scholarly journals Thermal Prestress in Composite Compliant Shell Mechanisms

2019 ◽  
Vol 11 (2) ◽  
Author(s):  
Jonathan P. Stacey ◽  
Matthew P. O'Donnell ◽  
Mark Schenk
Keyword(s):  
Mechanical Properties ◽  
Thermal Analysis ◽  
Finite Element ◽  
Composite Laminate ◽  
Compliant Mechanisms ◽  
Low Energy ◽  
Spring Model ◽  
Energy Landscapes ◽  
Thermally Induced ◽  
Good Agreement

This paper explores the ability to tailor the mechanical properties of composite compliant shell mechanisms, by exploiting the thermal prestress introduced during the composite laminate cure. An extension of an analytical tape spring model with composite thermal analysis is presented, and the effect of the thermal prestress is studied by means of energy landscapes for the cylindrical composite shells. Tape springs that would otherwise be monostable structures become bistable and exhibit greater ranges of low-energy twisting with thermally induced prestress. Predicted shell geometries are compared with finite element (FE) results and manufactured samples, showing good agreement between all approaches. Wider challenges around the manufacture of prestressed composite compliant mechanisms are discussed.

Collapse of Tubes Under Combined Bending and Axial Compression Loads

2018 ◽  
Author(s):  
Shan Jin ◽  
Shuai Yuan ◽  
Yong Bai
Keyword(s):  
Mechanical Properties ◽  
Finite Element Method ◽  
Finite Element ◽  
Axial Compression ◽  
Local Buckling ◽  
Practical Application ◽  
Buckling Modes ◽  
Combined Loads ◽  
Bending Loads ◽  
Good Agreement

In practical application, pipelines will inevitably experience bending and compression during manufacture, transportation and offshore installation. The mechanical behavior of tubes under combined axial compression and bending loads is investigated using experiments and finite element method in this paper. Tubes with D/t ratios in the range of 40 and 97 are adopted in the experiments. Then, the ultimate loads and the local buckling modes of tubes are studied. The commercial software ABAQUS is used to build FE models to simulate the load-shortening responses of tubes under combined loads. The results acquired from the ABAQUS simulation are compared with the ones from verification bending experiment, which are in good agreement with each other. The models in this paper are feasible to analyze the mechanical properties of tubes under combined axial compression and bending loads. The related results may be of interest to the manufacture engineers.

scholarly journals Approaches for process and structural finite element simulations of braided ligament replacements

2016 ◽  
Vol 47 (3) ◽  
pp. 408-425 ◽  
Author(s):  
Thomas Gereke ◽  
Oliver Döbrich ◽  
Dilbar Aibibu ◽  
Jorg Nowotny ◽  
Chokri Cherif
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Process Model ◽  
Structural Model ◽  
Structural Parameters ◽  
Healing Process ◽  
Resorbable Polymers ◽  
Wide Range ◽  
Experimental Trials ◽  
Good Agreement

To prevent the renewed rupture of ligaments and tendons prior to the completed healing process, which frequently occurs in treated ruptured tendons, a temporary support structure is envisaged. The limitations of current grafts have motivated the investigation of tissue-engineered ligament replacements based on the braiding technology. This technology offers a wide range of flexibility and adjustable geometrical and structural parameters. The presented work demonstrates the possible range for tailoring the mechanical properties of polyester braids and a variation of the braiding process parameters. A finite element simulation model of the braiding process was developed, which allows the optimization of production parameters without the performance of further experimental trials. In a second modelling and simulation step, mechanical properties of the braided structures were virtually determined and compared with actual tests. The digital element approach was used for the yarns in the numerical model. The results show very good agreement for the process model in terms of braiding angles and good agreement for the structural model in terms of force-strain behaviour. With a few adaptions, the models can, thus, be applied to actual ligament replacements made of resorbable polymers.

scholarly journals Thermal Prestress in Composite Compliant Shell Mechanisms

2018 ◽  
Author(s):  
Jonathan P. Stacey ◽  
Matthew P. O’Donnell ◽  
Mark Schenk
Keyword(s):  
Thermal Effects ◽  
Compliant Mechanisms ◽  
Large Angle ◽  
Torsional Stiffness ◽  
Internal Stresses ◽  
Structural Behaviour ◽  
Thermally Induced ◽  
Composite Tape ◽  
Out Of Plane ◽  
Good Agreement

