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Casellas, Daniel
Publications (10 of 11) Show all publications
Parareda, S., Casellas, D., Frómeta, D., Martínez, M., Lara, A., Barrero, A. & Pujante, J. (2020). Fatigue resistance of press hardened 22MnB5 steels. International Journal of Fatigue, 130, Article ID 105262.
Open this publication in new window or tab >>Fatigue resistance of press hardened 22MnB5 steels
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2020 (English)In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 130, article id 105262Article in journal (Refereed) Published
Abstract [en]

In press hardened steels, fatigue behaviour is very sensitive to surface defects or irregularities, either intrinsic or introduced during trimming operations. This work addresses the understanding and prediction of fatigue resistance of press hardened steels from a fracture mechanics approach. The size of fatigue originating defects were evaluated and used to estimate the fatigue limit for different surface conditions (coated and uncoated), different coatings (Al-Si and Zn) and different edge condition (polished and mechanically trimmed). Good agreement was found between calculated and experimental values, which shows the potential of fracture mechanics to estimate the fatigue performance of press hardened steels.

Place, publisher, year, edition, pages
Elsevier, 2020
Keywords
Press hardening, Edge damage, Fracture mechanics
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-75945 (URN)10.1016/j.ijfatigue.2019.105262 (DOI)000491639300010 ()2-s2.0-85072299111 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-10-02 (johcin)

Available from: 2019-09-10 Created: 2019-09-10 Last updated: 2019-11-19Bibliographically approved
Jonsén, P., Svanberg, A., Ramirez, G., Casellas, D., Hernández, R., Marth, S., . . . Oldenburg, M. (2019). A Novel Method for Modelling of Cold Cutting of Microstructurally Tailored Hot Formed Components. In: Mats Oldenburg, Jens Hardell, Daniel Casellas (Ed.), CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel, 2019: . Paper presented at CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel, Luleå, Sweden, June 2nd to 5th 2019 (pp. 645-652). , 7
Open this publication in new window or tab >>A Novel Method for Modelling of Cold Cutting of Microstructurally Tailored Hot Formed Components
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2019 (English)In: CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel, 2019 / [ed] Mats Oldenburg, Jens Hardell, Daniel Casellas, 2019, Vol. 7, p. 645-652Conference paper, Published paper (Refereed)
Abstract [en]

In the last decade, hot metal forming of advanced high strength steel (AHSS) have improved passenger safety and open possibilities for lightweight design. Hot metal forming can be applied to locally tailor the microstructure of components and gradual vary mechanical properties to improve crash resistance behaviour and optimized weight for e.g. safety related parts. Sometimes post punching or trimming must be done on hardened parts. Such conditions induce damage and fractures in the trimmed edge. Another issue is that high pressures are required in cutting operations due to the high yield stress of press hardened parts, which accelerate wear and produce premature fracture in tools. Optimizing cutting operations to minimize damage and wear are essentials and numerical simulations of cutting operations can be of good assistance. One of the main challenges in the numerical modelling consists of numerically be able to treat the extremely large deformation occurring in the cutting zone. A second challenge is to find suitable failure models. In this work, the punching process of soft and hard microstructures obtained by press hardening is experimentally studied, but also modelled with a combination of smoothed particle Galerkin (SPG) method and finite element method (FEM). Laboratory punching tests with different clearance values were carried out using sheets of different fracture strengths. All experimental cases are numerically modelled. Validation is conducted by comparing numerical results with experimental measurements of punch force and displacement. In addition, morphology of the final cutting edges from both real and virtual are compared. Numerical results show good agreement against experimental measurements. Furthermore, the combined method gives robust-ness and stability as it can handle large deformations efficiently.

