Brazilian disc tests were undertaken on a number of red sandstone samples with different water absorption ratios.The tensile strength of the red sandstone decreases as the water absorption ratio increases.The fracture...Brazilian disc tests were undertaken on a number of red sandstone samples with different water absorption ratios.The tensile strength of the red sandstone decreases as the water absorption ratio increases.The fracture surfaces of failed red sandstone discs were scanned by Talysurf CLI 2000.With the aid of Talymap Gold software,based on ISO25178,a set of statistical parameters was obtained for the fracture surfaces.The maximum peak height(S_p),maximum pit height(S_v) and maximum height(S_z) of the fracture surfaces exhibited the same decreasing trend with increasing water absorption.Sa and Sku values for the fracture surfaces showed a downward trend as the water absorption ratio increased.The fractal dimensions of fracture surfaces were calculated and found to decrease as the water absorption ratio increased.Through analysis of PSD curves,the smallest dominant wavelength was observed to reflect the roughness of the fracture surfaces.Additionally,the results suggest that the roughness of fracture surfaces becomes small as the water absorption ratio increases.展开更多
Geological exploration cores obtained from shale gas wells several kilometers deep often show different height-diameter ratios(H/D)because of complex geological conditions(core disking or developed fractures),which ma...Geological exploration cores obtained from shale gas wells several kilometers deep often show different height-diameter ratios(H/D)because of complex geological conditions(core disking or developed fractures),which makes further standard specimen preparation for mechanical evaluation of reservoirs difficult.In multi-cluster hydraulic fracturing,shale reservoirs between planes of hydraulic fractures with different lengths could be simplified to have different H/D ratios.Discovering the effect of H/D on the mechanical characteristics of shale specimens with different bedding orientations will support mechanical evaluation tests of reservoirs based on disked geological cores and help to optimize multicluster fracturing programs.In this study,we performed uniaxial compression tests and acoustic emission(AE)monitoring on cylindrical Longmaxi shale specimens under five bedding orientations and four H/D ratios.The experimental results showed that both the H/D-dependent mechanical properties and AE parameters demonstrated significant anisotropy.Increasing H/D did not change the uniaxial compressive strength(UCS)evolution versus bedding orientation,demonstrating a V-shaped relationship,but enhanced the curve shape.The stress level of crack damage for the specimens significantly increased with increasing H/D,excluding the specimens with a bedding orientation of 0°.With increasing H/D,the cumulative AE counts of the specimens with each bedding orientation tended to exhibit a stepped jump against the loading time.The proportion of low-average-frequency AE signals(below 100 kHz)in specimens with bedding orientations of 45°and 60°increased to over 70%by increasing H/D,but it only increased to 40%in specimens with bedding orientations of 0°,30°,and 90°.Finally,an empirical model that can reveal the effect of H/D on anisotropic UCS of shale reservoir was proposed,the anisotropic proportion of tensile and shear failure cracks in specimens under four H/D ratios was classified based on the AE data,and the effect of H/D on the anisotropic crack growth of specimens was discussed.展开更多
In this paper the Auerbach＇s scaling law of Hertzian fracture induced by a spherical indenter pressing on a brittle solid is studied. In the analysis, the singular integral equation method is used to analyze the frac...In this paper the Auerbach＇s scaling law of Hertzian fracture induced by a spherical indenter pressing on a brittle solid is studied. In the analysis, the singular integral equation method is used to analyze the fracture behavior of the Hertzian contact problem. The results show that the Auerbach＇s constant sensitively depends on the Poisson＇s ratio, and the effective Auerbach＇s domain is also determined for a given value of the Poisson＇s ratio.展开更多
In part I and II of this series, experimental investigation in both EPFM and LEFM had been discussed. In this part, further theoretical analysis is given. The theoretical development of Two Parameter Fracture Mechanic...In part I and II of this series, experimental investigation in both EPFM and LEFM had been discussed. In this part, further theoretical analysis is given. The theoretical development of Two Parameter Fracture Mechanics by Hancock etc, has rationalized our experimental results. This method can be applied to engineering practice, and will allow the advantage of enhanced toughness for specimens with low levels of constraint to be taken into account for defect assessment.展开更多
