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2 Archives of Civil and Mechanical Engineering

2 2021

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Study on constitutive behavior of Ti-45Nb alloy under transversal ultrasonic vibration-assisted compression

Wang Xingxing, Qi Zhenchao, Chen Wenliang

Archives of Civil and Mechanical Engineering

2021

Vol. 21, no. 1

518--532

Ultrasonic vibration technology has been widely applied in plastic forming processes due to its advantages of material properties improvement. In this study, a transverse ultrasonic vibration-assisted compression (TUVC) system with the range of vibration amplitude from 16 to 48 µm is developed to compress the difficult-to-deformation materials. The experiment found that the temperature of the compressed sample with the vibration amplitude of 38 µm arrived at 164 ℃, hence the current constitutive models are deficient for the description of TUVC deformation behavior with the large vibration amplitudes. The results show that the flow stress declines under the coupling action of volume effect and surface effect, especially the amplitude is larger than 38 µm. To accurately depict the constitutive behavior of titanium alloy under TUVC, a hybrid constitutive model considering the difference of softening mechanism was proposed based on crystal plasticity theory, and the predicted curves are in good agreement with experimental results. Finally, the microstructure further revealed the differences of softening mechanism in TUVC, and numerous secondary α phase was precipitated. Consequently, the studies provide an insight into the deformation mechanism of TUVC and promote the application of ultrasonic vibration-assisted forming for the difficult-to-deformation alloy.

Investigation of acoustic-plastic constitutive modeling based on Johnson-Cook model and numerical simulation application

Wang Xingxing, Qi Zhenchao, Chen Wenliang

Archives of Civil and Mechanical Engineering

2021

Vol. 21, no. 2

605--620

In this paper, a modified acoustic-plastic Johnson–Cook model for Ti–45Nb alloy was established, which can be used to reveal the metallic deformation behavior under ultrasonic vibration-assisted (TUV) forming. First, the experiments of traditional compression and TUV compression were carried out, the influence of vibration amplitude on yield strength, strain hardening coefficient and index, and strain rate hardening coefficient. The yield strength reduction is caused by the acoustic softening effect. The yield strength and strain hardening coefficient present a negative correlation with amplitude increase, the strain hardening index and strain rate hardening coefficient present a positive correlation with amplitude increase. Further, the accuracy of the developed constitutive model was quantitatively identified, the relative coefficient is as high as 0.954, the mean absolute percentage error less than 5.42%. On this basis, a user-defined subroutine was developed to implement the numerical simulation of the TUV forming processes using the finite element method, the results of numerical simulation and experiment are in good agreement, and prediction accuracy is as high as 95.25%. Therefore, the developed constitutive model can be well revealed the material deformation behavior and provides an application guide.