Collision avoidance systems have become an integrated part of modern vehicles and aim to avoid accidents or mitigate the crash severity for the occupant. For example, the autonomous emergency braking system influences the pre-crash state of the occupant in sitting posture, stress state, or velocity. The occupant might try to retain its posture by activating muscles, which induce muscle bracing and could counteract the movement of the occupant in the pre-crash phase.  Therefore, it is essential to study the influence of active musculature on occupant response in pre-crash and crash events. A finite element human body model (HBM) with and without closed-loop muscle activation control was used to simulate the occupant response during those events. Comparing the HBM responses & head kinematics reveal an influence of muscle bracing in the evasive braking manoeuvre. Simulating the pre-crash and in-crash phase in two stages can provide multiple benefits. However, the correlation between a single-stage simulation (baseline) and a two-stage simulation needs to be investigated. The baseline simulation uses an active HBM to model an occupant during an evasive braking manoeuvre and the muscles are deactivated when entering the frontal impact phase. The parameters of the final pre-crash state, which are needed to mimic the baseline’s response when transitioning from the pre-crash to the in-crash event are investigated in this study. For that reason, sitting position, stress state and velocity are transferred respectively to the initial passive in-crash HBM state. The simulations enabled the comparison of occupant response and calculation of cross-correlation. Each retainment strategy gave a good cross-correlation with the baseline simulation. / Kollisionsundvikande system har blivit en viktig del i moderna fordon där syftet är att undvika olyckor samt att minska allvarhetsgraden av olyckor för de åkande. Ett exempel är nödbromssystem som kan påverka den åkandes initiala tillstånd direkt före en krock som, till exempel, sittposition, spänningstillstånd, eller initial hastighet inför krock. Den åkande kan försöka att bibehålla sin hållning genom att aktivera sina muskler vilket påverkar rörelsen av dess kropp under för-krocks fasen. Det är därför viktigt att studera hur aktiva muskler påverkar rörelsen av kroppen hos den åkande under både före krocksfasen och själva krockfasen. En finit element humanmodell (HBM) med och utan reglerad muskelaktivitet används för att prediktera responsen hos den åkande i båda faserna. En jämförelse mellan simuleringarna visar att aktiva muskler kan påverka åkandekinematiken under bromsningsförloppet. Att simulera fasen före krock och fasen under krock i två steg kan medföra flera fördelar. Korrelationen mellan en enkelstegssimulering (originalsimulering) och en tvåstegssimulering måste dock studeras. Som originalsimulering används en aktiv HBM för att modellera den åkande under för-krocksfasen där den reglerade muskelaktiviteten inaktiveras under krockfasen. I denna studie undersöks den åkandes initiala tillstånd före krocken som behövs för att efterlikna originalsimulerings respons vid övergången från för-krocksfasen till krockfasen. Av den anledningen mappas det passiva HBM-tillståndet till det slutliga tillståndet av före krocksfasen för sittposition, spänningstillstånd respektive hastighet. Simuleringarna möjliggjorde en jämförelse av åkande respons och beräkning av korskorrelation. Varje mappningsstrategi gav en bra korskorrelation med originalsimuleringen.

The application of thermoplastics as load-carrying components in furniture applications is an attractive prospect at IKEA. Thermoplastics can be used instead of metal where advanced geometries and aesthetics are considered. In this thesis work in solid mechanics, it is of interest to investigate different test setups proposed in the literature for compression testing of thermoplastics while taking into account the complex stress fields induced in the test samples during the compression test.  The simulations have showed that the main cause of complex stress fields in compression test specimens is the presence of friction between the specimen and the machine heads. Friction prevents perfect Poisson contractions during the test which shifts the orientation of the local stress tensors from the direction of loading. Out of the shapes investigated in this thesis, it has been concluded that cube-shaped specimens were the most suitable to utilize in compression tests. The results were based on exploiting measures that pertain to accuracy and robustness parameters within stress and strain. Furthermore, manufacturing impact and ease of test measurements were considered. / Användningen av termoplaster som lastbärande komponenter i möbelapplikationer har ökat under de senaste åren inom IKEA. Då det förutom att vara estetiskt tilltalande för hela möbler är främsta användningen i komponenter som har mer komplicerade geometrier. I detta examensarbete i hållfasthetslära är det av intresse att undersöka olika provkroppar vilket föreslås i litteratur för kompressionsprovning av termoplaster med hänsyn till de komplexa spänningstillstånden som orsakas under provning.  Simuleringarna har påvisat de komplexa spänningstillstånd i kompressionsprov som uppkommer på grund av friktion mellan provstaven och grepen. Friktion förhindrar perfekt tvärkontraktion, vilket förändrar orienteringen av de lokala spänningstensorerna från belastningsriktningen, vilket är enaxlig. Utifrån de former som undersöktes i detta examensarbete blev slutsatsen att kubformade provkroppar var de mest lämpliga att använda i kompressionsprovning. Resultaten baserades på att utnyttja åtgärder som avser noggrannhetsparametrar inom spänning och töjning men även tillverknings och provmätningens lätthet.

