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Vibration Response Study to Understand Hand-Arm Injury

Shrikant Pattnaik, Robin DeJager-Kennedy Jay Kim

Department of Mechanical Engineering, University of Cincinnati, Cincinnati, OHIO

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Research focus: how vibration affects hand and arm injuries

• Develop hypotheses that can explain the mechanism with scientific rationale – Musculoskeletal disorder– Vascular disorder

• Develop scientific approaches– Engineering models– Develop numerical analysis methods– Direct or indirect Experimental validation

Presentation summary

• Vibration analysis models• A hypothetical model proposed to explain a

cause of vascular system disorder • Plan to work on discrete system models

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Initial FEA Vibration Model

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Goals: Obtain basic data for further analysis of Musculoskeletal and vascular systems •Step 1 : Pre compression, non linear contact analysis•Step 2 : Extraction of natural modes•Step 3 : Steady state dynamic analysis

Displacement

Strain

Issues

• Overly simplified boundary conditions and models– Un-modeled parts, initial configuration/posture, grip,

significantly influences natural modes and dynamic responses significantly

– Effects of grip force and length of handling are not difficult to be considered

• Overly simplified muscle forces– Active tendon forces are not included– Most finger musculo-tendon structure extends to

elbow

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LifeMOD

Building a ModelSegmentsJointsSoft Tissues

Passive ModelingContactHybrid III Parameters

Active ModelingMotion Capture integrationLifeMOD Inverse and Forward dynamics

Post Processing and Export

• The LifeMOD Biomechanics Modeler is a plug-in module to the ADAMS physics engine.

• LifeMOD allows full functionality of ADAMS/View.

• Human models can be combined with any ADAMS model for full dynamic interaction.

Multi-level Approach based in Adams/LifeMod

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The LifeMOD Suite

CervicalSIM

KneeSIM

LifeMOD

LumbarSIM

HipSIM

HandSIM – shrikant

Development of Hand Model

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Tissue-wrapping

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Forearm model with the flexor digitorum profundus set up to slide with respect to the third metacarpal bone.

The flexor digitorum profundus muscle group before slide points are introduced (left) and after (right).

Muscle Model (Nonlinearity)

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Muscle Matrix for the active muscle groups

A – they are tension only elementsB – there is redundancy

Active + Passive contribution

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Muscle Fatigue

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• Tetanic Frequency full motor unit recruitment

• maintained for a short period of time, 6 s

• 70% max the blood flow is completely occluded and fatigue

• hyperbolic relationship with an asymptote at roughly 15% of maximum strength

Frequency Analysis

• In terms of passive muscle, this means that at very low or high frequencies the forcing function and muscle response are practically in phase

• elastically dominated by either the series elastic element (KSE) for very high frequencies (i.e., the dashpot cannot respond sufficiently quickly, eliminating the parallel elastic element from the model) or

• by a combination of both elastic elements KSE/(KSE + KPE) for very low frequencies (i.e., the dashpot responds, stretching the parallel elastic element with it).

• Around the critical break frequency the muscle is fully viscoelastic with the dashpot involved.

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FRF Analysis: Input point impedance

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Strategy of complete Frequency Analysis

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o Grip the required hand toolo Find the equilibrium o Train the muscle and jointso Find natural Frequencies and modeso Identify critical elements from the natural modes

• Forced response for particular configuration• Introduce fatigue model – endurance analysis• connect with individual flexible part in

Adams/Flex

Integration of Rigid + Flexible body

• Originally ADAMS – rigid body with 3 translation and 3 rotational DOF.

• Adams/Flex, flexible body • Deformation = linear combination of linear mode shapes from

FEA or Experimental modal analysis• Component Mode Synthesis – selected modes transferred

using MNF (mode neutral files) from say Abaqus. • Generalized stiffness is diagonalized, Mass matrix formulated

using inertia invariants, Damping specified as fraction of critical damping.

