this umat is for hydrogel swelling， please ensure you understand the constitution equation of hydrogel and then set all the parameters to use abaqus to simulate the swelling of hydrogel, and be cautious about the copyright(this umat is for hydrogel swelling,please ensure you understand the constitution equation of hydrogel and then set all the parameters to use abaqus to simulate the swelling of hydrogel,and be cautious about the copyright)