Behavior Evaluation of Deformation, Damage and Fracture of Biological Soft Tissue by Using Indentation Test

2016 ◽  
Author(s):  
Atsushi Sakuma ◽  
Katsuya Igarashi
Keyword(s):  
Stress Response ◽  
Soft Tissue ◽  
Deformation Behavior ◽  
Reaction Force ◽  
Indentation Test ◽  
Impact Testing ◽  
Ball Impact ◽  
Damage And Fracture ◽  
The Impact ◽  
Biological Soft Tissue

In this study, two types of indentation tests were used for the observation of deformation behavior of biological soft tissue, because indentation testing is an easy method to manage observation and control of the condition of complex tissue specimens. First, a fundamental indentation test was used to evaluate quasi-static deformation behavior of soft tissue. In the evaluation of the quasi-static behavior, elasticity, damage, and fracture of the tissue were analyzed from the profile of reaction force during the indentation. Ball-impact testing with subsonic indentation velocity was used for the evaluation of dynamic behaviors of soft tissue. In the impact test, the viscoelastic characteristics of specimens were evaluated by analyzing stress response, using extended Hertzian contact theory and wave equations, at the moment when a simple ball bullet shot from an airsoft gun strikes the specimen. In the experimental results of the test, an obvious relationship between quasi-static and impact responses of the specimen were observed subjectively. The results are evaluated to analyze the damage and the fracture of the soft tissue for the objective formulation of tissue mechanics. The plateau behavior of reaction force in relation to stress response was also reviewed, in order to quantify the beginning of tissue fracture.

scholarly journals Characterization of Maple and Ash Material Properties for the Finite Element Modeling of Wood Baseball Bats

2018 ◽  
Vol 8 (11) ◽  
pp. 2256 ◽  
Author(s):  
Joshua Fortin-Smith ◽  
James Sherwood ◽  
Patrick Drane ◽  
David Kretschmann
Keyword(s):  
Finite Element ◽  
Finite Element Modeling ◽  
Material Properties ◽  
Charpy Impact ◽  
Impact Testing ◽  
Charpy Test ◽  
Ball Impact ◽  
Element Modeling ◽  
The Impact ◽  
Baseball Bats

To assist in developing a database of wood material properties for the finite element modeling of wood baseball bats, Charpy impact testing at strain rates comparable to those that a wood bat experiences during a bat/ball collision is completed to characterize the failure energy and strain-to-failure as a function of density and slope-of-grain (SoG) for northern white ash (Fraxinus americana) and sugar maple (Acer saccharum). Un-notched Charpy test specimens made from billets of ash and maple that span the range of densities and SoGs that are approved for making professional baseball bats are impacted on either the edge grain or face grain. High-speed video is used to capture each test event and image analysis techniques are used to determine the strain-to-failure for each test. Strain-to-failure as a function of density relations are derived and these relations are used to calculate inputs to the *MAT_WOOD (Material Model 143) and *MAT_EROSION material options in LS-DYNA for the subsequent finite element modeling of the ash and maple Charpy Impact tests and for a maple bat/ball impact. The Charpy test data show that the strain-to-failure increases with increasing density for maple but the strain-to-failure remains essentially constant over the range of densities considered in this study for ash. The flat response of the ash data suggests that ash-bat durability is less sensitive to wood density than maple-bat durability. The available SoG results suggest that density has a greater effect on the impact failure properties of the wood than SoG. However, once the wood begins to fracture, SoG plays a large role in the direction of crack propagation of the wood, thereby determining if the shape of the pieces breaking away from the bat are fairly blunt or spear-like. The finite element modeling results for the Charpy and bat/ball impacts show good correlation with the experimental data.

