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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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Application of inverse FEM analysis for materials curve determination based on indentation test
Brumek, J. ; Strnadel, B. ; Dlouhý, Ivo
Study of instrumented indentation test is focused on prediction of the strain hardening behavior of the carbon steels. Indentation tests were applied on several steels samples. We proposed an improved technique to determine the plastic properties of material from the loaddisplacement curve from ball indentation test. The inverse finite element method was used for prediction of material properties. Results were found in good agreement with the data from conventional standard test. This non-destructive assessment of deformation behavior has good potential for the other materials.
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Instrumented indentation test used for mechanical properties determination
Brumek, J. ; Strnadel, B. ; Dlouhý, Ivo
Focusing on the materials with non-linear stress-strain behavior an instrumented indentation study is presented. Indentation tests were applied on steel R7T. The observed data were analyzed and mechanical properties, such as yield stress, strain hardening exponent and elastic modulus were assessed. Experimental results of load-depth (P-h) test were compared with FEM solution. FEM analysis was applied on two-dimensional model described by elastic-plastic elements. Presented method of prediction in mechanical characteristics is useful to judge deformations of steel and other materials under contact stressing. Experimental results of P-h relation and additional FEM analysis of indentation test provide very helpful information of mechanical behaviors in contact of two bodies.
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Mechanical properties evaluation by means of instrumented indentation test
Brumek, J. ; Strnadel, B. ; Dlouhý, Ivo
An instrumented indentation study focusing on the materials with non-linear stress-strain behavior is presented. Indentation tests were applied on steel R7T. The observed data were analyzed and mechanical properties, such as yield stress, strain hardening exponent and elastic modulus were assessed. Experimental results of load-indentation depth test were compared with FEM solution. FEM analysis was applied on two-dimensional model described by elastic-plastic elements. Presented approach to prediction of mechanical characteristics is useful for estimation of remanent lifre of steels and other materials by using indentation method.
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