design of a support system for the vertical beam transfer ... · for the vertical beam transfer...

Design of a support system for the vertical beam transfer lines of the ELENA project

September 2016

Author: Kristiyan Bozhkov

Supervisors: Antti Juhani Kolehmainen Diego Perini

CERN Summer Student Report 2016

of 15

Table of contents

1. Introduction .................................................................................................................................... 2

2. Support system requirements ....................................................................................................... 3

3. First design ...................................................................................................................................... 3

4. Simulation results for the first design ........................................................................................... 5

4.1 Deformation and stress results for the girder ....................................................................... 5

4.2 Deformation and stress results for the alignment table....................................................... 6

4.3 Static structural analysis of the vessels ................................................................................. 7

4.3.1 FE model ......................................................................................................................... 8

4.3.2 Overall deformation results ........................................................................................... 9

4.3.3 Mechanical properties of the quadrupole, the U-shaped plates and the pins ............ 9

4.3.4 Stress results ................................................................................................................. 10

5. Second design ............................................................................................................................... 12

6. Simulation results for the second design .................................................................................... 13

6.1 Overall deformation results ................................................................................................. 13

6.2 Stress results ......................................................................................................................... 13

7. Conclusion .................................................................................................................................... 15

8. References .................................................................................................................................... 15

http://en-dep.web.cern.ch/en-dep/index.html

of 15

1. Introduction During my stay in CERN as a summer student I was introduced to work in the engineering department

and more precisely in the group of mechanical and materials engineering.

My work was in relation with the ELENA (Extra Low ENergy Anti-proton) project which is a new

accelerator currently being built inside the anti – proton decelerator. ELENA is an upgrade of the Anti-

proton Decelerator (AD) at CERN and is devoted to special experiments with physics using low energy

anti-protons. ELENA will increase the number of useful anti-protons by about two orders of magnitude

and will allow to serve up to four experiments, ATRAP, ALPHA, ASACUSA and AEGIS, simultaneously

with anti-protons of reduced energy from 5.3 MeV to 100 keV.

The reduction of the energy is carried out by small ring of circumference 30.4 m where the anti-

protons travel. Then they are sent through the beam lines to the experiments. The ring and the rest

of the beam lines can be seen in figure 1.

Most of the design for all supports and components for the horizontal lines is already done and

engineers and technicians are currently installing them for the first phase of ELENA, the ELENA ring.

My task during my stay in CERN was to create and design the support of the two vertical lines that are

going towards the ATRAP experiment. They are surrounded in red in figure 1 and better represented

(by zooming and hiding some of the parts) in figure 2.

Figure 1 – ELENA lines

Figure 2 – Vertical lines and quadrupole

Welded jaw

connectors

Measurement

equipment


of 15

2. Support system requirements The support system must be able to carry the supported equipment on its place, with no change to its

position, during the life-time of the decelerator. The life-time is expected to be 20 years. The system

must be able to resist the gravitational load and the forces resulting from the pressure differences

between the atmospheric pressure and the Ultra High Vacuum inside the equipment.

The support system must allow the equipment to be aligned within ±0.2 mm with respect to the

theoretical beam line. The support for the two vertical beam lines can be the same.

The support system must allow the thermal expansion resulting from the bake-out (heating the

equipment up to 250 °C on the internal surfaces) to occur without any damages to the equipment or

to the support system. When temperature returns to ambient, around 20 °C, the equipment must

return to its original position.

No fixation of the support system might be placed on the roof or on the walls of the tunnel hosting

the beam line. When looking downstream on the beam line, the right-hand-side of the beam line must

be left free for passage.

