Research on Glass Fiber Reinforced Plastic Head Cover of High-

Speed Train

Chunmian Chen

Hunan Railway Professiona1 Technology College, Zhuzhou,Hunan, China

Keywords: High-speed train; head cover; glass fiber reinforced plastic; stiffeners.

Abstract: The role of the high-speed train head cover was discussed in this paper. According to the actual situation of

the train operation, comparing the theoretical calculation to experimental analysis, the calculation load of

the high-speed train head cover was confirmed, strength and mode calculation on the glass fiber reinforced

plastic head cover by using ANSYS software were performed, and the result was analyzed in order to

provide some reference for future work.

1 INTRODUCTION

The high-speed train head cover is the part at the

front of the train that covers the coupler, which is

closed during normal operation constitutes a

streamlined shape to ensure the aerodynamic

performance of the train. In the case of a shunting

operation, rescue, and double-linking, the head cover

of the vehicle needs to be opened to expose the

mounting and operating space for the lifting hooks

and the lifting rods of the coupler.

At present, many kinds of high-speed trains

produced in China have adopted streamlined car

body. If the head cover adopts a fixed structure,

disassembly and storage are inconvenient. China has

already conducted research on the automatic

opening and closing head cover and has applied it to

production

[1]

. However, there are also

imperfections. It is necessary to conduct in-depth

research on the structural design of the head cover in

order to achieve the desired results.

2 PROBLEM ANALYSIS

During train operation, the air resistance is

proportional to the square of the speed. When the

train speed reaches 200km/h, the air resistance

accounts for more than 70% of the total running

resistance. The aerodynamic load on the head cover

at the front end of the train head is more

complicated.

In order to ensure the aerodynamic performance

of the train, the head cover and supporting

mechanism of the head of the locomotive must meet

the following requirements: (1)The head cover itself

should have a certain strength and cannot be

destroyed by steady state pressure or transient

pressure wave impact; (2) Under the action of wind

load, the head cover itself cannot produce large

deformations that affect aerodynamic performance,

nor can they cause unexpected opening and closing

actions; (3) The support mechanisms of the head

cover should have sufficient support/self-locking

capability and resistance to wind pressure.

There are no specific standards and

specifications as reference for the complex wind

load that the train. To solve the above problems, it is

necessary to rely on the combination of theoretical

calculation and experimental analysis to determine

the calculation load of the head cover. On this basis,

the ANSYS was used to theoretically calculate the

strength and natural frequency of the head cover

under certain load conditions, and the basic

structural form and size range of the head cover

were determined based on the calculation results.

Which will provide institutions for designing of

opening and closing mechanism of the head cover.

3 LOAD SOURCE AND BASIS

In order to obtain good aerodynamic performance,

the shape of the train head cover is a freeform

surface. Its mathematical expression is:

(1)

In the formula: x, y, and z are positional

parameters.

During the operation of a high-speed train, the

actual load on the head cover mainly comes from the

surface pressure caused by air resistance, and the

surface pressure changes with time. That is to say,

during the running of the train, the actual load

received at a certain point on the head cover needs to

be expressed by a four-variable functional

relationship:

(2)

In the formula: t is the time parameter.

If the load in the calculation process according to

its actual stress, the calculation process will be

extremely tedious. While use the FLUENT to

simulate the load of the high-speed train head flow

field at speed 200km/h, compared with the dynamic

real vehicle test, found that the error is small, the

accuracy meets practical requirements, can be used

as the calculated load[2]. Therefore, assuming that

the surface pressure of the train does not change

with time, this paper uses the aforementioned

calculation results as the source of the load data, and

converts it into a load with a running speed of 300

km/h using the Bernoulli equation [3]. The

conversion formula is as follows:

300

200

ρνρν

（3）

In the formula:

- pressure coefficient;

- the density of air;

200

300

— train speed,

200

= 200km/h,

300

= 300km/h;

200

，

300

,—surface pressure experienced at

train speeds of 200km and 300km.

In order to simplify the calculation, in the actual

analysis, the head cover is divided into 8 pieces

along the horizontal plane and a certain section of

the longitudinal section to load. In the place where

the curvature changes smoothly, the blocks are

sparse; in the places where the curvature is more

severe, the blocks are dense. Take the pressure value

at one point in each block as the surface pressure

value of the entire block. And fully consider the

fluctuation of the load caused by the speed change,

the selection of all data complies with the principle

of safety and conservation. Figure 1 shows the block

diagram along the coordinates of the head cover.

Fig.1 Block of head cover and its surface load.

Table 1 Block Loading Data Table.

The loads in this calculation are the distributed

loads applied to the surface of the head cover. All

the loads are added to the finite element model

(nodes and units). The head cover and the opening

and closing mechanism are connected by four

supporting seats (as shown in Fig. 2), and each of

the six degrees of freedom of each support base is

restrained.

Figure 2. Head Cover Structure.

3 HEAD COVER INTRODUCTION

3.1 Selection of Head Cover Material

The material of the head cover must ensure that it

has sufficient strength and rigidity; the free curved

surface is difficult to process using conventional

methods, so the material used to manufacture the

head cover must have excellent processing

properties. Glass fiber reinforced plastic, commonly

known as fiberglass, it has so many advantages

ensure that the free-form-shaped head cover can be

manufactured at a lower cost. Therefore, FRP is

used as the material of the head cover in this

calculation.

