Structural modeling and analysis of FRP composite product subsystems—A systems approach

This study derives a new mathematical model aimed to consider virtual design and manufacturing procedures for developing highly competitive, complex geometry composite products for various engineering applications. The fiber‐reinforced polymer (FRP) composite industry faces several critical issues right from selection (of product, process, equipment, tooling, materials) to manufacturing the final products by meeting several design criteria and customer requirements. An attempt has been made in this article to identify different subsystems and other constituents of five main systems–resin system, reinforcement system, process equipment, tooling system, and product design of total composite product system. Intermediate processes, alternative designs, process sequence, technological changes, chemical reactions, and other performance affecting parameters have been discussed. Graph theoretical models, variable permanent adjacency matrix models, and permanent functions of these systems based on graph theory–matrix algebra–permanent function methodology are developed. Analytical tests for structural analysis of composite product system are derived to select optimum constituents in each of these five systems of composite product. Coefficient of similarity and dissimilarity are useful aid to take right decision between alternative solutions. Permanent function is a unique representation and to be used by composite industry for coding, evaluation, comparison, ranking, and optimum selection. Structural models are useful for basic understanding of complete composite product system, leading to right decisions for manufacturing and business strategies. Step‐by‐step procedure is developed to assist composite industry to implement the proposed method in a right way. Usefulness of the proposed methodology to composite industry is also presented. POLYM. COMPOS., 27:681–699, 2006. © 2006 Society of Plastics Engineers     

Phase formation, microstructure and magnetic properties investigation in Cu and Fe substituted SmCo5 melt-spun ribbons

Magnetic properties and microstructure were investigated in Sm_17.24Co_66.20Cu_8.28Fe_8.28 ribbons melt-spun at different wheel speeds of 5, 15, 30, 40 and 50 m/s. X-ray diffraction studies revealed that the ribbons melt-spun at lower wheel speed (<15 m/s) were comprised of three phases viz. SmCo₇, Sm₂Co₇ and SmCo₅, while higher wheel speed ribbons exhibited single phase SmCo₅. The coercivity was found to increase with increase of the wheel speed. A high coercivity of 33 kOe was obtained in ribbon prepared at 50 m/s.     

Spectroscopic and 1.06 μm laser properties of Nd-doped K–Sr–Al phosphate and fluorophosphate glasses

Optical absorption, fluorescence and decay curves for the ⁴F_3/2 level of Nd³⁺ ions in phosphate (P₂O₅–K₂O–SrO–Al₂O₃) and fluorophosphate (P₂O₅–K₂O–SrO–Al₂O₃–AlF₃ and P₂O₅–K₂O–SrO–Al₂O₃–BaF₂) glasses doped with three concentrations (0.1, 1.0 and 2.0 mol%) of Nd³⁺ ions have been investigated. The Judd–Ofelt (JO) theory has been applied to the absorption spectra of 1.0 mol% Nd³⁺-doped glasses to derive JO intensity parameters which are in turn used to calculate the radiative properties of the Nd³⁺ ion fluorescent levels. The assigned energy level data of Nd³⁺ (4f³) ions are analysed in terms of a parametrized free-ion Hamiltonian model that consists of 20 interaction parameters of atomic nature. The stimulated emission cross section and branching ratios have been calculated using the emission spectra. The relatively higher branching ratio for ⁴F_3/2 → ⁴I_11/2 transition shows the suitability of these glasses for laser application. It is interesting to note that the measured decay curves of the ⁴F_3/2 level remain nearly single exponential even for higher Nd³⁺ ion concentration but with shortening of lifetime.     

Abrasive slurry wear behavior of stainless steel surface produced by plasma transferred arc hardfacing process

Abrasive slurry wear is generally defined as a mechanical interaction in which material is lost from a surface which is in contact with a moving particle-laden liquid. Slurry wear abrasion occurs in extruders, slurry pumps, and pipes carrying slurry of minerals and ores in mineral processing industries. The life of components used under slurry abrasion conditions is governed by the process parameters, properties of the abrasive particles in the slurry and the material properties. This paper analyzes in detail the effects of operating variables such as abrasive particle size, slurry concentration, speed of rotation and slurry bath temperature on the abrasive slurry wear behavior of a stainless steel surface produced by Plasma transferred arc (PTA) hardfacing process. Of the four variables considered in this investigation, it is found that the slurry concentration has a predominant effect on wear rate of hardfaced surfaces compared to other variables. Microstructural analyses of the worn surfaces were carried out using SEM. Both experimental and mathematical investigations show that the wear resistance of the PTA hardfaced stainless steel surface is four times better than that of the carbon steel substrate.     

Synthesis and characterization of electrodeposited Ni-Pd alloy electrodes for methanol oxidation

A wide compositional range of Ni-Pd alloy catalysts were prepared by electrodeposition for use as anode materials for methanol oxidative fuel cells in alkaline conditions. Structural characterization of the electrocatalysts in their as-plated condition revealed that the Ni-Pd catalysts synthesized were nanocrystalline, single phase, face centered cubic materials, indicating the formation of complete solid solution in the alloy. Compositional analysis of the alloys indicated that the palladium composition of the alloy increased with decrease in current density. This change in the composition of the alloy resulted in a shift in the X-ray diffraction peaks. The percentage shift in the d-spacing calculated from X-ray diffraction is in good agreement with percentage of palladium in the alloy. The electrocatalysts prepared are active for methanol oxidation in alkaline medium.     

