Fatigue Failure Of Bolt Research Articles

Mechanical testing of intelligent fastening

Loosening of threaded fasteners can lead to a decrease in preload, cause fatigue failure of bolts and seriously reduce the reliability of mechanical structures. Timely detection of such a weakening is an effective method of early prevention of a man-made disaster or economic losses. A promising direction in the field of monitoring the condition of complex structures during their operation is associated with the creation of intelligent materials or smart systems based on the use of sensor elements. The paper considers the main technical problems of operation of an intelligent fastener – a bolted connection with an integrated fiber Bragg grating (VBR). Calculations and strength tests of intelligent fasteners are given, problems arising during the operation of such systems and ways to solve them are described

Analysis of Effect of Slight Pitch Difference on the Fatigue Life of Bolt

In this work fatigue failure is examine for bolt with nut connections, when a slight pitch difference is established between bolt and nut. To improve the fatigue life, there are three types of slight pitch difference processed on the specimens and results are discussed in terms of FEM analysis. Taking into consideration the standard dimension bolt and nut connection having pitch difference of (α) =0 μm, the bolt fracture does not happen at the No. 1 thread by introducing a slight pitch difference of (α) =5 μm and pitch difference (α) =15 μm, is observed. Furthermore, it is having been discovered that the fatigue life of bolt can be increase by introducing some slight pitch differences. The effect of bolt-nut connection with slight pitch difference, on the fatigue failure of bolt is discovered.

622 軸直角方向負荷下のねじ締結体のすべり・ゆるみ挙動

The thread joint has been frequently used for the efficient productivity and maintainability as a machine element. However, many troubles such as loosening of bolted joints or fatigue failure of bolt were often experienced. Many attentions must be paid on the improvement of the strength and the reliability of the thread joints. It is generally said that the fastening axial force rapidly decreases by the rotation loosening of nuts if the relative slippage on the interfaces between nuts and fastened body goes beyond a certain critical limit. This critical relative slippage (Scr) that prescribes the upper limit for preventing the loosening behavior has been estimated according to the theoretically obtained equation considering the bending deformation of bolt and the geometrical constraint condition. In this paper, we present the investigated results of the deformation behavior of bolt-nut joint under transverse loading condition. The bending moment of bolt is measured by the quasi-static loading test. The reaction force moment by nut used in the equation for estimating the Scr is evaluated by the comparison of experimental and analytical results from estimated equation. The new equation for estimating the reaction force moment which agrees with measured value is examined and proposed.

Simulation of Fatigue Failure of Rail Joint Bolts by FEA

It is well known that the fatigue failure of bolts can affect the performance of rail joint and the safety of train running. In this work, the influence of the bolt torque and radius of rounded root of rail bolt on the fatigue strength of the rail bolt are studied by Finite Element Contact Analysis method. And the influence effects of the wheel impact and temperature force of the rail caused by temperature changed on bolt failure are studied. The results indicate that properly torque and increasing the radius of rounded root rail bolt can reduce the stress concentration at the root of rail bolt and this will improves the fatigue strength and the working life of the rail bolt and rail joint. The repeated temperature force of the rail and wheel impact force are playing an important role in the influencing factors on fatigue failure of the rail joint bolts. Due to this, the two bolts near the rail joints will to be fatigue failure almost earlier than others. That is one of the reasons why the bolts should be preloaded or replaced regularly.

Loosening and Sliding Behaviour of Bolt-Nut Fastener under Transverse Loading

The thread joint has been frequently used for the efficient productivity and maintainability as a machine element. However, many troubles such as loosening of bolted joints or fatigue failure of bolt were often experienced. Many attentions must be paid on the improvement of the strength and the reliability of the thread joints [1, 2]. It is generally said that the fastening axial force rapidly decreases by the rotation loosening of nuts if the relative slippage on the interfaces between nuts and fastened body goes beyond a certain critical limit [3]. This critical relative slippage (Scr ) that prescribes the upper limit for preventing the loosening behaviour has been estimated according to the theoretically obtained equation considering the bending deformation of bolt and the geometrical constraint condition. In this paper, firstly we present the equation for estimating the Scr based on the fundamental cantilever deformation model. Then we present the investigated results of the deformation behaviour of bolt-nut joint under transverse loading condition considering the reaction moment by nut (Mn ). Finaly we can confirmed that these estimated results of critical relative slippage coincided well with the experimental results [4, 5].

軸直角方向負荷下でのボルト-ナット締結体のすべり・ゆるみ挙動 : 第1報,ナットによる限界拘束モーメント評価式の検討及び修正(<小特集>締結・接合・接着部の評価技術)

The thread joint has been frequently used for the efficient productivity and maintainability as a machine element. However, many troubles such as loosening of bolted joints or fatigue failure of bolt were often experienced. Many attentions must be paid on the improvement of the strength and the reliability of the thread joints. It is generally said that the fastening axial force rapidly decreases by the rotation loosening of nuts if the relative slippage on the interfaces between nuts and fastened body goes beyond a certain critical limit. This critical relative slippage (S_<cr>) that prescribes the upper limit for preventing the loosening behavior has been estimated according to the theoretically obtained equation considering the bending deformation of bolt and the geometrical constraint condition. In this paper, we present the investigated results of the deformation behavior of bolt-nut joint under transverse loading condition. The bending moment of bolt is measured by the quasistatic loading test. The reaction force moment by nut used in the equation for estimating the S_<cr> is evaluated by the comparison of experimental and analytical results from estimated equation. The new equation for estimating the reaction force moment which agrees with measured value is examined and proposed.

2939 軸直角方向振動下におけるボルト・ナット締結体のゆるみ・疲労挙動に関する研究(S58-2 ねじ(2),S58 機械要素の設計・製造・応用技術)

2939 軸直角方向振動下におけるボルト・ナット締結体のゆるみ・疲労挙動に関する研究(S58-2 ねじ(2),S58 機械要素の設計・製造・応用技術)

シェル要素とビーム要素を用いたボルト締結部の簡易モデル化手法と強度評価

The stiffness of an engineering structure with joint depends not only on the materials and dimensions of the structure but also on the stiffness of the fasteners that connect its components. To evaluate the mechanical behavior of a complex structure with bolted joints, we first developed a simple finite element (FE) modeling technique that was simplified by using shell and beam elements and accounts for the effect of the stiffness of jointed plates and bolts. In evaluating the mechanical behavior, we also need a method for evaluating the strength of bolt joints from the results of FE analysis. In this study, we have developed a strength evaluation method for the beam forces of FE analysis by considering the mechanics of bolt joints. This method can be used to evaluate static failure and fatigue failure of bolts and slippage on clamped plates and bearing surfaces. We can easily evaluate the strength of bolt joints of industrial products with many bolted joints by using this method.