Full Scale Experimental Analysis of Stress State in Welding Repairs of Drilled Pipelines

2006 ◽  
Author(s):  
Jian Shuai ◽  
Wenping Bu
Keyword(s):  
Shear Stress ◽  
Stress State ◽  
Failure Strain ◽  
Maximum Shear Stress ◽  
Full Scale ◽  
Loading Capacity ◽  
Yield Limit ◽  
Strain Gages ◽  
Similar Yield ◽  
Short Tube

Recently, drilling holes in petroleum transmission pipelines is becoming of major concern for pipeline companies. These drilled pipelines must be repaired through welding ways. There are two ways to repair these pipelines in fields. One is welding a short tube with a cap. Another is welding a patch. In this paper, full scale experiments were conducted to assess the stresses state and the loading capability of the repaired pipelines. The φ711×10 pipelines repaired by welding a tube cap or a patch were pressured to burst failure. Strain gages have been used extensively to monitor stress state in full scale pipeline tests. It was showed that welding a tube cap or a patch resulted in the non-uniform stresses distribution and the stress concentration in the extent. These two kinds of the repaired pipeline has almost the similar yield limit pressure which are approximately equal to 85% of that of pipelines that were not damaged. Patching repair has more restriction to the deformation around a hole than tube capping repair, therefore it may have a little better loading capacity than tube capping repair. The burst pressures in these tests are close to that of pipeline which has not been damaged, whereas the location of burst failure is far from where a short tube or a patch is welded. The burst is a ductile fracture by maximum shear stress.

Discussions on Fracture Factors of Brittle Materials under the Shear-Compression Condition

2011 ◽  
Vol 250-253 ◽  
pp. 90-94
Author(s):  
Zhi Hui Li ◽  
Jun Ping Shi ◽  
An Min Tang
Keyword(s):  
Shear Stress ◽  
Stress State ◽  
Uniaxial Compression ◽  
Frictional Force ◽  
Shear Fracture ◽  
Maximum Shear Stress ◽  
Brittle Materials ◽  
Fracture Mechanisms ◽  
Initiation Point ◽  
Fracture Angle

Based on fundamental ideas in tribology and basic concept of stress state in solid mechanics, the existence of frictional force on shear plane is discussed under uniaxial compression of brittle materials. On account of macroscopic fracture forms and mesoscopic fracture mechanisms, the key factors influencing shear fracture angle are analyzed. The results show that, when brittle materials are compressed and shear fracture occurs, shear fracture surface at the crack initiation point is consistent with the maximum shear stress. But the reason of shear fracture angle examined in experiment greater than 45º lies in that, the existence of frictional force between endface of specimen and pressure head of testing machine, and additional tensile stress produced in the materials when harder crystalline grain wedge in softer medium have changed original uniaxial compression stress state and the direction of maximum shear stress on next fracture path.

Mechanical Stress Measurements in Damascene-Fabricated Aluminum Interconnect Lines

1999 ◽  
Vol 594 ◽  
Author(s):  
Paul R. Besser
Keyword(s):  
Shear Stress ◽  
Stress State ◽  
Aspect Ratio ◽  
Tensile Stress ◽  
Mechanical Stress ◽  
Hydrostatic Stress ◽  
Maximum Shear Stress ◽  
Compressive Stresses ◽  
Biaxial Tensile Stress ◽  
Interconnect Lines

AbstractThe mechanical stress state of damascene-fabricated Al interconnect lines was determined on an array of lines on the product die of a logic technology device. Narrow, unpassivated, damascene Al lines have a purely hydrostatic stress (108 MPa). The hydrostatic stress of damascene Al lines (411 MPa) is much larger once the dielectric is deposited. However, the maximum shear stress remains small in magnitude, compared to RIE Al lines of similar thermal history and aspect ratio. The stress of damascene lines was measured as a function of linewidth. Unpassivated, wide lines, have compressive stresses along the length and width and zero along the line height. Passivated wide lines have a biaxial, tensile stress in-plane and zero along the line height.

