scholarly journals 3D printed cellular solid outperforms traditional stochastic foam in long-term mechanical response

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
A. Maiti ◽  
W. Small ◽  
J. P. Lewicki ◽  
T. H. Weisgraber ◽  
E. B. Duoss ◽  
...  
Keyword(s):  
Mechanical Response ◽  
Mechanical Performance ◽  
Compressive Strain ◽  
Mechanical Strain ◽  
Element Analysis ◽  
Cellular Solid ◽  
3D Printed ◽  
Long Term Performance ◽  
Term Performance

Abstract 3D printing of polymeric foams by direct-ink-write is a recent technological breakthrough that enables the creation of versatile compressible solids with programmable microstructure, customizable shapes, and tunable mechanical response including negative elastic modulus. However, in many applications the success of these 3D printed materials as a viable replacement for traditional stochastic foams critically depends on their mechanical performance and micro-architectural stability while deployed under long-term mechanical strain. To predict the long-term performance of the two types of foams we employed multi-year-long accelerated aging studies under compressive strain followed by a time-temperature-superposition analysis using a minimum-arc-length-based algorithm. The resulting master curves predict superior long-term performance of the 3D printed foam in terms of two different metrics, i.e., compression set and load retention. To gain deeper understanding, we imaged the microstructure of both foams using X-ray computed tomography, and performed finite-element analysis of the mechanical response within these microstructures. This indicates a wider stress variation in the stochastic foam with points of more extreme local stress as compared to the 3D printed material, which might explain the latter’s improved long-term stability and mechanical performance.

Analysis of thermo-mechanical coupling damage behavior in long-term performance of microelectromechanical systems actuators

2021 ◽  
pp. 105678952110339
Author(s):  
Jiaxing Cheng ◽  
Zhaoxia Li
Keyword(s):  
Damage Mechanics ◽  
Microelectromechanical Systems ◽  
Mechanical Performance ◽  
Damage Model ◽  
Irreversible Damage ◽  
Damage Behavior ◽  
Thermal Actuators ◽  
Long Term Performance ◽  
Term Performance

Effective numerical analysis is significant for the optimal design and reliability evaluation of MEMS, but the complexity of multi-physical field couplings and irreversible damage accumulation in long-term performance make the analysis difficult. In the present paper, the continuum damage mechanics method is used to develop a creep damage model and conduct long-term performance analysis for MEMS thermal actuators with coupled thermo-mechanical damage behavior. The developed damage model can make a connection between the material deterioration due to microstructure changes and the macroscopic responses (the change of thermo-mechanical performance or structure failure). The numerical simulations of coupled thermo-mechanical behavior in long-term performance are implemented using the finite element method, which is validated through comparison with previous literature. The numerical results demonstrate that the proposed damage model and numerical method can provide effective assessment in the long-term performance of MEMS thermal actuators.

scholarly journals Durability of Textile Reinforced Concrete: Existing Knowledge and Current Gaps

2021 ◽  
Vol 11 (6) ◽  
pp. 2771
Author(s):  
Mohammad Alma’aitah ◽  
Bahman Ghiassi ◽  
Ali Dalalbashi
Keyword(s):  
Reinforced Concrete ◽  
Mechanical Performance ◽  
Mechanical Tests ◽  
Textile Reinforced Concrete ◽  
Standard Procedures ◽  
Long Term Performance ◽  
Term Performance ◽  
Existing Data

This paper aims to provide a review of the current literature on the durability of textile-reinforced concrete and mortar (TRC/TRM) composites. Most previous studies have focused on the role of chemical attacks, freeze-thaw conditions, and high temperatures on the mechanical performance of these composites. Information on the long-term performance of TRCs under synergistic action of mechanical and environmental loads is scarce. Considering the variety of fabrics and matrices used for the production of TRC composites, the existing data are still very limited and comprehensive studies are needed in this field. Additionally, due to the lack of standard procedures, different approaches are often followed for durability or post-ageing mechanical tests, or sufficient data on the curing and post-ageing preparation procedures followed are not provided. These have led to incompatibility of the existing data and in some cases contradictory results on the durability of these materials.

