Plastic Region Tightening Research Articles

Downsizing of Boltz by an Application of Plastic Region Tightening Method to Flange Joint

Plastic region tightening has been applied to the flange joint assembly in order to downsize the bolt and flange. The tightening procedure follows the modified HPIS flange tightening procedure, which employs the angle control method instead of the torque control method. Tightening tests is conducted using JPI 4 inch flanges and spiral wound gaskets. Bolts of M 16 with the reduced shank are used to adjust the tightening force. The estimation method is proposed for the yield tightening force of the bolt with reduced shank of hollow cylinder. The scatter of the axial bolt force is 10% or less after the tightening process is completed. The uniformity of the axial bolt forces obtained by plastic region tightening is equivalent or superior to that of elastic region tightening by HPIS procedure. In the tightening process, the increase in axial bolt force is very small in the plastic region of the bolt, so that the influence of the elastic interaction is also small, which is advantageous with respect to the uniformity of the axial bolt force. Application of plastic region tightening to the flange joint can downsize the bolts from M 16 to M 8 due to higher tightening bolt forces and their uniformity.

A Study of Self-Loosening and Fatigue Failure of Bolted Joint under Transverse Vibration - Influences of Property Class of Bolt and Plastic Region Tightening

In our previous study, loosening-fatigue tests under small transverse vibrations had been performed to elucidate bolt behavior and loosening-fatigue mechanism in the long life region. In this study, the influences of bolt property class and the plastic region tightening on loosening-fatigue characteristics under transverse vibration have been investigated. Result shows that bolt property class has little influence on the loosening-fatigue limits under transverse vibration. Result also shows that the transverse loosening-fatigue limit of the bolt which has been tightened to within the plastic region is lower than the transverse loosening-fatigue limit of the bolt that has been tightened to within the elastic region. This result is the opposite of the result of the axial fatigue characteristics of bolted joints.

3102 ねじの塑性域締結シミュレーション(J22 設計における情報共有・ナレッジマネジメント,J22 設計における情報共有・ナレッジマネジメント)

3102 ねじの塑性域締結シミュレーション(J22 設計における情報共有・ナレッジマネジメント,J22 設計における情報共有・ナレッジマネジメント)

123 AEモニタリングによるボルトの塑性域締め管理(非破壊評価とモニタリング1)

123 AEモニタリングによるボルトの塑性域締め管理(非破壊評価とモニタリング1)

ねじの塑性域締付けの解析(S46-2 機構の開発とシミュレーション(II),S46 機構の開発とシミュレーション)

ねじの塑性域締付けの解析(S46-2 機構の開発とシミュレーション(II),S46 機構の開発とシミュレーション)

Application of the Compressive Force Method to the Angle Control Method of Bolt Tightening.

In this study, the new angle control method to reduce the scatter band of clamping forces has been developed. The present method simultaneously loads a bolt with torque and compressive force, and measures torque and angle. The friction coefficients, the snug point and the spring constants of the bolted joint can be accurately evaluated during tightening process. Thus, the scatter band of clamping force in the elastic-region can be reduced within the error of 10% under oil free or lubricated conditions by the present method. The present method have high reliability and never loss tightening efficiency. It is possible to apply the present method to the plastic region tightening.

A Study on the Tensile Test Behavior and Fatigue Life Rate of Bolted Joint in Elastic Region Tightening and Bolted Joint in Plastic Region Tightening of the SCM435H

A Study on the Tensile Test Behavior and Fatigue Life Rate of Bolted Joint in Elastic Region Tightening and Bolted Joint in Plastic Region Tightening of the SCM435H

塑性域締結におけるねじ締結体の挙動 剛塑性体モデルによる解析

The axial tension of the bolt in the plastic region tightening method depends on the yield point load of the threaded portion under the combined loads of the axial tension and the thread torque induced by the tightening. A new estimation method for the yield point load of the threaded portion is proposed taking account of the general yield criterion based on the rigid-plastic solution for combined loads. Considering the coefficient of friction at the flank of the thread and the residual thread torque after tightening, simple formulas are derived for the yield clamping force and the maximum additional axial tension under externally loading. It is confirmed from the experimental results obtained by a combined loading test that the proposed estimation method is superior to the conventional one taking into account only the local yield criterion. Upon applying the local or general yield criterion, the range of the initial clamping force is bounded between the elastic region tightening, the yield point tightening and the plastic region tightening.

