Load Recovery of a Bolted Joint With a Shape Memory Alloy Stud

2011 ◽  
Author(s):  
Nazim Ould-Brahim ◽  
Abdel-Hakim Bouzid ◽  
Vladimir Brailovski
Keyword(s):  
Shape Memory ◽  
Analytical Model ◽  
Experimental Studies ◽  
Thermal Exposure ◽  
Element Model ◽  
Bolted Joint ◽  
Creep Properties ◽  
Material Creep ◽  
Low Stiffness ◽  
Joint Assembly

Creep is an important factor that contributes to the clamp load loss and tightness failure of bolted joints. Retightening of the joint can be expensive, time consuming and therefore is an undesirable solution. Currently, most efforts are put towards reducing load losses directly by tightening to yield, improving material creep properties or making joint less rigid. An alternative solution of current interest is the use of bolts in Shape Memory Alloys (SMA). However very few experimental studies are available that demonstrates its feasibility. The objective of this study is to exploit the benefit of the shape memory and superelasticity behaviors of a SMA stud to recover the load losses due to creep and thermal exposure of a gasket in a bolted joint assembly. This paper explores several venues to investigate and model the thermo-mechanical properties of a bolted joint with a nickel-titanium SMA stud. A stiffness-based analytical model which incorporates the Likhachev model of SMA is used as a representation of an experimental bolted joint assembly. Using this model, the rigidity of the experimental setup is optimized to make the best use of the SMA properties of the stud. This analytical model is compared with a Finite Element Model which also implements the Likhachev’s material law. Finally an experimental test bench with a relatively low stiffness representative of EN and JIS flanges is used, with and without gaskets to demonstrate the ability of the SMA stud to recover load losses due to gasket creep.

On the Use of Shape Memory Alloy Studs to Recover Load Loss in Bolted Joints

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Nazim Ould-Brahim ◽  
Abdel-Hakim Bouzid ◽  
Vladimir Brailovski
Keyword(s):  
Shape Memory ◽  
Analytical Model ◽  
Experimental Studies ◽  
Thermal Exposure ◽  
Element Model ◽  
Bolted Joints ◽  
Bolted Joint ◽  
Creep Properties ◽  
Material Creep ◽  
Joint Assembly

Creep is an important factor that contributes to the clamp load loss and tightness failure of bolted joints with and without gaskets over time. Retightening of the joint can be expensive and time consuming; therefore, it is an undesirable solution. Currently, most efforts are put towards reducing load losses directly by tightening to yield, improving material creep properties, or making joint less rigid. An alternative solution of current interest is the use of bolts in shape memory alloys (SMAs). However, very few experimental studies are available, which demonstrate the feasibility of these alloys. The objective of this study is to explore the benefit of shape memory and superelasticity behavior of an SMA stud to recover load losses due to creep and thermal exposure of a gasket in a bolted-joint assembly. This paper explores several venues to investigate and model the thermomechanical behavior of a bolted joint with a nickel–titanium SMA stud. A stiffness-based analytical model which incorporates the Likhachev model of SMA is used as a representation of an experimental bolted-joint assembly. Based on this model, the rigidity of the experimental setup is optimized to make the best use of the SMA properties of the stud. This analytical model is compared with a finite element model, which also implements the Likhachev's material law. Finally, an experimental test bench with a relatively low stiffness representative of standard flanges is used, with and without gaskets to demonstrate the ability of the SMA stud to recover load losses due to gasket creep.

Experimental Characterization and Modelling Validation of Shape Memory Alloy Negator Springs

2013 ◽  
Author(s):  
Andrea Spaggiari ◽  
Eugenio Dragoni ◽  
Ausonio Tuissi
Keyword(s):  
Finite Element ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Analytical Model ◽  
Element Model ◽  
Design Tool ◽  
Experimental Characterization ◽  
Finite Element Software ◽  
Spiral Spring ◽  
Force Displacement

This paper is aimed at the experimental characterization and modelling validation of shape memory alloy (SMA) negator springs. A Negator spring is a spiral spring made of strip of metal wound on the flat with an inherent curvature such that, in repose, each coil wraps tightly on its inner neighbour. The main feature of a Negator springs is the nearly-constant force displacement behaviour in the unwinding of the strip. Moreover the stroke is very long, theoretically infinite as it depends only on the length of the initial strip. A Negator spring made in SMA is built and experimentally tested to demonstrate the feasibility of this actuator. The shape memory Negator spring behaviour is predicted both with an analytical model and with a a finite element software. In both cases the material is modelled as elastic in austenitic range while an exponential continuum law is used to describe the martensitic behaviour. The experimental results confirms the applicability of this kind of geometry to the shape memory alloy actuators and the analytical model is confirmed to be a powerful design tool to dimension and predict the spring behaviour both in martensitic and austenitic range, as well as the finite element model developed.

