Aug. 18, 2014

Ultrasonic additive manufacturing uses sound waves to merge layers of metal foil.

A common problem with sensors is that they degrade over time due to corrosion, wear and impact. It is possible to extend its operating life by housing them in sold metal for protection. A new technology, called ultrasonic additive manufacturing (UAM), can help embed sensors in protective metal housings, without any damage.

Ultrasonic Additive Manufacturing (UAM) is a revolutionary 3D printing technology that uses sound wave to merge layers of metal drawn from featureless foil stock. The process produces true metallurgical bonds with full density and works with a variety of metals such as aluminum, copper, stainless steel, and titanium.

The UAM process involves building up solid metal objects through ultrasonically welding a succession of metal tapes into a 3D shape, with periodic machining operations to create the detailed features of the resultant object.

In combining additive and subtractive process capabilities, UAM can create deep slots, hollow, latticed, or honeycombed internal structures, and other complex geometries which are impossible to replicate with conventional subtractive manufacturing processes.

Additionally, because the metals do not have to be heated for bonding, many electronics can be embedded without damage. In the past the biggest challenge in joining smart materials using conventional welding techniques is that any melting greatly degrades the properties of the smart materials. Because the UAM process is solid state and involves no melting, the process can be used to embed wires, strips, and foils and so called 'smart materials' such as sensors, communication circuits and actuators into fully dense metallic structures, without any damage.

This photo shows the embedment of ‘sensor’ plastic strips in solid aluminum. The plastic has piezoelectric properties that produce a voltage when the plastic is stretched. This voltage can be used to measure the stress/strain in a metal part under load.

 

Active or "smart" materials can convert from one form of energy into another. The most common smart materials are piezoelectric, electrostrictive, and electroactive polymers (electromechanical coupling), magnetostrictive (magnetomechanical coupling), and shape memory alloys (thermomechanical coupling). The UAM process enables 'smart structures' that can be used as passive sensors or as active elements to change the parts' material properties on the fly.

Benefits

  • High-speed process for additive manufacturing of metals
  • Solid state welding enables:
    − Bonding of dissimilar metals
    − Cladding
    − Metal matrix composites
    − "Smart" or reactive structures
  • Low-temperature process enables:
    − Electronics embedding in tamper-proof structures
    − Non-destructive, fully-encapsulated fiber embedding
  • Complex geometries

Numerous applications have been postulated that are only possible with UAM embedding of shape memory alloy materials. One application is particularly relevant to the aerospace market: to solve the problem of thermal expansion.

When most engineering materials are heated they expand; and when cooled they contract. This physical property is called the material's coefficient of thermal expansion (CTE). In most applications the CTE has a negative effect on the operation of engineered structures: warped brake rotors, varying gaps in turbines, fatigue cracks. Over certain temperature ranges, shape memory alloys act in the opposite direction and actually contract on heating. By embedding shape memory alloys in another metal, one can reduce the CTE of the overall structure. This low CTE material has application in high precision rotating parts such as aircraft turbines.

Other applications with UAM embedding of shape memory alloy materials include the lamination of a smart material into spring steel to develop network of switches that realize a multiband/broadband aperture with expanded frequency bandwidth.

While smart materials have held great interest for industry, UAM will help to achieve the exact mechanical properties and it will also enable a new class of products with integrated sensing and physics based actuation.

 

Source: Fabrisonic

Posted in 3D Printing Technology

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