Influence Of Ultrasonic Vibrations Research Articles

Influence of ultrasonic vibrations on tube spinning process

The main objective of this paper is to study the influence of longitudinal ultrasonic vibrations on the tube spinning process. A robust experimental tube spinning system was designed and manufactured, in which the preform and mandrel can be excited by ultrasonic vibrations. Tube spinning experiments under ultrasonic vibrations were carried out on annealed AA-6061 preforms. A modal analysis was used to study the vibrational behavior of the system. The forming forces acting on the non-vibrating roller were measured in radial, axial, and tangential directions. Experimental results showed that low power longitudinal ultrasonic vibrations can improve the inner surface quality of annealed 6061 aluminum samples. In addition, high power ultrasonic vibrations can affect forming forces and material escape. Analysis of forming forces variations under ultrasonic vibration revealed that these changes are mostly because of contact effects of ultrasonic vibrations.

Performances of two heat exchangers assisted by ultrasound

In this experimental work, performances of a double-tube heat exchanger are investigated with and without the influence of ultrasonic vibrations. A comparison is made with results obtained previously for an analogous shell-and-tube heat exchanger. The system of interest is made of two concentric straight pipes. An external ultrasonic transducer is connected to the largest one in order to make it vibrate at 35 kHz. A smaller pipe is inserted into the vibrating one in order to build a double-tube heat exchanger, always using water as working fluid. The ratio between the overall heat transfer coefficients with and without ultrasound, named the enhancement factor, was used alongside energy balances as means of comparison between experiments and heat exchangers performances. This enhancement factor was found between 1.5 and 2.3, and slightly more for the shell-and-tube heat exchanger. Nevertheless, whatever the heat exchanger configuration, the use of ultrasonic vibrations appears to be an interesting way for the enhancement of thermal performances.

Influence of Ultrasonic Vibrations on the Static Friction Characteristics of a Rubber/Aluminum Couple

A novel ultrasonic vibration approach is introduced into a chloroprene rubber/aluminum friction couple for improving the static friction properties between rubber and metal. Compared to the test results without vibrations, the static friction force of a chloroprene rubber/aluminum couple decreases observably, leading to the ultimate displacement of rubber. The values of the static friction force and ultimate displacement can be ultimately reduced to 23.1% and 50% of those without ultrasonic vibrations, respectively.

Temperature effects in aluminium melts due to cavitation induced by high power ultrasound

Extensive research has been carried out previously in ultrasonic (cavitation) melt treatment. Such treatment can reduce grain size and improve material homogeneity. However, it is still not well understood which of the mechanisms is responsible for cavitation aided grain refinement. For better understanding of the processes which take place during solidification under the influence of ultrasonic vibrations, it is very important to consider the change in the cooling conditions during such treatment and thermal effects which are generated in the cavitation zone and in the bulk of liquid. The current paper presents the results of an experimental work on temperature effects in aluminium alloys and their impact on resultant microstructures. The results are discussed based on heat flow, nucleation and fragmentation during solidification.

Influence of ultrasonic vibrations on dry grinding of soft steel

Dry machining has been increasingly investigated in order to decrease the negative environmental impact of the cutting fluids, diminishing problems concerning waste disposal demand and also due to interest in decreasing manufacturing costs. However, generally in dry grinding, as there are no cutting fluids to transfer the heat from the contact zone, problems frequently occur in terms of high heat generation on grinding wheel surface and workpiece surface, increasing the grinding energy, wear of grinding wheel, low material removal rate (regarding relatively low depth of cuts) as well as poor surface roughness compared to conventional grinding. A recent and promising method to overcome these technological constraints is the use of ultrasonic assistance, where high-frequency and low amplitude vibrations are superimposed on the movement of the workpiece. The design of an ultrasonically vibrated workpiece holder and the experimental investigation of ultrasonically assisted dry grinding of 100Cr6 are presented. The surface roughness and grinding forces of the ultrasonically and conventionally ground workpieces were measured and compared. The obtained results show that the application of ultrasonic vibration can eliminate the thermal damage on the workpiece, increase the G-ratio and decrease the grinding forces considerably. A decrease of up to 60–70% of normal grinding forces and up to 30–50% of tangential grinding forces has been achieved.

