Traction stress analysis and modeling reveal that amoeboid migration in confined spaces is accompanied by expansive forces and requires the structural integrity of the membrane–cortex interactions

2015 ◽  
Vol 7 (10) ◽  
pp. 1196-1211 ◽  
Author(s):  
Ai Kia Yip ◽  
Keng-Hwee Chiam ◽  
Paul Matsudaira

Neutrophil-like cells, confined between two non-fibronectin-coated gels, form blebs and generate expansive forces against opposing surfaces during amoeboid cell “chimneying”.

Author(s):  
Michael S. L. Hollis

Abstract The U.S. Army Armament Research. Development, and Engineering Center (ARDEC) recently expressed a need for a tank-cannon-launched training projectile with reduced penetration capability. The expressed primary design goals for this projectile were to minimize the probability of personnel injury and materiel loss in the event of an accidental impact during a training exercise. In order to meet these design goals, the solid-steel flight body of a current kinetic energy (KE) training projectile, the M865IP, was replaced with a hollow aluminum configuration. Because of the incorporation of aluminum, the structural integrity of the entire projectile during launch was put in question. Thus, a thorough stress analysis of the new design was conducted to alleviate concerns about its structural integrity. Two-dimensional, axisymmetric, quasi-static stress analyses were performed on two new KE training projectile designs. The first analysis indicated that structural failure was possible in the aft portion of the projectile due to compressive loading by the gun gases. Structural failure in this case would be circumferential yielding of the hollow flight body. The aft portion of the round was redesigned, and subsequent stress analysis showed the possibility of structural failure to be resolved. The finite-element modeling approach, the applied boundary conditions, and the results of the stress analyses conducted, based on use of the von Mises failure criterion, will be discussed in detail.


Author(s):  
M. Cao ◽  
S. Butler ◽  
J. T. Benoit ◽  
Y. Jiang ◽  
R. Radhakrishnan ◽  
...  

Aiming at understanding the structural integrity of a concentrating photovoltaic (CPV) module configuration, Finite Element (FE) thermal stress analysis is carried out in this investigation. Nonlinear viscoplastic analysis using the temperature profile of CPV cell fatigue test, is performed to evaluate the structure strength and subsequently predict the life of a CPV module. The result reveals that the maximum characteristic stresses of the PV cell components and heat sink are below the strength allowable for the corresponding materials under both the steady-state and over-night idle conditions. Critical locations on the solder that are potentially susceptible to structural failure after a few thousand thermal cycles due to excessive shear stress are identified. A rough estimation of the module life is provided and compared with the fatigue test. This investigation provides firsthand understanding of the structural integrity of CPV modules and is thus beneficial for the solar energy community.


2008 ◽  
Vol 130 (2) ◽  
Author(s):  
M. Cao ◽  
S. Butler ◽  
J. T. Benoit ◽  
Y. Jiang ◽  
R. Radhakrishnan ◽  
...  

Aiming at understanding the structural integrity of two representative concentrating photovoltaic (CPV) module configurations, finite element thermal stress analysis is carried out in this investigation. This study covers the nominal and extreme operating conditions, including system startup and shutdown. While the first CPV module is bonded by epoxy-type material, the bonding material for the second CPV module is lead-free solder. The analysis of the first module confirms that this CPV module can endure the thermal stress under steady-state operation. However, residual stress analysis shows that the epoxy holding together the PV cell/aluminum nitride and aluminum nitride/heat sink pairs will likely break, first at some sporadic spots, and then in a good part of the bond causing the failure of the CPV module, as the cell temperature drops from 100°Cto0°C. Nonlinear viscoplastic analysis using the temperature profile of CPV cell fatigue test ongoing at United Technologies Research Center (UTRC) is performed to evaluate the structure strength and subsequently predict the life of the second CPV module. The result reveals that the maximum characteristic stresses of the PV cell components and heat sink are below the strength allowable for the corresponding materials under both the steady-state and overnight idle conditions. Critical locations on the solder that are potentially susceptible to structural failure after a few thousand thermal cycles due to the excessive shear stress are identified. A rough estimation of the module life is provided and compared with the fatigue test. This investigation provides firsthand understanding of the structural integrity of CPV modules and is thus beneficial for the solar energy community.


