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Strain rate and temperature are influential factors that significantly impact the mechanical properties of long glass fiber-reinforced polypropylene composites. This study aims to investigate the tensile properties of these composites, analyzing the effects of temperature, strain rate, and their interplay on variables such as tensile stress, tensile strength, fracture stress, and fracture morphology through a series of comprehensive tensile experiments. The experimental results demonstrate a notable increase in both tensile strength and tensile fracture stress when the temperature is set at 25 °C, accompanied by strain rates of 10-4, 10-3, 10-2, and 10-1 s-1. Conversely, a significant decrease is observed in the aforementioned properties when the strain rate is fixed at 10-4, while varying temperatures of -25 °C, 0 °C, 25 °C, 50 °C, and 75 °C are applied. At lower temperatures, cracks manifest on the fracture surface, while matrix softening occurs at higher temperatures. Additionally, in the context of strain rate-temperature coupling, the decreasing trend of both tensile strength and tensile fracture stress decelerates as the temperature ranges from -25 °C to 75 °C at a strain rate of 10-1, compared to 10-4 s-1. These findings highlight the significant influence of both strain rate and temperature on high fiber content long glass fiber-reinforced polypropylene composites.

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Cleavage fracture of the V and Ti-V microalloyed forging steels was investigated by the four-point bending testing of the notched specimens of Griffith-Owen's type at -196 °C, in conjunction with the finite element analysis and the fractographic examination by scanning electron microscopy. To assess the mixed microstructure consisting mostly of the acicular ferrite, alongside proeutectoid ferrite grains and pearlite, the samples were held at 1250 °C for 30 min and subsequently cooled instill air. Cleavage fracture was initiated in the matrix under the high plastic strains near the notch root of the four-point bending specimens without the participation of the second phase particles in the process. Estimated values of the effective surface energy for the V and the Ti-V microalloyed steel of 37 Jm-2 and 74 Jm-2, respectively, and the related increase of local critical fracture stress were attributed to the increased content of the acicular ferrite. It was concluded that the observed increase of the local stress for cleavage crack propagation through the matrix was due to the increased number of the high angle boundaries, but also that the acicular ferrite affects the cleavage fracture mechanism by its characteristic stress-strain response with relatively low yield strength and considerable ductility at -196 °C.

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Ductile-to-brittle transition (DBT) temperature and brittle fracture stress, σF, are important toughness criteria for structural materials. In this paper, low-carbon steels with an ultrafine elongated grain (UFEG) structure (transverse grain size 1.2 µm) and with two ferrite (α)-pearlite structure with grain sizes 10 µm and 18 µm were prepared. The UFEG steel was fabricated using multipass warm biaxial rolling. The tensile tests with a cylindrical specimen and three-point bending tests with a single-edge-notched specimen were performed at -196 °C. The local stress near the notch was quantitatively calculated via finite element analysis (FEA). The σF for each sample was quantified based on the experimental results and FEA. The relationship between σF and dα in the wide range of 1.0 µm to 138 µm was plotted, including data from past literature. Finally, the conditions of grain size and temperature that cause DBT fracture in low-carbon steel were shown via the stress-d-1/2 map. The results quantitatively showed the superiority of α grain size for brittle fracture.

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Self-healing materials have been recognized as a promising type of next-generation materials. Among them, self-healing ceramics play a particularly important role, and understanding them better is necessary. Therefore, in this study, we applied the oxidation kinetics-based constitutive model to finite element analysis of a series of damage-healing processes in self-healing ceramics (alumina/SiC composites). In the finite element analysis, the data on the microstructure distribution, such as relative density, size and aspect ratio of pores, and grain size, were taken as input values and reflected onto the parameters of a continuum damage model using a fracture mechanical model. We then performed a 3-point bending analysis, to consider both the self-healing effect under certain temperature and oxygen partial pressure conditions and scatter of the strength of the ceramics. Our results confirmed that the proposed methodology can reasonably reproduce both strength recovery and damage propagation behavior in self-healing ceramics.

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We report the structural and mechanical behavior of multicomponent hydrogels comprising the commercial poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymer F127 and alginate. Previous studies on this system have shown thermoreversible behavior in shear rheology. Here we explore the properties of these materials under compression and large deformations, relevant to applications such as wound dressings that require mechanical robustness. For gels with lower F127 concentration, we find that the stiffness of the gels can be ascribed to the alginate network, and that the Young's modulus and fracture stress do not strongly depend on temperatures. However, for gels with an F127 concentration of 30 wt %, the Young's modulus is enhanced at higher temperatures. Under large deformations, the fracture stress and fracture strain of the materials can be independently varied using the alginate and F127 concentrations, respectively; without the trade-off in these properties that is often observed in rigid polymer networks. Small-angle X-ray scattering shows a power-law dependence scattering intensity on q arising from the alginate network and scattering peaks consistent with rearranging micelles. For gels with lower F127 concentrations, we find a disordered-body-centered cubic (BCC)-face-centered cubic (FCC) progression of states with temperature, and a BCC/FCC mixture for gels with higher F127 concentrations.

