CN113435085B - Complex-morphology magnetic head steady-state flight modeling method considering viscous effect - Google Patents

Abstract

The invention discloses a steady-state flight modeling method of a magnetic head with complex morphology and considering viscous effect, which comprises the steps of firstly, utilizing magnetic head surface etching model coordinates established by Hypermesh preprocessing software; establishing a head-disk interface magnetic head flight state dynamics solving model by utilizing COMSOL commercial finite element software; considering the influence of viscous force and intermolecular acting force under the micro-nano scale, and improving a head disc interface dynamic model; the method is beneficial to researching the flight attitude and the bearing characteristic of the magnetic head under the nanometer scale, and provides a foundation for the design and the manufacture of the magnetic head.

Description

A Steady-state Flight Modeling Method for Magnetic Heads with Complex Shapes Considering Viscous Effects

technical field

The invention relates to a method for studying the mechanical characteristics of a magnetic head of a mechanical hard disk, in particular to a method for modeling the steady-state flight of a magnetic head with complex shapes considering the viscous effect.

Background technique

With the advent of the information age and the development of high-tech such as Internet cloud computing, from the perspective of the electronic storage industry, mechanical hard drives are widely used in various industries due to their ultra-stable working conditions and high cost performance. The stability of the magnetic head flight directly affects the information writing of the magnetic head, and the continuous reduction of the distance between the head and disk will cause collision and wear between the head and disk, resulting in the loss of stored information. Since storage involves important fields such as finance, communications, national defense, and aerospace, damage and loss of mechanical hard drives will cause immeasurable losses. Therefore, the dynamic analysis of the magnetic head at ultra-low flight has important engineering significance for the quality improvement and reliability of future products.

When the head-disk interface reaches the nanometer level, small changes on the surface of the magnetic head will cause changes in the pressure distribution. The special structure of the air bearing surface will provide a balance between the gas dynamic pressure and the near-field force, thereby affecting the stability of the flight. Therefore, The description of the ABS surface of the magnetic head slider cannot be simplified in consideration of the flying height, and the geometric shapes of the real slider and the air bearing need to be considered in the modeling; secondly, the traditional fluid governing equations are derived based on continuum mechanics. The situation of the head-disk interface under ultra-low flight is no longer applicable; in addition, the further reduction of the head-disk makes the influence of the thin layer of lubricant molecules and the asperities on the surface cannot be ignored. The interaction force is only applicable to the flying height of 10nm, and it is no longer applicable to the flying height state of <5nm. Research shows that viscous force and intermolecular force have also become one of the main failure modes in the process of miniaturization and work. It is very difficult to accurately measure the interaction force between the head and disk under ultra-low flight, so it is very necessary to predict the flight state through modeling, which is of great significance to the head-disk contact, friction and ABS surface design . To sum up, there are still deficiencies in the construction of dynamic simulation models for mechanical hard disks under ultra-low flight conditions. The invention improves the contact dynamic model of the head-disk interface based on the micro-nano scale, and simplifies the modeling of the flying head system to solve the flying attitude and mechanical characteristics of the magnetic head under a specific preload force.

Contents of the invention

The object of the present invention is to provide a kind of modeling method of steady-state flight modeling of magnetic head with complex shape considering viscous effect, to overcome the shortcoming of prior art, the present invention has the characteristics of reliability, high accuracy, etc. Its flight attitude and mechanical properties have important engineering application value.

To achieve the above object, the present invention adopts the following technical solutions:

A method for modeling the steady-state flight of a magnetic head with complex shapes considering the viscous effect, comprising the following steps:

(1) Modeling method of surface topography of air bearing of flying magnetic head

Based on the surface topography of the magnetic head air bearing, use the Hypermesh pre-processing software to establish a simulation model of the surface topography etching depth of the magnetic head air bearing, and obtain the simulation coordinates of the surface topography etching depth of the magnetic head air bearing;

(3) Simulation analysis method for surface topography etching depth of magnetic head air bearing

