Mesh Force Modelling and Parametric Studies for Compound Oscillatory Roller Reducer

A compound oscillatory roller reducer(CORR)with a first-stage gear transmission and a second-stage oscillatory roller transmission is presented.The transmission principle of oscillatory roller transmission is introduced,and the tooth profile equation of the inner gear is derived.The analytical model of mesh force considering the installation errors and manufacturing errors is proposed.Then,parametric studies considering different errors on the mesh force are conducted.Results show that the design parameters are significant factors for mesh force.The mesh force is reduced by 17%as the eccentricity of disk cam increases from 2.5 mm to 4 mm.When the radius of the movable roller increases from 7 mm to 20 mm,the mesh force decreases by 8%.As the radius of disk cam increases from 125 mm to 170 mm,the mesh force is decreased by 26.5%.For the impacts of errors,the mesh force has a noticeable fluctuation when these errors exist including the manufacturing error of disk cam,the installation error of disk cam and the manufacturing error of movable roller change.The prototype of the reducer is manufactured and preliminary run-in test proved the feasibility of the transmission principle.

PARAMETRIC STUDIES ON THE STATIC BEHAVIOUR OF MARINE RISER

The behaviour of marine risers is investigated under the forces produced by selfweight, wave and current and quasistatic motion of the top vessel. The parameters include the applied tension, geometric nonlinearity, magnitude of surge, heave and pitch motion of the top vessel and wave height. The study shows that the above parameters have considerable influence on the riser response.

Parametric Analysis of A Submerged Cylindrical Shell Subjected to Shock Waves

In this study, an FEM-SBFEM （scaled boundary finite element method） coupling procedure proposed by Fan et al. （2005） is adopted to obtain the dynamic responses of a submerged cylindrical shell subjected to plane step or exponential acoustic shock waves. The coupling procedure can readily be applied to three-dimensional problem, however for clarity, the problems to be presented are hmited to two-dimeusional domain. In the analyses, the cylindrical shell is modeled by simple beam elements （using FEM）, while the effects of the surrounding infinite fluid is modeled by the SBFEM. In it, no free surface and seabed are involved. Compared with Fan and his co-authors＇ works, the FEM-SBFEM coupling procedure is further verified to be feasible for shock waves by benchmark examples. Furthermore, parametric studies are performed and presented to gain insight into effects of the geometric and material properties of the cylindrical shell on its dynamic responses.

Parametric Study on the Behavior of An Innovative Subsurface Tension Leg Platform in Ultra-Deep Water

This study focuses on a new technology of Subsurface Tension Leg Platform （STLP）, which utilizes the shallow- water rated well completion equipment and technology for the development of large oil and gas fields in ultra-deep water （UDW）. Thus, the STLP concept offers attractive advantages over conventional field development concepts. STLP is basically a pre-installed Subsurface Sea-star Platform （SSP）, which supports rigid risers and shallow-water rated well completion equipment. The paper details the results of the parametric study on the behavior of STLP at a water depth of 3000 m. At first, a general description of the STLP configuration and working principle is introduced. Then, the numerical models for the global analysis of the STLP in waves and current are presented. After that, extensive parametric studies are carried out with regarding to SSP/tethers system analysis, global dynamic analysis and riser interference analysis. Critical points are addressed on the mooring pattern and riser arrangement under the influence of ocean current, to ensure that the requirements on SSP stability and riser interference are well satisfied. Finally, conclusions and discussions are made. The results indicate that STLP is a competitive well and riser solution in up to 3000 m water depth for offshore petroleum production.

Parametric study of natural convection over horizontal annular finned tube

Natural convection heat transfer from annular finned tubes was studied numerically. Effects of fin spacing, temperature difference and tube diameter on flow pathlines and local heat transfer were also studied. It was shown that pathlines remain mostly circular for different geometries. Moreover, the contributions of fin periphery, fin side and bare tube to heat transfer were specified. It was shown that the heat transfer per unit area of fin periphery can be several times that of other parts. Moreover, in higher finspacing, the heat transfer from the bare tube can be more important than fin sides.

