The article examines how cracks behave in materials that can be squished and stretched. They used a special theory and math to study this. They found that the stress near the crack tip is super strong, just like in regular materials, but the strength is affected by the material's ability to be squished and stretched. They tested this on two metals and saw how the material's squishiness and stretchiness changed the stress, crack opening, energy, and shape near the crack.