Shape-control Capability Research Articles

A One-Stone-Two-Birds Strategy for Photothermal Shape Memory Polyurethane Utilizing Lignin as Monomer and Internal Photothermal Agent.

Photothermal-triggering shape memory polyurethane allows for precise and controllable shape transformation under remote light stimulation, making it highly desirable for applications in intelligent devices. This study develops a sustainable and high-performance lignin-based polyurethane (LPU) using a one-stone-two-birds strategy, wherein lignin serves as both a synthetic monomer and an internal photothermal agent. The incorporation of lignin significantly improved the mechanical properties of LPU, achieving a tensile strength of 42.1MPa and an impressive elongation at break of 1558%. Additionally, the LPU exhibited exceptional photothermal heating capabilities due to the inherent intramolecular π-π conjugations and intermolecular π-π stacking effects of lignin, which facilitated the precise and contactless remote photoheating. Furthermore, the rigid structure of lignin and robust hydrogen bonding interactions provided LPU with excellent multi-cycle shape memory performance, with shape fixation and shape recovery rates exceeding 93% after five cycles. Under near-infrared irradiation, LPU demonstrated precise non-contact heating and remote photothermal shape-control capabilities. This research not only offers a sustainable and high-value application for lignin but also advances the development of environmentally friendly intelligent shape memory polyurethane materials.

Research Progress in Shape-Control Methods for Wire-Arc-Directed Energy Deposition.

Wire-arc-directed energy deposition (WA-DED) stands out as a highly efficient and adaptable technology for near-net-shaped metal manufacturing, with promising application prospects. However, the shape control capability of this technology is relatively underdeveloped, necessitating further refinement. This review summarizes the latest advancements in the shape control of WA-DED technology, covering four pivotal areas: the regulation of various process parameters, optimization of the deposition paths, control through auxiliary energy and mechanical fields, and synergy between additive and subtractive manufacturing approaches. Firstly, this review delves into the influence of deposition current, travel speed, wire feed speed and other parameters on the forming accuracy of additively manufactured parts. This section introduces control strategies such as heat input and dissipation management, torch orientation adjustment, droplet behavior regulation, and inter-layer temperature optimization. Secondly, various types of overlap models and techniques for designing overall deposition paths, which are essential for achieving desired part geometries, are summarized. Next, auxiliary fields for shape and property control, including magnetic field, ultrasonic field, and mechanical field, are discussed. Finally, the application of milling as a subtractive post-process is discussed, and the state-of-the-art integrated additive-subtractive manufacturing method is introduced. This comprehensive review is designed to provide valuable insights for researchers who are committed to addressing the forming defects associated with this process.

A new cubic trigonometric Nu-Spline with shape control parameter and its applications

This study introduces a novel Cubic Trigonometric Nu-Spline (CTNS) with a shape parameter tailored for curve designing, ensuring geometric continuity of order 2. The CTNS possesses fundamental geometric properties such as convex hull, partition of unity, affine invariance, and variation diminishing, which are thoroughly discussed herein. Notably, our spline technique is enriched with Nu-Spline constraints, offering compelling local and global shape control capabilities. These capabilities encompass point tension, interval, or global tensions, enhancing versatility across various shape impacts. Beyond its curve designing prowess, the proposed technique exhibits commendable precision in estimating control points. Furthermore, its utility extends to diverse fields including electronics, medical image interpolation, manipulator path planning, and discrete time signal processing. Through numerical experimentation, we demonstrate the simplicity of implementing the CTNS algorithm alongside its superior accuracy compared to existing techniques.

Unveiling the mechanisms of Moso bamboo's motor function and internal growth stress.

