scholarly journals Aerospace Fasteners: Use in Structural Applications

2019 ◽  
Author(s):  
George Nadim Melhem
Keyword(s):  
Galvanic Corrosion ◽  
Laser Beam Welding ◽  
High Stress ◽  
Electrical Potential ◽  
Fatigue Cracking ◽  
Strength Properties ◽  
Inert Gas ◽  
High Stress Concentration ◽  
Fiber Reinforced Polymer Composites ◽  
Increased Strength

Aircraft components need to be selected and manufactured to adequately combat the environment, temperature, loading, compatibility, and so on. When structural materials such as aluminum alloys or fiber-reinforced polymer composites need to be joined in aircraft, the selection of fasteners, bolts, rivets, adhesives, and other methods need to be quantitatively assessed in order that the correct design for the component and joining method is identified. There is a variety of fasteners, bolts, and rivets, made using a variety of materials. Aluminum rivets are often used to join aluminum components in an aircraft. Rivets do not perform well under tension loading, but perform better in shear, thus limiting the application specifically for these purposes. Bolts are designed to clamp material together, and even though the bolt may be adequate to support a particular structure and load requirement, consideration must also be given to the modulus of elasticity and stiffness of the components that are being clamped together. Therefore, an understanding of each of the materials being clamped or joined together is necessary. Bolts manufactured from steel, for instance, have coatings applied in order to help protect them from corrosion. The use of composites translates to a reduced number of rivets and fasteners to be used. Drilling of holes into composites to insert fasteners poses many challenges because the fibers are damaged, a region of high stress concentration may be formed, and the hole is a site for the ingress of water or moisture. The insertion of aluminum fasteners or the contact of aluminum components with carbon fibers creates galvanic corrosion due to the large difference in electrical potential. Titanium alloy (Ti-6Al-4V) is a typical fastener where there is composite joining due to its better compatibility (elimination of galvanic corrosion) and increased strength properties. Substitution of rivets and fasteners for welding is also on the increase in aircraft because laser beam welding (LBW) and friction stir welding both reduce cracking, porosity, and better properties achieved due to deeper penetration, and reduce the heat-affected zone which would typically be undesirable with conventional arc welding such as metal inert gas and tungsten inert gas welding. The shear and compressive stresses are increased, and fatigue cracking, weight, and cost are also reduced as a result of LBW, including the elimination of stresses and corrosion associated with rivets and the elimination of adhesives. Dissimilar metals such as the 7000 series and the 2000 series can be joined with a filler metal compatible to both metals to mitigate galvanic corrosion.

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.

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.

A Review: Natural Fiber as Reinforcement in Waste Paper Recycling and its Processing Methods

2013 ◽  
Vol 315 ◽  
pp. 443-447 ◽  
Author(s):  
S.K.A. Saferi ◽  
Y. Yusof
Keyword(s):  
Natural Fiber ◽  
Natural Fibers ◽  
Strength Properties ◽  
Hibiscus Cannabinus ◽  
Waste Paper ◽  
Kenaf Fiber ◽  
Healthy Environment ◽  
Wide Range ◽  
Increased Strength ◽  
The Right

As demand for clean and healthy environment, people make many alternate solutions to save the environment. To save trees and overcome landfill of waste material and waste disposal by burning activities issues (cause to losing energy and increase pollution), people nowadays take recycling as a recovery. Recycling waste paper into new product increased over the years. Shortage of wood supply required new sources of natural fiber for papermaking industry. Many researchers have studied new sources of natural fibers from non wood materials, such as oil palm residues, kenaf (Hibiscus Cannabinus), pineapple leaf, banana, and coconut fiber. Kenaf is choose as reinforcement agent for recycled waste paper to maximize the use of kenaf in industry application due its wide range of advantages where pineapple leaf are choose as reinforcement agent because abundantly of these material in Malaysia. Reinforcement of natural fiber into waste paper during recycling process expected to increased strength properties of final product. To understand the right and suitable processing method for kenaf fiber and pineapple leaf leaves previous work from other researchers are studied to investigate pulping procedure of natural fiber and its effect on mechanical strength.

