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Kev lag luam yooj yim- tawm hauv titanium rhaub tsim rau cov roj silicone degraded
Silicone roj da dej feem ntau yog siv rau cov ntawv thov kub (150-200 degree) vim lawv cov thermal resilience. Txawm li cas los xij, kev ua haujlwm ntev - lub sijhawm ua haujlwm ntawm qhov kub thiab txias thaum muaj cov pa oxygen lossis noo noo ua rau tsim cov khoom degradation ntawm silicone roj raws li cov lej ntawm formic acid (HCOOH) thiab lwm yam uas tsis muaj molecular hnyav siloxanes. Formic acid tawm tsam titanium, tshwj xeeb tshaj yog thaum kub kub, ua rau pitting. Lub pitting yog stochastic- nws pib ntawm qhov chaw tsis sib xws ntawm lub plhaub npoo- thiab tuaj yeem pom los ntawm acoustic emission (AE) sensors uas khaws cov ultrasonic vibrations generated thaum lub qhov dej nucleates thiab nthuav. Phab ntsa thickness cuam tshuam lub sij hawm rau thawj lub qhov (induction lub sij hawm) raws li nws txiav txim siab qhov kub thiab txias lub xeev ntawm lub passive txheej. Qhov pib pib yog nrawm los ntawm cov phab ntsa tuab uas yog kub dua thiab uas tseem damp acoustic emissions, ncua kev tshawb pom. Qhov kev sib txuas ntawm phab ntsa thickness, lub sij hawm mus rau thawj lub qhov, thiab acoustic emission detectability yog muaj nyob rau hauv qhov kev tshawb fawb no.

Formic Acid Pitting Mechanism cuam tshuam rau Mechanical Integrity
Ntawm 180℃me me (10-100 ppm) ntawm formic acid hauv silicon roj puas titanium los ntawm pitting mechanism. Cov tshuaj tiv thaiv mus rau: Ti + 4HCOOH → Ti(HCOO) 4 + 2H 2 Lub titanium formate yog soluble nyob rau hauv cov roj thiab li no tsis muaj txheej tiv thaiv. Pitting yog pib ntawm qhov chaw tsawg kawg ntawm cov yeeb yaj kiab passive lossis ntawm thaj chaw muaj kuab paug. Lub sij hawm induction (lub sij hawm mus rau thawj lub qhov) ua raws qhov kev sib txuas ntawm Arrhenius nrog qhov kub thiab txias: t ind=A x exp (E a ​​/ RT). Rau 10 o C nce nyob rau hauv qhov kub thiab txias lub sij hawm induction yog txo los ntawm ib ncig ntawm 50%.

At the same power density, the thicker titanium wall (2.0 mm vs 1.0 mm) has the higher temperature on the outside surface (by 2–4℃) due to the electrical resistance. Qhov ntsuas kub me ntsis no txo ​​qis lub sij hawm induction los ntawm 10-20% . 1.0 hli phab ntsa ntawm 180℃tej; nto kub ~ 187 degree, induction lub sij hawm ~ 800 teev . 2.0 hli phab ntsa: nto temp. ≈ 190 degree, induction lub sij hawm ≈ 650 teev. Thicker phab ntsa ua ntej lub qhov.

Kev cuam tshuam ntawm Kev Ua Haujlwm Thermal: Damping ntawm Acoustic Emission Signal
Pit nucleation ua rau acoustic emission signals uas muaj kev ntxhov siab ntau zaus (100 kHz-1 MHz). Cov nthwv dej no yog attenuated los ntawm lub sij hawm lawv ncav cuag AE sensor (tso rau ntawm qhov kawg txias los yog ntawm lub tank phab ntsa) los ntawm phab ntsa titanium. Lub attenuation coefficient rau titanium yog nyob ib ncig ntawm 5 dB / mm ntawm 500 kHz. Ib phab ntsa 1.0 hli txo cov teeb liab lub zog los ntawm 5 dB. Ib phab ntsa 2.0 hli txo cov teeb liab zog los ntawm 10 dB. Rau txhua txhua 6 dB ntawm attenuation lub teeb liab amplitude ntawm lub sensor yog halved. Yog li ntawd, AE teeb liab los ntawm lub qhov taub ntawm phab ntsa 2.0 hli yog 3-5 npaug tsawg dua ntawm phab ntsa 1.0 hli thiab yog qhov nyuaj dua los kuaj xyuas. Lub qhov taub tuaj yeem dhau los ua qhov loj heev thaum lub sijhawm kuaj pom lub teeb liab.

