Sisebenzisa amakhukhi ukuthuthukisa ulwazi lwakho.Ngokuqhubeka nokuphequlula leli sayithi, uyavumelana nokusebenzisa kwethu amakhukhi.Ulwazi Olwengeziwe.
Ukukhiqiza okungeziwe (AM) kufaka phakathi ukudala izinto ze-3D, ungqimba olulodwa oluncane kakhulu ngesikhathi, okulwenza lubize kakhulu kunokucubungula okuvamile.Kodwa-ke, ingxenye encane kuphela ye-powder ihlanganiswe engxenyeni ngesikhathi senqubo yomhlangano.Okunye akuhlanganisi, ngakho-ke kungasetshenziswa kabusha.Ngokuphambene, uma into idalwe ngendlela ye-classical, ngokuvamile idinga ukugaya nomshini ukuze kukhishwe izinto.
Izakhiwo ze-powder zinquma imingcele yomshini futhi kufanele zicatshangelwe kwasekuqaleni.Izindleko ze-AM ngeke zibe ukonga uma kubhekwa ukuthi i-powder engancibilikisiwe ingcolile futhi ayikwazi ukuphinda isetshenziswe.Ukuwohloka kwempushana kubangela izenzakalo ezimbili: ukuguqulwa kwamakhemikhali omkhiqizo kanye nezinguquko ezimpahleni zemishini ezifana nokuma komhlaba kanye nokusabalalisa usayizi wezinhlayiyana.
Esimweni sokuqala, umsebenzi oyinhloko ukudala izakhiwo eziqinile eziqukethe ama-alloys ahlanzekile, ngakho-ke sidinga ukugwema ukungcoliswa kwe-powder, isibonelo, ngama-oxides noma ama-nitrides.Kulesi simo sakamuva, le mingcele ihlotshaniswa nokuguquguquka nokusabalala.Ngakho-ke, noma yikuphi ukuguqulwa kwezakhiwo ze-powder kungaholela ekusatshalalisweni okungeyona into efanayo yomkhiqizo.
Idatha evela ekushicilelweni kwakamuva ibonisa ukuthi i-flowmeters yakudala ayikwazi ukunikeza ulwazi olwanele mayelana nokusatshalaliswa kwe-powder ku-AM ngokusekelwe kumbhede wempuphu.Mayelana nokubonakala kwempahla eluhlaza (noma impushana), kunezindlela ezimbalwa zokulinganisa ezifanele emakethe ezinganelisa le mfuneko.Isimo sokucindezeleka kanye nenkambu yokugeleza kwempushana kufanele kufane ekusetheni ukulinganisa kanye nenqubo.Ukuba khona kwemithwalo ecindezelayo akuhambisani nokugeleza kwendawo yamahhala esetshenziswa kumadivayisi e-IM kubahloli be-shear kanye nama-rheometer akudala.
I-GranuTools isungule ukugeleza komsebenzi kokuhlukanisa i-AM powder.Umgomo wethu oyinhloko uwukuhlomisa ijiyomethri ngayinye ngethuluzi elinembile lokulingisa inqubo, futhi lokhu kuhamba komsebenzi kusetshenziselwa ukuqonda nokulandelela ukuvela kwekhwalithi yempushana ezinqubweni ezihlukahlukene zokuphrinta.Amaalloyi amaningana ajwayelekile e-aluminium (AlSi10Mg) akhethelwe ubude besikhathi obuhlukene emithwalweni ehlukene yokushisa (kusuka ku-100 kuya ku-200 °C).
Ukuwohloka kokushisa kungalawulwa ngokuhlaziya ikhono lempushana ukuqoqa ukushaja kagesi.Ama-powders ahlaziywa ukugeleza (insimbi ye-GranuDrum), i-kinetics yokupakisha (insimbi ye-GranuPack) nokuziphatha kwe-electrostatic (insimbi ye-GranuCharge).Izilinganiso ze-kinetics zokuhlanganisa nokupakisha zifanele ukulandelela ikhwalithi yempushana.
Ama-powder okulula ukuwasebenzisa azobonisa izinkomba eziphansi zokuhlangana, kuyilapho ama-powder anama-dynamics okugcwalisa ngokushesha azokhiqiza izingxenye zemishini nge-porosity ephansi uma kuqhathaniswa nobunzima obuningi bokugcwalisa imikhiqizo.
