J.C. Pimenta Claro

University of Minho · Mechanical Engineering Department (DEM)

The intervertebral disc (IVD) is a central piece for spine biomechanics. When the IVD fails, there is a high chance that one is suffering from degenerative disc disease (DDD), which is one of the largest health problems faced worldwide. However, DDD and back pain are also strictly related to the other structures in the spine, such as the vertebral...

Friction exists in most mechanical systems, and it can have a major influence on their dynamic performance and operating conditions. As a consequence of frictional contact phenomena, energy is dissipated and the state of a system can change slowly and rapidly, depending on the nature of the contact, continuous or impact condition. Other effects ass...

[Link to Extended Abstract: http://www.ibertrib-2017.dem.uminho.pt/PDFs/61-CO.pdf] Hydrodynamic journal bearings have been long used in rotating machinery for the support of high speed/highly loaded shafts. Their design procedure has evolved over the years, often involving a combination of numerical simulations and empirical data. Recent trends in...

Programa do 7º Congresso Nacional de Biomecânica - Program of the 7th National Congress on Biomechanics

Ischaemic heart diseases are a global health problem that have been increasing in the recent years [1]. Most of ischaemic heart diseases is caused by atherosclerosis, a clinical pathology characterized by the deposition of fatty material on the arteries walls what may lead to thickening, hardening and blocking of these blood vessels, reducing the b...

This study is aimed at examining and comparing several friction force models dealing with different friction phenomena in the context of multibody system dynamics. For this purpose, a comprehensive review of present literature in this field of investigation is first presented. In this process, the main aspects related to friction are discussed, wit...

This study is aimed at examining and comparing several friction force models dealing with different friction phenomena in the context of multibody system dynamics. For this purpose, a comprehensive review of present literature in this field of investigation is first presented. In this process, the main aspects related to friction are discussed, wit...

The intervertebral disc is submitted to complex loading during its normal daily activities which are responsible for variations of the hydrostatic pressure in its structure. Thus, the determination of the magnitude of failure hydrostatic pressure is essential as a potential for the evaluation of the mechanisms that promote the weakening and the dis...

Purpose: The study of axial loading is essential to determine the properties of intervertebral disc. The objectives of this work are (1) to quantify the mechanical properties of porcine lumbar intervertebral discs under static and cyclic compressive loading and (2) to determine the parameters of a five-parameter rheological model for porcine and co...

The intradiscal pressure has been essential for prevent the spinal complaints by forming a basis for clinical advice to promote the correct sitting postures. As a consequence, it is evident the need of an accurate method for measure the intradiscal pressure, to better understand the disc response to hydrostatic pressure fluctuations. Numerous revie...

Degenerative disc disease is the most common cause of low back pain, affecting 70-85% of the general population at some time in life. Considering this fact, it is essential to characterize the behavior of the intervertebral disc and its degeneration mechanisms. To study this problem, numerical modeling presents itself as an advantageous approach, b...

Evaluation of the loads on spine is very important since it is closely related to the spine biomechanics and its pathologies. In this study, a simplified multibody model of the human skeleton is presented, able to estimate forces and moments acting on the lumbar spine during simple daily activities. The model was validated by comparing the forces a...

A novel 3D multibody system (MBS) model of the human lumbar spine is presented, allowing the dynamic study of the entire lumbar spine and/or of each one of its intervertebral discs (IVD) by itself, predicting the complex stress conditions due to any arrangement of the main movements: flexion-extension, lateral bending and axial rotation, compressio...

This work overviews an extensive analysis in the context of mechanical characterization of human biomaterials, carried out over a broad set of published experimental data. Focused on main lumbar spine ligaments, several test procedures are exhaustively analyzed, in order to identify possible causes for divergences that have been found in some resul...

A novel 3D multi-body system model of the human lumbar spine is presented, allowing the dynamic study of the all set but also to access mechanical demands, characteristics and performance under work of the individual intervertebral discs. An advanced FEM analysis was used for the most precise characterization of the disc 6 DOF mechanical behavior,...

The loaded disk culture system is an intervertebral disk (IVD)-oriented bioreactor developed by the VU Medical Center (VUmc, Amsterdam, The Netherlands), which has the capacity of maintaining up to 12 IVDs in culture, for approximately 3 weeks after extraction. Using this system, eight goat IVDs were provided with the essential nutrients and submit...

The Intervertebral Disc (IVD) is subjected to several types of loading during daily routine events. However, the overloading on this structure induces higher Intradiscal Pressure (IDP), which could cause severe damage on its structure. This study describes a new approach to that allows monitorize and pressurize nuclear region of the IVD, with a car...

The performance of hydrodynamic journal bearings is affected by the conditions under which the lubricant is fed to the bearing gap. Axial grooves are often used and, depending on their location relatively to the load line, they might substantially interfere with the hydrodynamic pressure generation and the thermal behaviour of the bearing. However,...

