ƘWANƘWASA TSABAR KUƊI, KA JI DA ME AKA YI TA

Tsabobin azurfa na ajiya (bullion) abin sha’awa ne ga masu jabu, domin darajarsu kusan gaba ɗaya tana cikin ƙarfen. Na jabu mai gamsarwa kawai yana buƙatar ya yi daidai da faɗin tsabar, kaurinta, nauyinta da kamanninta — duka an wallafa su, duka suna da sauƙin kwaikwayo da ƙarfe mai rahusa.

Kowane gwaji na yau da kullum yana tsayawa a wani wuri. Maganadisu yana kama na jabu masu tsakiyar ƙarfe, amma ba sauran ba. Yawa (density) yana ba da bayani, amma tsakiyar da aka zaɓa don ta yi daidai da zinariya ko azurfa tana wucewa, kuma “tsakiyar tungsten mai girman da ya dace tana wucewa”. X-ray fluorescence — haska hasken X-ray kan tsabar da karanta hasken da take mayarwa — tana karanta haɗin sinadarai ne kawai a saman, don haka shafi mai kauri yana ɓoye ciki. Ultrasound tana binciken cikin ƙarfen amma tana buƙatar na’urar taɓawa, jel da kayan aiki na musamman.

Ƙara ba siffar azurfa ba ce

Ƙwanƙwasa tsaba da saurara — “gwajin ping” (ping test) — ana amfani da shi tun tuni. Manhajoji suna kwatanta mitar ƙarar tsabar da mitocin da aka naɗa ga irin wannan tsaba. Mafi ci gaba daga cikinsu ya ƙunshi tsabobin azurfa 23 a lokacin da marubutan suka duba na ƙarshe, kuma mai sayar da shi ya lura cewa ba a gwada tsabobin da kamfanoni masu zaman kansu suka ƙera — guntayen ƙarfe masu siffar tsaba waɗanda ba wata gwamnati ta fitar da su ba — da tabbaci sosai.

Marubutan sun fayyace matsalar: “Mita ba siffar azurfa ba ce — siffar wannan guntun azurfa ce, a wannan faɗin da wannan kaurin.” Canza girma kuma sautin yana canzawa, don haka kowane irin tsaba yana buƙatar nasa abin kwatance.

Sylvia Dong, ɗaliba a Lynbrook High School a San José, California, da Takyiu Liu, na West Valley College a Saratoga, sun yi niyyar kawar da ɗakin karatun. Daga ƙarar, radius da yawan sarari, suna lissafa saurin raƙuman farantin (plate wave speed) — yadda raƙuman lanƙwasa ke gudu ta cikin falle na wannan ƙarfen —, tabbataccen ma’auni na abu wanda ya dogara da taurinsa (Young’s modulus), yawansa da Poisson’s ratio ɗinsa (yadda yake kumbura a gefe idan aka matsa shi).

Matsaloli biyu

Tsabobi sun yi kauri ga dabarar littafin karatu. Tsohuwar ka’idar sirarun faranti masu jijjiga tana kasawa a siffar tsaba. Ta hanyar daidaita (calibrate) kan faya-fayan aluminium biyar da aka sassaƙa da injin, marubutan sun auna wani abin gyara wanda ya rage mafi munin kuskure daga 8.9% zuwa 0.75%.

Tsabar da aka buga ba faifai mai lebur ba ce. Zanen tudunta yana cire ƙarfe, don haka abin aunawa (callipers) yana nuna kauri fiye da wanda ke jijjiga a zahiri. Babban ra’ayinsu shi ne abin cikawa (fill factor): ainihin yawan sararin tsabar, wanda aka auna ta hanyar auna ta a rataye cikin ruwa, a raba da yawan sararin silinda mara zane. Tsabobin da aka buga sun fito tsakanin 0.70 da 0.91. Ninka kaurin da abin aunawa (callipers) ya nuna da wannan abin cikawa yana ba da kauri mai tasiri na ƙarfen da ke jijjiga a zahiri.

Tsarin mai sauƙi ne: akwati da aka lulluɓe da soson shanye sauti, mazauni da aka buga da firintar 3D da ke riƙe tsabar a tsakiyarsa, na’urar naɗar sauti mai ɗaukuwa, ƙarfen bugawa na gram 31 da ake amfani da shi da hannu, da sikeli. Daga ƙwanƙwasawa 2,163, an riƙe 1,937. Mitar ƙarar ta maimaita cikin 0.15% daga wani zama zuwa wani.

Abin da ƙarfen ke faɗi

• A kan tsabobin jan ƙarfe guda shida da aka buga waɗanda ba su da wani matsayi a daidaitawar, hanyar ta samo Young’s modulus na 119.1 ± 6.7 GPa (gigapascal, ma’aunin tauri), a tsakiyar iyakar da aka yarda da ita ga jan ƙarfe ta GPa 110 zuwa 128.
• Saurin raƙuman motsi ya rarrabu bisa abu: azurfa tsantsa kusan m/s 2,870, azurfar sterling kusan m/s 3,040, jan ƙarfe kusan m/s 3,880, aluminium m/s 5,410.
• Tsabobi biyar da aka saya saboda ana shakkar ingancinsu: huɗu sun amsa wa maganadisu kuma suna da yawa da saurin raƙuma masu daidaita da karfen carbon na yau da kullum; na biyar, da tagulla (brass). Babu ɗayansu da ya wuce a matsayin azurfa.
• Ƙarin sautuka (overtones) ba jituwar kiɗa (harmonics) ba ne: kashi 83.7% na ƙololuwa 1,970 sun yi daidai da salon jijjigar faranti mara ɗauri, kashi 10.4% kawai ninki cikakke na sautin tushe. “Faifan da aka ƙwanƙwasa ba igiya ba ne.”

Wani abin mamaki ya zo daga kasafin kuskure. Ya yi hasashen cewa ingantaccen makirufo ba zai canza komai ba kuma sikeli mafi kyau zai canza komai. Auna har zuwa milligram 0.1 maimakon gram 0.1 ya rage rashin tabbas ga kowace tsaba daga 1.6–30% zuwa 0.5–2.6%, kuma ya rage wani bayyanannen son kai na kashi 11% a kan wani zanen azurfa mai zurfin tudu zuwa ’yan kashi kaɗan.

Na jabun da bai iya ji ba

Me ya sa ma ake auna sassauci (elasticity)? Domin na jabu na iya kwaikwayon yawa amma ba tauri ba. Zinariya da tungsten sun bambanta da kashi 0.3% kawai a yawa, amma saurin raƙuman farantinsu m/s 2,240 da 4,810 ne — bambancin ninki 2.1.

A wannan binciken, dokar yanke shawara da aka sanya a gaba — rashin amsa wa maganadisu da yawa sama da kg/m³ 9,000 — tana wuce da kowane ƙarfe mai yawa a matsayin azurfa: faifan tungsten yana wucewa. Hanyar sauti ya kamata ta ƙi shi, amma babu ɗayan samfuran tungsten biyu da ya ba da ƙarar da za a iya ganowa. Don haka wannan ƙin hasashe ne, ba a nuna shi ba.

Marubutan sun lissafa wasu iyakoki: ba a gwada rarrabuwar a makance (blind) ba, sakamakon ya dogara da Poisson’s ratio da aka ɗauka (kusan ±3%), kuma ba a taɓa tabbatar da haɗin sinadaran tsabobin da ake shakka ta hanyar nazarin sinadarai ba. Matakai na gaba: samfurin tungsten da ke ƙara, da gwaji a makance.