Beatriz Romero-Ángeles

Numerical Analysis of Masticatory Forces on a Lower First Molar considering the Contact between Dental Tissues

The aim of the present work is to identify the reactions of the dental organs to the different forces that occur during chewing and the transcendence of the union and contact maintained by the dental tissues. The study used a lower first molar biomodel with a real morphology and morphometry and consisting of the three dental tissues (enamel, dentin, and pulp) each with its mechanical properties. In it, two simulations were carried out, as would the process of chewing a food. One of the simulations considers the contact between the enamel and the dentin, and the other does not take it into account. The results obtained differ significantly between the simulations that consider contact and those that do not, establishing the importance of taking this contact into account. In this way, the theories that establish horizontal and lateral occlusion forces are present during the functional chewing process which are viable to be correct. The case studies carried out present not only the reasons for the failure of enamel but also the failure of the restoration materials used. This reflection will allow the development of more adequate materials, mechanical design of prostheses, implants, and treatment.

Residual Stress Interaction against Mechanical Loading during the Manufacturing Process of an Assault Rifle Component

This paper presents results obtained on the harmful effect that a lamination process can cause in AISI 1018 steel during the manufacturing process of spring bed components in fire guns. The sequel presented by the induction of a residual stress field is analyzed as well. It has been established that the consequences produced by the residual stresses, could be minimized either by changing the geometric configuration of the component, or changing the manufacturing process, or regeneration of the microstructure of the material by heat treatment. This work analyzes the effects that consistently become apparent by the regeneration of the microstructure of the material, such as; level of the residual stress field, possible fracture and micro-structural changes. This article evaluates both the longitudinal and transverse residual stress that takes place during the punching process of the spring bed made of AISI 1018 steel. The Crack Compliance Method (CCM) for measurement the residual stress field was applied. Additionally, it is applied a micro-structural analysis of the component. A comparison between experimental results of grain size is shown. From this study it is possible to validate the correct behavior of the mechanical component and certify the expected useful life.

Evaluation of the Impact of Residual Stresses in Crack Initiation with the Application of the Crack Compliance Method Part II, Experimental Analysis

The present work is based on a previous numerical simulation used for the introduction of a residual stress field in a modified compact tensile specimen. The main objective in that paper was to evaluate the effect that previous history has in crack initiation and to establish the new loading conditions needed to propagate a fracture. The experimental analysis presented in this paper was performed to compare and validate the numerical procedure. Several modified compact tensile specimens from a biocompatible material (AISI 316L) were manufactured to estimate the beneficial effect of a residual stress field. The specimens were separated in four batches; an initial group of uncracked specimens was used to establish an evaluation of the induction of a residual stress field produced by an overload; the remaining specimens were separated into three groups where a crack was introduced in each specimen (1 mm, 5 mm and 10 mm respectively) and the residual stress field caused by the application of an overload was determined. The assessment of all the residual stress fields introduced into the specimens was done by the application of the crack compliance method (CCM). The results obtained have provided useful information on the correlation between the numerical and experimental procedures. Furthermore, data concerning the understanding of diverse factors related to crack initiation are discussed in this paper. Finally, the beneficial aspects of the residual stresses are discussed.

New Procedure to Construct an Anisotropic Elastic FE-Model Based on Swine Femoral Bones Using Numerical Modeling

This work presents a new procedure to determine the density of bone tissue from collected data by means of computed axial tomography (CAT) and bone density correlations of cancellous and cortical tissue with their elastic properties which were obtained from structure reconstruction software to determine the apparent density of bone. The main objective is to determine the anisotropic elastic properties in swine femoral bones on two orthogonal directions to produce a most real behavior of bone FE-model. A TC Brilliance axial scanner (tomograph) was used to obtain the desired images, which were then processed in the Digital Imaging and Communication in Medicine format using different software packages, including Scan IPTM, Scan FE v3.1TM, and ANSYS vl2 TM. Five Duroc-Jersey type swine femur specimens were used for the analysis. These specimens are considered to be equivalent to human specimens of 50 to 55 years of age, since they have been used for eighteen months in experimental processes. The experimental procedure included the processing of 60 tomographic cuts, which allowed the determination of the zone where the density maximum and minimum values of the bone tissue seem to be located. The results obtained displayed the anisotropic elastic behavior for each bone specimen within a voxel unit of precision. The findings of this study could allow a significant advance in the development of customized endo-prostheses by determining the elastic properties of the bone and developing more accurate FE-models. This will contribute to the improvement of the performance of artificial implants as well as to increasing the service life of these prostheses.