Analytical Modeling of the Mechanics of Re-Torque

2011 ◽  
Author(s):  
Ali P. Gordon ◽  
James Williams ◽  
Maricela De Santiago
Keyword(s):  
Analytical Modeling ◽  
Mechanical Response ◽  
Time Dependent ◽  
Fiber Glass ◽  
Creep Stress ◽  
Gasket Material ◽  
Long Term Performance ◽  
Term Performance ◽  
Dwell Period

A secondary torque, i.e., re-torque, is generally applied in order to confer long term bolt tightness of certain gasketed-flange configurations that have undergone a primary torque with some relaxation. In some sense, the initial torque conditions the viscoelastic gasket material for long term performance under service loading. While prior research has been carried out to analytically model the mechanical response of gasket materials under either creep, stress relaxation, or creep relaxation, the mechanics of gasket re-torque has received much less attention. In the current study, a candidate fiber-glass reinforced gasket material is subjected to creep relaxation after a series of primary and secondary torques. Test variables considered here include values of either torque, dwell period, or gasket thickness. The over-arching goal addressed in this study is the identification of the conditions that confer the minimal initial dwell period without loss of long term load retention. In all cases, specimen-sized samples were used on a raised-face, serrated flange assembly. Based on the experimental test data and observations from scanning electron microscopy, an viscoelasticity model is developed to analytically predict the response of the time-dependent solid.

scholarly journals Erratum: Corrigendum: 3D printed cellular solid outperforms traditional stochastic foam in long-term mechanical response

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
A. Maiti ◽  
W. Small ◽  
J. P. Lewicki ◽  
T. H. Weisgraber ◽  
E. B. Duoss ◽  
...  
Keyword(s):  
Mechanical Response ◽  
Cellular Solid ◽  
3D Printed

Acoustic Emission Monitoring of Cement-Based Structures Immobilising Radioactive Waste

2007 ◽  
Author(s):  
L. M. Spasova ◽  
M. I. Ojovan ◽  
M. Hayes ◽  
H. Godfrey
Keyword(s):  
Acoustic Emission ◽  
Radioactive Waste ◽  
Mechanical Performance ◽  
Cement Matrix ◽  
Properties Of Materials ◽  
Long Term Performance ◽  
Term Performance ◽  
Physical And Chemical ◽  
Non Destructive

The long term performance of cementitious structures immobilising radioactive waste can be affected by physical and chemical processes within the encapsulating materials such as formation of new phases (e.g., vaterite, brucite), degradation of cement phases (e.g., CSH gel, portlandite), degradation of some waste components (e.g., organics), corrosion of metallic constituents (aluminium, magnesium), gas emission, further hydration etc. The corrosion of metals in the high pH cementitious environment is of especial concern as it can potentially cause wasteform cracking. One of the perspective non-destructive methods used to monitor and assess the mechanical properties of materials and structures is based on an acoustic emission (AE) technique. In this study an AE non-destructive technique was used to evaluate the mechanical performance of cementitious structures with encapsulated metallic waste such as aluminium. AE signals generated as a result of aluminium corrosion in a small-size blast furnace slag (BFS)/ordinary Portland cement (OPC) sample were detected, recorded and analysed. A procedure for AE data analysis including conventional parameter-based AE approach and signal-based analysis was applied and demonstrated to provide information on the aluminium corrosion process and its impact on the mechanical performance of the encapsulating cement matrix.

Fine Particle Mass Monitoring with Low-Cost Sensors: Corrections and Long-Term Performance Evaluation

2019 ◽  
Author(s):  
Carl Malings ◽  
Rebecca Tanzer ◽  
Aliaksei Hauryliuk ◽  
Provat K. Saha ◽  
Allen L. Robinson ◽  
...  
Keyword(s):  
Performance Evaluation ◽  
Fine Particle ◽  
Low Cost ◽  
Particle Mass ◽  
Long Term Performance ◽  
Term Performance

Long-term performance of the Hancock bioprosthetic conduit for aortic root replacement

2008 ◽  
Vol 56 (S 1) ◽  
Author(s):  
CC Badiu ◽  
W Eichinger ◽  
D Ruzicka ◽  
I Hettich ◽  
S Bleiziffer ◽  
...  
Keyword(s):  
Aortic Root ◽  
Aortic Root Replacement ◽  
Long Term Performance ◽  
Term Performance
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