Optimization strategies for discrete multi-material stiffness optimization

2011 ◽  
Vol 44 (2) ◽  
pp. 149-163 ◽  
Author(s):  
Christian Frier Hvejsel ◽  
Erik Lund ◽  
Mathias Stolpe
Author(s):  
Yicong Zhou ◽  
Qiyin Lin ◽  
Jun Hong ◽  
Nan Yang

The characteristics of contact interfaces such as the distribution uniformity of the contact pressure and the effective contact area play a crucial role in engineering equipment. To investigate the influences of the variable material stiffness optimization (VMSO) design on the contact characteristics of the contact interfaces in an assembly, an heuristic-based VMSO algorithm is developed in this paper. A bi-objective function is defined by including both the distribution uniformity of the contact pressure and the effective contact area. A single bolted joint model is adopted as a design example. The results indicate that optimizing the stiffness of the materials around the contact interface is an effective approach to enhance the distribution uniformity of the contact pressure, increase the effective contact area and decrease the maximum contact pressure. Furthermore, the improvement effectiveness provided by the proposed variable stiffness design is better than that provided by the traditional variable thickness design.


2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Qiyin Lin ◽  
Nan Yang ◽  
Jun Hong ◽  
Lian Liu ◽  
Yuhan Zhang

Abstract Material stiffness, a significant parameter of a contact interface, is investigated to improve the uniformity of the contact pressure. A contact interface material stiffness optimization design algorithm is developed based on the modified solid isotropic material with the penalization (SIMP) method. The uniformity of the contact pressure field is represented by its variance and is defined as the optimization objective. A node-to-node frictionless elastic contact theory is adopted to perform the contact analysis. The effectiveness of the interface material stiffness design for improving the uniformity of the contact surface is verified based on two contact cases. Because the relationship between the material stiffness and the hard-and-soft degree of a contact interface is always a positive correlation, the results in this paper could be extended so that the design of the contact interfaces’ hard-and-soft degree will improve the distributing uniformity of the contact surface.


AIAA Journal ◽  
1999 ◽  
Vol 37 ◽  
pp. 1483-1488 ◽  
Author(s):  
X. Y. Yang ◽  
Y. M. Xie ◽  
G. P. Steven ◽  
O. M. Querin

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1080
Author(s):  
Clever Aparecido Valentin ◽  
Marcelo Kobelnik ◽  
Yara Barbosa Franco ◽  
Fernando Luiz Lavoie ◽  
Jefferson Lins da Silva ◽  
...  

The use of polymeric materials such as geosynthetics in infrastructure works has been increasing over the last decades, as they bring down costs and provide long-term benefits. However, the aging of polymers raises the question of its long-term durability and for this reason researchers have been studying a sort of techniques to search for the required renewal time. This paper examined a commercial polypropylene (PP) nonwoven geotextile before and after 500 h and 1000 h exposure to ultraviolet (UV) light by performing laboratory accelerated ultraviolet-aging tests. The state of the polymeric material after UV exposure was studied through a wide set of tests, including mechanical and physical tests and thermoanalytical tests and scanning electron microscopy analysis. The calorimetric evaluations (DSC) showed distinct behaviors in sample melting points, attributed to the UV radiation effect on the aged samples. Furthermore, after exposure, the samples presented low thermal stability in the thermomechanical analysis (TMA), with a continuing decrease in their thicknesses. The tensile tests showed an increase in material stiffness after exposition. This study demonstrates that UV aging has effects on the properties of the polypropylene polymer.


2005 ◽  
Vol 888 ◽  
Author(s):  
Stephen Andrew Sarles ◽  
Todd Bullions ◽  
Thompson Mefford ◽  
Judy Riffle ◽  
Don Leo

ABSTRACTIn attempts to provide an active solution for the rigidization of flexible space structures, internal resistive heating is applied to a novel thermosetting resin. Carbon-fiber tow coated in U-Nyte Set 201A, which cures at ∼150°C, was heated by passing electric current through the reinforcing material. Using a proportional-integral (PI) controller, precise temperature control of the heating process was established. Samples cured via controlled internal resistive heating were heated to 160°C and underwent material consolidation in less than 7 minutes. A change in material stiffness was measured to be almost two orders of magnitude greater than that of an uncured material.


