# AFC

Asymmetrical Friction Connection

## Theory

The `AFC` model is a bilinear hardening model with an unloading stiffness differs from the initial stiffness. The term AFC comes from "asymmetric friction connection" which is a type of energy dissipaters. But this model can be used in other applications.

## Syntax

```
material AFCS (1) (2) (3) (4) (5)
material AFC02 (1) (2) (3) (4) (5)
# (1) int, unique tag
# (2) double, elastic modulus
# (3) double, yield stress
# (4) double, hardening modulus
# (5) double, unloading modulus

material AFC (1) (2) (3) (4) (5) (6) (7) (8)
material AFC01 (1) (2) (3) (4) (5) (6) (7) (8)
# (1) int, unique tag
# (2) double, elastic modulus
# (3) double, tension yield stress
# (4) double, tension hardening modulus
# (5) double, tension unloading modulus
# (6) double, compression yield stress
# (7) double, compression hardening modulus
# (8) double, compression unloading modulus
```

## History Variable Layout

| location             | value           |
| -------------------- | --------------- |
| `initial_history(0)` | load\_sign      |
| `initial_history(1)` | max\_strain     |
| `initial_history(2)` | reverse\_strain |
| `initial_history(3)` | start\_strain   |
| `initial_history(4)` | start\_stress   |
| `initial_history(5)` | end\_strain     |
| `initial_history(6)` | end\_stress     |

## Remarks

1. `AFC02` is a wrapper of `AFC01`. It provides a symmetric behavior while `AFC01` provides an asymmetric behavior.

## Examples

```
material AFC02 1 100 10 5 200
materialTest1D 1 1E-3 150 25 125 100 100 200 100 300 125 150
exit
```

![example one](https://4006314410-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-MQ5rMqEBbzA9NgGETGX%2Fuploads%2Fgit-blob-7461b31567a3cea00aa4b18f742ea3a5829bcbd0%2FAFC.EX1.svg?alt=media)

```
material AFC01 1 100 10 5 200 20 2 300
materialTest1D 1 1E-3 150 25 125 100 100 200 100 300 125 150
exit
```

![example two](https://4006314410-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-MQ5rMqEBbzA9NgGETGX%2Fuploads%2Fgit-blob-a2e818f34a1e6e11591d0099c68c6aa3e6532b49%2FAFC.EX2.svg?alt=media)

```
material AFC02 1 100 10 .1 500
materialTest1D 1 1E-2 20 40 60 80 100 120 140 160 80
exit
```

![example three](https://4006314410-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-MQ5rMqEBbzA9NgGETGX%2Fuploads%2Fgit-blob-3bce8ede39e1a580756598de2e9e469c21c81050%2FAFC.EX3.svg?alt=media)