Ngemva kwezinyanga ezimbalwa zokugcina endaweni yethu yaselabhorethri, ama-aluminium alloy powders amathathu anezinhlayiyana ezihlukene zokusabalalisa (AlSi10Mg) kanye nesampula eyodwa yensimbi engagqwali engu-316L akhethiwe, lapha okubhekiselwa kuwo njengamasampula A, B kanye no-C. Izakhiwo zamasampuli zingahluka kwabanye abakhiqizi.Ukusabalalisa usayizi wezinhlayiyana zesampula kukalwe ngokuhlaziywa kwe-laser diffraction/ISO 13320.
Ngenxa yokuthi zilawula imingcele yomshini, izakhiwo ze-powder kufanele zicatshangelwe kuqala, futhi uma izimpushana ezingancibilikisiwe zibhekwa njengezingcolile futhi zingenakuphinda zisetshenziswe, khona-ke ukukhiqiza okungeziwe akukona ukonga njengoba umuntu angase abe nethemba.Ngakho-ke, kuzophenywa imingcele emithathu: ukugeleza kwempushana, amandla okupakisha kanye ne-electrostatics.
Ukusabalala kuhlobene nokufana kanye "nobushelelezi" bongqimba lwempushana ngemva kokusebenza kabusha.Lokhu kubaluleke kakhulu njengoba izindawo ezibushelelezi kulula ukuziphrinta futhi zingahlolwa ngethuluzi le-GranuDrum elinesilinganiso senkomba yokunamathela.
Ngenxa yokuthi ama-pores angamaphuzu abuthakathaka entweni, angaholela ekuqhekekeni.Gcwalisa i-dynamics iyipharamitha yesihluthulelo sesibili njengoba ama-powder okugcwalisa ngokushesha ahlinzeka nge-porosity ephansi.Lokhu kuziphatha kukalwa nge-GranuPack ngevelu engu-n1/2.
Ukuba khona kwamacala kagesi ku-powder kudala amandla ahlangene aholela ekwakhiweni kwama-agglomerate.I-GranuCharge ikala ikhono lezimpushana zokukhiqiza ishaje ye-electrostatic lapho ithintana nezinto ezikhethiwe phakathi nokugeleza.
Ngesikhathi sokucubungula, i-GranuCharge ingabikezela ukuwohloka kokugeleza, isibonelo, lapho yenza isendlalelo ku-AM.Ngakho-ke, izilinganiso ezitholiwe zizwela kakhulu esimweni sokusanhlamvu (i-oxidation, ukungcola kanye nokuqina).Ukuguga kwempushana etholiwe bese kubalwa ngokunembile (± 0.5 nC).
I-GranuDrum iyindlela yokulinganisa ukugeleza kwempushana ehleliwe esekelwe kumgomo wesigubhu esijikelezayo.Ingxenye yesampula yempushana iqukethwe kusilinda evundlile enezindonga ezisobala eziseceleni.Isigubhu sizungeza i-axis yayo ngesivinini esingu-2 kuya ku-60 rpm, futhi ikhamera ye-CCD ithatha izithombe (kusuka ku-30 ​​kuya ku-100 izithombe ngezikhathi zesekhondi elingu-1).Isixhumi esibonakalayo somoya/impuphu sikhonjwa esithombeni ngasinye kusetshenziswa i-algorithm yokuthola unqenqema.
Bala ukuma okumaphakathi kwesixhumi esibonakalayo kanye nama-oscillations azungeze lesi simo esimaphakathi.Ngesivinini ngasinye sokuzungezisa, i-engeli yokugeleza (noma “i-engeli eguqukayo yokuphumula”) i-αf ibalwa ukusuka endaweni yokusebenzelana emaphakathi, futhi isici esiguqukayo sokuhlangana esingu-σf esihlotshaniswa ne-intergrain bonding siyahlaziywa ngokuguquguquka kwesixhumi esibonakalayo.
I-engeli yokugeleza ithintwa imingcele eminingana: ukungqubuzana, ukuma nokuhlangana phakathi kwezinhlayiya (van der Waals, electrostatic and capillary forces).Izimpushana ezihlangene ziphumela ekugelezeni kwezikhawu, kuyilapho izimpushana ezingezona i-viscous ziphumela ekugelezeni okuvamile.Amanani aphansi we-engeli yokugeleza αf ahambisana nokugeleza okuhle.Inkomba ye-adhesion eguquguqukayo eduze ne-zero ihambisana ne-powder engahlangene, ngakho-ke njengoba ukunamathela kwe-powder kwanda, inkomba yokunamathela iyanda ngokufanele.
