Mechanical Behaviors of Bolted Joint in Various Clamping Configurations

1998 ◽  
Vol 120 (3) ◽  
pp. 226-231 ◽  
Author(s):  
T. Fukuoka ◽  
T. Takaki
Keyword(s):  
Stress Concentration ◽  
Bolted Joints ◽  
Elastic Contact ◽  
Bolted Joint ◽  
Mechanical Behaviors ◽  
Stress Concentrations ◽  
Tightening Torque ◽  
Pitch Error ◽  
Manufacturing Errors ◽  
Multi Body

In a bolted joint, failures usually initiate at the first root of the bolt thread. However, rupture around the bolt head is sometimes reported for a tap bolt because of high stresses produced by tightening torque applied to the bolt head. It is also well known that manufacturing errors of internal threads in a tapped hole are generally much larger than those of external threads, thus leading to the failures concerned. In this paper, mechanical behaviors of bolted joints in various clamping configurations are analyzed using FEM as multi-body elastic contact problem, and the effects of nominal diameter, friction and pitch error upon stress concentrations are evaluated for through bolts, studs, and tap bolts. It is then quantitatively estimated on the effectiveness of “recessed internal threads” for reducing the stress concentration occurred around the far end of bolt hole. In addition, the tightening process and strength of a bottoming stud, which have seldom been studied despite favorable performance in preventing stress concentration at the runout of threads, are also investigated.

Improvement of Axial Tension Distribution of Bolted Joints Tightened by Calibrated Wrench Method From Viewpoint of Quality and Process Control Using Elliptical Confidence Limit

2019 ◽  
Author(s):  
Soichi Hareyama ◽  
Ken-ichi Manabe ◽  
Satoshi Kobayashi
Keyword(s):  
Process Control ◽  
Statistical Method ◽  
Confidence Limit ◽  
Bolted Joints ◽  
Independent Random Variables ◽  
Tension Stress ◽  
Bolted Joint ◽  
Tightening Torque ◽  
Tension Distribution ◽  
Axial Tension

Abstract When tightening a large number of bolted joints, the calibrated wrench method is used. Since this method is indirect, the axial tension varies greatly in many cases. However, the calibrated wrench method is still widely used because of the simplicity of the tool and easy standardization. When the tightening torque and axial tension are considered to be two independent random variables, the axial tension (stress) is distributed within an elliptical confidence limit. Conventionally, it is thought that the shape of this distribution is a rhombus. Considering the permitted limit for a working load (stress) on a bolted joint, the elliptical variation has a larger margin to the yield point than that of a conventional rhombus. On the basis of this feature, we show in this paper that a higher tightening target torque and a higher axial tension can be set than before. By applying the elliptical confidence limit, one can obtain higher tightening torque and initial axial tension than the conventional values within a smaller range of variations. In this study, in the case of tightening a large number of bolted joints at factories and so forth, tightening reliability is considered as a problem associated with quality or process control and a probabilistic statistical method is investigated. Finally, we carry out analysis to establish the optimum tightening torque for bolted joints.

scholarly journals Identification of Pre-Tightening Torque Dependent Parameters for Empirical Modeling of Bolted Joints

2021 ◽  
Vol 11 (19) ◽  
pp. 9134
Author(s):  
Yu Tian ◽  
Hui Qian ◽  
Zhifu Cao ◽  
Dahai Zhang ◽  
Dong Jiang
Keyword(s):  
Experimental Data ◽  
Thin Layer ◽  
Empirical Equation ◽  
Model Updating ◽  
Bolted Joints ◽  
Empirical Modeling ◽  
Bolted Joint ◽  
Tightening Torque ◽  
Torque Wrench ◽  
Interface Parameters

The vibration characteristics of bolted structures are crucially affected by the pre-tightening torque. An approach for identifying the pre-tightening torque dependent stiffness parameters of bolted joints is proposed in this paper. Firstly, the interface of the bolted joint is characterized by the thin layer element with the isotropic material property, and the parameter value of the property is assigned relative to the distance from the center of the bolt; the influence of the bolt is ignored. Secondly, the model updating method is adopted to identify the parameters of thin layer elements using experimental data, and modal data under different values of pre-tightening torque in the range of 2 N·m~22 N·m are obtained; the torque wrench is used to determine the pre-tightening torque in the modal test. Finally, after identifying the material parameters using partial experimental data on pre-tightening torque range, the empirical equation of the interface parameters with the pre-tightening torque parameter is obtained by curve fitting and the rest of the experimental data are used to verify the accuracy of the fitted empirical equations. It is concluded that this method can obtain all the parameters of the equivalent thin layer elements within a certain range of pre-tightening torque, which can provide a reference for the empirical modeling of bolted structures, improve modeling efficiency and reflect the characteristic performance of real structural dynamics.

