Among NiTi base high temperature Shape memory alloys,NiTiHf alloys seem to be more attention,because of their high transformation temperatures,good thermal stability and lower price in comparison with other Shape memory alloys,recovery strain and recovery ratio of this alloys in comparison with binary NiTi alloys is less,One of methods for improvement of recovery strain is thermomechanical treatment,In this research,the Ni50Ti40Hf10 Shape memory alloy was casted by vacuum arc melting and after homogenization,specimens were cold rolled and annealed,By bending test,applied strain from 2,6 to 5,4 carried out on specimens and then amount of recovery strain and recovery ratio were measured,The result showed that with increasing applied strain,the amount of recovery strain increased,In all of cold rolled samples until 3% applied strain,recovery is complete 100% but in applied strain above this amount due to occurrence of slip deformation,recovery is less than 100%,In cold rolled specimens,due to increasing of hardness and also strength,recovery strain in comparison with casting specimen increased,Maximum recovery strain in casting specimen,was amount of 5 with 87% recovery ratio and with applying 10% and 20% rolling,recovery strain to 5,25 and 5,28 and also recovery ratio to 92% and 93,6% increased,

Shape memory polymers (SMPs) have the ability to store the deformation and recover the original Shape. Shape memory behavior is associated with two features: Shape recovery and stress recovery. Full Shape recovery and increase the stress recovery value are the challenges ahead of the SMPs. In this paper, the polyurethane and polycaprolactone (PCL) were blended. The thermal stimulated SMPs ware fabricated by melt mixing and solution mixing method and thermo-viscoelastic behavior of SMPs ware analyzed. Two types of polyurethanes with the same chemical structure were used as the hard phase and polycaprolactone was used as the soft phase in SMP blend. The results show that the solution mixing method has advantages such as proper appearance without defect, free from cracks and cavities, higher storage and loss modulus values without fluctuations over temperature. The blend of PCL with low hardness polyurethane one showed better Shape memory behavior. In order to investigate the Shape memory effect, Shape recovery test was carried out with 25% pre-strain at 60° C. Also, the stress recovery was carried out by 25% pre-strain at different temperatures (60° C, 45° C and 37° C) on the samples made by solution method. The stress-recovery function was highly affected by the deformation temperature. The maximum stress and maximum recovery rate were observed in the sample with a deformation temperature of 45° C. A stent was made by the solution method and its Shape recovery results showed that recovery was done completely in less than 0. 5 seconds at 60° C.

4D printing is an emerging technology in which the printed parts can change their Shapes when exposed to an external stimulus. In this research, a relationship between the pre-stress stored in the printed discs and the amount of Shape recovery was obtained using FE simulations. Then, the effect of layer height, bed temperature, nozzle temperature, and printing speed on the amount of pre-stress applied in the printed discs based on polylactic acid material in the Fused deposition modeling 3D printing was investigated. In this paper, 27 experimental tests were performed using a central composite design, and modeling was done with the least cost and time and the most reliability and accuracy. Then a relationship between the mentioned parameters and the amount of pre-stress applied to the printed discs was obtained. R2 and Adj R2 of the model were obtained more than 99% which shows the high accuracy of the model. In order to validate the experimental model, simulation and experimental tests were carried out in the conditions of the highest amount of Shape recovery. The results showed that the experimental model error is 5. 9% and the error between the applied pre-stress and the amount of Shape recovery is 2. 95%.

In this paper the effects of thickness ratio on pseudoelastic, Shape memory and thermal recovery properties of NiTi/NiTiCu bilayer composite was investigated by using FEM simulation and experimental results. The NiTi/NiTiCu bi-layer composites with different thickness ratios designed and analyzed in ABAQUS software using SMA constitutive 3D model presented by Lagoudas et al. The pseudoelastic and Shape memory strain values for different composites were studied and measured as well as thermal recovery strain and its rate. For validating the results of the FEM study NiTi/NiTiCu bi-layer composites were made and tensile tested. The results indicate a high correlation between two methods that leads to reduce the number of experiments to optimizing the composite behavior, also, considering the results of the FEM method, the NiTi/NiTiCu bi-layer composite shows high potential in adjusting pseudoelastic and Shape memory properties and also deformation parameters such as stress and strain plateau with changing the thickness ratio that can be considered in SMA components design.

Memory-Shaped polymers are thermally induced subsets of intelligent materials that require thermomechanical behavior to accurately understand their function. In this study, polymeric memory scaffolds were fabricated using polylactic acid by molten labeling method in reticular honeycomb, rhombic and elliptical forms. Parameters such as longitudinal dimensions and the wall thickness of printed scaffolds compared to the designed scaffolds and solutions were presented to enhance the printing accuracy. Built-in scaffolds can be a good option for stent use. Formal memory properties experiments with 30% axial strain were performed to study the Shape memory behavior of polymer on scaffolds. The results showed that the percentage of Shape recovery in scaffolds with symmetric angular grid networks was higher than elliptical reticular stents. The minimum percentage of longitudinal recovery belonged to the elliptical reticular stent and was 74. 5%. The percentage of longitudinal recovery of honeycomb and rhododendron reticular stents is approximately equal to 80. 3%. The results of this study can be used to optimize the stent grid geometry to increase the retrieval force to resolving vascular clogging.

