what actions are possible at a ball and socket joints?
Answers
The hip is a ball-and-socket joint realized by the acetabulum (the socket) and the head of the femur (the ball). As any ball-and-socket type joint, the hip has a wide range of motion, including flexion, extension, abduction, adduction, internal rotation and external rotation.
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Answer:
Ball joint sockets (Fig. 9.24(c–f))
Modern medium and heavy duty ball and socket joints may use the ball housing itself as the half socket formed around the neck of the ball pin. The other half socket which bears against the ball end of the ball pin is generally made from oil impregnated sintered iron (Fig. 9.24(c)); another type designed for automatic chassis lubrication, an induction hardened pressed steel half socket, is employed (Fig. 9.24(d)). Both cases are spring loaded to ensure positive contact with the ball at all times. A helical (slot) groove machined across the shoulder of the ball ensures that the housing half socket and ball top face is always adequately lubricated and at the same time provides a bypass passage to prevent pressurization within the joint.
Ball and socket joints for light and medium duty To reduce the risk of binding or seizure and to improve the smooth movement of the ball when it swivels, particularly if the dust cover is damaged and the joint becomes dry, non-metallic sockets are preferable. These may be made from moulded nylon and for some applications the nylon may be impregnated with molybdenum disulphide. Polyurethane and Teflon have also been utilized as a socket material to some extent. With the nylon sockets (Fig. 9.24(e)) the ball pin throat half socket and the retainer cap is a press fit in the bore of the housing end float. The coil spring accommodates initial settling of the nylon and subsequent wear and the retainer cap is held in position by spinning over a lip on the housing. To prevent the spring loaded half socket from rotating with the ball, two shallow tongues on the insert half socket engage with slots in the floating half socket. These ball joints are suitable for light and medium duty and for normal road working conditions have an exceptionally longer service life.
For a more precise adjustment of the ball and socket joint, the end half socket may be positioned by a threaded retainer cap (Fig. 9.24(f)) which is screwed against the ball until all the play has been taken up. The cap is then locked in position by crimping the entrance of the ball bore. A Belleville spring is positioned between the half socket and the screw retainer cap to preload the joint and compress the nylon.
Tribology of materials for biomedical applications
Prasanta Sahoo, ... J. Paulo Davim, in Mechanical Behaviour of Biomaterials, 2019
1.6.1.2 Materials for hip arthroplasty
Hip replacement is based on a ball and socket joint. The femoral stem and ball fit into and have relative movement against the cup or acetabular component, as shown in Fig. 1.6. There are a variety of materials from which each of the components can be fabricated. Each manufacturer has different models, but each style falls into one of four basic material categories