225 research outputs found
The Influence of Geometry of the Specimen and Material Properties on the Q-Stress Value Near the Crack Tip for SEN(T) Specimen
No full textIn the paper the short theoretical backgrounds about elastic-plastic fracture mechanics were presented and the O’Dowd-Shih theory was discussed. Using ADINA System program, the values of the Q-stress determined for various elastic-plastic materials for SEN(T) specimen – single edge notched plates in tension – were presented. The influence of kind of the specimen, crack length and material properties (work-hardening exponent and yield stress) on the Q-parameter were tested. The numerical results were approximated by the closed form formulas. Presented in the paper results are complementary of the two papers published in 2007 (Graba, 2007) and in 2010 (Graba, 2010), which show and describe influence of the material properties and crack length for the Q-stress value for SEN(B) and CC(T) specimens respectively. Presented and mentioned papers show such catalogue of the Q-stress value, which may be used in engineering analysis for calculation of the real fracture toughness
Graba-Landry PhD thesis: The effect of increasing temperature to algae-fish interactions on coral reefs
No full text<p>This thesis investigated the role of temperature in influencing algae-fish interactions on coral reefs. Specifically the aims of the thesis were to determine: (1) the relative influence of natural variations in water temperature on the feeding rates of herbivorous fishes; (2) how rates of turf algae growth and feeding rates of herbivorous fishes change with seasonal variation in temperature; (3) how predicted increases in temperature are likely to affect the growth and survival of common coral reef macroalgae; (4) how individual metabolism, feeding rates, growth and body condition of a common herbivorous fish changes with temperature.  These aims were addressed in the following five chapters.</p><p>Chapter 2 investigates the influence of natural variation in temperature versus resource availability in influencing herbivore feeding rates by quantifying feeding of three functionally distinct herbivores among three latitudes and two seasons on the Great Barrier Reef (GBR), and among reefs with distinct algal communities.</p><p>Chapter 3 builds on the findings of Chapter 2, and investigates how seasonal variation in temperature influences the relative rates of herbivore feeding and turf algal growth in the northern GBR.</p><p>Chapter 4 uses experimental manipulation of temperature to investigate the influence of increasing temperature on the growth, survival, tissue quality and susceptibility to herbivory of adult and juvenile life stages of the common coral reef macroalgae Sargassum.</p><p>Chapter 5 uses juvenile Siganus doliatus, a common herbivorous reef fish, to investigate the effect of rearing temperature on physiological processes (i.e., oxygen uptake, feeding rate, growth and body condition).</p><p>This dataset consists of 27 files in comma-separated values (.csv) format:</p><ul><li>Benthic_Latitude_sub_1.csv - Chapter 2: Benthic Count data from point intercept transects across three latitudes</li><li>Cross_Shelf_Benthos_MDS.csv - Chapter 2: Benthic Count data from point intercept transects across the continental shelf in the northern GBR</li><li>Cross_Shelf_Feeding_nonorthpoint.csv - Benthic Count data from point intercept transects across the continental shelf in the northern GBR, no north point site</li><li>Latitude_with_resource.csv - Chapter 2: Herbivore feeding data across the three latitudes along the GBR</li><li>CrossShelf_with_Resource.csv - Chapter 2: Herbivore feeding data across the continental shelf in the northern GBR</li><li>RESOURCE_Seasonal_Comparison.csv - Chapter 2: Herbivore feeding data between two seasons in the northern GBR</li><li>Community_Subreps_Total_R.csv - Chapter 3: Feeding rate data of herbivore assemblages from video analysis on 1m^2 quadrats</li><li>Dry_Wt_n10.csv - Chapter 3: Algal growth data from tiles across four seasons at Lizard Island</li><li>Lizard_Temp_8.8.csv - Chapter 3: Temperature data from AIMS loggers at 8.8 m at Lizard Island</li><li>Seasonal_Benthic.csv - Chapter 3: Benthic Count data from point intercept transects over four seasons at Lizard Island</li><li>Seasonal_Feeding_Contrasts .csv - Chapter 3: Seasonal Feeding Contrasts for catapillar plots</li><li>Seasonal_with_Resouce.csv - Chapter 3: Herbivore Feeding rates of 8 species over four seasons at Lizard Island</li><li>Fish_Abundance_Counts.csv - Chapter 3: Herbivore Count data from 50x5m transects over four seasons at Lizard Island</li><li>Carbon_New.csv - Chapter 4: Carbon data for three species of Sargassum grown in different temperatures</li><li>Nitrogen_New.csv - Chapter 4: Nitrogen data for three species of Sargassum grown in different temperatures</li><li>glm_mass_consumed.csv - Chapter 4: Data for mass consumed by the wild herbivore assemblage on Sargassum grown in three different temperature treatments.