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A model to quantify fatigue crack growth by cyclic damage accumulation calculated by strip-yield procedures 用带屈服法计算循环损伤累积来量化疲劳裂纹扩展的模型
Fracture and Structural Integrity Pub Date : 2017-06-28 DOI: 10.3221/IGF-ESIS.41.18
Samuel Elias Ferreira, J. Castro, M. Meggiolaro
{"title":"A model to quantify fatigue crack growth by cyclic damage accumulation calculated by strip-yield procedures","authors":"Samuel Elias Ferreira, J. Castro, M. Meggiolaro","doi":"10.3221/IGF-ESIS.41.18","DOIUrl":"https://doi.org/10.3221/IGF-ESIS.41.18","url":null,"abstract":"Elber's hypothesis that DeltaKeff can be assumed as the driving force for fatigue crack growth (FCG) is the basis for strip-yield models widely used to predict fatigue lives under variable amplitude loads, although it does not explain all load sequence effects observed in practice. To verify if these models are indeed intrinsically better, the mechanics of a typical strip-yield model is used to predict FCG rates based both on Elber's ideas and on the alternative view that FCG is instead due to damage accumulation induced by the cyclic strain history ahead of the crack tip, which does not need or use DeltaKeff ideas. The main purpose here is to predict FCG using the cyclic strains induced by the plastic displacements calculated by strip-yield procedures, assuming there are strain limits associated both the with the FCG threshold and with the material toughness. Despite based on conflicting principles, both models can reproduce quite well FCG data, a somewhat surprising result that deserves to be carefully analyzed.","PeriodicalId":300868,"journal":{"name":"Fracture and Structural Integrity","volume":"84 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130741957","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 2
Carbon nano-tubes in improving the mechanical property of cement-based composite materials 碳纳米管在改善水泥基复合材料力学性能中的作用
Fracture and Structural Integrity Pub Date : 2017-06-28 DOI: 10.3221/IGF-ESIS.41.50
Xuan Wu, Libing Dai
{"title":"Carbon nano-tubes in improving the mechanical property of cement-based composite materials","authors":"Xuan Wu, Libing Dai","doi":"10.3221/IGF-ESIS.41.50","DOIUrl":"https://doi.org/10.3221/IGF-ESIS.41.50","url":null,"abstract":"Carbon nano-tubes as a kind of novel nanometer material have been extensively applied in cement-based composite materials to improve their properties. This study prepared carbon nano-tubes cement based composite materials by evenly scattering carbon nano-tubes in cement materials using ultrasonic method and emphatically investigation the improvement of the mechanical property. The results demonstrated that, the addition of carbon nano-tubes could significantly relieve the mechanical properties of cement based composite materials. When the mixing amount of carbon nano-tubes reached the optimal value, i.e., 0.1%, the improvement of the mechanical property of the carbon nano-tubes cement based composite materials was the best. The microstructure analysis using scanning electron microscope suggested that, carbon nano-tubes produced bridging and pullout effects in the cement-based materials, which enhanced the damage resistance of the cement based materials.","PeriodicalId":300868,"journal":{"name":"Fracture and Structural Integrity","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134218151","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 6
Crack tip field in circumferentially-cracked round bar (CCRB) in tension affected by loss of axial symmetry 轴对称性损失对拉伸环裂纹圆棒裂纹尖端场的影响
Fracture and Structural Integrity Pub Date : 2017-06-28 DOI: 10.3221/IGF-ESIS.41.19
J. Toribio, B. González, J. Matos