National Category
Applied Mechanics
Identifiers
urn:nbn:se:ltu:diva-75748 (URN)
Conference
CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel, Luleå, Sweden, June 2nd to 5th 2019
Available from: 2019-08-29 Created: 2019-08-29 Last updated: 2019-08-29
Frómenta, D., Parareda, S., Lara, A., Casellas, D., Pujante, J., Jonsén, P., . . . Oldenburg, M. (2019). Fracture Toughness Evaluation of Thick Press Hardened 22MnB5 Sheets for High Crash Performance Applications in Trucks. In: Mats Oldenburg, Jens Hardell, Daniel Casellas (Ed.), CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel, 2019: . Paper presented at CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel, Luleå, Sweden, June 2nd to 5th 2019 (pp. 113-121).
Open this publication in new window or tab >>Fracture Toughness Evaluation of Thick Press Hardened 22MnB5 Sheets for High Crash Performance Applications in Trucks
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2019 (English)In: CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel, 2019 / [ed] Mats Oldenburg, Jens Hardell, Daniel Casellas, 2019, p. 113-121Conference paper, Published paper (Refereed)
National Category
Applied Mechanics
Identifiers
urn:nbn:se:ltu:diva-75751 (URN)
Conference
CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel, Luleå, Sweden, June 2nd to 5th 2019
Available from: 2019-08-29 Created: 2019-08-29 Last updated: 2019-08-29
Golling, S., Frometa, D., Casellas, D. & Jonsén, P. (2019). Influence of microstructure on the fracture toughness of hot stamped boron steel. Materials Science & Engineering: A, 743, 529-539
Open this publication in new window or tab >>Influence of microstructure on the fracture toughness of hot stamped boron steel
2019 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 743, p. 529-539Article in journal (Refereed) Published
Abstract [en]

The automotive industry's desire for weight reduction while maintaining crashworthiness demands development of materials and material properties within the economic framework of consumers. The industrial process of hot stamping provides a technique to utilize steel in an efficient way. In hot stamping, microstructural characteristics of a steel blank are influenced by controlling the cooling rate. Hot stamping has become a prevalent method for lightweight solutions in car bodies without sacrificing passenger safety. The process of hot stamping applies sequential forming and quenching in a single production step. During the cooling of the blank, various microstructures can be formed depending on the cooling rate or holding temperature. Special tooling allows the application of different cooling rates within the same blank. Thus, the microstructure and mechanical properties can be influenced in designated areas of a blank.

Fracture toughness properties of sheet metal are necessary to better understand fracture initiation and crack propagation during crash loading as well as improve crashworthiness predictions. This paper focus on fracture toughness of low-alloyed boron steel sheet common in the automotive industry. A heat treatment process is used to form different microstructures, predominately consisting of one single phase or mixed microstructures with two distinct phases. The fracture toughness of the present microstructures is evaluated using the Essential Work of Fracture methodology. Results are discussed in terms of the different microstructures obtained and the consequent part performance.

Results show a strong connection between microstructure and fracture toughness. The bainitic grade shows favorable fracture toughness while a mixed microstructure of bainite and martensite shows a very brittle fracture behavior. A post heat treatment in the form of paint bake curing shows a negligible effect on fracture toughness of martensite.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Fracture toughness, Essential work of fracture, Heat treatment, 22MnB5, Hot stamping
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-71682 (URN)10.1016/j.msea.2018.11.080 (DOI)000456891500060 ()2-s2.0-85057313484 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-01-31 (johcin) 

Available from: 2018-11-20 Created: 2018-11-20 Last updated: 2019-09-13Bibliographically approved
Frómeta, D., Lara, A., Molas, S., Casellas, D., Rehrl, J., Suppan, C., . . . Calvo, J. (2019). On the correlation between fracture toughness and crash resistance of advanced high strength steels. Engineering Fracture Mechanics, 205, 319-332
Open this publication in new window or tab >>On the correlation between fracture toughness and crash resistance of advanced high strength steels
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2019 (English)In: Engineering Fracture Mechanics, ISSN 0013-7944, E-ISSN 1873-7315, Vol. 205, p. 319-332Article in journal (Refereed) Published
Abstract [en]

