Identification of material model of TiN using numerical simulation of nanoindentation test

The development of the model of the multistep nanoindentation test with Berkovich indenter, accounting for the residual stress distribution, is one of the aims of the present paper. The specimen is unloaded in the intervals between the deformation steps. Substrate, which is composed of a ferritic steel and biocompatible pulsed laser deposition TiN coating, is considered. The selection of the TiN was inspired by its perspective application as the coating for a constructional element of the heart prosthesis (blood chamber and aortic valves). Sensitivity analysis of the model predictions with respect to its parameters is presented in the present paper. The theory of elastic-plastic deformations is used in the finite element model, which simulates both loading and unloading phases, accounting for the real geometry of the indent. The main goal of the present paper was to inversely analyse the tests for coating/substrate system. Square root error between measured and predicted forces is the objective function in the analysis. Results of the inverse calculations, which are presented in the present paper, may be helpful in simulations of the behaviour of TiN deposited on substrate in various applications as bionanomaterials.     

An alternative analytical solution for water-wave motion over a submerged horizontal porous plate

This study gives an alternative analytical solution for water-wave motion over an offshore submerged horizontal porous-plate breakwater in the context of linear potential theory. The matched-eigenfunction-expansions method is used to obtain the solution. The solution consists of a symmetric part and an antisymmetric part. The symmetric part is also the solution of wave reflection by a vertical solid wall with a submerged horizontal porous plate attached to it. In comparison with previous analytical solutions with respect to finite submerged horizontal porous plates, no complex water-wave dispersion relations are included in the present solution. Thus, the present solution is easier for numerical implementation. Numerical examples show that the convergence of the present solution is satisfactory. The results of the present solution also agree well with previous results by different analytical approaches, as well as previous numerical results by different boundary-element methods. The present solution can be easily extended to the case of multi-layer submerged horizontal porous plates, which may be more significant in practice for meeting different tide levels.     

Multidisciplinary topology optimization solved as a Nash game

In the present work, multidisciplinary optimization is formulated in the game theory framework. We choose a coupled heat transfer—thermoelastic system as the case study for which a topology design approach is developed. The multidisciplinary optimization problem is solved as a non‐cooperative game and we determine a Nash equilibrium. The game has two players and the parameterization of the design domain is such that the design variables describe the material density and a parameter which influences the heat flow by convection to the surrounding fluid. The first player controls the structure and the second player controls the temperature distribution in the structure. For the second player, we present mathematical proof of existence of a discrete valued optimal solution and it is concluded that no regularization of the suboptimization problem is needed. We present two numerical examples which illustrate the proposed methodology. One of the examples is also solved by weighting the objectives to a scalar valued objective function and the result is compared with the Nash game solution. Copyright © 2004 John Wiley & Sons, Ltd.     

A SIMPLE AND EFFICIENT MIXED FINITE ELEMENT FOR AXISYMMETRIC SHELL ANALYSIS

An efficient, perhaps simplest, three-noded mixed finite element is proposed for axisymmetric shell analysis. The key feature in the present formulation is to start with a better variational principle in which the independent unknowns are only the quantities that can be prescribed at the shell edges. If the consistency for field approximations is satisfied, no other numerical consideration is necessary in the present element. Several examples confirm the satisfactory numerical behaviour of the present mixed element.     

Cyclic Temperature Stress Testing of Pharmaceuticals

In a previous communication the present authors have commented on some aspects of stability testing (1). The objective of the present brief paper is to comment on the design and application of cyclic temperature stress testing for pharmaceuticals. We believe it to be timely to offer such comments now because of the present increased interest in this topic and because at present there is considerable variance in the design of such tests. It is our contention that there are some aspects of the design of cyclic temperature stress tests which could now, with considerable advantage to all concerned, be standardized and others which must be adjusted to meet the specific needs of individual drug products. The purpose of this communication is to distinguish between these two types of attribute.     

New evidence for GP zones in binary AlLi alloys

The DSC results described above are thought to present a relatively complete and persuasive picture of the characteristics of an AlLi phase which is metastable with respect to δ′. The phase is not present immediately after quenching; it appears at room temperature with kinetics that are similar to those of GP zones in other Al base alloys, it dissolves in the 75–150°C temperature range with an enthalpy typical of GP zones, and the kinetics of its dissolution are also similar to those of other GP zones. The DSC measurements are not an artifact caused by the dissolution of δ′, which is significantly more stable and which is also probably present. Finally, the existence of GP zones was predicted independently on sound theoretical grounds. According to the above results, optimum conditions for observation of the zones would be after long-term aging of a 2 to 2.5 wt% alloy in the 50 to 75°C temperature region; TEM examinations of such samples are currently underway.     

