Delicate Parts Research Articles

Three-Dimensional Blade Stacking Strategies and Understanding of Flow Physics in Low-Pressure Steam Turbines—Part II: Stacking Equivalence and Differentiators

Optimization of blade stacking in low-pressure (LP) steam turbine development constitutes one of the most delicate and time-consuming parts of the design process. This is the second part of two papers focusing on stacking strategies applied to the last stage guide vane and represents an attempt to discern the aerodynamic targets that can be achieved by each of the well-known and most often used basic stacking schemes. The effects of lean and twist have been investigated through an iterative process, involving comprehensive 3D computational fluid dynamics (CFD) modeling of the last two stages of a standard LP, where the basic lean and twist stacking schemes were applied on the last stage guide vanes while keeping the throat area (TA) unchanged. It has been found that it is possible to achieve the same target value and pattern of stage reaction by applying either tangential lean or an equivalent value of twist. Moreover, the significance of axial sweep on hub reaction has been found to become pronounced when the blade sweep is carried out at constant TA. The importance of hub-profiling has also been demonstrated and assessed. Detailed analysis of the flow fields has provided an overall picture, revealing the differences in the main flow parameters as produced by each of the alternative basic stacking schemes.

Three-Dimensional Blade-Stacking Strategies and Understanding of Flow Physics in Low-Pressure Steam Turbines—Part I: Three-Dimensional Stacking Mechanisms

Optimization of blade stacking in the last stage of low-pressure (LP) steam turbines constitutes one of the most delicate and time-consuming parts of the design process. This is the first of two papers focusing on the stacking strategies applied to the last stage guide vane (G0). Following a comprehensive review of the main features that characterize the LP last stage aerodynamics, the three-dimensional (3D) computational fluid dynamics (CFD) code used for the investigation and options related to the modeling of wet steam are described. Aerodynamic problems related to the LP last stage and the principles of 3D stacking are reviewed in detail. In this first paper, the results of a systematic study on an isolated LP stator row are used to elucidate the effects of stacking schemes, such as lean, twist, sweep, and hub profiling. These results show that stator twist not only has the most powerful influence on the reaction variation but it also produces undesirable spanwise variations in angular momentum at stator exit. These may be compensated by introducing a positive stagnation pressure gradient at entry to the last stage.

Automated on-line liquid–liquid extraction system for temporal mass spectrometric analysis of dynamic samples

Most real samples cannot directly be infused to mass spectrometers because they could contaminate delicate parts of ion source and guides, or cause ion suppression. Conventional sample preparation procedures limit temporal resolution of analysis. We have developed an automated liquid–liquid extraction system that enables unsupervised repetitive treatment of dynamic samples and instantaneous analysis by mass spectrometry (MS). It incorporates inexpensive open-source microcontroller boards (Arduino and Netduino) to guide the extraction and analysis process. Duration of every extraction cycle is 17 min. The system enables monitoring of dynamic processes over many hours. The extracts are automatically transferred to the ion source incorporating a Venturi pump. Operation of the device has been characterized (repeatability, RSD = 15%, n = 20; concentration range for ibuprofen, 0.053–2.000 mM; LOD for ibuprofen, ∼0.005 mM; including extraction and detection). To exemplify its usefulness in real-world applications, we implemented this device in chemical profiling of pharmaceutical formulation dissolution process. Temporal dissolution profiles of commercial ibuprofen and acetaminophen tablets were recorded during 10 h. The extraction-MS datasets were fitted with exponential functions to characterize the rates of release of the main and auxiliary ingredients (e.g. ibuprofen, k = 0.43 ± 0.01 h−1). The electronic control unit of this system interacts with the operator via touch screen, internet, voice, and short text messages sent to the mobile phone, which is helpful when launching long-term (e.g. overnight) measurements. Due to these interactive features, the platform brings the concept of the Internet-of-Things (IoT) to the chemistry laboratory environment.

