Final Desired Shape Research Articles

Experimental Investigation on the Effects of Tool Geometry and Cutting Conditions on Machining Behavior during Edge Finishing of Granite Using Concave and Chamfered Profiling Tools.

Granite edge finishing through grinding is a common process in the granite processing industry, crucial for achieving the final desired shape and edge quality of products. This study focuses on the granite industry, specifically delving into the significance of grinding and polishing for improving aesthetics and extending material longevity. The experimental design entails a comprehensive factorial experiment plan involving two workpiece materials (white and black granite samples) and two cutting tool edge shapes (chamfer and concave), each with two grit sizes: G150 and G600. The cutting conditions varied and consisted of variations in spindle speeds (1500, 2500, 3500 rpm), feed rates (500, 1000, 1500 mm/min), and lubrication modes (wet/dry). The results uncover intricate relationships among these parameters and part quality, underscoring the pivotal role of tool geometry in achieving superior surface finishes and in controlling the cutting forces. These findings contribute to a nuanced understanding of the dynamic interplay between tool characteristics, material properties, and machining conditions within the granite industry.

Improving the formability and mechanical properties of TiAl alloy by direct forging of uncondensed powder

The limited plasticity and poor formability of TiAl alloys constitute primary constraints on their widespread applicability. In this regard, an innovative forming method is proposed, characterized by the direct forging of unconsolidated pre-alloyed Ti–48Al–2Cr–2Nb powders. In this procedure, spherical powders with a broad particle size distribution are pre-encapsulated and subjected to vacuumed treatment, followed by direct high-temperature forging to attain the final desired shape. Throughout the process, the powders undergo pre-heating to various forming temperatures and are forged at different speeds, enabling a comparative analysis of the effect of forging temperature and speed on densification and the microstructural characteristics of the forged billet. Experimental results indicate that the powders can be nearly fully densified when direct forging is conducted within the α-phase region. By combining the finite element modeling and microstructural characterization, three mechanisms dominating the consolidation process of powders are revealed. Initial particle clustering and spatial rearrangement predominantly occur during the early deformation stage, enhancing densification. Subsequent fragmentation of particles, induced by severe plastic deformation, governs the entire deformation process, leading to the elimination of the prior particle boundaries and substantial densification improvement. The closure of the micrometer-scale voids is controlled by high-temperature diffusion and creep, which plays a pivotal role in weakening the detrimental effect of micro defects on mechanical properties. The above mechanisms act alternately or simultaneously, resulting in a homogeneous microstructure composed of α2+γ lamellae and bulk γ with small sizes, and a good synergy of strength and ductility. Therefore, this novel approach holds considerable potential as a cost-effective alternative strategy for producing TiAl components.

PRODUCTION OF TRANSLUCENT ALUMINA CERAMICS BY TAPE CASTING

Alumina powders are utilized in many industries like electronics, metallurgy optoelectronics, and fine ceramic composites. In this study, non-aqueous-based tape casting of alumina was carried out in a non-continuous single-blade tape casting machine. A slurry of alumina powder in a solvent was cast on a stationary surface with additives like dispersants, binders, and plasticizers. After the green tapes were dried, they were sintered to obtain the final desired shape. The hydraulic pressing method was used to increase the density of the alumina tapes. Layered alumina ceramics were produced at 5 different temperatures by pressureless sintering method (1450°C, 1500°C, 1550°C, 1600°C and 1650°C) for 5 h to observe the effect of sintering temperature. Results revealed the sintering conditions for obtaining translucent alumina, with the utilized slurry composition. Translucent alumina ceramics have gained importance as parts of semiconductor devices, substrates for electric parts, as heat/corrosion materials in reaction tubes and crucibles, and are used in medical equipment.

Experimental Investigation on Part Quality and Dust Emission during Minimum Quantity Lubricated (MQL) Edge Finishing of Granite.