Author(s):  
Aaron D. Gupta

Abstract A stress analysis of the target enclosure structure at the R14B firing range at Aberdeen Proving Ground (APG), MD, subjected to an internal blast and worst-case fragment impact was conducted to assure structural integrity and safe operation of the structure during tests. The reflected dynamic pressure loads due to explosive blast were estimated from the CONWEP explosion effects code developed by the U.S. Army Waterways Experiment Station and were modeled as exponentially decaying pressure pulses which could be approximated as triangular loads with equivalent impulses. Fragment impact loads are approximated from a momentum-impulse balance formulation as step loading functions. A closed-form solution of the equation of motion of a sidewall of the structure subjected to a triangular blast load was obtained and verified by a three-dimensional (3-D) finite element model.


Author(s):  
Bing Li ◽  
Dan Neill ◽  
D. K. Vijay

In one Ontario CANDU reactor unit, the horizontal feeders are interlinked with feeder spacer rods, which are installed to prevent the contact between adjacent feeders. In the normal operating conditions, spaces do not carry any loads. Therefore, the individual feeder model is used without spacers for the horizontal feeders. This reactor unit is under extensive fuel channel shifting in order to extend the life time. The axial shifting of channels is expected to put additional loads on spacers and may constrain feeder movement. In order to determine how the spacer affects the feeder stress and feeder movement due to the extensive fuel channel shifting, multifeeder models that include spacers are created for stress analysis. Multi-feeder modelling capability is not readily available in AUTOPIPE. A novel approach of inter connecting feeders with structural elements is developed for AUTOPIPE. A significant increase in feeder stress under the extensive fuel channel shift loading condition is found when the feeder spacers are included in the model. However, the feeder stresses for Design, Level A&B loading under fuel channel shift configuration meet the ASME B&PV Code NB-3600 stress limit requirements. The feeder spacer assessment results also show that the structural integrity of feeder spacers is not affected by the fuel channel shifting. In addition, this study confirmed that it is unnecessary to release the feeder spacers to prevent spacer break or feeder overstress during the post fuel channel sifting operation, thus saving significant outage time to achieve shifting configuration.


Author(s):  
Xiaoyan Wang ◽  
Shifeng Zhu ◽  
Xiao Wang ◽  
Yun Cao

To guarantee the safety of nuclear reactor, the stress analysis and structural integrity evaluations of the reactor pressure vessel (RPV) are very important for Thorium-based Molten Salt Reactor (TMSR), whose design temperature and design pressure are 700 °C and 0.5MPa respectively. In this paper, the structural analysis is firstly carried out by using a 3D coarse model of the RPV. Secondly, the reactor core support are recalculated by a sub-model with a fine mesh and the analysis results are evaluated according to ASME NH code, including stress evaluation, strain and deformation evaluation and creep-fatigue evaluation. It was found that the initial structural did not meet the requirements of creep-fatigue limits. Finally, structural optimization designs are proposed, such as T-shaped modified structure and fillet design, whose results can satisfy the requirements of creep-fatigue limits. These analysis methods and results provide some practical engineering guidance to the structural design and safety evaluation of the RPV in TMSR.


2006 ◽  
Vol 326-328 ◽  
pp. 1027-1030 ◽  
Author(s):  
Seung Kee Koh ◽  
Eui Gyun Na ◽  
Tae Hyun Baek ◽  
K.J. Kang ◽  
S.T. Ahn ◽  
...  

In order to evaluate the structural integrity of the breech system used for a thick-walled cylinder subjected to pulsating high internal pressure, fatigue life simulation of a breech system was performed. A stress analysis of the breech was performed to locate the critical region vulnerable to crack initiation. Low-cycle fatigue behavior of the breech material was investigated to obtain the fatigue crack initiation properties. Elastic-plastic finite element stress analysis resulted in a stress concentration at the breech ring groove root. Strains at the breech ring and block were experimentally measured using strain gages and resulted in similar values compared to the calculated strains. Local strain approach was employed to estimate the fatigue life of the breech system for crack initiation at the groove root of the breech ring. Fatigue tests using simulation specimens were performed and an averaged fatigue life was obtained, showing a very good agreement with the calculated fatigue life within a factor of two.


2014 ◽  
Vol 106 (2) ◽  
pp. 787a-788a
Author(s):  
Effie Bastounis ◽  
Reudi Meili ◽  
Begoña Álvarez-González ◽  
Juan Carlos del Álamo ◽  
Juan Lasheras ◽  
...  

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