1. Test Principle
Bending tests for
Display Micro Screws involve applying symmetrical or asymmetrical bending loads to the specimen and observing its behavior during elastic deformation, plastic deformation, and eventual fracture. This allows for the acquisition of indicators such as bending strength, yield strength, deflection, and fracture characteristics. For Display
Micro Screws, three-point bending or four-point bending tests are commonly used:
Three-point bending: The specimen is placed on two support points, with a concentrated load applied at the middle loading point. Stress is concentrated in the mid-span region, suitable for evaluating the material's local bending resistance.
Four-point bending: The load is applied from two symmetrical loading points, resulting in a uniform stress distribution in the mid-span region, more suitable for testing the overall uniformity of the material.
2. Specimen Preparation
Specimens must conform to national standards (such as GB/T 232 "Metallic Materials - Bending Test Method") or international standards (ASTM E290):
Shape: Rectangular cross-section (commonly 10mm × 10mm × 50mm) or circular cross-section. Samples must be taken from critical parts of the Display Micro Screws (such as the edges of the punch and die), or standard specimens made of the same material as the Display Micro Screws should be used;
Surface Treatment: The specimen surface must be smooth and free of scratches or defects to avoid affecting the accuracy of the test results due to surface damage.
3. Test Equipment and Procedure
Equipment: Material testing machine (equipped with bending fixture), extensometer (for measuring deflection), microscope (for observing cracks);
Procedure:
① Place the specimen on the fixture and adjust the support span (usually about 16 times the specimen thickness);
② Apply a load at a constant rate (e.g., 2 mm/min) and record the load-deflection curve;
③ Observe the specimen deformation process: elastic stage (load is proportional to deflection), plastic stage (deflection increases but load increases slowly), fracture (load suddenly decreases);
④ After the test, measure the fracture deflection and observe the crack morphology (e.g., crack location, propagation direction).
