Sheets Of Different Thicknesses Research Articles

Experience with high-frequency mechanical impact method for weldments of sheets of different thicknesses

The interim results of two projects of the Technology Agency of the Czech Republic are presented, the subject of which is the verification of the potential of the industrial use of the high-frequency mechanical impact (HFMI) method for increasing the load-bearing capacity and fatigue of the material. The fatigue life of welds of steel sheets of various thicknesses and in a wide range of strengths of welded steels for the construction of rolling stock and steel bridges are experimentally verified.The authors have already presented partial results, Kepka jr. et al. (2022). The new results are based on a larger number of test samples. First findings on the application of the HFMI method to thin (4 mm) and very thick (90 mm) sheet welds are included. The results are compared with the general recommendation of the International Institute of Welding (2016).Partial attention was also paid to the endurance of compressive stresses introduced into the weld area by the application of HFMI. The fatigue tests were completed by measuring residual stresses by X-ray diffraction on selected test specimens with the application of HFMI before and after the completion of 10 million loading cycles.

On-line heating rolling behavior of Mg9999 sheets under large single pass reduction

Pure magnesium foil has a great potential for rechargeable magnesium battery anode application, the formation of edge crack and break during Mg sheet rolling highly decreases the yield and thus increase the cost. In this paper, pure magnesium sheets of different thicknesses (0.3 mm, 0.4 mm, 0.5 mm and 0.6 mm) were prepared from 1 mm pure magnesium sheets by on-line heating rolling in a single pass. The edge cracking and breaking behavior of pure magnesium sheets were characterized by scanning electron microscope (SEM), X-ray diffractometer (XRD), electron backscatter diffractometer (EBSD), energy dispersive spectroscopy (EDS) and laser scanning confocal fluorescence microscope (LSCM). The results show that the number of edge cracks of pure magnesium sheets increases with the increase of rolling reduction. As the rolling reduction increases to 70%, due to the severe edge crack of 0.3 mm thick sheet and the formation of grooves on the magnesium sheet surface, the breaking of pure magnesium sheets occurs. The mechanism of edge cracking and breaking of ultra-thin pure magnesium rolled sheet is discussed.

Effect of medium-speed forming on formability of tailor welded blanks

Despite the widespread use of tailor welded blanks (TWB) in manufacturing auto-body panels and considering that different forming processes are performed at various speeds, it is necessary to examine the forming speed consequences. So, this study aims to investigate the forming speed effect on the formability of TWB and its constituent sheets. TWB consisting of St14 steel sheets of different thicknesses were welded using a fiber laser. Uniaxial tensile tests were conducted at various strain rates, and formability experiments were carried out at the quasi-static and medium-speed forming to construct forming limit curves (FLC). Tensile test results showed that some strain-hardening indicators decreased by strain rate increasing. The flow stress of base metals at different strain rates was successfully predicted by the constitutive model considering variable parameters. At medium-speed forming of base metals, the peak of major strain and fracture moved to the dome center. But, the strain concentration of most TWB samples at two forming speeds occurred in the thin sheet near the dome center. Also, the limiting dome height (LDH) at medium-speed forming decreased. Medium-speed FLC of base metals shifted downward and to the more positive minor strain compared to quasi-static FLC. Medium-speed FLC of TWB was lower than quasi-static FLC, especially on the tension-compression side. The reduction of medium-speed formability was attributed to the strain-hardening lowering, friction reduction, and inertial effects due to increased forming speed.

Thermal Effect on Thin-Film Formation of the Polymer Sheets by the CO2 Laser with the Copper Base.

A method that makes polymer sheets partially thinner with continuous-wave carbon dioxide (CO2) lasers has been developed. This method can create thin polymer films by attaching the polymer sheets to the copper base by vacuum suction through the holes in the base. Applying the method to polypropylene (PP), polyethylene terephthalate (PET), polystyrene (PS), and polytetrafluoroethylene (PTFE), the thin-film formation is confirmed in PP, PET, and PS but not PTFE. These polymers have the similar thermal properties. PP, PET, and PS show fluidity with increased temperature, but PTFE does not have fluidity. These characteristics of the polymers indicate that the fluidity of polymer is the important characteristic for film formation. The experiments with PP and PET sheets of different thickness show that thicker sheets make thicker films. The fluid flow of the molten polymer is considered to form the thin film at the bottom of the groove made by laser scribing. The numerical simulation of the 2D thermal model also indicates the week cooling effects of the base on the film formation and importance of polymer fluidity. The results of Fourier transform infrared spectrometer (FT-IR) show thermal degradation of the films. To decrease the heat’s effect on the films, the polymer sheets should be processed at the highest laser-beam scanning speed that can make thin films.

