Feature based feedback into the early stages of design

At Chemnitz University of Technology, at the chair of manufacturing theory, there has been generated a model supporting feature based feedback of production planning and manufacturing knowledge into the early design stages. This model is integrated into the partial model B2 of the common research projec5 SFB 361 entitled “Models and methods to aggregate manufacturing knowledge for early stages of design”. The model is destined to carry out design in a computer aided and integrated manner, on the one hand. On the other hand, the designer is to be supported to evaluate and select design variants at high level.     

Minimum weight design of sandwich and laminated composite structures

Conclusions The illustrative examples presented above show that the proposed optimum design method based on planning of experiments is an efficient method for the minimum weight design of sandwich and laminated composite plates. Vibration and damping constraints can be modeled using simple mathematical expressions. These expressions are obtained using the finite element solution in the experiment points. Reference points in the search domain are determined from plans of experiment. The advantage of the proposed method is its minimum computational effort for repeated finite element solutions. The major advantage of the method is the possibility of using the data not only from the computer solution, but also the data obtained experimentally in the reference points. In this case, simple mathematical models represent both theoretical and experimental data.Published in Mekhanika Kompozitnykh Materialov, Vol. 31, No. 1, pp. 51–64, January–February, 1995.     

Reverse logistics network design and planning utilizing conditional value at risk

Nowadays, due to some social, legal, and economical reasons, dealing with reverse supply chain is an unavoidable issue in many industries. Besides, regarding real-world volatile parameters, lead us to use stochastic optimization techniques. In location–allocation type of problems (such as the presented design and planning one), two-stage stochastic optimization techniques are the most appropriate and popular approaches. Nevertheless, traditional two-stage stochastic programming is risk neutral, which considers the expectation of random variables in its objective function. In this paper, a risk-averse two-stage stochastic programming approach is considered in order to design and planning a reverse supply chain network. We specify the conditional value at risk (CVaR) as a risk evaluator, which is a linear, convex, and mathematically well-behaved type of risk measure. We first consider return amounts and prices of second products as two stochastic parameters. Then, the optimum point is achieved in a two-stage stochastic structure regarding a mean-risk (mean-CVaR) objective function. Appropriate numerical examples are designed, and solved in order to compare the classical versus the proposed approach. We comprehensively discuss about the effectiveness of incorporating a risk measure in a two-stage stochastic model. The results prove the capabilities and acceptability of the developed risk-averse approach and the affects of risk parameters in the model behavior.     

Selection properties of uniform and related structures

In this paper we present some results on selection properties in asymmetric generalized metric and uniform spaces. We demonstrate differences between selection properties of these spaces and selection properties of metric and uniform spaces.     

A memetic algorithm based on multiple learning procedures for global optimal design of composite structures

The mechanical properties of composite structures are sensitive to the choice of the material systems, the distribution of laminates on the structure, and the sizing at the laminate level. This sensitivity depends on many variables. To overcome the difficulties in attaining a global solution for the optimisation problem of composite structures, a new strategy is proposed based on the hybridisation of the memetic algorithm (MA) and the selfish gene (SG) algorithm. Instead of a local search, as performed in MAs, the selfish gene (SG) theory is applied, which follows a different learning scheme in which the conventional population of the individuals is replaced by a virtual population of alleles. The proposed approach, which is called the memetic-based selfish gene algorithm (MA + SG), is a mixed model that applies multiple learning procedures to explore the synergy of different cultural transmission rules in the evolutionary process. The principal aspects of the approach are as follows: co-evolution of multiple populations, species conservation, migration rules, self-adaptive multiple crossovers, local search in hybrid crossover with local genetic improvements, controlled mutation, individual age control, and feature-based allele statistical analysis. To discuss the capabilities of the proposed approach, numerical examples are represented to compare the results of MA + SG with those obtained using genetic algorithms (GA) and MA. The numerical results of the comparison tests showed that the GA and the MA maintained long periods without the evolution of the best-fitted individual/solutions. This behaviour during evolution is associated with the slow maturation of the elite group of populations in the GA and MA approaches. This behaviour is avoided when the MA + SG proposed approach is used with computational cost benefits.     

