A family of noniterative integration methods with desired numerical dissipation

A new family of unconditionally stable integration methods for structural dynamics has been developed, which possesses the favorable numerical dissipation properties that can be continuously controlled. In particular, it can have zero damping. This numerical damping is helpful to suppress or even eliminate the spurious participation of high frequency modes, whereas the low frequency modes are almost unaffected. The most important improvement of this family method is that it involves no nonlinear iterations for each time step, and thus it is very computationally efficient when compared with a general second‐order accurate integration method, such as the constant average acceleration method. Copyright © 2014 John Wiley & Sons, Ltd.     

Effect of postweld treatment on the fatigue crack growth rate of electron-beam-welded AISI 4130 steel

This article studies the effect ofin-chamber electron beam and ex-chamber furnace postweld treatments on the fatigue crack growth rate of electron-beam-welded AISI 4130 steel. Mechanical properties of the weldment are evaluated by tensile testing, while the fatigue properties are investigated by a fatigue crack propagation method. Microstructural examination shows that both postweld treatments temper the weldment by the appropriate control of beam pattern width, input beam energy, and furnace temperature. In addition, the ductility, strength, and microhardness of the weldment also reflect this tempering effect. The fatigue crack growth rate is decreased after both postweld treatments. This is mainly caused by the existence of a toughened microstructure and relief of the residual stress due to the fact that (1) the residual stress becomes more compressive as more beam energy is delivered into the samples and (2) postweld furnace tempering effectively releases the tensile stress into a compressive stress state. Formerly Lecturer, Department of Mechanical Engineering, Chung Cheng Institute of Technology     

PERFORMANCE OF A WETTED-WALL SHEET BUNDLE COLUMN

The performance of a wetted-wall sheet bundle column with vertically aligned sheets placed inside as liquid film supports was investigated as an alternative to a wetted-wall fiber bundle column used for gas and liquid contacting. It avoids or simplifies some of the design problems associated with using fibers and still retains the advantages possessed by the fibers such as low pressure drop and high mass transfer coefficient. A comparison with the conventional Raschig ring packings and stainless steel tube bundles show that the fibers and sheets which were made of light weight material has definite advantages in reducing the weight and cost of the packing material in the column substantially     

Effect of the second filler which melted during composite fabrication on the electrical properties of short fiber polymer-matrix composites

This paper presents a method for greatly enhancing the electrical conductivity and electromagnetic interference shielding effectiveness of short conducting fiber filled polymers. This method involves the addition of a small proportion of metal particles as a second filler to the fiber polymer-matrix composite. The key to the method is that the metal particles melt during the composite fabrication, so that the metal electrically connects the metal-coated carbon fibers to a certain degree, thereby resulting in a partially connected three-dimensional network. By adding 2 vol% tin-lead particles to 20 vol% short nickel-coated carbon fiber filled polyether sulfone, the electrical resistivity was decreased by a factor of 2000, while the shielding effectiveness at 1 GHz was increased from 19 to 45 dB. No such improvement was found for the same volume fraction of tinlead particles added to an uncoated carbon fiber composite. This difference is due to the superior wetting of solder with nickel compared to that of solder with carbon, as shown by contact angle measurements. This paper is an extended version of a paper presented at the 6th Int. SAMPE Electron. Mater, and Processes Conf., June 1992.     

Gas absorption with or without chemical reaction in laminar non-newtonian falling liquid films

An analytical solution is presented for gas absorption with or without a first-order or zero-order chemical reaction in a laminar non-Newtonian power-l model falling liquid film. For physical absorption, the first ten eigenvalues, series coefficients and related quantities are computed accurately by a quasinumerical method which shows considerable improvement over previous investigations. The range of applicability of the penetration theory solution is also established to indicate in what regions will the finite film thickness and complete velocity profile be important in determining the absorption rate. It is found that the range of dimensionless axial contact length X* in which the penetration theory is valid diminishes rapidly with increasi values of the power-law index n. For chemical absorption, the solution can be obtained by a linear superposition principle in terms of a “transie part” in which the effect of hydrodynamics within the liquid film is of importance and a “steady part” in which the reaction rate is controlling. In the “transient part” solution, the first ten eigenvalues and related quantities are reported for a variety of values of n and the dimensionl reaction rate parameter k_l* or k₀*. Certain asymptotic solutions from the penetration theory are also given and their range of applicab estimated. For any given n, it is estimated that only when k₁* or k₀* is less than approximately 10 will the finite film thickness and velocity profile have any effect on the absorption rate as compared to that calculated from the penetration theory with chemical reaction. The non-Newt character of the liquid film also has a significant influence on the absorption rate. At a fixed X*, the absorption enhancement due to reaction is when n = ∞ and is smallest when n = 0. The solutions obtained in this work are useful either for predicting absorption rates or for deter molecular diffusivity (and reaction rate constant) of gases in non-Newtonian falling liquid films.