Short Term Relaxation Modeling of Valve Stem Packings

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Mohammed Diany ◽  
Abdel-Hakim Bouzid
Keyword(s):  
Contact Pressure ◽  
Analytical Model ◽  
Viscoelastic Behavior ◽  
Threshold Value ◽  
Element Model ◽  
Creep Properties ◽  
Valve Stem ◽  
Sealing Material ◽  
Important Design

The long term tightness performance of stuffing-box packings, used in valves, is conditioned by the capacity of its sealing material to maintain a contact pressure to a predetermined minimal threshold value. Due to the creep, this contact pressure decreases with time depending on the creep properties and the stiffness of the housing. Assessing relaxation is a key parameter in determining the tightness performance of a valve stem packing over time. An analytical model based on the packing viscoelastic behavior is developed to assess the contact pressures between the packing material and the stem and the housing and their variation with time. In parallel, an axisymmetric 2D finite element model was build to validate and support the analytical model. The valve stem packing relaxation performance is an important design parameter to consider when selecting compression packings.

scholarly journals Experimental and Numerical Investigation on the Perforation Resistance of Double-Layered Metal Shield under High-Velocity Impact of Armor-Piercing Projectiles

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 626
Author(s):  
Riccardo Scazzosi ◽  
Marco Giglio ◽  
Andrea Manes
Keyword(s):  
High Strength Steel ◽  
Steel Plate ◽  
Experimental Studies ◽  
Practical Interest ◽  
High Strength ◽  
Experimental Tests ◽  
Element Model ◽  
Transportation Systems ◽  
Metal Shield ◽  
Softening Parameter

In the case of protection of transportation systems, the optimization of the shield is of practical interest to reduce the weight of such components and thus increase the payload or reduce the fuel consumption. As far as metal shields are concerned, some investigations based on numerical simulations showed that a multi-layered configuration made of layers of different metals could be a promising solution to reduce the weight of the shield. However, only a few experimental studies on this subject are available. The aim of this study is therefore to discuss whether or not a monolithic shield can be substituted by a double-layered configuration manufactured from two different metals and if such a configuration can guarantee the same perforation resistance at a lower weight. In order to answer this question, the performance of a ballistic shield constituted of a layer of high-strength steel and a layer of an aluminum alloy impacted by an armor piercing projectile was investigated in experimental tests. Furthermore, an axisymmetric finite element model was developed. The effect of the strain rate hardening parameter C and the thermal softening parameter m of the Johnson–Cook constitutive model was investigated. The numerical model was used to understand the perforation process and the energy dissipation mechanism inside the target. It was found that if the high-strength steel plate is used as a front layer, the specific ballistic energy increases by 54% with respect to the monolithic high-strength steel plate. On the other hand, the specific ballistic energy decreases if the aluminum plate is used as the front layer.

scholarly journals Effect of long-term thermal exposure on microstructure and creep properties of DD5 single crystal superalloy

China Foundry ◽  
2021 ◽  
Vol 18 (3) ◽  
pp. 185-191
Author(s):  
Xu-dong Wang ◽  
Zhong Yang ◽  
Qiang Gao ◽  
Li-rong Liu
Keyword(s):  
Single Crystal ◽  
Thermal Exposure ◽  
Single Crystal Superalloy ◽  
Creep Properties

Effect of Creep on the Residual Stresses in Tube-to-Tubesheet Joints

2010 ◽  
Author(s):  
Nor Eddine Laghzale ◽  
Abdel-Hakim Bouzid
Keyword(s):  
Contact Pressure ◽  
Analytical Model ◽  
Nuclear Power ◽  
Structural Integrity ◽  
Environmental Safety ◽  
Maintenance Cost ◽  
Joint Interface ◽  
Plant Safety ◽  
Material Creep ◽  
Nuclear Power Plant Safety

Steam generators are the subject of major concern in nuclear power plant safety. Within these generators, in addition to the structural integrity, the gross tightness barrier, which separates the primary and secondary circuits, is primarily ensured by the presence of a residual contact pressure at the tube-to-tubesheet joint interface. Any leakage is unacceptable, and its consequences are very heavy in terms of the human and environmental safety as well as maintenance cost. Some studies have been conducted to understand the main reasons for such a failure. However, no analytical model able to predict the attenuation of the residual contact pressure under the effect of material creep relaxation behavior. The development of a simple analytical model able to predict the change of the residual contact pressure as a function of time is laid out in this paper. The results from the analytical model are checked and compared with those of finite elements.

