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Subject: Viscoplastic Modeling of Solder
Author: Michael King ansys_user@
Date: 1999-08-24 15:26:00Hello. I was wondering if anyone had experience with using ANSYS to do
viscoplastic modeling and could answer a question. I'm trying to model a
solder material that is encountering time and spatially dependent thermal
loads and structural loads due to a CTE mismatch. The solder's reaction to
both temperature and to strain rate are important--it is essentially a
viscoplastic material. From the reading I've done, it seems that the best
way to represent the rate and temperature dependence of solder materials is
with a temperature dependent, rate independent elastic-plastic mathematical
model combined with a rate and temperature dependent vicsoplasticity
mathematical model such as Anand's. I know that ANSYS supports Anand's
model through usage of one of the VISCO elements (I'm using VISCO107) and
table input from the material property table (E, NUXY, ALPX) and the ANAND
data table. However, I'm not sure of the following:
1). Do these elements (VISOC107) include both rate independent plasticity
and rate-dependent viscoplasticity? ARe these both built into the ANAND
model? I noticed that ANSYS will also accept input for VISCO107 from the
BISO or MISO elastic-plastic tables. Do I need to define a MISO table in
addition to the ANAND table in order to have the elements take both effects
into account? And does the program even draw input from both tables at the
same time, or from just one or the other?
2). If the VISCO elements do include both the rate independent plasticity
and the rate dependent viscoplasticity, is there a way to use the ANSYS
postprocessor to differentiate between the plastic and the viscoplastic
strains, the way you can with differentiate between plastic and creep
strains when using creep elements?
3). Does doing this require a user-programmed function?
Thanks a lot. I appreciate any input anyone has.
--Mike King
* Michael J. King *
* mking@c... *
* Technical Staff *
* MIT Lincoln Lab *
* Lexington, MA *