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Intermediate 10 min read Updated 21/09/2026

How to Graph a Modified Goodman Diagram in Excel

Learn how to create a modified Goodman diagram in Excel for fatigue analysis, including setting up stress calculations, plotting the failure lines, and interpreting the results for mechanical component design.

In this tutorial:

Setting up stress data
Creating the Goodman line
Adding yield strength lines
Plotting operating points

You'll need:

Excel (2010 or newer)
Material properties data
Basic knowledge of fatigue analysis

Creating a Modified Goodman Diagram in Excel

Step 1: Setting Up Material Properties

Enter Material Properties


                            A1: Ultimate Tensile Strength (Sut)

                            A2: Yield Strength (Sy)

                            A3: Endurance Limit (Se)

                            A4: Safety Factor (n)

Enter numeric strengths in B1:B3 in the same stress unit. Use material and component-specific fatigue data; a chart alone is not a design approval.

Create Stress Table

Mean Stress	Alternating Stress
0	Se
Sut	0

Step 2: Creating the Basic Plot

Insert Scatter Plot

• Select your stress data
• Insert > Scatter Plot
• Choose "Scatter with Straight Lines"

Format Axes

• X-axis: Mean Stress (0 to Sut)
• Y-axis: Alternating Stress (0 to Se)
• Add gridlines for better readability

Step 3: Adding Yield Strength Lines

Yield Line Equations:

For positive yield line:

σa + σm = Sy

For negative yield line:

σm − σa = −Sy

Create Additional Data Series

Add columns for yield lines using the equations above.

For nonnegative mean stress, plot the Goodman boundary with X values 0 and $B$1, and Y values $B$3 and 0. The tensile yield boundary is σa = Sy − σm; plot (0, $B$2) and ($B$2, 0) as a separate series. The compression-side yield line needs a negative X range, so it is not visible on a 0-to-Sut axis.

Step 4: Plotting Operating Points

Add Operating Points


                            Create new columns:

                            Operating_Mean_Stress | Operating_Alt_Stress

For each load cycle, calculate σm = (σmax + σmin)/2 and σa = (σmax − σmin)/2, then add that X/Y pair as a scatter series. For positive mean stress, the Goodman utilization is σa/Se + σm/Sut; compare yield separately using (σm + σa)/Sy. A safety factor can be estimated as the inverse of the governing utilization only within the model's assumptions.

Pro Tips and Best Practices

Formatting Tips:

Use different colors for different lines
Add a legend for clarity
Include grid lines for easy reading

Analysis Tips:

Check safety factor at critical points
Consider stress concentration factors

Common Issues and Solutions

Graph Not Displaying Correctly:
Check data ranges and axis settings
Lines Not Intersecting:
Verify material property values and calculations