• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.15 no.1
• /
• pp.61-70
• /
• 2005

This study investigated the spinal loads(L5/S1 disc compression and shear forces) predicted from four biomechanical models: one EMG model and three optimization models. Three objective functions used in the optimization models were to miminize 1) the cubed muscle forces : MF3, 2) the cubed muscle stress : MS3, 3) maximum muscle intensity : MI. Twelve healthy male subjects participated in the isometric voluntary exertion tests to six directions : flexion/extension, left/right lateral bending, clockwise/ counterclockwise twist. EMG signals were measured from ten trunk muscles and spinal loads were assessed at 10, 20, 30, 40, 50, 60, 70, 80, 90%MVE(maximum voluntary exertion) in each direction. Three optimization models predicted lower L5/S1 disc compression forces than the EMG model, on average, by 31%(MF3), 27%(MS3), 8%(MI). Especially, in twist and extension, the differences were relatively large. Anterior-posterior shear forces predicted from optimization models were lower, on average, by 27%(MF3), 21%(MS3), 9%(MI) than by the EMG model, especially in flexion(MF3 : 45%, MS3 : 40%, MI : 35%). Lateral shear forces were predicted far less than anterior-posterior shear forces(total average = 124 N), and the optimization models predicted larger values than the EMG model on average. These results indicated that the optimization models could underestimate compression forces during twisting and extension, and anterior-posterior shear forces during flexion. Thus, future research should address the antagonistic coactivation, one major reason of the difference between optimization models and the EMG model, in the optimization models.

• Journal of Technologic Dentistry
• /
• v.40 no.1
• /
• pp.41-47
• /
• 2018

Purpose: The purpose of this study was to analyze the biomechanical properties of the dental implants on the supporting bone using three-dimensional finite element method when three different abutment materials were applied to the implant system. Methods: Three different dental implant models were fabricated by applying Ti, PEEK, and CRE-PEEK (60% carbon-reinforced PEEK) to abutment material. The abutment and connecting screw from the fixture was applied with a tightening torque of 20 Ncm. And then, total loads of 150 N were applied in an $30^{\circ}oblique$ direction (to the vertical). The structural stability of dental implants on the supporting bone was analyzed using Von Mises stress and principal stress values. Results: The maximum tensile stress of the cortical bone was highest at 12.6 MPa in the PEEK abutment (Model-B). Ti abutment (Model-A) and CRE-PEEK abutment (Model-C) showed similar stress distributions (10.6 and 10.3 MPa, respectively). And the maximum compressive principal stress was similar in all models. The Von Mises stress value delivered to the bone around the implant was highest at 16.5 MPa in Model-B. On the other hand, Model-A and C showed similar stress distributions (14.0 and 13.8 MPa, respectively). In addition, the maximum equivalent stress applied to the abutment was highest at 629.8 MPa in Model-A. The stress distribution in Model-C was 573.9 MPa. Whereas, Model-B showed the lowest value at 165.6 MPa. Conclusion : The dental implant supporting bone system using PEEK material seems to have the possibility of supporting bone fracture. It was found that the CRE-PEEK abutment can reduce the elastic deformation and reduce the stress value of the interfacial bone.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.06a
• /
• pp.1921-1924
• /
• 2005

In this paper, three-dimensional finite element analysis have been performed to investigate the biomechanics of vertebroplasty in patient. In order to apply various properties of the spine, the functional relation between the well-known apparent density and HU(Hounsfield unit) from CT image were employed and thus real material property can be assigned to each element of FE model. The FE analysis showed similar results with the experiments. With this approach accurate analysis of the spine and the clinical application can be expected.

• Journal of the Ergonomics Society of Korea
• /
• v.29 no.5
• /
• pp.727-734
• /
• 2010

The objective of this study was to evaluate the resting postures of the fingers and wrist based on the biomechanical model in term of hand posture (neutral, pronation, and supination) and gender (male and female). The finger and wrist joint angles were measured with VICON motion system. The EMG system was used to examine the muscle activity in the resting condition. The participants consisted of twenty male and twenty female students. The angles of the fingers and wrist were analyzed by means of the coordinate system associated with the International Society of Biomechanics. Hand posture was significant for all the joints. The finger and wrist joint flexed in supination more than in neutral and pronation. The hand posture and gender were not significant for the results of muscle activity, but it had larger muscle activities in supination more than in neutral and pronation.

