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F Z Xuan - One of the best experts on this subject based on the ideXlab platform.
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unified Constraint parameter solutions for axial and circumferential surface cracks in pressurized pipes under creep condition
Engineering Fracture Mechanics, 2017Co-Authors: H S, G. Z. Wang, S. Liu, F Z XuanAbstract:Abstract Unified creep Constraint parameter Ac for axial and circumferential surface cracks in pressurized pipes have been calculated and investigated by three-dimensional finite element method. It has been shown that the parameter Ac can Effectively characterize in-plane and out-of-plane creep Constraints in pressurized pipes. The overall Constraint levels of pipe cracks increase with increasing crack depth, length, pipe wall thickness and radius-thickness ratio. The parameter Ac solutions have been obtained for different pipe geometries and crack sizes. In creep life assessments of pressurized pipes, the overall Constraint Effect can be incorporated by the unified Constraint parameter Ac. For shallower and shorter surface cracks in pipes, more benefits can be gained by incorporating Constraint Effect.
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fracture assessment based on unified Constraint parameter for pressurized pipes with circumferential surface cracks
Engineering Fracture Mechanics, 2017Co-Authors: G. Z. Wang, F Z XuanAbstract:Abstract The fracture assessment capability and methodology based on the unified Constraint parameter Ap have been comparably investigated with the conventional procedures without considering Constraint Effect and the assessment approach based on the Constraint parameter Q for pressurized pipes with circumferential surface cracks. The results show that the Ap can be used in failure assessment diagram based fracture assessment by modifying the fracture toughness using the unified correlation formulae of fracture toughness with Ap. A fracture assessment methodology based on the parameter Ap for incorporating both in-plane and out-of-plane Constraints has been proposed. The Constraint characterization and fracture assessment using the parameter Ap for the pipe cracks may get the best accuracy and can reduce excessive conservatism of the conventional assessments. The benefits from the unified Constraint assessments increase with decreasing crack depth and length.
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correlation of material Constraint with fracture toughness of interface regions in a dissimilar metal welded joint
Fatigue & Fracture of Engineering Materials & Structures, 2016Co-Authors: K Fan, G. Z. Wang, F Z XuanAbstract:In this work, the Constraint parameter Ap based on crack-tip equivalent plastic strain was calculated by finite element analyses for the cracks located at different locations in two interface regions in a dissimilar metal weld joint (DMWJ). The capabilities of the parameter Ap for characterizing material Constraint and establishing correlation of material Constraint with fracture toughness of the interface region cracks have been examined. The results show that the parameter Ap can characterize material Constraint Effect caused by material mismatch and initial crack positions in the interface regions. Based on the Ap, the correlation lines and formulae of material Constraint with fracture toughness of the interface region cracks in the DMWJ can be established, and they may be used for obtaining material Constraint-dependent fracture toughness for the interface region cracks. The results in this work combining with those in the previous studies indicate that the parameter Ap may be a unified Constraint parameter that can characterize both geometry Constraint (including in-plane and out-of-plane Constraints) and material Constraint, and it may be used in accurate fracture assessments of welded components with different geometry and material Constraints.
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creep crack growth prediction and assessment incorporating Constraint Effect for pressurized pipes with axial surface cracks
Engineering Fracture Mechanics, 2016Co-Authors: S. Liu, G. Z. Wang, F Z XuanAbstract:Abstract Creep crack growth life is firstly predicted and assessed by two-parameter concept to incorporate Constraint Effect for pressurized pipes with inner axial surface cracks. The prediction and assessment results are compared with those based on conventional single-parameter C∗ and finite element calculations. For shallower and shorter cracks, the life assessments based on single-parameter C∗ are excessively conservative. To reduce excess conservativity, it is strongly recommended to incorporate Constraint Effect. With decreasing initial crack sizes, the benefits gained from two-parameter assessments increase. The crack growth profile may also be correctly predicted by two-parameter calculations. The C∗ calculation of reference stress method leads to extra conservativity.
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local fracture resistance behavior of interface regions in a dissimilar metal welded joint
Engineering Fracture Mechanics, 2015Co-Authors: K Fan, G. Z. Wang, F Z XuanAbstract:The finite element method based on Gurson–Tvergaard–Needleman damage mechanics model is used to investigate local fracture resistance behavior of two interface regions in a dissimilar metal welded joint. The variation of local fracture resistance with crack locations is analyzed by local material Constraint Effect. The results show that when initial cracks are located in hard and soft materials in interface regions, respectively, the local material Constraint has opposite Effect on local fracture resistance. The degree and distance range of material Constraint Effect increase with increasing the degree of mismatches in yield strength and work hardening between two materials.
