Journal of Mechanical Science and Technology 26 (2) (2012) 531~536

www.springerlink.com/content/1738-494x DOI 10.1007/s12206-011-1034-3

Durability evaluation of a composite bogie frame with bow-shaped side beams†

Jung Seok Kim1,*, Kwang Bok Shin2, Hyuk Jin Yoon1 and Woo Geun Lee3 1Railroad Structural Research Department, Korea Railroad Research Institute, 374-1 Woulam-dong, Uiwang-shi,Gyeonggi-do, Korea

2Division of Mechanical Engineering, Hanbat National University, Korea 3Railway System Engineering, University of Science and Technology, Daejeon, Korea

(Manuscript Received April 7, 2011; Revised October 7, 2011; Accepted October 24, 2011)

----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Abstract In the current study, the static structural safety and durability of two composite bogie frame models were evaluated using a finite ele-

ment analysis. Prior to evaluation, the in-plane and out-of-plane mechanical properties of the base material were measured. The fatigue property was also measured to evaluate the durability of two composite bogie frames. Based on material data, the static structural safety was examined using the Tsai-Wu failure criterion under ten different loading conditions. Stress combination data were used to evaluate durability of two composite bogie frames. Analysis results indicate that the maximum Tsai-Wu failure indices of the two composite bogie frames under a twisting load were 0.48 and 0.57. Based on the durability evaluation using Goodman diagrams, all combined stress data of the two models were within the endurance limit. In the bogie frames with a side beam height of 50 mm, the side beam bottom area was the most affected region. The joint center area revealed higher mean stress and stress amplitude values in the bogie frames with a side beam height of 150 mm.

Keywords: Durability; Composite; Bogie frame; Out of plane; Goodman diagram ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- 1. Introduction

Composite materials have been used in a wide range of ap-plications because of their relatively superior mechanical properties over those of conventional materials. Therefore, their use in railway vehicles is currently being considered. The bogie of a railway vehicle sustains the weight of the car body, controls the wheel sets on straight and curved tracks, and ab-sorbs vibrations [1]. The bogie weighs around 37% of the total vehicle weight. Thus, reducing the weight of the components comprising the bogie system is essential for lightweight rail-way vehicle designs. Specifically, the bogie frame, which accounts for approximately 20% of the bogie weight, supports heavy static and dynamic loads: These loads include the verti-cal load by the vehicle body, braking and accelerating loads, twisting load induced by track twisting, lateral loading by lateral vibration of the railway vehicle, and traction load. Due to these demands, bogie frames are typically manufactured using solid steel (particularly freight bogies) or welded struc-tures to produce rigid and heavy bogie frames, weighing 1 ton to 2 tons. They have to be equipped with suspensions and damping systems to ensure the convenience of passengers and

to absorb vibration caused by uneven railway tracks. Few attempts have been conducted to develop bogie frames using composite materials. Geuenich et al. [2-4] built the world’s first bogie frame made of glass fiber reinforced plastics, which targets the bogie frame of a passenger train.

Using composite elements for the frames approximately re-duces weight by 25%, enabling minimization of power capac-ity, energy consumption, and wear. Maurin et al. [5] assessed the mechanical reliability of a side beam for a composite-based bogie frame using a Fiber Bragg Grating sensor and noted that the ultimate load of the composite side beam before the first failure appeared to be greater than 350 kN.

To replace a conventional steel bogie with a composite bogie, glass/epoxy composite bogie frames with two different shapes were designed in the present study, which can be used in the future for urban subway train bogies. Their durability was evalu-ated using Goodman diagrams and finite element (FE) analyses under different loading conditions. Fatigue tests using specimens under the stress ratio of R = -1 were conducted to obtain the fatigue limit of the glass/epoxy used in the bogie frame.

2. Composite bogie frame with bow-shaped side beams

2.1 Configurations

The traditional bogie frame of an urban subway train is produced in a welded steel box format (like a hollow tube) to

† This paper was recommended for publication in revised form by Associate Editor Seong Beom Lee

*Corresponding author. Tel.: +82 31 460 5663, Fax.: +82 31 460 5289 E-mail address: jskim@krri.re.kr

© KSME & Springer 2012

532 J. S. Kim et al. / Journal of Mechanical Science and Technology 26 (2) (2012) 531~536

lighten its weight. Two side beams and two cross beams com-pose a bogie frame. These beams are assembled together in a closed box construction, welded together by upper and lower cover plates as well as inner and outer side plates with vertical rib plates in the box. The upper and lower cover plates are typically 10 mm to 15 mm thick. SM490A steel is usually used as the base material.

