Thin Cross Research Articles

Laser beam welding of atmosphere aluminum die cast material using high frequency beam oscillation and brilliant beam sources

In the serial production of components for automotive applications such as cooling and air-conditioning systems, aluminum die-cast materials are frequently used due to their excellent castability. The aim of providing light weight components can be approached with thin walled cross sections even for complex structural parts. However, cast components are usually connected to semifinished products such as profiles or tubes. The connections have to be mostly pressure tight. The joining technique for these applications has to be highly productive to obtain high component outcome and cost-efficient. Laser beam welding techniques are especially suitable for these tasks. Die-cast components have limited or no weldability due to their manufacturing process. This is due to entrapped gases within pores or cavities under high pressure conditions. Furthermore, the mold release agents for the die-cast process are inappropriate for obtaining homogeneous and sound weld seams. Consequently, this results in a larger number of pores in the weld seam and stochastic melt pool blow-outs, which prohibit mostly the use of the component. To solve these issues, a new welding technique, remoweld®T, has been developed at Fraunhofer IWS. This unique method has been extensively tested and used for serial-production. The decisive step was to use laser sources with brilliant beam quality in combination with a high frequency beam oscillation within the melt pool. In this paper, the technological approach will be presented. With the remoweld®T method, it was possible to obtain homogeneous weld seams with low porosity and a strongly reduced distortion for the first time. Minor component tolerances and a reproducible joining technique with a high output for serial production can be achieved.

Fabrication of 3D Shapes of Carbon By Origami

We present preliminary experiments leading to a novel approach to manufacture 3D complex shapes of thin carbon using origami. Origami is an ancient art of paper folding, where a 3D complex shape can be fabricated by folding planar paper along the creases. Paper is generally a random network of cellulose fibers. Cellulose decomposes to carbon upon heat treatment around 900 °C in inert atmosphere. The cellulose derived carbon resembles to glass-like carbon and possesses interesting properties such as low density, high electrical conductivity, biocompatibility, and high resistance to high temperature and corrosive environment1,2. Here, we aim to demonstrate the capability to manufacture 3D complex origami structures of carbon by heat treating the precursor paper origami structures. These complex 3D structures of thin cross section carbon have huge potentials as multifunctional material in different applications such as tissue engineering scaffold, catalyst support and biomedical devices. We used Fisherbrand pure cellulose chromatography paper (Sigma Aldrich, Cat. No. 05-714-1) because of its cellulosic nature and minimal impurity. A cutting plotter machine (Graphtec CE6000-40, USA) was used to pre-crease the paper. The pre-creasing method started with generating CAD models to define the location of the creases. CAD models for the creases on both sides of the paper must be created separately. Registration marks were printed on the both sides of the chromatography (CG) paper by a laser-jet printer for accurate alignment during pre-creasing. The CG paper was fed to the cutting plotter machine and pre-creased with a ball-point pen mounted on the cutting plotter machine using specific equipment parameters. Once pre-creasing is done on one side, the CG paper was flipped and creased on the other side. Excess portion of the paper was then trimmed and folded manually along the creases to obtain paper origami structures. The paper origami structures were carbonized in a tube furnace (TF1400, Across International, Japan) at 900 °C for 75 minutes in a nitrogen atmosphere. This process was repeated for three different origami tessellations, which are Miura-ori, Waterbomb-base and Yoshimura in descending order of complexity. SEM and XRD were performed to characterize the effect of carbonization on the microstructure and the material composition of the carbonized sample respectively. The compressive strength of the carbonized Miura-ori was characterized by compression test. Figure 1 shows the origami tessellations before and after carbonization. The carbonized samples retained the original precursor origami structure during the heat treatment, although surface wrinkling could be observed for the carbonized structures. Around 90% weight loss occurred during the carbonization. A significant shrinkage was also observed for the carbonized origami structures. Although the overall shrinkage was dependent on the complexity of the origami structures, around 75-90% shrinkage was observed in the fibril structures when compared the microstructures of CG paper and carbonized samples as shown in Figure 2a and 2b respectively. Our hypothesis is escape of the gaseous substances from the cellulose during the carbonization results in the weight loss and the shrinkage. The XRD pattern of the carbonized sample as shown in Figure 2c confirms the formation of amorphous carbon during the carbonization process. The compressive strength to weight ratio of the carbon Miura-ori was measured to be 96.4 ± 0.48 kPa/g, which is over 5 times that of paper Miura-ori as shown in Figure 2d. Ongoing work is on characterizing the scalability of this manufacturing process; infiltrating the paper origami structure with metal precursor to obtain metal impregnated carbon origami structure through carbothermal reduction reaction for structural electrode or sensor application; and infiltrating the carbon structure with bio-epoxy to increase the strength of the carbon origami structures.

