Development of hull material for high-altitude airship: A parametric study

2022 ◽  
pp. 073168442110548
Author(s):  
Ang Li ◽  
Rahul Vallabh ◽  
Philip D Bradford ◽  
David Kim ◽  
Abdel-Fattah M Seyam
Keyword(s):  
High Altitude ◽  
Process Parameters ◽  
Parametric Study ◽  
Failure Modes ◽  
Progressive Failure ◽  
Weight Ratio ◽  
Barrier Property ◽  
Structural Parameter ◽  
Gas Barrier ◽  
Lamination Process

The development of hull material with ideal properties to meet all the operation requirements has posed the greatest challenge to flying the airship at high altitude for extended periods. Materials developed in our previous study with a laminated structure achieved high strength-to-weight ratio and excellent gas barrier property at a relatively low total weight. To optimize this novel design and obtain a more comprehensive understanding of the laminate properties, a parametric study involving lamination process parameters (temperature and time), and laminate structural parameter (reinforcement fabric construction), was conducted. The effects of lamination parameters on tensile, peel, tear and helium permeability tests were carried out to assess the laminates. It was found that the tensile strength of the laminate is predominantly determined by the fabric reinforcement material properties. The peel and tear strength results showed that increasing the lamination temperature from 185 °C to 200 °C improved respective strength values. Additionally, the analysis of failure modes and tear propagation suggested that laminate samples with progressive failure have better tear resistant property over those with brutal failure. Extremely low helium permeability was achieved, yet the gas barrier property was not affected by the lamination process parameters and fabric type.

scholarly journals UV Nanoimprint Lithography: Geometrical Impact on Filling Properties of Nanoscale Patterns

Nanomaterials ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 822
Author(s):  
Christine Thanner ◽  
Martin Eibelhuber
Keyword(s):  
Layer Thickness ◽  
Process Parameters ◽  
Nanoimprint Lithography ◽  
Failure Modes ◽  
Production Method ◽  
Efficient Production ◽  
Comprehensive Overview ◽  
Replication Method ◽  
Wide Range ◽  
Pattern Size

Ultraviolet (UV) Nanoimprint Lithography (NIL) is a replication method that is well known for its capability to address a wide range of pattern sizes and shapes. It has proven to be an efficient production method for patterning resist layers with features ranging from a few hundred micrometers and down to the nanometer range. Best results can be achieved if the fundamental behavior of the imprint resist and the pattern filling are considered by the equipment and process parameters. In particular, the material properties and pattern size and shape play a crucial role. For capillary force-driven filling behavior it is important to understand the influencing parameters and respective failure modes in order to optimize the processes for reliable full wafer manufacturing. In this work, the nanoimprint results obtained for different pattern geometries are compared with respect to pattern quality and residual layer thickness: The comprehensive overview of the relevant process parameters is helpful for setting up NIL processes for different nanostructures with minimum layer thickness.

scholarly journals Analytical Investigation of Tension Loaded Deformed Rebar Anchors in Concrete

CivilEng ◽  
2021 ◽  
Vol 2 (2) ◽  
pp. 442-458
Author(s):  
Sandip Chhetri ◽  
Rachel A. Chicchi
Keyword(s):  
Test Data ◽  
Parametric Study ◽  
Failure Modes ◽  
Experimental Testing ◽  
Analytical Investigation ◽  
Failure Behavior ◽  
Capacity Design ◽  
Simulation Results

Experimental testing of deformed rebar anchors (DRAs) has not been performed extensively, so there is limited test data to understand their failure behavior. This study aims to expand upon these limited tests and understand the behavior of these anchors, when loaded in tension. Analytical benchmark models were created using available test data and a parametric study of deformed rebar anchors was performed. Anchor diameter, spacing, embedment, and number of anchors were varied for a total of 49 concrete breakout simulations. The different failure modes of anchors were predicted analytically, which showed that concrete breakout failure is prominent in the DRA groups. The predicted concrete breakout values were consistent with mean and 5% fractile concrete capacities determined from the ACI concrete capacity design (CCD) method. The 5% fractile factor determined empirically from the simulation results was kc = 26. This value corresponds closely with kc = 24 specified in ACI 318-19 and ACI 349-13 for cast-in place anchors. The analysis results show that the ACI CCD formula can be conservatively used to design DRAs loaded in tension by applying a kc factor no greater than 26.

scholarly journals Numerical simulation method for predicting a flood hydrograph due to progressive failure of a landslide dam

Landslides ◽  
2021 ◽  
Author(s):  
S. Takayama ◽  
S. Miyata ◽  
M. Fujimoto ◽  
Y. Satofuka
Keyword(s):  
Field Experiments ◽  
Failure Modes ◽  
Initial Conditions ◽  
Progressive Failure ◽  
Landslide Dam ◽  
Failure Model ◽  
Reservoir Water ◽  
Erosion Model ◽  
Flood Hydrograph ◽  
Overtopping Erosion