Edge-finishing of granites by grinding is a process frequently used in the granite processing industry to generate the final desired shape and edge quality of products. However, this process releases significant amounts of fine and ultrafine particles (FPs and UFPs) containing crystalline silica. When inhaled, this dust can cause silicosis disease and threaten the health and safety of workers. The purpose of this study is to optimize the process by decreasing the concentrations of dust generated while also maintaining the required surface finish. Experimental tests were planned and performed on granite samples using a full factorial design. Two cutting tool edge shapes were studied (chamfer and concave) using G150 and G600 grit size tools, at various spindle speeds (1500, 2500, 3500 rpm), feed rates (500, 1000, 1500 mm/min) and lubrication flow rates (20, 40, 60 mL/min). The findings show that the particle emissions as well as the surface finish depend on the tool shape, its grit size, and the machining and lubrication parameters used. Higher MQL flow rates led to better finished surface quality and lower concentrations of fine dust. Polishing with flood lubrication reduces the maximum number concentration of FPs corresponding to particles smaller than 1 µm diameter by about 85% as compared to dry polishing and produced the best surface finish. Polishing with lubrication in MQL mode at 60 mL/min led to the production of part with Ra-value comparable with that obtained in flood lubrication condition.

Experimental Investigation of Three-Roller Bending Operation for Multi-Pass Cylindrical Forming of Plates

Roller bending is a sequential process where bending operation is done in single or multiple passes. Producing cylinders in single pass is most economical and efficient method, but accuracy in final dimensions depends upon experience and expertise of operator. In small scale industries, bending operation has been performed in a very non-symmetrical manner and hence keeping accuracy in final dimensions is utmost concern. For getting accuracy in final desired shape of the component, utilization of multiple pass bending is generally recommended in many industries. Predicting accurate number of passes required to complete cylindrical bending needs to be evaluated. Considering this objective, the author proposed a methodology, in this paper, for accurate prediction of number of passes for forming cylindrical bending on three roller bending machine. An emerging combination of dimensional analysis and modern design of experimentation techniques is presented. The model consists of geometrical, operational, and material parameters. Effect of each parameter on dependent variable is also discussed. Obtained model results are compared with experimental results to validate the model. Average RMSE is found to be less than 10 %, showing correctness of applied methodology.

Shape transformable bifurcated stents

Non-invasive delivery of artificial implants, stents or devices in patients is vital for rapid and successful recovery. Unfortunately, because the delivery passage is often narrower than the size of the delivered object, a compromise between the shape that is effective at the targeted location and a thin form that allows smooth unobstructed travel to the destination is needed. We address this problem through two key technologies: 3D printing and shape memory polymers (SMPs). 3D printing can produce patient-customizable objects, and SMPs can change their initially formed shape to the final desired shape through external stimulation. Using these two technologies, we examine the design and fabrication of bifurcated stents. This study presents a mock-up where blood vessels are fabricated using moulded silicon, which supports the effectiveness of the proposed method. The experimental results reveal that a bifurcated stent with a kirigami structure can smoothly travel inside a vessel without being obstructed by branched parts. We believe that this work can improve the success rate of stent insertion operations in medicine.

Determining optimized radial scan path in 3D laser forming of steelAISI 304 plates to produce bowl shapes

Determining an appropriate scanning pattern to achieve the final desired shape is the most significant factor in 3D laser forming process. In this manuscript, attempts are made to propose the optimum radial scanning path, which produces bowl shapes. The radial scanning pattern could be used to form the bowl shapes from the circular blanks. This pattern is categorized into two groups, whether the laser scan path crosses the center of the circular plate or not. In cross scan path, three patterns of diagonal scan, convergent radial scan, and divergent radial scan are proposed. Besides, in non-cross scan path, three patterns of non-cross scan without angular step, convergent scan path with 30-degree angular step, and divergent scan path with 30-degree angular step are introduced. Based on the numerical results, convergent radial path and convergent radial path with 30-degree angular step, respectively, are selected as the best scan patterns of cross and non-cross scan lines. In the experiments, these two scan patterns were implemented on the plate surface of AISI 304 plates. Measurements showed that the non-cross convergent radial scan path with 30-degree angular step produces the most uniform final bowl shapes.

