Almen Saturation Curve Calculator 4.0  

Introduction                                                     For details e-mail:

The shape of Almen Saturation curves has distinct characteristics - a rapid initial increase in arc height/time followed by a sharp "knee", after which, increases in arc height/time are at a much lesser rate but appear to continue indefinitely. Saturation is defined as the point on the curve where, doubling the exposure time, results in arc height increases of 10%. This is a straightforward specification.

However, actual determination of Almen Intensity is a complicated processes as illustrated by the hypothetical part below: 

Part Number:         IPW1837 

 Intensity:              .0050A to .0070A 

 Strip Locations:     1, T1, Before, After 

 Coverage:                   200%

The part can be peened only by making multiple passes until 200% coverage is attained. Fractional passes are  not possible (i.e. by increasing pass-speed). Almen strip fixture simulates the part. Setup run  is shown below - all arc heights are in/1000.


 Pass                        1               2              4                8                     16  



 Arc Height                3.2            4.6            5.9             6.6              6.7 


 Arc Height:             3.8            5.0            6.1             6.5              7.1

 It would appear that IPW1837 was peened at the start of the run at an intensity of >5.9A and <6.6A (at T1 >4 and T1<8). At the end of the run, the part was peened at >5.0A and <6.1A  (at T1 >2 and T1<4). Intensity was within the range at the start of the run. It also appears to be within range at the end of the run.

Uncertainties and inaccuracies are eliminated with the Almen Saturation Curve Calculator 4.0 since it draws a curve that represents the true shape of Almen Saturation Curves. Estimated intensities are supported by data and experience.

Software Curve Generation :

Fig. 1 (Before)
     IPW1837 was peened at 6.019A at the start of the run (T1=5 passes)

Fig. 2 (After)   IPW1837 was peened at an intensity of 5.995A at the end of the run (T1=4 passes)

Fig. 3 (Average Intensity)  IPW1837 was peened at 5.995A to 6.019A for an average of 6.01A , average T1=5 passes.


Fig. 4 (Format Flexibility)   Powerful features designed to meet unique and variable requirements that may be encountered in use.

  1.  Manual and Automatic filter of outliers.
  2. The default model is based on the true shape of Almen Saturation Curves. However, a User-Defined model is provided to meet other specifications such as the French NFL 06-832 which requires the equation of a*x/(b+x). 
  3. Default point of saturation is set at 10% (Shown under SatPt above as 1.10). These may be changed to values other than 10%.
  4. Goodness of fit is evaluated in terms of coefficient of correlation (%Fit) and Standard Deviation (SD).
  5. Up to 5 data sets of up to 20 points each may be entered and the average calculated.
  6. T2 may be traced in the graph by checking the box after "Draw T2". This may also be suppressed by uncheking this box to minimize "clutter" in cases where multiple curves are drawn.
  7. Part number, strip number and machine ID may be entered and saved together with the data.