Laboratory tests have been carried out in order to assess the influence of groove activation and deactivation on the performance of a twin axial groove steadily loaded hydrodynamic journal bearing. Temperature distribution at the oil-bush interface, oil outlet temperature, total oil flow rate, partial oil flow rate (at each groove), and motor consu...

Most conventionalhydrodynamicjournalbearingperformancetoolscannotsuitablyassesstheeffectof lubricant feedingconditionsonbearingperformance,eventhoughtheseconditionsareknowntoaffect important performanceparameterssuchaseccentricityandpowerloss. A thermohydrodynamicanalysissuitabletodealwithrealisticfeedingconditionshasbeenproposed. Special attention...

The hydrodynamic journal bearing is still one of the most geometrically simple mechanical components, yet highly reliable and efficient and, above all, unique in what concerns to heavy duty – high load, high speed – support of rotating shafts. Analytical studies, not only to understand the physical basis of its performance, but also to develop prac...

The Finite Element (FE) Analysis is an essential tool to study the biomechanical behaviour of the spine, and particularly of the intervertebral disc (IVD). The 3D reconstruction of a patient-oriented IVD has numerous obstacles. Difficulties arise mainly due to the complexity and dimensions of the IVD's constituent structures. The lack of detailed d...

This paper describes the phenomenon of negative flow rate (hot oil reflux) occurring in one of the grooves of twin axial groove hydrodynamic journal bearings. This rarely described phenomenon, which can occur under severe operating conditions, increases the risk of bearing seizure. Existing codes for predicting bearing behaviour do not seem to be s...

The medical imaging resolution, i.e., pixel size and spacing between slices, plays an important role on the accuracy of 3D geometrical reconstruction of anatomical structures from 2D medical images. In order to study the impact of medical imaging resolution, a procedure for the generation of virtual and segmented 2D medical images is designed and i...

The aim of this work is to develop a dynamic model for the biological human knee joint. The model is formulated in the framework of multibody systems methodologies, as a system of two bodies, the femur and the tibia. For the purpose of describing the formulation, the relative motion of the tibia with respect to the femur is considered. Due to their...

Finite Element (FE) meshes are usually highly refined and dense and, consequently, computationally very expensive. Therefore, after the preliminary FE mesh generation, it is necessary to decrease its size by diminishing the total number of nodes and elements while maintaining both geometrical accuracy and a physically-meaningful FE mesh refinement....

Extended abstract. Available at http://www.utwente.nl/ctw/euromech524/program/Program%2BAbstracts.pdf

Low back pain affects approximately 80% of the population at some point of their life, and lumbar degenerative disc disease is often indicated as the cause of that symptom. The main goal of this work is to develop a biomechanical lumbar spine model, using multibody systems methodologies, useful for dynamic analysis, such as in the biomechanical beh...

Development of a multibody lumbar spine model, using multibody systems methodologies, useful for simulation of this spinal region in several conditions such as the test of the physiologic range of motion.

It is often assumed that a twin groove arrangement will provide a more effective lubrication and a cooler operation than a single groove one, but little evidence has been found in support of this claim. Furthermore, there are no experimental works, to the authors’ knowledge, that compare the performance of single and twin axial groove bearings with...

A comprehensive combined numerical and experimental study on the dynamic response of a slider-crank mechanism with revolute clearance joints is presented and discussed in this paper to provide an experimental verification and validation of the predictive capabilities of the multibody clearance joint models. This study is supported in an experimenta...

An experimental assessment of the influence of lubricant feed temperature (Tf) on the behaviour of twin groove hydrodynamic journal bearings has been undertaken. Several loads, shaft speeds and bearing geometries were tested under constant lubricant feed pressure (pf), while Tf took four different values between 29°C and 58°C. It was found that the...

An experimental assessment of the influence of angle between the groove axis and the load line on the thermohydrodynamic behaviour of twin groove hydrodynamic journal bearings has been undertaken. At nine different loading direction angles, the oil–bush interface temperature profiles, oil outlet temperature, maximum bush temperature, total flow rat...

The main purpose of this work is to present a general methodology for modeling lubricated revolute joints in constrained rigid multibody systems. In the dynamic analysis of journal-bearings, the hydrodynamic forces, which include both squeeze and wedge effects, generated by the lubricant fluid, oppose the journal motion. The hydrodynamic forces are...

This paper deals with the kinematic analysis and design optimization of disc cam mechanisms with eccentric translating roller followers. The objective function considered in the present work takes into account the three major parameters that influence the final cam size, namely the base circle radius of the cam, the radius of the roller and the off...

