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Title |
Page |
| TUPLS127 |
Permanent Deformation of the LHC Collimator Jaws Induced by Shock Beam Impact: an Analytical and Numerical Interpretation
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1801 |
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- A. Bertarelli, O. Aberle, R.W. Assmann, A. Dallocchio, T. Kurtyka, M. Magistris, M. Mayer, M. Santana-Leitner
CERN, Geneva
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Inspections carried out on jaws of the LHC collimator prototype, which underwent the 450 GeV robustness test in CERN TT40 extraction line, revealed no visible damage, except a permanent deformation of the jaw metal support of ~300 um. An explanation of this phenomenon is proposed in this paper. The temperature increase on the metal support induced by the thermal shock, though limited to ~70°C, led to a sudden expansion of the copper-based support which was partially prevented by the inertia of the material itself, thus generating compressive stresses exceeding the elastic limit of OFE-copper. An analytical assessment of the process, followed by a finite-element transient elasto-plastic analysis, is presented. Numerical results are in good agreement with measured data. In order to confirm this analysis, a special test on series production jaws, where OFE-copper has been replaced by Dispersion Strengthened Copper (Glidcop®), is scheduled for the second half of 2006.
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| TUPLS128 |
A New Analytical Method to Evaluate Transient Thermal Stresses in Cylindrical Rods Hit by Proton Beams
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1804 |
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- A. Dallocchio, A. Bertarelli, T. Kurtyka
CERN, Geneva
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This paper presents an analytical solution for the thermo-mechanical problem of CNGS target rods rapidly heated by fast extracted high energy proton beams. The method allows the computation of the dynamic transient elastic stresses induced by a proton beam hitting off-axis the target. The studies of such dynamic thermo-mechanical problems are usually made via numerical methods. However, an analytical approach is also needed to quickly provide reference solutions for the numerical results. An exact solution for the temperature field is first obtained, using Fourier-Bessel series expansion. Quasi-static thermal stresses are then computed as a function of the calculated temperature distribution, making use of the thermoelastic displacement potential for the equivalent isothermal two-dimensional stress problem. Finally, the contribution of dynamic stresses due to longitudinal and bending stress waves is determined by means of the modal summation method. This method can be effectively applied to any solid having cylindrical shape, made out of isotropic elastic material.
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