Thglimited - Heavy Industries

title: Study of wave shaping techniques of split Hopkinson pressure bar using finite element analysis authors: Tasneem, Nazia brabstract: The split Hopkinson pressure bar (SHPB) continues to be one of the most common methods of testing materials at high rates of strain. Elevated rates of strain, such as those found in impact and explosive applications, have been shown to induce phenomena such as strain hardening and phase transitions that can significantly affect the strength of most materials. Due to its relative simplicity and robustness, the SHPB remains one of the preferred platforms for evaluating mechanical properties of materials at rates of strain approaching 10 4 in/in-s (s -1 ). At the National Institute for Aviation Research (NIAR), research has been conducted to study the wave shaping techniques of SHPB using finite element analysis. The SHPB consists of two long, slender cylindrical bars, denoted input and output bars that "sandwich" a cylindrical test specimen. Utilizing a high-pressure gas gun, a third cylindrical steel bar, known as the striker bar, is fired at the input bar, causing a compressive stress wave to travel through the input bar to the input bar - test specimen interface. At this interface, a portion of the stress wave propagates through the test specimen while the remainder of the pulse reflects back through the input bar as a tensile stress wave. brdescription: Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering. br

title: Dielectric properties of MWCNTs reinforced polyacrylonitrile (PAN) nanofibers at varying temperatures authors: Khan, Waseem; Ceylan, M.; Asmatulu, R. brabstract: Electrospinning is one of the easiest and straightforward processes of fabricating nanofibers. In this study, MWCNTs in the range of 0%, 1% and 2% up to 15% were added into polymeric solution containing PAN and dimethylformamide, and morphology and dielectric properties of electrospun nanocomposite fibers at elevated temperature were studied. Dielectric properties were measured in the temperature range between 23 and 90 0C and it was found that the dielectric constant increased with increasing the carbon nanotubes content. This may be due to conductivity and polarization effects of the nanocomposite fibers. brdescription: Paper presented to the 5th Annual Symposium on Graduate Research and Scholarly Projects (GRASP) held at the Hughes Metropolitan Complex, Wichita State University, May 1, 2009. br

title: Fatigue behavior of plasma spray coatings on polymer matrix composite materials authors: Haqu, Ziaul brabstract: The majority of coated structural components are subjected to fluctuating internal and/or applied stress because of oscillating mechanical loads. The fatigue behavior of coatings and the overall cyclic failure response of coated structures have remained relatively unexplored. This study was an effort to investigate the fatigue behavior of plasma spray coatings on polymer matrix composite materials. Since no ASTM standard is available, we designed our own experiment to determine coatings suitability under cyclic loading, response in dynamic loading conditions, fatigue failure modes and fatigue life. Coatings were tested at different stress levels and frequencies. The stresses versus number of cycles (S-N) curves for the coatings were generated. The results indicate that the plasma spay coatings on polymer matrix composite materials are suitable for dynamic loading conditions. brdescription: Wichita State University, College of Engineering, Dept. of Mechanical Engineering br

title: Guiding nonmagnetic particles by external magnetic field in a microfluidic device authors: Zhang, Bangwei brabstract: This report presents the fabrication of a micro fluidic device using the UV lithography method in order to separate nonmagnetic fluoresbrite carboxy microspheres from the mixed ferrofluids in microchannels. The microfluidic device is fabricated using a SU8-50 negative photoresist that is exposed to the UV lights with a mask (Y shape) on the top of the photoresist. By applying the external magnet from a side of the microchannel, the fluoresbrite carboxy microspheres and ferrofluids are separated into different channels because of the magnetic force acted on the nonmagnetic spheres. During the fabrication, a number of different parameters, such as UV exposure times, UV power, photoresist thickness, etc. were conducted and optimized for our needs. In addition, in the magnetic field testing, different pumping speeds, and particle concentrations associated with the different distances between the magnet and the microfluidic system were studied for an efficient separation. brdescription: Wichita State University, College of Engineering, Dept. of Mechanical Engineering br