Import the established air bearing surface topography coordinates into COMSOL finite element software, and analyze the influence of the etching depth of D1 and D2 on the flying attitude of the magnetic head. The etching depth of D1 affects the positive pressure effect of the front and rear pressure pads, so as to realize the control of flying height and pitch angle; D2 mainly affects the two positions of the rear negative pressure area and the front negative pressure area, and its main function is to increase the stiffness, so that The negative pressure center moves like the rear end, assisting the stability of loading and unloading, and reducing the pitch angle;

(3) Research method of the influence of intermolecular force and viscous force on the flying attitude of the magnetic head

Establish the dynamic model of the flying attitude of the magnetic head at the head-disk interface at the micro-nano scale, use the method for designing the etching depth of the magnetic head surface proposed in the present invention, and use COMSOL commercial finite element software to establish a head that considers viscous force and intermolecular force Disk interface simulation model to analyze the influence of viscous force and intermolecular force on the flight characteristics and mechanical properties of the head-disk interface at the micro-nano scale.

Step (1) is specifically:

First, according to the real topography of the ABS surface of the mechanical hard disk head, the topography parameters of the real surface are measured;

Then, based on the real shape of the magnetic head, a simplified simulation model of the etching depth of the air bearing surface of the magnetic head is designed and manufactured, and the hypermesh pre-processing software is used to divide the mesh and obtain the coordinates of the etching depth of the initial simulation shape.

Step (2) is specifically:

First, import the simulation coordinates into COMSOL general finite element software, and establish a dynamic model based on the surface topography and etching depth of the air bearing of the simulated magnetic head;

Secondly, by controlling the etching depth of D1 and D2, the flight attitude and mechanical characteristics of the magnetic head under the influence of the topographical etching depth are simulated and calculated to obtain the influence of this variable on the flying roll angle and pitch angle of the magnetic head;

Finally, the calculation is performed by repeating the foregoing steps until the desired etching depth coordinates of the surface topography of the air bearing are obtained.

Step (3) is specifically:

Using the method for designing the etching depth of the surface topography of the air bearing of the magnetic head proposed by the present invention, a dynamic model of the flight attitude of the magnetic head slider based on the complex ABS topography under the micro-nano scale is established, and the COMSOL commercial finite element software is used to establish The head-disk interface simulation model of hysteresis and intermolecular force is used to analyze the influence of viscous force and intermolecular force on the flight characteristics and mechanical properties of the head-disk interface at the micro-nano scale.

Compared with the prior art, the present invention has the following beneficial technical effects:

The present invention utilizes the coordinates of the magnetic head surface etching model established by Hypermesh pre-processing software, and the obtained data can be directly used in COMSOL commercial finite element software to establish a dynamic solution model of the magnetic head flight state at the head-disk interface. Through the analysis of the influence of the etching depth of the surface topography of the air bearing of the magnetic head on the flying attitude of the magnetic head, it can assist the design of the surface topography of the air bearing of the magnetic head under specific conditions. Using this etching scheme to consider the viscous force at the micro-nano scale, etc. The influence of the field force is used to improve the head-disc interface dynamics model, which effectively enhances the accuracy of the model. The invention uses a dynamic model considering the etching depth and viscous force of the air bearing surface topography at the micro-nano scale, and can realize the simulation research on the flight attitude and mechanical characteristics of the magnetic head. Its advantage lies in that the above method is used to study the flight attitude and mechanical properties of the magnetic head. The invention has the characteristics of reliability and high accuracy, which is beneficial to characterize the flight attitude and mechanical properties of the magnetic head at the nanometer scale, and has important engineering application value.

