The Relationship between X-Ray Stress Measured Value and Applied Stress in Elastic/Plastic Deformation Region in Tensile Testing

Practical residual strain field around the microcrack tip of fully lamellar γ- TiAl alloy was estimate the by digital image correlation (DIC) technology with in-situ SEM observation. And the macro plastic deformation before fracture of such low ductility alloys was observed. The results showed that the size of plastic zone around microcrack tip was 2 ~ 10µ m which was much more smaller than the calculated value by fracture mechanics. During the magnified observation on the plastic deformation region, a series of microcracks were observed in the specimen without macro cracking. Furthermore, the size of distribution region of the microcracks were in the same order of magnitude with the calculated plastic zone near primary crack tip which just reflected the comprehensive effect of microcracks and the plastic deformation on the tips of them.

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Study of Metal Seal of Coiled Tubing Wellhead Hanging Device

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.628.133 ◽

2014 ◽

Vol 628 ◽

pp. 133-136

Author(s):

Xian Yong Zhang ◽

Wei Guo Ma

Keyword(s):

Plastic Deformation ◽

Finite Element Method Analysis ◽

Clearance Ratio ◽

Deformation Region ◽

Coiled Tubing ◽

Metal Seal ◽

Excitation Force ◽

Initial Clearance ◽

Plastic Deformation Region ◽

Method Analysis

A U-shaped metal seal in coiled tubing wellhead hanging device was designed, the metal seal material is brass(H59, H70). The contact stress of sealing interface was analyzed by finite element method analysis, the U-shaped seal has elastic-plastic deformation after excitation force applied, and the plastic deformation region concentrated in contact areas. The influence of U-shaped metal seal initial clearance on sealing effect was presented, the reasonable initial clearance ratio region are 0.8 to 0.9. Excitation forces in different excitation angles were calculated, the reasonable excitation angle region are 15° to 20°. Metal seal overcomes the defects of conventional rubber elastomers, that ensure the safety of wellhead hanging device construction, also improve the service life.

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Validation on the Relationship Between J Integral and CTOD for Offshore Structural Steel Weldments by Experimental and Numerical Analyses

Volume 9: Mechanics of Solids, Structures and Fluids ◽

10.1115/imece2014-37660 ◽

2014 ◽

Author(s):

Dong Hyun Moon ◽

Jeong Soo Lee ◽

Jae Myung Lee ◽

Myung Hyun Kim

Keyword(s):

Plastic Deformation ◽

Crack Tip ◽

J Integral ◽

Crack Tip Opening Displacement ◽

Opening Displacement ◽

Constraint Factor ◽

Element Analysis ◽

Elastic Plastic ◽

Plastic Constraint ◽

The Relationship

Elastic plastic fracture mechanics (EPFM) is the domain of fracture analysis which considers extensive plastic deformation at crack tip prior to fracture. J integral and crack tip opening displacement (CTOD) have been commonly used as parameters for EPFM analysis. The relationship between these parameters has been extensively studied by industry and academia. The plastic constraint factor can serve as a parameter to characterize constraint effects in fracture involving plastic deformation. Therefore, the characteristics of plastic constraint factor are important in EPFM analysis. In this study, the relationship between J Integral and CTOD was investigated by conducting fracture toughness tests using single edge notched bend (SENB) specimens. Also, plastic constraint factor was investigated by using finite element analysis. Numerical analysis was carried out using ABAQUS elastic-plastic analysis mode.

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Martensite decay in micropitted gears

Proceedings of the Institution of Mechanical Engineers Part J Journal of Engineering Tribology ◽

10.1243/135065005x9790 ◽

2005 ◽

Vol 219 (2) ◽

pp. 77-83 ◽

Cited By ~ 27

Author(s):

A Oila ◽

B. A. Shaw ◽

C. J. Aylott ◽

S. J. Bull

Keyword(s):

Plastic Deformation ◽

Phase Transformations ◽

Deformation Region ◽

Metallographic Examination ◽

Microstructural Constituent ◽

Initiation And Propagation ◽

New Type ◽

Plastic Deformation Region

Metallographic examination performed on a number of micropitted gears has revealed microstructural features similar to those reported in the literature in fatigued bearings, namely, dark etching regions and white etching bands. In addition, a new type of fatigue-induced microstructural constituent was observed close to the surface below asperities referred to as the plastic deformation region. Finally, it is shown that the initiation and propagation of cracks leading to the formation of micropits are related to the phase transformations mentioned previously.

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