Recent advances in finite element modeling of the human cervical spine

The human cervical spine is a complex structure that is the most frequently injured site among all spinal injuries. Therefore, understanding of the cervical spine injury and dysfunction, and also biomechanical response to external stimuli is important. Finite element (FE) modeling can help researchers to access the internal stresses and strains in the bones, ligaments and soft tissues more realistically, and it has been widely adopted for spine biomechanics research. Although in recent years numerous techniques have been developed, there are no recent literature reviews on FE models of the cervical spine. Our objective was to present recent advances in FE modeling of the human cervical spine in terms of component modeling, material properties, and validation procedures. Model applications and further development are also discussed. The integration of new technologies will allow us to generate more accurate and comprehensive model of the cervical spine, which can increase efficiency and model applicability. Finally, the FE modeling can help to facilitate diagnosis, treatment, and prevention technologies for cervical spine injuries.     

Chute design of mackerel automatic grader using multibody dynamics

An automatic mackerel grader is a machine that automatically sorts mackerel according to size. The chute spreads the mackerel to allow the latter to enter each roller evenly. Sorting is simulated to confirm that the multibody dynamics model of the automatic grader correctly sorts the mackerel. This process is completed according to the shape of the chute to confirm the effect on performance. A new shape of the chute and the application are proposed and evaluated by a comparison with conventional chute shapes. RecurDyn, a multi-body dynamics program, is used for the sorting simulation. The contact parameters are defined by Hertzian contact theory using the material information of mackerel and C/S steel. A rigid-body mackerel model is used to express the behavior of mackerel. Sorting is simulated for each shape. The sorting accuracy and error of the new shape are compared with those of two existing shapes. The new shape shows a 0.29 mm sorting error and better sorting accuracy than the existing shapes.     

Measurement of residual stress using linearly integrated GMR sensor arrays

Tubular-type transmission towers have several advantages, but could be compromised if welding defects from the construction process are not found during deployment. This research derived an equation that illustrates how a change in stress accompanied with mechanical deformation triggered a change in distribution of magnetic flux density. Furthermore, it verified experimentally that a change in distribution of magnetic flux density occurred due to a change in stress at the welding zone. Using this principle, this research proposes a system to measure residual stress occurred in the welding zone of tubular-type transmission tower. The ultrasound examination results were compared and the result showed that ultrasound signals revealed defects in a place where sudden distribution of magnetic flux density was presented. However, when a number of welding defects occurred across the large area, the distribution of magnetic flux density may not change due to the alleviating effect of the stress concentration.     

Numerical investigation on residence time of cooling water and surface temperature distribution of water-cooled grates

Waste incineration is a treatment system that reduces waste volume while capturing or destroying potentially harmful substances and recovers energy and chemical contents from wastes. Grate incinerator is one of the thermal treatment methods in waste incinerations. The incineration grates are exposed to high heat flux due to the occurrence of combustion on their surface. Therefore, cooling the incineration grate is one of the main issues in these treatments. In this study, the conjugate heat transfer between the cooling water and incineration grate is investigated numerically. We consider different geometries of the internal guide vane in the cooling channel and analyze the effects of the shapes of the guide vane on the heat transfer performance in the incineration grate. We also calculate the fluid residence time in the cooling channel and investigate the relation between the heat transfer performance and residence time of the cooling fluid. Results confirm that the maximum residence time of the cooling fluid can be reduced, from which the heat transfer performance can be improved.     

A new equation of state to predict S-CO<Subscript>2</Subscript> flow with real gas effects

The accuracy of the thermodynamic properties prediction from the different Equation of state (EOS) varies upon the range of temperature and pressure. Despite the variety of EOS available, there is no de facto for selecting an EOS for particular computational modeling. The EOS model recently developed by Kumar and Kim (K-K EOS) determines more accurately the thermodynamic properties of CO₂ than earlier models. In this present study, K-K EOS is successfully implemented in the computational analysis of compressible supercritical CO₂ flow (S-CO₂) in the thermodynamic region near and away from the vapour-liquid critical point. Computational results of SCO₂ flow with the real gas properties predicted with the K-K EOS is compared with Span and Wagner (SW EOS) and ideal EOS.     

