Non-uniform Thickness Distribution Research Articles

Ribbed floors with optimized thickness distribution for maximized broadband impact sound insulation

Impact sound insulation of floors is one of the main concerns when designing multi-story buildings. While conventional floor systems use flat or regularly ribbed configurations, interesting opportunities to improve performance are given by enhancing the design of the load-bearing slab. In this work, we propose a methodology to maximize broadband impact sound insulation by designing slabs with a non-uniform material thickness distribution, which is numerically optimized. In the design process, efficient and accurate sound insulation predictions are employed through a detailed finite element floor model coupled with a diffuse room model. In particular, we minimize a Single Number Quantity (SNQ) that represents the aggregate broadband sound pressure level in the receiving room under point-load excitation. The design of single slab floors is considered first. Results indicate that, even if the optimization effectively minimizes the sound pressure level in the different third-octave bands, it does not lead to noteworthy decreases in the SNQ. The design of floating floors is then considered. In this case, a better overall performance is obtained, corresponding to significant improvements at low frequencies and a slight degradation at high frequencies, where, nevertheless, floating floors already perform well. This slight high-frequency decline is linked with the resonances of the thin sub-plate regions present between the optimized ribs, akin to what is observed in waffle ribbed floors. Finally, the robustness of the optimized results against changes in the initial guess is assessed by showing that no SNQ improvements are obtained when transitioning from flat to waffle ribbed initial design.

Improving uniformity and performance of electroformed copper using rare earth element additives

Electroforming can realize high precision and complex shape parts manufacturing, making it widely used in the field of micromachining and micromanufacturing. The drawback lies in the nonuniform thickness distribution, which can cause quality issues including voids, pitting, and particles. In order to enhance the microstructure uniformity and electroforming performance, lanthanum chloride and cerium chloride were employed as additives in the copper electroforming experiment. This study analyzes the effects of lanthanum chloride and cerium chloride on the surface morphology, microhardness, tensile strength, and uniformity of electroformed copper deposits. The results show that adding rare earth elements into the electrolyte solution can improve thickness uniformity, promote ion mass transfer, and refine the copper deposit’s grain. Compared to the microstructure without adding additives, the copper deposit’s nonuniformity prepared with 1.0 g/L lanthanum chloride is 76.9% lower, and with cerium chloride, it is 72% lower. Additionally, the copper deposit prepared with lanthanum chloride exhibits superior overall quality compared to that prepared with cerium chloride.

Predictive Methodology for Quality Assessment in Injection Molding Comparing Linear Regression and Neural Networks.

The use of recycled polypropylene in industry to reduce environmental impact is increasing. Design for manufacturing and process simulation is a key stage in the development of plastic parts. Traditionally, a trial-and-error methodology is followed to eliminate uncertainties regarding geometry and process. A new proposal is presented, combining simulation with the design of experiments and creating prediction models for seven different process and part quality output features. These models are used to optimize the design without developing additional time-consuming simulations. The study aims to compare the precision and correlation of these models. The methods used are linear regression and artificial neural network (ANN) fitting. A wide range of eight injection parameters and geometry variations are used as inputs. The predictability of nonlinear behavior and compensatory effects due to the complex relationships between this wide set of parameter combinations is analyzed further in the state of the art. Results show that only Back Propagation Neural Networks (BPNN) are suitable for correlating all quality features in a single formula. The use of prediction models accelerates the optimization of part design, applying multiple criteria to support decision-making. The methodology is applied to the design of a plastic support for induction hobs. Furthermore, this methodology has demonstrated that a weight reduction of 27% is feasible. However, it is necessary to combine process parameters that differ from the standard ones with a non-uniform thickness distribution so that the remaining injection parameters, material properties, and dimensions fall within tolerances.

Deep drawability of electron beam welded tailored blanks of commercially pure titanium thin sheets

In this work, commercially pure titanium tailor-welded blanks (TWBs) were fabricated from sheets of thicknesses 1.0 mm (Ti1.0) and 1.2 mm (Ti1.2) using electron beam welding (EBW). It was observed that the titanium base materials had an equiaxed microstructure, whereas the FZ of the weld consisted of coarsened prior β grains with internal α substructures. Transverse and longitudinal tensile tests were conducted to evaluate weld integrity and weld properties, respectively. The deep drawing behaviour of both the base materials and TWB had been investigated by conducting laboratory-scale deep drawing tests. The limiting drawing ratios (LDR) of the Ti1.0 and Ti1.2 base materials were 2.14 and 2.21, respectively. The LDR of TWB was 2.14, which was same as that of the Ti1.0 base material. The CPB06 yield criterion and weld properties were incorporated in the FE modelling to study the deep drawing behaviour of the TWB for the first time. The FE model successfully predicted the non-uniform material flow and thickness distribution in the deep drawn TWB. Moreover, the weld line movement was found to be towards the Ti1.0 side at the cup top region and towards the Ti1.2 side at the cup bottom of the TWB deep-drawn cup.

