A study on the mechanical properties of ti-8ta-3nb alloy for biomaterials

Ti-8Ta-3Nb has been developed as a new biomaterial. The experimental specimens are as-cast and forged Ti-8Ta-3Nb alloys. Treatment in a solution, ranging from 760 to 960°C has carried out. The microstructural research has carried out after the solution treatment and the hardness was measured. The specific heat and the length variations of Ti-8Ta-3Nb were also measured. The optimum temperature for the solution heat treatment of Ti-8Ta-3Nb was found to be 880°C. This was based on the mechanical properties and the volume fraction of α phase and their phases shown from the results of the solution heat treatment. From the results, the β transition temperature of Ti-8Ta-3Nb was found to be between 860° and 880°C.     

Spectral element analysis for an axially moving viscoelastic beam

In this paper, a spectral element model is derived for the axially moving viscoelastic beams subject to axial tension. The viscoelastic material is represented in a general form by using the one-dimensional constitutive equation of hereditary integral type. The high accuracy of the present spectral element model is verified first by comparing the eigenvalues obtained by the present spectral element model with those obtained by using the conventional finite element model as well as with the exact analytical solutions. The effects of viscoelasticity and moving speed on the dynamics of moving beams are then numerically investigated.     

LDV measurement,flow visualization and numerical analysis of flow distribution in a close-coupled catalytic converter

Results from an experimental study of flow distribution in a close-coupled catalytic converter (CCC) are presented. The experiments were carried out with a flow measurement system specially designed for this study under steady and transient flow conditions. A pitot tube was a tool for measuring flow distribution at the exit of the first monolith. The flow distribution of the CCC was also measured by LDV system and flow visualization. Results from numerical analysis are also presented. Experimental results showed that the flow uniformity index decreases as flow Reynolds number increases. In steady flow conditions, the flow through each exhaust pipe made some flow concentrations on a specific region of the CCC inlet. The transient test results showed that the flow through each exhaust pipe in the engine firing order, interacted with each other to ensure that the flow distribution was uniform. The results of numerical analysis were quali-tatively accepted with experimental results. They supported and helped explain the flow in the entry region of CCC.     

Molecular dynamics study on external field induced crystallization of amorphous argon structure

A molecular dynamics study has been conducted on an external-force-field-induced isothermal crystallization process of amorphous structures as a new low-temperature athermal crystallization process. An external cyclic-force field with a dc bias is imposed on molecules selected randomly in an amorphous-phase of argon. Multiple peaks smoothed out in the radial distribution functions for amorphous states appear very clearly during the crystallization process that cannot be achieved otherwise. When the amorphous material is locally exposed to an external force field, crystallization starts and propagates from the interfacial region and crystallization growth rates can be estimated.     

Tribological Properties of Polymer Composites Containing Barite (BaSO4) or Potassium Titanate (K2O · 6(TiO2))

Tribological properties of particulate barite (BaSO₄) and potassium titanate (K₂O·6(TiO₂)) whiskers, the two major ingredients currently used for commercial brake friction materials, were investigated. A novolac resin was used as a binder for test specimens and a block-on-disk tribometer was used to assess friction characteristics of the two ingredients. Experimental results showed that the BaSO₄-filled composite produced large frictional oscillations and created severe damage on the gray iron counter surface, while the composite filled with the same amount of K₂O·6(TiO₂) whiskers showed smooth sliding without large friction force fluctuation. The cause of the different frictional behavior was investigated by considering stick-slip and mechanical properties of the composites, which was largely based on the morphology of the two ingredients and their role in reinforcing the composite. The results from this comparative study suggest that the friction characteristics of commercial friction materials can be strongly affected by the two ingredients, which have been considered as minor constituents for brake performance.     

An Improved Method for the Determination of 3D Cutting Force Coefficients and Runout Parameters in End Milling

A simple improved method is suggested for determining constant cutting force coefficients, irrespective of the cutting condition and cutter rotation angle. This can be achieved through the combination of experimentally deternimed cutting forces with those from simulation, performed by a mechanistic cutting force model and a geometric uncut chip thickness model. Additionally, this study presents an approach that estimates runout-related parameters, and the runout offset and its location angle, using only one measurement of cutting force. This method of estimating 3D end milling force coefficients was experimentally verified for a wide range of cutting conditions, and gave significantly better predictions of cutting forces than any other methods. The estimated value of the runout offset also agreed well with the measured value.     