Factors Influencing Nut Factor Test Results

2017 ◽  
Author(s):  
Warren Brown ◽  
Stewart Long
Keyword(s):  
Test Results ◽  
Bolted Joint ◽  
Factors Influencing ◽  
Applied Torque ◽  
Bolt Diameter ◽  
Joint Assembly

Nut Factor is used to establish a bolt load for a given applied torque in bolted joint assembly. In previous papers the effects of different factors influencing Nut Factor results were examined, which included the type of anti-seize, bolt and nut material, bolt diameter and amount of anti-seize applied. This paper examines those factors further and then includes additional factors which have been shown to have significant effect on the measured Nut Factor. The knowledge of these factors has been used to adjust the proposed ASTM specification for determining Nut Factor. It is also relevant to application in the field and to ensure that any testing conducted in a laboratory will be applicable in the field.

scholarly journals Bio-inspired Miniature Suction Cups Actuated by Shape Memory Alloy

10.5772/7228 ◽  
2009 ◽  
Vol 6 (3) ◽  
pp. 29 ◽  
Author(s):  
Hu Bing-Shan ◽  
Wang Li-Wen ◽  
Fu Zhuang ◽  
Zhao Yan-zheng
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Analytical Model ◽  
Basic Structure ◽  
Thin Elastic Plate ◽  
Climbing Robots ◽  
Suction Cup ◽  
Sma Actuator ◽  
Suction Cups ◽  
Pressure Suction

Wall climbing robots using negative pressure suction always employ air pumps which have great noise and large volume. Two prototypes of bio-inspired miniature suction cup actuated by shape memory alloy (SMA) are designed based on studying characteristics of biologic suction apparatuses, and the suction cups in this paper can be used as adhesion mechanisms for miniature wall climbing robots without air pumps. The first prototype with a two-way shape memory effect (TWSME) extension TiNi spring imitates the piston structure of the stalked sucker; the second one actuated by a one way SMA actuator with a bias has a basic structure of stiff margin, guiding element, leader and elastic element. Analytical model of the second prototype is founded considering the constitutive model of the SMA actuator, the deflection of the thin elastic plate under compound load and the thermo-dynamic model of the sealed air cavity. Experiments are done to test their suction characteristics, and the analytical model of the second prototype is simulated on Matlab/simulink platform and validated by experiments.

Effect of plasticity at out-of-plane electronic speckle pattern interferometry diagnostics of axisymmetric stresses by the hole-drilling method

2017 ◽  
Vol 53 (1) ◽  
pp. 3-14 ◽  
Author(s):  
Alexander L Popov ◽  
Sergei E Alexandrov ◽  
Victor M Kozintsev ◽  
Alexander L Levitin ◽  
Dmitri A Chelyubeev
Keyword(s):  
Plastic Material ◽  
Speckle Pattern ◽  
Finite Thickness ◽  
Experimental Studies ◽  
Median Plane ◽  
Element Model ◽  
Electronic Speckle Pattern Interferometry ◽  
Hole Drilling ◽  
Disk Model ◽  
Blind Hole

Theoretical, calculated, and experimental results of studies on the registration of the accounting effect of plasticity in the diagnosis of axisymmetric stresses by the hole method and speckle-interferometric detection of the field of normal displacements in its vicinity are presented. Theoretical and computational studies were carried out on a disk model of finite thickness from an ideally elastic–plastic material. The theoretical model considers the formation of elastoplastic deformations in the vicinity of the through hole; the calculated finite element model considers in the vicinity of both through and blind holes of different depths. It was noted that at the blind hole, the most informative are the movements of the axisymmetric bend caused by the violation by the blind hole of symmetry of the disk with respect to its median plane. At the same time, an approximate analytical method has been developed to calculate the stresses that cause only elastic deformations. Experimental studies were carried out on a series of samples in the form of steel disks with axisymmetric stresses near the yield point. These stresses were induced by the hot fit of grinded rings from hardened high-strength steel onto disks made of steel with a low yield strength. Examples are given which show that the stress values determined from normal displacements in the vicinity of the probe holes from the calculated–theoretical and experimental are similar.

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