FSW: Multiple Choice

A set of questions on friction stir welding to prepare for your exam

Answering the following multiple choice questions will help you to assess your level of knowledge about friction stir welding, e.g. when you prepare yourself for an exam. Only one of the four answers is correct.

Threads

Examples of right-handed threads, neutral threads or left-handed threads in combination with the welding direction and the recommended direction of the tool rotation.

Which type of threads is generally preferred? Please, press one of the four buttons.

Right handed threads

Neutral threads or no threads

It depends on the joint design and the direction of the rotation of the machine

Left handed threads

Tool Offset from the Centreline

Cross-sectional macrostructures of Al-Cu friction stir welds made using various offsets

© Nima Eslami, Yannik Hischer, Alexander Harms, Dennis Lauterbach and Stefan Böhm, CC BY 4.0

Which offset should be used for welding dissimilar materials? Please, press one of the four buttons.

The tool centre line should always match the weld line

The offset should be 75 to 100 % of the pin diameter

No offset is permitted according to ISO 25239

Offseting the tool by 0 to 50% of the pin diameter is useful

Flash

FSW AA6061/AA6061 + 40 vol% SiC Plates at Cenim-CSIC, DTU and AIMEN. Optical micrograph (a) and schematic illustration (b) of the cross-section. Dark-gray and light-gray regions correspond to the MMC and the AA6061 alloy, respectively. Intermediate shading corresponds to the area which appears to be one broad band close to the plate bottom and which splits into two narrower individual bands on the advancing side. Dashed lines indicate the approximate location of the pin during FSW.

© S Señorís-Puentes, RF Serrano, G González-Doncel, JH Hattel; OV Mishin, CC BY 4.0

If you look at the flash on the left-hand-side and on the right-hand-side of a friction stir weld, you will note that...

The flash is always larger on the advancing side

The generation of flash depends on the material combination etc

The flash is often larger on the retreating side

The flash is always larger on the retreating side

Plasticised Material underneath the Tool

A certain amount of plasticised material should be visible underneath a tool that is tilted by 2.5°

If the the FSW tool, which is tilted by 2.5°, has been plunged at the correct tool heel plunge depth, the following amount of plasticised material should be visible:

⅓ to ⅔ of the circumference of the FSW tool

An FSW tool segment with 90-120° opening angle

75-95 % of the circumference of the tool shoulder

40-50 % of the area underneath the FSW tool

Onion Rings

Onions on Flish and Chips

© AluStir

The mixture of the workpiece materials causes a refined microstructure in the nuggets, which some metallurgists describe colloquially as "onion rings", should be as follows:

Onion rings are generally bad and not desired

Onion rings are generally good but not required

Onion rings are a sign of insuffient mixing, which will result in cracks

Onion rings do only occur when welding dissimilar materials