Deformation mechanics in single-point and accumulative double-sided incremental forming

Single-point incremental forming (SPIF) uses one small hemispherically ended tool moving along a predefined toolpath to locally deform a completely peripherally clamped sheet of metal such that the sum total of the local deformations yields the final desired shape of the sheet. While SPIF is characterized by greater formability than conventional forming processes, it suffers from significant geometric inaccuracy. Accumulative double-sided incremental forming (ADSIF) is a substantial improvement over SPIF in which one hemispherically ended tool is used on each side of the sheet metal. The supporting tool moves synchronously with the forming tool, therefore acting as a local but mobile die. ADSIF results in considerably enhanced geometric accuracy and increased formability of the formed part as compared to SPIF. In light of the aforementioned advantages of ADSIF as compared with SPIF, an investigation of the mechanics associated with the ADSIF process, which has yet to be presented in the literature, is warranted. The present study sheds light on the differences in deformation mechanisms between SPIF and ADSIF. Finite element analyses are performed to simulate deformation in the two processes, and a detailed analysis of the deformation history is presented. It is shown that the presence of the supporting tool in ADSIF elicits substantial differences in the plastic strain, hydrostatic pressure, and shear strains as compared to SPIF. The implications of these trends on the prevalent modes of deformation in ADSIF along with possible explanations for increased formability observed in the process arediscussed.

Robust Shape Control of Deformable Objects Using Model-Based Techniques

Shape control of a deformable object by a robotic system is a challenging problem because of the difficulty of imposing shape change by a finite number of actuation points to an essentially infinite-dimensional object. In this paper, a new approach to shape changing of deformable objects by a system of manipulators is presented. First, an integrated dynamic equation of motion for a system of multiple manipulators handling a deformable object is developed. A shape correspondence between the initial contact points of the multiple manipulators on a deformable object and a two-dimensional curve that represents the final desired shape is determined. A shape Jacobian that contains the local shape information of the desired shape of the object is formulated and is introduced into the control law. We develop a shape estimator with a second-order dynamics that is used to estimate the curve parameters corresponding to the end-effector position in each time step as the initial object is deformed to its desired final shape. Finally, we design a robust controller for the shape changing task that can work in the presence of modeling uncertainty. The simulation results demonstrate the efficacy of the proposed method.

Shape optimization of the initial blank in the sheet metal forming process using equivalent static loads

In the sheet metal forming process, forming the final desired shape is difficult to obtain due to wrinkling, tearing, failure of material, etc. Various conditions of the forming process should be controlled for the desired shape. These conditions are the velocity of the punch, the friction factor, the blank holding force, the initial shape of the blank and others. Many researchers have conducted studies to predetermine the initial blank shape. The structural optimization technique is one of them. Non-linear response structural optimization is required because non-linearities are involved in the analysis of the metal forming process. When the conventional method is utilized, the cost is extremely high due to repeated non-linear analysis for function and sensitivity calculation. In this paper, the equivalent static loads (ESLs) method is used to determine the blank shape which leads to the final desired shape and reduced wrinkling. The ESLs method is a structural optimization method where non-linear dynamic loads are transformed into ESLs, and these ESLs are utilized as external loads in linear response optimization. The design is updated in linear response optimization. Non-linear analysis is performed with the updated design and the process proceeds in a cyclic manner. An optimization formulation is defined for the examples, the formulated problems are solved to verify the proposed method and the results are discussed. Non-linear analysis is performed using the commercial software LS-DYNA, NASTRAN is used for calculating the ESLs and linear response optimization, and an interface program for LS-DYNA and NASTRAN is developed. Copyright © 2010 John Wiley & Sons, Ltd.

Dielectrophoretic alignment of metal and metal oxide nanowires and nanotubes: A universal set of parameters for bridging prepatterned microelectrodes

Nanowires and nanotubes were synthesized from metals and metal oxides using templated cathodic electrodeposition. With templated electrodeposition, small structures are electrodeposited using a template that is the inverse of the final desired shape. Dielectrophoresis was used for the alignment of the as-formed nanowires and nanotubes between prepatterned electrodes. For reproducible nanowire alignment, a universal set of dielectrophoresis parameters to align any arbitrary nanowire material was determined. The parameters include peak-to-peak potential and frequency, thickness of the silicon oxide layer, grounding of the silicon substrate, and nature of the solvent medium used. It involves applying a field with a frequency >10 5 Hz, an insulating silicon oxide layer with a thickness of 2.5 μm or more, grounding of the underlying silicon substrate, and the use of a solvent medium with a low dielectric constant. In our experiments, we obtained good results by using a peak-to-peak potential of 2.1 V at a frequency of 1.2 × 10 5 Hz. Furthermore, an indirect alignment technique is proposed that prevents short circuiting of nanowires after contacting both electrodes. After alignment, a considerably lower resistivity was found for ZnO nanowires made by templated electrodeposition (2.2–3.4 × 10 −3 Ωm) compared to ZnO nanorods synthesized by electrodeposition (10 Ωm) or molecular beam epitaxy (MBE) (500 Ωm).

