Damping apparatus, use of a shape memory alloy and method for changing damping characteristics
A damping and shock absorbing method and apparatus for permanent or non-permanent use in the human body and having a shape memory alloy material cycled through stress-strain hysteresis to dissipate energy for effective damping. A sufficiently high pre-stress is applied to the damping element(s) to ensure that the damping working range is within the superelastic cycle. The damping apparatus can work in tension or compression or both in tension and compression. Moreover, damping elements from a shape memory alloy can also work in flexion and extension as well in rotation. The damping apparatus can have a stroke and force suitable for use in the human body by the design, the structure and the chemical composition of the shape memory alloy and their pre-set properties, such as plateau stresses of the superelastic cycle depend on the ambient temperature, the force of damping elements can also be changed in-situ by changing the temperature of the damping elements. The damping elements made out of a shape memory alloy can be combined with elastic elements made out of other materials to achieve stress-strain behavior more suitable for use in the individual human body.
1. A damping apparatus for absorbing shocks in the human body, comprising: at least one damping element made of a shape memory alloy and exhibiting superelastic stress-strain behavior over a predetermined range of temperatures, and biasing means for applying a non-zero biasing force to said damping element, wherein said non-zero biasing force effects an absolute strain of 0.5% to 3% on said damping element over said predetermined range of temperatures, and wherein said damping element exhibits a symmetrical response under compression vs. tension.
2. A damping apparatus, comprising: at least one damping element made of a shape memory alloy and exhibiting superelastic stress-strain behavior over a predetermined range of temperatures, and biasing means for applying a non-zero biasing force to said damping element, wherein the damping apparatus absorbs shocks in a human body and wherein said damping element exhibits a symmetrical response under compression vs. tension.
3. A damping apparatus for absorbing shocks in the human body, comprising: at least one damping element made of a shape memory alloy and exhibiting superelastic stress-strain behavior over a predetermined range of temperatures, the damping element adapted to achieve damping through a superelastic stress-strain cycle, wherein the damping element exhibits a symmetrical response under compression vs. tension.