EXTENSÔMETROS EM ENGENHARIA CIVIL: TEORIA E APLICAÇÔES

Este artigo é o primeiro de uma sequência de dois artigos que têm como principal objetivo apresentar a teoria dos extensômetros resistivos e algumas de suas aplicações na área de engenharia civil. Não é intenção dos autores fazer uma abordagem extensiva do assunto. A meta é, pelo menos, possibilitar aos estudantes e profissionais da área de engenharia civil adquirirem algum conhecimento dessa importante tecnologia. Portanto, procurou-se dar a este primeiro artigo um enfoque mais pedagógico de modo a facilitar a compreensão do extensômetro e do seu funcionamento

ANALYSIS OF THE ROM, PASSIVE TORQUE, STIFFNESS AND WORK ABSORPTION AFTER CONCENTRIC AND ECCENTRIC MUSCLE ACTIONS

Muscular strength and flexibility are two important physical capacities that are frequently assessed and trained in athletes before and during sporting competitions (Nobrega et al. 2005), but their interactions are not well established. The purpose of this study was to determine the acute effects of concentric and eccentric contractions on the range of motion (ROM), passive peak torque (PPT), stiffness and work absorption

THE CHRONIC EFFECT OF STRENGTH AND FLEXIBILITY TRAINING ON STIFFNESS AND RANGE OF MOTION

Twelve male subjects were in the training group (T) who performed concentric strength training (CON) on one side and concentric plus flexibility training (CON_F) on the other side; other 10 subjects served as a control (C). A strength and stretch tests were administered before and after the training period. After 6 weeks of training a significant difference between pre and posttest was found for the 1 repetition maximum (1RM) test on T group. The ROM increased significantly only in CONC_F group. No differences between groups or time existed was found for stiffness. Concentric training was able to enhance strength without any alterations in the stiffness of muscle-tendon unit (MTU). The concentric training combined with flexibility training was able to increase strength and ROM without any augmentation in stiffness

RANGE OF MOTION AND STRETCH TOLERANCE AFTER ECCENTRIC STRENGTH TRAINING

The purpose of this study was to examine whether eccentric strength training alone and eccentric strength training combined with flexibility training of hamstring muscles can alter the maximum range of motion (ROM) and the stretch tolerance (ST) in the human hamstring muscles. Thirteen male (physical education students) performed strength eccentric training (Ecc) on one leg and eccentric and flexibility training (Ecc_F) on their other leg for 6 weeks; nine other subjects, not involved in any of these exercise performed served as a control group (CON). Strength and flexibility tests were administered before and after the training period. After 6 weeks of training, a significant difference between pretest and posttest was found for the one maximum repetition (1- RM) test on the Ecc and Ecc_F (

Non-invasive methods of computer vision in the posture evaluation of adolescent idiopathic scoliosis

Purpose: Reviewing techniques for non-invasive postural evaluation of adolescent idiopathic scoliosis (AIS) based on information extraction from images based on computer methods. Methods: The Scopus, Web of Science, MEDLINE, ScieLo and PubMed databases were used, for the period 2011-2015. Results: 131 articles were found based on keyword of which 15 articles met the established eligibility criteria. Of these, 4 were based on photogrammetry, and 11 based on laser, structured light, ultrasound, and Moire projection. In these studies, the methodological quality varied from low to high. Conclusions: The findings indicated diversity in methodologies; 14/15 articles reviewed were limited to the evaluation of the topography of the posterior back. A study, using two-dimensional photogrammetry, presented a whole body postural evaluation. As the asymmetry in AIS can be extended to the whole body, more attention should be given to develop full body assessment techniques to provide important additional data to aid in treatment decisio

Three-dimensional geometric model of the middle segment of the thoracic spine based on graphical images for finite element analysis

Abstract Introduction: Biomedical studies involve complex anatomical structures, which require specific methodology to generate their geometric models. The middle segment of the thoracic spine (T5-T10) is the site of the highest incidence of vertebral deformity in adolescents. Traditionally, its geometries are derived from computed tomography or magnetic resonance imaging data. However, this approach may restrict certain studies. The study aimed to generate two 3D geometric model of the T5-T10 thoracic spine segment, obtained from graphical images, and to create mesh for finite element studies. Methods A 3D geometric model of T5-T10 was generated using two anatomical images of T6 vertebra (side and top). The geometric model was created in Autodesk® Maya® 3D 2013, and the mesh process in HiperMesh and MeshMixer (v11.0.544 Autodesk). Results The T5-T10 thoracic segment model is presented with its passive components, bones, intervertebral discs and flavum, intertransverse and supraspinous ligaments, in different views, as well as the volumetric mesh. Conclusion The 3D geometric model generated from graphical images is suitable for application in non-patient-specific finite element model studies or, with restrictions, in the use of computed tomography or magnetic resonance imaging. This model may be useful for biomechanical studies related to the middle thoracic spine, the most vulnerable site for vertebral deformations

SUSCEPTOBILITY TO THERMAL FATIGUE OF CLOSED DIE HOT FORGING DIES

Hot forging dies providing high productive performance reduce production costs. The lifetime of the dies is expressed by the number of forgings (production cycle) produced before being rejected by the presence of a failure mechanism, associated with unacceptable dimensions and or geometry of the end product or even breakage of the dies. One of the failure mechanisms of hot forging dies is thermal fatigue, caused by cyclic heating and cooling. A subroutine, based on the work of Maim and Norstrom [1], was developed for the DEFORM 2D numerical software, using the finite element method, in order to predict die regions susceptible to thermal fatigue. The use of adequate coefficients for the description of the heat transfer phenomena allowed the validation of the proposed subroutine

Relationship between head posture and lumbar curve in a sitting position: a biomechanical study

Abstract Introduction: The sitting position routinely used for a wide variety of tasks increases the potential of developing forward head posture, which can seriously compromise the health of different systems in the human body. Objective: A static equilibrium analysis was conducted, comparing the position of the head with the lumbar curve in three different sitting positions. Methods: The approximate force and flexion moment of the head extensor muscles in static equilibrium was calculated in each of the following positions: (A) without a backrest; (B) using a backrest with a 100° tilt angle; (C) using a 100° tilted backrest associated with a cylindrical lumbar support cushion at the level of the L3 vertebra. Results: The C7-tragus angles were 43°, 50° and 52°; Frankfort horizontal plane (FH) angles were 5°, 9° and 9°; force of the head extensor muscles was 53.0N, 59.7N and 43.5N and flexion moments were 2.60Nm, 2.05Nm and 1.78Nm, in positions A, B and C, respectively. Conclusion: The results revealed that the sitting position using a 100° tilted backrest and lumbar support with the smallest L3-tragus horizontal distance required less effort by the head and neck extensor muscles to retain the head in equilibrium. This study demonstrated the need to preserve the physiology of the lumbar spine, characterized by the position of the L3 vertebra, in order to ensure good head position