Wire Oscillation Research Articles

Investigation of cladding layer formation in uphill wire laser additive manufacturing on inclined substrate

In wire laser additive manufacturing (WLAM), the position posture of substrate is highly related to the formation process of the cladding layer which will affect the forming quality and service performance of the manufacturing parts. The forming quality of the cladding layer is often difficult to be controlled under the condition of the inclined substrate. Therefore, a three-dimensional dynamic model is established in this paper to investigate the WLAM process on inclined substrate. The influence of the inclined substrate on the forming quality of the cladding layer is analyzed from the evolution of wire molten metal transfer process and oscillation behaviors of the molten metal in the molten pool. It is found that the backward gravity component plays a major role in promoting the backward oscillation process of the molten metal in the molten pool on inclined substrate. The backward oscillation process of the molten metal is the main factor for the formation of cladding layer with wave morphology. The calculated cladding layer morphology is validated by the experimental results. The proposed model is of great theoretical significance for understanding the molten pool dynamic behaviors of the WLAM process and improving the forming quality of the cladding layer on inclined substrate further.

A new method for refinement of Ti-6Al-4 V prior-β grain structure in the alternating magnetic field assisted narrow gap gas tungsten arc welding (AMF-GTAW) via filler wire oscillation

This study presents a new method for refining Ti-6Al-4 V prior-β grain in the alternating magnetic field assisted narrow gap gas tungsten arc welding (AMF-GTAW) process by stirring the molten pool, which is accomplished directly through the use of an oscillating filler wire. The wire feed rate can be increased from 1.8 m/min to 2.2 m/min by filler wire oscillation in the traditional AMF-GTAW process with minimal heat input. This method greatly increases welding efficiency by efficiently utilizing the energy of the arc and molten pool. Using a high-speed camera, the flow behavior of the molten pool was investigated under different filler wire oscillating amplitudes. The results showed that the oscillation of the filler wire can cause a violent stir in the molten pool. By increasing the oscillating amplitude of filler wire, one can refine the columnar prior-β grain structure and attain a morphology of the upper layer of the welded joint that is nearly equiaxed with crystallographic texture, all while maintaining a fixed heat input. This is because the wire's insertion into the molten pool also creates a negative thermal gradient and the filler wire's high-frequency and high-amplitude oscillation creates an intense convection that prevents randomly oriented nuclei and/or dendrite fragments from remelting and promotes nucleation activation. The oscillating amplitude of 6 mm and the oscillating frequency of 100 Hz are the ideal values for this effect.

Metal wire embrittlement monitoring by the measurement of wire oscillation frequency

In the process of irradiation of materials by fluxes of heavy particles (protons, neutrons, alpha particles), damage to material structure is often observed. As a result of the accumulation of such damages, there is a subsequent change in the properties of materials, in particular, its embrittlement and hardening. Monitoring of the embrittlement process is important for nuclear reactor vessels exposed to high neutron fluxes. In this work, to observe the effect of heavy irradiation particles on the mechanical properties of metals, we propose to use vibrating wire resonators, in which the natural frequency of oscillations of the wire strongly depends on its tension. The change in the elastic characteristics of the wire alters the value of the natural frequency of wire oscillations. The natural oscillations are generated by a special circuit. Preliminary experiments to study the embrittlement effect of a stretched wire are performed by heating the wire with an electric current. In the case of short pulses, a significant increase in frequency is achieved, which is explained by the process of hardening of the material as a result of the thermal impact on the wire (rapid heating and cooling).

Study on the influence of operational conditions on weld bead morphology produced through TIG process with longitudinal wire oscillation

Study on the influence of operational conditions on weld bead morphology produced through TIG process with longitudinal wire oscillation

Damping oscillations in a wire bending process

This paper presents an approach to modify CAD/CAM generated motion profiles for wire bending machines, in order to damp wire oscillations without decreasing machine throughput. Two different methodologies are presented, both leveraging on a simple and easily identifiable model of wire oscillations, the first one based on a filtering approach, the second one on an optimisation approach. The two methodologies are both characterised by a low computational complexity, allowing them to be integrated directly in the bending machine user interface, and can rely on a standard camera to identify wire oscillation parameters. A thorough experimental validation of the approaches is also presented, showing promising results in damping oscillations with wires of different materials.

Characterization of micrometer-size laser beam using a vibrating wire as a miniature scanner.

A new method for profile measurements of small transverse size beams by means of a vibrating wire is presented. A vibrating wire resonator with a new magnetic system was developed and manufactured to ensure that the wire oscillated in a single plane. Presented evidence gives us confidence that the autogenerator creates vibrations at the natural frequency of the wire in a plane of the magnetic system, and these vibrations are sinusoidal. The system for measuring the laser beam reflected from the vibrating wire by means of a fast photodiode was upgraded. The experiments allowed the reconstruction of a fine structure of the focused beam of the semiconductor laser using only a few vibrating wire oscillations. The system presented here would eventually enable the implementation of tomographic measurements of the thin beam profile.

