Stress concentrations due to simulated corrosion pits in buried metal pipes under longitudinal bending

2021 ◽  
Author(s):  
Haitao Lan ◽  
Guohao Ma ◽  
Neil A. Hoult ◽  
Ian D. Moore
Keyword(s):  
Stress Concentrations ◽  
Metal Pipes ◽  
Longitudinal Bending ◽  
Corrosion Pits

Variations in Stress Concentration Factors Near Simulated Corrosion Pits as Monitored by Magnetic Flux Leakage, Magnetic Barkhausen Noise and Neutron Diffraction

1998 ◽  
Author(s):  
L. Clapham ◽  
K. Mandal ◽  
R. Sabet-Sharghi ◽  
D. L. Atherton ◽  
T. Holden ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Magnetic Flux ◽  
Electrochemical Machining ◽  
Local Stress ◽  
Magnetic Flux Leakage ◽  
Barkhausen Noise ◽  
Magnetic Barkhausen Noise ◽  
Stress Concentrations ◽  
Corrosion Pits ◽  
Flux Leakage

The conditions under which a pit defect is formed in a pipe can influence local stress concentrations which, in turn, affect the Magnetic Flux Leakage (MFL) signal. In this study MFL, Magnetic Barkhausen Noise (MBN) and neutron diffraction (ND) techniques are used to monitor and compare the local stress distributions surrounding simulated pits in plate and pipeline samples. Our study shows two important findings. Firstly, mechanically machining of simulated corrosion pits creates considerable machining stresses around the defect Conversely, electrochemical machining (ECM) produces no measurable residual stresses. Secondly, all three techniques indicate that, provided stresses are high enough hr produce local yielding, there are significant differences in local stress concentrations depending on whether the pit was electrochemically machined prior to stress application or while the sample was under stress. The latter case is more relevant to pipelines which corrode whilst in service since operating line pressures normally produce pipe wall hoop stresses of up to 70% yield strength.

Sem Examinations of Glass Knives

1970 ◽  
Vol 28 ◽  
pp. 282-283
Author(s):  
J. Temple Black
Keyword(s):  
Plastic Deformation ◽  
Tensile Loading ◽  
Resultant Force ◽  
Stress Concentrations ◽  
Edge Chipping ◽  
Surface Flaws ◽  
Edge Defects ◽  
Microscopic Surface

There are two types of edge defects common to glass knives as typically prepared for microtomy purposes: 1) striations and 2) edge chipping. The former is a function of the free breaking process while edge chipping results from usage or bumping of the edge. Because glass has no well defined planes in its structure, it should be highly resistant to plastic deformation of any sort, including tensile loading. In practice, prevention of microscopic surface flaws is impossible. The surface flaws produce stress concentrations so that tensile strengths in glass are typically 10-20 kpsi and vary only slightly with composition. If glass can be kept in compression, wherein failure is literally unknown (1), it will remain intact for long periods of time. Forces acting on the tool in microtomy produce a resultant force that acts to keep the edge in compression.

Glass Knife Geometry as Seen by the SEM

1971 ◽  
Vol 29 ◽  
pp. 454-455
Author(s):  
J. Temple Black
Keyword(s):  
Low Cost ◽  
Amorphous Material ◽  
Stress Concentrations ◽  
Basic Tool ◽  
Tool Materials ◽  
Optical Inspection ◽  
Surface Flaws ◽  
Slip Planes ◽  
Glass Knife ◽  
Diamond Knife

In ultramicrotomy, the two basic tool materials are glass and diamond. Glass because of its low cost and ease of manufacture of the knife itself is still widely used despite the superiority of diamond knives in many applications. Both kinds of knives produce plastic deformation in the microtomed section due to the nature of the cutting process and microscopic chips in the edge of the knife. Because glass has no well defined slip planes in its structure (it's an amorphous material), it is very strong and essentially never fails in compression. However, surface flaws produce stress concentrations which reduce the strength of glass to 10,000 to 20,000 psi from its theoretical or flaw free values of 1 to 2 million psi. While the microchips in the edge of the glass or diamond knife are generally too small to be observed in the SEM, the second common type of defect can be identified. This is the striations (also termed the check marks or feathers) which are always present over the entire edge of a glass knife regardless of whether or not they are visable under optical inspection. These steps in the cutting edge can be observed in the SEM by proper preparation of carefully broken knives and orientation of the knife, with respect to the scanning beam.