A composite bogie frame has the same external shape as a conventional frame (Fig. 1). It also has two side beams and two cross beams. The composite bogie frame is 2,540 mm long and 2,325 mm wide. To meet structural requirements, the inside of the side beams is filled with composite chords, ribs, and foam cores. The glass/epoxy prepregs are stacked on the inner structures to form a skin.

The present study evaluates the structural safety of two composite bogie frames with different side beam heights of 50 mm and 150 mm (Figs. 1(a) and 1(b)).

2.2 Material property evaluation

2.2.1 In-plane properties Before evaluating the durability of the composite bogie

frame, the mechanical properties of the base material used for the bogie frame were measured. In the composite bogie frame, the base material was a 4-harness satin fabric glass/epoxy (GEP224, SK Chem., Korea). Firstly, in-plane material prop-erty evaluation tests for the glass/epoxy were performed based on the standards set by the American Society for Testing and Materials (ASTM), namely, ASTM D3039 (tensile test) [6], ASTM D3410 (compressive test) [7], and ASTM D5379 (shear test) [8]. The test specimens were cured in an autoclave, wherein the curing cycles included a 2.5 oC/min ramp to 80 oC and a 1.5 oC/min ramp to 135 oC. After completing the curing process, the test specimens were cut and prepared for the tests, based on the above ASTM standards. An instron-4400 univer-sal test machine was used for the material property tests. The test machine was equipped with a high-speed data acquisition system of load - displacement. Each test included six speci-mens. The test setup and the final fractured specimen are shown in Fig. 2. Table 1 lists the obtained material properties of the glass/epoxy composites.

2.2.2 Out-of-plane properties

The out-of-plane material property evaluation tests for the

glass/epoxy were conducted based on ASTM D7291 (through-thickness flatwise tensile) [9] and ASTM D2344 (interlaminar shear strength) [10]. For the through-thickness tensile modulus and strength, the coupons, as recommended by ASTM D7291, are cylindrical with either a constant cross-sectional area or a reduced gage section. The present study used the coupons with the reduced gage section. Five coupons were used for each test. The test setup and a final fractured specimen are shown in Fig. 3. Table 2 lists the average out-of-plane material properties. The measured out-of-plane proper-ties were used as the input properties of the 3D layered solid FE model. In the current study, G13 and G23 were not meas-ured. These values were calculated in Eq. (1) [11].

50mm 150mm

A

A

Side beam

Cross beam

(a) (b) Fig. 1. Composite bogie frame with side beam heights of (a) 50 mm;(b) 150 mm.

Table 1. In-plane material properties of the glass/epoxy composites.

Modulus Values Strength Values

E11 34.42 GPa Xt 636.1 MPa

E22 13.19 GPa Xc 565.6 MPa

G12 7.05 GPa Yt 107.0 MPa

ν12 0.24 Yc 217.0 MPa

- - S 71.7 MPa

Table 2. Out-of-plane material properties of the glass/epoxy compos-ites.

Modulus Values Strength Values

E33 6.73GPa Zt 37.08 MPa

ν13 0.28 ν23 0.28

G13 5.15 GPa S13 107.0 MPa

G23 5.15 GPa S23 217.0 MPa

(a) (b) (c) Fig. 2. Setup and final fractured specimen in the in-plane material property evaluation tests: (a) tensile; (b) compressive; (c) shear.

(a) (b) Fig. 3. Test setup and final fractured specimen of the out-of plane material property evaluation tests: (a) tensile; (b) interlaminar shear.

J. S. Kim et al. / Journal of Mechanical Science and Technology 26 (2) (2012) 531~536 533

)1(2 23

22313 ν+==

EGG (1)

2.2.3 Fatigue properties

Generally, the composite bogie frame will be subject to an alternating load condition. Therefore, the fatigue test of the glass/epoxy composite with a layup of [0/90] was conducted under a sinusoidal cyclic load, R = -1. Three specimens were used for each stress level. A loading frequency of 5 Hz was selected to make the temperature increase in the test specimen during the fatigue test negligible [12, 13]. The test setup and a final fractured specimen in the fatigue property evaluation tests are shown in Fig. 4. The anti-buckling jig was used to prevent buckling, as shown in Fig. 4.