Bamboo, a renewable resource with rapid growth and an impressive height-to-diameter ratio, faces mechanical instability due to its slender structure. Despite this, bamboo maintains its posture without breaking in its battle against environmental and gravitational forces. But what drives this motor function in bamboo? This study subjected Moso bamboo (Phyllostachys edulis) to gravitational stimulation, compelling it to grow at a 45° angle instead of upright. Remarkably, the artificially inclined bamboo exhibited astonishing shape control and adjustment capabilities. The growth strain was detected at both macroscopic and microscopic levels, providing evidence for the presence of internal stress, namely growth stress. The high longitudinal tensile stress on the upper side, along with a significant asymmetry in stress distribution in tilted bamboo, plays a pivotal role in maintaining its mechanical stability. Drawing upon experimental findings, it can be deduced that the growth stress primarily originates from the broad layers of fiber cells. Bamboo could potentially regulate the magnitude of growth stress by modifying the number of fiber cell layers during its maturation process. Additionally, the microfibril angle and lignin disposition may decisively influence the generation of growth stress.

Member control efficiency and shape control capability of a loaded cable dome

In this paper, the control efficiency of the members and shape control ability of a loaded adaptive cable dome consisting of 16 cables and 4 struts are investigated. The structure uses specially designed cables and electric telescopic struts integrated with an actuation control system, and all members of the structure are length-adjustable. Initially, an intelligent algorithm is employed to solve the structural shape optimization control model, thereby determining the optimal adjustment amounts. Subsequently, active adjustment and active control tests are conducted to evaluate the control efficiency of the members and the shape control capabilities of the cable dome. The results indicate that the ridge and diagonal cables exhibit the most effective control, followed by the upper and lower hoop cables, while the struts show the lowest control efficiency, primarily influencing the displacement of the joints at their two ends. Moreover, the cables' internal force control efficiency is 3–4 times higher than that of the struts. The ridge and diagonal cables' internal force and displacement control efficiency is about 1.5 times higher than that of the upper and lower hoop cables. The loaded test model exhibits the ability to restore the vertical coordinates of upper joints to their target coordinates, while reducing the internal forces of the components by at least 15 %, and the shape control capability of the structure can be enhanced by incorporating various types of active units. The measured values correlate well with the simulation results, validating the accuracy of the simulations.

A Novel Variable Stiffness and Tunable Bending Shape Soft Robotic Finger Based on Thermoresponsive Polymers

In this study, a soft robotic finger with variable stiffness and tunable bending shape capability is proposed. The finger employs shape memory polymers (SMP) as the variable stiffness element and polyimide (PI) electrothermal films as the flexible heaters for segmental heating. SMP and PI electrothermal films constitute the variable stiffness structure. The SMP part exhibits a reversible transition from glass state to rubber state during the heating/cooling process. The whole transition process results in an elastic modulus range of three orders of magnitude. The finger can obtain multiple bending shapes and adapt to the outer contours of diverse objects because of the segmental stiffness modulation capability of the variable stiffness structure. Supercoiled polymer artificial muscles (SCPAMs) are used as actuators for the finger. SMPs and SCPAMs are thermoresponsive and can be activated by thermal heating with electricity, making the whole finger structure compact. Experimental results show that the stiffness of the finger at room temperature (25 °C) is 10.54 times that at 70 °C when the actuators are on. The performance of the finger is further validated via the sequential motion demonstration and grasping tests with variable stiffness and bending shape control capabilities, showing the proposed design’s potential in soft grippers and robotic design.

Enhancement of the ASDEX Upgrade Real-Time Plasma Position Reflectometry Diagnostic

