Fracture Resistance of Wire-Wrapped Cylinders

1973 ◽  
Vol 95 (1) ◽  
pp. 219-226 ◽  
Author(s):  
A. K. Shoemaker ◽  
T. Melville ◽  
J. E. Steiner
Keyword(s):  
Yield Strength ◽  
Fracture Resistance ◽  
Crack Extension ◽  
Shear Fracture ◽  
Steel Wire ◽  
Crack Opening ◽  
High Strength ◽  
Opening Displacement ◽  
Propagating Crack ◽  
The Wire

Steel cylinders wrapped with steel wire have the capability of offering not only an economical high-strength structure, but also a structure with improved fracture resistance compared with that of an unwrapped cylinder of equivalent strength. Accordingly, 2000-psi-pressure hydraulic burst tests were therefore conducted to determine the fracture resistance of 36-in-dia, 60-ksi yield-strength, 1000-psi-pressure wire-wrapped cylinders at different levels of shell notch ductility, which was varied by testing at different temperatures. The cylinders were prestressed with 1/4-in-dia cold-drawn wire, and the shells contained part-through-wall flaws. A similarly flawed unwrapped cylinder was tested for comparison. The working-stress level was 72 percent of the specified minimum yield strength in the shell and 60 percent of the minimum tensile strength in the wire. The results showed that at a pressure double that of the unwrapped shell, no crack extension occurred at a temperature at which the steel exhibited fully ductile shell behavior (+110 deg F). A 2-ft crack extension occurred at a temperature (+10 deg F) at which the steel was still in the transition temperature range from ductile-to-brittle behavior (about 20 percent shear fracture), but a brittle crack (−70 deg F) propagated to the end of the wire-wrapped shell. Except for the brittle propagating crack, wire wrapping appears to provide sufficient constraint of a shell defect or propagating crack to limit bulging and crack-opening displacement. A model based on the compatibility in displacements between the crack opening and the local wire strain is presented for calculating the arrest conditions of the propagating crack in the test at 10 deg F. The same flaw size was critical at the constant failure pressure for all test temperatures, and showed that, as predicted, ductile initiation occurs even at the −70 deg F temperature in both the wrapped and unwrapped-cylinder tests. A circumferential flaw was shown to be less critical than a longitudinal flaw of the same size.

scholarly journals Mechanical properties, deformation and fracture mechanisms of bimodal Cu under tensile test

2021 ◽  
Vol 60 (1) ◽  
pp. 15-24
Author(s):  
Silu Liu ◽  
Yonghao Zhao
Keyword(s):  
Yield Strength ◽  
Grain Refinement ◽  
Volume Fraction ◽  
Shear Fracture ◽  
High Strength ◽  
Tensile Specimen ◽  
Deformation Mechanisms ◽  
Fracture Mechanisms ◽  
Fracture Angle ◽  
Area Reduction

Abstract Metals with a bimodal grain size distribution have been found to have both high strength and good ductility. However, the coordinated deformation mechanisms underneath the ultrafine-grains (UFGs) and coarse grains (CGs) still remain undiscovered yet. In present work, a bimodal Cu with 80% volume fraction of recrystallized micro-grains was prepared by the annealing of equal-channel angular pressing (ECAP) processed ultrafine grained Cu at 473 K for 40 min. The bimodal Cu has an optimal strength-ductility combination (yield strength of 220 MPa and ductility of 34%), a larger shear fracture angle of 83∘ and a larger area reduction of 78% compared with the as-ECAPed UFG Cu (yield strength of 410 MPa, ductility of 16%, shear fracture angle of 70∘, area reduction of 69%). Grain refinement of recrystallized micro-grains and detwinning of annealing growth twins were observed in the fractured bimodal Cu tensile specimen. The underlying deformation mechanisms for grain refinement and detwinning were analyzed and discussed.

