Systems Effectiveness Associates, Inc.
20 Vernon Street
Norwood, MA 02063
Phone: 781-762-9252
Fax: 781-769-9422

Stress Screening Strength Estimator

Hughes SDO Model SS Calculation
per RADC-TR-86-149
December 12, 1996
Based on a Paper "Calculating Screening Strength for ESS Environments"
by Gene Bridgers.
Project Name:  
Analyst Name:  
Analysis Date  
Normal Use Conditions: Level (units)  
Box Ambient Temperature (C) Note: This should be the ambient at the box or system level.
Card Temperature Rise (C) Note: This is the temperature rise from the box ambient to the board.
Normal Use Vibration (G)  
Temperature Soak ESS: Level (units)  
Temperature Soak Time (i.e. T) (hours)  
Temperature Soak Level for Box equivalent (C)  
  • T = Soak Time (in hours)
  • Range = Soak Temperature - Ambient Temperature (in degrees C)
Temperature Soak ESS   =     1-(EXP((-0.0017)*((R + 0.6)^0.6)*(hours)))
Temperature Cycle ESS: Level (units)  
Temperature Cycles (i.e. Ncy) (cycles) Note: 2 transitions = 1 cycle
Hot Temperature Level (C)  
Cold Temperature Level (C)  
Transition Rate (i.e. dT/dt) (C/minute)  
  • Range = Hot Temperature - Cold Temperature (in degrees C)
  • dT = Thermal Rate of Change (in degrees C per minute)
  • Ncy = Number of Cycles (in complete cycles)
Temperature Cycle SS = 1 - (EXP((-0.0017)*((R + 0.6)^0.6)*(((LN(2.718 + dT))^3))*(Ncy)))
Fixed Frequency Sine Vib. ESS: Level (units)  
Fixed Vib. Level (i.e. G) (G)  
Fixed Vib. Time (i.e. T) (minutes)  
Fixed Frequency Sine SS = 1 - (EXP((-0.00047)*((G)^0.49)*(minutes)))
Sine Sweep Vib. ESS: Level (units)  
Sweep Vib. Level (i.e. G) (G)  
Sweep Vib. Time (i.e. T) (minutes)  
Sine Sweep Vib. SS = 1 - (EXP((-0.000727)*((G)^0.863)*(minutes)))
Random Vibration ESS: Level (units)  
Random Vib. Level (i.e. G) (G)  
Random Vib. Time (i.e. T) (minutes)  
Random Vibration SS = 1 - (EXP((-0.0046)*((G)^1.71)*(minutes)))
Hughes Cumulative SS