Plates Of Different Thicknesses Research Articles

Stress intensity factor solutions for spot welds in square overlap parts of cross-tension specimens of different thicknesses and materials

Closed-form stress intensity factor solutions for spot welds in square overlap parts of cross-tension specimens are investigated in this paper. The opposite outer edges of the square overlap parts of cross-tension specimens are under combined opening and counter bending conditions. The closed-form analytical structural stress solutions for a rigid inclusion in a square plate under the combined opening and counter bending conditions are first reviewed. Then, the J integral and stress intensity factor solutions for spot welds between square plates of different thicknesses and materials under the combined opening and counter bending conditions are developed in terms of the closed-form structural stress solutions for a strip model. The results of three-dimensional finite element analyses for spot welds between square plates of different thicknesses and materials under the combined opening and counter bending conditions are then presented. The analytical stress intensity factor solutions at the critical locations for spot welds based on the structural stress solutions with the equivalent and fitting coefficients are compared with the computational results. The results indicate that the computational stress intensity factor solutions agree well with those based on the structural stress solutions with only the equivalent coefficients. Based on the closed-form structural stress solutions, complete sets of the normalized in-plane stress intensity factor solutions at the critical locations of spot welds in square overlap parts of cross-tension specimens as functions of the ratio of the plate width to the spot weld diameter are presented for combinations of steel, aluminum and magnesium sheets and combinations of aluminum and copper sheets for convenient engineering applications.

Optical study of a diffuse bipolar nanosecond pulsed dielectric barrier discharge with different dielectric thicknesses in air

In this paper, a bipolar nanosecond high-voltage pulse power supply with about 20 ns rising time is employed to generate a diffuse dielectric barrier discharge using dielectric plates of different thicknesses. Dielectric thickness, which is regarded as an important discharge parameter, can improve diffuse discharge characteristics. Both the images of the diffuse dielectric barrier discharge and the optical emission spectra with different dielectric thicknesses are recorded successfully under severe electromagnetic interference. The effects of the discharge gap distance, pulse peak voltage, and pulse repetition rate on the emission intensity of N2 (C3Πu → B3Πg) of nanosecond pulsed dielectric barrier discharge with different dielectric thicknesses were investigated. It was found that increasing dielectric thickness is not conducive to acquiring a larger area of diffuse discharge. Also, the intensity of discharge decays and the discharge volume constricts in a horizontal direction with increasing dielectric thickness. The experimental result also shows that the emission intensity of N2 (C3Πu → B3Πg) decreases with the increase of the dielectric thickness and the discharge gap distance, but rises with both increasing both pulse peak voltage and pulse repetition rate.

The Numerical Method as Applied to Impact Resistance Analysis of Ogival Nose Projectiles on 6061-T651 Aluminum Plates

ABSTRACTThis research takes the resistance formula of spherical cavity expansion theory as its foundation. It establishes a predictive model of the residual velocity, ballistic limit velocity, and penetration depth of ogival nose projectiles striking metal target plates at high speed. They are aimed at 6061-T651 aluminum plates of different thicknesses using the iterative algorithm of the numerical method, thereby investigating the theoretical calculation of the residual velocity, penetration depth, ballistic limit velocity, and changes in resistance of ogival nose projectiles when making a normal impact target. In addition to analyzing the resistance undergone by the projectile nose section, this predictive model also considers the effects of friction resistance of the projectile shank section. In this research, we also used the finite element software LS-DYNA to perform a simulated analysis on the penetration depth of the aluminum plate after normal perforation by ogival nose projectiles. Ballistic test experiments were then performed using 0.30” AP (armor piercing) bullets. Finally, a comparative analysis was performed based on the theoretical model, experiments, and numerical simulation results.