Chao Liu - One of the best experts on this subject based on the ideXlab platform.
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out of plane Constraint Effect on local fracture resistance of a dissimilar metal welded joint
Materials & Design, 2014Co-Authors: Jie Yang, Fuzhen Xuan, Guoying Wang, Chao LiuAbstract:Abstract An experimental investigation on Effect and mechanism of out-of-plane Constraint induced by specimen thickness on local fracture resistance of two cracks (A508 heat-affected-zone (HAZ) crack and A508/Alloy52Mb interface crack) located at the weakest region in an Alloy52M dissimilar metal welded joint (DMWJ) between A508 ferritic steel and 316L stainless steel in nuclear power plants has been carried out. The results show with increasing out-of-plane Constraint (specimen thickness), the fracture mechanism of the two cracks changes from ductile fracture through mixed ductile and brittle fracture to brittle fracture, and the corresponding crack growth resistance decreases. The crack growth path in the specimens with different out-of-plane Constraints deviates to low-strength material side, and is mainly controlled by local strength mismatch. For accurate and reliable safety design and failure assessment of the DMWJ structures, it needs to consider the Constraint Effect on local fracture resistance. The new safety design and failure assessment methods incorporating both in-plane and out-of-plane Constraint Effects need to be developed for the DMWJ structures.
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an experimental investigation of in plane Constraint Effect on local fracture resistance of a dissimilar metal welded joint
Materials & Design, 2014Co-Authors: Jie Yang, F Z Xuan, Guoying Wang, Chao LiuAbstract:Abstract In this paper, an experimental investigation on Effect and mechanism of in-plane Constraint induced by crack depth on local fracture resistance of two cracks (A508 heat-affected-zone (HAZ) crack and A508/Alloy52Mb interface crack) located at the weakest region in an Alloy52M dissimilar metal welded joint (DMWJ) between A508 ferritic steel and 316L stainless steel in nuclear power plants has been carried out. The results show that the local fracture resistance of the two cracks is sensitive to in-plane Constraint. With increasing in-plane Constraint (crack depth a / W ), the fracture mechanism of the two cracks changes from ductile fracture through mixed ductile and brittle fracture to brittle fracture, and the corresponding crack growth resistance decreases. The crack growth path in the specimens with different in-plane Constraints deviates to low-strength material side, and is mainly controlled by local strength mismatch, rather than toughness mismatch. For accurate and reliable safety design and failure assessment of the DMWJ structures, it needs to consider the Effects of in-plane Constraint on fracture mechanism and local fracture resistance. The new safety design and failure assessment methods incorporating Constraint Effect need to be developed for the DMWJ structures.
Jie Yang - One of the best experts on this subject based on the ideXlab platform.
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out of plane Constraint Effect on local fracture resistance of a dissimilar metal welded joint
Materials & Design, 2014Co-Authors: Jie Yang, Fuzhen Xuan, Guoying Wang, Chao LiuAbstract:Abstract An experimental investigation on Effect and mechanism of out-of-plane Constraint induced by specimen thickness on local fracture resistance of two cracks (A508 heat-affected-zone (HAZ) crack and A508/Alloy52Mb interface crack) located at the weakest region in an Alloy52M dissimilar metal welded joint (DMWJ) between A508 ferritic steel and 316L stainless steel in nuclear power plants has been carried out. The results show with increasing out-of-plane Constraint (specimen thickness), the fracture mechanism of the two cracks changes from ductile fracture through mixed ductile and brittle fracture to brittle fracture, and the corresponding crack growth resistance decreases. The crack growth path in the specimens with different out-of-plane Constraints deviates to low-strength material side, and is mainly controlled by local strength mismatch. For accurate and reliable safety design and failure assessment of the DMWJ structures, it needs to consider the Constraint Effect on local fracture resistance. The new safety design and failure assessment methods incorporating both in-plane and out-of-plane Constraint Effects need to be developed for the DMWJ structures.
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unified correlation of in plane and out of plane Constraints with fracture toughness
Fatigue & Fracture of Engineering Materials & Structures, 2014Co-Authors: Jie Yang, Guoying Wang, F Z XuanAbstract:In this paper, the specimens with different geometries and loading configurations were used to study the unified correlation of in-plane and out-of-plane Constraints with fracture toughness by using numerical simulation method. The results show that the unified Constraint parameter Ap which was defined on the basis of the areas surrounded by the equivalent plastic strain isolines ahead of crack tip can characterise both in-plane and out-of-plane Constraints induced by different specimen geometries and loading configurations. A sole linear relation between the normalised fracture toughness JIC/Jref and was obtained. The JIC/Jref - line is a unified correlation line of in-plane and out-of-plane Constraints with fracture toughness of a material, and the Constraint dependent fracture toughness of a material can be determined from the unified correlation line. The results also demonstrate that the out-of-plane Constraint Effect is related to the in-plane Constraint Effect, and there exists interaction between them. The higher in-plane Constraint strengthens the out-of-plane Constraint Effect, whereas the lower in-plane Constraint is not sensitive to the out-of-plane Constraint Effect.
