The influence of fiber-crack angle on the crack tip parameters in orthotropic materials

2016 ◽  
Vol 231 (3) ◽  
pp. 418-431 ◽  
Author(s):  
M Fakoor ◽  
R Rafiee ◽  
M Sheikhansari
Keyword(s):  
Experimental Study ◽  
Structural Design ◽  
Critical Angle ◽  
Design Procedure ◽  
Crack Tip ◽  
Maximum Load ◽  
Orthotropic Materials ◽  
Fiber Direction ◽  
Catastrophic Failure ◽  
Crack Angle

Identification of the critical angle between fiber and crack direction in orthotropic materials for avoiding catastrophic failure is necessary. Recognition of the optimum regions for creating notches in orthotropic materials for creation of maximum load-bearing capability is an important parameter in structural design. In this paper, the critical angles between crack and fiber direction are predicted, extracting crack tip parameters in orthotropic materials using stress series expansion and numerical method. The variations of crack tip parameters with respect to the angle between crack and fiber for modes I and II are presented. The presented functions for these variations can be used in the optimum design procedure of orthotropic structures. The obtained results are validated using experimental study.

Transition angle, a novel concept for predicting the failure mode in orthotropic materials

2012 ◽  
Vol 227 (10) ◽  
pp. 2157-2164 ◽  
Author(s):  
Mahdi Fakoor ◽  
Roham Rafiee
Keyword(s):  
Failure Mode ◽  
Damage Zone ◽  
Laminated Composite ◽  
Theoretical Method ◽  
Orthotropic Materials ◽  
Fiber Direction ◽  
Catastrophic Failure ◽  
Fiber Fracture ◽  
Laminated Composite Materials ◽  
Novel Concept

In this article, transition angle, a new concept for predicting failure mode in orthotropic materials, has been proposed. This angle is introduced as a transition angle from fiber fracture mode to matrix one of orthotropic part. Theoretical calculation of this angle is performed using the concept of microcracks in crack tip damage zone. In order to ensure about the consistency of the proposed approach with the nature of the fracture phenomena in wood, the results obtained from theoretical method are put into contrast with those obtained from practical testing. Transition angle is usable in introducing a safe domain for an angle in loading vector to fiber direction at laminated composite materials and prevents catastrophic failure.

scholarly journals Design and Analysis of an Aerostatic Pad Controlled by a Diaphragm Valve

Lubricants ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 47
Author(s):  
Federico Colombo ◽  
Luigi Lentini ◽  
Terenziano Raparelli ◽  
Andrea Trivella ◽  
Vladimir Viktorov
Keyword(s):  
Sensitivity Analysis ◽  
High Precision ◽  
Load Capacity ◽  
Design Procedure ◽  
Maximum Load ◽  
Air Gap ◽  
Diaphragm Valve ◽  
Compensation Methods ◽  
Aerostatic Bearings ◽  
Gap Height

Because of their distinctive characteristics, aerostatic bearings are particularly suitable for high-precision applications. However, because of the compressibility of the lubricant, this kind of bearing is characterized by low relative stiffness and poor damping. Compensation methods represent a valuable solution to these limitations. This paper presents a design procedure for passively compensated bearings controlled by diaphragm valves. Given a desired air gap height at which the system should work, the procedure makes it possible to maximize the stiffness of the bearing around this value. The designed bearings exhibit a quasi-static infinite stiffness for load variation ranging from 20% to almost 50% of the maximum load capacity of the bearing. Moreover, the influence of different parameters on the performance of the compensated pad is evaluated through a sensitivity analysis.