Due to the anisotropic nature of fibre-reinforced laminates, thermally-induced internal stresses can remain in the material after manufacture. Mismatches between coefficients of thermal expansion are especially prominent in thin shells with fewer plies or large angle variations. Such stresses cause out-of-plane warping and are therefore often deliberately avoided. Utilising their effects on structural behaviour however, can enable stiffness-tailored composite compliant mechanisms. Work detailed in this paper aims to exploit thermal prestress to reduce the torsional stiffness of cross-ply tape laminate springs. An extension of an analytical tape spring model with composite thermal analysis is presented, which shows that thermal effects cause significant changes to the energy landscapes of thin composite shells. Tape springs that would otherwise be monostable structures become bistable and exhibit greater ranges of low-energy twisting when thermally-induced prestress is present. Predicted shell geometries are compared with finite element models and manufactured samples, showing good agreement between all approaches. The limited feasibility of zero torsional stiffness composite tape springs is discussed, as well as wider challenges involved in manufacturing prestressed composite compliant mechanisms such as fibre misalignment and moisture ingress.

scholarly journals Effect of repair methods on mechanical behaviors of repair area in composite laminate fuselage skin with different damage size

2018 ◽  
Vol 2 (3) ◽  
Author(s):  
Liping Liu 1 ◽  
Yucan Wang 1 ◽  
Jing Tian 1 ◽  
Ruifeng Wang 1 ◽  
Jianxin Xu 1
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Composite Laminates ◽  
Composite Laminate ◽  
Simulation Models ◽  
Mechanical Behaviors ◽  
Adhesive Film ◽  
Element Simulation ◽  
Hybrid Repair ◽  
Fuselage Skin

Composite laminates are widely used in the large civil aircrafts because of their excellent mechanical properties. The maintenance and repair of composite laminates become essential. In this paper, a new adhesive-rivet hybrid repair of composite laminate fuselage skin is presented. For the circular hole damage with the diameter of 90mm and 50mm, the finite element simulation models of adhesive repair and adhesive-rivet hybrid repair were built respectively. Uniform pressure load was applied on these finite element models. The mechanical properties of laminate motherboard, patch and adhesive film for these four models were analyzed. The effects of adhesive repair, adhesive-rivet hybrid repair on mechanical behaviors of repair areas of composite laminate fuselage skins with different damage size were studied. By analyzing the mechanical behaviors of these two repair methods, a suitable repair method can be obtained.

Thermally Induced Seizure in Journal Bearings During Startup and Transient Flow Disturbance

2003 ◽  
Vol 125 (4) ◽  
pp. 833-841 ◽  
Author(s):  
Rajesh Krithivasan ◽  
M. M. Khonsari
Keyword(s):  
Finite Element ◽  
Transient Flow ◽  
Empirical Relationship ◽  
Element Model ◽  
Flow Disturbance ◽  
Thermally Induced ◽  
Modeling And Analysis ◽  
Start Up ◽  
Insight Into ◽  
Good Agreement

This paper presents a finite element model that describes the thermomechanical interactions of a journal bearing undergoing thermally induced seizure (TIS). Two Categories of TIS are studied; the first part deals with occurrence of seizure during the start-up period followed by an investigation of TIS due to a transient flow-disturbance. The paper outlines the finite element modeling and analysis procedure involved in simulating TIS. An extensive set of parametric simulations covering load, speed, shaft radius, operating clearance, bearing length, friction coefficient and thermal expansion coefficient are performed to gain insight into the phenomenon of TIS. A statistical procedure is applied to the simulated results and an empirical relationship is derived. Good agreement between the empirical and published results attests to the capability of the model and its potential for predicting thermally induced seizure during system start up and during flow disturbance.

scholarly journals Modeling of macro fiber composite actuated laminate plates and aerofoils

2019 ◽  
Vol 31 (4) ◽  
pp. 525-549
Author(s):  
Peter R Thomas ◽  
Ángela Carmen Blázquez Calzada ◽  
Kevin Gilmour
Keyword(s):  
Finite Element ◽  
Composite Laminate ◽  
Numerical Models ◽  
Fiber Composite ◽  
Element Analysis ◽  
Bending Strain ◽  
Glass Fiber Composite ◽  
Macro Fiber Composite ◽  
Distributed Actuator ◽  
Good Agreement

This article investigates the modeling of macro fiber composite-actuated laminate plates with distributed actuator patches. The investigation details an analytical and finite element modeling, with experimental validation of the bending strain and deflection of an epoxy E-glass fiber composite laminate. An analytical approach is also developed to estimate the plate deflection from the experimental strain measurements. The analytical method uses direct integration of single dimensional plate bending moments obtained by strain-induced shear moments from the macro fiber composite actuators. Finite element analysis software was used with the composite laminate modeled in ANSYS ACP. The results from both analytical and numerical models show good agreement with the experimental results, with strain values agreeing within 20 ppm and the maximum difference in deflection not exceeding 0.1 mm between models. Finally, an application of the analytical model for developing morphing aerofoil designs is demonstrated.

scholarly journals Modelling the mechanical response of urushi lacquer subject to a change in relative humidity