3. First design The design of the supports for the horizontal lines was also introduced to the vertical lines. The system

and its functioning is represented in figure 3. The quadrupoles and the secondary emittance monitor

between them are hidden to better represent the support.

fixed point

Boundary conditions Figure 3 – Support tables

Pins

4 anti-buckling

columns

6 screw supports

4 U-shaped support plates

8 M16x40 bolts fixing the

base plate to the girder

4 M16x137 threaded rods

4 Hex screws M8x60


of 15

The ELENA quadrupoles represent a vacuum vessel supported by four jaw connectors. The connectors

are welded together with the vessel using fillet welds placed on the upper and lower extremity of each

jaw. The jaw connectors are screwed to the U-shaped support plates designed to allow for an elastic

deformation. The support plates can slide on the foot plate thanks to seven-spring bolts and permit

the longitudinal and transversal expansion of the tanks during the bake-out (thermal expansion). Two

additional connectors for supporting the measurement equipment are welded on the other side of

the vessel. The model with component description is shown in Figure 2.

The foot plate, which acts as a common base plate for the two quadrupoles and the SEM, is aligned

on the alignment table thanks to the 6 screw supports and then fixed to it with 4 hex screws

represented in figure 3. Four pins were added to the top “U” shaped plate which allow to avoid the

eventual rotation due to the force coming from the difference of the pressure inside and outside the

vessel, and resulting in axial force in the assembly.

The design of the girder to which the base plate of the alignment table is attached is represented in

figure 4.

Two reinforcement plates are added to each side for more security. The profiles and the reinforcement

plates are screwed to the support as shown on figure 4 (view from below). The safety screw support

is added as an extra security for the base plate attached to the girder.

2 reinforcement

plates

Concrete

2670 mm

Safety screw

support

Figure 4 - Girder

2 profiles 80x240x2670

3 profiles 80x240x170

Support plate

Support plate – view from below


of 15

4. Simulation results for the first design In order to start the simulation, calculation of the different forces was established as shown in figure 5.

4.1 Deformation and stress results for the girder For every simulation a simplified assembly was first created. A remote force of 2100 N (1050 N if

symmetry) was applied on the theoretical axis of the beam lines. Symmetry was also applied to reduce

the simulation time. Results of the simulation of the girder are shown on figure 6.

Figure 5 – Calculation of the applied force

Figure 6 – Simulation results for the girder

Worst case during maintenance

Normal operation


of 15

The stress and the deformation on the girder are significantly small and therefore acceptable, and the

design can be approved. The material is aluminium EN AW 6063 T66 with R0.2% = 200 MPa [1]

4.2 Deformation and stress results for the alignment table For the simplified assembly a small bloc was created to which the base plates were attached. The bloc

is fixed and again a remote force of 2100 N was applied on the axis of the beam lines. Firstly, the plates

were designed to have three rods so the system can be isostatic, thus easier to align. Results for this

design are shown in figure 7.

Top 2 threaded rods

Bottom 2 threaded rods

Figure 7 – Simulation results for the base plates with 3 rods

Figure 8 – Simulation results for the base plates with 4 rods


of 15

On figure 8 are shown the results for the design with 4 rods. The highest stress values 271 MPa and

211 MPa on the bottom threaded rods are due to the edge where the anti-buckling column and the

threaded rod are connected. These values could be a numerical error because a refinement was done

on this particular area and they became bigger. Moreover, each value was applied on one particular

element. For an extra – security the design with 4 threaded rods will be accepted even if the system

will then become hyperstatic.

A small calculation was done to calculate the actual stress on one rod. The following formula was used:

𝜎 =M. e

𝐼𝑦𝑦=

𝐹. 𝑙. 𝑒𝜋

64𝑑4

= 95 𝑀𝑃𝑎

The plates and the anti – buckling columns are made of aluminium EN AW-6082 (T6) and the treaded

rods - stainless steel 316 1.4401. Linear elastic isotropic models of the two materials were

implemented within ANSYS. Mechanical properties only for the stainless steel are shown on table 1

since all the stress is applied on the threaded rods.

Material: Stainless Steel 316 1.4401 [1]

Temperature

20 °C

Poisson

ratio

Elastic

modulus Density Rp0.2 Rp1.0

Tensile

strength

Number - (GPa) (kg/m3) (MPa) (MPa) (MPa)

1.4401 0.29 193 7950 220 260 530-680

4.3 Static structural analysis of the vessels For this simulation an assembly with only the foot plate, the U-shaped supports, the pins and the

vessels was created. First, an atmospheric pressure of 0.1 MPa on the three vessels was applied.

