Influence of the Pulse Duration in the Anthropomorphic 

Test Device (ATD) Lower-Leg Loading Mechanics

by Masayuki Sakamoto

ARL-SR-0331 August 2015 

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Army Research Laboratory

Adelphi, MD 20783-1138

ARL-SR-0331 August 2015 

Influence of the Pulse Duration in the Anthropomorphic 

Test Device (ATD) Lower-Leg Loading Mechanics

Masayuki Sakamoto

Japanese ESEP Research Engineer 

at Weapons and Materials Research Directorate, ARL 

Approved for public release; distribution unlimited. 
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4. TITLE AND SUBTITLE

Influence of the Pulse Duration in the Anthropomorphic Test Device (ATD) 

Lower-Leg Loading Mechanics

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6. AUTHOR(S)

Masayuki Sakamoto 

(Japanese Engineer Scientist Exchange Program Research Engineer) 

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ESEP

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Survivability and Firepower Analysis Section, Ballistic Research Division, Ground 

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ATTN: Masayuki Sakamoto 

2-9-54, Fuchinobe, Chuo-ku, Sagamihara-shi, Kanagawa-ken 252-0206, JAPAN

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masayuki@cs.trdi.mod.go.jp, Phone:+81-42-752-2941, Address:2-9-54, Fuchinobe, Chuo-ku, Sagamihara-shi, Kanagawa-ken 252-0206, 

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14. ABSTRACT

This report was written by the author under the Engineer Scientist Exchange Program in the US Army Research Laboratory 

(ARL) from April 2013 to September 2014. To understand the loading mechanics of the anthropomorphic test device’s 

(ATD’s) lower leg in the presence of the blast-mitigating floor mat, the Finite Element Analysis (FEA) was conducted in 

various loading conditions. Through the FEA’s results, the pulse-duration dependency was indicated in the ATD lower-tibia 

peak load, and the dependency was confirmed though the loading experiment. The ATD lower-leg loading mechanics are

discussed with regard to pulse duration. 

15. SUBJECT TERMS

ESEP, blast-mitigating floor mat, CSBES, LS-DYNA

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 ABSTRACT

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 PAGES

38 

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Robert G Kargus

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(301) 394-5738 

Standard Form 298 (Rev. 8/98)

Prescribed by ANSI Std. Z39.18
iii

Contents

List of Figures iv

List of Tables v

Acknowledgments vi

1. Introduction 1

2. Analysis and Experiment Methods 1

2.1 Finite Element Model.......................................................................................................... 1

2.2 Loading Conditions in the FEA.......................................................................................... 4

2.3 Lower-Leg Loading Test .................................................................................................... 6

3. Results and Discussion 9

3.1 FEA Results......................................................................................................................... 9

3.2 Experimental Results......................................................................................................... 19

3.3 ATD Lower-Leg Loading Mechanics..............................................................................23

4. Conclusions 26

5. References 28

6. List of Symbols, Abbreviations, and Acronyms 29

Distribution List 30
iv

List of Figures

Fig. 1 FE model for the ATD lower-leg loading.......................................................................... 2

Fig. 2 Definition of the lower-tibia load Fz in the ATD lower-leg FE model ........................... 3

Fig. 3 Definition of the toe part and heel part on the boot sole................................................... 3

Fig. 4 Schematic of boundary conditions in the FEA.................................................................. 5

Fig. 5 Velocity histories on the floor plate in FEAs for 3.0-m/s loading ................................... 5

Fig. 6 Velocity histories on the floor plate in FEAs for 6.5-m/s loading ................................... 6

Fig. 7 Velocity histories on the floor plate in FEAs for 10-m/s loading .................................... 6

Fig. 8 Test setup for the lower leg loading test with the whole-body ATD and floor mat........ 7

Fig. 9 Sheets of the butyl rubber as the floor mat on the CSBES floor plate............................. 7

Fig. 10 Arrangements of sensors in the test setup.......................................................................... 8

Fig. 11 Representative load histories of the ATD lower tibia in the FEA, X065_08 (∆V = 

6.5 m/s, ∆T = 8 msec) .................................................................................................................... 9

Fig. 12 Representative ATD lower-leg motion in the FEA, X065_08 (∆V = 6.5 m/s, ∆T = 

8 msec) .......................................................................................................................................... 11

Fig. 13 Pressure distribution under the boot sole in the FEA result, X065_02 (∆V = 6.5 

m/s, ∆T = 2 msec)......................................................................................................................... 11

Fig. 14 Pressure distribution under the boot sole in the FEA result, X065_06 (∆V = 6.5 

m/s, ∆T = 6 msec)......................................................................................................................... 12

Fig. 15 Pressure distribution under the boot sole in the FEA result, X065_10 (∆V = 6.5 

m/s, ∆T = 10 msec)....................................................................................................................... 12

Fig. 16 Example of load histories of the ATD lower leg in the FEA, X065_02 (∆V = 6.5 

m/s, ∆T = 2 msec)......................................................................................................................... 13

