Tertiary Zone Research Articles

2D FEM simulation and experimental verification of Al 7075‐T6 during turning process

AbstractIn this work, temperature distribution, effective stress and strain distribution in Al 7075‐T6 material and plastic flow of materials during turning process have been studied using Deform 3D v11.0 software. The four different points (P1, P2, P3, and P4) were chosen at the different locations in the cylindrical workpiece and the graph has been plotted with different parameters namely, temperature distribution, effective stress and strain. For temperature distribution, a good agreement has been found between simulation and experimental results at P4. The following results obtained from the simulation: In tertiary zone, the maximum temperature of specimen reaches upto 142 °C at points P1 due to friction between the tool rack face and the lower surface of chip. Maximum effective stress value reaches upto 650 MPa and 704 MPa at P1 and P4 respectively in the first sticking zone due to the combined effect of high normal force by tool edge and ploughing force. The effective strain value at P1 and P4 obtained, strain at P4 reaches maximum compare to P1 due to friction and unven temperature distribution. Additionally, chip analysis has been performed with microscopic image.

Can slope spectrum information entropy replace slope length and steepness factor: A case study of the rocky mountain area in northern China

Slope spectrum information entropy (SSIE) can reflect the overall fluctuation characteristics of the topography with convenient calculation. In order to explore whether the complex slope length and steepness factor (LS factor) can be replaced by SSIE in the evaluation of soil erosion in the rocky mountain area, this study took the rocky mountain area in northern China (the first zone of soil and water conservation) as the research object. The soil texture of study area is the most typical “soil-rock dual structure”. The SSIE, soil erosion intensity (SEI), and LS factor were calculated using ASTER GDEM and Landsat8 image data (30 m × 30 m). The correlation between the SSIE and SEI was revealed, and a functional relationship model of SSIE and LS factor was built. This study clarified whether SSIE could replace the LS factor to evaluate soil erosion in the “soil-rock dual structure” area. The results showed that: (1) The slope spectrum curves of the six secondary zones of soil and water conservation in the study area presented “L” shape, and the SSIE was between 0.59 and 2.79 nat. SEI grades were mainly micro-erosion, with strong erosion and above accounting for 1.7%. The spatial distribution difference was significant and strong erosion and above was mostly distributed in mountainous and hilly areas. The LS factor of the whole region was between 0 and 55.03, with an average value of 1.37. The regions with an average LS factor < 5 accounted for more than 82% in each secondary zone. (2) The significant logarithmic function relationship of SSIE and SEI was displayed on the secondary zone (R2 = 0.9372, P < 0.01), tertiary zone (R2 = 0.7908, P < 0.01), and basin scales (R2 = 0.3534, P < 0.01). (3) The relationship of SSIE and LS factor also was significant logarithmic function on the secondary zone (R2 = 0.7866, P < 0.05), tertiary zone (R2 = 0.8269, P < 0.01), and basin scales (R2 = 0.8958, P < 0.01). It was indicated that in the typical hydraulic erosion areas of “soil-rock dual structure”, SSIE can replace the LS factor to evaluate SEI and soil erosion modulus.

Improving the friction model for the simulation of cutting processes

The here developed friction model for numerical simulations of machining processes takes account of the physical‐mechanical phenomena occurring in different cutting zones by determining the concentrated forces acting in these zones. The forces acting in the primary and tertiary zones were divided from the general cutting forces obtained by experiment or calculated analytically. The forces in the plastic and elastic contact of the secondary cutting zone were identified by eliminating the elastic contact due to a reduction in the rake face of the cutting wedge. For each respective zone, a coefficient of friction was determined as a quotient of normal and tangential forces.

Empirical correlation of the modified wheel tracker (MWT) and the dynamic creep test for evaluating the permanent deformation of hot mix asphalt (HMA)

The wheel tracking test (WTT) has been extensively used for laboratory characterization of permanent deformation of hot mix asphalt (HMA). However, the fully-confined setup of the device is unable to capture the tertiary zone where shear deformation takes place. This makes the permanent deformation resistance characteristics of HMA difficult to analyze. Hence, a modified wheel tracker (MWT), with unconfined lateral sides along the wheel tracking direction was utilized in this study, which can capture the tertiary flow (referred to as the flow number (FN)). The dynamic creep test, which yields FN, is a common laboratory test which has the ability to characterize permanent deformation considering the shear behavior. The study investigated the relationship of the MWT and the dynamic creep test utilizing the permanent deformation and permanent microstrain data from the respective tests. A novel parameter, FN-Index was explored. The permanent deformation parameters derived from the MWT were well correlated with the dynamic creep test. The MWT showed promising repeatability for the FNs.

