Dynamic Characteristics Analysis And Experimental Investigation Of Head/Disk System

The hard disk drive(HDD)is a very important constituent part of computer,and also a main data storage unit.The data size also grows rapidly with the rise of cloud computing and big data.The require for hard disk design is increasingly higher because of the demand on hard drive capacity is bigger and bigger in reality.To gain a larger hard drive capacity,it is necessary to have a higher storage density,which makes the interval between the head and disk become smaller.Under such small head-disk interval,it will make the head and disk contact,cause friction and abrasion,and lead to the damage of the head and the scratch of disk surface when there is uncleanness and foreign matter in the disk and when hard disk suffers some external shock.The head and disk will be contacted,when the hard disk suffers certain external shock.thereby it cause friction and abrasion.The head will be damaged or the disk platter will be scratched.It will further make data lost and even cause the hard disk disruption.So,it is of great importance to study the dynamic characteristics of head/disk system in improving the hard disk design.In order to study the dynamic characteristics of hard disk,a new model called linearized flow rate(LFR)model of gas film rarefied effect corrected Reynolds equation is taked as the theoretical basis in this text,and the least square finite difference(LSFD)method and the finite element(FV)method is adopted to separately solve the corrected gas film lubrication equation.This text makes an exploration and research from simple plane slider to actually similar complicated slider from shallow to deep.To investigate effect of disk surface asperity on static characteristics of air bearing films at the head/disk interface(HDI),Reynolds equation based on a linearized flow rate(LFR)model is solved by using a mesh-less method called least square finite difference(LSFD)method.The effects of asperity size and its location,the disk's rotating speed,the boundary pressure on the static characteristics of air bearing films are investigated.Numerical results show that the asperity's location on the disk surface has obvious effect on the pressure distribution of the air bearing film and its load carrying capacity.The boundary pressure and the size of asperity have obvious effects on the air bearing film's pressure changes.Via study on such simple situation of an asperity on disk,it will lay a solid theoretical basis for the simulation study on disk dynamic characteristics by building Ansys model.To carry out the simulation study on hard disk system,a perfect hard disk finite element model is established by applying Ansys and the flying parameters of hard disk system head is solved used the model.The gas film lubrication equation is solved by the LFR numerical model and FV method to compile and solve the solver of gas film lubrication equation.The load carrying capacity is calculated based on the flying parameters solved by the finite element model and the solved load carrying capacity is applied on the finite element model.The mutual transferring of data between Ansys finite element model and solver is realized by the restarting function of LS-DYNA.Carry out a study on The dynamic characteristics of the hard/disk interface are simulated when the HDD is subjected to the impulse load of parabolic linear acceleration of quadratic function in different cycles and different amplitudes.It shows that the increasing of the load amplitude will lead to the increasing of changing amplitude of flying parameters,and that the cycle increase will cause change delay of flying parameters.Based on the relation equation of the read back voltage signal and distance between the head and disk,an experimental platform is set up.The distance between the head and disk when the shell suffers displacement loading for hard disks identical with the numerical simulation is tested.The testing results are compared with the numerical simulation in the same condition.The result shows that the change frequency of distance between the head and disk measured from the test is the same with that of the numerical simulation results,and its error is within the tolerance interval.