把XX掰成两半 snap sth in half / in two

例句

Do you know why the teacher always snap the chalk in two?

老师为啥总是把粉笔掰两段？

突然失去自制力，突然崩溃，一下无法自持

XX snapped / something snapped inside XX 

例句

My nerves almost snapped under the pressure of work.

我的神经在工作压力下几乎崩溃了。

When he said that, something snapped inside her.

听他说到这里，她内心的感情一下子翻腾起来。

For the first and only time she snapped.

生平第一次也是唯一一次，她失控了。

I snapped, okay? 

我失控了，行不?

恶声恶气地说；凶别人，吼别人snap at XX

例句

I'm sorry, I didn't mean to snap at you like that.

对不起，我并不是有意要凶你的。

Well， don't snap at me. Snap at the rain.

可别朝我发火，要发火朝雨发去。

Dude, I totally get why you snapped at me.

兄弟，我完全理解你为啥凶我。

snap at 还有一个意思就是（小动物）突然咬, 猛咬

The dog snapped at my ankle.

这狗咬了我的脚脖子。

咔嚓 snap 还有拍照的意思

If you snap someone or something, you take a photograph of them.

还有一个有趣的表达，oh snap！，这里snap是一个语气词，常用来表达说话者的情绪、态度，如：惊讶、沮丧、欢快、赞扬等。中文里可考虑翻译为：噢惨了，或噢完蛋了。