Fig. 17 Example of load histories of the ATD lower leg in the FEA, X065_06 (∆V = 6.5 

m/s, ∆T = 6 msec)......................................................................................................................... 13

Fig. 18 Example of load histories of the ATD lower leg in the FEA, X065_10 (∆V = 6.5 

m/s, ∆T = 10 msec)....................................................................................................................... 14

Fig. 19 Example of the relation between the peak load and pulse duration on various 

interfaces in the ATD lower leg, X065 series (∆V = 6.5 m/s)...................................................14

Fig. 20 Example of the relation between the applied impulse and pulse duration on various 

interfaces in the ATD lower leg, X065 series (∆V = 6.5 m/s)...................................................15

Fig. 21 Relation between the peak load and pulse duration in the ATD lower-tibia axial 

force Fz from FEA results............................................................................................................ 16

Fig. 22 Relation between the applied impulse and pulse duration in the ATD lower-tibia 

axial force Fz from FEA results ..................................................................................................16
v

Fig 23 Interaction among the ATD foot, boot, and floor mat, X065_02 (∆V = 6.5 m/s, ∆T 

= 2 msec)....................................................................................................................................... 17

Fig. 24 Interaction among the ATD foot, boot, and floor mat, X065_06 (∆V = 6.5 m/s, ∆T 

= 6 msec)....................................................................................................................................... 17

Fig. 25 Interaction among the ATD foot, boot, and floor mat, X065_10 (∆V = 6.5 m/s, ∆T 

= 10 msec)..................................................................................................................................... 17

Fig. 26 Rotation-angle histories of the boot sole against the horizontal line in the FEA, 

X065 series (∆V = 6.5 m/s) ......................................................................................................... 18

Fig. 27 Representative load histories of the ATD lower tibia in the experiment, 

X065_06_03 Right Leg (∆V = 6.3 m/s, ∆T = 8.6 msec) ...........................................................19

Fig. 28 Load histories of the ATD lower-tibia axial direction force Fz in the loading 

condition X065_04 (∆V = 6.5 m/s, ∆T = 4.5 msec)...................................................................20

Fig. 29 Load histories of the ATD lower-tibia axial direction force Fz in the loading 

condition X065_08 (∆V = 6.4 m/s, ∆T = 8.6 msec)...................................................................20

Fig. 30 Load histories of the ATD lower-tibia axial direction force Fz in the loading 

condition X065_10 (∆V = 6.5 m/s, ∆T = 10.6 msec) ................................................................21

Fig. 31 Relation between the peak load and pulse duration in the ATD lower-tibia axial 

force Fz.......................................................................................................................................... 22

Fig. 32 Rotation-angle histories of the boot sole against the horizontal line in the 

experiment..................................................................................................................................... 23

Fig. 33 Representative ATD lower-leg motion in the experiment, X065_08_03 (∆V = 6.3 

m/s, ∆T = 8.6 msec) ..................................................................................................................... 23

Fig. 34 Schematic of the ATD lower-leg loading mechanics for 3 durations of loading..........25

Fig. 35 Relation between the peak load and pulse duration in the ATD lower- tibia axial 

force Fz with the peak acceleration of the loading pulse...........................................................26

List of Tables

Table 1 FE material models for the floor-mat and floor-plate parts.............................................. 2

Table 2 Loading conditions for the lower-leg FEA........................................................................ 4

Table 3 Specifications of sensors used in the ATD lower-leg loading test................................... 8

Table 4 Loading conditions for the ATD lower-leg loading test ................................................... 9

Table 5 Summary of experimental results.....................................................................................10

Table 6 Summary of experimental results.....................................................................................21
vi

Acknowledgments

This report was written by the author in the Engineer Scientist Exchange Program in the US 

Army Research Laboratory (ARL) from April 2013 to September 2014. I would like to take this 

opportunity to thank the ARL for giving me the chance to learn and investigate blast-loading 

issues in the state-of-the-art research environment. Especially, I would like to mention that the 

Crew Survivability Blast Effects Simulator played an important role in this study to confirm the 

complex mechanics of the lower-leg loading in the laboratory environment. I also would like to 

thank the members of the Blast Protection Branch and its specialists for supporting the numerical 

analysis, experiment, data processing, and various discussions that gave me valuable ideas.
1

1. Introduction 

Lower leg injury is a major injury mode induced by under body blast loading associated with 

IED (improvised explosive device) attacks against ground fighting vehicles.

1–4 Blast- mitigating 

floor mats are regarded as an effective countermeasure for injury prevention,

5,6 and the 

methodology for their selection and optimization is in immediate need. However, the loading 

mechanics in the lower leg in the presence of the floor mat is not fully understood. Thus, we

determined a need to clarify the mechanics through the Finite Element Analysis (FEA) by 

combining the Hybrid III 50th Percentile Anthropomorphic Test Device (ATD) lower leg and the 

butyl-rubber floor mat. 