The maximum stress-fatigue life curve of the glass/epoxy is shown in Fig. 5. According to the test, the fatigue limit of the [0/90] laminate was determined to be 89.2MPa. In the present study, the stress value at which the failure did not occur was determined as fatigue limit.

3. FE modeling

3.1 Loading conditions

The present study considered ten load cases (vertical, dy-namic, ±twisting, ±lateral, ±traction, and ±braking). The verti-cal load is induced by the body weight of the car. The dy-namic load, which considers the dynamic effect acting on the

car body, corresponds up to 1.3 times the vertical load. The twisting load corresponds to the force induced by a track twist. The track twisting condition in the opposite direction is de-noted by +twisting and –twisting. Table 3 presents the load cases and values applied to the bogie frame.

3.2 Finite element modeling

The FE modeling and the boundary conditions of the com-posite bogie frame are presented in Fig. 6. Aside from the air spring seats, other brackets typically used to install the sub-components, including the braking device, dampers, and trac-tion devices, were not included in the FE model. To apply the loads to the locations of theses brackets, nodes were modeled at these points and connected with the bogie frame using

Fig. 4. Test setup and finally fractured specimen in the fatigue property evaluation tests.

Fig. 5. S-N curve of the glass/epoxy composite.

Table 3. Load cases applied to the composite bogie frame [14].

Load case Stress symbol Load value (kN) Remark

A 140 Static (1.0 g) Vertical load B 182 Dynamic (1.3 g)

C1 16 mm displacement +twisting Twisting load C2 16 mm displacement -twisting

D1 95 Running forward Traction load D2 95 Running backward

E1 95 Left Lateral load E2 95 Right

F1 50 Running forward Braking load F2 50 Running backward

0

0

==

===

yx

zyx

URUR

UUU

0

0

==

===

yx

zyx

URUR

UUU

0

0

==

==

yx

zy

URUR

UU

0

0

==

==

yx

zy

URUR

UU

x

z y

Vertical load

Vertical load

Skin•Ply thickness : 0.27mm•Layup : [0]56T•Shell element : S4R

12

3

Rib•Ply thickness : 1.0mm•Layup : [0/90/45/-45/0]S•Continuum shell element : C3D8R

Composite chord•Ply thickness : 0.27mm•Layup : [0]72T•Continuum shell element : C3D8R

Foam core•Solid element : C3D8I

•Element size : 10mm

Bracket for braking device

Bracket for traction device

Bracket for latera l buffer

Fig. 6. Finite element modeling and boundary conditions of the com-posite bogie frame.

534 J. S. Kim et al. / Journal of Mechanical Science and Technology 26 (2) (2012) 531~536

model predictive control (MPC) constraints, as provided in ABAQUS [15] (Fig. 6). Four supporting points on the bogie frame model pertaining to locations of the wheel rotation cen-ter are the illustrated in Fig. 6. The left supporting points were allowed to rotate only about the z-axis, Ux=Uy=Uz=φx=φy=0. By contrast, translation along the longitudinal direction and rotation about the z-axis were possible at the right supporting points (Uy=Uz=φx=φy=0). For the finite element analysis of the composite bogie frame, the composite chords and ribs were modeled with C3D8R solid elements and the foam cores were modeled using C3D8I solid elements (Fig. 6). S4R lay-ered shell elements were used to model the skin part. The total number of elements for the two composite bogie frames with different side beam heights of 50 mm and 150 mm were 31,492 and 63,226, respectively. Excluding the foam core, the layup structure definition (such as the fiber orientation, ply thickness, local coordinate definition, and number of integra-tion points through the ply thickness) of the three composite parts, was completed using the composite layup module pro-vided by ABAQUS. The layered shell elements of the skin part were connected with the inner parts meshed by the solid elements using tie constraints.

4. Analysis results and discussion

4.1 Failure index distributions

The Tsai-Wu failure index was calculated and evaluated to test the structural safety of the composite bogie frame under various loading conditions. The Tsai-Wu failure index was calculated using Eq. (2).

0.12 221112

21266

22222

21111222111 =+++++ σσσσσσσ FFFFFF (2)

where iF and ijF are strength tensors and ijσ is the calcu-lated stress.