Numerical Analysis of the Knee Articulation Leg. The Angular Position Parameters and Forces Acting on the Joint Were Obtained and Applied into the Corresponding, During Different Stages of the Gait Process

The knee is a diarthrodial joint or a wide mobility joint (or a wide mobility joint), which involves an extremely complex mechanical analysis. The knee possesses a great stability in complete extension to support the corporal weight, and has the necessary mobility to perform diverse daily activities (jump, gait, trot, run, among others) and efficiently orients the foot in relation to the irregularities of the ground. At present, a general understanding is possessed of the forces acting onto the bone structural components of the knee joint during daily activities. On the other hand, by applying Finite Element algorithms it is possible to numerically simulate the anatomic systems that constitute the human body. This algorithm has turned out to be an important tool to determine research behavior of the bone is not an organism, to determinate the behavior of bones from a mechanical point of view. Additionally, they are applied as a foundation for prosthesis design and numerical model generation to solve problems related to clinical conditions. For example, the degenerative osteoarthritis of the knee is a chronic degenerative disease that is active in persons between the ages of 50 to 60 years old and involves severe wear of the joint. This condition can be accelerated by multiple circumstances, the main one big effect of articulated overload (obesity, knee deformation, meniscus injuries, among others). In this paper we propose that a static structural analysis of the knee joint, which involves three phases of the human gait: normal support, contact (foot-ground) and balancing of the leg. The angular position parameters and the forces acting on the joint were obtained, and applied into the corresponding numerical analyses for each gait phase. The numerical analyses are based on the kinetic and kinematic studies of the knee, to determine the orientation and range of mobility of the joint. The numerical model of the knee joint was developed from a Computed Axial Tomography scan which would assure bio-fidelity in the numerical evaluation. Obtaining as results: the von Misses equivalent stress, the maximum and minimum principal stresses and the total displacement. It was determined by this research, that the knee capacity to support the loads in each step of the gait process and it helped to establish a data base for the design and development of joint knee prosthesis.

Design and Manufacture of a Forearm Prosthesis by Plastic 3D Impression for a Patient with Transradial Amputation Applied for Strum of a Guitar

At the present, the development of prostheses has been extremely wide and focused on restoring the patient to their daily activities. Nevertheless, not much has been done to restore the capability of playing musical instruments, perhaps due to the complexity and sensibility needed to perform certain movements. For example, the fingering movements on a guitar or a piano, are random and require of different amounts of force to be applied to the instrument. Furthermore, the playing of an instrument is accomplished by muscular memory. Nowadays, in order to emulate such movements, the application of robotically programmed prostheses has improved. Nevertheless, this is not a good option for musicians, as this solution do not offer the sensation of actually playing the instrument. One of the options to achieve the mentioned aim, would be the development of mechanical prostheses that apply myoelectric technology, however these devises do not possess sufficient sensibility to perform the movements needed to play an instrument. In this research, a mechanical design to be manufactured using 3D impression of a forearm prosthesis for a transradial amputated patient that is able to be used to play the guitar, is presented. The prosthesis is capable to provide the service for basic rehabilitation or train a recently amputated patient recently amputated. The proposed prosthesis was manufactured by the use of a plastic 3D impression machine using ABS-P400 strings. The prosthesis consists of two parts; the first one is the main socket that is attached to the forearm while the second part, that supports the nib guitar. The mechanical design of the prosthesis was based on data obtained by videometry of a musician developing the basic strum on a guitar. With these data was possible to define the basic strum technique, the movements that are involved (displacements, speed, acceleration, forces, etc.) and the joints involved in the strum of a guitar. The obtained results are very encouraging, since the prosthesis can be applied to restore the musician ability to perform the basic tasks to execute on his instrument, as well as, rehabilitation activities. This first proposal could be optimized to produce a final product with higher quality and with a wider area of applicability.

