PhD Fekete - SZIE version - 2.2 - Szent István Egyetem

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Materials and Methods 3.6. The new numerical-kinematical model 3.6.1. Introduction The currently applied numerical approaches in contact mechanics can be divided into two main groups: Finite Element Method and approaches based on Multibody dynamics. The Finite Element Method is undisputedly the most powerful numerical method in the field of contact mechanics. It is well suited for particularly high accuracy requirements but with that, a very high computational effort is coupled for contact treatment that causes some practical difficulties e.g. very long computation times, divergence problems, etc. In certain situation when a modestly decreased accuracy is suitable and deformation is not primarily in interest, multibody approach can also model the contact with acceptable precision and considerably less computational effort compared to Finite Element methods. In addition, considering the practicality how multibody software can deal with very complex geometries in dynamic contact situations, it is a suitable choice for modelling the knee joint during squatting. As for the software, MSC.ADAMS has been chosen to carry out kinematical and kinetical simulations. MSC.ADAMS is worldwide used program that helps engineers to study moving parts, elements, or even complete systems and improve their performances. In contrast with simple CAD systems, MSC.ADAMS incorporates real physics by simultaneously solving linear or non-linear Ordinary Differential Equations (ODE) and nonlinear Differential-Algebraic Equations (DAE) for kinematics, statics, quasi-statics, and dynamics. 3.6.2. Limitations and advancements of the model In this part of the thesis, the investigation is restricted to the sliding-rolling ratio and the contact kinetics under standard squat movement. The new numerical-kinematical model includes some simplifications as follows: a) The bones, such as the tibia, patella and femur were assumed as rigid bodies, since the influence of deformation in this study is neglected, b) The patellar tendon modelled as an inextensible spring, c) The quadriceps is modelled as one single linear spring, d) No cruciate ligaments were modelled. The new model complements the earlier models in some extent, thus it holds new features: α β γ δ The numerical-kinematical model is three-dimensional, based on commercial prosthesis geometries, Both lateral and medial sliding-rolling ratio can be studied due to the three dimensional surfaces, Realistic friction condition is considered between the contact surfaces e.g. patellofemoral and tibiofemoral connection, Kinetical investigation is also possible with this model. – 108 –
3.6.3. Geometrical models Materials and Methods Geometric models were mapped by CCD camera system by the use of five prosthesis geometries. These prostheses are namely: − − − − − Prosthesis 1.: Prototype from the SZIU, non-commercial, Prosthesis 2.: Biotech TP Primary knee, Prosthesis 3.: Biotech TP P/S Primary knee, Prosthesis 4.: BioMet Oxford Partial knee, Prosthesis 5.: DePuy PFC. The geometric models were mapped with a Breuckmann OptoTop-HE 3D monochrome scanner with the 75 µm of resolution at the <strong>Szent</strong> <strong>István</strong> University, by the following steps (Figure 3.29 and Figure 3.30). Figure 3.29. Scanning settings Figure 3.30. Setting the focus (left) and actual scanning (right) The scanned surfaces were processed and assembled in the OptoCat 2010 program and saved as STL files. The STL files (Stereolithography) are widely used in the 3D prototyping or computer aided manufacturing. However, the STL is built up as an unstructured, triangulated surface, which cannot be directly used in a CAD system, but needs to be converted into either a surface or a body model. – 109 –
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SZENT ISTVÁN UNIVERSITY KINETICS A
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CONTENTS NOMENCLATURE AND ABBREVIAT
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NOMENCLATURE AND ABBREVIATIONS F pf
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ψ : Angle between the quadriceps t
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v CTt : Tangential velocity compone
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Introduction 1. INTRODUCTION AND OB
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1.3. Aims of the PhD thesis Introdu
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Literature review 2. LITERATURE REV
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Literature review Figure 2.3. The f
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Literature review Figure 2.6. Patel
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Literature review Figure 2.8. Compo
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Literature review The knee carries
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Literature review For this reason,
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Literature review Figure 2.12. Thre
