Effect of ultrasonic and mechanical vibration treatments on evolution of Mn-rich phases and mechanical properties of Al−12Si−4Cu−1Ni−1Mg−2Mn piston alloys

Effects of ultrasonic vibration(UV)and mechanical vibration(MV)on the Mn-rich phase modification and mechanical properties of Al−12Si−4Cu−1Ni−1Mg−2Mn piston alloys were investigated.The results show that the UV and UV+MV treatments can significantly refine and fragmentize the microstructures.In addition,UV treatment can significantly passivate the primary Mn-rich Al15Mn3Si2 intermetallics.The formation mechanisms of refinement and passivation of the grains and non-dendrite particles were discussed.Compared with the gravity die-cast alloys,the UV and UV+MV treated alloys exhibit improved tensile and creep resistance at room and elevated temperatures.These results can be attributed to the refinement of theα(Al)grains and the secondary intermetallics,the increased proportion of refined heat-resistant precipitates,and the formation of nano-sized Si particles.The ultimate tensile strength of the UV treated alloys at 350℃ exceeds that of commercial piston alloys.This indicates the high application potential of the developed piston alloys in density diesel engines.

Research on modeling and self-excited vibration mechanism in magnetic levitation-collision interface coupling system

The modeling and self-excited vibration mechanism in the magnetic levitation-collision interface coupling system are investigated.The effects of the control and interface parameters on the system's stability are analyzed.The frequency range of self-excited vibrations is investigated from the energy point of view.The phenomenon of self-excited vibrations is elaborated with the phase trajectory.The corresponding control strategies are briefly analyzed with respect to the vibration mechanism.The results show that when the levitation objects collide with the mechanical interface,the system's vibration frequency becomes larger with the decrease in the collision gap;when the vibration frequency exceeds the critical frequency,the electromagnetic system continues to provide energy to the system,and the collision interface continuously dissipates energy so that the system enters the self-excited vibration state.

Dynamic analysis of a novel multilink-spring mechanism for vibration isolation and energy harvesting

Due to technical limitations,existing vibration isolation and energy harvesting(VIEH)devices have poor performance at low frequency.This paper proposes a new multilink-spring mechanism(MLSM)that can be used to solve this problem.The VIEH performance of the MLSM under harmonic excitation and Gaussian white noise was analyzed.It was found that the MLSM has good vibration isolation performance for low-frequency isolation and the frequency band can be widened by adjusting parameters to achieve a higher energy harvesting power.By comparison with two special cases,the results show that the MLSM is basically the same as the other two oscillators in terms of vibration isolation but has better energy harvesting performance under multistable characteristics.The MLSM is expected to reduce the impact of vibration on high-precision sensitive equipment in some special sites such as subways and mines,and at the same time supply power to structural health monitoring devices.

Microstructure and forming mechanism of metals subjected to ultrasonic vibration plastic forming: A mini review

Compared with traditional plastic forming,ultrasonic vibration plastic forming has the advantages of reducing the forming force and improving the surface quality of the workpiece.This technology has a very broad application prospect in industrial manufactur-ing.Researchers have conducted extensive research on the ultrasonic vibration plastic forming of metals and laid a deep foundation for the development of this field.In this review,metals were classified according to their crystal structures.The effects of ultrasonic vibration on the microstructure of face-centered cubic,body-centered cubic,and hexagonal close-packed metals during plastic forming and the mech-anism underlying ultrasonic vibration forming were reviewed.The main challenges and future research direction of the ultrasonic vibra-tion plastic forming of metals were also discussed.