In this study, we conducted the FEA and experiments on the ATD lower-leg loading in various 

conditions. Then, we clarified the stress distribution on the boot sole and investigated the 

correlation between the foot motion and lower-tibia load that is a major criterion for the lower 

leg injury. Moreover, we focused on the influence of the pulse duration in the ATD lower-tibia 

force and clarified the loading mechanics from this point of view. 

2. Analysis and Experiment Methods 

2.1 Finite Element Model 

The finite element (FE) model was built on LS-DYNA for the ATD lower-leg loading with the 

butyl-rubber floor mat, as shown in Fig. 1. In this model, the lower-leg part was composed of the 

boot and the right leg from the Hybrid III 50th Percentile ATD FE model developed by

Livermore Software Technology Corporation (LSTC). The lower-leg part was positioned in the 

0–90–0 configuration, and the boot sole was settled on the floor mat to touch the surface. The 

butyl-rubber floor mat was composed of 2 sheets; the dimensions of each sheet were 8 inches × 8 

inches × 20 millimeters (mm). 
2

Fig. 1 FE model for the ATD lower-leg loading 

The material cards used for the floor mat and floor plate are listed in Table 1. The FE material 

model for the butyl rubber was the ARL model; a previous report concluded that this model was

suitable for the analysis of underbody blast-loading events.

7 The ARL model showed high 

accuracy, especially in 4–8-millisecond (msec) pulse loading with 3.0–6.0 meters per second 

(m/s) velocity change.

Table 1 FE material models for the floor-mat and floor-plate parts

In this study, we focused on the lower-tibia load and boot-sole load for the clarification of the 

ATD lower-leg loading mechanics. The lower-tibia loads, Fx, Fy, and Fz, were measured as the 

section force in the ATD tibia bone as shown in Fig. 2.

Side View

Number of Elements: 213217 Mesh Size (Floor Mat): 2.5mm

Iso View

Boots

Hybrid III 50th

ATD Right Leg

Floor

Mat

Floor

Plate
3

Fig. 2 Definition of the lower-tibia load Fz in the ATD lower-leg FE model

As will be discussed in Section 3, there were distinct high-stress areas in the toe part and heel

part on the boot sole. Therefore, we defined the toe part and heel part (Fig. 3) and measured the 

applied loads respectively. Moreover, an SAE600 filter was applied to each load output in LSPrepost. 

Fig. 3 Definition of the toe part and heel part on the boot sole

Global

Coordinate

V

H Fz

Toe Heel 
4

2.2 Loading Conditions in the FEA

To clarify the ATD lower-leg loading mechanics, the loading conditions listed in Table 2 were 

planned for the FEA. 

Table 2 Loading conditions for the lower-leg FEA

These loading conditions were applied to the FE model as the velocity histories on the floor 

plate. The boundary conditions in the FEA are shown in Fig. 4. 
5

Fig. 4 Schematic of boundary conditions in the FEA

The velocity histories on the floor plate were determined by using the loading conditions and

assuming haversine-type acceleration inputs. Moreover, 5-msec initialization phases were 

considered in the velocity histories for the lower-leg FE model to be settled down on the floor 

mat. Thus, the velocity history shown in Figs. 5–7 was generated on the floor plate in each 

loading condition.

Fig. 5 Velocity histories on the floor plate in FEAs for 3.0-m/s loading

Gravity

Velocity Histories

Pivot Rotation

-2.0

0.0

2.0

4.0

6.0

8.0

10.0

0 5 10 15 20 25

Velocity (m/s)

Time (msec)

X025_02

X025_04

X025_06

X025_08

X025_10
6

Fig. 6 Velocity histories on the floor plate in FEAs for 6.5-m/s loading

Fig. 7 Velocity histories on the floor plate in FEAs for 10-m/s loading

2.3 Lower-Leg Loading Test

The lower-leg loading test was conducted on the Crew Survivability Blast Effects Simulator 

(CSBES) at the Adelphi Laboratory Center, ARL. As shown in Fig. 8, the whole body of the 

Hybrid III 50th Percentile ATD (I-Dummy) was used in this experiment. However, only the local 

loading function (Floor Motion Simulator) was activated in the CSBES to load the ATD lower 

leg as the loading in the FEA. The test setup was adjusted in the same way as the FE model: the 

ATD lower leg with boot was positioned in the 0–90–0 configuration on the floor mat, and the 

boot sole was settled on the floor mat to touch the surface. 