{"title":"Crack tip field in circumferentially-cracked round bar (CCRB) in tension affected by loss of axial symmetry","authors":"J. Toribio, B. González, J. Matos","doi":"10.3221/IGF-ESIS.41.19","DOIUrl":"https://doi.org/10.3221/IGF-ESIS.41.19","url":null,"abstract":"In this paper, the stress intensity factor (SIF) is computed in a circumferentially-cracked round bar (CCRB) subjected to tensile loading, considering that the resistant ligament is circular and exhibits certain eccentricity in relation to the cylinder axis. The computation was performed by means of the finite element method (FEM) using a three dimensional (3D) model and the J-integral, the analyzed variable being the eccentricity of the circular ligament. Results show that the SIF is higher at the deepest point of the crack and that an increase of eccentricity (in relation to the bar axis) raises the difference between the SIF values along the crack front. From a certain value of the misalignment a bending effect appears, so that the crack remains closed in the area near the point of lower depth.","PeriodicalId":300868,"journal":{"name":"Fracture and Structural Integrity","volume":"600 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134327220","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 2
The heat energy dissipated in a control volume to correlate the crack propagation rate in stainless steel specimens 在控制体积内耗散的热能与不锈钢试样裂纹扩展速率相关
Fracture and Structural Integrity Pub Date : 2017-06-28 DOI: 10.3221/IGF-ESIS.41.40
G. Meneghetti, M. Ricotta
{"title":"The heat energy dissipated in a control volume to correlate the crack propagation rate in stainless steel specimens","authors":"G. Meneghetti, M. Ricotta","doi":"10.3221/IGF-ESIS.41.40","DOIUrl":"https://doi.org/10.3221/IGF-ESIS.41.40","url":null,"abstract":"Metallic materials dissipate thermal energy when subjected to fatigue. Some of them, due a favorable combination of thermo-physical material properties, exhibit a significant temperature rise, which can be easily measured in-situ by means of thermocouples or infrared cameras. The heat energy dissipated in a unit volume of material per cycle (the Q parameter) has proven to be effective as a fatigue damage index in case of AISI 304L plain and notched specimens. Originally conceived and applied as a point-related quantity, recently Q has been averaged at the tip of propagating fatigue cracks (the Q* parameter) in order to correlate crack growth data gathered from fracture mechanics tests. The use of Q* seems interesting because (i) it can be evaluated in-situ from infrared temperature maps and (ii) crack acceleration due to excessive plasticity is likely to be accounted for.","PeriodicalId":300868,"journal":{"name":"Fracture and Structural Integrity","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131336996","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 2
Variable mode-mixity during fatigue cycles – crack tip parameters determined from displacement fields measured by digital image correlation 疲劳循环过程中的变模混合-裂纹尖端参数由数字图像相关测量的位移场确定
Fracture and Structural Integrity Pub Date : 2017-06-28 DOI: 10.3221/IGF-ESIS.41.42
M. Vormwald, Yiğiter Hoș, J. Freire, G. Gonzáles, Jorge G. Díaz
{"title":"Variable mode-mixity during fatigue cycles – crack tip parameters determined from displacement fields measured by digital image correlation","authors":"M. Vormwald, Yiğiter Hoș, J. Freire, G. Gonzáles, Jorge G. Díaz","doi":"10.3221/IGF-ESIS.41.42","DOIUrl":"https://doi.org/10.3221/IGF-ESIS.41.42","url":null,"abstract":"This paper focusses on discussing equivalent stress intensity factors and kink angles after a change of mode-mixity from one cycle to the next and when the mode-mixity changes continuously during the fatigue cycles. Thin-walled tubes with through-wall cracks have been loaded by proportional and non-proportional tension and torsion. In the experimental investigation, the region of fatigue crack growth was observed by applying the digital image correlation technique. Data on the variations of the displacement and strain fields during the cycles were acquired and used to determine mixed-mode variations of stress intensity factors associated with opening modes I, II and III. For each specific specimen the crack path was observed in order to relate its curvature – both kinks and continuously developing warped cracks – with the variations of the displacement field and associated stress intensity factors.","PeriodicalId":300868,"journal":{"name":"Fracture and Structural Integrity","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114438799","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 5
Crack initiation life in notched Ti-6Al-4V titanium bars under uniaxial and multiaxial fatigue: synthesis based on the averaged strain energy density approach 缺口Ti-6Al-4V钛棒在单轴和多轴疲劳下的裂纹起裂寿命:基于平均应变能密度法的综合
Fracture and Structural Integrity Pub Date : 2017-06-28 DOI: 10.3221/IGF-ESIS.41.02
