Buckling analysis of angle-ply multilayered and sandwich plates using the enhanced Refined Zigzag Theory

The recent enhancement of the standard Refined Zigzag Theory (RZT), herein named the enhanced Refined Zigzag Theory (en-RZT), has extended the range of applicability of the RZT to angle-ply multilayered and sandwich plates. The aim of the present investigation is to assess the numerical performances of the en-RZT for the buckling analysis of angle-ply multilayered and sandwich rectangular plates under in-plane normal loads. The linearized stability equations are obtained using the Ritz method in conjunction with the principle of virtual work, by means of Gram–Schmidt orthogonal polynomials. In order to assess the accuracy of the en-RZT, buckling loads of angle-ply laminated and sandwich plates are evaluated and compared with the numerical results available in open literature. The numerical investigation highlights the high accuracy of the en-RZT in predicting buckling loads. The study contains a parametric analysis aimed to investigate the influence of various design parameters, such as plate aspect ratio, thickness, lamina orientations, in-plane load combinations and boundary conditions on the buckling loads

Experimental and numerical investigation of the Refined Zigzag Theory for accurate buckling analysis of highly heterogeneous sandwich beams

The Refined Zigzag Theory (RZT) is a structural theory developed for the analysis of composite multilayer and sandwich beams. However, the accuracy of RZT for buckling analysis of sandwich beams has not been experimentally investigated, and for RZT and Timoshenko Beam Theory (TBT) the effect of the degree of heterogeneity on their accuracy requires further study. The aim of this work was to validate the use of the RZT for predicting the critical buckling loads of sandwich beams, even with highly heterogeneous material properties, and to assess the use of the TBT for the same application. Buckling experiments were conducted on five foam-core sandwich beams, which varied in geometry and included highly heterogeneous configurations. For each beam, two finite element (FE) models were analyzed using RZT- and TBT-beam FEs. The comparison between the numerical and the experimental results highlighted a major capability of RZT to correctly predict the critical buckling load for all the beams considered. The dependence of the TBT results on the beam characteristics was further investigated through a parametric analysis, which showed the dominant effect to be a close to linear relationship between the TBT error and the beam face-to-core thickness ratio. The work demonstrated the outstanding accuracy of the RZT predictions, including the superior capabilities with respect to TBT, and has application for rapid and accurate analysis of industrial structures

Application of Wave Propagation to Pyroshock Analysis

Pyroshocks are high frequency transients due to pyrotechnic devices used in aerospace engineering in order to deploy solar arrays and antennae, separate subsystems from the spacecraft or separate the spacecraft itself from the base stage booster; their prediction is usually complex and very time consuming.The aim of this article is to investigate on the application of the analysis of transmission of waves in elastic media in order to predict the dynamic response to pyroshocks. The work is completed by numerical examples, related to components of common use in the aerospace engineering field, showing the comparison between results obtained by using both MSC-NASTRAN and this novel application of wave propagation analysis

Full-field strain reconstruction using uniaxial strain measurements: Application to damage detection

This work investigates the inverse problem of reconstructing the continuous displacement field of a structure using a spatially distributed set of discrete uniaxial strain data. The proposed technique is based on the inverse Finite Element Method (iFEM), which has been demonstrated to be suitable for full-field displacement, and subsequently strain, reconstruction in beam and plate structures using discrete or continuous surface strain measurements. The iFEM uses a variationally based approach to displacement reconstruction, where an error functional is discretized using a set of finite elements. The effects of position and orientation of uniaxial strain measurements on the iFEM results are investigated, and the use of certain strain smoothing strategies for improving reconstruction accuracy is discussed. Reconstruction performance using uniaxial strain data is examined numerically using the problem of a thin plate with an internal crack. The results obtained highlight that strain field reconstruction using the proposed strategy can provide useful information regarding the presence, position, and orientation of damage on the plate

In vitro analysis of the fracture resistance of CAD-CAM monolithic zirconia molar crowns with different occlusal thickness