Automotive industry players have devoted large efforts to identify the material parameters governing the crash resistance of Advanced High Strength Steels (AHSS). Such knowledge is essential to improve impact performance prediction and optimize new steel development. Nevertheless, there is still an open discussion about which are the most relevant properties on AHSS crashworthiness. In this work, the authors investigate the correlation between the fracture toughness of different AHSS and their crash failure behaviour. Fracture toughness is measured in the frame of fracture mechanics, through the essential work of fracture methodology. Two fracture resistance parameters are characterized: the fracture toughness at cracking initiation, wei, and the essential work of fracture, we. Toughness values are compared with the results of axial impact tests, which are evaluated according to the energy absorbed and the cracking behaviour observed in crash boxes. Results show that fracture toughness permits to describe different crash events in terms of crack initiation and crack propagation and allows ranking AHSS impact resistance; steels with higher we present better crash performance. Therefore, fracture toughness is proposed as a key material property to predict the crash resistance of AHSS and as a relevant design parameter for crash resistant parts.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Fracture toughness, Crash resistance, Axial impact tests, Advanced high strength steels, Essential work of fracture
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-71332 (URN)10.1016/j.engfracmech.2018.10.005 (DOI)000453766000023 ()2-s2.0-85054877980 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-01-30 (inah)

Available from: 2018-10-24 Created: 2018-10-24 Last updated: 2019-01-30Bibliographically approved
Lara, A., Roca, M., Parareda, S., Cuadrado, N., Calvo, J. & Casellas, D. (2018). Effect of Sandblasting on Low and High-Cycle Fatigue Behaviour after Mechanical Cutting of a Twinning-Induced Plasticity Steel. In: Henaff G. (Ed.), MATEC Web of Conferences: 12th International Fatigue Congress (FATIGUE 2018). Paper presented at 12th International Fatigue Congress, FATIGUE 2018; Poitiers Futuroscope; France; 27 maj - 1 juni 2018. EDP Sciences, 165, Article ID 18002.
Open this publication in new window or tab >>Effect of Sandblasting on Low and High-Cycle Fatigue Behaviour after Mechanical Cutting of a Twinning-Induced Plasticity Steel
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2018 (English)In: MATEC Web of Conferences: 12th International Fatigue Congress (FATIGUE 2018) / [ed] Henaff G., EDP Sciences, 2018, Vol. 165, article id 18002Conference paper, Published paper (Refereed)
Abstract [en]

In the last years, car bodies are increasingly made with new advanced high-strength steels, for both lightweighting and safety purposes. Among these new steels, high-manganese or TWIP steels exhibit a promising combination of strength and toughness, arising from the austenitic structure, strengthened by C, and from the twinning induced plasticity effect. Mechanical cutting such as punching or shearing is widely used for the manufacturing of car body components. This method is known to bring about a very clear plastic deformation and therefore causes a significant increase of mechanical stress and micro-hardness in the zone adjacent to the cut edge. To improve the cut edge quality, surface treatments, such as sandblasting, are often used. This surface treatment generates a compressive residual stress layer in the subsurface region. The monotonic tensile properties and deformation mechanisms of these steels have been extensively studied, as well as the effect of grain size and distribution and chemical composition on fatigue behaviour; however, there is not so much documentation about the fatigue performance of these steels cut using different strategies. Thus, the aim of this work is to analyse the fatigue behaviour of a TWIP steel after mechanical cutting with and without sandblasting in Low and High-Cycle Fatigue regimes. The fatigue behaviour has been determined at room temperature with tensile samples tested with a load ratio of 0.1 and load amplitude control to analyse High-Cycle Fatigue behaviour; and a load ratio of -1 and strain amplitude control to determine the Low-Cycle Fatigue behaviour. Samples were cut by shearing with a clearance value of 5%. Afterwards, a part of the cut specimens were manually blasted using glass microspheres of 40 to 95 microns of diameter as abrasive media. The results show a beneficial effect of the sandblasting process in fatigue behaviour in both regimes, load amplitude control (HCF) and strain amplitude control (LCF) tests, when these magnitudes are low, while no significant differences are observed with higher amplitudes. low-cycle fatigue, high-cycle fatigue, mechanical cutting, sandblasting, high manganese steel, TWIP steel.