Developing an Empirical Relationship to Predict Tensile Strength of Friction Stir Welded AA2219 Aluminum Alloy

AA2219 aluminum alloy (Al-Cu-Mn alloy) has gathered wide acceptance in the fabrication of lightweight structures requiring a high strength-to-weight ratio and good corrosion resistance. Friction stir welding (FSW) process is an emerging solid state joining process in which the material that is being welded does not melt and recast. This process uses a nonconsumable tool to generate frictional heat in the abutting surfaces. The welding parameters such as tool rotational speed, welding speed, axial force, etc., and tool pin profile play a major role in deciding the joint strength. An attempt has been made to develop an empirical relationship between FSW variables to predict tensile strength of the friction stir welded AA2219 aluminum alloy. To obtain the desired strength, it is essential to have a complete control over the relevant process parameters to maximize the tensile strength on which the quality of a weldment is based. Therefore, it is very important to select and control the welding process parameter for obtaining maximum strength. To achieve this various prediction methods such as response surface method (RSM), analysis of variance (ANOVA), Student’s t-test, coefficient of determination, etc., can be applied to define the desired output variables through developing mathematical models to specify the relationship between the output parameters and input variables. Four factors, five levels central composite design have been used to minimize number of experimental conditions. The developed mathematical relationship can be effectively used to predict the tensile strength of FSW joints of AA2219 aluminum alloy at 95% confidence level.     

Tribo‐investigation of PEEK‐short carbon fibre composites in severe testing conditions

A series of composites of polyetheretherketone (PEEK) containing short carbon fibre (CF) in the range of 0–30% (w/w) was developed. Their wear behaviour in low amplitude oscillating wear (LAOW) mode was studied under various operating parameters such as load and temperature. The LAOW mode was studied in ball‐on‐plate configuration against steel (100 Cr 6) at ambient temperature and at 100°C. In this mode, the coefficient of friction (µ), specific wear rate (Ko) and limiting loading pressure‐sliding speed (PV) values were investigated. It was observed that with increase in %CF, the wear performance and utility of PEEK (limiting PV value) improved significantly. Thirty percent CF was best performing composite in all aspects. The µ, however, was hardly influenced with the inclusion of CF or variation in operating parameters. The same composites were also evaluated in abrasive wear mode to study the influence of severe operating conditions on wear and friction performance. In this wear mode, the CF‐filled composites showed poorer wear resistance than did neat PEEK. The specific wear rate was correlated with strength properties and it was observed that these composites closely followed the predictions of the Ratner–Lancaster plot. Scanning electron microscopy was used to examine the microstructural features of worn surfaces. Copyright © 2007 John Wiley & Sons, Ltd.     

Similarities of stress concentrations in contact at round punches and fatigue at notches: implications to fretting fatigue crack initiation

A linear elastic model of the stress concentration due to contact between a rounded flat punch and a homogeneous substrate is presented, with the aim of investigating fretting fatigue crack initiation in contacting parts of vibrating structures including turbine engines. The asymptotic forms for the stress fields in the vicinity of a rounded punch-on-flat substrate are derived for both normal and tangential loading, using both analytical and finite element methods. Under the action of the normal load, P , the ensuing contact is of width 2 b which includes an initial flat part of width 2 a . The asymptotic stress fields for the sharply rounded flat punch contact have certain similarities with the asymptotic stress fields around the tip of a blunt crack. The analysis showed that the maximum tensile stress, which occurs at the contact boundary due to tangential load Q , is proportional to a mode II stress intensity factor of a sharp punch divided by the square root of the additional contact length due to the roundness of the punch, Q /(√( b − a )√ π b ). The fretting fatigue crack initiation can then be investigated by relating the maximum tensile stress with the fatigue endurance stress. The result is analogous to that of Barsom and McNicol where the notched fatigue endurance stress was correlated with the stress intensity factor and the square root of the notch-tip radius. The proposed methodology establishes a 'notch analogue' by making a connection between fretting fatigue at a rounded punch/flat contact and crack initiation at a notch tip and uses fracture mechanics concepts. Conditions of validity of the present model are established both to avoid yielding and to account for the finite thickness of the substrate. The predictions of the model are compared with fretting fatigue experiments on Ti–6Al–4V and shown to be in good agreement.     

Atom probe field ion microscopy investigation of boron containing martensitic 9 pct chromium steel

The chemical compositions of the ferrite matrix and various other phases in an Fe-0.17 C-9 Cr-1.55 Mo-0.27 V-0.015 N-0.01B (mass pct) steel in as-received and crept conditions were measured with atom probe field ion microscopy (APFIM). The results showed the presence of some residual boron within the ferrite matrix. Analyses showed that boron was distributed within M₂₃C₆, M₆C, MX, and Laves phases. Phosphor atoms were detected at the M₂₃C₆-ferrite interface in the crept condition. The results are compared to predictions from thermodynamic calculations.     

Atom probe field ion microscopy investigation of boron containing martensitic 9 Pct chromium steel

The chemical compositions of the ferrite matrix and various other phases in an Fe-0.17 C-9 Cr-1.55 Mo-0.27 V-0.015 N-0.01B (mass pct) steel in as-received and crept conditions were measured with atom probe field ion microscopy (APFIM). The results showed the presence of some residual boron within the ferrite matrix. Analyses showed that boron was distributed within M₂₃C₆, M₆C, MX, and Laves phases. Phosphor atoms were detected at the M₂₃C₆-ferrite interface in the crept condition. The results are compared to predictions from thermodynamic calculations. P. HOFER, formerly Graduate Student, Institute of Materials Science, Welding and Forming, Technical University Graz.