# Common Patterns and Workflows

Complete examples and patterns for typical PyDyna tasks.

## Pattern Index

- [Load and Modify](#load-and-modify)
- [Build from Scratch](#build-from-scratch)
- [Material Management](#material-management)
- [Model Merging](#model-merging)
- [Parameterization](#parameterization)
- [Validation Workflows](#validation-workflows)

---

## Load and Modify

### Simple Property Update

```python
from ansys.dyna.core import Deck

# Load model
deck = Deck()
deck.load("model.k")

# Update material properties
for mat in deck.get_kwds_by_type("MAT"):
    if mat.mid == 1:
        mat.e = 2.5e11  # Update Young's modulus
        mat.pr = 0.33   # Update Poisson's ratio

# Save
deck.write("modified_model.k")
```

### Bulk Modifications

```python
# Scale all node coordinates
for node in deck.get_kwds_by_type("NODE"):
    node.x *= 1.5
    node.y *= 1.5
    node.z *= 1.5

# Offset geometry
for node in deck.get_kwds_by_type("NODE"):
    node.z += 10.0  # Move everything up by 10 units

# Update all material densities
for mat in deck.get_kwds_by_type("MAT"):
    mat.ro *= 1.1  # Increase all densities by 10%
```

### Conditional Updates

```python
# Update only specific materials
for mat in deck.get_kwds_by_type("MAT"):
    if 100 <= mat.mid <= 199:  # Material IDs 100-199
        mat.e *= 1.2  # Increase stiffness

# Clamp node positions
for node in deck.get_kwds_by_type("NODE"):
    if node.z < 0:
        node.z = 0.0  # Set minimum z to zero
    if node.z > 100:
        node.z = 100.0  # Set maximum z to 100
```

---

## Build from Scratch

### Simple Beam Model

```python
from ansys.dyna.core import Deck, keywords

# Create deck
deck = Deck(title="Simple Beam")

# Control cards
control_term = keywords.ControlTermination()
control_term.endtim = 1.0
deck.append(control_term)

# Material
mat = keywords.Mat001()  # MAT_ELASTIC
mat.mid = 1
mat.ro = 7850   # kg/m³
mat.e = 2.1e11  # Pa
mat.pr = 0.3
deck.append(mat)

# Section
section = keywords.Section001()  # SECTION_BEAM
section.secid = 1
section.elform = 1
deck.append(section)

# Part
part = keywords.Part()
part.pid = 1
part.secid = 1
part.mid = 1
deck.append(part)

# Nodes
for i in range(11):
    node = keywords.Node()
    node.nodes = pd.DataFrame({"nid": [i+1], "x": [i * 10.0 ], "y": [0.0], "z": [0.0]})
    deck.append(node)

# Elements (beam between consecutive nodes)
for i in range(10):
    elem = keywords.ElementBeam()
    elem.elements = pd.DataFrame({"eid": [i+1], "pid": [1], "n1": [i+1], "n2": [i+2]})
    deck.append(elem)

# Save
deck.write("beam_model.k")
```

### Shell Structure

```python
from ansys.dyna.core import Deck, keywords

deck = Deck(title="Shell Plate")

# Material
mat = keywords.Mat001()
mat.mid = 1
mat.ro = 7850
mat.e = 2.1e11
mat.pr = 0.3
deck.append(mat)

# Shell section
section = keywords.Section002()  # SECTION_SHELL
section.secid = 1
section.elform = 16  # Fully integrated shell
section.t1 = 1.0     # Thickness
deck.append(section)

# Part
part = keywords.Part()
part.parts = pd.DataFrame({"pid": [1], "secid": [1], "mid": [1])
deck.append(part)

# Create 10x10 grid of nodes
node_id = 1
for i in range(11):
    for j in range(11):
        node = keywords.Node()
        node.nodes = pd.DataFrame({"nid": [node_id], "x": [i * 10.0 ], "y": [j * 10.0], "z": [0.0]})
        deck.append(node)
        node_id += 1

# Create shell elements
elem_id = 1
for i in range(10):
    for j in range(10):
        elem = keywords.ElementShell()
        elem.elements = pd.DataFrame({
            "eid": [elem_id],
            "pid": [1],
            "n1": [i * 11 + j + 1],
            "n2": [n1 + 1],
            "n3": [n1 + 12],
            "n4": [n1 + 11]
        })
        elem.eid = elem_id
        deck.append(elem)
        elem_id += 1

deck.write("shell_plate.k")
```