I-GranuDrum ikuvumela ukuthi ulinganise i-engeli yokuqala ye-avalanche kanye ne-aeration yempushana ngesikhathi sokugeleza, kanye nokulinganisa inkomba yokunamathela engu-σf kanye ne-engeli yokugeleza αf kuye ngesivinini sokujikeleza.
Ukuminyana kwenqwaba ye-GranuPack, ukuminyana kokuthepha kanye nezilinganiso zesilinganiso se-Hausner (ezaziwa nangokuthi “izivivinyo zokuthepha”) zilungele ukwenziwa kwezinhlamvu zempushana ngenxa yokukhululeka kwazo kanye nesivinini sokulinganisa.Ubuningi be-powder kanye nekhono lokwandisa ukuminyana kwayo kuyimingcele ebalulekile ngesikhathi sokugcina, ukuthutha, i-agglomeration, njll. Izinqubo ezinconyiwe zichazwe ku-Pharmacopoeia.
Lesi sivivinyo esilula sinezinkinga ezintathu ezinkulu.Ukulinganisa kuncike ku-opharetha, futhi indlela yokugcwalisa ithinta ivolumu yokuqala ye-powder.Ukulinganisa ivolumu ephelele kungaholela emaphutheni amakhulu emiphumeleni.Ngenxa yobulula bokuhlolwa, asizange sikucabangele ukuhlanganisa amandla phakathi kwezilinganiso zokuqala nezokugcina.
Ukuziphatha kwempushana efakwe esitokisini esiqhubekayo kwahlaziywa kusetshenziswa okokusebenza okuzenzakalelayo.Linganisa ngokunembile i-coefficient ye-Hausner Hr, ukuminyana kokuqala ρ(0) kanye nokuminyana kokugcina ρ(n) ngemva kokuchofoza kuka-n.
Inombolo yompompi ivamise ukumiswa kokuthi n=500.I-GranuPack iyisilinganiso sokuminyana sokuthepha esizenzakalelayo nesithuthukisiwe esisekelwe ocwaningweni lwakamuva oluguquguqukayo.
Ezinye izinkomba zingasetshenziswa, kodwa azinikezwa lapha.Impushana ifakwa eshubhu lensimbi ngenqubo eqinile yokuqalisa okuzenzakalelayo.I-extrapolation yepharamitha engu-n1/2 kanye nokuminyana okukhulu ρ(∞) kukhishiwe kwijika lokucinana.
Isilinda esingenalutho esingasindi sihlala phezu kombhede oyimpushana ukuze kugcinwe ileveli yokusebenzelana kwempushana/yomoya ngesikhathi sokuminyana.Ishubhu equkethe isampula yempushana ikhuphukela kubude obungashintshi ΔZ futhi iwela ngokukhululekile ekuphakameni okuvamise ukumiswa kokuthi ΔZ = 1 mm noma ΔZ = 3 mm, okukalwa ngokuzenzakalelayo ngemva kokuthintwa ngakunye.Bala ivolumu V yenqwaba ukusuka ekuphakameni.
Ukuminyana isilinganiso se-mass m kuya kumthamo we-powder layer V. Ubuningi be-powder m buyaziwa, ukuminyana ρ kusetshenziswe ngemva komthelela ngamunye.
I-Coefficient ye-Hausner Hr ihlobene nento ehlanganisayo futhi ihlaziywa ngesibalo Hr = ρ(500) / ρ(0), lapho u-ρ(0) kuwukuminyana kokuqala kwenqwaba kanye no-ρ(500) ukugeleza okubaliwe ngemva kwemijikelezo engu-500.Ukuminyana kampompi.Uma usebenzisa indlela ye-GranuPack, imiphumela ikhiqizwa kusetshenziswa inani elincane lempushana (imvamisa i-35 ml).
Izakhiwo ze-powder kanye nezakhiwo zezinto lapho idivayisi yenziwe khona yimingcele eyinhloko.Ngesikhathi sokugeleza, amashaji e-electrostatic akhiqizwa ngaphakathi kwempushana ngenxa yomphumela we-triboelectric, okuwukushintshaniswa kwezindleko lapho okuqinile kuhlangana.
