High Precision in Situ Structural Deflection Mapping in Commercial Battery Testing Tooling
In situ deflection mapping decouples test tooling flexure from cell swelling to restore true electrochemical capacity and volumetric degradation profiles.
Compression Platen Bending
Meaning
Undesired deformation of the flat plates in a universal testing machine during high-load mechanical evaluations. Excessive compression platen bending introduces errors into displacement measurements by adding the flex of the machine to the compression of the sample. This phenomenon occurs when the specimen area is significantly smaller than the platen area.
Measurement Error
Calculated strain values become artificially high when the machine ignores the curvature of the steel plates. Because compression platen bending varies with the applied force, the error is non-linear throughout the test duration. High-precision sensors like extensometers are required to bypass the movement of the platens and measure the sample directly.
Load Distribution
Concentrated forces at the center of the plate cause the edges to lift slightly away from the supporting crosshead. Standard procedures for compression platen bending mitigation involve using thicker plates or hardened inserts to increase the stiffness of the contact surface. The choice of material for the platens (such as tungsten carbide) affects the degree of deflection observed under peak loads.
Correction Method
Mathematical models can subtract the known stiffness of the testing frame from the raw data to improve accuracy. Calibration of compression platen bending involves pressing two plates together without a sample to map the deformation of the system. This baseline allows the software to isolate the behavior of the battery cell or material specimen during the actual crush test.
Rigidity in the testing hardware ensures the validity of the resulting stress-strain curves.