Pipe bends, frequently appertained to as elbows, are twisted pipe corridor extensively used in pipeline systems of artificial shops or power stations. Their mechanical gesture compared with straight pipe parts, is significantly further flexible and associated with significantly advanced stresses and strains, and veritably pronounced cross-sectional distortion. Because of their inflexibility, they can accommodate thermal expansions and applied to a tube, pipe or cylinder, during the original stages of lading, the cross section slightly shrinks, maintains its indirect shape up to a critical pressure. Less, at a certain stage, they collapse and distortion of the sampling occurs suddenly. Any similar collapse failure typically will develop into a propagating collapse failure, since the critical collapse pressure of a indirect cylinder is several times larger than the propagation pressure. The external collapse pressure of veritably thin aluminium pipe 6061 is governed by classical elastic buckling formula; still, for thicker tubes more involved elasto-plastic considerations have to be taken into account. There are numerous factors that have some degree of influence on the external pressure that produce the collapse of a aluminium tube, among them:
- slenderness rate ( outside periphery/ length)( D/ l rate),
- yield stress of the tube, shape of the tube sections( outside periphery),
- shape and consistence distribution),
- residual stresses locked in the tube, and
- on a thin aluminium tubes is calculated
localized defects introduced either in the tubes product, in the tubes handling or due to localized wear and tear. In the present work it's shown that external pressure absorb other externally- convinced lading, but they're considered as critical factors for the structural integrity of pipeline systems. For the case of extreme lading conditions, their mechanical response is characterized by a biaxial state of stress and strain, which may lead to pipe elbow failure, in a mode relatively different than the one anticipated in straight pipes. When invariant external pressure theoretically and Finite Element Analysis system that corroborates with experimentally determined values well within the admissible errors.
1.1 Potentiodynamic Polarization Test
Potentiodynamic polarization tests of the chromium nitride carpeted were conducted in 0.5 M NaCl result at 35oC. These tests were carried out on each sample after absorption of 72 hours in result. Potentiodynamic polarization angles of chromium nitride samples prepared and tested in 0.5 M NaCl result in comparison with the uncoated aluminium 6061 pipe. The oxidation process of the essence occurs at the anodic spots of the electrode; this process builds up the semiconducting oxide layeron the electrode and restricts the prolixity of the negative ions through the coatings. The catthodic responses involve the reduction of oxygen or hydrogen which is an electron transfer response through the electrolyte/ coating interface. It can be also observed from these angles that the anodic part of uncoated samples is flatter than the carpeted samples suggesting the adsorption of the essence hydroxide complexes to the sample face which restricts the current inflow.
1.2 Experimental Procedure
The main feature of the response of buried pipeline elbows is the interaction of the deforming pipe with the surrounding soil shows a buried pipeline bend, subjected to axial tension in one end, while been infinitely long at the other end and a finite element model that represents the above physical problem. This employs shell elements for modelling the pipeline, solid elements for modelling the surrounding soil and friction contact conditions for the soil-pipe interface. The aluminium 6061 pipeline under consideration has a 18.5 mm diameter, a thickness of pipe is 1.75mm, and material grade X65 according to API 5L. The elbow is a 90 degree “hot bend” with bend radius parameter R/D equal to 4. The pipeline is pressurized at a level of 5 bar, which is 56% of the maximum design pressure. The pipe is subjected to an axial force F at the right end, and it is considered to be infinitely long at the left end. The latter condition is enforced by the use of special-purpose nonlinear spring elements, which account for pipeline continuity to a length .
- Vertical Length = 200 mm
- Horizontal Length = 200 mm
1.3 Materials and Methodology
Elastic behaviour of Aluminium 6061 Elbow pipe:
In this work, the time dependent elastic deformation of Aluminum Alloy (6061-T6) under constant and variable stress, temperature has been discussed. Creep is employed to generate the mechanical and physical property of materials for various applications at high temperature which are utilized to generate materials embedded with high strength and light weight. The microstructure change has an impact on the creep behavior of the aluminum alloy with heat treatment. The modeling and analysis of specimen were carried out using ANSYS APDL, 14.5. From the numerical analysis result it was found that, the creep rate (strain rate) goes on increases/decreases by gradually increasing the temperature to maximum limit. It was also observed that for a temperature 200°C, creep stain rate was found to be constant. Beyond the predetermined limit (35°C, 0.5 MPa) both increasing the load or temperature, has increase the strain rate and specimens got fractured. It was concluded that for better creep life of Aluminum Alloy (6061-T6) the optimum load range was found to be 100MPa and optimum temperature range was found to be 200°C. The equivalent creep strain analysis was carried out using ANSYS WORKBENCH.
- Design the elbow pipe with the help of Catia v5 with proper dimensions.
- Study the pressure acting over the pipe using ansys workbench.
- Determine the stress distribution due to presence of pressure on pipe.
- Then optimize the pipe using ansys workbench.
Mechanical Properties:
Tensile Yield Strength
|
276 MPa
|
Ultimate Tensile Strength
|
310 MPa
|
Shear Strength
|
207 MPa
|
Fatigue Strength
|
96.5 MPa
|
Modulus of Elasticity
|
68.9 GPa
|
Shear Modulus
|
26GPa
|
Density
|
2.7 g/cm3
|
Poissons Ratio
|
0.33
|
Table No. 1 Mechanical Propertiesof Aluminium 6061
Chemical Compositon:
Element
|
Composition (Mass Percentage
|
Al
|
95.85–98.56
|
Mg
|
0.8–1.2
|
Si
|
0.4–0.8
|
Fe
|
0.2–0.7
|
Cu
|
0.15–0.40
|
Cr
|
0.04–0.35
|
Zn
|
0.5–0.25
|
Ti
|
0.4–0.25
|
Mn
|
0.3–0.15
|
Table No. 2 Chemical Composition of Aluminium 6061
Observations:
The corrosion eventuality of the chromium nitride flicks increases with increase in the deposit power of the flicks. The effect of deposit power of the chromium nitride films on the polarization angles of these flicks is also observable from figure. The corrosion gesture of aluminum blends Al 6061 was developed in a low carbon energy conforming of concentrated waterless results of chromium nitride. The high corrosion resistance of aluminium blends in the result containing up to 1 weight sodium chloride support a safe operation of these accoutrements for construction of storehouse holders and pipeline of these results.