A New Shaft Coupling Design for a High-Speed Rotor Wheel

1995 ◽  
Author(s):  
Tibor Kiss ◽  
Wing-Fai Ng ◽  
Larry D. Mitchell
Keyword(s):  
High Speed ◽  
High Stress ◽  
Critical Issue ◽  
Working Environment ◽  
Outer Diameter ◽  
Stress Concentrations ◽  
Coupling Region ◽  
Rotor Wheel ◽  
High Stress Concentration ◽  
Safety Margins

Abstract A high-speed rotor wheel for a wind-tunnel experiment has been designed. The rotor wheel was similar to one in an axial turbine, except that slender bars replaced the blades. The main parameters of the rotor wheel were an outer diameter of 10“, a maximum rotational speed of 24,000 RPM and a maximum transferred torque of 64 lb-ft. Due to the working environment, the rotor had to be designed with high safety margins. The coupling of the rotor wheel with the shaft was found to be the most critical issue, because of the high stress concentration factors associated with the conventional coupling methods. The efforts to reduce the stress concentrations resulted in an advanced coupling design which is the main subject of the present paper. This new design was a special key coupling in which six dowel pins were used for keys. The key slots, now pin-grooves, were placed in bosses on the inner surface of the hub. The hub of the rotor wheel was relatively long, which allowed for applying the coupling near the end faces of the hub, that is, away from the highly loaded centerplane. The long hub resulted in low radial expansion in the coupling region. Therefore, solid contact between the shaft and the hub could be maintained for all working conditions. To develop and verify the design ideas, stress and deformation analyses were carried out using quasi-two-dimensional finite element models. An overall safety factor of 3.7 resulted. The rotor has been built and successfully accelerated over the design speed in a spin test pit.

Strength of Elastomers. A Perspective

1978 ◽  
Vol 51 (2) ◽  
pp. 225-252 ◽  
Author(s):  
Thor L. Smith
Keyword(s):  
High Speed ◽  
Elevated Temperatures ◽  
High Stress ◽  
High Strength ◽  
Extension Rate ◽  
Stress Concentrations ◽  
Chain Mobility ◽  
Growing Crack ◽  
High Elongation ◽  
Progressive Growth

Abstract The strength and extensibility of an elastomer depend on its overall viscoelastic properties, as reflected in the time and temperature dependence of stress-strain curves, and also on those discrete processes, including crack formation and growth, that culminate in high-speed crack propagation. The discrete processes determine the lifetime of a specimen; the viscoelastic characteristics affect the dependence of stress on deformation. The interplay between these effects causes strength and extensibility to depend strongly on test conditions. An elastomeric network composed solely of highly mobile chains is very weak indeed and fractures at a low elongation. This characteristic differs diametrically from that expected of an idealized network of mobile chains. If such a network were stretched, stress concentrations and unbalanced forces at the molecular level, which can result from short chains, entanglements, and network imperfections, would be vitiated rapidly by stress-biased segmental diffusion, especially at the elevated temperature. Therefore the network should be able to withstand a high elongation and thus a high stress. Hence, the low strength always exhibited by a single-phase non-crystallizable elastomer at elevated temperatures is incompatible with the characteristics ascribed to a network in the molecular theory of rubber elasticity. A network of mobile chains is weak for two reasons. First, microcracks develop readily in a stretched specimen. Their formation is usually attributed to stress concentrations near heterogeneties either within or on the surface of a specimen. Second, and most importantly, a microcrack—once it forms—encounters little resistance to growth because the chains are highly mobile. High strength results not because microcracks do not develop but because their growth is impeded. Unless processes that impede growth come into play, a microcrack enlarges rapidly and catastrophic propagation soon follows. When chain mobility is relatively low, the dissipation of energy through viscoelastic processes near the tip of a slowly growing crack retards its progressive growth. But this source of strength is rather ineffective except within narrow ranges of temperature and extension rate, or time scale more generally. Thus, high strength and toughness result from other mechanisms that impede crack growth. Effective mechanisms usually come into play and impart toughness if colloidal particulate fillers or plastic domains are present, except at low concentration.