Laser Brazing with Wire Oscillation

Laser Brazing with Wire Oscillation

Vibrating wire monitor: Versatile instrumentation for particle and photon beam measurements with wide dynamic range

The vibrating wire monitor proposed herein is based on the strong dependence of the frequency of the pinched wire on its temperature. This dependence allows the measurement of a particle/X-ray/gamma-ray beam that deposits part of its energy on the wire. A wide measured temperature range from fractions of mK to hundreds of degrees allows the detection of beam properties at a given position of the wire in space. It also enables preparing profiling of a beam in a large dynamic range by scanning the wire through the beam. This review paper presents information on various applications of a vibrating wire, including the method of resonance target and the use of wire oscillations as a scanner for the profiling of thin beams.

Вплив амплітуди і частоти коливань електродного дроту при дуговому наплавленні на формування і структуру наплавленого металу і проплавлення основного металу

Вплив амплітуди і частоти коливань електродного дроту при дуговому наплавленні на формування і структуру наплавленого металу і проплавлення основного металу

Influence of amplitude and frequency of oscillations of electrode wire in arc surfacing on formation and structure of the deposited metal and penetration of base meta

Influence of amplitude and frequency of oscillations of electrode wire in arc surfacing on formation and structure of the deposited metal and penetration of base meta

Maxwell stress excitation of wire vibrations at difference and sum frequencies of electric currents in separate circuits.

Oscillating electric currents through a wire under tension can excite transverse vibrational modes of the wire when a perpendicular static magnetic field is present and the frequency of the current is close to the natural frequency of the mode of interest. The excitation of the mode is associated with temporally oscillating Maxwell stresses on the wire, often also known as oscillating Lorentz forces. That excitation process is sometimes demonstrated in educational contexts. The investigation here concerns situations where a temporally oscillating magnetic field generated by oscillating electric currents in a cylindrical coil replaces the imposed perpendicular static magnetic field. The frequencies of the currents in the wire and in the coil are related to the frequency of the oscillating stress. In this experiment, this effect is documented for sum-frequency excitation (with input frequencies in the range of half that of the excited lowest vibrational mode of the wire) and the difference-frequency excitation (with input frequencies an order-of-magnitude larger than the mode frequency). This coupling may be useful when it is desirable to use only high-frequency currents. The experiment uses tone-burst stress excitation and a differential photodiode for detecting transverse low-amplitude wire oscillations. Signal envelopes decayed exponentially after the tone-burst.

Capillary forces as a limiting factor for sawing of ultrathin silicon wafers by diamond multi-wire saw

Succeeding with ultrathin silicon wafer sawing by diamond multi-wire saw, is not only a matter of optimization; the challenges of thin wafer production and the capability limit have not yet been fully understood. In this work, we have seen that regular pairing of wires occurs when the wire-wire separation distance is reduced below some critical value. The wire pairing leads to wire jumps on the wire guide rolls, and if the run is not stopped, it leads to wire breakage. Moreover, it effectively obstructs the production of wafers thinner than the critical wire-wire distance.We suggest that the physical explanation to the observed limitations to ultrathin wafer sawing, by diamond multi-wire saw, is related to the capillary force acting on the wires due to the sawing liquid bridge connecting the wires. The hypothesis is supported by simplified mathematical modelling including capillary and spring forces between infinitely long, parallel wires. The calculations suggest that capillary forces are the main reason for wire pairing, and that wire pairing will occur when the wire distance is below some critical distance. This matches the observed, experimental behavior. The critical distance will vary with wafer saw design and operation.To succeed with cutting very thin wafers, we recommend using lower surface tension sawing fluid or even dry in-cut, to reduce the capillary forces and thus decrease the critical wire separation distance, and to reduce wire oscillations to decrease the probability of sub-critical wire-wire separation distance. To reduce the vibration amplitude, shorter distance between the wire guide rolls, thinner wires, and increased wire tension are suggested.

Analysis of molten pool behavior with buttonhole formation in laser keyhole welding of sheet metal

A cavity, so-called buttonhole, was observed in the molten pool directly behind the oscillating laser beam and the supplied wire by means of suitable process control. A high seam surface quality was produced in the case with the buttonhole formation. A three-dimensional heat and mass transfer model was developed to understand the effect of the buttonhole in laser keyhole welding of sheet metal with a filler wire and one-dimensional laser beam oscillation. For a given welding condition, a stable catenoid-like buttonhole was shown which helped to reduce molten pool dynamics by its self-sustainability. The buttonhole formation was sensitive to the welding parameter of the air gap.

Manipulation of the cyclic wetting process using longitudinal filler wire oscillation in the laser brazing of zinc-coated steel sheets

In this study, the effects of a longitudinal filler wire oscillation on the wetting process in laser brazing are analyzed. High-speed recordings are carried out, and the seams are characterized by light-microscopy analysis with respect to the quality of the seam edges. It is shown that the filler wire oscillation is capable of influencing both the frequency and the amplitude of the wetting front movement. In contrast to the process without filler wire oscillation, which is accompanied by repetitive but irregular collapses of the wetting fronts, the longitudinal filler wire oscillation prevents such collapses and thus increases the seam edge quality.