Microwave O-mode reflectometry is a diagnostic technique that will play an important supplementary role for plasma position control for ITER and forseeably for DEMO. Density profiles from reflectometry will provide, at high temporal resolutions, estimates of the gap between the plasma magnetic separatrix and the tokamak vessel walls. These estimates will be used to detect and correct drifts in the magnetic gap measurements, the primary measurements used for plasma position and shape control. The feasibility of this alternative feedback control approach was demonstrated in 2011 on ASDEX Upgrade (AUG) , where the reflectometry gap estimate actually replaced the corresponding magnetic measurement in the position control loop. Presently, the AUG’s real-time (RT) reflectometry diagnostic is being upgraded to improve not only its density range coverage but also its acquisition and RT data processing performance. The diagnostic is now capable of acquiring a total of 16 channels (previously 8) from which 8, corresponding to microwave bands K, Ka, Q and V from both the high (HFS) and low field side (LFS) reflectometers, are used in the RT density profile and separatrix gap calculations. The modern NUMA hardware architecture of the updated data processing server allows for an efficient and separate handling of the data-flows produced by the hosted acquisition systems. The higher RAM and CPU interconnection bandwidths allow the implementation of new operation modes that exploit the very high data throughput ( $> 1.2~\hbox{GB/s}$ ) of each of the two used acquisition boards. RT reconstruction of the density profiles is a complex algorithm, whose performance will also be improved by the additional processing power (16 cores instead of 8). The system was specified to acquire and store HFS and LFS density profile data every $ whilst simultaneously producing profile measurements for RT control every 1 ms. In this new operation mode, identical to the one planned for the ITER plasma position reflectometer (PPR), the diagnostic can reach an inbound data throughput (ADCs to RT processing host) and a computational load that are closer to the ones expected to be generated by each of the planned 4 ITER PPRs ( $ \approx 3 ~\hbox{GB/s}$ maximum inbound and outbound data stream bandwidth per PPR). Herein we discuss the enhancements introduced in the AUG’s RT reflectometry diagnostic to implement the new operation mode and perform the aimed control experiments. Preliminary RT experimental data obtained in both the HFS and LFS is shown to illustrate the system’s plasma position and shape control capabilities to be demonstrated during AUG’s 2014 experimental campaign.

Shape control of shape memory alloy composite beams in the post-buckling regime

The aim of the paper is to investigate active shape control of post-buckled elastic beams subjected to in-plane compressive loadings using surface-bonded shape memory alloy (SMA) layer actuators. A robust macroscopic SMA model is used to simulate main features of the SMA layer under dominant axial and transverse shear stresses during non-proportional thermo-mechanical loadings. The SMA model is able to reproduce martensite transformation/orientation, pseudo-elasticity, shape memory effect and in particular reorientation of martensite and ferro-elasticity effects. Non-linear equations of equilibrium for the moderately thick smart beam are derived by means of the principle of minimum total potential energy based on the first-order shear deformation theory and von Kármán geometrical non-linearity. The governing equations of equilibrium are solved using Ritz based finite element method along with an iterative numerical algorithm. Effects of the pre-strain state, thickness and temperature of the SMA layer actuator are examined, and their implications upon the pre/post-buckling behavior of the smart beam under in-plane compressive loadings are highlighted. The obtained results reveal that installing the SMA layer actuator can play a significant beneficial role toward confining deformation of the smart structure in the post-buckling regime. Due to lack of similar results in the specialized literature, the results of this research are expected to contribute to a better understanding of active shape control capability of the SMA composite beams under in-plane mechanical loadings.

α Extension of a Class of T-Bezier Curve

By introducing the concept of weights in NURBS curve into a blending technique,the paper extends the representation of the T-Bezier curve.The generalized T-Bezier curve is denoted as α Extension T-Bezier curve,whose shape-control capability is shown to be much better than that of T-Bezier curve.The representation and properties of the extension curve is studied.The curve is easy and intuitive to reshape by varying the parameters;so it is useful in some applications of CAD/CAM .

Blending of the Trigonometric Polynomial Spline Curve with Arbitrary Continuous Orders

In order to develop the theory of trigonometric polynomial spline curve, the representation of trigonometric polynomial spline curve is blended to a general form based on blending of trigonometric polynomial curves. Moreover, some properties of the blending curve are discussed in details. The research shows that the basis of the trigonometric polynomial curve is relative simple, and the blending curve includes the original trigonometric polynomial spline curve and shows much better shape-control capability than the original curve. Meanwhile, the blending curve keeps the same degree of original one. It is easy to find that the curve can be reshaping by adjusting the shape factor. At the same time, a new method of the representation of closed curve is given and can also accurately represent the whole ellipse arc and other conic curve.