Synthesis ntawm kev sib haum xeeb: Phab ntsa thickness thiab AE nrhiav tau
Phab ntsa Thickness (mm) Qhov kub thiab txias (degree) Lub Sijhawm rau Lub Qhov Ncauj Ua Ntej (teev) AE Teeb Pom Kev Attenuation (dB) Tus txheeb ze AE Amplitude Lub Sijhawm Pom Zoo AE (teev) 0.8 hli 186℃850 teev 4 dB 1.6 × lub hauv paus 850 teev
1.0 hli 187℃800 h 5 dB 1.0x lub hauv paus 800 h
1.2 hli 188℃750 teev 6 dB 0.8 × 800 xuab moos (qhib tshawb pom)
1.5 hli 189℃700 hr 7.5 dB 0.6 × 800 hr (qhov loj hlob ua ntej kuaj pom)
2.0 hli 190℃650 teev 10 dB 0.3 × 900 teev (nrhiav tom qab kev loj hlob tseem ceeb)
Phab ntsa Thicker txo lub sij hawm induction (qhov tshwm sim ua ntej) thiab tsis muaj zog AE cov cim (nrhiav tau ncua). Qhov kev sib xyaw ua ke no txhais tau hais tias cov pits ntawm phab ntsa 2.0 hli tuaj yeem ncav cuag qhov tob ntawm 50-100 µm ua ntej yuav raug txheeb xyuas thaum cov pits ntawm phab ntsa 1.0 mm tau lees paub ntawm qhov tob ntawm 10-20 µm.

Engineering Beyond the Wall: Qhov chaw ntawm AE Sensors thiab Fluid Management
Attenuation tuaj yeem kov yeej ntawm AE sensor qhov chaw. Feem ntau cov phab ntsa attenuation yog tshem tawm los ntawm mounting lub sensor ncaj qha rau ntawm lub titanium sheath ntawm qhov kub kawg (siv lub siab kub waveguide los yog sib nqus clamp). Phab ntsa thickness muaj me ntsis cuam tshuam rau kev kuaj pom hauv kev kho ncaj qha. Qhov tseem ceeb tshaj, kev tiv thaiv ntawm silicone roj deterioration nce lub sij hawm induction tsis hais ntawm phab ntsa thickness. Ntxiv cov tshuaj antioxidant (xws li . 0.1% phenothiazine) rau cov roj silicone txo cov cim ntawm formic acid 10-20X, thiab nce lub sij hawm induction rau 8,000+ teev. Cov roj ruaj khov nrog cov phab ntsa 1.5 hli muaj lub neej ntev dua qhov tsis muaj qhov tsis zoo dua cov roj uas tsis zoo nrog phab ntsa 1.0 hli.

Xaus: Thin Wall (1.0 mm) yog qhov zoo rau AE Saib Xyuas
In the case of a silicone oil bath heated by a titanium electric heating tube that has deteriorated to trace formic acid, the thinner wall (1.0 mm) shows earlier identification of pitting by acoustic emission and a somewhat longer induction time (800 hours against 650 hours for 2.0 mm). The 1.0 mm wall offers a lower surface temperature (delaying pit commencement) and reduced acoustic attenuation (5 dB versus 10 dB) for detection of tiny pits. The suggested standard for AE monitored heaters is Grade 2 titanium with wall thickness of 1.0-1.2 mm + antioxidant added to the silicone oil for longer induction time. Thicker (>1.5 mm) phab ntsa ncua kev tshawb nrhiav thiab tso cai rau kev loj hlob ntawm cov pits tsis pom. • Qhia qhov kwv yees cov roj degradation tus nqi thiab txoj hauj lwm ntawm AE sensors thaum qhia cov cua sov rau silicone roj da dej nrog kev saib xyuas. Thiab cov phab ntsa nyias nyias yog qhov zoo dua rau kev txhim khu kev qha AE kev tshawb pom ntawm pitting thaum ntxov.