Shape memory alloy based smart landing gear for an airship

The design and development of a shape memory alloy based smart landing gear for aerospace vehicles is based on a13; novel design approach. The smart landing gear comprises a landing beam, an arch, and a superelastic nickeltitanium shape memory alloy element. This design is of a generic nature and is applicable to a certain class of light13; aerospace vehicles. In this paper a specixFB01;c case of the shape memory alloy based smart landing gear design and13; development applicable to a radio controlled semirigid airship (radio controlled blimp) of 320 m3 volume is13; presented.Ajudicious combination of carbon xFB01;ber reinforced plastic for the landing beam, cane (naturally occurring13; plant product) wrapped with carbon xFB01;ber reinforced plastic for the arch, and superelastic shape memory alloy is13; used in the development. An appropriate sizing of the arch and landing beam is arrived at to meet the dual requirement of low weight and high-energy dissipation while ndergoing x201C;large elasticx201D; (large nonlinear recoverable13; elastic strain) deformations to ensure soft landings when the airship impacts the ground. The soft landing is required13; to ensure that shock and vibration are minimized (to protect the sensitive payload). The inherently large energydissipating character of the superelastic shape memory alloy element in the tensile mode of deformation and the superior elastic bounce back features of the landing gear provide the ideal solution.Anonlinear analysis based on the classical and xFB01;nite element method approach is followed to analyze the structure. Necessary experiments and tests have been conducted to check the veracity of the design. Good correlation has been found between the analyses and testing. This exercise is intended to provide an alternate method of developing an efxFB01;cient landing gear with satisfactory geometry for a x201C;certain class of light aerospace vehiclesx201D; such as airships, rotorcraft, and other light unmanned air vehicles

A smart material based approach to morphing

This presentation gives an overview of the Shape Memory Alloy (SMA) based approach to the research and13; development of adaptive/smart/morphing airframe structural technologies at the Advanced Composites13; Division, NAL. Central to this approach is the efficient integration of thermal NiTi SMA elements with13; polymeric carbon composites. The SMA elements could be either externally placed or embedded in the13; polymeric composite. The external connection could be in the form of mechanisms / devices

Development and Wind Tunnel Evaluation of a SMA Based Trim Tab Actuator for a Civil Aircraft

This paper presents about the development and wind tunnel evaluation of an SMA based smart trim tab for a typical 2 seater civil aircraft. SMA actuator was housed in the port side of the elevator for actuating the trim tab. Wind tunnel tests were conducted on a full scale Horizontal Tail model with Elevator and Trim Tab at free stream speeds of 25, 35 & 45 m/sec and also for a number of deflections of the elevator (30° up, 0° neutral & 25° down) and trim-tab 11° & 21° up and 15° & 31° down). To measure the hinge moment experienced by the trim-tab at various test conditions, two miniaturized balances were designed and fabricated. Gain scheduled proportional integral controller was developed to control the SMA actuated smart trim tab. It was confirmed during the tests that the trim-tab could be controlled at the desired position against the aerodynamic loads acting on it for the various test conditions

NiTi Super Elastic Shape Memory Alloys for Energy Dissipation in Smart Systems for Aerospace Applications