-2.0

0.0

2.0

4.0

6.0

8.0

10.0

0 5 10 15 20 25

Velocity (m/s)

Time (msec)

X050_02

X050_04

X050_06

X050_08

X050_10

-2.0

0.0

2.0

4.0

6.0

8.0

10.0

0 5 10 15 20 25

Velocity (m/s)

Time (msec)

X100_02

X100_04

X100_06

X100_08

X100_10
7

Fig. 8 Test setup for the lower leg loading test with the whole-body ATD and floor mat 

The floor mat was composed of 4 sheets of butyl rubber (Fig. 9), and the dimensions of each 

sheet were 8 inches × 8 inches × 20 mm. The sheets at first were replaced by new ones at every 

shot but later reused after the confirmation of the material’s condition. The interval between the 

usages of a sheet was kept to more than an hour for the material’s relaxation. 

Fig. 9 Sheets of the butyl rubber as the floor mat on the CSBES floor plate

The arrangements of sensors in the test setup are shown in Fig. 10, and the specifications are 

listed in Table 3. The signals from sensors were recorded in the data-acquisition systems 

Front View Right View (Lower Leg)
8

(Spectral Dynamics’s VXI Model VX2824 and Diversified Technical Systems’ SLICE) at the 

sampling frequency of 250 kHz. Then, direct-current offset and filters (Table 3) were applied to 

each signal in postprocessing on the data-analysis software (MathWorks, MATLAB). The test 

was also recorded by the high-speed imaging camera (Phantom, Miro) for the confirmation of 

the contact between the boot sole and floor mat.

Fig. 10 Arrangements of sensors in the test setup

Table 3 Specifications of sensors used in the ATD lower-leg loading test 

As will be discussed, the FEA results indicated there was a relation between the pulse duration 

and peak load in the ATD lower tibia. Therefore, the loading conditions listed in Table 4 were 

planned to confirm the relation through the experiment.
9

Table 4 Loading conditions for the ATD lower-leg loading test

3. Results and Discussion 

3.1 FEA Results

Representative load histories of the ATD lower tibia in the FEA are shown in Fig. 11, and FEA 

results are summarized in Table 5. As compared with the lower-tibia axial force Fz, the 

perpendicular forces Fx and Fy are much smaller; the ATD lower tibia is probably loaded 

vertically through the boot heel. Therefore, we mainly focus on Fz in the following discussion.

Fig. 11 Representative load histories of the ATD lower tibia in the FEA, 

X065_08 (∆V = 6.5 m/s, ∆T = 8 msec) 

-2.5

0.0

2.5

5.0

7.5

10.0

12.5

15.0

5 10 15 20 25

Load (kN)

Time (msec)

Lower Tibia, Fx

Lower Tibia, Fy

Lower Tibia, Fz
10

Table 5 Summary of experimental results

A typical ATD foot motion in the FEA is shown in Fig. 12. In the initial loading phase, the floor 

plate and floor mat translate upward as one, and the boot sole sinks into the floor mat. In the 

following phase, the foot rotates slightly around the ankle joint, and the boot toe possibly loses 

contact with the floor mat.

2.6 14.2

6.8 19.4

2 0.7 4.4

Loading

Condition

Velocity 

Change, 

∆V

 (m/s)

Pulse

Duration,

∆T

(msec)

Peak

Lower Tibia

Load, Fz

(kN)

Applied

Impulse

(Nsec)

X065_04

X065_02 2 2.9 10.0

4 1.6 5.6

X100_10 10 11.3 49.2

X100_08 8 12.6 41.3

X100_02 2 5.6 16.4

X065_10

6 2.2 7.6

X065_08 8 6.9 23.9

X030_08 8 2.6 9.1

X030_10 10 2.6 10.9

X065_06

X100_04

X100_06

3.0

6.5

9.8

X030_06

X030_04

X030_02

12.4

10.3 24.2

32.7

4

6

4

6

10 6.6 26.0
11

Fig. 12 Representative ATD lower-leg motion in the FEA, X065_08 (∆V = 6.5 m/s, 

∆T = 8 msec) 

As shown in Figs. 13–15, representative pressure distributions on the footprint also indicate this 

motion. The boot toe does not always touch the floor mat during the loading, although the boot 

heel is pressed onto the floor mat during the whole period of the loading. 

Fig. 13 Pressure distribution under the boot sole in the FEA result, X065_02 (∆V = 6.5 m/s, 

∆T = 2 msec) 

5msec 7msec 9msec 11msec

13msec 15msec 17msec 19msec

21msec 23msec

Loading

Duration

5msec 7msec 9msec 11msec 13msec

15msec 17msec 19msec 21msec 23msec

Stress

(MPa)

0

1

Toe

Heel

Loading

Duration
12

Fig. 14 Pressure distribution under the boot sole in the FEA result, X065_06 (∆V = 6.5 m/s, 

∆T = 6 msec) 

Fig. 15 Pressure distribution under the boot sole in the FEA result, X065_10 (∆V = 6.5 m/s, 

∆T = 10 msec) 

Moreover, the load histories on the ATD lower tibia, boot toe, boot heel, and whole boot are 

shown in Figs. 16–18 for representative loading conditions. Thus, the pulse duration of the 

loading probably affects the ATD lower-tibia load. From this point of view, we will discuss the 

ATD lower-leg loading mechanics later in this report.