Design and Development of a Simplified Wear Simulator for Total Knee Replacement (TKR) Based on Pin-Disc Machine

The failure of polyethylene inserts in the prostheses of diverse members is the main cause for total replacement of the articulation. In this study, the most influential conditions for the different types of failures for a total knee replacement (TKR) causing the main wear or rupture were analyzed. Mexico, little research has been done on total knee prostheses (Rodriguez in Int J Phys Sci 7(43): 5779–5786, 2012, [1]), this being one of the main problems of national health. In the previous publications a few studies were conducted concerning the gait cycle in Mexican patients were made. One of the cases involved the TKR Scorpio™ II Stryker™ (Rodriguez in Revista Colombiana de Biotecnologia XV(1): 28–41, 2013, [2]) where axial and shear stresses have been analyzed and the way this functions in the gait cycle considering this type of prosthesis (Rodriguez in Revista Colombiana de Biotecnologia XV(1): 28–41, 2013, [2]). Due to the scarce resources with which it had to operate, the design of the components of the machine had to be improvised or modified, which is quite useful in two different cases. In present case, a hybrid-machine was developed, adapting new mechanical components on the pin-disk machine modified. The results of effects the wear of UHMWPE inserts are not involved in this research, only those related to the design and adaptation of the new components to the wear of the pin-disc machine are presented as results of this work.

Proposal by simple design of the lower limb exoskeleton of continuous use, provided of own mobility and body load support. Case: application due to an illness

In recent times it has established a debate between experts and academics about the social and economic impact of advances in robotics. The robotic exoskeletons mounted as suits on affected parts of the human body, represent one of the most significant examples of which is oriented towards robotics. With recent technological advances have increased the fields of application of these devices widely with respect to the first applications were teleoperation and increase in strength of a human being for various tasks. The aim of this work is to contribute as much as possible, to start a discussion about the vision of offering future developments in socio-economic terms and its impact resulting from the use of robotic exoskeletons, especially with regard to its application in medical rehabilitation of lower member and especially its use permanent, replacing cumbersome devices such as crutches, walkers, canes. All this, focused on the health sector, which is most affected by different diseases cannot have access to these devices. In this paper, only it proposes a design that could be inexpensive and used for various ailments.

Numerical simulation of the shot peening process under previous loading conditions

This research presents a numerical simulation of the shot peening process and determines the residual stress field induced into a component with a previous loading history. The importance of this analysis is based on the fact that mechanical elements under shot peening are also subjected to manufacturing processes, which convert raw material into finished product. However, material is not provided in a virgin state, it has a previous loading history caused by the manner it is fabricated. This condition could alter some beneficial aspects of the residual stress induced by shot peening and could accelerate the crack nucleation and propagation progression. Studies were performed in beams subjected to strain hardening in tension (5y) before shot peening was applied. Latter results were then compared in a numerical assessment of an induced residual stress field by shot peening carried out in a component (beam) without any previous loading history. In this paper, it is clearly shown the detrimental or beneficial effect that previous loading history can bring to the mechanical component and how it can be controlled to improve the mechanical behavior of the material.

Numerical Simulation on the Residual Stress Induction due to Welding Process and Assessment by the Application of the Crack Compliance Method

Residual stresses are mechanical effects that remain in a body after all external loads have been removed. In this sense and because a weldment is locally heated by a welding heat source, the temperature distribution is not uniform and changes as welding progresses. During the welding thermal cycle, complex transient thermal stresses are produced in the weldment and the surrounding joint. With the advancement of modern computers and computational techniques (such as the finite-element and the finite-difference methods), a renewed effort has been made in recent years to study and simulate residual stresses and the related phenomena. This paper discusses the procedure applying a finite element analysis by a 2D model to determine the residual stresses and distortions of steel AISI 316 bars under an arc welding process; additionally, the state of the stresses in the component is determined by the application of the crack compliance method (CCM); this is destructive experimental method based on fracture mechanics theory. This research also demonstrates that the residual stress distribution and the magnitude inducted into the component must be carefully assessed, or it could result in a component susceptible to failure.