title: Crashworthiness of a pre NCAP safety standard light truck and corresponding suspension analysis authors: Virginia, Mark Anthony brabstract: With current safety regulations, standards and safety equipment, commuters have never been safer while driving an automobile. An increasingly popular past time is to restore or repair antique and vintage automobiles that do not benefit from the current safety standards, regulations and equipment. The driver and occupants of the vehicles are at a much higher risk of injury or fatality because of a lack of current safety devices. Older vehicles also suffer from poor ride and handling characteristics that will affect how well the vehicle will behave in an accident avoidance event. Due to the lack of safety equipment and regulations for older vehicles, and poor ride and handling characteristics, a full vehicle finite element model and multi body dynamic model was created of a 1965 Nissan Patrol G60. The computer models were used to assess the crash and vehicle handling characteristics of the vehicle. The crashworthiness is evaluated by comparing the finite element models performance in a full frontal crash per NCAP criteria. The finite element model was validated by comparing acceleration pulses with an existing finite element model of a 1994 C1500 light pick up truck. Once validated, the acceleration pulses at different location in the finite element model were compared to physical test data of a 2007 jeep wrangler with similar construction and weight. The differences in the crash pulses were used to evaluate the crashworthiness of the pre safety standard vehicle. To evaluate the ride and handling of the vehicle, a multi body dynamic model was developed and simulated performing a single lane change event. The measure for improvement was to minimize the ride steer of the vehicle during the single lane change event. A full factorial design of experiments was created to minimize the ride steer by modifying the rear suspension mounting points within an allowable design space. The results from the finite element model correlated well with the validation model and thus can be used with reasonable assurance for evaluating safety improvements to the vehicle and comparison to physical test data. Comparison with physical test data showed that the current configuration of the vehicle performs well considering the age of the vehicle. With the data from the computer aided crash test and suspension analysis, improvements to the 1965 Nissan patrol can be identified and used to update the vehicle to meet current safety standards. A similar approach can be applied to any vehicle manufactured prior to safety standards and regulations. brdescription: Wichita State University, College of Engineering, Dept. of Mechanical Engineering br

title: Numerical investigation of self-piercing riveted dual layer joint authors: Krishnappa, Uma Shankar brabstract: Self-piercing riveting (SPR) is a high-speed mechanical fastening technique for point joining of sheet-material components. SPR is becoming important in automotive applications for aluminium vehicle body assembly. However, compared with current sheet-metal joining processes in the automotive industry, the effects of various parameters such as mechanical properties, rivet setting methods and systems, methods of removing self-piercing rivets, etc. A study examining the effect of specimen configuration on the mechanical behavior of self-piercing riveted, dual-layer joints in aluminium alloys was conducted. It has observed that the specimen configuration had a significant effect on the strength and failure mechanism of a self-piercing riveted dual-layer joint. The basic aspects of SPR process forming by conducting both explicit and implicit analysis have been investigated in this thesis. It was found that the operating force-deformation curve of SPR process was determined by the rivet deformation force and its displacement. Under certain process conditions, an increase in inertia effect due to high velocity of metal forming process results was not significant to an extent. In this research, the springback characteristic parameters of the SPR process were also studied. The springback analysis carried out at the end of the forming process showed that the dimensional change in the part due to springback was not significant. brdescription: Wichita State University, College of Engineering, Dept. of Mechanical Engineering br

