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.

Parametric modeling and updating for bolted joints of aeroengine casings

2016 ◽  
Vol 230 (16) ◽  
pp. 2940-2951 ◽  
Author(s):  
Xue Zhai ◽  
Cheng-Wei Fei ◽  
Jian-Jun Wang ◽  
Xing-Yu Yao
Keyword(s):  
Thin Layer ◽  
Model Updating ◽  
Parametric Modeling ◽  
Bolted Joints ◽  
Maximum Relative Error ◽  
Fe Model ◽  
Fe Modeling ◽  
Bolted Joint ◽  
Static Stiffness ◽  
Fe Model Updating

To establish accurate finite element (FE) model of bolted joint structures of aeroengine stator system (casings), this work implements the parametric FE modeling and updating of bolted joints of aeroengine stator system with multi-characteristic responses (multi-object). Firstly, the parametric FE modeling approach of bolted joint structure was developed based on the thin layer element method. And then the FE model updating thought of aeroengine stator system was developed based on the probabilistic analysis method. Finally, the parametric modeling and updating of the bolted joints of aeroengine stator system with multi-characteristic responses was completed by the optimization iteration calculation of objective function based on the proposed methods and the static stiffness testing data. Through the parametric modeling of bolted joint structures based on the thin layer method, the complexity of FE model of aeroengine casings with many bolted joint structures is reduced. As shown in the FE model updating of casings with multi-characteristic responses analysis, the static stiffness from the updated model are very close to the test data, in which the maximum relative error decreases to 3.9% from 30.52% and the others are less than 3%, so that the design precision of aeroengine stator system with the many and wide variety of bolted joints gets a great improvement. Moreover, the proposed methods of parametric modeling and model updating for multi-characteristic responses are validated to be effective in the simulation and equivalent of the mechanical characteristics of bolted joints in complex systems like aeroengine stator system.

Representation of bolted joints in a structure using finite element modelling and model updating

2020 ◽  
Vol 14 (3) ◽  
pp. 7141-7151 ◽  
Author(s):  
R. Omar ◽  
M. N. Abdul Rani ◽  
M. A. Yunus
Keyword(s):  
Finite Element ◽  
Dynamic Behaviour ◽  
Model Updating ◽  
Complex Structure ◽  
Bolted Joints ◽  
Model Parameters ◽  
Fe Model ◽  
Bolted Joint ◽  
Fe Modelling ◽  
Joint Structure

Efficient and accurate finite element (FE) modelling of bolted joints is essential for increasing confidence in the investigation of structural vibrations. However, modelling of bolted joints for the investigation is often found to be very challenging. This paper proposes an appropriate FE representation of bolted joints for the prediction of the dynamic behaviour of a bolted joint structure. Two different FE models of the bolted joint structure with two different FE element connectors, which are CBEAM and CBUSH, representing the bolted joints are developed. Modal updating is used to correlate the two FE models with the experimental model. The dynamic behaviour of the two FE models is compared with experimental modal analysis to evaluate and determine the most appropriate FE model of the bolted joint structure. The comparison reveals that the CBUSH element connectors based FE model has a greater capability in representing the bolted joints with 86 percent accuracy and greater efficiency in updating the model parameters. The proposed modelling technique will be useful in the modelling of a complex structure with a large number of bolted joints.

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.

Finite Element Simulation in the Dynamics Calculation of Bolted-Joint Interface

2012 ◽  
Vol 215-216 ◽  
pp. 1009-1012
Author(s):  
Yan Ting Ai ◽  
Yan Bai ◽  
Xue Zhai ◽  
Dan Zhao
Keyword(s):  
Experimental Data ◽  
Material Properties ◽  
Interface Layer ◽  
Bolted Joints ◽  
Joint Interface ◽  
Bolted Joint ◽  
Linear Dynamic ◽  
Element Simulation ◽  
Aero Engine ◽  
Dynamics Calculation

Many components in modern mechanical structure are connected with bolts, and the behaviour of joints significantly affects the dynamic response of these structures. Based on the software of MSC. patran, firstly, a linear dynamic model for bolted joints and interface is developed. The joint interface is modeled using a technology of interface layer element(ILE) and multi-point constrains(MPC) technique. And then, using the MATLAB language, the properties of ILE material are optimized to simulate the bolted-joint interface stiffness. The material properties parameters are identified by using experimental data. This work takes aero-engine case model as an example, researching its model analysis under different pre-stress conditions to check the method and provide insight on how to model the joint interface in the dynamics calculation of bolted structure.