Neighborhood spillover effects between rezoning and housing price

The objective of this research was to investigate neighborhood spillover effects between rezoning of vacant parcels and housing price in the Knoxville, TN area. The study is unique in that it correctly highlights the need to analyze the dynamics of zoning structure and accommodates the neighborhood spillover effects associated with the real estate market. Results indicate that the probability of rezoning vacant land is expected to increase as housing price in a neighboring location increases. The rise in the housing price in a neighboring location implies increasing pressure on housing demand. This increased pressure on housing demand likely contributes to greater demands for residential development and commercial development that complements residential use. Currently, the major guidelines for the approval of rezoning petitions, according to the planners in the Knoxville area, are consistency with long-and short-range land use plans adopted by state, municipality, and county governments, and consistency with surrounding land use and environmental constraints, e.g., slope, flooding, and drainage. Local planning authorities can modify and update consistency measures in the current guidelines by accounting for varying degrees of housing demand pressure. For example, consistency measures can be strengthened in areas with greater housing-price increases, if preservation is desirable because these areas are likely to experience greater rezoning pressure.     

Prediction of the combination of failure modes for an arch bridge system

An innovative prediction method for the combination of failure modes of an arch bridge is proposed for its probabilistic risk assessment and is compared with the conventional system reliability analysis method. The suggested method reveals various combinations of failure modes in significantly reduced time and efforts in comparison to the previous permutation method or the conventional system reliability analysis method. Additionally, the suggested method can be used for the verification of the system reliability with more specific predictions of the failure modes.Component reliabilities of girders have been evaluated by using response surfaces of the design variables at the selected critical sections, i.e. the maximum shear and negative moment locations. Response Surface Method (RSM) is successfully applied for the reliability analyses of complex structure with relatively small probability of failure. Previous methods such as Monte Carlo Simulations or First Order Second Moment method cannot easily calculate the derivative terms of implicit limit state functions. Hence, the target bridge system is modeled as a series-connection system for the analysis of its system reliability. The upper and lower bound of the probabilities of failure for the structural system have been evaluated and are compared with the suggested prediction method for all possible combination of failure modes.     

Remote robotic system for 3D measurement of concrete damage in tunnel with ground vehicle and manipulator

To ensure the safety of a concrete structure, periodic and accurate inspection for damage is necessary. However, there is a high risk of inaccurate diagnosis of the structure condition because the manual inspection method is dependent on operator experience and subjective judgment. Additionally, in future society, it may become increasingly difficult to maintain high-quality infrastructure, as the number of inspection personnel will also decrease with a decrease in population. For this purpose, the demand for accurate and automated inspection technology is increasing. To meet these issues, in this study, an objective and automated inspection method is proposed by developing an inspection robot and management system. The inspection robot comprises an artificial intelligence sensor, a manipulator, and a ground vehicle; it can autonomously drive inside a tunnel and inspect the damage on concrete surfaces using stereo vision. The management system remotely controls the robot through wireless communication and monitors the inspection status in real time. In addition, damage is automatically restored in three dimensions based on the images, and the physical size of the damage is analyzed with an average relative error of 0.39%. This method is expected to be used as a core technology for unmanned and automated tunnel maintenance in the future.     

Sorbed atrazine shifts into non-desorbable sites of soil organic matter during aging

Soil-chemical contact time (aging) is an important determinant of the sorption and desorption characteristics of the organic contaminants and pesticides in the environment. The effects of aging on mechanism-specific sorption and desorption of atrazine were studied in soil and clay slurries. Sorption isotherm and desorption kinetic experiments were performed, and soil-water distribution coefficients and desorption rate parameters were evaluated using linear and non-linear sorption equations and a three-site desorption model, respectively. Aging time for sorption of atrazine in sterilized soil and clay slurries ranged from 2 days to 8 months. Atrazine sorption isotherms were nearly linear (r(2)>0.97) and sorption coefficients were strongly correlated to soil organic carbon content. Sorption distribution coefficients (K(d)) increased with increase in age in all five soils studied, but not for K-montmorillonite. Sorption non-linearity did not increase with increase in age except for the Houghton muck soil. Desorption profiles were well described by the three-site desorption model. The equilibrium site fraction (f(eq)) decreased and the non-desorbable site fraction (f(nd)) increased as a function of aging time in all soils. For K-montmorillonite, f(nd) approximately 0 regardless of aging, showing that aging phenomena are sorbent/mechanism specific. In all soils, it was found that when normalized to soil organic matter content, the concentration of atrazine in desorbable sites was relatively constant, whereas that in non-desorbable site increased. This, and the lack of aging effects on desorption from montmorillonite, suggests that sorption into non-desorbable sites of soil organic matter is primary source of increased atrazine sorption in soils during aging.