Vibration Response Study to Understand Hand-Arm Injury

1. Vibration Response Study to Understand Hand-Arm Injury Shrikant Pattnaik, Robin DeJager-Kennedy Jay Kim Department of Mechanical Engineering, University of Cincinnati, Cincinnati, OHIO

2. 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

3. Presentation summary Vibration analysis models A hypothetical model proposed to explain a cause of vascular system disorder Plan to work on discrete system models

4. Initial FEA Vibration Model Displacement • 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 Strain

5. 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

6. LifeMOD • Building a Model • Segments • Joints • Soft Tissues • Passive Modeling • Contact • Hybrid III Parameters • Active Modeling • Motion Capture integration • LifeMOD 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.

7. Multi-level Approach based in Adams/LifeMod

8. The LifeMOD Suite HandSIM– shrikant KneeSIM LumbarSIM LifeMOD CervicalSIM HipSIM

9. Development of Hand Model

10. Tissue-wrapping Forearm model with the flexor digitorumprofundus set up to slide with respect to the third metacarpal bone. The flexor digitorumprofundus muscle group before slide points are introduced (left) and after (right).

11. Muscle Model (Nonlinearity) A – they are tension only elements B – there is redundancy Muscle Matrix for the active muscle groups

12. Active + Passive contribution

13. Muscle Fatigue • 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

14. 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.

15. FRF Analysis: Input point impedance

16. Strategy of complete Frequency Analysis • Grip the required hand tool • Find the equilibrium • Train the muscle and joints • Find natural Frequencies and modes • 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

17. 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

18. 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 fingertip by a ABACUS model • Contact analysis • Vibration analysis • Review the time histories of the forces in the bone joint and tendon

19. Test/Demo Case I – continue Shown is the example of 1st phalange Muscle and Joints 1st Phalange 2nd Phalange 3rd Phalange Hand

20. Test/Demo Case II Tools pushed Tools lifted • 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

21. Integration Ergonomic Standards Hand Model 5%ile Pressure Data Muscle/Tendon Forces Hand Model 50%ile Joint Forces Motion Capture Hand Model 95%ile Validation Risk+Pain+Discomfort Assessment Consumer Research Database Chosen Hand configurations Test New Designs Pain Locations Guidelines for new packages

22. Data Collection Pressure Mat Vicon Motion Capture Cyber Glove Pressure Map

23. Example Animation with plot

24. 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

25. Wave propagation in Artery wall Surrounding tissue Artery wall, radius R p Fluid flow in artery Artery cross-section Continuity Fluid eq. Moens-Korteweg wave speed

26. Wave propagation in artery wall disturbance Wall-blood wave 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

27. Artery wall as a cylindrical shell natural frequency when n=0 and m=1 Circular cylinder shell simply supported m=1 Equations of motion Assumed solution

28. Rough estimation of resonance condition of a typical rat tail artery Critical Frequencies, f* = 950Hz, 1850Hz • 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? f(n=0,m=1)

29. Comparison of Various Lumped Parameter Hand-Arm Models Lumped parameter hand-arm model A compact tool Vibration response of hand-held tool Vibration response of free-suspended tool Comparison of the prediction of the pair by the model and measurement to qualitatively evaluate hand-arm models

30. 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.

31. Hand-Arm Models Models vary in complexity from 1 DOF to many DOFs. Various values for constants are available for the different models.

32. Data Collection • Acceleration data collected for: • Free suspended • Held in hands • Test procedure is with grinder running freely.

33. Sample Acceleration Data Data collected for DeWalt handheld DW818 grinder

34. 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