Many experimental investigations have previously been performed and recentlydone on different shipbuilding structural steels where the specimens size and crack depth/specimenwidth (a/W) were varied. A series of intere...Many experimental investigations have previously been performed and recentlydone on different shipbuilding structural steels where the specimens size and crack depth/specimenwidth (a/W) were varied. A series of interesting results have been gained. It is worthwhile to havea review on the effect of a/W ratio on fracture toughness, and further theoretical analysis isnecessary. In this paper, experimental work in elastic-plastic fracture mechanics (EPFM) wasdiscussed. Tests had been carried out on 10 kinds of strength steels. Results showed that J_i andδ_i. values increased with decreasing a/W when a/W【0.3 for three-point bend specimens and thatshallow crack specimens which have less constrained flow field give markedly higher values oftoughness than deeply notched specimens. However, for a/W】0.3, the toughness was found to beindependent of a/W. Slip line field analysis shows that for shallow cracks, the hydrostatic stressis lower than that from standard deeply cracked bend specimen which develops a high level of cracktip constraint, provides a lower bound estimate of toughness, and will ensure an unduly conservativeapproach when applied to structure defects especially if initiation values of COD / J-integral areused.展开更多
In part I of this series, experimental investigation in EPFM （elastic-plastic fracture mechanics） had been discussed. In this paper, experimental investigation in LEFM （ linear elastic fracture mechanics） is given...In part I of this series, experimental investigation in EPFM （elastic-plastic fracture mechanics） had been discussed. In this paper, experimental investigation in LEFM （ linear elastic fracture mechanics） is given. Fracture toughness tests had been carried out on three different strength steels, using both through-cracked specimens with different α/W ratio and semi-elliptical cracked specimens with variable crack size and shape. Results show that the fracture toughness KIC increases with decreasing α/W when α/W 〈 0.3 for three-point-bend specimens, and that for α/W 〉 0.3, it is independent of α/W. Shallow crack specimens, both through-cracked and surface-cracked, gave markedly higher values than deeply notched specimens. However, the effect of crack shape on fracture toughness is negligible. Results also show that the LEFM approach to fracture is not tenable for design stresses where αc is often very small, far less than 2.5 （ KIC/σy）^2.展开更多
Objective:To explore the relationship between peripheral blood neutrophil/lymphocyte ratio(NLR)and osteoporotic femoral neck fractures and to evaluate the prognosis.Methods:The subjects were 102 patients who received ...Objective:To explore the relationship between peripheral blood neutrophil/lymphocyte ratio(NLR)and osteoporotic femoral neck fractures and to evaluate the prognosis.Methods:The subjects were 102 patients who received osteoporotic femoral neck fracture in the First Affiliated Hospital of Guangzhou University of Chinese Medicine from 2008 to 2017.Patients were divided into three groups according to the BMD values in the diagnostic criteria of primary osteoporosis:normal bone mass group(T≥-1.0),reduced bone mass group(-2.5<T<-1.0)and osteoporosis group(T≤-2.5).In addition,during postoperative follow-up,patients receiving internal fixation were divided into the high NLR group(NLR>2.33)and the low NLR group(NLR≤2.33)according to their NLR values.The clinical data of patients with osteoporotic femoral neck fracture who underwent peripheral blood routine examination were prospectively analyzed.The statistical indicators included age,gender,fracture cause and other general conditions,fracture type,peripheral blood neutrophil/lymphocyte ratio,bone mineral density(BMD)level and blood lipid level,and prognosis of 102 patients who were followed up for more than 2 years after surgery.The relationship between peripheral blood NLR and the above indexes was observed.Statistical methods including normal data analysis of variance between groups,SNK-q test is compared between two groups,the partial correlation analysis between the two factors,the relationship between multiple factors using multi-factor linear regression analysis,and normal data comparison between the two groups using t test,two sets of independent data frequency distribution of binary classification variables compared by chi-square test.Moreover,NLR is also a major factor affecting the prognosis and rehabilitation of osteoporotic femoral neck fractures.Results:The analysis of variance between the two groups(SNK-q test of the comparison between the two groups),single-factor partial correlation analysis,multi-factor linear regression analysis showed that compared with the normal group and the reduced group,the levels of age,triglyceride and NLR in the osteoporosis group were increased,while BMD was significantly decreased.BMD in patients with osteoporotic femoral neck fracture was negatively correlated with NLR and triglyceride(P<0.05).In multi-factor linear regression analysis,NLR and triglyceride were the main influencing factors of BMD in patients with osteoporotic femoral neck(P<0.05).In addition,increased peripheral blood NLR in patients treated with internal fixation may increase the risk of postoperative femoral head necrosis,nonunion of the broken end of the fracture,and prolong the time of postoperative functional recovery.Conclusion:The level of peripheral blood NLR in patients with osteoporotic femoral neck fracture is increased and correlated with bone mineral density,which suggested that peripheral blood NLR can be used as one of the clinical indicators for early screening and prevention of osteoporotic femoral neck fracture.In addition,peripheral blood NLR is also a major factor affecting the prognosis and rehabilitation of osteoporotic femoral neck fractures.展开更多
