154010010
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Dear Ashish,

Thanks for your response. I want to apply a force that is a  function of the instantaneous mass displacement, but, I couldn't find such a force defined in your code. I have copied my code below.

To put it in equations, I have m*x\ddot + k*x = f(x,t)  not  m*x\ddot + k*x = f(t).

I understand that applying a state dependent force requires to be able tap into output at every step and extract displacement/velocity at every instant and redefine the force on nodes depending on these vales. I thought my code should do the same, but, as mentioned in my previous posts results are not as expected. Please help me understand the issue.

/title,Spring Mass Controller force

FINISH
/Clear

/PREP7
ET,1,MASS21
!* 
ET,2,COMBIN14  
!* 
R,1,0.001, , , , ,
R,2,1,0,0, , ,50,

!Defining Material properties (Not needed for this problem though)
MPTEMP,1,0 
MPDATA,EX,1,,210000
MPDATA,DENS,1,,7800E-12  
MPDATA,PRXY,1,,0.3 

!Defining two nodes
n,1,,,
n,2,50,,

! MODEL Definition
!Defining element attributes before creating elements
TYPE, 1  
MAT,  1
REAL, 1  
ESYS, 0  

!Creating mass element at node 2
E,2,    !Element 1 definition

!Defining element attributes before creating elements
TYPE,2
MAT,1
REAL,2
ESYS,0

!Creating spring between node1 and node2
E,1,2,

!Defining boundary condition (Fix node1)
D,1,all,all

! Setup analysis
/solu
antype,transient
trnopt,full

time,0.001
solve

*DO,t,0.01,3,0.01    !Begining of DO loop
    TIME,t                    !Time at the end of load step
        *IF,t,LT,0.1,THEN,    !Begining of IF condition        
            F,2,FX,0
        *ELSEIF,t,EQ,0.1,THEN    
            F,2,FX,2    ! A 2N force applied at 0.1s
        *ELSEIF,t,GT,0.1,AND,t,LT,1
            F,2,FX,0    ! Zero external force
        *ELSE
            *GET,error,NODE,2,U,X    ! Obtain the deformation of node2
            F,2,FX,error*0.5    ! Applying the force
        *ENDIF    !End of IF Condition
    SOLVE
*ENDDO    !END of DO loop

!Post processing
/post26
nsol,3,2,u,x,
plvar,3

 

Regards,

Kumara