scholarly journals Numerical modeling of cracking behavior in Cr coating for ATF cladding under three-point bending

2021 ◽  
Vol 2076 (1) ◽  
pp. 012088
Author(s):  
Mingduo Yuan ◽  
Ziyan Pan ◽  
Zhenyu Zou ◽  
Weijian Zhang ◽  
Mingyue Du ◽  
...  
Keyword(s):  
Cohesive Zone Model ◽  
Local Stress ◽  
In Situ Observation ◽  
Zone Model ◽  
Cracking Behavior ◽  
Three Point Bending ◽  
Interfacial Cracks ◽  
Crack Tips ◽  
Cr Coating

Abstract In-situ three-point bending tests and finite element modeling based on the cohesive zone model were developed to study the stress evolution and cracking behavior of the Cr coated Zr-4 alloy for accident tolerant fuel claddings. The initiation and propagation of micro-cracks were captured by in-situ observation and predicted by the numerical simulation. The results showed that vertical cracks first initiated from the coating surface and propagated to the Cr/Zr4 interface. Under larger bending strain, interfacial cracks began to initiate from the vertical crack tips driven by large local stress concentration.

scholarly journals Three-point bending study on the microscopic fracture behavior of pre-oxidized Cr-coated Zr-4 alloys

2021 ◽  
Vol 2076 (1) ◽  
pp. 012051
Author(s):  
Mingyue Du ◽  
Chenxue Wang ◽  
Jishen Jiang ◽  
Xianfeng Ma
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Fracture Behavior ◽  
Early Stage ◽  
Bending Test ◽  
Cracking Behavior ◽  
Three Point Bending ◽  
Crack Penetration ◽  
Cr Coating

Abstract In this study, an in situ three-point bending test was carried out to study the mechanical properties and cracking behavior of the Cr-coated Zr-4 alloy considering the effect of pre-oxidation. The results showed that high temperature pre-oxidation led to the formation of intermetallic ZrCr2 at the coating/substrate interface and an α-Zr(O) layer beneath the interface. During the three-point bending test, the Cr coating and Zr-4 substrate showed good plastic deformation. However, the brittle intermetallic ZrCr2 diffusion layer exhibited cracks in the early stage, which accelerated the crack penetration to the Cr coating and the Zr-4 substrate, leading to the pre-failure of the pre-oxidized sample.

scholarly journals An Improved Cohesive Zone Model for Interface Mixed-Mode Fractures of Railway Slab Tracks

2021 ◽  
Vol 11 (1) ◽  
pp. 456
Author(s):  
Yanglong Zhong ◽  
Liang Gao ◽  
Xiaopei Cai ◽  
Bolun An ◽  
Zhihan Zhang ◽  
...  
Keyword(s):  
Interface Crack ◽  
Cohesive Zone ◽  
Mixed Mode ◽  
Cohesive Zone Model ◽  
Complex Loading ◽  
Bending Test ◽  
Mixed Mode Fracture ◽  
Zone Model ◽  
Slab Track ◽  
Interfacial Cracks

The interface crack of a slab track is a fracture of mixed-mode that experiences a complex loading–unloading–reloading process. A reasonable simulation of the interaction between the layers of slab tracks is the key to studying the interface crack. However, the existing models of interface disease of slab track have problems, such as the stress oscillation of the crack tip and self-repairing, which do not simulate the mixed mode of interface cracks accurately. Aiming at these shortcomings, we propose an improved cohesive zone model combined with an unloading/reloading relationship based on the original Park–Paulino–Roesler (PPR) model in this paper. It is shown that the improved model guaranteed the consistency of the cohesive constitutive model and described the mixed-mode fracture better. This conclusion is based on the assessment of work-of-separation and the simulation of the mixed-mode bending test. Through the test of loading, unloading, and reloading, we observed that the improved unloading/reloading relationship effectively eliminated the issue of self-repairing and preserved all essential features. The proposed model provides a tool for the study of interface cracking mechanism of ballastless tracks and theoretical guidance for the monitoring, maintenance, and repair of layer defects, such as interfacial cracks and slab arches.

SEM In Situ Investigation on Fatigue Cracking Behavior of X80 Pipeline Steel with Inclusions

2011 ◽  
Vol 284-286 ◽  
pp. 1096-1100 ◽  
Author(s):  
Ke Tong ◽  
Yan Ping Zeng ◽  
Xin Li Han ◽  
Yao Rong Feng ◽  
Xiao Dong He
Keyword(s):  
Crack Initiation ◽  
Pipeline Steel ◽  
Fatigue Cracking ◽  
Fatigue Loading ◽  
In Situ Observation ◽  
X80 Pipeline Steel ◽  
Cracking Behavior ◽  
The Matrix ◽  
Extension Period

The micro-mechanical behavior of inclusions in X80 pipeline steel under fatigue loading was investigated by means of SEM in situ observation. The influence of sizes and shapes of inclusion on crack initiation and propagation was analyzed. The result shows that for large-size single-particle inclusion, cracks initiate from the interior under the fatigue loading. When a certain circulation cycles are reached, cracks initiate at the matrix near the sharp corner of the inclusion. The cracks extend at the matrix during the stable extension period and unstable extension period following the crack initiation, until fracture occurred. For chain inclusion, cracks first initiate at the interface between inclusion and matrix within the chain area, and the circulation cycles needed for initiation are far less than single inclusion. Cracks steadily extend after the initiation, and then fracture after very short circulation cycles. A chain of inclusion with the shape corners is serious harmful to the fatigue properties.

scholarly journals On the tensile fracture behavior of Cr coating for ATF cladding considering the effect of pre-oxidation

2021 ◽  
Vol 2076 (1) ◽  
pp. 012047
Author(s):  
Ziyan Pan ◽  
Mingduo Yuan ◽  
Zhenyu Zou ◽  
Weijian Zhang ◽  
Mingyue Du ◽  
...  
Keyword(s):  
Interfacial Strength ◽  
Tensile Fracture ◽  
Fracture Mechanisms ◽  
Failure Behavior ◽  
Premature Failure ◽  
Interfacial Cracks ◽  
Micro Cracks ◽  
Coating Microstructure ◽  
Cr Coating

Abstract In this study, the fracture mechanisms of Cr-coated Zr4 alloy samples were studied by in-situ tensile testing with high-resolution observations. Both original sample and pre-oxidized sample were studied to study the effects of pre-oxidation on the cracking and failure behavior. For the Cr-coated Zr4 sample, with the increase of tensile strain, multiple surface cracks were dominant and less interfacial cracks were formed, indicating good interfacial strength of Cr coating. For the pre-oxidized samples, there was a thin oxide layer formed on the Cr coating surface, revealing improved oxidation resistance and protection effects. However, a brittle ZrCr2 diffusion layer was formed in the same while at the Cr/Zr4 interface underneath the Cr coating, which would lead to earlier micro-cracks formed under tensile stress and evidently degrade the interfacial strength. The findings in the study indicated the importance of optimizing coating microstructure in future study to avoid forming the above-mentioned brittle diffusion interlayer and the associated premature failure.

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