Effect of axial ratcheting deformation on torsional low cycle fatigue life of lead-free solder Sn–3.5Ag

Multiaxial fatigue tests were conducted on Sn–3.5Ag solder specimens under axial/torsional loading at room temperature. It was found that the ratcheting strain increased while the fatigue life decreased with the increase of axial stress and shear strain amplitude. A power relationship of ratcheting strain rate versus fatigue life was observed. Equivalent strain approach and critical plane approaches were evaluated with fatigue life data obtained in the tests. Since those approaches excluded the consideration of the ratcheting strain and mean stress, the methods for fatigue life prediction were improper for multiaxial fatigue with ratcheting strain. Coffin model, considered the effect of ratcheting on fatigue life depending on the ratio of ratcheting strain to material ductility, brought the fatigue life predictions on non-conservative side if the ratcheting deformation was large. For this reason, a model with the maximum shear strain range and axial ratcheting strain rate was proposed as a new damage parameter. The new model could not only describe the fatigue life in torsion test, but also predicted torsional fatigue life of the lead-free solder with axial ratcheting.     

Sensitivity analysis and shape optimization based on FE–EFG coupled method

By use of 4-node isoparametric quadrangle interface element between finite element (FE) and meshless regions, a collocation approach is introduced to couple firstly FE and element-free Galerkin (EFG) method in this paper. By taking derivative of discreteness equilibrium equation at interface element with respect to design variable, a numerical method for discreteness-based shape design sensitivity analysis in interface element is obtained. The design sensitivity analysis (DSA) of coupled FE–EFG method is achieved by employing the DSA of nodal displacement at the interface element. The numerical method presented is testified by examples. It can be observed excellent agreement between the numerical results and the analytical solution. Finally the shape optimization of fillet is achieved by using coupled FE–EFG method. The result obtained show that imposing of the essential boundary condition is easy to implement, the computational time is reduced and the distortion of mesh is avoided.     

Synthesis of porous–acoustic absorbing systems by an evolutionary optimization method

Topology optimization is frequently used to design structures and acoustic systems in a large range of engineering applications. In this work, a method is proposed for maximizing the absorbing performance of acoustic panels by using a coupled finite element model and evolutionary strategies. The goal is to find the best distribution of porous material for sound absorbing panels. The absorbing performance of the porous material samples in a Kundt tube is simulated using a coupled porous–acoustic finite element model. The equivalent fluid model is used to represent the foam material. The porous material model is coupled to a wave guide using a modal superposition technique. A sensitivity number indicating the optimum locations for porous material to be removed is derived and used in a numerical hard kill scheme. The sensitivity number is used to form an evolutionary porous material optimization algorithm which is verified through examples.     

An approach for the aging process optimization of Al–Zn–Mg–Cu series alloys

A new model based on least square support vector machines (LSSVM) and capable of forecasting mechanical and electrical properties of Al–Zn–Mg–Cu series alloys has been proposed for the first time. Data mining and artificial intelligence techniques of aluminum alloys are used to examine the forecasting capability of the model. In order to improve predictive accuracy and generalization ability of LSSVM model, a grid algorithm and cross-validation technique has been adopted to determine the optimal hyper-parameters of LSSVM automatically. The forecasting performance of the LSSVM model and the artificial neural network (ANN) has been compared with the experimental values. The result shows that the LSSVM model provides slightly better capability of generalized prediction compared to back propagation network (BPN) in combination with the gradient descent training algorithm. Considering its advantages of the computation speed, unique optimal solution, and generalization performance, the LSSVM model is therefore considered to be used as an alternative powerful modeling tool for the aging process optimization of aluminum alloys. Furthermore, a novel methodology hybridizing nondominated sorting-based multi-objective genetic algorithm (MOGA) and LSSVM has been proposed to make tradeoffs between the mechanical and electrical properties. A desirable nondominated solution set has been obtained and reported.     

NOL-ring based evaluation of freeze and freeze–thaw exposure effects on FRP composite column wrap systems

Four different fiber reinforced polymer (FRP) composite column wrap systems are evaluated for durability after exposure to freeze (−15°F) and freeze–thaw conditions. Response and failure mechanisms are characterized through Naval Ordinance Laboratory-ring burst tests, short-beam-shear tests, dynamic mechanical thermal analysis and microscopy. It is shown that freeze–thaw exposure after salt soak can have a significant detrimental effect and results in reductions in both tensile strength and interlaminar shear strength. The adhesive layer used in the prefabricated adhesively bonded system is shown to be the weak link in that system with degradation and failure taking place either within the adhesive or at the adhesive–composite interface. Effects of incomplete ambient cure, pre-existing voids and process induced residual stresses are shown to be critical aspects for the other three systems. It is shown that, in comparison to the freeze–thaw conditions, sustained exposure to −15°F conditions has a much lower effect on all properties except modulus which is seen to increase due to matrix hardening and transition of material response to a predominantly brittle regime.     