Dryout quality prediction in helical coils based on non-uniform liquid film thickness distribution: A model study

Dryout occurrence has an adverse effect on the thermal efficiency of helically coiled steam generators used in thermal energy storage systems. In this study, a mechanistic model based on the non-uniform annular liquid film thickness distribution was developed to evaluate the quality of dryout occurrence in helical coils. The inner-side and outer-side liquid films were investigated, including the local effects of entrainment, deposition, and dryout, while the film interface profile in the tube cross-section was simplified as a half-ellipse. The deposition correlations reported in the literature were modified by considering the centrifugal effect. The entrainment correlations were compared and optimized to improve the dryout prediction. The proposed model achieved satisfactory agreement on a boiling crisis dataset of 994 test points with a mean absolute error of 35.2%, which is better than existing models. The current work can be used in thermohydraulic design and performance prediction for thermal energy storage systems.

Theoretical and experimental analysis of guided wave propagation in plate-like structures with sinusoidal thickness variations

Guided waves have attracted significant attention for non-destructive testing (NDT) and structural health monitoring (SHM) due to their ability to travel relatively long distances without significant energy loss combined with their sensitivity to even small defects. Therefore, they are commonly used in damage detection and localization applications. The main idea of incorporating guided waves in NDT and SHM is based on processing the received signals and appropriate interpretation of their characteristics. A great amount of research devoted to diagnostics of plate-like structures considers specimens with constant thickness, which significantly facilities the diagnostic process. In such a case the velocity is also assumed to be constant. However, the developed diagnostic methods should be applicable, especially for the structures exposed to an aggressive environment, excessive load, or unfavorable weather conditions, etc., when the probability of damage occurring is much higher. In such cases, the assumption about the uniform thickness alongside the propagation path cannot be applied in every case. Thus, the present study is focused on wave propagation in metallic plates with variable thickness. The results of theoretical, numerical and experimental investigations of antisymmetric Lamb mode propagation in aluminum plates with a sine-shaped surface are presented. In the first step, the influence of non-uniform thickness distribution on wave velocity has been described. Next, the inverse problem aimed at shape reconstruction based on time of flight (ToF) analysis and spatially varying wave velocity was solved and compared with the standard dispersion curve-fitting method.

Experimental investigation of a method for diagnosing wall thinning in an artificially thinned carbon steel elbow based on changes in modal characteristics

Curved cylindrical structures such as elbows have a non-uniform thickness distribution due to their fabrication process, and as a result have a number of complex mode shapes, including circumferential and axial nodal patterns. In nuclear power plants, material degradation is induced in pipes by flow accelerated erosion and corrosion, causing the wall thickness of carbon steel elbows to gradually thin. The corresponding frequencies of each mode shape vary according to the wall thinning state. Therefore, the thinning state can be estimated by monitoring the varying modal characteristics of the elbow. This study investigated the varying modal characteristics of artificially thinned carbon steel elbows for each thinning state using numerical simulation and experimental methods (MRIT, Multiple Reference Impact Test). The natural frequencies of specified mode shapes were extracted, and results confirmed they linearly decreased with increasing thinning. In addition, by comparing single FRF (Frequency Response Function) data with the results of MRIT, a concise and cost effective thinning estimation method was suggested.

Non-Uniform Effect of the Contact Conditions on the Earing Profile in Cylindrical Cups of Anisotropic Materials

The earing profile of cylindrical cups is mainly dictated by the in-plane anisotropic behavior of the metal sheet. Nevertheless, for materials with a strong anisotropic behavior the contact conditions between the blank and the blank-holder can also affect the material flow due to the non-uniform distribution of the contact forces. The main objective of this study is to numerically assess the influence of the friction conditions on the cup earing profile using the AA3104 aluminum alloy. The strong anisotropy of the r-values of this material leads to a non-uniform thickness distribution along the circumferential direction of the flange, resulting in increased thickening in the transverse direction. The effect of the friction coefficient on the earing profile is approximately 4 times larger in the transverse direction than in the rolling direction.

