Electromechanical Surface Research Articles

Control of electroactive shear waves in a piezoelectric waveguide by different surface actions

Abstract In various cases of electromechanical surface actions, the problems of surface control of the propagation of an electroactive transverse wave in a piezoelectric waveguide (piezoelectric class 6 mm of hexagonal symmetry) are considered. In both problems, one of the surfaces of the piezoelectric waveguide is mechanically free, and an electrical displacement normal to the surface acts. The second surface of the waveguide is firmly clamped and grounded, in one task, or there is a drift of electrons over the surface and there are no mechanical effects, in another task. The formulated initial boundary value problems are solved by the method of Fourier series. True electromechanical fields are built in the form of series of eigenmodes of electroacoustic oscillations in accordance with the harmonics of surface effects. Analytical and numerical calculations of the control process in cases of surface action are given.

Study of Wear Resistance of Cylindrical Parts by Electromechanical Surface Hardening

The work scientifically substantiates the use of an effective technology for increasing the wear resistance of cylindrical parts, using the example of protective sleeves of cantilever pumps, due to electromechanical surface hardening. A review of research was carried out and it was established that the achievement of the highest values of microhardness of the surface layer at a depth of up to 1.2 mm is possible during electromechanical processing of protective sleeves of cantilever pumps. The application of various modes and schemes of electromechanical surface hardening (EMSH) is accompanied by a change in structure and, as a result, an increase in the hardness of the surface layer of the bushings. The actual contact area of the tool roller with the processed surface and the depth of the temperature-deformation effect depend on the physical and mechanical properties of the materials and the pressing force. The formation of a temperature gradient in the hardened zone at a depth of up to 1.2 mm from the surface has been proven. Metallographic analysis of the surfaces of the sleeves treated by EMSH shows the formation of a white layer with reduced etchability and increased hardness in the hardening zones. The results of the X-ray structural analysis confirmed the formation of the martensite phase in the hardening zone. The microhardness of the hardened steel zone increased by 2.6...3.6 times compared to the initial values at a depth of up to 1 mm from the surface, depending on the materials. In the case of their overlap, the alternation of a fully hardened zone, a partially hardened zone, and a self-relief zone is observed. At the same time, the microhardness of steels along the surface depends on the hardening scheme.
 Wear tests under friction conditions of parts of cantilever pumps paired with stuffing boxes showed that the wear resistance of protective sleeves after EMSH increased by 3.1 times for 45 steel, 1.9 times for U8 steel, 2.5 times for SHKH15 steel, for cast iron by 1.9 times compared to the initial values. The use of U8 steel samples after EMSH, instead of serial bushings made of steel 45, allows to increase the wear resistance of parts by 6.1 times, which allows us to recommend U8 steel for use in the manufacture of protective bushings for console pumps. On the basis of the research, recommendations are given for the application of EMSH for the formation of a surface layer with increased wear resistance of protective sleeves during their production and during repair of console pumps in workshops or service centers of agribusiness companies.

Electro-mechanical surface wrinkling of a finite block of dielectric elastomers accounting for the pre-stretch and the aspect ratio

Surface instability of elastomers is of great interest in engineering science, especially in the characterization of flexible electronic materials and the manufacture of micro-nano surface topography. There is limited research on how the geometry of the block affects wrinkle appearance in a multiphysics environment. In this paper, we formulate the boundary-value problem and its incremental forms to analyze the sinusoidal surface instability of a neo-Hookean dielectric block subjected to electromechanical loads. We discover that the competition between the Maxwell stress, induced by the voltage, and the mechanical stress caused by the stretch, plays a crucial role in inducing surface wrinkling. Furthermore, we find that the aspect ratio of the block can modify the critical value of the combination of voltage and pre-stretch required for wrinkling. In addition to this, the aspect ratio also affects the shape of the wrinkling. Specifically, if the elastomer block has a smaller aspect ratio, its sinusoidal wrinkling will have a larger wavenumber. Our paper enhances the understanding of surface instability in electrostrictive elastomers and provides guidance on triggering it without breaking down the elastomer.