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.

Cross median crashes have become a serious problem in recent years. Most of the median cross sections used for divided highways have terrains with steep slopes. Traffic barriers, frequently used on slopes, are generally designed based on the findings obtained from crash tests performed on flat terrain. For barriers placed on roadside and median slopes, vehicle impact height varies depending on the trajectory of the vehicle along the ditch section and lateral offset of the barrier. Thus depending on the placement location on a relatively steep slope, a barrier can be impacted by an errant vehicle at height and orientation more critical compared to those considered during its design. Hence, detailed study of performance of barriers on roadside and median slopes is needed to achieve acceptable safety performance. In this study, performances of modified G4(1S) W-beam, Midwest Guardrail System (MGS), modified Thrie-beam, modified weak post W-beam, and box-beam guardrail systems on sloped terrains are investigated using numerical simulations. A procedure is developed that provide guidance for their placement on roadside and median slopes. The research approach consists of nonlinear finite element analyses and multi-rigid-body dynamic analyses approach. Detailed finite element representation for each of the barriers is developed using LS-DYNA. Model fidelity is assessed through comparison of simulated and measured responses reported in full scale crash test studies conducted on flat terrain. LS-DYNA simulations of vehicle impacts on barriers placed on flat terrain at different impact heights are performed to identify performance limits of the barriers in terms of acceptable vehicle impact heights. The performances of the barriers are evaluated following the guidelines provided in NCHRP Report 350. Multi-rigid-body dynamic analysis code, CARSIM, is used to identify trajectories of the vehicles traversing various roadside and median cross-slopes. After analyzing vehicle trajectories and barrier performance limits, a guideline has been prepared with recommendations for the placement of barriers along roadside and median slopes. This guideline is then verified and refined using the responses obtained from full-scale LS-DYNA simulations. These simulations capture the full encroachment event from departure of the vehicle off the traveled way through impact with the barrier.

<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>

<p>This report is a review of some failure models today used for determine failure in thin sheets of high strength steels. Focus has been given on phenomenlogical models and only some simple simulations have been carried out. The phenomenlogical models that have been summarized here are of four different categories, namely stress based, strain based, combined stress and strain based and damaged models. However, the simulations have only been preformed for some of the models.</p>

This report is a review of some failure models today used for determine failure in thin sheets of high strength steels. Focus has been given on phenomenlogical models and only some simple simulations have been carried out. The phenomenlogical models that have been summarized here are of four different categories, namely stress based, strain based, combined stress and strain based and damaged models. However, the simulations have only been preformed for some of the models.

The master thesis deals with a stress-strain analysis of the front crash structure of a race car by using the finite element method. The structure is loaded by an impact loading. This type of analysis belongs to the transient analysis so the explicit formulation of the finite element method is used. The LS-DYNA software was used for calculations. The goal of this thesis is to express the influence of the crash structure to the change of the car's kinetic energy as well as the amount of absorbed energy in case of frontal impact.

The main subject of this master thesis is the computational modeling of stress-strain analysis of the loaded front part of Toyota Yaris from the year 2010 using an explicit finite element method (FEM). The aim of this thesis is the assessment of resistance of the front part of the car (longeron) at the impact stress. This thesis describes the selection, editing, and creation of the computational model of longeron and simulation of the barrier collision. The objective of the thesis is to use a real vehicle, suggest modified longerons to be implemented in it, test various shape and material versions of the longeron and make their comparison.

In 1995 was published a regulation from RCAR company which determines rules for crash tests in maximum speed of 15 km/h on vehicles lighter than 2,5 ton. The main reason was to reduce costs for car reparation in case of crash in low speed. My diploma thesis is focused on the modifications of deformation part in the car alias absorption part of the vehicle. In the first part of my diploma thesis has been done a research about organisations doing basic car crashes as well as topic focused on nonlinear mechanics and description of explicit FEM. In the second part of my work are settled conditions for crash simulation of a barrier into the car. There is an evaluation of critical force on the stringer. Afterwards the calculating simulation simplified on loading of absorption part and there are some material and form adjustments. In the final part of my diploma thesis is done a result comparison and development of the absorption part.