Simulation Study On The Reliability Of Hard Disk Drives With Ultra-high Magnetic Recording Density

With the rapid development and application of new technologies such as the Internet of Things,cloud computing,the Internet,and intelligence,the amount of information and data has been increasing explosively.Big data,as an important strategic asset,has penetrated into all walks of life in varying extent.National information infrastructure and important institutions,especially financial institutions,military agencies,scientific research institutes,etc.,carry a huge amount of information and data,and they have extremely high requirements for information security.Semiconductor storage and optical storage can no longer meet the growing demand for such massive amounts of data.Magnetic storage typically represented by hard disk drives(HDDs)is still an important way to solve this problem.Hard disk drives are developing towards high density,stability,reliability,low cost,and safety.It is of great significance to realize the storage target of ultra-high magnetic recording density of 10 Tb/in2 for promoting the economic and social development of our country,and ensuring the security of the large data base environment.In order to achieve the storage target of ultra-high magnetic recording density of 10 Tb/in2,new magnetic recording technologies are required,but at the same time,the lower head flying height,higher disk rotational speed,and more accurate seek position bring a great challenge to the reliability of HDDs.(1)The head flying height of HDDs with ultra-high magnetic recording density of 10 Tb/in2 will be less than 5 nm,the vibration of the suspension along the off-plane direction will greatly increase the possibility of the collision between the head and the disk(hereinafter referred to as "head-disk"),and threaten the reliability of the head-disk system.(2)The wear particles generated by the head-disk collision will travel with the airflow and are eventually trapped by the surfaces of key components such as disk and head,which threaten the reliability of the head-disk system.(3)In a faster seek,the vibration of suspension along the off-track direction will increase the position error and position time,which will greatly affect the reliability of data reading and writing.In this thesis,a 2.5-inch HDD is taken as the object of research to improve the head-disk system and seek position reliability for research purposes.The studies on suppressing the vibration of the suspension and particle trajectories are carried out.It includes:(1)Active suppressing the vibration of the suspension by the sound pressure:(a)The "fluid-structure interaction(FSI)" method was used to analyze the micron/submicron vibration characteristics of the head caused by high-speed rotary flow in the hard disk drive.(b)Study on the active suppression mechanism of the micron/submicron vibration of the head based on sound pressure.(c)The "fluid-structure-acoustic interaction" method was applied to simulate and calculate the transfer function of the suspension vibration from the excitation voltage of the piezoelectric transducer(PZT)to the sound pressure,and the proper excitation voltage of the PZT required to effectively suppress the vibration of the suspension was determined.(2)Tracking position error.The effect of track-seeking motion on off-track residual vibrations of the head-gimbal assembly(HGA)is investigated for air and helium environments using the "dynamic mesh method" and the "FSI" methods in ANSYS Workbench.Three different angular acceleration profiles(a square wave,a triangular wave,and a sinusoidal wave)are investigated as a function of seeking time(10 ms and 5 ms).(3)Particle trajectories and trapping status inside the HDD:(a)On the basis of the particle-surface collision theory,the trapping boundary conditions of HDD inner surfaces for particles trapped are established.(b)Based on the discrete phase model(DPM)of the commercial software ANSYS Fluent,the boundary conditions of HDD inner surfaces are user-defined by the subroutine of ANSYS Fluent.Effects of trapping condition,temperature and track-seeking motion on particle trajectories and trapping status are analyzed.