The current study reports the phenomenon of DROP IMPACTs on a hyDROPhobic surface in the substrate deposition regime (non-splashing), focusing on the characterization of each stage upon IMPACT and different non-dimensional parameters involved such as spreading factor, recoil height and the durations of several phases. The results indicate that the DROP dynamics is determined by an interplay of DROP inertia, viscosity and surface tension. Apart from Reynolds number (Re) and Weber number (We) which are conventionally used to characterize DROP IMPACTs, a new non-dimensional IMPACT parameter, ξ (= 𝑊 𝑒 1/4𝑅 𝑒 1/5) is introduced, and it is found out that the spreading factor and the different non-dimensional phase durations involved in the DROP IMPACT dynamics on a hyDROPhobic surface, scale fairly well with this newly defined IMPACT parameter. Further, systematic studies into the non-dimensional durations of each phase upon IMPACT, spreading factor and recoil factor (i. e. non-dimensional recoil height) with respect to different non-dimensional parameters are reported.

Protective steel doors are widely used in buildings due to their high resistance against the IMPACT loads. However, its heavy weight has been always considered as a major drawback for these doors. In this paper, a new optimized stiffened IMPACT-protective steel door incorporating sandwich panel with aluminum foam core (OSSA) is examined. This door consists of two face sheets, main and secondary stiffeners, and aluminum foam as the inner core. In order to optimize the door, at first the rigidity and weight functions of the stiffened steel door were extracted. Then an optimal door weighing 42% less than the primary door was obtained. Due to the high energy absorption capacity of the combined foam core and stiffened steel door structure, the use of aluminum foam core in the optimized steel door was proposed. By doing numerical analysis, and depending on the thickness of the face sheet of OSSA, 20 to 32% reduction in the maximum displacement was observed. The results also showed that, with 67% increase in the peak overpressure, OSSA has kept almost the same maximum displacement as that of the steel door without an aluminum foam. In other words, by using aluminum foam core in the optimized stiffened door, the door will resist 67% more IMPACT load.

In this research, the robust strength slabs made of concrete, self-compacting, multi-layer reinforced steel and nylon fibers and a combination them under the influence of IMPACT load is investigated. To achieve this goal, 30 concrete slabs one layer and three layers with dimensions 40 40 7. 5 cm are made. The slabs come from 10 different types, one type of non-fibrous as a control, and other slabs all have a fixed volume 1% fiber, hence the type and percentage of fiber varies in the layers. The IMPACT weight loss test was performed on the made slabs. In this test, steel ball weighing 5. 8 kg at a distance 1. 5 m repeatedly hit and The number of blows to make the first crack and the destruction recorded. The results the test indicate a very high effect steel fibers and the slight IMPACT nylon fibers on the slab resistance the slabs. Multi-layered slabs in the firstcracks are the same as the slabs a uniform laminate layer, but the resistance to the destruction and absorption the final energy these slabs increases compared to one-layer samples, which can be due to an increase in the percentage fiber in the outer layers and the layered layout the fibers.

The capillary wave and initial spreading velocity in the spreading phase of DROP IMPACTing on a glass surface are studied experimentally, while the DROP photos are obtained by using a high-speed video camera, which can catch up to 9000 images per second with an exposure time of 4 μ s. A wide range of IMPACT velocities are studied by varying the fall height, showing different capillary waves. All attention is given to the capillary wave and initial spreading velocity of DROP. A non-linear relation between the wavelength and the IMPACT velocity is found experimentally. Combined with the minimum spreading radius theory, a linear relation between the initial spreading velocity and the IMPACT velocity is acquired.