Expanding the envelope for spall modeling using porosity mechanics incorporating microinertia

• Main Authors: Qamar, Sayyad Basim, Moore, John A., Barton, Nathan R.
• Format: Conference Proceeding
• Language: English
• Subjects: Damage; Dynamic loads; High strain rate; Nucleation; Porosity; Residual stress; Shock waves; Strain analysis
• ISSN: 0094-243X; 1551-7616
• DOI: 10.1063/12.0020402

Spall failure is a phenomenon commonly observed under dynamic loading when shock waves are involved, leading to the nucleation, growth and coalescence of porosity. At elevated strain rates, such as those observed under laser-driven spall experiments, inertia at the microstructural scale becomes significant and can affect the porosity growth process and thereby affect the damage process. A semi-coupled Cocks-Ashby model accounting for microinertia is used to show microinertial contributions to spall experiments. The results show that the presence of microinertia alters the internal stress state as well as the apparent macroscopic spall strength and can lead to underestimations of both if ignored. The effect of microinertia is seen to grow with increasing strain rate. Complementary analysis shows that this effect is mitigated by thicker targets leading to lower strain rates and spall strengths. Attention is also brought to the importance of laser drive conditions, demonstrating the difference between square and triangular pulses. Square pulses lead to higher stresses and more diffuse damage compared to triangular pulses. These concepts can help to better understand spall at high strain rates and also expand the envelope for designing spall experiments that can access a wider range of stress and strain states.