Stress concentrations are localized areas within a component where stress is significantly higher than the surrounding region. These typically occur near geometric discontinuities such as sharp corners, holes, notches, grooves, keyways, or sudden changes in cross-section. If not addressed, stress concentrations can lead to premature failure through cracking or fatigue, even when the average stress on the component is within acceptable limits.
How to Identify Stress Concentrations:
- Geometric Discontinuities:
- Sharp corners or notches.
- Holes (especially circular or oval).
- Keyways or grooves.
- Abrupt changes in thickness or cross-section.
- Simulation Tools:
- Use Finite Element Analysis (FEA) to visualize stress distribution.
- Look for high-stress areas (often color-coded red) near features that break symmetry or continuity.
- Theoretical Stress Concentration Factors (Kt):
- Use known formulas and charts from design handbooks to estimate stress concentration factors for common features.
- Physical Testing:
- Strain gauges and photoelasticity methods can reveal high-stress zones in prototypes.
How to Reduce Stress Concentrations:
- Add Fillets and Radii:
- Replace sharp internal corners with fillets (rounded corners). Even a small radius can dramatically reduce peak stress.
- Gradual Transitions:
- Avoid abrupt changes in geometry; use tapers or blended transitions to reduce sudden stress spikes.
- Hole Positioning:
- Avoid placing holes too close to edges or other stress-sensitive features. Use reinforcing bosses or ribs around holes if needed.
- Use Stress-Relief Features:
- Add notches or slots to control and redirect stress flow in a predictable and safe way.
- Material Selection:
- Choose materials with good toughness and fatigue resistance, especially in areas likely to experience stress concentrations.
- Load Path Optimization:
- Align loads with the component’s geometry to minimize bending or torsion that could concentrate stress.
Example Applications:
- In aircraft and automotive structures, filleted joints and ribbed reinforcements are widely used to reduce stress.
- In plastic injection-moulded parts, generous radii and proper ribbing help maintain strength without increasing material.