ВОССТАНОВИТЕЛЬНАЯ НАПЛАВКА И ЭЛЕКТРОМЕХАНИЧЕСКАЯ ПОВЕРХНОСТНАЯ ЗАКАЛКА ЗАМКОВ БУРИЛЬНЫХ ТРУБ

The main reason for the wear of the drill pipe locks when rotating in an open borehole is the presence of a solid layer in aggressive geological formations. (Research purpose) The research purpose is increasing the physical and mechanical properties of the surface layer by researching and developing a technology for hardening the outer surfaces of drill pipe locks restored by electromechanical surface hardening. (Materials and methods) Surfacing was performed on the coupling parts of drill pipes with thread Z-147 in the strength group G105. They were fused with a powder wire of various chemical composition back-to-back with three belts on each sample. Wear tests of surfacing were carried out on a test bench using a special technique (resistance to abrasive wear). The chemical composition of the surfacing indicates a carbon content in the surface layer of 0.28 to 0.40 percent. Methods of restoration of locks by surfacing were examined and the physical and mechanical properties of the surface layer of the restored drill pipes were evaluated, the microstructural state of the base and deposited metal was analyzed. (Results and discussion) It was noted that despite the large number of technologies for surfacing drill pipe locks, the special equipment used, the high labor intensity and cost of surfacing processes and subsequent turning on pipe-cutting machines, it is not possible to increase their wear resistance. This is due to the insufficient hardness of the surface layer of the deposited locks (no more than 28-32 on the Rockwell scale), which does not exceed the surface hardness of the new drill pipe. An experimental increase in the hardness of the surface layer of the deposited samples after electromechanical surface hardening was confirmed. (Conclusions) The results of wear tests of deposited materials indicate the effectiveness of electromechanical surface hardening of reducing surfacing.

On the role of surface stress tensor in the nonlinear response of time-dependent mechanical actuated nanoplate-type energy piezo-harvesters

In the present exploration, the role of surface stress tensor as one of the most important size effects at nanoscale in the nonlinear dynamical behavior of nanoplate-type energy piezo-harvesters under a time-dependent mechanical actuation is investigated. The general form of the energy functional associated with a quasi-3D nanosize energy piezo-harvester incorporating the surface Lame constants and the residual surface stress is derived. After that, by taking the Hamilton’s principle into consideration, the weak form of the surface continuum mechanics-based governing equations for a nanoplate-type energy piezo-harvester is achieved. Afterwards, the meshless collocation strategy is utilized to numerically solve the established coupled electromechanical surface elastic-based nonlinear problem with the aid of implementing a combined form of the polynomial-kind and radial-kind basis functions to eliminate any singularity which may be observed for the associated moment matrices. One can find that for the nanoplate-type energy piezo-harvesters under simply edge supports owning the thickness of and the average value of the achieved voltages are equal to and respectively. However, by taking the role of surface stress tensor into consideration, these values in order reduce to and Moreover, for the nanoplate-type energy piezo-harvesters under clamped edge supports owning the thickness of and the conventional average values of the attained voltages are, respectively, and However, by taking the role of surface stress tensor into consideration, these values in order decrease to and respectively. Therefore, it is deduced that the role of surface stress tensor in the nonlinear dynamical behavior of nanoplate-type energy piezo-harvesters owing lower thickness is more prominent.

