Free Vibrations of Bernoulli-Euler Nanobeams with Point Mass Interacting with Heavy Fluid Using Nonlocal Elasticity.

Eigenfrequencies of a nanobeam with a point mass interacting with a heavy fluid are calculated using Bernoulli-Euler kinematics and consistent nonlocal elasticity model. The proposed approach is applicable to a variety of nanotechnology materials and structures, especially mass nanosensors. Eigenfrequencies are compared with those of local theory and conclusions are drawn. Influence of nonlocal effects, heavy fluid interaction and added point mass on dynamic responses is analyzed and the results are documented. Size phenomena are noted and discussed.

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.