Piero Pavan - Academia.edu (original) (raw)

Papers by Piero Pavan

The First IEEE/RAS-EMBS International Conference on Biomedical Robotics and Biomechatronics, 2006. BioRob 2006., 2006

The analysis of the interaction phenomena occurring between biorobots and biological tissues requ... more The analysis of the interaction phenomena occurring between biorobots and biological tissues requires in-depth knowledge of the biomechanical response of tissues. Most phenomenological models are based on hyperelastic formulation and this entails a careful evaluation of the model constitutive parameters, which are defined on the basis of data obtained from experimental tests. The choice of the test to be developed depends on the tissue characteristics to be studied and the procedure to be used to define the parameters . The aim of the present work is to describe a procedure used to define constitutive parameters for hyperelastic soft tissue constitutive models by considering combinations of data from uniaxial, equibiaxial and shear testing conditions of tissue specimens and to discuss the results obtained. The parameters are estimated using a stochastic optimization procedure, considering the complex behaviour of the cost function. The mechanical tests to be adopted and their combination are discussed with regard to the reliability and efficiency of the procedure to be used in the numerical modelling of tissue-robot interaction phenomena.

Proceedings of the Institution of Mechanical Engineers, Part P: Journal of Sports Engineering and Technology, 2014

The analysis of interaction phenomena occurring between the plantar region of the foot and insole... more The analysis of interaction phenomena occurring between the plantar region of the foot and insole was investigated using a combined experimental-numerical approach. Experimental data on the plantar pressure for treadmill walking of a subject were obtained using the Pedar Ò system. The plantar pressure resultant was monitored during walking and adopted to define the loading conditions for a subsequent static numerical analysis. Geometrical configuration of the foot model is provided on the basis of biomedical images. Because the mechanical behaviour of adipose tissues and plantar fascia is the determinant factor in affecting the paths of the plantar pressure, specific attention was paid to define an appropriate constitutive model for these tissues. The numerical model included sole and insole, providing for friction contact conditions between foot-insole and insole-sole pairs as well. Two different numerical analyses were performed with regards to different loading conditions during the gait cycle. The plantar pressure peaks predicted by the numerical model for the two loading conditions are 0.16 and 0.12 MPa, and 0.09 and 0.12 MPa in the posterior and anterior regions of the foot, respectively. These values are in agreement with experimental evidence, showing the suitability of the model proposed.

Volume 2: Automotive Systems, Bioengineering and Biomedical Technology, Fluids Engineering, Maintenance Engineering and Non-Destructive Evaluation, and Nanotechnology, 2006

Soft biological tissues show a strongly non linear and time-dependent mechanical response and und... more Soft biological tissues show a strongly non linear and time-dependent mechanical response and undergo large strains under physiological loads. The microstructural arrangement determines specific anisotropic macroscopic properties that must be considered within a ...

Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine, 2014

This work aims to present a constitutive model suitable to interpret the biomechanical response o... more This work aims to present a constitutive model suitable to interpret the biomechanical response of human pericardial tissues. The model is consistent with the need of describing large strains, anisotropy, almost incompressibility, and time-dependent effects. Attention is given to human pericardial tissue because of the increased interest in its application as a substitute in reconstructive surgery. Specific, even limited, experimental investigation has been performed on human samples taken from surgical grafts in order to verify the capability of the constitutive model in supplying a correct description of tissue mechanical response. Experimental data include uni-axial tensile tests and stress relaxation tests up to 300 s, developed along different directions of the tissue. The grafts tested show different mechanical characteristics for what concern the level of anisotropy of the tissue. The constitutive model proposed shows to adapt to the different configurations of the human peri...

Acta of bioengineering and biomechanics / Wrocław University of Technology, 2014

Numerical models represent a powerful tool for investigating the biomechanical behavior of articu... more Numerical models represent a powerful tool for investigating the biomechanical behavior of articular cartilages, in particular in the case of complex conformation of anatomical site. In the literature, there are complex non-linear-multiphase models for investigating the mechanical response of articular cartilages, but seldom implemented for the analysis of high organized structure such as the foot. In the present work, the biomechanical behavior of foot cartilage is investigated by means of a fiber-reinforced hyperelastic constitutive model. The constitutive parameters are obtained through the comparison between in vitro experimental indentation tests on cartilage and numerical analysis data interpreting the specific experimental conditions. A finite element model of the hindfoot region is developed. Particular attention is paid to model cartilage in order to respect its morphometric configuration, including also the synovial capsule. The reliability of the procedure adopted is eval...