AbstractReducing the damage due to landslide dam failures requires the prediction of flood hydrographs. Although progressive failure is one of the main failure modes of landslide dams, no prediction method is available. This study develops a method for predicting progressive failure. The proposed method consists of the progressive failure model and overtopping erosion model. The progressive failure model can reproduce the collapse progression from a dam toe to predict the longitudinal dam shape and reservoir water level when the reservoir water overflows. The overtopping erosion model uses these predicted values as the new initial conditions and reproduces the dam erosion processes due to an overtopping flow in order to predict a flood hydrograph after the reservoir water overflows. The progressive failure model includes physical models representing the intermittent collapse of a dam slope, seepage flow in a dam, and surface flow on a dam slope. The intermittent collapse model characterizes the progressive failure model. It considers a stabilization effect whereby collapse deposits support a steep slope. This effect decreases as the collapse deposits are transported downstream. Such a consideration allows the model to express intermittent, not continuous, occurrences of collapses. Field experiments on the progressive failure of a landslide dam were conducted to validate the proposed method. The progressive failure model successfully reproduced the experimental results of the collapse progression from the dam toe. Using the value predicted by the progressive failure model, the overtopping erosion model successfully reproduced the flood hydrograph after the reservoir water started to overflow.

Revisiting the generalized scaling law for adhesion: role of compliance and extension to progressive failure

Soft Matter ◽  
2017 ◽  
Vol 13 (41) ◽  
pp. 7529-7536 ◽  
Author(s):  
Ahmad R. Mojdehi ◽  
Douglas P. Holmes ◽  
David A. Dillard
Keyword(s):  
Fracture Mechanics ◽  
Failure Modes ◽  
Progressive Failure ◽  
Scaling Law ◽  
Load Train ◽  
Adhesion Role

The generalized scaling law for adhesion is revisited, based on the classical fracture mechanics approach, leading to a revised scaling law that accounts for the role of load train compliance and extends to progressive failure modes.

Rainwater effect on bearing strength of glass–epoxy laminated composite pinned joints

2016 ◽  
Vol 50 (30) ◽  
pp. 4269-4278 ◽  
Author(s):  
Onur Sayman ◽  
Ümran Esendemir
Keyword(s):  
Room Temperature ◽  
Failure Modes ◽  
Failure Load ◽  
Weight Ratio ◽  
Laminated Composite ◽  
Hole Diameter ◽  
Plastic Container ◽  
Specimen Width ◽  
Bearing Load ◽  
Pinned Joints

Composite materials are used in areas that have varying environmental conditions due to their advantages such as generally higher stiffness- and strength-to-weight ratio, and corrosion resistance compared to metallic alloys. This experimental study is carried out to investigate the bearing strengths and failure modes of woven glass–epoxy composite pinned joints subjected to rainwater. The specimens were immersed in rainwater in a closed plastic container indoors for 20 month periods at room temperature. The ratio of edge-distance-to-hole diameter (E/D) and the ratio of the specimen width-to-hole-diameter (W/D) were selected as parameters. Failure modes were determined by observing the failure regions on the specimens. Damage of immersed and unimmersed specimens was examined using scanning electron misroscopy for the same failure load. Experimental results showed that the bearing load values obtained from the specimens immersed in rainwater decreased in comparison to unimmersed specimens.

scholarly journals Weldability Investigation and Optimization of Process Variables for TIG-Welded Aluminium Alloy (AA 8006)

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
T. Sathish ◽  
S. Tharmalingam ◽  
V. Mohanavel ◽  
K. S. Ashraff Ali ◽  
Alagar Karthick ◽  
...  
Keyword(s):  
Experimental Design ◽  
Aluminium Alloy ◽  
Process Parameters ◽  
Surface Hardness ◽  
Weight Ratio ◽  
Welding Process ◽  
Tig Welding ◽  
Low Weight ◽  
Superior Corrosion Resistance ◽  
Welding Processes

Aluminium and its alloys play a significant role in engineering material applications due to its low weight ratio and superior corrosion resistance. The welding of aluminium alloy is challenging for the normal conventional arc welding processes. This research tries to resolve those issues by the Tungsten Inert Gas welding process. The TIG welding method is an easy, friendly process to perform welding. The widely applicable wrought aluminium AA8006 alloy, which was not considered for TIG welding in earlier studies, is considered in this investigation. For optimizing the number of experiments, the Taguchi experimental design of L9 orthogonal array type experimental design/plan was employed by considering major influencing process parameters like welding speed, base current, and peak current at three levels. The welded samples are included to investigate mechanical characterizations like surface hardness and strengths for standing tensile and impact loading. The results of the investigation on mechanical characterization of permanent joint of aluminium AA8006 alloy TIG welding were statistically analyzed and discussed. The 3D profilometric images of tensile-tested specimens were investigated, and they suggested optimized process parameters based on the result investigations.

