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1. Thermal Stress and Strain Subject – Strength of Materials (SOM) AE3K

2. Introduction Thermal Stress and Strain occur due to temperature changes in a material. When a body is constrained and subjected to a temperature change, internal stresses develop. Important in automobile components (e.g., engine parts, brake systems).

3. Thermal Expansion ΔL = α × L × ΔT ΔL = Change in length α = Coefficient of thermal expansion (per °C) L = Original length ΔT = Temperature Change (°C)

4. Free vs. Constrained Expansion Free Expansion: - Body expands freely when heated. - No stress developed. Constrained Expansion: - Body is fixed or restrained. - Thermal stress is generated due to restriction.

5. Thermal Stress Formula σ = E × α × ΔT σ = Thermal stress (N/mm²) E = Young's Modulus of material (N/mm²) α = Coefficient of Thermal Expansion (per °C) ΔT = Temperature Change (°C)

6. Thermal Strain Formula ε = α × ΔT ε = Thermal strain (dimensionless) α = Coefficient of Thermal Expansion ΔT = Temperature Change

7. Practical Example in Automobile Engine Components (Piston, Cylinder): - Subjected to high temperature changes. - Constrained expansion can cause stress → Potential failure. Brake Discs: - Rapid heating during braking → Thermal stresses → Distortion risk. Exhaust Systems: - Thermal fatigue due to repeated heating and cooling cycles.

8. Factors Affecting Thermal Stress - Material properties (E, α) - Magnitude of temperature change (ΔT) - Constraints in the system - Time rate of heating (Fast or slow)

9. Importance in Design - Avoid failure due to thermal stresses by: ✔️ Proper material selection ✔️ Allowing expansion gaps ✔️ Using flexible joints ✔️ Adequate cooling systems

10. Conclusion - Thermal stress and strain are critical in automobile design. - Understanding them ensures safety and durability of parts. - Essential for preventing thermal fatigue and distortion in engines and braking systems.

11. Thank you Presented by – VEDANT AMBAVALE ANMOL SHINDE ATHARVA DABHADE PRABHJEET KALSI