成凹 meaning in English

foveation

Poisonous snakes have hollow or grooved fangs for injecting venom
毒蛇有中空或成凹槽的尖牙以射毒液。
Struction : the inside is hollow , but elastic , the diameter can change with the needed wire
构造:号码管内部成凹型,具有弹性,内径能随著电线大小而伸缩
In sheet metal , drawing is a process of forming flat sheet metal into hollow shapes by means of a punch that causes the metal to flow into the die cavity
在钣金中，制图的过程，就是将一个平钣金冲压成凹状，通过一个冲孔使金属流入型腔。