Tire failure, mechanism

Solid residue was obtained by two processes to reduce discarded tires pyrolysis and thermal shock. Techniques such as X-ray, FTIR, TGA and SEM were used to characterize the samples. Two types of polyethylenetherephtalate, PET (virgin and recycled) were analysed physicochemical and mechanically to be used as matrix. A composite material was manufactured by employing a Brabender mixing chamber in order to nse the grannies as fdler on PET at different concentrations. The mixed material was laminated and tension test were undertaken in samples to acquire the mechanical properties. Studies of ffactography were performed to understand the failure mechanics. 

For mechanical explosions a reaction does not occur and the energy is obtained from the energy content of the contained substance. If this energy is released rapidly, an explosion may result. Examples of this type of explosion are the sudden failure of a tire full of compressed air and the sudden catastrophic rupture of a compressed gas tank. 

Tliere are a host of reasons why accidents occur in industry. Tire primary causes are mechanical failure operational error (human error), process upset, and design error. Figure 16.1.1 provides the relative number of accidents that have occurred in tlie petrochemical field. ... 

In the event of a mechanical failure when operating under high pressure, the gas inventory released would be less than that from a punctured bicycle tire, and in the case of explosion of this amount of gas its detonating power would be comparable with that of a small firecracker. 

Salt-bath Explosions. Tire third type of disaster in which after-the-fact protection is much less important than prevention is the molten salt-bath explosion. There have been serious disasters involving such baths, because personnel involved on both the management and the operating level failed to appreciate the potential hazards of the situation. Due to mechanical failure or human failure, or a combination of both, molten salt baths have been allowed to explode. The hazards of molten salt baths may be summarized as follows ... 

Each of tliese elements is a critical component of tlie stability program, but tire proper operation of environmental chambers is one element tliat is most often assumed. It is often taken for granted tliat in tire absence of external factors such as power loss or mechanical failure, a chamber, will maintain its predefined storage condition over tlie leiigtli of tire stability study, but tliis is rarely tire case. How do we ensure tliat tlie chamber will perform and maintain its set-point conditions as expected over tlie course of tlie stability study A properly executed qualiflcatioii program of tlie chamber prior to its routine use in a stability program will verify tliat tlie chamber can perform as expected. 

It is now well established that wear of rubber is not a purely mechanical failure process in that it contains a contribution due to thermal-oxidative breakdown of the polymer (226—228). Still, under severe conditions, which apply to all accelerated laboratory tests as well as to many situations encountered in tire wear, abrasion is dominated by tearing processes. 

We also note two reports on tire degradation of stacked films of oriented PET. In the first [36], photodegradation is said to be two-step in nature with weak links cleaving first followed by a much slower cleaving of the strong links . The chain scission process was tracked versus exposure time by measurement of solution viscosity [37]. In tire second paper [38], the surface nature of the degradation was reported and die rationale elucidated for why surface degradation causes overall mechanical failure limited by that layer, much as we have discussed in die impact properties of die PECT (see above). 

Whether these corrosive gas tests are reaUstic for materials other than those used for connectors or for operating electronic equipment is not clear. The test should be carried out, but the observation of no failures should not be taken to mean there will be no field failures in typical urban environments. Similarly, any failures that are observed should be carefully evaluated to ensure that the same mechanism would he operative in field situations. Connectors tire a somewhat unique part of an electronic assembly in that the active part is frequently a noble mettil and the sensitivity of the mated surfaces to failure may be lower thtin many other parts of electronic assemblies. Most failures in electronic assemblies attributable to the environment are due to ionic particle contamination in conjunction with atmospheric moisture. In 20 years of evaluating field failures in the United States, the author has never seen a failure that could be attributed to the effects of SOj, has seen a few caused by H2S or HCl, has heard of a few caused by NOx, and has seen several hundred that were caused by ionic contamination. Clearly, valid accelerated testing of electronic components, circuit boards, and assemblies must include ionic contamination. Emerging methods are discussed in the Fine Particle Testing section in this chapter. 

Xenobiotic-induced liver injury has become the most frequent cause of acute liver failure in humans in the United States and aroimd the world, exceeding all other causes combined (Watkins and Seef, 2006). Owing to its detoxification mechanisms, the liver protects tire individual against xenobiotic-induced injury. Certainly, the liver toxicity caused by chemical warfare agents (CWAs) is a potential area of concern. 

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