The relationship between fracture toughness VGC and critical void growth RC/RO was studied for ten kinds of Steel. The macroscopic fracture toughness VGC was determined by using notched tensile specimens. and the micr...The relationship between fracture toughness VGC and critical void growth RC/RO was studied for ten kinds of Steel. The macroscopic fracture toughness VGC was determined by using notched tensile specimens. and the microscopic parameters of critical void growth ratio RC/RO were quantitatively measured under SEM. Then, the coefhcient C in the relation VGC = C In(RC/RO) proposed in author's past work was specifically explored. The correlation of C with tensile proderty parameter φ=σyδ/(Eφn) was presented for the Steel investigated, and the effects of low temperature on C were also discussed. Results show that the coefficient C is linearly related to the parameter and insensitive to low temperature.展开更多
The distribution and intensity of tectonic fractures within geologic units are important to hydrocarbon exploration and development. Taken the Upper Triassic Yanchang Formation interbedded sandstone-mudstone in the Or...The distribution and intensity of tectonic fractures within geologic units are important to hydrocarbon exploration and development. Taken the Upper Triassic Yanchang Formation interbedded sandstone-mudstone in the Ordos Basin as an example, this study used the finite element method（FEM） based on geomechanical models to study the development of tectonic fractures. The results show that the sandstones tend to generate tectonic fractures more easily than mudstones with the same layer thickness, and the highest degree of tectonic fractures will be developed when the sandstone-mudstone thickness ratio is about 5.0. A possible explanation is proposed for the tectonic fracture development based on two important factors of rock brittleness and mechanical layer thickness. Generally, larger rock brittleness and thinner layer thickness will generate more tectonic fractures. In interbedded sandstone-mudstone formations, the rock brittleness increases with the increasing mechanical layer thickness, hence, these two factors will achieve a balance for the development of tectonic fractures when the sandstone-mudstone thickness ratio reaches a specific value, and the development degree of tectonic fractures is the highest at this value.展开更多
Fatigue fracture is one of the main failure modes of Ti-6A1-4V alloy,fracture toughness and crack closure have strong effects on the fatigue crack growth（FCG）rate of Ti-6A1-4V alloy.The FCG rate of Ti-6A1-4V is inve...Fatigue fracture is one of the main failure modes of Ti-6A1-4V alloy,fracture toughness and crack closure have strong effects on the fatigue crack growth（FCG）rate of Ti-6A1-4V alloy.The FCG rate of Ti-6A1-4V is investigated by using experimental and analytical methods.The effects of stress ratio,crack closure and fracture toughness on the FCG rate are studied and discussed.A modified prediction model of the FCG rate is proposed,and the relationship between the fracture toughness and the stress intensity factor（SIF）range is redefined by introducing a correcting coefficient.Notched plate fatigue tests（including the fracture toughness test and the FCG rate test）are conducted to investigate the influence of affecting factors on the FCG rate.Comparisons between the predicted results of the proposed model,the Paris model,the Walker model,the Sadananda model,and the experimental data show that the proposed model gives the best agreement with the test data particularly in the near-threshold region and the Paris region,and the corresponding calculated fatigue life is also accurate in the same regions.By considering the effects of fracture toughness and crack closure,the novel FCG rate prediction model not only improves the estimating accuracy,but also extends the adaptability of the FCG rate prediction model in engineering.展开更多
Micromechanics-based models provide powerful tools to predict initiation of ductile fracture in steels. A new criterion is presented herein to study the process of ductile fracture when the effects of both stress tria...Micromechanics-based models provide powerful tools to predict initiation of ductile fracture in steels. A new criterion is presented herein to study the process of ductile fracture when the effects of both stress triaxiality and shear stress on void growth and coalescence are considered. Finite-element analyses of two different kinds of steel, viz. ASTM A992 and AISI 1045, were carried out to monitor the history of stress and strain states and study the methodology for determining fracture initiation. Both the new model and void growth model (VGM) were calibrated for both kinds of steel and their accuracy for predicting fracture initiation evaluated. The results indicated that both models offer good accuracy for predicting fracture of A992 steel. However, use of the VGM leads to a significant deviation for 1045 steel, while the new model presents good performance for predicting fracture over a wide range of stress triaxiality while capturing the effect of shear stress on fracture initiation.展开更多
Although pre-Northridge earthquake steel moment resisting frame buildings have been shown to be susceptible to brittle connection failures,they still represent a large fraction of the existing steel buildings in the U...Although pre-Northridge earthquake steel moment resisting frame buildings have been shown to be susceptible to brittle connection failures,they still represent a large fraction of the existing steel buildings in the United States of America.In this study,the performance of the 3-and 9-story Los Angeles pre-Northridge SAC buildings are analyzed considering ductile and brittle beam-column connection failures,and their uncertainty.This paper contributes to understanding the influence of uncertainty associated with connections brittle fracture on building interstory deformation capacity and its impact on bias and variability of fragility functions and loss assessment.The results show that considering brittle connections leads to significantly l arger d rift demands a nd t o h igher r epair costs,particularly under intense ground shaking.New fragility curve parameters are derived that account for the effect of the uncertainty of the strength and deformation capacity of brittle connections.展开更多
