The main fragmentation effect of the explosion, primary fragmentation, comes from the shrapnels. The particles propelled from the explosion seat and the environment is the secondary fragmentation. The blast mostly makes the buildings collaped and windows broke. The velocity of the blast travel in the air takes the free particles on and travels far away with tremendous speed and energy creating pressure of thousands of pascals which causes fatal wounds on the body. As the distance from the blast epicenter increases, the effect of blast reduces and the effect of fragments and debris propelled by the explosive becomes more important. Conventional military explosives may create multiple fragments with supersonic initial velocities (Glover, 2002).
If the explosion takes place in a closed environment with glasses, then the broken windows travels in the air with tremendous velocities and energy. This is one of the main reasons for killings and woundings. The pressure needed for a window breakage is ≤0,5 psi Maynard et al., 1997.
These flying projectiles can produce both penetrating and blunt trauma, depending on the size of the projectile and the speed at which they travel. With these velocities, the victim does not have to be in close proximity to the explosion. Individuals far from the scene of an explosion can be struck and injured by this debris (Wightman & Gladish, 2001). The human tolerance treshold for these effects are limited. At the literature was stated that the velocity nedded for a particle to penetrate the human skin is approximately 30 m/s (100 ft./sn.) Seyhan, 2015.
Fragmentation type hand granades were designed to kill and give damage to people to a defined distance. This is the fact that it can cause fatal woundings and killings when detonated near living beings. The threshold value for ear drum rapture is 5 psi; lung damage is 12 psi and fatal wounding is 40 psi Glover, 2002.
The death and woundings took place due to the direct blast or blast reflection and the primary and secondary fragmentation effect. In addition to the fragmentation/shrapnel effect, broken windows and concerete etc. are the causes for severely wounding and deaths too. The shrapnels from the grenade body and the secondary fragments from environment travel at air by the effect of detonation blast and give fatal damages. Glass causes many of the secondary blast injuries (up to 50% of all blast injuries). Victims that are peppered with glass are often difficult to distinguish from victims that are peppered with glass and have penetrating injuries (White et al., 2008; Wong et al., 1997).
Tertiary blast injuries are caused when the victim’s body is propelled into another object by the blast winds. Tertiary effects result from the bulk flow of gas away from the explosion. Blast winds can generate a body acceleration of over 15 g’s. They most often occur when the victim is quite close to the explosion (Candole, 1967; Stuhmiller et al., 1991). This displacement of the victim can take place relatively far from the point of detonation if the victim is unfortunately positioned in the path where gases must take to vent from a structure, such as a doorway, window, or hatch.
With this respect, the possible effects expected for DM-41 defence hand grenade in a closed environment like a room can be assessed as follows;
Possible effects inside the room
(a) It was positively defined at the forensic laboratory that two DM-41 model fragmentation type hand grenades were detonated in the incident site. The main charge used in these grenades is 165 g of Composition B (60% RDX + 40% TNT). Composition B (60% RDX + 40% TNT) detonates with 7900 m/s detonation velocity and applying 268 kPa (38,870,137,116 psi) peak pressure with a fatal radius of 20 m. The fragmentation effect is provided with a grooved steel sleeve (Bailey & Murray, 1989). The steel sleeve has 31 wrap with 1000–1010 grooves on it. The base plug also has 33–36 round shape steel fragmentation on it (Fig. 3).
(b) Two DM-41 hand granades originally designed for providing fragmentation effect have total of 2000–2100 grooved steel fragments (including the base plug). The initial detonation velocity is 7900 m/s and the blast value is 268 kPa (38,870,137,116 psi).
This means that two handgrenades detonated inside a room with a peak pressure of 268 kPa (268,000 Pa pressures on 1 m2) in very less than a second and the blast wave started to travel inside room with an initial velocity of 7900 m/s (Fig. 4).
(c) The shock front with supersonic velocity will move inside the room and hit the walls and be reflected. It will breake the windows and gives damages to the walls (Fig. 5).
The particles and the broken windows will be expected to propel around dragging the free particles away all causing shrapnel effect on its way (Fig. 6).
Possible effects on living beings
(a) Two handgrenades detonated inside a room with a peak pressure of 268 kPa (268,000 Pa pressures on 1 m2) in very less than a second and the blast wave started to travel inside room with an initial velocity of 7900 m/s.
(b) 2000–2100 grooved steel fragments with the dragged metals, stones and broken windows will travel along the shock wave with an initial velocity of at least 7900 m/s and peak pressure of 268 kPa (~38,87 psi) (Fig. 7).
As the fatal wounding threshold value is around 40 psi and the peak pressure for DM-41 hand grenade is 268 kPa (~38,87 psi), it is definite that the value is between the limits of fatal wounding. So, it can be stated that a human inside this room will suffer the initial velocity and peak pressure at the highest level if not concealed behind a conceret, steel or other likewisw concelements.
(c) Propelling and severe dragging of the human body exposed to the blast effect is one of the main reasons for post blast killings and woundings. The physical injuries occur not only for the direct blast effect but also for dragging of the body. The walking/running person’s balance is inclined towards front. When a body running or walking exposed to a blast with supersonic speed, it is expected to lose the balance and fall. Even with the threshold value, a moving body can be expected to fall down with 268 kPa (38,87 psi) pressure and 7900 m/s.