A320neo Crack
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An IndiGo A320 was forced to return to Indore after the windshield developed a crack following takeoff. Flight 6E 6195 was flying from Indore to Chennai when it was forced to turn around just minutes into the flight. The flight landed safely and no injuries were reported.
Aircraft windshields are built to withstand everything from bird strikes to rapid heating and cooling during takeoffs and landings. However, they also require routine maintenance and replacement every few years once they reach a certain usage. Incidents of cracked windshields are relatively rare but certainly not unheard of in planes.
The plane will likely undergo checks to see what caused the cracked windshield, with many possible reasons. Additionally, a windshield replacement will also be carried out to get the plane back in the sky soon.
A Go First flight heading from Delhi to Guwahati was diverted to Jaipur after the A320neo aircraft's windshield cracked mid-air, aviation regulator Directorate General of Civil Aviation officials said.
After the pilots observed that the windshield on the plane has cracked, they wanted to return to Delhi but could not do so due to heavy rains on Wednesday afternoon, the officials said, adding the A320neo plane was then diverted to Jaipur.
Due to the Hail storm, the Radome of the aircraft was also damaged requiring repairs to it, while the outer pane of both the Windshields (LH +RH) were found with multiple cracks , requiring replacement of the same.
In case of Such 'Windshield crack event' in flight, Pilots prefer to land at nearest destination at earliest, if they could not differentiate the crack location, i.e. , if crack is on Outer pane (layer) of the of the windshield or Inner Pane of the windshield ! Many aircrafts have allowable limits to continue the flight, in case of an Windshield Outer Pane crack incident.
Landing gear system is one of the critical systems of an aircraft and is configured along with the aircraft structure because of its substantial influence on the aircraft structural configuration itself. Landing gear and its attachments are one of the principal structural elements and are useful for aircraft during taxiing, take-off and landing. In this research, A MLG sliding tube from one airline operated A320 aircraft, was returned by user, after a crack indication was discovered at one end of the axle arm. The part had completed about 25,000 cycles since new and 8,000 cycles since overhaul. The mode of crack propagation was intergranular, the crack surface was heavily corroded. A region on the outer diameter encompassing the crack had been blended prior to the receipt. No specific initiation site could be found, it was suspected based on the shape of the crack that initiation occurred from the outer diameter. Deformation was observed on the unblended inner diameter, suggesting that this location suffered a significant impact which imparted residual stress into the component. The Barkhausen noise inspection results support this.
Under cyclic loading and unloading, matrix cracking and fiber/matrix interface debonding occur inside of CMCs [3]. The hysteresis loops appear as the fiber slips relative to matrix in the interface debonded region [4]. The shape, location, and area of hysteresis loops can reveal the internal damage evolution of CMCs subjected to cyclic loading [5]. Many researchers investigated characteristics of hysteresis loops. Kotil et al. [6] investigated the effect of interface shear stress on the shape and area of hysteresis loops in unidirectional CMCs. Pryce and Smith [7] investigated the effect of interface partially debonding on hysteresis loops of unidirectional CMCs by assuming purely frictional load transfer between fibers and the matrix. Ahn and Curtin [8] investigated the effect of matrix stochastic cracking on hysteresis loops of unidirectional CMCs and compared with the Pryce-Smith model [7]. Solti et al. [9] investigated the effect of interface partially and completely debonding on hysteresis loops in unidirectional CMCs using the maximum interface shear strength criterion to determine interface slip lengths. Vagaggini et al. [10] investigated the effect of interface debonded energy on hysteresis loops of unidirectional CMCs based on the Hutchinson-Jensen fiber pull-out model [11]. Cho et al. [12] investigated the evolution of interface shear stress under cyclic-fatigue loading from frictional heating measurements. Li et al. investigated the effect of interface debonding [13], fibers Poisson contraction [14], fiber fracture [15], and interface wear [16] on hysteresis loops of unidirectional CMCs, and developed an approach to estimate interface shear stress in unidirectional CMCs through hysteresis loop area [17]. Kuo and Chou [18] investigated matrix multicracking in cross-ply CMCs and classified the multiple cracking states into five modes, in which cracking mode 3 and mode 5 involve matrix cracking and interface debonding in the 0° plies.
The undamaged state and five damaged modes of cross-ply ceramic composites: (a) undamaged composite; (b) mode 1: transverse crack; (c) mode 2: transverse crack and matrix crack with perfect fiber/matrix bonding; (d) mode 3: transverse crack and matrix crack with fiber/matrix interface debonding; (e) mode 4: matrix crack with perfect fiber/matrix bonding; and (f) mode 5: matrix cracking with fiber/matrix debonding.