Study of structure and properties of surface layer of 38Cr2MoA steel after ion-plasma nitriding and

In the article the results of study of the structure and micro-hardness of the surface layer of 38Cr2MoAl steel after volumetric quenching and high tempering, followed by ion-plasma nitriding, in comparison with electromechanical surface hardening (EMSH) are presented. Experimentally confirmed, that after the EMSH of 38Cr2MoAl steel, a gradient microstructure of finely dispersed martensite, bainite and austenite with a residual hardness of up to 8100 HV MPa and a depth of up to 0.8 mm is formed in the surface layer. At the same time, the maximum microhardness of the surface layer is not on the surface, but at a depth of 0.1 mm. The EMSH is formed by gradient surface layers of metal of high hardness on the surface of products. For a wide range of machine parts, EMSH can be used as a finishing treatment, since it is not accompanied by the presence of defects in the decarburization of the surface layer and deterioration of roughness. After ion-plasma nitriding for 8 hours, the microhardness of the surface layer of 38X2MYA steel was 9030 HV MPa at a depth of 0.1 mm and 8650 HV MPa at a depth of 0.2 mm. At a depth of 0.3 mm, the microhardness of the surface after nitriding and EMP are almost equal, respectively 7230 and 7170 HV MPa. The results of wear tests according to the “rubber roller — fixed sample” scheme and the American Society for Testing and Materials (ASTM G65) “Standard Method for Measuring Abrasive Abrasion using the “Dry Sand” Installation/Rubber wheel” showed high wear resistance of nitrided samples. However, with the continuation of the tests, due to the shallow depth of the nitrided layer (up to 0.3 mm), the wear resistance of the nitrided and hardened samples is leveled. The practical significance of the study is associated with the possibility of reducing the cost of manufacturing parts from nitrided steels by hardening the executive surfaces of the products of the EMSH. In addition, the EMSH allows steel 38Cr2MoAl for surface hardening and subsequent finishing by finishing turning on metal-cutting machines.

ПОВЫШЕНИЕ ИЗНОСОСТОЙКОСТИ ВТУЛОК ЗАЩИТНЫХ КОНСОЛЬНЫХ НАСОСОВ ЭЛЕКТРОМЕХАНИЧЕСКОЙ ПОВЕРХНОСТНОЙ ЗАКАЛКОЙ

Based on the analysis of the working condition of the cradle-mounted pumps and the specific defects of protective bushings,the authors offer a technological solution for increasing the wear resistance of the outer surface of parts by the method of electromechanical surface hardening (ESH). The article describes the effects of progressions in the structure and microhardness of the surface layer of bushings made of steel 45 and U8. The authors experimentally found that the microhardness of the samples after ESH increased from 240 НV to 765 НV for steel 45 and from 340 НV to 876 НV for steel U8. The authors designed a stand, conducted wear tests of the samples, and reproduced the application environment of the “protective sleeve – stuffing box” connection of the cradle-mounted pump. The test results have shown that, compared with standard technologies for strengthening bushes, ESH increased the wear resistance of specimens from steel 45 in 3.1 times, while those of steel U8-1.9 times. In particular, using samples made of U8 steel after ESH, instead of serial bushes made of steel 45, may increase the wear resistance of products in 6.1 times. The research results give reasons to recommend the ESH technology to improve the wear resistance of protective bushings during their manufacture and the repair of the cradle-mounted pump.

Formation of structure and properties of surface layer of case-hardened steel by electromechanical surface hardening

The researching results of the structure and microhardness of the surface layer of steel 20 after vacuum cementation of cylindrical samples to a depth of 1,0 mm and their hardening by volumetric heat treatment in comparison with electromechanical surface hardening are presented. The maximum microhardness of the surface layer of cemented steel 20 is at a depth of 0,05 mm and corresponds to 9650 HV MPa, and gradually decreases within the hardened layer to 8190 HV MPa at a depth of up to 0,75 mm after electromechanical surface hardening has been experimentally established. There isn’t decarbonized layer after the electromechanical surface hardening of cemented steel samples 20. The reaserch practical significance is associated with the possibility of improving the quality and reducing the cost of parts producting from cemented steels by replacing heat treatment after cementation with the technology of hardening the working surfaces by electromechanical surface hardening.