Texture formation in metal alloys with cubic crystal structures

The present paper gives a concise overview of a number of current issues in the literature on texture formation in alloys with cubic crystal structures, mainly steel and aluminium alloys. As crystallographic texture determines to a large extent the anisotropy of material properties, it is of paramount importance to understand and control the physical mechanisms by which the texture is formed in the subsequent stages of metals manufacturing processes. In the present overview three key solid-state transformation processes are considered: allotropic phase transformations, plastic deformation and recrystallisation. The intention is to highlight a number of key elements in the literature and some recent tendencies, which may provide some insight to scientists and engineers dealing with texture issues in daily practice.     

五次非线性自激系统的同宿解及其分岔

推广了双曲函数Lindstedt-Poincaré (L-P)法摄动步骤,定量求解一类派生系统含五次强非线性项的自激振子的同宿解及其分岔值。对极限环的同宿分岔参数进行摄动展开,给出同宿摄动解奇异项的定义,以消除同宿摄动解奇异项作为确定极限环同宿分岔点的条件,给出能够严格满足同宿条件的同宿轨道显式摄动解,推导出任意阶解和同宿分岔点判别的一般表达式。应用该法具体分析了一类推广的Liénard振子的同宿解和同宿分岔问题,指出方法的优点和存在的问题。算例表明,在相平面内该方法的结果与Runge-Kutta法数值周期轨道的逼近结果较吻合,相应的同宿分岔点判定值也具备较好的精度。该方法可以进一步研究推广应用于分析其它形式更一般的系统的同(异)宿解和同(异)宿分岔问题。     

Kitting and time efficiency in manual assembly

The present paper focuses on parts presentation in manual assembly. Its aim is to determine how kitting affects the time spent by the assembler fetching parts and, more specifically, what is the impact of the proportion of parts included in the kit. The present paper is based on four case studies of automobile assembly, in which parts presentation by kitting is compared with parts presentation in component racks. In the case studies, kitting enabled shorter distances between parts presentation and assembly object and thereby a potential reduction in the time spent fetching parts. However, when only a proportion of parts were kitted, the time spent fetching parts was not always reduced, in spite of this potential. The present paper finds that when deciding which parts should be kitted, attention should be paid to how and in what order assembly operations are performed.     

Evaluation of geometric efficiency and radiation exposure in z-axis for volume scan

The International Electrotechnical Commission (IEC) recommended that a display be provided on the operating console of medical computed tomography (CT) scanners when the geometric efficiency (GE) in the z-axis is 70% or less. Taking into account the increase in the number of detector rows and the changes in the scanning method, the present study was conducted to review the GE and to evaluate the exposure dose in the z-axis direction. The GE for a single-rotation scan was calculated in accordance with IEC-606024 Ed. 2. The findings of the present study suggest that 320-row area detector computed tomography volume scan (single axial scan with no table movement in which it just happened to use a very large beam width) extends 18.8 mm beyond the nominal beam collimation, even when the GE is >70%. However, compared with the helical scan, which is the present mainstream of CT examinations, the dose beyond the scan length is narrower in volume scan for a limited scan length of 160 mm or less.     

Numerical solution of the point contact problem using the finite element method

The elastohydrodynamic lubrication problem, in which the lubricant pressure and film thickness are sensitive to surface deformation, is solved by using a finite element procedure and the Newton method. The numerical procedure is applied to the point contact problem, in which a thin lubricant film is maintained between two balls loaded together by a high load under conditions of pure rolling. The present analysis shows that pressure spikes are formed near the outlet region, a result which has been found in the line contact problem and which has been conjectured in the present problem.     

On two pairs of simultaneous dual integral equations

Summary This paper considers a system of coupled pairs of dual integral equations with constant coefficients involving Bessel functions of orders zero and unity. A solution is obtained in terms of the coefficients by reducing the system to a single integral equation of the Wiener-Hopf type with both the sum and difference kernels present.A simple transformation of the system causes the coefficient of the sum kernel to vanish. The transformation leaves the Wiener-Hopf equation unaltered except for the coefficients which become complex. An equation of this type was solved by Spence in 1967. Although Spence's solution does not cover complex coefficients it can be modified to do so.The result is quoted in this paper and is used to solve the system of coupled pairs of dual integral equations of the present paper.The adhesive contact problem recently solved by Gladwell is one in which the solution technique of the present paper has proved useful.On leave of absence from the Department of Mathematics, University of Southampton.     