Nanoscale repetitive impact testing of polymer films

2004 ◽  
Vol 19 (1) ◽  
pp. 237-247 ◽  
Author(s):  
Ben D. Beake ◽  
Stephen R. Goodes ◽  
James F. Smith ◽  
Fengge Gao
Keyword(s):  
Plastic Deformation ◽  
Strain Rate ◽  
Polymer Films ◽  
High Strain ◽  
Fatigue Behavior ◽  
Indentation Test ◽  
Impact Testing ◽  
Thin Polymer Film ◽  
Poly Ethylene ◽  
The Impact

The deformation of polymer films under repetitive contact at high strain rates was investigated using nanoscale impact testing. Four systems were studied: (i) rubber-modified acrylonitrile-butadiene-styrene (ABS) (0–25 wt% rubber), (ii) uniaxially and biaxially drawn poly(ethylene terephthalate) film; (iii) poly(ethylene oxide)–clay nanocomposites, and (iv) nylon 6–organoclay nanocomposites. The initial results suggest that the technique has much potential in evaluating the fatigue behavior of thinner polymer films and coatings that are unsuitable for conventional methods designed for bulk samples. The extent of impact-induced deformation may be used as a measure of ductility because ductile failures are associated with significant plastic deformation before failure whereas brittle failures usually involve little plastic deformation. The nano-impact technique provides valuable highly localized information about deformation under high strain rate, which is complementary to low strain rate tests such as nanoindentation and nano-scratch. The technique has been shown to be sensitive to nano-/microstructural variations in ABS–rubber film when Berkovich indenters and low impact forces were used. The impact behavior of the nanocomposites is only significantly worse than that of the virgin polymers at the highest clay loading studied (15 wt%). This could be a factor when assessing the suitability of novel nanocomposite materials for applications where toughness is important. On ABS film, there is only an approximate correlation between the plastic work function determined from nanoindentation and the rubber loading in the film while the correlation between the rubber loading and nano-impact data is clear, suggesting that the dynamic test is a more useful predictor of thin polymer film toughness than the slow-loading quasi-static indentation test.

scholarly journals Fuel Tank Integrity Research: Fuel Tank Analyses and Test Plans

2013 ◽  
Author(s):  
Karina Jacobsen ◽  
Patricia Llana ◽  
Michael Carolan ◽  
Laura Sullivan
Keyword(s):  
Dynamic Loading ◽  
Deformation Behavior ◽  
Impact Testing ◽  
Fuel Tank ◽  
Loading Conditions ◽  
Dynamic Impact ◽  
Research Activities ◽  
Blunt Impact ◽  
Fuel Tanks ◽  
The Impact

The Federal Railroad Administration’s Office of Research and Development is conducting research into fuel tank crashworthiness. Fuel tank research is being performed to determine strategies for increasing the fuel tank impact resistance to mitigate the threat of a post-collision or post-derailment fire. In accidents, fuel tanks are subjected to dynamic loading, often including a blunt or raking impact from various components of the rolling stock or trackbed. Current design practice requires that fuel tanks have minimum properties adequate to sustain a prescribed set of static load conditions. Current research is intended to increase understanding of the impact response of fuel tanks under dynamic loading. Utilizing an approach that has been effective in increasing the structural crashworthiness of railcars, improved strategies can be developed that will address the types of loading conditions which have been observed to occur in a collision or derailment event. U.S. rail accident surveys reveal the types of threats fuel tanks are exposed to during collision, derailments and other events. These include both blunt impacts and raking impacts to any exposed side of the tank. This research focuses on evaluating dynamic impact conditions for fuel tanks and investigating how fuel tank design features affect the collision performance of the tank. Research activities will include analytical modeling of fuel tanks under dynamic loading conditions, dynamic impact testing of fuel tank articles, and recommendations for improved fuel tank protection strategies. This paper describes detailed finite element analyses that have been developed to estimate the behavior of three different fuel tanks under a blunt impact. These analyses are being used to understand the deformation behavior of different tanks and prepare for planned testing of two of these tanks. Observations are made on the influence of stiffeners, baffles, and other design details relative to the distance from impact. This paper subsequently describes the preliminary test plans for the first set of tests on conventional passenger locomotive fuel tanks. The first set of tests is designed to measure the deformation behavior of the fuel tanks with a blunt impact of the bottom face of the tanks. The test articles are fuel tanks from two retired EMD F-40 locomotives. A blunt impact will be conducted by securing the test articles to a crash wall and impacting them with an indenter extending from a test cart. This set of tests is targeted for late summer 2013 at the Transportation Technology Center (TTC) in Pueblo, Colorado. Both blunt and raking impact conditions will be evaluated in future research. Tests are also being planned for DMU fuel tanks under dynamic loads.