塑性域締結におけるねじ締結体の挙動 ねじ部の降伏軸力の推定方法

The axial tension of the bolt in plastic region tightening is influenced by the yield point load of the threaded portion under combined loads of axial tension and thread torque induced by tightening, namely interaction curve for yield. However the traditional estimation method for the interaction curve of the threaded portion has some problems. Firstly, a new estimation method for the interaction curve of the threaded portion is proposed based on the flow theory. Secondly, a combined load testing machine is developed in order to apply the tensile and torsional combined load on the threaded portion of the bolt, and the interaction curves of the threaded portion are obtained experimentally. In conclusion, it is shown that the new method is superior to the traditional one considering only the local yield condition.

弾性域と塑性域ねじ締結のゆるみ特性の比較 軸直角繰返し衝撃外力を受ける場合

Taking account of the reuse of bolts and nuts, this paper describes a comparison of threaded-fastener loosening characteristics of bolted joint in the elastic region tightening with those in plastic region tightening and the reason for the difference between them. The experiments are carried out by using the threaded-fastener loosening test machine which applies repeated transverse impact-force. The experimental results are as follows ; in the first use of bolts and nuts, the initial loosening in plastic region tightening is larger than that in elastic region tightening, but for the steady loosening the reverse tendency is found. At the reuse in elastic one, both initial and steady loosening are smaller than those in the first use, but in plastic one both loosenings are larger than those in the first use. The above mentioned results can be explained by the measurements of bolt end displacement, impact block displacement and twisting torque in the loosening test.

塑性域ねじ締結の特性 Ｔ字形フランジ締結体の耐疲労特性

The experimental considerations are performed to clarify the fatigue behavior of the bolt tightened up to the plastic region in the joint. The T-flange joint is treated as an example of bolted joints. The experiments are executed as the co-operative investigation by six bolt makers and a laboratory of the university. Firstly tension tests, tightening experiments, and fatigue tests of the bolt-nut joint are done in order to examine the mechanical properties of the bolt. Secondly the fatigue tests of the T-flange joints are performed in the same loading condition and in the three different tightening conditions - (a) elastic region tightening, (b) elastic limit tightening, and (c) plastic region tightening. As a result, the failure probability is found to be least in case (c), and greatest in case (a). These results coincide with the estimation from the stress measurements for the bolt in the T-flange joint. On the other hand, the difference in the behavior of the preload loss during fatigue tests are not so remarkable between three tightening conditions. Finally it is concluded that the bolted joints in the plastic region tightening have the more safety against fatigue because of higher preload, i. e. lower load amplitude on the bolt.

塑性域締付けにおけるボルトの再使用特性

In this paper, the comparison of the elastic region tightening with the plastic region tightening is investigated with emphasis on reusing characteristics of bolts. The tightening and loosening of bolts and nuts are repeated in tightening tests by the torque gradient, the angle and the torque control methods, respectively. The following results are experimentally confirmed: (1) The tightening axial force increases with number of repetitions by every control method, but the torque gradient control method which tightens bolts to the limit of elasticity is the most stable one. (2) The torque gradient control method is superior to other ones with regard to the reusing characteristics in the condition that an external force is loaded and unloaded to the fastened bodies in the direction of the bolt axis. (3) Plastic elongation of the bolts by the angle control method of plastic region tightening generates at the idle thread part between the fastened bodies, and then spreads to the fitting part of the bolts and nuts as the number of repeated tightening increases, so that the number of reusing cycle is limited.