Application of Internal Friction to Analysis of Plastic Behaviour of Crystals

Лебедев, А. Б.

doi:10.1051/jp4:1996855

Cited by 3 publications

(6 citation statements)

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“…A vibrational stress that gives rise to the amplitude dependent damping (ADD) and Young's modulus defect (ADMD) is compared, usually, as a function of temperature with a temperature dependence of the yield point. In this case, we compare micro-and macro-plastic properties and, sometimes, one can find similar behavior [4][5].…”

Section: Introductionmentioning

confidence: 93%

“…A correlation of acoustic (Young's modulus, internal friction) and mechanical (plasticity and strength) properties of crystals has been discussed for a long time [1][2][3][4][5][6][7]. Non-destructive acoustic techniques allow to investigate in detail dislocation mechanisms that control, in some way, both plastic deformation and mechanical strength.…”

Section: Introductionmentioning

confidence: 99%

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Micro- and Macro-Plastic Properties of Be Polycrystals

Kardashev

Kupriyanov²

2012

SSP

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The Young’s modulus and internal friction of Be polycrystals (grain sizes 6-60 μm) prepared with a powder metallurgy technique were studied acoustically in both amplitude independent and-dependent damping ranges. The measurements were made by composite oscillator at resonant frequencies of longitudinal vibrations of about 100 kHz in the temperature range of 100-873 K. The data were used to get information about micro-flow properties at vibration stresses of 0,2-30 MPa. It was found that the micro-flow diagrams became non-linear at amplitudes higher than 5 MPa. Mechanical properties (acoustic micro-flow stress σy, yield point σ0.2 and ultimate strength σВ) as functions of grain size have shown clearly a correlation in the framework of Hall and Petch law at room temperature but this similarity is not complete: stresses σ0.2 and σВ are one order of magnitude higher and change more steeply with grain size as compared to σy. The similarity is not observed for the temperature dependences. The values of σ0.2(Т) and σВ(T) decrease smoothly at higher temperatures but σу(Т) demonstrates an unusual minimum at ~400 K. The different behavior of the acoustic and mechanical stresses proves, evidently, that the ultrasonic energy losses and the flow stress level are due to the different nature of obstacles for the vibration (near equilibrium positions) and translation movement of dislocations in beryllium.

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Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Micro- and Macro-Plastic Properties of Be Polycrystals

Kardashev

Kupriyanov²

2012

SSP

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“…According to [25] in nonlocalized friction theory r changes from 0 to 4 for power amplitude dependences of h d and M M ¡ . Lebedev [26] investigated the influence of the shape of ( ) e s on the ratio ( )…”

Section: Different Kinds Of Hysteretic Stress-strain Loopmentioning

confidence: 99%

“…The curves ( ) taken from 24 works (see References in [26]). It is seen that the majority of experimental points occupies the field of curves for nonlocalized friction models.…”

Section: Different Kinds Of Hysteretic Stress-strain Loopmentioning

confidence: 99%

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Amplitude - Dependent Internal Friction and Plasticity of Crystals