Fracture Initiation in Low Strength Steel Pressure Vessels

1970 ◽  
Vol 92 (1) ◽  
pp. 79-85 ◽  
Author(s):  
A. Cowan ◽  
N. Kirby
Keyword(s):  
Yield Strength ◽  
Crack Opening ◽  
Fracture Initiation ◽  
Pressure Vessels ◽  
Plastic Collapse ◽  
Low Alloy Steel ◽  
Opening Displacement ◽  
Bend Testing ◽  
Failure Conditions ◽  
Energy Failure

Tests to failure have been made on 5 ft dia × 1 in. thickness steel pressure vessels containing longitudinal slits through wall thickness representing natural defects. Steels of from 33,000 to 70,000 psi yield strength have been tested over a range of temperatures with defects of 6, 12 and 24 in. length. When the toughness exceeds 20/30 ft lb Charpy V-notch energy, failure occurs by plastic collapse, and failure conditions can be predicted from the tensile properties of the steel. At lower levels of toughness the concept of a constant crack opening displacement (COD) at fracture initiation of defects in pressure vessels and in notched bend specimens can be used to predict vessel failure conditions. Recognition must be made of the variables found in COD notched bend testing, and tests are necessary to determine the most embrittled area of a pressure vessel. Examples are given of the method of application of COD and the degree of embrittlement possible in a low alloy steel.

scholarly journals PREDICTION OF TENSILE AND FRACTURE PROPERTIES OF CRACKED CARBON STEEL WIRES USING FINITE ELEMENT SIMULATION

2014 ◽  
Vol 20 (2) ◽  
pp. 159-168 ◽  
Author(s):  
Kazeem K. Adewole ◽  
Steve J. Bull
Keyword(s):  
Finite Element ◽  
Carbon Steel ◽  
Fracture Mechanics ◽  
Finite Element Simulation ◽  
Shear Fracture ◽  
Steel Wire ◽  
Fracture Properties ◽  
Steel Wires ◽  
Element Simulation ◽  
The Wire

Steel wires are used as a bridge construction material and as pre-stressing strands or tendons in pre-stressed structural units among other applications in civil engineering. To date, the estimation of the load carrying capacity of a cracked wire has been based on purely experimental classical fracture mechanics work conducted with non-standardised classical fracture mechanics specimens as standard test specimens could not be manufactured from the wire owing to their size. In this work, experimental mechanical tests and finite element simulation with the phenomenological shear fracture model has been conducted to investigate the effect of miniature cracks with dimensions less than or equal to 0.2 mm (which is the limit of the current non-destructive detection technology) on the tensile and fracture properties of flat carbon steel wire. The investigation revealed that the reduction in the displacement at fracture of the wire due to the presence of cracks shallower than 0.2 mm is significantly higher than the reduction in the fracture load of the wire. Consequently, the displacement at fracture and by extension the fracture strain capacity of the wire could serve as a more appropriate parameter to assess the quality and the structural integrity of cracked wires.

Predictions of Creep Crack Initiation Periods

2010 ◽  
Author(s):  
C. M. Davies ◽  
G. A. Webster ◽  
K. M. Nikbin
Keyword(s):  
Power Generation ◽  
Crack Initiation ◽  
Ferritic Steel ◽  
Crack Extension ◽  
Crack Opening ◽  
Data Availability ◽  
Opening Displacement ◽  
Creep Crack ◽  
Time Periods ◽  
High Temperature Components

Several procedures are available for estimating creep crack initiation (CCI) time periods prior to the onset of creep crack extension from an existing defect in high temperature components. The applicability of a procedure depends on the required material’s data availability. Various methods are described including methods based on the creep fracture mechanics term C*, the crack opening displacement concept and the sigma-d approach. These procedures are applied to, and compared for, an austenitic and ferritic steel of relevance to the electric power generation industry. It is shown that reliable and conservative predictions can be obtained with all methods.

Effect of modes of patenting carbon wire on its properties

2020 ◽  
pp. 44-48
Author(s):  
I. Yu. Mezin ◽  
◽  
A. S. Limarev ◽  
V. M. Salganik ◽  
I. G. Gun ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Carbon Content ◽  
Steel Wire ◽  
Physical And Mechanical Properties ◽  
High Strength ◽  
Strength Properties ◽  
Urgent Task ◽  
Starting Point ◽  
Steel Grades ◽  
The Wire