1999 ◽  
Author(s):  
James Mayrose ◽  
T. Kesavadas ◽  
Senthil K. Narayanasamy

Abstract Accurate models of human body tissues and organs have tremendous applications in the medical field. Modeled organs within virtual environments are increasingly being used as research tools in medicine. In the near future, these research tools will make their way into teaching and clinical practice. These virtual environment simulations allow researchers to study the behavior of human organs and to develop large databases of organ characteristics. The 3D viewing and interaction available through virtual reality make it possible for physicians to practice many medical procedures without ever touching a patient. The main goal of this study is to evaluate the effectiveness of a “sensory data glove”, developed by the authors, for calculating the stiffness of an object beneath a surface of varying stiffness.


2021 ◽  
pp. 095605992110416
Author(s):  
Pierre Latteur ◽  
Julien Geno ◽  
Marie Vandamme

Building with raw timber allows to reduce the price of construction and to make it more competitive with respect to concrete or steel construction. For a few years now, the combination of parametric design and robotic tools make possible the fast and precise milling of timber logs for their accurate connection. However, the spans are quickly limited by the logs length. In this context, reciprocal structures are relevant, since they allow to build large spans structures with short beams. Finally, the architectural interest of reciprocal structures is not to prove. However, the choice of the most efficient reciprocal frame, as well as its structural relevance in terms of mass and stiffness is, most of the time, ruled by subjective considerations. This paper focuses on rectangular floors composed of reciprocal moduli and has three objectives: (1) to develop a general mass and stiffness optimization method for reciprocal floors, which is not only necessary to limit the price, but also to reduce their thickness, (2) to define design rules for reciprocal floors, in particular for the choice of the best engagement ratio, and (3) to compare the structural efficiency of reciprocal floors with the one of “traditional” floors with parallel logs. Coming from a dimensionless transformation of the equilibrium equations, the results of this article will thus give the designers keys to better design reciprocal structures, evaluate their structural performances and relevance, and justify their choices.


2017 ◽  
Vol 37 (suppl_1) ◽  
Author(s):  
Qingyu Wang ◽  
Dalin Tang ◽  
Gador Canton ◽  
Jian Guo ◽  
Xiaoya Guo ◽  
...  

It is hypothesized that artery stiffness may be associated with plaque progression. However, in vivo vessel material stiffness follow-up data is lacking in the literature. In vivo 3D multi-contrast and Cine magnetic resonance imaging (MRI) carotid plaque data were acquired from 8 patients with follow-up (18 months) with written informed consent obtained. Cine MRI and 3D thin-layer models were used to determine parameter values of the Mooney-Rivlin models for the 81slices from 16 plaques (2 scans/patient) using our established iterative procedures. Effective Young’s Modulus (YM) values for stretch ratio [1.0,1.3] were calculated for each slice for analysis. Stress-stretch ratio curves from Mooney-Rivlin models for the 16 plaques and 81 slices are given in Fig. 1. Average YM value of the 81 slices was 411kPa. Slice YM values varied from 70 kPa (softest) to 1284 kPa (stiffest), a 1734% difference. Average slice YM values by vessel varied from 109 kPa (softest) to 922 kPa (stiffest), a 746% difference. Location-wise, the maximum slice YM variation rate within a vessel was 306% (139 kPa vs. 564 kPa). Average slice YM variation rate within a vessel for the 16 vessels was 134%. Average variation of YM values from baseline (T1) to follow up (T2) for all patients was 61.0%. The range of the variation of YM values was [-28.4%, 215%]. For progression study, YM increase (YMI=YM T2 -TM T1 ) showed negative correlation with plaque progression measured by wall thickness increase (WTI), (r= -0.6802, p=0.0634). YM T2 showed strong negative correlation with WTI (r= -0.7764, p=0.0235). Correlation between YM T1 and WTI was not significant (r= -0.4353, p= 0.2811). Conclusion In vivo carotid vessel material properties have large variations from patient to patient, along the vessel segment within a patient, and from baseline to follow up. Use of patient-specific, location specific and time-specific material properties could potentially improve the accuracy of model stress/strain calculations.


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