This study investigated multi-response optimization of the pulse metal active gas-tungsten inert gas( PMAG-TIG) twin arc hybrid root welding process for an optimal parametric combination to yield favorable back bead g...This study investigated multi-response optimization of the pulse metal active gas-tungsten inert gas( PMAG-TIG) twin arc hybrid root welding process for an optimal parametric combination to yield favorable back bead geometry of welded joints using grey relational analysis and Taguchi method.Eighteen experimental runs based on an orthogonal array following the Taguchi method were performed to derive objective functions to be optimized within the experimental domain.The objective functions were selected in relation to parameters of PMAG-TIG twin arc root welding back bead geometry: back bead width to root reinforcement ratio and deposited metal height.The Taguchi approach was followed by grey relational analysis to solve the multi-response optimization problem.The significance of factors on overall quality characteristics of the weld joint was also evaluated quantitatively using analysis of variance.Optimal results were verified through additional experiments,and showed to feasibility of applying grey relation analysis in combination with Taguchi technique for continuous improvement of product quality in the manufacturing industry.展开更多
Cruciform joints in ships are prone to fatigue damage and the determination of type of weld plays a significant role in thefatigue design of the joint. In this paper, the effect of weld geometry on fatigue failure of ...Cruciform joints in ships are prone to fatigue damage and the determination of type of weld plays a significant role in thefatigue design of the joint. In this paper, the effect of weld geometry on fatigue failure of load carrying cruciform joints inships is investigated using Effective Notch Stress (ENS) approach. A fictitious notch of 1 mm radius is introduced at theweld root and toe and fatigue stress is evaluated. The effect of weld leg length (l) and weld penetration depth (p) on ENS atweld root and toe are determined. The critical weld leg length (lcr) at which fatigue failure transitions from weld root toweld toe is investigated. An approximation formula for determination of the critical weld leg length considering weldpenetration depth (p) is proposed.展开更多
Many researchers have focused their efforts on fatigue failures occurring on weld toes. In recent years, more and more fatigue failures occur on weld roots. Therefore, it is important to explore the behaviour of weld ...Many researchers have focused their efforts on fatigue failures occurring on weld toes. In recent years, more and more fatigue failures occur on weld roots. Therefore, it is important to explore the behaviour of weld root fatigues. This paper investigates numerically the Magnification factors （Mk） for types of semi-elliptical cracks on the weld root of a T-butt joint. The geometry of the joint is determined by four important parameters： crack depth ratio, crack shape ratio, weld leg ratio and weld angle. A singular element approach is used to generate the corresponding finite element meshes. For each set of given four parameters of the semi-elliptical root crack, the corresponding T-butt joint is numerically simulated and its Mk at the deepest point of the weld root crack is obtained for the respective tension and shear loads. The variation range of the four parameters covers 750 cases for each load, totaling 1500 simulations are completed. The numerical results obtained are then represented by the curve to explore the effects of four parameters on the Mk. To obtain an approximate equation representing Mk as a function of the four parameters for each load, a multiple regression method is adopted and the related regression analysis is performed. The error distributions of the two approximate equations are compared with the finite element data. It is confirmed that the obtained approximate functions fit very well to the database from which they are derived. Therefore, these two equations present a valuable reference for engineering applications in T-butt joint designs.展开更多
Floating offshore wind turbine platforms typically use stiffened tubular joints at the connections between columns and braces.These joints are prone to fatigue due to complex weld geometries and the additional stress ...Floating offshore wind turbine platforms typically use stiffened tubular joints at the connections between columns and braces.These joints are prone to fatigue due to complex weld geometries and the additional stress concentrations caused by the stiffeners.Existing hot-spot stress approaches may be inadequate for analysing these joints because they do not simultaneously address weld-toe and weld-root failures.To address these limitations,this study evaluates the fatigue strength of stiffened tubular joints using the effective notch strain approach and the structural strain approach.Both methods account for fatigue at the weld toe and weld root and can be applied to both low-cycle fatigue(LCF)and high-cycle fatigue(HCF)regimes.Reanalyzes of a series of fatigue-tested specimens confirm the effectiveness of both approaches.The stiffener-shell fillet weld root is identified as the most critical fatigue location,which is consistent with fractographic observations.Although the brace-to-shell weld root exhibits lower stress levels in finite element(FE)models,weld quality was determined to be a crucial factor in fatigue failure.Furthermore,the results emphasise the importance of material plasticity in the LCF regime and demonstrate that full weld penetration significantly enhances fatigue strength.These findings provide valuable insights for the fatigue design of stiffened tubular joints in floating offshore wind turbine platforms.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.11375038)Science Fund for Creative Research Groups of NSFC(Grant No.51621064)
文摘This study investigated multi-response optimization of the pulse metal active gas-tungsten inert gas( PMAG-TIG) twin arc hybrid root welding process for an optimal parametric combination to yield favorable back bead geometry of welded joints using grey relational analysis and Taguchi method.Eighteen experimental runs based on an orthogonal array following the Taguchi method were performed to derive objective functions to be optimized within the experimental domain.The objective functions were selected in relation to parameters of PMAG-TIG twin arc root welding back bead geometry: back bead width to root reinforcement ratio and deposited metal height.The Taguchi approach was followed by grey relational analysis to solve the multi-response optimization problem.The significance of factors on overall quality characteristics of the weld joint was also evaluated quantitatively using analysis of variance.Optimal results were verified through additional experiments,and showed to feasibility of applying grey relation analysis in combination with Taguchi technique for continuous improvement of product quality in the manufacturing industry.