Experimental evaluation of primary measures for NOX and dust emission reduction in a novel 200 kW multi-fuel biomass boiler

The aim of this work is to utilize various biogenic fuels without ash slagging and to significantly reduce NOX and particulate matter emissions in comparison to modern combustion technologies. For this purpose, a novel small-scale multi-fuel biomass grate furnace technology was developed and experimentally investigated. It employs a low oxygen concentration in the fixed-bed and a double air staging, including the supply of flue gas recirculation. In this way slagging is prevented on the grate, reducing the release of ash-forming volatiles, NOX emissions are minimized in the reduction zone and an efficient flue gas burnout is achieved in the tertiary zone. Wood pellets and chips as well as miscanthus briquettes were investigated.The measured total particle emissions showed a reduction of 68% for pellets and 70% for wood chips compared to typical small-scale furnaces. Furthermore, a reduction of NOX emissions of 39% for wood chips, 40% for wood pellets and 45% for miscanthus briquettes was achieved compared to typical small-scale furnaces. The experimental parameter study provided fundamental insights into the various mechanisms involved in this novel technology, which is close to market introduction, and proved its high fuel flexibility and great potential for particulate matter and NOX emission reduction.

Thermal modeling of drilling process in titanium alloy (Ti-6Al-4V)

In drilling in titanium alloys, heat trapped in a hole adversely affects tool life, hole surface quality and integrity. Therefore, modeling temperature distribution in drilling is vital for effective heat dissipation and improving quality of drilled surfaces. The existing numerical and finite element models consider only frictional heat, whereas the effect of shear heat generation and tertiary heat generation is neglected. In the present work, a comprehensive thermal model of the drilling process is developed by considering all heat generated in shear, friction and tertiary zones. The drill cutting edges are divided into a series of independent elementary cutting tools (ECT). The calculated heat flux loads are applied on an individual ECT in the finite element model to determine the temperature distribution and the maximum temperature around the cutting edge. The temperature in the drill was also measured experimentally with the help of an Infrared (IR) camera. The results of numerical simulations lie within the error of ∼8.75% when compared to the prior studies, and ∼5.41% when compared to our experimental work. The thermal model gives the temperature distribution, and the maximum temperature observed at the corner of cutting edge was 604.2°C at a cutting speed of 35 m/min.

A Two-Dimensional Transient Thermal Model for Coated Cutting Tools

Prediction of temperature in the tool, chip, and workpiece surface is important to study tool wear, residual stresses in the machined part, and to design cutting tool substrates and coating. This paper presents a finite difference method-based prediction of temperature distribution in the tool, chip, and workpiece surface for transient conditions. The model allows inclusion of anisotropic materials such as coating or different material properties. The energy is created in the primary shear zone where the metal is sheared, the secondary deformation zone where the chip moves on the tool rake face with friction, and the tertiary zone where the flank face of the tool rubs against the finished part surface. The model allows both sticking and sliding friction contact of the moving chip on the rake face of the tool. The distribution of temperature is evaluated by meshing chip, workpiece surface zone, and tool into small discrete elements. The heat transfer among the elements is modeled, and the temperature is predicted at the center of each element. The heat transfer to the tool, workpiece, and chip is iteratively evaluated. The predicted temperature values are compared against the experimental measurements collected with coated tools in turning.