α Extension of the Cubic Ball Curve

Ball curve； curve design； shape parameter Abstract. Ball curve is found similar to Bézier curve，also it has a good property of shape preserving，and in some respects，it has better properties than the Bézier curve. Therefore, In the shape design，Ball curve is paid more and more attention, it has a wide application. By introducing the concept of weights in NURBS curve into a blending technique, the paper extends the representation of the cubic Ball curve. The generalized cubic Ball curve is denoted as α extension cubic Ball curve, whose shape-control capability is shown to be much better than that of Ball curve. The representation and properties of the extension curve are studied. The curve is easy and intuitive to reshape by varying the parameters; so it is useful in some applications of CAD/CAM.

Edge Shape Control Technology Research of Very Thin Specifications DI Tinplate in Baosteel Cold Rolling

This paper study the key technique of very thin specifications DI tinplate based on 1420 tandem cold mill in Baosteel, to improve the strip edge shape quality. In our paper we put forward the idea to improve the DI tinplate edge drop control performance using the work roll contour technology, enhance the flatness control ability using the intermediate roll contour technology. The mill type of this CVC tandem cold mill is improved by these technologies, and its edge shape control capability is significantly increased. Production trial show that the improved mill type can effectively improve the edge shape quality of the very thin specifications DI tinplate, improve production efficiency and have a good application.

Research on the Roll Contour Configuration for Schedule Free Rolling in Hot Wide Strip Mills

In order to satisfy the flexible rolling schedule of hot steel production, principles and theory for choice of roll contour configuration were described. Additionally, the several typical roll contour configurations which are popular in the world nowadays, and their shape control capability for “rolling of large quantities of strips in same width” and “rolling by strip width increase in sequence” were analyzed with established finite element model of roll stacks. Then, the optimum roll contour configuration for SFR (schedule free rolling) was obtained.

A Rotating-Tip-Based Mechanical Nano-Manufacturing Process: Nanomilling

We present a rotating-tip-based mechanical nanomanufacturing technique, referred to here as nanomilling. An atomic force microscopy (AFM) probe tip that is rotated at high speeds by out-of-phase motions of the axes of a three-axis piezoelectric actuator is used as the nanotool. By circumventing the high-compliance AFM beam and directly attaching the tip onto the piezoelectric actuator, a high-stiffness arrangement is realized. The feeding motions and depth prescription are provided by a nano-positioning stage. It is shown that nanomilling is capable of removing the material in the form of long curled chips, indicating shearing as the dominant material removal mechanism. Feature-size and shape control capabilities of the method are demonstrated.

A NUMERICAL SIMULATION OF STRIP PROFILE IN A 6-HIGH COLD ROLLING MILL

Shape control is always a key issue in the six-high rolling mill, in which the shifting of the intermediate roll and the work roll have been used to enhance the shape control capability. In this paper, a finite element method (FEM) model has been developed to simultaneously simulate the strip deformation and the roll stack deformation for the six-high rolling mill. The effects of the work-roll bending, the shifting of the intermediate roll and the work roll on the strip crown and edge drop are discussed in details. Results have shown that both higher bending force and more roll shifting will significantly reduce the strip crown. The edge drop is also reduced with the bending force and the roll shifting.

Strip shape control capability of hot wide strip rolling mills

The elasticity deformation of rolls was analyzed by means of two-dimensional finite element method (FEM) with variable thickness. Three typical mills were used as objects for analysis. A thorough study was done on the control capabilities of these mills on the strip shape. Then the strip shape control capabilities of the three mills was compared synthetically.