Ileal Smooth Muscle Thickness is Greater in Young Obese Zucker Rats

Obesity is a risk factor for many pathologies including heart disease, type 2 diabetes and certain types of cancers. At this time little is known about how obesity effects the morphology of the small intestine or gut. The purpose of this study was to determine what morphological differences exist in the smooth muscle of the small intestine, between lean and obese Zucker rats. We hypothesized that the thickness of the circular and longitudinal muscle layers of the small intestine from obese Zucker rats would be greater compared to their lean counterparts. Ileum and jejunum from lean and obese Zucker rats were harvested, fixed in buffered formalin overnight, processed, and embedded in paraffin. Thin cross sections of the tissues were mounted on slides, stained with H&E followed by analyses of longitudinal and circular smooth muscle layer thicknesses using digital photos and FIJI/IMageJ software (version 1.5). Smooth muscle thickness data was exported from an Excel document and statistics performed utilizing GraphPad Prism (version 6.0). In addition, ileum from lean and obese Zucker rats was harvested, bisected lengthwise with the lacteals facing up, and fixed in 4% PFA overnight and then washed with sucrose solutions. The ileum tissues were pinned onto 6‐well silicone plates and strips of villi (1‐2 thick) were cut under a dissecting microscope. The villi strips were incubated with a LYVE‐1 antibody to identify lymphatic endothelial cells of the lacteals and a PECAM‐1 antibody to label microcirculation within the villi. Longitudinal and circular smooth muscle layers, identified in the ileum with H&E staining, were significantly thicker in 8‐week old obese Zucker rats compared to lean rats. No significant differences in smooth muscle thickness were observed in 12‐week or 26–32‐week old obese versus lean rats in either the ileum or the jejunum. Histological data obtained from the small intestine partially supports the hypothesis that intestinal smooth muscle layer thickness in obese juvenile Zucker rats was greater, but only at the 8‐week time point. Preliminary immunolabeling with LYVE‐1 positively identified the structure of the lacteal, while the PECAM‐1 labeling was strong within the microvasculature of the villi. Although additional studies with human tissue, e.g., samples derived from intestinal biopsies or surgical resection, are required to understand the biomedical significance of our findings, our data raise the possibility that for humans at a young age obesity may cause structural changes in the small intestine.Support or Funding InformationThis work was supported by an APS IOSP Undergraduate Summer Research Fellowship IOS‐1238831.

Characterization of Ta-B-C nanostructured hard coatings

Microstructure and mechanical properties of Ta-B-C nanocrystalline layers prepared by magnetron sputtering were studied. DC magnetron sputtering was used to prepare thin layers on rotated substrates. Various deposition parameters were tested. Microstructure of layers was studied by means of scanning and transmission electron microscopy on thin lamellar cross sections prepared using a focussed ion beam. Both undisturbed layers and the volume under relatively large indentation prints (load of 1 N) were observed. The microstructure observations were correlated with mechanical properties characterized by means of nanoindentation experiments in both the static and the dynamic loading regime. Elastic modulus, indentation hardness and fracture resistance of prepared nanostructured coatings were evaluated and discussed.

Unusual twig "twistiness" in pawpaw (Asimina triloba) provides biomechanical protection for distal foliage in high winds.