Experimental Study of Ductile Fracture for Non-Aligned Multiple Flaws in a Plate

2009 ◽  
Author(s):  
Katsumasa Miyazaki ◽  
Kunio Hasegawa ◽  
Koichi Saito ◽  
Bostjan Bezensek
Keyword(s):  
Experimental Study ◽  
Ductile Fracture ◽  
Estimation Procedure ◽  
Maximum Load ◽  
Experimental Results ◽  
Collapse Load ◽  
Plate Specimen ◽  
Fracture Tests ◽  
Almost All

The fitness-for-service code requires the characterization of non-aligned multiple flaws for the flaw evaluation, which is performed using a flaw proximity rule. Worldwide almost all codes provide own proximity rule, often with unclear technical bases of the application of proximity rule to ductile fracture. To clarify the appropriate proximity rule for non-aligned multiple flaws in fully plastic fracture, fracture tests on flat plate specimen with non-aligned multiple through wall flaws were conducted at ambient temperature. The emphasis of this study was put on the flaw alignment rule, which determines whether non-aligned flaws are treated as independent or aligned onto the same plane for the purpose of flaw evaluations. The effects of the flaw separation and flaw size on the maximum load were investigated. The experimental results were compared with the estimations of the collapse load using the alignment rules in the ASME Section XI, BS7910 and API 579-1 codes. A new estimation procedure specific to the fully plastic fracture was proposed and compared with the comparison with the experimental results.

A Knowledge-Based Approach to Design Partial Journal Bearings

1994 ◽  
Author(s):  
M. Affan Badar ◽  
Rao R. Guntur
Keyword(s):  
Expert System ◽  
Design Procedure ◽  
Maximum Load ◽  
Journal Bearings ◽  
Decision Criteria ◽  
Utility Value ◽  
Knowledge Based ◽  
Bearing Design ◽  
Design Solutions ◽  
Rule Bases

Abstract Various methods for designing hydrodynamic partial journal bearings are reviewed and an integrated and dependable design procedure is (developed. Knowledge and rule bases pertaining to the design of journal bearings having arcs of 180°, 120°. and 60° are either gathered or derived and represented properly. An expert system is developed using the databases and rulebases. The bearing design is based on one of the following decision criteria: the maximum load, the minimum friction, or the optimal clearance The expert system makes an exhaustive search for all the design solutions. Utility value of each of the final solutions is calculated and the design solutions having utility values above a certain limit are stored The results are presented to demonstrate the usefulness of the knowledge-based approach.

Aerodynamic and structural design for the development of a MALE UAV

2018 ◽  
Vol 90 (7) ◽  
pp. 1077-1087 ◽  
Author(s):  
Pericles Panagiotou ◽  
Efstratios Giannakis ◽  
Georgios Savaidis ◽  
Kyros Yakinthos
Keyword(s):  
Structural Design ◽  
Design Procedure ◽  
Unmanned Aircraft ◽  
Content Type ◽  
Parameterized Design ◽  
Detail Design ◽  
Aerial Vehicle ◽  
Structural Parts ◽  
Long Endurance ◽  
Structural Aspects

Purpose The purpose of this paper is to present the preliminary design of a medium altitude long endurance (MALE) unmanned aerial vehicle (UAV), focusing on the interaction between the aerodynamic and the structural design studies. Design/methodology/approach The classic layout theory was used, adjusted for the needs of unmanned aircraft, including aerodynamic calculations, presizing methods and CFD, to estimate key aerodynamic and stability coefficients. Considering the structural aspects, a combination of layout, finite element methods and custom parameterized design tools were used, allowing automatic reshapes of the skin and the internal structural parts, which are mainly made of composite materials. Interaction loops were defined between the aforementioned studies to optimize the performance of the aerial vehicle, maximize the aerodynamic efficiency and reduce the structural weight. Findings The complete design procedure of a UAV is shown, starting from the final stages of conceptual design, up to the point where the detail design and mechanical drawings initiated. Practical implications This paper presents a complete view of a design study of a MALE UAV, which was successfully constructed and flight-tested. Originality/value This study presents a complete, synergetic approach between the configuration layout, aerodynamic and structural aspects of a MALE UAV.

