Superelastic Hinges Research Articles

Accurate Analysis of Double Ten Bar Mechanism Linked by one joint

ترغب أكثر الشركات بتقليل أعمال الصيانة والمحافظة على إمكانية إنجاز نفس الهدف بوزن أقل وبدون احتكاك ولو كان ذلك أكثر كلفة، عند تصنيع أي آلة. هذه المتطلبات تتحقق باستخدام المفاصل المرنة في منظومة ما كحد أدنى. لدينا منظومة ميكانيكية مستوية مكونة من آلة عشارية مضاعفة وبمفاصل دورانية، نبدل المفاصل الدورانية بمفاصل عالية المرونة. يقود ذلك لإمكانية بناء منظومة متينة تنجز نفس الهدف باستخدام أدنى حد للطاقة. إن الهدف الرئيسي للعمل هو بناء خوارزمية رياضية قادرة على تقييم الإزاحات للمنظومة المعتبرة قبل وبعد التبديل آخذين بعين الاعتبار أن المنظومة الجديدة ينتج عنها إزاحات إضافية (ناتجة عن المرونة العالية) كبيرة.

Cyclic behavior of extended end-plate connections with shape memory alloy bolts

The use of shape memory alloys (SMAs) has been seriously considered in seismic engineering due to their capabilities, such as the ability to tolerate cyclic deformations and dissipate energy. Five 3-D extended end-plate connection models have been created, including one conventional connection and four connections with Nitinol bolts of four different prestress forces. Their cyclic behaviors have been investigated using the finite element method software ANSYS. Subsequently, the moment-rotation responses of the connections have been derived by subjecting them to cyclic loading based on SAC protocol. The results obtained in this research indicate that the conventional connections show residual deformations despite their high ductility and very good energy dissipation; therefore, they cannot be repaired after loading. However, while having good energy dissipation and high ductility, the connections equipped with Nitinol bolts have good recentering capability. Moreover, a connection with the mentioned specifications has been modeled, except that only the external bolts replaced with SMA bolts and assessed for seismic loading. The suggested connection shows high ductility, medium energy dissipation and very good recentering. The main objective of this research is to concentrate the deformations caused by cyclic loading on the connection in order to form super-elastic hinge in the connection by the deformations of the shape memory alloy bolts.

Adaptive ankle–foot orthoses based on superelasticity of shape memory alloys

This article presents two innovative adaptive solutions for the ankle–foot orthosis based on mechanical and structural stiffness control of shape memory alloys. These concepts address gait abnormality in drop foot patients for various walking conditions such as different walking speeds. In the first design, a superelastic rod provides variable torsional stiffness that is adjusted by a controlled axial load. In the second design, the active length of superelastic hinge is adjusted in order to control the bending stiffness of the element. By adjusting the stiffness, variable level of compliance is achieved at the ankle. In both concepts, during powered plantarflexion in the stance phase of the gait, energy is stored in the shape memory alloy element. Release of this energy through superelasticity enables the ankle–foot orthosis to provide the desired controlled dorsiflexion motion in the sagittal plane and to raise the foot during the swing phase of the gait. The ultimate goal is to assist the patients in achieving a more natural gait and to prevent muscle atrophy. For the presented designs, numerical simulations are carried out to evaluate the stiffness properties of the active component under different gait speeds. To this end, experimental data of human gait are used to calculate the variation in ankle stiffness. The superelastic elements mimic the experimental ankle stiffness profiles.

Deployable Trusses Based on Large Rotation Flexure Hinges

Formulations for the strength, stiffness, mass efficiency, and packaging of deployable trusses using flexure hinges are developed and comparedwith the experimentwithin. The equations are based on classical buckling theory, Euler buckling with engineering approximations, and finite element-based models to predict the column and bending strengths of solid rod and tubular trusses with slender flexure hinges. Flexure hinge material performance metrics are derived and used to show that, while bothmass efficient trusses of solid rods and trusses of tubes are feasible with existing materials, trusses of solid rods are significantly more strain limited. A representative high compaction ratio deployable truss with pultruded carbon fiber reinforced plastic rods and super elastic nickel-titanium alloy flexure hinges was fabricated and tested. The compressive strength of the truss was 48% less than predicted and the compressive stiffness of the truss was 12% less than predicted.