Effect of mechanical vibration process parameters on the cement plugs properties for abandoned wells

A high-quality plug of the abandoned wellbore is considered an essential technical aspect of the oil and gas well abandonment technology system. This paper presents a method of active mechanical excitation to enhance the quality of wellbore plug barriers. An indoor simulation platform is developed, and the effects of different combinations of vibration frequency, amplitude and duration on the properties of the wellbore plug cement material are investigated. It is observed that the optimal combination of excitation parameters occurs at a vibration frequency of 15 Hz, a vibration time of 6 min, and a vibration amplitude of 3 mm. Compared with the condition without the vibration process, the cementing strength, compressive strength, and tensile strength of wellbore cement plug with the optimal mechanical vibration process could increase by 51%, 38% and 20%, respectively, while the porosity decreases by 5%. As determined by scanning electron microscopy of the set cement's microstructure, mechanical vibration effectively eliminates internal porosity and improves the set cement's density. The optimal excitation parameters obtained from the test can guide the design of the vibration plugging tool. The designed vibration plugging tool is simulated in the near field. The cement plug cementation quality tester tests the vibrating and non-vibrating samples, and the cementation ratio is calculated. The test results show that the average cementation ratio of vibrating samples is 0.89375, and that of non-vibrating samples is 0.70625, and the cementation quality is improved by 27%. It is concluded that it not only provides essential data for the design of mechanical vibration plug apparatus, on-site vibration plugs, and the development of operational specifications for vibration plugs, but also provides solid engineering guidance.

Effects of mechanical vibration on filling and solidification behavior, microstructure and performance of Al/Mg bimetal by lost foam compound casting

Al/Mg bimetal was prepared by lost foam solid-liquid compound casting,and the effects of mechanical vibration on the filling and solidification behavior,microstructure and performance of the bimetal were investigated.Results show that the mechanical vibration has a remarkable influence on the filling and solidification processes.It is found that after mechanical vibration,the filling rate increases and the filling rate at different times is more uniform than that without vibration.In addition,the mechanical vibration also increases the wettability between liquid AZ91D and A356 inlays.The mechanical vibration reduces the horizontal and vertical temperature gradient of the casting and makes the temperature distribution of the whole casting more uniform.Compared to the Al/Mg bimetal without vibration,the shear strength is improved by 39.76%after the mechanical vibration is applied,due to the decrease of the inclusions and Al_(12)Mg_(17) dendrites,and the refinement and uniform distribution of the Mg_(2)Si particles in the interface of the Al/Mg bimetal.

Influence of high frequency vibration on microstructure and mechanical properties of TIG welding joints of AZ31 magnesium alloy

A device for superimposing vibration on workpiece in both horizontal and vertical directions during tungsten-arc inert gas （TIG） welding was developed, with maximum power output of 2 kW at frequency of 15 kHz. AZ31 sheets with thickness of I and 3 mm were used in the vibratory welding. Microstructures along with the mechanical properties of the weld joints under different vibrating conditions （vibration direction, vibration amplitude and groove angle） were examined. It is observed that the grain size in welding zone decreases remarkably with the application of vibration, while the amount of second phase β-Mg_17Al_12 within the zone decreases slightly; meanwhile, microhardness of the weld joints, macroscopic tensile strength and elongation of the weldment increase. Vibration, especially the one along vertical direction, has more impact on the performance of the thick weldments. Influence of vibration on mierostructure and mechanical properties of weldments is affected by wave energy transferring in the melt and depends on the processing and geometric parameters including amplitude and direction of vibration, thickness, and groove angles.

Grain refinement of Al-5%Cu aluminum alloy under mechanical vibration using meltable vibrating probe

A mechanical vibration technique to refine solidified microstructure was reported. Vibration energy was directly introduced into a molten alloy by a vibrating horn, and the vibrating horn was melted during vibration. Effects of vibration acceleration and mass ratio on the microstructure of Al-5% Cu alloy were investigated. Results show that the present mechanical vibration could provide localized cooling by extracting heat from the interior of molten alloy, and the cooling rate is strongly dependent on vibration acceleration. It is difficult to refine the solidified microstructure when the treated alloy keeps full liquid state within the entire vibrating duration. Significantly refined microstructure was obtained by applying mechanical vibration during the initial stage of solidification. Moreover, mechanisms of grain refinement were discussed.