Fifteen cases of fresh fractures have been studied, including 14 cases of tubu-lar bone fractures with age from 28 to 60 years and one case of vertebral fracture ofdorsolumbar region, 16 years of age. There were 13 ma...Fifteen cases of fresh fractures have been studied, including 14 cases of tubu-lar bone fractures with age from 28 to 60 years and one case of vertebral fracture ofdorsolumbar region, 16 years of age. There were 13 male and 2 female patients. Theyhad no endocrine disturbances or other bone diseases. The ratio ofhydroxyproline/creatinine (HP/Cr) in these cases increased gradually within 20-30 daysafter fracture and then reached the peak value which was about 3-4 times of normal, thepeak value maintained for a long time. If the trauma was mild or the patient was young,the peak began to decline on the 60th day after fracture. While in those severe cases withprolonged confinement to bed, the peak only began to come down about 110th dayafter fracture. The ratio of HP/Cr decreased rapidly from the peak at first, then pursueda slow course. Generally, the ratio of HP/Cr returned to normal on the 240th to 310thday. Bone union began at a time when peak value started to decline, and with completionof the remodelling process, the HP/Cr value returned to normal.展开更多
The interaction problem among fractures under the action of compressional stress is studied in this paper by using the finite element method and boundary element method respectively.The mechanical criteria which diffe...The interaction problem among fractures under the action of compressional stress is studied in this paper by using the finite element method and boundary element method respectively.The mechanical criteria which differentiate between the independent fractures and fracture systems and their computation methods are presented in this paper.The proportional conditions between length and spacing of fractures that exist interaction for several kinds of fracture groups of different geometric arrangement are given.The effect of interaction among fractures on the displacement field,stress field and strain energy distribution are computed.The relations between the fracture system of conjugate array and conjugate earthquakes are also discussed in this paper.展开更多
In this paper, investigation on the initial fracture behavior was carried out on roving glass woven fabric reinforced composites which were manufactured by hand lay-up method. Two kinds of roving glass woven fabrics o...In this paper, investigation on the initial fracture behavior was carried out on roving glass woven fabric reinforced composites which were manufactured by hand lay-up method. Two kinds of roving glass woven fabrics of different FAW (Fabric Area Weight) and crimp ratio, Type A of 570 g/m2 and Type B of 800 g/m2, were adopted as reinforcement in this study. Tensile test was conducted and tensile properties were discussed on specimens of 6 degrees 0°/5°/10°/80°/85°/90°. The initial fracture behavior was observed on 0 degree and 90 degree and the fracture mechanism was compared and discussed among 5°/10°/80°/85°. The results showed that Type B has higher tensile modulus and tensile strength than that of Type A. And different initial fracture behaviors between two kinds of materials was observed and analyzed, which indicated that the crimp ratio plays an important role of woven fabric reinforced composites in fracture mechanism.展开更多
Taking 91105 working face as the research object, the observation method of water flowing fracture<span style="font-family:Verdana;">d</span><span style="font-family:Verdana;"> zo...Taking 91105 working face as the research object, the observation method of water flowing fracture<span style="font-family:Verdana;">d</span><span style="font-family:Verdana;"> zone and the layout of mining holes were determined by analyzing the field geological structure</span><span style="font-family:Verdana;">. </span><span style="font-family:Verdana;">It was shown that the fractured zone height and the ratio given by the measured method were 52.33 and 12.46, respectively. By the numerical simulation method with the software of UDEC, the fractured zone height and the ratio were 42.5 and 10.12. By comparison of measured height data and UDEC numerical simulation, there were some differences between the measured height and the calculated results of UDEC numerical simulation method. The method of simulation can be used as the technical basis for the design of waterproof coal pillar in the future.</span>展开更多