Shape Memory Alloys (SMAs) have attracted the attention of a wide range of researchers from several disciplines. This is because they possess very special and unusual properties and have potential for use in numerous applications. The nuances and subtleties associated with these unusual properties indeed pose challenges for the discerning researcher and designer. Even more exciting and demanding is to conceive, build and test a device exploiting the intrinsic property of these materials for aerospace applications where the weight and volume budgets are most stringent. Such an effort would involve material characterization, arriving at the design envelope of the material and effectively integrating it into the device. The SMAs exhibit complex non-linear thermo–mechanical behavior. They exhibit hysteresis both in the thermal and stress loading domains. SMAs can undergo large pseudo elastic deformations (typically 4 – 6%) in the low temperature martensite phase at low stresses. These deformations are completely recovered on heating to the high temperature austenite phase. This effect which is thermally induced is known as the thermal Shape Memory Effect. There is also a large pseudo elastic deformation which results from the application of stress in SMAs. This is obtained by stressing the SMA (loading) in the austenite phase and inducing stress induced martensite (SIM). During the process of inducing the SIM, pseudo elastic deformations of the order of 6 – 8% accrue. These ‘large pseudo elastic’ deformations are completely recovered when the stress is removed from the material. The removal of stress (unloading) takes the material back to the austenite phase. The path taken during unloading is different from the path taken during loading resulting in a stress hysteresis. Associated with the stress hysteresis is the dissipation of energy in these materials which is several orders higher compared to conventional materials such as steels, aluminium or other metal systems. The objective here is to develop an alternate method to build an efficient smart landing gear device with superior energy dissipating features exploiting the large energy dissipating characteristics of Super Elastic (SE) SMAs applicable to a wide variety of vehicles. It is pertinent here to mention that polymeric carbon composites are gaining increased acceptance for airframes and other structural subsystems due to their superior stiffness and strength properties. The focus of this study is to systematically investigate the energy dissipation capability of NiTi SMA Systems and effectively blend them with carbon composites to realize efficient landing gear systems. The heat treatment given to the SE SMA materials hold the key to the control of their mechanical properties. Like other smart materials SE SMAs possess bifunctional properties. Associated with the energy dissipation characteristics is the sensory function of SE SMA. The study covers the effect of heat treatment on the energy dissipation characteristics, evaluation of the sensory behavior, effects of strain rate on energy dissipation and other related mechanical properties. It also details the design, fabrication, analysis and testing aspects associated with integrating the NiTi SMA with the polymeric carbon composite based smart landing gear system that is applicable to a large category of ground and air vehicles

Hybrid Composites for Morphing Applications

This work is directed towards realizing large scale shape changes of wing like structures. It is relevant to discuss the work carried out in this area so far. AMR BAZ (ref l) details the work in which SMA is embedded in sleeves located at the neutral planes and arranged parallel to the longitudinal axis of the composite beam. Here emphasis is placed on describing quasi-static theory of shape control and implementation of this theory to composites incorporated with SMA. Emphasis has been placed on full utilization of shape memory effect without compromising on structural stiffness of the composite beam. Koryo Miura et a1 (ref.2) explain about adaptive structures and their use in aerospace applications. Here a variable geometry (VG) truss concept is presented. Comparison is made between tetrahedral and octahedral truss elements. Since octahedral is richer in symmetry, it is considered to be adequate for adaptive structures. DC motor is used as an actuator. It is shown that VG truss is the basic form of adaptive structures. The basic formulations for its geometrical as well as vibrational properties are established. Some applications such as second generation manipulator arm, support architecture for a space station and others are discussed here. Deepak.S. Ramrakhyani et a1 (ref.3) explains about the use of compliant cellular truss where tendons are used as active elements. This tendon actuated elements can be used for local or global shape changes. Here an octahedral unit cell is developed for bending deformations and compliant joints are made of cylindrical elements of superelastic shape memory alloys. Several concepts of morphing skin were also presented. Tendon actuators are presently under development. The tendons could be actuated locally or combined from a remote location such as the root of the wing. Since we are looking for large deflection of thin beams we have deliberately embedded the SMA wires off the neutral axis of the beam. In the literatures there is hardly any material that deals with this type of an approach. In this the effect of embedding the thermal SMA wires off the neutral plane of thin beams was studied. These wires were prestrained and embedded off the neutral axis to produce high amount of recovery forces when electrically energized. Superelastic SMA (SESMA) wires were used on the other side of the beam so as to increase the spring back effect of the beam when de-energized. Thus we were able to obtain large deflection together with faster return back to original position when de-energized

Development of a Door Steering Mechanism for a Large Autoclave

Davit arms are usually employed to handle doors of large size autoclaves. These arms require a guiding mechanism to guide the door in a desired path and locate in the desired position. In this work, various options of door handling / steering mechanisms were examined and finally a four bar mechanism is chosen for detailed design. A Geometric model was developed to understand the path traced by the door for various link angles and lengths. Solid modeling of the door was carried out using Solidworks R and simulation of the path of the door for various angles and lengths of the links of the 4 bar mechanism was also done. The prototype model of the autoclave door was fabricated with a 4 bar mechanism mounted on the davit arm of the door. Number of trials were made by changing link lengths and angles to determine the path of the door, using the CAD geometric model. These results are in agreement with the experimental results obtained using fabricated model