Failure Analysis of Tubular Hydroforming

2000 ◽  
Author(s):  
Z. C. Xia
Keyword(s):  
Internal Pressure ◽  
Process Parameters ◽  
Deformation Theory ◽  
Failure Modes ◽  
Tensile Loading ◽  
Failure Criteria ◽  
Material Anisotropy ◽  
Governing Equations ◽  
Compression Load ◽  
Failure Diagram

Abstract A mathematical analysis of failure developments for tubular hydroforming under combined internal pressure and end feeding is presented in this paper. Under considerations are two distinct failure modes, namely the bursting and the wrinkling. Bursting is an instability phenomenon where the tube can’t sustain any more tensile loading. Splitting usually follows due to extreme deformations in the bursting area. Wrinkling is due to high compression load, which deteriates the qulity of the final product. The deformation theory of plasticity is utilized in this study that takes into account of material anisotropy. The governing equations for the onset of both failure modes are established. The results are presented as Hydroforming Failure Diagram in the End Feed – Internal Pressure space. A parametric study of the failure criteria for a variety of materials and process parameters is performed. It is shown that the material anisotropy plays a significant role. The results provide guidelines for product designers and process engineers for the avoidance of failure during hydroforming. The validity and applicability of current study are also discussed.

Process Characterization and the Effect of Process Defects on Flip Chip Reliability

1999 ◽  
Author(s):  
Brian J. Lewis ◽  
Hilary Sasso
Keyword(s):  
Process Parameters ◽  
Flip Chip ◽  
Failure Modes ◽  
Shock Testing ◽  
Fine Pitch ◽  
Process Characterization ◽  
Solder Bumps ◽  
Optimum Height ◽  
High Yields

Abstract Processing fine pitch flip chip devices continues to pose problems for packaging and manufacturing engineers. Optimizing process parameters such that defects are limited and long-term reliability of the assembly is increased can be a very tedious task. Parameters that effect the robustness of the process include the flux type and placement parameters. Ultimately, these process parameters can effect the long-term reliability of the flip chip assembly by either inhibiting or inducing process defects. Therefore, care is taken to develop a process that is robust enough to supply high yields and long term reliability, but still remains compatible with a standard surface mount technology process. This is where process optimization becomes most critical and difficult. What is the optimum height of the flux thin film used for a dip process? What force is required to insure that the solder bumps make contact with the pads? What are the limiting boundaries in which high yields and high reliabilities are achieved, while maintaining a streamlined, proven process? The following study evaluates a set of process parameters and their impact on process defects and reliability. The study evaluates process parameters including, flux type, flux application parameters, placement force and placement accuracy to determine their impact. Solder voiding, inadequate solder wetting, and crack propagation and delamination in the underfill layer are defects examined in the study. Assemblies will be subjected to liquid-to-liquid thermal shock testing (−55° C to 125°C) to determine failure modes due to the aforementioned defects. The results will show how changes in process parameters effect yield and reliability.

Microstructural and Mechanical Properties of a Solid-State Additive Manufactured Magnesium Alloy

2021 ◽  
pp. 1-21
Author(s):  
Thomas Robinson ◽  
Malcolm Williams ◽  
Harish Rao ◽  
Ryan P. Kinser ◽  
Paul Allison ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Additive Manufacturing ◽  
Solid State ◽  
Magnesium Alloy ◽  
Magnesium Alloys ◽  
Process Parameters ◽  
Weight Ratio ◽  
Structural Components ◽  
Friction Stir ◽  
Magnesium Alloy Az31b

Abstract In recent years, additive manufacturing (AM) has gained prominence in rapid prototyping and production of structural components with complex geometries. Magnesium alloys, whose strength-to-weight ratio is superior compared to steel and aluminum alloys, have shown potential in lightweighting applications. However, commercial beam-based AM technologies have limited success with magnesium alloys due to vaporization and hot cracking. Therefore, as an alternative approach, we propose the use of a near net-shape solid-state additive manufacturing process, Additive Friction Stir Deposition (AFSD), to fabricate magnesium alloys in bulk. In this study, a parametric investigation was performed to quantify the effect of process parameters on AFSD build quality including volumetric defects and surface quality in magnesium alloy AZ31B. In order to understand the effect of the AFSD process on structural integrity in the magnesium alloy AZ31B, in-depth microstructure and mechanical property characterization was conducted on a bulk AFSD build fabricated with a set of acceptable process parameters. Results of the microstructure analysis of the as-deposited AFSD build revealed bulk microstructure similar to wrought magnesium alloy AZ31 plate. Additionally, similar hardness measurements were found in AFSD build compared to control wrought specimens. While tensile test results of the as-deposited AFSD build exhibited a 20 percent drop in yield strength, nearly identical ultimate strength was observed compared to the wrought control. The experimental results of this study illustrate the potential of using the AFSD process to additively manufacture Mg alloys for load bearing structural components with achieving wrought-like microstructure and mechanical properties.

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