case studied. However, for the material modeling it gives more conservative results when using a strain rate independent material model compared to the strain rate dependent model, and is advised to be used in the future.

The goal of this thesis was the verification of the advanced time-dependent elasto-plastic material model for modeling diaphragm walls. Currently, this type of construction is solved usually with a combination of linear-elastic volume and plate elements. To express time-dependent behaviour, there are both, volume and plate, elements active in short-term conditions, then only volume elements in long-term conditions, while plate elements are deactivated. In this thesis, the Shotcrete material model, which can capture the time-dependent behaviour without combining two types of construction elements, is used. First, a theory of time-dependent behaviour is presented and a design of concrete structures by Eurocode 2 is discussed. Next, the Shotcrete material model is described, then used for modeling a biaxial test and calibration of compression and bending test. Following the gained knowledge, a real boundary value problem of deep excavation supported by diaphragm walls with the strut was solved. To calculate values of the internal forces and horizontal deformation in diaphragm walls, three types of material models are used.

In this paper the mechanical behaviour, both elastic and plastic, of single-crystal nickel-based superalloys has been investigated. A theoretic base has been established in crystal plasticity, with concern taken to the shearing rate on the slip systems. A model of the mechanical behaviour has been implemented, by using FORTRAN, as a user defined material model in three major FEM-programmes. To evaluate the model a simulated pole figure has been compared to an experimental one. These pole figures match each other very well. Yielding a realistic behaviour of the model.

<p>In this paper the mechanical behaviour, both elastic and plastic, of single-crystal nickel-based superalloys has been investigated. A theoretic base has been established in crystal plasticity, with concern taken to the shearing rate on the slip systems. A model of the mechanical behaviour has been implemented, by using FORTRAN, as a user defined material model in three major FEM-programmes. To evaluate the model a simulated pole figure has been compared to an experimental one. These pole figures match each other very well. Yielding a realistic behaviour of the model.</p>

The use of bearings can be found in virtually all aspects of mechanical systems today. Reliability of these critical components is an important issue. Fatigue performance of bearings is a function of many factors, including service conditions, loading, material properties, environmental factors, and manufacturing processes. Crack nucleation, first spall generation and spall growth in rolling contact fatigue are known to be highly sensitive to the heterogeneity of the microstructure. Yet the current state-of-the-art in the design of high performance bearing materials and microstructures is highly empirical requiring substantial lengthy experimental testing to validate the reliability and performance of these new materials and processes. The approach presented here is designed to determine relative rolling contact fatigue performance as a function of microstructural attributes. A fully three-dimensional finite element modeling allows for end effects to be captured that were not previously possible with two-dimensional plane-strain models, providing for a more realistic assessment of inclusion morphology and arbitrary orientations. The scaling of the finite element models has been optimized to capture the cyclic microplasticity around a modeled inclusion accurately and efficiently. To achieve this, two scales of geometric models were developed to incorporate different sized microstructural phenomena, with both models using traction boundary conditions derived from Hertzian contact stresses. A microstructure-sensitive material model adds additional capability. A hybrid model that includes both martensite and austenite phases with additional internal state variable to track the volume fraction of retained austenite due to stress-assisted transformation were developed. This represents an advance over previous models where transform plasticity and crystal plasticity were not simultaneously accounted for in a homogenized element containing both phases. Important links between microstructural features and fatigue indicator parameters (and relative fatigue performance) were determined. Demonstration cases show the relationship between inclusion orientation and relative fatigue performance, allowing for the identification of critical angles which maximize fatigue and reduce performance. An additional case study showed that increasing initial volume fraction of retained austenite reduces relative fatigue life. The tools developed allow for investigations of the influence of many microstructural aspects on relative fatigue performance with a numerical model that were not previously possible.

This thesis deals with propagation of pressure and flow pulsations, which are strongly affected by the tube flexibility. There are two mathematic models introduced, which are derived from basic physical relations. First model assumes velocity only in the axis direction. Second one assumes also non-zero radial velocity. Kelvin-Voigt model for viscoelasticity was used. Furthermore, experimental measurement was designed and evaluated. Measured data was used to calculate material properties. In addition, dynamic transfer was determined.