Abstract:PurposeElectron-beam welding has been widely used in industry to join different titanium alloys (Ti-6Al-4V) components. During welding production defects, such as porosity, lack of penetration or thinning are often observed. High-cycle fatigue (HCF) tests have been performed on welded specimens to understand the effect of weld defects on fatigue capabilities. The fatigue life of different types of “defective” welds has been compared against a non-welded reference specimen.Design/methodology/approachThe results… Show more
“…Recent studies on rotary Friction welding (RFW) of Grade 5 -Titanium alloy by Nu et al [16,17] has shown axial pressure to be the most influential factor for high tensile strength and hardness. Many researchers have reported the effect of heat treatments on mechanical properties of Grade 5 -Titanium alloy fusion welds [18][19][20], some on LFW of Grade 5 -Titanium alloy [21] and FSW [22]. In RFW of Grade 5 -Titanium alloy, heat treatment effects were not reported.…”
Titanium and its alloys are extensively used in automobile, aerospace and biomedical applications. There are many problems associated with the fusion welding of titanium. Thus, friction welding is an alternative technique for joining titanium without defects. In this study, Ti-6Al-4V (Grade 5 -Titanium alloy) rods were welded using a rotary friction process. Before welding, pre-heat treatments were carried in α-β and β conditions followed by stress relieving on Grade 5 -Titanium alloy rods and some rods were stress relieved after welding. After several trials, friction welding at rotational speed, 1500 rpm and 5kN upset force obtained defect-free joints. α-β heat treatment enhanced ductility as compared with β heat treatment. α-β heat treatment lead formation of bimodal microstructure in the base metal and β heat treatment produced lamellar Coarse β grains with colonies of α within β grains. Among different heat treatment conditions, high hardness was observed in the α-β heat treatment condition with stress-relieving. Stress-relieving of the welds resulted in an improvement in the hardness because of β precipitates. Fracture morphology is brittle in β treated conditions and ductile in α-β conditions. All welded samples failed away from the weld region irrespective of heat treatments applied, this shows that the weld region is much stronger than the base region due to acicular α and β phases. Mechanical properties were correlated as evidenced by microstructural features.
“…Recent studies on rotary Friction welding (RFW) of Grade 5 -Titanium alloy by Nu et al [16,17] has shown axial pressure to be the most influential factor for high tensile strength and hardness. Many researchers have reported the effect of heat treatments on mechanical properties of Grade 5 -Titanium alloy fusion welds [18][19][20], some on LFW of Grade 5 -Titanium alloy [21] and FSW [22]. In RFW of Grade 5 -Titanium alloy, heat treatment effects were not reported.…”
Titanium and its alloys are extensively used in automobile, aerospace and biomedical applications. There are many problems associated with the fusion welding of titanium. Thus, friction welding is an alternative technique for joining titanium without defects. In this study, Ti-6Al-4V (Grade 5 -Titanium alloy) rods were welded using a rotary friction process. Before welding, pre-heat treatments were carried in α-β and β conditions followed by stress relieving on Grade 5 -Titanium alloy rods and some rods were stress relieved after welding. After several trials, friction welding at rotational speed, 1500 rpm and 5kN upset force obtained defect-free joints. α-β heat treatment enhanced ductility as compared with β heat treatment. α-β heat treatment lead formation of bimodal microstructure in the base metal and β heat treatment produced lamellar Coarse β grains with colonies of α within β grains. Among different heat treatment conditions, high hardness was observed in the α-β heat treatment condition with stress-relieving. Stress-relieving of the welds resulted in an improvement in the hardness because of β precipitates. Fracture morphology is brittle in β treated conditions and ductile in α-β conditions. All welded samples failed away from the weld region irrespective of heat treatments applied, this shows that the weld region is much stronger than the base region due to acicular α and β phases. Mechanical properties were correlated as evidenced by microstructural features.
“…welding (Giannella et al 2017a;Fellinger et al 2018)) to the latest cutting-edge processes recently entering the industry (e.g. advanced welding procedures (Carlone et al 2016;Rubino et al 2020Rubino et al , 2021 or additive manufacturing (Caggiano et al 2019(Caggiano et al , 2021). Considering the inhomogeneous microstructure and non-uniform mechanical properties of metal materials, including crystal defects, grains boundary, dislocations, etc., cracks may encounter diversiform microstructures, in turn demonstrating variable strength against FCG.…”
The reliability of the damage tolerance approach to engineering design is affected by numerous sources of uncertainty that can lead to unsafe predictions, in turn jeopardizing the safety of structures. This work presents a robust stochastic framework for fatigue crack-growth predictions applied to a round bar under tension–compression loading conditions. Multi-source uncertainties were taken into account to derive the lifespan distribution for the bar in such a way to cover the uncertainties typically appearing in a structural integrity assessment. The sensitivity of each input variable was obtained and the influences of variables on the life predictions were derived and ranked accordingly.
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