Prediction of Clamp Load Loss Under Fully Reversed Cyclic Loads in Bolted Joints

2005 ◽  
Author(s):  
Payam H. Matin ◽  
Sayed A. Nassar
Keyword(s):  
Equilibrium Point ◽  
Strain Hardening ◽  
Compressive Force ◽  
Linear Range ◽  
Half Cycle ◽  
Clamping Force ◽  
Bolted Joint ◽  
Service Load ◽  
Non Linear ◽  
Reversed Cyclic

The amount of clamp load loss due to a fully reversed cyclic service load is determined for a bolted assembly in which both the fastener and the joint were initially tightened beyond their respective proportional limits. After the initial tightening of the fastener, the joint is subsequently subjected to a fully reversed cyclic load that acts as a tensile separating force in the first half cycle, and as a compressive force on the joints during the second half cycle of the loading. During the first quarter cycle, the separating force would increase the fastener tensile stress further into the non-linear range. Such separating force would simultaneously reduce the clamping force in the bolted joint. At the end of the following quarter of the cycle, the bolted joint system reaches a new equilibrium point between the fastener tension and the joint clamping force. At the new equilibrium point, the clamp load is reduced from its initial value, due to the plastic elongation of the fastener. In the third quarter of the cycle, the compressive service load would increase the joint compressive stress into the non-linear range. Similarly, the clamp load loss would be increased at the end of the second half cycle, due to the plastic compression in the joint. The total clamp load loss may significantly lead to joint leakage, loosening, or fatigue failure. A non-linear strain hardening model is implemented in order to determine the clamp load loss due to accumulative effect of the permanent set in the fastener and the joint after the service load had been removed. Various rates of strain hardening are used for modeling the behavior of the fastener and joint materials. The effect of three non-dimensional variables on the amount of clamp load loss is investigated. The variables include the joint-to-fastener stiffness ratio, the ratio of the initial fastener tension to its elastic limit, and the ratio of the external force to its maximum tensile value that would cause joint separation to start.

Fastener Tightening Beyond Yield

2004 ◽  
Author(s):  
Sayed A. Nassar ◽  
Payam H. Matin
Keyword(s):  
Equilibrium Point ◽  
Joint Stiffness ◽  
Cyclic Loads ◽  
Clamping Force ◽  
Bolted Joint ◽  
Permanent Set ◽  
Clamp Force ◽  
Service Load ◽  
The Mean ◽  
Initial Assembly

The effect of fastener tightening beyond yield on the amount of clamp load loss, due to the application of a separating force, is investigated for a system in which the bolted joint remains within its elastic range. After the initial assembly, the joint is subsequently subjected to a tensile separating force, which increases the tensile stress in the fastener further into the plastic range. Simultaneously, the separating force reduces the clamping force. Upon the removal of the separating service load from the system, the system reaches a new equilibrium point between the fastener tension and the joint clamping force. At the new equilibrium point, the tension in the fastener is reduced due to its plastic elongation. The reduction in fastener tension translates to a partial, yet permanent, reduction in the clamping force. Excessive loss of the clamp load is a failure mode that may lead to joint leakage, loosening, or fatigue failure. Additionally, the loss of the clamp force reduces the mean stress, which may significantly affect the fatigue performance of the system under subsequent cyclic loads. A discretized non-linear model is established in order to describe the fastener behavior, and to determine the clamp load loss due to the permanent set in the fastener. The effect of two non-dimensional variables on the amount of clamp load loss is investigated. The first variable is the fastener-to-joint stiffness ratio, and the second is the ratio of initial fastener tension to its yield strength. Analytical results are presented for a range of stiffness ratios that simulates both soft and hard joint applications.