锈蚀钢筋混凝土结构可靠度评估

钢筋锈蚀是混凝土结构破坏最主要的原因之一,目前钢筋混凝土结构可靠度研究大多数没有考虑锈蚀的影响。提出了锈蚀钢筋混凝土结构可靠度评估方法。首先分析大气环境下和氯离子环境下钢筋锈蚀的模型,然后考虑钢筋面积和粘结强度的降低,建立锈蚀钢筋混凝土结构抗力的随机模型,最后采用一次二阶矩实用分析法计算可靠度指标,以评估大气环境下和氯离子环境下混凝土结构可靠度。两个算例表明,该方法可用于锈蚀钢筋混凝土结构可靠度评估。     

Buckling analysis for delaminated composites using plate bending elements based on higher‐order zig‐zag theory

A finite element based on the efficient higher‐order zig‐zag theory with multiple delaminations is developed. The bending part of the formulation is constructed from the concept of DKQ element. Unlike conventional elements, a developed element has its reference in the bottom surface which simplifies zig‐zag terms on formulation. Exact patch solutions are developed on elements which have the bottom reference system. The present element passes proper bending patch tests in the arbitrary mesh configurations in isotropic materials. Zig‐zag formulation is adopted to model laminated plates with multiple delaminations. To assess the accuracy and efficiency of the present element based on higher‐order zig‐zag theory with multiple delaminations, the linear buckling problem of laminated plates with multiple delaminations has been analysed. The results have been compared with three‐dimensional elasticity solutions. The present element works as an efficient tool for analysing the behaviour of the laminated composites with multiple delaminations. Copyright © 2002 John Wiley & Sons, Ltd.     

Uniform rational approximation by differential correction and remes-differential correlation

We present two self-contained programs which have given excellent results for uniform approximation of functions (or discrete data) by generalized rational functions. The first program is an extension of a program published in 1975 which uses a linear programming approach known as the differential correction algorithm. The present version is more robust, and allows for the use of a multiplicative weight function and restrictions on the values of the approximating function. These features make the program more suitable for applications such as digital filter approximation. The second program uses a combination of the Remes and differential correction algorithms which combines some of the good features of both algorithms. Given here is a discussion of the algorithms together with several examples. A FORTRAN listing can be obtained from the first author.     

一种考虑晶界能各向异性模拟晶粒长大的Monte Carlo方法

一般的Monte Carlo模型都没有考虑晶界能的差异。奉研究根据晶界两侧晶粒的取向差及其与重合晶界的关系提出了晶界能分布的连续函数表达式,并且将其应用于Monte Carlo模型模拟晶粒长大过程。引入了该能量函数的Monte Carlo模型模拟的结果显示,随着晶粒长大的进行,具有低能量的重合晶界百分数增大,同时该模型模拟的重合晶界百分数明显地强于未引入该能量函数的Monte Carlo模型模拟的结果。并且采用该模型模拟的微观组织更加接近于实际观察到的平衡组织。     

A lateral field excited liquid acoustic wave sensor

Lateral field excited (LFE) AT-cut quartz acoustic wave sensors in which the electrodes are located on the reference surface have been fabricated and tested in liquid environments. The sensing surface, which is opposite to the reference surface, is free allowing the electric field of the thickness shear mode (TSM) to penetrate into the liquid. This results in increased sensitivity to both mechanical and electrical property changes of the liquid. In the present paper, several 5-MHz LFE sensors with a range of electrode spacings were exposed to liquid environments in which the viscosity, relative permittivity, and conductivity were varied. The LFE sensors demonstrate sensitivity to viscosity that is more than twice that obtained for the standard quartz crystal microbalance (QCM), and sensitivity to relative permittivity and conductivity about 1.5 times that of the QCM sensors with modified electrodes. The present results clearly indicate that the LFE sensors may have a wide range of liquid phase applications in which sensitivity is crucial.     

STEP-based automatic system for recognising design and manufacturing features

In the present work, a STEP-based platform-independent system for design and manufacturing feature recognition is developed. A manufacturing feature taxonomy with multiple levels, which is based on the access directions of the feature, is proposed. The system can recognise both design and manufacturing features from the lower level geometry and topology available in the STEP file. The developed system can recognise intersecting features, which is a major shortcoming of previous attempts based on neutral formats. A more complete feature relationship analysis than available in the literature is carried out to find the relationships between all the types of features. Removal volumes and access directions of the features are determined to couple the feature recognition with down line applications. Raw material geometry is also considered while recognising the features. The present system is limited to parts that can be machined on a three-axis machining centre.