Forming analysis of AZ31 magnesium alloy sheets by means of a multistep inverse approach

This article applies a multistep inverse approach to predict the forming of AZ31 magnesium alloy sheets. A finite element code was developed that implements the inverse approach formulation for the forming analysis. This inverse approach uses the deformation theory of plasticity and assumes that the deformation is independent of the loading history for each intermediate configuration. Failure during forming is predicted by a stress-based criterion or a forming limit diagram-based criterion. The inverse analysis predictions have been compared with experimental results found in the literature and incremental analysis using ABAQUS. The multistep inverse analysis has been shown to very quickly and fairly accurately predict stress, plastic strain, thickness distributions and failure locations on deeply drawn parts made of AZ31 magnesium alloy. The capability of INAPH to predict the formability of magnesium alloys has also been demonstrated at various temperatures. As magnesium alloys possess very limited formability at room temperature, and their formability becomes better at higher temperatures (>100 °C), the inverse analysis constitutes an efficient and valuable tool to predict forming of magnesium alloy parts as a function of temperature. In addition, other processing and design parameters such as the initial dimensions, final desired shape, blank holder forces, and friction can be quickly adjusted to assess the forming feasibility.

Stylized highlights for cartoon rendering and animation

We propose a new highlight shader for the 3D objects used in cel animation. Without using a texture-mapping technique, our shader makes highlight shapes and animations in a cartoon style. Our shader makes an initial highlight shape using Blinn's (1977) traditional specular model. It then interactively modifies the initial shape through geometric, stylistic, and Boolean transformations for the highlight until we get our final desired shape. Moreover, once these operations specify highlight shapes for each keyframe, our shader automatically generates the highlight animation. In other words, our shader offers a new definition of highlighting 3D objects for cel animation.

Individualized lung shields constructed from lead shot embedded in plastic.

Earle and Bagshaw (2) described a rapid optical method for preparation of complex field shapes for megavoltage therapy. In their technic, treatment simulation is carried out under conditions which are exactly similar to the therapeutic conditions. With optical methods, it is possible to produce a minified image of required size and shape, to guide construction of lung shields for the purpose of reducing dosage to these radiosensitive normal structures. At the same time prescribed dosage is delivered to areas of or presumed areas of tumor involvement. While it is a simple matter to prepare the complex field shape, the preparation of an individualized shield is a separate and more difficult problem. Highly desirable features include ease and rapidity of construction and also simplicity of modification, since modification is often necessary to obtain the final desired shape. We describe here a rapid, simply constructed lung shield which is readily modifiable and which fulfills the above requirements for a highly individualized lung shield. With minor change it can be used for any shielding problem of complex shape, involving external beam, megavoltage x-ray or γ-ray therapy. Moreover, it also permits one to take account of beam divergence and differences in anterior and posterior lung block shape. Finally, it is practical and economical. Materials And Methods Transparent cutouts of film outlines were prepared, using an optical method. The tracings were transferred to a 10 em thickness of polyethylene foam. This can then be cut with a band saw or, if beam divergence correction is necessary, by appropriately designed devices, using either a hot wire or angle blade. Once cut, the mold serves as a receptacle for pouring the lung shields. Lead, in the form of small shot, was used for the shielding material. Heated themoplastic compound- is initially and concurrently poured into the mold until the entire form is filled. Agitation aids the settling process. After setting, the form can be cut from the polyethylene, and after additional port films, minor alterations and trimming to the required shape can easily be accomplished with a band saw. The final, completed product is shown in Figure 1, along with a port radiograph of the mantle field. Results and Preliminary Evaluation A 10-cm-thick lung shield can be made easily for reversible anteroposterior and postero-anterior usage, or shields may be constructed for each port to be treated. Beam-divergence correction may also be easily taken into account, owing to the simplicity of construction of each shield. Such considerations are of greater importance for blocks placed close to the collimator, and of less importance for blocks placed close to the patient. A transmission curve for the lead-shot-in-plastic shield is shown in Figure 2, relative to that for lead metal (3). The resulting half-value layer was about 2.0 cm.