Kinematic model of savannah monitor locomotion

Postprint (published version

Coupling finite element analysis and multibody system dynamics for biological research

Flexible Multibody System Dynamics (FMSD) is a simulation technique that can be used to study the behavior of the mechanical systems that consists of one or more deformable bodies. A deformable body can be modeled using a number of approaches while the floating frame of reference formulation is a widely used approach. In that approach, flexibility within Multibody System Dynamics (MSD) is described by employing the Finite Element Analysis (FEA) with a modal reduction approach. The applicability of an FMSD in the feeding mechanism of vertebrate structures is tested in order to utilize the potential of the method in biological research. Flexible Multibody System Dynamics is explored studying the feeding mechanism in a skull of Edingerella madagascariensis. Firstly, a static structural analysis is done using FEA and secondly, dynamic solutions based on FMSD are obtained by varying the number of deformation modes used in the modal reduction analysis. The conclusion is that use of this approach is feasible and efficient for the study of feeding mechanisms in vertebrate structures when a dynamic response should be evaluated.Peer ReviewedPostprint (published version

Estimating Lower Limb Skeletal Loading

Introduction: Osteoporosis, accidents and subsequent bone fractures cause suffering on an individual level, as well as an economical burden to the society (Ortiz-Luna et al., 2009; Stevens & Olson, 2000). It has been estimated that, in Finland alone, between 30,000 to 40,000 osteoporosis-related fractures occur annually and that 400,000 Finnish people have osteoporosis (Duodecim, 2008). There are a few potential ways of preventing bone fracture, i.e. strengthening bones and/or preventing falls (Ortiz-Luna et al., 2009; Stevens & Olson, 2000). In order to withstand prevalent loading without breaking; while remaining relatively light in weight to allow for locomotion, bones have the ability to adapt their structure to functional loading (Frost, 2000; 2003; Sievänen, 2005). It has been demonstrated that physical activity affects the weight bearing skeleton more than the non-weight bearing one (Mikkola et al., 2008), and it may therefore be argued that, the skeleton is loaded mainly by locomotory actions that impart strains on bones. Bones are loaded in daily activities by muscles accelerating and decelerating body segments and resisting the pull of gravity (Burr et al., 1996). Since falling is the single most significant bone fracture risk factor (Järvinen et al., 2008) and up to 90% of fractures are caused by falls (Cummings & Melton, 2002; Stevens & Olson, 2000; Wagner et al., 2009), exercise can be viewed as a potential intervention for fracture prevention. Exercise seemingly has a potential of both reducing the fall rate and also increasing bone strength. In agreement, exercise interventions have been shown to successfully decrease the fall rate (Kemmler et al., 2010; Korpelainen et al., 2006), to strengthen the bones and to decrease the fracture rate (Korpelainen et al., 2006; Sinaki et al., 2002). [Continues, please see the article]nonPeerReviewe

DETC2009-86831 A DYNAMIC SIMULATION OF A HUMAN GAIT USING THE HYBRID MUSCLE MODEL AND A QCT-BASED FLEXIBLE TIBIA DETC2009-86831

ABSTRACT The flexible multibody simulatio

Coupling finite element analysis and multibody system dynamics for biological research

Flexible Multibody System Dynamics (FMSD) is a simulation technique that can be used to study the behavior of the mechanical systems that consists of one or more deformable bodies. A deformable body can be modeled using a number of approaches while the floating frame of reference formulation is a widely used approach. In that approach, flexibility within Multibody System Dynamics (MSD) is described by employing the Finite Element Analysis (FEA) with a modal reduction approach. The applicability of an FMSD in the feeding mechanism of vertebrate structures is tested in order to utilize the potential of the method in biological research. Flexible Multibody System Dynamics is explored studying the feeding mechanism in a skull of Edingerella madagascariensis. Firstly, a static structural analysis is done using FEA and secondly, dynamic solutions based on FMSD are obtained by varying the number of deformation modes used in the modal reduction analysis. The conclusion is that use of this approach is feasible and efficient for the study of feeding mechanisms in vertebrate structures when a dynamic response should be evaluated.Peer Reviewe

Merge of motion analysis, multibody dynamics and finite element method for the subject-specific analysis of cartilage loading patterns during gait : differences between rotation and moment-driven models of human knee joint

Understanding joint loading is important when evaluating sports training methods, sports equipment design, preventive training regimens, post-op recovery procedures, or in osteoarthritis' etiology research. A number of methods have been introduced to estimate joint loads but they have been limited by the lack of accuracy in the joint models, including primarily the lack of patient-specific motion inputs in the models with sophisticated, fibril-reinforced material models. The method reported here records and applies patient-specific human motion for in-depth cartilage stress estimation. First, the motion analysis of a subject was conducted. Due to skin motion, multibody simulation was used to correct motion capture. These data was used as an input in a finite element model. The model geometry was based on magnetic resonance imaging and cartilage was modeled as a fibril-reinforced poroviscoelastic material. Based on the experimental motion data (motion analysis and multibody simulation), two models were created: a rotation-controlled and a moment-controlled model. For comparison, a model with motion input from the literature was created. The rotation-controlled model showed the most even stress distribution between lateral and medial compartments and smallest stresses and strains in a depth-wise manner. The model based on the literature motion simulated very high stresses and uneven stress distribution between the joint compartments. Our new approach to determine dynamic knee cartilage loading enables estimations of stresses and strains for a specific subject over the entire motion cycle.Peer reviewe