Dirk Bähre

Energy Efficiency Engineering—Towards an Integrated Method Framework for Energy-Oriented Product and Production Development

Energy efficiency in all areas of the product lifecycle gets more and more important. Besides the use phase that is often addressed through technological solutions, the production phase is also in focus as it determines the environmental impacts of a company to a high degree. Established operational methods that consider energy efficiency reactively are often already exploited. This contribution therefore focuses on methods that are applied in early phases of the product and production development process. On the basis of a correlation matrix that correlates the interrelationships between the three dimensions product, material and production, promising areas in the product creation process are analysed. This framework provides a general basis for the development and application of integrated analysis and improvement methods.

Electrochemical dissolution of cast iron in NaNO3 electrolyte

The electrochemical dissolution of three cast iron types in NaNO3 electrolyte was investigated by cyclic voltammetry, chronoamperometry, and numerical simulations. The measurements were performed with commercially available materials with different iron matrix compositions and graphite particle shapes: lamellar graphite particles in a ferritic/perlitic matrix, spheroidal graphite particles in a ferritic matrix, and spheroidal graphite particles in a ferritic/perlitic matrix. With regard to electrochemical machining (ECM) applications, the measurements were performed in different kinds of flow cells which realize the high electrolyte flow of an ECM experiment. It could be shown that the electrochemical dissolution was especially influenced by the microstructure of the cast iron and the pH of the electrolyte. Electrochemical measurements as well as numerical simulations show that the graphite geometry and the matrix structure are responsible for inhomogeneities of the electric field in the outer sample surface region which were formed during the dissolution process. The resulting shape of the electric field is responsible for different dissolution mechanisms. The kinetics of the dissolution reaction was influenced in the same manner. Finally, it was found that an alkaline electrolyte pH impedes the dissolution process, whereas no significant difference can be observed between acidic and neutral electrolytes.

Selecting Manufacturing Process Chains in the Early Stage of the Product Engineering Process with Focus on Energy Consumption

Manufacturing process chains describe the concept of how the transformation of a raw material into a finished product is achieved. Within the planning phase of the process chains not only technical and economic requirements must be met but also ecological aspects need to be considered, e.g. the energy consumption during the production phase. The aim of this chapter is to illustrate how the energy consumption of process chains can be considered in the early stage of the planning phase. It provides an overview of the methods that are available to describe and predict the energy demand of consumers in process chains. The presented method is based on planning data like characteristic power consumption parameters of manufacturing equipment and related time parameters. It aims at predicting the energy consumption per product. The data is needed for predictive assessment of alternative process chains and to assess the impact of energy consumption during the production phase in life cycle considerations. Finally, this chapter presents an example for the energy-aware design and selection of a preferred process chain from several alternatives. By this it is illustrated how the presented heuristic approach can be applied.

Pulse electrochemical machining of cast iron: a layer-based approach for modeling the steady-state dissolution current

In this paper, a new layer-based simulation method for predicting the steady-state current of a pulse electrochemical machining (PECM) process is described. The basic concept of the method is a simple two-layer model consisting of a porous oxide and an adsorption layer. The oxide layer of PECM-machined samples, characterized by Raman spectroscopy and electron microscopy measurements, shows a similar structure as the oxide layer formed in electrochemical impedance spectroscopy (EIS) measurements. Therefore, the electronic equivalent circuit developed according to EIS results was used as analogy for the description of the overall impedance of the PECM model. The difference between the assumed layers of a PECM and EIS measurement is modeled with a material-dependent adjustment function. In this way, the calculated values of the equivalent circuit elements can be directly derived from experimental PECM data. It could be shown that the procedure allows the calculation of the steady-state current of PECM processes for different work conditions (e.g., pulse on-times, pulse frequencies). The procedure is applied to the electrochemical dissolution of three different types of cast iron in NaNO3 electrolyte on realistic machining conditions. All samples were characterized according to their chemical composition, graphite particle morphology/structure, and their anodic dissolution behavior.

Modeling and Measurement of Residual Stresses along the Process Chain of Autofrettaged Components by Using FEA and Hole-Drilling Method with ESPI

The incremental hole-drilling method is a well-known mechanical measurement procedure for the analysis of residual stresses. The newly developed PRISM® technology by Stresstech Group measures stress relaxation optically using electronic speckle pattern interferometry (ESPI). In case of autofrettaged components, the large amount of compressive residual stresses and the radius of the pressurized bores can be challenging for the measurement system. This research discusses the applicability of the measurement principle for autofrettaged cylinders made of steel AISI 4140. The residual stresses are measured after AF and after subsequent boring and reaming. The experimental residual stress depth profiles are compared to numerically acquired results from a finite element analysis (FEA) with the software code ABAQUS. Sample preparation will be considered as the parts have to be sectioned in half in order to access the measurement position. Following this, the influence of the boring and reaming operation on the final residual stress distribution as well as the accuracy of the presented measurement setup will be discussed. Finally, the usability of the FEA method in early design stages is discussed in order to predict the final residual stress distribution after AF and a following post-machining operation.

