Standard Mechanical Test Specimen Processing & Customization
When customizing specimens, the first step is to define applicable standards, commonly GB/T, ISO, and ASTM systems. Tensile, Izod impact, Charpy impact, and flexural specimens have fixed dimensional parameters for length, width, thickness, arc transitions, and grip sections that must not be altered arbitrarily. For tensile specimens, key dimensions include parallel section width/thickness and transition arc radius. For impact specimens, precise control of V-notch angle, depth, and root fillet is critical. For flexural specimens, span distance and surface parallelism must be ensured. Taking plastic tensile specimens as an example, Type 1A under GB/T 1040/ISO 527 and Type I under ASTM D638 have strict tolerance requirements. Cavity machining tolerances must be controlled within ±0.02mm to avoid cross-sectional area errors exceeding ±2%, which would invalidate tensile strength and modulus data.
2. Mold Customization and Cavity Machining
The injection molding process directly impacts specimen quality and dimensional stability. Different materials require tailored parameters: for glass fiber-reinforced PA and PC/ABS alloys, control barrel temperature, mold temperature, injection speed, and holding pressure to avoid shear-induced degradation or insufficient holding leading to shrinkage cavities. Process consistency is critical: barrel temperature fluctuations must stay within ±5℃, mold temperature within ±3℃, and injection/holding pressure repeatability ≤5% to ensure uniform crystallinity and orientation, minimizing batch-to-batch mechanical property variation. For warpage-prone materials like PPS and LCP, optimize cooling circuits to maintain uniform cavity temperature and prevent deformation.
4. Post-Treatment and Surface Finishing
After molding, specimens require post-treatment to eliminate residual stress and surface defects. Remove gate remnants with precision tools to avoid affecting grip section integrity. Light flash must be polished with fine sandpaper, ensuring no scratches on the parallel section to prevent premature fracture during testing. For machined specimens cut from plates, control cutting speed and feed rate to avoid work hardening or surface damage that would misrepresent material properties.
| Parameter Item | GB/T 1040.2 (Type 1A) | ISO 527-2 (Type 1A) | ASTM D638 (Type I) |
| Overall Length | 170±2 mm | 170±2 mm | 165±2 mm |
| Grip Section Width | 20±0.2 mm | 20±0.2 mm | 19±0.4 mm |
| Parallel Section Width | 10±0.2 mm | 10±0.2 mm | 12.7±0.2 mm |
| Specimen Thickness | 4.0±0.2 mm | 4.0±0.2 mm | 3.2±0.2 mm |
| Gauge Length | 50±0.5 mm | 50±0.5 mm | 50±0.5 mm |
| Parallel Section Length | 80±2 mm | 80±2 mm | 57±0.5 mm |
| Transition Arc Radius | 24±1 mm | 24±1 mm | 76±2 mm |
| Application Scenario | Domestic injection molding specimen | International general injection molding | American standard & export testing |
5. Final Inspection and Quality Control