Effect of Separating Load Eccentricity on the Clamp Load Loss in a Bolted Joint Using a Strain Hardening Model

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Sayed A. Nassar ◽  
Mohan Ganganala
Keyword(s):  
Equilibrium Point ◽  
Strain Hardening ◽  
Elastic Limit ◽  
Closed Form Solution ◽  
Tensile Load ◽  
Load Level ◽  
Form Solution ◽  
Clamping Force ◽  
Bolted Joint ◽  
Load Rate

A nonlinear model is proposed for studying the effect of the eccentricity of applied tensile forces on the clamp load loss in bolted joints that were initially tightened beyond the bolt elastic limit while the joint remained in the elastic range. A closed form solution is obtained for the amount of clamp load loss due to a cyclic separating force. The proposed model takes into account two sources of nonlinearity, namely, the strain hardening behavior of the yielded bolt material as well as the nonlinear deformation behavior of the clamped plates under an external separating load. After the initial tightening of the fastener past its elastic limit, the subsequent application of a tensile separating force on the joint tends to increase the fastener tension in a nonlinear fashion, and, simultaneously, reduce the clamping force in the bolted joint from its initial value. Upon the removal of the cyclic tensile load, the bolted joint system reaches a new equilibrium point between the residual fastener tension and the joint clamping force. At the new equilibrium point, the fastener tension is reduced from its preload due to its plastic elongation; simultaneously, a partial yet permanent loss in the clamp load level takes place. Excessive clamp load loss may lead to joint leakage, fastener loosening, or fatigue failure. For a known amplitude of the external cyclic tensile load, the increase in bolt tension and corresponding reduction in the joint clamp load are highly sensitive to the eccentricity of the tensile load (from the bolt center). Variables studied include the eccentricity value of the separating load, rate of strain hardening of the bolt material, compressive and tensile stiffness of the clamped plates, bolt stiffness, bolt preload, and magnitude of the separating tensile load.

Clamp Load Loss due to Fastener Elongation Beyond its Elastic Limit

2005 ◽  
Vol 128 (3) ◽  
pp. 379-387 ◽  
Author(s):  
Sayed A. Nassar ◽  
Payam H. Matin
Keyword(s):  
Equilibrium Point ◽  
Elastic Limit ◽  
Clamping Force ◽  
Bolted Joint ◽  
Proportional Limit ◽  
Joint System ◽  
Analytical Results ◽  
Service Load ◽  
Permanent Loss ◽  
Joint Separation

The amount of clamp load due to an externally applied separating force is determined for a boiled assembly in which the fastener is elongated past its proportional limit, while the clamped joint remained within its elastic range. After the initial tightening of the fastener, the joint is subsequently subjected to a tensile separating force, which further increases the fastener tensile stress into the nonlinear range. Such separating force will simultaneously reduce the clamping force in the bolted joint. Upon the removal of the separating service load, the bolted joint system reaches a new equilibrium point between the fastener tension and the joint clamping force. At the new equilibrium point, the fastener tension is reduced from its value at initial assembly, due to the plastic elongation of the fastener. The reduction in fastener tension translates into a partial—yet permanent—loss of the clamping load that may lead to joint leakage, loosening, or fatigue failure. A nonlinear model is established in order to describe the fastener behavior past the proportional limit of its material, and to determine the clamp load loss due to the permanent set in the fastener after the separating force has been removed. Two fastener materials with significantly different rates of strain hardening are used for modeling the behavior of the bolted joint system. The effect of three nondimensional variables on the amount of clamp load loss is investigated. The first variable is the stiffness ratio of the joint and the fastener. The second is the ratio of initial fastener tension to the fastener elastic limit, and the third variable is the ratio of the separating force to the force that causes joint separation to start. Analytical results are presented for a range of stiffness ratios that simulates both soft and hard joint applications. Experimental verification of the analytical results is presented.