The different types of glass fiber reinforced

plastic and its fiber winding methods have a great

influence on the physical properties of FRP

materials. Considering the particularity of the

working environment of the vehicle head cover, this

calculation proposes the physical properties that

should be possessed by the head cover and the

parameters used in the calculation [4]:

Density/kg•m-3 1.8×103

Tensile strength/MPa ≥80

Quasi-static compression modulus ≥ 10

Dynamic compression modulus/GPa ≥15

Elastic Modulus/GPa 10

Poisson's ratio 0.4

3.2 Head Cover Structure

In this calculation, the thickness of the head cover

shell is 10 mm, and the four Q235 steel stiffeners are

connected to the head cover via the opening and

closing mechanism support bases fixedly (see Figure

2). The role of stiffeners is to increase the stiffness

of the head cover.

4 CALCULATION MODEL

The calculation model includes two parts: head

cover and stiffeners. The model is built using solid

modeling. The head cover is plate shell elements

(Shell 63) and the stiffeners are beam elements

(Beam 188). The grid is divided into free meshes.

The discrete data of the finite element model are as

follows: Shell63 and Beam188 have 543 and 96

cells, and the total number of cells is 639.The total

number of nodes is 679.

5 CALCULATION CONTENTS AND

RESULTS

In this calculation, the head cover was subjected to

strength analysis and modal analysis.

The corresponding calculation results are shown in

Table 2, Table 3 and Table 4.

Table 2 Calculation results of counterforce and counter-

torque.

Note: Fx, Fy, and Fz represent the counterforce along

the x-axis, y-axis, and z-axis respectively; Mx, My, and

Mz represent the counter-torque around the x-axis, y-axis,

and z-axis respectively.

Table 3 Displacement and stress change with the cross

section of the stiffeners.

Table 4 Modal calculation results when the cross section

of the stiffeners is 40mm ×12mm (sixth-order natural

frequency).

When the cross section size of the stiffeners is

changed, the results of the modal calculations varies

very small, so only the modal calculation results of

40mm×12mm are calculated here.

6 CALCULATION RESULTS

ANALYSIS

From Table 2, it can be seen that during the

operation of the train, the head cover is subjected to

a force of 2974.7N in the direction of the wind, so

the head cover itself should have sufficient strength.

The torque in the height direction of the support base

1 reaches 117.43N·m, which requires that the

influence of this factor on the operation of the head

cover should be fully taken into consideration when

designing the support mechanism, the movement

mechanism and the locking mechanism of the head

cover.

As long as the value of the surface load and the

position of the restraint do not change, the bearing

reaction force will not change; but the change in the

cross section size of the stiffeners has little effect on

the modal calculation results, so this is mainly based

on the results of the displacement and stress，the

cross section size of the stiffeners was determined.

This is also the reason why only the stiffeners cross

section size of 40mm×12mm was calculated in the

modal analysis. From the calculation results, it can

be seen that the first-order natural frequency of the

head cover is 52.595 Hz, and the natural frequency

of the general high-speed motor car body is not

bigger than 20 Hz[5], so the head cover does not

generate resonance with the car body.

In view of the current literature on the

calculation of FRP materials, from the perspective of

safety, the safety factor of 4 is used in this

calculation, that is, the allowable stress [σ] = 20MPa

for FRP materials. From Table 3, it can be seen that

the maximum stress reaches 54.722MPa, which

greatly exceeds the allowable stress of FRP

materials and is very unsafe. Therefore, it must be

reinforced. When the cross section thickness was

changed from 8 mm to 10 mm, the maximum

translational displacement vector and the maximum

stress were all reduced significantly. When the

thickness was changed from 10 mm to 12 mm or

more, the change was not significant. When the

cross-sectional area is equal, the greater the height of

the stiffeners, the more significant the effect of

reducing the stress concentration. Based on the

above results and taking into account the weight of

the head cover, it is more appropriate for this type of

head cover to use a cross section size of 40 mm×12

mm. If you want to better ensure the safety of train

operations, the cross section size of the stiffeners can

be 40mm × 14mm, 40mm × 16mm or even 40mm ×

20mm.

With regard to the aging problem of glass fiber

reinforced plastics, various countries are conducting

research, but no obvious results have yet been

obtained. Therefore, the question of the service life

of glass fiber reinforced plastic head cover needs

further study. For different shapes of the head cover,

the distribution of the head flow field is not the same

and the loads are not the same. Therefore, the shape

and distribution of the stiffeners are also different.

The requirements for the support structure of the

head cover are also different. These need to be given

specific analysis during the design process.

REFERENCES

1. Nie Yonghong. Design of Automatic Opening and

Closing Mechanism for the Head Cover of

Streamlined Vehicle Head., 2002. Electric

Transmission for Locomotives, 2002 (4): 22-24.

2. Central South University., 2003. Train Aerodynamic

Vehicle Test Study and Assessment Report. Changsha:

Central South University

3. Anderso,J.D., 2010. Fundamentals of Aerodynamics,

Aviation Industry Press. Beijing

4. Dong Junguo., 2000. Practical Materials Handbook,

Mechanical Industry Press, Beijing

5. Wang Yali., 2001. Analysis of response of random

track irregularity to high-speed motor car. Changsha:

Central South University.