151 Apparatus for Providing Large Plastic Strain on Material and its Application

2009 ◽  
Vol 2009.58 (0) ◽  
pp. 31-32
Author(s):  
Minoru YAMASHITA ◽  
Joji SATO ◽  
Toshio HATTORI
Keyword(s):  
Plastic Strain ◽  
Large Plastic Strain

The effect of cumulative large plastic strain on the structure and properties of a Cu–Zn alloy

1998 ◽  
Vol 242 (1-2) ◽  
pp. 137-140 ◽  
Author(s):  
Z.Y Liu ◽  
G.X Liang ◽  
E.D Wang ◽  
Z.R Wang
Keyword(s):  
Plastic Strain ◽  
Structure And Properties ◽  
Large Plastic Strain ◽  
Zn Alloy

Fitness-For-Service Assessment of the Pipelines with Localized Geometric Imperfections such as Buckles and Wrinkles

2008 ◽  
Vol 385-387 ◽  
pp. 173-176
Author(s):  
Zheng Mao Yang ◽  
Shashi Bhushan Kumar ◽  
Jens P. Tronskar
Keyword(s):  
Plastic Strain ◽  
Fracture Resistance ◽  
Assessment Procedure ◽  
Test Results ◽  
Single Edge ◽  
Large Plastic Strain ◽  
Failure Assessment ◽  
Critical Flaw ◽  
Edge Notch ◽  
Girth Welds

In this paper, FFS assessment procedure for the buckle damaged pipeline with cracks in the girth welds is presented. For FFS assessment the tensile and J R-curve data from a pre-strained pipeline material, API 5L X65 were obtained in the laboratory to study the influences of the large plastic strain on the material properties and the fracture resistance of the pipeline girth welds. Tensile and single edge notch bend specimens in as-received, 10% pre-strained and 20% prestrained conditions were tested. The test results show significant increase in yield and tensile strength in the pre-strained specimens. Generally, the elongation and fracture resistance decreased after pre-straining. In FFS material specific failure assessment diagrams (FADs) generated based on the stress-strain curves obtained from testing were used. The critical flaw sizes of the pipeline girth welds were calculated, and the influence of the large plastic strain on the FFS results was discussed.

Influence of Localized Geometric Imperfections i.e. Buckles and Wrinkles on the Integrity of Pipelines

2008 ◽  
Author(s):  
Zhengmao Yang ◽  
Kumar Shashi ◽  
Jens P. Tronskar
Keyword(s):  
Stress Concentration ◽  
Plastic Strain ◽  
Material Properties ◽  
Fracture Resistance ◽  
Axial Strain ◽  
Compressive Strain ◽  
Mechanical Damage ◽  
Local Deformation ◽  
Local Geometry ◽  
Large Plastic Strain

Pipelines are relied upon to transport hazardous liquids and gasses over long distances. A major threat to the integrity of pipelines is mechanical damage, caused by outside natural forces. According to the AGA report [1], 39% of offshore and 37.7% land based natural gas pipeline failures were caused by outside force. During the installation of offshore pipelines the pipe wall at the 6 o’clock position sees large compressive strain and local buckling may occur. Dents may also occur by impact onto hard objects such as the rollers on the stinger or rocks on the seabed and by anchor impact etc. These kinds of imperfections change the local geometry of the pipe, and therefore, a stress concentration and local bending stress will be induced. The stress concentration factor can be up to 10 depending on the geometry of the imperfection. As a result, the local stresses will be much higher than the design stresses for the pipeline in operation subject to internal pressure and axial strain, and fracture and fatigue capacity of the pipelines with these imperfections will decrease dramatically. Because of the large local deformation, the materials in the deformed pipe region have undergone large local plastic strains i.e. 10–20% plastic deformation. The material properties of the pipe with large plastic strain will be drastically changed, and therefore the fracture resistance of the pipe is expected to be decreased, especially when the damage is located at the seam or girth welds. To assess the criticality of such damage which often can be associated with strain induced flaws in the heavily deformed parent metal and welds, ‘fitness-for-service’ assessment is required. The objective is to determine the severity of the flaws in the deformed pipe and to make the repair/replacement decision. At present there are no definitive assessment guidelines that consider these aspects and how to incorporate the behaviour and fracture capacity of the heavily deformed material. In this paper, a numerical model of typical local imperfections i.e. buckles and wrinkles was established from the in-situ geometry measurements. The local stress distributions of the pipes were analyzed. Based on this stress analyses, the stress concentration around the local imperfections in operation were obtained and the fracture capacity and fatigue life of the pipeline was assessed. The tensile and J R-curve data for deformed pipeline materials were obtained by the DNV Energy laboratory to study the influences of the large plastic strain on the material properties, and the fracture resistance and fatigue crack growth of the pipe. Based on the numerical analysis and test results, a fracture combined fatigue assessment was performed to decide on the mitigation and remediation strategies for the pipeline.

The Pattern of Plastic Deformation in a Deeply Notched Bar With Semicircular Roots

1956 ◽  
Vol 23 (1) ◽  
pp. 56-58
Author(s):  
L. Garr ◽  
E. H. Lee ◽  
A. J. Wang
Keyword(s):  
Plastic Deformation ◽  
Free Surface ◽  
Velocity Field ◽  
Plastic Strain ◽  
Plane Strain ◽  
Cross Section ◽  
Finite Deformation ◽  
Large Plastic Strain ◽  
Step Method ◽  
Square Grid

Abstract The plastic deformation in a notched bar with deep semicircular roots pulled in plane strain is determined theoretically. The finite deformation is analyzed according to plastic-rigid theory. The motion is unsteady, and the velocity field at any instant is given in terms of the current geometry of the deformed free surface. A graphical step-by-step method is used to determine the deformation of a square grid scribed on the undeformed cross section. The deformed pattern details the regions of large plastic strain, and may be useful in considering the initiation of fracture cracks.

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