How to get yield strength from stress strain curve?

As an engineering student who just finished materials science, here's how to find yield strength from a stress-strain curve:For materials with a clear yield point (like mild steel):- Look for the sudden drop in stress - that's the upper yield point- The stress value where this occurs is your yield strengthFor materials without a clear yield point (most metals):- Use the 0.2% offset method- Draw a line parallel to the elastic region starting at 0.2% strain- Where this line intersects the curve - that stress value is your yield strength (σ_y)Remember: Yield strength is the stress at which material deformation changes from elastic to plastic. Once you've passed this point, the material won't return to its original shape when the load is removed.It's one of the most important material properties for design engineers!

I teach materials engineering and here's the detailed method for determining yield strength:Step-by-Step 0.2% Offset Method:1. Identify the elastic region - the straight line portion at the beginning2. Draw a best-fit line through this elastic region3. From the strain axis (x-axis), start at 0.002 (which is 0.2%)4. Draw a line parallel to your elastic line from this point5. Find where this parallel line intersects your stress-strain curve6. Drop straight down to the stress axis - this value is your yield strengthWhy 0.2%? It's an arbitrary but standardized amount of plastic deformation that's considered acceptable for most engineering applications.Pro tip: Use graph paper or digital tools for accuracy. Small errors in drawing the offset line can lead to significant errors in your yield strength calculation.The ASM Materials Handbook has great examples if you need visual references!