Function Of Sheet Thickness Research Articles

Fracture toughness of martensitic stainless steel resistance spot welds

The paper is focused on the strength and fracture toughness of AISI420 martensitic stainless steel resistance spot welds under the tensile-shear loading. The failure behavior of AISI420 spot welds was featured by quasi-cleavage interfacial failure with low load bearing capacity and weak energy absorption capability which was a function of the weld fusion microstructure, predominately carbon and chromium rich martensite plus δ-ferrite. Fracture toughness of the fusion zone proved to be the most important factor controlling the peak load of the spot welds made on AISI420 failed in interfacial mode. A geometry-independent fracture toughness of the weld nugget (c.a. 23 MPam0.5) was determined using fracture mechanics concept. Through modeling it was found that there is a critical fracture toughness which beyond that the pullout failure mode can be obtained which is a function of sheet thickness and tensile strength of the base metal.

Analysis of crease-wrinkle interaction for thin sheets

In this paper, geometrically non-linear post-buckling analyses were performed to study the effect of sheet thickness, deployment angle, and load ratio on the crease-wrinkle interaction. A square sheet configuration with a single transverse crease was modeled using thin shell elements. The analysis proceeded by initially providing a realistic deployed state of a creased membrane sheet. Then an uneven corner loading was applied to introduce wrinkling. The effects of the induced anisotropy from the crease on the fine-scale detail of the wrinkle evolution, as a function of sheet thickness, loading, and crease deployment angle were systematically investigated. Significant differences were found in sheet compliance and crease-wrinkle interaction as these parameters were varied.

Cutting Parameters for the Reduction in Material Degradation in the Laser Cutting of Advanced High-Strength Steels

This article presents the optimum cutting conditions for advanced high-strength steel (AHSS) laser cutting. Different series of AHSSs, used in the automotive industry at present, have been tested with different laser cutting parameters. The influence of laser cutting in the material and the changes in metallurgical characteristics have been studied. The results, as expected, demonstrate very different behaviours as a function of sheet thickness, while the variation in cutting parameters due to the influence of the material is less important. The results have been divided into two large groups with thicknesses of more than 1 mm and less than 1 mm. Parameter variation inside each group mainly depends on sheet material coating. The optimum cutting areas and the quality of the cut evaluated with different criteria are presented. Finally, the best position for the laser beam has been observed to be underneath the sheet.

Kapitza resistance and thermal conductivity of Mylar at superfluid helium temperature

The Kapitza resistance and the thermal conductivity of type A Mylar sheets in the temperature range between 1.4 and 2.1 K have been determined. Four sheets with varying thickness from 37 μm to 255 μm, have been tested in steady-state condition. For a small temperature difference (10–30 mK) and heat flux density smaller than 30 Wm −2, the total thermal resistance of the sheet is determined as a function of sheet thickness and bath temperature. The Kapitza resistance is given by R K = (1.28 ± 0.08) T −3 × 10 −3 Km 2 W −1, and the thermal conductivity, κ = [(8.83 ± 0.75) + (11.73 ± 0.43) × T] × 10 −3 Wm −1 K −1.

Kapitza resistance and thermal conductivity of Kapton in superfluid helium

We have determined simultaneously the Kapitza resistance, R K, and the thermal conductivity, κ, of Kapton HN sheets at superfluid helium temperature in the range of 1.4–2.0 K. Five sheets of Kapton with varying thickness from 14 to 130 μm, have been tested. Steady-state measurement of the temperature difference across each sheet as a function of heat flux is achieved. For small temperature difference (10–30 mK) and heat flux density smaller than 30 W m −2, the total thermal resistance of the sheet is determined as a function of sheet thickness and bath temperature. Our method determines with good accuracy the Kapitza resistance, R K=(10540±444) T −3×10 −6 K m 2 W −1, and the thermal conductivity, κ=[(2.28±0.54)+(2.40±0.32)× T]×10 −3 W m −1 K −1. Result obtained for the thermal conductivity is in good agreement with data found in literature and the Kapitza resistance’s evolution with temperature follows the theoretical cubic law.

