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應力於壓力容器及薄壁圓環壓力容器(PRESSURE VESSEL)由於壓力作用故會有上下及左右裂開成兩半之傾向,故筒必有三個互相垂直之主應力,即周向應力St (hoop stress or circumferential stress) 與縱向應力 Sl (longitudinal stress) 以及徑向應力Sr(radial stress)
Sr =[(Pi * ri² - Po * ro²) /(ro²- ri²)] -[(ro²*ri²*(Pi-Po)/r²*(ro²-ri²)] St=[(Pi*ri²)-(Po*ro²)/ro²-ri²] + [ro²*ri² * (Pi-Po)/r²*(ro²-ri²)] 當 r = ro ,Sr = -Po r = ri, Sr = -Pi 如果為密閉容器則設為 Po = 0 St = Pi*ri²/(ro²-ri²) * (1+ro²/r²) Sr = Pi*ri²/(ro²-ri²) * (1-ro²/r²) 內圓各點為破壞點,則 St = P ((ro² + ri²) / (ro²-ri²)) Sr = -P Sl = (Pi * ri²) / (ro² - ri²) 若筒壁厚度 t 與圓筒內半徑ri的比值 t /ri 小於 1/20時,可以合理假設周向應力與縱向應力對整個壁厚皆為一定數,而徑向應力值比周向應力與縱向應力皆為微小,可以忽略不計. t < = 1/20 * ri (Sr << St, Sr 近似為 0) St,av = P * di / 2*t St,max = Pi*(di + t) / 2*ti Sl = Pi*di / 4 * t |
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