Permeability evolution mechanism and the optimum permeability determination of uranium leaching from low-permeability sandstone treated with low-frequency vibration

Low-frequency vibrations can effectively improve natural sandstone permeability,and higher vibration frequency is associated with larger permeability.However,the optimum permeability and permeability evolution mechanism for uranium leaching and the relationship between permeability and the change of chemical reactive rate affecting uranium leaching have not been determined.To solve the above problems,in this study,identical homogeneous sandstone samples were selected to simulate lowpermeability sandstone;a permeability evolution model considering the combined action of vibration stress,pore water pressure,water flow impact force,and chemical erosion was established;and vibration leaching experiments were performed to test the model accuracy.Both the permeability and chemical reactions were found to simultaneously restrict U6þleaching,and the vibration treatment increased the permeability,causing the U6þleaching reaction to no longer be diffusion-constrained but to be primarily controlled by the reaction rate.Changes of the model calculation parameters were further analyzed to determine the permeability evolution mechanism under the influence of vibration and chemical erosion,to prove the correctness of the mechanism according to the experimental results,and to develop a new method for determining the optimum permeability in uranium leaching.The uranium leaching was found to primarily follow a process consisting of(1)a permeability control stage,(2)achieving the optimum permeability,(3)a chemical reactive rate control stage,and(4)a channel flow stage.The resolution of these problems is of great significance for facilitating the application and promotion of lowfrequency vibration in the CO_(2)+O_(2) leaching process.

Mechanical properties of 2024-T4 aluminium alloy joints in ultrasonic vibration enhanced friction stir welding

Ultrasonic vibration enhanced friction stir welding （UVeFSW） is a recent modification of conventional friction stir welding （FSW）, which transmits ultrasonic vibration directly into the localized area of the workpiece near and ahead of the rotating tool. In this study, a high strength aluminium alloy （2024-T4） was welded by this process and conventional FSW, respectively. Then tensile tests, microhardness tests and fracture surface analysis were performed successively on the welding samples. The tests results reveal that ultrasonic vibration can improve the tensile strength and the elongation of welded joints. The microhardness of the stir zone also increases.

The dynamic characteristics of harvesting energy from mechanical vibration via piezoelectric conversion

As an alternative power solution for low-power devices, harvesting energy from the ambient mechanical vibration has received increasing research interest in recent years. In this paper we study the transient dynamic characteristics of a piezoelectric energy harvesting system including a piezoelectric energy harvester, a bridge rectifier, and a storage capacitor. To accomplish this, this energy harvesting system is modeled, and the charging process of the storage capacitor is investigated by employing the in-phase assumption The results indicate that the charging voltage across the storage capacitor and the gathered power increase gradually as the charging process proceeds, whereas the charging rate slows down over time as the charging voltage approaches to the peak value of the piezoelectric voltage across the piezoelectric materials. In addition, due to the added electrical damping and the change of the system natural frequency when the charging process is initiated, a sudden drop in the vibration amplitude is observed, which in turn affects the charging rate. However, the vibration amplitude begins to increase as the charging process continues, which is caused by the decrease in the electrical damping （i.e., the decrease in the energy removed from the mechanical vibration）. This electromechanical coupling characteristic is also revealed by the variation of the vibration amplitude with the charging voltage.

Influence of mechanical vibration on the solidification of a lost foam cast 356 alloy

Mechanical vibration was applied to the solidification of a lost foam cast(LFC) 356 aluminum alloy.Effects of mechanical vibration,with different peak acceleration,on the size and morphology of α-Al phase,and also on the mechanical properties of the castings were studied.Results indicated that α-Al dendrites gradually grow into equiaxed grains as the peak acceleration of vibration is increased.When the peak acceleration is between about 1 to 4 g,α-Al phase distribution is uniform and is refined obviously.α-Al dendrites are reduced and the mechanical properties of the castings are improved significantly when compared to those of the castings that are produced without vibration.However,when the peak acceleration is higher than 4 g,strong vibration will lead to defects formation,such as sand adhesion,while the amount and size of pores will be increased.And due to the turbulent flow that caused by strong vibration,the chance of forming large pores in the matrix has been increased significantly.The increase in defects will result in the deterioration of mechanical properties.

