Tsis muaj universal txhais ntawm "hnav thiab tsim kua muag". Nws yog feem ntau ntseeg hais tias hnav yog qhov tshwm sim ntawm kev puas tsuaj tas mus li los yog poob ntawm cov ntaub ntawv ntawm qhov chaw ua hauj lwm ntawm ib qho khoom nyob rau hauv kev txheeb ze. Kuj tseem muaj ntau txoj hauv kev los faib kev hnav, yog tias muab faib los ntawm kev hnav khaub ncaws, nws tuaj yeem muab faib ua abrasive hnav, nplaum hnav, hnav corrosion, yaig hnav, hu rau qaug zog hnav, cuam tshuam hnav, fretting hnav thiab lwm yam. Hauv kev lag luam, cov khoom siv abrasive thiab cov nplaum nplaum rau feem ntau ntawm cov khoom hnav tsis ua haujlwm, thiab hnav tsis ua haujlwm xws li yaig, corrosion, qaug zog, thiab fretting feem ntau tsim nyob rau hauv kev ua haujlwm ntawm qee yam tseem ceeb, yog li lawv muaj nqis ntxiv. Raws li kev ua haujlwm, ntau daim ntawv hnav feem ntau tshwm sim tib lub sijhawm lossis ua tiav, thiab kev sib cuam tshuam ntawm kev hnav tsis ua haujlwm nthuav tawm ntau daim ntawv. Kev txiav txim siab txog hom workpiece hnav tsis ua haujlwm yog lub hauv paus rau kev xaiv tsim nyog lossis kev txhim kho ntawm hnav-cov hlau tsis muaj zog.
Tsis tas li ntawd, qhov hnav ntawm qhov chaw yog qhov teeb meem engineering, thiab muaj ntau yam uas cuam tshuam rau kev hnav, nrog rau kev ua haujlwm (load, ceev, txav hom), lubrication tej yam kev mob, ib puag ncig yam (humidity, kub, ib puag ncig nruab nrab, thiab lwm yam), cov khoom yam tseem ceeb (muaj pes tsawg leeg, qauv, mechanical zog), nto zoo thiab lub cev thiab tshuaj zog ntawm qhov chaw. Ib qho kev hloov pauv ntawm txhua yam no tuaj yeem hloov pauv qhov hnav thiab txawm tias hnav mechanism. Nws tuaj yeem pom tau tias cov khoom siv tsuas yog ib qho ntawm cov yam ntxwv cuam tshuam rau kev hnav ntawm lub workpiece, thiab txhawm rau txhim kho qhov hnav tsis kam ntawm cov hlau, nws yog ib qho tsim nyog yuav tsum pib los ntawm kev sib txhuam thiab hnav system tag nrho raws li cov xwm txheej tshwj xeeb kom ua tiav cov txiaj ntsig xav tau.
