As the fleet ages, there's an increasing need for embedded wireless strain sensors capable of detecting and tracking accumulated strains — "precursors" to crack initiation, according to the official.
Only if this short crack extends long enough and blunted wide enough, can it affect the principal crack extension and the distribution of stress and plastic strain.
只有小裂纹扩展到足够长并钝化到足够宽，才能够影响主裂纹的扩展及其前端应力、应变的分布。
3
The authors suggest that this effect is due to the change in the strain rate of crack tip metal thus altering the thermodynamics of crack onset and growth.