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X-WR-CALNAME:iMEMS Lab
X-ORIGINAL-URL:https://imemslab-iisc.in
X-WR-CALDESC:Events for iMEMS Lab
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BEGIN:VTIMEZONE
TZID:UTC
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TZOFFSETFROM:+0000
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DTSTART:20190101T000000
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BEGIN:VEVENT
DTSTART;TZID=UTC:20251006T080000
DTEND;TZID=UTC:20251006T170000
DTSTAMP:20260429T123945
CREATED:20251124T174905Z
LAST-MODIFIED:20251124T174921Z
UID:10746-1759737600-1759770000@imemslab-iisc.in
SUMMARY:AE Seminar - Recent advancements in Machine Learning approaches for solid body mechanics ​
DESCRIPTION:Abstract: \nMachine learning methods have attracted growing interest across many fields\, including solid mechanics. Constitutive artificial neural networks (CANNs) have shown high efficiency and accuracy for modeling hyperelastic materials\, while physics-informed neural networks (PINNs) provide a data-free alternative to conventional simulation techniques. However\, standard PINNs often require large\, complex networks and dense sampling in the simulation domain to achieve stable and accurate results. This presentation gives an overview of several current NN-based approaches for both constitutive modeling and simulation. It introduces extended ML-based constitutive models for cyclic plasticity\, concrete damage plasticity\, and magneto-active polymers. These approaches enable simplified and accelerated material characterization while maintaining high accuracy. An integrated framework for simulation and material characterization is also proposed. As an example\, a coupled CANN–DEM approach is presented: the material behavior is first learned from a limited set of complex experiments\, and the resulting model is then used to simulate new loading scenarios with promising accuracy and robustness. In addition\, the quadrature-based Deep Energy Method (Q-DEM) is discussed\, offering significant improvements in accuracy and stability. Finally\, oscillatory PINNs (oPINNs) are introduced for combined transient and modal analysis. By circumventing Dahlquist’s barriers\, oPINNs achieve substantial stability gains compared to traditional time-stepping schemes.​
URL:https://imemslab-iisc.in/event/ae-seminar-recent-advancements/
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20250624T080000
DTEND;TZID=UTC:20250624T170000
DTSTAMP:20260429T123945
CREATED:20251124T173546Z
LAST-MODIFIED:20251124T174404Z
UID:10739-1750752000-1750784400@imemslab-iisc.in
SUMMARY:PhD Thesis Defence - Effect of Laser Shock Peening on Residual Stress and Mechanical behaviour of Aluminium alloy AA2219 Friction Stir Weld​
DESCRIPTION:Abstract:\n \nAA2219 is a heat treatable wrought aluminium alloy and has high specific strength and fracture toughness. Large-volume propellant tanksof space launch vehicles are manufactured by joining AA2219 aluminium alloy through the Friction Stir Welding (FSW) process. Thepropellant tanks are designed optimally to improve the payload capability of aerospace vehicle. Improvement in the performance of theFSW joint will lead to enhancement in either payload or structural margins. Hence\, there is a strong need to improve AA2219 FSW jointperformance. Several post-weld treatments are suggested to improve the performance of weld joints\, such as post-weld heat treatment\,surface treatment\, etc. Laser shock peening (LSP) is one of the most promising surface treatment techniques for improving theperformance of the FSW joint. In this work\, an attempt is made to improve the performance of the AA2219 T87 FSW joint through LaserShock Peening (LSP). The impact of LSP on Residual Stress (RS)\, microhardness\, global tensile behaviour at various temperatures\, localtensile behaviour\, stress corrosion cracking behaviour and surface roughness was investigated.