斷裂韌性及測(cè)量方法-免費(fèi)閱讀
【正文】 此外，彈性模量和斷裂能隨氣孔率的變化亦間接影響著強(qiáng)度值。 ? 更高 Ki階段，裂紋擴(kuò)展與環(huán)境無(wú)關(guān)，而受材料組成與溫度的影響。 ? 裂紋擴(kuò)展速度為聲速的 40%60%,并會(huì)產(chǎn)生新的斷裂紋。而導(dǎo)致材料斷裂的必要條件是：在裂紋擴(kuò)展過(guò)程中系統(tǒng)的自由能必須下降（熱力學(xué)條件） ? K與外加應(yīng)力、裂紋長(zhǎng)度、裂紋 種類 及受力狀態(tài)等有關(guān)的系數(shù)，稱為 應(yīng)力場(chǎng)強(qiáng)度因子，它反映裂紋尖端應(yīng)力場(chǎng)強(qiáng)度。m1/2 while the toughness of MgO partially stabilized zirconia(PSZ)(Young’s modulus 138GPa) is about 10MPa m1/2. ? a) Estimate the fracture surface energy of (i) alumina and (ii) PSZ assuming these toughness values were obtained under conditions of plane stress. ? b) Polycrystalline ceramics often have intergranular cracks in them due to thermal expansion mismatch. Their strength is therefore limited by these cracks whose size is on the order of the grain size. Calculate the maximum strength you would expect to observe in (i) alumina with 20umdiameter grain size and (ii) PSZ with a 50umdiam
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