scholarly journals The impact of bZIP Atf1ortholog global regulators in fungi

2021 ◽  
Author(s):  
Éva Leiter ◽  
Tamás Emri ◽  
Klaudia Pákozdi ◽  
László Hornok ◽  
István Pócsi
Keyword(s):  
Transcription Factors ◽  
Stress Response ◽  
Secondary Metabolite ◽  
Plant Pathogens ◽  
Leucine Zipper ◽  
Secondary Metabolite Production ◽  
Special Focus ◽  
Human Pathogens ◽  
Metabolite Production ◽  
The Impact

Abstract Regulation of signal transduction pathways is crucial for the maintenance of cellular homeostasis and organismal development in fungi. Transcription factors are key elements of this regulatory network. The basic-region leucine zipper (bZIP) domain of the bZIP-type transcription factors is responsible for DNA binding while their leucine zipper structural motifs are suitable for dimerization with each other facilitiating the formation of homodimeric or heterodimeric bZIP proteins. This review highlights recent knowledge on the function of fungal orthologs of the Schizosaccharomyces pombe Atf1, Aspergillus nidulans AtfA, and Fusarium verticillioides FvAtfA, bZIP-type transcription factors with a special focus on pathogenic species. We demonstrate that fungal Atf1-AtfA-FvAtfA orthologs play an important role in vegetative growth, sexual and asexual development, stress response, secondary metabolite production, and virulence both in human pathogens, including Aspergillus fumigatus, Mucor circinelloides, Penicillium marneffei, and Cryptococcus neoformans and plant pathogens, like Fusarium ssp., Magnaporthe oryzae, Claviceps purpurea, Botrytis cinerea, and Verticillium dahliae. Key points • Atf1 orthologs play crucial role in the growth and development of fungi. • Atf1 orthologs orchestrate environmental stress response of fungi. • Secondary metabolite production and virulence are coordinated by Atf1 orthologs.

scholarly journals Simulation of Energy Absorption Performance of the Couplers in Urban Railway Vehicles during a Heavy Collision

Machines ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 91
Author(s):  
Sunghyun Lim ◽  
Yong-hyeon Ji ◽  
Yeong-il Park
Keyword(s):  
Reaction Force ◽  
Crash Test ◽  
Railway Vehicle ◽  
Buffer System ◽  
Railway Vehicles ◽  
Hydraulic Shock Absorber ◽  
Coupling Buffer ◽  
Absorption Performance ◽  
Different Characteristics ◽  
The Impact

Railway vehicles are generally operated by connecting several vehicles in a row. Mechanisms connecting railway vehicles must also absorb front and rear shock loads that occur during a train’s operation. To minimize damage, rail car couplers are equipped with a buffer system that absorbs the impact of energy. It is difficult to perform a crash test and evaluate performance by applying a buffer to an actual railway vehicle. In this study, a simulation technique using a mathematical buffer model was introduced to overcome these difficulties. For this, a model of each element of the buffer was built based on the experimental data for each element of the coupling buffer system and a collision simulation program was developed. The buffering characteristics of a 10-car train colliding at 25 km/h were analyzed using a developed simulator. The results of the heavy collision simulation showed that the rubber buffer was directly connected to the hydraulic shock absorber in a solid contact state, and displacement of the hydraulic buffer hardly occurred despite the increase in reaction force due to the high impact speed. Since the impact force is concentrated on the vehicle to which the collision is applied, it may be appropriate to apply a deformation tube with different characteristics depending on the vehicle location.