Place, publisher, year, edition, pages
EDP Sciences, 2018
Series
MATEC Web of Conferences, E-ISSN 2261-236X ; 165
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-69557 (URN)10.1051/matecconf/201816518002 (DOI)2-s2.0-85048085817 (Scopus ID)
Conference
12th International Fatigue Congress, FATIGUE 2018; Poitiers Futuroscope; France; 27 maj - 1 juni 2018
Available from: 2018-06-15 Created: 2018-06-15 Last updated: 2018-06-19Bibliographically approved
Parareda, S., Lara, A., Sieurin, H., Darmas, H. & Casellas, D. (2018). Increasing fatigue performance in AHSS thick sheet by surface treatments. In: Henaff G. (Ed.), MATEC Web of Conferences: 12th International Fatigue Congress (FATIGUE 2018). Paper presented at 12th International Fatigue Congress, FATIGUE 2018; Poitiers Futuroscope; France; 27 maj - 1 juni 2018. EDP Sciences, 165, Article ID 22015.
Open this publication in new window or tab >>Increasing fatigue performance in AHSS thick sheet by surface treatments
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2018 (English)In: MATEC Web of Conferences: 12th International Fatigue Congress (FATIGUE 2018) / [ed] Henaff G., EDP Sciences, 2018, Vol. 165, article id 22015Conference paper, Published paper (Refereed)
Abstract [en]

Advanced High Strength Steels (AHSS) have been widely applied in the automotive industry as an affordable solution for car lightweighting, mainly in parts subjected to crash requirements. Heavy duty vehicle (HDV) can also benefit from the expertise learned in cars, but parts must be designed considering fatigue resistance, especially on trimmed areas, and stiffness. Mechanical surface treatments, as blasting or shot peening, help increasing fatigue life of AHSS in trimmed areas and will allow weight reduction in HDV through gauge downsizing. The expected decrease in stiffness through thickness reduction can be improved by design changes. However, scarce information about the effect of mechanical surface treatments on AHSS are available. Thus, the aim of this work is to evaluate the increment in fatigue life of two different steel grades (350 MPa, and 500MPa of yield strength) in thick sheet by means of mechanical surface treatment - sandblasting. High Cycle Fatigue [HCF] tests were conducted at alternating load [R=-1]. Residual stresses were measured by an X-ray tensometry prior fatigue tests. Also the surface roughness [Rz] and form is measured using an optical non-contact 3D microscope. On the other hand, the fracture surfaces of the test specimens were observed via scanning electron microscope (SEM) in order to determine the crack initiation points. The evaluation of fatigue life in terms of SN curves is also discussed, analysing how the sandblasting process modifies the surface roughness and introduce compressive residual stresses on the external layer of the material. Both phenomena enhance the fatigue strength of the evaluated steel grades. 

Place, publisher, year, edition, pages
EDP Sciences, 2018
Series
MATEC Web of Conferences, E-ISSN 2261-236X ; 165
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-69563 (URN)10.1051/matecconf/201816522015 (DOI)2-s2.0-85048093027 (Scopus ID)
Conference
12th International Fatigue Congress, FATIGUE 2018; Poitiers Futuroscope; France; 27 maj - 1 juni 2018
Available from: 2018-06-15 Created: 2018-06-15 Last updated: 2018-06-15Bibliographically approved
Casellas, D., Frómeta, D., Lara, T., Molas, S., Jonsén, P., Golling, S. & Oldenburg, M. (2017). A fracture mechanics approach to develop high crash resistant microstructures by press hardening. In: Mats Oldenburg, Braham Prakash, Kurt Steinhoff (Ed.), 6th International Conference Hot Sheet Metal Forming of High-Performance Steel CHS2: June 4-7 2017, Atlanta, Georgia, USA : proceedings. Paper presented at 6th International Conference Hot Sheet Metal Forming of High-Performance Steel CHS2, Atlanta, Georgia, 4-7 June 2017 (pp. 101-107). Warrendale, PA: Association for Iron & Steel Technology, AIST
Open this publication in new window or tab >>A fracture mechanics approach to develop high crash resistant microstructures by press hardening
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2017 (English)In: 6th International Conference Hot Sheet Metal Forming of High-Performance Steel CHS2: June 4-7 2017, Atlanta, Georgia, USA : proceedings / [ed] Mats Oldenburg, Braham Prakash, Kurt Steinhoff, Warrendale, PA: Association for Iron & Steel Technology, AIST , 2017, p. 101-107Conference paper, Published paper (Refereed)
Abstract [en]

