NOMENCLATURE NOMENCLATURE
\(a_{0}\) initial crack length
\(A_{1}\), \(A_{2}\), \(n\) material constants related to strain hardening
\(B\) thickness of specimen
\(c\) sound speed in incident bar
\(c_{1}\) experimental constant
\(C\), \(p\) material constant related to strain-rate hardening
\(D\) displacement of incident bar end initially in contact with specimen
\(E\) elastic modulus
\(F_{Q}\) load at intersection point of load-deflection curve and line OFd
\(J\) J-integral
\(J_{\text{Id}}\) dynamic fracture toughness
\(K_{1}\) experimental constant
\(K_{I}\) stress intensity factor
\(K_{\text{IC}}\) static fracture toughness
\(K_{\text{Id}}\) dynamic fracture toughness
\({\dot{K}}_{\text{Id}}\) loading rate
\(K_{\text{Id}}^{r}\) reference fracture toughness value
\({\dot{K}}_{\text{Id}}\) reference loading rate
\(K_{\text{rd}}\) ratio of stress intensity factor at crack tip to dynamic fracture toughness of material
\(L_{\text{rd}}\) ratio of loading condition assessed for plastic limit load of structure \(L_{\text{rd}}=\frac{\sigma_{\text{ref}}}{\sigma_{\text{yd}}}\)
\(\text{L\ }_{\text{rd}}^{\max}\) cut-off value of Lrd
\(L\) length of specimen
\(P_{\max}\) peak load
\(S\) span of specimen
\(t_{d}\) propagating time of strain wave from crack tip to position of strain gauge
\(t_{f}\) crack initiation time
\(t_{p}\) time corresponding to peak strain signal
\(W\) width of specimen
\(\varepsilon_{\text{eq}}\) equivalent strain
\({\dot{\varepsilon}}_{\text{eq}}\) equivalent strain rate
\(\varepsilon_{i}\) incident strain
\(\varepsilon_{r}\) reflected strain
\(\sigma_{\text{eq}}\) equivalent stress
\(\sigma_{\text{ref}}\) reference stress
\(\rho\) density of incident bar
\(\upsilon\) Poisson’s ratio