PFA lub tshuab hluav taws xob txhawb nqa- siv los tso cov cua sov hauv cov tso tsheb hlau luam lossis los tuav cov cuab yeej pabcuam- qee zaus dais cov khoom siv hluav taws xob ruaj khov ntawm qhov kub siab. Ntawm 180℃(ze PFA qhov kev siv tsis tu ncua ntawm 200 degree), creep rupture yog qhov tseem ceeb tsis ua hauj lwm hom rau loaded brackets. Rau lub bracket loaded ntawm 5 MPa (ib txwm rau 10 kg rhaub dai los ntawm 50 mm² cross-section support), qhov tseeb creep rupture lub neej yog 500-2,000 teev, nyob ntawm PFA qib, crystallinity, thiab manufacturing zoo. Qhov no yog luv luv tshaj li cov kev pab cuam lub neej ntawm lub rhaub dej kub (10,000-30,000 teev). Yog li ntawd, PFA brackets yuav tsum tsis txhob siv rau kev txhawb nqa siab tshaj 2 MPa ntawm 180 degree. Rau kev thauj khoom siab dua 2 MPa, siv cov hlua hlau nrog PFA txheej lossis cov hlau sib cais. Cov ntaub ntawv creep rupture hauv qab no muab kev taw qhia rau kev nyab xeeb tsim.
Creep Repture Mechanisms ntawm 180 degree
Ntawm 180 degree, PFA yog siab dua nws cov iav hloov pauv (Tg=-15℃) tab sis hauv qab nws cov ntsiab lus melting (305℃). Lub polymer nthuav tawm viscoelastic creep: nyob rau hauv tas li load, nws deforms tsis tu ncua. Hauv thawj theem creep (thawj 0-100 teev), strain nce ntawm tus nqi qis. Nyob rau hauv theem nrab creep (100-1,000 teev), strain rate yog tas li. Nyob rau hauv tertiary creep (tshaj li 1,000 teev), strain accelerates raws li voids daim ntawv thiab tus ntoo khaub lig zoo -section txo, ua rau rupture. Rau PFA bracket loaded ntawm 5 MPa ntawm 180 degree, ib txwm lub sij hawm mus txog tertiary creep yog 200-500 teev; rupture tshwm sim ntawm 500-2,000 teev. Lub neej tawg ua raws li Larson-Miller parameter: LMP=T × (C + log t), qhov twg T yog qhov kub (K), t yog lub sijhawm tawg (teev), thiab C yog cov khoom siv tas li (≈20 rau PFA). Rau ib qho LMP muab, qhov kub siab dua txo lub neej exponentially.
Lub crystallinity ntawm PFA muaj zog cuam tshuam rau creep kuj. High-crystallinity PFA (55–65%) muaj 2–3 × ntev nkag lub neej dua li qis-crystallinity PFA (35–45%). Annealed brackets (post{10}}moulding annealing ntawm 200℃rau 4 teev) kuj qhia tau tias lub neej ntev dua (saib Tshooj #41). Lub bracket geometry tseem ceeb: cov kaum ntse ntse tsom rau kev ntxhov siab thiab txo lub neej los ntawm 50-80% piv rau cov qauv hluav taws xob.
Creep Repture Lub neej los ntawm kev ntxhov siab thiab kub
| Kub (degree) | Kev ntxhov siab (MPa) | PFA Qib | Crystallinity (%) | Rupture Life (teev, raug) | Hom kev ua tsis tiav |
|---|---|---|---|---|---|
| 180 | 2 | Txuj | 45 | 8,000–15,000 | Ntau dhau deflection (creep) |
| 180 | 3 | Txuj | 45 | 3,000–6,000 | Creep rupture |
| 180 | 4 | Txuj | 45 | 1,000–2,500 | Rupture nrog void tsim |
| 180 | 5 | Txuj | 45 | 500–1,500 | rupture ceev |
| 180 | 6 | Txuj | 45 | 200–500 | Tam sim ntawd deflection, rupture |
| 180 | 5 | Siab -crystallinity (annealed) | 60 | 1,200–2,500 | 2 × lub neej vs |
| 180 | 5 | Tsawg-crystallinity (unannealed) | 38 | 300–800 | 50% lub neej vs |
| 160 | 5 | Txuj | 45 | 3,000–6,000 | Qhov kub qis dua ncua lub neej |
| 200 | 3 | Txuj | 45 | 500–1,500 | Nyob ze qhov txwv siab tshaj rau PFA |
| 150 | 5 | Txuj | 45 | 6,000–12,000 | Txais tau rau kev sib tshuam loads |
Cov lus pom zoo tsim kev nyab xeeb
For PFA support brackets at 180°C, the maximum sustained stress should not exceed 2 MPa for long-term service (>5,000 teev). Xam kev ntxhov siab li σ=F / A, qhov twg F yog qhov thauj khoom (N) thiab A yog qhov tsawg kawg nkaus hla- ntu ntu ntawm lub bracket (mm²). Rau 50 N load (≈5 kg), yuav tsum muaj thaj tsam A=F/σ=50 / 2=25 mm². Ib txoj hlua khi nrog tus ntoo khaub lig- ntu ntawm 5 mm × 5 mm (25 mm²) yog qhov tsawg kawg nkaus. Rau 100 N load (10 kg), qhov tsawg kawg nkaus yog 50 mm² (7 mm × 7 mm). Cov no yog qhov tsawg kawg nkaus; brackets loj dua muab kev nyab xeeb margin.