Crashworthiness is a relevant engineering property for car parts. However it is not easy to measure at laboratory scale and complex impact tests have to be carried out to determine it. Crash resistance for high strength steel is commonly evaluated in terms of cracking pattern and energy absorption in crashed specimens. Accordingly, the material resistance to crack propagation, i.e. the fracture toughness, could be used to rank crashworthiness. It has been proved in a previous work by the authors, so the measure of fracture toughness, in the frame of fracture mechanics in small laboratory specimens, would allow determining the best microstructure for crash resistance parts. Press hardening offers the possibility to obtain a wide range of microstructural configurations, with different mechanical properties. So the aim of this work is to evaluate the fracture toughness following the essential work of fracture methodology for ferrite-pearlite, bainite, ferrite-bainite, martensite and martensite-bainite microstructures. Results showed that bainitic microstructures have high fracture toughness, similar to TWIP and CP steels, which allows pointing them as potential candidates for obtaining high crash resistance in parts manufactured by press hardening.

Place, publisher, year, edition, pages
Warrendale, PA: Association for Iron & Steel Technology, AIST, 2017
Series
CHS2-series ; 6
National Category
Other Mechanical Engineering Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-64054 (URN)978-1-935117-66-7 (ISBN)
Conference
6th International Conference Hot Sheet Metal Forming of High-Performance Steel CHS2, Atlanta, Georgia, 4-7 June 2017
Available from: 2017-06-15 Created: 2017-06-15 Last updated: 2017-11-24Bibliographically approved
Golling, S., Frómeta, D., Casellas, D., Granström, J., Jonsén, P. & Oldenburg, M. (2017). Determination of the essential work of fracture at high strain rates. In: Mats Oldenburg, Braham Prakash, Kurt Steinhoff (Ed.), 6th International Conference Hot Sheet Metal Forming of High-Performance Steel CHS2: June 4-7 2017, Atlanta, Georgia, USA : proceedings. Paper presented at 6th International Conference Hot Sheet Metal Forming of High-Performance Steel CHS2, Atlanta, Georgia, 4-7 June 2017 (pp. 261-269). Warrendale, PA: Association for Iron & Steel Technology, AIST
Open this publication in new window or tab >>Determination of the essential work of fracture at high strain rates
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2017 (English)In: 6th International Conference Hot Sheet Metal Forming of High-Performance Steel CHS2: June 4-7 2017, Atlanta, Georgia, USA : proceedings / [ed] Mats Oldenburg, Braham Prakash, Kurt Steinhoff, Warrendale, PA: Association for Iron & Steel Technology, AIST , 2017, p. 261-269Conference paper, Published paper (Refereed)
Abstract [en]

During the last decades, the use of ultra-high strength steel (UHSS) has increased as its favorable ratio between strength and mass allows the design of lighter body-in-white while maintaining passenger safety. Modeling impact loads of components made of UHS steel requires reliable descriptions of the material deformation and fracture behavior.

Traditional stress or strain based fracture criteria are used in finite element modeling. A different approach in modeling fracture in components uses the fracture energy as a model parameter.

Fracture toughness is difficult to measure in thin sheets; a method termed Essential Work of Fracture (EWF) provides the possibility to determine the fracture toughness in sheet metal. With knowledge of the fracture toughness the understanding of fracture behavior and crack propagation in ultra-high strength steel can be increased. The obtained EWF is related to the fracture energy and can be used in numerical models as a material parameter.

In the present work results from preliminary testing are shown and a discussion on cross-head speed and strain rate in the critical specimen cross section is given. The use of digital image correlation provides information about the displacement field in the vicinity of the notch and hence about the strain- and strain rate distribution. Furthermore, the difficulties in reliable measurement of force and elongation in high speed tensile testing machines are elucidated. Issues encountered during the development of the high-speed DENT specimen are not limited to the specific geometry presented in this paper.

The present work aims at the development of a test specimen to obtain the Essential Work of Fracture (EWF) at high test speed. This work contributes to the overall goal to model fracture behavior and crack propagation, dependent on the strain rate. For the investigation, a high-speed tensile testing machine equipped with an in-house developed load cell and an optical elongation measurement system was used with a high-speed camera to obtain data for digital image correlation.

