Handout 1 - Clemson University

an underpressure of absolute magnitude po - P,-. Finally, a total after time of ta+T++T- it
returns to ambient pressure. The quantity Ps+ is usually termed overpressure. peak Two
major phases in the pressure - time history are evident. The portion of the time history
with positive overpressure is named positive of phase, duration T+, while the portion
below ambient pressure is the negative with phase amplitude P,- and duration T-. At
this point, it should be noted that in accordance with the majority of literature on the
issue of blast wave mechanics, any quantity that is denoted with a plus sign superscript
will refer to the positive phase while a minus sign will refer to the negative phase.
UJ
Cx
0
0 ta t++t++T
TIME
Figure 3.1-1: Ideal blast wave [35]
0ta+a++taT+T
Positive and negative impulses are define by:
is * = (p (t) -p,, )dt
is= J(Po - P(t))dt
ta+T'
POSITIVE PHASE
PHS
Equation 3.1-1