Description of drawings

Fig. 1 is technical path of the present invention;

Fig. 2 is the surface morphology of the air bearing of the magnetic head of the present invention;

Fig. 3 is the area division of the air bearing surface topography of the magnetic head of the present invention;

Figure 4 is the impact of etching depth D1 on the flying attitude of the magnetic head;

Figure 5 is the impact of etching depth D2 on the flying attitude of the magnetic head;

Fig. 6 is the influence of viscous force on flight attitude and pressure of flying head;

detailed description

The present invention is described in detail below in conjunction with accompanying drawing and specific embodiment:

Refer to Fig. 1 for the technical route of the overall implementation of the present invention; the simulated coordinates of the surface topography etching depth of the magnetic head air bearing obtained through the Hypermesh pre-processing software; the definition of topography functions and variables through COMSOL LiveLink for MATLAB, and the introduction of real sliders and the geometric shape of the air bearing, conduct modeling and simulation, and analyze the influence of the etching depth of the air bearing surface of the magnetic head on its flight attitude and mechanical properties; and then obtain the realization of different surface etching depths through parameter-assisted scanning, thereby simplifying the The process from scanning to importing surface topography is realized, and the above steps are repeated until the air bearing surface topography etching design parameters that meet the working requirements of the hard disk are obtained; at the micro-nano scale, using the topography etching parameters, considering The impact of force and intermolecular force on the flight attitude and mechanical characteristics of the magnetic head, the dynamic model of the head-disk interface head at the micro-nano scale is obtained, and the influence of the intermolecular force and viscous force on the flight attitude and mechanical characteristics of the magnetic head is analyzed. impact on carrying capacity.

A kind of complex shape magnetic head steady-state flight modeling method that the present invention proposes considering the viscous effect is implemented according to the following specific steps:

(1) Modeling method of surface topography of air bearing of flying magnetic head

Due to the ultra-low flight of the magnetic head, the surface morphology of the air bearing has a non-negligible impact on the flight state. At the same time, its shape design needs to meet the requirements of flight stability. For example, the uniformity of flying height is selected as the evaluation index:

为n个飞行半径下飞高的均值。Among them, FH _ave is the evaluation index, FH _i (i=1...n) is the flying height under different flight radii,

is the mean value of flying height under n flying radii.

The surface topography of the air bearing is processed by ion etching technology. Due to its different depth, under the high-speed rotating air flow, different positive and negative pressure effects will be generated. The present invention uses Hypermesh pre-processing software to obtain the simulated shape coordinates of the magnetic head surface, and the basic shape design of the magnetic head is shown in FIG. 2 .

According to the etching depth, it can be divided into three types, 0 surface, D1 depth, D2 depth, and D3 depth, which are respectively marked in Figure 3 by different gray levels. In the range of 0<D1<D2<D3, the control of flying height, roll angle and pitch angle can be realized. In the present invention, the characterization of the fly height includes the surface etching depth, and the effects of the fly height and the etching depth on the flight stability and pressure distribution are considered, only the rotation of the disk and the microcosmic interaction force are considered, and the heat transfer is not considered.

(2) Simulation analysis method for surface topography etching depth of magnetic head air bearing

Import the established air bearing surface topography coordinates into COMSOL finite element software, and analyze the influence of the etching depth of D1 and D2 on the flying attitude of the magnetic head through COMSOL LiveLink for MATLAB and the parameter-assisted sweep solver. The etching depth of D1 affects the positive pressure effect of the front and rear pressure pads, so as to realize the control of flying height and pitch angle; D2 mainly affects the two positions of the rear negative pressure area and the front negative pressure area, and its main function is to increase the stiffness, so that The center of negative pressure moves to the rear end, assisting the stability of loading and unloading, and reducing the pitch angle.

(3) Research method of the influence of near-field force on the flying attitude and bearing capacity of the magnetic head

Due to the extremely low flight altitude, the force between molecules will have a certain impact on the static balance. The flight attitude mainly includes flight altitude, roll angle, and pitch angle. Fly Height (FH) represents the distance between the writer and the disk, pitch represents the angular displacement around the y-axis, and roll represents the angular displacement around the x-axis. The factors affecting flight attitude mainly include: load size, roll pitch stiffness, static roll pitch angle, temperature, humidity, etc. If calculated according to the Lennard-Jones potential, the head-disc force is the intermolecular force and the expression is as follows:

The viscosity expression is as follows:

Under the same conditions, the Lennard-Jones potential (hereinafter referred to as the action of molecular force) and the action containing viscous force (hereinafter referred to as the action of viscous force) were simulated and compared, and the effects of viscous force and intermolecular force on the flight attitude were obtained. Influence, so as to obtain a dynamic model of the head-disk interface magnetic head at the micro-nano scale that is more in line with the actual situation.

