Investigation of residual stress and mechanical properties of equal channel angular rolled St12 strips

The Journal of Strain Analysis for Engineering Design

2018

In recent decades, ultrasonic vibrations are used in manufacturing processes because they can improve tool life, material performance, and quality. One of them which can be integrated with ultrasonic vibrations is friction stir welding called ultrasonic assisted friction stir welding. In previous studies, the effect of ultrasonic vibrations on the mechanical, metallurgical, and thermal properties was investigated and there is not any residual stress investigations on ultrasonic assisted friction stir welding. Since residual stress plays an important role in performance and stability of components, the influence of ultrasonic power on the longitudinal residual stress in friction stir welding is investigated in this work. In spite of residual stress, tensile strength and quality of weldment were investigated as complementary terms to ensure successful performance of ultrasonic assisted friction stir welding. The findings indicated that high-frequency vibrations with power of 200 W can reduce the maximum tensile residual stress about 45% and significantly increase tensile strength. Also, ultrasonic vibrations prevent defect such has voids and tunnel in weld zone due to peening effect in ultrasonic assisted friction stir welding.

Section: Introductionmentioning

confidence: 99%

Residual stress, tensile strength, and macrostructure investigations on ultrasonic assisted friction stir welding of AA 6061-T6

Alinaghian

Amini

The Journal of Strain Analysis for Engineering Design

2018

“…[7][8][9] In recent years, SPD techniques are widely applied in producing the UFG structures in bulk metallic alloys. [10][11][12][13][14] Equal channel angular pressing (ECAP), 15,16 high pressure torsion (HPT), equal channel angular rolling (ECAR), [18][19][20] constrained groove pressing, [21][22][23][24][25] non-equal channel angular pressing 26 and cyclic close die forging (CCDF) 27 are some of the SPD processes which have been recently investigated.…”

Section: Introductionmentioning

confidence: 99%

The effects of combined cyclic close die forging and aging process on microstructure and mechanical properties of AA7075

Moazam

Proceedings of the Institution of Mechanical Engineers, Part L:

2020

Self Cite

It is well known that applying severe plastic deformation methods on the precipitation hardenable aluminum alloys at room temperature is very difficult because of crack formation and segmentation of the specimen during the processes. In this study, several procedures were experimentally examined for performing the cyclic close die forging (CCDF) and improving the mechanical properties of AA7075. The experimental tests revealed that supersaturated solid solution of AA7075 after water quenching is formable for only about 5 min and performing the CCDF process in this limited time is possible. Optical and scanning electron microscopy and transmission electron microscopy were used to study the microstructure of the processed samples. It was observed that by applying two passes of CCDF, the grain size of the material reduced from 30 µm to about 200–300 nm. In addition, the X-ray diffractometer results demonstrated that Guinier–Preston zone picks of the processed samples are very weak and the equilibrium η-phase does not exist in none of the suggested procedures. Furthermore, it was found that by combining CCDF and aging processes according to the proposed procedures, the mechanical properties of the processed AA7075 were improved when compared with the AA7075-T6. To put it more clearly, micro-hardness, yield strength and ultimate tensile stress of the processed sample were improved as much as 38.6%, 25% and 23%, respectively.

“…9 This method was employed to study residual stresses of different materials and manufacturing processes. 11,12,[14][15][16][17][18][19][20][21] Laser bending is a thermal forming process that can be used in different industrial applications. Temperature gradient mechanism (TGM) is one of the common mechanisms of laser forming.…”

Section: Introductionmentioning

confidence: 99%

Through-depth residual stress measurement of laser bent steel–titanium bimetal sheets

Kotobi

The Journal of Strain Analysis for Engineering Design

2018

Laser bending is one of the thermal forming processes which in each pass of it, the temperature of sample increases at heat-affected zone during irradiation time considerably and then it cools to near ambient temperature after passing the laser beam. Consequently, it can be predicted that the process can induce significant residual stress in the sample. In this article, laser bending process of the explosive welded steel-titanium bimetal sample was done and the through-thickness residual stress profile of it was investigated by the slitting method experimentally. The pulse-regularization approach was used to calculate the residual stress in the bimetal sample. Also, simulation of the laser bending process was performed and the numerical residual stress profile was compared with the experimental one. Furthermore, the effects of process parameters including laser power, scanning velocity and number of scanning passes on the bending angle of bimetal samples were investigated experimentally. Besides, the effect of laser bending process on the surface microhardness was studied. The results demonstrated that the laser bending process can create significant residual stress at the heataffected zone of specimen. In the residual stress profile of bimetal sample, a discontinuity was seen at the interface of the materials, as was expected. There was a good agreement between experimental and numerical results. The maximum compressive and tensile residual stresses raised by increase laser power and number of scanning passes. Both of them reduced by magnifying scanning velocity. The laser bending process can increase the surface microhardness at the heat-affected zone which can be attributed to the reduction of grain size at the heat-affected zone.