Abstract: The effects of dynamic locking tongue (DLT)on dummy injury and the optimization scheme of its single product performance are studied in this paper. Firstly the theorecical study on the working principle of DLT in terms of its structure and the model for the forces acting on dummy chest. Then the effects of DLT on belt force and dummy chest deflection are futher determined by sled experiment, and it is found that with DLT the dummy chest deflection can be effectively reduced by lowering the belt force at shoulder section B4, hence improving chest injury. Finally two optimization schemes for DLT single product are qualitatively analyzed by LS-DYNA simulation with a result showing that shortening response time and increasing locking retention force can effectively enhance the restraint performance of DLT, resulting in smaller dummy chest deflection

Key words: seat belt, dynamic locking tongue, restraint performance, chest deflection