---

## Material Management

### Material Library

```python
from ansys.dyna.core import Deck, keywords

def create_steel_material(mid):
    """Create a steel material."""
    mat = keywords.Mat001()
    mat.mid = mid
    mat.ro = 7850
    mat.e = 2.1e11
    mat.pr = 0.3
    mat.user_comment = "Structural steel"
    return mat

def create_aluminum_material(mid):
    """Create an aluminum material."""
    mat = keywords.Mat001()
    mat.mid = mid
    mat.ro = 2700
    mat.e = 7.0e10
    mat.pr = 0.33
    mat.user_comment = "Aluminum 6061"
    return mat

# Build material library
materials = Deck(title="Material Library")
materials.append(create_steel_material(1))
materials.append(create_aluminum_material(2))
materials.write("materials.k")
```

### Material Substitution

```python
# Replace material in parts
def replace_material(deck, old_mid, new_mid):
    """Replace all references to old material ID with new ID."""
    for part in deck.get_kwds_by_type("PART"):
        if part.mid == old_mid:
            part.mid = new_mid

    # Optionally remove old material definition
    indices_to_remove = []
    for i, mat in enumerate(deck.keywords):
        if mat.keyword == "MAT" and mat.mid == old_mid:
            indices_to_remove.append(i)

    for idx in reversed(indices_to_remove):
        deck.remove(idx)

# Usage
deck = Deck()
deck.load("model.k")
replace_material(deck, old_mid=1, new_mid=2)
deck.write("model_new_material.k")
```

---

## Model Merging

### Combine Models

```python
from ansys.dyna.core import Deck

# Load multiple models
deck1 = Deck()
deck1.load("model1.k")

deck2 = Deck()
deck2.load("model2.k")

# Combine (watch for ID conflicts!)
combined = deck1 + deck2

# Or extend in place
deck1.extend(deck2.keywords)

combined.write("combined_model.k")
```

---

## Parameterization

### Using Python Variables

```python
from ansys.dyna.core import Deck, keywords

# Parameters
beam_length = 100.0
num_elements = 10
steel_density = 7850
steel_modulus = 2.1e11

# Build parameterized model
deck = Deck(title="Parameterized Beam")

mat = keywords.Mat001()
mat.mid = 1
mat.ro = steel_density
mat.e = steel_modulus
mat.pr = 0.3
deck.append(mat)

# ... rest of model using parameters
```

---

## Validation Workflows

### Pre-Write Validation

```python
from ansys.dyna.core import Deck

deck = Deck()
deck.load("model.k")

# Validate before writing
errors = deck.validate()

if errors:
    print("Validation errors found:")
    for error in errors:
        print(f"  - {error}")
    print("\nFix errors before proceeding")
else:
    print("No errors - safe to write")
    deck.write("output.k")
```

---

## Advanced Patterns

### Processing Multiple Files

```python
import os
from ansys.dyna.core import Deck

def process_directory(input_dir, output_dir, transform_func):
    """Process all .k files in directory."""
    for filename in os.listdir(input_dir):
        if filename.endswith('.k'):
            input_path = os.path.join(input_dir, filename)
            output_path = os.path.join(output_dir, filename)

            deck = Deck()
            deck.load(input_path)
            transform_func(deck)
            deck.write(output_path)
            print(f"Processed: {filename}")

# Process all files
process_directory("input_models/", "output_models/", scale_model)
```
---

## See Also

- [Deck Operations](deck.md) - Detailed deck manipulation
- [Keywords Guide](keywords.md) - Working with individual keywords
