Cov khoom siv yog ib qho ntawm plaub lub xeev ntawm kev sib sau ua ke uas qhov teeb meem nyob ib puag ncig peb tuaj yeem ua tau. Nyob rau hauv tsab xov xwm no, peb yuav xav txog dab tsi txhua yam khoom muaj nyob rau hauv cov khib nyiab, coj mus rau hauv tus account lub peculiarities ntawm lawv cov qauv sab hauv.
Cov khoom siv yog dab tsi?
Tej zaum sawv daws tuaj yeem teb lo lus nug no. Ib daim hlau, lub computer, cutlery, tsheb, dav hlau, pob zeb, daus yog tag nrho cov piv txwv ntawm cov khib nyiab. Los ntawm qhov pom ntawm lub cev, cov khoom sib sau ua ke ntawm lub xeev tau nkag siab tias nws muaj peev xwm khaws nws cov duab thiab ntim raws li ntau yam kev cuam tshuam. Nws yog cov cuab yeej cuab tam ntawm cov khoom khib nyiab uas paub qhov txawv ntawm cov pa roj, kua, thiab plasmas. Nco ntsoov tias cov kua kuj khaws cov ntim (yog incompressible).
Cov piv txwv saum toj no ntawm cov khoom siv yuav pab kom nkag siab ntau ntxiv txog lub luag haujlwm tseem ceeb uas lawv ua rau tib neeg lub neej thiab kev tsim kho thev naus laus zis hauv zej zog.
Muaj ntau yam kev qhuab qhia lub cev thiab tshuaj lom neeg uas kawm txog lub xeev ntawm cov teeb meem hauv kev xav. Peb teev tsuas yog qhov tseem ceeb ntawm lawv:
- khoom physicslub cev;
- deformation mechanics;
- khoom siv science;
- khoom chemistry.
qauv ntawm cov ntaub ntawv nyuaj
Ua ntej xav txog cov khoom siv kho tshuab ntawm cov khib nyiab, ib tus yuav tsum paub txog lawv cov qauv sab hauv ntawm qib atomic.
Ntau yam khoom siv hauv lawv cov qauv zoo heev. Txawm li cas los xij, muaj kev faib tawm thoob ntiaj teb, uas yog raws li cov txheej txheem ntawm lub sijhawm ntawm kev teeb tsa ntawm cov ntsiab lus (atoms, molecules, atomic pawg) uas ua rau lub cev. Raws li kev faib tawm no, tag nrho cov khib nyiab tau muab faib ua cov hauv qab no:
- crystalline;
- amorphous.
Cia peb pib nrog qhov thib ob. Lub cev amorphous tsis muaj cov qauv txiav txim. Atoms los yog molecules nyob rau hauv nws yog teem random. Qhov no feature ua rau lub isotropy ntawm cov khoom ntawm amorphous cov ntaub ntawv, uas yog, cov khoom tsis nyob ntawm qhov kev taw qhia. Qhov piv txwv zoo tshaj plaws ntawm lub cev amorphous yog iav.
Crystalline lub cev lossis cov khoom siv lead ua, tsis zoo li cov khoom siv amorphous, muaj cov txheej txheem ntawm cov qauv txiav txim hauv qhov chaw. Ntawm microscale, lawv tuaj yeem paub qhov txawv ntawm cov dav hlau crystalline thiab cov kab sib txuas atomic. Vim cov qauv no, cov muaju yog anisotropic. Ntxiv mus, anisotropy manifests nws tus kheej tsis tau tsuas yog nyob rau hauv lub mechanical zog ntawm solids, tab sis kuj nyob rau hauv cov khoom ntawm hluav taws xob, electromagnetic, thiab lwm yam. Piv txwv li, tourmaline siv lead ua tuaj yeem tsuas yog xa cov kev vibrations ntawm lub teeb nthwv dej hauv ib qho kev taw qhia, uas ua raupolarization ntawm electromagnetic hluav taws xob.
Piv txwv ntawm cov muaju yog yuav luag txhua yam khoom siv hlau. Lawv feem ntau pom muaj nyob rau hauv peb lub lattices: lub ntsej muag-centered thiab lub cev-centered cubic (fcc thiab bcc, feem) thiab hexagonal kaw-packed (hcp). Lwm qhov piv txwv ntawm crystals yog cov lus ntsev. Tsis zoo li cov hlau, nws cov nodes tsis muaj atoms, tab sis chloride anions lossis sodium cations.
Elasticity yog cov cuab yeej tseem ceeb ntawm txhua yam ntaub ntawv nyuaj
Los ntawm kev siv txawm tias qhov kev ntxhov siab me tshaj plaws rau ib qho khoom, peb ua rau nws deform. Qee zaum qhov deformation tuaj yeem ua rau me me uas nws tsis tuaj yeem pom. Txawm li cas los xij, tag nrho cov khoom siv deformed thaum siv cov khoom siv sab nraud. Yog tias, tom qab tshem tawm cov khoom no, qhov deformation ploj, ces lawv hais txog elasticity ntawm cov khoom.
Ib qho piv txwv zoo ntawm qhov tshwm sim ntawm elasticity yog compression ntawm lub caij nplooj ntoos hlav hlau, uas tau piav qhia los ntawm Hooke txoj cai. Los ntawm qhov quab yuam F thiab qhov nruj nruj (compression) x, txoj cai no tau sau raws li hauv qab no:
F=-kx.
Ntawm no yog tus lej.
Thaum cov hlau loj, Hooke txoj cai feem ntau yog sau raws li kev siv cov kev ntxhov siab sab nraud σ, tus txheeb ze strain ε thiab Young's modulus E:
σ=Eε.
