vibration control is aimed to suppress or eliminate unwanted vibration to ensure proper operation of machines. on the other hand, energy harvesting intends to scavenge energy from ambient vibrations to power electronical devices such as wireless sensors. it is much desired to achieve simultaneous vibration control and energy harvesting. a great amount of effort has been focused on the use of a linear vibration absorber for this purpose. the shortcoming of such an approach is that its effectiveness is limited to a narrow bandwidth of frequency. the goal of this research is to develop a device in order to achieve simultaneous vibration suppression and energy harvesting in a broad frequency band. instead of using a linear vibration absorber, a nonlinear energy sink (nes) is considered. since it is very challenging to realize a true nes as it requires a zero linear stiffness, this study focus on developing a variant nes that possesses a low linear stiffness but high nonlinear stiffness. three designs and their corresponding apparatus are introduced. a base excitation is conducted to determine the spring restoring force in order to character the stiffness of each design. the apparatus that best emulates the nes is chosen. a stiff primary system and a flexible primary system are also developed by changing the primary spring’s stiffness. the behaviors of the chosen variant nes are further investigated in two combined system: weakly coupled one (a stiff primary system plus the variant nes) and the strongly coupled one (a flexible primary system plus the variant nes). the transient responses of the two combined systems are investigated numerically and experimentally. the steady state responses of the two combined systems to a harmonic base excitation are investigated in numerically and experimentally. the results from both the weakly coupled and the strongly coupled systems show some typical features of the nes: 1:1 resonance, targeted energy transfer (tet), initial energy or excitation level dependence, jumping phenomena, and strongly modulated response (smr), etc.