Non-destructive method for evaluation of deterioration of austenitic stainless steel using initial magnetic phase

We report a novel non-destructive evaluation method (NDE) that relies on the magnetic properties of the inherent ferromagnetic phase in austenitic stainless steel (SUS) parts to assess the state of damage. The effects of the volume fraction, internal stress, and shape anisotropy of the ferromagnetic phase on the electromagnetic impedance signal used in the NDE are discussed on the basis of experimental results for cold-rolled SUS 304 steel plates of different thicknesses with and without stress relief annealing. In particular, the influence of shape anisotropy is clarified on the basis of measurements conducted on 0.5-mm-thick samples both parallel and perpendicular to the rolling direction. The results of the measurements show that the parameters obtained by the proposed method are indicative of damage.

Closed-form structural stress and stress intensity factor solutions for spot welds in square plates under opening loading conditions

Closed-form structural stress and stress intensity factor solutions for spot welds in square plates under opening loading conditions are investigated here. First, the existing analytical axisymmetric solutions for a rigid inclusion in a circular plate with simply supported and clamped outer edges are reviewed. Then the results of axisymmetrical finite element analyses for a rigid inclusion in a circular plate are presented. The results indicate that the finite element model with one element across the plate thickness is an appropriate model to investigate the structural stress solutions for a rigid inclusion in a square plate to avoid the local effect of the reaction force due to the constraint applied to the rigid inclusion. Next, the results of three-dimensional finite element analyses for a rigid inclusion in a square plate with simply supported and clamped outer edges are presented. The results indicate that, as the ratio of the plate width to the rigid inclusion diameter becomes large about 6, the structural stress solutions along the circumference of the rigid inclusion become almost uniform. Approximate equivalent radius solutions are then determined in order to use the analytical structural stress solutions for a rigid inclusion in a circular plate to calculate the structural stress solutions along the circumference of the rigid inclusion in a square plate. Then, the results of three-dimensional finite element analyses for spot welds between square plates of different thicknesses and materials are presented. The results indicate that the computational stress intensity factor solutions agree well with those based on the structural stress solutions with the equivalent radius. Based on the closed-form structural stress solutions, complete sets of the normalized stress intensity factor solutions for spot welds between square plates of different thicknesses and materials under opening loading conditions are presented for combinations of steel, aluminum and magnesium sheets and combinations of aluminum and copper sheets for convenient engineering applications.

Residual ultimate compressive strength of dented square plates

Thin steel plates are widely used in many structural applications because of its high load carrying capacity with less weight. The load carrying capacity of thin plates mainly depends on its buckling behavior which in turn is affected by the imperfections present in it. Dent is one of the common geometrical imperfections present in thin shell structures which may be formed due to mechanical damage caused by accidental loading or impact. In this work, influence of various dent parameters (dent length, dent width, dent depth and angle of orientation of the dent) on the static ultimate strength of thin square plates of different thicknesses under uniaxial compressive loading is studied. The dent is modeled on the FE surface of perfect thin square plate of size 1000mm (of different thickness) for different sizes and angles of orientation of the dent at the center of the plate. These dented plates are analyzed using non-linear static buckling analysis of general purpose FE software ANSYS V12. From the results obtained, it is found that both shorter and longer dents reduce the ultimate strength drastically. But in case of shorter dents, variation of ultimate strength of dented plates due to variation of size and angle of orientation of dents is insignificant, whereas in the case of longer dents, size and angle of orientation of dents have significant effect. It is also found that the reduction in ultimate strength of thin plates with a dent of same size and orientation increases with increase in shell thickness.

X射线硬化对面密度测量灵敏度的影响

Hardening trends of X-ray beams from three X-ray machines of different energies traversing aluminium plates of different thickness were simulated by means of Monte-Carlo method, as well as the processes of areal density measuring，and corresponding experimental researchwas done.The effects of X-ray beams hardening on the measurement sensitivity were analyzed. For the X-ray beams from X-ray machine the same energy, X-ray beams harden more with the areal density increasing, which brings about the reduction of the measurement sensitivity;The lower the energy of photons is , the more quicklythe measurement sensitivity reduces, and vice versa. For a certain areal density range, when X-ray photons can just traverse the part of the maximum areal density by adjusting the X-ray tube voltage, the best measurement sensitivity can be obtained.

