Thaum lub tshuab cua sov PFA ua tsis tiav los ntawm kev tawg, kev txheeb xyuas lub hauv paus ua rau -kev qaug zog lossis kev ntxhov siab ib puag ncig (ESC)- yog qhov tseem ceeb rau kev kho. Siv lub stereo microscope (20–50 ×) los yog scanning electron microscope (SEM, 500–5,000 ×), morphological txawv txawv tshwm sim. Cov nplaim hluav taws kub hnyiab yog ncaj, sib luag, thiab sib npaug (1-5 hli sib nrug), khiav ncig ncig lub tshuab cua sov. Lawv muaj cov lus qhia blunt thiab qhia striations (peach marks) los ntawm kev loj hlob zuj zus. ESC cov kab nrib pleb yog qhov tsis sib xws, tawg (xws li cov cag ntoo), thiab randomly oriented. Lawv tshwm sim ntawm qhov tsis xws luag lossis khawb thiab muaj cov lus qhia ntse uas tsis muaj kev sib tw. ESC cov kab nrib pleb kuj tseem qhia tau qhov chaw crazing (micro-fibrils bridging qhov tawg) nyob rau hauv siab magnification. Ib puag ncig PFA hauv ESC cov ntaub ntawv yuav o los yog tsis muaj xim los ntawm tshuaj tua kab mob. Cov kab nrib pleb ntawm qhov kub thiab txias tshwm sim hauv thaj chaw kub tshaj plaws (ze ntawm cov kua kab lossis sab saud); ESC cov kab nrib pleb tshwm sim nyob txhua qhov chaw ntawm kev sib cuag nrog cov tshuaj phem. Microscopy distinguishes lawv ntseeg.
Cov yam ntxwv pom ntawm 20–50 × Magnification
| Feature | Thermal Fatigue Cracks | Environmental Stress Cracking (ESC) |
|---|---|---|
| Cracking orientation | Circumferential (nyob ib ncig ntawm lub rhaub axis) | Random, branching, meandering |
| Kev sib cais | Tsis tu ncua (1-5 mm sib nrug) | Irregular, tsis muaj qauv |
| Txoj kev tawg | Ncaj nraim, tsis yog - ceg | branching (ntoo-zoo li), cag-zoo li |
| Kov ntug | Smooth, blunt | Ntse, jagged |
| Nto kev ntxhib los mos nyob ze ntawm tawg | Smooth, tej zaum yuav muaj oxidation xim (daj / xim av) | Crazing (zoo fibrils), tej zaum yuav muaj tshuaj residue |
| Keeb kwm point | Siab - cheeb tsam kev ntxhov siab (khoov, weld, interface) | Nto khawb, tsis xws luag, los yog tshuaj tua kab mob |
| Nrog kev puas tsuaj | Discoloration ntawm tshav kub (daj mus rau xim av) | o, softening, chemical deposit |
Microscopy Images (Kev piav qhia)
Ntawm 50 × magnification, thermal qaug zog tawg zoo li ib txoj kab huv si khiav perpendicular mus rau lub rhaub axis (circumferential). Cov npoo yog me ntsis sib npaug (los ntawm kev ua kom sov). Ntau cov kab nrib pleb yog pom, sib npaug spaced. Cov khoom ntawm cov kab nrib pleb tsis zoo.
Ntawm 50 ×, ib qho ESC tawg tshwm raws li jagged, branching qauv. Cov microfibrils zoo (0.5-2 µm tuab) nthuav tawm qhov qhib tawg (crazing). Lub puab tsaig yog ntse. Cov chaw ua haujlwm me me tawg tawm ntawm cov ces kaum ntawm 30-60 degree. Qhov saum npoo tej zaum yuav muaj xim dawb los yog daj ntseg los ntawm cov tshuaj tua kab mob.
Ntawm 500 × (SEM), thermal qaug zog qhia striations (peach marks) ntawm qhov tawg, qhia txog kev loj hlob zuj zus. ESC qhia tau hais tias lub pob txha tawg ntawm qhov chaw nrog cov khoom siv polymer filaments thiab tsis muaj kev sib tw.