Characterization of the Welding Zone of Automotive Sheets of Different Thickness (DP600 and DP800) Joined by Resistance Spot Welding

Characterization of the Welding Zone of Automotive Sheets of Different Thickness (DP600 and DP800) Joined by Resistance Spot Welding

Optimization of channels and I-shaped bended closed profiles with tubular shelves from sheets of different thicknesses

The continuation of optimization of channels and I-beams bent closed profiles (BCP) with tubular flanges made of rolled sheet of different thicknesses is presented. Such profiles are intended for light steel thin-walled structures (LSWS), which are distinguished by high technical and economic indicators and massive demand in industrial and civil construction, which confirms the relevance of their further development. The main results of the calculation of the optimal bending arrangement of composite sections of I-beams from sheet blanks of different thicknesses, including channel-type BCPs unified in terms of optimal parameters, are also presented. The aim of the study is to show that the characteristics of the LSWS can be further improved by shaping profiles, combining straight and round outlines of closed and open contours in a composite section. Methods. By means of experimental design studies, solution of optimization problems and variant design of I-profiles, their composite sections from sheet blanks of different thicknesses, including blanks of channel profiles, have been refined. The originality of channels and I-shaped BCP has been confirmed by patent examination. Results. The I-shaped BCP consists of two tubular shelves and one double thickness wall. Calculation of the optimal layout of an I-shaped BCP made of rolled sheet of different thicknesses for bending showed that the bearing capacity is limited by the ratio of the thickness of the flanges and the wall of its composite section. In particular, when the thickness of the flanges is 2 times the wall thickness, the strength is maximum at a ratio of width to height of 1/11, and when the thickness of the flanges is 0.6 times the wall thickness, the strength is maximum at a ratio of 1/3.3. With the ratios of the width and height of I-shaped BCP of 1/2.68...1/3 and channel-type BCPs of 1/5.36...1/6, their composite sections should be optimally assembled from standardized blanks.

Evaluation of Testing Uncertainties for the Impact Resistance of Machine Guards

Abstract Machine guards provide protection against the ejection of parts during operation, such as chips or workpiece fragments. They are considered safe if the impact resistance is at least as high as the resulting projectile energy in the worst case of damage. To protect the machine operator, the impact resistance of machine guards is determined according to ISO standards. The bisection method can be used to determine the impact resistance through impact tests. However, this method is inaccurate for a small number of impact tests and does not indicate uncertainties in the determination. Moreover, the result of testing is validated in different ways depending on the standard utilized for testing. Relevant uncertainties affecting impact testing and a new probabilistic approach for assessing the impact resistance using the Recht and Ipson equation are presented. With multiple impact tests at different initial velocities a Recht and Ipson best-fit curve and a confidence interval for a ballistic limit can be obtained, which is used to determine the impact resistance by defining a velocity reduction coefficient. This method can be applied to any machine guard made of ductile material. This paper validates the Recht and Ipson method by performing impact tests with a standardized 2.5 kg projectile on polycarbonate sheets of different thicknesses. Determination of the ballistic limit showed good agreement with experimental results. With the ballistic limits, the velocity reduction coefficients have been found to determine the impact resistances. Therefore, an alternative method for standardized tests to determine the impact resistance was found.

On the size dependence of the dielectric breakdown strength of solid insulators at room temperature

The dielectric breakdown strength of solid insulators is usually dependent on the dimensions of the sample. In particular, for “thick” insulating sheets, the dielectric breakdown strength is often found to be roughly proportional to the inverse of the square root of the sample thickness. In this contribution, the hypothesis is examined that the latter type of size dependence is related to electric field inhomogeneities associated with the geometrical electrode configuration. In order to test the hypothesis, DC dielectric breakdown experiments have been performed for alumina ceramic sheets of different thicknesses ranging from 0.25 mm to 2 mm for both polarities and voltage ramp rates in the range between 0.1 and 5.8 kV/s. An electrode configuration has been used which allows for an analysis of the local electric field enhancement at the electrode edge in terms of fracture mechanics concepts. It is concluded from a comparison of experimental and theoretical results that the mentioned dependence of the dielectric breakdown strength on sample thickness is likely related to electrode edge effects.

