Key principles.
I, T, box
Hollow cross-sections (box, tube) give same stiffness with less material. I-beam optimal for bending. Solid blocks waste material.
Avoid sharp corners
Sharp internal corners concentrate stress 3-5×. Generous fillets (R=0.2× section) reduce concentration to 1.5×.
60% wall thickness
Ribs perpendicular to deflection direction add stiffness without mass. Standard rule: rib thickness 60% of base wall.
Higher cost works
7075-T6 vs 6061: 80% stronger. Inconel vs 4140: better at temperature. Match grade to need.
Cyclic loading
For cyclic loads, fatigue limit matters not yield. Steel ~50% UTS, aluminum no true limit (use endurance).
Long thin members
Compression members at risk. Critical load = π²EI/L². Add lateral support if needed.
FAQ
Static: yield/UTS limits. Fatigue: 30-50% of yield for 10⁷ cycles. Cyclic loading dominated by fatigue.
No. Higher strength often less ductile, more notch-sensitive. For impact loads, balanced strength and ductility better than max strength.
CFRP much stronger per weight, expensive. Use for weight-critical applications (aerospace, racing).
We refer to engineering partners for FEA analysis. Most parts manufactured per drawing; FEA validation by customer or designer.
Yes, especially fatigue. Rough surfaces initiate cracks. Polished or shot-peened surfaces extend fatigue life 2-4×.
Fastener holes, welds, joints — stress concentrators. Design joints away from peak stress regions when possible.
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