Analysis and design of damped structures

Damping can be one of the more perplexing aspects of structural dynamics because it is much less intuitive and “clean-cut” than concepts like stiffness and mass. Nevertheless, analysts should not view damping simply as an unfortunate side issue in structural dynamics, but as an opportunity for creative design work aimed at suppression of unwanted vibrations. This paper presents a review of some basic concepts in damping and how damping is treated in finite element analysis. It also presents some new techniques that have been developed to support optimization of damping for structures.     

Vector structures and solutions of linear matrix equations

A variety of systems problems give rise to special cases of the linear matrix equation

$\text{∑}\text{i}\text{A}{}_{\mathrm{i}}\text{p×s}\text{X}\text{s×t}\text{B}{}_{\mathrm{i}}\text{t×q}\text{+}\text{∑}\text{j}\text{C}{}_{\mathrm{j}}\text{p×t}\text{X}{}^{\mathrm{T}}\text{t×s}\text{D}{}_{\mathrm{j}}\text{s×q}\text{=}\text{F}\text{p×q}\text{(Z)}$

. F(Z) may be a matrix-valued function of a matrix argument Z. It is the purpose here to summarize and extend some of the applicable solution procedures through a systematic use of operators which convert the matrix equation to vector and dimension-reduced vector forms. The format and details of the results are convenient for machine computation.     

Problems of the mechanics of winding thick-walled composite structures

Conclusions Dividing the winding process into individual stages, examination of the interply compliance of the composites, and the introduction of the circular metals made it possible to link the parameters of this process and, in particular, the tensioning force, with the properties of the completed component. It was thus possible to propose engineering methods of calculating thick-walled wound components with an allowance made for technological prior history. Structures for specific applications were constructed and a new technological method proposed and applied. These methods include the methods of producing spatial reinforced driveshafts whose load-carrying frame is produced on the basis of the system of the single filament. The studies examined in this work were used as a starting point for further investigations and development of the mechanics of winding in a number of scientific centers of the country.Translated from Mekhanika Kompozitnykh Materialov, No. 5, pp. 618–626, September–October, 1992.     

Multi-scale method for the quasi-periodic structures of composite materials

In this paper, we shall present a new second-order and two-scale approximate solution of boundary value problems for the linear elasticity systems with quasi-periodic structures by multi-scale analysis. The computation of strain and stress is presented here. This idea can apply to the damage computation of composite materials. Because the computation of the local stress by this method having more precision, it can provide some inspiration for construct optimal design. Finally numerical results show that the method presented in this paper is effective and reliable.     

Novel composite function solutions of the modified KdV equation

A Wronskian form expansion method is proposed to construct novel composite function solutions to the modified Korteweg-de Vries (mKdV) equation. The method takes advantage of the forms and structures of Wronskian solutions to the mKdV equation, and Wronskian entries do not satisfy linear partial differential equations. The method can be automatically carried out in computer algebra (for example, Maple).     

Viscoelastic characteristics of the interaction between structures and soils

The shear coefficients of a body relative to the soil and the shear creep and relaxation kernels are determined from the data of creep and relaxation tests.Urazbaev Institute of Mechanics and Earthquake Resistance of Structures, Academy of Sciences of the SSR, Tashkent. Translated from Mekhanika Polimerov, No. 2, pp. 207–211, March–April, 1973.     

Aggregation and the design of models for medium-term planning of production

A major issue in the design of an aggregate multi-period model for medium-term planning of production is the determination of the aggregation level of the variables. In the process of model design, one has to examine if and how the outcomes of the model are effected by applying different modes and levels of aggregation. This is especially important with regard to those outcomes which will be used for medium-term decisions and for laying out short-term and detailed plans. Also dependent on the aggregation level is the operational convenience of the model for decision support. In this paper it will be shown that simulation experiments with a preliminary model for medium-term planning can yield valuable information to aid this design problem.