Destructive testing failure

The trainee will visit other departments in the head office to learn about the supporting facilities which are available such as non-destructive testing, metallurgical and failure analysis, hazard analysis and quality assurance. Emphasis is laid on safety, i.e. the integrity and safety of the plant in operation and on the surveyor s own personal safety. It is important that the trainee understands the techniques involved, particularly the limitations of their application. 

More typically, the failure to preserve evidence can hurt the company in a lawsuit. For example, where a defense expert in a product liability case conducts destructive testing on the product, thereby rendering it unfit or unavailable to the plaintiff s expert, the court may sanction the conduct by excluding the testimony of the defense expert. Alternatively, if crucial documents are destroyed or lost, thejudge may instruct thejury to assume the worst—that the documents contained information harmful to the defendant s position in the litigation. 

To demonstrate, statistically, low failure rates on EED s requires that enormously large number of destructive tests be performed. And separate tests, in large numbers, are required for each new type of EED appearing on the market. It is evident that the destructive method is expensive and time con-sumin g and for this reason, the need for alternative or, at least complimentary techniques, became recognized... 

One recourse is to use low-destructive test methods that can quantify the efficacy of protective agents [27] and provide evidence of improper use or application of the silicone [4, 15, 27, 28, 32, 36, 37], High-resolution microscopy would offer the advantage of visualizing the reasons for failure of hydrophobic treatments just after application, before they became visible very much later when the weathered materials started to fail [38, 39]. Weak areas such as inadequate uptake of the treatment, poor penetration depth, and incompleteness of coating could be documented just after the masonry treatment had been applied. 

Mechanical properties. Hardness is the most common mechanical test. See Chapter 5, Mechanical Testing. Hardness testing, for instance, may be used to indicate whether fasteners in specific critical services are greater or less than the value required to avoid a premature failure. Mechanical tests other than hardness are destructive. If a destructive test is required to ensure compliance it is performed on a sample piece from the lot. Mechanical tests are time consuming and only used when required by the specification. 

The physics of failure (PoF) approach to determine the mode and mechanism of failure of an electronic part or assembly has been used successfully for many years. PoF is a step-by-step approach that assures that information is not irretrievably lost. Thus, in performing a failure analysis, it is important to perform all the tests that are nondestructive first. These tests may or may not give a clue about the cause of failure but, if omitted, either can no longer be performed or are compromised by the subsequent destructive tests. 

Investigations around the world has shown extensive problems with poor grouting of the ducts and consequent leakage of water, with and without chlorides, onto the steel cables with subsequent severe corrosion. In some cases this has lead to failure of bridges and other structures (e.g. Woodward and Williams, 1988). The problem is that once the steel has been placed 50-100 mm or deeper within a structure, surrounded by a steel or polymer conduit, normal non-destructive test techniques are not effective. 

Because of the unavoidable fluctuations of data that result from destructive testing after immersion, we frequently report a composite rating that represents the range in which retention of properties falls when the best straight line is extended to 10 years. If any of the three measured properties falls below 50% retention, that resin/medium combination is rated as unacceptable. Resins that are so badly deteriorated as to be unmeasurable are labeled complete failure. The rating is the average of the ratings for the three measured properties if no failure occurs. 

Tests to measure the bond which can be obtained with the concrete of the structure to be strengthened are best carried out on the structure itself. A possibility is to utilise a pull-off test as developed for the non-destructive testing of concrete(21). A circular steel probe is bonded to the concrete surface and specially designed portable apparatus is then used to pull off the probe, along with a bonded mass of concrete, by applying a direct tensile force. Any defects in bond would be revealed by the occurrence of failures at the adhesive-concrete interface. 

The development of the WPCs for load-bearing structural applications necessitates the characterization of their strain rate-dependent mechanical properties. In this regard, the effect of strain rate on flexural properties of WPG was addressed by Tamrakar and Lopez [49]. The strain at failure was not significantly influenced by the strain rate variation. A prediction model for the effects on strain rate on the modulus of elasticity (MOE) of WPG material was demonstrated based on the viscoelastic standard solid model. Yu et al. [50] analyzed the variability of the dynamic young s modulus of WPG, which was measured by different non-destructive test (NDT) methods. They also estimated the correlativity between the dynamic Young s modulus and the static MOE of WPG. 

Non-destructive test (1) A test that yields information about failure under mechanical stress without actually stressing to failure. (2) More broadly, any test to evaluate a property of a material, part, or structure that does not significantly damage the part. Techniques used include ultrasound, magnetic inspection of metals and welds. X-ray inspection, infrared, nuclear magnetic resonance, and sonic analysis. Although an indentation-hardness test leaves a permanent mark, in many tests of parts it is nondestructive. 

Evaluating the need for laboratory tests, such as destructive/nondestructive failure analysis... 

Non-destructive testing (NDT) Design demands on materials selection Failure analysis... 

The examples given are for documents. Types of destructive testing carried out on production software products (typically described as deliverables) are well known and include module, integration and system testing. Specialized types of testing are common in specific environments, but all should have the same focus - cost of failure. 

Inspection - a maintenance action involving the careful scrutiny of an item of electrical equipment, using, if necessary, all the senses to detect any failure to meet an acceptable and safe condition. An inspection does not include any dismantling of the item of equipment. Examination - an inspection together with the possible partial dismantling of an item of electrical equipment, including measurement and non-destructive testing as required, in order to arrive at a reliable conclusion as to its condition and safety. 

A highly modified, toughened low viscosity epoxy offering excellent mechanical and thermal properties in addition to a very low moisture absorption and a fiammability rating of V-0. Suitable for radomes, antennae and other critical electrical applications. Aiiows self adhesion under vacuum or pressure cure, to honeycomb without the use of a fiim adhesive, and displays cohesive honeycomb failure during destructive testing, a. 1.47 j. 1.2% at saturation after 100 hour boil. k. 156 m. 3... 

However, bond appearance after destructive testing is not the only element of a bond specification. Nondestructive proof testing of bonded parts and minimum failure loads are also used routinely. 

The objective of surface treating is to obtain a joint where the weakest link is the adhesive layer and not the interface. Thus, destructively tested joints should be examined for mode of failure. If failure is cohesive (within the adhesive layer or adherend), the surface treatment is the optimum for that particular combination of adherend, adhesive, and testing condition. However, it must be realized that specimens could exhibit cohesive failure initially and interfacial failure after aging. Both adhesive and surface preparations need to be tested with respect to the intended service enviroiunent. 

The most commonly used methods for evaluation of adhesive bonds are mechanical tests such as tensile shear and peel tests that determine the weakest link in a bonded assembly. Although these tests are useful in the development and quality control of adhesives, they are destructive and cannot offer failure prediction for in-service components. Ultrasonic inspection is the most commonly used non-destructive test method and can accurately assess de bonding in single adhesive bonds, providing that the sensor is perpendicular to the defect plane. However, ultrasound has some limitations in... 

Use of nondestructive techniques is limited to research study for characterization of failure mechanisms, or when investigating root cause of a field failure. Destructive techniques commonly include cross-sectioning combined with optical inspecfion, and SEM and EDX. Chemical etching solutions are used to reveal features of solder alloy microstructures and interface in-termetalUc formation. Mechanical destructive tests such as lead pull test for leaded packages and dye-and-pry for area packages are also performed to determine quality and damage levels. 

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