Abstract: Topological metamaterials, a frontier in condensed matter physics, have shown tremendous potential for diverse applications in information processing and energy utilization, owing to their remarkable physical phenomena. In recent years, inspired by the insights from topological phenomena in condensed matter physics, there has been a growing interest in mechanical topological phenomena in classical wave systems. Elastic waves, pivotal as carriers of vibration, permeate both engineered structures and natural environments. As vector waves, elastic waves exhibit more complex multi-component transmission characteristics compared to scalar waves such as acoustic waves and electromagnetic waves, which pose numerous challenges in wave manipulation and mechanical applications. In this study, we focus on the exploration of elastic wave decomposition and mechanical applications based on topological valley metamaterials. Firstly, the phononic crystals with double Dirac cones are designed to realize separated topological phases of in-plane (IP) and out-of-plane modes (OP) through geometric perturbations. Through the combination of different topological phases, the topological edge states with different wave transmission properties are constructed. Consequently, the in-plane and out-of-plane components of elastic waves are separated within the fabricated phononic crystal plate. Furthermore, drawing inspiration from the topological whispering gallery phenomenon renowned for its high energy density, the potential application of mode separation of elastic waves in energy localization are investigated. Based on the energy localization achieved by the topological whispering gallery mode, the energy of in-plane and out-of-plane waves is concentrated in different regions, thereby providing ideas for efficient vibrational energy harvesting. Experimental verification is conducted to verify the observed mode separation phenomena and the localized energy behavior of elastic waves. This study illustrates the great potential of topological valley metamaterials in wave manipulation and energy utilization. These advancements hold significant promise for various mechanical applications, including vibration signal processing and energy harvesting, thereby underscoring their positive significance in advancing engineering and scientific frontiers.