Force stuborn drive to unmount

I have a single partition disk whose filesystem will not mount properly. I don't care about the data and I would like to try reformatting the disk but I keep getting errors related to a failure unmounting the drive. I have tried the following in both normal and recovery mode:

• reformatting in the Disk Utility GUI


• sudo diskutil partitionDisk /dev/disk3 GPT JHFS+ New 0b


• sudo diskutil unmountDisk force /dev/rdisk3


• sudo fdisk -i -a hfs /dev/rdisk3


• sudo gpt destroy /dev/rdisk3

All of these attempts have yielded errors either saying that the "drive can not be unmounted" or that the "resource is busy". Is this indicative of a hardware issue in the drive as opposed to just a corrupt file system? Is there anything else I can try?