Fabrication and characterisation of a novel smart suspension for micro-CMM probes

In tactile micro coordinate metrology, miniature probing systems are required to allow geometric measurements of miniature, delicate, high precision components. These probing systems typically comprise of a small stylus of only a few mm in length, with a spherical tip of around 100μm in diameter or less. The stylus is mounted to a flexible suspension structure which is designed to deflect during measurement, and defines the stiffness of the probing system. Stiffness is of critical importance for optimum measurement performance, and selection of the correct stiffness involves a difficult trade-off. Stiff probes are needed to overcome surface attraction forces which are significant for the small stylus tips, while flexible probes are needed for contact with delicate parts to reduce contact stress and ensure no damage is caused. To eliminate the need for compromise a novel micro tactile probing system with active stiffness control using a novel suspension structure has been designed. This paper presents the initial fabrication and the test of the suspension structure. The stiffness of the structure is assessed by measuring the modal frequencies of the suspension structure that correspond to vertical and lateral probe motion. Using this method results show it is possible to reduce the vertical and torsional frequency by 69% and 33%, respectively. Using finite element analysis it is shown that this equates to vertical and lateral stiffness reductions to 12% and 46% of their initial value, respectively.

A novel Region of Interest (ROI) imaging technique for biplane imaging in interventional suites: high-resolution small field-of-view imaging in the frontal plane and dose-reduced, large field-of-view standard-resolution imaging in the lateral plane.

Endovascular-Image-Guided-Interventional (EIGI) treatment of neuro-vascular conditions such as aneurysms, stenosed arteries, and vessel thrombosis make use of treatment devices such as stents, coils, and balloons which have very small feature sizes, 10's of microns to a few 100's of microns, and hence demand a high resolution imaging system. The current state-of-the-art flat panel detector (FPD) has about a 200-um pixel size with the Nyquist of 2.5 lp/mm. For higher-resolution imaging a charge-coupled device (CCD) based Micro-Angio -Fluoroscope (MAF-CCD) with a pixel size of 35um (Nyquist of 11 lp/mm) was developed and previously reported. Although the detector addresses the high resolution needs, the Field-Of-View (FOV) is limited to 3.5 cm × 3.5 cm, which is much smaller than current FPDs. During the use of the MAF-CCD for delicate parts of the intervention, it may be desirable to have real-time monitoring outside the MAF FOV with a low dose, and lower, but acceptable, quality image. To address this need, a novel imaging technique for biplane imaging systems has been developed, using an MAF-CCD in the frontal plane and a dose-reduced standard large FOV imager in the lateral plane. The dose reduction is achieved by using a combination of ROI fluoroscopy and spatially different temporal filtering, a technique that has been previously presented. In order to evaluate this technique, a simulation using images acquired during an actual EIGI treatment on a patient, followed by an actual implementation on phantoms is presented.

Automated Modular and Part-Flexible Feeding System for Micro Parts

In the assembly, efficient part feeding is a decisive factor for a successful automation. Therefor an automated modular and part-flexible feeding system for micro parts on the basis of piezoelectric vibratory conveyors has been developed at the wbk Institute of Production Science. Very different parts can be conveyed, positioned and partly be rotated around their vertical axis by the system. The sliding conveyance offers also the possibility to feed extremely delicate parts. In this article the design and the commissioning results of the system are presented. In the end an outlook is given on future work to increase productivity and efficiency of the system.

Simulation as a Support for Ultrasonic Testing

Ultrasonic testing is a very important non-destructive method for testing components for safety of nuclear power plants and other security and delicate parts in other industries. Nowadays, thanks to the development of computer technology, it is possible to simulate processes which occur during ultrasonic testing. That is why numerical simulations are becoming an integral part of non-destructive testing. Simulations are used to determine parameters of ultrasonic examination, especially parameters of probes and scan plan and also in the analysis of results. They are used in such cases, when it is necessary to verify applicability of probes and methods. This verification could be provided on the weld and test block which are not manufactured. It could be also provided on defects, which are not manufactured in test block, but their presence is possible in given weld joint. Simulations are very useful for verifying the propagation of ultrasonic signal in given area (e.g. weld area). If movement of probe is limited, possibility of whole volume scan should be verified.

Book Review: A Nineteenth-Century Clockmaker, Heinrich Johann Kessels (1781–1849): Ein bedeutender Verfertiger von Chronometern und Präzisionspendeluhren

