仿真结果不满意？？？

第二幅图，是工具头轨迹，可是第一第三幅应变图上，明显不是圆。在最初加工时显示都是圆，但是越往下走，圆就慢慢变成了类似菱形的样子，这是为什么？？？工具头轨迹是没有问题的，望大神指导。。。

轨迹导入采用的是amplitude-smooth step

** MATERIALS

** 

*Material, name=Material-1

*Density

 2.7e-09,

*Elastic

71000., 0.34

*Plastic

 90.,      0.

131., 0.00159

171., 0.00649

211.,  0.0177

251.,  0.0395

291.,  0.0776

331.,   0.139

391.,   0.295

** 

** INTERACTION PROPERTIES

** 

*Surface Interaction, name=IntProp-1

*Friction

 0.2,

*Surface Interaction, name=IntProp-2

*Friction

 0.1,

** 

** BOUNDARY CONDITIONS

** 

** Name: BC-2 Type: Displacement/Rotation

*Boundary

ban, 1, 1

ban, 2, 2

ban, 3, 3

ban, 4, 4

ban, 5, 5

ban, 6, 6

** Name: BC-3 Type: Displacement/Rotation

*Boundary

rfxiaban, 1, 1

rfxiaban, 2, 2

rfxiaban, 3, 3

rfxiaban, 4, 4

rfxiaban, 5, 5

rfxiaban, 6, 6

** Name: BC-X Type: Displacement/Rotation

*Boundary

rftool, 1, 1

** Name: BC-Y Type: Displacement/Rotation

*Boundary, amplitude=Amp-equallyY

rftool, 2, 2

** Name: BC-Z Type: Displacement/Rotation

*Boundary

rftool, 3, 3

** Name: BC-rftoolfix Type: Displacement/Rotation

*Boundary

rftool, 4, 4

rftool, 5, 5

** Name: BC-toolrotation Type: Velocity/Angular velocity

*Boundary, type=VELOCITY

rftool, 6, 6

** ----------------------------------------------------------------

** 

** STEP: Step-1

** 

*Step, name=Step-1, nlgeom=YES

*Dynamic, Explicit

, 60.22

*Bulk Viscosity

0.06, 1.2

** Mass Scaling: Semi-Automatic

**               Whole Model

*Fixed Mass Scaling, factor=200.

** 

** BOUNDARY CONDITIONS

** 

** Name: BC-2 Type: Displacement/Rotation

*Boundary, op=NEW

ban, 1, 1

ban, 2, 2

ban, 3, 3

ban, 4, 4

ban, 5, 5

ban, 6, 6

** Name: BC-3 Type: Displacement/Rotation

*Boundary, op=NEW

rfxiaban, 1, 1

rfxiaban, 2, 2

rfxiaban, 3, 3

rfxiaban, 4, 4

rfxiaban, 5, 5

rfxiaban, 6, 6

** Name: BC-X Type: Displacement/Rotation

*Boundary, op=NEW, amplitude=Amp-smoothX

rftool, 1, 1, 1.

** Name: BC-Y Type: Displacement/Rotation

*Boundary, op=NEW, amplitude=Amp-smoothY

rftool, 2, 2, 1.

** Name: BC-Z Type: Displacement/Rotation

*Boundary, op=NEW, amplitude=Amp-smoothZ

rftool, 3, 3, 1.

** Name: BC-rftoolfix Type: Displacement/Rotation

*Boundary, op=NEW

rftool, 4, 4

rftool, 5, 5

** Name: BC-toolrotation Type: Velocity/Angular velocity

*Boundary, op=NEW, type=VELOCITY

rftool, 6, 6, 1000.

** 

** INTERACTIONS

** 

** Interaction: Int-1

*Contact Pair, interaction=IntProp-1, mechanical constraint=PENALTY, cpset=Int-1

Surf-tool, Surf-bantop

** Interaction: Int-2

*Contact Pair, interaction=IntProp-2, mechanical constraint=PENALTY, cpset=Int-2

Surf-xiaban, Surf-banbottom

** 

** OUTPUT REQUESTS

** 

*Restart, write, overlay, number interval=1, time marks=NO

** 

** FIELD OUTPUT: F-Output-1

** 

*Output, field, number interval=5000

*Node Output, nset=Part-3dplan-1.Set-ban

U, 

*Element Output, elset=Part-3dplan-1.Set-ban, directions=YES

MISES, PE, PEEQ, S, STH

** 

** FIELD OUTPUT: F-Output-2

** 

*Node Output, nset=b_Set-tool

U, V

** 

** HISTORY OUTPUT: H-Output-1

** 

*Output, history, time interval=0.00669111

*Energy Output

ETOTAL, 

** 

** HISTORY OUTPUT: H-Output-2

** 

*Element Output, elset=Set-banelement

STH, 

** 

** HISTORY OUTPUT: H-Output-3

** 

*Node Output, nset=rftool

VR3, 

*End Step