Study of sulphidation of Cu–In nanoparticle precursor films with an air-stable process

The large-grained and high crystalline CuInS₂ films were prepared based on a metal-nanoparticle ink method, assisted by an air heat treatment (air-stable) process. Cu–In nanoparticles were firstly prepared in polyol by a simple chemical reducing method. And then, Cu–In nanoparticles, polyvinyl pyrrolidone, and alcohol were used to compose inks, which were drop-coated onto substrates to form precursor films. Moreover, Cu–In nanoparticle precursor films were sulphurised to form CuInS₂ films in H₂S atmosphere at different temperatures. An additional air-heat treatment (air-stable process) was also introduced before sulphurising to improve quality of the prepared CuInS₂ films. At first, grain sizes of prepared CuInS₂ were very small. And then, grain sizes of prepared CuInS₂ grew largely by sulphurising Cu–In nanoparticle precursor films with an air-stable process. Finally, XRD, Raman measurement, transmittance, absorbance spectra and Hall Effect were adopted to identify the films. The results show that the air-stable process is feasible to improve the CuInS₂ films prepared by solution-based deposition techniques.     

Optimality criteria-based topology optimization of a bi-material model for acoustic–structural coupled systems

This article investigates topology optimization of a bi-material model for acoustic–structural coupled systems. The design variables are volume fractions of inclusion material in a bi-material model constructed by the microstructure-based design domain method (MDDM). The design objective is the minimization of sound pressure level (SPL) in an interior acoustic medium. Sensitivities of SPL with respect to topological design variables are derived concretely by the adjoint method. A relaxed form of optimality criteria (OC) is developed for solving the acoustic–structural coupled optimization problem to find the optimum bi-material distribution. Based on OC and the adjoint method, a topology optimization method to deal with large calculations in acoustic–structural coupled problems is proposed. Numerical examples are given to illustrate the applications of topology optimization for a bi-material plate under a low single-frequency excitation and an aerospace structure under a low frequency-band excitation, and to prove the efficiency of the adjoint method and the relaxed form of OC.     

Real-time optimization of plug-in hybrid electric vehicles based on Pontryagin’s minimum principle

Clean Technologies and Environmental Policy - Battery aging can greatly reduce the energy efficiency of plug-in hybrid electric vehicles (PHEVs). This paper presents a novel real-time energy...     

Uncertain process–based reliability and maintenance modeling for systems under mutually dependent degradation and shock processes

For the systems that experience competing failure processes, an uncertain process–based degradation model is developed to describe the systems. The competing degradation process is composed of internal continuous degradation and external shocks, and the mutual dependence between them is considered. When the magnitude of the internal degradation exceeds the threshold, the soft failure occurs. While for the shock processes involving the randomness and the subjective information, we adopt the uncertain random renewal reward process to characterize it. Hard failure occurs when the damage of the shock process exceeds the strength threshold of the system. By using the belief reliability metric, the reliability of the degraded system is defined as the chance measure that neither soft failure nor hard failure occurs. And the effect of the degradation-shock dependence on the system reliability is performed by the parametric studies. Then the proposed degradation model is introduced into the preventive maintenance strategy to minimize the average maintenance cost. Using the microelectromechanical systems as an example, the effectiveness of the constructed degradation model and maintenance strategy is illustrated, and the proposed model can characterize the system degradation process in a superior way to the stochastic process model. These methods can be applied to other similar degraded systems and provide support for maintenance decisions.     

Cationic or anionic sites? Selectivity optimization of ion-selective electrodes based on charged ionophores

The influence of ionic sites on the selectivities of ionophore-based ion-selective electrodes (ISEs) is described on the basis of a phase boundary potential model. The discussion presented here is significantly more general than previous ones. It is formulated for primary and interfering ions of any charges and it is valid for ISEs based on electrically charged or neutral ionophores. Furthermore, it also applies to membranes that contain more than one type of complex of the primary or interfering ion. It has been believed thus far that only ionic sites of the same charge sign as the primary ion improve the selectivities of ISEs based on charged ionophores. However, it is shown here that the charge sign of the ionic sites that give the highest potentiometric selectivities depends on the charge number of the primary and interfering ions and on the stoichiometry of their complexes with the ionophore. The validity of our model was confirmed experimentally with three ISEs based on different charged ionophores. ISEs based on lasalocid or 1-(N,N-dicyclohexylcarbamoyl)-2- (N,N-dioctadecylcarbamoyl)ethylphosphonic acid monomethyl ester (ETH 5639) as the ionophore responded selectively to Sr2+ or Mg2+, respectively, and discriminated well against other alkaline earth cations when their membranes contained anionic sites. These two electrodes are the first examples of ISEs based on charged ionophores for which maximum selectivities are obtained with membranes containing ionic sites with a charge sign opposite to that of the primary ion. On the other hand, the experimental F- selectivities of membranes based on oxo(5,10,15,20-tetraphenylporphyrinato)molybdenum-(V) improved gradually when the concentration of anionic sites was increased from 0 to 75 mol%. The selectivity-modifying influence of ionic sites for these three types of ISEs can be explained by considering the different stabilities of the 1:2 ion-ionophore complexes of the primary and of the interfering ions.     