The ultra-fine grained(UFG)pure titanium was prepared by equal channel angular pressing(ECAP)and rotary swaging(RS).The strain controlled low cycle fatigue(LCF)test was carried out at room temperature.The fatigue life...The ultra-fine grained(UFG)pure titanium was prepared by equal channel angular pressing(ECAP)and rotary swaging(RS).The strain controlled low cycle fatigue(LCF)test was carried out at room temperature.The fatigue life prediction model and mean stress relaxation model under asymmetrical stress load were discussed.The results show that the strain ratio has a significant effect on the low cycle fatigue performance of the UFG pure titanium,and the traditional Manson-coffin model can not accurately predict the fatigue life under asymmetric stress load.Therefore,the SWT mean stress correction model and three-parameter power curve model are proposed,and the test results are verified.The final research shows that the threeparameter power surface model has better representation.By studying the mean stress relaxation phenomenon under the condition of R≠-1,it is revealed that the stress ratio and the strain amplitude are the factors that significantly afiect the mean stress relaxation rate,and the mean stress relaxation model with the two variables is calculated to describe the mean stress relaxation phenomenon of the UFG pure titanium under different strain ratios.The fracture morphology of the samples was observed by SEM,and it was concluded that the final fracture zone of the fatigue fracture of the UFG pure titanium was a mixture of ductile fracture and quasi cleavage fracture.The toughness of the material increases with the increase of strain ratio at the same strain amplitude.展开更多
基金Project(E21527)supported by Open Research Fund Program of Hunan Provincial Key Laboratory of Shale Gas Resource Utilization,Hunan University of Science and Technology,ChinaProjects(51174088,51174228)supported by the National Natural Science Foundation of China+1 种基金Project(2013CB035401)supported by the National Basic Research Program of ChinaProject(2015zzts077)supported by the Fundamental Research Funds for the Central Universities,China
文摘Brazilian disc tests were undertaken on a number of red sandstone samples with different water absorption ratios.The tensile strength of the red sandstone decreases as the water absorption ratio increases.The fracture surfaces of failed red sandstone discs were scanned by Talysurf CLI 2000.With the aid of Talymap Gold software,based on ISO25178,a set of statistical parameters was obtained for the fracture surfaces.The maximum peak height(S_p),maximum pit height(S_v) and maximum height(S_z) of the fracture surfaces exhibited the same decreasing trend with increasing water absorption.Sa and Sku values for the fracture surfaces showed a downward trend as the water absorption ratio increased.The fractal dimensions of fracture surfaces were calculated and found to decrease as the water absorption ratio increased.Through analysis of PSD curves,the smallest dominant wavelength was observed to reflect the roughness of the fracture surfaces.Additionally,the results suggest that the roughness of fracture surfaces becomes small as the water absorption ratio increases.
基金funded by the National Natural Science Foundation of China(Grant Nos.51927808,52174098 and 52374151).
文摘Geological exploration cores obtained from shale gas wells several kilometers deep often show different height-diameter ratios(H/D)because of complex geological conditions(core disking or developed fractures),which makes further standard specimen preparation for mechanical evaluation of reservoirs difficult.In multi-cluster hydraulic fracturing,shale reservoirs between planes of hydraulic fractures with different lengths could be simplified to have different H/D ratios.Discovering the effect of H/D on the mechanical characteristics of shale specimens with different bedding orientations will support mechanical evaluation tests of reservoirs based on disked geological cores and help to optimize multicluster fracturing programs.In this study,we performed uniaxial compression tests and acoustic emission(AE)monitoring on cylindrical Longmaxi shale specimens under five bedding orientations and four H/D ratios.The experimental results showed that both the H/D-dependent mechanical properties and AE parameters demonstrated significant anisotropy.Increasing H/D did not change the uniaxial compressive strength(UCS)evolution versus bedding orientation,demonstrating a V-shaped relationship,but enhanced the curve shape.The stress level of crack damage for the specimens significantly increased with increasing H/D,excluding the specimens with a bedding orientation of 0°.With increasing H/D,the cumulative AE counts of the specimens with each bedding orientation tended to exhibit a stepped jump against the loading time.The proportion of low-average-frequency AE signals(below 100 kHz)in specimens with bedding orientations of 45°and 60°increased to over 70%by increasing H/D,but it only increased to 40%in specimens with bedding orientations of 0°,30°,and 90°.Finally,an empirical model that can reveal the effect of H/D on anisotropic UCS of shale reservoir was proposed,the anisotropic proportion of tensile and shear failure cracks in specimens under four H/D ratios was classified based on the AE data,and the effect of H/D on the anisotropic crack growth of specimens was discussed.
基金supported by the National Natural Science Foundation of China(No.10772058)
文摘In this paper the Auerbach＇s scaling law of Hertzian fracture induced by a spherical indenter pressing on a brittle solid is studied. In the analysis, the singular integral equation method is used to analyze the fracture behavior of the Hertzian contact problem. The results show that the Auerbach＇s constant sensitively depends on the Poisson＇s ratio, and the effective Auerbach＇s domain is also determined for a given value of the Poisson＇s ratio.
文摘In part I and II of this series, experimental investigation in both EPFM and LEFM had been discussed. In this part, further theoretical analysis is given. The theoretical development of Two Parameter Fracture Mechanics by Hancock etc, has rationalized our experimental results. This method can be applied to engineering practice, and will allow the advantage of enhanced toughness for specimens with low levels of constraint to be taken into account for defect assessment.