Deciduous woody species invest considerable resources in the growth of new foliage and distal stems. This new growth is at risk for mechanical damage from high winds and storms. Pawpaw has large leaves borne distally on thin twigs. Following a storm, pawpaw branches sometimes exhibit a persistent "flipped" orientation, slowly returning upright over 24 h. We investigated biomechanical properties of pawpaw twigs, comparing them to co-occurring species with similarly high leaf areas and loads, which do not exhibit this "flipping". Our goal was to determine biomechanical and structural properties in these species and how variation in form might relate to functional differences. We measured flexural stiffness, torsional stiffness, and viscoelastic creep in pawpaw and co-occurring trees Liriodendron tulipifera and Carya cordiformis. We also recorded twig/foliage reconfiguration in high winds. We stained thin cross sections of distal twigs and recorded images using fluorescent light microscopy. Flexural and torsional stiffness increased with twig radius in pawpaw and tulip tree, although torsional stiffness increased more slowly in pawpaw. Pawpaw had a high ratio of flexural to torsional stiffness (EI/GJ) across a range of twig radii and significant viscoelastic creep compared with the other species. Biomechanical data showed that pawpaw twigs were "twistier" than the comparison species, which were shown previously to alleviate drag-induced damage by reorienting petioles and leaves. Pawpaw has an unusual strategy of low torsional stiffness in twigs, allowing for reorientation of the entire distal appendage, likely minimizing drag-induced damage in storms.

Minimum Longevity and Growth of the Invasive Green Anole,Anolis carolinensis, in Chichi-jima of the Ogasawara Islands, Japan

Abstract: We studied the longevity and growth pattern of the wild populations of invasive green anoles (Anolis carolinensis) in Chichi-jima Island, Japan. We estimated specimen age using skeletochronology and counted the number of lines of arrested growth (LAGs) on thin cross sections of femur bones. We observed from zero to five of LAGs for both male and female specimens. This indicated that the green anoles can survive at least five years in Chichi-jima Island. Body size increased with the number of LAGs, but the growth rate decreased when individuals had two LAGs. Our results suggest that the wild anoles might expend more energy for reproduction rather than for growth at this stage.

Structural characterization of rat ventricular tissue exposed to the smoke of two types of waterpipe.

this study focused on the effect of waterpipe smoke exposure toxicity on the structure of albino rat's ventricular tissue and their recovery. Albino rats were divided into three groups: control, flavored, and unflavored. The control group was exposed to normal air while the flavored and unflavored groups were exposed to waterpipe smoke for a period of 90 days. Each group was followed by a period of 90 days of fresh air exposure. Following each period, the ventricular tissue was removed for biochemical and histopathological studies. The ventricular tissues of waterpipe exposed rats showed some degree of separation between cardiac muscle fibers, infiltration of lymphocytes, and congestion of blood vessel. Also, thin cross sections of ventricular cells revealed pleomorphic mitochondria with partially disrupted cristae, partial disruption of the myofibrils, and deposited toxic materials. The unflavored waterpipe has more deleterious effects on heart ventricular tissues than the flavored one. Waterpipe smoke didn't induce apoptosis in the ventricular tissue. We also found very high levels of plasma thiocyanate after exposure to smoke in the flavored and unflavored groups, while the control group showed no increase. After the recovery period, those tissues showed partial recovery. Waterpipe smoke induces structural changes in the heart ventricle tissues, causing a negative impact on the capacity of the cardiac muscle for pumping blood and may lead to heart attack due to accumulation of free radicals and tissue inflammation. Cessation of smoking is important in returning most of these changes to their normal structure.

Machinability Studies in Drilling of Inconel 718 Super Alloy

Inconel 718, a Nickel based superalloy is widely used for aerospace applications mainly due to its high temperature resistance and high strength to weight ratio. Its poor machinability is a limiting factor in commercial, cost intensive applications. This paper investigates the machinability of Inconel 718 in high speed drilling. The impact of the material on thrust forces, torque and chip microstructure have been measured at four different cutting speeds – 19, 27,43 and 67 m/min. The high tensile strength coupled with low thermal conductivity compounds the machining process. The thrust forces decrease with cutting speed, but the torque fluctuates at intermediate cutting speeds. Chip formation is continuous across cutting speeds, with thin cross sections and evidence of saw tooth edges. Inconel work hardens more than titanium alloys and shows good ductile to brittle transition at low temperatures creating chips of lesser length as observed using scanning electron microscopy.