A NINETEENTH-CENTURY CLOCKMAKER Heinrich Johann Kessels (1781-1849): Ein bedeutender Verfertiger von Chronometern und Prazisionspendeluhren. Gunther Oestmann (Acta Historica Astronomiae, xliv; Verlag Harri Deutsch, Frankfurt aM, 2011). Pp. 271. euro24.80. ISBN 978-3-8171-1884-7.Volume xliv of the Acta Historica Astronomiae is dedicated to the life and work of the clockmaker Heinrich Johann Kessels. Gunther Oestmann, author of this work, is a clockmaker and historian of science, whose researches in the field of history of horology, navigation, astronomy, scientific instruments and mathematical geography are well known.The volume is divided into three sections. The first deals with the life and professional achievement of Kessels. He was born in Maastricht, but very little is known of his early years. Certainly he spent some time in England where he learned the art of clock making, working in some of the most renowned workshops of the time. Unfortunately we do not know who his masters were; but he clearly developed a very high level of skill that allowed him to undertake several important works when in 1815 he moved to Paris and entered the shop of the renowned maker, Abraham Louis Breguet. In Paris, Kessels worked on the most sophisticated mechanical timekeepers then being produced, such as marine and pocket chronometers, tourbillons, and highly sophisticated clocks. There he became a highly qualified clockmaker.In Paris Kessels met the German astronomer and geodesist Heinrich Christian Schumacher, one of Breguet's clients. Their relationship played a fundamental role in Kessels's decision to move to northern Germany, first to Hamburg and in 1823 in the nearby Altona, where Schumacher had installed his own astronomical observatory. Kessels established his own workshop there, married in 1829, and became Danish citizen. The time and the conditions for founding a precision clock-making workshop were favourable. In the first half of the nineteenth century, several important astronomical and naval observatories would be founded. Many amateur astronomers were equipping their own private observatories. At the same time, important governmental geodetic surveys were undertaken and the navy as well as the commercial navigation in Denmark and in Northern Germany were fast developing. Altona and Hamburg quickly became important ports. All these activities required an increasing number of scientific instruments, especially box chronometers and astronomical regulators (clocks). Such time-keeping apparatus had to be periodically adjusted. And the Danish King Frederik IV was highly interested in astronomy and related sciences. Schumacher, who had an excellent relationship with the king and the government, could thus facilitate the development of Kessels's business and support his career.Unfortunately, information about Kessels's workshop is scarce. Presumably he had several employees. As general manager of his firm, he supervised the different types of work, personally made or completed the most delicate parts and arranged the final assemblies and tests. …

(Invited) Dry Adhesives for MEMS Assembly, Manipulation and Integration: Progress and Challenges

Bioinspired synthetic dry adhesives offer unique potential in the field of micro assembly and manipulation. These adhesives, which take their basic operating principle from animals like geckos, use van der Waals adhesion forces and mechanical fiber optimization to produce significant forces. For several years, these materials have been of interest for climbing robots and adhesive surfaces due to potential characteristics like self-cleaning or anti-fouling behavior, anisotropic adhesion strengths and non-transferring materials. These same strengths would make these materials an ideal mechanism for handling delicate parts or manipulating structures in the field of micro-electro-mechanical systems (MEMS) packaging. In this paper, I review the specific fabrication processes developed by our group and examine some of the challenges in their integration with MEMS assembly and packaging processes. Improving normal adhesion strength and directionality of adhesives has been completed and work is beginning to focus on reducing polymer transfer and improving the anti-static compatibility of the structural materials used in the adhesives.

Incorporating ergonomic factors in disassembly sequence planning

Due to awareness of the environmental and economical reasons the objective of modern technology is turning away from deposition and incineration of end-of-life products towards a far reaching product reuse. Disassembly is the main stage in the product end-of-life treatment. As disassembly process is mainly manual in nature, we assume that ergonomic factors are considered to have an effect on the process. The aims of this study is to investigate the level of involvement of ergonomic aspects in the disassembly workplace with the effect of their absence on the human performance which in turn may reflect on the losses in the disassembly outcomes and modelling an optimum disassembly plan incorporating the ergonomic factors within the model. This model is trying to find a disassembly scheme which maximizes the output revenue of the process via the minimization of the losses caused by the human error without jeopardizing the logic technical sequence. To investigate the human error in the disassembly workplaces and to develop the disassembly cost index score model, a survey was conducted in a variety of commercial electronic and delicate parts disassembly facilities, especially on the personal computers (PCs) disassembly. Based on this survey a multifactor weighted estimation scheme was proposed with the four factors; the need for special hand manoeuvring, visibility of parts, complexity of disassembly task and instruction of disassembly.