Place, publisher, year, edition, pages
Warrendale, PA: Association for Iron & Steel Technology, AIST, 2017
Series
CHS2-series ; 6
National Category
Other Mechanical Engineering Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-64050 (URN)978-1-935117-66-7 (ISBN)
Conference
6th International Conference Hot Sheet Metal Forming of High-Performance Steel CHS2, Atlanta, Georgia, 4-7 June 2017
Available from: 2017-06-15 Created: 2017-06-15 Last updated: 2017-11-24Bibliographically approved
Jonsén, P., Golling, S., Frómeta, D., Casellas, D. & Oldenburg, M. (2017). Fracture mechanics based modelling of failure in advanced high strength steels. In: Mats Oldenburg, Braham Prakash, Kurt Steinhoff (Ed.), 6th International Conference Hot Sheet Metal Forming of High-Performance Steel CHS2: June 4-7 2017, Atlanta, Georgia, USA : proceedings. Paper presented at 6th International Conference Hot Sheet Metal Forming of High-Performance Steel CHS2, Atlanta, Georgia, 4-7 June 2017 (pp. 15-23). Warrendale, PA: Association for Iron & Steel Technology, AIST
Open this publication in new window or tab >>Fracture mechanics based modelling of failure in advanced high strength steels
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2017 (English)In: 6th International Conference Hot Sheet Metal Forming of High-Performance Steel CHS2: June 4-7 2017, Atlanta, Georgia, USA : proceedings / [ed] Mats Oldenburg, Braham Prakash, Kurt Steinhoff, Warrendale, PA: Association for Iron & Steel Technology, AIST , 2017, p. 15-23Conference paper, Published paper (Refereed)
Abstract [en]

In the last decade, the favorable properties of the press hardening process for advanced high strength steel (AHSS) have increased the demands concerning passenger safety and lightweight design. AHSS show excellent mechanical properties from e.g. tensile test measurements, but it has previously been shown that results from tensile elongation or energy calculation of un-notched and smooth specimen are not appropriate to classify the crash behavior of steel grades. This is because they completely underestimate the post-uniform region from start of necking to failure. Another issue, the mechanical behavior of a notched or cracked component is different than a smooth and un-notched component. If the mechanical behavior in some loading is dominated by crack propagation, it should be rationalized in terms of the materials crack propagation resistance. Therefore, the evolution of the material property that controls crack propagation, i.e. the fracture toughness, is an interesting approach to evaluate loading and deformation of AHSS. Process modelling including fracture toughness depending properties gives valuable information and additional understanding of fracture behavior and crack propagation mechanisms in AHSS components. Fracture toughness in thin sheets can be readily measured through the application of the Essential Work of Fracture (EWF) methodology. The damage evolution law can be specified in terms of fracture energy (per unit area) or in terms of equivalent plastic failure strain as a function of triaxiality and lode angle. In this work, DENT test samples have been experimentally evaluated and finite element simulations of the DENT tests have been performed. By this approach the numerical study includes mechanical response of AHSS specimen including sharp cracks. In the numerical model, the J-integral was evaluated using the virtual crack-tip extension (VCE) method. From the comparison of the numerical and experimental results of load-displacement for different ligament length cases it is obvious that there are in agreement. Also, the numerically obtained value of fracture toughness Jc, is in agreement with the experimentally measured value of essential work of fracture we.

 

When finite element based fracture mechanics is applied to practical design, the fracture toughness can be used as design criteria. One appealing property of the evaluation of the J-integral is that it can be evaluated from the far field solution, which facilitates computation as many numerical errors arise close to the crack tip. Evolution of stress- and strain field, plastic zone, J-integral value and other mechanical properties is interesting to study with the combination of experimental and numerical investigations.

Place, publisher, year, edition, pages
Warrendale, PA: Association for Iron & Steel Technology, AIST, 2017
Series
CHS2-series ; 6
National Category
Other Mechanical Engineering Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-64052 (URN)978-1-935117-66-7 (ISBN)
Conference
6th International Conference Hot Sheet Metal Forming of High-Performance Steel CHS2, Atlanta, Georgia, 4-7 June 2017
Available from: 2017-06-15 Created: 2017-06-15 Last updated: 2017-11-24Bibliographically approved
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