塑性理论中常采用等向硬化、随动硬化和混合硬化的假定来描述硬化函数的演化规律，这需要在屈服函数上增加相应的函数项，但这些关于硬化模式的假定不是必须的。提出了利用虚强度参数来描述介质塑性硬化规律，即在不改变屈服/破坏函数形式的条件下，只将其中的强度参数替换为塑性硬化参量的函数，便可以实现既避免硬化规律的先验假设，又可体现介质的硬化过程。采用一组煤岩的三轴加卸载试验数据研究了基于Coulomb-Mohr准则和基于Drucker-Prager准则及其强度参数的塑性硬化函数。结果表明，这2个函数的塑性硬化面子午线在应力空间中以平移和旋转2种方式体现介质的塑性硬化过程，并与已有煤岩试验数据一致。所提出的虚强度参数的概念为破坏准则中真实强度参数替换后作为硬化函数提供了一个逻辑的桥梁。

Isotropic hardening, kinematic hardening and mixed hardening are three frequently-used laws to describe hardening patterns in plasticity. However, they are just reasonable and idealized assumptions and these assumptions are not necessary as some materials do not accord with them during the hardening. A new plastic hardening pattern based on virtual strength parameters which does not need priori assumptions is presented. The main idea is that hardening yield functions can be acquired simply by replacing real strength parameters with virtual ones that are respectively constructed as the functions of the hardening parameter. With a group of stress-strain data of coal rock samples under several confining pressures, a hardening function based on Coulomb-Mohr criterion and a hardening function based on Drucker-Prager criterion were respectively investigated. It shows that meridian lines in both functions expand in stress space through translations and rotations. The viewpoint of virtual strength parameter provides with a logical bridge for extending failure function, by replacing its real strength parameters with virtual ones, to hardening function.