Resistance spot welding (RSW) is difficult to apply to aluminium automotive alloys. High power ultrasonic spot welding (HP-USW) is a new alternative method which is extremely efficient, using ∼2% of the energy of RSW. However, to date there have been few studies of the mechanisms of bond formation and the material interactions that take place with this process. Here, we report on a detailed investigation where we have used X-ray tomography, high resolution SEM, and EBSD, and dissimilar alloy welds, to track the interface position and characterise the stages of weld formation, and microstructure evolution, as a function of welding energy. Under optimum conditions high quality welds are produced, showing few defects. Welding proceeds by the development and spread of microwelds, until extensive plastic deformation occurs within the weld zone, where the temperature reaches ∼380 °C. The origin of the weld interface ‘flow features’ characteristic of HP-USW are discussed.

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Mechanisms of joint and microstructure formation in high power ultrasonic spot welding 6111 aluminium automotive sheet

Application of ultrasonic vibrations in welding and metal processing: A status review

Effect of ultrasonic welding parameters on microstructure and mechanical properties of dissimilar joints

This work compares three aluminium sheet joining processes to determine their capability, efficiency and cost for mass production applications in automotive structures and closures. The joining processes investigated are Resistance Spot Welding (RSW), SelfPierce Riveting (SPR) and Spot Friction Joining (SFJ). Quantitative comparisons have been made on the basis of tensile strength (shear and peel), process time, equipment price and running cost. RSW is the most commonly employed joining method for steel sheet in the automotive industry. Its principle benefits are high speed and low cost operation, plus the ability to weld a wide range of joint configurations with the same gun. The main process limitations for aluminium are weld consistency and electrode-life, though recent work has shown that both of these can be largely overcome with regular electrode polishing

Comparison of Self-Pierce Riveting, Resistance Spot Welding and Spot Friction Joining for Aluminium Automotive Sheet

HAZ development and accelerated post-weld natural ageing in ultrasonic spot welding aluminium 6111-T4 automotive sheet

Ultrasonic spot welding offers cost and performance advantages for joining of aluminium vehicle body parts.

Ultrasonic spot welding: A new tool for aluminum joining

An apparatus and method for ultrasonically welding workpieces that reduces sonotrode adhesion during the ultrasonic welding process. The sonotrode includes a contact surface wherein a fluid is deposited on the contact surface prior to the welding process. The fluid may be applied in different ways, including providing an aperture in the contact surface of the sonotrode. In addition, the sonotrode may be cooled below the dew point of the surrounding atmosphere thus causing moisture to form on the contact surface of the sonotrode. Cooling the sonotrode to a temperature above the dew point also reduces sonotrode adhesion during the ultrasonic welding process.

Sonotrode for ultrasonic welding apparatus

A method and apparatus for joining multiple layers of materials using an ultrasonic welding apparatus. The ultrasonic welding apparatus utilizes a sonotrode to perform a weld between at least the top and intermediate layer of the multi-layer member. Then, either the multi-layer member or the ultrasonic welding apparatus is rotated such that the bottom layer is positioned adjacent the sonotrode wherein the sonotrode forms a weld between at least the bottom layer and intermediate layer of the multi-layer member. The apparatus includes an ultrasonic welding gun having a C-shape frame including a base portion and a head portion. An ultrasonic welding device, including a sonotrode, is secured to the head portion and an anvil secured to the base portion. The ultrasonic welding gun is connected to a robot operative to position the ultrasonic welding gun to perform the welding operation.

Apparatus and method for joining layers of materials

of EP1302271A method and apparatus for joining multiple layers (26,28,30) of materials using an ultrasonic welding apparatus is disclosed. The ultrasonic welding apparatus utilizes a sonotrode (14) to perform a weld between at least the top and intermediate layer (26,28) of a multi-layer member (24). Then, either the multi-layer member (24) or the ultrasonic welding apparatus is rotated such that the bottom layer (30) is positioned adjacent the sonotrode (14) so that the sonotrode (14) can form a weld between at least the bottom layer (30) and intermediate layer (28) of the multi-layer member (24). The apparatus includes an ultrasonic welding gun having a C-shape frame (80) including a base portion (82) and a head portion (84). An ultrasonic welding device (95) including a sonotrode (112) is secured to the head portion (82) and an anvil (90) is secured to the base portion (84). The ultrasonic welding gun is connected to a robot operative to position and rotate the ultrasonic welding gun to perform the welding operation.

Jan Birger Skogsmo

Papers

Ultrasonic spot welding: A new tool for aluminum joining

Sonotrode for ultrasonic welding apparatus

Apparatus and method for joining layers of materials

A method for ultrasonic welding stacked materials