An economic model for raw material selection

An economic model for raw material selection is presented and a case analysis is given. The model considers two decision factors: initial raw material cost and additional manufacturing costs incurred due to inappropriateness of raw material quality. This additional manufacturing cost may include items such as: extra operator cost, extra machine cost and extra quality cost.     

Integrating the economic production model with deteriorating raw material over multi-production cycles

This paper considers an Economic Production Quantity (EPQ) model with deteriorating raw material and investigates the impact of deterioration on the production process. The EPQ base case with no deterioration is presented where raw material is ordered for multiple production cycles. We present the differential equations to calculate the on-hand inventory of raw material and present closed-forms expressions for the required order of raw material to result in a desired amount of effective raw material per order cycle. Closed-form expression for the total profit per unit time is obtained and we solve for the optimal production quantity of finished product per production cycle and the order quantity of raw material. We present numerical examples where we compare our model to a system which ignores the impact of deterioration and results in shorter production cycles due to an insufficient amount of effective raw material.     

Weibull model selection for reliability modelling

A large number of models have been derived from the two-parameter Weibull distribution and are referred to as Weibull models. They exhibit a wide range of shapes for the density and hazard functions, which makes them suitable for modelling complex failure data sets. The WPP and IWPP plot allows one to determine in a systematic manner if one or more of these models are suitable for modelling a given data set. This paper deals with this topic.     

大型原料药用冻干机设计

对于搁板面积50 m2以上的原料药用冻干机,以双干燥箱 单一水汽凝结器组合为多见.由于其存在一些不足之处,开发了相同干燥面积的单一干燥箱 双水汽凝结器组合的原料药用冻干机,并溶合了交替真空除霜、小门装置、螺杆压缩机、在位清洗和消毒等设计新理念.     

Accident modelling and economic evaluation

This paper summarizes contributions to the IDBRA workshop made by Votey, Krupp and Jones-Lee. Votey set out the basic principles of costs and benefits as applied to accident control measures and discussed the various elements of effective economic analysis. Krupp presented information relating to the determination of the costs of injury accidents in the Federal Republic of Germany, and Jones-Lee discussed in more general terms the principle ways in which accident costs might be determined. The final section draws some general conclusions relating to the workshop as a whole.     

A comprehensive VIKOR method for material selection

In engineering design, material alternatives evaluate according to different criteria depending on the objectives of the problem. Performance ratings for different criteria are measured by different units, but in the decision matrix in order to have a valid comparison all the elements must be dimensionless. However, a lot of normalization methods have been developed for cost and benefit criteria, not only there has not been enough attention for engineering design situations in which approaching the target values are desirable but also the available methods have shortcomings. A new version of VIKOR method, which covers all types of criteria with emphasize on compromise solution, is proposed in this paper. The proposed comprehensive version of VIKOR also overcomes the main error of traditional VIKOR by a simpler approach. Suggested method can enhance exactness of material selection results in different applications, especially in biomedical application where the implant materials should possess similar properties to those of human tissues. Five examples are included to illustrate and justify the suggested method.     

Review of methodologies for composite material modelling incorporating failure

Advanced composite materials are finding increasing application in aerospace, marine and many other industries due to the advantages in performance, structural efficiency and cost they provide. However, despite years of extensive research around the world, a complete and validated methodology for predicting the behaviour of composite structures including the effects of damage has not yet been fully achieved. The Cooperative Research Centre for Advanced Composite Structures (CRC-ACS) is leading a currently running collaborative project to develop a methodology for determining mechanical behaviour and failure in composite structures. Key drivers of the project are the use of multi-axial testing machines for material characterisation and an appreciation of the issues involved due to the different length scales of any analysis. As part of the project, a critical review was performed to assess the state of the art in material constitutive modelling and composite failure theories. This paper summarises the results of the review, which includes a discussion of the various theories and approaches within the context of the dissipated energy density framework. The results of the review will be applied within the project to select appropriate constitutive modelling and failure approaches for implementation within a data-driven material characterisation methodology.     

Digital tools for material selection in product design

The increasing number of normalized materials, promoters and users led to a significant amount and diversity of databases and software for material selection, presenting differentiating abilities for the materials selection process.     

Using raw material measurements in robust process optimization

Unwanted variation due to variable raw material quality is often a problem in production processes. Robust process optimization seeks to reduce the effects of such variation by identifying settings of the adjustable factors that makes the process less sensitive to the variations. This paper develops a unified framework for studying and developing robust process optimization and process control techniques. We divide the factors of the process into groups based on characterizations of their properties. We also develop a robust process optimization technique for batch-wise processes, called batch-wise robust process optimization, which utilizes all available measurements of raw material qualities at the start of each production batch. The technique achieves a reduction of variability due to variation in raw material qualities, compared to ordinary robust process optimization. Two examples taken from baking of hearth bread illustrate the technique.     

Numerical modelling for scattering of waves in three-dimensional cracked material

In this paper, a mathematical model is proposed for the problem of the scattering of plane waves in a three-dimensional cracked materials. Instead of obtaining closed-form solutions as in conventional theoretical analysis methods, this approach, called the Equivalent Nodal Force (ENF) method formulates the mechanical effects of cracks as an equivalent nodal force in a numerical procedure, and physically translates cracked material into an equivalent continuous one. Several mechanical relations between waves and cracks are evident from this method. Also the results of several numerical calculations are presented and these are compared with those obtained by the conventional methods.     