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an experimental investigation of in plane Constraint Effect on local fracture resistance of a dissimilar metal welded joint
Materials & Design, 2014Co-Authors: Jie Yang, F Z Xuan, Guoying Wang, Chao LiuAbstract:Abstract In this paper, an experimental investigation on Effect and mechanism of in-plane Constraint induced by crack depth on local fracture resistance of two cracks (A508 heat-affected-zone (HAZ) crack and A508/Alloy52Mb interface crack) located at the weakest region in an Alloy52M dissimilar metal welded joint (DMWJ) between A508 ferritic steel and 316L stainless steel in nuclear power plants has been carried out. The results show that the local fracture resistance of the two cracks is sensitive to in-plane Constraint. With increasing in-plane Constraint (crack depth a / W ), the fracture mechanism of the two cracks changes from ductile fracture through mixed ductile and brittle fracture to brittle fracture, and the corresponding crack growth resistance decreases. The crack growth path in the specimens with different in-plane Constraints deviates to low-strength material side, and is mainly controlled by local strength mismatch, rather than toughness mismatch. For accurate and reliable safety design and failure assessment of the DMWJ structures, it needs to consider the Effects of in-plane Constraint on fracture mechanism and local fracture resistance. The new safety design and failure assessment methods incorporating Constraint Effect need to be developed for the DMWJ structures.
Hongyang Jing - One of the best experts on this subject based on the ideXlab platform.
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enhanced models of creep crack initiation prediction coupled the stress regime creep properties and Constraint Effect
European Journal of Mechanics A-solids, 2019Co-Authors: Hongyang Jing, Lei Zhao, Yongdian HanAbstract:Abstract In this work, enhanced theoretical analysis and finite-element (FE) simulation were carried out to evaluate the creep crack initiation times by coupling the stress-regime creep strain rate and creep ductility and Constraint Effect. Firstly, the enhanced theoretical approaches were derivated based on the ductility exhaustion model, 2RN (2 regimes Norton) creep model and the Fermi's fit (between the creep ductility and creep strain rate), and several analytical models of CCI prediction were proposed under the different stress field condition. Then the Constraint Effect was coupled into the enhanced C*-Q* approaches. The comparison of CCI time predictions between the FE solutions and the enhanced C*-Q* approaches verified the accuracy of the latter. Reasonable and conservative predictions of CCI time could be obtained from the theoretical solutions when the Constraint Effects were considered in the K-RR and HRR-RR controlled models when compared with FE solutions. The K-RR and solutions were accurate when initial stress intensity factor K was at low and high range, respectively. Finally, the accuracy of the enhanced approaches and the suitability of finite element simulation were validated by the experimental data of 316H steel.
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analytical approaches of creep crack initiation prediction coupled with the residual stress and Constraint Effect
European Journal of Mechanics A-solids, 2018Co-Authors: Hongyang Jing, Lei Zhao, Yongdian HanAbstract:Abstract In this work, the coupled Effects of residual stress and Constraint on creep damage and creep crack initiation time (CCI) were analyzed by the analytical approaches based on the ductility exhaustion model. The elastic follow-up factor, Z, as well as the reference stress method and Constraint parameter Q* , were considered as part of the analytical method. The variation of hydrostatic stresses, triaxiality and multiaxial strain factor considering the Constraint was discussed. The suitability of the analytical method to the conditions that coupled secondary stress and the Constraint Effects was then investigated. Reasonable and conservative predictions of CCI time could be obtained from the theoretical solutions when the coupled Effects were taken into account within the Hutchinson-Rice-Rosengren--Riedel-Rice (HRR-RR) (initiation initially under the elastic-plastic Hutchinson-Rice-Rosengren (HRR) field and then under transient creep stress conditions, the Riedel-Rice (RR) controlled stress field) and stress intensity factor—Riedel–Rice (K-RR) control (initially by K, then by transient creep stress or Riedel–Rice conditions) controlled model when compared with finite element (FE) solutions. The K-RR solutions were more accurate when primary initial stress intensity factor K P I 1/2 , and the HRR-RR solutions were more appropriate when K P I >6 MPam 1/2 .