A specific application example is given below, and the effectiveness of the present invention in modeling and simulation is verified simultaneously:

Step 1: Simulation modeling of the etching depth of the surface topography of the air bearing of the magnetic head. According to the magnetic head with the size of 8.5mm×7mm×3mm, a simulation model of the surface topography etching depth of the air bearing of the magnetic head is designed and manufactured, as shown in Figure 2, the initial simulation topography etching is obtained by using the Hypermesh pre-processing software to divide the mesh depth coordinates;

The second step: the simulation analysis of the etching depth of the surface topography of the air bearing of the magnetic head. Import the simulation coordinates into COMSOL general finite element software to simulate the flight attitude and mechanical characteristics of the magnetic head under the influence of the shape etching depth;

Step 3: Use COMSOL LiveLink for MATLAB to use parameter-assisted scanning to repeat the first and second steps. By controlling the etching depth of D1 and D2, obtain the influence of this variable on the roll angle and pitch angle of the magnetic head flight until the air that meets the requirements is obtained. Etching depth coordinates of bearing surface topography;

Observing Figure 4, it can be seen that D1 has a relatively large impact on the flight altitude and pitch angle. With the increase of D1, the flight altitude and pitch angle both show a trend of first increasing and then decreasing. It can be seen from the curve that D2 has a relatively large influence on the flying height and a small influence on the pitch angle. With the increase of D1, the flying height and pitch angle increase, resulting in a decrease in positive pressure; continue to increase D1, the flying height decreases, because the pitch angle has not reached the maximum value, and the pressure is maintained at a relatively moderate level at this time ; continue to increase D1, the flying height is further reduced, and the pitch angle is also reduced at this time, and the pressure does not show an obvious increasing trend. The overall height function increases (micron scale), therefore, the pressure still shows a downward trend. Negative pressure is often used to indicate the stiffness of the air film, and the greater the stiffness of the air film, the better the impact resistance of the flying head. Therefore, if the minimum flying height of the magnetic head is required to be lower than 6nm, the pitch angle is lower than 100μm, and the magnetic head has good impact resistance, the selection of D1 should be less than 0.2μm.

Compared with the influence of D1 on pressure, the influence of D2 is more intuitive. Observing Figure 4, it can be concluded that the minimum flying height decreases with the increase of D2, while the pitch angle increases with the increase of D2, but basically meets the requirement of less than 100urad, and the change range is not large, which is consistent with the conclusion of D1 . For the pressure, with the increase of D2, the pressure presents a trend of increasing first and then decreasing, which indicates that the stiffness first increases and then decreases. D2 can make the center of pressure shift back, which is beneficial to the realization of loading and unloading.

It can be seen from Figure 5. D3 has little effect on flying height and pitch angle, only a simple analysis;

Step 4: Establish a dynamic model of the flying attitude of the magnetic head at the head-disk interface at the micro-nano scale. Using the method for designing the etching depth of the magnetic head surface proposed by the present invention, using COMSOL commercial finite element software, a head-disc interface simulation model considering viscous force and intermolecular force is established, and the intermolecular force and viscous force at the micro-nano scale are analyzed. The effect of hysteresis on the flying attitude and bearing capacity of the magnetic head.

The analysis results are shown in Figure 6. According to the observation, it can be found that the influence trend of viscous force and molecular force on flight attitude with TFC power is relatively consistent. With the increase of TFC power, the minimum fly height showed a linear decrease trend, using the viscous force model can reduce the minimum fly height by 1.6%-2.5%, and with the increase of TFC power, the decrease rate gradually increased. For the roll angle and pitch angle, as the TFC power increases, the absolute value of the molecular force model is lower than that of the viscous force model. After considering the viscous force, the flight is more stable due to the increase of part of the attractive force, but it affects Not much, with a drop between 0.1% and 0.2%.