Full Exploitation of Lightweight Design Potentials by Generating Pronounced Compressive Residual Stress Fields with Hydraulic Autofrettage

Internally pressurized components in hydraulic systems are subjected to high mechanical stresses. In case of dynamic pressure profiles this may lead to fatigue and hence a limited lifetime. This is particularly the case for fuel injection systems in combustion engines. Components of diesel injection systems in automobiles are popular examples for these demands. They have to withstand pressures of 2,200 bar and higher for at least 250,000 km. The increasing usage of high-strength materials and higher wall thicknesses will lead to a dead end as the weight and the complex manufacturing will tie up costs and resources. Autofrettage is a manufacturing process with high potential for the lightweight design of highly stressed hydraulic components. By considering the same wall thickness and applying optimal parameters, the fatigue strength may be increased by a factor of 3.5. If transferred to lightweight concepts wall thickness reductions as well as cost and resource savings by more than 45 % may be realized. However, from the manufacturing perspective the Autofrettage process poses some challenges. This paper presents results from Finite Element simulations and experiments and discusses the interaction between manufacturing processes with respect to residual stresses and deformations. The scientific findings may be used to tear down barriers in the application of Autofrettage and to optimize process chain layouts. It also serves to make a significant contribution to weight reduction in car manufacturing and other high performance hydraulic applications. Abbreviations: AF : Autofrettage; AFM : Abrasive Flow Machining; ECM : Electro-Chemical Machining; FEA : Finite Element Analysis; K-ratio : outer to inner radius ratio; L = length of the cylinder (mm); pAF : Autofrettage pressure (bar); pWP : working pressure (bar); piY : pressure to initiate yielding at the bore (bar); Ra : roughness average (μm); Rz : average maximum height of the roughness profile (μm); RPM : Revolutions Per Minute (1/min.); ri : inner radius (mm); ro : outer radius (mm); ρ : density (kg/dm3); σVM : von Mises equivalent stress (MPa); σy : yield stress (MPa); σt : tensile stress (MPa); σY : yield strength (MPa); SF : Safety Factor;

Planning Energy Efficiency in Manufacturing Process Chains – an Innovative Approach for an Industrial Product-Service System

Due to competitors in low-wage countries, many manufacturing companies must pursue new business solutions to convince industrial customers about their products. Offering solutions that meet customer needs by products with integrated services, so called Industrial Product-Service Systems (IPS2), is one option to ensure competitiveness. One challenge is how to compensate for energy costs in an IPS2 by energy efficient manufacturing. In this paper, a scenario is considered where a consortium of Original Equipment Manufacturers (OEMs) and Energy Planning Consultants act as an IPS2 provider to acquire new customers by energy efficient manufacturing operations.

Energy Consumption as One Possible Exclusion Criterion for the Reuse of Old Equipment in New Production Lines

The reuse of production equipment represents a promising approach to saving investment costs. Therefore, more and more companies are taking the topic of reuse into consideration. However, there are also risks and disadvantages concerning the reuse of old production equipment. In some cases, reusing old equipment can eventually be more expensive than buying new resources. Therefore, an adequate reuse assessment is necessary. Not only technical factors and investment costs have to be considered, life cycle aspects such as energy consumption play a crucial role as well. In this paper, an approach to a risk-reduced reuse of old equipment is presented.

Frictional Performance Assessment of Cemented Carbide Surfaces Textured by Laser

Cemented carbides are advanced engineering materials often used in industry for manufacturing cutting tools or supporting parts in tribological system. In order to improve service life, special attention has been paid to change surface conditions by means of different methods, since surface modification can be beneficial to reduce the friction between the contact surfaces as well as to avoid unintended damage. Laser surface texturing is one of the newly developed surface modification methods. It has been successfully introduced to fabricate some basic patterns on cemented carbide surfaces. In this work, Direct Laser Interference Patterning Technique (DLIP) is implemented to produce special line-like patterns on a cobalt (Co) and nickel (Ni) based cemented tungsten carbide grade. It is proven that the laser-produced patterns have high geometrical precision and quality stability. Furthermore, tribology testing using a nano-tribometer unit shows that friction is reduced by the line-like patterns, as compared to the polished one, under both lubricated and dry testing regimes, and the reduction is more pronounced in the latter case.

Energy Consumption: One Criterion for the Sustainable Design of Process Chains

Rising energy costs lead to rising product costs and cause companies to search for methods to reduce energy consumption in production process chains. Therefore, sustainability becomes a matter of competitiveness. Energy consumption in production is determined by the design of parts and the manufacturing process chains. If companies manage to assess and optimize the energy consumption of manufacturing process chains during the design phase, they will be able to reduce energy consumption and to take important competitive advantages. For the decision–making process, it is crucial to know at what point in the planning phase a decision about alternatives in production process chains can be taken. This paper presents an approach to take into account the energy consumption in the early stage of process chain design.