A numerical study on bolted end-plate connection using shape memory alloys

Superelastic shape memory alloys (SMAs) have the ability to recover their original shape after experiencing large strains. A new beam-to-column connection incorporating long shank SMA bolts is presented in this paper. By using the unique characteristics of SMAs, the connection possesses self-centering abilities. The 3D connection model is created using the software ANSYS, and Auricchio’s model is used to simulate the superelastic behavior of the SMA bolts. With cyclic loads applied on the beam ends, the behavior of the connection is studied. The results show the semi-rigid and moderate energy dissipation characteristics of the connection. Since the moment-carrying capacity of bolt cluster controlled below the elastic flexural capacity of connecting beam, a superelastic hinge forms just at the beam-to-column interface. The inelastic interstory drift angle of the connection reaches 0.035 rad, and 94% of the total rotations are recoverable upon unloading.

A Concept for Monolithic Shape Memory Alloy Micro-Devices

Most of Shape Memory Alloy (SMA) devices use only the SMA material as the actuating part or in some cases as the flexible part of the device (superelastic hinges). Commonly, simple wires, strips or springs are used for the actuating part. All these systems need an assembly procedure which raises several problems in the micro-system field : careful assembly, sometimes friction, .... The concept of monolithic SMA micro-devices presented in this paper is to integrate all functions of the device within the same material. For example, in a micro-gripper, the jaws and the moving part are made out of the same piece of material. With this technology, we avoid any assembly in the small dimensions. Moreover sub-millimeter devices can easily be designed and further miniaturization can be achieved. As an illustration, two micro-devices based on this concept are presented.

Displacement Analysis of Pantograph Mechanisms with Superelastic Hinges.

For handling of a micromachine element and / or its parts, use of a micromechanical system is suitable. Thus, a pantograph mechanism is made from a plastic resin and superelastic hinges simultaneously using a small injection molding machine. The shape memory alloy having an effect of superelasticity is used as superelastic hinges. Therefore it is possible for superelastic hinges to have large bending displacements. The input and output displacements of the pantograph mechanism with superelastic hinges are measured and their linear relationship is confirmed. Then a micromechanical system for microbonding by adhesives is constructed using piezoelectric actuators, the pantograph mechanism and a needle. We confirmed that the proposed mechanical system performs well for microbonding by adhesives.

Design System of Superelastic Hinges and Its Application to Micromanipulators.

In order to develop a micromanipulator system for microbonding by adhesive, the characteristics of superelastic hinges made of superelastic materials, for example, shape memory alloy, have been analyzed and represented in the form of charts which enable rational design of micromanipulators. Making use of the characteristic charts, shapes and sizes of hinges can be considered in the determination of the kinematic parameters of a pantograph mechanism with superelastic hinges. The effective performance of the design system is demonstrated using an example of a manipulator for microbonding by adhesive.

Characteristic Analysis of Pantograph Mechanisms with Superelastic Hinges.

To handle a micromachine element and/or its parts, a micromechanical system is suitable. Thus, a pantograph mechanism is made from a plastic resin and superelastic hinges simultaneously by using a small injection molding machine. Superelastic hinges made of shape memory alloy have an effect of super-elasticity. Therefore it is possible for superelatsic hinges to have great bending displacements. The input and output displacements of the pantograph mechanism with superelastic hinges are measured and their linear relationship is confirmed. Then a micromechanical system for microbonding by adhesives is made from piezoelectric actuators, the pantograph mechanism and a needle. We confirmed that the proposed mechanical system performs well for microbonding by adhesives.

Design System of Super Elastic Hinges and its Application to Micro-manipulators.

In order to develop a micro manipulator system for micro-bonding by adhesive, the characteristics of super elastic hinges made of super elastic materials, for example, made of shape memory alloy, have been analyzed and represented in the form of charts which enable rational design of the mechanisms as micromanipulators. Making use of the characteristic charts ; shapes and size of hinges can be directly considered in the determination of kinematic parameters of the pantograph mechanism with super elastic hinges. The effective performance of the design system is demonstrated with an example of the manipulator for micro-bonding by adhesive.