ZOCHITIKA PAKATSUKA KATUNDU KOKHALA
Kusintha kwa zinthu pansi pa mphamvu ya kupsinjika ndi chochitika chovuta kwambiri, choncho kuyenera kufotokozeredwa m’njira zosiyanasiyana kuti kumveke. Chimodzi mwa zofotokozazi ndi kuganiza kuti katundu amaikidwa pang’onopang’ono, monga mmene zimachitidwira ndi zitsanzo pa mayeso a kukoka ndi kukanikiza.
Ngati ndodo yachitsulo yonyamula pa kukokedwa iyikidwa pa katundu womwe ukuwonjezeka pang’onopang’ono ndipo dilatation ℇ yake iyesedwa, timapeza diagramu yosonyezedwa pachithunzicho.
_1= Malire a proportionality _2 =Malire a elasticity 3 =Malire apansi a kusefukira 3’= Malire apamwamba a kutuluka
Poyambirira, kutambasuka kumakhala kochepa kwambiri ndipo kumayenderana ndi kupsinjika, monga lamulo la Hooke limafunira. Kuyambira pa kupsinjika kwina kotsimikizika, kufanana kumasiya ndipo kutambasuka kumachuluka mofulumira kwambiri. Malo enieni a malire amenewa a kufanana n’kovuta kudziwika. Kuyeza kukakhala kolondola kwambiri, umapezeka wotsika kwambiri. Kwa zinthu zambiri umakhala pa δ=0, ndipo lamulo la Hooke limayimira pamenepo ngati kuyandikira koyambirira kwa khalidwe la elastiki, liwu loyamba la kutukuka mu mndandanda wa Taylor wa ntchito ℇ=ℇ (δ) m’malo oyandikana ndi chiyambi cha ma coordinates. Ngati ndodo itamasulidwa ku katundu, zimadziwika kuti, pamene kupsinjika sikunali kwakukulu kwambiri, kusintha kwa mawonekedwe kumatheranso mogwirizana ndi lamulo la Hooke. Koma ngakhale izi zimasintha ngati kupitirira kupsinjika kwinakwake komwe kuli pafupi ndi malire a proportionality, otchedwa malire a elasticity; pamenepo kusintha konse kumakhala ndi gawo la elastic (lobwerera) ndi gawo la non-elastic (losatha). Ngakhale malire a elasticity sangatsimikizidwe molondola, amapezeka kutsika kwambiri pamene kulondola kwa kuyeza kuli kwakukulu.
Komabe, popeza ili ndi tanthauzo lalikulu laukadaulo, chifukwa imayimira malire a kufunikira mu pafupifupi mawerengedwe onse a mphamvu ya zinthu, ndipo nthawi yomweyo ndi malire amene kuwonongeka koyamba kosatha kumachitika, poyesa zitsanzo limafotokozedwa mwatsatanetsatane ndi konvetseni yovomerezedwa, kotero mwachitsanzo, ngati malire a 0,2% amasonyezedwa nkhawa imene pa iyo kusintha kosatha kumafika pa 0,2%.
Nthawi yomweyo pambuyo pa kupitirira malire a kulimba kwa elastic, kupindika kumawonjezeka mwadzidzidzi ndipo kungawonekere ndi maso; pa kupsinjika komwe kuli pafupifupi kosasintha ndodo imatalikirabe mosalekeza. Kupsinjikaku kumatchedwa malire a kuyenda pulasitiki.
Pa makina a hayidroliki oyesera zinthu, pambuyo pa kuyamba kwa kuwunikira kungawonekere kutsika kwa kupsinjika kooneka bwino kwambiri kapena pang’ono, monga momwe chisonyezedwera pa graph ndi mzere wodukaduka; pamenepo kuchuluka kwakukulu kumatchedwa malire apamwamba a kuwunikira, ndipo kupsinjika kokhazikika kwa kuwunikira komwe kumatsatira kumatchedwa malire otsika a kuwunikira.
Pambuyo poti kufutukuka kofotokozedwako kufikire, komwe kuli pafupifupi kosasintha, kupsinjika kumayambanso kukwera, zinthu zimakhala zolimba. M’gawoli la katundu pamachitika kuchepa kooneka kwa gawo lodutsa la ndodo chifukwa cha kontrakisheni ya m’mbali (yosasintha), ndipo kupitirira kwa chithunzi cha kupsinjika ndi kusintha kumadalira choyamba pa funso loti, pakawerengedwa kupsinjika, mphamvu yokoka P yomwe imachita pa ndodo imagawidwa ndi gawo loyambirira Fo kapena gawo la panopa F. Pa zolinga zaukadaulo kupsinjika P/F ndi kofunika. Kupsinjikaku kumadutsa pa maximum, yomwe imatchedwa mphamvu ya zinthu, ndipo pamene maximum ameneyo wadutsa, ndodoyo imachepa kwambiri pamalo amodzi ndipo imathyoka. “Kupsinjika chenicheni” P/F kumakwera kufikira kusweka.
Khalidwe la zitsulo zina limasiyana kwambiri ndi lofotokozedwa pano. Kuyenda kwa pulasitiki nthawi zambiri sikumawoneka bwino, ndipo kuuma kumayamba mwachindunji pambuyo pa kupitirira malire a elastiki.
In brittle materials (stone, glass, concrete) inelastic deformations are generally small, and failure occurs already at a small elongation. The total elongation that the material undergoes up to failure is a measure of the ductility (opposite: brittleness) of the material, and for steel it is precisely specified in the technical requirements. However, since immediately before failure the further deformation concentrates around the necked section, a different value of elongation at fracture is obtained, depending on whether a larger or smaller part of the bar is taken as the gauge length, so that to obtain unambiguous and mutually comparable results, a certain convention must be adopted in advance. Elongation at fracture is usually measured by marking on a round bar of diameter d, before the test, a gauge length l = 10 d and calculating the elongation at fracture ℇSl = ∆1/1 from its extension ∆l.
Ngati kuli kofunika kuyesa ndodo zokhala ndi gawo lina losiyana, kutalika kwa muyeso kumatsimikiziridwa malinga ndi m’mimba mwake wa ndodo ya cylindrical yozungulira yokhala ndi dera lofanana la gawo lopingasa.