SMA Wire Elevator Rope for Small Pulley Fatigue
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Solution Overview
Problem
Suspension and traction systems, such as elevators, face increased wear and reduced fatigue lifetime due to stress and contact issues when using smaller pulleys, as the smaller pulley diameter exacerbates bending stresses and localized contact pressures on ropes or belts.
Innovation Solution
Incorporating shape memory alloy (SMA) wires in the load-bearing sections of suspension and traction elements, which undergo martensitic transformation at room temperature, providing superelasticity and allowing for flexible deformations without significant stress increase, thus reducing wear and contact pressures when passing through pulleys with diameters less than or equal to 130 mm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the pulley diameter is reduced to save space and optimize shaft usage, then the space utilization improves, but the wear and fatigue lifetime of the suspension and traction element deteriorates due to increased bending stresses and contact pressures
Solution Approach 1:
The patent changes the material parameters of the suspension element by incorporating shape memory alloy (SMA) wires with specific Af temperatures below room temperature. This material parameter change enables the element to undergo martensitic transformation under bending stress, fundamentally altering its mechanical response to small pulley diameters and allowing reduced pulley sizes without compromising reliability
Solution Approach 2:
The patent uses composite construction by combining shape memory alloy wires with other materials in the suspension element. This composite structure leverages the superelastic properties of SMA to withstand the increased bending stresses and contact pressures that result from using smaller pulleys, thereby maintaining fatigue lifetime while enabling space optimization
2Area of stationary object
If the pulley diameter is reduced, then the space requirements decrease, but the stress and contact pressure on the suspension element increase, causing greater wear
Solution Approach 1:
The patent changes the stress-pressure parameters by utilizing the phase transformation characteristics of shape memory alloys. When the SMA wires are subjected to contact pressure from smaller pulleys, they undergo austenite-to-martensite transformation, which allows them to accommodate higher pressures without permanent deformation, effectively decoupling pulley size reduction from pressure increase
Solution Approach 2:
The patent exploits the phase transition phenomenon in shape memory alloys, specifically the austenite-martensite transformation that occurs at temperatures below room temperature. This phase transition enables the suspension element to dynamically adjust its mechanical properties under varying contact pressures, allowing the system to use smaller pulleys without experiencing excessive wear
3Stability of the object's composition
If shape memory alloy wires with Af temperature below room temperature are used, then flexibility and recoverable deformation increase, but the material selection and manufacturing complexity increase
Solution Approach 1:
The patent specifies precise temperature parameter ranges for the shape memory alloy (Af temperature below room temperature) to achieve the desired flexibility and recoverable deformation. By establishing clear parameter criteria, the patent balances the need for enhanced mechanical properties with manufacturability, allowing standard manufacturing processes to be applied within defined material specifications
Solution Approach 2:
The patent employs shape memory alloy wires that can undergo significant deformations and recover, effectively allowing the suspension element to experience repeated stress cycles without permanent damage. This approach replaces the need for overly robust, complex structures with a material-based solution that achieves reliability through controlled material behavior rather than increased structural complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The use of SMA wires homogenizes stresses and reduces contact pressures, preventing damage and extending the lifetime of ropes or belts by allowing smaller pulley diameters without permanent deformations and minimizing fatigue and wear.
Implementation Method 1
the degradation is considerably reduced when a martensite transformation takes place in bearing elements provided with at least one shape memory alloy wire
Implementation Method 2
The added value of shape memory alloys is based on the unique property that such materials have, i.e., superelasticity. This property originates in the special characteristics of martensite transformation occurring in these materials when they are subjected to a certain level of stress
Implementation Method 3
The material, in an initial austenitic state, elastically deforms until reaching a critical stress level (σM s) such that the austenitic structure becomes thermodynamically unstable and its transformation into detwinned martensite is induced
Data Source
Figure 1a~1b
Figure 2a~2c
Figure 3
AI summary
The present invention relates to a suspension and traction system provided with at least one suspension and traction element and at least one pulley, wherein pulley diameter, Øpulley, is less than or equal to 130 mm, the suspension and traction element comprises a load bearing section with at least one shape memory alloy wire having diameter Øsmawire, said shape memory alloy being chosen from shape memory alloys the characteristic Af temperature of which is below room temperature, and the value of the quotient Øpulley/Øsmawire is between 50 and 2000. The fatigue lifetime is improved with this configuration.