Parametric study on mass loss of penetrators

Earth penetration weapon （EPW） is applicable for attacking underground targets protected by reinforced concrete and rocks. With increasing impact velocity, the mass loss/abrasion of penetrator increases, which significandy decreases the penetration efficiency due to the change of nose shape. The abrasion may induce instability of the penetrator, and lead to failure of its structure. A common disadvantage, i.e. dependence on corresponding experimen- tal results, exists in all the available formulae, which limits their ranges of application in estimating the mass loss of penetrator. In this paper, we conduct a parametric study on the mass loss of penetrator, and indicate that the mass loss of penetrator can be determined by seven variables, i.e., the initial impact velocity, initial nose shape, melting heat, shank diameter of projectile and density and strength of target as well as the aggregate hardness of target. Further discussion on factors dominant in the mass abrasion of penetrator are given, which may be helpful for optimizing the target or the projectile for defensive or offensive objectives, respectively.

Parametric study of control mechanism of cortical bone remodeling under mechanical stimulus

The control mechanism of mechanical bone remodeling at cellular level was investigated by means of an extensive parametric study on a theoretical model described in this paper. From a perspective of control mechanism, it was found that there are several control mechanisms working simultaneously in bone remodeling which is a complex process. Typically, an extensive parametric study was carried out for investigating model parameter space related to cell differentiation and apoptosis which can describe the fundamental cell lineage behaviors. After analyzing all the combinations of 728 permutations in six model parameters, we have identified a small number of parameter combinations that can lead to physiologically realistic responses which are similar to theoretically idealized physiological responses. The results presented in the work enhanced our understanding on mechanical bone remodeling and the identified control mechanisms can help researchers to develop combined pharmacological-mechanical therapies to treat bone loss diseases such as osteoporosis.

High Purity Hydrogen Production by Metal Hydride System:A Parametric Study Based on the Lumped Parameter Model

The simulation of hydrogen purification in a mixture gas of hydrogen/carbon dioxide (H2/CO2) by metal hydride system was reported.The lumped parameter model was developed and validated.The validated model was implemented on the software Matlab/Simulink to simulate the present investigation.The simulation results demonstrate that the purification efficiency depends on the external pressure and the venting time.An increase in the external pressure and enough venting time makes it possible to effectively remove the impurities from the tank during the venting process and allows to desorb pure hydrogen.The impurities are partially removed from the tank for low external pressure and venting time during the venting process and the desorbed hydrogen is contaminated.Other parameters such as the overall heat transfer coefficient,solid material mass,supply pressure,and the ambient temperature influence the purification system in terms of the hydrogen recovery rate.An increase in the overall heat transfer coefficient,solid material mass,and supply pressure improves the hydrogen recovery rate while a decrease in the ambient temperature enhances the recovery rate.

Development of an occupant restraint system model and parametric study on equivalent crash pulse in vehicle frontal offset crash

Studies were conducted to evaluate driver injury metrics with varying crash pulse in offset crash. First, a vehicle finite element （ FE ） model and an occupant restraint system （ORS） model were developed and validated against tests; then, the crash pulse collected from the test vehicle was equivalent to a dual-trapezoid shape pulse which will be quantitatively described by six parameters and was put into the ORS model; finally, parametric studies were conducted to analyze the sensitivi- ties of parameters of equivalent crash pulse on head resultant acceleration, head injury criteria （HIC）, neck axial force and chest deformation. Results showed that the second peak value of the crash pulse was statistically significant on all these injury criteria （P = 0. 001, 0. 000, 0. 000, 0. 000 re- spectively）, the first peak level had a negative significantly effect on all the criteria aforementioned except the chest deformation （P = 0. 011, 0. 038, and 0. 033 respectively）, and the interaction of the time-points of first and second peak values had a significant influence on head resultant acceleration （P = 0. 03 ）. A higher first peak value and a lower second peak value of the crash pulse could bring deeply lower injury metrics.