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The effect of addition of high amylose corn starch (Hylon VII or H) to wheat flour (WF) on the mechanical properties of the resulting binary composite gels (BCG) under small and large deformations was evaluated. To this end, the composite gels at different ratios of WF/H including 95:5, 90:10, and 85:15 were tested under a linear viscoelastic regime (LVE) in oscillatory angular frequency and a texture profile analysis in compression mode. However, the gel firmness was increased by Hylon VII addition, but the springiness was reduced. Since the adhesiveness and cohesiveness were not significantly different, no dilution effect was observed for the samples. Furthermore, the dominance of G' than G″ over the range of LVE and high fracture stress at high level of Hylon VII confirmed the high gel strength which can be attributed to the retrogradation of amylose and reduction of amylopectin from WF. The less frequency dependency of BCG revealed the solid-like response and strong gels structures with more elastic network. High value of α revealed a lower number of interactions within the gel network structures. Consequently, due to the high gel strength of BCG of WF/H, it can be exploited at high thermal operations such as retort processing as well as it can be utilized for dysphagia therapy due to the special textural parameters. PRACTICAL APPLICATIONS: Small and large deformation properties can provide profound insights toward the gel structure. The former gets knowledge about dynamic rheology and the latter gives the textural properties of the gel matrices. Since, achieving the desired texture of foods has a chief impact on the target consumers, and chewing and swallowing disorders such as dysphagia are common problems in older people, more effort is needed to modify the texture of food with a soft structure. On the contrary, supplying a more gel strength network, which can withstand at high thermal processing and not collapse, is so vital. Therefore, the current work was accomplished to provide some knowledge about the binary composite gel of WF and Hylon VII starch such as the gel strength, fracture stress, fracture strain and material stiffness which enables us to evaluate the nature of starch gels for further applications such as drug delivery systems, elderly diet and further processes.

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We report an 82-year-old woman who underwent fixation with a long-spanning cable-plate for a bisphosphonate-induced Vancouver B1 periprosthetic femoral fracture. Non-union and breakage of the plate occurred at 16 months and necessitated revision surgery using a long-stem femoral prosthesis augmented with a cable-plate construct. Bone union was achieved eventually after 10 months.

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This paper describes characteristics of transgranular cleavage fracture in structural steel, viewed at different size-scales. Initially, consideration is given to structures and the service duty to which they are exposed at the macroscale, highlighting failure by plastic collapse and failure by brittle fracture. This is followed by sections describing the use of fracture mechanics and materials testing in carrying-out assessments of structural integrity. Attention then focuses on the microscale, explaining how values of the local fracture stress in notched bars or of fracture toughness in pre-cracked test-pieces are related to features of the microstructure: carbide thicknesses in wrought material; the sizes of oxide/silicate inclusions in weld metals. Effects of a microstructure that is 'heterogeneous' at the mesoscale are treated briefly, with respect to the extraction of test-pieces from thick sections and to extrapolations of data to low failure probabilities. The values of local fracture stress may be used to infer a local 'work-of-fracture' that is found experimentally to be a few times greater than that of two free surfaces. Reasons for this are discussed in the conclusion section on nano-scale events. It is suggested that, ahead of a sharp crack, it is necessary to increase the compliance by a cooperative movement of atoms (involving extra work) to allow the crack-tip bond to displace sufficiently for the energy of attraction between the atoms to reduce to zero.

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The industrially-important WC-Co composite materials provide a useful, albeit complicated materials system for understanding the combined influences on hardness and strength properties of the constituent WC particle strengths, the particle sizes, their contiguities, and of Co binder hardness and mean free paths, and in total, the volume fraction of constituents. A connection is made here between the composite material properties, especially including the material fracture toughness, and the several materials-type considerations of: (1) related hardness stress-strain behaviors; (2) dislocation (viscoplastic) thermal activation characterizations; (3) Hall-Petch type reciprocal square root of particle or grain size dependencies; and (4) indentation and conventional fracture mechanics results. Related behaviors of MgO and Al2O3 crystal and polycrystal materials are also described for the purpose of making comparisons.