The bolted joints between the U-shaped support plates and the jaw connectors were replaced by

bonded contacts. Exception makes the contact between the top U-shaped support and the top

connectors – it was replaced by “no separation”, to be able to evaluate the stress transmitted on the

pins. The contact between the pins and the support plate with the connector is also bonded.

The contacts between the U-shaped supporting plates and foot plate were considered as “no

separation” to allow a limited sliding. Again, exception makes the top supporting plate – the contact

is bonded because the supporting plate cannot slide the longitudinal direction (figure 3). Since the

other three U-shaped plates can slide the longitudinal direction, the boundary conditions were

considered as symmetric and symmetry was applied to simplify the model. The foot plate is considered

as fixed.

In order to model the welds between the jaw connectors and the vessels, face to face and edge to

face contacts were defined (figure 9). They restrain the relative rotation of the vessel around the weld

that simulate the real behaviour of the welds. The edge to face contacts are considered as bonded

and the face to face contacts as “frictional” with a coefficient of friction f = 0.7 (between stainless

steels [4]). The rest of the contacts between the components were generated automatically and set

as bonded.

F – Force on one rod =2100

4= 525 𝑁

𝑙 – length of the rod = 73 𝑚𝑚

𝑒 – Radius of the rod = 8 𝑚𝑚

𝐼𝑦𝑦 – moment of inertia with

Table 1 – Mechanical properties of St. steel 316 at 20 °C


of 15

4.3.1 FE model In order to simplify the model and use advantageous shell elements, the internal surface of the tanks

was extracted and 3 mm thickness was assigned. A geometry cleaning was done to prepare the FE

model. Some simplifications were made. The unnecessary holes and non-essential components were

removed. The bolted joints between the support plates and welded connectors were replaced by the

bonded contacts between the faces.

The mesh for the quadrupoles (Figure 10) was generated with focus on the region with welded joints

between the vessels and the connectors. The most critical regions were refined to capture the stress

triggered by the vertical load of 2100 N on the centre axis of the vessels. The top U-shaped plate was

also refined because it’s fixed and therefore it triggers some stress.

no separation contact face to face contact -

frictional

edge to face contact -

bonded

Figure 9 – Contacts

U-shaped plates

3 mm

3 mm

3 mm

2 mm

0.5 mm

2 mm

1 mm

1 mm

15 mm

Figure 10 – Meshed equipment with refinement

Sym

met

ry


of 15

4.3.2 Overall deformation results A maximum deformation of 0.65 mm is obtained for the installation. As shown on figure 11 the

deformation is propagated through the whole assembly. Therefore, a conclusion can be drawn that

the equipment is rigid enough. During normal operation, a force of 270 N is applied (case 3). The

deformation is, as expected, smaller – 0.26 mm (figure 12). Before integrating the vertical equipment

this displacement should be first discussed with the equipment responsible.

4.3.3 Mechanical properties of the quadrupole, the U-shaped plates and the

pins All components of the quadrupole, including the jaw connectors, are made of the stainless steel

1.4429 (316LN), the U-shaped plates of stainless steel 1.4301 and the pins of hardened martensitic

stainless steel, grade C1, class 110. Linear elastic isotropic model of these materials was implemented

within ANSYS. The mechanical properties of these materials for 20˚C were needed in order to calculate

the stresses due to the vertical load of 2100 N.

Material: Stainless Steel 1.4429, 1.4301 and C1 110 [1] [3]

Temperature

20 °C

Poisson

ratio

Elastic


Max

allowable

stress

Tensile

strength

Number - (GPa) (kg/m3) (MPa) (MPa) (MPa) (MPa)

1.4429 0.27 196 7950 280 320 213 550-700

1.4301 0.29 200 7900 230 260 173 540-750

C1 110 0.3 200 7850 820 - - 1100

Figure 11 – Total deformation –

case 1 – 2100 N

Table 2 – Mechanical properties of St. steel 1.4429 and 1.4301 at 20 °C

Figure 12 – Total deformation –

case 3 – 270 N


of 15

4.3.4 Stress results

Figure 13 – Overall stress intensity

Figure 14 – Welded connector – back view

Figure 16 – Welded connector – front view Figure 17 – Stress intensity for the pins

Figure 15 – Stress intensity for the top vessel

Figure 18 – Stress intensity for the support plate


of 15

The main stresses are concentrate on the top weld connector because it’s attached to the top U-

shaped plate which is fixed to the plate. The results for this connector are shown in figure 14 and 16.