Packaging Materials for Flip Chip and WLP: Underfill Design Using FEM for FC-BGA, FC-CSP, and Moving Towards 2.5/3D.

2014 ◽  
Vol 2014 (DPC) ◽  
pp. 001295-001327
Author(s):  
Brian Schmaltz ◽  
Yukinari Abe ◽  
Kazuyuki Kohara
Keyword(s):  
Stress Concentration ◽  
Dielectric Layer ◽  
Flip Chip ◽  
Failure Modes ◽  
High Stress ◽  
Lead Free ◽  
Typical Result ◽  
Stress Concentrations ◽  
High Stress Concentration ◽  
Technology Nodes

As technology nodes progress to 16/14nm and beyond underfill materials are presented with the significantly challenging task of maintaining bump protection while ensuring low warpage for ultra low-K dielectric (ULK/ELK) integrity. This challenge is further complicated by the trend toward RoHS compliancy (lead-free) and an ever increasing die size (beyond 25x25mm). Through extensive research and testing, several specifically formulated underfill materials were determined acceptable solutions for these complex issues. As technology nodes progress to smaller processes high stress concentrations are seen at the dielectric layer during thermal cycling. This stress is a typical result of a high glass transition temperature (Tg) / high strength material that often leads delamination or a cracking failure mode of the thin dielectric layer. Too low of a Tg presents a high stress concentration on the bumps which once again constitutes failure, this time, however, the crack is typically seen at the bump location. This high stress concentration seen at the bumps is more significant when lead free bumps are considered due to their inherent fragile nature. Underfill materials must now be specifically optimized for variable package conditions to solve these failure modes for a large variation of package designs. Desired material properties must be quickly calculated using finite element methods. This paper will discuss solutions to typical failure modes currently seen in reliability testing of present and future technologies.

scholarly journals Design Optimization for the Thin-Walled Joint Thread of a Coring Tool Used for Deep Boreholes

2020 ◽  
Vol 10 (8) ◽  
pp. 2669 ◽  
Author(s):  
Yu Wang ◽  
Chengyuan Qian ◽  
Lingrong Kong ◽  
Qin Zhou ◽  
Jinwu Gong
Keyword(s):  
Stress Distribution ◽  
Large Diameter ◽  
High Stress ◽  
Three Dimensional ◽  
Outer Diameter ◽  
Stress Concentrations ◽  
Core Drilling ◽  
Drilling Tools ◽  
Deep Boreholes ◽  
Thread Structure

Threaded joints are key components of core drilling tools. Currently, core drilling tools generally adopt the thread structure designed by the API Spec 7-1 standard. However, fractures easily occur in this thread structure due to high stress concentrations, resulting in downhole accidents. In this paper, according to the needs of large-diameter core drilling, a core barrel joint was designed with an outer diameter of Φ135 mm and a trapezoidal thread profile. Subsequently, a three-dimensional simulation model of the joint was established. The influence of the external load, connection state and thread structure on the stress distribution in the joint was analyzed through simulations, from which the optimal thread structure was determined. Finally, a connection test was carried out on the threaded joint. The stress distribution in the joint thread was indirectly studied by analyzing gas leaks (i.e., the sealing effect) under axial tension. According to the test data and the simulation results, the final joint thread structure was optimized, which lays a good foundation for the design of a core barrel.

scholarly journals Determination of Fracture Origin in Ceramic Radial Rotor by Taking Photographs at Failure From Two or Three Directions

1990 ◽  
Author(s):  
Nobuo Kamiya ◽  
Mitsuru Asai ◽  
Akinobu Bessho ◽  
Shigetaka Wada
Keyword(s):  
Silicon Nitride ◽  
Injection Molding ◽  
High Speed ◽  
High Stress ◽  
Outer Diameter ◽  
Fracture Origin ◽  
Cracking Modes