Actuators are the controllable work-producing devices with an input of thermal, electrical or magnetizing stimuli and an output of mechanical energy. Regarding their widespread use, smart polymers have recently been used in producing actuators. Smart polymers are a group of neat or composite materials, which have inherent smartness along with self-adaptive capabilities against external stimuli. Shape memory polymers which are also a group of smart polymers, can recover their initial and permanent Shape under external stimuli. In this work an actuator was made of a Shape memory cross-linked polyethylene and the effects of different factors such as the content of cross-linking agent, deformation temperature, strain ratio, strain rate, type of cooling and heating rate on final Shape recovery, recovery speed and the actuator behavior between 10% and 90% of final recovery were investigated. The results show that the actuator made of cross-linked polyethylene has a controllable behavior in this range.

In this research work a Shape from shading (SFS) technique which incorporates a Lambertian model is implemented for the automatic generation of a digital terrain model (DTM) using a single view aerial image. The developed algorithm is tested on both simulated and real data. The estimated accuracy of the generated DTM from the simulated data, which has a bilinear surface, is about ±3 cm. The real data is a scanned aerial photograph taken over a low texture hilly terrain. The generated DTM by the SFS technique is compared with a DTM acquired by the manual measurement of the stereo image of the same area using a photogram metric plotter. The estimated rimes of the discrepancies between the grid nodes of the measured and the automatically generated DTM is about ±4 meters. The unsuccessful reconstruction of the terrain surface for the real data is due to the fact that a simple Lambertian model does not take into account, in a perfect way, different nondeterministic influential factors such as the terrain alb Edo variations and the random noise. The influence of the latter case was reduced by a low pass filter applied as a preprocessing stage.

Additive manufacturing is one of the advanced manufacturing processes that is being developed nowadays due to the capability of manufacturing parts with complex structures, speed, and low production cost. 3D printing of Shaped memory parts in the form of 4D printing is an emerging phenomenon, which is referred to as the future of additive manufacturing. In this study, the effect of three-dimensional printing fusion layer parameters including layer thickness, print speed, and nozzle diameter on the rate of Shape recovery of Polylactic acid was investigated. To reduce the cost and time as well as to increase the validity and accuracy, the Central Composite Design method, one of the subsets of the Response Surface Methodology, was used. Seventeen experiments were performed and a model was obtained to determine the effect of 3D printing geometrical parameters on Shape recovery. R 2 and Adj R2 of the model were obtained above of 0. 99 and 0. 98, respectively, which indicate the high accuracy of the model and the similarity of laboratory data and experimental model. This model showed that the layer thickness, nozzle diameter, and printing speed have a greater effect on the amount of torsional Shape recovery, respectively. This process was simulated to investigate the Shape recovery behavior. As a result, the relationship between the recovered Shape torsion angle and the applied pre-stress was obtained. To validate the model, the effect of 3D printing parameters on the Shape recovery, and the relationship between the pre-stress and the rate of Shape recovery, the desired torsion angle of 200 degree was considered. The model error for the experiment was calculated as 2% and the simulation results were obtained in accordance with the Shape memory behavior of the sample.

Air-conditioning is used in many commercial buildings and houses today and the energy required for the air conditioning system can be very high in extreme conditions. In this paper, for the purpose of intensifying heat and mass transfer and reducing the pressure drop, new structures for the membrane of these converters have been used; these structures include a curved membrane with a semicircular profile and a curved membrane with convex surfaces. This paper analyzes the numerical study of new membrane such as curvature and circular, using COMSOL Multiphysics. Modeling involves the transfer of heat and mass for turbulent flow. The pressure drop, the average Nsult number and Sherwood calculated and correlated with different reynolds. The results of this study show that the curved membrane with a semicircular profile increases the heat and mass transfer by about 7% and 6%, and the curved membrane improves the pressure drop by about 50% compared to the triangular heat exchanger.

Background & Aim: Extrusion of debris from apex is one of the main factors of flare up (inflammation, pain or combination of both). Various studies have been conducted toward the amount of debris extrusion but no one compared this drawback on one – Shape and xp-Shaper system in curved root canals. So, this study aimed to determine the amount of apical debris extrusion following preparation of canal by one-Shape or xp-Shaper in curved canals of mesiobuccal root in mandibular first molars.Material & Method: This experimental study was done on 34 mandibular first molars with 30 to 40 degree curved mesiobuccal root canal. The samples were randomly divided in two groups. First group had one –Shape for root canal preparation while the other had xp-Shaper. Roots of the teeth were fixed in pre weighted fluxes till cervical area so that all apical debris were collected in vials. After desiccation process, the vials were weighted again. The difference between original and secondary weight of vials containing debris is considered as weight of debris extrusion. Data were analyzed using T-test.Results: Amount of debris extrusion in one– Shape group was 0.018±0.014 and in xp-Shaper group was 0.01±0.007 and the difference was statistically significant (0.01).Conclusion: Considering the situation and limitation of this in vitro study, xp-Shaper rotary system was associated with less debris extrusion compared to one – Shape systems.