Marino Brčić

Tool Material Behavior at Elevated Temperatures

In this article experimentally obtained data related to material mechanical properties, material behavior at elevated temperatures and numerical modeling of material creep responses are presented. Tensile tests at different elevated temperatures are carried out, and for some of these temperatures one-dimensional short time creep tests for different constant stresses are made. Before presented experimental investigations the used materials were not treated. The curves representing specimen strain elongation are also presented. The materials under consideration are 56NiCrMoV7 (1.2714) and X153CrMoV12 (1.2379).

Analysis of the Mechanical Behavior, Creep Resistance and Uniaxial Fatigue Strength of Martensitic Steel X46Cr13

The article deals with the analysis of the mechanical behavior at different temperatures, uniaxial creep and uniaxial fatigue of martensitic steel X46Cr13 (1.4034, AISI 420). For the purpose of considering the aforementioned mechanical behavior, as well as determining the appropriate resistance to creep and fatigue strength levels, numerous uniaxial tests were carried out. Tests related to mechanical properties performed at different temperatures are presented in the form of engineering stress-strain diagrams. Short-time creep tests performed at different temperatures and different stress levels are presented in the form of creep curves. Fatigue tests carried out at stress ratios R=0.25 and R=−1 are shown in the form of S–N (fatigue) diagrams. The finite fatigue regime for each of the mentioned stress ratios is modeled by an inclined log line, while the infinite fatigue regime is modeled by a horizontal line, which represents the fatigue limit of the material and previously was calculated by the modified staircase method. Finally, the fracture toughness has been calculated based on the Charpy V-notch impact energy.

Mechanical Properties, Short Time Creep, and Fatigue of an Austenitic Steel

The correct choice of a material in the process of structural design is the most important task. This study deals with determining and analyzing the mechanical properties of the material, and the material resistance to short-time creep and fatigue. The material under consideration in this investigation is austenitic stainless steel X6CrNiTi18-10. The results presenting ultimate tensile strength and 0.2 offset yield strength at room and elevated temperatures are displayed in the form of engineering stress-strain diagrams. Besides, the creep behavior of the steel is presented in the form of creep curves. The material is consequently considered to be creep resistant at temperatures of 400 °C and 500 °C when subjected to a stress which is less than 0.9 of the yield strength at the mentioned temperatures. Even when the applied stress at a temperature of 600 °C is less than 0.5 of the yield strength, the steel may be considered as resistant to creep. Cyclic tensile fatigue tests were carried out at stress ratio R = 0.25 using a servo-pulser machine and the results were recorded. The analysis shows that the stress level of 434.33 MPa can be adopted as a fatigue limit. The impact energy was also determined and the fracture toughness assessed.

Study of the Effects of High Temperatures on the Engineering Properties of Steel 42CrMo4

Abstract The paper presents and analyzes the experimental results of the effect of elevated temperatures on the engineering properties of steel 42CrMo4. Experimental data relating to the mechanical properties of the material, the creep resistance as well as Charpy impact energy. Temperature dependence of the mentioned properties is also shown. Some of creep curves were simulated using rheological models and an analytical equation. Finally, an assessment of fracture toughness was made that was based on experimentally determined Charpy impact energy. Based on the obtained results it is visible that the tensile strength (617 MPa) and yield strength (415 MPa) have the highest value at the room temperature while at the temperature of 700 °C (973 K) these values significantly decrease. This steel can be considered resistant to creep at 400 °C (673 K), but at higher temperatures this steel can be subjected to low levels of stress in a shorter time.

Comparison of Material Properties and Creep Behavior of 20MnCr5 and S275JR Steels

t is well known that the optimization procedure has an important role in the structure design. Furthermore, experimentally obtained data of material behavior is known to serve as the most relevant data in the mentioned design procedure. Therefore, this paper sets out to examine some experimentally determined data of the material subjected to certain environmental conditions. Based on these parameters, some analyses of material behavior can be made. In addition, data are of such nature that it is possible to make an appropriate comparison between the two investigated materials. Materials under considerations were 20MnCr5 steel and S275JR steel. Both of materials have been subjected to the same environmental conditions and the following properties can be singled out: ultimate tensile strength, 0.2 offset yield strength, the modulus of elasticity, elongation, creep behavior and Charpy impact energy. Each of the mentioned details are determined by the corresponding test, e.g. data related to strengths and to creep behavior are determined by tensile tests while impact energy is determined by Charpy impact test. In this way, the obtained values are presented in the form of the engineering stress-strain diagrams, creep curves and impact energy data.

Multiscale Modeling of Nanocomposite Structures with Defects

A method for the numerical modeling of mechanical behavior of nanocomposite materials reinforced with the carbon nanotubes, based on the computational homogenization as a multiscale method, is presented. The matrix reinforcement interactions, based on the weak van der Waals forces are incorporated into the multiscale model and are represented by the nonlinear rod elements. The reinforcements, i.e. carbon nanotubes, are modeled as a space frame structure, using beam finite elements. Computational homogenization and representative volume element (RVE) are the basis of the presented numerical model of the nanocomposites. Nanoscale model is based on beam and non-linear rod finite elements. An algorithm is developed for the analysis of the presented nanostructure, and for the purpose of the software verification, examples, i.e. models of the nanocomposite material are presented. Also, the nanocomposite model with various vacancy defects in the reinforcement, i.e. nanotube, has been prepared and the obtained results are compared and discussed.Keywords Nanocomposite materials · Carbon nanotubes · Multiscale modelling · Computational homogenization

Analysis of the Dependence of Material Properties on Temperature – Steel 1.4122

Abstract This article presents an analysis of experimental data with reference to material properties, short-time creep and relaxation phenomena of 1.4122 steel (AISI 420RM) at high temperatures. The behaviour of the material subjected to uniaxial stress is indicated by engineering stress – strain diagrams. The data referring to tensile strength, 0.2 percent offset yield strength, the modulus of elasticity and total deformation, are shown through tables and curves presenting the dependence of these quantities on temperature. Creep and relaxation curves regarding certain level of stresses at selected temperatures are also shown. In addition, modelling of both creep and relaxation phenomena is presented.