Tetsugi Ueoka

Ultrasonic butt welding of aluminum, aluminum alloy and stainless steel plate specimens.

Welding characteristics of aluminum, aluminum alloy and stainless steel plate specimens of 6.0 mm thickness by a 15 kHz ultrasonic butt welding system were studied. There are no detailed welding condition data of these specimens although the joining of these materials are required due to anticorrosive and high strength characteristics for not only large specimens but small electronic parts especially. These specimens of 6.0 mm thickness were welded end to end using a 15 kHz ultrasonic butt welding equipment with a vibration source using eight bolt-clamped Langevin type PZT transducers and a 50 kW static induction thyristor power amplifier. The stainless steel plate specimens electrolytically polished were joined with welding strength almost equal to the material strength under rather large vibration amplitude of 25 microm (peak-to-zero value), static pressure 70 MPa and welding time of 1.0-3.0 s. The hardness of stainless steel specimen adjacent to a welding surface increased about 20% by ultrasonic vibration.

Transverse and torsional complex vibration systems for ultrasonic seam welding of metal plates

Transverse and torsional complex vibration systems for ultrasonic seam welding of metal plate specimens, using a 27 kHz complex vibration disk welding tip vibrating in transverse and torsional vibration modes, were studied. Using a complex vibration welding system with a welding tip vibrating in elliptical or circular locus, thick plate specimens can be welded with a more uniform and larger area compared to a conventional ultrasonic welding system. The disk welding tip vibrates in an elliptical or circular locus. The complex vibration system can continuously weld multiple parts of metal plate specimens such as heat sinks with a large number of fins.

Welding Characteristics of Aluminum and Copper Plate Specimens Welded by a 19 kHz Complex Vibration Ultrasonic Seam Welding System

The welding characteristics of aluminum and copper plate specimens welded using a 19 kHz ultrasonic welding system with a complex-vibration welding tip were studied. The welding tip part vibrates in an elliptical or circular locus. The seam welding system uses a rotating circular disk welding tip and a shifting stage for continuous welding of the metal sheets. Using the complex-vibration system, metal plates of various thicknesses can be welded continuously at multiple positions with large and uniform welded areas and large weld strengths independently of the welding position and direction. The required complex-vibration amplitude is less than one-half of that of a conventional linear-vibration system. Aluminum-aluminum, aluminum-copper and copper-copper plate specimens were welded with weld strengths almost equal to the specimen strength.

Welding Characteristics of Ultrasonic Seam Welding System Using a Complex Vibration Circular Disk Welding Tip

The continuous welding characteristics of a 27 kHz ultrasonic seam welding system using a complex vibration circular disk welding tip are studied. The vibration characteristics of a complex vibration converter were improved compared with the prototype model. The circular disk welding tip vibrates in both transverse and torsional vibration modes and an elliptical vibration locus is obtained at the circumference of the circular disk welding tip. An ultrasonic seam welding equipment consists of a complex vibration circular disk welding tip that is driven by a longitudinal vibration system through a longitudinal-torsional vibration converter, and an automatic specimen shifting stage. A large number of aluminum plate specimens of 0.3 mm to 0.5 mm thickness and 50 mm to 300 mm length were continuously joined to a thick aluminum plate at multiple welding parts.

New methods of ultrasonic welding of metal and plastic materials

New ultrasonic welding methods of metal and plastic materials have been proposed by the author and have shown their effectiveness. For welding of thick and large metal specimens, (1) an ultrasonic butt welding method of joining thick metal specimens end to end is proposed. Large capacity vibration sources and solid-state power amplifiers of 50, 100 kW have been developed. (2) The welding method of using two vibration systems crossed at a right angle is effective, and 10 mm thick aluminum plates have been joined successfully. For medium size metal welding specimens, (3) complex vibration welding tips have been shown to be very effective, and one-dimensional complex vibration systems are developed to simplify the systems. For welding of small metal specimens, (4) higher vibration frequency, and complex vibration wire bonding systems are proposed and it is shown that they are significantly effective. Bonding systems of 60 to 600 kHz have been designed. For welding of plastic materials, (5) high frequency and two-vibration-system welding methods are effective.

Welding characteristics of 27 kHz and 40 kHz complex vibration ultrasonic metal welding systems

Complex vibration ultrasonic lap spot and seam welding systems of 27 kHz and 40 kHz are studied. Welding characteristics of 27 kHz and 40 kHz complex vibration lap spot welding systems with a longitudinal-torsional vibration converter were compared using aluminum plate specimens. And also, a lap seam welding system with a complex vibration disk welding tip was designed. Aluminum plates of various thickness were continuously joined at multiple positions uniformly using the complex vibration system.