Numerical singularities were observed as a result of the contacts that replace welds.

The stress on the support plate (figure 18) is distributed around the edge of the plate and there could

be some plasticization but it should not affect the whole installation. The peak values of the stress are

due to the edge effect, where the foot plate is connected, and do not affect the overall strength of

the structure.

High stress values were also found for the pins (figure 17) and on the holes where they are attached

to the connector (figure 16). To be able to calculate the actual stress on the pins a new simulation was

performed without the pins. A bonded surface was considered between the support plate and the

welded connector. By extracting the axial forces, the global force was then calculated as follows:

𝐹 = √𝐹𝑧2 + 𝐹𝑦

2 = 1138 𝑁

Stress results for the vessel where the connector is welded are shown in figure 15. The stress found

at the bottom left part of the vessel is a little bit higher than the elastic limit of this material – 280

MPa. Multiple simulations were done to check carefully the stress on the vessel and the welds of the

jaw connectors. A calculation of the stress on the welds was done by creating a coordinate system on

the weld (45° between the edge and the Y axis) and by extracting forces on every direction and

referring to the EN welding code [5]:

𝜎𝑤𝑒𝑙𝑑 = √𝜎┴2 + 3(𝜏┴

2 + 𝜏||2) ≈ 14,5 𝑀𝑃𝑎

During the thermal expansion, the temperature is rising up to 250 °C. The yield strength of the material

of the vessels (stainless steel 316LN 1.4429) is descending down to 155 MPa at that temperature. The

conclusion is that the obtained stress value is not a numerical singularity since it’s applied on multiple

elements as shown on figure 15. Some plasticization can arise on the vessel in this particular area. The

welds will sustain the load on the equipment but since the structure is twisting they may penetrate

the vessel and small fractures or fissures can occur.

The welds were therefore seen as a risky part to support the vessels. A supporting was planned to be

connected to a part robust enough itself to resist the load – the uppermost flange. The final decision

was to create a new design which will replace the top U – shaped support plate fixed to the foot

plate.

Material: Stainless Steel 1.4429 [1]

Temperature

250 °C

Poisson

ratio

Elastic


Max

allowable

stress

Tensile

strength

Number - (GPa) (kg/m3) (MPa) (MPa) (MPa) (MPa)

1.4429 0.27 196 7950 155 183 122 -

and thus the shear stress also: 𝜏 =𝐹

𝑆𝑝𝑖𝑛= 58 𝑀𝑃𝑎

Table 3 – Mechanical properties of St. steel 1.4429 at 250 °C

Figure 19 –

Coordinating

system on

the weld


of 15

5. Second design The second design consisted on creating a more rigid support than the U-shaped support plate. For

this purpose two brackets were created and positioned under the uppermost flange (figures 20 and

21). They were fixed to the foot plate using two supporting plates and one connecting the two

brackets. The holes created on the brackets allow the bolts and the washers, used to close the vacuum

flanges together, to be inserted. The brackets are fixed to the jaw connectors via small plate and three

M8 bolts.

Support

plates

Small plate

Connecting plate

Brackets

Pins

Spring

washers stack

Vertical

M8 bolt

Touching

top surface

Figure 20 – Brackets under flange

Figure 21 – Brackets

Figure 22 – Pins and washers

Four pins were also added (figure 22) to the sides of the brackets. Beside them, a spring washer

stack is placed and then tightened with M10 bolts. During the thermal expansion of the vessel, the

pins will retreat and they will return back when the temperature decrease. Two vertical M8 bolts

(figure 22) are screwed to each side through the bracket and tightened till the top surface of the

top jaw connector. The goal is that when a vertical load of 315 N is applied upwards during

maintenance (case 2 – figure 5) the bolt will transfer the vertical load to the bracket and thus to

the connection bracket – flange.


of 15

6. Simulation results for the second design The same mesh was used again. A refinement was done on the new brackets as well on the small

plates connecting the brackets with the top jaw connectors. All bolted joints were replaced again with

bonded contacts. A “no separation” contact was applied between the bracket and the flange.