Mechanism of burst feeding in ZL205A casting under mechanical vibration and low pressure

The burst feeding behavior of ZL205 A casting under mechanical vibration and low pressure was investigated by casting experiment and physical model. Experimental results indicated that the burst feeding appeared repeatedly during solidification and left a shrinkage cavity with layered structure under mechanical vibration. The castings with less shrinkage and higher density could be achieved through the vibration. The calculation results of physical model showed that the burst feeding could perform spontaneously under vibration while difficultly without vibration in low-pressure die casting. The obstruction of a casting could be broken and the grains could be rearranged by the vibration. And the obstruction could be carried away due to the inner and outer pressure difference, causing a burst feeding.

Combined effects of ultrasonic vibration and manganese on Fe-containing inter-metallic compounds and mechanical properties of Al-17Si alloy with 3wt.%Fe

The research studied the combined effects of ultrasonic vibration （USV） and manganese on the Fe-containing inter-metallic compounds and mechanical properties of AI-17Si-3Fe-2Cu-1Ni （wt.%） alloys. The results showed that, without USV, the alloys with 0.4wt.% Mn or 0.8wt.% Mn both contain a large amount of coarse plate-like δ-AI4（Fe,Mn）Si2 phase and long needle-like β-A15（Fe,Mn）Si phase. When the Mn content changes from 0.4wt.% to 0.8wt.% in the alloys, the amount and the length of needle-like β-AI5（Fe,Mn）Si phase decrease and the plate-like δ-A14（Fe,Mn）Si2 phase becomes much coarser. After USV treatment, the Fe- containing compounds in the alloys are refined and exist mainly as δ-AI4（Fe,Mn）Si2 particles with an average grain size of about 20μm, and only a small amount of β-AI5（Fe,Mn）Si phase remains. With USV treatment, the ultimate tensile strengths （UTS） of the alloys containing 0.4wt.%Mn and 0.8wt.%Mn at room temperature are 253 MPa and 262 MPa, respectively, and the ultimate tensile strengths at 350 ℃ are 129 MPa and 135 MPa, respectively. It is considered that the modified morphology and uniform distribution of the Fe-containing inter-metallic compounds, which are caused by the USV process, are the main reasons for the increase in the tensile strength of these two alloys.

Microstructure and mechanical characteristics of AA6061-T6 joints produced by friction stir welding,friction stir vibration welding and tungsten inert gas welding:A comparative study

This study compared the microstructure and mechanical characteristics of AA6061-T6 joints produced using friction stir welding(FSW),friction stir vibration welding(FSVW),and tungsten inert gas welding(TIG).FSVW is a modified version of FSW wherein the joining specimens are vibrated normal to the welding line during FSW.The results indicated that the weld region grains for FSVW and FSW were equiaxed and were smaller than the grains for TIG.In addition,the weld region grains for FSVW were finer compared with those for FSW.Results also showed that the strength,hardness,and toughness values of the joints produced by FSVW were higher than those of the other joints produced by FSW and TIG.The vibration during FSW enhanced dynamic recrystallization,which led to the development of finer grains.The weld efficiency of FSVW was approximately 81%,whereas those of FSW and TIG were approximately 74%and 67%,respectively.

