Extrusion & Post
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Cyclic pressure fatigue failure of polyolefin plastomer PPR pipes (Variant: strengthened measures)
Fenómeno del problema
PPR/PP-R pipes suffer fatigue failure in cyclic pressure tests, with cracks initiating from the inner wall and expanding outward.
Fatigue failure is the main failure mode of pipes in actual use.
Especially on the original basis, additional attention is needed, and this problem is more prominent and requires key attention.
Análisis de la causa
(1) Micro defects on pipe inner wall cause stress concentration
(2) Unsmooth inner wall at welded joint causes stress concentration
(3) Pipe material toughness insufficient, fatigue cracks propagate fast
(4) Improper extrusion process parameters cause processing defects on pipe inner wall
(5) Pipe wall thickness design safety factor low
(6) On the original basis, additional attention is needed: process parameter fluctuations or equipment state changes aggravate this problem
Solución
(1) Ensure the pipe inner wall is smooth and defect-free, inner wall Ra≤3.2μm
(2) Improve welding quality, avoid weld beads on the inner wall of joints
(3) Select materials with good toughness, ensure elongation at break >500%
(4) Optimize extrusion process, control inner wall quality
(5) Ensure pipe wall thickness reaches the SDR design value, select a higher SDR value if necessary
(6) And strengthen process monitoring; on the original basis, additional attention is needed, paying special attention to parameter stability
Conclusión clave
Fatigue failure is caused by internal defects and stress concentration, and needs to be improved from the three aspects of pipe inner wall quality, welding quality and material toughness.
Targeted preventive measures need to be taken in different production scenarios.
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