Welding behavior

By considering the influence of the interphase upon annealing, it is possible to shed a little light on the welding behavior of semi-crystalline polymers, which has received much less attention than that of amorphous polymers. Because of the ill-defined morphology of the interphase the welding characteristics of semi-crystalline polymers are quite different from amorphous polymers and are far from well understood. 

Figure 3 shows the findings. The thin film of 0.25 mm showed a definite S-shaped variation, going from transparency to nearly complete absorption as the carbon black level went from 0.03 to 0.07 percent. If polymers are formulated with carbon black levels in this range, their welding behavior can be expected to be highly sensitive to tiny variations in formulation. 

Thus, weld behavior was quite variable, depending on crack location and temperature. These differences arose from a number of metallurgical effects, including compositional variations between the BM and weld wire and thermal cycling of the HAZ. Such factors altered the microstructure and influenced the austenite phase stability. A complex residual stress system was present in the welds as a result of weld metal solidification shrinkage and local plastic deformation of the HAZ. However, a detailed accounting of these factors is beyond the scope of this study. 

Fig. 1 Characteristical welding behavior depicted by a schematical diagram presenting the dependence of the welding depth to the applied irradiance...

Rajaraman, H., and Cakmak, M., The Effect of Glass Fiber Fillers on the Welding Behavior of Poly P-... 

Festa, D., and Cakmak, M., Spin Welding Behavior and Structure Development in a Thermotropic Liquid Crystalline Polymer, ANTEC Conf. Proc., Soc. Plastics Eng., 1992. 

Simulations of that kind result in a wide variety of A-scans and wavefront snapshots. The first screening of this material reveals, that the simulations in which the transducer is coupling partly to the V-butt weld and partly to the steel exhibit quite a number of pulses in the A-scans because the coupling at the interface of the weld results — due to the anisotropic behavior of the weld — in a complicated splitting of the transmitted wavefront. The different parts of the splitted wavefront are reflected and diffracted by the backwall, the interface, and — if present — by the notch and, therefore, many small signals are received by the transducer, which can only be separated and interpreted with great difficultie.s. 

Total interpenetration of chains (X approaches Rg) is not necessary to achieve complete strength when M > M and x < 7). However, a word of caution while complete strength may be obtained in terms of critical fracture measures such as G c and A lc, the durability, measured in sub-critical fracture terms, such as the fatigue crack propagation rate da/AN, may be very far from its fully healed state at r. We have shown that while the weld toughness A lc increases linearly with interdiffusion depth X as K f. X, the fatigue crack propagation behavior of partially healed welds behaves as [1]... 

All aspects of the material s chemical, mechanical and physical properties which are included in the specification should be capable of measurement and certification. For critical duties all material supplied should be fully tested and certified by competent approved, independent test laboratories. All items of plant should be purchased with material certification. Additional certification is required in cases where the fabricator, in manufacturing an item of plant, used techniques such as welding or heat treatment which may affect the corrosion behavior of the construction materials. 

The battery is maintenance-free and the battery housing is completely sealed by welding. In the case of the failure of one cell in a cell string, the failed cell shorts itself, which means the battery can be operated further even cell failures occur. The reason for this behavior is that in the case of cell failures the ceramic breaks and the sodium reacts with NaAlCl4 forming of a sponge of A1, which builds up in the cell between the cell case and the positive current collector. Freeze/thaw cycles have no adverse effect on the cells, and batteries will not fail by cooling down. 

Table 8-43 Plastics behavior with ultrasonic welding...

Bar joists have adequate lateral support to prevent the top chords of the joists from laterally buckling under the loads published in the manufacturer s load tables. For required resistance higher than the load tables or for plastic behavior of the joists, additional lateral bracing may be required. Evaluations should be based on as-built dimensions and field inspections at the elements and welds. If rebound resistance is required, additional uplift bridging may be required. 

J. O Donnell, H. Huthmann, and A. A. Tavassoli, The Fracture Toughness Behavior of Austenitic Steels and Weld Metal Including the Effects of Thermal Aging and Irradiation , Int. J. Pres. Ves. Piping, 65 (1996), 209-220. 

Habib, K.E., Weld, K.P., Rice, K.C., Pushkas, J., Champoux, M., Listwak, S., et al. (2000) Oral administration of a corticotropinreleasing hormone receptor antagonist significantly attenuates behavioral, neuroendocrine, and autonomic responses to stress in primates. Proc Natl Acad Sci USA 97 6079-6084. 

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