Preliminary study of an innovative Non-Destructive Testing technique concept for detection of surface cracks in non-ferromagnetic materials

The research presented in this thesis is framed in the preliminary study for the development of an innovative Non-Destructive Testing (NDT) technique concept based on deposition of a ferrofluid consisting of magnetic nanoparticles in the test-piece surface. The proposed technique is applicable to inspection of any type of materials except to ferromagnetic materials. Thus, it is specially suited to detect surface defects in a wide range of materials typically used in aerospace applications, i.e., non-ferromagnetic materials like aluminum alloys or composite materials like CFRP or GFRP. The proposed technique aims at meeting the requirements of NDT end-users in the form of a significant reduction of surface inspection costs, as compared with the most commonly used techniques at present day, aside from visual inspection.La investigacio presentada en aquesta tesi s’emmarca en l’estudi preliminar d’un concepte innovador per al desenvolupament d’una tècnica d’assajos no destructius (NDT). Aquesta tècnica es basa en la deposiciió d’un ferrofluid format de nanopartícules magnètiques sobre la superfície de la peça de prova. La tecnologia proposada és aplicable per a la inspecciió de qualsevol tipus de materials excepte els materials ferromagnètics. Així doncs, és especialment adequat per detectar defectes en la superfície d’una amplia gamma de materials utilitzats típicament en aplicacions aeroespacials, és a dir, materials no ferromagnètics com són els aliatges d’alumini o materials compostos com els CFRP o els GFRP. La tècnica proposada te com a objectiu el compliment dels requisits tècnics dels usuaris d’NDT aconseguint una reducció significativa dels costos d’inspecció, en comparació ́amb les tècniques més utilitzades en l’actualitat, a part de la inspecció visual

Innovative NDT technique for detection of surface cracks based on ferrofluids excited with DC and AC magnetic fields

Innovative NDT technique for detection of surface cracks based on ferrofluids excited with DC and AC magnetic fieldsAn innovative NDT technique is proposed for surface inspection of materials not necessarily magnetic or conductive, based on local magnetic field variations due to ferrofluid deposited in the cracks. The feasibility of the technique is assessed preliminarily, based on signal detectability without applied external magnetic field, and under applied DC and AC fields. The signals are quantified analytically, experimentally and numerically. In DC, detection is based on local magnetic flux density variations. In AC, detection is based on the existing phase lag between the field close to the crack and the applied field. This approach has inherent advantages: the phase lag, as opposed to the magnetic flux density, is independent of the quantity of ferrofluid in the crack and the magnitude of the applied field. The model agrees well with the tests, showing that the signal increases with the applied field strength, up to the saturation magnetization of the ferrofluid, and decreases with the distance to the crack longitudinal axis, and thus it can provide useful estimations of the signal. The proposed technique, requiring application of external fields to magnetize the ferrofluid to enhance the signal, seems promising: the model suggests that signals associated to cracks significantly smaller than the minimum detectable surface cracks for comparable classical NDT techniques are easily detectable with commercial magnetometers.Postprint (published version

Preliminary study of an innovative Non-Destructive Testing technique concept for detection of surface cracks in non-ferromagnetic materials

The research presented in this thesis is framed in the preliminary study for the development of an innovative Non-Destructive Testing (NDT) technique concept based on deposition of a ferrofluid consisting of magnetic nanoparticles in the test-piece surface. The proposed technique is applicable to inspection of any type of materials except to ferromagnetic materials. Thus, it is specially suited to detect surface defects in a wide range of materials typically used in aerospace applications, i.e., non-ferromagnetic materials like aluminum alloys or composite materials like CFRP or GFRP. The proposed technique aims at meeting the requirements of NDT end-users in the form of a significant reduction of surface inspection costs, as compared with the most commonly used techniques at present day, aside from visual inspection.La investigacio presentada en aquesta tesi s’emmarca en l’estudi preliminar d’un concepte innovador per al desenvolupament d’una tècnica d’assajos no destructius (NDT). Aquesta tècnica es basa en la deposiciió d’un ferrofluid format de nanopartícules magnètiques sobre la superfície de la peça de prova. La tecnologia proposada és aplicable per a la inspecciió de qualsevol tipus de materials excepte els materials ferromagnètics. Així doncs, és especialment adequat per detectar defectes en la superfície d’una amplia gamma de materials utilitzats típicament en aplicacions aeroespacials, és a dir, materials no ferromagnètics com són els aliatges d’alumini o materials compostos com els CFRP o els GFRP. La tècnica proposada te com a objectiu el compliment dels requisits tècnics dels usuaris d’NDT aconseguint una reducció significativa dels costos d’inspecció, en comparació ́amb les tècniques més utilitzades en l’actualitat, a part de la inspecció visual

Preliminary study of an innovative Non-Destructive Testing technique concept for detection of surface cracks in non-ferromagnetic materials

