How high can ESR go to?

ESR, or Elasticity Stress Ratio, can vary significantly depending on the specific context, such as the material in question and the conditions under which it is measured. In general, there isn't a definitive maximum for ESR, as it is influenced by factors like temperature, material composition, and structural design. However, in practice, extremely high ESR values are often limited by the material's yield strength and ductility. In engineering applications, it's essential to consider these factors to ensure safety and performance.