Critical Plane Search Method for Biaxial and Multiaxial Fatigue Analysis

2016 ◽  
Author(s):  
Kumarswamy Karpanan
Keyword(s):  
Shear Stress ◽  
Stress State ◽  
Strain Amplitude ◽  
Stress Amplitude ◽  
Maximum Shear Stress ◽  
Fatigue Analysis ◽  
Search Method ◽  
Stress Range ◽  
Critical Plane ◽  
Stress Strain

For complex cyclic loadings, stress- or strain-based critical plane search methods are commonly used for fatigue analysis of the structural components. Complex loadings can result in a non-proportional type loading in which it is difficult or impossible to determine the plane with maximum shear stress/strain amplitude. ASME Sec VIII, Div-3 fatigue analysis for non-welded components is a shear stress based fatigue analysis method and, for non-proportional loading, uses the critical plane search method to calculate the plane with maximum shear stress amplitude. For a two-dimensional non-proportional stress state, analytical stress transformation equations can be used to calculate the shear stress or strain amplitude on any plane at a point. The shear stress range on each plane is the difference between the maximum and minimum shear stress. For a three-dimensional stress state, shear stress amplitude calculations are much more complicated because the shear stress is a vector and both magnitude and direction change during the loading cycle. In ASME VIII-3, the maximum shear stress range among all planes, along with the normal stress on the plane, is used to calculate the stress amplitude. This paper presents a method to calculate the shear stress/strain amplitude using 3D transformation equations. This method can be used for any stress- or strain-based critical plane search method. This paper also discusses ASME proportional and non-proportional fatigue analysis methods in detail.

scholarly journals Studying the performance of fully encapsulated rock bolts with modified structural elements

2021 ◽  
Author(s):  
Jianhang Chen ◽  
Hongbao Zhao ◽  
Fulian He ◽  
Junwen Zhang ◽  
Kangming Tao
Keyword(s):  
Shear Stress ◽  
Load Transfer ◽  
Maximum Shear Stress ◽  
Coupling Model ◽  
Numerical Approach ◽  
Rock Bolt ◽  
Structural Elements ◽  
Rock Bolts ◽  
Two Stage ◽  
Bolt Diameter

AbstractNumerical simulation is a useful tool in investigating the loading performance of rock bolts. The cable structural elements (cableSELs) in FLAC3D are commonly adopted to simulate rock bolts to solve geotechnical issues. In this study, the bonding performance of the interface between the rock bolt and the grout material was simulated with a two-stage shearing coupling model. Furthermore, the FISH language was used to incorporate this two-stage shear coupling model into FLAC3D to modify the current cableSELs. Comparison was performed between numerical and experimental results to confirm that the numerical approach can properly simulate the loading performance of rock bolts. Based on the modified cableSELs, the influence of the bolt diameter on the performance of rock bolts and the shear stress propagation along the interface between the bolt and the grout were studied. The simulation results indicated that the load transfer capacity of rock bolts rose with the rock bolt diameter apparently. With the bolt diameter increasing, the performance of the rock bolting system was likely to change from the ductile behaviour to the brittle behaviour. Moreover, after the rock bolt was loaded, the position where the maximum shear stress occurred was variable. Specifically, with the continuous loading, it shifted from the rock bolt loaded end to the other end.

Flow and Thermal Fields in a Pendant Droplet Moving on Lyophobic Surface

2010 ◽  
Author(s):  
Basant Singh Sikarwar ◽  
K. Muralidhar ◽  
Sameer Khandekar
Keyword(s):  
Heat Transfer ◽  
Contact Angle ◽  
Reynolds Number ◽  
Shear Stress ◽  
Heat Transfer Coefficient ◽  
Wall Shear Stress ◽  
Transfer Coefficient ◽  
Maximum Shear Stress ◽  
Computational Domain ◽  
Wall Shear