6.1 Overall deformation results The deformation obtained for the new design is no more than 0.2 mm for both of the cases as shown

on figures 23 and 24. This deformation is due to the atmospheric pressure applied on the vessels.

There is almost no deformation coming from the vertical load (2100 N or 270 N) applied on the

equipment which means that the installation is robust and rigid.

6.2 Stress results The stress is almost equally distributed through the whole assembly. Some numerical singularities

were found again on the welds of the connectors (figure 27). The stress on the vessel was carefully

checked (figure 26) and the highest value found is 95 MPa due to the atmospheric pressure as there

is vacuum inside the quadrupoles. This stress is fully acceptable as the elastic limit of the material is

280 MPa (table 2).

The stress for the small plate, the support plate and the bracket was also checked (figures 28, 29 and

30). The material of these parts is the same as for the U-shaped support plates – stainless steel 1.4301

(table 2). The biggest stress found – 73 MPa, is again completely acceptable.

The final conclusion is that the second design is reliable and acceptable with stresses no bigger than

95 MPa which leaves a large margin of safety factor – 𝑆𝐹 =𝐸𝐿

95≈ 3 for 20 °C and 𝑆𝐹 =

𝐸𝐿

95≈ 1.6 for

250 °C.

Figure 23 – Overall deformation – second

design – worst case - 2100 N

Figure 24 – Overall deformation – second

design – normal operation - 270 N


of 15

Figure 29 – Stress – support plate

Figure 26 – Stress on the vessels

Figure 27 – Stress – welded connector

Figure 25 – Overall stress intensity – second design

Figure 28 – Stress – small plate

Figure 30 – Stress – bracket


of 15

7. Conclusion The simulations showed that the stress intensity for the quadrupoles and other parts of the second

design during the vertical load of 2100 N is acceptable. The simulations for the other two cases of the

vertical load don’t have significant difference.

The final conclusion is that the second design is reliable but maybe too complicated to be integrated.

Still some design upgrades can be done but the main idea of putting a more rigid support instead of a

U-shaped plate can be approved. Since the interface plate, placed between the top flange and the

sector valve is not yet designed, fixing the support on this part could be a good idea.

I would like to express my gratitude to my supervisors and the design and simulation office, to the

help they provided to me during my internship in the group MME.

I would like to thank also the summer student team for all the effort and good organization making

the summer student program an interesting event.

I also acknowledge all the lecturers and professors for these six weeks of interesting lectures that they

provided to the summer students.

I thank also all the summer students for making this stay a truly valuable experience.

Throughout these months I have gained highly appreciated experience in the designing and simulation

field by strengthening my knowledges in CATIA V5 and ANSYS programs.

8. References [1] https://www.rk-rose-krieger.com/fileadmin/catalogue/profiltechnik/bl_aluprofilsystem_en.pdf - page 470,

appendix

[2] EN 10088-2, Stainless steels. Part 2: Technical delivery conditions for sheet/plate and strip of corrosion

resisting steels for general purposes. September 2005 – Tables 10 and 15.

[3] ISO 3506-1, Mechanical properties of corrosion resistant stainless-steel fasteners – Table 3.

[4] Website http://www.roymech.co.uk/Useful_Tables/Tribology/co_of_frict.htm#coefficients

[5] Website http://www.mitcalc.com/doc/welding/help/en/welding.htm


https://www.rk-rose-krieger.com/fileadmin/catalogue/profiltechnik/bl_aluprofilsystem_en.pdf

http://www.roymech.co.uk/Useful_Tables/Tribology/co_of_frict.htm#coefficients

http://www.mitcalc.com/doc/welding/help/en/welding.htm

design of a support system for the vertical beam transfer ... · for the vertical beam transfer...

Documents