空気圧制動系における非線形粘着状態観測器

This paper shows that the VSS observer has the possibility to estimate adhesion force using wheel slip simulation and wheel slip experiments. It has been shown that the disturbance observer was effectives in estimation of adhesion force. To apply a strain gauge to the brake caliper in order to measure the braking torque is difficult, because the delicate parts on bogies are to be avoided at the train depot. When all the axles of vehicles slip, the wheel slip prevention cannot work sufficiently. Moreover, the brake systems of railway vehicles possess strong nonlinear characteristics with variable parameters, such as adhesion force and friction coefficient of brake materials. It is important that the estimation method has robustness against such disturbance and parameter changes, and it is known that the Variable Structure System (VSS) observer has robustness against parameter change, disturbance input and so on. However, there have been no research reports about a Variable Structure System (VSS) observer for the brake system or wheel slip preventing methods in a railway vehicle. In order to compare the theoretical value of adhesion force with estimated value by a VSS observer, wheel slip simulation was preformed. Simulation results show that the VSS observer can estimate the adhesion force efficiently. Moreover, estimation experiments of adhesion force using VSS observer were performed, and it has been clarified that the VSS observer can efficiently estimate the tangential force coefficient from the experimental results.

Identifying Subscripts and Superscripts in Mathematical Documents

In mathematical OCR, it is necessary to analyze two-dimensional structures of the component characters and symbols in mathematical expressions printed in scientific documents. In this paper, we analyze the positional relationships between adjacent characters for the purpose of automatic discrimination between baseline characters, subscripts, and superscripts, which is one of the most important and delicate parts of structure analysis. It has been proven through a large-scale experiment that this discrimination can be carried out almost perfectly (~ 99.89%) by using the relative size and position of adjacent characters.

Dimensional measurement of 3D microstruture based on white light interferometer

Dimensional metrology for micro/nano structure is crucial for addressing quality issues and understanding the performance of micro-fabricated products and micro-fabrication processes. Most of the established methods are based on optical microscopy for planar dimensions and stylus profilometry for out-of-plane dimensions. Contact profilers suffer from slow speed of measurement for three-dimensional profiles and are not suitable for delicate surfaces and parts. Advanced systems using white light interferometer are equipped with CCD cameras and interfaced with a microscope to conduct an array of measurements ranging from two-dimensional to three-dimensional profiles and surface roughness analysis. This paper presents a methodology based on white light interferometer for the dimensional measurement of 3D micro-structures, demonstrated on micro-gears and moulds produced by UV lithography and vacuum casting, respectively. Physical artifacts, such as gauge blocks, are also utilized to verify and validate the measurements on the microcomponents.

Piezo actuated vibratory feeding with vibration control

This research investigated the effect of decoupling the motion of a conventional vibratory feeder in order to develop a one-axis vibratory sliding mode for feeding tiny delicate parts that could ultimately be adapted to two axes. This research investigated a new type of vibratory drive by employing a piezoelectric actuator. In a decoupled design, the action of the horizontal and vertical vibration would be separately controlled to achieve a desired part trajectory and consequently the feed rate of the part. A computer control scheme was used to develop voltage input waveforms to control these actuators to produce movements that cause the parts to move forward relative to the track and overcome backsliding and other inefficient feeding motions. There are two advantages to this type of design. First, it can handle the parts in a more controlled manner by keeping them in constant contact with the track while maintaining a high conveying speed. This results in good protection for fragile parts. Secondly, this concept results in feedback control schemes that could allow the computer to adjust the drive waveforms to optimize feeder performance. Due to the non-sinusoidal nature of driving waveforms, the higher harmonic components can excite undesired deformation of the responding trajectory. A self-tuning control based on dynamic system identification was employed to counteract the higher harmonic effect. A one-dimensional hardware model is built and experiments were conducted to verify the precision and feasibility of the controlled actuation.

Novel design and development of an active feeder

PurposeThis paper aims to focus on the novel design and development of an automatic feeding system which is capable of feeding cylindrical parts which are fragile and powdery in nature and possess asymmetrical features such as a groove near to one end.Design/methodology/approachIt is an active feeder, performing its task without having to reject any feeding part by performing active orientation of feeding parts that are in the undesired orientation. This design incorporating active orientating capability is aimed at 100 percent feeding efficiency. The system is controlled and driven by a programmable logic controller and electropneumatics.FindingsSystem evaluation results showed that the average jam rate is below 5 percent and the percentage of correctly orientated parts is above 95 percent. With enhancement and fine tuning, the system could become a very useful feeder for industry in the future.Research limitations/implicationsThe scope of this paper focuses on presentation of the design concept, development and evaluation of the feeder only and design calculations are not included.Originality/valueThis paper is of value to those who are involved in the manufacturing of small delicate and powdery engineering parts such as those providing performs to the semiconductor industry for encapsulation of integrated circuit chips.