Method for determining of the optimal thickness of sheets of magnetic cores of electrical machines by the wattmeter method

The problem of reducing magnetic losses (no-load losses) in the steel of the magnetic cores of electrical machines is investigated. The tasc of determining the optimal thickness of steel sheets of the magnetic circuit of an electric machine is considered. The criterion for optimality is the minimum power of magnetic losses in steel. Currently, this problem does not have an exact solution due to the fact that the exact ratio of the hysteresis and eddy current components of magnetic losses in steel is unknown. Analyzed the power of magnetic losses in modern electrical machines and devices, depending on the thickness of the sheets of electrical steel. A method is proposed for determining the optimal thickness of steel sheets of the magnetic circuit of an electric machine based on the wattmeter method. In the course of the experiment, two identical magnetic circuits were selected from steel sheets of different thicknesses, for which the losses in steel were measured at different frequencies of magnetization reversal and the optimal thickness of the sheets was calculated. The proposed formula for calculating the thickness of the sheets is valid for both isotropic and anisotropic steel. The proposed technique can be used for both transformers and electric motors and generators.

The Air that we Breathe: Neutral and volatile PFAS in Indoor Air.

Sources of exposure to per- and polyfluorinated alkyl substances (PFAS) include food, water, and given that humans spend typically 90% of our time indoors, air and dust. Quantifying PFAS prevalent indoors, such as neutral, volatile PFAS, and estimating their exposure risk to humans is thus important. To accurately measure these compounds indoors, polyethylene (PE) sheets were employed and validated as passive detection tools, and analyzed by gas chromatography-mass spectrometry. Air concentrations were compared to dust and carpet concentrations reported elsewhere. Partitioning between PE sheets of different thicknesses suggested that interactions of the PEs with the compounds are occurring by absorption. Volatile PFAS, specifically fluorotelomer alcohols (FTOHs), were ubiquitous in indoor environments. For example, in carpeted Californian kindergarten classrooms, 6:2 FTOH dominated with concentrations ranging from 9-600 ng m-3, followed by 8:2 FTOH. Concentrations of volatile PFAS from air, carpet and dust were closely related to each other, indicating that carpets and dust are major sources of FTOHs in air. Nonetheless, air posed the largest exposure risk of FTOHs and biotransformed perfluorinated alkyl acids (PFAA) in young children. This research highlights inhalation of indoor air as an important exposure pathway and the need for further reduction of precursors to PFAA.

Kerf profile analysis and neural network-based modeling of increasing thickness PMMA sheets cut by CO2 laser

One crucial issue in laser beam cutting is the proper selection of processing factors to achieve straight kerfs. In this study, the influence of cutting speed, laser power, gas pressure, and focal point position on the CO2 laser cutting of polymethylmethacrylate (PMMA) sheets of different thicknesses is analyzed to select optimal operational parameters. A design of experiment (DOE) of response surface type was then carried out to identify the influence of each factor and set the optimal ranges of the process parameters to achieve flat kerfs without streaks or surface imperfections. A laser with power values ranging from 3000 to 4200 W was used as an energy source. The interest intervals for the rest of the process parameters were justified by the literature consulted. Three new criteria were established to estimate a kerf profile deviation (KPD) response considering all the kerf area cut by the laser, defining these criteria as the difference between the resulting kerf profile and a straight kerf. As final results, the kerf profile deviation response was improved by 22.6%, 42.4%, 15.6%, and 22.1% in PMMA having thicknesses of 4, 8, 12, and 20 mm, respectively. Finally, an artificial neural network (ANN)-based model is used to predict the value of KPD, taking into account all the variables involved in the cutting process and the different criteria applied to classify the stage of profile deviation. The contributions of this paper are, in the first place, the proposal of new metrics to evaluate the kerf profile in PMMA sheets. Secondly, establishing optimal cutting parameters and ANN as an accurate method in geometrical modeling and relating the influential variables on the laser cutting process.

2-Piece Cork Stoppers as Alternative for Valorization of Thin Cork Planks: Analysis by LCA Methodology.