文摘Many experimental investigations have previously been performed and recentlydone on different shipbuilding structural steels where the specimens size and crack depth/specimenwidth (a/W) were varied. A series of interesting results have been gained. It is worthwhile to havea review on the effect of a/W ratio on fracture toughness, and further theoretical analysis isnecessary. In this paper, experimental work in elastic-plastic fracture mechanics (EPFM) wasdiscussed. Tests had been carried out on 10 kinds of strength steels. Results showed that J_i andδ_i. values increased with decreasing a/W when a/W【0.3 for three-point bend specimens and thatshallow crack specimens which have less constrained flow field give markedly higher values oftoughness than deeply notched specimens. However, for a/W】0.3, the toughness was found to beindependent of a/W. Slip line field analysis shows that for shallow cracks, the hydrostatic stressis lower than that from standard deeply cracked bend specimen which develops a high level of cracktip constraint, provides a lower bound estimate of toughness, and will ensure an unduly conservativeapproach when applied to structure defects especially if initiation values of COD / J-integral areused.
文摘In part I of this series, experimental investigation in EPFM （elastic-plastic fracture mechanics） had been discussed. In this paper, experimental investigation in LEFM （ linear elastic fracture mechanics） is given. Fracture toughness tests had been carried out on three different strength steels, using both through-cracked specimens with different α/W ratio and semi-elliptical cracked specimens with variable crack size and shape. Results show that the fracture toughness KIC increases with decreasing α/W when α/W 〈 0.3 for three-point-bend specimens, and that for α/W 〉 0.3, it is independent of α/W. Shallow crack specimens, both through-cracked and surface-cracked, gave markedly higher values than deeply notched specimens. However, the effect of crack shape on fracture toughness is negligible. Results also show that the LEFM approach to fracture is not tenable for design stresses where αc is often very small, far less than 2.5 （ KIC/σy）^2.
基金Scientific Research Project of Guangdong Bureau of Traditional Chinese Medicin(No.20201335)。
文摘Objective:To explore the relationship between peripheral blood neutrophil/lymphocyte ratio(NLR)and osteoporotic femoral neck fractures and to evaluate the prognosis.Methods:The subjects were 102 patients who received osteoporotic femoral neck fracture in the First Affiliated Hospital of Guangzhou University of Chinese Medicine from 2008 to 2017.Patients were divided into three groups according to the BMD values in the diagnostic criteria of primary osteoporosis:normal bone mass group(T≥-1.0),reduced bone mass group(-2.5<T<-1.0)and osteoporosis group(T≤-2.5).In addition,during postoperative follow-up,patients receiving internal fixation were divided into the high NLR group(NLR>2.33)and the low NLR group(NLR≤2.33)according to their NLR values.The clinical data of patients with osteoporotic femoral neck fracture who underwent peripheral blood routine examination were prospectively analyzed.The statistical indicators included age,gender,fracture cause and other general conditions,fracture type,peripheral blood neutrophil/lymphocyte ratio,bone mineral density(BMD)level and blood lipid level,and prognosis of 102 patients who were followed up for more than 2 years after surgery.The relationship between peripheral blood NLR and the above indexes was observed.Statistical methods including normal data analysis of variance between groups,SNK-q test is compared between two groups,the partial correlation analysis between the two factors,the relationship between multiple factors using multi-factor linear regression analysis,and normal data comparison between the two groups using t test,two sets of independent data frequency distribution of binary classification variables compared by chi-square test.Moreover,NLR is also a major factor affecting the prognosis and rehabilitation of osteoporotic femoral neck fractures.Results:The analysis of variance between the two groups(SNK-q test of the comparison between the two groups),single-factor partial correlation analysis,multi-factor linear regression analysis showed that compared with the normal group and the reduced group,the levels of age,triglyceride and NLR in the osteoporosis group were increased,while BMD was significantly decreased.BMD in patients with osteoporotic femoral neck fracture was negatively correlated with NLR and triglyceride(P<0.05).In multi-factor linear regression analysis,NLR and triglyceride were the main influencing factors of BMD in patients with osteoporotic femoral neck(P<0.05).In addition,increased peripheral blood NLR in patients treated with internal fixation may increase the risk of postoperative femoral head necrosis,nonunion of the broken end of the fracture,and prolong the time of postoperative functional recovery.Conclusion:The level of peripheral blood NLR in patients with osteoporotic femoral neck fracture is increased and correlated with bone mineral density,which suggested that peripheral blood NLR can be used as one of the clinical indicators for early screening and prevention of osteoporotic femoral neck fracture.In addition,peripheral blood NLR is also a major factor affecting the prognosis and rehabilitation of osteoporotic femoral neck fractures.
