Analytical description of ultrasonic hardening and softening

Rusinko, Andrew

doi:10.1016/j.ultras.2011.02.003

Cited by 66 publications

(30 citation statements)

References 11 publications

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“…Also, the sound velocity in solid metals can be determined by c L ¼ ffiffiffiffiffiffiffiffiffiffi ffi E=q 0 p for a longitudinal wave. According to earlier literature observations ( Ref 4,6,22,24), the dislocation density evolution shows some changes when the metal experiences ultrasonic vibration during and after stopping of metal forming process. This phenomenon as an acoustic hardening effect can be considered by modification in dislocation density evolution Eq 4.…”

Section: Constitutive Model For Mechanical Behaviormentioning

confidence: 71%

Effect of Ultrasonic Vibration on Compression Behavior and Microstructural Characteristics of Commercially Pure Aluminum

Bagherzadeh

Abrinia

2015

J. of Materi Eng and Perform

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The principle objective of this research is to investigate the modeling of compression behavior and microstructural evolution of pure aluminum in the ultrasonic-assisted compression test. A dislocation density-based constitutive model was developed based on the existing frameworks and calibrated using experimental data to predict the stress-strain response of pure aluminum during UAC tests. An experimental set-up was designed to work at resonance condition with frequency of around 20 kHz and variant longitudinal vibration amplitudes at the range of 0$20 lm. The verified model and experimental samples were used for parameter studies and the study of grain formation of aluminum after conventional and ultrasonic upsetting. Results showed that the developed constitutive model was able to predict compression behavior of aluminum suitably. An increase in the flow stress drop, residual flow stress, and dislocation density occurred when the applied vibration intensity was raised. In addition, it was observed that the more homogenous microstructure with nearly equiaxed grains and also the higher microhardness values can be achieved when ultrasonic vibration is imposed on samples during compression test.

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Section: Constitutive Model For Mechanical Behaviormentioning

confidence: 71%

Effect of Ultrasonic Vibration on Compression Behavior and Microstructural Characteristics of Commercially Pure Aluminum

Bagherzadeh

Abrinia

2015

J. of Materi Eng and Perform

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“…Another group of work models acoustic softening effects by considering the modification of the yield surface and/or reduction in strain hardening [41][42][43][44]. A reduction in the interfacial friction has also been proposed as a cause of ultrasonic softening [23,24] but this idea was subsequently rejected based on finite-element predictions [28] as well as the experimental findings that ultrasonic softening was still observed even when friction was negligible [25,26].…”

mentioning

confidence: 99%

Understanding acoustoplasticity through dislocation dynamics simulations

Siu

Ngan

2011

Philosophical Magazine

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The acoustoplastic effect in metals is routinely utilized in industrial processes involving forming, machining and joining, but the underlying mechanism is still not well understood. There have been earlier suggestions that dislocation mobility is enhanced intrinsically by the applied ultra-sound excitation, but in subsequent deliberations it is routinely assumed that the ultra-sound merely adds extra stresses to the material without altering its dislocation density or intrinsic resistance to deformation. In this study, dislocation dynamics simulation is carried out to investigate the interactions of dislocations under the combined influence of quasistatic and oscillatory stresses. Under such combined stress states, dislocation annihilation is found to be enhanced leading to larger strains at the same load history. The simulated strain evolution under different stress schemes also resembles closely certain experimental observations previously obtained. The discovery here goes far beyond the simple picture that the ultra-sound effect is merely an added-stress one, since here, the intrinsic strain-hardening potency of the material is found to be reduced by the ultra-sound, through its effect on enhancing dislocation annihilation.

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“…The shear strength of the BM declined to 96 MPa after heating to 520 °C and 30 s of USV, which is 8.6% below the strength of the as-received BM. This reduction of shear strength is the result of the reinforced phase reduction and the ultrasonic softening caused by a hybrid field of thermal and USV [33,34,35].…”

Section: Resultsmentioning

confidence: 99%

Microstructure and Formation Mechanism of Ultrasound-Assisted Transient Liquid Phase Bonded Magnesium Alloys with Ni Interlayer

Peng

et al. 2019

Materials

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Ultrasound-assisted transient liquid phase bonding (U-TLP) has been regarded as a promising brazing process to join magnesium alloys with a Sn and Zn interlayer; however, the formation of brittle magnesium intermetallic compounds (Mg2Sn, MgZn, and MgZn2) compromises the mechanical properties of the joints. In this study, Mg alloy U-TLP joints with a Ni interlayer were evaluated based on shear strength and hardness measurement. Microstructural evolution along with ultrasonic duration time and intermetallic compound formation were characterized using X-ray diffraction and electron microscopy methods. The results show that incremental ultrasonic durations of up to 30 s lead to the microstructural evolution from the Mg2Ni layer, eutectic compounds (Mg2Ni and α-Mg) to α-Mg (Ni), accompanied by shear strength increases. The maximum value of the shear strength is 107 MPa. The role that ultrasound vibration played in brazing was evaluated, and showed that the MgO film was broken by the acoustic softening effect when the interlayer and base metal were solid. As the MgO and Mg substrate have different stress reduction τ, this plastic mismatch helps to break the oxide film. Additionally, the diffusion between the solid Mg substrate and Ni interlayer is accelerated greatly by the acoustic pressure based on the DICTRA dynamic calculation.

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Analytical description of ultrasonic hardening and softening

Cited by 66 publications

References 11 publications

Effect of Ultrasonic Vibration on Compression Behavior and Microstructural Characteristics of Commercially Pure Aluminum

Effect of Ultrasonic Vibration on Compression Behavior and Microstructural Characteristics of Commercially Pure Aluminum

Understanding acoustoplasticity through dislocation dynamics simulations

Microstructure and Formation Mechanism of Ultrasound-Assisted Transient Liquid Phase Bonded Magnesium Alloys with Ni Interlayer

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