• Subset of mode shapes goes to solver

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Test/Demo Case I

• Initial Equilibrium Analysis using the full hand-arm model; for the given contact force; – Find how muscles/tendons are loaded– Find how joint forces are loaded

• Detail analysis of the fingertipby a ABACUS model– Contact analysis– Vibration analysis– Review the time histories

of the forces in the bone jointand tendon

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Test/Demo Case I – continue

1st Phalange 2nd Phalange3rd PhalangeHand

19Muscle and Joints

Shown is the example of 1st phalange

Test/Demo Case II

• LifeMod model of Hand-Arm• Find Gripping force to hold two different type of tools• Ensuing vibration analysis

– Response characteristics; comparison to discrete models; possible experiments

20Tools lifted

Tools pushed

Integration

Hand Model 5%ilePressure Data

Motion Capture

Hand Model50%ile

Hand Model95%ile

Risk+Pain+Discomfort Assessment

Muscle/Tendon Forces

Joint Forces

Ergonomic Standards

Test New Designs

Guidelines for new packages

Validation

Consumer Research Database Pain Locations

Chos

en H

and

confi

gura

tions

Data CollectionPressure Mat Vicon Motion Capture

Cyber GlovePressure Map

Example Animation with plot

Vascular system disorder: A view from wave propagation / fluid-structure dynamics

• Desire to understand why vibration is detrimental to vascular disorder

• Blood in an artery comprise a fluid-structure system

• Optimal wave propagation condition may be responsible

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Wave propagation in Artery wall

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2

2

2

2

2tWR

xPA

kW

REtKWt

RWEWKP

~22

RWEtEttRWKP

2

2

2

2

~2

tP

kR

xPA

2 W uR dx A dxt x

tu

xP

2

~2 R

EtkRCMoens-Korteweg wave speed

Fluid flow in artery

Continuity

Fluid eq.

Artery cross-section

Artery wall, radius R

Surrounding tissue

p

Wave propagation in artery wall

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cf

/ 2L

Wall-blood wave

wave speed c

Section behaves like a cylindrical shell of n=0 mode (membrane mode)

Critical condition: when the resonance frequency of the cylindrical membrane of length coincides with / 2L /c f

disturbance

22R Etc k

R

Artery wall as a cylindrical shell

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Circular cylinder shell simply supported

01

01

01

23

233

2

23

2

2

tuh

aNQ

axQ

tuh

aQN

axN

tuhN

axN

x

x

xxxx

Assumed solution

)(cossin),(

)(sinsin),(

)(coscos),(

3

nLxmCxU

nLxmBxU

nLxmAxU x

Equations of motionm=1

natural frequency when n=0 and m=1

Rough estimation of resonance condition of a typical rat tail artery

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5.08.01.0

/1050

303

mmrmmh

mkg

kPaE

0 1000 2000 3000 4000 5000 60000

0.0002

0.0004

0.0006

0.0008

0.001

0.0012

0.0014

0.0016

f vs f(m=1,n=0)

ff(m=1,n=0)

Freqnecy (Hz)

Leng

th (m

)

fcL

Lfc

2

2

Critical Frequencies, f* = 950Hz, 1850Hz

f(n=0,m=1)

1, 0 ( )n mf f L

The above is only a very preliminary estimation•Data should be refined•Is the surrounding tissue has a more added mass effect or Winkler foundation effect?

Comparison of Various Lumped Parameter Hand-Arm Models

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Lumped parameter hand-arm model

A compact tool

2me

e

toolM

Vibration response of hand-held tool

2me

e

toolM

Vibration response of free-suspended tool

Comparison of the prediction of the pair by the model and measurement to qualitatively evaluate hand-arm models

Research Plan

• Select models to compare.• Collect acceleration data for two or three

tools.• Use data to determine input force to apply to

models.• Simulate response of models.• Compare simulated response to measured

response of hand-held tool.

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Hand-Arm Models

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• Models vary in complexity from 1 DOF to many DOFs.

• Various values for constants are available for the different models.

Data Collection

• Acceleration data collected for:– Free suspended– Held in hands

• Test procedure is with grinder running freely.

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Sample Acceleration Data

330 500 1000 1500 2000 2500 3000 3500

-250

-200

-150

-100

-50

0

50

100

150

200

Accelerometer Data, Accel 1, X axis

Sample #

Acc

eler

atio

n, m

/s2

0 500 1000 1500 2000 2500 30000

50

100

150

200

250

RSS, Accel 1

Sample #

Acc

eler

atio

n, m

/s2

Data collected for DeWalt handheld DW818 grinder

Open Discussions

• Refinement of the models• Expansion or simplification of the models• Possible validations

– Direct / indirect validations– Qualitative / quantitative validations

• Application ideas• Criticisms and suggestions

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