Young's modulus yog tus nqi tas li rau ib qho khoom tshwj xeeb.
Feature ntawm elastic deformation, uas txawv nws los ntawm yas deformation, yog reversibility. Cov txheeb ze hloov pauv hauv qhov loj ntawm cov khoom hauv qab elastic deformation tsis pub tshaj 1%. Feem ntau lawv pw hauv cheeb tsam ntawm 0.2%. Cov khoom elastic ntawm cov khib nyiab yog tus cwj pwm los ntawm qhov tsis muaj kev hloov pauv ntawm txoj haujlwm ntawm cov qauv hauv cov khoom siv lead ua lattice tom qab kev txiav tawm ntawm cov khoom sab nraud.
Yog tias lub zog siv hluav taws xob sab nraud loj txaus, tom qab txiav nws qhov kev txiav txim ntawm lub cev, koj tuaj yeem pom qhov seem deformation. Nws hu ua yas.
YPlasticity ntawm solids
Peb tau txiav txim siab cov khoom elastic ntawm cov khoom. Tam sim no cia peb mus rau cov yam ntxwv ntawm lawv cov plasticity. Ntau tus neeg paub thiab tau pom tias yog tias koj ntaus tus ntsia hlau nrog rauj, nws yuav flattened. Qhov no yog ib qho piv txwv ntawm cov yas deformation. Nyob rau theem atomic, nws yog txheej txheem nyuaj. Yas deformation tsis tuaj yeem tshwm sim hauv lub cev amorphous, yog li lub iav tsis deform thaum nws raug ntaus, tab sis tawg.
Lub cev muaj zog thiab lawv lub peev xwm los ua cov yas deform nyob ntawm cov qauv crystalline. Qhov xav tias irreversible deformation tshwm sim vim lub zog ntawm tshwj xeeb atomic complexes nyob rau hauv lub ntim ntawm crystal, uas yog hu ua dislocations. Cov tom kawg tuaj yeem yog ob hom (marginal thiab ntsia hlau).
Ntawm tag nrho cov khoom siv, cov hlau muaj cov yas zoo tshaj plaws, vim tias lawv muab ntau lub dav hlau plam mus rau ntawm cov ces kaum sib txawv hauv qhov chaw rau kev txav mus los. Hloov pauv, cov ntaub ntawv nrog covalent lossis ionic bonds yuav nkig. Cov no tuaj yeem raug ntaus nqigems los yog lub rooj ntsev.
Brittleness thiab toughness
Yog tias koj pheej siv lub zog sab nraud rau txhua yam khoom siv, tom qab ntawd sai lossis tom qab nws yuav tawg. Muaj ob hom kev puas tsuaj:
fragile;
Thawj yog tus yam ntxwv ntawm qhov tsos thiab kev loj hlob sai ntawm cov kab nrib pleb. Cov pob txha tawg ua rau muaj kev puas tsuaj loj hauv kev tsim khoom, yog li ntawd, lawv sim siv cov ntaub ntawv thiab lawv cov kev ua haujlwm nyob rau hauv uas qhov kev puas tsuaj ntawm cov khoom yuav ua rau ductile. Cov tom kawg yog tus cwj pwm los ntawm kev loj hlob qeeb qeeb thiab nqus ntawm lub zog loj ua ntej ua tsis tiav.
Rau txhua yam khoom muaj qhov kub thiab txias uas qhia txog kev hloov pauv ntawm nkig. Feem ntau, qhov txo qis hauv qhov kub hloov pauv qhov tawg ntawm cov khoom tawg mus rau nkig.
Cyclic thiab ruaj khov loads
Nyob hauv engineering thiab physics, cov khoom ntawm cov khib nyiab kuj yog yam ntxwv ntawm cov khoom siv rau lawv. Yog li, qhov cuam tshuam tsis tu ncua ntawm cov khoom siv (piv txwv li, nro-compression) tau piav qhia los ntawm qhov hu ua qaug zog. Nws qhia tau hais tias muaj pes tsawg lub voj voog ntawm daim ntawv thov ntawm ib qho tshwj xeeb ntawm kev ntxhov siab cov khoom tau lees tias yuav tiv taus yam tsis muaj kev tawg.
Kev qaug zog ntawm cov khoom siv kuj tau kawm nyob rau hauv qhov kev thauj khoom tas li, los ntawm kev ntsuas qhov sib txawv ntawm lub sijhawm.
Hardness of material
Ib qho ntawm cov khoom tseem ceeb ntawm cov khoom yog hardness. Nws txhaislub peev xwm ntawm cov khoom siv los tiv thaiv kev taw qhia ntawm lub cev txawv teb chaws rau hauv nws. Empirically, nws yog qhov yooj yim heev los txiav txim siab qhov twg ntawm ob lub cev nyuaj dua. Nws tsuas yog tsim nyog los khawb ib qho ntawm lawv nrog lwm tus. Pob zeb diamond yog cov siv lead ua nyuaj tshaj plaws. Nws yuav khawb lwm yam khoom siv.
Lwm yam khoom siv kho tshuab
Cov ntaub ntawv tawv muaj qee yam khoom siv uas tsis yog cov tau sau tseg saum toj no. Peb sau lawv luv luv:
- ductility - lub peev xwm los ua ntau yam duab;
- ductility - lub peev xwm ncab rau hauv cov xov nyias;
- muaj peev xwm tiv taus hom tshwj xeeb ntawm deformation, xws li khoov lossis twisting.
Yog li, cov qauv microscopic ntawm cov khoom loj loj txiav txim siab lawv cov khoom.
