Joint design -general

Self-fastening joint designs generally produce very high stresses in the plastic part during the assembly operation. With brittle plastics, such as thermosets, press-fit assembly may cause the plastic to crack if conditions are not carefully controlled. In addition, certain plastics, especially thermoplastics, are subject to cold flow under stress. Under continued stress, which is the fundamental adhesive that holds self-fastened parts together, the plastic may relax, causing the joint to fad. 

Aspects of this subject are also dealt with in other articles, notably Acrylic adhesives. Durability - fundamentals. Joint design general. Joint design cylindrical joints. Joint design strength and fracture perspectives. In the article on Toughened acrylic adhesives, some properties are compared with those of Epoxide adhesives and anaerobic adhesives. 

Most adhesive joint configurations are either flat or cylindrical this article is concerned with the latter type. Broader aspects of design are discussed in Joint design -general. 

Joint design - general C WATSON Flat and cylindrical joints good and bad practice... 

Design. Detailed adhesively bonded joint design and analysis methods are discussed elsewhere in this volume. General issues associated with bonded assembly design will be considered here. 

Joint design and selection generally involves compromising between the ideal and practical. A number of manufacturers produce patented or proprietary joints that embody many ideal characteristics. Some are excellent products and are well suited to special applications. Valves and fittings are often available with proprietary joints that have gained wide acceptance however, consideration should be given to the possible impact on product delivery time and cost. 

Standard taper joints are used in matching inner and outer (also called male and female) members. They are made in a variety of standardized sizes and shapes. Figures 3.2 and 3.3 illustrate the shape variations available. In general, how a joint will be used determines which joint design should be selected. 

Certain specifications and standards provide excellent tutorials on adhesives and sealants. For example, MIL-HDBK-691 offers a complete handbook on adhesive bonding, and MIL-HDBK-725 provides a guide to the properties and uses of adhesives. ASTM C 962 provides an excellent source of information regarding sealant joint design and the types of sealants that are appropriate for various substrates. Although this specification is primarily for construction sealants, much of the information that it contains is generally useful for other sealant applications. 

While developments described above were underway in the UK, the USA developed a variety of respirators for various purposes, including the M9 and M17 for general purpose and infantry use, followed by the M40 , and the M24 and M25 , followed by the M42 and M43 , for tank crews. All these respirators are similar in the way they operate, but their designs differ according to the requirements of particular user groups. These respirators are to be replaced by the new M50 Joint Services General Purpose Mask by... 

Wear inhibitors (WI) are substances able to alleviate mechanochemical wear in friction joints [18]. The notion of WI helps to generalize numerous means of fighting corrosion in machines and mechanisms independently of their friction joint design and composition. 

Closed form solutions. Structural adhesive joints are generally designed to be loaded in shear so that treatments of joint analyses are confined essentially to the transfer of load by shear, with some consideration of the transverse normal stresses induced by eccentricities in the load path. In the simplest case the adhesive and the adherends are assumed to behave elastically. The most refined analyses attempt to model the situation when the adhesive yields so that the adhesive and, eventually, the adherends behave plastically as the imposed load is raised. Closed-form analyses are difficult to apply to other than simple geometrical configurations, while a major difficulty with the elasto-plastic model is how to characterise the adhesive. 

There are certain fundamental rules in the bonded joint design that have to be followed throughout the design. These rules, or principles, also form the basis to how the different Joining techniques are dealt with in the EUROCOMP Design Code and, more generally, how the bonded Joint sections of the Code are structured. The main joint design principles are listed below, followed by further explanations ... 

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