A nonprobabilistic reliability–based topology optimization method of compliant mechanisms with interval uncertainties

On account of the inevitable multisource uncertainty factors in compliant mechanisms, which seriously affect the accuracy of output motion, a nonprobabilistic reliability–based topology optimization (NRBTO) framework for compliant mechanisms with interval uncertainties is introduced. Combined with the solid isotropic material with penalization (SIMP) model and the set-theoretical interval method, the uncertainty quantification analysis is conducted to obtain mathematical approximations and boundary laws of considered mean compliance. By normalization treatment of the limit-state function, a new quantified measure of the nonprobabilistic reliability is then defined. The compliance-based NRBTO design method ensures the output motion realizing its target value accurately considering the uncertainty factors. The sensitivities of the nonprobabilistic reliability index with respect to design variables are calculated by the adjoint vector method. Two engineering examples are eventually presented to illustrate the applicability and the validity of the present problem statement as well as the proposed numerical techniques.     

Assessing the sustainability of a manufacturing process using life cycle assessment technique—a case of an Indian pharmaceutical company

Clean Technologies and Environmental Policy - Manufacturing organizations are under continuous pressure to implement sustainability in their activities. There is a need to identify the...     

Strengthening behavior of Al–Cu–Mg alloy sheet in hot forming–quenching integrated process with cold–hot dies

The novel technology combining hot forming and quenching together has been developed to improve formability and avoid thermal distortion for heat-treatable aluminum alloy forming. In this paper, cold–hot composite dies are proposed to use in hot forming–quenching integrated process. Heated lower dies are used to avoid rapid temperature decrease of heated sheet. Water-cooled upper dies are then used to accomplish quenching and reduce thermal distortion. The effects of temperature of lower dies, quenching condition and precipitate distribution on strengthening behavior in this process were investigated systematically. The strengths were measured by Vickers hardness and uniaxial tensile tests. It was found that the upper cold dies could ensure effective quenching. Lower dies could be heated to avoid rapid temperature decrease of heated sheet resulting in good strength of parts. The corresponding hardness, yield and tensile strengths were 140.7 HV, 295.7 and 469.2 MPa, respectively. For comparison, the process with both hot dies at temperatures ranging from 100 to 350 °C was investigated. The temperature of both hot dies could only be improved to 250 °C, otherwise the strength decreased. The strengthening phase was dispersed lath-shaped S phase with an average cross-section of approximately 50 × 100 nm, which was observed with TEM and SEM methods.     

Influence of preoxidation cycle on the bond strength of CoCrMoSi–porcelain dental composites

The purpose of this study was to evaluate the effect of preoxidation cycle on the shear bond strength (SBS) of CoCrMoSi alloy–porcelain dental composites. The porcelain was fired onto three types of metal surfaces: non-preoxidized, preoxidized and, preoxidized followed by grinding. The bond strength of metal–porcelain composites was investigated by the means of a shear test. The metal–ceramic interfaces and the fractured surfaces were analyzed using Optical Microscopy, Stereomicroscopy and SEM/EDS. Data was analyzed with Shapiro–Wilk test to test the assumption of normality. The t-test was used to compare shear bond strength results (p < 0.05). The analysis of the three types of surfaces was performed prior to porcelain firing. It was also performed a complementary analysis of an alumina-blasted preoxidized CoCrMoSi surface. The greater metal–porcelain adhesion was obtained for non-preoxidized specimens.Non-preoxidized specimens showed significantly (p < 0.05) higher shear bond strength than preoxidized/ground specimens, 115.5 ± 7.5 MPa and 74.8 ± 8.5 MPa, respectively. Porcelain showed no adhesion to preoxidized specimens. All preoxidized specimens exhibited adhesive failure type while non-preoxidized presented both adhesive and mixed failure types. Preoxidation heat treatment revealed a detrimental effect on the adhesion of CoCrMoSi–porcelain composites for dental restorations. Hence, in order to enhance CoCrMoSi–porcelain adhesion, the preoxidation heat treatment conditions, as performed in this study, should not be performed.     

