Failure steels

To achieve large deformations without failure, steel members must be sufficiently laterally braced and connected to avoid buckling and instability problems. As unstifTened elements buckle, the cross sectional properties are reduced and the... 

Failure Type Bond Failure Steel Break off Steel Break off Bond Failure... 

A particularly insidious failure mechanism that is commonly found in carbon-steel tubing is under-deposit corrosion. In many cases, corrosion products fomi a scab that can mask the presence of the pitting, making it difficult to quantitatively assess using conventional NDT methods. However, by combining proper cleaning procedures with laser-based inspection methods, the internal surface of the tubing can be accurately characterized and the presence of under-deposit corrosion can be confirmed and quantified. 

The principal type of shear test specimen used in the industry, the lap shear specimen, is 2.54 cm wide and has a 3.23-cm overlap bonded by the adhesive. Adherends are chosen according to the industry aluminum for aerospace, steel for automotive, and wood for constmction appHcations. Adhesive joints made in this fashion are tested to failure in a tensile testing machine. The temperature of test, as weU as the rate of extension, are specified. Results are presented in units of pressure, where the area of the adhesive bond is considered to be the area over which the force is appHed. Although the 3.23-cm ... 

The steel shell that encloses the refractory is exposed to significant forces from the expansion of the refractory as well as the load from the refractory and the charge within the furnace. Similarly, the stmctures that support the furnace and the foundations must be designed to assure safe operation. A failure of any component can have serious consequences. 

Fig. 16. Maximum shear stress at bore vs number of cycles to failure for specimens of EN25 T steel at various k values. +, / = 1.2 Q = 1-4 ...

Steel Surface hardness, HRC Method of hardening Number of shafts tested Cycles to failure x 10 ... 

Eor steel and other ferromagnetic materials, property deterrnination is more difficult. Other tests are made to measure the continuity of protective metallic coatings. Residual stresses induced in welded stmctures and in components in service owing to chemical attack may contribute to early failure. 

Structural Considerations. Sdos, bins, and hoppers fail, in one way or another, each year. The causes of silo failures are many and varied (9). Such failures can range from a complete and dramatic stmctural coUapse, to cracking in a concrete wall, or denting of a steel shell. This last is often a danger signal indicating that corrective measures are required. 

Wear owing to corrosion and/or erosion can be particularly dangerous. For example, as carbon steel corrodes, the reduced wall thickness can eventually lead to a stmctural failure. This problem can be compounded through erosive wear of the silo wall. 

The bellows is formed from a length of thin-walled tubing by extmsion in a die. The metals used in the constmction of the bellows must be ductile enough for reasonably easy fabrication and have a high resistance to fatigue failure. Materials commonly used are brass, bronze, beryllium copper, alloys of nickel and copper, steel, and Monel (5). 

Insoluble Sulfur. In natural mbber compounds, insoluble sulfur is used for adhesion to brass-coated wire, a necessary component in steel-belted radial tires. The adhesion of mbber to the brass-plated steel cord during vulcanization improves with high sulfur levels ( 3.5%). Ordinary rhombic sulfur blooms at this dose level. Crystals of sulfur on the surface to be bonded destroy building tack and lead to premature failure of the tire. Rubber mixtures containing insoluble sulfur must be kept cool (<100°C) or the amorphous polymeric form converts to rhombic crystals. 

Calcium—Silicon. Calcium—silicon and calcium—barium—siUcon are made in the submerged-arc electric furnace by carbon reduction of lime, sihca rock, and barites. Commercial calcium—silicon contains 28—32% calcium, 60—65% siUcon, and 3% iron (max). Barium-bearing alloys contains 16—20% calcium, 9—12% barium, and 53—59% sihcon. Calcium can also be added as an ahoy containing 10—13% calcium, 14—18% barium, 19—21% aluminum, and 38—40% shicon These ahoys are used to deoxidize and degasify steel. They produce complex calcium shicate inclusions that are minimally harm fill to physical properties and prevent the formation of alumina-type inclusions, a principal source of fatigue failure in highly stressed ahoy steels. As a sulfide former, they promote random distribution of sulfides, thereby minimizing chain-type inclusions. In cast iron, they are used as an inoculant. 

For knitted fabrics exhibiting high extensibiUty to failure, the ball burst test is recommended (ASTM D3787). A poHshed steel ball is pressed onto a rigidly held circle of knitted fabric. The force on the ball required to mpture the fabric is reported as breaking strength. 

Rotating Beam Fatigue Test for Steel Cords. The purpose of this test method is to evaluate steel cord for pure bending fatigue (121). The test sample consists of a 3-mm diameter mbber embedded with steel cord. Different bending stress levels are appHed and the time to failure is recorded. The test stops at 1.44 million cycles. The fatigue limit is calculated from S—N (stress—number of cycles) curve. 

Ceramic ball beatings are also sometimes effective ki operation with water which would result ki rapid failure with steel beatings. This capabiUty may result from a thin hydrodynamic film formed from very small hydrated Si N wear particles and the water (44). 

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