Dear Sir, Thank you for reply. Sir due to some confidentiality issue i cant post on it, but i can tell that my structure is electronics enclosure assembly which has pcb and other components in it. As my modal was getting so big with quad elements i have to reduced it by using linear element , as i have used Multizone (hexa core) method for some part it has created the lower order pyramid  elements. i have used quad element for those part which is meshed using tetrahydron patch conforming method. the max aspect ratio i am getting is almost 220 and avg is 2.8.