5msec

17msec 19msec 21msec 23msec

7msec 9msec 11msec 13msec

15msec

Toe

Heel

Loading

Duration

Stress

(MPa)

0

1

5msec

17msec 19msec 21msec 23msec

7msec 9msec 11msec 13msec

15msec

Toe

Heel

Loading

Duration

Stress

(MPa)

0

1
13

Fig. 16 Example of load histories of the ATD lower 

leg in the FEA, X065_02 (∆V = 6.5 m/s, ∆T = 2 msec) 

Fig. 17 Example of load histories of the ATD lower 

leg in the FEA, X065_06 (∆V = 6.5 m/s, ∆T = 6 msec) 

0.0

2.5

5.0

7.5

10.0

12.5

15.0

17.5

5 10 15 20 25

Load (kN)

Time (msec)

Lower Tibia, Fz

Boots Toe

Boots Heel

Whole Boots

0.0

2.5

5.0

7.5

10.0

12.5

15.0

17.5

5 10 15 20 25

Load (kN)

Time (msec)

Lower Tibia, Fz

Boots Toe

Boots Heel

Whole Boots
14

Fig. 18 Example of load histories of the ATD lower 

leg in the FEA, X065_10 (∆V = 6.5 m/s, ∆T = 10 msec) 

The relation between the peak load and pulse duration on each interface are shown in Figs. 19

and 20 for a representative velocity change of 6.5 m/s. 

Fig. 19 Example of the relation between the peak

load and pulse duration on various interfaces

in the ATD lower leg, X065 series (∆V = 6.5 m/s) 

0.0

2.5

5.0

7.5

10.0

12.5

15.0

17.5

5 10 15 20 25

Load (kN)

Time (msec)

Lower Tibia, Fz

Boots Toe

Boots Heel

Whole Boots

0.0

2.5

5.0

7.5

10.0

12.5

15.0

17.5

0 2 4 6 8 10 12

Peak Load (kN)

Pulse Duration (msec)

Lower Tibia, Fz

Boots Toe

Boots Heel

Whole Boots
15

Fig. 20 Example of the relation between the applied

impulse and pulse duration on various interfaces

in the ATD lower leg, X065 series (∆V = 6.5 m/s) 

Moreover, the peak loads and applied impulses in the ATD lower tibia are summarized for 

various loading conditions in Figs. 21 and 22. Then, the peak loads of the ATD lower tibia and 

boot heel are increasing between 2 and 8 msec as the pulse duration increases, whereas those of 

boot toe are decreasing except for 2 msec. Note also that the applied impulse is clearly increasing 

on every interface, although the increase on the boot toe is small.

The ATD lower-tibia loads in short-duration loadings are expected to be higher than those of 

long-duration loadings with the same ∆V because the acceleration in the loading pulse is higher. 

However, the FEA results indicate the opposite tendency as discussed above. This is probably

caused by the change in the contact status on the boot sole because the impulse is increasing (as 

shown in Fig. 20). 

0

25

50

75

0 2 4 6 8 10 12

Applied Impulse (Nsec)

Pulse Duration (msec)

Lower Tibia, Fz

Boots Toe

Boots Heel

Whole Boots
16

Fig. 21 Relation between the peak load and pulse

duration in the ATD lower-tibia axial force 

Fz from FEA results

Fig. 22 Relation between the applied impulse and

pulse duration in the ATD lower-tibia axial 

force Fz from FEA results

The interactions among the ATD foot, boot, and floor mat are shown in Figs. 23–25 for 

representative loading conditions.

0.0

2.5

5.0

7.5

10.0

12.5

15.0

17.5

0 2 4 6 8 10 12

Peak Load (kN)

Pulse Duration (msec)

FEA, 3.0m/s

FEA, 6.5m/s

FEA, 9.8m/s

0

25

50

75

0 2 4 6 8 10 12

Applied Impulse (Nsec)

Pulse Duration (msec)

FEA, 3.0m/s

FEA, 6.5m/s

FEA, 9.8m/s
17

Fig 23 Interaction among the ATD foot, boot, and floor mat, X065_02 (∆V = 6.5 m/s, ∆T = 2 msec) 

Fig. 24 Interaction among the ATD foot, boot, and floor mat, X065_06 (∆V = 6.5 m/s, ∆T = 6 msec) 

Fig. 25 Interaction among the ATD foot, boot, and floor mat, X065_10 (∆V = 6.5 m/s, ∆T = 10 msec) 

Moreover, the rotation-angle histories of the boot sole are shown in Fig. 26 for a representative 

∆V; the validity of the ATD lower-leg FE model is not quantitative but qualitative in the 

rotational movement around the ankle joint. Considering these boot-sole contact data, the 

following phases now are assumed for the ATD lower-leg loading: 

1) In the initial phase of loading, the boot toe and heel are loaded almost uniformly. At this 

point, the load histories on these 2 interfaces are similar. 