Clusters of liquid drops growing and moving on physically or chemically textured lyophobic surfaces are encountered in drop-wise mode of vapor condensation. As opposed to film-wise condensation, drops permit a large heat transfer coefficient and are hence attractive. However, the temporal sustainability of drop formation on a surface is a challenging task, primarily because the sliding drops eventually leach away the lyophobicity promoter layer. Assuming that there is no chemical reaction between the promoter and the condensing liquid, the wall shear stress (viscous resistance) is the prime parameter for controlling physical leaching. The dynamic shape of individual droplets, as they form and roll/slide on such surfaces, determines the effective shear interaction at the wall. Given a shear stress distribution of an individual droplet, the net effect of droplet ensemble can be determined using the time averaged population density during condensation. In this paper, we solve the Navier-Stokes and the energy equation in three-dimensions on an unstructured tetrahedral grid representing the computational domain corresponding to an isolated pendant droplet sliding on a lyophobic substrate. We correlate the droplet Reynolds number (Re = 10–500, based on droplet hydraulic diameter), contact angle and shape of droplet with wall shear stress and heat transfer coefficient. The simulations presented here are for Prandtl Number (Pr) = 5.8. We see that, both Poiseuille number (Po) and Nusselt number (Nu), increase with increasing the droplet Reynolds number. The maximum shear stress as well as heat transfer occurs at the droplet corners. For a given droplet volume, increasing contact angle decreases the transport coefficients.

A critical look at the Wallace-Bott hypothesis in fault-slip analysis

2013 ◽  
Vol 184 (4-5) ◽  
pp. 299-306 ◽  
Author(s):  
Richard J. Lisle
Keyword(s):  
Shear Stress ◽  
Maximum Shear Stress ◽  
Fault Slip ◽  
Shear Stresses ◽  
Homogeneous State ◽  
Slip Direction ◽  
Fault Surface ◽  
State Of Stress ◽  
Simultaneous Movement

AbstractThe assumption is widely made that slip on faults occurs in the direction of maximum resolved shear stress, an assumption known as the Wallace-Bott hypothesis. This assumption is used to theoretically predict slip directions from known in situ stresses, and also as the basis of palaeostress inversion from fault-slip data. This paper examines different situations in relation to the appropriateness of this assumption. Firstly, it is shown that the magnitude of the shear stress resolved within a plane is a function with a poorly defined maximum direction, so that shear stress values greater than 90% of the maximum occur within a wide angular range (± 26°) degrees. The situation of simultaneous movement on pairs of faults requires slip on each fault to be parallel to their mutual line of intersection. However, the resolved shear stresses arising from a homogeneous state of stress do not accord with such a slip arrangement except in the case of pairs of perpendicular faults. Where fault surfaces are non-planar, the directions of resolved shear stress in general give, according to the Wallace-Bott hypothesis, a set of slip directions of rigid fault blocks, which is generally kinematically incompatible. Finally, a simple model of a corrugated fault suggests that any anisotropy of the shear strength of the fault such as that arising from fault surface topography, can lead to a significant angular difference between the directions of maximum shear stress and the slip direction.These findings have relevance to the design of procedures used to estimate palaeostresses and the amount of data required for this type of analysis.

Study on Thermal Cycling of Sn0.7Cu Solder

2013 ◽  
Vol 791-793 ◽  
pp. 362-365
Author(s):  
Li Yang ◽  
Ju Li Li ◽  
Jing Guo Ge ◽  
Meng Li ◽  
Nan Ji
Keyword(s):  
Shear Stress ◽  
Steady State ◽  
High Temperature ◽  
Thermal Cycling ◽  
Shear Strain ◽  
Maximum Shear Stress ◽  
Steady State Creep ◽  
Maximum Shear Strain ◽  
Cycle Number ◽  
State Cycle

Thermal cycling of a unit Sn0.7Cu solder was studied based on the steady-state creep constitutive equation and Matlab software. The results show that there is a steady-state cycle for the thermal cycling of unit Sn0.7Cu eutectic solder. In steady-state thermal cycling, the shear stress is increased with the increase of temperature. There is a stage of stress relaxation during high temperature. A liner relationship between maximum shear stress and maximum shear strain is observed during thermal cycling. The metastable cycle number is declined greatly with the increase of maximum shear strain.

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