Kauj Ruam -los ntawm -Txoj Kev Sib Cuam Tshuam Txheej Txheem
Ntxuav lub tshuab rhaub tsis ua haujlwmnrog isopropanol kom tshem tawm cov khib nyiab. Tsis txhob txhuam; yaug maj mam.
Tshawb xyuas qhov muag tsis pom kev: Cov kab nrib pleb qaug zog feem ntau pom zoo li cov nplhaib. ESC cov kab nrib pleb tsis pom tsis muaj qhov loj.
Siv stereo microscope ntawm 20–30 ×. Nrhiav kev taw qhia (circumferential=thermal fatigue; random=ESC).
Tshawb nrhiav crazing: Ntawm 50 ×, yog tias zoo fibrils hla qhov tawg, nws yog ESC. Yog tias du, nws yog thermal qaug zog.
Tshawb xyuas keeb kwm: Taug qab qhov tawg mus rau nws pib. Yog hais tias nyob rau hauv ib tug weld, flange, los yog txias kawg, xav tias thermal qaug zog. Yog tias ntawm khawb lossis tshuaj tso nyiaj, xav tias ESC.
Tshawb xyuas thaj tsam ib puag ncig: Discoloration (xim av/daj)=thermal qaug zog. o lossis softening=ESC.
Common Pitfalls hauv Diagnosis
| Kev soj ntsuam | Kev kuaj mob tsis raug | Kev kuaj mob kom raug | Vim li cas |
|---|---|---|---|
| Circumferential tawg nyob ze flange | ESC | Thermal qaug zog | Flange yog kev ntxhov siab rau thermal cycling |
| Ceg tawg ntawm nto khawb | Thermal qaug zog | ESC | Scratch yog kev ntxhov siab rau kev tawm tsam tshuaj lom neeg |
| Nroj tsuag nrog daj discoloration | ESC | Thermal qaug zog | Yellowing yog los ntawm tshav kub, tsis yog tshuaj |
| Txhaum nrog dawb deposit | Thermal qaug zog | ESC | Deposit yog chemical residue (ntsev, acid) |
| Ntau cov kab nrib pleb | ESC | Thermal qaug zog | Parallel=thermal cycling puas |
Tswv yim piv txwv
Lub tshuab cua sov PFA ua tsis tiav tom qab 6 lub hlis hauv 20% HCl tank ntawm 80 degree. Microscopy (40 ×) qhia tawm cov kab nrib pleb uas tshwm sim los ntawm qhov khawb ntawm qhov chaw, nrog rau qhov tsis zoo thiab tsis muaj xim. Kev kuaj mob: ESC vim yog acid nres ntawm khawb. Kev daws: Tiv thaiv khawb thaum lub sijhawm teeb tsa; smooth nto tiav.
Lwm lub rhaub dej ua tsis tiav hauv lub tank dej kub (95 degree) tom qab 2 xyoos. Cov kab nrib pleb yog ib puag ncig, sib luag, sib npaug sib npaug, nrog daj -xim av xim av. Kev kuaj mob: Thermal qaug zog. Kev daws: Txo qhov kub thiab txias los yog watt ntom ntom, lossis siv tsis yog -ib puag ncig winding.
Xaus: Microscopy Clearly Distinguishes Crack Hom
Siv lub stereo microscope ntawm 20–50 × magnification, thermal qaug zog tawg yog qhov txawv ntawm ib puag ncig kev ntxhov siab tawg los ntawm kev taw qhia (circumferential vs. random), qhov sib nrug (tsis tu ncua vs. tsis xwm yeem), branching (tsis pom thiab tam sim no), thiab muaj crazing (tsis muaj vs. microscopic fibrils). Thermal fatigue cracks yog kub-txog thiab tshwm sim nyob rau hauv siab - kev ntxhov siab cyclic kev pab cuam; ESC cov kab nrib pleb yog tshuaj lom neeg - cuam tshuam thiab yuav tsum muaj lub ntsej muag kev ntxhov siab. Kev kuaj mob kom raug tso cai rau kev kho kom raug: txo qis thermal cycling rau qaug zog; tshem tawm cov tshuaj lom neeg los yog kev ntxhov siab rau ESC. Ob qhov tawg, ob qho laj thawj, ob txoj kev kho. Saib ntawm lub lens, saib tus qauv, kho qhov teeb meem. Lub microscope tsis dag. Siv nws.
