# RD-E: 4400 Blow Molding with AMS

Blow molding with Advanced Mass Scaling (AMS).

## Options and Keywords Used

- Advanced Mass Scaling (/AMS)
- Time Step for Advanced Mass Scaling (/DT/AMS/Iflag)
- TYPE7 interface (/INTER/TYPE7)
TYPE7 interface has been defined between mold and plastic parison with friction 0.7.

- Visco Elastic Plastic Piecewise Linear Material law (/MAT/LAW66)
- Shell property (/PROP/TYPE1 (SHELL))
- Rayleigh damping (/DAMP)
- Rigid body (/RBODY) and Boundary condition
(/BCS)
Using rigid body, two molds have been fixed in all direction of rotation and translations of y-direction and x-direction. They are only free in z-direction (translation).

- Impose displacement (/IMPDISP)
Two molds are moved in opposite directions with imposed displacement.

- Pressure Load (/PLOAD)The air pressure on the plastic parison is modeled using pressure load /PLOAD from inside towards outside.

## Input Files

## Model Description

Units: mm, s, Mg, N, MPa

**Material Properties****Value**- Initial density
- 7.8e-9 Mg/mm
^{3} - Young's modulus
- 200000 $\left[\mathrm{MPa}\right]$
- Poisson's ratio
- 0.3

**Material Properties****Value**- Initial density
- 1e-9 Mg/mm
^{3} - Young's modulus
- 4 $\left[\mathrm{MPa}\right]$

### Model Method

- Define /AMS in Starter. Select the part group which will use AMS. If the part group has not been specified, then the whole model will use AMS.
- Use /DT/AMS in Engine. For
example:
`/DT/AMS 0.67 1.15e-4`

## Results

### Performance

Using the AMS technique, CPU time is reduced by a factor of approximately 3, in this case.

- Without time step control (no mass scaling)
- With standard mass scaling /DT/NODE/CST
- With AMS

Without Time Step Control | With Standard Mass Scaling /DT/NODA/CST | With AMS | |
---|---|---|---|

Time Step(s) | 1.15e-4 | 0.34e-04 | 1.15e-4 |

Total Number of Cycle | 78200 | 24280 | 6966 |

CPU Time(s) | 2027.82 | 723.02 | 522.83 |

Speed-up | - | 2.80 | 3.88 |

Results Quality | - | Bad | Good |

It shows at time 0.4s for the same speed up factor with AMS you get more accurate results compare with no mass scaling test than with node mass scaling.

### Conclusion

To obtain a CPU saving factor of about 3, the target time step should be about 10 times higher than the one without AMS; AMS treatment itself is taking some CPU cost.

Standard mass scaling technique can also speed up the calculation by a factor of about 3, but the results quality will be affected.

In general, AMS technique for a given speed up, returns more accurate results than standard mass scaling.

The AMS technique does not change the total mass; the mass is added only on non-diagonal terms of the mass matrix.

It is applicable to the entire model.

- Result accuracy, in terms of stress and strains, is normally not affected; by the way AMS is affecting Eigen modes of the structure(s) to which it is applied. Higher frequencies are lowered.
- AMS technique is highly scalable; large models could show even more significant speed up factors.