文摘The relationship between fracture toughness VGC and critical void growth RC/RO was studied for ten kinds of Steel. The macroscopic fracture toughness VGC was determined by using notched tensile specimens. and the microscopic parameters of critical void growth ratio RC/RO were quantitatively measured under SEM. Then, the coefhcient C in the relation VGC = C In(RC/RO) proposed in author's past work was specifically explored. The correlation of C with tensile proderty parameter φ=σyδ/(Eφn) was presented for the Steel investigated, and the effects of low temperature on C were also discussed. Results show that the coefficient C is linearly related to the parameter and insensitive to low temperature.
基金financially supported by the Fundamental Research Funds for the Central Universities(No.2015QNA69)the State Key Laboratory of Continental Tectonics and Dynamics(No.K201406)the PetroChina Major Science and Technology Project(No.2011E-2602)
文摘The distribution and intensity of tectonic fractures within geologic units are important to hydrocarbon exploration and development. Taken the Upper Triassic Yanchang Formation interbedded sandstone-mudstone in the Ordos Basin as an example, this study used the finite element method（FEM） based on geomechanical models to study the development of tectonic fractures. The results show that the sandstones tend to generate tectonic fractures more easily than mudstones with the same layer thickness, and the highest degree of tectonic fractures will be developed when the sandstone-mudstone thickness ratio is about 5.0. A possible explanation is proposed for the tectonic fracture development based on two important factors of rock brittleness and mechanical layer thickness. Generally, larger rock brittleness and thinner layer thickness will generate more tectonic fractures. In interbedded sandstone-mudstone formations, the rock brittleness increases with the increasing mechanical layer thickness, hence, these two factors will achieve a balance for the development of tectonic fractures when the sandstone-mudstone thickness ratio reaches a specific value, and the development degree of tectonic fractures is the highest at this value.
基金Supported by the Joint Funds of National Natural Science Foundation of ChinaCivil Aviation Administration Foundation of China(Grant No.U1233201)Science and Technology Support Plan of Tianjin,China(Grant No.13ZCZDGX00200)
文摘Fatigue fracture is one of the main failure modes of Ti-6A1-4V alloy,fracture toughness and crack closure have strong effects on the fatigue crack growth（FCG）rate of Ti-6A1-4V alloy.The FCG rate of Ti-6A1-4V is investigated by using experimental and analytical methods.The effects of stress ratio,crack closure and fracture toughness on the FCG rate are studied and discussed.A modified prediction model of the FCG rate is proposed,and the relationship between the fracture toughness and the stress intensity factor（SIF）range is redefined by introducing a correcting coefficient.Notched plate fatigue tests（including the fracture toughness test and the FCG rate test）are conducted to investigate the influence of affecting factors on the FCG rate.Comparisons between the predicted results of the proposed model,the Paris model,the Walker model,the Sadananda model,and the experimental data show that the proposed model gives the best agreement with the test data particularly in the near-threshold region and the Paris region,and the corresponding calculated fatigue life is also accurate in the same regions.By considering the effects of fracture toughness and crack closure,the novel FCG rate prediction model not only improves the estimating accuracy,but also extends the adaptability of the FCG rate prediction model in engineering.
基金the National Science Foundation (Grant 1344592)the National Natural Science Foundation of China (Grant 51778462)the National Key Research and Development Plan (Grants 2017YFC1500700 and 2016YFC0701400).
文摘Micromechanics-based models provide powerful tools to predict initiation of ductile fracture in steels. A new criterion is presented herein to study the process of ductile fracture when the effects of both stress triaxiality and shear stress on void growth and coalescence are considered. Finite-element analyses of two different kinds of steel, viz. ASTM A992 and AISI 1045, were carried out to monitor the history of stress and strain states and study the methodology for determining fracture initiation. Both the new model and void growth model (VGM) were calibrated for both kinds of steel and their accuracy for predicting fracture initiation evaluated. The results indicated that both models offer good accuracy for predicting fracture of A992 steel. However, use of the VGM leads to a significant deviation for 1045 steel, while the new model presents good performance for predicting fracture over a wide range of stress triaxiality while capturing the effect of shear stress on fracture initiation.
文摘Although pre-Northridge earthquake steel moment resisting frame buildings have been shown to be susceptible to brittle connection failures,they still represent a large fraction of the existing steel buildings in the United States of America.In this study,the performance of the 3-and 9-story Los Angeles pre-Northridge SAC buildings are analyzed considering ductile and brittle beam-column connection failures,and their uncertainty.This paper contributes to understanding the influence of uncertainty associated with connections brittle fracture on building interstory deformation capacity and its impact on bias and variability of fragility functions and loss assessment.The results show that considering brittle connections leads to significantly l arger d rift demands a nd t o h igher r epair costs,particularly under intense ground shaking.New fragility curve parameters are derived that account for the effect of the uncertainty of the strength and deformation capacity of brittle connections.
