剖分式軸承按運動元件摩擦性質的不同，軸承可分為滾動軸承和滑動軸承兩大類。其中滾動軸承已經標準化、系列化，但與滑動軸承相比它的徑向尺寸、振動和噪聲較大，價格也較高。滾動軸承一般由外圈、內圈、滾動體和保持架四部分組成，嚴格的說是由外圈、內圈、滾動體、保持架、密封、潤滑油 六大件組成。簡單來說，只要具備外圈、內圈、滾動體就可定義為滾動軸承。按滾動體的形狀，滾動軸承分為球軸承和滾子軸承兩大類。壽(shou)(shou)(shou)(shou)命(ming)(ming)(ming)(ming)(ming)以(yi)轉數(shu)(shu)（或(huo)(huo)以(yi)一定轉速下的(de)(de)工作的(de)(de)小時數(shu)(shu)）定義：在(zai)(zai)此壽(shou)(shou)(shou)(shou)命(ming)(ming)(ming)(ming)(ming)以(yi)內的(de)(de)軸(zhou)(zhou)承，應在(zai)(zai)其任何軸(zhou)(zhou)承圈或(huo)(huo)滾動體上發生初步疲勞損(sun)壞(huai)（剝落或(huo)(huo)缺損(sun)）。然而(er)無論在(zai)(zai)實(shi)驗室試(shi)驗或(huo)(huo)在(zai)(zai)實(shi)際使用(yong)(yong)中，都(dou)可(ke)明顯的(de)(de)看(kan)到，在(zai)(zai)同(tong)(tong)(tong)(tong)(tong)樣的(de)(de)工作條件(jian)下的(de)(de)外觀相(xiang)同(tong)(tong)(tong)(tong)(tong)軸(zhou)(zhou)承，實(shi)際壽(shou)(shou)(shou)(shou)命(ming)(ming)(ming)(ming)(ming)大不(bu)(bu)(bu)相(xiang)同(tong)(tong)(tong)(tong)(tong)。此外還有數(shu)(shu)種不(bu)(bu)(bu)同(tong)(tong)(tong)(tong)(tong)定義的(de)(de)軸(zhou)(zhou)承“壽(shou)(shou)(shou)(shou)命(ming)(ming)(ming)(ming)(ming)”，其中之一即所(suo)謂的(de)(de)“工作壽(shou)(shou)(shou)(shou)命(ming)(ming)(ming)(ming)(ming)”，它(ta)表(biao)示某一軸(zhou)(zhou)承在(zai)(zai)損(sun)壞(huai)之前可(ke)達到的(de)(de)實(shi)際壽(shou)(shou)(shou)(shou)命(ming)(ming)(ming)(ming)(ming)是(shi)由磨損(sun)、損(sun)壞(huai)通常并非由疲勞所(suo)致，而(er)是(shi)由磨損(sun)、腐(fu)蝕、密封損(sun)壞(huai)等原因造成。為(wei)確定軸(zhou)(zhou)承壽(shou)(shou)(shou)(shou)命(ming)(ming)(ming)(ming)(ming)的(de)(de)標準，把軸(zhou)(zhou)承壽(shou)(shou)(shou)(shou)命(ming)(ming)(ming)(ming)(ming)與可(ke)靠性聯系起來。由于制造精(jing)度，材(cai)料均勻程度的(de)(de)差異，即使是(shi)同(tong)(tong)(tong)(tong)(tong)樣材(cai)料，同(tong)(tong)(tong)(tong)(tong)樣尺(chi)寸的(de)(de)同(tong)(tong)(tong)(tong)(tong)一批軸(zhou)(zhou)承，在(zai)(zai)同(tong)(tong)(tong)(tong)(tong)樣的(de)(de)工作條件(jian)下使用(yong)(yong)，其壽(shou)(shou)(shou)(shou)命(ming)(ming)(ming)(ming)(ming)長(chang)短(duan)也不(bu)(bu)(bu)相(xiang)同(tong)(tong)(tong)(tong)(tong)。若以(yi)統計壽(shou)(shou)(shou)(shou)命(ming)(ming)(ming)(ming)(ming)為(wei)1單(dan)(dan)位，最(zui)長(chang)的(de)(de)相(xiang)對壽(shou)(shou)(shou)(shou)命(ming)(ming)(ming)(ming)(ming)為(wei)4單(dan)(dan)位，最(zui)短(duan)的(de)(de)為(wei)0.1-0.2單(dan)(dan)位，最(zui)長(chang)與最(zui)短(duan)壽(shou)(shou)(shou)(shou)命(ming)(ming)(ming)(ming)(ming)之比為(wei)20-40倍。90%的(de)(de)軸(zhou)(zhou)承不(bu)(bu)(bu)產(chan)生點蝕，所(suo)經歷(li)的(de)(de)轉數(shu)(shu)或(huo)(huo)小時數(shu)(shu)稱為(wei)軸(zhou)(zhou)承額定壽(shou)(shou)(shou)(shou)命(ming)(ming)(ming)(ming)(ming)。