• Proceedings of the KSME Conference
• /
• 2007.05a
• /
• pp.746-750
• /
• 2007

Vertebroplasty has drawn much attention as a medical treatment for the compression fracture of spine, which strengthens the vertebral body and corrects deformity, and relieves pain in patients by injecting bone cement. However vertebroplasty can cause fracture on adjacent vertebra due to relative stiffness change. This study involves the biomechanical evaluation of the vertebroplasty especially on adjacent vertebral body. The finite element method has been employed to analyze the patient who was treated vertebroplasty under static and dynamic loading. For this study, a three-dimentioal model of the three-level ligamentous lumbar segment ($L1{\sim}L3$)is created from medical image data (CT)and compared with the experimental results in vitro.

• Journal of the Ergonomics Society of Korea
• /
• v.26 no.4
• /
• pp.85-90
• /
• 2007

This study shows a way to develop ergonomic design of a plier through quality function deployment (QFD) approach. User needs for pliers, as well as the engineering characteristics which have influence on the ergonomic quality of pliers were determined from the interviews and questionnaires with various user groups. This information was entered in the house of quality, and the results show that the handle is the most important quality factor. A new model was proposed in which ergonomic and gender aspects were considered. QFD is considered a suitable method especially for the manufacturing and/or design fields where biomechanical or physiological background is not present.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2006.05a
• /
• pp.187-188
• /
• 2006

A 3-D finite element model of human thoracolumbar spine (T12-L2) was reconstructed from CT images. Various anterior and posterior instrumentation techniques were performed with long cage after corpectomy. Six loading cases were applied up to 10 Nm, espectively. The rotations of T12 with respect to L2 were measured and the stiffnesses were calculated as the applied forces divided by the segmental rotations. The posterior fixation technique increased the stiffness of the spine the most. The addition of anterior rod from 1 to 2 increased the stiffness significantly without posterior fixation, but no effect was found with posterior fixation. We found that different fixation techniques changed the stiffness of the spine.

• Journal of Korean Institute of Industrial Engineers
• /
• v.18 no.2
• /
• pp.1-9
• /
• 1992

The purpose of this paper is to investigate the dynamic situation of the biomechanical responses of a pilot that occur before the black out during high gravity maneuvering. The computer biodynamic simulations using the Articulated Total Body(ATB) model show the following results : 1) the center of gravity(c. g) offsets of a helmet have significant effects on the head deflection angle which is closely connected with the head down : 2) the average and maximum gravity forces are smaller in the curvilinear type of an acceleration than in the straight type of the acceleration, and it is applied to the case of the head deflection angle. We suggest that the new concept of protective device should be necessary to prevent the head down during high gravity maneuvering.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.27 no.3
• /
• pp.90-96
• /
• 2004

The objective of this study was to develop a model for safe work load based on a physiological model of metabolic energy of manual material handling tasks. Fifteen male subjects voluntarily participated in this study. Lifting activities with four different weights, 0, 8, 16, 24kg, and four different working frequencies (2, 5, 8, 11 lifts/min) for a lifting range from floor to the knuckle height of 76cm were considered. Oxygen consumption rates and heart rates were measured during the performance of sixteen different lifting activities. Simplified predictive equations for estimating the oxygen consumption rate and the heart rate were developed. The oxygen consumption rate and the heart rate could be expressed as a function of task variables; frequency and the weight of the load, and a personal variable, body weight, and their interactions. The coefficients of determination ($r^2$) of the model were 0.9777 and 0.9784, respectively, for the oxygen consumption rate and the heart rate. The model of oxygen consumption rate was modified to estimate the work load for the given oxygen consumption rate. The overall absolute percent errors of the validation of this equation for work load with the original data set was 39.03%. The overall absolute percent errors were much larger than this for the two models based on the US population. The models for the oxygen consumption rate and for the work load developed in this study work better than the two models based on the US population. However, without considering the biomechanical approach, the developed model for the work load and the two US models are not recommended to estimate the work loads for low frequent lifting activities.

• Structural Engineering and Mechanics
• /
• v.63 no.6
• /
• pp.771-777
• /
• 2017

The applications of smartphones or other portable smart devices have dramatically changed people's lifestyle. Researchers have been investigating useage of smartphones for structural health monitoring, earthquake monitoring, vibration measurement and human posture recognition. Their results indicate a great potential of smartphones for measuring pedestrian-induced loads like walking, jumping and bouncing. Smartphone can catch the device's motion trail, which provides with a new method for pedestrain load measurement. Therefore, this study carried out a series of experiments to verify the application of the smartphone for measuring human-induced load. Shaking table tests were first conducted in order to compare the smartphones' measurements with the real input signals in both time and frequency domains. It is found that selected smartphones have a satisfied accuracy when measuring harmonic signals of low frequencies. Then, motion capture technology in conjunction with force plates were adopted in the second-stage experiment. The smartphone is used to record the acceleration of center-of-mass of a person. The human-induced loads are then reconstructed by a biomechanical model. Experimental results demonstrate that the loads measured by smartphone are good for bouncing and jumping, and reasonable for walking.