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By R. Demont, A. Pranesh, S. Rakheja

Ethical concerns of in-vivo procedures and poor repeatability of non-invasive techniques have been major limitations in estimating vibration-induced spine loads through experiments. The biodynamic models of seated human body exposed to whole-body vibration (WBV) have evolved for defining the frequency-weightings, enhancement of human responses to WBV, and developing anthropodynamic manikins for seating assessment activities. The widely reported mechanical-equivalent models, solely based on through- or to-the-body biodynamic response functions, do not seem to resemble the biomechanical structure and do not yield information on the dynamic loading and deflections of segments of concern, namely the spine. On the other hand, biomechanical models with representative anatomical structure and anthropometry are being attempted to simulate segmental movements and the coupling effects, using Finite elements (FE) or multi-body dynamics (MBD) formalisms, which could provide important insights into the inter-vertebral forces [1]. While the FE models pose considerable complexities primarily related to characteristics of the bio-material properties, the MBD technique with discrete rigid bodies offers the flexibility to create multi-segment models with relative ease and lower computational cost. In this study, a preliminary multibody dynamic model of a seated human body exposed to WBV along the vertical direction is formulated using MSC/ADAMS software. The model validity is demonstrated by comparing selected responses with the available measured data. Methods The seated human is represented by nine rigid body segments, including: head, neck, thoracic and lumbar torso, pelvis, hands and thighs, as shown in Fig. 1. The rigid bodies are coupled through different rotational and translational joints, some of which are force elements to allow vertical translations and sagittal–plane rotations of the segments. The measurements of transmission of vertical vibration through-the-body generally require subjects to voluntarily maintain a vertical head position to reduce head-accelerometer orientation errors. The head–neck–shoulder joint is thus considered to be rigid. The shoulders are assumed to be rigidly attached to the thoracic segment. The torso is made up of three (upper, middle and lower) segments connected by visco-elastic revolute and translational joints to permit relative pitch and vertical motions. The forces and torques generated by the joints are derived assuming linear stiffness and damping properties, which were identified from published studies. The pelvis is connected to the rigid seat by similar elements representing the visco-elastic properties of the buttock tissues. The two thighs are rigidly connected to the pelvis, while the segment masses are chosen from the anthropometric data for the 50th percentile male subject. The initial model parameters for the joints were obtained from [2]. The model was analyzed to determine the force-motion relationship at the buttock-seat interface expressed in terms of

Jan 6, 2006

By H. Nelisse, S. K. Patra, A. Natani, S. Rakheja

The current laboratory methods for assessing the vibration attenuation performance of seats involve repetitive trials with a number of human occupants, and raise certain ethical concerns. Moreover, the measurements with human subjects yield considerable variability in the data. Alternatively, several anthropodynamic manikins have been developed for effective assessments of the coupled seat occupant system [1]. The effectiveness of a manikin in predicting the response of a coupled seat-occupant system lies in its ability to reproduce the biodynamic response of the seated human body in terms of force-motion relationship at the body-seat interface, such as apparent mass (APMS). A number of prototype manikins have thus been developed on the basis of biodynamic characteristics of vertical vibration-exposed seated occupants of different body masses in the vicinity of 5th, 50th and 95th percentile male population. This study concerns with the analysis of a passive prototype manikin to enhance its ability to reproduce the idealized APMS response characteristics of the vibration-exposed seated human subjects defined in ISO-5982[2] for mean body masses of 55, 75 and 98 kg. Methods The APMS responses of a prototype anthropodynamic passive manikin were thoroughly characterized in the laboratory under different excitations and body mass configurations. The manikin was designed with sufficient flexibility to configure mechanical-equivalent models corresponding to seated body masses of 55, 75 and 98 kg, by adding/removing specified masses and springs (Fig. 1). The manikin, configured for a specific body mass, was positioned on a rigid seat without a backrest, which was fixed to the force platform of a whole-body vertical vibration simulator. The simulator was programmed to synthesize random vertical vibration with flat acceleration power spectrum in the 0.4-20 Hz frequency range with two different magnitudes: 1 and 2 m/s2 overall rms acceleration. The total static and dynamic forces of the manikin to and the seat were measured using the force platform, while a single axis accelerometer was installed on the seat pan to measure acceleration due to vertical excitation. The measured data was appropriately corrected for the rigid seat inertia force, and the apparent mass [ ]