Analysis of the Torsional Stability of Split Phases

The specificity of overhead power lines is associated with the fact that the length of conductors between the supporting structures can reach tens of thousands of meters. Wires and their components are exposed to climatic factors, viz. wind, rain, ice, snow. As compared to other structural elements, conductors are of the highest flexibility and lowest rigidity, and, therefore, they are the most sensitive elements to these effects. Since the early fifties of the XX century, the increase in energy consumption has caused the construction of high and ultra-high voltage overhead lines with split phases. For these types of conductors, new forms of oscillations have been noticed in the areas between the struts, the essence of which is torqueing the split phase. As a result, there is a violation of the torsional stability of the phase: collision of wires in the middle of sub-span and friction of wires of stranded conductor against each other, which leads to damaging conductors and, as a consequence, to disruption of power supply to consumers. Almost any overhead lines may be subjected to oscillations of wires in the span under the influence of wind. One of the types of such mechanical oscillations is galloping, i. e. low-frequency oscillations of wires with an amplitude reaching the value of the boom of wire sagging, and, taking into account the possibility of elongation of the wire, even exceeding it. Fluctuations in the galloping can cause significant mechanical forces and last long enough to lead to the destruction of structural elements of power lines, viz. wires, insulators, fittings and even pillars. Due to the large amplitude of oscillations, conductors of neighboring phases can approach each other at an unacceptable distance, resulting in a short circuit. The boundary value problem of the torsional stability calculation of the split phase with a given multiplicity of splitting has been set and solved. The critical lengths of the sub-spans at which the stable violation of torsional stability is most likely have been determined. A computer program has been developed, which can be used in the design of high-voltage lines with split phase.

Development of New Algorithm in the Method of a Resonant Vibrating Target for Large Scanning Speeds

The work is devoted to the study of scanning the transverse profile of a beam using a vibrating wire. A new algorithm has been developed that allows the use of a resonant vibrating target method for high scanning speeds. The method is based on the idea of measuring secondary/reflected particles/radiation generated from the interaction of the beam particles with the wire material, synchronously with the frequency of the wire oscillation. The proposed algorithm for using a differential signal with sign inversion on consecutive measurements from half-periods of wire oscillations is generalized for the case when the scanning speed is much higher than the average speed of the wire oscillation.

Design of a wire measurement system for dynamic feeding TIG welding using instantaneous angular speed

Over the last years, a profusion of new versions of arc welding processes has overwhelmed the international welding scenario in the industry and academia. Innovations have been made possible not only by means of electronics and software developments but also through new concepts in mechanical design and mechanisms. With respect to the tungsten inert gas (TIG) process, low productivity is often a disadvantage, when compared to other arc welding processes. In order to manage this drawback, as well as to better deal with hard wetting materials (Ni-Cr alloys for example), a forward and backward wire oscillation movement has been implemented in TIG systems and finds good acceptability in the industry. However, dedicated wire feed measuring systems for this new operating regime are not available, which limits the process monitoring as a whole and hinders phenomena understanding and parametrization stage. The present paper thus addresses the development of a measuring methodology combined with a transducer, based on an optical encoder, for acquisition of instantaneous angular speed (IAS). The study covers analysis of the performance of previous instrumentation (found unsuitable), description of the dedicated system, and verification methodologies. Results lead to the validation of the system. Therefore, valuable information can now be extracted to provide feedback for this welding process version and avoid instabilities.

Thermoelectric Properties and Shubnikov-de Haas Oscillations in Tin-Doped Bismuth Wires

Thermoelectric Properties and Shubnikov-de Haas Oscillations in Tin-Doped Bismuth Wires

Vibrating Wire for Profile Measurements of Thin Beams in Particle Accelerators: Preliminary Tests Using a Laser Beam

The possibility of using a vibrating wire as a target in the method of scanning transverse profiles of the thin beams in particle accelerators has been studied. In the case where the transverse dimensions of the beam are comparable to the amplitude of the wire oscillations, the vibrating wire can be used for a fast measurement of the transverse beam profile without moving the sensor. The scanning procedure is replaced by the use of the movement of the wire during its mechanical oscillations. The method is tested on a focused beam of a semiconductor laser with a spot size at the focus of ∼0.1 mm. The reconstruction of the transverse profile is performed on the basis of the measurements of the photons reflected from the vibrating wire by using fast photodiodes.

Determine of the wave equation in the task of electrical oscillations

One of the basic equations of mathematical physics (for instance function of two independent variables) is the differential equation with partial derivatives of the second order (3). This equation is called the wave equation, and is provided when considering the process of transverse oscillations of wire, longitudinal oscillations of rod, electrical oscillations in a conductor, torsional vibration at waves, etc… The paper shows how to form the equation (3) which is the equation of motion of each point of wire with abscissa x in time t during its oscillation. It is also shown how to determine the equation (3) in the task of electrical oscillations in a conductor. Then equation (3) is determined, and this solution satisfies the boundary and initial conditions.