Biomaterial actuator of M13 bacteriophage in dynamically tunable plasmonic coupling structure

Nano-gap plasmonic nanostructures like nanoparticle on a metallic film (NPOM) exhibit enhanced near-field properties because of surface plasmon coupling. Utilizing metallic NPs shape, size, material choice, and dielectric film-induced nano-gap (or hot-spots), it is possible to exploit potential applications in sensors. To achieve dynamic sensing, the application of tunable nano-gaps in response to external stimuli has been attempted using biopolymers. M13 bacteriophages are viable candidates as nano-gap materials owing to their widely adjustable physicochemical properties by genetic engineering technology. Here, we demonstrate a collective light-scattering spectrum of the surface-enhanced plasmonic resonance characterized by the surface morphology of the employed M13 bacteriophage thin film. Our NPOM (Ag nanocube/M13 bacteriophage film/Au film) nanostructure revealed differences in experimental and simulated scattering peak wavelength shift when nano-gap size(s) are varied. An AFM (Atomic Force Microscopy) surface morphology analysis of the M13 bacteriophage film showed its non-uniform thickness distribution explaining the differences in scattering peak wavelength properties. We confirmed that the M13 bacteriophage performs well as a sensor based on static and dynamic moisture exposure. Benefitting from the adaptability and sensitivity of the M13 biomaterial, our gap plasmonic coupling structure can be used for sensing VOCs as a biosensor.

Optimization of Two-Stage Hybrid Forming Process via Quantitative Assessment of Mechanical Properties in AA5052

Superplastic forming (SPF) is a promising approach used for manufacturing parts with complex geometries, especially in the automotive, aerospace, and marine industries. However, the wider use of this method is limited by issues of low forming rate, high-temperature requirement, non-uniform thickness distribution, and expensive base materials. The two-stage hybrid forming (HF) method, in which hot-punch forming is executed before the SPF, was introduced to overcome these limitations. In this study, a conventional non-superplastic grade 5052 aluminum (AA5052) alloy with an average grain size of 70 µm was used to evaluate the applicability of two-stage HF for manufacturing parts with complex geometries from coarse grain alloys. Before implementing the two-stage HF, the optimal experimental conditions for hot drawing and hot blowing were first determined. The optimum HF conditions were identified, as follows: a hot-punching temperature of 400oC, punch depth of 35 mm, punching speed of 150 mm/min, blow forming temperature of 500oC, and gas pressure of 2.5 MPa. The HF results were also verified using the finite element method. The finite element analyses results for thickness distribution and optimal process condition were compared with the experimental results for one-stage and two-stage forming, and showed acceptable similarity.

Quantification and statistical analysis on the cranial vault morphology for Chinese children 3–10 years old

Background and ObjectiveHead injury is the leading cause of fatalities and disabilities in children. Characterizing the variation in cranial size/shape and thickness during growth is important for developing finite element models of child heads and evaluating head injury risk at different ages. However, the quantitative morphological features of the cranial vault (size/shape and non-uniform thickness distribution) have not been accounted for in children aged between 3 and 10 years old (YO). MethodsGeometrically equivalent discrete points were identified on 42 head CT scans of 3–10 YO children by separation, curve dividing, and point fitting. Based on discrete points, the principal component analysis and regression (PCA&R) method was used to develop a statistical model of the cranial vault as a function of age and head circumference. ResultsThe ontogeny of three-dimensional cranial morphology and non-uniform thickness from 3 to 10 years of age was quantified and cranial vault morphologies for 3–10 YO children were generated in 1 year intervals. ConclusionsThe automatic method, the procedure of identifying discrete points from CT scans, and the developed quantitative cranial vault model are reliable and accurate.

Capturing 3D water layers and water-filled micropores in carbonate rock by high-resolution neutron tomography

Knowledge of micrometer-scale wetting layers and microporosity in rocks is crucial for a deeper understanding of immiscible fluid displacement, and especially capillary trapping. It is an established fact that the amount of capillary trapping is a result from the competition between flow via wetting layers and piston-like displacement. Despite the large amount of experimental work published, there are many open questions about fluid displacement mechanisms in complex porous media, particularly the role of microporosity in the disconnection and entrapment of the nonwetting phase. Here, we applied the state-of-the-art neutron tomography technique (with the best spatial resolution available at neutron imaging facilities) to reveal the 3D distribution of water layers and water-filled micropores in a carbonate rock. Our results revealed wetting layers with a non-uniform thickness distribution completely covering the rock surface. During imbibition at a low capillary number, a marked increase in the amount of water-filled micropores with the concomitant swelling of wetting layers were observed. This approach can be used as a platform to explore a huge range of interfacial phenomena, such as enhanced oil recovery and CO2 storage.

