The Eurecat technology centre has developed and patented two innovative technologies to predict the behaviour of sheet metal in the forming process and in use and also to evaluate its fatigue strength and fracture toughness more quickly and cost-effectively. This is especially significant when it comes to high-strength steels and aluminium alloys used to build lighter vehicles.
The new fast-track procedure for assessing sheet metal fracture toughness provides a leaner solution based on an innovative tool which allows a large number of samples to be taken in just a few minutes, thereby making the test simpler and cheaper.
Eurecat “has recently shown in several scientific publications that fracture toughness is an excellent indicator of the impact strength of sheet metal and how it can be formed in high volume production processes with no defects,” says Daniel Casellas, the technology centre’s scientific director.
“This technology enables Eurecat to provide businesses with an affordable method for assessing the fracture toughness of high-strength sheet metal,” adds Montse Vilaseca, director of Eurecat’s Metal and Ceramic Materials Unit. “This is extremely significant in optimising material selection.”
The system “makes it possible to get a large number of samples in just a few minutes and it can be used in a universal testing machine with no need for special equipment,” explains David Frómeta, a researcher in the Metal and Ceramic Materials Unit at Eurecat. “This saves time and money compared to conventional sample preparation procedures for toughness testing.”
The new process consists of three stages, the first of which is preparing specimens or samples for testing where sharp radius notches are inserted by means of a simple shearing process. The second is the tensile test when the notched specimens with different bond lengths (length between the two notches) are stretched to fracture in a universal testing machine. The third stage consists of calculating the material’s toughness value based on mathematical and statistical processing of the fracture energy values derived from specimens with different bonds.
Quick fatigue limit determination
Eurecat has also developed another new test which makes it possible to determine the fatigue limit of sheet metal in just a few hours and using only three samples. The new method has been validated as part of the European FormPlanet project and is designed to meet the needs of a variety of organisations to ensure its uptake and use in laboratories.
This method has been developed “as a support tool for the metal component design team so that they can address multiple test conditions and efficiently get the fatigue resistance for each one,” says Sergi Parareda, a researcher at Eurecat’s Metal and Ceramic Materials Unit.
The test is based on monitoring the evolution of material stiffness while applying cyclic loads and provides a more robust solution than using conventional fatigue equipment. The method allows for improved material selection and development by gaining a better understanding of how part forming parameters, heat treatments and other processes influence the fatigue strength of the end component.
Both technologies have been validated under the European FormPlanet project which involves steel and aluminium manufacturers, sheet metal companies and vehicle makers.
The results achieved with these new methodologies “confirm Eurecat’s position as a leading technology centre in mechanical evaluation of high-strength materials for the automotive industry,” comments Daniel Casellas. “They enable us to meet the needs of this and other sectors when it comes to selecting advanced materials and delivering sheet metal products that are highly impact resistant and allow for further reductions in vehicle weight.”
The methods devised will join the catalogue of services offered by the FormPlanet project, an Open Innovation Test Bed which will provide sheet metal forming companies with new services in characterisation and modelling of metal parts in order to predict and optimise their performance and reduce time to market for new developments in this field.
FormPlanet is coordinated by Eurecat and comes under the European Union’s Horizon 2020 programme. It involves a European consortium made up of three technology and research centres (Eurecat, Fraunhofer IWU and COMTES FHT AS), two universities (Luleå Tekniska Universitet and Università di Pisa), three companies (LETOMEC, Granta DESIGN and APPLUS – LGAI Technological Center, SA), eight industrial firms (CRF – Stellantis, ArcelorMittal, Arania, Estamp, Arcelik, ALUDIUM, AP&T and Lamera) and UNE as a standardisation body.
