Fatigue Life Assessment and Experiment Design for EMU Corbel

Wenxue Qian

, Qingjie Wang

, Zijian Sun

, Xiaowei Yin

and Liyang Xie

School of Mechanical Engineering and Automation, Northeastern University, Shenyang 110819, P. R. China

Department of Mechanical Engineering, Shenyang Institute of Engineering, Shenyang 110136, P. R. China

qwx99@163.com

Keywords: EMU corbel, Fatigue evaluation, Local stress-strain method, Experiment design.

Abstract: In order to ensure the safe operation of EMU, the fatigue assessment for corbel which a key components of

EMU has been done. To refine the mesh quality for the weak parts of corbel though building a substructure

using workbench software. According to finite element analysis, the local stress-strain method is adopted to

estimate the fatigue life of the corbel. An analysis fatigue condition for corbel to determine the location and

size of loading. Compared the body with single corbel finite element analysis results, determine the beam

fatigue test program.

1 INTRODUCTION

With the development of economy and technology,

the speed of EMU is increasing and the light weight

requirement of car body is improved continuously.

The safety problem of EMU is becoming the key to

the development of motor vehicle technology. The

safety of motor vehicles is not only to meet the

requirements of strength and stability, but also

fatigue life is one of the important indicators. The

corbel is an important component of EMU and the

fatigue performance directly affects the safety of

train operation. The fatigue analysis of corbel's

traction seats were carried out by some

researchers(Han 2012). But right now, the EMU

sleeper fatigue research is less at home and abroad.

At present, the fatigue assessment of large

components mainly include the nominal stress

method, the local stress-strain method, the stress

field intensity method and so on(Zhang 2011). With

the development of the finite element software, the

local stress and strain of the dangerous part of the

large component can be obtained by software

simulation. This has been widely used in the

engineering(Tong 2011). In this paper, the fatigue

life of the corbel is evaluated by using the local

stress strain method combined with the finite

element analysis results. And the fatigue test design

of corbels is carried out combined with the actual

operation of the EMU.

2 FINITE ELEMENT ANALYSIS

2.1 Establishing model and meshing of

corbel

According to the 2D drawing to establish three-

dimensional model of corbel as shown in Figure 1

(a). In the analysis of complex parts, it is necessary

to use rough mesh to determine the dangerous parts,

then the weak parts are refined by using the sub

structure method(Song 2013, Japan Industrial

Standards 2016). The corbel dangerous parts of the

mesh for unit length of 10mm hexahedral elements,

transition region for unit length of 15mm free mesh,

other parts for the unit length of 30mm tetrahedral

elements, the total number of nodes is 1064732,

number of units is 549074.The mesh of key weak

part shows as Figure 1 (b).

2.2 Finite element analysis and

determine working conditions

EMU is great sensitive to environmental changes

because of its high speed. According to the(Wang

2014), it is known that the fatigue condition is

mainly based on the vibration, such as the stability

of the track, body vertical and lateral vibration

Yin X., Sun Z., Xie L., Wang Q. and Qian W.

Fatigue Life Assessment and Experiment Design for EMU Corbel.

DOI: 10.5220/0006442800080012

In ISME 2016 - Information Science and Management Engineering IV (ISME 2016), pages 8-12

ISBN: 978-989-758-208-0

which is caused by the passengers get on or off car,

acceleration and braking of the car to produce

longitudinal vibration. The change of conditions: the

loads of body change between the preparation

conditions (AW0) and overload condition (AW3).

Calculating loads through the AW3 conditions ：

Vertical vibration acceleration to take (1+0.15 g);

lateral and longitudinal acceleration take 0.15g. The

main loads of corbel include the vertical load of air

spring seat and the load of the center pin(Liu

2012).The loads condition is shown as Table 1 and

Figure 7.

Using the static structural module of the finite

element software of Workbench to make an

evaluation of the fatigue condition for the corbel.

The material parameters are shown in Table 2

(Sankaran 2011). The constraint boundary

conditions at both ends of the corbel is fixed

constraint. The two load step is set in the program,

and the loading condition is shown in Table 1.1.

Enhanced Lagrange method is used to solve the

model. The equivalent stress and strain calculation

results as shown in Figure 2, the greatly weak point

is the intersection of left the through tube 1 and left

corbel.

At the load step 1, the maximum stress value is

126.13Mpa and the maximum strain value is

1.7781E(-3). At the load step 2, the maximum stress

value is 103.59Mpa, the maximum strain value is

1.46031.4603E(-3), and the other dangerous parts of

the stress cloud is shown in Figure 3.