Temperature Rise and Welding Characteristics of Various-Frequency Ultrasonic Plastic Welding Systems

Welding characteristics and temperature increases of ultrasonic plastic welding parts over a frequency range from 27 to 94 kHz are studied. Using 27, 40, 67, and 94 kHz ultrasonic plastic welding systems, temperature increases at welding surfaces of lapped 1.0-, 2.0-, and 3.0-mm-thick polypropylene plates and polymethyl methacrylate plates are measured using 0.1- and 0.2-mm-diameter thermocouples inserted between plates, and temperature distributions at cross sections of lapped plate specimens are measured using a thermotracer. The 94 kHz vibration system used for ultrasonic plastic welding consists of a bolt-clamped Langevin-type longitudinal vibration source using four 30-mm-diameter piezoelectric ceramic (PZT) rings, a stepped horn (vibration velocity transform ratio N=3.0) and a catenoidal horn (N=3.13) with an 8-mm-diameter welding tip. The other vibration systems have similar configurations. In the case of using a higher-frequency system, increases in temperature measured at the welding parts are larger. Temperature rises are larger for lapped plate specimens than that for a one-piece specimen owing to the vibration loss of welding surfaces.

Ultrasonic plastic welding using fundamental and higher resonance frequencies.

Ultrasonic plastic welding using fundamental and higher resonance frequency vibrations simultaneously was studied. Using higher frequency, welding characteristics is improved due to the larger vibration loss of plastic materials. The 26 kHz welding tip vibrates in maximum velocity of over 4.5 m/s (peak-to-zero value) under a fundamental resonance frequency and there are several higher resonance frequencies up to 95 kHz whose vibration velocities are over one-third that of the fundamental frequency. Welding characteristics of 1.0-mm-thick polypropylene sheets are measured in the cases the vibration system are driven under combined driving voltages of fundamental and higher resonance frequencies. Welded area increases as number of driven higher frequencies increases. The welded area by three frequencies is about three to four times that of the case where only the fundamental frequency is driven. The welding characteristics of ultrasonic plastic welding are improved significantly by driving higher resonance frequencies simultaneously.

Transmission Conditions of Vibration Stresses to Welding Specimens of Ultrasonic Plastic Welding using Various Two-Vibration-System Equipments

Ultrasonic plastic welding is applied for welding various thermoplastic materials and is widely used in various industrial fields. The two-vibration-system welding method and a high frequency equipment are effective in improving the welding characteristics. A high frequency 90 kHz system can weld plastic sheets under a 1/3 velocity amplitude as compared with that of a low 27 kHz system, but it is difficult to weld large specimens successfully because a high frequency vibration stress cannot be transmitted uniformly due to the stress relaxation effect by the small vibration displacement. To improve the direct welding characteristics, three types of two-vibration-system ultrasonic welding equipments using linear vibration loci of (1) 90 kHz and 27 kHz longitudinal vibration systems, (2) 90 kHz longitudinal and 20 kHz torsional vibration systems, and elliptical vibration loci of (3) 27 kHz complex vibration systems are studied. Transmission conditions of the vibration stresses are measured by pressure sensitive films (Prescale) which are inserted between the plastic sheets. It was shown that a high frequency vibration stress with a small displacement amplitude may be induced uniformly in the welding specimens by combining a low frequency vibration with large displacement amplitude. These welding systems are effectively used to join plastic sheets successfully.

Measurement of the Temperature Rise at the Welding Surface of Different Metal Specimens Joined by a 15 kHz Ultrasonic Butt Welding System

The temperature rise at the welding surface of different metal specimens joined by a 15 kHz ultrasonic butt welding system is studied. The welded zone of the ultrasonic welding is limited to a very thin area and a clear melted structure cannot be observed and also the temperature rise at the welding surface cannot obtained by clearly measured. Temperature rises at the welding surfaces of different metal specimens are measured directly by the thermoelectromotive force between them, using a system with a small time constant. The temperature rises are measured using a 15 kHz ultrasonic butt welding with which it is possible to join the welding specimens directly end to end. Aluminum, copper and steel plates of 6 mm thickness were successfully joined end to end. The measured temperature rise rate is very high at the initial welding stage and decreases, or the temperature saturates, as the welding process progresses and the welding strength increases.