Lapho impushana igeleza ngaphakathi kwedivayisi, umphumela we-triboelectric uyenzeka lapho kuthintana phakathi kwezinhlayiya kanye nasekuxhumaneni phakathi kwezinhlayiya nedivayisi.
Lapho ithintana nezinto ezikhethiwe, i-GranuCharge ikala ngokuzenzakalelayo inani le-electrostatic charge elakhiwe ngaphakathi kwempushana ngesikhathi sokugeleza.Isampula yempushana igeleza ngaphakathi kweshubhu ye-V edlidlizayo futhi iwela enkomishini ye-Faraday exhunywe ku-electrometer ekala inkokhiso etholwe njengoba impushana ihamba ngaphakathi kwe-V-tube.Ukuze uthole imiphumela ekwazi ukukhiqiza, sebenzisa idivayisi ezungezayo noma edlidlizayo ukuze uphakele amashubhu e-V njalo.
Umphumela we-triboelectric ubangela into eyodwa ukuthi ithole ama-electron ebusweni bayo futhi ngaleyo ndlela ishajwe kabi, kuyilapho enye into ilahlekelwa ama-electron futhi ngaleyo ndlela iba nokushajwa kahle.Ezinye izinto zithola ama-electron kalula kunezinye, futhi ngokufanayo, ezinye izinto zilahlekelwa ama-electron kalula.
Iyiphi impahla eba yinegethivu futhi eba yinhle incike ekuthambekeleni okuhlobene kwezinto ezihilelekile ukuzuza noma ukulahlekelwa ama-electron.Ukumela lezi zitayela, uchungechunge lwe-triboelectric oluboniswe kuThebula 1 lwakhiwe.Izinto ezinokuthambekela kokushaja okuhle nezinye ezinethrendi yokushaja engeyinhle zibaliwe, nezindlela ezibonakalayo ezingabonisi noma iyiphi inkambiso yokuziphatha zibalwe maphakathi nethebula.
Ngakolunye uhlangothi, ithebula linikeza kuphela ulwazi mayelana nezitayela ekushajweni kwezinto zokwakha, ngakho-ke iGranuCharge yadalwa ukuze inikeze amanani anembile ezinombolo zokuziphatha kokushaja kwezimpushana.
Kwenziwa izivivinyo eziningana ukuze kuhlaziywe ukubola kokushisa.Amasampula abekwe ku-200 ° C ihora elilodwa kuya kwamabili.Impushana ibe isihlaziywa ngokushesha ngeGranuDrum (igama elishisayo).Impushana ibe isifakwa esitsheni ize ifinyelele izinga lokushisa elizungezile bese ihlaziywa kusetshenziswa iGranuDrum, GranuPack kanye neGranuCharge (okungukuthi “kubanda”).
Amasampula aluhlaza ahlaziywa kusetshenziswa i-GranuPack, i-GranuDrum ne-GranuCharge ekamelweni elifanayo lomswakama/izinga lokushisa (okungukuthi 35.0 ± 1.5% RH kanye nezinga lokushisa elingu-21.0 ± 1.0 °C).
Inkomba yokuhlangana ibala ukugeleza kwezimpushana bese ihlotshaniswa nezinguquko endaweni yesixhumi esibonakalayo (impushana/umoya), okungamandla amathathu kuphela okuxhumana (van der Waals, capillary kanye namandla e-electrostatic).Ngaphambi kokuhlolwa, umswakama womoya ohlobene (RH, %) nezinga lokushisa (°C) kwarekhodwa.Khona-ke impushana yathululelwa esigubhini, futhi ukuhlolwa kwaqala.
Siphethe ngokuthi le mikhiqizo ayingenwa kalula yi-agglomeration uma sicabangela amapharamitha e-thixotropic.Kuyathakazelisa ukuthi ukucindezeleka okushisayo kwashintsha ukuziphatha kwe-rheological kwezimpushana zamasampula A no-B kusukela ekuqinisweni kwe-shear kuya ekunciphiseni ukugunda.Ngakolunye uhlangothi, amasampuli C kanye ne-SS 316L awazange athintwe izinga lokushisa futhi abonise kuphela ukujiya kwe-shear.Impushana ngayinye yayinokusabalala okungcono (okungukuthi inkomba yokuhlangana ephansi) ngemva kokushisisa nokupholisa.
