Hairline crack

There are no hard-and-fast rules to follow in setting safety factors for any given material unless experience exists. The most important consideration is of course the probable consequences of failure. For example, a little extra deflection in an outside wall or a hairline crack in one of six internal screw bosses might not cause concern, but the failure of a pressure vessel or aircraft wing might have serious safety or product-liability implications. 

Spalling—hairline metal surface cracks, flakes or splinters... 

Hairline cracks, flakes, or splinters that can occur out of the surface of a refractory or steel as a result of changes in furnace temperature or long-term overheating. 

In the case of epoxide cements at temperatures lower than 20° C, the viscosity increases so much that pumping becomes difficult [342]. Small amounts of aromatic solvents reduce the viscosity satisfactorily. Ethylene glycol butyl ether also changes the interfacial tension so that the polymer may penetrate into hairline cracks and fine capillaries. This is advantageous in blocking liquid or gas migration. 

Poor adhesion of membrane to metal is the leading cause of failure in solid-state potentiometric sensors [116], For glass membranes, the mismatch of thermal coefficients of expansion between thin glass membrane and metal (mostly Pt) has been attributed to premature failure due to hairline crack formations in the glass layer [60], For polymer-based membranes, water vapor penetration was reported to compromise the membrane-metal interface, therefore affecting the sensor s performance. 

Timely and consistent maintenance provides assurance that the system is physically in the condition intended. When more than hairline cracking appears, the openings should be cleaned out and filled with new material according to the manufacturer s instructions. Loss of bonding to the substrate may be detected by surface bulges or an abnormal sound when the surface is tapped with a light hammer. 

Piezoelectric devices have found a host of other aerospace applications. For example, one of the most troublesome problems faced by airlines is the detection of tiny hairline fractures in an aircraft body. These fractures often appear long before they can be observed visually during routine maintenance procedures. Yet, once they begin to develop, they can quite suddenly and dramatically lead to much larger cracks and failures that result in disastrous accidents. For this reason, airline companies are constantly... 

Imaging is a common technique for assessing materials. For example, airliner structural materials are often X-ray-imaged to check for hairline cracks or other signs of imminent failure. In scientific applications, advances in nanotechnology have produced a parallel need for improved methods of imaging nanomaterials on the molecular scale. 

The University of Illinois developed a technology for repairing hairline cracks in RPs by embedding microcapsules containing monomers corresponding to the plastic matrix.403 404... 

Bubble point test. For separation applications, it is critical that the membranes are free of defects such as hairline cracks or pinholes. A simple technique widely used in the membrane industry to detect any defect or very large pores in organic or inorganic membranes is the bubble point test. 

The critically important pore size and its distribution can be determined by a host of measurement techniques. The bubble point test is used primarily for delecting any defects or hairline cracks and for estimating the average pore size. Traditionally mercury porosimetry and nitrogen adsorption/desorpiion have been the workhorse for determining the pore size distribution of a porous membrane. They arc, however, usually limited to a pore diameter range of >3 nm and 1.5-100 nm, respectively. Determination... 

In reinforced elements, cracks of small width (hairline cracks less than 0.1 mm) are generally of little consequence and can be tolerated without affecting the serviceability of the structure (Hewlett and Morgan, 1982). Cracks of widths much greater than 0.5 mm, however, can seriously weaken the structure and increase the deflections under load and in already weakened structures they increase the possibility of reinforcement corrosion, which leads to further downgrading (Hewlett and Morgan, 1982). In order to prevent further deterioration it is most important to repair such cracks. 

Gun-grade sealant Thixotropic sealants are commonly referred to as gun-grade sealants as they are applied with the aid of an application gun. Hairline cracks Small cracks of a random pattern in an exposed concrete surface. 

Film formation Avoidance of hairline cracks/crazing... 

The memorial has become a totem, so much so that its tiniest imperfections make news. Last fall somebody noticed a few minute cracks at the seams between several of the granite panels. The cause of the hairlines is still unknown, and the builders are a little worried. 

The operation can be ended by depolarization (see footnote above) or by a hairline crack in the piezo materials. 

Besides delamination, actual cracking of silicon die is a failure mode that can occur from excessive adhesive stresses, voids, and moisture absorption. Residual stresses in adhesive-attached single-chip devices become critical as the size of the device increases and dissimilar die and leadframe materials are used. Several types of fractures that can occur within the die or within the adhesive are shown in Fig. 6.8. A hairline crack in an 1C chip that resulted from adhesive stress is shown in Fig. 6.9. 

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