​ \n​ \nThe surface residual stress distribution is non-uniform across the weld\, and the joint exhibits peak tensile residual stress of +123.5 MPa(longitudinal) in the TMAZ region on the top surface. The LSP process reduces the peak tensile RS to -20 MPa\, -130.2 MPa and -195.5 MPa(compressive) with single\, three and six layers\, respectively. The longitudinal through-thickness residual stress distribution is also non-uniform across the weld and through-thickness. Tensile residual stress exists near the weld center with a peak value of 160 MPa at mid-thickness\, which is 41% of the yield strength of base metal\, and it changes to compressive away from the weld center. Tensile RS is due tothermal cycle and rigid clamping experienced during FSW processing. Six layers of LSP reduced peak RS to + 65 MPa (55% reduction). TheLSP process has redistributed tensile residual stress due to self-equilibration. The LSP process has an influence not only on a surface levelbut also on the sub-surface. Results from this study indicate that the LSP process can mitigate tensile RS throughout the thickness (7 mm)of the FSW joint. RS reduction is due to increased dislocation density caused by plastic deformation of the surface due to the impact ofthe high-energy laser pulse during the LSP process. ​ \n​ \nAA2219 T87 FSW joint exhibits yield strength of 197 MPa and ultimate strength of 348 MPa yield and ultimate strength at ambienttemperature with elongation of 13.7%. The LSP process increased YS by 7%\, 10% and 14% with single\, three and six layers of LSP\,respectively. In cryogenic temperatures (77K & 20K)\, the increase in YS is 5-6%\, 7-8% and 10-12% with single\, three and six layers ofpeening\, respectively. The increase in YS is less at elevated temperatures (423 K) i.e. 1%\, 2% and 7% with single\, three and six layers ofLSP. At all investigated temperatures\, LSP resulted in an increase in yield strength. Repeated layers of LSP led to a proportional increase inyield strength at all studied temperatures. The increase in the yield strength is due to the strain hardening effect caused by surfacecompressive stress induced by laser shock peening. Surface compressive stress increases dislocation density and plastic deformationresistance. However\, LSP has not influenced UTS and elongation at all investigated temperatures. ​ \n​ \nAA2219 T87 FSW weld has a heterogeneous microstructure with wide variation in grain size\, orientation\, and precipitate distribution. Theresponse of different zones of FSW joint to LSP was investigated using the digital image correlation technique. The weld nugget regionshows an increase of 7%\, 8% and 16% in yield strength with single\, three and six layers of peening\, respectively. Meanwhile\, TMAZshowed an increase of 5%\, 10%\, and 21%. HAZ does not exhibit a significant increase in yield strength. However\, the increase in YS in theroot side is not significant (5%) compared to the crown side. This is due to higher hardness due to a lower temperature and the heat sinkeffect of the backing bar. ​ \n​ \nMicro-hardness on the top (crown side) and bottom (root side) surface of the weld increases due to laser peening in all regions of theFSW joint\, which agrees with the tensile properties and indicates strain-hardening behaviour. Single-layer\, three-layer and six-layer laserpeening increased average hardness by 7%\, 17% and 20%\, respectively\, in the weld nugget region of the crown side of the weld. Single-pass peening has affected < 0.5 mm depth\, whereas three and six passes of peening have influenced a depth of ~ 1.0 mm and more than2 mm\, respectively. LSP increases hardness both in surface and subsurface levels\, and repeated layers of LSP led to higher hardness in thesub-surface. ​ \n​ \nThe LSP process has increased surface roughness\, and the increase is substantial in the weld nugget and TMAZ regions\, which are thesoftest regions of the weld joint. AA2219 T87 FSW joint exhibits good SCC resistance in as-welded and LSP conditions\, i.e. SCC index > 0.9\,irrespective of the number of layers of LSP. ​ \nLaser shock peening of the AA2219 T87 FSW joint reduces residual stress (surface and sub-surface level) and improves yield strengthwithout compromising stress corrosion cracking behaviour. The research outcome of this work will be useful in improving the safetymargins of aerospace structures and pressure vessels. ​ \n​ \nKeywords: AA2219\, Friction Stir Weld (FSW)\, Laser Shock Peening (LSP)\, Residual Stress (RS)\, Tensile properties\, Microhardness.​ \n 
URL:https://imemslab-iisc.in/event/phd-thesis-defence-effect-of-laser/
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20250319T150000
DTEND;TZID=UTC:20250319T170000
DTSTAMP:20260429T123945
CREATED:20251111T083446Z
LAST-MODIFIED:20251124T174142Z
UID:10602-1742396400-1742403600@imemslab-iisc.in
SUMMARY:Thesis Colloquium – Elastic Wave Dispersion Analysis and Mode Shape Investigation of Higher-order Beam Theory for Thick Beams.