Prediction of the liquid film reversal of annular flow in vertical and inclined pipes

This work proposes a simplified model and a unified model to predict the critical gas velocities of film reversal based on the conservative momentum principle. The simplified model is expressed by an analytical solution of dimensionless form, while the unified model is presented by an iterative solution. The measured datasets of different pipe angles and diameters from the present and published works were used for model evaluation. The proposed simplified model is recommended to predict the film reversal because it can accurately predict the critical velocity with the total relative errors of 10.18% in the laboratory and 27.03% in the field, outperforming the unified model and published models. The unified model has a total relative error of 11.56% in the laboratory and 34.26% in the field. The contributions of the proposed two models are discussed by model comparisons. The results show that the simplified model integrates the merits of simple form and high accuracy; but, owing to the simplifications, the simplified model is not rigorous in the mechanism. In contrast, the unified model is more rigorous because it considers the interior liquid film viscosity, the droplet entrainment, and the non-uniform film thickness distribution in inclined pipes. The superiority of the unified model is discussed by comparing it with previous models in vertical and inclined pipes. The unified model contributes to understanding the underlying mechanism of film reversal. In general, the proposed simplified model and unified model complement each other to improve the prediction of the film reversal practically and theoretically.

Machine learning aided design of conformal cooling channels for injection molding

During the injection molding process, the cooling process represents the largest portion of the cycle time. The effectiveness of the cooling system significantly affects the production efficiency and part quality, where it is limited by the conventional cooling channels manufactured by the drilling and casting process. Although the maturing advanced additive manufacturing (AM) technology allows the design and fabrication of complex conformal cooling channels, the temperature variance caused by non-uniform thickness distribution of the part remains unsolved. This issue is caused by the fact that the existing conformal cooling designs do not create the channels conformal to the part thickness distributions. In this work, a machine learning aided design method is proposed to generate cooling systems which conform not only to the part surface but also to the part thickness values. Three commonly used conformal cooling channel topologies including spiral, zig-zag, and porous are selected. A surrogate model is derived for each cooling channel topology to approximate the relationship between the design parameters of the cooling channels, part thickness, and the resulting part surface temperature. Based on the surrogate model, the design parameters of each type of cooling channels are optimized to minimize the part surface temperature variation. At the end of the paper, design cases are studied to validate the effectiveness of the proposed method. Based on the proposed method, much lower temperature variance and a smaller coolant pressure drop are achieved compared with the conventional conformal cooling design.

Investigation of the two-stage SPF process of aluminum alloy door frames

The superplastic forming process has been used extensively in aerospace applications for its advantages in manufacture of complicated components. But it has been limited to the long production cycle and the non-uniform thickness distribution of the final formed part. The two-stage SPF process in opposite directions for 5083 aluminum alloy door frames was investigated. A finite element model in PAMSTAMP was used to simulate the forming process. Analyzed the effect of pre-forming die parameters on the minimum thickness of the final formed part by the Response Surface Methodology and optimized the pre-forming die parameters. Moreover, the influence of different rated pressure on the forming quality and forming time of the door frames under the same strain rate were investigated to determine the ideal pressure profile. The result was that the minimum thickness meets the requirements (thinning not exceeding 40%) while reducing the production cycle. Finally, the two-stage superplastic forming experiment in opposite directions was conducted to verify the accuracy of the numerical simulation and produce the door frames with high quality.

Robot assisted incremental sheet forming of Al6061 under static pressure: Preliminary study of thickness distribution within the deformation region

Incremental sheet forming (ISF) has a basic advantage over the conventional forming processes such as deep drawing in terms of increased formability of the sheet due to delayed necking as a result of localized deformation. In this process, a forming tool is mounted on the traditional CNC machines and is programmed to move so as to impart the deformation to the sheet. The non-uniform thickness distribution in the sheet and sheet thinning are among the drawbacks of the process. The use of back hydrostatic pressure provides a promising way to overcome this problem. The process called incremental sheet hydroforming (ISHF) uses back fluid hydrostatic pressure as a support to deform the sheet. In this work, the six axes industrial robot has been used for the deformation of the Al6061. The conical (with diameter 28 cm and the height 14.2 cm) and pyramidal shapes (dimension of the rhombohedral pyramid is 28 cm × 28 cm × 14 cm) with wall angle 40 degrees have been obtained by this process. The spiral tool path has been used for the shape generation and the speed of the tool was 200 mm/sec making the process faster than the conventional ISF process. The thickness variation of the sheet has been found to be more uniform as in the case of incremental sheet forming with back hydrostatic pressure.