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Literature review As a short overvi
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Literature review Moment arm 60 [mm
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Literature review I. They demonstra
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Literature review The presented mod
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Literature review ε angle [˚] 100
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Literature review Fpf/Fq [-] 1.2 1
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Literature review β angle [˚] Mal
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Literature review Figure 2.35. Mech
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Literature review Moment arm 60 [mm
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Literature review Let us follow the
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Literature review Finally, the pate
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Literature review Figure 2.43. Tota
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Literature review One great advanta
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Literature review Implant wear is t
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2.3.2. General numerical models Lit
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a) The tibia plateau is a flat surf
Page 61 and 62: Literature review From their calcul
Page 63 and 64: Literature review Although a simila
Page 65 and 66: Literature review Slide/Roll [-] 1
Page 67 and 68: Literature review Figure 2.62. Mult
Page 69 and 70: Materials and Methods 3.1. Methodol
Page 71 and 72: Materials and Methods For the sake
Page 73 and 74: Materials and Methods 9 th QUESTION
Page 75 and 76: Materials and Methods 3.3. New anal
Page 77 and 78: Materials and Methods 3.3.3. Free-b
Page 79 and 80: Materials and Methods Figure 3.6. F
Page 81 and 82: Materials and Methods By the introd
Page 83 and 84: Materials and Methods 3.4. Experime
Page 85 and 86: Materials and Methods Figure 3.7. C
Page 87 and 88: Materials and Methods All of the pa
Page 89 and 90: Materials and Methods 3.4.5. Measur
Page 91 and 92: x c Materials and Methods ∑ Fi
Page 93 and 94: Materials and Methods Probability D
Page 95 and 96: Materials and Methods Figure 3.18.
Page 97 and 98: Materials and Methods By doing so,
Page 99 and 100: 3.4.7.2. Steps of the approach Mate
Page 101 and 102: Materials and Methods All the funct
Page 103 and 104: Materials and Methods β [º] 40 20
Page 105 and 106: Materials and Methods If the center
Page 107 and 108: Materials and Methods By the use of
Page 109 and 110: Materials and Methods Thus, one pri
Page 111: Materials and Methods I. The patter
Page 115 and 116: Materials and Methods − − −
Page 117 and 118: 3.6.4.3. Contact [MSC.ADAMS] Materi
Page 119 and 120: Materials and Methods Besides the k
Page 121 and 122: Materials and Methods By multiplyin
Page 123 and 124: Results 4. RESULTS 4.1. Results reg
Page 125 and 126: Results This closely equal percenta
Page 127 and 128: Results Fpf/BW [-] 8 Fekete et al.
Page 129 and 130: Results In reality, human subjects
Page 131 and 132: Results 4.2. Results regarding the
Page 133 and 134: Results 0.8 Χ [-] 1 Sliding-rollin
Page 135 and 136: Results Χ [-] 1 Sliding-rolling ra
Page 137 and 138: Results Among the tested prostheses
Page 139 and 140: Results χ [-] 1 Averaged sliding-r
Page 141 and 142: Results Χ [-] 1 Sliding-rolling ra
Page 143 and 144: 4.3. New scientific results Results
Page 145 and 146: Results 3 rd Thesis: Based on the m
Page 147 and 148: Conclusions and Suggestions 5. CONC
Page 149 and 150: Conclusions and Suggestions Suggest
Page 151 and 152: Summary 6. SUMMARY In this doctoral
Page 153 and 154: Appendix APPENDIX A1. Bibliography
Page 155 and 156: Appendix [31] Csizmadia B. M., Nán
Page 157 and 158: Appendix [61] Gill H. S., O’Conno
Page 159 and 160: Appendix [93] Klebanov B. M., Barla
Page 161 and 162: Appendix [123] Nägerl H., Frosch K
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Appendix [154] Reuben J. D., McDona
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Appendix [187] Wahrenberg H., Lindb
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Appendix 6. Fekete G., Kátai L.: M
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Appendix Figure 3. Setting Stitchin
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Appendix Fpf/Fq [-] 1.2 h = 6 mm h
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Appendix η1 angle [˚] 6 Hirokawa
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Appendix Figure 13. Mechanical mode
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Appendix Ψ angle [˚] 10 Van Eijde
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Appendix Figure 19. Mechanical mode
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Appendix - 177 -
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PhD Fekete - SZIE version - 2.2 - Szent István Egyetem

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