Investigation of the dimensional stability of carbon epoxy cylinders manufactured by resin transfer moulding

The prediction of process-induced dimensional variability and residual stresses occurring during the manufacturing of composite structures is critical to produce parts where tight tolerances are required. Therefore, the development of material constitutive models and processing properties, and the validation of these models, are two essential steps in order to accurately simulate the behaviour of the materials involved. In this paper, the material constitutive models of a one-part epoxy resin were implemented in a three-dimensional finite element software based on the ABAQUS/COMPRO platform to investigate the dimensional stability of a composite structure manufactured by resin transfer moulding (RTM). A simplified geometry was used as a representative structural component with different layup configurations. Both heat transfer analysis and stress analysis were conducted. Contact interactions were implemented in the stress analysis to simulate the tool–part interaction. The presented analysis predicted the angle variation and the composite debonding caused by the coefficient of thermal expansion mismatch between the mould and the composite part and the resin volumetric chemical shrinkage.     

Role of tool-part interaction in process-induced warpage of autoclave-manufactured composite structures

The role of tool-part interaction in process-induces warpage of a large composite structure was studied using a three-dimensional process model, developed by integrating sub-models that describe the evolution of cure and properties of composite as well as various physical phenomena encountered, during autoclave processing. The process model was implemented through user sub-routines interfaced with the finite element software, ABAQUS. The tool-part interaction during processing was modeled using contact elements. The predicted temperature and warpage of an aircraft part, using a frictional tool-part interface and experimentally measured cure-dependent tool-part interfacial friction coefficients, compared very well with experimental temperature and warpage, validating the 3-D process model. A comparison of predictions using various models for the tool-part interface suggests that the two components of tool-part interaction that contribute to warpage are change in shape of the tool and part, and process-induced stress caused by constrained deformation of the tool and the part.     

Efficiency parameters estimation in gemstones cut design using artificial neural networks

This paper deals with the problem of estimating cut results for faceted gemstones. The proposed approach applies artificial neural networks for a faceted gemstones analysis tool that could be further developed for incorporation in a computer-aided-design (CAD) context. Basic concepts concerning gemstone processing are introduced and the design of computational tools using neural networks is discussed. The model presented proposes two criteria to assess the efficiency of lapidary designs for rock crystal quartz: brilliance and yield. Closing the article, 62 different lapidary models were used to train and test the neural network tool.     

Minimizing the expected processing time on a flexible machine with random tool lives

We present a stochastic version of economic tool life models for machines with finite capacity tool magazines and a variable processing speed capability, where the tool life is a random variable. Using renewal theory to express the expected number of tool setups as a function of cutting speed and magazine capacity, we extend previously published deterministic mathematical programming models to the case of minimizing the expected total processing time. A numerical illustration with typical cutting tool data shows the deterministic model underestimates the optimal expected processing time by more than 8% when the coefficient of variation equals 0.3 (typical for carbide tools), and the difference exceeds 15% for single-injury tools having an exponentially distributed economic life (worst case).     

Simulation as a planning technique for a complex machine shop

A deterministic simulation study of a complex machine shop consisting of 69 work centres is presented. The purpose of the simulation study was to develop a planning tool to evaluate effects on overtime, work centre bottlenecks, in-process inventory buildup, delivery delays and other output variables caused by individual part delays of different load mixes, modifications in work centre capacities, installation of more automated machinery, and modification in scheduling rules.

The simulation programme and the machine shop it models are described. It was found that the developed simulation programme can be used as a useful planning tool for evaluating short-term and intermediate-term alternatives.     

An experimental method for quantifying tool–part shear interaction during composites processing

The success with which dimensional control during processing of composite structures can be modelled depends on the level of understanding of the underlying mechanisms that drive the accumulation of residual stresses in the part. Tool–part shear interaction during processing can cause substantial warpage in initially flat laminates, yet this phenomenon remains poorly understood. This paper presents an experimental technique in which a thin tool, instrumented with strain gauges, is used for characterizing the interfacial shear stresses that arise between the tool and part during processing. The results show that a sliding interface condition occurs during the majority of the cure cycle, although, at times the tool and part adhere together resulting in high interfacial shear stresses. This tool–part interaction occurs despite the use of a release agent, though the use of a fluoroethylenepropylene (FEP) release film at the tool–part interface reduces the effect.     

Cost estimation system for machined parts

Estimating the manufacturing cost of a machined part is a critical task with high importance to manufacturing firms. Accurate cost estimation is important for cost control, successful bidding for jobs, and maintaining a competitive position in the marketplace. There are three main approaches towards cost estimation: estimation based on past experience (variant cost estimation), estimation based on explicit cost computations, and parametric cost estimation. This paper presents a hybrid cost estimation system for rotational parts that uses a combination of the variant approach and explicit cost calculations. The variant approach is used to retrieve machining parameters from a database of past parameters. The explicit cost calculations are based on the part geometry, the cutting tools available and the machining parameters retrieved. The system presented calculates the time that a part needs to stay on the machine. This time, which includes processing, set-up (chucking and re-chucking) as well as tool changes, is used to find the machining cost.     

