An explicit integration scheme for rate-dependent crystal plasticity （CP） was developed. Additive decomposition of the velocity gradient tensor into lattice and plastic parts is adopted for describing the kinematics...An explicit integration scheme for rate-dependent crystal plasticity （CP） was developed. Additive decomposition of the velocity gradient tensor into lattice and plastic parts is adopted for describing the kinematics; the Cauchy stress is calculated by using a hypo-elastic formulation, applying the Jaumann stress rate. This CP scheme has been implemented into a commercial finite element code （CPFEM）. Uniaxial compression and roiling processes were simulated. The results show good accuracy and reliability of the integration scheme. The results were compared with simulations using one hyper-elastic CPFEM implementation which involves multiplicative decomposition of the deformation gradient tensor. It is found that the hypo-elastic implementation is only slightly faster and has a similar accuracy as the hyper-elastic formulation.展开更多
The EU H2020 ORCHYD project seeks to enhance drilling efficiency in hard rock environments,particularly for deep geothermal wells,by integrating innovative rock weakening techniques.In this context,3D finite element s...The EU H2020 ORCHYD project seeks to enhance drilling efficiency in hard rock environments,particularly for deep geothermal wells,by integrating innovative rock weakening techniques.In this context,3D finite element simulations of bit-rock interactions were performed to assess how combining high pressure water jetting(HPWJ)-induced groove and bottom-hole geometry can contribute to improve the down-hole percussive drilling performance.A Red Bohus granite rock was modelled using a continuum,elasto-visco-plastic,and damage-based model calibrated using Brazilian,uniaxial compression,and triaxial material tests as well as single insert impact tests.Bit-rock interaction with an HPWJ groove was studied through modelling of twelve different groove depths and bottom-hole configurations.Results demonstrate that deeper grooves significantly reduce impact loads by up to 35%and increase penetration up to 40%,leading to higher material removal(up to 240%).Groove depth also influences damage propagation between adjacent indents,with grooves facilitating a broader zone of fractured rock,particularly near the groove itself.Notably,the drilling efficiency benefits from HPWJ slotting are highly dependent on bit design:flat and concave bit profiles exhibit 70%greater improvement in drilling performance compared to other profiles.展开更多
文摘An explicit integration scheme for rate-dependent crystal plasticity （CP） was developed. Additive decomposition of the velocity gradient tensor into lattice and plastic parts is adopted for describing the kinematics; the Cauchy stress is calculated by using a hypo-elastic formulation, applying the Jaumann stress rate. This CP scheme has been implemented into a commercial finite element code （CPFEM）. Uniaxial compression and roiling processes were simulated. The results show good accuracy and reliability of the integration scheme. The results were compared with simulations using one hyper-elastic CPFEM implementation which involves multiplicative decomposition of the deformation gradient tensor. It is found that the hypo-elastic implementation is only slightly faster and has a similar accuracy as the hyper-elastic formulation.
基金supported by the ORCHYD project,an EU Horizon 2020 research and innovation programme under grant agreement N101006752.
文摘The EU H2020 ORCHYD project seeks to enhance drilling efficiency in hard rock environments,particularly for deep geothermal wells,by integrating innovative rock weakening techniques.In this context,3D finite element simulations of bit-rock interactions were performed to assess how combining high pressure water jetting(HPWJ)-induced groove and bottom-hole geometry can contribute to improve the down-hole percussive drilling performance.A Red Bohus granite rock was modelled using a continuum,elasto-visco-plastic,and damage-based model calibrated using Brazilian,uniaxial compression,and triaxial material tests as well as single insert impact tests.Bit-rock interaction with an HPWJ groove was studied through modelling of twelve different groove depths and bottom-hole configurations.Results demonstrate that deeper grooves significantly reduce impact loads by up to 35%and increase penetration up to 40%,leading to higher material removal(up to 240%).Groove depth also influences damage propagation between adjacent indents,with grooves facilitating a broader zone of fractured rock,particularly near the groove itself.Notably,the drilling efficiency benefits from HPWJ slotting are highly dependent on bit design:flat and concave bit profiles exhibit 70%greater improvement in drilling performance compared to other profiles.