title: Evaluation of drill bit performance for carbon-fiber composites authors: Rahman, Khan Habeeb Ur brabstract: Ever since composite materials have been used in the aerospace industry, there have been problems with cutting and machining them. One of the reasons for this problem was the dearth of available tooling to machine composites. As research in composites progressed and as composites found wide application in the aerospace industry, efforts have been made to develop good and efficient tools to machine them. Nevertheless, this effort is still ongoing to develop better tools, as the problems faced during machining have not been totally eliminated. Of the different machining operations performed on composite materials, drilling is the most common. The major problems faced during the drilling of composite materials are delamination and fibers pull out. Delamination reduces the strength of the composite. Another problem that persists is the effect of excess cutting temperatures on the quality of the drilled hole. Excess cutting temperatures affect the dimensional accuracy of the drilled hole and deteriorate its surface finish. Excess cutting temperatures during drilling may melt the matrix and char the drilled hole. Research and experiments conducted on drilling of composite materials have shown that as the cutting edges of the drill bit wear out, the heat generated and the thrust force produced increases. Increase in thrust force gives rise to delamination. Also tool geometry plays a big role in producing a hole with an acceptable quality. Hence, it is important to thoroughly investigate the performance of the drill bit in terms of producing a good hole quality. The objective of this research work was to evaluate the performance of drill bits when drilling carbon-fiber composites. Drill bits were evaluated for temperature, Hole oversize, surface roughness, roundness, thrust force, torque, damage area, and tool wear. By conducting experiments using different drill bits, the drill bit performance was determined for every parameter in question. Based on the results of these experiments, it was possible to determine which drill bit performs optimally for the different parameters investigated in this research work. Also by evaluating the Hole oversize, roundness, and surface roughness, it was be possible to study the effect of speed and feed rate on these parameters. Also tool wear analysis was carried out as a part of this research work. brdescription: Wichita State University, College of Engineering, Dept. of Mechanical Engineering br

title: Correlation between rheological and mechanical properties in a low-temperature cure prepreg composite authors: Gernaat, Christopher Ronald brabstract: With an ever growing fleet of commercial airplanes utilizing composite structures, it is increasingly important to develop cost-effective and robust repair procedures. Issues invariably occur during on-site repair which casts doubt on the structural suitability of the part. This makes the ability to quantify the relationship between dwell temperature, cure state, and mechanical properties extremely important. Curing temperatures play a vital role in the difficulty of repairs. Lower cure temperatures mean lower cost, less possibility of damage to surrounding material, and therefore, the potential for a more robust repair scheme. As such, low temperature cure materials are of great interest to the composite repair community. Current state-of-the-art says that cure must be very precise to ensure structural integrity. As such, any repair with thermocouple readings outside a very narrow band must be reworked at substantial cost. Often, when rejected repair materials are tested, they are found to be structurally sound. The search for a solution to this problem has been the motivation for this study. Rheometer testing quantifies the viscoelastic properties of the composite material as it cures. This ex-situ approach allows a very detailed and accurate view of cure state properties. These properties include glass transition temperature (Tg), gel time, vitrification time, G’ (storage modulus), G” (loss modulus), and Tan_ (G”/G’). Glass transition temperature, gel time, and G’ were used to correlate viscoelastic properties with mechanical properties. The mechanical properties of interest were short beam shear strength, compression strength, compression modulus, compressive Poisson’s ratio, tension strength, and tension modulus. Correlations were attempted for all mentioned mechanical properties. It was found that the highly resin-dominated compression and short beam shear strengths showed a strong correlation with viscoelastic properties. Both of these mechanical properties showed a very strong relationship to the nearly constant portion of the storage modulus G’ after curing is complete. Compression and short beam shear strengths showed a weaker relationship with Tg, and none of the properties considered showed good correlation with gel time. All other mechanical properties showed little or no change based on dwell temperature and, therefore, no acceptable correlation to viscoelastic properties was achieved. Mechanical properties which correlated well with the viscoelastic properties showed no statistical difference for dwell temperatures from 200°F to 260°F, and the nonresin-dominated properties showed little difference from 180°F to 260°F. This significant finding indicates that fiber-dominated properties remain constant for a wide range of cure temperatures. Resin-dominated properties remain statistically constant over a much larger cure temperature range than currently utilized by industry. brdescription: Wichita State University, College of Engineering, Dept. of Mechanical Engineering br

