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Fig 1. The ‘lifecycle’ of a functional product and related activities (click image to enlarge)

Value creation is the core of business. Several industries, particularly in business-to-business, are shifting towards value creation as their products. This is a continuous process from service contracts, via leasing of products, to Functional Products (FPs). Selling an FP requires much more than service contracts, as an example, and therefore affects not only the product and service development but also the business models of companies. The provider of an FP has the ownership as well as the responsibility for any of the functions offered. This enables better and more sustainable solutions and will be an important contribution to the circular economy.

A functional product can be defined by its constituents: hardware (HW); software (SW); service support system (SSS); and management of operation (MO). The ownership of these constituents remains with the provider who charges for the function generated by the product at a contracted level of availability. The lifecycle of FPs becomes more uncertain as the different constituents have varying technical lifecycles. In addition, there are economic lifecycles of FPs that are governed by different contracts. Functional product innovation (FPI) is the focus of VINNOVA’s excellence centre – the Faste Laboratory – at Luleå University of Technology where research is undertaken on various multidisciplinary challenges.

Fig 2. Hägglunds hydraulic motor. Insert shows part of a cam ring. Courtesy Bosch Rexroth

Functional products are much more extensive than leasing contracts as the provider takes full responsibility for the product’s performance according to the contracted availability and cost. In addition, FPs are designed and produced for their specific purposes in contrast to leasing contracts, which use the same products as traditional sales. Designing the constituents of an FP is a complex process as they are interconnected, but they lead to more sustainable solutions since the provider becomes responsible for its constituents throughout the lifecycle as illustrated in the next section. This responsibility encourages greater resource efficiency and increased recycling and reuse, which need to be considered during development.

Furthermore, customers are only charged for the availability of the delivered functions. This is in contrast to traditional businesses where the customer is charged for the hardware before operation commences and for the related services during operation regardless of whether the function is available or not. It may even be more profitable for the provider when the product does not work.

Fig. 3. Simulations in FP development correspond to dashed line in the lower ‘SDD’ box. Simulations in FP operation are denoted by the dashed line in the ‘Prediction’ box

In this article a subset of simulation driven design (SDD) will be described where the focus is on hardware, in this case a hydraulic motor. SDD-methodologies are commonly used in product development and are even more important for functional product development since additional constituents need to be considered. The article also shows why FPs offer more sustainable solutions as well as having a role in the circular economy.

The business case of a hydraulic motor

Bosch Rexroth delivers hydraulic motors, branded as ‘Hägglunds hydraulic motors’ (Fig. 2) for heavy-duty applications. The basic functionality of the motor is to produce high torque at low speeds. Today, a customer can buy the motor using the standard business model, usually with some limited warranty connected to compulsory services. The purchaser may choose an unnecessarily large motor to minimise the risk of failure, which in turn leads to less energy efficient operation. With traditional business models the provider has limited motivation to convince the customer to purchase a smaller model. The cost is initially high if no down payment or loan is arranged (although this would only add to the total cost).

Fig. 4. Model for prediction of induction hardening giving residual stress state and hardening depth. Only a part of the ring is modelled due to cyclic symmetry

However, with an FP business model the costs for enabling the function stay with the service provider. Hence, the financing cost is lower than the price the customer would pay in the case of a standard purchase. This reduced financing cost will be shared between the provider and customer, which therefore contributes to the win-win perspective of FP business. Another benefit, which is much more important, is that the provider will monitor the performance and health of the FP in order to assure its performance, availability and customer usage – Fig. 3. This will improve design and maintenance as described in the next section.

Simulations of HW in hydraulic motors 

Models can be used in SDD to predict various aspects of the performance of the hydraulic motor. The residual stress state from manufacturing, its microstructure and the expected in-service loads are important factors for the life of the cam ring in Fig. 2, and therefore need to be predicted by simulations. However, the models are usually only utilised in the design or redesign phase, sometimes for failure analysis. These models can also be used in the management of operations in the case of FP business.

An advantage in the FP case is that modelling of the in-service loads can be updated based on the specific FP as it is monitored during service. Thus there will be an individual model acting as a digital copy for each FP. The feedback from the actual use of the FP has three important benefits, as it gives the FP provider a better understanding of the product as well as its use for specific markets/customers i.e.

Fig. 5. Comparison between calculated phase changes, lines, and measured phase changes, lines with circles, during continuous cooling of the steel of the cam ring (click image to enlarge)

• The feedback from the FP in service can be used to estimate its status in order to determine the required maintenance. This may even lead to motors being replaced by a different sized one. If so, the old motor will be refurbished and become part of another FP business. Thus the life of the different constituents of the FP is maximised;
• The feedback can be used when designing new FPs; and
• The gained knowledge can be used when making FP business with additional customers.

The dashed lines in Fig. 3 denote the first two issues. Simulations thus play a role in SDD and MO for functional products.

The induction hardening of the cam ring of the hydraulic motor in Fig. 2, is simulated. Fig. 4 shows the set up where a limited part of the ring is modelled due to cyclic symmetry. The inner body is the induction heating tool made of copper. A current runs through this tool and generates eddy currents in the cam ring that quickly heat the surface. Thereafter the current is turned off and the surface is flushed with water, which gives the effect of a fast cooling and generates martensite and compressive stresses at the surface of the ring. Fig. 5 shows the Continuous Cooling Transformation (CCT) diagram for the material where the computed microstructure evolution of the steel is compared to measurements.  The start of the formation of a phase (F=ferrite, P=pearlite, M=martensite) is recorded when 5% is formed. Thus F in Fig. 5 denotes when 5% ferrite has been formed. The measurements show the same but ferrite and pearlite are brought together. (F+P)s denotes 5% of the sum, (F+P)m is 50% and (F+P)f corresponds to 95%.

Fig. 6. Simulation of in-service loads give combined stresses for useful estimates of remaining life

The load on the hydraulic motor during its operation causes a pressure on the rollers shown in Fig. 2. A representative amplitude of this pressure is applied on the model in Fig. 6. ‘Representative’ indicates that the load will not need be updated continuously, but only at regular intervals that will be adapted according to the use of the FP. This analysis gives stress amplitudes that together with the residual stresses from manufacturing are used to update ‘used’ or fatigued life. This is then, together with expected future loading, used to predict the need for maintenance, repair or replacement.

The future

Functional products are a natural evolution from today’s sales of products packaged with more and more extensive customer care and warranties. The same is true for the monitoring part, essential for an FP, which is embedded in many products today. The use of leasing has grown not only in business-to-business relations, but also among private customers of vehicles. The merger and strengthening of these trends lead towards business models based on functional products. This in turn will give larger driving forces for the provider to develop sustainable products. The life of a product can be extended as long as it is beneficial and even after the expiry of the contract with the initial customer and will thus contribute to a circular economy.

Lars-Erik Lindgren Professor in Material Mechanics, http://www.ltu.se/org/tvm/Avdelningar/Material-och-solidmekanik?l=en

Magnus Karlberg, Associate Professor in Computer Aided Design and Director of the Faste Laboratory, http://www.ltu.se/centres/Fastelaboratoriet-Vinnexc-Center?l=en