Jan 6, 2006

By Fred N. Kissell

In This Chapter [Ventilation and methane sampling guidelines for conventional shafts Dealing with restricted spaces where methane can accumulate Ventilation and methane sampling at raise bore drills and Filling shafts at closed coal mines] It is not unusual to encounter methane gas during shaft excavation or shaft-filling operations. Shafts into coalbeds usually produce the most methane, so the information in this chapter applies primarily to shafts at coal mines. Nevertheless, much of the information is relevant for noncoal mines that have methane in the mine or in the overlying strata. METHANE IN SHAFTS EXCAVATED BY CONVENTIONAL MEANS (DRILL, BLAST, MUCK) [ ] Ventilation. Shafts excavated by conventional means are ventilated with a fan on the surface connected to ductwork that extends down into the shaft (Figure 9–1). Shafts into coalbeds should have ventilation systems designed to handle the higher gas flows to be expected as the shaft excavation passes through any over-lying gas-containing strata and nears the coal-bed to be mined. Following are some simple ventilation guidelines for the minimum amount of air required and the selection of the ventilation duct: • Provide enough air to meet the mini-mum OSHA tunnel requirement of 30 ft/min air velocity in the open shaft, as specified in 29 CFR2 1926.800(k)(3). For example, a 20-ft-diam shaft having

Jan 6, 2006

By Douglas Ketcham, Thomas Jetzer

While the neurological and vascular aspects of Hand-Arm Vibration Syndrome (HAVS) has been generally accepted as a medical condition, the medical criteria and the clinical findings used to establish the diagnosis has been more difficult to bring to consensus. The criteria was first quantified by the Taylor-Palmear scale.1 This criteria was subsequently modified in 1986 at the 1st Stockholm Workshop2,3 to included more acceptance for the neurological effects that characterized the predominate findings in some workers. The relationship between hand-arm vibration and Carpal Tunnel Syndrome was defined in NIOSH 97-1414. While the aforementioned documents have defined the clinical entities associated with hand-arm vibration exposure, agreement on the clinical findings and test to confirm the diagnosis has be been more difficult to bring to consensus. Clinicians assessing HAVS has relied on a number of varied neurological and vascular tests. The neurological testing has focused on assessing damage to the sensory capability of the fingers for the neurological component including tests to measuring ability to sense vibration, cold or other end point finger sensor functions. However, the vascular testing has been traditionally focused on the ability to either measure vascular function or to reproduce the vascular blanching that occurs in HAVS with cold water provocation. Recent assessment of this testing in the United Kingdom Coal Miner’s study has questioned the value of this testing especially in reviews by McGeoch.5 In an attempt to provide some type of definitive testing to substantiate vascular damage from hand-arm vibration exposure, angiography is an alternative or adjunct to cold water provocation testing. The standards that have been established to predict the level, type and incidence of HAVS have been based on clinical studies and reports that have essentially been all male populations. However, the recent entry of women into more vibration intensive jobs has brought about the exposure of some women to high levels of vibration previously only previously experienced by men. However, there have been only few studies that look at HAVS in women6. Although exposed the same vibration levels, it has not been clear that the latency and type of pathology of HAVS in women will be the same as for men. The purpose of this study is to look at recent case studies of men and women exposed to jobs with high levels of hand-arm vibration with extensive clinical testing for both the neurological and vascular components of HAVS as well as other associated upper extremity conditions such as Carpal Tunnel Syndrome.

Jan 6, 2006

By James D. Noll, Jon A. Hummer, Shawn E. Vanderslice, Aleksandar D. Bugarski, George H. Jr. Schnakenberg, Steven E. Mischler, Larry D. Patts

The National Institute for Occupational Safety and Health designed and conducted a study in an underground metal mine to assess the effects of selected diesel emissions control technologies on the concentrations of diesel particulate matter and gases in underground mine air. The control technologies studied included diesel particulate filter (DPF) systems, filtration system with disposable filter elements, diesel oxidation catalytic converter, and biodiesel blends. Each technology was tested on a mining vehicle operated in an isolated area of an underground mine supplied with fresh air. These isolated zone tests allowed for the operation of vehicles under conditions and over duty cycles that closely mimic actual duty cycles of production equipment. The DPF systems reduced the elemental carbon (EC) concentrations in mine air between 88% and 99%. The same systems reduced total particulate matter (TPM) concentrations in mine air by approximately 75%. The biodiesel blends B20 and B50 caused a reduction in the EC concentrations of 26% and 48%, respectively. Those blends also reduced TPM concentrations by 9% and 24%, respectively. The use of #1 diesel fuel reduced EC concentration by 13% compared to #2 diesel fuel. An increase in nitrogen dioxide concentration of up to two times was seen when platinum-catalyzed DPF systems were tested.