Nonlinear Strain Hardening Model for Predicting Clamp Load Loss in Bolted Joints

2005 ◽  
Vol 128 (6) ◽  
pp. 1328-1336 ◽  
Author(s):  
Sayed A. Nassar ◽  
Payam H. Matin
Keyword(s):  
Equilibrium Point ◽  
Strain Hardening ◽  
Closed Form Solution ◽  
Form Solution ◽  
Clamping Force ◽  
Bolted Joint ◽  
Proportional Limit ◽  
Hardening Model ◽  
Nonlinear Strain ◽  
Initial Assembly

Closed form solution for the amount of clamp load loss due to an externally applied separating force is determined for a bolted assembly in which the fastener is initially tightened beyond its proportional limit. The joint may or may not have been yielded at initial assembly, however. After the initial tightening of the fastener, the joint is subsequently subjected to a tensile separating force, which further increases the fastener tensile stress into the nonlinear range. Such a separating force will simultaneously reduce the clamping force in the bolted joint. Upon the removal of the separating service load, the bolted joint system reaches a new equilibrium point between the fastener tension and the joint clamping force. At the new equilibrium point, the fastener tension is reduced from its value at initial assembly, due to the plastic elongation of the fastener. The reduction in fastener tension translates into a partial—yet permanent—loss of the clamping load, which may lead to joint leakage, loosening, or fatigue failure. A nonlinear strain hardening model is implemented in order to describe the fastener behavior past the proportional limit of its material, and to determine the clamp load loss due to the permanent set in the fastener after the separating force has been removed. In order to study the effect of strain hardening, various rates of strain hardening are used for modeling the behavior of the fastener material. The effect of three nondimensional variables on the amount of clamp load loss is investigated. This includes the joint-to-fastener stiffness ratio, the ratio of initial fastener tension to its elastic limit, and the ratio of the separating force to its maximum value that would cause joint separation to start. Analytical results are presented for a range of stiffness ratios that simulates both soft and hard joint applications.

Effect of Load Eccentricity on the Behavior of a Bolted Joint With a Yielded Fastener

2009 ◽  
Author(s):  
Sayed A. Nassar ◽  
Mohan Ganganala
Keyword(s):  
Equilibrium Point ◽  
Strain Hardening ◽  
Elastic Limit ◽  
Closed Form Solution ◽  
Tensile Load ◽  
Load Level ◽  
Form Solution ◽  
Clamping Force ◽  
Bolted Joint ◽  
Tensile Forces

A nonlinear model is proposed for studying the effect of the eccentricity of applied tensile forces on the clamp load loss in bolted joints that were initially tightened beyond the bolt elastic limit. The joint may not have been yielded at initial assembly, however. A closed form solution is obtained for the amount of clamp load loss due to a cyclic separating force. The proposed model takes into account two sources of nonlinearity; namely, the strain hardening behavior of the yielded bolt material as well as the nonlinear deformation behavior of the clamped plates under an external separating load. After the initial tightening of the fastener past its elastic limit, the subsequent application of a tensile separating force on the joint tends to increase the fastener tension in a nonlinear fashion, and simultaneously reduce the clamping force in the bolted joint from its initial value. Upon the removal of the cyclic tensile load, the bolted joint system reaches a new equilibrium point between the residual fastener tension, and the joint clamping force. At the new equilibrium point, the fastener tension is reduced from its preload due to its plastic elongation; simultaneously, a partial-yet permanent-loss in the clamp load level takes place. Excessive clamp load loss may lead to joint leakage, fastener loosening, or fatigue failure. For a known amplitude of the external cyclic tensile load, the increase in bolt tension and corresponding reduction in the joint clamp load are highly sensitive to the eccentricity of the tensile load (from the bolt center). Variables studied include the eccentricity value of the separating load, the rate of strain hardening of the bolt material, compressive and tensile stiffnesses of the clamped plates, bolt stiffness, bolt preload, and the magnitude of the separating tensile load.

Cumulative Clamp Load Loss Due to a Fully Reversed Cyclic Service Load Acting on an Initially Yielded Bolted Joint System

2006 ◽  
Vol 129 (4) ◽  
pp. 421-433 ◽  
Author(s):  
Sayed A. Nassar ◽  
Payam H. Matin
Keyword(s):  
Cyclic Load ◽  
Elastic Limit ◽  
Half Cycle ◽  
Joint System ◽  
Direction Parallel ◽  
Permanent Set ◽  
Service Load ◽  
Cyclic Service ◽  
Joint Separation ◽  
Reversed Cyclic

