Mental cruelty

Removal of Mangal suthra etc. will not comes under cruelty. But for simple allegations on each other comes under mental cruelty. So do not put allegations on her instead show & try to solve her problems get love & affection from her. 

Technically tying mangalasutra for solomanizing  a hindu marriage is only traditional but has no legal bearing. May have been done in a fit of anger or depression, so try to repair the damage by mutual mediation.

I have come across this point

(ii)Removal of mangalsutra by wife at the instance of her husband does not amount to mental cruelty; S. Hanumantha Rao v. S. Ramani, AIR 1999 SC 1318

So it means without the consent of husband removal of mangalsutra does amount to cruelty, whether my implication is correct sir.

absolutely correct

Thank you @ Sainath devalla sir

Thank you @Ramachary sir

Please do not keep pondering over such petty issues.  Take a defense on any major issue between you both which cannot be resolved.