Alfa fibers for Cereplast bio-composites reinforcement: Effects of chemical and biological treatments on the mechanical properties

2021 ◽  
pp. 096739112110060
Author(s):  
Mouna Werchefani ◽  
Catherine Lacoste ◽  
Hafedh Belguith ◽  
Chedly Bradai
Keyword(s):  
Charpy Impact ◽  
Impact Testing ◽  
Hot Water ◽  
Cellulose Content ◽  
Twin Screw ◽  
Electron Microscopy Analysis ◽  
Alfa Fibers ◽  
Charpy Impact Testing ◽  
Water Treatments ◽  
The Impact

The present work is a comparative study of the impact of Alfa fiber modifications on the Cereplast composites mechanical behavior. Various treatments have been employed, including mechanical, soda, saltwater-retting, hot-water treatments and enzymatic treatment using xylanase. Chemical and morphological analyses were carried out in order to determine the changes of the biochemical composition and the dimensions of fibers. Cereplast composites reinforced with Alfa fibers were fabricated using a twin-screw extrusion followed by an injection molding technique with a fiber load of 20 wt. %. Resulting materials were assessed by means of tensile, flexural and Charpy impact testing. Scanning Electron Microscopy analysis was carried out to investigate the interfacial properties of the composites. The results have shown a significant enhancement of mechanical strengths and rigidities for the xylanase-treated fiber composites, owing to the increase of cellulose content, the enhancement of defibrillation level and the improvement of matrix-fiber adhesion. The data proved that the technology of enzymes can be used as a powerful and eco-friendly approach to modify fiber surfaces and to increase their potential of reinforcement.

Analysis of the intervention effect and self-satisfaction of sports dance exercise on the psychological stress of college students

Work ◽  
2021 ◽  
pp. 1-13
Author(s):  
Changliang Zheng ◽  
Hongmei Ji
Keyword(s):  
College Students ◽  
Stress Response ◽  
Psychological Stress ◽  
Rating Scale ◽  
Response Characteristic ◽  
Control Group ◽  
Observation Group ◽  
Excessive Pressure ◽  
Psychological Pressure ◽  
The Impact

BACKGROUND: College students are a high-risk subpopulation of psychological disorders. The problem of various adverse phenomena and consequences caused by excessive pressure on college students has gradually become the focus of social and psychological academic circles. However, studies related to individual self-concept and psychological pressure are rare. OBJECTIVE: To explore the impact of sports dance exercises on college students’ psychological pressure and improve the psychological effects of their self-satisfaction. METHODS: College students were taken as research objects, randomly divided into a control group and an observation group. The observation group is intervened with sports dance exercises. The observation group was intervened with sports dance exercises. The stress response characteristic questionnaire and multidimensional self-satisfaction rating scale were utilized to measure college students’ conditions before and after the intervention. Finally, the obtained data were statistically analyzed. RESULTS: Generally, the psychological stress response of college students was mild, with self-satisfaction and various dimensions at a moderately higher level. No significant differences were discovered in the psychological stress response and self-satisfaction level between the control group and the observation group before intervention (P >  0.05), which were homogeneous. Compared with the data obtained before the intervention, after the intervention, the control group scores were slightly reduced in all dimensions of the psychological stress response and self-satisfaction. In contrast, the scores were significantly increased in the experimental group (P <  0.05). Psychological stress response could reliably explain 30.4%of the total self-satisfaction variance (P <  0.01). The negative self-evaluation was the most important variable affecting self-satisfaction, followed by poor interpersonal communication and poor sleeping quality. CONCLUSIONS: Sports dance exercises could alleviate the psychological stress of college students and improve their self-satisfaction. Colleges and universities should include sports dance in the content of optional public courses and encourage more college students to actively participate in sports dance exercises to improve their mental health.

scholarly journals m5U54 tRNA Hypomodification by Lack of TRMT2A Drives the Generation of tRNA-Derived Small RNAs

