Set Of Bolts Research Articles

Análise de falha em flanges ocasionada por perda ou danos em estojos

As uniões flangeadas são amplamente utilizadas na indústria e a sua aplicação em equipamentos sub-sea requer um alto grau de confiabilidade, tendo em vista as condições ambientais e carregamentos, principalmente nas condições de águas profundas. A confiabilidade de uma união flangeada consiste na manutenção da sua característica de vedação, sendo o componente responsável pela vedação a junta. A vedação exercida pela junta é decorrente da ação de deformação ocasionada pela força de aperto dos estojos, sendo estes, elementos críticos das uniões flangeadas. Com o propósito de investigar falhas neste componente, é desenvolvida uma metodologia numérica, utilizando o método de Elementos Finitos, para avaliar o impacto da perda sucessiva de estojos em uma união flangeada. Também é investigado o relaxamento de tensão ocasionado por uma trinca em estojos. O estudo tem como objetivo conhecer os limites de operação segura, e neste trabalho é apresentado a análise de um flange da classe API 17D, de 4 polegadas com 8 estojos, sendo a metodologia desenvolvida aplicável a qualquer outro flange. O estudo numérico foi desenvolvido e simulado no software ANSYS Workbench 12.1 (2010). O resultado indica além do número mínimo de estojos necessários para manter a vedação, o incremento de tensão nos estojos remanescentes do flange, causado pela sucessiva perda de estojos.

What Makes Usain Bolt Unique as a Sprinter?

For both casual and avid fans alike, Olympic and other sporting events can provide a wealth of data for simple physics analyses. One of the most impressive performances in recent Olympic history is that of Usain Bolt in the track-and-field sprinting events during the 2008 Summer Games. Over a seven-day span, Bolt set world records in the 100-m and 200-m individual sprints and in the 4 × 100-m sprint relay. In addition, Bolt left us all wondering what record time he might have run had he not eased into the finish line in the 100-m dash. Naturally, one question many fans and observers immediately ask is: What makes Usain Bolt unique as a sprinter?

The Variations of Quality Characteristics According to Environmental Factors of High Tension Bolt, Nut and Washer Set

Because the fastener tension of high strength bolt, nut, and washer set is subject to the environmental factors such as temperature, humidity and storage period, extreme care should be taken during the joining and storage of such products. In case quality change is anticipated, the parts shall certainly be inspected.

The Influence on the Axial Force by the Size Scattering of High Tension Bolt, Nut and Washer Sets

In order to secure the uniformity and to reduce the scattering of torque coefficient value, which is a decisive factor in the quality of high tension bolt nut and washer sets, effort is required from the manufacturer to standardize manufacturing process and to continuously improve the quality.

Catastrophic failure of a raise boring machine during underground reaming operations

This paper describes the investigation of the catastrophic failure of a raise boring machine used for underground reaming operations. The results of the investigation indicate that failure was due to the fracture of the 32 drive head bolts, 30 of which had failed as a result of corrosion-induced fatigue. Metallurgical examination confirmed that the bolts had been manufactured in accordance with the SAE J429 Specification. A number of recommendations have since been implemented by the mine, who have also introduced a quality system specifically for the control of drive head bolt sets. The equipment has now operated without problems for several years.

高力ボルトの遅れ破壊に関する実験的研究 : (その1 限界拡散性水素濃度法の提案)

For developing the high strength bolts, for example, F15T bolt set which tensile stress is about 150Kgf/mm^2 (about 1.5GPa) and higher than that of the conventional strength bolt, the problem on delayed fracture must be solved. And it is evident from the past studies that the delayed fracture is concerned with the diffusible hydrogen in steel. In this paper, firstly from considering the past studies, the practical and easy method of the accelerated tests in which the diffusible hydrogen concentration is used for estimating the sensibility of the high strength bolts to the delayed fracture is proposed. And the results of this proposal accelerated tests on three types steels for high strength bolts are reported herein. From the consideration of these results, it is made up clear that the critical diffusible hydrogen concentration which is obtained by the proposal method can adequately estimate the sensibility of high strength bolt steels to the delayed fracture. Secondaly the results of this accelerated tests on four different notch shaped specimens are reported. And the influence of the notch shape on the critical diffusible hydrogen concentration in proposal method is discussed. Lastly the results of these tests on ten types specimens made from ten different F10T bolts set lots are reported. The F10T bolt set is the most popular and conventional high strength bolt in Japan. So from the consideration of these results of F10T bolts, the requirement on the critical diffusible hydrogen concentration for developing the F15T bolts sets is obtained.

析出硬化型ステンレス鋼(SUS630)高力ボルトの製法とその特性

High strength hexagon bolt sets of stainless steel are manufactured, where SUS 630 (JIS G 4032-1989), a kind of precipitation hardening stainless steels is adopted. The conditions of solution heat treatment and precipitation hardening heat treatment are discussed. Referring to the experimental results, manufacturing processes are standardized. Dimensioins, mechanical properties, absorbed energies by V-notch Charpy impact tests and torque coefficients by use of the bolt sets, trially manufactured, are measured. It is concluded that the equivalent strength level to F10T (JIS B 1186-1989, tensile strength σ_u・ 100〜120kgf/mm^2) can be obtained if produced according to the proposed manufacturing process.