Effects of mechanical vibration on the physical,metallurgical and mechanical properties of cast A308(LM21)aluminum alloy

This study investigated the microstructure,physical,and mechanical properties of die-cast A308 alloy subjected to mechanical vibration during solidification.Different frequencies(0,20,30,40,and 50 Hz)at constant amplitude(31μm)were employed using a power amplifier as the power input device.X-ray diffraction,optical microscopy,and scanning electron microscopy were used to examine the morphological changes in the cast samples under stationary and vibratory conditions.Metallurgical features of the castings were evaluated using Image J software.The average values of metallurgical features,including primaryα-Al grain size,dendrite arm spacing,average area of eutectic silicon,aspect ratio,and percentage porosity,reduced by 34%,59%,56%,22%,and 62%,respectively,at 30 Hz frequency compared with stationary casting.Mechanical tests of the cast samples showed that the yield strength(YS),ultimate tensile strength(UTS),percentage elongation(%EL),and microhardness(HV)increased by 8%,13%,17%,and 16%,respectively,at 30 Hz frequency compared with stationary casting.The fractured surface of the tensile specimens exhibited mixed-mode fracture behavior because of brittle facets,cleavage facets,ductile tearing,and dimple morphologies.The presence of small dimples showed that plastic deformation occurred before fracture.

Design and dynamic analysis of integrated architecture for vibration energy harvesting including piezoelectric frame and mechanical amplifier

Vibration energy harvesters(VEHs) can transform ambient vibration energy to electricity and have been widely investigated as promising self-powered devices for wireless sensor networks, wearable sensors, and applications of a micro-electro-mechanical system(MEMS). However, the ambient vibration is always too weak to hinder the high energy conversion efficiency. In this paper, the integrated frame composed of piezoelectric beams and mechanical amplifiers is proposed to improve the energy conversion efficiency of a VEH. First, the initial structures of a piezoelectric frame(PF) and an amplification frame(AF) are designed. The dynamic model is then established to analyze the influence of key structural parameters on the mechanical amplification factor. Finite element simulation is conducted to study the energy harvesting performance, where the stiffness characteristics and power output in the cases of series and parallel load resistance are discussed in detail. Furthermore, piezoelectric beams with variable cross-sections are introduced to optimize and improve the energy harvesting efficiency. Advantages of the PF with the AF are illustrated by comparison with conventional piezoelectric cantilever beams. The results show that the proposed integrated VEH has a good mechanical amplification capability and is more suitable for low-frequency vibration conditions.

Effects of electromagnetic vibration on the structure and mechanical properties of Al-6%Si alloy during directional solidification

The effects of electromagnetic vibration on the grain refinement in directional solid- ification were investigated. It was found that the electromagnetic vibration applied in the melt not only can refine grains remarkably but also can enhance both tensile strength and ductility values of Al-6%Si alloy. SEM graphs show that coarse dendrite structure was broken up into a somewhat globular structure, and the morphology of eutectic silicon was changed from flaky to fibrous under electromagnetic vibration treatment. The refine mechanism under electromagnetic vibration was discussed.

Generating Electricity from Mechanical Vibrations:Optimization of Linear a Generator

Energy preservation is one of the key components in developing eco-friendly machines.In industry,the majority of machines lose a considerable amount of energy through mechanical vibrations.However,the wasted energy through vibration can be utilized as a renewable energy source to compensate for the overall energy loss.The research work presented in this paper discusses the ability to design a linear power generator utilizing Nd Fe-B magnets,which can generate energy through mechanical vibrations.A pilot model was developed and simulated to understand the efficiency and limitation.The results showed that the model could reduce 14% rotor bulk with a marginal impact on the current generation.

Influences of Mechanical Vibration on Rapidly Solidified Al_2O_3/YSZ Ceramics Prepared by Combustion Synthesis

Al2O3/YSZ composite ceramics was fabricated with combustion synthesis technology, and the influences of mechanical vibration on its microstructures and properties were investigated. It is found that under the mechanical vibration of ever-increasing frequency, increasing combustion temperature, accelerating ceramics/metal liquid-liquid separation and quickening ceramic solidification could not only reduce the average diameter and the size distribution of aligned ZrO2 nano-micron fibers in rod-shaped Al2O3 matrix grains, but also make the randomly-oriented rod-shaped grains finer and increase their aspect ratios. As a result, a remarkable increase in flexural strength and fracture toughness of the ceramics can be observed.