Research interests and Projects

 

Drop Test Simulation of Hard Disk Drives                                                                                               Ü   

Drop Test Simulation of of Computer Hard Disk Drives
 

This project aims to develop a method for predicting the displacement and failure of the Hard Actuator assembly (HAA) during a drop test by FEM. This prediction is vital for short design cycle in an increasingly fast changing data storage industry. FEM simulation can achieve this by reducing the expensive process of prototype testing.


Dropping, striking or bouncing a drive against a hard surface can damage it internally with no external evidence of damage. The contact with hard surface will bring the HAA to rest in a short duration of time, typically a few milliseconds. In this short duration, the HAA experiences a pulse load resulting from a high deceleration up to 1000g, as well as large deformation. A drive that is subjected to this type of shock may fail on initial use or the damage could simply cause the reliability of the drive to degrade over time. New methods of analysis have brought better understanding of the interaction between all the mechanical components in the drive. By considering the drive as a complete mechanical system, the effects of shock events can be fully evaluated. The information gained can be used to modify and fine tune different mechanical components to improve their robustness so that shock events will be absorbed through the drive, preventing damage to the sensitive elements inside.


Finite Element Method (FEM) is a computer-aided design technique that mathematically models the behavior of mechanical systems. FEM can be used to calculate stress in a  mechanical  system, the  impact  of  vibration, elastic and inelastic deformity and other effects caused by internal and external forces. A Finite Element Analysis can be used to predict the response of the mechanical system to shocks within a specified range. This project uses FEM in the prediction of the displacement and failure of the Hard Actuator Assembly (HAA). During early prototyping, the parameters of the Finite Element Model is measured against the actual parameters of the prototype. This process allows the engineers to further refine the accuracy of their model, improving their ability to predict the behavior of the final design and insuring that design will meet specifications for mechanical shock performance.

 

 

LSDYNA FEM Simulation of the Drop Test of Hard Disk Assembly

Hard Disk Drives (HDD) have been developed rapidly in conjunction with the IT industry. These advances have created a need for HDDs to achieve higher bandwidth of tracking servo and fine positioning of magnetic head. An unexpected drop of the hard disk drives may results in damaging of the Hard Disk Assembly (HAD), which is an important component of HDD. It is necessary that the effects of shock on an HDA be studied.

There is relatively little published work related to the drop test simulation. This is partly due to the complex phenomenon makes reliable prediction more difficult. This project aims to develop a method for predicting the displacement and failure of the Hard Disk Assembly (HDA) during a drop test. As a HAD is dropped from a certain height, it will accelerate due to gravity until it hits the ground with a certain speed. The contact with ground will bring the HAD to rest in a short duration of time, typically a few milliseconds. In this short duration, the HAD experience a pulse load resulted from a high deceleration up to 1000g, as well as deformation. The prediction of this deformation is vital for short design cycle in an increasing fast changing data storage industry. FEM simulation can do achieve this by reducing the expensive and process of prototype testing. The present project aims to overcome some of the difficulties encountered in the FEM simulation through in-depth understanding of the drop test.

Modeling of the HAD will be finally achieved with the above preparation using LSDYNA software. The simulation results will be verified with results from the literature as well as compared with the results separately obtained in Seagate R&D laboratory.