Jan 5, 2006

By Edward L. McHugh, Charles Sabine, Jami Dwyer, David G. Long

Slope failure accidents were responsible for about 12% of U.S. surface mine fatalities between 1995 and 2003. Small surface movements on a mine highwall may be precursors of failure that, if detected, could provide sufficient warning to enable workers and machinery to be withdrawn to safety. Radar interferometry offers the necessary precision to detect these movements. Radar has some advantages over other methods in its ability to cover large surface areas for true two-dimensional monitoring day and night under almost any weather condition. Radar’s active transmit/receive mode of operation provides for more direct sampling than do passive optical methods that depend on solar illumination. Improvements in microprocessor speeds and capacities have led to the development of a number of small, portable, ground-based systems; such systems are now being deployed at several locations around the world. As part of an ongoing study of monitoring technologies, researchers from the National Institute for Occupational Safety and Health and Brigham Young University, Provo, UT, cooperated to assess the feasibility of using interferometric radar to monitor mine slope stability. Field tests of a device incorporating prototype equipment were successful in that small, centimeter-scale displacements on rock slopes were detected.

Jan 4, 2006

By D. R. Tesarik, F. M. Jones, J. B. Seymour, L. A. Martin, T. J. Williams

Determining backfill stress is an important part of evaluating mine safety, whether personnel are working in proximity to backfill or in other areas of the mine where backfill is an integral part of regional support. To assist in determining stress in backfill more accurately, researchers from the Spokane Research Laboratory of the National Institute for Occupational Safety and Health, Placer Dome, Inc. (Turquoise Ridge Mine), Peabody Energy Co. (Foidel Creek Mine), and Hecla Mining Co. (Lucky Friday Mine) used temperature readings recorded by thermistors to correct for the influence of temperature on stress data. These thermistors were positioned in the stems of earth pressure cells installed in backfill. Corrections were then calculated and compared using four different methods: polynomial equations fit to temperature-versus-stress plots before the pressure cells were loaded by overburden, a factor provided by the manufacturer, a theoretically derived factor, and a linear correction factor based on information collected during periods when no mining was taking place. To evaluate the accuracy of these methods, corrected stresses were calculated using each method and results compared to cumulative stresses caused by blasting at one of the mines. Results indicated that only a small percentage of the temperature effect on stress was corrected using the factor from the manufacturer because that factor accounted for only the pressure transducer and not the entire instrument body. Stresses adjusted with a linear correction factor based on information collected during periods when no mining was taking place were the most accurate. Stresses recorded at two other mines were corrected using the theoretical method and the polynomial equations method; the two methods produced similar results. For some time intervals, the results were identical.

Jan 4, 2006

The NIOSH suite of coal mine ground control software addresses nearly every aspect of coal mine ground control planning, including geologic characterization, mine layout, pillar design, and support selection. Mine planners who use the soft-ware have access to the knowledge gained during years of NIOSH research—packaged in a simple, easy-to-use format. Several of these software packages have recently been updated and improved. Analysis of Roof Bolt Systems (ARBS) (Figure 1) helps select the proper roof bolt system design from the immense variety of available bolt types and patterns. It was developed from statistical analysis of extensive bolt performance and roof fall data. New features in Version 2 include— • The capability to analyze roof bolt systems that use two types of bolts; and • A roof support cost module that estimates the total in-stalled cost of different patterns, considering the costs of consumables, labor, maintenance, and other factors. The Support Technology Optimization Program (STOP) (Figure 2) can be used to make judgments regarding which secondary support system will be the most effective in a particular mine condition and to evaluate the advantages or dis-advantages of alternative support systems. Version 3.0 includes additional improvements: • Supports with large load-shedding following yielding can be designed based on the peak loading capability as well as the residual loading capability; • Seven new support systems have been added to the program; and • Easier access to photo gallery has been provided. The Coal Mine Roof Rating (CMRR) replaces com-plicated geologic information with a simple numerical rating that mine planners can use in many ground control applications. The CMRR can be readily integrated into a geologic exploration program, and the software package is capable of generating an AutoCAD CMRR "layer." Version 1.2 contains— • The complete CMRR database with more than 250 ratings obtained from 70 different U.S. coal seams; and • An all-new "Help" file that clearly explains all aspects of the program. Analysis of Horizontal Stress in Mining (AHSM) can help find the optimum mine layouts for control of horizontal stress. It can be used to analyze both development and longwall retreat designs, and it shows how the stress condition varies as the entry, crosscut, and panel orientations are changed. Version 2 features— • Improved graphics that enable the user to observe the effect of design changes without adjusting the display on the computer screen; and • Resource files containing information on stress map-ping, advance-and-relieve mining, stress measurements in U.S. coal mines, and other topics. [ ]

