In the present paper, the following topics are reviewed in detail: (a) the available adhesives, as well as their recent advances, (b) thermodynamic factors affecting the surface pretreatments including adhesion theories, wettability, surface energy, (c) bonding mechanisms in the adhesive joints, (d) surface pretreatment methods for the adhesively bonded joints, and as well as their recent advances, and (e) combined effects of surface pretreatments and environmental conditions on the joint durability and performance. Surface pretreatment is, perhaps, the most important process step governing the quality of an adhesively bonded joint. An adhesive is defined as a polymeric substance with viscoelastic behavior, capable of holding adherends together by surface attachment to produce a joint with a high shear strength. Adhesive bonding is the most suitable method of joining both for metallic and non-metallic structures where strength, stiffness and fatigue life must be maximized at a minimum weight. Polymeric adhesives may be used to join a large variety of materials combinations including metal-metal, metal-plastic, metal-composite, composite-composite, plastic-plastic, metal-ceramic systems. Wetting and adhesion are also studied in some detail in the present paper since the successful surface pretreatments of the adherends for the short- and long-term durability and performance of the adhesive joints mostly depend on these factors. Wetting of the adherends by the adhesive is critical to the formation of secondary bonds in the adsorption theory. It has been theoretically verified that for complete wetting (i.e., for a contact angle θ equal to zero), the surface energy of the adhesive must be lower than the surface energy of the adherend. Therefore, the primary objective of a surface pretreatment is to increase the surface energy of the adherend as much as possible. The influence of surface pretreatment and aging conditions on the short- and long-term strength of adhesive bonds should be taken into account for durability design. Some form of substrate pretreatment is always necessary to achieve a satisfactory level of long-term bond strength. In order to improve the performance of adhesive bonds, the adherends surfaces (i.e., metallic or non-metallic) are generally pretretead using the (a) physical, (b) mechanical, (c) chemical, (d) photochemical, (e) thermal, or (e) plasma method. Almost all pretreatment methods do bring some degree of change in surface roughness but mechanical surface pretreatment such as grit-blasting is usually considered as one of the most effective methods to control the desired level of surface roughness and joint strength. Moreover, the overall effect of mechanical surface treatment is not limited to the removal of contamination or to an increase in surface area. This also relates to changes in the surface chemistry of adherends and to inherent drawbacks of surface roughness, such as void formations and reduced wetting. Suitable surface pretreatment increases the bond strength by altering the substrate surface in a number of ways including (a) increasing surface tension by producing a surface free from contaminants (i.e., surface contamination may cause insufficient wetting by the adhesive in the liquid state for the creating of a durable bond) or removal of the weak cohesion layer or of the pollution present at the surface, (b) increasing surface roughness on changing surface chemistry and producing of a macro/microscopically rough surface, (c) production of a fresh stable oxide layer, and (d) introducing suitable chemical composition of the oxide, and (e) introduction of new or an increased number of chemical functions. All these parameters can contribute to an improvement of the wettability and/or of the adhesive properties of the surface.

Adhesively-bonded joints and repairs in metallic alloys, polymers and composite materials: Adhesives, adhesion theories and surface pretreatment

Cloud-enabled prognosis for manufacturing

Traditionally, metal working fluids (MWF) are known to improve machining performance despite poor ecological and health side effects. A new sustainable process that has minimized the use and application of MWFs is NDM (near dry machining). Although there is much controversy on the effectiveness of NDM, it is agreed that a lack of science-based modeling prevents its widespread use. This paper presents a new method to predict tool-wear/tool-life performance in NDM by extending a Taylor speed-based dry machining equation. Experimental work and validation of the model was performed in an automotive production environment in the machining of steel wheel rims. Machining experiments and validation of the new equation reveal that tool-wear can be predicted within 10% when the effect of NDM is statistically different than dry machining. Tool-wear measurements obtained during the validation of the model showed that NDM can improve tool-wear/tool-life over four times compared to dry machining which underlines the need to develop sustainable models to match current practices.

A comprehensive tool-wear/tool-life performance model in the evaluation of NDM (near dry machining) for sustainable manufacturing

Computer-aided design of acoustic horns for ultrasonic machining using finite-element analysis

In the light of growing global competition, organizations are increasingly under pressure to produce products of high quality and reliability at reasonable cost. The integration of design and manufacturing activities into one common engineering effort has been recognized as a key strategy for survival and growth. Design for Manufacturability (DFM) aims at integrating product design and process design to achieve cost and quality objectives. The implementation of the DFM approach requires the collaboration of both the design and manufacturing functions within an organization. However, due to the divergent orientations of these functions, implementation of the DFM approach has been found to be neither straightforward nor easy. Of the several methodologies available, process-driven design is recognized as one of the more effective DFM approaches.
The primary objective of this research is to address the major criteria for manufacturability in the DFM approach using expert systems methodology. An expert system has been developed in two modules--one for process selection and manufacturing cost estimation and the other for evaluation of design features for manufacturability on a CAD system. The expertise for primary process selection is developed for casting and forging processes. The specialized processes considered are die casting, investment casting, sand casting, precision forging, conventional die forging, and open die forging. The processes considered for secondary process selection are end milling and drilling. The cost estimation expertise is developed for the die casting process, milling and drilling operations, and manual assembly operations. A design for a hanger used in the furniture industry is used to demonstrate the process selection and cost estimation capability of the expert system. Three different solid models created in CATIA are used to demonstrate evaluation of design features for manufacturability with respect to milling and drilling operations on a CNC milling machine. The set of manufacturability criteria considered are: (1) perpendicularity of holes to drill entry and exit surfaces, (2) conformance of hole diameters to available standard tool sizes, (3) compatibility of hole depths with respect to hole diameters, (4) adjacency of holes lying on the same surface, (5) rounded inside corners instead of sharp corners in square holes, and (6) chamfered corners instead of rounded external corners.
The results obtained from the application of the expert system suggest that the use of a knowledge-based approach to generate accurate cost estimates and analyze design features for manufacturability during the design phase is certainly feasible. Such systems would enhance the quality of design decisions in organizations, resulting in improved competitiveness in the market.

A knowledge-based approach to design for manufacturability

Modern manufacturing process engineering , Modern manufacturing process engineering , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Benjamin W. Niebel

Papers

Modern manufacturing process engineering

Product design and process engineering