DESCRIPTION:Abstract:\nThe dynamic behavior of structural components over broad frequency ranges\, particularly thick beams under different constraints\, is important in many engineering applications where reduced dimensional modeling is required for design. Applications are aerospace structures\, mechanical systems and civil infrastructure. The rigid cross-section assumption in Euler-Bernoulli and even third-order beam theories cannot accurately capture the effects of stress-free or finite surface conditions and higher-order stress distribution under dynamic situations. While some higher-order beam theories satisfy shear stress boundary conditions\, they do not fullyaccount for normal stress. The higher-order beam theory employed in this study addresses these limitations. It satisfies both shear and normal traction conditions simultaneously. Another problem in guided wave behavior within thick beams is accurately modeling consistent surface or interior dynamics. For this\, the transverse displacement is approximated using a trigonometric variation across the thickness\, characterized by a fundamental wave vector consistent with the necessary stress variation throughout the thickness\, which is particularly relevant for thick structures. \nThere remains a lack of comprehensive comparison between different reduced-order models\, particularly in terms of their accuracy in predicting wave dispersion characteristics and dynamic deformation mode shapes in the short and long wavelength limits to evaluate the acceptability of specific models in specific applications. Also\, the choice of beam theory directly influences these properties. This study compares four different theories: Euler-Bernoulli\, Timoshenko\, Third-order shear\, and proposed higher-order theory with surface constraints. The dispersion characteristics of each beam theory are obtained by solving the characteristic equations using the polynomial eigenvalue method\, and dispersion curves are plotted to compare wave propagation behavior predicted by different theories. This comparison highlights the limitations of the lower-order theories\, especially in their ability to accurately capture the behavior of thick beams\, and demonstrates how higher-order theory provides improved predictions of wave behavior. \nTwo numerical validation techniques are employed to validate and investigate higher-order wave modes present in higher-order beam theory: one is based on the two-dimensional Fast Fourier Transform (2D FFT)\, and the other uses particle displacement vector plots. In the first approach\, a time-varying excitation is applied to the beam with a specific tonal frequency\, and time-domain response data is collected. The 2D FFT is then performed to extract the dominant wave modes. This method generates the flexural and axial modes at 300kHz frequency as an example\, which is better predicted using the higher-order beam theory. In the second approach\, wave motion is visualized as particle trajectories by plotting displacement components along axial and transverse directions. This method enables the generation of pure wave modes by solving the displacement field directly\, eliminating dependencies on boundary conditions and external excitation. This method validates all mode shapes present in the Higher-order beam theory. \nIn summary\, this thesis presents a comparative study of various beam theories to highlight the importance of higher-order beam theories where relevant physics needs to be captured. The dynamic effects are relevant in applications in vibrating machinery\, dynamic contact effects\, bearings\, and advanced contact force-based testing like resonance and force microscopy. \n—All are welcome
URL:https://imemslab-iisc.in/event/thesis-colloquium-elastic-wave-dispersion-analysis/
LOCATION:Hybrid mode\, AE Conf Hall and virtual meeting via Teams
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20250313T150000
DTEND;TZID=UTC:20250313T170000
DTSTAMP:20260429T123945
CREATED:20251111T085237Z
LAST-MODIFIED:20251111T090123Z
UID:10607-1741878000-1741885200@imemslab-iisc.in
SUMMARY:PhD Thesis Colloquium – Effect of Laser Shock Peening on Residual Stress and Mechanical behaviour of Aluminium alloy AA2219 Friction Stir Weld.
DESCRIPTION:Abstract:\nAluminium alloy AA2219 is a precipitation hardenable wrought alloy with copper as a major alloying element. Large-volume propellant tanks of space launch vehicles are manufactured by joining AA2219 aluminium alloy through Friction Stir Welding (FSW) and it is designed optimally to improve the payload capability. An increase in the strength of the FSW joint results in payload improvement of space launch vehicles. Residual stress is one of the crucial parameters for the design of pressure vessels\, and it is also necessary to mitigate or reduce the same to improve structural margins. The main challenge is understanding the cause of residual stress\, its evaluation\, and mitigation due to the FSW process. Laser shock peening (LSP) is one of the most promising surface modification techniques to improve the performance of weld joints. In the LSP process\, a high-energy laser beam impacts the surface of the specimen and generates ionized plasma by evaporating a thin ablative layer on the specimen. When a high-energy laser pulse passes through the transparent layer and hits the sample\, the thin ablative layer is vaporized and continues to absorb the laser energy resulting in the generation of ionized plasma. Rapidly expanding plasma is entrapped between the