文摘Fifteen cases of fresh fractures have been studied, including 14 cases of tubu-lar bone fractures with age from 28 to 60 years and one case of vertebral fracture ofdorsolumbar region, 16 years of age. There were 13 male and 2 female patients. Theyhad no endocrine disturbances or other bone diseases. The ratio ofhydroxyproline/creatinine (HP/Cr) in these cases increased gradually within 20-30 daysafter fracture and then reached the peak value which was about 3-4 times of normal, thepeak value maintained for a long time. If the trauma was mild or the patient was young,the peak began to decline on the 60th day after fracture. While in those severe cases withprolonged confinement to bed, the peak only began to come down about 110th dayafter fracture. The ratio of HP/Cr decreased rapidly from the peak at first, then pursueda slow course. Generally, the ratio of HP/Cr returned to normal on the 240th to 310thday. Bone union began at a time when peak value started to decline, and with completionof the remodelling process, the HP/Cr value returned to normal.
文摘The interaction problem among fractures under the action of compressional stress is studied in this paper by using the finite element method and boundary element method respectively.The mechanical criteria which differentiate between the independent fractures and fracture systems and their computation methods are presented in this paper.The proportional conditions between length and spacing of fractures that exist interaction for several kinds of fracture groups of different geometric arrangement are given.The effect of interaction among fractures on the displacement field,stress field and strain energy distribution are computed.The relations between the fracture system of conjugate array and conjugate earthquakes are also discussed in this paper.
文摘In this paper, investigation on the initial fracture behavior was carried out on roving glass woven fabric reinforced composites which were manufactured by hand lay-up method. Two kinds of roving glass woven fabrics of different FAW (Fabric Area Weight) and crimp ratio, Type A of 570 g/m2 and Type B of 800 g/m2, were adopted as reinforcement in this study. Tensile test was conducted and tensile properties were discussed on specimens of 6 degrees 0°/5°/10°/80°/85°/90°. The initial fracture behavior was observed on 0 degree and 90 degree and the fracture mechanism was compared and discussed among 5°/10°/80°/85°. The results showed that Type B has higher tensile modulus and tensile strength than that of Type A. And different initial fracture behaviors between two kinds of materials was observed and analyzed, which indicated that the crimp ratio plays an important role of woven fabric reinforced composites in fracture mechanism.
文摘Taking 91105 working face as the research object, the observation method of water flowing fracture<span style="font-family:Verdana;">d</span><span style="font-family:Verdana;"> zone and the layout of mining holes were determined by analyzing the field geological structure</span><span style="font-family:Verdana;">. </span><span style="font-family:Verdana;">It was shown that the fractured zone height and the ratio given by the measured method were 52.33 and 12.46, respectively. By the numerical simulation method with the software of UDEC, the fractured zone height and the ratio were 42.5 and 10.12. By comparison of measured height data and UDEC numerical simulation, there were some differences between the measured height and the calculated results of UDEC numerical simulation method. The method of simulation can be used as the technical basis for the design of waterproof coal pillar in the future.</span>
基金Funded by National Natural Science Foundation of China(No.51474170)the Key Laboratory Project of Shaanxi Provincial Department of Education(No.20js075)。
文摘The ultra-fine grained(UFG)pure titanium was prepared by equal channel angular pressing(ECAP)and rotary swaging(RS).The strain controlled low cycle fatigue(LCF)test was carried out at room temperature.The fatigue life prediction model and mean stress relaxation model under asymmetrical stress load were discussed.The results show that the strain ratio has a significant effect on the low cycle fatigue performance of the UFG pure titanium,and the traditional Manson-coffin model can not accurately predict the fatigue life under asymmetric stress load.Therefore,the SWT mean stress correction model and three-parameter power curve model are proposed,and the test results are verified.The final research shows that the threeparameter power surface model has better representation.By studying the mean stress relaxation phenomenon under the condition of R≠-1,it is revealed that the stress ratio and the strain amplitude are the factors that significantly afiect the mean stress relaxation rate,and the mean stress relaxation model with the two variables is calculated to describe the mean stress relaxation phenomenon of the UFG pure titanium under different strain ratios.The fracture morphology of the samples was observed by SEM,and it was concluded that the final fracture zone of the fatigue fracture of the UFG pure titanium was a mixture of ductile fracture and quasi cleavage fracture.The toughness of the material increases with the increase of strain ratio at the same strain amplitude.