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two parameter approach of creep crack initiation times considering the Constraint Effect induced by specimen geometry
Theoretical and Applied Fracture Mechanics, 2018Co-Authors: Dongquan Wu, Lianyong Xu, Hongyang Jing, Lei ZhaoAbstract:Abstract In this paper, a two-parameter approach and finite element method were conducted to investigate the Constraint Effect of six different types of cracked specimen geometries on the creep crack initiation (CCI) time. The theoretical enhanced model of the C∗–Q∗ approach, which considers the load-independent Constraint parameter Q∗, was proposed to predict the CCI time around a sharp crack tip. The order of Q∗ values and the creep damage accumulation rate for the different specimen geometries was C(T) > CS(T), SEN(B) > SEN(T) > DEN(T) > M(T). Whereas the CCI times were ordered conversely. The influence of the Constraint on hydrostatic stresses, triaxiality and multiaxial strain factor was discussed. The suitability of the two-parameter approach was verified due to the comparison of CCI times between theoretical and simulated results, which demonstrated that the C∗–Q∗ two-parameter prediction approach under stress intensity factor—Riedel–Rice (K-RR) control (initially by K, then by transient creep stress or Riedel–Rice conditions) and Hutchinson–Rice–Rosengren—Riedel–Rice (HRR-RR) control (initially by plastic HRR control, then by RR conditions) could conservatively and Effectively predict the CCI times. The K-RR solutions were more accurate when initial stress intensity factor K 6 MPa m1/2.
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quantifying the Constraint Effect induced by specimen geometry on creep crack growth behavior in p92 steel
International Journal of Mechanical Sciences, 2015Co-Authors: Lei Zhao, Lianyong Xu, Hongyang JingAbstract:Abstract In this paper, the Effect of the specimen geometry on the creep crack growth behavior in P92 steel was quantified and six different types of cracked specimens (including C-ring in tension CS(T), compact tension C(T), single notch tension SEN(T), single notch bend SEN(B), middle tension M(T), and double edge notch bend tension DEN(T)) were employed. Results revealed that the creep crack growth rate against C ⁎ relations varied with changing specimen geometry. For a given C ⁎ value, C(T) and CS(T) showed the highest crack growth rates, which were three times as the lowest crack growth rates in M(T). This revealed that distinctions in specimen geometry influenced the in-plane Constraint level ahead of crack tip. Moreover, Constraint parameter Q was introduced to quantify the in-plane Constraint. During the creep crack propagation, the distributions of Q varied as specimen geometry changed. The specimen order in terms of Q values from high to low was CS(T), C(T), DEN(T), SEN(B), SEN(T) and M(T), which basically represented the Constraint level in these specimens.
B K Mishra - One of the best experts on this subject based on the ideXlab platform.
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an improved methodology based on continuum damage mechanics and stress triaxiality to capture the Constraint Effect during fatigue crack propagation
International Journal of Fatigue, 2020Co-Authors: V B Pandey, I V Singh, S S Samant, B K MishraAbstract:Abstract An improved continuum damage mechanics (CDM) and extended finite element method (XFEM) methodology is proposed to consider the Effect of crack tip Constraints on the fatigue crack growth (FCG) behavior. Several FCG experiments are conducted on compact tension (CT), single edge notch bending (SENB) and middle tension (MT) specimens prepared from modified 9Cr-1Mo steel. Combined CDM-XFEM methodology is improved to capture the crack tip Constraints Effect. Experimental and simulated FCG lives are compared to each other and found in good agreement. This analysis shows that the triaxiality parameter is a key parameter for estimating the crack tip Constraints correctly.
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a new framework based on continuum damage mechanics and xfem for high cycle fatigue crack growth simulations
Engineering Fracture Mechanics, 2019Co-Authors: V B Pandey, I V Singh, B K Mishra, S Ahmad, Venugopal A Rao, Vikas KumarAbstract:Abstract In this paper, we have developed a continuum damage mechanics (CDM) based methodology for high cycle fatigue crack growth simulations. A fatigue damage law is proposed and implemented in the framework of extended finite element method (XFEM). A new criterion is proposed based on damage evolution to identify the appropriate definition of stress triaxiality for acquiring the Constraint Effect on the stress state correctly. Few mesh regularization schemes are also employed for reducing the mesh sensitivity in the results. Simulations are performed on fracture specimens of different materials subjected to constant amplitude fatigue loading. The fatigue life of a turbine disc is also predicted under constant amplitude loading. The results obtained from present methodology (CDM and XFEM) are found in good agreement with the published experimental results. These simulations highlight that the continuum damage mechanics is a simple and Effective tool to perform crack growth simulations under high cycle fatigue conditions.