European Journal of Sport Science, 2014

Valid and reliable accessible measures of balance are required in a health-related fitness test b... more Valid and reliable accessible measures of balance are required in a health-related fitness test battery, both in the general population and in groups with special needs. For this purpose, the capability of the Wii Balance Board (WBB) in evaluating standing balance was analysed and compared with a laboratory-graded force platform (FP). A 30-s double limb standing test with open and closed eyes was performed by 28 individuals (12 male and 16 female, mean age = 23.8, SD = ±2.7 years). A simple method of acquisition of the centre of pressure (CoP) over time was applied to compare WBB and FP simultaneously on the same signal. User-defined software was developed to obtain the CoP from WBB over time and the resulting related measures and graphical representations. The comparison of measures, such as sway path and maximum oscillations along the anterior-posterior and medial-lateral direction, obtained with the FP and the WBB shows that the latter, in conjunction with the user-defined developed software, can be appropriate, considering prescribed limits, and an easy-to-use tool for evaluating standing balance.

Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2009

According to the standard surgical protocols, the press fit is obtained inserting an implant in a... more According to the standard surgical protocols, the press fit is obtained inserting an implant in a drilled hole that is provided with a lower diameter. In this way, it is induced a relevant strain state in the peri-implant bone that favors the primary stability of the implant. Experimental evaluation of this phenomenon is very difficult and does not offer a complete set of information. A numerical analysis is adopted to describe the mechanical phenomena occurring in the peri-implant tissue. At this purpose, suitable constitutive models are adopted for the bone tissue for the evaluation of plastic and viscous effects caused by the real strain field induced. Specific numerical procedures are developed to model the press fit action of an implant against the surrounding bone tissue and the subsequent viscoelastoplastic effects determined. The results of the numerical analysis make it possible to estimate the deformation caused by the insertion of the implant and the evolutionary trend after insertion by considering the inelastic time-dependent behavior of bone tissue in peri-implant region. According to the viscous characteristic of the bone tissue, the numerical analyses show a stress relaxation in the order of 30% around the implant.

Journal of Biomechanics, 2006

Journal of Biomechanical Engineering, 2008

The periodontal ligament (PDL), as other soft biological tissues, shows a strongly non-linear and... more The periodontal ligament (PDL), as other soft biological tissues, shows a strongly non-linear and time-dependent mechanical response and can undergo large strains under physiological loads. Therefore, the characterization of the mechanical behavior of soft tissues entails the definition of constitutive models capable of accounting for geometric and material non-linearity. The microstructural arrangement determines specific anisotropic properties. A hyperelastic anisotropic formulation is adopted as the basis for the development of constitutive models for the PDL and properly arranged for investigating the viscous and damage phenomena as well to interpret significant aspects pertaining to ordinary and degenerative conditions. Visco-hyperelastic models are used to analyze the time-dependent mechanical response, while elasto-damage models account for the stiffness and strength decrease that can develop under significant loading or degenerative conditions. Experimental testing points out that damage response is affected by the strain rate associated with loading, showing a decrease in the damage limits as the strain rate increases. These phenomena can be investigated by means of a model capable of accounting for damage phenomena in relation to viscous effects. The visco-hyperelastic-damage model developed is defined on the basis of a Helmholtz free energy function depending on the strain-damage history. In particular, a specific damage criterion is formulated in order to evaluate the influence of the strain rate on damage. The model can be implemented in a general purpose finite element code. The accuracy of the formulation is evaluated by using results of experimental tests performed on animal model, accounting for different strain rates and for strain states capable of inducing damage phenomena. The comparison shows a good agreement between numerical results and experimental data.

Journal of Adhesion Science and Technology, 2009

... 8. AN Natali, PG Pavan and AL Ruggero, Dental Mater. 22, 388 (2006). 9. SC Cowin (Ed.), Bone ... more ... 8. AN Natali, PG Pavan and AL Ruggero, Dental Mater. 22, 388 (2006). 9. SC Cowin (Ed.), Bone Mechanics Handbook. CRC Press, Boca Raton, FL (2001). 10. SC Cowin and Q.-C. He, J. Biomech. 38, 141 (2005). 11. A. É. Melnis, IV Knets and PA Moorlat, Mech. ...

