Numerical simulation of deformation behavior of aluminum alloy sheets under processing by groove pressing method

The results of theoretical estimation of capabilities of the material structure modification of 1560 aluminum alloy sheets under processing by severe plastic deformation are presented in this paper. Severe plastic deformation of flat specimens is effected by the constrained groove pressing method in original dies with trapezoidal teeth. The numerical simulation results of the sheet specimen treatment process by severe plastic deformation were used for dies designing. The stress-strain state of flat aluminum alloy specimens and the steel dies at high processing temperature, support reaction force during pressing and the degrees of plastic strain accumulation at the optimum mode of pressing were estimated. The main numerical result is the value of accumulated plastic strain in the specimen per one pressing cycle which is about 1.14. Large degrees of strain are the reasons of grain structure and material texture changes, which leads to inevitable change of its physical-mechanical properties. Increasing the number of pressing cycles leads to proportional increase of the degree of accumulated plastic strain

Damage formation, fatigue behavior and strength properties of ZrO[2]-based ceramics

It is suggested that a non-destructive testing technique using a three-dimensional X-raytomography be applied to detecting internal structural defects and monitoring damage formation in a ceramic composite structure subjected to a bending load. Three-point bending tests are used to investigate the fatigue behavior and mechanical and physical properties of medical-grade ZrO[2]-based ceramics. The bending strength and flexural modulus are derived under static conditions at a loading rate of 2 mm/min. The fatigue strength and fatigue limit under dynamic loading are investigated at a frequency of 10 Hz in three stress ranges: 0.91-0.98, 0.8-0.83, and 0.73-0.77 MPa of the static bending strength. The average values of the bending strength and flexural modulus of sintered specimens are 43 MPa and 22 GPa, respectively. The mechanical propertiesof the ceramics are found to be similar to those of bone tissues. The testing results lead us to conclude that the fatigue limit obtained from 10{5} stress cycles is in the range 33-34 MPa, i.e. it accounts for about 75% of the static bending strength for the test material

Damage formation, fatigue behavior and strength properties of ZrO[2]-based ceramics

It is suggested that a non-destructive testing technique using a three-dimensional X-raytomography be applied to detecting internal structural defects and monitoring damage formation in a ceramic composite structure subjected to a bending load. Three-point bending tests are used to investigate the fatigue behavior and mechanical and physical properties of medical-grade ZrO[2]-based ceramics. The bending strength and flexural modulus are derived under static conditions at a loading rate of 2 mm/min. The fatigue strength and fatigue limit under dynamic loading are investigated at a frequency of 10 Hz in three stress ranges: 0.91-0.98, 0.8-0.83, and 0.73-0.77 MPa of the static bending strength. The average values of the bending strength and flexural modulus of sintered specimens are 43 MPa and 22 GPa, respectively. The mechanical propertiesof the ceramics are found to be similar to those of bone tissues. The testing results lead us to conclude that the fatigue limit obtained from 10{5} stress cycles is in the range 33-34 MPa, i.e. it accounts for about 75% of the static bending strength for the test material

Mechanical properties of weld joints of high-strength steel under dynamic loading

The paper represents a computational model for predicting the mechanical behavior of welded joints in steel constructions under dynamic load, taking into account the change in the properties of the steel in the welding zone. Plastic deformation localization and formation of cracks in welded joints subjected to tensile loading have been studied numerically. Numerical modeling confirms that the model proposed in the work can predict the strength and mechanical behavior of welded joints in steel constructions in a wide range of strain rates, taking into account the phase and granular structure in the weld area. The results confirm that residual stresses of ~ 100–150 MPa do not significantly affect the formation of the fracture zone in arc welded joints of 09G2S steel subjected to dynamic loading. Fracture of considered welded joints exhibits ductile behavior at initial temperature of 295K and high strain rates. The results have shown that mesoscopic cracks nucleate in the heat-affected zone at effective strains above 12%

Algorithm for J-Integral Measurements by Digital Image Correlation

The work is devoted to the testing of the algorithm for calculating J-integral based on the construction of vector fields by digital image correlation (DIC) method. A comparative analysis of J-integral values calculated using DIC and instrumental data obtained in accordance with ASTM E 1820 "Standard Test Method for Measurement of Fracture Toughness" has made. It is shown that this approach can be used for cases when the standard technique for measuring the J-integral cannot be applied, or the standard technique does not allow achieving the required accuracy for the integral determination in local areas of the loaded material

Evaluation of the possibility of obtaining welded joints of plates from Al-Mg-Mn aluminum alloys, strengthened by the introduction of TiB2 particles

In the work, the possibility of obtaining strong welded joints of aluminum alloys modified with particles is demonstrated. For research, strengthened aluminum alloys of the Al-Mg-Mn system with the introduction of TiB2 particles were obtained. TiB2 particles in specially prepared Al-TiB master alloys obtained by self-propagating high-temperature synthesis were introduced ex situ into the melt according to an original technique using ultrasonic treatment. Plates from the studied cast alloys were butt-welded by one-sided welded joints of various depths. To obtain welded joints, the method of electron beam welding was used. Mechanical properties of the studied alloys and their welded joints under tension were studied. It was shown that the introduction of particles resulted in a change in the internal structure of the alloys, characterized by the formation of compact dendritic structures and a decrease in the average grain size from 155 to 95 µm. The change in the internal structure due to the introduction of particles led to an increase in the tensile strength of the obtained alloys from 163 to 204 MPa. It was found that the obtained joints have sufficient relative strength values. Relative strength values reach 0.9 of the nominal strength of materials already at the ratio of the welded joint depth to the thickness of the welded plates, equal to 0.6 for the initial alloy and in the range of 0.67–0.8 for strengthened alloys