The Addition of a Krackow Rip Stop Suture Augment After Achilles Tendon Debridement for Insertional Achilles Tendinopathy: A Biomechanical Study

2021 ◽  
pp. 193864002110336
Author(s):  
LT Thomas J. Kelsey ◽  
LT Kyle W. Mombell ◽  
CDR Todd A. Fellars
Keyword(s):  
Achilles Tendon ◽  
Suture Anchor ◽  
Maximum Load ◽  
Achilles Tendinopathy ◽  
Catastrophic Failure ◽  
Double Row ◽  
Average Load ◽  
Load To Failure ◽  
Insertional Achilles Tendinopathy ◽  
Repair Techniques

Background In the operative treatment of insertional Achilles tendinopathy, the Achilles tendon is often released from its insertion to allow for adequate debridement of pathologic tissue. The use of a double row suture anchor construct has become increasingly favorable among surgeons after Achilles tendon debridement. This study hypothesized that the addition of a Krackow rip stop suture augment to the double row suture anchor construct would increase the repair’s maximum load to failure. A biomechanically stronger repair would potentially decrease the risk of catastrophic failure with early weight-bearing or accidental forced dorsiflexion after operative management for insertional Achilles tendinopathy. Methods Fourteen cadaveric specimens were used to compare the 2 repair techniques. Achilles tendons were debrided and repaired using either a double row suture anchor with and without the additional Krackow rip stop suture augment. The 2 repair techniques were compared using an axial-torsion testing system to measure average load to failure. Results The average load to failure for the double row suture anchor repair alone was 152.00 N. The average load to failure for the tendons with the double row suture anchor with the Krackow rip stop augment was 383.08 N. An independent-samples Mann-Whitney U-test was conducted and the suture anchor plus Krackow augment group had a significantly higher load to failure ( P = .011, Mann-Whitney U = 5.00, n1 = n2 = 7, P < .05, 2-tailed). Conclusion This study confirmed that the addition of a Krakow rip stop augment to the double row suture anchor is able to increase the maximum load to failure when compared to the double row suture anchor alone. These results suggest the potential of this added technique to decrease the risk of catastrophic failure.

On prismatic and bending bifurcations of fiber-reinforced elastic membranes under swelling with application to aortic aneurysms

2021 ◽  
pp. 108128652110587
Author(s):  
Murtadha J. Al-Chlaihawi ◽  
Heiko Topol ◽  
Hasan Demirkoparan ◽  
José Merodio
Keyword(s):  
Axial Loading ◽  
Material Constant ◽  
Exponential Model ◽  
Aortic Aneurysms ◽  
Orthotropic Materials ◽  
Fiber Direction ◽  
Fiber Reinforced ◽  
The Matrix ◽  
Elastic Membranes ◽  
Fiber Winding

The influence of swelling on prismatic and bending bifurcation modes of inflated thin-walled cylinders under axial loading is examined. The bifurcation criteria for a membrane cylinder subjected to combined axial loading, internal pressure, and swelling is provided. We consider orthotropic materials with two preferred directions which are mechanically equivalent and symmetrically disposed. The mechanical behavior of the matrix is described by a swellable isotropic model. The isotropic material is augmented with two functions that are equal, each one of them accounting for the existence of a unidirectional reinforcement. Two reinforcing models that depend only on the stretch in the fiber direction are considered: the so-called standard reinforcing model and an exponential one. The analysis of bifurcation modes for these models under the conditions at hand may establish the connection with modeling of the normal and diseased aorta in arterial wall tissue. The effects of the axial stretch, the strength of the fiber reinforcement and the fiber winding angle on the onset of prismatic and bending bifurcations are investigated. It is shown that for membranes without fibers, prismatic bifurcation is not feasible. On the other hand, bending bifurcation is more likely to occur for swollen cylinders. However, for a particular model of fiber-reinforced membranes, the standard model, there exists a domain of deformation values together with material constant values that may trigger prismatic bifurcation. The exponential model does not allow prismatic bifurcations. Both models allow bending bifurcation and may or may not trigger it depending on the deformation together with material parameters.

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