Rupture and leakage are recognized problems associated with silicone breast implants. Data are scarce about the durability of the silicone shell, and the life span of this device is unknown. The purpose of this study was to investigate the strength of silicone breast implants. Thirty implant shells were subjected to mechanical testing. Twenty-nine of the shells were tested after explanation, and one unused implant served as a control to validate the testing method. Implantation time varied from 4 months to 20 years, and all shells were tested, regardless of condition. Fourteen implant shells were intact, eight were leaking, and seven were ruptured. All ruptured implants had been in place for 10 years or longer. The breaking force of all excised shell specimens ranged from 2.6 to 22.4 N (0.6 to 5.0 lb.). Specimens from the control "high performance" shell required 15.5 to 25.6 N (3.5 to 5.8 lb) of force to fail. The weakest group was from thin-shelled implants between 10 and 16 years of age. More than half these specimens failed with less than 1 lb of force. The average breaking force of ruptured shell material was less than that of intact shells. A comparison of strength data in this study with manufacturers' data suggests that breaking force is dependent on implant type, shell thickness, and implantation time.

A new theory for the propagation of pressure pulses in an inviscid compressible fluid contained in a thin-walled elastic tube is presented. This theory represents an improvement over the classical waterhammer theory because the restriction that the speed of sound in the tube material must be much greater than that in the fluid has been removed and because the restriction that the pulse length must be much greater than the tube diameter has been somewhat relaxed. The new theory is applied to a water-filled copper tube with an axial impulsive force of very short duration applied either to a piston inserted in the anchored end of the tube or to a cap on the free end of the tube. Numerical solutions using the method of characteristics are presented, and comparison is made with the predictions of classical waterhammer theory. A check on the numerical solution is provided by the analytical solution for the capped tube and for the special case when the speeds of sound in the tube material and in the fluid are equal.

Stresses in the individual wires of complex wire rope are determined for rope constructions having an internal-wire-rope (IWRC). The ropes may be pulled, twisted, and bent over a sheave or drum. The effects of friction are neglected. Specific results for a 6 × 25 filler-wire IWRC rope that is prevented from twisting indicate that the maximum stresses (exclusive of contact stresses) are typically 1.5 to 3 times as large as the nominal rope stress based on rope load and total metallic area.