A technique involving taking moment photographs from two or three directions at failure of ceramic radial rotor was developed to determine the position of fracture origin of the radial rotor revolving at a high speed. The position of the fracture origin of the silicon nitride radial rotor, 60mm in outer diameter and fabricated by injection molding, was demonstrated to be the fillet at the base of the shaft subjected to high stress. Furthermore, the dependence of cracking modes of rotors on the position of fracture origin was demonstrated using ceramic rotors with artificial flaws.

An Experimental and Numerical Study of Hybrid III Dummy Response to Simulated Underbody Blast Impacts

2017 ◽  
Vol 139 (12) ◽  
Author(s):  
Karthik Somasundaram ◽  
Anil Kalra ◽  
Don Sherman ◽  
Paul Begeman ◽  
King H. Yang ◽  
...  
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
High Stress ◽  
Fe Model ◽  
Loading Conditions ◽  
Stress Concentrations ◽  
Vertical Loading ◽  
Laboratory Setup ◽  
Body Regions ◽  
Hybrid Iii

Anthropometric test devices (ATDs) such as the Hybrid III dummy have been widely used in automotive crash tests to evaluate the risks of injury at different body regions. In recent years, researchers have started using automotive ATDs to study the high-speed vertical loading response caused by underbody blast impacts. This study analyzed the Hybrid III dummy responses to short-duration, large magnitude vertical accelerations in a laboratory setup. Two unique test conditions were investigated using a horizontal sled system to simulate underbody blast loading conditions. The biomechanical responses in terms of pelvis acceleration, chest acceleration, lumbar spine force, head accelerations, and neck forces were measured. Subsequently, a series of finite element (FE) analyses were performed to simulate the physical tests. The correlation between the Hybrid III test and numerical model was evaluated using the correlation and analysis (cora) version 3.6.1. The score for the Wayne State University (WSU) FE model was 0.878 and 0.790 for loading conditions 1 and 2, respectively, in which 1.0 indicated a perfect correlation between the experiment and the simulated response. With repetitive vertical impacts, the Hybrid III dummy pelvis showed a significant increase in peak acceleration accompanied by a rupture of the pelvis foam and flesh. The revised WSU Hybrid III model indicated high stress concentrations at the same location, providing a possible explanation for the material failure in actual Hybrid III tests.

Microcalcification Acts as a Stress and Stretch Amplifier in the Coronary Atherosclerotic Plaque Affecting Its Vulnerability: An IVUS-Based Finite Element Study

2012 ◽  
Author(s):  
Yuan Huang ◽  
Wenkai Wang ◽  
Zhongzhao Teng ◽  
Daniel R. Obaid ◽  
Jing He ◽  
...  
Keyword(s):  
Finite Element ◽  
Plaque Rupture ◽  
High Stress ◽  
Material Strength ◽  
Stress Concentrations ◽  
Mortality And Morbidity ◽  
High Stress Concentration ◽  
Fibrous Cap ◽  
High Stress Level ◽  
Rupture Site

Atherosclerotic disease remains a leading cause of mortality and morbidity worldwide despite significant advances in its management (1). Atherosclerosis, characterized by plaque consisting a lipid-rich necrotic core encapsulated in a fibrous cap, may result in plaque rupture and subsequently cause acute ischaemic events such as myocardial infarction and stroke. Under physiological conditions, plaque is subjected to mechanical loading due to blood pressure and flow and rupture possibly occurs if these extra loadings exceed the material strength of the fibrous cap (2–4). This hypothesis has been indirectly validated by the combination of histological examination and finite element simulations that the rupture site often bears a high stress concentration either in carotid (3, 5, 6) or coronary (2) plaques. It has been noted that most rupture sites are located at the shoulder region (2), where the curvature is locally large (4) leading to a high stress level (7). However, the rupture site does not always coincide with the site where high stress concentrations appear and about thirty to forty percent of ruptures occur in the middle region where the calculated stress is relatively low (2, 8). This demonstrates the limitations of current approaches.