(a) Three-dimensional model of corbel (b) Meshing of corbel

Figure 1: Model and mesh of corbel

Table 1: Loads condition

Project Number Loads（KN） The direction

Load of the center pin 1 15.5±15.5

With a transverse angle of

45 degrees

Load of air spring seat 2 120±18 Vertical

Table 2: The main corbel Aluminum Alloy material characteristics

Material Position

Elastic

modulus（

GPa）

Poisson

ratio

Density（

Kg/m3）

Elastic limit（MPa）

Fatigue strength

（MPa）

Base

metal

Welding

Base

metal

Welding

A7N01P-T4

(JISH4000)

Corbel

reinforcing

plate

69 0.3 2710

195 176 135

A7N01S-T5

(JISH4100)

Corbel left（

right）

245 205 119

Fatigue Life Assessment and Experiment Design for EMU Corbel

(a) Stress cloud at the load step 1 (b) Strain cloud at the load step 1

Figure 2: Stress or strain cloud of the weak point

(a) The intersection of right the through tube 2 and

right corbel.

(b) The intersection of lower cover plate and side member.

(c)The intersection of right the through tube 1 and

corbel inside.

(c)The intersection of left the floor and side member

Figure 3: Stress cloud at different risk positions

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ISME 2016 - International Conference on Information System and Management Engineering

3 FATIGUE LIFE PREDICTION

OF CORBEL

Corbel as large structures whose nominal stress is

difficult to gain, but the local stress and strain can be

obtained by finite element method. So using local

stress-strain method to evaluate the fatigue life of

the corbel. The strain life curve is usually described

by Manson-Coffin formula, which is based on the

low cycle fatigue strain life relationship (Manson-

Coffin formula) and the high cycle fatigue stress life

relationship (Basquin equation).As type (1)

(2 ) (2 )

εε

Δ= + (1)

In formula (1),

Δ represent the total strain

when the average stress is 0;

represent the

fatigue strength coefficient;

represent the fatigue

ductility coefficient; b represent the fatigue strength

index; c represent the fatigue ductility index; N

represent the fatigue life(Yin 2010, Qian 2012).

In equation (1) for the Manson-coffin formula

under fluctuating load, the non fluctuating load need

to be modified to the average stress, and the average

stress is modified by the total strain of Morrow,

follow the formula (2):

Δ= Δ

−

(2)

In formula(2)：

represent total strain whose

average stress is corrected;

S represent the average

stress value.

Through finite element analysis to ensure the

critical points of corbel is in through pipe. The

maximum stress is 126.13Mpa，and the minimum

stress is 103.56mpa，whose material is A7N01S-

T5. Material’s tensile strength is 245Mpa 、

reduction of area is

11.5%

. Calculating that：

114.86

，

0.16252

= ，

0.16087

= ,

618.8

= , applying the

parameter to (1)、(2)：

0.12 0.6

618.8

1.228 (2 ) 0.1681(2 )

69 10

−−

−

⎡

⎤

Δ= × +

⎢

⎥

⎣

⎦

The finite element calculation results show that

the dangerous point strain is

3.178E( 4)

Δ= −

The fatigue life of corbel is

10N > .

4 CORBEL FATIGUE TEST

test points. Using the finite element software to

analyze the body of fatigue working condition and

the same conditions corbel analyzed separately

scheduled monitoring results as shown in Figure 4,

the same detection should be a smaller force

deviation, corbel constraint and load method is

reliable. The constraint imposed on the side beam

and corbel test loading clamp mode is shown in

Figure 6, load size as shown in Table 1.1 shows,

load location and direction as shown in Figure 7.

Load test for hydraulic drive, the test frequency is

3Hz, corbel fatigue test site as shown in Figure 5.

igure 4: Results of key point of vehicle and corbel alone

Figure 5: Fatigue experiment

Fatigue Life Assessment and Experiment Design for EMU Corbel

Figure 6: Fixture of corbel test Figure 7: Loading position and direction

5 CONCLUSIONS

1) The evaluation of fatigue life by local stress strain

method is conservative and accurate, and it is safe to

be applied in engineering application;

2) Using the finite element software workbench to

analyze corbel fatigue working condition, Applying

the results of analysis to Manson coffin equation to

obtain the dangerous position of the corbel fatigue

life, which is

10N > . Satisfying fatigue life

requirements;

3) Corbel fatigue test can be carried out

independently. Do not need to analyze the whole

body.

ACKNOWLEDGMENTS

This work was partially supported by the National

Natural Science Foundation of China (Grant No.

51305275, 51335003, 51275221), the Program for

Liaoning Excellent Talents in University (Grant No.

LR2015044), the Fundamental Research Funds for

the Central Universities (Grant No. N140301001),

and the Natural Science Foundation of Liaoning

Province of China (Grant No. 2015020138).

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