HDF5 File Structure

Each simulation is stored as a self-contained HDF5 file (~35 MB). This page documents the complete structure.

File Organization

simulation_{id}.h5
├── Attributes (root level)
│   ├── Geometry_Parameters: [radius, bottom_radius, wall_angle]
│   └── Material_Parameters: [MAT, FC, SHTK, BF]
│
├── OP10/ (deep drawing operation)
│   ├── blank/   → Sheet metal workpiece
│   ├── die/     → Lower tool
│   ├── punch/   → Upper tool
│   ├── binder/  → Blank holder
│   └── general/ → Simulation metrics
│
└── OP20/ (cutting operation)
    └── blank/   → Part after cutting

Inspecting Structure

Use the display_structure function to inspect any HDF5 file:

from ddacs import display_structure
display_structure("path/to/simulation.h5")

Field Reference

Node Fields

Field	Shape	Description
node_ids	(n,)	Unique integer identifiers for each node
node_coordinates	(n, 3)	Initial XYZ positions [mm]
node_displacement	(t, n, 3)	Position at each timestep [mm]
node_velocity	(t, n, 3)	Velocity vectors [mm/s]
node_acceleration	(t, n, 3)	Acceleration vectors [mm/s²]

Element Fields

Field	Shape	Description
element_shell_ids	(m,)	Unique element identifiers
element_shell_node_ids	(m, 4)	Global node IDs defining each element
element_shell_node_indexes	(m, 4)	Node indices for each quad element
element_shell_part_indexes	(m,)	Part membership labels
element_shell_thickness	(t, m)	Current thickness [mm]

Stress and Strain Fields

Field	Shape	Description
element_shell_stress	(t, m, 3, 6)	Stress tensor at 3 integration points
element_shell_strain	(t, m, 2, 6)	Strain tensor at 2 integration points
element_shell_stress_all_ipt	(m, 7, 6)	Stress at all 7 through-thickness points
element_shell_stress_all_ipt_thickness	(1, 7)	Normalized positions of integration points
element_shell_effective_plastic_strain	(t, m, 3)	Effective plastic strain
element_shell_effective_plastic_strain_all_ipt	(m, 7)	Plastic strain at all integration points

Stress/strain tensor components: [σxx, σyy, σzz, τxy, τyz, τzx]

Integration point layers:

• Index 0: Bottom surface
• Index 1: Middle (most representative for overall behavior)
• Index 2: Top surface

Force Fields

Field	Shape	Description
element_shell_bending_moment	(t, m, 3)	Bending moments [N·mm]
element_shell_normal_force	(t, m, 3)	Normal forces [N]
element_shell_shear_force	(t, m, 2)	Shear forces [N]
element_shell_internal_energy	(t, m)	Internal energy [mJ]

Global Fields (in general/ group)

Field	Shape	Description
global_timesteps	(t,)	Simulation time values
global_internal_energy	(t,)	Total internal energy [mJ]
global_kinetic_energy	(t,)	Total kinetic energy [mJ]
global_total_energy	(t,)	Sum of all energy [mJ]
global_velocity	(t, 3)	Global velocity [mm/s]
part_internal_energy	(t, 4)	Internal energy per part
part_kinetic_energy	(t, 4)	Kinetic energy per part
part_hourglass_energy	(t, 4)	Hourglass energy (mesh quality)
part_mass	(t, 4)	Mass per part [kg]

Shape Notation

• t = number of timesteps (3 for tools, 4 for OP10/blank, 2 for OP20/blank)
• n = number of nodes
• m = number of elements

Component Availability

Not all fields are available for all components:

Field Category	blank	die	punch	binder
Node data	✓	✓	✓	✓
Element connectivity	✓	✓	✓	✓
Stress/strain	✓	-	-	-
Thickness	✓	-	-	-
Forces	✓	-	-	-

Example: Reading Data

import h5py
import numpy as np

with h5py.File("simulation.h5", "r") as f:
    # Get thickness after springback (last timestep)
    thickness = np.array(f["OP10/blank/element_shell_thickness"])[-1]

    # Get Von Mises stress at middle integration point
    stress = np.array(f["OP10/blank/element_shell_stress"])[-1, :, 1, :]

    # Get node positions at final timestep
    positions = np.array(f["OP10/blank/node_displacement"])[-1]