Program PPR

PPR determines the stress-strain properties of paperboard from test data. Program PPR converts a data base containing paper basis weight, thickness, strength, and stiffness data obtained from specimens at specific basis weights into a data base of fundamentally more general stress-strain properties for making calculations at arbitrary basis weights. A primary feature is that this program can estimate a complete set of paper stress-strain properties when some of the basic paper data are missing.

Each entry in the table of Paperboard Test Data specifies a paper, first by its Material Code, Basis Weight, and Cost. Then, any combination of from one through eight optional data are used to specify Compressive Strength per Unit Width, Extensional Stiffness per Unit Width, Flexural Stiffness per Unit Width in the cross machine direction CD and the machine direction MD and thickness. Thickness can be specified according to Caliper, Effective Thickness, or both.

Cost represents an overall average assigned value per unit of weight. Setup charges, labor, production factors, or other fixed costs are not separately accounted for. To more accurately account for production factors the output from PPR would need to be made the input to linear programming or inventory management software.

If any of the eight optional inputs are not specified, Program PPR invokes a set of equations, based on theory and correlations, to estimate the missing data values. The missing data constants depend on the combination of test methods used to evaluate them. Default values based on some common test methods are provided.

PPR outputs the stress-strain properties in the cross machine direction and in the machine direction. These stress-strain properties become inputs to Program ECT. With stress-strain properties determined with respect to a normalized basis weight, ECT calculations can be made for arbitrary basis weight values.