Microseismicity-derived fracture network characterization of unconventional reservoirs by topology

The advent of horizontal drilling technology, combined with multistaged hydraulic fracturing to create a complex fracture network within the relatively impermeable rock mass, has made natural gas production from tight reservoirs economically feasible. Understanding of the generated fracture network properties, such as its spatial distribution, extension, connection, and ability to percolate, plays a significant role in evaluation of the stimulation efficiency, optimizing analytical frac models, and ultimately enhancing completion programs. We have developed a unique approach to understand the influence of fractures on fluid flow and production from impermeable reservoirs and evaluate completion effectiveness. We characterize the microseismicity-derived discrete fracture network in a North American shale-gas reservoir using modified scanline and topology methods. Using concepts of node and branch classification and assessing the number of connections (fracture intersections), the network connectivity is established volumetrically. The zones of permeability enhancement are then identified using the connection per branch and line ([Formula: see text] and [Formula: see text]), tied to percolation thresholds of the fracture system. These zones consist of a primary zone with a high proportion of doubly connected fractures, a secondary zone populated with partially connected fractures, and a tertiary or unstimulated zone dominated by isolated fractures. These divisions are reflected in the deformation that is observed in the reservoir as measured through a cluster-based description of the microseismicity. The primary and secondary zones are considered spanning fracture clusters, and they take part in production, whereas the tertiary zone is recognized as nonspanning fractures, and though it may enhance the bulk permeability of the rock mass, it is unlikely to contribute to reservoir production.

A unified analytical cutting force model for variable helix end mills

The paper proposes a unified analytical cutting force model based on a predictive machining theory for variable helix end mill considering cutter runout. The variable helix end mill is divided into a set of differential oblique elements along the axial direction. The cutting process of oblique element is based on the non-equidistant shear zone model and the equivalent plane method. The cutting forces of oblique element are modeled by shearing force components due to shearing at the shear zone and edge force components due to rubbing in the tertiary zone. In the primary shear zone, a modified Johnson-Cook model is introduced to account for the material size effect affected by varying instantaneous uncut chip thickness (IUCT) during milling process. In the tertiary zone, edge radius and the partial effective rake angle are included in the analytical model in order to take into account the rubbing effect precisely. The total instantaneous cutting forces are obtained by summing up the cutting forces acting oblique elements on all flutes. The unified analytical cutting force model is verified by experimental data using four different types of end mills, and a good agreement of the predicted and measured cutting forces shows that the proposed model is valid for variable helix end mills.

Particle fracture and debonding during orthogonal machining of metal matrix composites

This paper investigates the particle fracture and debonding during machining of metal matrix composite (MMC) due to developed stress and strain, and interaction with moving tool by finite element analysis. The machining zone was divided into three regions: primary, secondary and tertiary deformation zones. The tendency of particles to fracture in each deformation zone was investigated. The findings of this study were also discussed with respect to the experimental results available in the literature. It was found that particles at the cutting path in the tertiary deformation zone fractured as it interacted with tool. In the secondary deformation zone, particles interacted with other particles as well as cutting tool. This caused debonding and fracture of huge number of particles as those were moving up along the rake face with the chips. No particle fracture was noted at the primary deformation zone. The results obtained from finite element analysis were very similar to those obtained from experimental studies.

EFFECT OF Sn ON THE SOLIDIFICATION PROCESS AND MICROSTRUCTURE OF Al-Pb MONOTECTIC ALLOYS

When a homogeneous, single-phase liquid of monotectic alloy is cooled into the miscibility gap, the components are no longer miscible and two liquid phases develop. Generally, the liquid-liquid decomposition causes the formation of the microstructure with serious phase segregation. Many efforts have been made to use the demixing phenomenon for the production of well dispersed composite materials. It has been demonstrated that the rapid directional solidification technique is an effective method to prevent the formation of the phase segregated microstructure in immiscible alloys. Directional solidification experiments were carried out to study the influence of the addition of Sn on the solidification process of Al-Pb alloys. The experimental results show that the addition of a small amount of Sn causes a decrease in the interface energy between the matrix and the minority phase liquids and, thus, an increase in the nucleation rate of the minority phase droplets during the liquid-liquid phase transformation or a decrease in the average size of the minority phase particles. With the increase of the Sn content, both the volume fraction of the minority phase droplets and the temperature range of the liquid-liquid phase zone and the liquid-liquid-solid tertiary phase zone of the phase diagram increase. These are favorable for the coarsening of the minority phase droplets. The addition of Sn leads to the formation of a dendrite solid/liquid interface. This may promote the formation of a well dispersed microstructure and shows great effect on the distribution of the minority phase particles.