РАСЧЕТ ТЕМПЕРАТУРНОГО ПОЛЯ УПРОЧНЕННОГО СЛОЯ ПРИ ЭЛЕКТРОМЕХАНИЧЕСКОЙ ПОВЕРХНОСТНОЙ ЗАКАЛКЕ

The main methods of surface hardening during electromechanical processing (EMP) include finishing-hardening electromechanical processing (FHEMP) and electromechanical surface hardening (EMSH). EMSH, as compared with the FHEMP modes, features a slow processing speed (0.6…1.4 m/min), a long contact width of up to 5 mm, a significant electric current strength of the secondary circuit – 1200…3000 A. The article presents a three-dimensional model for predicting and determining the temperature fields of the hardened layer of U8 steel bushings during EMSH made in the ANSYS Workbench program. The authors carried out finite element modeling of the EMSH process consisting of successive transient structural strength analysis and transient thermal analysis. During EMSH, the thermomechanical cycle “heating – keeping – deformation – cooling” is carried out in the closed contact zone of the tool and the workpiece in hundredths of a second. It was found that during EMSH a temperature gradient is formed along the depth of the hardened zone as there is intensive cooling of the surface layer heated to 1559°C, as a result of heat removal by the underlying metal layers. After EMSH a fine-dispersed martensite is formed in the hardened zone. The study results are useful for developing the EMSH processing technology of the surface layer of bushings made of U8 steel based on the hardening mode with the following parameters: hardening speed of 1.2 m/min, the current strength in the secondary circuit of 1600 A, the secondary circuit voltage of 3 V; the width of the contact electric effect of 4 mm; the pressing force of the tool roller of 400 N.

Analysis of the Regular Macrostructure of a Carbon Steel Surface Layer Subjected to Electromechanical Treatment and Surface Plastic Deformation

Analysis of the Regular Macrostructure of a Carbon Steel Surface Layer Subjected to Electromechanical Treatment and Surface Plastic Deformation

Investigation into morphological and electromechanical surface properties of reduced-graphene-oxide-loaded composite fibers for bone tissue engineering applications: A comprehensive nanoscale study using atomic force microscopy approach

We decided to implement an extensive atomic force microscopy study in order to get deeper understanding of surface-related nanoscale properties of 3D printed pristine polycaprolactone and its reduced-graphene-oxide-loaded composites. The study included surface visualization and roughness quantification, elastic modulus and adhesion force assessment with force spectroscopy, along with kelvin probe force microscopy evaluation of local changes of surface potential. Atomic force microscopy examination was followed by scanning electron microscopy visualization and wettability assessment. Moreover, systematic examination of reduced graphene oxide flakes fabricated exclusively for this study was performed, including: scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and combustion elemental analysis.The addition of reduced graphene oxide resulted in thickening of the composite fibers and surface roughness enhancement. In addition, elastic modulus of composite fibers was higher and at the same time adhesion forces between scanning probe and tested surface was lower than for pristine polymeric ones. Lastly, we recorded local (nanoscale) alterations of surface potential of fibers with addition of graphene-derivative. The results clearly suggest graphene derivative’s dose-dependent alteration of elastic modulus and adhesion force recorded with atomic force microscope. Moreover, changes of the material's surface properties were followed by changes of its electrical properties.

Увеличение ресурса оборудования электромеханической поверхностной закалкой

The paper analyzes traditional methods of hardening. The results of comparative wear tests of the samples made of 20KhNZA steel after nitrocementation and electromechanical surface quenching are presented. The results of the wear tests of the samples made of steel 20KHN3A after nitrocementation and electromechanical surface quenching indicate the high efficiency of the electromechanical processing technology. A competitive feature of the technology of electromechanical surface quenching of parts made of 20KHNZA steel is the possibility of flexible control of the parameters of high-speed electric heating and simultaneous thermoplastic deformation of the material of the surface layer of the most loaded parts in order to form gradient fast-quenched structures at a depth of up to 0.05…0.1 mm in the manufacture and repair of parts. Conclusions and recommendations on the method of using these types of hardening are providedю English version of the article is available at URL: https://panor.ru/articles/increasing-the-equipment-service-life-by-electromechanical-surface-quenching/64911.html

The Influence of Surface Hardening by Combined Thermo-Forced Impacts on the Fatigue Life and Damage of the VT22 Titanium Alloy

