# OS-V: 0760 MacNeal-Harder Solid Patch Test

MacNeal-Harder TestThe patch test is a classical benchmark problem for the element, if it produces correct results for the test, the result for any problem solved with the element will converge toward the correct solution. The intended purpose of proposed problem set is to ascertain the accuracy of finite element in various applications.

## Benchmark Model

The outer dimension have unit cube of 1mm size. A mesh of cube having node location as mentioned in the table with first order CHEXA element. The eight corners of the cube are constrained in all three translational direction and free in all three rotational directions. Displacement is enforced using SPCD on the eight nodes of cylinder in X, Y and Z translation directions of the cube.

**Material Properties****Value**- Young's Modulus
- 1 x 106 Pa
- Poisson's Ratio
- 0.25

x | y | z | |
---|---|---|---|

1 | 0.249 | 0.342 | 0.192 |

2 | 0.826 | 0.288 | 0.288 |

3 | 0.850 | 0.649 | 0.263 |

4 | 0.273 | 0.750 | 0.230 |

5 | 0.320 | 0.186 | 0.643 |

6 | 0.677 | 0.305 | 0.683 |

7 | 0.788 | 0.693 | 0.644 |

8 | 0.165 | 0.745 | 0.702 |

The arbitrarily distorted element shapes are an essential part of the test. The principal virtue of a patch test is that if an element produces correct results for the test, the results for any problem solved with the element will converge toward the correct solution as the elements are subdivided. On the other hand, passing the patch test does not guarantee satisfaction, since the rate of convergence may be too slow for practical use. The above patch test is an extension of Robinson’s patch test to three dimensions.

- u
- ${10}^{-3}\left(2x+y+z\right)/2$
- v
- ${10}^{-3}\left(x+2y+z\right)/2$
- w
- ${10}^{-3}\left(x+y+2z\right)/2$

## Results

${\epsilon}_{x}=\text{}{\epsilon}_{y}=\text{}{\epsilon}_{z}=\text{}{\gamma}_{xy}=\text{}{\gamma}_{yz}=\text{}{\gamma}_{zx}=\text{}{10}^{-3}$

${\sigma}_{x}=\text{}{\sigma}_{y}=\text{}{\sigma}_{z}=\text{}2000$

The results CHEXA elements agree with the reference results.

## Model Files

Refer to Access the Model Files to download the required model file(s).

The model files used in this problem include:

chexa_mh_patch_test.fem

## Reference

MacNeal, R.H., and Harder, R.L., A Proposed Standard Set of Problems to Test Finite Element Accuracy, Finite Elements in Analysis and Design, 1 (1985) 3-20