Advantage of Elliptical Confidence Limit Method for Bolted Joint Tightening Reliability

2015 ◽  
Author(s):  
Soichi Hareyama ◽  
Ken-ichi Manabe
Keyword(s):  
Process Control ◽  
Yield Point ◽  
Confidence Limit ◽  
Equivalent Stress ◽  
Bolted Joints ◽  
Bolted Joint ◽  
Tightening Torque ◽  
Axial Tension ◽  
Control Capability ◽  
Joint Tightening

The calibrated wrench method is often used for tightening. When tightening bolted joints, it is important to apply high initial axial tension. However, since the axial tension is indirectly applied in this method, it varies and is widely distributed in the case of tightening carried out in the production line of a factory, for example. However, the calibrated wrench method is still widely used because of the simple tool used and easy standardization. Conventionally, this type of distribution has been considered to lie within a rhombus. In our previous paper, we analyzed and discussed the case when the distribution of the tightening torque and the equivalent stress of the bolted joint are considered to be independent random variables; in this case, the distribution becomes elliptical. Using this feature, a higher target tightening torque can be set than before. Finally, we established a procedure for the analysis and calculation of the optimum tightening torque for bolted joints. To ensure sufficient long-term tightening reliability to prevent breakage and loosening, a high initial axial tension and high equivalent stress can be realized using this proposed method. In this study, we analyze and discuss the case of differences in the tightening work condition (process control capability) and the tightening design condition. The tightening work coefficient a depends on the management state, the tightening working posture, and the process control capability of a tool or shop floor at a production site. According to the results of our trial calculation in Appendix A, the improvement ratio of the proposed target tightening torque is approximately 8.3% compared with the conventional method for dry friction and approximately 7.5% in the case of oily friction. Furthermore, in bolted joint tightening design, the tightening conditions under which the design conditions are satisfied are derived analytically. For the tightening design conditions of (1) a minimum axial stress of at least 50% at the yield point, and (2) an equivalent stress of 70% to 90% at the yield point, both the conventional and proposed areas of the confidence limit are obtained by precise analysis. Although the permitted limit of the tightening design condition cannot be realized by the conventional method, it can be realized by the proposed elliptical confidence limit method. Finally, we establish a method for maintaining the tightening reliability that involves applying high axial tension by increasing the target design tightening torque using the elliptical confidence limit.

Identifying Magnitudes and Locations of Loads on Slender Beams With Welded and Bolted Joints Using a Strain Gage Based Force Transducer With Application to a Portable Army Bridge

2013 ◽  
Author(s):  
E. T. Bednarz ◽  
W. D. Zhu
Keyword(s):  
Strain Gage ◽  
Calibration Method ◽  
Force Transducer ◽  
Bolted Joints ◽  
Bottom Surface ◽  
Strain Gages ◽  
Bolted Joint ◽  
Stress Concentrations ◽  
Slender Beams ◽  
Aluminum Beam

A strain gage based force transducer has been developed to identify magnitudes and locations of loads on non-continuous slender beams with welded and bolted joints. The slopes of the bending moment curves on the two sides of a load are calculated from measured strains on a beam. Four uniaxial strain gages are mounted to the bottom surface of the beam, with two strain gages on each side of the load. A calibration method developed earlier can be used to account for the discrepancies between the theoretical and actual scaling factors arising from stress concentrations and unpredictable stress patterns in the beams due to the presence of the joints. The force transducer methodology is experimentally validated on a continuously tapered aluminum beam with a series of welded joints, an aluminum beam with a constant cross section and a bolted joint, a half aluminum and half steel beam with two different cross sections and a bolted joint, and a full scale portable army bridge at the US Army Aberdeen Test Center.

Mitigating stress concentration through defense hole system for improvement in bearing strength of composite bolted joint, Part 1: Numerical analysis

2017 ◽  
Vol 51 (26) ◽  
pp. 3685-3699 ◽  
Author(s):  
AR Othman ◽  
Khudhayer J Jadee ◽  
M-Z Ismadi
Keyword(s):  
Numerical Analysis ◽  
Stress Concentration ◽  
Stress Reduction ◽  
Progressive Failure ◽  
Material Behavior ◽  
Bolted Joints ◽  
Nonlinear Material ◽  
Bolted Joint ◽  
Failure Model ◽  
Bearing Strength