specimen and the transparent layer\, generating high surface pressure and propagating into the sample as a shock wave. When the peak pressure exceeds the material’s yield strength\, plastic deformation occurs in the specimen. \nThe present work aims to investigate the impact of LSP on residual stress\, microhardness\, global tensile behaviour\, tensile behaviour of various zones (local tensile behaviour)\, stress corrosion cracking behaviour and surface roughness of AA2219 T87 FSW. Surface and through-thickness residual stress were investigated in this work. In as-welded conditions\, tensile residual stress exists in the weld region with a peak value of +123.5 MPa in the Thermo-Mechanically Affected Zone (TMAZ). LSP has significantly affected all the regions of\nthe weld and reduced tensile residual stress to compressive. Longitudinal residual stress is non-uniform through thickness as well as across the weld. Peak tensile residual stress is +160 MPa at the centre of the weld in mid-thickness\, and the LSP process led to a 55% reduction. \nAA2219 T87 FSW exhibits a yield strength of 197 MPa and an ultimate tensile strength of 348 MPa at ambient temperature. The LSP process increased the yield strength of the FSW joint by 7 –14%. A similar increase is seen in cryogenic temperatures also. The increase in the yield strength is due to the strain-hardening effect induced by LSP. The response of different zones of FSW to tensile lading and LSP was investigated using the digital image correlation technique. LSP led to an increase in YS in Weld Nugget and TMAZ. However\, HAZ does not exhibit a significant increase in YS. The LSP process led to an increase in microhardness of 7 -20%. Single-layer peening has affected < 0.5 mm depth\, whereas three and six layers of peening have influenced a depth of 1.0 mm and more than 2 mm\, respectively. Metallographic study of LSP specimen confirms an increase in dislocation density\, which is the cause for the increase in YS and microhardness. The LSP process has increased surface roughness in all regions of FSW\, and the increase is substantial in the weld nugget and TMAZ regions. The LSP process has not affected stress corrosion cracking resistance\, irrespective of the number of layers of peening. \nIn summary\, a systematic investigation of the effect of LSP on AA2219 T87 FSW joint is carried out using various experimental and characterization techniques and the benefits of LSP are clearly brought out. LSP of AA2219 FSW reduces tensile residual stress and increases YS. This study has also quantified the improvement in YS of various zones of AA2219 FSW due to the LSP. An increase in microhardness was also noticed due to LSP. In addition\, resistance to stress corrosion cracking is not compromised due to LSP. This research outcome will be useful in improving the structural safety margin or reducing the inert mass of aerospace structures and pressure vessels. \n—All are welcome
URL:https://imemslab-iisc.in/event/phd-thesis-colloquium/
LOCATION:online
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20250301T150000
DTEND;TZID=UTC:20250301T170000
DTSTAMP:20260429T123945
CREATED:20251111T090452Z
LAST-MODIFIED:20251111T090541Z
UID:10613-1740841200-1740848400@imemslab-iisc.in
SUMMARY:1st March 2025 Open Day presentation by iMEMS Lab team at IISc Aerospace Engineering\, Indian Institute of Science (IISc) campus.
DESCRIPTION:
URL:https://imemslab-iisc.in/event/1st-march-2025-open-day-presentation-by-imems-lab-team-at-iisc-aerospace-engineering-indian-institute-of-science-iisc-campus/
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20250128T150000
DTEND;TZID=UTC:20250131T170000
DTSTAMP:20260429T123945
CREATED:20251111T090710Z
LAST-MODIFIED:20251111T090751Z
UID:10615-1738076400-1738342800@imemslab-iisc.in
SUMMARY:Department of Aerospace Engineering (AERES\, 2025).
DESCRIPTION:
URL:https://imemslab-iisc.in/event/department-of-aerospace-engineering-aeres-2025/
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20200529T080000
DTEND;TZID=UTC:20200529T170000
DTSTAMP:20260429T123945
CREATED:20200529T152918Z
LAST-MODIFIED:20250311T181859Z
UID:6585-1590739200-1590771600@imemslab-iisc.in
SUMMARY:An overview on the Kalman filter
DESCRIPTION:Application to state-parameter estimation of fatigue model in composite aircraft structures\, Speaker: Prof. Lea Cot\, Venue: AE Auditorium\, Department of AE
URL:https://imemslab-iisc.in/event/an-overview-on-the-kalman-filter/
LOCATION:AE Auditorium\, Department of AE\, India
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20200529T080000
DTEND;TZID=UTC:20200529T170000
DTSTAMP:20260429T123945
CREATED:20200529T152543Z
LAST-MODIFIED:20250311T192049Z
UID:6583-1590739200-1590771600@imemslab-iisc.in
SUMMARY:Low Observable Aircraft
DESCRIPTION:Design Challenges & Way Forward\, Speaker: Dr. Vijay Sutrakar\, Venue: AE Auditorium\, Department of AE
URL:https://imemslab-iisc.in/event/low-observable-aircraft/
LOCATION:Imems Lab
CATEGORIES:Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20200529T080000
DTEND;TZID=UTC:20200529T170000
DTSTAMP:20260429T123945
CREATED:20200529T152110Z
LAST-MODIFIED:20200529T152110Z
UID:6579-1590739200-1590771600@imemslab-iisc.in
SUMMARY:Thesis Defence
DESCRIPTION:Plasmon Phonon Coupled Dynamics of Nanocrystalline Structures\, Speaker: Brahmanandam Javvaji\, Venue: AE Seminar Hall\, Department of AE
URL:https://imemslab-iisc.in/event/thesis-defence/
LOCATION:Imems Lab
CATEGORIES:iMEMS Lab Talk
ORGANIZER;CN="Organizer Name":MAILTO:mail@mail.com
END:VEVENT
END:VCALENDAR