Luca Dassa – 23/03/2015 1 / 9CRAB cavities meeting

Stress linearization• Analysis performed on the sub-model (with previous remarks)• I think that in any case the main considerations are the same

FEM (1)

From test performed on material EDMS 1493400 -> Rp0.2 = 70 MPa

Standard FEM strength assessmentAccording to EN 13445-3:2002 -> f = Rp0.2/1.5 = 47 MPa

Design by analysis – method based on stress categoriesAccording to EN 13445-3:2002 -> 1.5*f = 70 Mpa

What about bending stress? Primary or secondary?I assume that they are primary stress

(𝜎𝑒𝑞 )𝑃𝑚≤ 𝑓

(𝜎𝑒𝑞 )𝑃𝑚+𝑃𝑏≤1.5∗ 𝑓

Luca Dassa – 23/03/2015 2 / 9CRAB cavities meeting

FEM (2)

Path 1

1.5 f = 70 MPa

Luca Dassa – 23/03/2015 3 / 9CRAB cavities meeting

FEM (3)Path 2

1.5 f = 70 MPa

Luca Dassa – 23/03/2015 4 / 9CRAB cavities meeting

FEM (4)Path 3

1.5 f = 70 MPa

Luca Dassa – 23/03/2015 5 / 9CRAB cavities meeting

FEM (5)

Conclusions:• Standard FEM strength assessment: NOT VERIFIED• Design by analysis – method based on stress categories: NOT VERIFIED

Design by analysis – Direct Route-> material constitutive law: linear-elastic ideal-plastic-> very complicate strength assessment

Should we go with strength assessment according to “Design by analysis – Direct Route“ ?

Luca Dassa – 23/03/2015 6 / 9CRAB cavities meeting

Galling

Galling on bolts• It seems that galling could be a problem, above all with super-clean bolts• Coating on Ti bolt never requested at CERN (phone call with M. Malabaila)• threaded inserts? (available in stainless steel and Nitronic 60 (Jeweka))

M6x1 L=9 mm available• A possible solution that we´ve researched only at present, is hardening the

Titanium Grade 5 surface of the fasteners by making use of Ion Implantation. Kolsterizing this material is not possible, but the results I´ve seen on paper from Ion Implantation look promising. Advantage of this message is, that it´s not a coating that can come off and produce particles.

Luca Dassa – 23/03/2015 7 / 9CRAB cavities meeting

Washers: another possibility?

Washers

Luca Dassa – 23/03/2015 8 / 9CRAB cavities meeting

Tests on bolts: works in progress

Test on bolts

Luca Dassa – 23/03/2015 9 / 9CRAB cavities meeting

HSE meeting

Meeting with HSE (C. Arregui Rementeria) on 20/03/2015:

• What has been stated by HSE in the past is not anymore valid• Voltage in the cavity is not a reason to be out of the scope of PED directive,

as well the exotic materials• The equipment should be CE marked!• Since we are dealing with category 1 equipment, an exemption could be

discussed, but it shall be supported by valid reasons