Jan 4, 2006

By Elaine Cullen, Launa Mallett, Mike Jenkins, C. M. K. Boldt, Thomas Camm

The material in this Information Circular was presented at the National Institute for Occupational Safety and Health’s (NIOSH) open-industry briefing held during the 2004 Northwest Mining Association conference in Spokane, WA. The open-industry briefing discussed results of recently completed and on-going mine safety- and health-related research conducted at NIOSH’s Spokane and Pittsburgh Research Laboratories on the human side of mining—the miner. The first paper sets the stage for what mining has achieved and what we mean by “getting to zero.” The second paper, “Help Experienced Miners Become Great On-the-Job Trainers,” distinguishes between experienced miners and trainers. This paper provides some key concepts for turning great miners into great trainers. “The Power of Story-Telling in Getting Through to Miners” explains the history and importance of stories in the culture and training of miners. Finally, “Understanding Self in Stressful Working Environments,” describes the personal and social aspects of the working environment, much of which parallels familial theories. The downward trend of deaths in U.S. mining has been remarkable. The number of miners killed or injured each year has decreased steadily over the past 100 years. Some charts show these trends overlain with important events such as World War II and the Mine Safety and Health Act. However, this downward trend in mining fatalities has flattened out. How can you get to zero accidents? Do you concentrate on technological advances and equipment maintenance to avoid malfunctions? Do you concentrate on developing work processes and organizational structures that minimize risk? Do you combine them and take a systems approach that links one to the other with an evaluative loop? Safety efforts in mining have used all of these approaches. What more can we do to get to zero? Getting to zero will require two objectives: A clear and unshakeable belief that it can be done and attention to the human side of mining. Getting to zero is not a new idea; it has been used by mine companies and safety professionals for years as the safety goal. But getting to zero is not so much a physical goal as it is a belief that there are no insurmountable barriers to achieving the goal.

Jan 3, 2006

To provide operators of large-opening mines with a ventilation planning tool that will help them develop a healthier, safer, and more efficient ventilation system in the underground workplace.

Jan 3, 2006

By J. Kempken, T. A. Schreiter, R. Degel, H. Schmieden

Keywords: Pyrometallurgy, SMS Demag, Germany, submerged arc furnace, ferro alloys, non-ferrous, FeCr, FeNi, FeMn, copper, cobalt, slag cleaning, PGM, rectangular furnace After a short summary of the SMS Metallurgy part of the SMS group, the paper will focus on Submerged Arc furnace technology. After general aspects of furnace design, the focus will shift to different applications and their specific furnace requirements. Finally, a state-of-the-art design tool as well as a new invention to improve slag-cleaning technology will be featured.

Jan 1, 2006

The Thermo-MIE personal DataRAM dust monitor (pDR) is a light-scattering instrument approved for use in gassy underground mines by the U.S. Mine Safety and Health Administration (MSHA). However, the use of light-scattering monitors has been inhibited by concerns about inaccurate readings resulting from changes in dust size distribution and composition, as well as concerns about the impact of moisture in the mine air. Because of this concern, the National Institute for Occupational Safety and Health (NIOSH) evaluated the pDR using available data from laboratory tests and mine surveys. The data show that accuracy can vary widely from test to test and mine to mine. In most cases, the results can be improved by using a companion gravimetric measurement to adjust the pDR data.

Jan 1, 2006

By E. Nejati, S. Khoshkooei, V. Firouzdor, M. Akbari, F. Khomamizadeh

In this study the effects of Si content on mechanical and thermal fatigue properties of Al-Si casting alloys were investigated. Repeated heating and cooling cycles were applied on the samples at 230°C to develop thermal fatigue cracks. Crack growth mechanisms and microstructural influences were investigated by optical and scanning electron microscopy. Thermal fatigue behaviors were improved successively by increasing of silicon content up to 7wt%. However, addition of more than 9wt% silicon decreased the thermal shock resistance of the alloy. Silicon contents of about 9wt% presented the best mechanical and thermal fatigue resistance in the alloy.