title: Implementation and evaluation of automotive child restraint systems in mass transit buses authors: Balwan, Nishant Kuber brabstract: Mass transportation systems and specifically bus systems are a key element of the national transportation network. Buses are one of the safest forms of transportation. Nonetheless, bus crashes resulting in occupant injuries and fatalities do occur. Each year, more than 5,800 children die, nearly 120,000 are permanently disabled, and more than 14 million are hurt seriously enough to require emergency medical care due to unintentional injury. Therefore, effort is needed to improve the performance of bus interior and structure. Child Safety is a continuing effort to improve the safety of children in mass transit buses. This project provides an overview of the implementation of two types of attachment systems Child Restraint Systems (CRS) in a mass transit buses. A series of sled tests were conducted in order to evaluate the performance of the Child Restraint Systems for typical frontal, side and rear crash scenarios. The results of the test indicate that the implementation of ISOFIX or LATCH attachments in transit bus seats mitigates the risk of severe injuries to the 12 month-old, and 3 year-old occupants; while not increasing the risk of severe injuries due to CRS interactions to other unrestraint adult passengers. In the next phase of this research, results from these sled tests were validated using the multibody analysis tool MADYMO to evaluate the performance of child safety in mass transit buses using the Federal Motor Vehicle Safety Standards (FMVSS 208) injury criteria. The Kinematics of sled tests are closely matching with that of simulations. Injury values for sled tests and simulations are well below injury criteria. The results from this study show the 20 % variation in injury signals. This study concludes that interior for mass transit bus with child seats and restraint can be utilized in mass transit buses to improve the safety performance of children. brdescription: Wichita State University, College of Engineering, Dept. of Mechanical Engineering br

title: An integrated system for transport aircraft cabin interior design and certification by analysis authors: Nagarajan, Harishanker brabstract: Every cabin configuration, in all types of aircraft (Transport, General Aviation and Rotorcraft), need to be certified as per the existing Code of Federal Regulation governing that particular type of aircraft. The current practice used to comply with Federal Aviation Regulations (FAR’s) related to aircraft seats and cabin interiors is to conduct full-scale system sled tests. This approach can be expensive and the test results are sensitive to changes in test conditions, such as the sled pulse, dummy calibration, seat belt elongation, etc., resulting in scatter in the results. With the development of the more robust codes for the analytical tools, it should be possible to successfully capture the test conditions by one of these tools and to obtain results which compare favorably with the actual tests results. For Part 25 category of transport aircrafts, 14CFR 25.562 states: “Each seat type design which approved for crew or passenger occupancy during takeoff and landing must successfully complete dynamic tests or be demonstrated by rational analysis based on dynamic tests of a similar type seat, in accordance with each of the following emergency landing conditions” and then the conditions are stated. When these federal regulations were enacted, the ability of analytical tools was limited and there did not exist enough data to show that certification could be performed using analysis. The objectives of this research are to identify the conditions under which a Part 25 type aircraft could be certified by analysis for compliance with the 14 CFR 25.562 regulation, and also to identify the validation criteria when using analytical tools. The validation criteria for the analytical model have been developed based on the scatter that is seen in actual testing. The underlying premise is that the analytical modeling of the testing should be allowed to predict the injury criteria within the same band of scatter as the actual tests. The study develops a validated model and this model is shown to be robust in predicting the protection/injury criteria that the tested configurations offer. Using these validated models, a full factorial design of experiment (DOE) analysis was performed to determine the effect the factors have on the dynamic response of the seat-dummy-restraint-cabin systems. In this study, the factors chosen were the seat cushion type, thickness of the cushion and the rigidity of the seat for the 14 CFR 25.562 Test -1 condition (up test) and the studied response was the resulting lumbar load. For 14 CFR 25.562 Test -2 condition (down test), the studied factors were the seat set back distance, seat belt type, type of bulkhead and the coefficient of friction of the impact surface, while the studied response was the resulting Head injury criteria (HIC) based on the impact of the dummy head with the frontal structure. Guidelines were developed in this study pertaining to the circumstance under which analytical tools could be considered as a valid replacement for the certification testing. Based on the sensitivity study, a new integrated analytical system methodology has been developed that would help the aerospace cabin interior designers in developing crashworthy cabin interiors. A graphical user interface was developed which would help the cabin interior designers to optimize their design by selecting component that would help in minimizing the injury criteria studied. This would reduce the time it takes to design these configurations and would reduce the cost of certification while improving the safety of the flying public. brdescription: Wichita State University, College of Engineering, Dept. of Mechanical engineering br