IEEE Engineering in Medicine and Biology Magazine, 2000

Dental Materials, 2009

d e n t a l m a t e r i a l s 2 5 ( 2 0 0 9 ) 573-581 a v a i l a b l e a t w w w . s c i e n c e... more d e n t a l m a t e r i a l s 2 5 ( 2 0 0 9 ) 573-581 a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . i n t l . e l s e v i e r h e a l t h . c o m / j o u r n a l s / d e m a

Connective Tissue Research, 2010

A constitutive model is proposed to describe the mechanical behavior of the plantar fascia. The m... more A constitutive model is proposed to describe the mechanical behavior of the plantar fascia. The mechanical characterization of the plantar fascia regards the role in the foot biomechanics and it is involved in many alterations of its functional behavior, both of mechanical and nonmechanical origin. The structural conformation of the plantar fascia in its middle part is characterized by the presence of collagen fibers reinforcing the tissue along a preferential orientation, which is that supporting the major loading. According to this anatomical evidence, the tissue is described by developing an isotropic fiber-reinforced constitutive model and since the elastic response of the fascia is here considered, the constitutive model is based on the theory of hyperelasticity. The model is consistent with a kinematical description of large strains mechanical behavior, which is typical of soft tissues. A fitting procedure of the constitutive model is implemented making use of experimental curves taken from the literature and referring to specimens of human plantar fascia. A satisfactory fitting of the tensile behavior of the plantar fascia has been performed, showing that the model correctly interprets the mechanical behavior of the tissue in the light of comparison to experimental data at disposal. A critical analysis of the model with respect to the problem of the identification of the constitutive parameters is proposed as the basis for planning a future experimental investigation of mechanical behavior of the plantar fascia.

Computer Methods in Biomechanics and Biomedical Engineering, 2002

The present work pertains to a numerical investigation of the casting process of titanium devices... more The present work pertains to a numerical investigation of the casting process of titanium devices adopted for dental implantology. The analysis of the titanium framework that connects different abutments, in a multi-implant configuration, is performed evaluating the characteristics of the material that depend on the manufacturing procedure. The connecting bar is obtained by a foundry process that is controlled through a numerical simulation by using a control volume technique. This analysis leads to the possibility to have detailed information on the process and control of the quality of the microstructure of the material produced that proves to be highly beneficial for defining mechanical properties. On the basis of the results obtained, a subsequent stress analysis can be performed, addressed to highlight critical conditions. Functional response of the whole bar-implant framework is studied by means of a numerical model, based on the geometric element method. This technique is particularly suited for describing complex morphology of the implant site. The present approach addresses a higher quality definition of the reliability of the device used in dental practice and represents a valuable tool in assisting optimisation procedures pertaining to manufacturing. In fact, the improvement of titanium devices is intended not only with regard to their mechanical performances, but also to requirements pertaining to manufacturing and clinical practice.

Computer Methods and Programs in Biomedicine, 2010

c o m p u t e r m e t h o d s a n d p r o g r a m s i n b i o m e d i c i n e 1 0 0 ( 2 0 1 0 ) 1... more c o m p u t e r m e t h o d s a n d p r o g r a m s i n b i o m e d i c i n e 1 0 0 ( 2 0 1 0 ) 158-165 Finite element analysis a b s t r a c t The biomechanical efficiency of oral implants is deeply influenced by mechanical properties of cortical and trabecular bone in the jaw and, in particular, in the peri-implant region. When the mechanical response of the implant-bone system is analysed by means of numerical models, the effective mechanical properties of bone and the possible change as a function of spatial position must be carefully considered. The procedure presented provides for the attribution of the mechanical properties of bone, considered as anisotropic elastic material, as a function of the spatial position making use of Fourier series and polynomial functions. The procedure is implemented in a general purpose finite element software, adopted to develop biomechanical analyses of prosthetic systems. This procedure allows for an accurate representation of bone tissue properties. Results pertaining to the analysis of commercial oral implants show the potential of the method adopted.

Meccanica, 2002

A numerical analysis of the biomechanical response of the periodontal ligament is presented. A mu... more A numerical analysis of the biomechanical response of the periodontal ligament is presented. A multi-phase media formulation is developed for representing soft tissue constitutive models, and implemented in a specific finite element code. It is possible to simulate the presence of liquid phase permeating the extracellular material and to interpret the consequent time-dependent behaviour due to the fluid flux through periodontal ligament. The analysis of the mobility of human upper incisor, under the application of short time transversal forces, is reported. The numerical results are compared with in vivo experimental data. The agreement of different approaches confirms the effectiveness of the proposed model for investigation of the biomechanical behaviour of periodontal ligament under application of low magnitude forces, and represents the basis for the definition of a general multi-phase constitutive model.