Current-voltage characteristics of manganite-titanite perovskite junctions.

After a general introduction into the Shockley theory of current voltage (J–V) characteristics of inorganic and organic semiconductor junctions of different bandwidth, we apply the Shockley theory-based, one diode model to a new type of perovskite junctions with polaronic charge carriers. In particular, we studied manganite–titanate p–n heterojunctions made of n-doped SrTi1−yNbyO3, y = 0.002 and p-doped Pr1−xCaxMnO3, x = 0.34 having a strongly correlated electron system. The diffusion length of the polaron carriers was analyzed by electron beam-induced current (EBIC) in a thin cross plane lamella of the junction. In the J–V characteristics, the polaronic nature of the charge carriers is exhibited mainly by the temperature dependence of the microscopic parameters, such as the hopping mobility of the series resistance and a colossal electro-resistance (CER) effect in the parallel resistance. We conclude that a modification of the Shockley equation incorporating voltage-dependent microscopic polaron parameters is required. Specifically, the voltage dependence of the reverse saturation current density is analyzed and interpreted as a voltage-dependent electron–polaron hole–polaron pair generation and separation at the interface.

Materials, Techniques, and Conservation of Historic Stained Glass “Grisailles”

A grisaille is a brown‐blackish paint applied onto the inner surface of stained glass to draw the contours and details of the figures and to produce the effect of shades and volumes. Grisailles were traditionally made of finely ground oxides of iron but also of copper, zinc, lead, or manganese mixed with a flux such as lead ground glass and a binder and fixed onto the flat glass by firing. The grisailles have typical layer thickness varying between 10 and 100 μm and are formed by a complex mixture of pigment particles, crystalline, and amorphous reaction compounds, aging, and weathering compounds. The high brilliance, collimation, energy selection, and monochromacity of the SR beam are ideal to obtain micro‐XRD patterns from thin cross sections of the grisailles. The analyses are complemented with SEM‐EDX and LA‐ICPMS. A selection of grisailles from several cathedrals and buildings in Spain, Avila, Burgos, Alcalá de Henares, and in particular from Segovia, dating from early 16th to the 20th century and belonging to several master glaziers are studied. Changes in the methods of production and materials in the different historical periods are obtained and also related to the conservation state of the materials.

Infrared and Raman spectroscopic methods for characterization of Taxus baccata L. – Improved taxane isolation by accelerated quality control and process surveillance

Different yew species contain poisonous taxane alkaloids which serve as resources for semi-synthesis of anticancer drugs. The highly variable amounts of taxanes demand new methods for fast characterization of the raw plant material and the isolation of the target structures during phyto extraction. For that purpose, applicability of different vibrational spectroscopy methods in goods receipt of raw plant material and in process control was investigated and demonstrated in online tracking isolation and purification of the target taxane 10-deacetylbaccatin III (10-DAB) during solvent extraction. Applying near (NIRS) and mid infrared spectroscopy (IRS) the amount of botanical impurities in mixed samples of two different yew species (R2=0.993), the leave-to-wood ratio for Taxus baccata material (R2=0.94) and moisture in dried yew needles (R2=0.997) can be quantified. By partial least square analysis (PCA) needles of different Coniferales species were successfully discriminated by Attenuated Total Reflectance-Fourier-Transform Infrared Spectroscopy (ATR-FT-IR). The analytical potential of ATR-FT-IR and Fourier Transform-Raman Spectroscopy (FT-RS) in process control of extraction and purification of taxanes is demonstrated for determination of the water content in methanolic yew extracts (R2=0.999) and for quantification of 10-DAB (R2=0.98) on a highly sophisticated level. The decrease of 10-DAB in the plant tissue during extraction was successfully visualized by FT-IR imaging of thin cross sections providing new perspectives for process control and design.

