Inappropriate Material

Design error Inappropriate material Manufacturing fault Incorrect installation Unexpected service conditions Deliberate or accidental misuse. 

Intrinsic faults in the design of a product generally imply a lack of appreciation of how the product is used in service, and what it is subjected to. This includes underestimating the stress or strain levels involved or not understanding the detailed distribution of stresses 

Inappropriate choice of material arises for basically the same reasons as poor design but in many cases it could be argued that those responsible were in a position to know better. Probably more than for the other reasons for failure, wrong choice of material stems from overlooking known problems and the experience of others. Also, in many cases the problem with the material selected would have been realised if adequate testing had been carried out. 

There are certainly cases where rubber components are specified by the user for incorporation into a product but the user s expertise in the material is questionable. Many years ago it amused staff at a mbber moulding company that a prestigious car manufacturer had black rubber written on the drawing as the material specification. Nevertheless he was always provided with the best quality. 

The author owned an outboard motor which was very well engineered except that the mbber sparking plug cover cracked in a matter of weeks. The company appeared unaware that there was more than one type of mbber nor that stress concentrations aided ozone cracking. 

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The principal economic implications of corrosion of a plant are the initial cost of construction, the cost of maintenance and replacement, and the loss of production through unplanned shutdowns. The initial cost of the plant is influenced by material selection, and a choice of material that is more corrosion resistant than is necessary for the safe operation of the plant over its design life is a very expensive error. This cost involves initial outlay of money, and plants have been built which could never be profitable because of the inappropriate materials selection. 

The consequence of this inappropriate materials selection is the squandering of natural resources that characterises the industrialised nations of the world, coupled with a growing problem of waste disposal. Control is certainly necessary to prevent the uncontrolled dumping of these non-degradable polymers in the environment. Arguably control is also needed to prevent these kinds of material being fabricated into barely serviceable items in the first place. 

The pesticide materials now available meet most of the requirements for good control of the prevalent diseases and pests in the tropics. Most urgently needed are accurate data to provide reliable guidance to commercial firms having pesticides for the market in tropical countries. In the tropics, as elsewhere, the more progressive farmers are always interested in improvements and better methods. Too often, unfortunately, they are disillusioned by control failures which are due to lack of information or to ineffective or inappropriate materials. 

Recent work on soil sample preparation is reviewed below. Rubio and Une [20] have discussed the risks of soil sample contamination using inappropriate materials, containers and tools as well as possible analyte loss during sample loading. 

Material failures can be caused by a number of factors, either individually, or in combination, including substandard materials, inappropriate materials selection, poor design, equipment abuse, unexpected stresses or environmental conditions, and poor maintenance practices and/or neglect. Many failures, in one way or another, involve human error to some extent. 

There are materials, which can form varieties of nonstoichiometric compounds. For example, Pb02 can coexist as PbO where x can have values from 0 to 2. Among these oxides, most photoactive oxide is PbOo.8- If PbOo.8 oxide is to be prepared by anodic oxidation of lead, it is possible that surface of the lead film might contain other forms of oxides as well. Thus, a PEC cell prepared by anodization of lead may give a low photoresponse, not because PbOo.8 is an inappropriate material but because anodized surface may be contaminated with other forms of oxides as well. There seems to have no nondestructive technique available to confirm the uniformity of surface with photoactive species, especially of a large area electrode. Sharon and coworkers [111] has recently developed a laser scanning system to overcome this problem. A laser... 

In this case the problem was primarily caused by use of inappropriate material. The local supplier of acetal resins advised that acetal is not recommended for prolonged exposure outdoors, that the copolymer grades (with ethylene oxide) are better than the homopolymer, and a good UV stabiliser is essential. 

FIGURE 7.2.3.3 Airflow in a Laboratory Hood. This idealized situation can be compromised by inappropriate materials in the hood, poor airflow, or rapid arm movement that can allow the interior atmosphere to flow back into the laboratory. 

The reasons for such defects to occur can be related to any of the process steps described before, e.g. lay-up, vacuum set-up or mould design. Some more generic defects may also be related to inappropriate material choices (e g. insufficient adhesion strength of bonded assemblies due to the use of inappropriate peel ply). 

Specification errors include mistakes and omissions made during the design process, such as incorrect actuator sizing or inappropriate materials of constmction selection. Specification errors exist from the point of installation and remain throughout the SIF life. 

Fatigue has important application in the automotive industry, in which components are subject to continuous vibration and, sometimes, rather large oscillations. Under these circumstances, components that use the inappropriate material or are inadequately designed may fail. In order to aid the design process, it is therefore vital to have some measure of the fatigue life of the material. 

Basic principles should be stressed throughout their education. An example is to visit only age-appropriate sites. Students under the age of thirteen should not have a Facebook account. Stress to students to search the Internet safely. Even though a school can have a firewall and apply filtering software, inappropriate materials can still come through. 

Only in a couple of long-term experiments was seal degradation observed, and this might have been the consequence of an inappropriate materials selection. Silicone seals in direct contact with a perfluorosulfonic acid membrane suffer from degradation, at the anode as well as at the cathode [84]. The degradation is probably caused by acidic decomposition of the sealing material, leading to... 

Electrostatic discharges from machinery, the decanting of solvents and other processes which are poorly managed due to a lack of procedures, training and use of inappropriate materials can also cause fires. 

In technical conditions, errors that stand out include mistakes in design and specifying standards and in selecting inappropriate materials and forms of ventilation. Furthermore, there can be serious operational and maintenance errors that can cause major failures and consequently undesired events. 

Error in the choice of the solution model. Wrong element type. Inappropriate material model. Inappropriate load model Etc... 

The current state of the world seismic codes with respect to nonengineered buildings is also a key concern, given the lack of seismic codes for residential buildings and the age of buildings. Many of these buildings are largely vulnerable, use heavy or inappropriate materials, and are not built based on historical earthquake or future... 

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