The Influence of Switch Temperature on Coke Drum Fatigue Life

2010 ◽  
Author(s):  
Fa´bio de Castro Marangone ◽  
Ediberto Bastos Tinoco ◽  
Carlos Eduardo Simo˜es Gomes
Keyword(s):  
Fatigue Life ◽  
Structural Model ◽  
High Stress ◽  
Axial Direction ◽  
Pressure Vessels ◽  
High Stress Concentration ◽  
Short Period ◽  
Bending Stresses ◽  
Switch Temperature ◽  
Lower Temperature

Coke drums are thin-walled pressure vessels that experience severe thermal cycling condition which consists of heating, filling and rapidly cooling the drum in a short period of time. After some years under operation, cracks at the vessel may occur, especially at high stress concentration areas such as the skirt support to shell attachment. During the filling phase of the cycle, when the empty and cooled coke drum is filled with hot oil, the shell and cone temperatures increase rapidly compared to the skirt temperature and the last is pushed outward, since its bottom is at lower temperature and fixed at a concrete base. During quenching (sudden cooling) phase, the coke drum is filled with water at about 80°C and tends to cool faster than the skirt, which is pulled inward until equilibrium is obtained. The skirt expansion and contraction movement results in bending stresses in axial direction on the top of skirt. As lower the switch temperature is, more severe is the bending effect. One of PETROBRAS delayed coke unit presented some operational problems at pre-heating phase, resulting in lower switch temperatures. This paper presents an analysis showing the influence of the switch temperature on coke drum fatigue life. At first, the transient loading conditions were established from thermocouple measurements at skirt attachment weld (hot box region). Later, a transient thermal analysis was performed with FEA and the temperature gradient at the skirt attachment during entire thermal cycle was obtained. The thermal results were then converted to a structural model which was solved for linear elastic stress including other loads such as pressure. Finally, the maximum stress components for both filling and quenching phases were determined and a complete stress range was calculated as per ASME Section VIII, Div 2. The procedure described above was applied for different switch temperatures scenarios in order to show its influence on the fatigue life of the coke drum.

scholarly journals The Effect of Implant Length and Diameter on Stress Distribution around Single Implant Placement in 3D Posterior Mandibular FE Model Directly Constructed Form In Vivo CT

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7344
Author(s):  
Akikazu Shinya ◽  
Yoshiki Ishida ◽  
Daisuke Miura ◽  
Akiyoshi Shinya
Keyword(s):  
High Stress ◽  
Three Dimensional ◽  
Clinical Situation ◽  
Mechanical Analysis ◽  
Fe Model ◽  
High Stress Concentration ◽  
Implant Placement ◽  
Implant Therapy ◽  
Mandibular First Molar

A three-dimensional (3D) finite element (FE) model of the mandibular bone was created from 3D X-ray CT scan images of a live human subject. Simulating the clinical situation of implant therapy at the mandibular first molar, virtual extraction of the tooth was performed at the 3D FE mandibular model, and 12 different implant diameters and lengths were virtually inserted in order to carry out a mechanical analysis. (1) High stress concentration was found at the surfaces of the buccal and lingual peri-implant bone adjacent to the sides of the neck in all the implants. (2) The greatest stress value was approximately 6.0 MPa with implant diameter of 3.8 mm, approx. 4.5 MPa with implant diameter of 4.3 mm, and approx. 3.2 MPa with implant diameter of 6.0 mm. (3) The stress on the peri-implant bone was found to decrease with increasing length and mainly in diameter of the implant.

Contact Damage Analysis of Hot Mill Spindle Assembly with Kinematics Simulation

2006 ◽  
Vol 326-328 ◽  
pp. 1121-1124 ◽  
Author(s):  
Seong Woo Byun ◽  
Young Shin Lee ◽  
Hyun Seung Lee ◽  
Je Jun Lee
Keyword(s):  
Contact Surface ◽  
High Stress ◽  
Spindle Assembly ◽  
Surface Damage ◽  
Rolling Process ◽  
Life Cycles ◽  
Damage Analysis ◽  
Contact Damage ◽  
High Stress Concentration ◽  
Kinematics Simulation

The hot mill spindle assembly is the important component of the hot rolling process and used for transmission of rotational power. The contact surface between end coupling and slipper metal have high stress concentration due to operation interference. The life cycles of slipper metal are reduced by the contact surface damage. In this study, the structural analysis and kinematics simulation are performed by applying the various driving angle and dynamic boundary condition of the mill spindle assembly. This study aims to minimize the contact damage which might happen in the production process.

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