Drying Shrinkage (Ceramic)
Compute the linear drying shrinkage of a ceramic piece, DS = (L_wet − L_dry)/L_wet·100%, the size reduction as it loses the forming water before firing. The water that separated the clay particles evaporates and they draw together. Excessive or non-uniform drying shrinkage causes cracks and warping — which is why drying is slow and controlled. Enter the wet and dry lengths.
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Retração de secagem (cerâmica)
Antes de ir ao forno, a peça cerâmica recém-conformada (por prensagem, extrusão ou colagem) está cheia de água — e ao secá-la, ela encolhe. A retração de secagem RS = (L_úmido − L_seco)/L_úmido·100% mede essa redução, que acontece por um mecanismo elegante: as partículas de argila, achatadas, estão separadas por finas películas de água; à medida que a água da superfície evapora, a tensão superficial puxa as partículas umas contra as outras, aproximando-as — e a peça encolhe enquanto a água que as separava some. Essa fase de retração continua até as partículas se tocarem (o 'ponto de Bigot'), a partir do qual a peça não retrai mais, apenas perde a água remanescente dos poros já formados (sem encolher). O grande risco da secagem é o diferencial: se a superfície seca e retrai muito mais rápido que o interior (ainda úmido e dilatado), surgem tensões que provocam trincas, empenamentos e até explosão da peça. Por isso a secagem industrial é lenta e controlada em estufas com umidade e temperatura graduais, e argilas muito plásticas (que retraem muito) costumam ser 'magras' com adição de chamote ou areia para reduzir a retração e o risco de trinca. A retração de secagem, somada à de queima, dá a retração total que o molde compensa. Informe o comprimento úmido e o seco.
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Total Shrinkage (Ceramic)
Compute the total linear shrinkage of a ceramic piece, TS = (L_wet − L_fired)/L_wet·100%, combining the drying and firing effects from the formed piece to the final product. It is the shrinkage the mold designer must compensate for: the cavity must be larger than the final piece by the total shrinkage, so the fired piece comes out at the exact size. Enter the wet (formed) and fired (final) lengths.
Loss on Ignition (Ceramic)
Compute the loss on ignition (LOI) of a ceramic raw material, LOI = (mass before − mass after ignition)/mass before·100%, the mass lost during heating at high temperature. It corresponds to the release of combined water (clay minerals), the burning of organic matter and the decomposition of carbonates (releasing CO₂). A high LOI indicates much clay/volatile matter and requires care to avoid defects (bubbles, cracks). Enter the mass before and after ignition.
Concrete Shrinkage Loss
Calculate the prestress loss from concrete shrinkage, Δσ = ε_cs·E_s, from the shrinkage strain ε_cs (dimensionless) and the steel modulus E_s (MPa). Shrinkage is the volume reduction concrete undergoes over time as it LOSES water by evaporation (drying shrinkage) and through cement hydration reactions (autogenous shrinkage), independent of loading. When the concrete of a prestressed member shrinks (shortens), the bonded steel tendon shortens too — and shortening, it LOSES tension, exactly as in elastic-shortening loss, except here the shortening is from shrinkage and occurs SLOWLY over months and years. The loss is simply the shrinkage strain times the steel modulus (the stress that shortening 'steals' from the tendon). The shrinkage strain ε_cs is typically 0.0002-0.0005 (200-500 microstrains) and depends on ambient humidity (drier = more shrinkage), member dimensions (thin members shrink more, losing water faster), mix and time. It is one of the three time-dependent losses (with creep and relaxation) reducing prestress over the structure's life. Enter the shrinkage strain and the steel modulus.
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