The stress analysis results for the composite bogie frame with a side beam height of 150 mm are shown in Figs. 7 and 8. The Tsai-Wu failure index contours under vertical and +twisting loadings are shown in Figs. 7(a) and 7(b), respec-

tively. The maximum Tsai-Wu failure index occurred at the bottom joint region between the side beam and the cross beam and acquired a value of 0.23. For the +twisting loading, a high Tsai-Wu failure index occurred at the same region as the ver-tical loading condition and obtained a value of 0.48. As indi-cated in Fig. 6, the maximum Tsai-Wu failure index appeared to be at the points in which the MPC constraints for the lateral buffer were applied to connect the two cross beams. In an actual composite frame, steel brackets are assembled not only to connect the two cross beams but also to install the lateral buffer at these points. Therefore, based on the analysis results, the steel brackets are expected to be subjected to severe tor-sional loads under twisting loading conditions.

The Tsai-Wu failure index contours under traction and braking loads are shown in Figs. 8(a) and 8(b), respectively. For traction loading, the maximum Tsai-Wu failure index value was 0.11, which occurred at the points in which the MPC constraints were applied. Except for these points, the index was below 0.1. For the braking loading, a high Tsai-Wu failure index value of 0.15 occurred around the joint region between the side beam and the crossbeam.

The Tsai-Wu failure index contours under the traction and lateral loadings of the composite bogie frame with side beam heights of 50 mm are shown in Figs. 9(a) and 9(b), respec-tively.

In this bogie frame, the regions where the Tsai-Wu failure

(a)

(b)

Fig. 7. Tsai-Wu failure index contours under: (a) vertical load; (b) +twisting load.

(a)

(b)

Fig. 8. Tsai-Wu failure index contours under: (a) traction; (b) braking loads.

(a)

(b)

Fig. 9. Tsai-Wu failure index contours under: (a) traction; (b) lateral loads.

J. S. Kim et al. / Journal of Mechanical Science and Technology 26 (2) (2012) 531~536 535

index appeared to assume a maximum value were almost the same as with the previous model. However, the Tsai-Wu fail-ure index showed maximum values at the four boundary areas under the traction and lateral loading conditions because of the thin end of the bogie frame. Table 4 summarizes the maxi-mum Tsai-Wu failure indices for the two bogie frames. Under the vertical load, the maximum Tsai-Wu failure index of the composite bogie frame with a side beam height of 50 mm increased by 113% compared with the composite bogie frame with a side beam height of 150 mm (Table 4). However, the increase was less than 23% under the other loading conditions.

Investigations of the Tsai-Wu failure index distribution, re-vealed that the joint region between the side beam and the cross beam is the critical part in the composite bogie frame. In addition, both composite bogie frame models were deemed safe under the Tsai-Wu failure criterion.

The warp direction (0-direction) stress along the bottom line of the frame under the five main loading conditions is shown in Fig. 10.

In Fig. 10, each region pertains to the following:

• Region from x=0 to : boundary area • Region from to : bare side beam • Region from to : jointing area between the side

beam and the cross beam • Region from to : bare cross beam • Region from to : MPC constraint imposing area for

the braking force application • Region from to : bare cross beam The stress component exhibited significant fluctuation un-

der all loading conditions. Specifically, the stress around the joint area between points and displayed severe variation and was higher than at that of the other regions. The maxi-mum stress occurred under the twisting load.

4.2 Durability evaluation

In the previous section, the structural safety of the compos-ite bogie frame was evaluated for individual static loading conditions. In this section, the durability of the composite bogie frame is evaluated using the Goodman diagram. Based on the stress values derived from the individual static loading conditions, the mean stress and stress amplitude were obtained using Eqs. (3) and (4) [14]. A, C, D, E and F in Eqs. (3) and (4) are the stress symbols defined in Table 3.

( ) ( ) ( )

( ) ( )

1 2 1 2

1 2 1 2

2 2

2 2

mC A C A D D

A

E E F F

σ− + − +

= + +

+ ++ +

(3)

( ) ( ) ( ) ( )

( ) ( )

2 1 2 1 22 2

1 2 1 22 2

{ } { }2 2

{ } { }2 2

aC A C A D D

B A

E E F F

σ− + − −

= − + +

− −+ +

(4)

The Goodman diagrams of the two composite bogie frames

with 50 mm and 150 mm side beam heights, respectively, under the ten load cases listed in Table 3 are shown in Fig. 11. Data of the diagram were selected from the three critical areas of each bogie frame: the side beam bottom, outer joint area, and joint center area. According to the diagram, the side beam bottom area was identified as the critical region in the bogie frame with a side beam height of 50 mm. In contrast to the other parts, the joint center area in the bogie frame with a side beam height of 150 mm revealed higher mean stress and stress amplitude values.

