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.

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.

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.

scholarly journals On the stress-optical effect in transparent solids strained beyond the elastic limit

1922 ◽  
Vol 101 (709) ◽  
pp. 165-169 ◽  
Keyword(s):  
Elastic Limit ◽  
Optical Effect ◽  
Transparent Material ◽  
Slow Recovery ◽  
Double Refraction ◽  
Permanent Set ◽  
The Past

Experiments carried out by one of the present authors with a slab of glass under flexure have indicated that artificial double refraction in glass strained beyond the elastic limit is probably proportional to the stress rather than to the strain. More recently, the experiments of Prof. E. G. Coker and Mr. K. C. Chakko have suggested that in celluloid or xylonite, whilst for the highest loads the double refraction is no longer proportional to either the stress or the strain, it is more nearly proportional to the former than to the latter. Further, casual observations in the past had shown one of us that, when a piece of transparent material, whether glass or celluloid, which had been overstrained, was released, a certain amount of residual illumination was visible between crossed Nicols in certain cases. The illumination gradually died out, showing that the artificial double refraction exhibited some of the characteristics of permanent set, with a slow recovery. No precise measurements of this effect, however, seem ever to have been made.

The reversed cyclic load tests of normal and pre-stressed concrete beams

2008 ◽  
Vol 30 (4) ◽  
pp. 1014-1023 ◽  
Author(s):  
Weichen Xue ◽  
Liang Li ◽  
Bin Cheng ◽  
Jie Li
Keyword(s):  
Cyclic Load ◽  
Concrete Beams ◽  
Load Tests ◽  
Reversed Cyclic

Application of ANSYS Program in Ductility Analysis of Reinforced Concrete Frame Structure with Specially-Shaped Columns

2012 ◽  
Vol 215-216 ◽  
pp. 1118-1121
Author(s):  
Kai Bin Wang ◽  
Chun An You ◽  
Li Min Xin
Keyword(s):  
Reinforced Concrete ◽  
Finite Elements ◽  
Cyclic Load ◽  
Frame Structure ◽  
Reinforced Concrete Frame ◽  
Concrete Frame ◽  
Reinforced Concrete Frame Structure ◽  
Reversed Cyclic

In this paper, the writer analyzed a three-ply reinforced concrete frame structure with specially shaped columns through compiling a program by finite elements program of ANSYS. The results of simulated approached to experimental dates by comparison them. Which mean that use ANSYS program simulated ductility performance of reinforced concrete frame structure with specially shaped columns under reversed cyclic load is feasible. The simulation reflected the ductility of reinforced concrete frame structure, in which from load-on till destruction is perfectly.

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.

scholarly journals Fatique durability of smooth cylindrical rods under uniaxial symmetric stretch – compression

2019 ◽  
pp. 82-85
Author(s):  
Ju. M. Kobzar
Keyword(s):  
Elastic Limit ◽  
Mass Density ◽  
Gray Iron ◽  
Half Cycle ◽  
Software Environment ◽  
Volume Deformation ◽  
High Tension ◽  
Proposed Model ◽  
Stress Changes ◽  
Model Algorithm

The paper proposes a model of fatigue, that is based on the reduction of the carrier mass of the substance at half-cycle compression and its density increase by half-cycle stretching. High tension and volume deformation are linearly related by Hooke's law. Mass and density changes and stress changes depending on the elastic properties of the rod, its initial mass, density and volume are received analytically for each cycle. The model usage limit is a cycle in which amplitude values stress reaches the elastic limit. The proposed model algorithm is implemented in software environment with which the destruction is determined fatigue limit and fatigue. The resulting design value curve is different from the curve of fatigue of gray iron that was investigated. This is due to the fact that scattering of the applied energy on internal friction and heating is not included in the model.

Theoretical and experimental behaviour of a hybrid semi-rigid glulam beam-to-column connection with top and seat angles

2020 ◽  
Vol 23 (10) ◽  
pp. 2057-2069
Author(s):  
Haotian Tao ◽  
Min Mao ◽  
Huifeng Yang ◽  
Weiqing Liu
Keyword(s):  
Theoretical Model ◽  
Cyclic Load ◽  
High Energy ◽  
Test Results ◽  
Glulam Beam ◽  
Energy Dissipation Capacity ◽  
The Moment ◽  
High Energy Dissipation ◽  
Reversed Cyclic ◽  
Theoretical Results

This article proposes to use the bolted top and seat angles to provide excellent moment resistance and high energy dissipation capacity for glulam beam-to-column connection. Angles are anchored on the glulam beam using the glued-in steel plate technology and connected to the column by anchorage bolts. A theoretical model is presented in this article to evaluate the moment-resistant properties of the connection based on the component method. To validate the accuracy of the theoretical model, several hybrid connections are tested under monotonic and reversed cyclic load. The test results showed that the proposed hybrid connection has a high rotational stiffness and excellent moment resistance. The theoretical results are also consistent with those of the experimental model.

scholarly journals II. On the stress-optical effect in transparent solids strained beyond the elastic limit

1923 ◽  
Vol 223 (605-615) ◽  
pp. 89-125 ◽  
Keyword(s):  
Elastic Limit ◽  
Optical Effect ◽  
Optical Behaviour ◽  
Transparent Material ◽  
Slow Recovery ◽  
Stress Strain ◽  
Double Refraction ◽  
Permanent Set ◽  
The Past ◽  
The Law

Experiments carried out by one of the present authors with a slab of glass under flexure have indicated that artificial double refraction in glass strained beyond the elastic limit is probably proportional to the stress rather than to the strain ( cf . L. N. G. Filon, ‘Phil. Trans.,’ A, vol. 207, pp. 303-305). More recently the experiments of Prof. E. G. Coker and Mr. K. C. Chakko (“The Stress-Strain Properties of Nitro Cellulose and the Law of its Optical Behaviour,” ‘Phil. Trans.,’ A, vol. 221, pp. 139-162) have suggested that in celluloid or xylonite, whilst for the highest loads the double refraction is no longer proportional to either the stress or the strain, it is more nearly proportional to the former than to the latter. Further, casual observations in the past had shown one of us that, when a piece of transparent material, whether glass or celluloid, which had been overstrained was released, a certain amount of residual illumination was visible between crossed nicols in certain cases. This illumination gradually died out, showing that the artificial double refraction exhibited some of the characteristics of permanent set, with a slow recovery. No precise measurements of this effect, however, seem ever to have been made.

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