Use FEM for Identifying Boundary Failure of Sheath Cylindrical Vessel

Ingrid Delyová; Peter Sivák; Darina Hroncová

doi:10.12691/ajme-3-6-6

American Journal of Mechanical Engineering

Vol. 3, No. 6, 2015, pp 186-189. doi: 10.12691/ajme-3-6-6 | Research Article

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Use FEM for Identifying Boundary Failure of Sheath Cylindrical Vessel

Ingrid Delyová^1,, Peter Sivák¹, Darina Hroncová²

¹Department of Applied Mechanics and Mechanical Engineering, Faculty of Mechanical Engineering, Technical university of Košice, Košice, Slovakia

²Department of Mechatronics, Faculty of Mechanical Engineering, Technical university of Košice, Košice, Slovakia

	Abstract
1.	Introduction
2.	The Boundary Faults of Membrane State
3.	Conclusion
	Acknowledgement
	References

Abstract

This article deals with the shape bottom effect to different types of stress and deformation process at the junction of the cylindrical part of the shell vessel and its bottom. With the FEM using the SolidWorks were different types of stress and deformations of vessel determined. The calculation is designed as a static and during the research it was not taken any technical process into account such as the temperature impact or the materials nonlinearity, the internal stress. There were used a variety of vessel and also the different types of results were compared during the analysis.

Keywords: FEM, membrane state, flat bottom, shell, bending moment, boundary fault

Cite this article:

Ingrid Delyová, Peter Sivák, Darina Hroncová. Use FEM for Identifying Boundary Failure of Sheath Cylindrical Vessel. American Journal of Mechanical Engineering. Vol. 3, No. 6, 2015, pp 186-189. https://pubs.sciepub.com/ajme/3/6/6

Delyová, Ingrid, Peter Sivák, and Darina Hroncová. "Use FEM for Identifying Boundary Failure of Sheath Cylindrical Vessel." American Journal of Mechanical Engineering 3.6 (2015): 186-189.

Delyová, I. , Sivák, P. , & Hroncová, D. (2015). Use FEM for Identifying Boundary Failure of Sheath Cylindrical Vessel. American Journal of Mechanical Engineering, 3(6), 186-189.

Delyová, Ingrid, Peter Sivák, and Darina Hroncová. "Use FEM for Identifying Boundary Failure of Sheath Cylindrical Vessel." American Journal of Mechanical Engineering 3, no. 6 (2015): 186-189.

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1. Introduction

The structure of all types of tanks and pressure vessels has been affected by the correct application of higher hardness steel theory. There are more and more solutions available now because of modern knowledge. From this reason the theory and its verification together with the practice of knowledge is getting better every day. Also the behavior of structure is much better understood at these days cause of modern information and measure technology. However, the common solution for the shell structures is still very hard to find. The form of the vessel bottom has one of the biggest influence on the stress concentration at the junction of cylindrical casing and the bottom of the vessel. There is also contravention on such places occurred very often. Boundary faults arising at the junction of cylindrical part of the vessel and its bottom are also depending on the length of the cylindrical part of the shell. The junction of cylindrical part of the vessel and its bottom subjects of boundary faults may cause to create unwanted rifts or breakage ^{[1, 2, 3, 4, 5]}.

2. The Boundary Faults of Membrane State

In technical practice there is often several exercises when the common state of stress caused by internal pressure is being simplified. It is because the scrolling forces, bending moment or torque are equal to zero or to very small number so we can neglect them. From the draft perspective it is the condition when the material is being used the best. It is known as the term of membrane stress state. The clean membrane internal state is possible to achieve when the relevant deformation and static balance is created by the membrane forces. However the membrane forces are often unsuccessful and won't achieve these expected deformations by themselves.

The bending state is often bounded to boundary condition which causes unwanted membrane state faults. This is boundary fault which prevents to create the right deformation of membrane state. These faults are getting reduce by the length of boundary. It is often referred as effective length (, it means 0,67% from the value for ). If the length of the cylinder is, then the effect from the one bottom to another one does not occur. However, the value of the length constant c has impact on the fault membrane length state.

The vessel which is strained by the inner overpressure at the junction of cylindrical casing and the bottom of the vessel is prevented of free deformation. From this reason the bending moment occurs on such places and creates the bending stress. Such bending faults of membrane stress create an unwanted condition of casing vessel ^[6].

In the bending state of rotationally symmetric shells is the length of edge fault very small and the limit is given by , where r is radius and t presents the vessel thickness. There is possibility to replace that short section at junction of cylindrical part on every rotational shell. The radius of spare vessel reflects the real forming curve of shell. The approximate solution is more accurate when direction of tangent to generating line will be closer to direction of rotationally axis of whole shell. The most accurate case is when the angle between the tangent of generating line and the rotationally axis will be moved around the90° ^{[1, 2]}.

2.1. The FEM Results of the Vessel Calculation with Its Bottom

With the FEM were monitored the reduced stress spikes and deformation at the sharp passages to spherical bottom if 90°, 60°, 30° and during the penetration to flat bottom at the same thickness of casing and shell.

In case that 90° the membrane effect prevails over the bending effect. The aim of vessel draft is to create the process when the junction of cylindrical part and sphere part is continuously. If 60° and 30° the bending effect at the junction of vessel has to be higher and the stress depends on ratio.

Figure 1 and Figure 2 presents the process of reduced stress lengthwise within the cylindrical casing with the transition to hemisphere bottom where the angle α = 90. The process of the cylindrical part deformation during the transition to hemisphere bottom with angle α = 90 is shown on Figure 3 and Figure 4.

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Use FEM for Identifying Boundary Failure of Sheath Cylindrical Vessel

Use FEM for Identifying Boundary Failure of Sheath Cylindrical Vessel

Abstract

Cite this article:

At a glance: Figures

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1. Introduction

2. The Boundary Faults of Membrane State

3. Conclusion

Acknowledgement

References

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