</li><li>Penetrometer_nocris2016.csv - Chapter 4: Physical toughness data for three species of Sargassum grown in three different temperature treatments</li><li>RGRNew.csv - Chapter4: Relative Growth Rate of Sargassum propagules grown in three different temperature treatments</li><li>Survival.csv - Chapter 4: Survival data for Sargassum propagules grown in three different temperature treatments</li><li>RGR_NEW.csv - Chapter 4: Relative Growth Rate of three different species of Sargassum grown in different temperature treatments</li><li>Mass_Std_glm.csv - Chapter 4: Mass standardized bites from the wild herbivorous fish assemblage on three species of Sargassum grown in different temperature treatments. From video analysis</li><li>Feeding_Assay_Total_Bites.csv - Chapter 5: Feeding assay: bites from fishes grown in different temperature treatments on different seaweeds</li><li>Hepatosomatic_Index.csv - Chapter 5: Hepatosomatic index of juvenile S. doliatus grown in different temperature treatments</li><li>MARFU Temperature Data.csv - Chapter 5: Tank temperature data for experimental duration</li><li>MO2_metadata_bottom_10.csv - Chapter 5: MO2 Rest data for fishes grown in different temperature treatments</li><li>RGR_LENGTH_ALL_R.csv - Chapter 5: Relative growth rate data for fish grown in different temperature treatments, by total length (cm)</li><li>RGR_WEIGHT_ALL_R.csv - Chapter 5: Relative growth rate data for fishes grown in different temperature treatments by wet weight (g)</li></ul><p> </p>
Populacijska varijabilnost običnoga graba (Carpinus betulus L.) u sjeveroistočnom dijelu Turske prema morfološkim obilježjima ovoja
No full textThe objective of this study was to investigate involucre morphological variability of common hornbeam (Carpinus betulus L., Betulaceae) populations in Turkey. In total, 12 natural populations of common hornbeam located in four different watersheds of the Eastern Black Sea Region were sampled from three different altitude zones up to 1200 m a.s.l. Involucres have been examined biometrically by analyzing 13 morphological characteristics. High phenotypic variability was determined both among and within the studied populations. Furthermore, grouping of populations according to the eco-geographic principle was revealed. Variation in most of involucre characteristics from the Camlıhemşin, Çaykara and Trabzon-Maçka watersheds appeared to be related mostly to altitude. The trees in the higher elevations were characterized with the smaller involucres than those in the lower elevations. However, this trend has not been observed in the populations from the Giresun-Espiye watershed. Moreover, trees from that region at lower altitude had the smallest involucres. Overall, our results confirm the Eastern Black see region as one of the hot spots of biodiversity and that the involucre morphological variability is the result of the complex evolutionary process related to the adaptation and plasticity.Cilj ovoga istraživanja bio je istražiti varijabilnost populacija običnoga graba (Carpinus betulus L., Betulaceae) u Turskoj prema morfološkim obilježjima ovoja. Ukupno je uzorkovano 12 prirodnih populacija običnoga graba, smještenih u četiri različita sliva istočnog Crnog mora iz tri različite visinske zone do 1200 m n.v. Ovoji su ispitani biometrijski, analizom 13 morfoloških karakteristika. Provedenim istraživanjem utvrđena je velika varijabilnost morfoloških obilježja, a za sve proučavane karakteristike potvrđene su razlike na međupopulacijskoj i unutarpopulacijskoj razini. Nadalje, otkriveno je grupiranje populacija prema eko-geografskom načelu. Varijabilnost ovoja iz slivova Camlıhemşin, Çaykara i Trabzon-Maçka bila je povezana s promjenom nadmorske visine. Stabla na višim nadmorskim visinama karakterizirali su sitniji ovoji u odnosu na stabla na nižim nadmorskim visinama. Međutim, ovaj trend nije uočen na području regije Giresun-Espiye. Štoviše, stabla na tom području na nižim nadmorskim visinama imala su manje ovoje u odnosu na stabla s viših nadmorskih visina. Sveukupno, naši rezultati potvrđuju da je regija istočnog Crnog mora jedno od žarišta biološke raznolikosti te da je morfološka varijabilnost ovoja rezultat složenog evolucijskog procesa povezanog s prilagodbom i plastičnošću
Short study about determining the limit loads for center cracked square plates in biaxial tension
No full textW artykule przedstawiona została tematyka wyznaczania obciążeń granicznych dla kwadratowych płyt zawierających
centralne pęknięcie, które poddane zostały dwuosiowemu rozciąganiu. W pracy przedstawiono krótką charakterystykę
tematu obciążeń granicznych, aspekty modelowania numerycznego oraz wybrane wyniki obliczeń numerycznych.