Rau kev thauj khoom siab tshaj 2 MPa ntawm 180 degree, siv lub nplhaib hlau (stainless steel, titanium, lossis Hastelloy) nrog PFA txheej lossis lub tes tsho los tiv thaiv cov tshuaj tua kab mob. Hlau bracket nqa lub load; PFA muab tshuaj tiv thaiv. Xwb, txhawb lub tshuab cua sov los ntawm sab saum toj (nruj) es tsis yog los ntawm hauv qab (compression) siv lub pas hlau los ntawm lub tshuab cua sov. PFA muaj zog nyob rau hauv compression dua nyob rau hauv nro; compressive creep lub neej yog 2-3 × ntev dua tensile creep lub neej rau tib qhov kev ntxhov siab.
Rau PFA brackets uas twb muaj lawm ua haujlwm ntawm kev ntxhov siab, tshuaj xyuas txhua xyoo rau deformation. Ntsuas tus bracket qhov qub qhov ntev thiab muab piv rau tam sim no. Ib qho deflection mus tas li tshaj 2 hli los yog ib qho kev pom tawg tuaj yeem hloov tam sim. Yog tias lub bracket tau deformed tab sis tsis tawg, nws tuaj yeem ua haujlwm txuas ntxiv tab sis muaj peev xwm txo qis. Rau cov ntawv thov tseem ceeb (lub tshuab cua sov tuaj yeem poob rau hauv lub tank), hloov deformed brackets tsis hais txog kev tawg.
Piv txwv teb
Cov nroj tsuag tshuaj siv PFA brackets los pab txhawb 15 kg lub rhaub (150 N load) ntawm 180℃. Lub bracket cross-section yog 10 mm × 8 mm (80 mm²), muab σ=150/80=1.9 MPa- nyob rau hauv qhov txwv tsis pub. Tom qab 18 lub hlis (≈13,000 teev), lub bracket pom 3 hli deflection tab sis tsis muaj kab nrib pleb. Lub tshuab cua sov tseem txhawb nqa. Thaum 2.5 xyoo (18,000 teev), deflection mus txog 6 hli, thiab lub rhaub yog sagging. Lub bracket tau hloov thaum lub sijhawm kaw. Lub bracket tsis tau ua tsis tiav tab sis nyob ze rau qhov kawg ntawm nws lub neej muaj txiaj ntsig. Cov nroj tsuag tau hloov kho nws cov qauv siv hlau brackets rau kev teeb tsa yav tom ntej, hais txog qhov xav tau rau lub neej tsis kawg.
Xaus: Txwv PFA Bracket Stress rau 2 MPa ntawm 180 degree
Qhov tiag tiag creep rupture lub neej ntawm PFA lub rhaub dej txhawb nqa ntawm 5 MPa thiab 180℃tsuas yog 500-2,000 teev-tsis txaus rau feem ntau cov ntawv thov. Rau kev ua haujlwm ntev -lub sijhawm (5,000+ teev), txwv kev ntxhov siab rau 2 MPa. Rau kev thauj khoom siab dua 2 MPa, siv cov hlua hlau nrog PFA txheej lossis cov hlau sib cais. Yog tias yuav tsum tau siv PFA brackets, qhia qhov siab -crystallinity, annealed PFA, vojvoog tag nrho cov ces kaum, thiab tshuaj xyuas txhua xyoo rau deflection. PFA yog ib qho khoom siv zoo heev rau cov tshuaj tiv thaiv tab sis cov khoom siv tsis zoo rau kev thauj khoom ruaj khov -cov kabmob ntawm qhov kub thiab txias. Tsis txhob nug PFA ua li cas hlau yuav tsum ua. Thaum tsis ntseeg, siv hlau. Tus nqi ntawm lub rhaub dej poob rau hauv lub tank thiab luv luv tiv thaiv phab ntsa yog ntau dua li tus nqi ntawm cov khoom siv hlau zoo. Engineer lub bracket rau lub load, tsis yog rau qhov yooj yim ntawm ib tug -cov ntaub ntawv tov.