ステンレス鋼のマルテンサイト変態を利用した接触応力測定法

The stress distribution at the contact area of a machine element has a large effect on the total performance of the machine. It is one of the important factors that closely relate to the performance of the element as a gear pair, a set of bolt and nut and so on. Many theoretical studies for estimating the contact stress were published. However, their validity has not been proved by experiments, because the known measuring methods are insufficient in accuracy or resolving power. The measuring method using martensite transformation is offered in this paper. If the stress is applied to the test piece made of 18-8 stainless steel at a temperature of 198 K, the stressed part of the test piece changes its structure from austenite to martensite. The martensite structure has the nature of ferromagnetism. Therefore, the contact stress distribution in the test piece can be obtained by measuring the distribution of remaining magnetism. For confirming the practical use of the method some experiments have been done using the block type (10 mm in thickness) and the film type (5 μm in thickness) test pieces of stainless steel. It has been confirmed that at the more stressed part, the more martensite transformation is induced in the test pieces, and that the test pieces have sensitivity for the measurement of the stress distribution. A homogeneous structure in the test piece is needed for the purpose of measurement.

Effects of the Interface Configurations on the Characteristics of Bolted Joints : the case where clamped parts are two hollow cylinders

In the design of bolted joints, it is important to examine the sealing performance and to estimate the force ratio (the ratio of an increment of bolt axial force to a load). Up to now, in order to improve the sealing performance, raised faces of the interfaces have been used. But the uses of these interfaces depend on experiments and the theoretical grounds are not made clear. In the present paper, in the case where two hollow cylinders having raised faces are fastened by a set of bolt and nut, a contact stress distribution is analyzed using three-dimensional theory of elasticity and point matching method. The force ratio of this joint is also analyzed. For verification, experiments are carried out. Analytical results are in a fairly good agreement with experimental ones. Then, discussion is made on effects of the interface configurations on the characteristics of the bolted joint.

A realistic evaluation of the factor of safety of a bolted bracket

A bolted bracket is analyzed when it is subjected to a pure bending moment of sufficient intensity to induce first an elastic, then an elastic-plastic, and finally a fully plastic stress distribution within the supporting set of bolts. It is shown that when the bracket is held in place by three equally spaced bolts, it can resist at least 28 per cent more load than a conventional elastic analysis of the problem indicates. This percentage is even larger when more bolts are used. In view of the widely differing results that are obtained by analyzing the problem from the conventional and the proposed points of view, it is suggested that the factor of safety be defined as the ratio of the load-carrying capacity of the unit, computed by including the effect of plastic flow, to the maximum specified external load.

ねじの摩擦係数測定裝置

A testing apparatus to measure coefficient of sliding friction between bolt and nut is producted. The axial compressive force is measured by three compressive helical coiled springs as shown in Fig. 1 and 2. A, B is the first set of bolt and nut, and A', B' the second. The spindle C fixed to A and A' by means of serration of C is turned slowly, and the torque to resist sliding friction between A and B, A' and B', is measured by F which is attached to the center of pendulum-shaft of torsion testing machine. The value of coefficient of friction is calculated by this torque and axial compressive force of springs, using equation (2). The value of coefficient of friction is about 0.2 between slightly lubricated mild pieces, and the value decreases with the increase of compressive force, as shown in Fig. 11-17. The typical diagrams of torque and twisted angle are shown in Fig. 5-10.

The limit of high flying when breathing oxygen

The experiments herein described were carried out at the works of Messrs. Siebe Gorman, Ltd., with the co-operation of Sir Robert Davis, who kindly placed at the author's use the necessary apparatus. A small cylindrical copper chamber was used about 20 inches long and 12 inches wide. One end was hermetically closed, and the other fitted with a removable lid; a thick glass disc formed the larger part of this lid, and served as an observation window. An air-tight junction was made between the lid and the chamber by means of thick rubber washers lubricated with glycerine. When a positive pressure was used a set of bolts and nuts secured the lid to the chamber and made the closure air-tight. The chamber was made to withstand pressure up to +130 lbs. It was fitted with valved inlet and outlet tubes; one tube connected the chamber with a pressure gauge. For evacuating the chamber and studying the effect of low pressures, an efficient pump was used with the piston working in oil. The stroke of the pump was driven by a band off the workshop shafting. The chamber was evacuated by this means down to the lowest pressure required (70 mm Hg), in about 6 minutes. To indicate the pressure during evacuation the chamber was connected to the top of a barometer tube, which was fitted with a scale; the bottom of this tube dipped in a cup of mercury. The chamber was placed in the vertical portion, and a wooden platform arranged inside on which the animals rested in full view under the glass window. The opening of the inlet tube used for ventilating the chamber was carried below this platform, so that the chamber could be thoroughly washed out with oxygen, or a mixture of oxygen and nitrogen. After the animals, e. g ., two rats, had been introduced, and the chamber closed, the inlet tube was connected, in the first series of experiments, with a cylinder of oxygen (99%) and the chamber well washed out with this gas. It was then repeatedly evacuated down to about 150 mm Hg, oxygen being admitted each time. This procedure secured a purity of oxygen in the chamber, as was shown by analysis. Finally the chamber was evacuated down to the pressure whereat symptoms of acute dyspnœa became manifest, a slow inflow of oxygen being maintained during this evacuation. The animals settle down, and quietly rest on the platform during the final evacuation, that is until the pressure drops to about 100 mm Hg, they then become restless, and when the pressure drops to 90-80 mm Hg their breathing becomes very deep and slow and they slow other signs of want of oxygen. Rats make convulsive leaps towards the window of the chamber, and on coming to rest their limbs straddle out, guinea pigs and pigeons fall over, monkeys close their eyes and fall asleep when the pressure falls below 120-110 mm Hg, and then as the pressure falls below 100 sink lower and lower down, but are still able to balance themselves in the sitting posture. Below 90 mm Hg the head falls against the side of the chamber and the monkey is unable to recover its balance when the chamber is shaken. The animals quickly recover when oxygen is let in, thus the evacuation could be repeated several times with like result, bloats were observed in a larger chamber which took about 35 minutes to evacuate. They were at first in the standing posture, but lay down when the pressure fell to 100-90 mm Hg and made convulsive movements when it reached 90-80 mm Hg.