Manufacturing Vaccines: An Illustration of Using PAT Tools for Controlling the Cultivation of Bordetella pertussis

An illustration of the operational consistency of the upstream part of a biopharmaceutical process is given. For this purpose four batch cultivations of Bordetella pertussis have been executed under identical conditions. The batches have been monitored by means of two fundamentally different process sensors. First, common single channel measurements such as temperature, pH, dissolved oxygen (DO), and flow rates are used and second, the multichannel measurements from the NIR (Near Infrared) analyzer. Because of the fundamental differences between the two types of measurements, two models have been developed to evaluate the operational consistency. The last sensor studied is a typical representative of process analyzers which are described in the PAT (Process Analytical Technology) guidance document issued in 2004 by the American Food and Drug Administration (FDA). Data from both sensors have been evaluated by a multivariate tool for data acquisition. This resulted in two different performance models. Again this approach is characteristic for the implementation of PAT for the manufacture of biopharmaceuticals.

With both performance models, we were able to explore the operational consistency of the batches. In addition, the performance models were also able to detect a deviating batch. Further, it was shown that both sensor types gave partly overlapping information since a deviation in the batch profiles of the logged process variables was accompanied by a deviation in the spectral batch profiles.

The performance models are valuable tools in developing advanced monitoring and control systems for biopharmaceutical processes. Using such models, advanced knowledge based systems can be developed to detect abnormal situations in an early stage and remove the cause.

The procedure of data processing described in this article is relatively new in the biopharmaceutical industry. The NIR analyzer and both performance models presented in this article are clear ingredients for better process understanding and process control, as intended in the FDA's PAT Initiative. This initiative is part of the FDA's strategy of cGMP (current good manufacturing practice) for the 21st century and aims at introducing innovations in both the manufacturing of biopharmaceuticals and the development of new biopharmaceuticals.

This study shows the feasibility of two typical PAT tools for controlling the manufacturing of biopharmaceuticals. To the best of our knowledge such feasibility study is not documented up to now in the scientific literature.     

A mathematical formulation of DNA computation

DNA computation is to use DNA molecules for information storing and processing. The task is accomplished by encoding and interpreting DNA molecules in suspended solutions before and after the complementary binding reactions. DNA computation is attractive, due to its fast parallel information processing, remarkable energy efficiency, and high storing capacity. Challenges currently faced by DNA computation are: 1) lack of theoretical computational models for applications and 2) high error rate for implementation. This paper attempts to address these problems from mathematical modeling and genetic coding aspects. The first part of this paper presents a mathematical formulation of DNA computation. The model may serve as a theoretical framework for DNA computation. In the second part, a genetic code based DNA computation approach is presented to reduce error rate for implementation, which has been a major concern for DNA computation. The method provides a promising alternative to reduce error rate for DNA computation.     

Microstructural processes in structural alloys

Summary Significant opportunities exist for improved microstructural modeling of the processing and in-service performance of structural alloys. The fundamental tool for linking size and time scales and for dealing with multiphysics phenomena will continue to be continuum, rate-theory-type models. The major challenge is to make these models more complete and accurate. In large part, this can be done based on available physical understanding. Atomistic modeling can also play an important implicit role by providing improved insight on key mechanisms and better estimates of fundamental material properties. Direct application of atomistic models will primarily benefit circumstances involving ultrafine-scale microstructures and local processes. Careful coupling of models to well-designed experiments will very often be the key to success.Providing a standard list of literature references is beyond the scope of this report. In a few cases speakers who gave talks at this Workshop pertinent to a topic are indicated in parentheses. However, these citations are not meant to be complete.     

高g值加速计和压电式力传感器的动态校准

本提出一种高g值加速度计的动态校准方法和装置,其最大加速度峰值超过100000g。这套装置还可以对压电式力传感器进行动态校准。中给出两个加速度计加速度峰值的二十余次实验结果,以及加速度计与力传感器的冲击响应实验曲线。同时,还求出它们的动态数学模型（包括差分模型、传递函数、频率特性）和动态性能指标。此外,还讨论了本的4个创新点。     

Multiperiod tool and production assignment in flexible manufacturing systems

Flexible manufacturing systems (FMSs) are usually composed of general purpose machines with automatic tool changing and integrated material handling. FMSs offer the advantages of high utilization levels and simultaneous production of a variety of part types with minimal changeover time. Although the trend in FMS operation appears to be towards unmanned production, there is much diversity in the policies under which FMSs can be operated. These policies are governed to some extent by the available technological resources. In this paper several policies are described. Tool loading and production assignment models for setting production plans over a short term planning horizon when using these policies are then formulated. Heuristics for the solution of these models are detailed and computational results are presented.     

Cure simulation with resistively in situ heated CFRP molds: Implementation and validation

In composite processing of parts with varying cross-sections, homogeneous cure is sought but poses a significant challenge. Electrically heated molds for resin transfer molding (RTM) processes offer the potential to locally introduce heat and, thus, achieve more homogeneous cure and enhanced part quality. However, low conductivity of CFRP poses a risk of uncontrolled exothermic reactions. To target this potential, an appropriate and efficient numerical method is presented in this study to simulate part cure governed by resistive heated CFRP molds. A numerical control algorithm for 3D finite element cure simulations is developed, which uses the reaction flux of a temperature boundary condition to calculate the arising tool temperature field. The capability of this method to predict non-uniform tool temperatures of self-heated CFRP molds with close to thermocouple accuracy during the cure process is shown by means of numerical verification and experimental validation on a self-heated CFRP plate.     