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The aim of this study was to investigate the fracture strength of endodontically treated teeth restored with different posts and variable ferrule heights. Sixty freshly extracted human canines were treated endodontically and randomly assigned to 6 groups (n=10), being restored with custom-made cast post-and-core (CP0 and CP3 groups), prefabricated post and composite resin core (PF0 and PF3 groups), and composite resin (CR0 and CR3 groups). The CP0, PF0 and CR0 groups presented no ferrule and the CP3, PF3 and CR3 presented 3 mm of coronal structure. All teeth were restored with full metal crowns. The fracture strength was measured in a universal testing machine at 45o to the long axis of the tooth until failure. Data were analyzed statistically by 2-way ANOVA and Tukey's test (?=0.05). When the mean fracture strength values were compared (CP0 group - 820.20 N, CP3 group - 1179.12 N; PF0 group - 561.05 N; PF3 group - 906.79 N; CR0 group - 297.84 N; and CR3 group - 1135.15 N) there was statistically significant among the groups (p<0.05), except for the three groups with 3 mm of coronal remaining, which were similar to each other. The results of this study showed that the ferrule in crowns promoted significantly higher fracture strength in the endodontically treated teeth.

O objetivo neste estudo foi avaliar a resistência à fratura de dentes tratados endodonticamente restaurados com diferentes pinos e diferentes alturas de remanescente dentinário da coroa. Sessenta caninos recém-extraídos foram tratados endodonticamente, separados em 6 grupos (n=10) e restaurados com núcleo metálico fundido (CP0 e CP3), pino pré-fabricado e núcleo em resina composta (PF0 e PF3) ou resina composta (CR0 e CR3). Os grupos CP0, PF0 e CR0 não possuíam férula e os grupos CP3, PF3 e CR3 apresentaram 3 mm de remanescente coronário. Todos os dentes foram restaurados com coroas totais metálicas. A resistência à fratura foi medida em máquina universal de ensaios com o longo eixo do dente posicionado a 45 graus em relação ao carregamento axial, até que ocorresse fratura. A análise de variância 2 critérios (?=0,05) mostrou diferença estatisticamente significativa entre os grupos. Quando as médias das forças para fratura foram comparadas (CP0 = 820,0 N; CP3= 1179,12 N; PF0 = 561,05 N; PF3 = 906,79 N; CR0 = 297,84 N; e CR3 = 1135,15 N) não foram observadas diferenças significativas entre os 3 grupos com 3 mm de remanescente coronal. Os resultados mostraram que a presença de férula em coroas aumenta significantemente a resistência à fratura de dentes tratados endodonticamente.

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The tensile properties of segmented block copolymers with mono-disperse hard segments were studied with respect to the hard segment content (16-44 wt.%) and the temperature (20-110 °C). The copolymers were comprised of poly(tetramethylene oxide) segments with the molecular weights of 650-2,900 Da and of mono-disperse bisester-tetra-amide segments (T6A6T) based on adipic acid (A), terephthalic acid (T) and hexamethylene diamine (6). An increasing content of T6A6T gave rise to an increased modulus, yield stress and fracture stress. The modulus could be modeled by a composite model. Moreover, a strain-softening was observed well below the yield stress, due to the shearing of the T6A6T crystallites. At strains >200%, a strain-hardening of the PTMO segments took place and this even for PTMO segments that were amorphous in the isotropic state. The strain hardening increased the tensile properties. An increase in temperature had little effect on the modulus of the copolymers, but was found to lower the yield and fracture stresses. At temperatures above the melting temperature of the oriented PTMO, no strain-hardening took place. The yield stress as a function of temperature could be described by the Eyring relationship, but a modulus-yield stress relationship could not be established.

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Objective To measure stress distribution of the main bone architecture of the normal adult cadaveric foot and discuss the effect of plantar ligament injury on stress distribution. Methods Seven fresh adult cadaveric feet were used and 10 strain gauges attached to the bones of the longitudinal foot arch,including the calcaneus,navicular,medial cuneiform,1-5 metatarsal trunk,the distal part of the tibia and fibular,respectively.After the loading Was added to 700 N by almighty test machine,resistance strainmeter was used to measure surface strain of these bones.The results were processed statistically. Results The strain was varied based on different bone segments attached and increased with loading.Tensile force was always found at the medial part of the navicular,the distal part of the tibia and fibular,while the others showed compression all the time.Peak strain was found at calcaneus.followed by the second and third metatarsal.Strain on the surface of the bone segments changed greatly with different ligament injury(P＜0.05).Conclusion The bone surface stress of the longitudinal foot arch changes significantly when the plantar ligament is injured.

