4、wist排列组合permutation and combination皮带stap疲劳极限fatigue limimt偏微分partial differential频率特性frequency characteristic平面磨削plane grinding剖视图profile chart气动夹紧pneuma lock气体状态方程equation of state of gas气压air pressure pneumatic pressure汽缸cylinder千分尺micrometer caliper前刀面rake face前角rake angle钳工locksmith强度int