Investigation of Combustion and Thermal-Flow Inside a Petroleum Coke Rotary Calcining Kiln With Potential Energy Saving Considerations

Calcined coke is a competitive material for making carbon anodes for smelting of alumina to aluminum. Calcining is an energy intensive industry and a significant amount of heat is exhausted in the calcining process. Efficiently managing this energy resource is tied to the profit margin and survivability of a calcining plant. To help improve the energy efficiency and reduce natural gas consumption of the calcining process, a 3D computational model is developed to gain insight of the thermal-flow and combustion behavior in the calciner. Comprehensive models are employed to simulate the moving petcoke bed with a uniform distribution of moisture evaporation, devolatilization, and coke fines entrainment rate with a conjugate radiation-convection-conduction calculation. The following parametric studies are conducted: rotation angles, tertiary air injection angles, devolatilization zone length, discharge end gas extractions without injecting natural gas, variations of coke bed properties (thermal conductivity and heat capacity), and coke bed sliding speed. A total of 19 cases have been simulated. The results of studying the effect of tertiary air injection angles show that employing 15 deg tertiary air injection angle provides the best calcining condition than using 30 deg and 45 deg injection angles by achieving a higher coke bed temperature and less coke fines entrainment and attrition rate. In an attempt to reduce natural gas consumption, employing gas extraction at the discharge end successfully draws the hot combustion gas from the tertiary air zone towards the discharge end without burning natural gas. The coke bed temperature between 6 and 21 m from the discharge end is successfully raised 10–100 K higher, but discharge end temperature is reduced 150 K without burning natural gas. The extracted gas at 1000 K is too low to be returned to the kiln, but it could be used to preheat the tertiary air.

On the paleogene coal-measure distribution over the China sea area

The Paleogene coal accumulation basins of China are part of the global Tertiary coal-accumulated zone of the Pacific Rim located in the eastern coastal provinces and areas. Although the coal-bearing basins of the China Sea area are faults and depressed basins, they come up in groups. The overall structures are suitable for the development of coal-bearing deposition. The continuity of basin groups are good, and the coal-bearing depositions are thick. For example, the coal-bearing deposition is more than a kilometer thick at the Qiongdongnan Basin and Xihu Sag in the East China Sea, which the continental Paleogene coal basins cannot reach. Research shows that the coal accumulation basins in the sea area consist of many sags. There are two types of coal accumulation sags: half-graben sag and graben sag. In terms of water depth, coal accumulation sags can also be classified as deep-water half-graben sag and shallow-water half-graben sag; the graben sag is the deep-water sag. There are two distinct coal-accumulated zones in the basin: gentle slope and steep slope, with the gentle slope being the dominant one. The marshes of the supratidal zone and intertidal zone in a tidal flat system is favorable for the coal accumulation process widely taking place. There are two types of peat accumulation: autochthonous accumulation and allochthonous accumulation. Because of tectonic activities in the basins, allochthonous accumulations may be the more important form of coal-forming activities in the sea area. The very thick coal-bearing deposition in the sea area provides a rich material base for the assemblage of coal-related gas. Also, as a result of the deep burial depth, the degree of coal metamorphism is relatively high, so the coal-bearing strata become good hydrocarbon source rocks.

The extension of a simple predictive model for orthogonal cutting to include flow below the cutting edge

A predictive model for orthogonal cutting that is able to accommodate the analysis of flow under a cutting edge is described. The model uses an upper-bound approach, in which the boundaries to the primary and secondary deformation zones are defined in such a way that both force and moment equilibrium of the rigid body chip is achieved. The remainder of the field is allowed to adjust so as to minimize the power consuming force, and finally force equilibrium is applied to estimate the edge forces acting under the tool. Solutions and comparison with previous theoretical and experimental observations are presented for different rake angles and chamfer or edge geometries; the influence of edge rounding or flank wear on the process are of particular interest. The model predicts a considerable change in flow geometry at high chamfer length/wear; this evidently occurs as a result of the field adjusting to balance the work in the primary and tertiary zones. The changing flow zone indicates that the hydrostatic stress at the tool edge increases as the chamfer or wear length increases.

