Bonded joints

Verbindung, /. compound combining, combination, union connection blending (of colors) joining, fastening, binding joint, bond tie, link communication union, alliance, society,... 

Derivation of the Gaussian Distribution for a Random Chain in One Dimension.—We derive here the probability that the vector connecting the ends of a chain comprising n freely jointed bonds has a component x along an arbitrary direction chosen as the x-axis. As has been pointed out in the text of this chapter, the problem can be reduced to the calculation of the probability of a displacement of x in a random walk of n steps in one dimension, each step consisting of a displacement equal in magnitude to the root-mean-square projection l/y/Z of a bond on the a -axis. Then... 

The type ir 2 can occur in molecules which have adjacent joint atoms and in which the main orbital density is in a joint-joint bond. It extends somewhat... 

FIGURE 3.9 Plot of tensile shear strength of an aluminum joint bonded with an elevated-temperature curing epoxy adhesive as a function of test temperature. 

FIGURE 10.3 Effect of silane adhesion promoter on the durability of a mild steel joint bonded with epoxy adhesives.16... 

Representative data are shown in Fig. 10.5 for aluminum joints bonded with an epoxy film adhesive and a standard chromate-containing primer. Up until recently, standard corrosion-resistant primers contained high levels of solvent, contributing to high levels of volatile organic compounds (VOCs) and chromium compounds, which are considered to be carcinogens. As a result, development programs have been conducted on waterborne adhesive primers that contain low VOC levels and little or no chrome. Data are presented on several of these primers in Tables 10.8 and 10.9. 

FIGURE 15.11 Effect of outdoor weathering on the strength of aluminum joints bonded with epoxy-polyamide.30... 

Table 15.17 shows the adverse effect of stress and tropical climates on aluminum joints bonded with various adhesives. If a 30-day saltwater spray were used as an accelerated test to determine the long-term performance of these adhesives in a tropical climate, it would be very misleading. Saltwater spray had very little effect on the strength of stressed or unstressed joints with the exception of one acrylic adhesive. However, the stressed specimens in Florida almost all completely degraded. Panama was not nearly as severe an environment. These data illustrate the point that permanence or durability must be tested in the specific environment. 

TABLE 16.3 Effect of Surface Treatment on Aluminum Alloy Joints Bonded with a Heat Cured Epoxy Adhesive (EC-3443, 3M Company)6... 

TABLE 16.4 Effect of Substrate Treatment on Strength of Aluminum Joints Bonded... 

Copper substrates are commonly bonded with epoxy adhesives in the microelectronics and marine industries. Compared to aluminum substrates, copper when bonded with epoxy adhesives provides lower initial strength. Depending on the adhesive and the type of test used, this can be as much as 50 percent lower. Similar to aluminum joints, copper joints bonded with epoxy adhesives can show poor durability in moist environments unless the interface is protected. 

TABLE 16.6 Effect of Heat Aging on Tensile Shear Strength of Copper Joints Bonded with a DGEBA Epoxy Cured with Tri-2-ethylhexoate Salt of DMP-30 and DEAPA29... 

Completely cured epoxy adhesives are almost nontoxic, although caution must be exercised when machining, grinding, etc., joints bonded with epoxies due to the proliferation of airborne particles. Also, decomposition products may exhibit substantial vapor pressures and pose health and safety issues. However, it is the exposure to the uncured components that can be the most harmful and is the subject of this chapter. 

We finally observe that the effective orbital probabilities of Eqs. (52-54) and the associated condensed probabilities of bonded atoms (Eq. 55) do not reflect the actual AO participation in all chemical bonds in AB, giving rise to comparable values for the bonding and nonbonding (lone-pair) AO in the valence and inner shells. The relative importance of basis functions of one atom in forming the chemical bonds with the other atom of the specified diatomic fragment is reflected by the (nonnormalized) joint bond probabilities of the two atoms, defined by the diatomic components of the simultaneous probabilities of Eqs. (52 and 53) ... 

The underlying joint atom-orbital probabilities, Pab(A,/),/ e B and Pab(B, /), / e A, to be used as weighting factors in the average conditional-entropy (covalency) and mutual-information (ionicity) descriptors of the AB chemical bond(s), indeed assume appreciable magnitudes only when the electron occupying the atomic orbital Xi of one atom is simultaneously found with a significant probability on the other atom, thus effectively excluding the contributions to the entropy/information bond descriptors due to the lone-pair electrons. Thus, such joint bond probabilities emphasize of AOs have both atoms are simultaneously involved in the occupied MOs. 

Some applications of ultrasonics are inspection for flaws in forgings, flat-rolled products such as strips, sheets and plates, castings, extrusion billets, rolling blooms or slabs, bar stock, pipes, welded joints, bonded joints, monitoring cracks, measurement of thickness, measurement of fluid levels, microstructural features and monitoring corrosion. 

Fig. 2 Typical force-displacement trace for a CFRP joint bonded with the epoxy-film adhesive. (Crack length, a, values in mm.)...

Fig, 5 Giic versus measured a for the CFRP joints bonded with the epoxy-paste adhesive. 

Fig. 7. Photographs of microcracking in the adhesive layer for a joint bonded with the epoxy-film adhesive. Magnification (a) X80 (b) XI80. (The vertical black lines in (a) are drawn Imni apart).

Fig. 8. Discrepancy between the effective and measured crack lengths (expressed as a %) for joints bonded with the epoxy-film adhesive plotted as a function of measured crack length.

In the reverse move, the energy differences for all external broken bonds have changed sign, but the energy differences for the joint bonds connecting cluster 1 and 2 are the same as in the forward move. Thus, cluster 1 is created with probability... 

Based on our history of physical and chemical experiences, we can think of molecules as mechanical assemblies made up of simple elements like balls (atoms), rods (bonds), and flexible joints (bond angles and torsional angles) —see Fig. 2. Eq. (12) can then be expressed as... 

Tensile Strength of the Dentin-Acrylic Joint Bonded with Various Cyanoacrylates... 

Table Strength of Dentin-Acrylic VI Resin Joint Bonded With ...

Residual Strains and Stresses in an AbOa-Ni Joint Bonded with a Composite Interlayer FEM Predictions and Experimental Measurements... 

For that reason, the properties of stainless steel joints bonded with epoxy systems are of special interest. According to the literature, the aging behavior of such joints is critical [1, 2]. Mechanical tests reveal that the combined attack of water and temperature causes a strong deterioration in their performance [3]. It is necessary to understand the processes that are going on during aging in order to improve the reliability of structural adhesive bonding. 

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