Laser Machining for Fabrication of Hohlraums and Capsules

Laser machining technology has been used to demonstrate the ability to rapidly perform jobs on all aspects of ICF targets. Lasers are able to rapidly perform modifications and repairs to the gold metal parts on hohlraums, make cuts in the delicate polymer parts of the hohlraum, and drill holes in the capsules to enable them to be filled with fuel. Lasers investigated in this work include 193 nm ArF and 248 nm KrF excimers and 810 nm chirped-pulse amplification Ti:Sapphire lasers. The excimer lasers showed a definite advantage in drilling and machining of polymeric materials and the ultrashort infrared pulses of the Ti:Sapphire laser were far better for the gold structures.

Determination of the loads acting on the pump rod of a water pumping windmill

One of the most delicate parts to size in a water pumping windmill is the pump rod. Indeed, frequent ruptures during the exploitation and experimentation of windmills shows that the determination of the real forces acting on the pump rod is quite difficult to evaluate. The calculation of these forces is traditionally achieved by taking as a maximal force the sum of the static loads. The calculation model used in this article takes into account the hydraulic pressure losses, inertia forces and the shock force caused by the water column on the piston. This will make it possible to better know the forces acting on the pump rod and therefore to perform better sizing.

Application of the Armstrong friction model to study dynamic transient response in workpiece-fixture systems

Dynamic interactions in the tool-workpiece and workpiece-fixture systems significantly impinge on the quality of machined workpieces. The dynamics of these systems are determined by many factors including fixture layout and frictional contact at the workpiece-fixture interface. In this paper, a multi-body flexible model of a frictional workpiece-fixture system is developed. A combination of the bristles concept with a modified version of the Armstrong friction model is employed to study dynamic interactions in the system. This analytical model enables the study of presliding and microsliding in the contact region along the transient dynamic response of the workpiece-fixture through an impact hammer test. Studying the behaviour of the bristles for various clamping forces indicates that the frictional damping decreases at higher clamping forces, which is due to increase in difference between the phase angles of oscillating bristles representing surface asperities. The model is validated by reproducing published experimental results. The presented modelling and solution methodology assists in detailed investigation of the contact region behaviour and can lead to optimal design of fixture elements specifically for delicate work parts and microelectromechanical systems (MEMS). The observed phase angle phenomenon can be utilized for determination of the optimal dynamic clamping forces. The simulated displacement history obtained via the presented modelling is very suitable for using to improve machining stability by extracting chatter stability lobes.

Productivity and quality improvements through orbital forming

Orbital forming is an efficient and precise process to assemble component parts. It provides strength, an attractive finished appearance, and batch‐to‐batch uniformity. Orbital forming machines can produce high‐torque assemblies and also freely swinging joints, and any degree of built‐in resistance in between. These machines quietly flare and form all malleable materials, including many engineering thermoplastics, and work safely on delicate and brittle parts. The machine controls provide infinitely variable cycle times (speed), forming pressure and tool stroke on the micrometer dial with resolution to 0.001 in.

A computational fluid-structure interaction analysis of a fiber-reinforced stentless aortic valve

The importance of the aortic root compliance in the aortic valve performance has most frequently been ignored in computational valve modeling, although it has a significant contribution to the functionality of the valve. Aortic root aneurysm or (calcific) stiffening severely affects the aortic valve behavior and, consequently, the cardiovascular regulation. The compromised mechanical and hemodynamical performance of the valve are difficult to study both ‘in vivo’ and ‘in vitro’. Computational analysis of the valve enables a study on system responses that are difficult to obtain otherwise. In this paper a numerical model of a fiber-reinforced stentless aortic valve is presented. In the computational evaluation of its clinical functioning the interaction of the valve with the blood is essential. Hence, the blood–tissue interaction is incorporated in the model using a combined fictitious domain/arbitrary Lagrange–Euler formulation, which is integrated within the Galerkin finite element method. The model can serve as a diagnostic tool for clinical purposes and as a design tool for improving existing valve prostheses or developing new concepts. Structural mechanical and fluid dynamical aspects are analyzed during the systolic course of the cardiac cycle. Results show that aortic root compliance largely influences the valve opening and closing configurations. Stresses in the delicate parts of the leaflets are substantially reduced if fiber-reinforcement is applied and the aortic root is able to expand.