Natural stoppers are a magnificent closure for the production of aging wines and unique wines, whose application is limited by the availability of raw materials and more specifically of cork sheets of different thickness and quality. The growing demand for quality wine bottle closures leads to the search for alternative stopper production. The two-piece stopper is an alternative since it uses non-usable plates in a conventional way for the production of quality caps. The present study has analyzed the impact of the manufacture of these two-piece stoppers using different methodologies and for different dimensions by developing an LCA (Life Cycle Assessment), concluding that the process phases of the plate, its boiling, and its stabilization, are the phases with the greatest impact. Likewise, it is detected that the impacts in all phases are relatively similar (for one kg of net cork produced), although the volumetric difference between these stoppers represents a significant difference in impacts for each unit produced.

Experimental investigations on the level ice resistance of ships with non-typical icebreaking bow shapes

ABSTRACT For non-typical icebreaking ships with high stem and/or small waterline angles, the hull–ice interaction process in level ice comprises a combination of many different phenomena which is difficult to be described by existing straightforward approaches. In order to gain knowledge about the level ice resistance of ships with non-typical icebreaking bow shapes, a methodology to improve the principal understanding of the hull–ice interaction process, ice failure, level ice resistance and its distribution along the ship hull during model scale ice tests is developed. For this purpose, one ship model has been manufactured and extensively instrumented. By performing resistance tests at several loading conditions, in model ice sheets of different thickness and at multiple speed values, relevant information on the nature of ice resistance of such ship type can be obtained. In this paper, the methodology is briefly summarized and part of the results of the model testing campaign are presented and discussed.

Ultimate Load-Carrying Ability of Rib-Stiffened 2024-T3 and 7075-T6 Aluminium Alloy Panels under Axial Compression.

Stringer-stiffened panels made of aluminium alloys are often used as structural elements in the aircraft industry. The load-carrying capacity of this type of structure cannot relieve the reduction in strength in the event of local buckling. In this paper, a method of fabrication of rib-stiffened panels made of EN AW-2024-T3 Alclad and EN AW-7075-T6 Alclad has been proposed using single point incremental forming. Panels made of sheets of different thickness and with different values of forming parameters were tested under the axial compression test. A digital image correlation (DIC)-based system was used to find the distribution of strain in the panels. The results of the axial compression tests revealed that the panels had two distinct buckling modes: (i) The panels buckled halfway up the panel height towards the rib, without any appreciable loss of rib stability, and (ii) the rib first lost stability at half its height with associated breakage, and then the panel was deflected in the opposite direction to the position of the rib. Different buckling modes can be associated with the character of transverse and longitudinal springback of panels resulting from local interaction of the rotating tool on the surface of the formed ribs.

The Clinching Joints Strength Performance of EN 10346: 2015 DX52D + Z Sheets

This study is based on the joint quality of zinc-coated EN 10346: 2015 DX52D + Z quality steel sheets with having different thicknesses, which are preferred in the automotive industry due to their formability. Joining problems in clinching applications with different positions and sheets of different thicknesses are discussed and experimental outcomes are discussed in terms of strength of joints. As a result of the tests carried out according to the standards, it has been found that the joining of the sheets with thickness close to each other is relatively good, as the thickness difference increases, the joint quality decreases and sometimes the joint does not form. It has been also found that if the thinner sheet is placed on the bottom die during clinching, a better joint strength is obtained.

WITHDRAWN: Challenges and possibilites in the resistance spot welding of dissimilar metals – A review

In order to get a defect free spot weld, both the metals are desired to have the same thermal and electrical conductivity. But when welding dissimilar metals or sheets of different thickness, the fusion zone of both the metals may not experience same heat input due to the difference in material properties. This leads to weld defects such as nugget offset, voids and intergranular cracks in the fusion zone. The existence of weld defects deteriorates the mechanical performance of welded joints. A thorough metallurgical analysis must be carried out to ensure that the weld nugget is free of defects. The resistance spot welding of various dissimilar metals in the recent research publications and its practical outcomes are analyzed.

