Search results for "mechanics"
showing 10 items of 9361 documents
Residual Stress Effects on Fatigue Crack Growth in Ti-6Al-4V Friction Stir Welds
2008
Recent studies have illustrated a predominant role of the residual stress on the fatigue crack growth in friction stir welded joints. In this study, the role of the residual stress on the propagation of fatigue cracks orthogonal to the weld direction in a friction stir welded Ti-6Al-4V joint was investigated. A numerical prediction of the fatigue crack growth rate in the presence of the residual stresses was carried out using AFGROW software; reasonable correspondence between the predictions and the experimental results were observed when the effects of residual stress were included in the simulation.
Comparison of frictional resistance between passive self-ligating brackets and slide-type low-friction ligature brackets during the alignment and lev…
2019
Background To compare the frictional resistance between passive self-ligating brackets and conventional brackets with low-friction ligature under bracket/archwire and root/bone interface during dental alignment and leveling. Material and methods A tridimensional model of the maxilla and teeth of a patient treated with conventional brackets, and slide ligatures was generated employing the SolidWorks modeling software. SmartClip self-ligating brackets and Logic Line conventional brackets were assembled with slide low-friction ligatures, utilizing archwires with different diameters and alloys used for the alignment and leveling stage. Friction caused during the bracket/archwire interface and s…
Dynamic Gait Parameters in Patients With Nonunion of the Tibia Following Treatment With the Ilizarov Method.
2020
Abstract The purpose of this study was a comprehensive assessment of the dynamic parameters of gait in patients who underwent Ilizarov treatment for nonunion of the tibia. The experimental group consisted of 24 individuals treated with the Ilizarov method for nonunion of the tibia. The control group comprised 31 healthy individuals, matched for BMI, sex, and age. The dynamic gait parameters in patients and in the control group were measured with a Zebris pedobarographic platform. The treatment group and the control group showed statistically significant differences in terms of the following gait parameters: maximum force during braking nonoperated-limb (NOL), time maximum force during braki…
Comparison between the directly measured achilles tendon force and the tendon force calculated from the ankle joint moment during vertical jumps.
1988
Summary The purpose of this study was to compare the relationship between the achilles tendon force and the tendon force estimated from the ankle joint moment (EATF) during vertical jump. A healthy male subject performed the following jumps on the force platform: (a) maximal vertical jump from a squat position without counter-movement; (b) maximal vertical jump from an erect standing position with a preliminary counter-movement; (c) repetitive submaximal hopping on the spot with preferred frequency. The achilles tendon force was measured directly with an implanted tendon transducer in all jumping conditions. In addition the joint moment obtained from the film and ground reaction force was u…
A reanalysis of spinal motion during vibration
1987
Calibrated film of the motion of the lumbar spine during vibration was reanalysed, making use of a number of computer based techniques to improve accuracy and reduce measurement noise. The results demonstrated resonant behaviour at about 4 Hz and indicated that at vibration levels of the order of 1 m/s2 there exists bending of the order of 1° (peak to peak) between adjacent vertebrae in the lumbar spine. The bending is complex and involves phase differences along the spine and possibly a rocking motion of the pelvis.
Numerical experimental analysis of hybrid double lap aluminum-CFRP joints
2015
Abstract Due to their reliability and ease of assembly, both the adhesively bonded and the mechanical joints are commonly used in different fields of modern industrial design and manufacturing, to joint composite materials or composites with metals. As it is well known, adhesively bonded joints are characterized by high stiffness and good fatigue life, although delamination phenomena localized near the free edges may limit their use, especially for applications where corrosive environments and/or moisture can lead to premature failure of the bonding. In these cases, a possible alternative is given by the well-known mechanical joints. On the contrary, these last joints (bolted, riveted) requ…
Different sitting positions influence cross country sit skiers performance : Sitting position influence on force generation and cycle characteristics
2018
Cross country sit skiing is a Paralympic discipline in which athletes due to physical impairment ski sitting on a sit-ski. The impairment influences performance directly and also through sitting position. Athletes with a better trunk control usually adopt a sitting position called “kneeing” in which the hip joints are higher than the knee joints. In contrast, athletes with high impact of impairment prefer a sitting position called “knee high” in which the hip joints are lower than the knee joints. Able bodied athletes skiing on the ergometer in these two sitting positions showed different performance. However, to the best of authors’ knowledge, no studies have examined performance, force pr…
Stiffness and Reinforcement Effect of electrical Resistance Strain Gauges
2007
: The increasing use of low-modulus materials, on which the reinforcement effect of the electrical resistance strain gauge is not negligible, has re-opened the research interest into this issue. This study deals with the evaluation of stiffness, and of the strain gauge Young's modulus involved in the estimation of both the global and the local reinforcement effect; the relationship between the strain gauge stiffness and the local reinforcement effect is also analysed. In particular, the experimental technique used to determine the stiffness of some commercial strain gauges is described. The results show that the strain gauge stiffness alone does not permit an accurate evaluation of the loc…
AB1057 risk factors associated with different lumbopelvic patterns of movement
2016
Background Rapid flexion movement increases the loading on the spine and it increases the risk of injuries 1 . In asymptomatic subjects lumbar-dominant and pelvis-dominant patterns of movement during trunk flexion have been observed 2,3 . However, little information about lumbar spine kinematics has been provided. Objectives To find out whether exhibiting different lumbopelvic patterns of movement during trunk flexion affects the kinematics of the lumbar spine in terms of velocity of motion. Methods Differential lumbar spine and pelvis angular displacement during the time course of a standardised sagittal trunk flexion from an upright position was recorded with an electromagnetic tracking d…
The distribution of cartilage thickness in the knee-joints of old-aged individuals -- measurement by A-mode ultrasound.
1997
Abstract Objective. To provide data on the normal distribution of cartilage thickness in the knee joints of old-aged individuals. Design. The accuracy and reproducibility of cartilage thickness measurements were evaluated with A-mode ultrasound, and the cartilage thickness distribution was examined throughout both knee joints of nine individuals aged between 62 and 94 yr. Background. Data on the variation of cartilage thickness in the joint surfaces are relevant for the design of computer models of diathrodial joints and for surgical and arthroscopic procedures, particularly the calculation of cartilage material properties from indentation tests. Methods. A 12.5 MHz A-mode ultrasound transd…