Jan 1, 2006

By J. A. Jr. Carpenter

Expanding world economic prosperity, probable peaking of conventional petroleum production in the coming decades and environmental concerns require efforts to increase the efficiency of, and the development of alternatives to, petroleum-based fuels used in automotive transportation. In January 2002, the U.S. Department of Energy (USDOE) and the U.S. Council for Automotive Research (USCAR) of the "Big Three" traditionally-USA-based automakers, DaimlerChrysler, Ford and General Motors, formed the Freedom Cooperative Automotive Research (FreedomCAR) Partnership to fund high-risk, high-payoff research into advanced automotive technologies with the potential for eventually lowering the USA's nearly complete (95%) dependence on petroleum, 55% imported, for its transportation fuels. FreedomCAR replaced the Partnership for a New Generation of Vehicles (PNGV) which existed from 1993 to 2001. In January 2003, the energy-supply industry joined with the FreedomCAR Partnership forming the FreedomCAR and Fuel Initiative (FC&FI) to develop the technologies needed for the mass production of fuel-cell vehicles using hydrogen as fuel and the infrastructure needed to deliver the hydrogen to the consumer. The goal is to enable the automotive and energy-supply industries to make commercialization decisions in 2015 on large-scale introduction of such vehicles and on developing the infrastructure beginning in 2020. In addition to work on fuel cells and hydrogen infrastructure, the FC&FI conducts research on technologies with the potential for nearer-term energy efficiency and environmental benefits, such as new engine concepts, lightweight materials, and engine-electric hybrid propulsion systems. Lightweighting is seen as crucial for shorter and for longer term benefits because hybrid and fuel-cell powertrains are expected, at least in the early stages of adoption, to be heavier and more costly per unit of power than the standard internal-combustion, gasoline- or diesel-fueled powertrains they replace. Research and development (R&D) on casting of aluminum automotive components were major parts of the PNGV and R&D on casting of magnesium automotive components have been and are so under FreedomCAR. This presentation will review those efforts.

Jan 1, 2006

By M. Kolahdoozan, H. Noori

"Molybdenite flotation at the Sarcheshmeh Copper Complex has been studied as a function of pulp potential controlled using two types of sodium sulfide (mineral and chemical origin). Air and either plant or laboratory nitrogen was used as a flotation carrier. Potential measurements were taken in the rougher cells as it was proved to be vital for molybdenite flotation. Flotation test with reducing potentials between -525 and -575 mv gave the highest molybdenum recovery (93%) and the lowest copper recovery of between 4 to 15% can be achieved. These potentials did not change considerably by adding increasing amounts of sodium sulfide. At more oxidizing potentials, i.e. more than -450 mv, the recovery of copper increases while the recovery of Molybdenite drops.INTRODUCTIONThe average copper ore feed grade to the Sarcheshmeh flotation circuit is typically set at about 1.2% Cu. to be delivered to processing unit is set at 1.2%. There is no control of molybdenum (Mo) which usually varies between 0.01 and 0.04%. During concentration, a Cu-Mo concentrate is produced by one stage of roughing, one stage of scavenging and two stages of cleaning. Final concentrate contains 0.5% of Mo and 32% of Cu while the particle size is 90% under 42 microns (325 mesh). Because of the high grade of Mo in this concentrate and economic interests, a molybdenite flotation circuit plant was built in 1984. This plant was designed to treat 1432 tons of Cu-Mo concentrate (on dry basis) and consists of one stage of roughing followed by seven stages of cleaning. After dewatering the concentrate contains 53.7% Mo which is dried and shipped overseas.The majority of molybdenite production worldwide comes as byproduct of copper porphyry ores. The Mo grade typically varies between 0.01 and 0.06% and accompanies chalcopyrite and chalcocite. Due to the hydrophobic nature of molybdenite, it can be floated along with copper sulfides. Thus the overall concentrate of Cu and Mo contains 0.2-1% of molybdenum as well as 20-42% of copper. To separate the Mo, Cu and Fe minerals, depressants are used. The most important of which are sodium sulfide, sodium hydrosulfide, Anomal D, sodium cyanide, ferropottasium and ferro-cyanide. The first three regeants have been extensively used for successfully treating porphyry ores [1]. In the molybdenum plant of the Sarcheshmeh Copper Complex only sodium sulfide has been used to date."