This paper presents a new technique for assessing the influence that clearance of spatial joints has on the kinematics and dynamics of multi-body systems. The technique is developed for the revolute joint in which the basic elements are the journal and bearing. Under certain working conditions, these two mechanical elements collide with each other...

A computational methodology for dynamic description of rigid multibody systems with translational clearance joints is presented and discussed in this work. Over the post years, extensive work has been done to study the dynamic effect of the revolute joints with clearance in multibody systems, in contrast with the little work devoted to model transl...

The collision is a prominent phenomenon in many mechanical systems that involve intermittent motion, kinematic discontinuities or clearance joints. As a result of an impact, the values of the system state variables change very fast, eventually looking like discontinuities in the system velocities and accelerations. The impact is characterized by la...

The role of each groove on the performance of a 50 mm journal bearing with two axial grooves located at ±90° to the load line was studied. With the twin groove bearing, at low eccentricity, most of the lubricant entered through the 90° groove. At high eccentricity, the opposite occurred, with most of the oil entering the bearing gap through the -90...

This paper deals with a general methodology to assess the influence of the clearance size and the friction coefficient on the dynamic response of planar rigid multi-body systems including revolute joints with clearance. When there is a clearance in a revolute joint, impacts between the journal and the bearing can occur, and consequently, local defo...

A comprehensive numerical and experimental study on the dynamic response of a slider-crank mechanism with clearance joints is presented and discussed in this work.

The main goal of this work is to develop a methodology for studying and quantifying the wear phenomenon in revolute clearance joints. In the process, a simple model for a revolute joint in the framework of multibody systems formulation is presented. The evaluation of the contact forces developed is based on a continuous contact force model that acc...

A systematic and general methodology for kinematic position errors analysis of multibody systems is investigated throughout this work, taking into account the influence of the manufacturing and assemble tolerances on the performance of planar mechanisms. The generalized Cartesian coordinates are used to mathematically formulate kinematic constraint...

The influence of the revolute joint model on the dynamic behavior of multibody systems is investigated throughout this work. In the process, under the framework of the multibody systems formulation, a general methodology for modeling revolute joints with clearance is presented. The numerical models for normal and tangential contact forces are revie...

This paper presents a new technique for assessing the influence that clearance of spatial joints has on the kinematics and dynamics of multi-body systems. The technique is developed for the revolute joint in which the basic elements are the journal and bearing. Under certain working conditions, these two mechanical elements collide with each other...

This work deals with a methodology to assess the influence of the spherical clearance joints in spatial multibody systems. The methodology is based on the Cartesian coordi-nates, with the dynamics of the joint elements modeled as impacting bodies and con-trolled by contact forces. The impacts and contacts are described by a continuous contact force...

In this work a methodology for the dynamical analysis of mechanical systems considering realistic joint characteristics, namely, joints with clearance and lubrication is presented. For the case of the joints with clearance modelled as a contact pair with dry contact, a technique using a continuous approach for the evaluation of the contact force is...

This work deals with contact-impact force models for both spherical and cylindrical contact surfaces. The incorporation of the friction phenomenon, based on the Coulomb friction law, is also discussed together with an effective computational strategy, which includes the automatic step size selection procedure. Impacts within a revolute clearance jo...

This paper deals with a methodology to assess the influence of the lubricated revolute joints in the kinematics and dynamics of mechanisms. The existence of the clearance at revolute joints is inevitable in all mechanical systems and most of them are designed to operate with a lubricant fluid. The infinitely-short journal-bearing approach for dynam...

The main purpose of this work is to offer a simplified and comprehensive wear model, under a general point of view and under the framework of the dynamics of multibody mechanical systems formulation

A computational methodology for dynamic analysis of multibody mechanical systems with imperfect cylindrical joints is presented and discussed in this work

This paper deals with a methodology to assess the influence of the lubricated revolute joints in the kinematics and dynamics of mechanisms. The existence of the clearance at revolute joints is inevitable in all mechanical systems and most of them are designed to operate with a lubricant fluid. The infinitely-short journal-bearing approach for dynam...

Presented at the III Congresso Ibérico de Tribologia, Universidade do Minho, Guimarães, June 16-17, 2005

Presented at the Multibody Dynamics 2005, ECCOMAS Thematic Conference Madrid, Spain, June 21-24, 2005

Presented at the Congreso de Métodos Numéricos en Ingeniería 2005 4-7 de Julio de 2005. Granada, España

Presented at the III Congresso Ibérico de Tribologia, Universidade do Minho, Guimarães, June 16-17, 2005

This work deals with the modelling of lubricated revolute joints in multibody mechanical systems. In most machines and mechanisms, the joints are designed to operate with some lubricant fluid. The high press- ures generated in the lubricant fluid act to keep the journal and the bearing apart. Moreover, the thin film formed by lubricant reduces fric...