Past, present and impendent hydroelastic challenges in the polar and subpolar seas

Current and emergent advances are examined on the topic of hydroelasticity theory applied to natural sea ice responding to the action of ocean surface waves and swell, with attention focused on methods that portray sea ice more faithfully as opposed to those that oversimplify interactions with a poor imitation of reality. A succession of authors have confronted and solved by various means the demanding applied mathematics associated with ocean waves (i) entering a vast sea-ice plate, (ii) travelling between plates of different thickness, (iii) impinging on a pressure ridge, (iv) affecting a single ice floe with arbitrarily specified physical and material properties, and (v) many such features or mixtures thereof. The next step is to embed simplified versions of these developments in an oceanic general circulation model for forecasting purposes. While targeted on specific sea-ice situations, many of the reported results are equally applicable to the interaction of waves with very large floating structures, such as pontoons, floating airports and mobile offshore bases.

Aerobic Biodegradation of Polyhydroxybutyrate in Compost

Aerobic biodegradation of polyhydroxybutyrate (PHB) was investigated. Mass loss experiments were performed to determine degradation kinetics. Tributyl citrate was blended with some test samples to determine the impact of a natural plasticizer on biodegradation. Effects of biodegradation in the physical, chemical, thermal, and mechanical properties of the materials tested were determined. Plates of different thicknesses (0.24, 1.2, 3.5, and 5.0 mm) were degraded to determine the effect of initial mass:initial surface area ratio on degradation rates. The mass:initial surface area is proportional to the plate thickness. PHB biodegradation rates obtained are dependent on the mass:surface area ratio. Temperature affects the relation of degradation rate to initial mass:initial surface area. PHB in plates up to a thickness of 3.5 mm can degrade completely in compost. Plates with an initial mass:initial surface area ratio of <67 will degrade in <4 months. Maximum degradation rates were obtained in plates 3.5 mm thick (1.57 mg cm−2 d−1) and the minimum in plates 0.24 mm thick (0.16 mg cm−2 d−1). Less than 14% degradation was observed in plates 1.2 mm thick with the additive tributyl citrate, compared to 100% for the plates of the same thickness without additive. No change in relative composition of molecular bonds, molecular weight, or thermal properties were observed. Impact strength of the specimens show little change until a significant loss of structure is observed.

Microscopic dose measurement with thin radiophotoluminescence glass plate

Abstract Thin RPL glass plates of different thicknesses from 170 to 1000 μm were fabricated by melting and polishing processes. The property of thin RPL glass plate was investigated by an RPL readout system based on a laser scanning microscope and a photon counting detector. The spatial resolving power of RPL image mapping was about 3 μm, owing to the limitation of laser spot size. Absorbed dose for low-energy photons generated from a 25 kV X-ray tube was effectively measured with a set of thin RPL glass plates. In a microscopic dose measurement, RPL images for alpha-rays were obtained using thin RPL glass plates. The signal-to-noise (S/N) ratio of RPL intensity was related to the determining RPL from photoluminescence. The use of thin RPL glass plate effectively improved the S/N ratio owing to reduction of the fraction of intrinsic photoluminescence in the photon counting. Therefore, the highest-contrast image for alpha-ray irradiation was successfully obtained with the thinnest RPL glass plate.

Feasibility of Raman microspectroscopic identification of biomarkers through gypsum crystals

The miniaturized Raman spectrometer is considered to be a candidate instrument for the Pasteur payload (the ExoMars mission scheduled for 2018). This mission will, for the first time, combine mobility and access to subsurface locations where organic molecules might be well preserved. Evaporitic crystals are among the potential protected habitats that have been postulated. Various concentrations of biomarkers (beta-carotene, glycine and phthalic acid) dispersed in a gypsum matrix were analyzed through transparent mineral (gypsum) plates of different thicknesses. By doing so, conditions were simulated in which biomarkers were trapped within evaporitic crystals. Using a long-working distance objective, all studied concentrations of biomarkers mixed in gypsum powder were detected. The characteristic Raman bands were easily observable for a 10% mixture of all chosen biomarkers not only through a 3.3 mm plate and but even through a 5.2 mm plate. It was possible to detect key Raman bands of 1% phthalic acid/gypsum mixture and 1% beta-carotene/gypsum mixture even through a 5.2 mm gypsum plate. The 1% beta-carotene/gypsum mixture was still clearly distinguishable through an 8.5 mm gypsum crystal due to the known resonance Raman effect of the molecule.