Objectives: To compare the fracture resistance and mode of failure of CAD-CAM monolithic zirconia crowns with different occlusal thickness. Material and methods: Forty CAD-CAM monolithic zirconia crowns with different occlusal thickness were randomly distributed into 4 experimental groups: 2.0 mm (group 1), 1.5 mm (group 2), 1.0 mm (group 3) and 0.5 mm (group 4). The restorations were cemented onto human molars with a self-adhesive resin cement. The specimens were loaded until fracture; the fracture resistance and mode of failure were recorded. The data were statistically analyzed with the one-way ANOVA followed by the Fisher's Exact test with Bonferroni's correction (p=0.05). Results: The fracture resistance values of all the specimens exceeded the maximum physiological occlusal loads in molar regions. All the crowns showed cohesive microcracks of the zirconia core; only 1 crown with a thickness of 0.5 mm was interested by a complete fracture. Conclusions: The occlusal thickness of CAD-CAM monolithic zirconia crowns did not influence either the fracture resistance and the mode of failure of the restorations; the occlusal thickness of CAD-CAM monolithic zirconia crowns can be reduced up to a lower bound of 0.5 mm keeping a sufficient strength to withstand occlusal loads; CAD-CAM monolithic zirconia crowns showed sufficient fracture resistance to be used in molar regions, even in a thin configuration (0.5 mm)

Cross-cultural adaptation, reliability and validity of the Italian version of the craniofacial pain and disability inventory in patients with chronic temporomandibular joint disorders

BACKGROUND: To develop an Italian version of the Craniofacial Pain Disability Inventory (CFPDI-I) and investigate its psychometric abilities in patients with temporomandibular disorders (TMD). METHODS: The CFPDI was translated following international standards. The psychometric analyses included reliability by internal consistency (Cronbach's alpha) and test/retest stability (intraclass correlation coefficient, ICC); construct validity was investigated by matching (a priori hypotheses) the CFPDI-I with the Italian Neck Disability Index (NDI-I), a pain intensity numerical rating scale (NRS), the Italian Pain Catastrophising Scale (PCS-I), the Italian Tampa Scale of Kinesiophobia (TSK-I), and the Italian Migraine Disability Assessment Score Questionnaire (MIDAS) (Pearson's correlation). Alpha was set at 0.05. RESULTS: Two hundred and twelve patients with chronic TMD completed the tool. The questionnaire was internally consistent (\u3b1 =\u20090.95) and its stability was good (ICCs\u2009=\u20090.91). As hypothesised, validity figures showed CFPDI-I strongly correlated with the NDI-I (r =\u20090.66, p <\u20090.05) and moderately correlated with the NRS (r =\u20090.48, p <\u20090.05), PCS (r =\u20090.37, p <\u20090.05), TSKI (r =\u20090.35, p <\u20090.05) and MIDAS (r =\u20090.47, p <\u20090.05). Similar estimates were shown by CFPDI-I subscales. CONCLUSIONS: The cross-culturally adapted version of the Craniofacial Pain and Disability Inventory (CFPDI-I) showed satisfactory psychometric properties that replicate those of the original version and, therefore, can be implemented in the clinical assessment of Italian people affected by TMD

Full-arch intraoral scanning: comparison of two different strategies and their accuracy outcomes

Aim To test if there is a difference in accuracy between full-arch scans performed as two separate halves and stitched together, or as one continuous scan from side to side. Materials and Methods A reference model with six implants was milled as a single titanium block. Six scan bodies were manufactured and screwed into the implants. A reference 3D model was created using an industrial optical scanner. The experiment was performed using the same intraoral scanning machine (3M True Definition Scanner). The ‘Stitching’ strategy had the scan started from #27 to #13;after saving this part, the same procedure was performed from #17 to #23 and the software stitched the two halves automatically. The ‘No Stitching’ strategy had the scan performed as a single procedure. Using engineering software, six copies of the scan body CAD file were substituted to the six scan bodies of the RM and the centre point of each one was determined. Linear measurements were made between the detected points; mean distance and standard deviation were calculated for each of the fifteen measurement sets created. Results Stitching and No Stitching did not show statistically significant differences (Stitching=0.0396 mm ±0.0409 mm, No Stitching=0.0452 mm ±0,0481 mm, p=.338) but they differed significantly comparing absolute errors (Stitching=0.0442 mm ±0.0358 mm, No Stitching=0.0555 mm±0,036 mm, p=.015). Conclusions Stitching showed a better precision compared to No Stitching, exhibiting a smaller standard deviation and a higher error density closer to zero