Nikanorov

2003

SSP

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IntoductionIt is well known that amplitude-dependent internal friction (ADIF) in crystals is created by the interaction between dislocations and point defects (PD). There is a number of theories of dislocation ADIF and numerous experimental tests of them. This review is devoted to works where base theories in this field were probed by means of experiments performed in Ioffe Physical -Technical Institute. A wide scope of investigation of ADIF in Ioffe Institute enables to pass in the review the main directions of developing in this field of Mechanical Spectroscopy. That approach gives rather full consideration of mechanisms and facilities of internal friction (IF) to study the plasticity of crystals. Of course, IF is indirect method of the study of plasticity. Therefore in the beginning of the overview of investigations in Ioffe Institute the main theories of ADIF will be given in their historic development.Read [1,2] in 1940 showed that plastic deformation influences on ultrasound damping in wide region of oscillation amplitudes. Some earlier, Davidenkov, 1938, in Ioffe Institute suggested the conception of ADIF as a result of nonlinear microplastic deformation [3]. It is possible to say that Read's experiments were the first confirmation of Davidenkov's hypothesis in dislocation terms. These works woke up the interest to ADIF and Young's modulus defect (YMD) of crystals in connection with the possibility to obtain new additional information about plastic deformation and dislocation dynamics by measurements at very low stress level. The most of dislocation theories of ADIF can be divided into two groups: the theory of the breakaway and the theory of unlocalized friction. The former is based on Granato-L cke theory [4]. According to this theory based on the string model of dislocation [5], there are two mechanisms of energy losses. The amplitudeindependent IF results from forced vibrations of free dislocation between the weak pinning points on the ends (dislocation resonance damping). This damping is determined only by dislocation viscous drag by phonons and electrons. The other mechanism, ADIF is explained by pulling the dislocations away from their weak pinning points (dislocation breakaway damping). This damping increases strongly with strain amplitude. The second group of models considers the motion of a dislocation by overcoming a number of potential barriers. The averaged friction stress operating on moving dislocation is considered in the framework of the models. Breakway ModelsAccording to Granato-L cke [6,7] the dislocation structure consists of segments of the length n L along which PD are randomly distributed. Segments are strictly pinned on the ends in the nods of dislocation net. The PD are the weak pinning points. The mean distance between them is l with n L l << .

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Influence of Ultrasonic Vibrations on Shape Memory Effect

Рубаник¹,

Klubovich²

2015

MSFo

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The results of studies on the influence of ultrasonic vibrations (UVs) on shape memory effect (SME) in NiTi alloys are presented. The appearance of shape memory effect is due to changes in the temperature and mechanical stress. They can operate simultaneously under the ultrasonic treatment. It has been found that the ultrasonic vibrations can initiate shape recovery processes in a material with shape memory effect. The reversion of the accumulated deformation occurs at the direct and reverse martensite transformations under the influence of ultrasonic vibrations. Since the process is accompanied by ultrasonic heating, small thermal-mechanical hysteresis loops have been observed during the direct transformation. The deformation reversion can be explained by ultrasonic heating of the sample due to the dissipation of vibrations and the formation of austenite.The vibration influence of ultrasonic frequency on a material causes its considerable heating due to the irreversible dissipation of acoustic energy in it. The temperature distribution along the length of the sample depends on the frequency of the applied vibrations. It is also associated with the occurrence of a longitudinal coincident ultrasonic wave in the sample.The TiNi sample surface has been studied using infrared thermography. The maximum heating is observed at the displacement of nodes and the minimum heating at antinodes of the mechanical vibration displacement during the ultrasonic influence. The differential temperature along the length of the sample during its heating is approximately 20C due to energy absorption of UVs. The UVs do not cause further heating of the waveguide in the austenite state. The temperature distribution along the sample is stabilized.It has been determined that the phase transformation in the material starts and finishes under the ultrasound action at a lower temperature. The interval of finishing temperature decrease of the reverse phase transformation is equal to 25C. It is explained by the fact that the mechanical alternating-sign stresses speed up the movement of interfaces, which are responsible for the SME realization.Ultrasonic heating can lead to a consistent implementation of the shape memory effect over the length of the sample ("sliding SME"). This is due to the localization of mechanical stress of ultrasonic vibrations that causes the separation of the sample by the phase transformation zone into two areas: the low and high temperatures. This way of deformation processes is different from the implementation of SME during heating of the material applying electric current or uniformly from the surface. It extends the use of constructions based on shape memory effect.It has been found that the variation of phase yield stress depends on the phase state of the material. The alloy shows "normal" acoustic softening in the martensite and austenite phases under the ultrasonic treatment. .It is similar to that observed for most metals that do not undergo the phase transformation. The anomalous behaviour of the yield stress...

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Application of Internal Friction to Analysis of Plastic Behaviour of Crystals

Cited by 3 publications

References 36 publications

Micro- and Macro-Plastic Properties of Be Polycrystals

Micro- and Macro-Plastic Properties of Be Polycrystals

Amplitude - Dependent Internal Friction and Plasticity of Crystals

Influence of Ultrasonic Vibrations on Shape Memory Effect

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