Combined joints

Classification of Combined (Joint) Toxic Actions of Two Compounds in Mixture... 

Placket and Hewlett (1952) provided a scheme of possibilities of combined (joint) actions, see Table 10.1. A major clue that can be taken from this scheme is that, in the initial assessment, it is important to evaluate whether interactions are actually occurring (present) or not (absent). 

This document, Publication No. 85, has recently been reissued as a combined Joint ISO and CIE Standard, ISO 10526 1999/C1E S005/E-1998 (11). The authors of these documents recognized the fact that the ultraviolet portion on the spectrum varied with many factors including geographical location, altitude, the time of year, etc. so they agreed to one standard set of values for reference purposes. This standard has been adopted worldwide. 

Chen, Lan-Tian (1986). Carbon-Titanium Combined Joints. In Chinese Journal of Biomedical Engineering 3, 55-61. 

Combined Joint—A Joint where the surfaces are held together by both adhesive and mechanical means. 

Combination joints using either screws or rivets may also be used and sheet metals can be successfully welded through a layer of suitable adhesive. 

Figure 7.18 Three different ways to apply the NCA in combined joints with ICA.

Combination joints are also used from time to time when composites, or other plastics, are involved. These employ either screws or rivets to reduce, or eliminate, peel and cleavage forces (Fig. 7.19). 

The project "Non-Invasive Inspection within an Asset Risk Management Strategy" is another joint industry project, funded by EC-THERMIE, representing the current trend towards onstream (non-invasive) inspection in combination with risk-based inspection philosophies to establish component condition. In this project, industry and authorities participate aiming at a beneficial use of today s NDT without sacrificing on safety. 

There is hardly a metal that cannot, or has not, been joined by some welding process. From a practical standpoint, however, the range of alloy systems that may be welded is more restricted. The term weldability specifies the capacity of a metal, or combination of metals, to be welded under fabrication conditions into a suitable stmcture that provides satisfactory service. It is not a precisely defined concept, but encompasses a range of conditions, eg, base- and filler-metal combinations, type of process, procedures, surface conditions, and joint geometries of the base metals (12). A number of tests have been developed to measure weldabiHty. These tests generally are intended to determine the susceptibiHty of welds to cracking. 

Stress and Distortion. The forces acting on a stmcture are transmitted through the welded joints that is, the joint is subjected to simple tension (or compression), bending, shear, or torsional stresses, or to combinations of these stresses owing to combined loading situations. Weldments must be of a proper size, length, and location to withstand the loads imposed during service. 

Emulsion Adhesives. The most widely used emulsion-based adhesive is that based upon poly(vinyl acetate)—poly(vinyl alcohol) copolymers formed by free-radical polymerization in an emulsion system. Poly(vinyl alcohol) is typically formed by hydrolysis of the poly(vinyl acetate). The properties of the emulsion are derived from the polymer employed in the polymerization as weU as from the system used to emulsify the polymer in water. The emulsion is stabilized by a combination of a surfactant plus a coUoid protection system. The protective coUoids are similar to those used paint (qv) to stabilize latex. For poly(vinyl acetate), the protective coUoids are isolated from natural gums and ceUulosic resins (carboxymethylceUulose or hydroxyethjdceUulose). The hydroHzed polymer may also be used. The physical properties of the poly(vinyl acetate) polymer can be modified by changing the co-monomer used in the polymerization. Any material which is free-radically active and participates in an emulsion polymerization can be employed. Plasticizers (qv), tackifiers, viscosity modifiers, solvents (added to coalesce the emulsion particles), fillers, humectants, and other materials are often added to the adhesive to meet specifications for the intended appHcation. Because the presence of foam in the bond line could decrease performance of the adhesion joint, agents that control the amount of air entrapped in an adhesive bond must be added. Biocides are also necessary many of the materials that are used to stabilize poly(vinyl acetate) emulsions are natural products. Poly(vinyl acetate) adhesives known as "white glue" or "carpenter s glue" are available under a number of different trade names. AppHcations are found mosdy in the area of adhesion to paper and wood (see Vinyl polymers). 

Clinical trials for r-IEN-y in RA indicated that the dmg is well tolerated (52). Consistent improvement in tender and swollen joint scores was observed, but a large number of patients were needed in the trial to show statistical significance for r-IEN-y treatment. In certain individuals, responses were remarkable. An additive effect between r-IEN-y and penicillamine was detected. Efficacy was lower when r-IEN-y was combined with gold therapy. Research is continuing. 

Hydroxyapatite (HA) coating on the surface of the hip stem and the acetabular cup is the most recent advancement in artificial hip joint implant technology. This substance is a form of calcium phosphate, which is sprayed onto the hip implant. It is a material found in combination with calcium carbonate in bone tissue, and bones can easily adapt to it. When bone tissue does grow into HA, the tissue then fixes the hip joint implant permanently in position. These HA coatings are only used in press-fit, noncemented implants. 

Biomaterials. Just as stem designs have evolved in an effort to develop an optimal combination of specifications, so have the types of metals and alloys employed in the constmction of total joint implants. Pure metals are usually too soft to be used in prosthesis. Therefore, alloys which exhibit improved characteristics of fatigue strength, tensile strength, ductihty, modulus of elasticity, hardness, resistance to corrosion, and biocompatibiUty are used. 

---