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.

EXPERIMENTAL ANALYSIS OF THE LOAD CAPACITY AND REPEATABILITY OF PRELOADED BOLTED JOINTS

Tribologia ◽  
2020 ◽  
Vol 292 (4) ◽  
pp. 71-77
Author(s):  
Marcin Szczęch ◽  
Wojciech Horak
Keyword(s):  
Axial Force ◽  
Experimental Analysis ◽  
Load Capacity ◽  
Bolted Joints ◽  
Test Results ◽  
Bolted Joint ◽  
Breaking Force ◽  
Torque Wrench ◽  
The Common ◽  
Lubrication Conditions

Bolted joints are among the most widespread and most important detachable connections used in mechanical engineering and construction. The common use of this connection group is reflected in the variety of types of screw connections. There are several geometric and material factors, and consequently tribological ones, that determine the load capacity and, which is often of key importance, the repeatability of the bolted joint. The paper presents a description of the test stand and the test results of preloaded bolted joints for different lubrication conditions. The measured parameters were the breaking force value of a double lap bolted joint and its repeatability and the axial force repeatability of the bolts tightened by an electronic torque wrench.

Experimental Investigation on the Friction Coefficients for Different Materials, Lubrication Conditions and Coatings in Bolted Joints

2020 ◽  
Author(s):  
Dario Croccolo ◽  
Massimiliano De Agostinis ◽  
Stefano Fini ◽  
Giorgio Olmi ◽  
Francesco Robusto ◽  
...  
Keyword(s):  
Bolted Joints ◽  
Design Parameters ◽  
Bolted Joint ◽  
Treatment Change ◽  
Friction Coefficients ◽  
Actual Application ◽  
Iron Aluminum ◽  
Torque Wrench ◽  
Zinc Coatings ◽  
Lubrication Conditions

Abstract The present paper investigates the influence of several design parameters on the frictional response of a bolted joint, involving screws from strength grades 8.8 to 12.9, with black oxidization coating or zinc coatings. The experimentation deals with different underhead and nut materials (cast iron, aluminum), lubrication conditions (dry, lubricated, two different threadlockers: medium and strong), roughness condition in the underhead (cast, machined, painted, underhead washers) and cosidering also the effect of repeated tightenings. The friction coefficients of the actual application, retrieved based on the relevant operating parameters, are needed to support a correct design. The experimentation has been carried out by a purposely developed specimen, consisting of two parts: an instrumented sleeve, with a double array of strain gauges capable of sampling both the axial preload and the underhead torque, and interchangeable underhead washers. The testing apparatus is provided with a device which allows preventing undesired rotation of the washers. The washer material and surface treatment change among the different specimen sets. The tightening torque is applied by means of a 10-120Nm digital torque wrench. The collected data have been processed by the tools of ANoVa. Such tools allowed assessing the significance of each factor, as well as related interactions.

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.

scholarly journals Bolted Joint Preload Distribution from Torque Tightening

2021 ◽  
Vol 71 (2) ◽  
pp. 329-342
Author(s):  
Welch Michael
Keyword(s):  
Friction Coefficient ◽  
Static Friction ◽  
Bolted Joints ◽  
Dynamic Friction ◽  
Bolted Joint ◽  
Classical Analysis ◽  
Joint Design ◽  
Static Friction Coefficient ◽  
Bolt Preload ◽  
Torque Wrench

Abstract The purpose of this paper is to develop an understanding of how bolt preloads are distributed within a joint as each bolt is tightened in turn by the use of a calibrated torque wrench. It discusses how the order that the joints nuts/bolts are tightened can affect the final bolt preload. It also investigates the effect on incrementally increasing the bolt preload through a series of applications of the controlled torque tightening sequence. Classical analysis methods are used to develop a method of analysis that can be applied to most preloaded bolted joints. It is assumed that the static friction coefficient is approximately 15% less than the dynamic friction. It is found that the bolt preload distribution across the joint can range from slightly above the target preload to significantly less than the target preload. The bolts with a preload greater than the target preload are found to be those tightened towards the end of the tightening sequence, usually located close to the outer edges of the joint’s bolt array. The bolts with a preload less than the target preload are those tightened early in the tightening sequence, located centrally within the joints bolt array. The methods presented can be used to optimise bolted joint design and assembly procedures. Optimising the design of preloaded bolted joints leads to more efficient use of the joints.

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).

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