Influence of ultrasonic vibrations on thermal diffuse scattering in X-ray dynamical diffraction conditions

A theory of thermal diffuse scattering (TDS) in a crystal disturbed by high frequency ultrasonic vibrations is considered. In this case additional X-ray reflexes (satellites) are formed which can be used for obtaining information about vibrational excitations in a crystal. By varying the incident angle one can excite all the satellites one after another and detect the variation in the TDS yield. The possibilities of the experimental observation of these phenomena will also be discussed.

Influence of ultrasonic vibrations on X-ray fluorescence under dynamical diffraction conditions

Influence of ultrasonic vibrations on X-ray fluorescence under dynamical diffraction conditions

Effects of changes in frequency of ultrasonic vibrations on heat transfer

The heat transfer coefficients during natural convection of water on a downward-facing horizontal surface and that on a vertical surface were measured under the influence of ultrasonic vibrations. The multi-type oscillation used in this experiment was able to operate at three frequencies—28, 45, and 100 kHz—not only continuously, but also intermittently. When ultrasonic vibrations of 28 and 45 kHz were applied to water, cavitation bubbles were generated and the heat transfer coefficient increased remarkably. When an ultrasonic vibration of 100 kHz was applied, the increase in the heat transfer coefficient was small compared to those at 28 and 45 kHz. At 100 kHz, cavitation was not observed at this low ultrasonic power. The uniformity of heat transfer, which depends on the profile of the standing wave due to the ultrasonic vibration, was improved by the method of repeatedly applying multiple vibrations. © 2000 Scripta Technica, Heat Trans Asian Res, 29(5): 358–372, 2000

Acoustoplastic effect in the shape memory alloy Ni–Ti–Re at ultrasonic frequency

The influence of ultrasonic vibrations on the deformation and phase transformation in the shape memory alloy Ni–Ti–Re was studied. The decrease in the sample's length under superimposed ultrasonics in the interval of phase transformation temperatures was measured. Acoustoplastic effect in the shape memory alloy was investigated. The increase in the hardening coefficient and the decrease in the stage of the pseudoelastic deformation under superimposed ultrasonics was found.

Influence of ultrasonic vibrations on the growth of semiconductor single crystals

The influence of ultrasonic vibrations on striations in InSb, GaAs and Bi-Sb alloy single crystals grown by a modified Czochralski method was investigated. Ultrasonic vibrations at frequencies of 0.15, 0.25, 0.6, 1.2, 2.5, 5 or 10 MHz were introduced into the melt parallel to the pulling axis. The introduction of ultrasonic vibrations at a frequency up to 5 MHz eliminates the striations in GaAs and Bi-Sb alloy single crystals growing with constant diameter. It was found that for Bi-Sb alloy single crystals of constant diameter growth, after ‘processing’ of the melt with ultrasonic vibrations, the striations do not reappear until after 2 h. The effectiveness of the influence of the ultrasonic vibrations on the decrease of growth striations in InSb, GaAs and Bi-Sb alloy growing crystals was estimated with the help of the calculation of the sound absorption coefficient.

Some aspects of the damage caused in metallic materials by ultrasonic vibrations

There has been a number of studies on the influence of ultrasonic vibrations on various metallurgical phenomena. In the present study, however, some investigations have been carried out on a relatively less familiar aspect of ultrasound, viz. its application towards bringing about a rapid fatiguing effect on materials under resonant conditions. Intense ultrasound was given to materials under resonance conditions to produce fracture in them by what is known as ultrasonic fatigue. The failure time was usually of the order of a few minutes and, sometimes, only a few seconds. Some well-known common materials such as commercially pure aluminium, age-hardenable aluminium alloys and armco iron in different heat-treated conditions were chosen for this study. The specimens were of dumb-bell shape conforming to resonance. The complete equipment for this purpose was designed, developed and fabricated in-house. Some aspects of the damage under these conditions are discussed here, primarily through fractography. The fractures appear to be different from conventionally produced fractures. The influence of ultrasonic loading (short of fracture) in affecting the strength of age-hardenable alloys is also discussed briefly, X-ray line broadening analysis seems to indicate a strong recovery of the matrix due to the rapid fatiguing effect.