Simulation of Combustion and Thermal-Flow Inside a Petroleum Coke Rotary Calcining Kiln—Part II: Analysis of Effects of Tertiary Airflow and Rotation

A computational model is established to simulate the combustion and thermal-flow behavior inside a petcoke rotary calcining kiln. The results show that peak temperature is located at the tertiary air zone and a cold region that exists between the natural gas combustion zone and the tertiary air zone causes the coke bed to lose heat to the gas stream. The cold tertiary air injections reduce the gas temperature inside the kiln, so preheating the tertiary air using extracted gas or other waste energy is essential to saving energy. The devolatilization rate and location have a pronounced effect on the simulated temperature distribution. As the calcining kiln rotates, the tertiary air injection nozzles will move relative to the coke bed and exert cyclic air-bed interactions. At zero angular position, the air injection nozzles are diametrically located away from the bed so the interactions between the tertiary air jets and the coke bed are minimal. As the kiln rotates to a 180 deg position, the stem of the air injection nozzles are actually buried inside the coke bed with the nozzles protruding outward from the bed. At this position, the tertiary air jets will provide a fresh layer of air just above the coke bed, and the interaction between the air flow and the coke bed becomes strong. The 45 deg rotational angle case shows a better calcination with a 100 K higher bed surface temperature at the discharge end compared with the rest of rotational angles. Without including the coke fines combustion and the coke bed, the lumped gas temperature for the rotational cases shows a peak temperature of 1400 K at Z/D=2, which is due to natural gas combustion; the lowest temperature is around 1075 K at two locations, Z/D=4 and 8. The exhaust gas temperature is approximately 1100 K. The insight gained from this study will be used to design innovative means to reduce natural gas consumption.

Etude géochimique et isotopique des aquifères dans la zone de Maicao (Colombie) / Study of the geochemistry and isotopic composition of aquifers in the Maicao region (Columbia)

A combined study of the hydrochemistry and environmental isotopes was carried out in the aquifers in the region of Maicao, in northern Colombia. The aim is to develop a conceptual circulation model for better management of the water resources. Three sedimentary aquifers can be defined by their geology: Cretaceous and Quaternary, which are unconfined, and a confined Tertiary zone. Two types of groundwater were identified. The first, of moderate salinity and having a recently renewed part (less than 50 years) is located in the Cretaceous aquifer and in a sector of the Quaternary aquifer near the Carraipía River (main surface water body in the study area). The second, of higher mineralization and older (more than 7900 years BP), which also shows more depleted isotopic values compared to the first group, is represented by the Tertiary aquifer and the Quaternary aquifer outside the zone of the Carraipia River. The absence of any actual recharge to the Quaternary aquifer, the most used water resource, enhances the need for the setting up of a rigourous regional water management policy.

Wear mechanisms and tool life management of WC–Co drills during dry high speed drilling of woven carbon fibre composites

Woven carbon fibre composites are extensively used in aerospace, automotive and civil applications. Optimization of high speed drilling of composites is an issue of great economical impact. Tool wear and part quality are central to the definition of the objective function and constraints of the optimization scheme. This paper presents an experimental investigation of the wear mechanisms of tungsten carbide (WC) drills during dry high speed drilling of quasi-isotropic woven graphite fibre epoxy composites. Tool wear was evaluated at spindle speeds of up to 15,000 rpm using a standard two flute drill. The paper examines the nonlinear behavior of this tribo-system and the interdependence of the wear process and cutting forces in relation to surface damage of the system components. It was found that chipping and abrasion were the main mechanisms controlling the deterioration of WC drill. The two friction regimes, the lightly and heavily loaded, were found to dictate the increase in forces, delamination of composite and surface roughness. The aggressive rubbing by fractured graphite fibres and WC grains against the soft epoxy matrix caused high temperature rise and consequently enhanced flank wear. During the primary and secondary wear stages, wear on the flank face of main cutting edges was found to be dominant, while adhesion of carbon was found to occur along with abrasion in the tertiary zone. Tool life results revealed the increase in the delamination and surface roughness with transition from the primary to tertiary wear regime. The correlation between tool wear, delamination damage and surface roughness was established. Finally it was concluded that a tool replacement strategy could be devised by monitoring the cutting forces.