A parametric study of methane decomposition into carbon nanotubes over 8Co-2Mo/Al_2O_3 catalyst

The effects of reaction temperature, partial pressure of methane, catalyst weight and gas hourly space velocity （GHSV） on methane decomposition were reported. The decomposition reaction was performed in a vertical fixed-bed reactor over 8Co-2Mo/Al 2 O 3 catalyst. The experimental results show that these four process parameters studied had vital effects on carbon yield. As revealed by the electron microscopy and Raman spectroscopy analyses, the reaction temperature and GHSV governed the average diameter, the diameter distribution and the degree of graphitization of the synthesized carbon nanotubes （CNTs）. Also, an evidence is presented to show that higher temperatures and higher GHSV favored the formation of better-graphitized CNTs with larger diameters.

Parametric Study of Hip Fracture Risk Using QCT-Based Finite Element Analysis

Various parameters such as age,height,weight,and body mass index(BMI)influence the hip fracture risk in the elderly which is the most common injury during the sideways fall.This paper presents a parametric study of hip fracture risk based on the gender,age,height,weight,and BMI of subjects using the subject-specific QCT-based finite element modelling and simulation of single-leg stance and sideways fall loadings.Hip fracture risk is estimated using the strain energy failure criterion as a combination of bone stresses and strains leading to more accurate and reasonable results based on the bone failure mechanism.Understanding the effects of various parameters on hip fracture risk can help to prescribe more accurate preventive and treatment plans for a community based on the gender,age,height,weight,and BMI of the population.Results of this study show an increase in hip fracture risk with the increase of age,body height,weight,and BMI in both women and men under the single-leg stance and the sideways fall configurations.

Modelling Strategy and Parametric Study of Metal Gaskets for Automotive Applications

This paper is focused on finite element simulation of cylinder head gaskets.Finite element codes support several methodologies,each of which has its own strengths and weaknesses.One of the key points lies in the influence of the gasket geometry on its final behaviour.Such a contribution can come from the detailed modelling of the gasket or by defining a global non-linear behaviour in which material and geometry non-linearities are summarised.Two approaches were used to simulate the gasket behaviour.The first one consists in using a 2D approach,which allows to model through-thickness non-linear behaviour of gasket.The second one consists in using conventional 3D finite element modelling.The numerical methods have been discussed and compared in relation to the accordance with experimental data,amount of information supplied and computational time required.Finally,a parametric study shows how some geometric parameters influence the compressive load and the elastic recovery of a single-layer steel gasket.

Exploration of nature-based biomimetic approach in landscape architectural design: parametric study of candelabra model design

This research provides an exploration of a biomimetic approach in the process of designing a candelabra model using linear shaped leaves of a Bell flower.The design process described in this research contains two steps:biological and geometrical.In the first biological step,a proper model for the creation of an urban element was found from nature in a Bell flower(Campanula persicifolia L.).The upper leaves of the selected plant,which are small with a linear spear and sharpening at the top,were chosen for the modeling process.The second step included applying two geometrical methods,i.e.,Voronoi diagrams and Delaunay triangulation.A geometrical leaf form of the selected plant species and the modeling process were obtained using aparametric modeling software,Blender.Using different Blender plug-ins and modifiers,Delaunay triangulation and Voronoi diagram were implemented by marking the starting points on the leaf form in the image data source,adjusting the Delaunay triangulation parameters,and creating Voronoi diagrams in which the Voronoi points were located at the shortest distance from the edges of the Voronoi polygon.Consequently,a three dimensional model of a candelabra was developed through this study.