Umphumela wokushisa nawo uncike endaweni ethile yezinhlayiya.Ukuphakama kokushisa okushisayo kwempahla, umphumela uba mkhulu kuzinga lokushisa (okungukuthi ???225°?=250?.?-1.?-1) kanye no-???316?.225°?=19?.?-1.?-1) Uma izinhlayiyana zincane, kuba mkhulu umphumela wokushisa.Izimpushana ze-aluminium alloy zinhle kakhulu ekusetshenzisweni kwezinga lokushisa eliphezulu ngenxa yokusabalala kwazo okukhulayo, ngisho nezibonelo ezipholile zithola ukugeleza okungcono kunezimpushana zangempela.
Ngokuhlolwa ngakunye kwe-GranuPack, isisindo sempushana sarekhodwa ngaphambi kokuhlolwa ngakunye, futhi isampula yashaywa izikhathi ezingu-500 ngemvamisa yomthelela engu-1 Hz ngokuwa kwamahhala okungu-1 mm kuseli lokulinganisa (amandla omthelela ∝).Isampula ikhishelwa kuseli yokulinganisa ngokuya ngemiyalelo yesofthiwe ezimele umsebenzisi.Khona-ke izilinganiso zaphindwa kabili ukuze kuhlolwe ukukhiqizwa futhi kuphenywe incazelo nokuchezuka okujwayelekile.
Ngemva kokuqedwa kokuhlaziywa kwe-GranuPack, ukuminyana kwenqwaba yokuqala (ρ(0)), ukuminyana kwenqwaba yokugcina (empompini eminingi, n = 500, okungukuthi ρ(500)), isilinganiso se-Hausner/Carr index (Hr/Cr) namapharamitha amabili okubhalisa (n1/2 kanye no-τ) ahlobene ne-compaction kinetics.Ukuminyana okuhle kakhulu ρ(∞) nakho kuyaboniswa (bona iSithasiselo 1).Ithebula elingezansi lihlela kabusha idatha yokuhlola.
Amanani 6 kanye no-7 abonisa ijika eliphelele lokuminyana (ukuminyana ngobuningi uma kuqhathaniswa nenani lemithelela) kanye nesilinganiso sepharamitha ye-n1/2/Hausner.Amabha amaphutha abalwe kusetshenziswa isilinganiso aboniswa kwijika ngalinye, futhi ukuchezuka okujwayelekile kubalwe ngokuhlolwa kokuphindaphinda.
Umkhiqizo wensimbi engu-316L ubuwumkhiqizo osinda kakhulu (ρ(0) = 4.554 g/mL).Mayelana nokuminyana kokuthepha, i-SS 316L ihlala iyimpushana enzima kakhulu (ρ(n) = 5.044 g/mL), ilandelwa Isampula A (ρ(n) = 1.668 g/mL), ilandelwa Isampula B (ρ(n) = 1.668 g/ml)./ml) (n) = 1.645 g/ml).Isampula C beliphansi kakhulu (ρ(n) = 1.581 g/mL).Ngokobuningi benqwaba yempushana yokuqala, sibona ukuthi isampula A ilula kakhulu, futhi kucatshangelwa amaphutha (1.380 g/ml), amasampula B no-C anenani elicishe lilingane.
Njengoba i-powder ishisa, isilinganiso sayo se-Hausner siyancipha, futhi lokhu kwenzeka kuphela ngamasampula B, C, kanye ne-SS 316L.Kusampula A, akwenzekanga ngenxa yosayizi wamabha wephutha.Ku-n1/2, ukudwetshwa kwethrendi yepharamitha kuyinkimbinkimbi kakhulu.Ngesampula A kanye ne-SS 316L, inani le-n1/2 lehla ngemva kwamahora angu-2 ngo-200 ° C, kuyilapho kuma-powder B no-C lenyuka ngemva kokulayisha okushisayo.
Isiphakeli esidlidlizayo sisetshenziswe ekuhloleni ngakunye kwe-GranuCharge (bona Umfanekiso 8).Sebenzisa amashubhu ensimbi engagqwali angu-316L.Izilinganiso ziphindwe izikhathi ezingu-3 ukuze kuhlolwe ukukhiqizwa kabusha.Isisindo somkhiqizo osetshenziswe esilinganisweni ngasinye sasicishe sibe ngu-40 ml futhi ayikho impushana etholakele ngemva kokulinganisa.
