## General Mechanical

#### [Concrete_SOLID65] Plasticity algorithm did not converge for element xxx

• 7121573
Subscriber

Hello everyone, I am currently working on an analysis of Rebar and Concrete bonds.

I am currently analyzing a Rebar and Concrete bond. I am using SOLID65 for the concrete elements, SOLID185 for the rebar elements, and CONTA174 and TARGE170 for the bond between the two. The analysis converges when SOLID65 is below APDL.

********************************************************************************

! Determination of elastic behavior of materials

Es = 27056 ! Modulus of Static Elasticity [MPa]

nus = 0.18 ! Poisson's ratio [-]

! SOLID65 value setting (TBDATA)

So = 0.35 ! Shear transfer coefficient of open cracks [-].

Sc = 1.0 ! Shear transfer coefficient of closed cracks [-].

Tc = 3.0 ! Uniaxial Tensile Cracking Stress [MPa]

Cc = -1 ! Uniaxial compressive failure stress [MPa]

! If the values of Tc and Cc are set to -1, the ability to crack and failure, respectively, is lost

!ET: Define element types from the element library

ET,MATID,SOLID65 ! Define

!MPTEMP: Define temperature of material properties

MPTEMP,,,,,,,, !?

MPTEMP,1,20 ! Define temperature as <20>

!MPDATA: Definition of material properties corresponding to the temperature set in MPTEMP

MPDATA,EX,MATID,,Es ! Define at temperature <20>

MPDATA,PRXY,MATID,,nus ! Define at temperature <20>

!TB: Activate data tables for entering material properties and special elements

TB,MISO,MATID,1,23,0 ! defined by <3> lines for <1> temperature

TBTEMP,20 ! Define temperature as <20>

! Define stress-strain curve

TBPT,,0.0000818796,2.2153333333

TBPT,,0.0001637591,4.4306666667

TBPT,,0.0002456387,6.6460000000

TBPT,,0.0003275182,8.8613333333

TBPT,,0.0004093978,11.0766666667

TBPT,,0.0005000000,13.2920000000

TBPT,,0.0005950000,15.5073333333

TBPT,,0.0007000000,17.7226666667

TBPT,,0.0008100000,19.9380000000

TBPT,,0.0009300000,22.1533333333

TBPT,,0.0010907468,24.3686666667

TBPT,,0.0012432646,26.5840000000

TBPT,,0.0014257215,28.7993333333

TBPT,,0.0016615890,31.0146666667

TBPT,,0.0022800000,33.2300000000

TBPT,,0.0023000000,33.2300000000

TBPT,,0.0024000000,33.2300000000

TBPT,,0.0025000000,33.2300000000

TBPT,,0.0026000000,33.2300000000

TBPT,,0.0027000000,33.2300000000

TBPT,,0.0028000000,33.2300000000

TBPT,,0.0029000000,33.2300000000

TBPT,,0.0030000000,33.2300000000

!TB: Activate data tables for entering material properties and special elements

TB,CONC,MATID,1,9, ! defines <9> values for <1> temperature

TBTEMP,20 ! Define temperature as <20>

TBDATA,1,So,Sc,Tc,Cc,, ! Define set values (5 to 9 are <0 (blank)>)

TBDATA,,,,,,,

********************************************************************************

However, for the following APDL, where neither the strength nor Young's modulus of the concrete has changed much, I get the error "Plasticity algorithm did not convert for element 63979,, material 1." and the analysis does not converge. (The study ends after about 1%.)

The element displayed in error is often on the concrete side of the interface between Rebar and concrete.

********************************************************************************

! Determination of elastic behavior of materials

Es = 26965.5110297712 ! Modulus of Static Elasticity [MPa]

nus = 0.18 ! Poisson's ratio [-]

!SOLID65 value setting (TBDATA)

So = 0.35! Shear transfer coefficient of open cracks [-].

Sc = 1.0 ! Shear transfer coefficient of closed cracks [-].

Tc = 3.0 ! Uniaxial Tensile Cracking Stress [MPa]

Cc = -1 ! Uniaxial compressive failure stress [MPa]

! If the values of Tc and Cc are set to -1, the ability to crack and failure, respectively, is lost

!ET: Define element types from the element library

ET,MATID,SOLID65 ! Define !MPTEMP: Define temperature of material properties

MPTEMP,,,,,,,, !?

MPTEMP,1,20 ! Define temperature as <20>

!MPDATA: Definition of material properties corresponding to the temperature set in MPTEMP

MPDATA,EX,MATID,,Es ! Define at temperature <20>

MPDATA,PRXY,MATID,,nus ! Define at temperature <20>

!TB: Activate data tables for entering material properties and special elements

TB,MISO,MATID,1,23,0 ! defined by <3> lines for <1> temperature

TBTEMP,20 ! Define temperature as <20>

! Define stress-strain curve

TBPT,,0.0000813328,2.1931800000

TBPT,,0.0001626656,4.3863600000

TBPT,,0.0002439983,6.5795400000

TBPT,,0.0003253311,8.7727200000

TBPT,,0.0004066639,10.9659000000

TBPT,,0.0004966611,13.1590800000

TBPT,,0.0005910267,15.3522600000

TBPT,,0.0006953255,17.5454400000

TBPT,,0.0008045910,19.7386200000

TBPT,,0.0009237896,21.9318000000

TBPT,,0.0010834630,24.1249800000

TBPT,,0.0012349623,26.3181600000

TBPT,,0.0014162008,28.5113400000

TBPT,,0.0016504932,30.7045200000

TBPT,,0.0022647746,32.8977000000

TBPT,,0.0022846410,32.8977000000

TBPT,,0.0023839732,32.8977000000

TBPT,,0.0024833054,32.8977000000

TBPT,,0.0025826376,32.8977000000

TBPT,,0.0026819699,32.8977000000

TBPT,,0.0027813021,32.8977000000

TBPT,,0.0028806343,32.8977000000

TBPT,,0.0029799665,32.8977000000

!TB: Activate data tables for entering material properties and special elements

TB,CONC,MATID,1,9, ! defines <9> values for <1> temperature

TBTEMP,20 ! Define temperature as <20>

TBDATA,1,So,Sc,Tc,Cc,, ! Define set values (5 to 9 are <0 (blank)>)

TBDATA,,,,,,,

********************************************************************************

If anyone knows the cause, I would appreciate it if you could let me know.

• Ashish Khemka
Ansys Employee

Hi,

For the error message:

Plasticity algorithm did not converge for element xxx

This message is displayed when Ansys is not able to converge plastic deformation increment. This generally occurs when the load is rapidly applied. I would suggest you apply load more slowly by increasing the number of substeps using the NSUBST command. // Command Reference // XV. N Commands // NSUBST.

Regards,

Ashish Khemka

• 7121573
Subscriber

Ashish Khemka Thank you very much for your advice on concrete analysis. What I am wondering this time is that one of the MISO models shown above errors rapidly, even though the behavior is almost the same. Also, even if I increase the sub-step to 10000, the error occurs at 1%. Why does only one of the MISO models converge? Any advice would be appreciated.