Nickel-titanium shape memory alloys in practice
Thanks to its extraordinary properties, technical applications of SMA / NiTi shape memory alloys can be found in many areas. While thermal shape memory for actuators is used in the aerospace industry, among others, pseudoelastic shape memory alloys are / Nitinol mainly used in medical technology where its high flexibility, good corrosion resistance and biocompatibility are of great advantage. In addition to the widespread use as stents, shape memory alloys are also used in medical technology as guide wires in minimally invasive surgery and as orthodontic wires for tensioning dental braces. Other applications include spectacle frames, vibration damping elements and solid-state joints
In this section you will be provided with the essential technical basics for your understanding of NiTi-SMA in application.
First you will become acquainted with semi-finished products and components available which can be integrated into your products in order to integrate functions and generate new added value. You will learn what in general must be considered during design, for example with regard to actuation paths, actuation forces and operating cycles. For a better understanding this is explained in depth using an example. In addition, you will become acquainted with technical basics for the integration/connection of shape memory alloy components and gain valuable insights into service life considerations. Would you like to find out more? Then simply download the complete course as a PDF HERE.
You will gain a basic understanding by reading through the detailed information we provide. At a later stage, you will be able to merely refer to the condensed summary attached to the file. This is how you will deepen your understanding of shape memory alloys and develop new possibilities for yourself and for your products. It will allow you to surprise your customers and positively inspire them. Because using SMA you can save them weight and costs, while making it possible to integrate functions. When considered in more detail, this alone results in further significant cost savings. With SMA you will not only increase your degree of innovation and profitability – you will also stay ahead of your market competitors.
Semi-finished products and components
The shape memory alloys (SMA) which are available to you at Ingpuls are based on the alloying elements Nickel (Ni) and titanium (Ti) (described as binary NiTi SMA). These can be obtained in various basic geometries (cylindrical, cubic, flat). Your semi-finished products are prepared individually for you via a suitable processing route, for example by forging, wire drawing or rolling, always accompanied by the associated heat treatments.
You may not wish to process the semi-finished product further yourself as it involves a lot of effort or does not fit into your strategy. If that is the case, then you can purchase ready-to-use NiTi shape memory alloy components from us – as do the majority of our customers. After discussing and agreeing on your requirements we will take care of the rest: You can conveniently procure the finished component and install it into your products. We have a number of processing options available for this purpose. Depending on your preference, you can then receive your components as fully-functional (usually heat-treated) or merely without a set functionality.
The SMA components which are available to you with Ingpuls and their respective advantages will be presented in more detail in the course (such as springs, wires, powder) and even more extensively in our standard catalogue. For more details, please find these in our standard catalogue.
We are always happy to take into account your specific requests and will always find a solution, even if your need should exceed our current abilities. That’s because Ingpuls does not only act in a regional sphere but has an excellent global network in research, science and industry at its hands. And you can benefit from our steadily growing network of excellent partner companies.
Special components for actuator
Actuator components carry out positioning processes after installation or after assembly. For this purpose you frequently will be installing wires, springs or sheet metal elements which you can obtain from us in prepared form (e.g. pre-cycled and ready for assembly). The pre-cycling is typically used in order to compensate for
fatigue effects of the first cycles and thus ensures that from the first cycles on the operating points of your actuator system comply with narrow tolerance limits – see also section Quality Assurance (cyclic behaviour). More details on this can be found in the SMA course.
Condition of surfaces
The respective surfaces can also be produced in accordance with your specific requests. Starting from an oxidised surface which is sometimes preferred for better
adhesion or insulation, over to various levels of levels of surface finishes and electrolytically polished surfaces which are often used in medical technology.
Systems based on SMA
If you are looking for ready-to use systems based on NiTi-SMA, you can also ask for pre-assembled modules or entirely functional actuator system; if required, you will also be able to obtain your electronic components for control (open loop) and regulation (closed loop).
That way you will receive the functionality of a complete actuator system and do not have to deal with technical, functional, design or alloying details saving you time and effort. Your actuator can then be delivered ready to plug & play.
Working principles specifically in actuators
Your shape memory alloy actuators usually operate by the principles of tension, compression, bending or torsion where each case of your application requires various technical parameters, such as forces or actuation paths. Furthermore, restrictions may also apply to your components relating to geometry or the environmental and use conditions. In case of actuators based on SMA, you can benefit not only from different activation principles but also from their combination and superposition. Intelligently combined, extremely complex systems with several motors, transmissions or brakes may be converged into a single system. This is the reason why many people often seem amazed how simple solutions based on shape memory alloys can be.