Influence of ultrasonic vibrations on the growth of InSb crystals

The influence of ultrasonic vibrations on striations in InSb crystals grown in the 〈111〉 direction by a modified Czochralski method was investigated. Ultrasonic vibrations at a frequency of 0.25, 0.6, 1.2, 2.5, 5 or 10 MHz were introduced into the melt parallel to the pulling axis. A modification, but not total elimination of the striations in the central part of the crystals was found to occur as a result of the ultrasonic vibrations.

The influence of ultrasonic vibrations on the austenite to martensite transformation in 304L stainless steel

The effect of ultrasonic vibrations on the austenite to martensite transformation in 304L stainless steel was examined by passing powerful acoustic ultrasonic energy into the specimen before transformation. The results indicate that ultrasonic treatment of 304L stainless steel influences the austenite to martensite transformation by activating the austenite. This activation has been attributed to the increase in dislocation density and point defects which enhance the number of martensite nucleation sites on ultrasonic treatment.

Influence of ultrasonic vibrations on the combustion of condensed systems with solid-phase reaction products

It has been shown in the example of the combustion of the Ti-B system that high-frequency mechanical vibrations under the conditions of the limiting action of liquid titanium filtration result in significant increase in the combustion velocity. The influence of ultrasonic vibrations on the formation of the final reaction product is investigated in this paper, with the system Ti-B-Fe selected for the tests.

Analysis and methods of reducing spurious vibration levels of structural elements in radiators for ultrasonic therapy

1. One of the principal reasons that prevent the full utilization of ultrasonic therapeutic techniques in medical institutions is the harmful influence of ultrasonic vibrations that has been detected in the organisms of the doctors and nurses who perform the procedures. This effect occurs when the palm of an operator is in contact with the surfaces of the handles on the ultrasonic radiators.

Influence of ultrasonic vibrations during corrosion of metals

The purpose of this investigation was to make an exploratory study of the effect the introduction of ultrasonic vibrations might have upon the corrosion of metals. Both dry and wet corrosion were studied. The ultrasonic frequency of vibrations used was 20 kHz with power levels up to 30 W/cm2 being introduced into the metals, and power levels up to 0.3 W/cm2 being introduced into the electrolytes. In dry corrosion, at elevated temperature, the introduction of ultrasonic vibrations produced a more dense corrosion film on the surface of the metal. In wet corrosion, it was found that ultrasonic vibrations generally increased the rate of corrosion and attempted to negate cathodic protection of the metal. Potentiostat experiments showed that the introduction of ultrasound substantially increased the flow of current in the system.

742. Influence of ultrasonic vibrations on the condensation process during vacuum deposition: V P Severdenko et al, Dokl Akad Nauk Bel SSR, 15 (8), 1971, 689– 691 ( in Russian)

742. Influence of ultrasonic vibrations on the condensation process during vacuum deposition: V P Severdenko et al, Dokl Akad Nauk Bel SSR, 15 (8), 1971, 689– 691 ( in Russian)

The formation of aluminum coatings on Armco iron under the influence of ultrasonic vibrations

1. Ultrasonic vibrations accelerate the process of aluminizing commercially pure iron and increase the depth of the coating. 2. With direct transmission of the ultrasonic vibrations to the sample, the depth of the aluminum coating is greater than in samples to which the ultrasonic vibrations are transmitted by the aluminizing mixture. 3. Ultrasonic vibrations substantially reduce the activation energy of diffusion, the effect being larger for samples connected directly to the wave guide. 4. Ultrasonic vibrations with the samples mounted directly on the wave guide substantially reduce the aluminum concentration in the surface of the coating. 5. Ultrasonic vibrations reduce the slope of the concentration curves, which indicates a larger effective diffusion coefficient (larger for the samples mounted directly on the wave guide).

Properties and structure of steel 40Kh after thermoultrasonic tempering

1. The influence of ultrasonic vibrations with a frequency of 19–20 kHz and amplitude of 8 μ during tempering at 100–500°C leads to higher hardness and resistivity of steel 40Kh, which is due to the difference in the degree of decomposition of martensite and the condition of the carbide phase. 2. Thermoultrasonic tempering does not eliminate irreversible temper brittleness, but narrows the temperature range in which it occurs (to 200°C in place of 350°C for standard tempering). The fracture toughness is lowest at 350°C regardless of the type of tempering.

Sintering of titanium carbide during continuous heating under the influence of ultrasonic vibrations

Sintering of titanium carbide during continuous heating under the influence of ultrasonic vibrations