2012 ◽  
Vol 468 (2147) ◽  
pp. 3533-3551 ◽  
Author(s):  
X. Liu ◽  
R. D. Wildman ◽  
I. A. Ashcroft ◽  
A. E. Elmahdy ◽  
P. D. Ruiz
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Relative Humidity ◽  
Moisture Content ◽  
Thin Layer ◽  
Mechanical Response ◽  
Experimental Measurements ◽  
Environmental Conditioning ◽  
The Relationship ◽  
Good Agreement

A hygromechanical model has been developed to simulate the in-service behaviour of the natural lacquer urushi , using a phenomenological description of viscoelasticity. The material and mechanical properties were determined as a function of the relative humidity (RH), and the relationship between RH and moisture content was determined. These properties served as inputs to a finite-element-based model that was then tested against experimental measurements of the depth-averaged stresses in a thin layer of urushi deposited on a substrate and exposed to changes in the environmental conditions. Good agreement was seen between the predicted and measured behaviour. The validated model was used to investigate the spatial and temperature variation of stress in urushi films subjected to cyclic environmental conditioning.

scholarly journals Effect of Pore Defects on Mechanical Properties of Graphene Reinforced Aluminum Nanocomposites

Metals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 468 ◽  
Author(s):  
Duosheng Li ◽  
Shengli Song ◽  
Dunwen Zuo ◽  
Wenzheng Wu
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Composite Material ◽  
Stress Distribution ◽  
Large Strain ◽  
Sharp Decrease ◽  
Material Failure ◽  
Element Simulation ◽  
The Matrix ◽  
Good Agreement

Pore defects have an important effect on the mechanical properties of graphene reinforced aluminum nanocomposites. The simulation study found that the pores affect the stress distribution in the matrix of the composite. Along the stretching direction, the larger stress appears on both sides of the pore, which is the source of potential cracks. It results in a sharp decrease in the mechanical properties of the composite. The higher the porosity, the greater the tendency of pore aggregation, and the risk of material failure is higher. The stress distribution in the matrix becomes more uneven as the pore size increases, and the large strain area around the pores also increases. Composites with circular pores have a higher strength than other irregularly shaped pores. The failure mode might be pore cracking, while composites with other shape pores are more prone to interface detachment. The simulation value of the stress-strain of the composite material is in good agreement with the experimental value, but the finite element simulation value is larger than the experimental value.

Modeling of Hydrogen Diffusion in Piled Slabs

2014 ◽  
Vol 783-786 ◽  
pp. 2201-2206
Author(s):  
Patrik Sidestam ◽  
Mats Karlberg ◽  
John Niska
Keyword(s):  
Thermal Analysis ◽  
Finite Element ◽  
Finite Element Modeling ◽  
Diffusion Model ◽  
Hydrogen Content ◽  
Hydrogen Diffusion ◽  
Hydrogen Solubility ◽  
Slow Cooling ◽  
Element Modeling ◽  
Good Agreement

Hydrogen is harmful in steel which makes it important to reduce the hydrogen content. Piling slabs after casting gives a slow cooling which increases the diffusion out of the steel. Finite element modeling has been used to simulate this process where hydrogen solubility and phase dependent diffusivity can be taken into account. The hydrogen diffusion model is using STEELTEMP® 2D for the thermal analysis. Measurements of temperature and hydrogen content in piled slabs have been done and the calculations are in good agreement.

Modeling of Mechanical Behavior of Porous Sintered Timing Wheel in Contact with Chain Wheels

2007 ◽  
Vol 561-565 ◽  
pp. 1649-1652
Author(s):  
M. Alizadeh ◽  
H. Khorsand ◽  
Ali Shokuhfar
Keyword(s):  
Experimental Data ◽  
Mechanical Properties ◽  
Finite Element ◽  
Tensile Strength ◽  
Mechanical Behavior ◽  
Sintered Density ◽  
Fem Model ◽  
Gear Contact ◽  
The Relationship ◽  
Good Agreement

The mechanical properties of sintered timing wheel in contact with chain wheels were analysed using Finite Element Methods (FEM), in which the timing wheel is modelled as a metal powder. The mechanical properties of sintered timing wheel were investigated as a function of sintered density. Tensile strength and Young’s modulus increased with a decrease in porosity. Current methods of calculating gear contact stresses use Hertz’s equations, which were originally derived for contact between sintered timing wheel and chain wheels. The results of the 2D dimensional FEM analyses from ANSYS are presented. The relationship between relative density of P/M steels and mechanical behavior is also obtained from FEM and compared with the experimental data. Good agreement between the experimental and FEM results is observed, which demonstrates that FEM can capture the major features of the P/M steels behaviour during loading. This indicates that the FEM model is accurate.

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