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To investigate the clinical diagnosis and treatment of stress fracture of the pubic ramus caused by military training, clinical data of 66 cases (18 males and 48 females, ranging from 18～21 years, mean age 19 6 years ) with stress fracture of the pubic ramus were retrospectively analysed. 55 cases were military recruits undergoing basic training, 11 army veterans undergoing intensive goose step training. 66 cases complained of chronic groin pain which increased in activity and relieved while at rest. The symptom occurred 3～10 weeks after the training began. The pain often lasted 1 week ～14 months. 22 cases who sought medical advice in medical team were mistaken for muscular injury. There were 76 stress fractures of the pubic ramus in 66 soldiers. 56 had stress fractures of one inferior pubic ramus, 6 both inferior pubic rami, and four had ipsilateral inferior and superior pubic rami fractures. Stress fracture of the pubic ramus is not rare, but it's quite easy to be neglected or misdiagnosed. The key to its diagnosis is getting a deeper understanding and making an adequate and early imaging examination in light of the clinical data.

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Objective To study the X-ray findings and evaluate the value of X-ray in diagnosis of stress fracture of the pubic ramus. Methods The X-ray findings of 66 cases (18 males and 48 females, ranging in age from 18-21 years, mean age 19.6 years) with stress fracture of the pubic ramus were retrospectively analyzed. Fifty-five cases were military recruits undergoing basic training, and 11 army veterans were undergoing intensive goose step training. Results Sixty-two cases had stress fractures of the inferior pubic ramus including right-sided in 26, left-sided in 30, and bilateral in 6. Four had ipsilateral inferior and superior pubic rami fractures. With 2 weeks after onset, the radiographs were normal in 3 cases. The 66 cases had either a slight transverse fissure (34 cases) or a small dense callus (65 cases) or both during the examination period of 4 weeks to 8 months. Then the calcium resorbed at the margins of the fracture and at the same time the callus increased and surrounded the bone. Finally, the resorptive zone disappeared and the callus became homogeneous. This callus formation persisted for several months and disappeared gradually. Conclusion X-ray examination is the first imaging method of choice for detecting stress fracture of the pubic ramus. With combining clinical data, correct diagnosis can be made in the majority.

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PURPOSE: To evaluate the MR imaging findings of fatigue fractures of the lower extremity in young soldiers. MATERIALS AND METHODS: In 22 cases of fatigue fractures of the lower extremity in young soldiers proven byclinical findings and radiological follow up, the MRI findings were retrospectively evalvated. All patients weremale and aged between 19 and 21 years. As seen on MRI, the bone marrow edema, intramedullary low signal intensityband, cortical fracture line, periosteal reaction, surrounding soft tissue edema, and enhancement pattern wereanalyzed and the site of involvement was determined in the axial plane. RESULTS: The locations of fatiguefractures of the lower extremity were the tibia (n=12), fibula (n=8), femur (n=1) and second metatarsus (n=1). Alloccurred in diaphyses: the junction of the proximal and middle (n=10), middle (n=9), proximal (n=2), and distalshaft (n=1). The sites of involvement were the posteromedial (n=6) and medial side (n=6) of the tibia, and theentire portion of the fibula(n=5) in the axial plane. MRI findings were bone marrow edema in 20 cases,intramedullary low signal intensity band in 14 (which were continuous with the cortex or cortical fracture line),cortical fracture line in 13, and periosteal reaction and surrounding soft tissue edema in all. Ongadolinium-enhanced images, enhancement was seen in the bone marrow in 19 cases, in the subperiosteal region in18, and in the surrounding soft tissue in 22. CONCLUSION: In fatigue fractures of the lower extremity in youngsoldiers, the main locations were the tibia and fibula, and characteristic MR imaging findings were intramedullarylow signal intensity bands, which were continuous with the cortex or cortical fracture line and often accompaniedby bone marrow edema, periosteal reaction, and surrounding soft tissue edema.

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PURPOSE: To determine correlation between stress fracture of the posterior tibia and flexor digitorum longusmuscle injury caused by athletic or sporting activity during adolescence. MATERIALS AND METHODS: Eleven casesdiagnosed as stress fracture after X-ray and MR imaging of the lower leg were reviewed. With regard to eachfracture, the following features were noted: age, sex, and athletic or sporting activity of the patient, and site.Using MR imaging techniques, axial and sagittal T1 and T2 weighted images were obtained in all cases and T1-GdDTPA images in seven. RESULTS: The activities undertaken were running (n=3), football (n=2), ballet (n=2),taekwando (n=1), badminton (n=1), field hockey (n=1), and basketball (n=1). MR images revealed localized corticalthickness (n=11), linear intramedullary callus showing a low signal on T1 and T2 weighted images (n=9), marrowhyperemia (n=7), and flexor digitorum longus muscle injury showing a high signal on T1-Gd DTPA and T2 weightedimage (n=7). CONCLUSION: Stress fracture of the posterior tibia might be induced by flexor digitorum longusmuscle activity induced by athletic or sporting activities during adoleseence.

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