To increase the competitiveness of carbon steel grades in enterprises, it is necessary to constantly improve the production process. The manufacture of high-strength wire is an urgent area for the enterprises of the hardware industry. One of the most important indicators determining the quality of the wire is the achievement of the specified physical and mechanical properties and microstructure. To this end, the wire is subjected to patenting, which is carried out in special units. To achieve the desired result during patenting, it is necessary to choose and observe the correct regimes depending on the diameter of the wire being processed and the chemical composition of the steel. When developing the modes, it is taken into account that martensite and a significant amount of excess ferrite along the grain boundaries are not allowed in the structure of patented steel. In the course of the work, an analysis was made of the most common carbon wire patenting modes in production, statistical dependences of the designated heating modes of the wire billet and cooling medium on the parameters of the steel wire, namely, its diameter and carbon content in steel, were obtained. An assessment of its strength properties is also carried out. According to the results of the analysis of patenting modes, it was found that certain difficulties arise when mastering the process of patenting steel wires of thick diameters and a carbon content of more than 0.8. Therefore, the solution of issues related to the course of these processes seems to be an urgent task. The results of the studies show the possibility of ensuring the necessary level of mechanical properties of steel in billets of thick diameters during the implementation of the process using lead melt. The data obtained can serve as a starting point for industrial testing and the prospective development of patenting processes.

The Relationship Between Stress Intensity Factor, Crack Opening Displacement and J-Integral in Zr-2.5 Percent Nb

1980 ◽  
Vol 102 (1) ◽  
pp. 97-100 ◽  
Author(s):  
L. A. Simpson
Keyword(s):  
Stress Intensity ◽  
Crack Opening Displacement ◽  
Crack Extension ◽  
Crack Opening ◽  
J Integral ◽  
Opening Displacement ◽  
Crack Face ◽  
Critical Crack ◽  
Wide Range ◽  
The Relationship

Crack opening displacement (COD) has been determined in Zr-2.5 percent Nb over a wide range of applied stress intensity, K. Prior to initiation of crack extension, COD was determined from measurements of stretch zones in specimens which had undergone hydrogen-induced, sub-critical crack growth. In post initiation measurements (during slow stable crack extension), COD was determined from crack face displacement. Both methods were self consistent and depended on the plastic-zone-corrected K in accordance with the Wells equation. The J-integral was also determined during stable crack extension using the method of Garwood, et al. The results are consistent with the COD measurements based on theoretical relationships between the two crack tip parameters.

scholarly journals Model for the Effect of Fiber Bridging on the Fracture Resistance of Reinforced-Carbon-Carbon

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
K. S. Chan ◽  
Y.-D. Lee ◽  
S. J. Hudak
Keyword(s):  
Structural Analysis ◽  
Fracture Resistance ◽  
Structural Integrity ◽  
Crack Opening ◽  
Initiation Toughness ◽  
Resistance Curve ◽  
Opening Displacement ◽  
Fiber Bridging ◽  
3D Composite ◽  
Bridging Law

A micromechanical methodology has been developed for analyzing fiber bridging and resistance-curve behavior in reinforced-carbon-carbon (RCC) panels with a 3D composite architecture and a SiC surface coating. The methodology involves treating fiber bridging traction on the crack surfaces in terms of a weight function approach and a bridging law that relates the bridging stress to the crack opening displacement. A procedure has been developed to deduce material constants in the bridging law from the linear portion of the K-resistance curve. This approach has been applied to analyzing R-curves of RCC generated using double cantilever beam and single cantilever bend specimens to establish a bridging law for RCC. The bridging law has been implemented into a micromechanical code for computing the fracture response of a bridged crack in a structural analysis. The crack geometries considered in the structural analysis include the penetration of a craze crack in SiC into the RCC as a single-edge crack under bending and the deflection of a craze crack in SiC along the SiC/RCC interface as a T-shaped crack under bending. The proposed methodology has been validated by comparing the computed R-curves against experimental measurements. The analyses revealed substantial variations in the bridging stress (σo ranges from 11 kPa to 986 kPa, where σo is the limiting bridging stress) and the R-curve response for RCC due to the varying number of bridging ligaments in individual specimens. Furthermore, the R-curve response is predicted to depend on crack geometry. Thus, the initiation toughness at the onset of crack growth is recommended as a conservative estimate of the fracture resistance in RCC. If this bounding structural integrity analysis gives unacceptably conservative predictions, it would be possible to employ the current fiber bridging model to take credit for extra fracture resistance in the RCC. However, due to the large scatter of the inferred bridging stress in RCC, such an implementation would need to be probabilistically based.

Sign in / Sign up

Export Citation Format

Share Document