Movement analysis of primate molar teeth under load using synchrotron X-ray microtomography

Mammalian teeth have to sustain repetitive and high chewing loads without failure. Key to this capability is the periodontal ligament (PDL), a connective tissue containing a collagenous fibre network which connects the tooth roots to the alveolar bone socket and which allows the teeth to move when loaded. It has been suggested that rodent molars under load experience a screw-like downward motion but it remains unclear whether this movement also occurs in primates. Here we use synchroton micro-computed tomography paired with an axial loading setup to investigate the form-function relationship between tooth movement and the morphology of the PDL space in a non-human primate, the mouse lemur (Microcebus murinus). The loading behavior of both mandibular and maxillary molars showed a three-dimensional movement with translational and rotational components, which pushes the tooth into the alveolar socket. Moreover, we found a non-uniform PDL thickness distribution and a gradual increase in volumetric proportion of the periodontal vasculature from cervical to apical. Our results suggest that the PDL morphology may optimize the three-dimensional tooth movement to avoid high stresses under loading.

An advanced technique for determining NC machining tool path to fabricate drawing die surface considering non-uniform thickness distribution in stamped blank

Drawing process represents a significant area of production technology since it influences the feasibility of producing auto-body die panels. In the drawing process, the plastic deformation of blank is not uniform due to the intermittent deformation behavior of the material. This primes a non-uniform thickness distribution in the formed panels, which directly affects the die life and the quality of panels. In the presented study, a new algorithm was proposed for constructing the numerical control machining tool path for the new die surface obtained from FEM simulation and mesh mapping. The commercial package LS-DYNA was employed for the FEM simulation and to calculate the thickness distribution in the drawn workpiece. In order to construct the new numerical control machining tool path according to the new die surface, the positions of all cutter location points relative to the movement of new die mesh were determined. A set of forming die was machined using the proposed algorithm to fabricate a real workpiece of steel DC04. A comparison between the measured thicknesses in the fabricated workpiece and the FEM simulation results shows that they agree with each other very well, which directly validates the proposed algorithm. The developed method can improve product quality, increase production efficiency, and reduce labor intensity.

Uniformity of thickness of metal sheets by patchwork blanks: potential of adhesive bonding

The sheet metal forming operations generally involve the production of parts characterized by a non-uniform thickness distribution. However, in some cases, a product characterized by a distribution of thicknesses that is as uniform as possible may be desirable. This result can be obtained by using multiphase processes or by subtraction or addition of material from the blank. In this work, which deals with the method for adding material, an innovative methodology has been proposed as an alternative to the welding process. Specifically, the methodology is based on the bonding of a patch (before the deformation process), on the base plate with a constant thickness, in the area that most suffers from the thinning caused by the forming process. In this way, it was possible to influence the deformation of the patchwork blank and its thicknesses distribution. Through finite element analysis, it was possible to study the formability of a patchwork blank by varying the thickness and size of the patch, in order to produce an axially symmetric component by stretching through a hemispherical punch. Preliminary experimental tests demonstrated the reliability of the bonding and the potential of this method to uniform the final thickness of the sheet.

Evaluation of AMSR-E Thin Ice Thickness Algorithm from a Mooring-Based Observation: How Can the Satellite Observe a Sea Ice Field with Nonuniform Thickness Distribution?

AbstractThe quantification of sea ice production in coastal polynyas is a key issue to understand the global climate system. In this study, we directly compared Advanced Microwave Scanning Radiometer-EOS (AMSR-E) data with the sea ice thickness distribution obtained from a mooring observation during the winter of 2003 off Sakhalin in the Sea of Okhotsk to evaluate the algorithm for estimation of sea ice thickness in coastal polynyas. By using thermal ice thickness as a target physical quantity, we found that the obtained relationship between the polarization ratio (PR) and ice thickness can provide an appropriate AMSR-E algorithm to estimate thin ice thickness, irrespective of the uniform or nonuniform ice thickness field. The relationship between the PR value and thermal ice thickness is likewise consistent with the local PR–thickness relationship that is observed at individual ice floes. This is because both the PR value and thermal ice thickness are more sensitive to thinner ice. Furthermore, we evaluated the method for detection of active frazil in a coastal polynya by comparing with the mooring data, and subsequently modified it to classify the coastal polynya into three thin ice types, namely, active frazil, thin solid ice, and mixed ice (mixture of active frazil and thin solid ice). The improved algorithm successfully represents the thermal ice thickness even for a relatively small-scale polynya off Sakhalin and is expected to be useful for better quantification of sea ice production in the global ocean owing to its high versatility.