The use of defense hole system allows the flow of the stresses to be redistributed by introducing auxiliary holes in the low stress area near the main hole. However, the question remains on the optimal configuration of the defense hole system for effective stress mitigation at the bolt-hole region and, hence, increasing the bearing capacity of particular composite bolted joints. This study presents the influence of defense hole system geometrical design on the stress reduction in a single-bolt, double-lap composite bolted joint. The nonlinear material behavior of the joint was simulated using ANSYS through a progressive failure model, considering the circumferential and radial stresses at bearing, shear-out, and net tension regions of the bolt-hole. It was found that the stress has been reduced between 2.3% and 6.1% for the narrow laminates over a range of E/ D ratios (1–5) with the benefits of the defense hole was clearly marked at DS = 2 D and DHD = 0.75 D. In contrast, for those of wider laminates, the stress reduction ranged from 1.9% to remarkably 18.6%.

scholarly journals Effect of Washer Type on Bearing Strength of Bolted-Joint Laminated Composites

2012 ◽  
Vol 21 (6) ◽  
pp. 096369351202100
Author(s):  
Yusuf Arman
Keyword(s):  
Laminated Composites ◽  
Bolted Joints ◽  
Bolted Joint ◽  
Tightening Torque ◽  
Bearing Strength ◽  
Failure Loads ◽  
Glass Fibre Reinforced ◽  
Load Displacement ◽  
Damage Tolerant ◽  
Composite Samples

There are various parameters for bolted joints used in so many industries. The main objective of this work was to investigate the influence of washer type as a bolting parameter on the bearing strength of bolted joints in laminated composites. Therefore, by using three different washer types; flat washer, spring washer and tooth lock washer, an experimental study was performed. Quasi-isotropic glass-fibre reinforced epoxy laminated composites were used in the study. Four different tightening torques ( T = 2, 3, 4, 5 Nm) were chosen for the bolted joints in the experiments, for each washer type. E/W ratio was chosen as 0.25, 0.5, 0.75 and 1 in order to investigate damage modes of composite samples. It was applied tensile test, through a centroidal axis, on each specimen. From these tests, load-displacement curves of the specimens were drawn. The maximum failure loads and bearing strengths of the bolted joints were obtained from the load-displacement curves. From the experimental results, it is noted that bearing strength of the specimens with flat washer is higher than the specimens with tooth lock and spring washer, respectively. Also, it is concluded that higher tightening torque increases the bearing strength, and E/W ratio should be determined as larger than 0.25 for a damage tolerant design in terms of bearing strength.

Evaluation of the Method for Lowering Stress Concentration at the Thread Root of Bolted Joints With Modifications of Nut Shape

1997 ◽  
Vol 119 (1) ◽  
pp. 1-9 ◽  
Author(s):  
T. Fukuoka
Keyword(s):  
Maximum Stress ◽  
Bolted Joints ◽  
Bolted Joint ◽  
Body Contact ◽  
Fine Pitch ◽  
Stiffness Matrices ◽  
Element Approach ◽  
Thread Root ◽  
Multi Body ◽  
Design Factors

Many studies have been devoted to investigate how the maximum stress occurred in the bolted joint could be reduced. Patterson and Kenny suggest that a modified nut with a straight bevel at the bearing surface is effective. However, they only dealt with M30, and estimations on the nut geometry had not been necessarily sufficient. In this study, an extensive finite element approach for solving general multi-body contact problem is proposed by incorporating a “regularization method” into stiffness matrices with singularity involved; thus, numerical analyses are executed to accurately determine the optimal shape of the modified nut for various design factors. A modified nut with a curved bevel is also treated, and it is concluded that the modified nuts are significantly effective for bolts with larger nominal diameter and fine pitch, and are practically useful compared to pitch modification and tapered thread methods.

Proposition of Helical Thread Modeling With Accurate Geometry and Finite Element Analysis

2006 ◽  
Author(s):  
Toshimichi Fukuoka ◽  
Masataka Nomura ◽  
Yuuya Morimoto
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Stress Concentration ◽  
Contact Pressure ◽  
Three Dimensional ◽  
Bolted Joints ◽  
Stress Concentrations ◽  
Element Analysis ◽  
Pressure Distributions ◽  
Thread Root

Distinctive mechanical behavior of bolted joints is caused by the helical shape of thread geometry. Recently, a number of papers have been published to elucidate the strength or loosening phenomena of bolted joints using three-dimensional finite element analysis. In most cases, mesh generations of the bolted joints are implemented with the help of sophisticated software. The mesh patterns so obtained are, therefore, not necessarily adequate for analyzing the stress concentration and contact pressure distributions, which are the primary concerns when designing bolted joints. In this paper, an effective mesh generation scheme is proposed, which can provide a helical thread model with accurate geometry in order to analyze such important characteristics as stress concentrations and contact pressure distributions along the thread helix. Using the FE models with accurate thread geometry, it is shown how the thread root stress and contact pressure vary along the helix and nut loaded surface and how the chamfering of the top threads of the nut mitigate the stress concentration concerned.