Flow-Induced Clogging in Microfiltration Membranes: Numerical Modeling and Parametric Study

Microfiltration membrane technology has been widely used in various industries for solid-liquid separation. However, pore clogging remains a persistent challenge. This study employs (CFD) and discrete element method (DEM) models to enhance our understanding of microfiltration membrane clogging. The models were validated by comparing them to experimental data, demonstrating reasonable consistency. Subsequently, a parametric study was conducted on a cross-flow model, exploring the influence of key parameters on clogging. Findings show that clogging is a complex phenomenon affected by various factors. The mean inlet velocity and transmembrane flux were found to directly impact clogging, while the confinement ratio and cosine of the membrane pore entrance angle had an inverse relationship with it. Two clog types were identified: internal (inside the pore) and external (arching at the pore entrance), with the confinement ratio determining the type. This study introduced a dimensionless number as a quantitative clogging indicator based on transmembrane flux, Reynolds number, filtration time, entrance angle cosine, and confinement ratio. While this hypothesis held true in simulations, future studies should explore variations in clogging indicators, and improved modeling of clogging characteristics. Calibration between numerical and physical times and consideration of particle volume fraction will enhance understanding.

Flexural behaviors of double-reinforced ECC beams

In order to investigate the flexural behaviors of engineered cementitious composites （ECC）, theoretical and experimental researches are done on flexural doublereinforced ECC beams. Based on the assumption of the plane section remaining plane in bending and simplified constitutive models of materials, the calculation methods of load carrying capacities for different critical stages are obtained. Then, these calculation methods are demonstrated by comparing the test results with the calculation results. Finally, based on the proposed theoretical formulae, the effects of the compression strength, compression strain and tension strength of ECC, and the reinforcement ratio on the flexural behaviors of double-reinforced ECC beams are analyzed. The calculated and measured results are in good agreement, which indicates that the theoretical model can be used to predict the momentcurvature response of steel reinforced ECC beams. And the results of parametric studies show that the increase in the compression strength of ECC can greatly improve the flexural performance of beams; the increase in the ultimate compression strain can significantly improve the ultimate curvature and ductility, but has little effect on the load bearing capacity of beams. little effect on the flexural The tensile strength of ECC has behaviors of ECC beams. The increase in the steel reinforcement ratio can lead to significant improvement of the load bearing capacity and the stiffness of beams, but a degradation of the ductility of beams. The theoretical model and parameter analysis results in this paper are instructive for the design of steel reinforced ECC beams.

Lateral Bearing Capacity of Modified Suction Caissons Determined by Using the Limit Equilibrium Method

The modified suction caisson(MSC) adds a short-skirted structure around the regular suction caissons to increase the lateral bearing capacity and limit the deflection. The MSC is suitable for acting as the offshore wind turbine foundation subjected to larger lateral loads compared with the imposed vertical loads. Determination of the lateral bearing capacity is a key issue for the MSC design. The formula estimating the lateral bearing capacity of the MSC was proposed in terms of the limit equilibrium method and was verified by the test results. Parametric studies on the lateral bearing capacity were also carried out. It was found that the lateral bearing capacity of the MSC increases with the increasing length and radius of the external skirt, and the lateral bearing capacity increases linearly with the increasing coefficient of subgrade reaction. The maximum lateral bearing capacity of the MSC is attained when the ratio of the radii of the internal compartment to the external skirt equals 0.82 and the ratio of the lengths of the external skirt to the internal compartment equals 0.48, provided that the steel usage of the MSC is kept constant.