Upon unloading and reloading, the frictional slip occurred between fibers and the matrix in the 0° plies is the major reason for the hysteresis loops of cross-ply CMCs [5]. In cross-ply laminates, besides the fiber debonding and relative fiber/matrix sliding, other events, i.e., delamination, relative ply sliding, near-tip matrix micro-cracking, and crack surface bridging followed by frictional fiber pull-out may also contribute to the hysteresis behavior. However, in the present analysis, the hysteresis loops models consider only the major factor of interface frictional slip in the matrix cracking mode 3 and mode 5. For matrix cracking mode 3, the hysteresis loops can be divided into four different cases, i.e., case 1: interface partially debonds and fiber slips completely relative to matrix; case 2: interface partially debonds and fiber slips partially relative to matrix; case 3: interface completely debonds and fiber slips partially relative to matrix; and case 4: interface completely debonds and fiber slips completely relative to matrix. The unloading and reloading strains when interface partially debonds are [21]:
For σmax = 60 MPa, the experimental and theoretical hysteresis loops are shown in Figure 3a, in which the proportion of matrix cracking mode 3 is η = 0.3. For matrix cracking mode 3, the hysteresis loops correspond to interface slip case 2, as shown in Figure 3b. Upon completely unloading, the interface counter-slip length approaches to 83.8% of interface debonded length, i.e., y(σmin)/ld = 86.5%, as shown in Figure 3b; upon reloading to peak stress, the interface new-slip length approaches to 86.5% of interface debonded length, i.e., z(σmax)/ld = 86.5%, as shown in Figure 3b. For matrix cracking mode 5, the hysteresis loops correspond to interface slip case 1, as shown in Figure 3b. Upon unloading, the interface counter-slip length approaches to interface debonded length at σtr_pu = 45 MPa, i.e., y(σtr_pu)/ld = 1, as shown in Figure 3b; upon reloading to σtr_pr = 15 MPa, the interface new-slip length approaches to interface debonded length, i.e., z(σtr_pr)/ld = 1, as shown in Figure 3b.
(a) The theoretical and experimental hysteresis loops; and (b) the interface slip lengths, i.e., y/ld and z/ld, of matrix cracking mode 3 and mode 5 of cross-ply C/SiC composite when σmax = 60 MPa.
For σmax = 80 MPa, the experimental and theoretical hysteresis loops are shown in Figure 4a, in which the proportion of matrix cracking mode 3 is η = 0.35. For matrix cracking mode 3, the hysteresis loops correspond to interface slip case 2, as shown in Figure 4b. Upon completely unloading, the interface counter-slip length approaches to 73.5% of interface debonded length, i.e., y(σmin)/ld = 73.5%, as shown in Figure 4b; upon reloading to peak stress, the interface new-slip length approaches to 73.5% of interface debonded length, i.e., z(σmax)/ld = 73.5%, as shown in Figure 4b. For matrix cracking mode 5, the hysteresis loops correspond to interface slip case 1, as shown in Figure 4b. Upon unloading, the interface counter-slip length approaches to interface debonded length at σtr_pu = 24 MPa, i.e., y(σtr_pu)/ld = 1, as shown in Figure 4b; upon reloading to σtr_pr = 56 MPa, the interface new-slip length approaches to interface debonded length, i.e., z(σtr_pr)/ld = 1, as shown in Figure 4b.
(a) The theoretical and experimental hysteresis loops; and (b) the interface slip lengths, i.e., y/ld and z/ld, of matrix cracking mode 3 and mode 5 of cross-ply C/SiC composite when σmax = 80 MPa.
For σmax = 100 MPa, the experimental and theoretical hysteresis loops are shown in Figure 5a, in which the proportion of matrix cracking mode 3 is η = 0.4. For matrix cracking mode 3, the hysteresis loops correspond to interface slip case 4, as shown in Figure 5b. Upon completely unloading, the interface counter-slip length approaches to matrix crack spacing at σtr_fu = 70 MPa, i.e., 2y(σtr_fu)/lc = 1, as shown in Figure 5b; upon reloading to σtr_fr = 30 MPa, the interface new-slip length approaches to matrix crack spacing, i.e., 2z(σtr_fr)/lc = 1, as shown in Figure 5b. For matrix cracking mode 5, the hysteresis loops correspond to interface slip case 1, as shown in Figure 5b. Upon unloading, the interface counter-slip length approaches to interface debonded length at σtr_pu = 95 MPa, i.e., y(σtr_pu)/ld = 1, as shown in Figure 5b; upon reloading to σtr_pr = 5 MPa, the interface new-slip length approaches to interface debonded length, i.e., z(σtr_pr)/ld = 1, as shown in Figure 5b. 2b1af7f3a8