2021 ◽  
Vol 22 (6) ◽  
pp. 2941
Author(s):  
Marisa Pereira ◽  
Diana R. Ribeiro ◽  
Miguel M. Pinheiro ◽  
Margarida Ferreira ◽  
Stefanie Kellner ◽  
...  
Keyword(s):  
Stress Response ◽  
Small Rnas ◽  
Mammalian Cells ◽  
Cellular Stress ◽  
Cellular Stress Response ◽  
Translation Regulation ◽  
Translation Efficiency ◽  
Down Regulation ◽  
Gene Expression Control ◽  
The Impact

Transfer RNA (tRNA) molecules contain various post-transcriptional modifications that are crucial for tRNA stability, translation efficiency, and fidelity. Besides their canonical roles in translation, tRNAs also originate tRNA-derived small RNAs (tsRNAs), a class of small non-coding RNAs with regulatory functions ranging from translation regulation to gene expression control and cellular stress response. Recent evidence indicates that tsRNAs are also modified, however, the impact of tRNA epitranscriptome deregulation on tsRNAs generation is only now beginning to be uncovered. The 5-methyluridine (m5U) modification at position 54 of cytosolic tRNAs is one of the most common and conserved tRNA modifications among species. The tRNA methyltransferase TRMT2A catalyzes this modification, but its biological role remains mostly unexplored. Here, we show that TRMT2A knockdown in human cells induces m5U54 tRNA hypomodification and tsRNA formation. More specifically, m5U54 hypomodification is followed by overexpression of the ribonuclease angiogenin (ANG) that cleaves tRNAs near the anticodon, resulting in accumulation of 5′tRNA-derived stress-induced RNAs (5′tiRNAs), namely 5′tiRNA-GlyGCC and 5′tiRNA-GluCTC, among others. Additionally, transcriptomic analysis confirms that down-regulation of TRMT2A and consequently m5U54 hypomodification impacts the cellular stress response and RNA stability, which is often correlated with tiRNA generation. Accordingly, exposure to oxidative stress conditions induces TRMT2A down-regulation and tiRNA formation in mammalian cells. These results establish a link between tRNA hypomethylation and ANG-dependent tsRNAs formation and unravel m5U54 as a tRNA cleavage protective mark.

scholarly journals Impact of Carcinogenic Chromium on the Cellular Response to Proteotoxic Stress

2019 ◽  
Vol 20 (19) ◽  
pp. 4901 ◽  
Author(s):  
Leonardo M. R. Ferreira ◽  
Teresa Cunha-Oliveira ◽  
Margarida C. Sobral ◽  
Patrícia L. Abreu ◽  
Maria Carmen Alpoim ◽  
...  
Keyword(s):  
Stress Response ◽  
Health Effects ◽  
Cellular Response ◽  
Molecular Mechanisms ◽  
Critical Role ◽  
Chemical Properties ◽  
Adverse Health Effects ◽  
Proteotoxic Stress ◽  
Adverse Health ◽  
The Impact

Worldwide, several million workers are employed in the various chromium (Cr) industries. These workers may suffer from a variety of adverse health effects produced by dusts, mists and fumes containing Cr in the hexavalent oxidation state, Cr(VI). Of major importance, occupational exposure to Cr(VI) compounds has been firmly associated with the development of lung cancer. Counterintuitively, Cr(VI) is mostly unreactive towards most biomolecules, including nucleic acids. However, its intracellular reduction produces several species that react extensively with biomolecules. The diversity and chemical versatility of these species add great complexity to the study of the molecular mechanisms underlying Cr(VI) toxicity and carcinogenicity. As a consequence, these mechanisms are still poorly understood, in spite of intensive research efforts. Here, we discuss the impact of Cr(VI) on the stress response—an intricate cellular system against proteotoxic stress which is increasingly viewed as playing a critical role in carcinogenesis. This discussion is preceded by information regarding applications, chemical properties and adverse health effects of Cr(VI). A summary of our current understanding of cancer initiation, promotion and progression is also provided, followed by a brief description of the stress response and its links to cancer and by an overview of potential molecular mechanisms of Cr(VI) carcinogenicity.

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