Introduction:
Stress concentration factor is a dimensionless parameter that quantifies the increase in stress at a specific location due to the presence of a geometrical discontinuity or notch. It is commonly used to design structures and components to ensure they can withstand the applied loads without failure.

Explanation:
Stress concentration factor is ignored in the case of ductile material under static load. Here's why:

Ductile Material:
Ductile materials have the ability to deform plastically before fracture. They exhibit a significant amount of plastic deformation before failure, making them suitable for applications where high toughness and resilience are required.

Static Load:
A static load is a load that remains constant over time. It does not vary in magnitude or direction. Examples of static loads include dead loads, such as the weight of a structure or component, and live loads, such as the weight of occupants or equipment.

Reasons to Ignore Stress Concentration Factor:
1. Ductile materials have the ability to distribute stresses more evenly due to their high plasticity. This means that localized stress concentrations are less likely to occur.
2. Ductile materials have a greater ability to absorb energy before fracture. This means that even if stress concentrations do occur, the material is less likely to fail catastrophically.
3. The stress concentration factor is typically more relevant for brittle materials, as they have less ability to deform plastically and absorb energy.

Implications:
Ignoring the stress concentration factor in the case of ductile materials under static load simplifies the design process. It allows engineers to design structures and components based on the average stress levels rather than considering the localized stress concentrations.

Conclusion:
In summary, stress concentration factor is ignored in the case of ductile materials under static load because ductile materials have the ability to deform plastically and distribute stresses more evenly. This reduces the likelihood of localized stress concentrations and catastrophic failure.