Application of friction stir welding to the car body

Friction stir welding of aluminium alloys

“…Examination of the literature has shown that the following generalisations can be made: (i) in simple S-N tests on cross-weld samples, the fatigue performance of friction stir butt welds is typically less good than that of the parent material tested under the same conditions. 327,328 Many studies have found that after milling the top surface, the fatigue performance of 2014, 6013 and 7475 FSW joints approached that of the parent alloys, [329][330][331] yet in other studies 332 the properties remain significantly below parent material benchmarks (ii) the fatigue performance of friction stir butt welds generally comfortably exceeds that of comparable fusion welds, 93,226,330,331,333,334 a trend reported for many alloy grades (iii) failure is normally (but not always) associated with an initiation event at the geometric stress concentration at the side of the weld on the upper surface; 335 where this has been machined away, failure normally initiates in the region of lowest strength. For many alloy groups, these two locations are very close together (iv) residual stresses can play a significant role in the fatigue behaviour 191,[336][337][338] and vary according to crack test geometry.…”

“…However, mechanical properties are only part of the picture: process economics are also of significance, as is the quality of the weld which can be reliably obtained. For example, Hori et al 330 have described work on a Japanese alloy (6N01) similar to 6005. Comparison of tensile properties with MIG and laser welding showed no improvement in tensile properties over laser or MIG (in fact FSW performed slightly worse), but a significant improvement in fatigue performance was reported.…”

Modelling of electrically enhanced friction stir welding process using finite element method

“…Since friction stir welding (FSW) was invented by The Welding Institute (TWI) in 1991, 1 it has attracted considerable interest and is being used in various industries like aerospace, automotive and military, especially for welding aluminium alloys. [2][3][4][5][6][7][8][9][10] The basic procedure of friction stir welding is as follows: a rotating tool pin is plunged into the joint of two workpieces butted against each other until the tool shoulder contacts the top surface of the workpiece (it may be noted that FSW has been used for fabricating other types of joints such as lap joints, in addition to butt joints). Heating is caused by rubbing of the tool faces against the workpiece and by plastic work dissipation at high strain rates developed through tool pin stirring of the materials.…”

Improvement of very high cycle fatigue properties in an AA7075 friction stir welded joint by ultrasonic peening treatment

“…As a result, investigations on fatigue properties of FSW joint have increasingly received attention, with much research being invested in exploring its fatigue strength and failure mechanism . One of the most important observations from previous studies is that surface quality of the FSW welds exerted a significant effect on the fatigue strength of the weld, in which most fatigue cracks were initiated from specimen surface, even though the surface had been highly polished. In very high cycle fatigue (VHCF) range, fatigue life of the FSW joint was limited by surface crack nucleation, which accounted for over 98% of the total fatigue life .…”