Knuckle

The Scania plant at Falun in Sweden manufaetures bus and truck steering knuckles. These are safety-critical components that are specified as having to be crack-free. For this reason, every component is now inspected using an automatic process that ensures the appropiate inspection is consistently canied out to the required standards of quality. Photos of the system are shown in Fig 1. The principle of operation is as follows. 

The chemist now gives her knuckles a crack and begins. An appropriate sized flask or PP container is placed in a tray of water on the stirplate. Into the flask is dumped 800mL acetone, 25mL... 

The code provides design requirements for closures which are flat, elhpsoidal, spherically dished, hemispherical, conical (without transition knuckles), conic convex to pressure, toriconical concave to pressure, and toriconical convex to pressure. 

Head attachment. UW-13. Fig. UW-13.1 Fillet welds. UW-18. UW-36 Table UW-12 Knuckle radius. UG 32. UCS-79 Torispherical head. Pressures. 

Internal-pressure design rules and formulas are given for cylindrical and spherical shells and for ellipsoidal, torispherical (often called ASME heads), hemispherical, and conical heads. The formulas given assume membrane-stress failure, although the rules for heads include consideration for buckling failure in the transition area from cylinder to head (knuckle area). 

Longitudinal joints in cylinders are more highly stressed than circumferential joints, and the code takes this fact into account. When forming heads, there is usually some thinning from the original plate thickness in the knuckle area, and it is prudent to specify the minimum allowable thickness at this point. 

Rules for the design of shells of revolution under internal pressure differ from the Division 1 rules, particularly the rules for formed heads when plastic deformation in the knuckle area is the failure criterion. Shells of revolution for external pressure are determined on the same criterion, including safety factors, as in Division 1. Reinforcement for openings uses the same area-replacement method as Division 1 however, in many cases the reinforcement metal must be closer to the opening centerline. 

The heatable areas of the diyer are the vessel wall and the screw. The diyer makes maximum use of the product-heated areas—the filling volume of the vessel (up to the knuckle of the dished head) is the usable product loading. The top cover of the vessel is easily heated by either a half-pipe coil or heat tracing, which ensures that no vapor condensation will occur in the process area. In addition to the conical vessel heated area, heating the screw effectively increases the heat exchange area by 15-30 percent. This is accomphshed via rotary joints at the base of the screw. The screw can be neated with the same... 

Kndchel, m. knuckle ankle (pi.) dice. Knochen. m. bone. 

Dished or Basket Heads consist of a spherical segment normally dished to a radius equal to the inside diameter of the tank cylinder (or within a range of 6 inches plus or minus) and connected to the straight cylindrical flange by a knuckle whose inside radius is usually not less than 6 per cent of the inside diameter of the cylinder nor less than 3 times the thickness of the head plate. Basket heads closely approximate hemi-ellipsoidal heads. 

Bumped Heads consist of a spherical segment joining the tank cylinder directly without the transition knuckle. The radius = D, or less. This type of head is used only for pressures of 10 pounds per square inch or less, excepting where a compression ring is placed at the junction of head and shell. 

MR = principal radius of head in feet mR = radius of knuckle in feet R = radius of cylinder in feet... 

Figure 4-359. Knuckle joint auxiliary tool. (Courtesy Bowen Tools, Inc.)...

Knuckle Joint with Overshot and Wallhook Guide contacting Fish in a cavity... 

Thus, there is an optimum depth of packing for each individual duty and, in practice, it is usually found that an intersection near the knuckle on the demand curve produces the most economic selection. 

Juvenile dermatomyositis (JDM) is perhaps the most uniform, in terms of clinical and histopathological features, of the whole PM/DM disease complex. Presentation may be before 5 years of age with peak incidence between 8 and 12 years. The disease may remit and recur until well into young adult life. The skin lesions include a facial rash in butterfly distribution across nose and cheeks. Erythematous skin changes are seen over extensor surfaces of joints, especially knees, knuckles and elbows. Muscle involvement is generally evident some time later and takes the form of weakness and stiffness, particularly affecting shoulder and pelvic musculature. Proximal muscles are often worse affected than distal muscles and extensors worse than flexors. In the absence of prompt and effective treatment contractures may occur at elbows, ankles, knees, and hips. Subcutaneous calcification and skin ulceration may be found calcification of deeper-lying connective tissue may be apparent on X-ray. 

In Figure 13.7 Rk is the knuckle radius (the radius of the torus) and Rc the crown radius (the radius of the sphere). For the spherical portion ... 

The ratio of the knuckle radius to crown radius should be made not less than 6/100 to avoid buckling. The stress will be higher in the torus section than the spherical section. 

There are two junctions in a torispherical end closure that between the cylindrical section and the head, and that at the junction of the crown and the knuckle radii. The bending and shear stresses caused by the differential dilation that will occur at these points must be taken into account in the design of the heads. One approach taken is to use the basic equation for a hemisphere and to introduce a stress concentration, or shape, factor to allow for the increased stress due to the discontinuity. The stress concentration factor is a function of the knuckle and crown radii. 

The ratio of the knuckle to crown radii should not be less than 0.06, to avoid buckling and the crown radius should not be greater than the diameter of the cylindrical section. Any consistent set of units can be used with equations 13.43 and 13.44. For formed heads (no joints in the head) the joint factor 7 is taken as 1.0. 

A formed section would normally be used for the transition between a cylindrical section and conical section except for vessels operating at low pressures, or under hydrostatic pressure only. The transition section would be made thicker than the conical or cylindrical section and formed with a knuckle radius to reduce the stress concentration at the transition, Figure 13.11. The thickness at the knuckle can be calculated using equation 13.46, and that for the conical section away from the transition from equation 13.45. 

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