The research presented in this thesis is framed in the preliminary study for the development of an innovative Non-Destructive Testing (NDT) technique concept based on deposition of a ferrofluid consisting of magnetic nanoparticles in the test-piece surface. The proposed technique is applicable to inspection of any type of materials except to ferromagnetic materials. Thus, it is specially suited to detect surface defects in a wide range of materials typically used in aerospace applications, i.e., non-ferromagnetic materials like aluminum alloys or composite materials like CFRP or GFRP. The proposed technique aims at meeting the requirements of NDT end-users in the form of a significant reduction of surface inspection costs, as compared with the most commonly used techniques at present day, aside from visual inspection.La investigacio presentada en aquesta tesi s’emmarca en l’estudi preliminar d’un concepte innovador per al desenvolupament d’una tècnica d’assajos no destructius (NDT). Aquesta tècnica es basa en la deposiciió d’un ferrofluid format de nanopartícules magnètiques sobre la superfície de la peça de prova. La tecnologia proposada és aplicable per a la inspecciió de qualsevol tipus de materials excepte els materials ferromagnètics. Així doncs, és especialment adequat per detectar defectes en la superfície d’una amplia gamma de materials utilitzats típicament en aplicacions aeroespacials, és a dir, materials no ferromagnètics com són els aliatges d’alumini o materials compostos com els CFRP o els GFRP. La tècnica proposada te com a objectiu el compliment dels requisits tècnics dels usuaris d’NDT aconseguint una reducció significativa dels costos d’inspecció, en comparació ́amb les tècniques més utilitzades en l’actualitat, a part de la inspecció visual

Innovative NDT technique based on ferrofluids for detection of surface crack

The final publication is available at Springer via http://dx.doi.org/10.1007/s10921-015-0309-5An innovative NDT technique is proposed for surface inspection of materials not necessarily magnetic or conductive, based on local magnetic field variations due to ferrofluid deposited in the cracks. The feasibility of the technique is assessed preliminarily, based on signal detectability without applied external magnetic field, and under applied DC fields. The signals (local magnetic flux density variations) are quantified analytically, experimentally and numerically. The model agrees well with the tests, showing that the signal increases with the applied field strength, up to the saturation magnetization of the ferrofluid, and decreases with the distance to the crack longitudinal axis, and thus it can provide useful estimations of the signal. The proposed technique, requiring application of external fields to magnetize the ferrofluid to enhance the signal, seems promising: the model suggests that signals associated to cracks significantly smaller than surface cracks in a target application like aircraft skin panel inspection NASA STD-5009 are easily detectable with commercial magnetometers.Peer Reviewe

Innovative NDT technique for detection of surface cracks based on ferrofluids excited with DC and AC magnetic fields

Innovative NDT technique for detection of surface cracks based on ferrofluids excited with DC and AC magnetic fieldsAn innovative NDT technique is proposed for surface inspection of materials not necessarily magnetic or conductive, based on local magnetic field variations due to ferrofluid deposited in the cracks. The feasibility of the technique is assessed preliminarily, based on signal detectability without applied external magnetic field, and under applied DC and AC fields. The signals are quantified analytically, experimentally and numerically. In DC, detection is based on local magnetic flux density variations. In AC, detection is based on the existing phase lag between the field close to the crack and the applied field. This approach has inherent advantages: the phase lag, as opposed to the magnetic flux density, is independent of the quantity of ferrofluid in the crack and the magnitude of the applied field. The model agrees well with the tests, showing that the signal increases with the applied field strength, up to the saturation magnetization of the ferrofluid, and decreases with the distance to the crack longitudinal axis, and thus it can provide useful estimations of the signal. The proposed technique, requiring application of external fields to magnetize the ferrofluid to enhance the signal, seems promising: the model suggests that signals associated to cracks significantly smaller than the minimum detectable surface cracks for comparable classical NDT techniques are easily detectable with commercial magnetometers

Innovative NDT technique based on ferrofluids for detection of surface crack

The final publication is available at Springer via http://dx.doi.org/10.1007/s10921-015-0309-5An innovative NDT technique is proposed for surface inspection of materials not necessarily magnetic or conductive, based on local magnetic field variations due to ferrofluid deposited in the cracks. The feasibility of the technique is assessed preliminarily, based on signal detectability without applied external magnetic field, and under applied DC fields. The signals (local magnetic flux density variations) are quantified analytically, experimentally and numerically. The model agrees well with the tests, showing that the signal increases with the applied field strength, up to the saturation magnetization of the ferrofluid, and decreases with the distance to the crack longitudinal axis, and thus it can provide useful estimations of the signal. The proposed technique, requiring application of external fields to magnetize the ferrofluid to enhance the signal, seems promising: the model suggests that signals associated to cracks significantly smaller than surface cracks in a target application like aircraft skin panel inspection NASA STD-5009 are easily detectable with commercial magnetometers.Peer Reviewe