Mechanical failure modes

ASTM C1624-05. (2010a) Standard Test Method for Adhesion Strength and Mechanical Failure Modes of Ceramic Coatings by Quantitative Single Point Scratch Testing, American Society for Testing Materials. 

A particular problem, which is explored in detail in Section 7.5.1, is that the storage environment itself is able to influence the properties of these materials, since they are susceptible to moisture uptake. In extreme cases, storage in water has been found to cause the mechanical failure mode to change from brittle to tough [25]. 

Theoretical analysis of the structure In this analysis, only mechanical failure modes are considered to illustrate the approach. The specified safety factor is OS bj = 1-16 with COV < 10% for the material and the stress this corresponds to a failure probability lower than 2.4 10 . ... 

The first three chapters discuss definitions, adhesion theories, surface characterization and analysis, surface energy measurement methods, adhesion mechanism, failure modes, and surface treatment of materials. 

European Standards Committee, Advanced Technical Ceramics - Methods of Test for Ceramic Coatings — Part 3 Determination of Adhesion and Other Mechanical Failure Modes by a Scratch Test, European Standard prEN 1071-3, March 5, 2001. 

Accelerating Environment Environments Failure Mechanism Failure Mode... 

Figure 12.5 shows a schematic of the structure of a V-ribbed belt. The most commonly reported mechanical failure mode for this type of belt is wear, with delamination not generally perceived as a problem. This is of interest as most flexible composite elements will have a delamination failure mode of some description, and so the most obvious question to ask is why the V-ribbed belt does not. The probable answer is that the belt cord in a V-ribbed belt is isolated from the major distortions of the belt through its position above the belt/pulley interface. The large majority of the distortion of the belt takes place in the belt ribs, away from the cord. If the four shear stresses identified previously by Gerbert and Fritzson for a V-belt are considered, it can be seen that of the four i) and ii) do not apply to the cord layer in a V-ribbed belt. The cord layer in a V-ribbed belt therefore does not incur shear stress to the same extent as that in a V-belt. Thus the V-ribbed belt may be considered a better design in composite terms, with the individual elements of the composite more effectively employed and protected. 

Cycle Life Degradation Mechanisms, Failure Modes, Mitigation... 

CYCLE LIFE DEGRADATION MECHANISMS, FAILURE MODES, MITIGATION STRATEGIES, AND TECHNICAL PERSPECTIVES OF NEGATIVE ELECTRODES... 

Rather, for reliability analysis of electronic components all significant failure modes need to be considered. On the one hand there are the failure modes based on electrical overstress which normally indeed show a constant failure rate. But on the other hand there are mechanical failure modes of parts inside the electronic component or its packaging which exhibit an increasing failure rate, i.e. a time-dependent failure rate. 

The shear strength of the wall in diagonal tensile failure is therefore given by the minimum strength of the two resisting mechanisms - failure modes ... 

Also, periodically cycling the valves during the service life could help mitigate the mechanical failure mode of sticking between seating surfaces, and would provide assurance that the valve and operator are functioning, although this action would introduce a potential for failure. 

Introduction to Failure Modes Involving Mechanical Damage... 

Surface defects, if sufficiently severe, may result in failure by themselves. More commonly, they act as triggering mechanisms for other failure modes. For example, open laps or seams may lead to crevice corrosion or to concentration sites for ions that may induce stress-corrosion cracking. 

All areas of the cooling water system where a specific form of damage is likely to be found are described. The corrosion or failure causes and mechanisms are also described. Especially important factors influencing the corrosion process are listed. Detailed descriptions of each failure mode are given, along with many common, and some not-so-common, case histories. Descriptions of closely related and similarly appearing damage mechanisms allow discrimination between failure modes and avoidance of common mistakes and misconceptions. 

Remember that the failure position of a valve refers to its failure mode if there is a utility failure. A valve can mechanically fail in any position it is possible for a fail closed valve to get stuck in the open position. When doing a process hazard analysis it is important to consider all possible failure positions of a valve, and not only the failure position resulting from utility failure. 

This report provides an aging assessment of electric motors and was conducted under the auspices of the USNRC NPAR. Pertinent failure-related information was derived from LERs, IPRDS, NPRDS, and NPE including failure modes, mechanisms, and causes for motor problems. In addition, motor design and materials of construction were reviewed to identify age-sensitive components. The study included consideration of the seismic susceptibility of age-degraded motor components to externally-induced vibrational effects. 

This study is a good reference for the construction of fault/event trees of systems that are affected by valve performance. The valve failure modes are identified, the associated mechanisms are described in detail, and preventive measures are offered. 

Appendix III contains failure rate estimates for various genetic types of mechanical and electrical equipment. Included ate listings of failure rates with range estimates for specified component failure modes, demand probabilities, and times to maintain repair. It also contains some discussion on such special topics as human errors, aircraft crash probabilities, loss of electric power, and pipe breaks. Appendix III contains a great deal of general information of use to analysts on the methodology of data assessment for PRA. 

The sections to follow describe the most common machine-train failure modes critical speeds, imbalance, mechanical looseness, misalignment, modulations, process instability, and resonance. 

An imbalance profile can be excited due to the combined factors of mechanical imbalance, lift/gravity differential effects, aerodynamic and hydraulic instabilities, process loading, and, in fact, all failure modes. 

There are defect limits that are associated with random failure modes. For example, if there is a leak from a mechanical seal on a pump, where do we decide that the leakage is excessive and requires immediate maintenance Vibration analysis severity levels are also typical examples of when do we have severe enough conditions to warrant equipment shutdown and overhaul. In such circumstances, the defect limit is dependent upon individual subjective judgment. 

The second limitation is the life dispersion of machinery components. It is difficult to predict time-dependent failure modes because even they do not occur at the exact same operating intervals. Consider the life dispersion of mechanical gear couplings on process compressors. Both components are clearly subject to wear. If we conclude that their MTBF (mean-time between failure), or mean-time-between-reaching-of-detect-limit is 7.5 years, it is possible to have an early failure after 3 years and another... 

The failure mode of ESDVs for gas processing areas should always fail in the closed position, since this is the only mechanism to resolve gas fed fires or prevent explosive vapor buildups. The valves should be provided with an automatic fail close device such as an actuator with spring return specification. 

The detection and alarm circuits of fire and gas detection systems should be continuously supervised to determine if the system is operable. Normal mechanisms provide for a limited current flow through the circuits for normal operation. During alarm conditions current flow is increased while during failure modes the current level is nonexistence. By measuring levels at a control point the health of the circuit or monitoring devices can be continuously determined. End-of-line-resistors (EOLR) are commonly provided in each circuit to provide supervisory signal levels to the control location. 

Different factors contribute to the mechanical properties of plant tissue cell turgor, which is one of the most important ones, cell bonding force through middle lamella, cell wall resistance to compression or tensile forces, density of cell packaging, which defines the free spaces with gas or liquid, and some factors, also common to other products, such as sample size and shape, temperature, and strain rate (Vincent, 1994). Depending on the sample properties (mainly turgor and resistance of middle lamella), two failure modes have been described (Pitt, 1992) cell debonding and cell rupture. 

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