Managing product variability by virtual products

A new paradigm for customer-oriented production is presented. A complete specification of a product variant is described as a virtual product, a bill of material represented as a data object. This object may be used as a basis for production management. A tool for creating, modifying and processing virtual products is presented, based on a generic product structure. This tool may act as a means to facilitate handling of individual customer-specified products in a serialoriented production environment.     

Design of an apparatus for measuring tool/fabric and fabric/fabric friction of woven-fabric composites during the thermostamping process

The thermostamping of prepreg woven fabrics shows promise as a low-cost high-volume manufacturing process for composite parts. One concern associated with the process is the unwanted formation of defects in the form of fabric wrinkling. This wrinkling can be prevented during the thermostamping process by inducing in-plane forces through the use of one or more metal binder rings. However, if the in-plane forces are too low, then the fabric may wrinkle as the fabric conforms to the shape of the punch, and conversely, if the in-plane forces are too high, then the yarns in the fabric can separate and the fabric may tear and yarns can break. The in-plane forces are a result of the friction between the fabric and the metal binder rings. As the fabric slides over the surfaces of the punch and die, further friction is induced between the metal tooling and the fabric part. In addition, most composite parts consist of multiple layers, and therefore as the fabric is drawn into the die adjacent layers of fabric may slide relative to one another. Thus, the friction at the tool/fabric interface and the interlaminar friction must be understood and quantified to predict part quality as a function of the processing parameters. In this paper, the design and implementation of a load-control test apparatus used to measure the friction between the tool and the fabric and between adjacent layers of fabric during a composite forming process is presented.     

A logistics scheduling model: scheduling and transshipment for two processing centers

Logistics scheduling refers to problems in which decisions on job scheduling and transportation are integrated into a single framework. A logistics scheduling model for two processing centers that are located in different cities is presented. Each processing center has its own customers. When the demand in one processing center exceeds its processing capacity, it is possible to use part of the capacity of the other processing center subject to a job transshipment delay. Such a coordinated scheduling situation can be modeled as a parallel-machine scheduling problem with transshipment between the machines. We study problems with different objective functions and constraints, and propose various algorithms to solve these problems. Discussions on the benefits and incentives for the coordinated approach are presented.     

非圆回转曲面CNC 磨削加工轨迹直接插补技术研究

针对非圆回转曲面数控磨削加工轨迹插补特点,动用曲面直接插补（ＳＤＩ）思想,提出一种适合于非圆回转曲面类零件轨迹处理的集成式ＣＮＣ轨迹插补模式,并系统研究了实时插补中加工工艺余量智能决策方法和轨迹自生成原理等,成功地解决了非圆回转曲面磨削加工的轨迹实时插补控制问题。     

Tool selection in three-axis rough machining

An approach to tool selection and sequencing is presented for three-axis rough machining. The trade-off in the selection of tools is as follows: larger tools have reduced access while smaller tools are capable of reduced cutting speed. Furthermore, every tool change incurs a time penalty. The objective of this paper is to select a tool sequence that minimizes the total rough-machining time. In our approach, the removal volume is stratified into 2.5D machining slabs and, for each tool, the area accessible in each slab is computed incrementally, keeping in mind the cutting portion of the tool and the shape of the tool holder and spindle assembly. This reduces the three-axis problem to a series of two-axis problems with complex precedence constraints. Two models are presented to understand this new form of the problem. First, an integer linear programming formulation is discussed to show the complexity of the task. Second, a network flow formulation is presented, by which we show that it is possible to obtain efficiently an approximate solution of the problem. Examples are discussed to illustrate the algorithms discussed.     

A concise treatise on model-based enhancements of cohesive powder properties via dry particle coating

This paper presents a review of our key advances in model-guided dry coating-based enhancements of poor flow and packing of fine cohesive powders. The existing van der Waals force-based particle-contact models are reviewed to elucidate the main mechanism of flow enhancement through silica dry coating. Our multi-asperity model explains the effect of the amount of silica, insufficient flowability enhancements through conventional blending, and the predominant effect of particle surface roughness on cohesion reduction. Models are presented for the determination of the amount and type of guest particles, and estimation of the granular Bond number, used for cohesion nondimensionalization, based on particle size, particle density, asperity size, surface area coverage, and dispersive surface energy. Selection of the processing conditions for LabRAM, a benchmarking device, is presented followed by key examples of enhancements of flow, packing, agglomeration, and dissolution through the dry coating. Powder agglomeration is shown as a screening indicator of powder flowability. The mixing synergy is identified as a cause for enhanced blend flowability with a minor dry coated constituent at silica < 0.01%. The analysis and outcomes presented in this paper are intended to demonstrate the importance of dry coating as an essential tool for industry practitioners.