Performance Analysis and Improvement of Flat Torque Converters Using DOE Method

Automotive torque converters have recently been designed with an increasingly narrower profile for the purpose of achieving a smaller axial size and reducing weight. Design of experiment(DOE) and computational fluid dynamics(CFD) techniques are applied to improve the performance of a flat torque converter. Four torque converters with different flatness ratios(0.204, 0.186, 0.172, and 0.158) are designed and simulated first to investigate the effects of flatness ratio on their overall performance, including efficiency, torque ratio, and impeller torque factor. The simulation results show that the overall performance tends to deteriorate as the flatness ratio decreases. Then a parametric study covering six geometric parameters, namely, inlet and outlet angles of impeller, turbine, and stator is carried out. The results demonstrate that the inlet and outlet angles play an important role in determining the performance characteristics of a torque converter. Furthermore, the relative importance of the six design parameters is investigated using DOE method for each response(stall torque ratio and peak efficiency). The turbine outlet angle is found to exert the greatest influence on both responses. After DOE analysis, an optimized design for the flat torque converter geometry is obtained. Compared to the conventional product, the width of the optimized flat torque converter torus is reduced by about 20% while the values of stall torque ratio and peak efficiency are only decreased by 0.4% and 1.7%, respectively.The proposed new optimization strategy based on DOE method together with desirability function approach can be used for performance enhancement in the design process of flat torque converters.

Seismic ground amplification induced by box-shaped tunnels

The growing use of underground structures,specifically to facilitate urban transportation,highlights the need to scrutinize the effects of such spaces on the seismic ground response as well as the surrounding buildings.In this regard,the seismic ground amplification variations in the vicinity of single and twin box-shaped tunnels subjected to SV waves have been investigated by the finite difference method.To evaluate the effects,generalizable dimensionless diagrams based on the results of parametric numerical analysis considering factors such as variations in the tunnels′depth,the distances between the tunnels,tunnel lining flexibility,and input wave frequency,have been presented.In addition,to assess the effects of underground box-shaped tunnels on the response spectrum of the ground surface,seven selected accelerograms have been matched based on a specific design spectrum for the stiff soil condition of Eurocode 8(CEN,2006).The results underline the significant amplification effect of the box-shaped tunnels on the ground motions,specifically in the case of horizontal twin tunnels,which should be given more attention in current seismic design practices for surface structures.

Developing a Computer Program for Detailed Study of Planing Hull＇s Spray Based on Morabito＇s Approach

Recently, Morabito(2010) has studied the water spray phenomena in planing hulls and presented new analytical equations. However, these equations have not been used for detailed parametric studies of water spray around planing hulls. In this paper, a straight forward analysis is conducted to apply these analytical equations for finding the spray geometry profile by developing a computer program based on presented computational process. The obtained results of the developed computer program are compared against existing data in the literature and favorable accuracy is achieved. Parametric studies have been conducted for different physical parameters. Positions of spray apex are computed and three dimensional profiles of spray are examined. It is concluded that spray height increases by an increase in the speed coefficient or the deadrise angle. Ultimately, a computational process is added to Savitsky's method and variations of spray apex are computed for different velocities. It is shown that vertical, lateral, and longitudinal positions of spray increase as the craft speed increases. On the other hand, two new angles are defined in top view and it is concluded that they have direct relation with the trim angle. However, they show inverse relation with the deadrise angle.

Effect prediction of stiffened-ring cylindrical shells subjected to drop mass impact

This study focuses on the effect of lateral mass impact on ring-stiffened thin-walled cylindrical shell.Cylindrical shells were fabricated to validate the numerical modeling and analytical techniques,and drop tests were performed using a rigid spherical indenter.Next,stiffened-ring cylindrical shells with various structural size parameters were simulated using ABAQUS software.The relationships between the impact force,deformation displacement,and rebound velocity were established,on the basis of impact mechanics theory and simulation results.It derived fitting functions to analyse the relationship between the maximum load and maximum displacement of ring-stiffened cylindrical shell under dynamic mass impact.Based on the validation of the simulation model,the fitting function data were compared with the simulation results,and the functions showed a good accuracy.Besides,the parameters,mass ratio and stiffened-ring mass ratio were used to reflect the effect of the mass change in the ring-stiffened cylindrical shell.Furthermore,parametric studies on ring-stiffened cylindrical shell models were conducted to analyse the progressive impact responses.