Determination of Johnson-Cook constitutive equation for Inconel 601

Due to their superior thermal and mechanical properties, super alloys widely used in the aerospace industry have been well-documented in terms of AdvantEdge-based analysis of cutting characteristics rather than experimental methods. However, the well-known super alloy Inconel 601 does not have any database of its material properties in AdvantEdge, which underscores the urgency to build such a database. Hence, the current study uses the Johnson-Cook equation to build a database of Inconel 601’s material properties in AdvantEdge. To that end, drawing on a room temperature tensile test, elevated temperature tensile test and orthogonal cutting test, the current study determines the Johnson-Cook constitutive equation for Inconel 601, and verifies the reliability of the determined Johnson-Cook constitutive equation by comparing the experimental values with the analytical values.     

A methodology for determining the true stress-strain curve of SA-508 low alloy steel from a tensile test with finite element analysis

The true stress-strain curve of a material should be determined for plastic property input to numerical analysis. This study proposes a simple methodology for determining the true stress-strain curve of SA-508 Grade 3 Class 1 low alloy steel using limited information from a general tensile test with finite element analysis. Measured engineering stresses and strains can be reasonably converted to true stresses and strains under uniform deformation before necking. True stress-strains are difficult to determine after necking because of nonuniform deformation without specialized measurement techniques. Five post-necking strain hardening models are considered, namely, linear, swift, Ludwick, Hollomon-linear (HL) and Hollomon-linear-constant (HLC) models. The equations for each model can be determined using the results of the tensile test, which include the true stress-strain value at the maximum load point and the corrected true stress-strain value at the fracture point plus the Considere instability criterion. The HL and HLC models suggested that the engineering stress-strains from the finite element analysis are consistent with the experimental results.     

Numerical analysis of wave energy dissipation by damping treatments in a plate with acoustic black holes

The reduction of vibration by acoustic black holes (ABHs) with damping treatments can be achieved in two stages: energy focalization and energy dissipation. The energy focalization is mainly due to changes of the local thickness by slowing down the flexural wave speed and energy dissipation can be achieved by using viscoelastic damping materials. In structures with embedded ABHs, the damping effectiveness can depend significantly on the types of damping treatments. In this paper, 4 different damping treatments according to the types of attached region are considered in order to estimate the effectiveness of damping treatments as 1) a fully-covered unconstrained damping treatment, 2) a fully-covered constrained damping treatment, 3) a partially-covered unconstrained damping treatment and 4) a partially- covered constrained damping treatment as well as no damping treatment as reference data. In this study, the performance of damping treatments is explored using numerical simulations of three-dimensional thin plate embedded truncated ABH(s). The wave energy in the ABH, the normalized total energy and the focalization ratio are introduced to compare the effectiveness of the damping treatments. The numerical results show that the fully-covered constrained damping treatment provides the most effective configuration in terms of the wave energy in ABH and the normalized total energy.     

The canonical stewart platform as a six DOF pose sensor for automotive applications

The growing demand for prolonged fatigue life of automotive parts and components requires elaboration of their motion in Cartesian space having six degrees of freedom (DOF). Recently, the canonical Steward platform, consisting of six displacement sensors mounted on two parallel platforms, was introduced to comply with this request. In order to apply this pose sensor to automotive applications, the following two important matters are investigated in this study. First, update Jacobian is proposed as a faster and more stable numerical method to solve the forward kinematic problem without any iteration process. Second, the attachment position and initial configuration of the Stewart platform must be adjustable to avoid the interference with other components due to space constraints under the hood of automotive vehicle. In this case, however, the Jacobian matrix which converts six displacement components into a six DOF pose vector is prone to be ill-conditioned so that the converting accuracy becomes worse. The L₁-norm of each row in the Jacobian matrix quantifies how much the error would be provoked according to the given kinematic geometry. Hence, it can be used here as a reliable error indicator. Furthermore, several numerical examples are discussed to demonstrate what to consider when designing a six DOF pose sensor for automotive applications.     

Self- and mutual-diffusion coefficients in the dodecane/polystyrene system

The self-diffusion coefficient of dodecane in cross-linked polystyrene was measured using pulsed gradient spin echo nuclear magnetic resonance (PGSE–NMR) spectroscopy. The concentration and temperature dependence of the diffusion coefficient was analyzed by the Fujita and Vrentas–Duda models. Parameters describing the Fujita model were determined from fitting of diffusion data to the PVT behavior of the system. Parameters describing the Vrentas–Duda model were determined from the analysis of the viscosity of dodecane, the viscoelastic relaxation properties, and the glass transition temperature of polystyrene as well as from the diffusion coefficient of the system, measured from independent experiments. Both the Fujita and Vrentas–Duda models described well the concentration and temperature dependence of the diffusion coefficient. Mutual diffusion coefficients were determined from these results. © 1994 John Wiley & Sons, Inc.