Improving Tightening Reliability on Bolted Joints for Calibrated Wrench Method (An Analysis on Optimum Tightening Torque by Confidence Limit Ellipse)

2013 ◽  
Author(s):  
Soichi Hareyama ◽  
Ken-ichi Manabe ◽  
Makoto Nakashima
Keyword(s):  
Conventional Method ◽  
Confidence Limit ◽  
Equivalent Stress ◽  
Plastic Region ◽  
Bolted Joints ◽  
Independent Random Variables ◽  
Bolted Joint ◽  
Tightening Torque ◽  
Axial Tension ◽  
Improvement Effect

On tightening bolted joints, the calibrated wrench method is used in manufacturing industries for a large amount of tightening work. It is important to give high initial axial tension in respect of tightening reliability, self-loosening prevention, the prevention from fatigue breakage, etc. In this method the axial tension of a bolt is controlled by grasping the wrench torque. However, since the axial tension grasp of this method is indirect, it varies greatly in lot of tightening. Therefore, the calibrated wrench method is not so accurate from the viewpoint of axial tension control. Turn-of-nut method, torque gradient control method and plastic-region tightening, etc. are developed as the methods of getting high initial axial tension with sufficient accuracy. But the calibrated wrench method is still widely used because of the simple tool and easy standardization. In this paper, the statistical distribution of the magnitude of the combined stress (equivalent stress) by shear strain energy criterion in bolted joint, which are tightened by the calibrated wrench method is formulated. Tightening torque and equivalent stress coefficients are considered to be two independent random variables. We show that the equivalent stress obtained by those products is distributed in a confidence limit ellipse. It is thought that distribution of this kind is conventionally varied in a rhombus. However, this proposed method shows that the distribution is varied inside the confidence limit ellipse. Now, when considering the permitted limit for working load stress on a bolted joint, ellipse-like variation has big margin to yield point than the shape of a conventional rhombus. Using this feature, we show that higher tightening target torque value can be set than before by this method. Finally, this research established the analysis and calculating routine for the optimum tightening torque on bolted joints. The merit and effect of this proposed method are as follows. 1) The optimum tightening torque can be raised by about 13% than conventional method by using the experimental thread characteristic values in this research. 2) In a large amount of tightening work, the axial tension distribution (tightening coefficient Q) and distribution of equivalent stress (tightening stress coefficient S) are presumed. The predicted value of the distribution of the Q is about 1.73, which has the 20% improvement effect compared to the conventional method. Also the distribution of the S is about 1.58, which has the similar improvement effect of 18%. As a rapid calculation, the nomograph of the optimum tightening torque can be obtained by combining the tightening torque and axial tension (axial stress) as well as the distribution of equivalent stress with dimensionless data of screw shape and strength. The example of nomograph on metric coarse screw is shown. In order to maintain the tightening reliability in bolted joints, standardization of the tightening work in a production site is very important. We think that this method is useful for establishment of the job standard (technical engineering standard).

Damping Variation Effects in Vehicle Semi-active MR Suspensions: A Stress Concentration Analysis

2021 ◽  
Vol 8 ◽  
Author(s):  
Carlos A. Vivas-Lopez ◽  
Juan C. Tudon-Martinez ◽  
Alfonso Estrada-Vela ◽  
Jorge de Jesus Lozoya-Santos ◽  
Ruben Morales-Menendez
Keyword(s):  
Stress Concentration ◽  
Mr Damper ◽  
High Amplitude ◽  
Stress Concentrations ◽  
Element Analysis ◽  
Vehicle Suspensions ◽  
Mechanical Components ◽  
Automotive Suspension ◽  
Suspension Model ◽  
Multi Body

Semi-active vehicle suspensions are used to improve the limited comfort performance of passive vehicle suspensions by varying the damping coefficient according to a control strategy. These benefits have been usually studied in a transient and frequency domain, but rarely in a multi-body dynamic analysis considering the mechanical components and their joints. In this study, the controllability effects of a magnetorheological (MR) damper on the mechanical components of a McPherson automotive suspension are investigated using a stress concentration analysis. Finite element analysis was used with a Quarter of Vehicle (QoV) suspension model configured with an MR damper, and then compared with the passive damper. The simulation results show that an SA damper in the suspension not only improves the dynamic behavior of a road vehicle, but it also has the positive effect of reducing the stress concentrations in a critical suspension element, the knuckle, that are generated by high amplitude road profiles such as rough roads or dangerous street bumps.

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