The influence of electromechanical surface treatment (EMT) and nonabrasive ultrasonic finishing (NAUF) on the titanium alloy and the complex influence of the above treatment methods and subsequent aging on the fatigue life and the change in the surface microhardness is studied. Specimens for research are made of rods manufactured of the transition VT22 alloy after the standard thermomechanical treatment. The EMT is conducted by rolling the surface of the specimen with a roller pressed to it and passing a high-density current between them. As a result, the surface thermomechanical treatment is conducted under fast local heating and cooling of the surface. The NAUF is performed by shock treatment with a striking ultrasonic emitter on the treated surface. The rotational bending loading of specimens at stress amplitude of 0.5σu upon the NAUF results in an increase in fatigue life by a factor of 1.8 in comparison with the untreated initial state, accompanied by a slight increase in the microhardness of up to 16%. The EMT reduces microhardness by almost 20% and fatigue life by 70%. The combined processing by EMT + NAUF insignificantly affects microhardness, but increases the life by 40% compared with the EMT. Aging at a temperature of 450°C for 5 h increases the microhardness upon the EMT by 30–40% with a simultaneous twofold increase in durability. The aging of the specimens subjected to EMT + NAUF practically does not increase microhardness, but it increases durability by almost three times compared with the EMT. A fractographic analysis of the fracture surface has shown that the reduction in the life after EMT is associated with a reduction in the stage of crack initiation, which virtually excludes this stage of accumulation of fatigue damage from the overall durability of the specimen.

Influence of surface hardening by combined thermal force impacts on VT22 titanium alloy fatigue life and damage

The study covers the influence of electromechanical surface treatment (EMT), non-abrasive ultrasonic finishing (NAUF), their complex influence with subsequent aging on the fatigue life and surface microhardness changes. Samples for research were made of VT22 transition alloy rods after standard thermomechanical treatment. EMT was carried out by sample surface rolling with a roller and applying a high density current between them. As a result, surface thermomechanical treatment was carried out with the local fast surface heating and cooling. NAUF were implemented by shock treatment with an ultrasonic emitter striking on the treated surface. This revealed 1.8 times higher fatigue life when loading by rotational bending (with amplitude of 0.5σв) for samples after NAUF in comparison with the untreated initial state together with a slight increase in microhardness (up to 16 %). EMT reduces microhardness and fatigue life by almost 20 % and 70 %, respectively. EMT + NAUF complex processing has an insignificant effect on microhardness, but it increases fatigue life by 40 % with respect to EMT. Aging at 450 °C for 5 hours increases microhardness after EMT by 30–40 % with a simultaneous increase in fatigue life by 2 times. The aging of samples subjected to EMT + NAUF revealed virtually no increase in microhardness, but increased fatigue life by almost 3 times (as compared to EMT). According to fractography results, the reduction in fatigue life after EMT is associated with a reduction in the crack initiation stage, which virtually excludes this stage of fatigue damage accumulation from the overall sample fatigue life.

Improving wear resistance of drill pipe sub thread by using final electromechanical surface hardening

Improving wear resistance of drill pipe sub thread is a vital task, and finding effective solution for it would much assist oil and gas companies to enhance well construction process. The report presents the results of comparative wear resistance tests for P147/147 and P133/133 subs of the top drive manufactured by OOO «NIGMASH» in Bashkortostan. The tests were performed by OOO «Tatburneft» holding company, a division of PAO «TATNEFT». Both, series and test subs were made from 40X2H4A steel. This report shows the results of metallographic studies and tests for improvement of the parts wear resistance, including the method of final electromechanical hardening (EMH) of the box and pin threads as compared with the conventional method of bulk heat treatment.The researches has developed the equipment, tools and technology for hardening of tool joint thread of drill pipe subs. The performed tests and studies aimed at enhancing efficiency of oil and gas well drilling. Their results are of much interest for oilfield operators, drilling and service contractors, as well as drilling subs manufacturers and repair companies.