Vegetative, Animal, and Cultural Semiosis: The semiotic threshold zones

The paper develops the concept of a “semiotic threshold zone” and a classification of major levels of semiotic systems, looking at this as both a theoretical and an empirical problem. The concept of a semiotic threshold zone both specifies and generalizes the notion of a semiotic threshold and is necessary in order to describe and understand the events that enable a system in its evolution to cross the threshold between the levels, and also at the same time to maintain it. The existence of systems based on different types of semiosis leads to secondary and tertiary semiotic threshold zones, in addition to the lower (primary) one that distinguishes semiosic and non-semiosic systems. We argue for the secondary threshold zones being the indexical and symbolic ones, which correspondingly separate the vegetative and animal semiosis (at the indexical threshold zone), and animal and cultural semiosis (at the symbolic threshold zone). We also argue that indexical semiosis is responsible for spatial representations and symbolic semiosis for temporal representations, which means that the vegetative umwelten are both non-spatial and non-temporal, the animal umwelten being spatial but non-temporal, and the cultural umwelten (Lebenswelten) being both spatial and temporal. Within these types of semiosis, the tertiary threshold zones could be found.

Quantification of movements of flat and elongated particles in hot mix asphalt subject to wheel load test

The objective of this study is to theoretically and experimentally characterize the internal structure in hot mix asphalt (HMA) mixtures. This is important to evaluate how the internal structures made of four different percentages of flat and elongated (F&E) aggregate change HMA's enginering properties in terms of rut depth, particle movement and orientation, and strain. A micromechanical model is developed to explain the behavior of the internal structure in an HMA mix. The experimental procedure relies on capturing images of the surface of an HMA specimen subject to wheel loading. The results demonstrate that the internal structure adjusts itself in the primary zone, reaches a preferred position in the secondary, but becomes stabilized in the tertiary zone. Low percentages of F&E aggregates result in a stable internal structure that could develop stone-on-stone contact and provide a better interlocking mechanism. The strain distribution within an HMA mix is influenced by particle configuration and mastic behavior, and is very localized.

Crustal control on the redox state of granitoid magmas: tectonic implications from the granitoid and metallogenic provinces in the circum-Japan Sea Region

ABSTRACTFelsic magmatism has occurred over a large region of East Asia since Jurassic times and has provided important mineral resources such as tin, tungsten, base metals and gold. The circum-Japan Sea region preserves various geological records of active continental margins, including Jurassic to Early Tertiary magmatic arcs and subduction zones and pre-Jurassic continental basements, which were separated by the opening of the Japan Sea during the Miocene. The felsic magmatism in this region shows a wide variation in terms of redox state and related mineralisation, encompassing east–west contrasts around the Pacific Ocean. A review of granitoids and associated ore deposits in this region indicates that the character of the crust, sedimentary versus igneous, is an essential factor to control the redox state, and a tectonic setting may be an additional factor in some cases.The reduced-type granitoids, characterised by tin mineralisation, were generated in carbonbearing sedimentary crust which was composed mainly of accretionary complex material and not influenced by previous magmatism. Involvement of sedimentary materials is corroborated by oxygen, sulphur and strontium isotope data. The oxidised-type granitoids, characterised by gold or molybdenum mineralisation, were generated in igneous crust which was depleted in reducing agents as a result of previous magmatism. Granitoid magmatism in a given area tends to become more oxidised with time.Jurassic accretionary complexes in East Asia are thought to have been largely displaced from the original place of accretion and stacked up against the northeastern margin in the Khingan and Sikhote–Alin Mountains. This region, dominated by sedimentary crust, was subsequently subjected to Cretaceous felsic magmatism and converted to a large province of reduced-type granitoids and tin–tungsten mineralisation. Diverse geodynamic processes, including the change of the arc-trench system, the creation and collapse of the back-arc basin and the collision of continents, may have prepared many favourable sites for the generation of reduced-type granitoids in northeast Asia. These processes may have resulted in a remarkable contrast with the Pacific margin of North America, where repeated arc magmatism during the Mesozoic formed granitoid batholiths of the oxidised-type.The granitoid types may also be controlled by the tectonic setting and mode of magma emplacement. In the northern Kitakami area of Northeast Japan, Early Cretaceous episodic magmatism occurred in a Jurassic accretionary complex, and formed the oxidised-type granitoids accompanied by submarine bimodal volcanism associated with kuroko mineralisation. Granitoids of fissure-filling type emplaced under extensional environments may be oxidised, irrespective of basement geology, because of insignificant crustal input.