“Cavity” formation in superplastically deformed aluminium alloys

1990 ◽  
Vol 48 (4) ◽  
pp. 958-959
Author(s):  
A. Cziráki ◽  
E. Ková-csetényi ◽  
T. Torma ◽  
T. Turmezey
Keyword(s):  
Grain Boundaries ◽  
Aluminium Alloys ◽  
Superplastic Deformation ◽  
Volume Fraction ◽  
Superplastic Forming ◽  
Polished Surface ◽  
Cavity Formation ◽  
Stress Concentrations ◽  
Electron Microscopic ◽  
Commercial Aluminium

It is known that the formation of cavities during superplastic deformation can be correlated with the development of stress concentrations at irregularities along grain boundaries such as particles, ledges and triple points. In commercial aluminium alloys Al-Fe-Si particles or other coarse constituents may play an important role in cavity formation.Cavity formation during superplastic deformation was studied by optical metallography and transmission scanning electron microscopic investigations on Al-Mg-Si and Al-Mg-Mn alloys. The structure of particles was characterized by selected area diffraction and X-ray micro analysis. The volume fraction of “voids” was determined on mechanically polished surface.It was found by electron microscopy that strongly deformed regions are formed during superplastic forming at grain boundaries and around coarse particles.According to electron diffraction measurements these areas consist of small micro crystallized regions. See Fig.l.Comparing the volume fraction and morphology of cavities found by optical microscopy a good correlation was established between that of micro crystalline regions.

Equilibrium Profile of Modern Belted Radial Ply Tires: Its Determination and Performance Benefits

2013 ◽  
Vol 41 (2) ◽  
pp. 127-151
Author(s):  
Rudolf F. Bauer
Keyword(s):  
Finite Element ◽  
Aspect Ratio ◽  
Finite Element Methods ◽  
Mathematical Analysis ◽  
Internal Stresses ◽  
Stress Concentrations ◽  
Equilibrium Profiles ◽  
Equilibrium Profile ◽  
And Performance ◽  
Beneficial Property

ABSTRACT The benefits of a tire's equilibrium profile have been suggested by several authors in the published literature, and mathematical procedures were developed that represented well the behavior of bias ply tires. However, for modern belted radial ply tires, and particularly those with a lower aspect ratio, the tire constructions are much more complicated and pose new problems for a mathematical analysis. Solutions to these problems are presented in this paper, and for a modern radial touring tire the equilibrium profile was calculated together with the mold profile to produce such tires. Some construction modifications were then applied to these tires to render their profiles “nonequilibrium.” Finite element methods were used to analyze for stress concentrations and deformations within all tires that did or did not conform to equilibrium profiles. Finally, tires were built and tested to verify the predictions of these analyses. From the analysis of internal stresses and deformations on inflation and loading and from the actual tire tests, the superior durability of tires with an equilibrium profile was established, and hence it is concluded that an equilibrium profile is a beneficial property of modern belted radial ply tires.

A new type of cracks adding to Griffith–Irwin cracks

2019 ◽  
Vol 485 (2) ◽  
pp. 162-165
Author(s):  
V. A. Babeshko ◽  
O. M. Babeshko ◽  
O. V. Evdokimova
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Tip ◽  
Stress Concentrations ◽  
New Type

The distinctions in the description of the conditions of cracking of materials are revealed. For Griffith–Irwin cracks, fracture is determined by the magnitude of the stress-intensity factor at the crack tip; in the case of the new type of cracks, fracture occurs due to an increase in the stress concentrations up to singular concentrations.

scholarly journals Effect of Laser Power on Microstructure and Micro-Galvanic Corrosion Behavior of a 6061-T6 Aluminum Alloy Welding Joints

Metals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 3
Author(s):  
Huiling Zhou ◽  
Fanglian Fu ◽  
Zhixin Dai ◽  
Yanxin Qiao ◽  
Jian Chen ◽  
...  
Keyword(s):  
Aluminum Alloy ◽  
Laser Power ◽  
Galvanic Corrosion ◽  
Gas Metal Arc Welding ◽  
Immersion Test ◽  
Intermetallic Particles ◽  
Metal Arc Welding ◽  
Corrosion Behaviors ◽  
Welding Joints ◽  
Corrosion Pits

The 6061-T6 aluminum alloy welding joints were fabricated using gas metal arc welding (GMAW) of various laser powers, and the effect of laser power on the microstructure evolution of the welding joints was investigated. The corrosion behaviors of 6061-T6 aluminum alloy welding joints were investigated in 3.5 wt% NaCl solution using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The results showed that the micro-galvanic corrosion initiation from Mg2Si or around the intermetallic particles (Al-Fe-Si) is observed after the immersion test due to the inhomogeneous nature of the microstructure. The preferential dissolution of the Mg2Si and Al-Fe-Si is believed to be the possible cause of pitting corrosion. When the laser power reached 5 kW, the microstructure of the welded joint mainly consisted of Al-Fe-Si rather than the Mg2Si at 2 kW. The relatively higher content of Al-Fe-Si with increasing in laser power would increase the volume of corrosion pits.

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