I have charged my Ipad more than hours. Apple logo display, but nothing happen at all.

Try a resset. Press and hold the Home and On/Off buttons simultaneously until the Apple logo appears then release. May take 10 to 15 seconds. Equivalent of a re-boot, you will not lose any data.

if its stuck in a boot loop of just the apple logo you might need to restore your iPad via iTunes with it in recovery mode. Here are the instructions to restore your iPad in recovery mode.

http://support.apple.com/kb/HT1808