Experimental investigation on the spreading progress after droplets impacting on to a vertical vibrating plate at low frequencies

•The maximum spread time of the inner lamella maintains a relatively stable value under all vibration conditions.•The impact phase and vibration frequency have a great effect on the maximum radius and spreading time, which is attributed to the existence of relative acceleration.•An empirical formula is built to accurately predict the maximum spread factor of droplets after impacting on the vibrating plate.