2) In this phase the boot sole and floor mat start to deform, which causes the arch in the boot 

sole and the foot to fit the floor mat and the boot insole, respectively. These deformations 

5msec 7msec 9msec

13msec 15msec 17msec

11msec

Loading

Duration

5msec 7msec 9msec

13msec 15msec 17msec

11msec

Loading

Duration

5msec 7msec 9msec

13msec 15msec 17msec

11msec

Loading

Duration
18

increase the contact among the floor mat, boot sole, boot insole, and foot, and enhance 

transmissibility of the load.

3) In the following phase of loading, the foot starts to rotate around the ankle joint. Then, the 

boot toe loses contact with the floor mat, and the load on the boot toe decreases. The 

opposite occurs with the boot heel, whose load increases because of its close contact with 

the floor mat.

Fig. 26 Rotation-angle histories of the boot sole 

against the horizontal line in the FEA, X065 

series (∆V = 6.5 m/s) 

In short-duration loading (2 and 4 msec), Phases 1 and 2 occur during the loading as shown in 

Figs. 16, 23, and 26. However, the deformation in Phase 2 is not as large as that in long-duration 

loading, and the boot sole is not sufficiently compressed during the loading. Moreover, Phase 3 

starts after the completion of the loading, and the ATD foot motion does not affect the load 

profile. Therefore, the load profiles of the boot toe and heel are similar (as shown in Fig. 16), and 

the peak load is much smaller than that of long-duration loading. By contrast, in long-duration 

loading (6–10 msec), Phase 3 starts during the loading at the same time as Phases 1 and 2 (as 

seen in Figs. 17, 25, and 26). Therefore, the boot sole and floor mat contact each other more 

closely on the boot heel. Together with the deformations in the boot sole and floor mat, this is 

probably the major cause of the increase in the boot-heel load. Then, as shown in Fig. 17 and 18, 

the load profiles of the boot toe and heel are different on the latter part of the loading. However, 

the peak load is slightly decreasing in 10-msec-pulse loading. This is probably due to the 

decrease of the peak acceleration in the loading pulse. 

Considering that the ATD lower tibia is loaded vertically, the load profiles of the boot heel are

reflected in those of the ATD lower tibia, including its pulse-duration dependency. Therefore, the 

peak load in the ATD lower tibia probably shows the curve with an inflection point as shown in 

-5

0

5

10

15

5 10 15 20 25

Rotation Angle (degree)

Time (msec)

X065_02

X065_04

X065_06

X065_08

X065_10
19

Fig. 19. This hypothesis on the ATD lower-leg loading mechanics will be confirmed in the 

following discussion of the experiment.

3.2 Experimental Results

Representative loading histories of the ATD lower tibia are shown in Fig. 27. In the ATD lower 

tibia, the perpendicular forces Fx and Fy are much smaller than the axial force Fz as in the FEA 

results.

Fig. 27 Representative load histories of the ATD

lower tibia in the experiment, X065_06_03 

Right Leg (∆V = 6.3 m/s, ∆T = 8.6 msec) 

The load histories are shown in Figs. 28–30 for each loading condition and experimental results 

are summarized in Table 6. The deviation of the test results in each loading condition is less than 

10%—less than 5% in the peak load—which is believed to be small enough for the detailed

comparison that follows. 

-2.5

0.0

2.5

5.0

7.5

10.0

12.5

15.0

5 10 15 20 25

Load (kN)

Time (msec)

Lower Tibia, Fx

Lower Tibia, Fy

Lower Tibia, Fz
20

Fig. 28 Load histories of the ATD lower-tibia axial 

direction force Fz in the loading condition

X065_04 (∆V = 6.5 m/s, ∆T = 4.5 msec) 

Fig. 29 Load histories of the ATD lower-tibia axial 

direction force Fz in the loading condition

X065_08 (∆V = 6.4 m/s, ∆T = 8.6 msec) 

0.0

2.5

5.0

7.5

10.0

12.5

15.0

17.5

5 10 15 20 25

Load (kN)

Time (msec)

X065_04_01(Left)

X065_04_01(Right)

X065_04_02(Left)

X065_04_02(Right)

X065_04_03(Left)

X065_04_03(Right)

0.0

2.5

5.0

7.5

10.0

12.5

15.0

17.5

5 10 15 20 25

Load (kN)

Time (msec)

X065_08_01(Left)

X065_08_01(Right)

X065_08_02(Left)

X065_08_02(Right)

X065_08_03(Left)

X065_08_03(Right)
21

Fig. 30 Load histories of the ATD lower-tibia axial 

direction force Fz in the loading condition

X065_10 (∆V = 6.5 m/s, ∆T = 10.6 msec) 

Table 6 Summary of experimental results

As shown in Fig. 31, the differences between the FEA results and experimental results are at 

most 20% in the peak load of the ATD lower tibia. However, as shown in Figs. 11 and 27, the 

