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NEW APPROACH TO STRESS-STRAIN CURVE PREDICTION USING BALL INDENTATION TEST
Brumek, J. ; Strnadel, B. ; Dlouhý, Ivo
This work is concerned with the method for predicting stress-strain behavior of material using instrumented indentation technique. High strength low alloy steel with different thermal treatment was taken into the analysis. Heat treatment for the steel was performed to obtain different mechanical properties. Assessment of mechanical properties was done by using inverse technique of the finite element analysis. The results were confronted with conventional test parameters and prediction procedure defined such Automated Ball Indentation Technique (ABIT). Comparison of the material curves shows good agreement with tensile test properties which makes this non-destructive method suitable for industrial application.
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Local approach in mechanical properties prediction
Brumek, J. ; Strnadel, B. ; Dlouhý, Ivo
Indentation technique was focused on the prediction of the strain hardening behaviour of carbide steels. An improved technique to determine the plastic properties of material from the load-displacement curve from a ball indentation test was proposed. The time severity for the search for an optimal solution for a non-linear constitutive model is dependent on a number of design variables. Common methods like gradient methods or linear programming can fail due the fact that they drop to the local minimum. The advantage of a genetic algorithm does not require knowledge of the target function. Proposed method was applied to the data from the instrumented indentation technique. Results were found to be in good agreement with the data from conventional, standard tests, and in less time.
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Nonlinear modeling of stable crack growth
Brumek, J. ; Strnadel, B. ; Dlouhý, Ivo
This paper presents numerical study to predict crack growth rate under fatigue loading in a high pressure cylinder wall made of high strength steel. Experimental fatigue crack growth data on three point bending test samples. were applied to simulate and predict crack growth process using detailed three dimensional parametric finite elements models. The fatigue crack propagation was based on linear elastic fracture mechanics and stress intensity factor determination. Finite element model provides results of crack growth analysis optimized for the stress levels of operating pressure level. Results are plotted on a-N. Results were compared with an experimental fatigue test.
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Hodnocení mechanických vlastností pomocí instrumentované indentační zkoušky
Brumek, J. ; Strnadel, B. ; Dlouhý, Ivo
Studie o instrumentované indentaci byla zaměřena na materiály s nelineárním napěťově deformačním chováním. Indentační zkoušky byly provedeny na perlitické oceli R7T. Získaná data byla analyzována a byly predikovány mechanické vlastnosti jako mez kluzu, koeficient deformačního zpevnění a modul pružnosti. Křivka zatížení vs. hloubka vtisku byla porovnávána s výpočty metodou konečných prvků. MKP byla aplikována na dvourozměrném modelu za použití elasto-plastických elementů. Prezentovaná metoda predikce mchanických vlastností je významná pro odhad zbytkové životnosti ocelí, případně i jiných materiálů za použití indentační metody.
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