In Vitro Mechanical Comparison of 2.0 and 2.4 Limited-Contact Dynamic Compression Plates and 2.0 Dynamic Compression Plates of Different Thicknesses

To compare the bending structural stiffness and bending strength of thick and thin 2.4 mm limited contact dynamic compression plates (2.4 LC-DCP), 2.0 mm LC-DCP (2.0 LC-DCP), and 2.0 dynamic compression plates (2.0 DCP). In vitro mechanical study. Two thicknesses of 2.4 LC-DCP, 2.0 LC-DCP, and 2.0 DCP stainless-steel plates were tested in 4-point bending. Data were collected during bending until implants plastically deformed. Bending structural stiffness and bending strength were determined from load displacement curves. Mechanical properties were compared between plates and the effects of plate type, size, and thickness on stiffness and strength were assessed using ANOVA. The thick 2.4 LC-DCP implant was the stiffest and strongest; the thin 2.0 DCP implant was most compliant and weakest. Larger sized plates, thicker plates, and limited contact design of plates enhanced stiffness and strength. For the plates studied, plate size had a larger effect than plate type or thickness on stiffness and strength. Increasing the size (width) and thickness of plates increases both the bending structural stiffness and strength. For the plates studied, LC-DCP implants were stiffer and stronger than DCP implants. Plate bending structural stiffness and strength can be most effectively enhanced by using a larger sized plate, but gains can also be achieved by using a thicker plate and/or an LC-DCP instead of a DCP implant when possible.

Spectral dependence of the refractive index of chemical vapor deposition ZnSe grown on substrate with an optimized temperature increase

Precise measurement of the refractive index of chemical vapor deposition (CVD) ZnSe with the Fourier-transform interference refractometry method from 0.9 to 21.7microm (from 11,000 to 460cm(-1)) with 0.1cm(-1) resolution is described. For this measurement, structurally homogeneous ZnSe plates were grown on a substrate with an optimized temperature increase. Using three ZnSe plates of different thicknesses, we managed to raise the measurement accuracy of the refractive index up to 2x10(-5) (being nearly 1 order of magnitude better than the available data) in the near IR and most of the middle IR wavelength range from 0.9 to 12.5microm (wavenumber range of 11,000-800cm(-1)) and up to 1...4x10(-4) in the 12.5-21.7microm (800-460cm(-1)) region. The experimental results are approximated by a generalized Cauchy dispersion function of the 8th power. Spectral wavelength dependencies of the first- and second-order derivatives of the refractive index are calculated, and the zero material dispersion wavelength is found to be lambda(0)=4.84microm.

Spectral dependence of the refractive index of single-crystalline GaAs for optical applications

The refractive index of crystalline GaAs is measured by the method of interference refractometry in the wavenumber range from 10 500 to 540 cm−1 (or the wavelength range from 0.9 to 18.6 µm) with a resolution of 0.1 cm−1. The measurement results are approximated by the generalized Cauchy dispersion formula of the 8th power. Spectral wavelength dependences of the first- and second-order derivatives of the refractive index are calculated, and the zero material dispersion wavelength is found to be λ0 = 6.61 µm. Using three GaAs plates of different thicknesses we managed to raise the refractive index measurement accuracy up to 4 × 10−4 or 0.02%, being nearly by an order of magnitude better than the data available.