The stress data of the two models were both within the en-durance limit.

5. Conclusions

In the present study, the in-plane and out of plane mechani-cal properties of the base material of a composite bogie frame were measured. In addition, the fatigue properties were meas-

Table 4. Maximum Tsai-Wu failure index for the two bogie configura-tions.

Side beam heights Loadings

150 mm 50 mm

Vertical (1.0g) 0.23 0.49

+Twisting 0.48 0.57

Traction 0.11 0.13

Braking 0.15 0.15

Lateral 0.13 0.16

0.0 0.2 0.4 0.6 0.8 1.0-50

-25

0

25

50

75

100

Vertical +twisiting Braking Lateral Traction

Stre

ss (σ

11)

Distance, x/L

xx=0

x=L

Center of the bogie frame

Center ofthe bogie frame

Fig. 10. Warp direction (0-direction) stress along the bottom line of the frame under the five main loading conditions.

536 J. S. Kim et al. / Journal of Mechanical Science and Technology 26 (2) (2012) 531~536

ured. The analysis results indicate that two types of composites

met the static structural safety requirements under the ten dif-ferent loading conditions. The maximum Tsai-Wu failure indices of the two composite bogie frames were 0.48 and 0.57, which were derived under the twisting load.

In the durability evaluation using Goodman diagrams, the two models were clearly deemed to be safe based on the test standard for performance test of the urban subway train and S-N curve data obtained R=-1 stress condition. In the further studies, the fatigue analysis will be performed under the ser-vice condition. The critical point identified was the side beam bottom area for the bogie frames with a side beam height of 50 mm. The joint center area revealed higher mean stress and stress amplitude values in the bogie frame with a side beam height of 150 mm.

References

[1] J. S. Kim, Fatigue assessment of tilting bogie frame for ko-

rean tilting train : Analysis and static tests, Eng. Fail. Anal., 13 (2006) 1326-1337.

[2] W. Geuenich, C. Guenther and R. Leo, Dynamics of fiber composite bogies with creep-controlled wheelsets, 8th IAVSD- Symposium, MIT (1983) 225-238.

[3] C. Guenther, R. Leo and P. Wackerle, New technologies for rail vehicle bogies and car body substructures, MRS, Europe (1985) 89-95.

[4] R. Leo and H. P. Lang, Fiber-composite bogies on test, Railway Gazette International (1986) 632-633.

[5] L. Maurin, J. Boussoir, S. Rougeault, M. Bugaud and P. Ferdinand, FBG-based smart composite bogies for railway applications, IEEE (2002) 91-94.

[6] ASTM D 3039, Standard test method for tensile properties of polymer matrix composite materials.

[7] ASTM D 3410, Standard test method for compressive prop-erties of polymer matrix composite materials with unsup-ported gage section by shear loading.

[8] ASTM D 5379, Standard test method for shear properties of composite materials by the v-notched beam method.

[9] ASTM D 7291, Standard test method for through-thickness “flatwise” tensile strength and elastic modulus of a fiber-reinforced polymer matrix composite material.

[10] ASTM D 2344, Standard test method for short-beam strength of polymer matrix composite materials and their laminates.

[11] K. Zimmermann, D. Zenkert and M. Siemetzki, Testing and analysis of ultra thick composites, Composites: Part B 41 (2010) 326-336.

[12] ISO 13003, Fibre reinforced plastics determination of fa-tigue properties under cyclic loading conditions.

[13] W. B. Hwang and K. S. Han, Fatigue of composites fatigue modulus concept and life prediction, JCM 20 (1986) 154-165.

[14] Minister of Land, Transport and Maritime Affairs: Standard for performance test of the urban subway train (2008).

[15] ABAQUS manual, Simulia.

Jung-Seok Kim received his M.S. and Ph.D. degrees in Aerospace Engineering from the Korea Advanced Institute of Science and Technology in 1994 and 1999, respectively. Dr. Kim is currently a principal researcher at the Department of Railway Structures at the Korea Rail Road Research Institute in Uiwang. His

main research interest is lightweight design of railway vehi-cles using composite materials.

(a)

(b) Fig. 11. Goodman diagram for the bogie frame with a side beam heightof (a) 50 mm; (b) 150 mm.