0.0

2.5

5.0

7.5

10.0

12.5

15.0

17.5

5 10 15 20 25

Load (kN)

Time (msec)

X065_10_01(Left)

X065_10_01(Right)

X065_10_02(Left)

X065_10_02(Right)

X065_10_03(Left)

X065_10_03(Right)

Avg. / SD 6.5 / 4% 10.6 / 3% 7.2 / 4% 49.1 / 8%

X065_10_03 6.3 / 6.9 10.8 / 10.5 7.0 / 7.4 45.2 / 51.5

X065_10_02 6.2 / 6.6 10.8 / 10.9 7.2 / 7.4 45.1 / 51.8

X065_10_01 6.5 / 6.6 10.1 / 10.6 6.8 / 7.6

Avg. / SD 6.4 / 3% 8.6 / 2% 7.9 / 4% 49.1 / 7%

47.2 / 53.9

X065_08_02 6.6 / 6.1 8.7 / 8.8 7.4 / 8.1 45.0 / 50.0

X065_08_03 6.5 / 6.1 8.7 / 8.4 8.1 / 8.0 49.0 / 51.8

43.1 / 6%

X065_08_01 6.6 / 6.4 8.5 / 8.8 7.7 / 8.2 45.6 / 53.2

Avg. / SD 6.5 / 2% 4.5 / 2% 7.5 / 2%

X065_04_02 6.4 / 6.4 4.5 / 4.5 7.4 / 7.3 41.2 / 45.7

X065_04_03 6.3 / 6.6 4.5 / 4.7 7.4 / 7.4 39.8 / 44.5

Shot

Code

Pulse

Duration, ∆T

Left / Right 

(msec)

Foot

Impactor

Velocity 

Change, ∆V

Left / Right

 (m/s)

Peak

Lower Tibia

Load

Left / Right

(kN)

Applied

Impulse

Left / Right

(Nsec)

X065_04_01 6.4 / 6.7 4.5 / 4.6 7.6 / 7.6 41.4 / 45.8
22

duration of the response pulse in the experiment is significantly longer than that in the FEA on 

the same loading condition. In the CSBES loading test, the loading profile in the floor plate is 

determined by the interaction between the foot impactor and upper mass (such as ATD leg and

boot and the floor plate). Therefore, the velocity histories on the floor plate are not the same as 

those of the FEAs in Fig. 5–7, although the acceleration histories are the same between the floor 

plate in FEA and foot impactor in the experiment. Thus, the actual duration of the loading pulse 

on the boot sole is longer than that in the FEA. This probably leads to the longer-duration 

response in the experiment and should be considered in the following discussion.

As to the lower-leg loading, the tendency is basically the same as that assumed on the FEA 

results; the peak load in the ATD lower tibia shows a curve with an inflection point as shown in 

Fig. 31. However, the tendency is not as clear as that of the FEA results, especially in the shortduration loading (4 msec). 

Fig. 31 Relation between the peak load and pulse

duration in the ATD lower-tibia axial force Fz 

A typical ATD foot motion in the experiment is shown in Fig. 32, and the rotation-angle histories 

of the boot sole are shown in Fig. 33. These show that the differences of the rising time and 

maximum angle of the foot rotation are smaller than those of the FEA results; this is probably 

because the rotational restriction around the ATD ankle joint was not perfectly controlled in the 

experiment. Therefore, together with the longer-duration response, this leads to the smaller 

difference of the peak load in the experiment.

0.0

2.5

5.0

7.5

10.0

12.5

15.0

17.5

0 2 4 6 8 10 12

Peak Load (kN)

Pulse Duration (msec)

FEA, 3.0m/s

FEA, 6.5m/s

FEA, 9.8m/s

Experiment, 6.5m/s
23

Fig. 32 Rotation-angle histories of the boot sole 

against the horizontal line in the experiment

Fig. 33 Representative ATD lower-leg motion in the experiment, X065_08_03 (∆V = 6.3 m/s, 

∆T = 8.6 msec) 

3.3 ATD Lower-Leg Loading Mechanics

The ATD lower-leg loading mechanics suggested by the FEA results have been confirmed 

qualitatively through the experimental results. According to the discussion in Sections 3.1 and 

3.2, the pulse duration of the loading is categorized into 3 types, and the loading mechanics are 

restructured as follows (see also the schematic in Fig. 34):

-5

0

5

10

15

5 10 15 20 25

Rotation Angle (degree)

Time (msec)

X065_04

X065_08

X065_10

5msec 7msec 9msec 11msec

13msec 15msec 17msec 19msec

21msec 23msec

Loading

Duration
24

1) In short-duration loading (2 msec), the boot sole deforms only slightly. Moreover, the foot 

rotation starts after the completion of the loading. Therefore, the loading pulse is not fully 

transmitted to the ATD lower tibia, and the peak load is smaller than that of longerduration loading.