The amount of clamp load loss due to a fully reversed cyclic service load is determined for a bolted assembly in which the fastener and the joint were both tightened initially beyond their respective proportional limits. The cyclic reversed load acts in a direction parallel to the bolt axis. During the first half of each cycle, the cyclic load acts as tensile separating force that increases the fastener tension further into the nonlinear range; it simultaneously reduces the joint clamping force. Thus, after the first one half of the cycle, the clamp load is reduced from its initial value due to the plastic elongation of the fastener. During the second half cycle, the cyclic load compresses the joint further into the plastic range; simultaneously, it reduces the fastener tension. Due to the permanent set in the compressed joint, the clamp load is decreased further at the end of the second half cycle of the service load. The cumulative clamp load loss due to the permanent set in both the fastener and the joint is analytically determined using a nonlinear model. Variables investigated in this study include the joint-to-fastener stiffness ratio, the ratio of the initial fastener tension to its elastic limit, and the ratio of the external force to its maximum tensile value that would trigger joint separation.

Plastic limit analysis with non linear kinematic strain hardening for metalworking processes applications

2011 ◽  
Vol 25 (11) ◽  
pp. 2859-2870 ◽  
Author(s):  
Ali Chaaba ◽  
Lahbib Bousshine ◽  
Mohamed Aboussaleh ◽  
Hassan El Boudaia
Keyword(s):  
Strain Hardening ◽  
Limit Analysis ◽  
Plastic Limit ◽  
Non Linear ◽  
Plastic Limit Analysis

Energy Balancing Method to Identify Nonlinear Damping of Bolted-Joint Interface

2016 ◽  
Vol 693 ◽  
pp. 318-323 ◽  
Author(s):  
Xin Liao ◽  
Jian Run Zhang
Keyword(s):  
Dry Friction ◽  
Harmonic Excitation ◽  
Joint Interface ◽  
Damping Factor ◽  
Viscous Damping ◽  
Bolted Joint ◽  
Energy Balancing ◽  
Stick Slip ◽  
Non Linear ◽  
Linear Damping

The interface of bolted joint commonly focuses on the research of non-linear damping and stiffness, which affect structural response. In the article, the non-linear damping model of bolted-joint interface is built, consisting of viscous damping and Coulomb friction. Energy balancing method is developed to identify the dry-friction parameter and viscous damping factor. The corresponding estimation equations are acquired when the input is harmonic excitation. Then, the vibration experiments with different bolted preloads are conducted, from which amplitudes in various input levels are used to work out the interface parameters. Also, the fitting curves of dry-friction parameters are also obtained. Finally, the results illustrate that the most interface of bolted joint in lower excitation levels occurs stick-slip motion, and the feasibility of the identification approach is demonstrated.

Non-Linear Analysis and Modeling of the Structure with Bolted Joints

2015 ◽  
Vol 656-657 ◽  
pp. 694-699
Author(s):  
Xin Liao ◽  
Jian Run Zhang ◽  
Dong Lu
Keyword(s):  
Dynamic Stiffness ◽  
Element Model ◽  
Outer Radius ◽  
Bolted Joints ◽  
Structure Model ◽  
Test Results ◽  
Bolted Joint ◽  
Joint Structure ◽  
Non Linear ◽  
Simulation Results

In this study, a non-linear finite element model for a simplified single-bolted joint structure model is built. Static analysis on the structure under different shear force and pretension effect is done, and the non-linear contact behavior is analyzed. Through comparing datum, it is found that interface area of each bolted joint region can be described an annular region around bolt hole, whose outer radius has increased by 85% compared with radius of bolt hole. Also, the frequency responses of the multi-bolted joint structure under sinusoidal excitation are investigated. Simulation results show that the resonance regions basically remain unchanged in different pretension effect and the largest amplitude will increase with the increasing preloads. Finally, the vibration experiments are conducted. Interface nonlinear affect dynamic stiffness considerably. The test results illustrate that dynamic behaviors of bolted joint agree with the simulation results and the proposed non-linear contact model was reasonable.

Sign in / Sign up

Export Citation Format

Share Document