On the [formula omitted]-integral and the out-of-plane constraint in a 3D elastic cracked plate loaded in tension

In this study, the behaviour of the J x 1 -integral and its components J P -integral and J A -integral is numerically investigated for 3D linear elastic cracked plates of different thicknesses loaded in tension. Unlike the path-independent J x 1 -integral, the components J P and J A are shown to be path dependent in a region that coincides with the out-of-plane constrained zone due to the thickness effect, enabling the characterization of this zone with such integrals. The distribution of the out-of-plane components σ 33 and ε 33 in the vicinity of the crack front is also analyzed for different thicknesses and confronted to 2D solutions. In addition, a novel tensor concept of the stress intensity k ij is introduced, showing a unique structure depending on K I irrespective of the specimen thickness. It is confirmed that a pure plane strain condition close and far from the crack front is only asymptotically reached when the specimen thickness is very large when compared to the in-plane dimensions. For thin plates, it is confirmed that the 2D plane stress condition is meaningless in the neighborhood of a 3D crack front under elastic behaviour.

Texture Distribution and Plane Strain Mechanical Behavior of AA 7xxx Plates of Different Thicknesses

Texture distribution of a rolled aluminum alloy type AA 7449 plate having two thicknesses is presented here. The mechanical behavior of these aluminum alloy plates under plane strain compression (PSC) was studied under different shear stress textures. Crystallographic texture of specimens was characterized by x-ray diffraction and the corresponding volume fractions of each texture component were determined. The obtained results show that shear stress texture components are concentrated at layers immediately below the surface, as it had been previously proposed. Additionally, specimens were subjected to hot PSC to mimic industrial hot rolling process under controlled conditions. The measured rheological parameters, strain rate sensitivity coefficient m, and activation energy Q, show that the mechanical behavior under PSC is more sensitive to test conditions than to the shear stress texture.

Computational approach to photonic drilling of silicon carbide

The ability of lasers to carry out drilling processes in silicon carbide ceramic was investigated in this study. A JK 701 pulsed Nd:YAG laser was used for drilling through the entire depth of silicon carbide plates of different thicknesses. The laser parameters were varied in different combinations for a well-controlled drilling through the entire thickness of the SiC plates. A drilling model incorporating effects of various physical phenomena such as decomposition, evaporation-induced recoil pressure, and surface tension was developed. Such comprehensive model was capable of advance prediction of the energy and time required for drilling a hole through any desired depth of material.

Efficiency analysis of laser hole cutting

The efficiency analysis of laser cutting of holes into Kevlar plates is carried out and the specific energy requirement for cutting is computed for different cutting speeds and laser output power levels. The maximum laser scanning speed required for cutting Kevlar plates of different thicknesses is determined. It is found that the minimum specific energy requirements decrease with increasing hole diameter. The energy and exergy efficiencies predicted are related to the resulting cut quality and it is concluded that cutting quality improves significantly at high energy and exergy efficiencies.

Speckle suppression in laser display using several partially coherent beams

An optical scheme for speckle suppression using two or three partially coherent beams in a projection system is proposed. Diffractive optical elements (DOE) placed in the intermediate image plane create several beams carrying the image to a screen. Transparent plates of different thicknesses are placed in the Fourier plane of the projective lens and used for beam decorrelation. The coherence matrix algorithm for speckle suppression is used to calculate the speckle contrast ratio. It is shown that for a small decorrelation length and using the same maximum thickness of the transparent plates, two partially coherent beams would provide better suppression than three beams with different diffraction orders. However, for a large decorrelation length, the three beam setup provides better speckle suppression for all three colors examined with a suppression coefficient close to theoretical limits. Verification of speckle suppression using three-beam decorrelation is reported.

Thermal effects on geometrically nonlinear vibrations of rectangular plates with fixed edges

Nonlinear forced vibrations and postbuckling of isotropic rectangular plates subjected to thermal variations are studied. Geometric imperfections are taken into account since they play a fundamental role. The plate is modelled by using the Von Kármán hypothesis and the equations of motion are obtained by using an energy approach. Plates with fixed edges and additional rotational elastic constraint are considered. A pseudo-arclength continuation method is used in order to obtain numerical results. Laboratory experiments have been performed on two plates of different thickness.