文摘Cruciform joints in ships are prone to fatigue damage and the determination of type of weld plays a significant role in thefatigue design of the joint. In this paper, the effect of weld geometry on fatigue failure of load carrying cruciform joints inships is investigated using Effective Notch Stress (ENS) approach. A fictitious notch of 1 mm radius is introduced at theweld root and toe and fatigue stress is evaluated. The effect of weld leg length (l) and weld penetration depth (p) on ENS atweld root and toe are determined. The critical weld leg length (lcr) at which fatigue failure transitions from weld root toweld toe is investigated. An approximation formula for determination of the critical weld leg length considering weldpenetration depth (p) is proposed.
基金Project supported by the National Basic Research Program (973 Program) of China (No. 2011CB711102)
文摘Many researchers have focused their efforts on fatigue failures occurring on weld toes. In recent years, more and more fatigue failures occur on weld roots. Therefore, it is important to explore the behaviour of weld root fatigues. This paper investigates numerically the Magnification factors （Mk） for types of semi-elliptical cracks on the weld root of a T-butt joint. The geometry of the joint is determined by four important parameters： crack depth ratio, crack shape ratio, weld leg ratio and weld angle. A singular element approach is used to generate the corresponding finite element meshes. For each set of given four parameters of the semi-elliptical root crack, the corresponding T-butt joint is numerically simulated and its Mk at the deepest point of the weld root crack is obtained for the respective tension and shear loads. The variation range of the four parameters covers 750 cases for each load, totaling 1500 simulations are completed. The numerical results obtained are then represented by the curve to explore the effects of four parameters on the Mk. To obtain an approximate equation representing Mk as a function of the four parameters for each load, a multiple regression method is adopted and the related regression analysis is performed. The error distributions of the two approximate equations are compared with the finite element data. It is confirmed that the obtained approximate functions fit very well to the database from which they are derived. Therefore, these two equations present a valuable reference for engineering applications in T-butt joint designs.
基金supported by the National Natural Science Foundation of China(Grant No.52101350).
文摘Floating offshore wind turbine platforms typically use stiffened tubular joints at the connections between columns and braces.These joints are prone to fatigue due to complex weld geometries and the additional stress concentrations caused by the stiffeners.Existing hot-spot stress approaches may be inadequate for analysing these joints because they do not simultaneously address weld-toe and weld-root failures.To address these limitations,this study evaluates the fatigue strength of stiffened tubular joints using the effective notch strain approach and the structural strain approach.Both methods account for fatigue at the weld toe and weld root and can be applied to both low-cycle fatigue(LCF)and high-cycle fatigue(HCF)regimes.Reanalyzes of a series of fatigue-tested specimens confirm the effectiveness of both approaches.The stiffener-shell fillet weld root is identified as the most critical fatigue location,which is consistent with fractographic observations.Although the brace-to-shell weld root exhibits lower stress levels in finite element(FE)models,weld quality was determined to be a crucial factor in fatigue failure.Furthermore,the results emphasise the importance of material plasticity in the LCF regime and demonstrate that full weld penetration significantly enhances fatigue strength.These findings provide valuable insights for the fatigue design of stiffened tubular joints in floating offshore wind turbine platforms.