As for the influence of viscous force on the bearing capacity, the bearing capacity increases slowly with the increase of TFC power, and the bearing capacity obtained by the viscous force model is larger than that obtained by the molecular force model, and the increase range is between 1.1% and 1.3%. The main reason is that compared with the molecular force model, the viscous force model considers more factors, and its attraction to the magnetic head is greater, and the balance pressure increases, the bearing capacity increases, and the flying height further decreases.

Claims (4)

1. A method for modeling the steady-state flight of a magnetic head with complex shapes considering the viscous effect, is characterized in that, comprising the following steps: (1) Modeling method of surface topography of air bearing of flying magnetic head Based on the surface topography of the magnetic head air bearing, use the Hypermesh pre-processing software to establish a simulation model of the surface topography etching depth of the magnetic head air bearing, and obtain the simulation coordinates of the surface topography etching depth of the magnetic head air bearing; (2) Simulation analysis method for surface topography etching depth of magnetic head air bearing Import the established air bearing surface topography coordinates into the COMSOL finite element software, and analyze the influence of the etching depth of D1 and D2 on the flying attitude of the magnetic head. In the range of 0<D1<D2<D3, by adjusting the etching depth of D1 and D2 It can realize the control of flying height, roll angle and pitch angle. The etching depth of D1 affects the positive pressure effect of the front and rear pressure pads, thereby realizing the control of flying height and pitch angle; D2 affects the rear negative pressure area and the front negative pressure area. There are two positions in the nip area, the function is to increase the stiffness, move the negative pressure center to the rear end, assist the stability of loading and unloading, and reduce the pitch angle; (3) Research method of the influence of intermolecular force and viscous force on the flying attitude of the magnetic head Using COMSOL commercial finite element software to carry out the dynamic modeling of the head-disk interface head flight attitude at the micro-nano scale, and establish the dynamic model of the head-slider flight attitude based on the complex ABS shape at the micro-nano scale, the model considers the head-disk The viscous force and intermolecular force between the interfaces are analyzed to analyze the influence of viscous force and intermolecular force on the flying characteristics and mechanical properties of the head-disk interface at the micro-nano scale. 2. a kind of complex shape magnetic head steady-state flight modeling method considering viscous effect according to claim 1, is characterized in that, step (1) is specifically: First, according to the real topography of the ABS surface of the mechanical hard disk head, the topography parameters of the real surface are measured; Then, based on the real shape of the magnetic head, a simplified simulation model of the etching depth of the air bearing surface of the magnetic head is designed and manufactured, and the hypermesh pre-processing software is used to divide the mesh and obtain the coordinates of the etching depth of the initial simulation shape. 3. a kind of complex shape magnetic head steady-state flight modeling method considering viscous effect according to claim 1, is characterized in that, step (2) is specifically: First, import the simulation coordinates into COMSOL general finite element software, and establish a dynamic model based on the surface topography and etching depth of the air bearing of the simulated magnetic head; Secondly, by controlling the etching depth of D1 and D2, the flight attitude and mechanical characteristics of the magnetic head under the influence of the topographical etching depth are simulated and calculated to obtain the influence of the etching depth of D1 and D2 on the flying roll angle and pitch angle of the magnetic head; Finally, the calculation is performed by repeating the foregoing steps until the desired etching depth coordinates of the surface topography of the air bearing are obtained. 4. a kind of complex shape magnetic head steady-state flight modeling method considering viscous effect according to claim 1, is characterized in that, step (3) is specifically: Using COMSOL commercial finite element software to carry out the dynamic modeling of the head-disk interface head flight attitude at the micro-nano scale, and establish the dynamic model of the head-slider flight attitude based on the complex ABS shape at the micro-nano scale, the model considers the head-disk The viscous force and intermolecular force between interfaces are used to analyze the influence of viscous force and intermolecular force on the flight characteristics and mechanical properties of the head-disk interface at the micro-nano scale.

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