Nonrigid registration of medical image by linear singular blending techniques

In this paper, a nonrigid registration method is presented for accommodating local shape variation when matching monomodal images or multimodal images. Affine transformation is adopted in global registration while local deformation is described by a free-form deformation based on a linear singular blending (LSB) B-spline, which can enhance the shape-control capability of the B-spline. This capability is derived from the blending parameters defined at the B-spline control points. The local deformation of images can be controlled by changing positions of the control points or altering values of blending parameters. Two voxel-based similarity measures, the SSD for monomodal images and mutual information for multimodal images are used. Experiments on simulated and real data have been performed to evaluate the accuracy of our method. We have also compared the results of the proposed approach to those obtained by affine and B-spline registration techniques. The results indicate that the proposed method is much better to describe the deformation than the affine algorithm and B-spline techniques.

A MEMS-basedflexible sensor and actuator system for space inflatable structures

Inflatable and other membrane structures are expectedto become increasingly important in space exploration due totheir light weight and low cost. Unlike rigid structures, thesestructures are typically fabricated of flexible polymers andrequire internal pressurization to achieve structural integrity. Due to this, inflatable structures are vulnerableto the harsh space environment and catastrophic failure fromstructural vibration. A MEMS-based health monitoring andcontrol system (HMCS) for space inflatables has been developedat the University of Arkansas. Fabricated mostly from polymericmaterials, the HMCS is lightweight, flexible and can beattached directly to the external surface of an inflatable toprovide health monitoring. Structure-wise, the HMCS is athree-dimensional multichip module with a sensor layer atthe top, a common polyimide substrate in the middle and anactuator layer at the bottom. The sensor layer consists of aninterconnected network of MEMS sensors for monitoring theenvironmental conditions around the inflatable and also thestructural vibration of the inflatable. The actuator layer,fabricated from electroactive polymers, provides atwo-dimensional shape control capability to the HMCS. Whenoperated with strain and vibration sensors in the sensorlayer, the polymer actuator can deform the surface contour ofthe inflatable to remove `wrinkles' and dampen structuralvibration.

Study of induced strain transfer in piezoceramic smart material systems

Smart materials such as piezoceramics are being used as actuators and sensors to achieve active control of elastic deformations of structures. Intelligent structures, with highly distributed actuators and sensors, can be designed with intrinsic vibration and shape control capabilities. Piezoceramics can be integrated with a structure either by being embedded within or bonded onto the structure. Particularly for the case of surface bonding, it is important to have an effective strain transfer from the smart material to the metallic substrate through the adhesive layer. In this paper, study of the strain transfer of piezoceramic actuators bonded to the surface of a structure with a finite-thickness adhesive bond is presented. A structure with actuators bonded to the top and bottom surfaces of a cantilever beam, which can deform in either bending or extension, is analysed. A detailed two-dimensional model of the structure is developed to study this strain transfer through an adhesive layer using the finite-difference method to solve the equations of elasticity, with appropriate boundary conditions. The resulting strains in the actuator and those induced in the substructure are compared with a finite-element model and two existing one-dimensional analytical models. The limitations of the simplified analytical models are brought out. The uniform-strain analytical model was found to be in agreement with the numerical models only for the case of extension actuation. The Bernoulli-Euler analytical bending model agreed with the numerical models only at points near the center of the structure. The finite-difference and finite-element models were in agreement in almost all cases. For the case of bending actuation, the finite-difference and finite-element methods differed in their predictions of induced strains.

αB-spline: a linear singular blending B-spline

A linear singular blending (LSB) technique can enhance the shape—control capability of the B-spline. This capability is derived from the blending parameters defined at the B-spline control vertices and blends LSB line segments or bilinear surface patches with the B-spline curve or surface. Varying the blending parameters between zero and unity applies tension for reshaping. The reshaped curve or surface retains the same smoothness properties as the original B-spline; it possesses the same strict parametric continuities. This is different from the β-spline, which introduces additional control to the B-spline by imposing geometrical continuities to the joints of curve segments or surface patches. For applications in which strict parametric continuities cannot be compromised, LSB provides an intuitive way to introduce tension to the B-spline.