Attendees: Emma Gautheron, Michael Guinchard, Ariel Haziot, Marco Masci, Diego Perini

Roland Piccin, Oscar Sacristian de Frutos, Davide Tommasini, Gianluca Vernassa

Comments on context description

• Title of the topic: "Nb3Sn coils: mechanical characterization and modelling"
• Issue (less aggressive): In some magnets, degradation occurs at computed global stresses below the limit, in other magnets, no degradation are observed at computed stress higher than the limit.
• Residual stresses after reaction: there is a dedicated line in HFM for this topic, Cedric Garion
• Objective: Improve modeling of the behavior of the coil during the life steps of a magnet (assembly, reaction, cooldown, powering) looking for a description that relies on properties measured on dedicated samples .

Models

• Description of the evolution of the model from MQXF to 11T (2019) and 11T (2021). 
• A strain/stress curve not including sitting effect is used for validation.
• Previous models are validated with stress only in the transversal direction. Little attention has been paid to model the behavior in the other directions.
• Incoherence are found with model 2021 while going from 3D to 2D.
• 12T today is still juggling between the BISO and MISO or another one not defined yet.

Tests to make toward a standardized 10-stack

• Understand which version of the keystoned stack is more representative of the non-keystoned stack (reference).
• Check the difference between global and local measurements on the exact same sample (displacement of the UTM crosshead combined with DIC).
• Check the influence of the length of the sample on the measurement.
• Check the distribution of stress as a function of the sample configuration using DIC.
• Check influence of load on CTE (experimental set-up to be designed)
• Test could be done with 11T/SMC cable or with MQXF/Flat-MQXF cable. The advantage of using the second one is that it gives us results on future 12T as well.

Considerations

• Michael: The fabrication of the samples should be documented carefully for the next 10-stacks to be made.
• Davide: How could we get the stress inside the sample and not at the interface? Adequate simulations must support this work.
• Diego: Manufacture the molds (reaction and impregnation) for all cables as soon as possible. Don't be shy !

Actions list

• Ariel and Gianluca prepare a test plan to asses the questions raised above
• Ariel launches the design/fabrication of moulds for MQXF and RMM
• Ariel launches the fabrication of 11T/SMC 10 stacks.
• Gather ideas on how to measure CTE as a function of load.