Development of SMA Based Actuator Mechanisms for Deployment of Control Surfaces

The research and development of SMA based actuator mechanisms are being pursued at many places. In this paper the on going research and development efforts at ACD, NAL to realize a SMA based actuator mechanism for deployment of a control surface model is discussed. The mechanism can be modified to either give a rotary or a linear output. The deployment of this control surface model was successfully demonstrated using the SMA based rotary actuator mechanism along with computerised powering devices and controls. This control surface model is deployed only during landing in order to improve the landing characteristics of the aircraft and remains retracted at all other times. The real challenge is the design and development of the SMA based mechanism, which will satisfy the weight and volume budget and more importantly consume minimum power. An innovative 3-gear relay arrangement was chosen primarily to save the power. In this type of arrangement 3 different input gears mounted on 3 independent input shafts are used to drive the same output shaft on which the control surface model is mounted. Independent banks of SMA wires drive each of the 3 input shafts. The actuation of the input shafts is done in a sequential manner and each them rotates the control surface model by different angles. At any given time only one bank of SMA is energized and therefore the power consumption reduces significantly in contrast to a case where the complete rotation of the control surface model has to be effected by a single input shaft power by a single bank of SMA. The state of art electronics and controls in order to achieve the above sequential actuation include miniaturized power devices, data acquisition, and controller of SMA actuation and health monitoring of SMA. The actuators have both hysterisis and non-linearity especially during the phase transformation when the electrical resistance changes abruptly. SMAs can be actuated by heating using external heaters or by resistive heating. For better control, high efficiency, compactness and silent operation, resistive heating is preferred. Individual miniaturized power devices (DC-DC converters) are developed to electrically isolate the SMA actuators. Adequate redundancy in terms of both mechanical actuators and powering devices is built in

SMA Based Adaptive Concept on Wings of Large Civil Aircraft

Shape memory alloys (SMA) are being increasingly tried out to achieve large shape changes such as Leading Edge (LE) droop of wings. LE droop of wings of large civil aircraft have to overcome two major forces in order to realize the droop. These are, structural load required for flexing the structure and the aerodynamic load that acts against the drooping force. Conventional actuators like pneumatic, hydraulic or electromechanical actuators have serious problems like concentrated actuator mass, stress concentration and also jamming. In the case of a power failure, the conventional actuators get jammed in that particular position and it is very difficult to revert them back to the neutral position. It becomes difficult for the pilot to control an aircraft with a jammed control surface. The proposed SMA based actuators overcome the limitations of the conventional actuators stated above. SMAs have distributed actuator mass and hence do not produce stress concentration, and also improve the dynamic characteristics of the structural components. Since they are active elements, in the event of a power failure, they revert back to the neutral position. For capturing large deformations due to the LE drooping non-linear analysis has been carried out by considering the geometric non linearity of the structure. In order to obtain the large deformations in the LE advanced structural concepts have thus been used

A smart material based approach to morphing

This presentation gives an overview of the Shape Memory Alloy (SMA) based approach to the research and development of adaptive/smart/morphing airframe structural technologies at the Advanced Composites Division, NAL. Central to this approach is the efficient integration of thermal NiTi SMA elements with polymeric carbon composites. The SMA elements could be either externally placed or embedded in the polymeric composite. The external connection could be in the form of mechanisms / devices. The various activities related to morphing technologies are briefly discussed below

Autoclaves for Aerospace Applications: Issues and Challenges

The National Aerospace Laboratories (NAL), Bangalore has been engaged in the research of autoclaves for the past three decades and has pioneered their development and usage in India for aerospace/aircraft structural applications. The autoclaves at NAL have played a significant role in all the major national aircraft / aerospace programs. The largest aerospace autoclave in India (working size of 4.4m diameter and 9.0 m length) has been successfully commissioned at NAL. This paper gives the technological challenges faced and innovative concepts that were introduced in these autoclaves