Standard Test Method for Tear Resistance (Graves Tear) of Plastic Film and Sheeting
APP-D1004Inspect your cutting die under magnification frequently; even microscopic nicks on the blade cause severe, low-biased tear outliers.
Challenge & Testing Gap
High material elongation and localized specimen necking at the die-cut notch can cause sample slippage and premature jaw-edge tears.
The Solution
Utilize precision pneumatic side-action grips featuring a constant clamping pressure paired with an ultra-sharp geometric die cutter.
Mechanics & Specimen Behavior
Primary Mechanics
Axial tensile loading applied to a notched geometric specimen to measure the peak resistance force required to initiate a tear.
Specimen Details
Graves template geometry featuring a sharp 90-degree internal notch designed to concentrate high localized stress vectors.
Mechanical Ratios & Properties
Specimen thickness measured to the nearest 0.002mm at the direct center of the notch to maintain equation calculation integrity.
Expert Engineering Commentary
Core Problem Identification
Tear propagation originating outside the internal notch vertex or specimen slippage across the jaw faces under extreme elongation.
Root Cause Analysis
Dull template cutting dies creating microscopic micro-cracks along the sample perimeter, causing premature out-of-bounds structural splits.
Hardware Specific Solutions
Pneumatic side-action grips fitted with ultra-smooth or fine-serrated wave jaw faces to guarantee non-slip operation without tearing.
Analysis & Calculation Standards
Event & Failure Detection
Instantaneous peak force registration coupled with secondary continuous tear propagation slope tracking.
Required Calculations
Graves Tear Resistance, Peak Force at Tear Initiation, Ultimate Elongation at Break, and Average Energy to Tear.
Statistical Outputs
Batch average limits, standard deviation of initiation forces, and structural lot compliance profiling tables.
High-frequency 1000Hz data logging tracks the instantaneous peak initialization force loop before rapid tear propagation drops the load.
Additional Commentary
Pristine, die-cut specimen edges isolate the stress vector purely to the template’s engineered notch vertex during test cycles.
Align the specimen perfectly vertical inside the jaw faces to ensure the tensile force is evenly distributed across the notch.
Common Pitfalls
Using standard manual mechanical screw grips that allow flexible thin films to slip as their thickness deforms down-stroke.