2) In middle-duration loading (4, 6, and 8 msec), both boot-sole deformation and foot rotation 

occur during the loading, and the loading pulse is fully transmitted to the ATD lower tibia. 

Therefore, as shown in Fig. 35, the peak load increases in spite of the decrease in the peak 

acceleration in the loading pulse.

3) In long-duration loading (10 msec), the loading mechanics are almost the same as that of 

the middle-duration loading, and the boot sole and floor mat closely contact. However, the 

decrease in the peak acceleration in the loading pulse probably leads to the decrease in the 

peak load under the close contact between the boot sole and floor mat.
25

Fig. 34 Schematic of the ATD lower-leg loading mechanics for 3 durations of loading 
26

Fig. 35 Relation between the peak load and pulse duration in the ATD lowertibia axial force Fz with the peak acceleration of the loading pulse

4. Conclusions 

In this study, we conducted the FEA of the ATD lower-leg loading to clarify the loading 

mechanics with the existence of the butyl-rubber floor mat. According to the FEA results, we 

proposed a hypothesis that the peak load in the ATD lower tibia had a dependency on the pulse 

duration of loading. We qualitatively confirmed this hypothesis through the ATD lower-leg 

loading test. Further, the ATD lower-leg loading mechanics have been clarified with these 3 

conclusions: 

1) The ATD lower tibia is loaded almost vertically through the boot heel.

2) The peak load in the ATD lower tibia is dependent on the pulse duration of loading; the 

longer-duration loading under the same ∆V leads to the higher peak load in the ATD lower 

tibia, whereas there is an exemption due to the low peak acceleration in the loading pulse.

3) The deformation of the boot sole and rotation of the foot have an effect on the dependency; 

in long-duration loading, the boot sole and floor mat contact more closely, and this 

enhances the transmissibility of the load.

Conclusion 2 is significant. Generally, shock-mitigating countermeasures including floor mats 

tend to decrease the peak value (acceleration, load) of loading. Moreover, that lengthens the 

pulse duration of loading under the law of conservation of momentum. However, according to 

Conclusion 2, this may lead to higher peak load in the ATD lower tibia. Therefore, several 

0

1000

2000

3000

4000

5000

6000

7000

0

2.5

5

7.5

10

12.5

15

17.5

0 2 4 6 8 10 12

Peak Input Acceleration (m/s2)

Peak Lower Tibia Load (kN)

Pulse Duration (msec)

Load_FEA, 3.0m/s

Load_FEA, 6.5m/s

Load_FEA, 9.8m/s

Load_Experiment,

6.5m/s

Acceleration_FEA, 

6.5m/s

Acceleration_Exper

iment, 6.5m/s
27

loading tests with different pulse durations are recommended in the evaluation of 

countermeasures so as to not overestimate the efficiency of the long-duration loading.
28

5. References 

1. Dougherty AL, Mohrle CR, Galarneau MR, Woodruff SI, Dye JL, Quinn KH. Battlefield 

extremity injuries in Operation Iraqi Freedom. Injury. 2009;40(7):772–777. 

2. Belmont PJ, Schoenfeld AJ, Goodman G. Epidemiology of combat wounds in Operation 

Iraqi Freedom and Operation Enduring Freedom: orthopaedic burden of disease. J Surg 

Orthop Adv. 2010;19(1):2–7.

3. Eskridge SL, Macera CA, Galarneau MR, Holbrook TL, Woodruff SI, MacGregor AJ, 

Morton DJ, Shaffer RA. Injuries from combat explosions in Iraq: injury type, location, and 

severity. Injury. 2012;43(10):1678–1682.

4. Test methodology for protection of vehicle occupants against anti-vehicular landmine 

effects. NATO; 2007. Report No.: TR-HFM-090.

5. Golan G, Asaf Z, Ran E, Aizik F. Occupant legs survivability: an assessment through the 

utilization of field blast test methodology. Paper presented at: MABS22. Proceedings of the 

22nd International Symposium on Military Aspects of Blast and Shock; 2012 Nov 4–9; 

Bourges, France.

6. Dong L, Zhu F, Jin X, Suresh M, Jiang B, Sevagan G, Cai Y, Li G, Yang KH. Blast effect on 

the lower extremities and its mitigation: a computational study. J Mech Behav Biomed 

Mater. 2013;28:111–124. 

7. Sakamoto M. Experimental validation of the butyl-rubber finite element (FE) material model 

for the blast-mitigating floor mat. Adelphi (MD); Army Research Laboratory (US). 2015 

Aug. Report No.: ARL-SR-0329.
29

6. List of Symbols, Abbreviations, and Acronyms 

ARL US Army Research Laboratory

ATD anthropomorphic test device

CSBES Crew Survivability Blast Effects Simulator

FE Finite Element

FEA Finite Element Analysis

IED improvised explosive device

kN kilonewton

LSTC Livermore Software Technology Corporation

mm millimeter 

msec millisecond

m/s meters per second 
30

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