Bucklings interactions in columns made by built-up thin, open, pultruded FRP shapes

This research evaluates the presence of buckling modes in built-up columns made from pultruded fiber reinforced polymer (FRP) profiles when flexural instability is coupled with torsional instability. This phenomenon is already well known in the field of steel construction and is tested and emphasized with the use of thin walled open cross sections of pultruded FRP materials in testing to analyze the effects of local buckling due to FRP’s orthotropy and high deformability. Also through previous tests on columns made by singular “C” shapes that create the built-up columns tested, the study presents the confidence between experimental results for the pultruded FRP built-up columns and the available formulas for calculating the expected buckling interactions. The investigation shows that torsional-flexural buckling is confirmed but is also combined with a local buckling that first influences the buckling interactions. From a practical application point of view, the study examines a comparison between experimental and formulation characterization of buckling analysis with open cross sections assumed as equivalent to the built-up cross sections. The ratio between the different critical loads and their chronology to collapse is described.

Seismic performance comparison of thin steel shear wall and cross brace by Non-linear static analysis

Steel shear wall system has been rapidly paid into attention as a resistant system against lateral loads within 3 recent decades. This system also is used for construction and retrofitting of important buildings entire the world particularly in seismicity countries such as Japan and the US. In addition, during the recent years, seismic design of the structures through changing design criterion from resistant methods to performance has been considerably welcomed by engineering society. For evaluation of constructed structures based on prior regulations, structures design regulations (regulation 2800) cannot be used and such instructions as instruction for seismic rehabilitation should be employed which evaluate and rehabilitate the structures using performance-based design concept. In present study, general performance parametric assessment of Intermediate Steel Moment Frame was carried out along with evaluation of thin Steel Shear Wall (SSW) and convergent cross brace. For this purpose, several steel frames were modeled using SAP 2000 software package. Performance assessment of each frame was conducted using non-linear static analysis or Push Over and performance point of each frame was specified using the concepts capacity spectrum and demand spectrum.

038 バウシンガー効果を考慮した薄肉断面フレームの軸圧壊特性予測

038 バウシンガー効果を考慮した薄肉断面フレームの軸圧壊特性予測

圆环杆与平板连杆的适合光路集成的二维正方晶格光子晶体

圆环杆与平板连杆的适合光路集成的二维正方晶格光子晶体

Anatomical, palynological and micromorphological study of seed, trichome and stomata of Cardaria draba L. Desv (Brassicaceae) in Sistan, Iran

In the present research, the anatomical study of leaves, stems, roots, besides palynological and micromorphological studies of seeds, trichome and stomata of Cardaria draba L. Desv (Brassicaceae) was carried out. This study, similar to other related studies was performed not only to improve knowledge of C. draba characteristics, but also to achieve systematic goals. In order to carry out anatomical studies, very thin cross sections of the above specified parts were manually prepared. After double staining of the leaf, stem and root parts, the results indicated that leaf midrib and mesophyll, petioles, the side stems and roots exhibited irregular semicircle, isobilateral, trilateral petioles, and bulge with thick cuticles, respectively. However, for micrmorphological evaluations, the scanning electron microscopy was used. From the present study, it can be safely suggested that the stomata type was anisocytic, and trichomes were non-glandular, single-celled, conical and warty. Moreover, pollen type was tricolpate and prolate. The overall shape of mericarp was trigonous, prolate spheroidal whereas surface mericarp ornamentation was reticulate and wrinkled.

An Optical Topographic Technique to Map the 3-D Deformed Profile of a Convex Lens under External Loading

A novel laser-aided topographic apparatus has been designed and constructed to capture the deformed profile of a hydrogel convex shell (contact lens) under an external load. A laser sheet illuminates a thin cross section of the deformed shell and scans the entire lens from one side. Two side cameras fixed on opposite sides of the sample contact lens and perpendicular to the laser sheet record the 3-dimensional geometry. The contact lens rests on the circular shoulder, while the loading shaft is lowered to a desirable depth, w 0, along the optical axis. The applied load, F, and vertical displacement of the shaft, w 0, are measured simultaneously with the video recording showing the progressive changes in indentation dimple radius, a, and the shell profile, w(r). The mechanical behavior is consistent with a previously developed solid mechanics model, and material parameters such as elastic modulus can be deduced.