An automated system for selection of a constructional material

A method for comparison of different materials is proposed. The use of any, including difficult to compare criteria such as strength, production properties, cost etc. is allowed as the criteria to be compared. All of the information for comparison is arranged in the form of material-properties stable matrices. Each line of the matrix describes a single material with certain of its properties. The material for replacement is selected by cluster analysis using a coalescence algorithm.Selection of the information for filling the original material-properties table is made under automated conditions with use of a data bank of physicomechanical properties of materials. A problem of transfer of original data from a general-purpose information base to applied user programs is solved. A system for replacement of a constructional material is developed and examples of its functioning are given.Translated from Problemy Prochnosti, No. 12, pp. 67–73, December, 1990.     

Design-optimization and material selection for a femoral-fracture fixation-plate implant

The problem of size/thickness optimization of a distal femoral-fracture fixation-plate is addressed computationally using a combined finite-element/design-optimization procedure. To obtain realistic physiological loading conditions associated with normal living activities (cycling, in the present case), a musculoskeletal multi-body inverse-dynamics analysis is carried out of a human riding the bicycle. While optimizing the design of the femoral-fracture locking-plate, realistic functional requirements pertaining to attain the required level of fracture-femur fixation and longevity/lifecycle were used. It is argued that these types of analysis should be used to complement pre-clinical implant-evaluation tests, the tests which normally include a limited number of physiological loading conditions and single pass/fail outcomes/decisions with respect to a set of lower-bound implant–performance criteria.     

White paste for stoneware tiles for pavement using raw clay material from Burkina Faso

Raw materials from Burkina Faso were used in the production of white pastes for stoneware tiles for pavement. The basic material which is kaolin clay (Loulouka) was added with some natural plastic clay (Korona), feldspar, talc, sand for the formulations of batches for these tiles. Four batches (S1, S2, S3 and S4) consisting of raw basic clay material, plastic clay, feldspar, talc and sand have been prepared for the elaboration of tiles sintered up to 1,150 °C. The changes during the sintering process of tiles were investigated by means of X-ray diffraction and scanning electron microscopy. Mainly mullite, enstastite and glassy phase were formed during the sintering at 1,150 °C. Also the physical properties (water absorption, linear shrinkage) and flexural strength of the tiles were measured. These above properties were improved notably with increasing temperature because of mainly the formation of mullite and glassy phase which reduces the number of pores and their size. The tiles fired at 1,150 °C obtained with batch consisting of 62 % mass of basic material, 20 % mass of feldspar, 10 % mass of sand, 5 % mass of plastic clay and 3 % mass of talc (S4) belong in Europeans Standards-class BIb.     

Computational multiscale modelling of heterogeneous material layers

A computational homogenization procedure for a material layer that possesses an underlying heterogeneous microstructure is introduced within the framework of finite deformations. The macroscopic material properties of the material layer are obtained from multiscale considerations. At the macro level, the layer is resolved as a cohesive interface situated within a continuum, and its underlying microstructure along the interface is treated as a continuous representative volume element of given height. The scales are linked via homogenization with customized hybrid boundary conditions on this representative volume element, which account for the deformation modes along the interface. A nested numerical solution scheme is adopted to link the macro and micro scales. Numerical examples successfully display the capability of the proposed approach to solve macroscopic boundary value problems with an evaluation of the constitutive properties of the material layer based on its micro-constitution.     

A parametric cubic modelling system for general solids of composite material

A new approach to modelling solids that are anisotropic and heterogeneous is presented with applications to structures of composite material. A parametric cubic modelling system is presented for lines, surfaces, volumes, and physical data that uses construction-in-context to generate numerical data. This system automates the construction of discrete element models and can reduce input data requirements by more than an order of magnitude. A tricubic isoparametric discrete element is presented that does not require displacement derivatives to define connectivity. This element is capable of exact displacement and strain continuity over a surface while permitting strain discontinuities at heterogeneous material interfaces. The shape of an element can be any hexahedron, pentahedron, or tetrahedron and the material properties are allowed to vary over the volume. Evaluation of modelling error with respect to closed-form solutions for curved geometries indicate a single element can model up to 90-degree segments with stresses accurate to 1 per cent. Applications of the system to composite structures are presented for interlaminar edge effects and attachment stresses in a sandwich panel.     

水泥生料中有机碳测定方法研究

采用K2Cr2O7容量法测定水泥生料中有机碳的方法,先以碳酸盐岩国家一级标准物质样品(GBW07135)进行条件试验,结果与标准值相符后再进行生料样品的测定。结果表明,在180℃下持续沸腾25~30 min,有机碳回收率最高;该方法测定结果与元素分析仪和TOC分析仪的测定结果相关性较高,相关系数分别为0.992 6和0.997 7;该法测得的新型干法窑和立窑生料有机碳的95%置信区间分别为0.17%~0.25%和4.36%~7.48%。由于成本低,操作简便,K2Cr2O7容量法是廉价、快速并且精确测定生料有机碳的首选方法。     

Structural optimization to include material selection

The mini-max dual method ia applied for solving the material selection structural optimization problems. A somewhat general objective function is introduced to consider structural weight and material cost simultaneously. It is expressed by the sum of scaled structural weight and material cost. The present formulation can yield minimum cost and minimum weight designs as two distinct special cases. It is shown that practically useful intermediate optimal designs can exist between the two extremes. Only truss structures are considered as a representative example. One numerical example is provided to illustrate the change in optimal material distribution when various objective functions are employed. A particular advantage in using the dual method for the material selection problem is also described.