scholarly journals KAJI NUMERIK PENCEGAHAN PERTUMBUHAN RETAK DENGAN MENGGUNAKAN METODE MODIFIKASI BENTUK STOP-DRILLED HOLE (SDH)

2017 ◽  
Vol 18 (2) ◽  
Author(s):  
Yudi Dwianda ◽  
Hendery Dahlan ◽  
Meifal Rusli
Keyword(s):  
Stress Concentration ◽  
Crack Propagation ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
High Stress ◽  
Fatigue Cracking ◽  
Stress Concentrations ◽  
High Stress Concentration ◽  
Hole Radius ◽  
Hole Model

ABSTRAK Salah satu mekanisme kegagalan yang utama dalam aplikasi teknik atau komponen mesin adalah penjalaran retak kelelahan. Penjalaran retak ini biasanya dimulai dari titik-titik pada daerah yang mengalami konsentrasi tegangan yang tinggi. Oleh karena itu salah satu metode untuk menghambat penjalaran retak adalah  mereduksi konsentrasi tegangan dimana salah satu metode yang digunakan adalah pemberian lubang di ujung retak atau dikenal dengan stop-drilled hole (SDH). Pada penelitian ini akan dikembangkan modifikasi bentuk model SDH. Pada dasarnya model yang dikembangkan ini adalah merubah bentuk pada sisi lubang agar tidak berbentuk lengkungan sehingga  konsentrasi tegangan menurun di daerah tersebut. Pemodelan lubang yang dikembangkan pada peneltian ini adalah penggambungan dua lubang dan tiga lubang pada ujung retak. Pada penelitian ini akan dilakukan penghitungan faktor konsentrasi tegangan untuk variasi jari-jari lubang yang diberikan. Dari penelitian yang telah dilakukan dapat disimpulkan bahwa pemberian dua lubang dan tiga lubang pada ujung cetak tersebut dapat mereduksi faktor konsentrasi tegangan dengan signifikan, nilai faktor konsentrasi tegangan antara dua lubang dan tiga lubang tidak berbeda signifikan terutama dengan meningkatnya nilai jari-jari lubang. Sementara itu, faktor konsentrasi tegangan tetinggi terjadi pada daerah perubahan geometri pada lubang untuk pemberian dua atau tiga lubang, akan tetapi faktor konsentrasi tegangannya masih cukup rendah jika dibandingkan dengan pemberian satu lubang. Kata Kunci : Konsentrasi Tegangan, Penjalaran Retak, Stop-Drilled Hole (SDH)   ABSTRACT One of the major failure mechanisms in engineering applications or machine components is the propagation of fatigue cracking. The spreading of these cracks usually are started from the points on the regions that are  experiencing high stress concentrations. Therefore, one of the method to inhibit this crack propagation is reducing the stress concentration in which one of the used methods  is the provision of a hole at the end of a crack or known as a stop-drilled hole (SDH). In this research will be developed  a modification form of SDH model. Basically the developed model is changing the shape on the hole side so there are not forming of the curve so that the stress concentration decreases in this area. The developed hole model in this research is the binding of two holes and three holes at the crack tip. This research will be calculated the stress concentration factor for variation of given hole radius. From the research that has been done, it can be concluded that the two holes and three holes on the tip of the crack can reduce the stress concentration factor significantly. Moreover,  the value of the stress concentration factor between two holes and three holes is not significantly different, especially with the increment of the hole radius. Meanwhile, the high stress concentration factor occured in the geometrical change area of the hole for two or three holes, but the stress concentration factor is still quite low when compared to the one hole. Keywords : Stress Concentration, Crack Propagation, Stop-Drilled Hole (SDH)