In cooperation with you, we will first choose suitable semi-finished products and components or work out a suitable system together. Which component you use, depends entirely on the function you are looking for in your product. Are you looking for tensile actuators, compression actuators or rather torsional or bending actuators? You will find out in the SMA course which semi-finished product or which component you should ideally use in which case.
The basic principles of SMA components can be combined in various ways and thus generate additional advantages: Applied this way, SMA will assume exactly the function you want for your product.
Download your free SMA course right now, to gain a better understanding of SMA and its potential.
Design of SMA
It is not to say that implementing the numerous advantages of shape memory allyos come at zero effort. In designing shape memory alloys, you will need to take into account more parameters than are ordinarily required. For many of our customers this proves an insurmountable obstacle. We will assist you every step of the way. We will even support you in determining the conditions of your application. Do you have a particular application in mind? Then feel free to request our comprehensive catalogue of requirements which in the end will depend on your operating conditions, in particular load and temperature. Due to the high complexity in the design of shape memory alloys, trying out things yourself will result in many questions.
The design process with shape memory alloys requires a high degree of experience and know-how in handling shape memory alloys. Therefore, it has proven very helpful to advise us at an early stage in detail about your project – which is why we created the requirements questionnaire. It will save you a lot of trouble and costs and at the same time it is essential for us in order to be able to meet your expectations: It’s the only way we can we can ensure targeted development results which in turn will result in visible commitment within your development department. Working closely together we will be able to develop innovative shape memory alloy solutions with a successful outcome.
Actuation paths and actuation forces of actuators
When it comes to the application of shape memory alloys in actuators, the forces and paths of actuation will be your primary concerns. The actuation path is the path which the actuating element of your actuator travels in both directions. With shape memory alloy actuators, the actuation path (or actuator stroke) is achieved by heating. How this process works exactly and how you should choose the basic design parameters for the operating point of your actuator,
you will be able to find out in the SMA course. But no need to worry: Apart from the course, from day one you will also receive helpful support during the design phase. This will help you achieve your desired result much faster than on your own by trial and error. It will save you money and assure you results which you can proudly present to your customers.
Switching times and response behaviour
You will also familiarise yourself with the characteristics of switching times and deepen your knowledge about your actuator’s response behavior. You will find out about the essential aspects relevant for the input and also discharge of the heat as well as the influence of the alloy and other requirements. These include parameters such as the geometry of your actuator, the temperature gradient in the system, the electrical voltage or delete mechanical stresses.
The course will teach you how an SMA actuator works based on a practical example. Having taken the course, you will understand why it says in this section Applications that in order to properly design your actuator, you should not only set the individual parameters correctly. You should also carefully coordinate their interaction with one another.
Service life of thermally activated and superelastic shape memory alloys
The service life of components of shape memory alloys depends on the load conditions that the component is exposed to. In other words, the service life, as with all cyclically loaded metallic materials, depends on the applied load(s).
Compared with conventional metal materials and exposed to the same stresses, the structural service life of shape memory alloys is much higher. In any case, for NiTi SMA the functional fatigue is much more relevant than its structural counterpart. For more details on which exact factors are involved, please see the SMA course. Actuator systems are often geared at serving over a long timespan. The achievable cycle numbers for thermally activated SMA components (i.e. not superelastic components) vary strongly and highly depend on your requirements: Typical service life range from a few thousand to several hundred thousands of cycles. If it is necessary or desirable, you can also significantly exceed several million cycles.
Superelastic components in SMA achieve very long service lives when designed correctly in accordance to the applied loads. This is important since they deal with your loads differently than thermally activated shape memory alloys. Stents in medical technology, for example, must withstand 800 million cycles at constant temperature during the validation until they receive approval for use. After the SMA course you will be able to qualitatively forecast yourself what service life you can expect from your components: This is because you will be able to distinguish between application types, allowing you to use basic technical parameters for a first educated guess.
Joining technology for shape memory alloys
For the implementation of the connection and integration of shape memory alloy components, a number of standard options are available to you: amongst those are some mechanical and technical joining options. A brief overview of the standard methods is included in the course.
In the applications section of the course you will learn:
- which semi-finished products, components and surfaces are available
- which components are used in actuator systems and why
- which general factors should be considered with regard to actuation force and actuation paths (actuator stroke) right from the early design stages
- what essential basics need to be covered to extend the service life of SMA components
- which technical basic options are available to you as standard with regard to the connection and integration of SMA components
Let’s recap what we’ve learnt in this section:
- At Ingpuls, you can obtain a highly diverse range of semi-finished products, components and actuators composed of NiTi SMA.
- There is a difference between structural and functional fatigue.
- The service life of your actuator can be designed and influenced by many parameters in order to suit your requirements.
- In addition to the alloy, thermal and mechanical loading conditions are key.
- The service life can be predicted very well by the design, its design is undertaken as to minimise cost.