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Hi all,

 

1- As sheet metal resistance to thinning is not the same in different directions (which is the subject of Lankford coefficients), how can we define FLD curve without considering rolling direction?

 

2- In Radioss one-step forming simulation in which we define r0, r45 and r90 during material definition, is there a pre-defined sheet rolling direction? Is it X axis or what?

 

Thanks in advance.

 

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On 2/25/2019 at 6:00 PM, GAJENDRA KUMAR NHAICHANIYA said:

r0, r45 & r90 are lankford cofficient. Hope ur both questions answered by this.

Thanks for your reply but my question is : As formability is not the same in different directions (relative to rolling one), how is it possible to predict the result without specifying rolling direction on raw material. Is there any default direction for rolling?

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Hello,

See the average Lankford coefficient R is calculated by R0 R45 & R90 (to consider plastic anisotropy)

Rformula.JPG.aa20b848ebbdfa00cc09bfaaa82515fa.JPG

Here R0 R45 & R90 values are calculated by R = Exy/Ez along 0,45 and 90 degree (assume any one direction as 0 degree for R0 and start calculating R45 & R90 )

Exy = in plane plastic strain & Ez = strain along thickness

so no matter which direction u r choosing for calculation of R, because R value not calculated by axial strain. it calculated by share strain (Exy).

 

For more u can go through link

https://en.wikipedia.org/wiki/Lankford_coefficient

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36 minutes ago, GAJENDRA KUMAR NHAICHANIYA said:

Hello,

See the average Lankford coefficient R is calculated by R0 R45 & R90 (to consider plastic anisotropy)

Rformula.JPG.aa20b848ebbdfa00cc09bfaaa82515fa.JPG

Here R0 R45 & R90 values are calculated by R = Exy/Ez along 0,45 and 90 degree (assume any one direction as 0 degree for R0 and start calculating R45 & R90 )

Exy = in plane plastic strain & Ez = strain along thickness

so no matter which direction u r choosing for calculation of R, because R value not calculated by axial strain. it calculated by share strain (Exy).

 

For more u can go through link

https://en.wikipedia.org/wiki/Lankford_coefficient

 

Thanks again.

You're right. But physically material does not act according to average values, but real ones. I mean in real world material will behave differently in different directions. So how can we consider rolling direction in simulations? Sometimes considering rolling direction is quite necessary in first forming stage and forming the sheet in wrong direction will cause failure.

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35 minutes ago, GAJENDRA KUMAR NHAICHANIYA said:

Hello,

The R0 is defined in X direction & R90 in Y direction.

Plz make sure your grain direction is along X axis. & draw direction should be Z.

 

Thanks a lot

 

35 minutes ago, GAJENDRA KUMAR NHAICHANIYA said:

 

 

 

 

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