**SUMMARY**

This article will describe the calculations used for LBR Test. CBR is calculated similarly but will use different division values.

**SOLUTION**

**LOAD [L]**

Recorded during test or manually entered by user.

**PENETRATION [P]**

Recorded during test or manually entered by user.

**CORRECTED LOAD [CL]**

CL = L- initial load + top cap weight.

**CORRECTED PENETRATION [CP]**

CP = P - initial displacement

**STRESS ON PISTON [SP]**

SP [psi] = CL [lbf] / 3

**LBR PERCENTAGE [LBR]**

**PENETRATION INDEXES [PI]** = 0.1 in.

LBR Values are calculated at closest CP to PI.

**DIVISION VALUES [DV] per FM 5-515 **=

800 @ 0.1 in

LBR @ PI = SP [psi] / CV * 100

DV is in PSI units.

**CORRECTED LBR PERCENTAGE [CLBR]**

Same as LBR but adjusted by correction line drawn.

From the correction line we get the correction lines **Slope [S]**, **Y-Int [B]**, and **Corr [C]**.

Next, we need to determine the displacement offset of the line. This is found with the line equation when y is zero.

**CORRECTION LINE PENETRATION CORRECTION VALUE [C]**

C = -B / S. This is derived from y = mx +b and we are solving for x.

The closest matching P value for the PI is adjusted with C yielding the Adjusted Penetration value.

**ADJUSTED PENETRATION [AP]**

AP = CP + C

Finally, we determine where the AP value intersects with the curve. A vertical line is used to determine intersection. This will yield the **ADJUSTED FORCE [AF]** value.

CLBR = AF / DV * 100

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