Integrity Assessment and On-Site Repair of a Floating Production Platform

2005 ◽  
Author(s):  
Mauro G. Marinho ◽  
Alexandre M. Pope ◽  
Luiz Claudio Meniconi ◽  
Luiz Henrique M. Alves ◽  
Cesar Del Vecchio
Keyword(s):  
High Stress ◽  
Local Strain ◽  
Business Unit ◽  
Gusset Plates ◽  
Strain Measurements ◽  
Integrity Assessment ◽  
High Stress Concentration ◽  
Production Platform ◽  
Welding Defects ◽  
Classification Society

Following the warning of a flooded bow horizontal brace of a semi-submersible production platform, an inspection diving team was mobilized and cracks were found at both bow and aft K-joints. Analysis of the service life of the platform, together with the results of structural analysis and local strain measurements, concluded that cracking was caused by fatigue initiated at high stress concentration points on the gusset plates inserted in the tubular joints. As a consequence of the fractured plates other cracks were nucleated close to the intersection lines of the braces that compose the K-joints. Based on this analysis different repair possibilities were proposed. To comply with the production goals of the Business Unit it was decided to repair the platform on-site and in production in agreement with the Classification Society. The proposed repair contemplated the installation of two flanges on the gusset plates between the diagonal braces by underwater wet (UWW) welding. Cracks at the gusset plates were also removed by grinding and wet welding. Defects located at the braces are being monitored and repaired by the installation of backing bars, by wet welding, followed by grinding and welding from the inside. To carry out the job two weld procedures and ten welder-divers were qualified.

An Experimental Study of Cavity Nucleation During Superplastic Deformation

1990 ◽  
Vol 196 ◽  
Author(s):  
Jiang Xinggang ◽  
Cui Jianzhong ◽  
Ma Longxiang
Keyword(s):  
Grain Boundary ◽  
Superplastic Deformation ◽  
Thermomechanical Processing ◽  
High Stress ◽  
High Strength ◽  
Optical Microscope ◽  
Grain Boundary Sliding ◽  
Cavity Nucleation ◽  
High Stress Concentration ◽  
Voltage Electron

ABSTRACTCavity nucleation during superplastic deformation of a high strength aluminium alloy has been studied using a high voltage electron microscope and an optical microscope. The results show that cavities nucleation is due only to superplastic deformation and not to pre-existing microvoids which may be introduced during thermomechanical processing. The main reason for cavity nucleation is the high stress concentration at discontinuties in the plane of the grain boundary due to grain boundary sliding.

The Effect of the EHD Pressure Spike on Rolling Bearing Fatigue

1987 ◽  
Vol 109 (3) ◽  
pp. 444-450 ◽  
Author(s):  
L. Houpert ◽  
E. Ioannides ◽  
J. C. Kuypers ◽  
J. Tripp
Keyword(s):  
Pressure Distribution ◽  
High Stress ◽  
Surface Damage ◽  
Rolling Bearing ◽  
Shear Stresses ◽  
Stress Concentrations ◽  
Surface Layers ◽  
Rolling Bearings ◽  
Life Model ◽  
Pressure Spike

A recently proposed fatigue life model for rolling bearings has been applied to the study of lifetime reduction under conditions conducive to microspalling. The presence of a spike in the EHD pressure distribution produces large shear stresses localized very close to the surface which may account for early failure. This paper describes a parametric study of the effect of such spikes. Accurate stress fields in the volume are calculated for simulated pressure spikes of different height, width and position relative to a Hertzian pressure distribution, as well as for different lubricant traction coefficients and film thicknesses. Despite the high stress concentrations in the surface layers, reductions in life predicted by the model are modest. Typically, the pressure spike may halve the life, with the implication that subsurface fatigue still dominates. In corroboration of this prediction, preliminary experimental work designed to reproduce microspalling conditions shows that microindents due to overrolling particles are a much more common form of surface damage than microspalling.

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