Voltage- and Frequency-Based Separation of Nanoscale Electromechanical and Electrostatic Forces in Contact Resonance Force Microscopy: Implications for the Analysis of Battery Materials

In piezoresponse force microscopy and electrochemical strain microscopy (PFM, ESM), not only nanoscale electromechanical surface displacements (e.g., Vegard strain in case of ESM) are amplified in ...

TECHNOLOGY OF COMBINED ELECTROMECHANICAL TREATMENT WITH PROFILE ROLLING

The technology of combined electromechanical treatment with profile rolling is presented, which is a combination of electromechanical treatment and surface plastic deformation, which allows to create on the surface directed regular microrelief. The proposed technology is tested during processing of parts of multipurpose tracked and wheeled machines operating under difficult loading conditions, signalternating dynamic loads, often with limited lubricant or presence of abrasive in its composition. Reasonable selection of relief (pattern) of treated surface makes it possible to maximize retention of lubricating material in zone of tribocontact, as well as to increase wear resistance of parts and to create residual compression stresses in surface layer. The mechanical properties of the surface layer of the sample with a strengthened geometric pattern by changing the microhardness of the smoothed surface and oil pockets (channels) obtained by surface plastic deformation were examined. Electromechanical treatment by rolling the profile makes it possible to create on the surface a strengthened surface layer with naturally varying parameters with the specified regular micro-relief including oil pockets (channels) and reinforced tracks, at the same time considerable increase of wear resistance of triboscreating is provided.

Visualization of moiré superlattices.

Moiré superlattices in van der Waals heterostructures have given rise to a number of emergent electronic phenomena due to the interplay between atomic structure and electron correlations. Indeed, electrons in these structures have been recently found to exhibit a number of emergent properties that the individual layers themselves do not exhibit. This includes superconductivity1,2, magnetism3, topological edge states4,5, exciton trapping6 and correlated insulator phases7. However, the lack of a straightforward technique to characterize the local structure of moiré superlattices has thus far impeded progress in the field. In this work we describe a simple, room-temperature, ambient method to visualize real-space moiré superlattices with sub-5-nm spatial resolution in a variety of twisted van der Waals heterostructures including, but not limited to, conducting graphene, insulating boron nitride and semiconducting transition metal dichalcogenides. Our method uses piezoresponse force microscopy, an atomic force microscope modality that locally measures electromechanical surface deformation. We find that all moiré superlattices, regardless of whether the constituent layers have inversion symmetry, exhibit a mechanical response to out-of-plane electric fields. This response is closely tied to flexoelectricity wherein electric polarization and electromechanical response is induced through strain gradients present within moiré superlattices. Therefore, moiré superlattices of two-dimensional materials manifest themselves as an interlinked network of polarized domain walls in a non-polar background matrix.

Free Radical Generation from High-Frequency Electromechanical Dissociation of Pure Water.

We reveal a unique mechanism by which pure water can be dissociated to form free radicals without requiring catalysts, electrolytes, or electrode contact by means of high-frequency nanometer-amplitude electromechanical surface vibrations in the form of surface acoustic waves (SAWs) generated on a piezoelectric substrate. The physical undulations associated with these mechanical waves, in concert with the evanescent electric field arising from the piezoelectric coupling, constitute half-wavelength "nanoelectrochemical cells" in which liquid is trapped within the SAW potential minima with vertical dimensions defined by the wave amplitude (∼10 nm), thereby forming highly confined polarized regions with intense electric field strengths that enable the breakdown of water. The ions and free radicals that are generated rapidly electromigrate under the high field intensity in addition to being convectively transported away from the cells by the bulk liquid recirculation generated by the acoustic excitation, thereby overcoming mass transport limitations that lead to ion recombination.

Structure and Microhardness of the Tubing Thread After Finishing Electromechanical Surface Quenching

We present the results of metallographic investigations of the structure and microhardness and the results of the bench tests of the threads of tubings made of steels of the strength class D after finishing electromechanical surface quenching in pairs with commercial couplings.