Study on simulation method of antenna electromechanical coupling based on model reconstruction北大核心CSCD

Electromechanical coupling involving the interaction of mechanics, electromagnetics and thermotics, which has a direct impact on product's performance. Data transfer between different physical fields is the key to the electromechanical coupling simulation. An method based on model reconstruction to analyze the electromechanical coupling of microwave antenna was presented and a simulation platform was developed. In the simulation platform, firstly, the mechanical analysis was carried out by ANSYS. Secondly, the APDL language was applied to obtain and export the deformed mesh of the structural analysis, and the deformation geometric entities was reconstructed by the Non-Uniform Rational B-Spline (NURBS) theory and deformed mesh. Finally, the deformation entities were imported into the HFSS (electromagnetic field analysis software) to calculate the performance of the deformation of antenna. The waveguide slot antenna was applied to verify the correctness between the method and measurement results. The study shows that the electromechanical coupling will affect the performance of antenna. This method can be used to analyze the electromechanical coupling of antenna at design stage.     

Influence of minute amount of elements Bi, Ag and In on surface tension and soldering process performance of tin–lead based solders

A new method of measuring surface tension of liquid alloy solders, based on the interference principle between laser wave and liquid surface tension stationary wave, was employed to characterize the surface-active effect of some elements which can remarkably reduce the surface tension of liquid solders. The focus was placed on investigating the influence of minute amounts of elemental bismuth (Bi), silver (Ag) and indium (In) on surface tension and soldering process performance of tin–lead (Sn–Pb) based solders. The dependences of the surface tension of Sn–Pb solders vs. weight percentage of elements Bi, Ag and In in the solders were investigated. The experimental results showed that elements Bi and In have a strong effect on reduction of the surface tension of solders with the minute addition amount of 0.8–1.0 wt %, and the effect of element Ag is relatively weak. However, Ag has the strongest effectiveness on improving the wettability of the solders due to the comprehensive excellent function of reducing both the surface tension of liquid solders and the interface tension between liquid solder and solid base metal.     

Study on preparation of Co–Pt–W alloy films by electrodeposition

Abstract

Co–Pt–W alloy films were prepared by the electroplating method to replace costly sputtering on a copper substrate. Effects of different pH values and current densities on composition, microstructure and magnetic properties of films were investigated. With the rise in pH values, the amounts of tungsten and cobalt decrease simultaneously as a result of less tungstate oxides in higher OH– concentration solution. Almost all the deposited films were crystalline and formed fcc CoPt(111) and hcp CoPt(002). Co–Pt–W alloy films intend to change from fcc to hcp structure when the current density was >20 mA cm^?2. It was found that hcp structures of Co–Pt–W alloy films possess high coercivity performance. Moreover, higher pH values induced lower saturation magnetisation while higher current densities could result in larger saturation magnetisation. Dissimilar surface morphology could be detected under different current densities. With increasing the current density, grains of films tend to agglomerate and grow perpendicularly to substrate. Bigger agglomerated particles and ‘hill-like’ structure could be observed when the current density was up to 30 mA cm^?2.     

Study on properties of Sn–9Zn–Ga solder bearing Nd

The effects of Nd on wettability, microstructure and mechanical properties of Sn–9Zn–Ga–xNd lead-free solder were investigated. The results indicate that adding moderate amount of rare earth Nd, the wettability as well as mechanical properties of Sn–9Zn–0.5Ga solder were evidently improved, and when the content of Nd is at 0.08 wt%, the best wettability and comprehensive properties of soldered joint were obtained. It was also found that the addition of rare earth Nd could refine the microstructure of the solder, but some dark NdSn₃ phase appeared when the addition of Nd exceeded 0.15 wt%. Moreover, the IMCs thickness at the solder/Cu interface was reduced with the addition of Nd which gave a favorable influence on the mechanical property of the soldered joints.     

Evaluation of asphalt–aggregate interaction based on the rheological properties

The silicon dioxide (SiO₂) and calcium oxide (CaO) analytical reagents are selected to prepare asphalt mastics and the effects of aggregate chemical composition on asphalt–aggregate interactions (AAI) are evaluated based on the complex modulus and phase angle. It is found that the oxide analytical reagents significantly affect the rheological properties such as complex shear modulus and phase angle, and the effects of CaO are greater than SiO₂ due to the stronger interaction between asphalt binder and CaO analytical reagents. Both the modulus stiffening ratio and the phase angle-based K. Ziegel-B coefficient could be used to evaluate the AAI, and the latter is the better index. Results show that the indexes increase with the test temperature, but decrease with the loading frequency, and tend to be constant. The higher adhesive strength between asphalt binder and limestone than basalt is likely attributed to the higher content of CaO in limestone aggregate and the stronger asphalt–CaO interaction.