Analysis of Active Oral Tactile Sensitivity in Individuals with Complete Natural Dentition

To evaluate the active tactile sensitivity in individuals with complete natural dentition, determining the smallest thickness detected by the participants, and clarifying if there is a difference between the thicknesses analyzed. Active tactile sensitivity was evaluated in 40 research participants. Inclusion criteria included participants with complete natural dentition, without active or history of periodontal disease, absence of temporomandibular disorders, bruxism, and restorations in the evaluated area. Exclusion criteria included age below 18 years. The active tactile perception threshold was evaluated by using carbon sheets of different thicknesses (0, 12, 24, 40, 80, 100, and 200 μm), which were inserted in the participants' premolars, bilaterally. The carbon sheet was inserted so as not to come into contact with the oral soft tissues. Subsequently, the participant occluded and was asked about the perception of the intraocclusal object 20 times in each occlusal contact. The collected data were tabulated considering the amount of positive and negative responses for each carbon thickness. Values of p < 0.05 were considered significant. The results showed that there was linearity in perception, on both sides, besides, the natural dentition was able to perceive difference in thickness from 12 μm. We conclude that the 12 μm thickness is noticeable in occlusion and can be differentiated from other thicknesses in natural dentition and that there is no difference between the tactile sensitivity of the right and left sides. A better understanding of active oral tactile sensitivity will contribute to numerous clinical applications in dentistry, including occlusal adjustment in dental rehabilitation, dental implants prosthesis design, and survival of prosthetic rehabilitation.

Investigating the Effect of Different Metal Sheets on Reducing Radiation Behind Intraoral Digital Phosphor Plates During Intraoral Radiography using Gray Value

Purpose: To assess the efficacy of metal sheets with different thicknesses on reducing the radiation behind the photostimulable phosphor plate (PSP) during intraoral periapical examinations. Materials and Methods: In this study, a phantom head was used to investigate the effect of using metal sheets of aluminum, stainless steel, and copper with three thicknesses of 0.5, 0.75 and 1mm on reducing the radiation behind PSP. Images were acquired at 66 kVp 8 mA, and 0.16 s using the long-cone paralleling technique. The images were saved and exported to DICOM format without any post-processing. Then, they were transferred to an image processing software (Mimics, Materialize, Leuven, Belgium), and their mean gray values (MGV) were determined. The acquired data were statically analyzed for accessing the significant difference in groups means using ANOVA, and the means of groups were compared using Tukey’s test procedure. Results: The MGV of the second PSP differed significantly from those PSPs slotted with various metals (p&lt;0.001). The MGV for lead and stainless steel at 0.5 mm thickness was insignificant (p = 0.852), but differed significantly from other metals. The MGV for PSPs with 0.75 mm stainless steel and 1 mm copper slots were varied significantly from those of all other PSP and metals. The 1 mm copper group was significantly different from all other groups (p&lt;0.001). Conclusion: Using the mean gray value of the PSP, the use of various metal sheets of different thicknesses could effectively reduce the radiation behind the PSPs during periapical radiographs.

Content Adaptation and Depth Perception in an Affordable Multi-View Display

We present SliceView, a simple and inexpensive multi-view display made with multiple parallel translucent sheets that sit on top of a regular monitor; each sheet reflects different 2D images that are perceived cumulatively. A technical study is performed on the reflected and transmitted light for sheets of different thicknesses. A user study compares SliceView with a commercial light-field display (LookingGlass) regarding the perception of information at multiple depths. More importantly, we present automatic adaptations of existing content to SliceView: 2D layered graphics such as retro-games or painting tools, movies and subtitles, and regular 3D scenes with multiple clipping z-planes. We show that it is possible to create an inexpensive multi-view display and automatically adapt content for it; moreover, the depth perception on some tasks is superior to the one obtained in a commercial light-field display. We hope that this work stimulates more research and applications with multi-view displays.

Thickness Measurement of Titanium Alloy Sheet Based on Eddy Current Method With a Novel Simplified Model

This article proposes a novel simplified model that describes the real part (in-phase component) of the difference in pickup coil voltage when an eddy current (EC) sensor consisting of two coils (excitation and pickup coils) is placed above the titanium (Ti) alloy sheet. A parameter that encapsulates the coil geometry factors is integrated into the classical Dodd–Deeds model, and then, the model is simplified by combining with the electromagnetic properties of Ti alloy. The use of the simplified model provides a thickness measurement method for Ti alloy sheets. The measured thickness can be calculated directly from the calibration signal by using the model, without the need to predict response by solving the forward model in advance. Experimental measurements were conducted on TC4 (Ti-6Al-4V) Ti alloy sheets of different thicknesses with a developed EC sensor and measurement system. The experiment verified the proposed model and measurement method. The experimental results shown that the maximum measurement error is less than 2.86%, which is greatly lower than the permissible error of the current industry standard. This study provides a theoretical basis and a fast method for EC thickness measurement of Ti alloy.