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Car Door Handle FEM Model Creation and Validation for Crash Simulations
Raffai, Peter ; Korouš, Jan (referee) ; Ramík, Pavel (advisor)
The aim of this master’s thesis was to create a component model of a door handle stiffener used by the Volkswagen concern, which can be used for crash computations. Also to tune its parameters the way, its behavior corresponds the most to the real part’s. In the theoretical part the current regulations of the Euro NCAP are presented, concerning the testing and evaluation of the passive safety of new vehicles. Attention is focused on the evaluation of the side impact barrier tests, where the effect of the door handle stiffener’s damage is reflected the most. Shown are the reasons for the effort to simulate the real behavior of the stiffener, the factors, which initialized the born of the studied problem. The practical part starts with the creation of the FEM mesh of the part based on its 3D CAD model, also describes the requirements for the mesh quality, as well as the used tools and methods. Further on investigated are the characters of real damages of the door handle area during side impacts, based on which the component tests are proposed for the validation of the simulation model. Experimental research consists of the stiffener’s testing for simple bend and twist loads, three specimens each. After the execution of the tests the results get compared with the corresponding simulations. Modifications are made on the model according to the acquired results: refinement of the FEM mesh, new material model usage with failure for shell elements and definition of real material characteristics for the used thermoplastics. The latest obtained simulation dependencies are compared with the measured values again, the results are evaluated at last.
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Microbiological quality of milk for cheese production
Korous, Jan ; Legarová, Veronika (advisor) ; Vladimír, Vladimír (referee)
This bachelor thesis is focused on microbiological quality of milk for cheese production. Besides that, it informs about the composition of milk and the processes in cheese production.
The composition of milk differs between animal species. Lactose is the main sugar of milk, with content about 4-8 %. The majority of fat found in milk is triacylglycerol type. Casein is the most important protein, which occurs in three fractions (alpha, beta a kappa). Milk also contains various minerals and vitamins. The most important mineral is calcium, which plays an important role in cheese production. The milk composition is a suitable environment for the growth of microorganisms (Pseudomonas, Enterobacter, etc.), that can contaminate raw milk. Despite this risk, the raw milk is commonly used for cheese production, because it gives the cheese better structure and taste compared with the treated milk. However, the majority of cheeses are manufactured from the treated milk. In most cases, the milk is treated by heat, especially by pasteurization and ultrahigh temperature. These procedures kill microorganisms in milk. In some cases, milk can be contaminated again after the treatment or by inactive spores that survived the treatment. They can become active under favourable conditions, for example during cheese making.
Cheeses can be divided into groups by several criteria (type of coagulation, water content or fat content in dry matter). Starting cultures are used during cheese making from treated milk. Thermophilic starting culture Lactobacillus casei is used for manufacturing of soft cheeses and cheeses with high-heated curd. Cheeses with holes are made by fermentation (Propionibacterium freudenreichii). Mesophilic bacteria Lactobacillus lactis are used for production of cheeses with low-heated curd. There are many other cultures used in cheese making. Another important process during a cheese making is coagulation. During this process, the milk fat is coagulated by enzymes (chymosin, pepsin). After the coagulation, the curd is cut and forms soft grains, which exude whey. The grains are often heated for the better whey secretion. Salt is used during the cheese production to slow the activity of microorganisms and enzymes and it also gives better taste to the final product. Cheese is then let to age, during this period of time, biochemical processes occur and unique characteristics of the cheese are gained.
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Car Door Handle FEM Model Creation and Validation for Crash Simulations
Raffai, Peter ; Korouš, Jan (referee) ; Ramík, Pavel (advisor)
The aim of this master’s thesis was to create a component model of a door handle stiffener used by the Volkswagen concern, which can be used for crash computations. Also to tune its parameters the way, its behavior corresponds the most to the real part’s. In the theoretical part the current regulations of the Euro NCAP are presented, concerning the testing and evaluation of the passive safety of new vehicles. Attention is focused on the evaluation of the side impact barrier tests, where the effect of the door handle stiffener’s damage is reflected the most. Shown are the reasons for the effort to simulate the real behavior of the stiffener, the factors, which initialized the born of the studied problem. The practical part starts with the creation of the FEM mesh of the part based on its 3D CAD model, also describes the requirements for the mesh quality, as well as the used tools and methods. Further on investigated are the characters of real damages of the door handle area during side impacts, based on which the component tests are proposed for the validation of the simulation model. Experimental research consists of the stiffener’s testing for simple bend and twist loads, three specimens each. After the execution of the tests the results get compared with the corresponding simulations. Modifications are made on the model according to the acquired results: refinement of the FEM mesh, new material model usage with failure for shell elements and definition of real material characteristics for the used thermoplastics. The latest obtained simulation dependencies are compared with the measured values again, the results are evaluated at last.
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Reliability assessment of steel tubes considering due to fracture
Marek, Pavel ; Korouš, Jan ; Bielak, O.
Cracks are most dangerous defects which can be found in real structures, Prediction of the crack instability is influenced by many factors of random nature. To take into account these random variables, SBRA approach can be adopted. The paper show how the probabilistic assessment can be used for calculation of fracture probability in a cracked pipe, as random variables, material properties and crack depth were assumed. The assessment resulted in fracture probability which can be compared with a target value
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Simulation of stable crack growth in piping using comlete Gurson model
Korouš, Jan
The paper deals with simulation of stable crack growth using the complete Gurson model. The cracks were situated in a piping. An advantage of the complete Gurson model consists in the fact that the critical volume fraction for coalescence is not an input value, however it is calculated on the basis of Thomason's limit criterion of an material element with an internal void. The FEM system WARP3D was used for calculations and crack growth of cimcumferential and longitudinal cracks was simulated. In case of the longitudinal cracks, a specific crack growth was observed which is not proportional along the crack-tip length. The initial eliptical shape of the crack tip changes and becomes canoe-like one. This effect was experimentally observed and described in literature. It can be explained using stress triaxility distribution in front of the crack tip.
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Simulation of resitance curves using Gurson plasticity model
Korouš, Jan ; Zemánková, Jaroslava
The concept of J-R curves is well established in structure assessment.However, the shape of J-R curves is influenced by constraint effectssignificantly. Such phenomena can be modelled using micromechanicalmodels of plasticity. The paper presents simulation of J-R curves usingthe complete Gurson model of plasticity, which was implemented into thefinite element system WARP3D.
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