The residual stresses that occur as a result of nonhomogeneous heating and cooling during welding may have a significant effect on the accumulation of fatigue damage in a welded joint.
After eruption in the Carboniferous, the Batamayineishan Formation volcanic reservoir in the Junggar Basin formed through dissolution, cooling, crystallization, welding and some other consolidation (approximately 359 320 Ma).
Scaling analysis and numerical calculations suggest a promising interpretation for the genesis of the columnar joints of the colonnades: three large explosive andesitic-dacitic eruptions lead to emplacement, cooling and welding of the Mudeungsan Tuff and the creation of large columnar joints in MMNG.
They found that high axial force promotes the squeeze of the molten polymeric material, preventing introduction of air into the weld and helps cooling of the weld, avoiding shrinkage, and voids formation.
The resulting tuff experienced cooling, compaction, and welding.
It is noticed that the hardness value of the FZ is higher than the HAZ and BM zone due to the difference in cooling rate during welding which promotes the formation of α′ martensitic phase in the FZ.
The results show that the application of water cooling during the welding process produces a matrix with a lower dilution ratio than that produced under the un-water-cooled condition.
Open image in new window Fig. 6 Measurement of thermal field of seam during cooling of a weld setup of TPS (a), a faulty weld (b), and an abnormal thermal profile (c) of the faulty weld (HKS Prozesstechnik 2013).
A better understanding of heat transfer and material flow for different stages (including plunge stage, dwell stage, welding stage, and cooling stage) of friction stir welding process is critical for the tool design and selecting appropriate welding variables.
Figure 6 shows an example of a weld inspection sensor based on a scanning thermal profile called ThermoProfilScanner (TPS), from HKS Prozesstechnik GmbH, for evaluation of weld quality and misalignment of welds during cooling.