Ngaphambi kokuhlolwa, isisindo sempushana (mp, g), umswakama womoya ohlobene (RH, %), nezinga lokushisa (°C) zarekhodwa.Ekuqaleni kokuhlolwa, ukuminyana kokushaja kwempushana eyinhloko (q0 ku-µC/kg) kukalwa ngokubeka impushana enkomishini ye-Faraday.Ekugcineni, i-powder mass yalungiswa futhi ukuminyana kokugcina kweshaji (qf, µC/kg) kanye ne-Δq (Δq = qf - q0) ekupheleni kokuhlolwa kubalwe.
Idatha ye-GranuCharge eluhlaza iboniswa kuThebula 2 nakuMfanekiso 9 (σ ukuchezuka okujwayelekile okubalwe kusukela kumiphumela yokuhlolwa kokukhiqiza kabusha), futhi imiphumela iboniswa njenge-histogram (kuboniswa kuphela u-q0 no-Δq).I-SS 316L ineshaja yokuqala ephansi kakhulu;lokhu kungase kube ngenxa yokuthi lo mkhiqizo une-PSD ephakeme kakhulu.Uma kuziwa ekulayisheni kokuqala kwe-primary aluminium alloy powder, azikho iziphetho ezingafinyelelwa ngenxa yobukhulu bamaphutha.
Ngemva kokuxhumana nepayipi lensimbi engagqwali engu-316L, isampula A ithole inani elincane lenkokhiso, kuyilapho izimpushana B no-C zibonise ukuthambekela okufanayo, uma i-SS 316L powder yagujwa ku-SS 316L, kwatholakala ukuminyana kokushaja okusondele ku-0 (bona uchungechunge lwe-triboelectric) .Umkhiqizo B usakhokhiswa kakhulu kuno-A. Kusampula C, ithrendi iyaqhubeka (inkokhiso yokuqala evumayo kanye nenkokhiso yokugcina ngemva kokuvuza), kodwa inani lezindleko liyakhuphuka ngemva kokuwohloka kokushisa.
Ngemuva kwamahora angu-2 okucindezeleka okushisayo ku-200 ° C, ukuziphatha kwe-powder kuba mnandi kakhulu.Kumasampuli A no-B, inkokhiso yokuqala yehla futhi inkokhiso yokugcina yasuka ekubeni inegethivu yaya kokuphozithivu.I-SS 316L powder yayinecala eliphakeme kakhulu lokuqala futhi ukuguqulwa kwayo kwe-charge density kwaba kuhle kodwa kwahlala kuphansi (okungukuthi 0.033 nC/g).
Siphenye umthelela wokuwohloka kokushisa ekuziphatheni okuhlanganisiwe kwe-aluminium alloy (AlSi10Mg) kanye nezimpushana zensimbi engagqwali ezingu-316L, kuyilapho izimpushana zangempela zahlaziywa ngemva kwamahora angu-2 ku-200°C emoyeni.
Ukusetshenziswa kwezimpushana emazingeni okushisa aphakeme kungathuthukisa ukugeleza komkhiqizo, umphumela obonakala ubaluleke kakhulu kuma-powders anendawo ethile ephezulu kanye nezinto ezine-conductivity ephezulu yokushisa.I-GranuDrum yasetshenziselwa ukuhlola ukugeleza, i-GranuPack yasetshenziselwa ukuhlaziywa kokupakisha okuguquguqukayo, futhi i-GranuCharge yasetshenziselwa ukuhlaziya i-triboelectricity ye-powder ethintana nepayipi yensimbi engagqwali engu-316L.
Le miphumela inqunywe kusetshenziswa i-GranuPack, ebonise ukuthuthukiswa kwe-Hausner coefficient ye-powder ngayinye (ngaphandle kwesampula A, ngenxa yobukhulu bamaphutha) ngemva kwenqubo yokucindezeleka okushisayo.Akukho ukuthambekela okucacile okutholakele kupharamitha yokupakisha (n1/2) njengoba eminye imikhiqizo ibonise ukwenyuka kwesivinini sokupakisha kuyilapho eminye ibe nomthelela ohlukile (isb. Amasampula B no-C).