High performance steel fibre reinforced concrete: residual behaviour at high temperature

Steel fibre reinforced concrete (SFRC) is considered as a profitable replacement for diffused reinforcement like welded steel mesh, especially for thin cross sections. In case of precast light roof elements, fire becomes a very important condition in the design. A previous experimental programme showed the benefits of steel fibre for fire resistance of bent members when macro-fibres (\(l_{\rm f}= 30\) mm; \(l_{\rm f}/d_{\rm f}=\) 45) are used with reduced contents (content by volume of 0.6 %). The interest to reduce the weight and to prevent the need of any water proofing membrane has suggested to use fibre reinforced high performance material. The material selected was also chosen self-compacting in order to be able to orient straight steel micro-fibres (\(l_{\rm f}= 13\) mm; \(l_{\rm f}/d_{\rm f}=\) 81) in the best direction just controlling the casting flow direction properly. The fibre content selected is equal to 100 kg/m3 (content by volume of 1.2 %), regarded as a minimum quantity to guarantee a safe hardening behaviour for thin elements in direct tension. The material has a cylindrical compressive strength of about 110 MPa. An experimental programme on prismatic specimens has been planned to investigate the behaviour of high perfomance cementitious composite reinforced by micro-fibres, when exposed to high temperatures. A third point bending set-up was adopted. The mechanical characterization was performed after thermal cycles up to three different thermal thresholds (200, 400 and 600 °C). Each thermal cycle was carried out in an electric furnace, by imposing a heating rate of 50 °C/h up to the maximum temperature, a two hours of stabilization phase, and a subsequent cooling at 25 °C/h. The tests confirmed the material as hardening in bending up to 400 °C. Moreover, the behaviour of the fibres were studied testing them at the same thermal damage level.

Simulation of Roundness, Hardness and Microstructure of Bearing Rings with Thin Cross Sections by Using Sysweld

The roller bearing is a component which helps to reduce friction on relative rotational or sliding movements of the machine parts. Nowadays, there are many kinds of rolling bearings whose production is constantly improving due to increasing demands on the mechanical properties and durability. An important and necessary step in the production of rolling bearings is the heat treatment. Technological heating process must be created rationally for the required mechanical properties such as hardness, toughness and also dimensional accuracy all with respect to the economic efficiency. Because of the economical demands, simulation software is increasingly beginning to be used in the projection of heat treatment. This simulation software can predict metallurgical and mechanical properties of components after heat treatment, and thus it is easier to select the optimal material design, heat treatment process and it can possibly identify construction deficiencies in the selected part. For simulation of the heat treatment the SWYSWELD software from ESI group was used. As the output value after the simulated heat treatment (quenching) was hardness, composition of microstructure, roundness and residual stresses. These results of the simulation were then compared with the real measured values [1, 2 and 3].

Optimization of thin noise barrier designs using Evolutionary Algorithms and a Dual BEM Formulation

This work aims at assessing the acoustic efficiency of different thin noise barrier models. These designs frequently feature complex profiles and their implementation in shape optimization processes may not always be easy in terms of determining their topological feasibility. A methodology to conduct both overall shape and top edge optimizations of thin cross section acoustic barriers by idealizing them as profiles with null boundary thickness is proposed. This procedure is based on the maximization of the insertion loss of candidate profiles proposed by an evolutionary algorithm. The special nature of these sorts of barriers makes necessary the implementation of a complementary formulation to the classical Boundary Element Method (BEM). Numerical simulations of the barriers׳ performance are conducted by using a 2D Dual BEM code in eight different barrier configurations (covering overall shaped and top edge configurations; spline curved and polynomial shaped based designs; rigid and noise absorbing boundaries materials). While results are achieved by using a specific receivers' scheme, the influence of the receivers' location on the acoustic performance is previously addressed. With the purpose of testing the methodology here presented, a numerical model validation on the basis of experimental results from a scale model test [34] is conducted. Results obtained show the usefulness of representing complex thin barrier configurations as null boundary thickness-like models.