Jan 1, 2006

Caterpillar said it will produce a Cat line of ac electric drive mining trucks. The world’s largest manufacturer of mining and construction equipment said the addition of an AC electric drive truck line will provide its customers with products to fit key applications. “We are very proud of the strong leadership position that Caterpillar has attained with its mechanical drive trucks, and we will continue to invest in strengthening that position,” said Chris Curfman, president of Caterpillar’s Global Mining Division and Caterpillar Inc. vice president. “We also recognize that there are unique applications that would make the addition of ac electric drive an important and attractive complement to our current truck line.” This is the largest investment Caterpillar has made in mining trucks in its history.

Jan 1, 2006

By Linli Wu

During the measurement of contact angle, a misty band was observed near the substrate. Hsien-Nan Ho and Shinn-Tyan Wu thought this was because the oxygen atoms on the interface migrate to the droplet surface to form an oxide band near the substrate. But from our experiments misty band appeared before the drop reach to the substrate. Theoretically speaking, the oxygen partial was the same everywhere in the vacuum furnace. So there was no condition to provide enough oxygen forming oxide. This appearance would be explained more reasonably with the optics principle. Most reflected light would be absorbed by the substrate and the light cannot reach the observation area, so the misty band formed.

Jan 1, 2006

By Jin He

Based on the simple-beam theory, a stress analysis model was established for undermining in multiple seam strip-pillar mining when the strip pillars were not columnized; the effects of various mining factors (e.g., mining depth, inter-burden thickness, recovery ratio, etc.) on inter-burden stability were analyzed; the changes in inter-burden stress distribution were investigated; and the important role that the inter-burden spacing and the mining width of the lower seams on inter-burden stability was studied. Finally, the actual practice used in Feng Feng Mine area was used as an example to demonstrate the rational mining width for a fixed mining depth.

Jan 1, 2006

By Muhannad T. Suleiman

Temperatures below freezing significantly enhance the soil shear strength and stiffness and to a lesser extent increase the compressive strength of concrete as well as the yield and ultimate strength of reinforcing steel. Consequently, the lateral load resistance of bridge columns supported by drilled shafts becomes dependent on seasonal weather conditions. To investigate the effects of seasonal freezing on the behavior of bridge columns supported by drilled shafts, large-scale field lateral load tests were conducted at 23°C (73.4°F) and -10°C (14°F) on two identical units at an field test site, which consisted of glacial till soil classified as low plastic clay. The bridge column-drilled shaft systems were subjected to cyclic lateral load with the maximum lateral column top displacements reaching approximately ±30 cm (±11.8 in.). The soil at the test site was characterized at different temperatures using unconfined compression tests in the laboratory as well as in-situ Cone Penetration and Pressuremeter Tests. Using these test results, the lateral load behavior of the column-drilled shaft systems were analyzed utilizing numerical models that consisted of beam elements representing the concrete column and the shaft and lateral springs representing nonlinear p-y response of soil. This paper focuses on comparing the calculated responses of test units with different p-y curves that were developed for the soil near the ground surface using the laboratory and in-situ tests. From the experimental study, the response of the unit tested at -10°C (14°F) was found to show 44% increase in lateral force resistance and 0.84 m (2.76 ft) upward shift of the maximum moment location compared to the response of the identical unit tested at 23°C (73.4°F). Theoretical behavior that included the temperature effects on soil, concrete and steel properties provided good correlation with the measured responses when the soil near the ground surface was modeled using the unconfined compression test or the Cone Penetration Test data, but not the Pressuremeter test data.

Jan 1, 2006

By S. Yue, P. Vo, M. Jahazi

The flow behaviour and microstructure development of a near-alpha titanium alloy during beta working has been investigated. Typical cogging conditions were simulated through compression testing of IMI834 at temperatures of 1025°C-1100°C, strain rates of 0.01 s-1 - 1 s-1 and post-deformation heat treatments up to 4h. Using a synthesis of available literature models, a finite element model has been developed and validated through quantitative measures of flow stress-strain data and beta grain characteristics. Flow behaviour was analyzed through a self-consistent method while the microstructure development was considered with regard to the kinetics of beta recrystallization. Deformation at beta or high alpha/beta working temperatures (T>l025°C) produced minor flow softening with complete grain refinement achieved through metadynamic recrystallization.

Jan 1, 2006