Spectral and global diffuse properties of high-performance translucent polymer sheets for energy efficient lighting and skylights.

A visible and near-IR spectral study is presented for a translucent smooth polymer sheet in which dopant particles are clear polymer with a refractive index close to that of the clear polymer host. Diffuse, specular, and total reflectance and transmittance and absorptance as a function of sheet thickness and dopant levels approach ideal behavior for lighting applications. A fourth optical parameter, side loss S(T), is introduced to fully account for the measured data. This covers radiation that is trapped by total internal reflection (TIR) and travels sideways sufficiently far, including to the sheet's edges, to miss detection on exit. S(T) has a strong spectral character, whereas total T and R spectra closely follow the spectrally flat wavelength dependence of the undoped clear sheet. Three distinct regimes are identified for the behavior with wavelength of the specular and diffuse components and are linked to rear surface TIR and side loss.

Development of an algorithm for tungsten inert gas welding of an austenitic stainless steel sheet

This paper examines the development of an algorithm for manual and robotic tungsten inert gas (TIG) welding of austenitic stainless steel sheet with a thickness of 0.9–2.0 mm. Generally, an algorithm is a means of describing an optimum course of a technological process and includes mathematical models for computation of individual quantities. In the present case the algorithm optimizes the course of TIG welding and welding parameters. It includes mathematical models for the computation of optimum welding current intensity, welding speed, energy input, arc length, gas flowrate and diameter of the non-consumable tungsten electrode as a function of sheet thickness. A general algorithm for manual and robotic welding of a butt-welded joint with a plain butt weld and a complete algorithm for four welded joints on a sheet with a thickness of 0.9–2.0 mm are stated. Conclusions are drawn and guidelines for future work are given.

Penetration of Hypervelocity Projectiles into Aluminum and Polyethylene Thin-Sheet Stacks

Nylon spheres of a nominal velocity of 3.6 km/s were penetrated into aluminum and polyethylene sheet stacks. Penetration depth, diameter of the holes produced on the sheets along the track, and mass of the recovered projectile fragments were determined to be a function of sheet thickness and spacing. As the sheet thickness decreased, but as long as the sheet spacing was sufficiently smaller than the projectile size, the results turned out to be similar to those for low-density continuous materials such as foamed polystyrene block.

Damage zone development in PVC under a multiaxial tensile stress state

The irreversible deformation mechanisms of poly(vinyl chloride) with a semicircular notch under slow tensile loading have been studied as a function of sheet thickness. Initially, core yielding was observed in the optical microscope as two families of slip lines growing from the notch surface in the centre of the specimen. The size and shape of the core yielding zone could be described by plasticity analysis. A stress-whitened zone subsequently initiated near the tip of the slip line zone. The stress whitening was caused by 1 μm voids that were visible in the scanning electron microscope. The mean stress for stress whitening was calculated to be 43.0±1.5 MPa by a plastic stress analysis of a pressure-dependent yield material. By assuming a constant mean stress along the boundary of the stress-whitened zone, the one-dimensional shift of the elastic stress distribution was obtained. At higher stresses, hinge shear and intersecting shear were observed for thick and thin sheet, respectively.

Hysteresis and Eddy Losses in Silicon Iron as a Function of Sheet Thickness

Pry and Bean have calculated energy losses in magnetic sheet materials using a simple domain model. A quantitative verification of these results for (110) [001] oriented 3.2% Si-Fe, varied in thickness from 13 to 2 mils, have been attempted. Domain wall spacings were measured visually from static Bitter patterns and calculated from measured 60 cy and dc hysteresis losses. It is pointed out that the calculated spacing must be the spacing between simultaneously moving walls and that this is several times as large as the visually observed one for the thin gauge sheets. At the thicker gauges, probably due to the skin effect, the discrepancy decreases.