Dyskutowano wpływ długości pęknięcia, granic plastyczności oraz współczynnika dwuosiowości obciążenia,
zdefiniowanego na potrzeby pracy. Podano również wybrane formuły aproksymacyjne.In the paper the short study about determining of the limit loads for center cracked square plate in biaxial tension was presented. Author presents the limit load topic, aspects of the numerical analysis and selected results of numerical calculations. The influence of the crack length, yield strength and a ratio of the biaxial external load were discussed. In the paper the approximation formulas were presented for selected results
The Characterization of the Stress Fields Near a Crack Tip for a Compact Specimen for Elastic-Plastic Materials Dominated by the Plane Strain State
No full textThe paper presents a comprehensive analysis of the stress field near a crack tip for a compact specimen dominated by the plane strain state using the finite element method. The analysis also includes the calculation of some parameters of in-plane constraints, both for small and large strain assumptions. It discusses the influence of the material characteristic, relative crack length and external load for the stress field, and the in-plane constraint parameter. The approximation formulas for some in-plane constraint parameters are presented
Experimental and Numerical Analysis of Fracture in 41Cr4 Steel – Issues of the Stationary Cracks
No full textThis paper analyzes the process of fracture in 41Cr4 steel on the basis of experimental and numerical data obtained for non-propagating cracks. The author’s previous and latest experimental results were used to determine the apparent crack initiation moment and fracture toughness for the material under plane strain conditions. Numerical simulations were carried out to assess changes in the J-integral, the crack tip opening displacement, the size of the plastic region and the distribution of stresses around the crack tip. A complex numerical analysis based on the true stress-strain curve was performed to determine the behavior of 41Cr4 steel under increasing external loads
On The Parameters of Geometric Constraints for Cracked Plates under Tension – Three-Dimensional Problems
No full textThis paper provides a comparative analysis of selected parameters of the geometric constraints for cracked plates subjected to tension. The results of three-dimensional numerical calculations were used to assess the distribution of these parameters around the crack front and their changes along the crack front. The study also involved considering the influence of the external load on the averaged values of the parameters of the geometric constraints as well as the relationship between the material constants and the level of the geometric constraints contributing to the actual fracture toughness for certain geometries
Proposal of the hybrid solution to determining the selected fracture parameters for SEN(B) specimens dominated by plane strain
No full textAbstractIn the paper, new hybrid (numerical-analytical) methods to calculate the J-integral, the CTOD, and the load line displacement are presented. The proposed solutions are based on FEM calculations which were done for SEN(B) specimens dominated by plane strain condition. The paper includes the verification of the existing limit load solution for SEN(B) specimen with proposal of the new analytical formulae, which were used for building hybrid equations for determining three selected fracture mechanics parameters.</jats:p
Numerical Analysis of the Influence of In-Plane Constraints on the Crack Tip Opening Displacement for SEN(B) Specimens Under Predominantly Plane Strain Conditions
No full textThis paper presents a numerical analysis of the relationship between in-plane constraints and the crack tip opening displacement (CTOD) for single-edge notched bend (SEN(B)) specimens under predominantly plane strain conditions. It provides details of the numerical model and discusses the influence of external load and in-plane constraints on the CTOD. The work also reviews methods for determining the CTOD. The new formula proposed in this paper can be used to estimate the value of the coefficient dn as a function of the relative crack length, the strain hardening exponent and the yield strength - dn ( n , σ0 /E, a/W ), with these parameters affecting the level of in-plane constraints. Some of the numerical results were approximated using simple mathematical formulae
Limit Load Solutions for SEN(T) Specimens – 2D and 3D Problems
No full textThis paper deals with the limit load solutions for SEN(T) specimens under plane stress and plane strain conditions. The existing solutions are verified using the Finite Element Method and extended to 3D cases. The numerical results can be used to assess the strength of a structural element with a defect. This paper is a verification and extension of the author’s previous paper [2]
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