G. Meneghetti, A. Campagnolo, F. Berto, Keisuke Tanaka
{"title":"Crack initiation life in notched Ti-6Al-4V titanium bars under uniaxial and multiaxial fatigue: synthesis based on the averaged strain energy density approach","authors":"G. Meneghetti, A. Campagnolo, F. Berto, Keisuke Tanaka","doi":"10.3221/IGF-ESIS.41.02","DOIUrl":"https://doi.org/10.3221/IGF-ESIS.41.02","url":null,"abstract":"The fatigue behaviour of circumferentially notched specimens made of titanium alloy, Ti-6Al-4V, has been analysed. To investigate the notch effect on the fatigue strength, pure bending, pure torsion and multiaxial bending-torsion fatigue tests have been carried out on specimens characterized by two different root radii, namely 0.1 and 4 mm. Crack nucleation and subsequent propagation have been accurately monitored by using the direct current potential drop (DCPD) technique. Based on the results obtained from the potential drop technique, the crack initiation life has been defined in correspondence of a relative potential drop increase ?V/?V0 equal to 1%, and it has been used as failure criterion. Doing so, the effect of extrinsic mechanisms operating during crack propagation phase, such as sliding contact, friction and meshing between fracture surfaces, is expected to be reduced. The experimental fatigue test results have been re-analysed by using the local strain energy density (SED) averaged over a structural volume having radius R0 and surrounding the notch tip. Finally, the use of the local strain energy density parameter allowed us to properly correlate the crack initiation life of Ti-6Al-4V notched specimens, despite the different notch geometries and loading conditions involved in the tests.","PeriodicalId":300868,"journal":{"name":"Fracture and Structural Integrity","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132174229","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 5
Fatigue assessment of steel rollers by means of the local energy 用局部能量法评价钢轧辊的疲劳
Fracture and Structural Integrity Pub Date : 2017-06-28 DOI: 10.3221/IGF-ESIS.41.56
F. Chebat, M. Cincera, S. Razavi, F. Berto, T. Welo
{"title":"Fatigue assessment of steel rollers by means of the local energy","authors":"F. Chebat, M. Cincera, S. Razavi, F. Berto, T. Welo","doi":"10.3221/IGF-ESIS.41.56","DOIUrl":"https://doi.org/10.3221/IGF-ESIS.41.56","url":null,"abstract":"This paper aims to analyses the fatigue behavior of steel rollers using the average strain energy density (SED) criterion. Considering the variability of the V-notch opening angle, a simple scalar quantity, i.e. the value of the strain energy density averaged in a control volume surrounding the notch tip, has been introduced to overcome the complexities in failure assessment of this component. The strain energy is obtained using close form solutions based on the relevant Notch Stress Intensity Factors (NSIF) for modes I, II and III. Referring to the conventional arc welding processes, the radius of the control volume is carefully identified with reference to conventional arc welding processes being equal to 0.28 mm for welded joints made of steel. In this paper firstly the employed methodology for the fatigue assessment is described and then the first synthesis of fatigue data by means of local SED for a specific geometry is shown.","PeriodicalId":300868,"journal":{"name":"Fracture and Structural Integrity","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134426791","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Sharp three-dimensional notches under combined nominal normal and shear fatigue loading 在联合名义法向和剪切疲劳载荷下的尖锐的三维缺口
Fracture and Structural Integrity Pub Date : 2017-06-28 DOI: 10.3221/IGF-ESIS.41.16
M. Vormwald, E. Shams
{"title":"Sharp three-dimensional notches under combined nominal normal and shear fatigue loading","authors":"M. Vormwald, E. Shams","doi":"10.3221/IGF-ESIS.41.16","DOIUrl":"https://doi.org/10.3221/IGF-ESIS.41.16","url":null,"abstract":"Many engineering structures are exposed to non-proportional fatigue loading. However, at the critical location of crack initiation, often only one of the load sequences dominates – the individual load cases result in different crack initiation sites. Based on engineering judgment a simplified local uniaxial or proportional loading situation may be assessed. In general, the critical location must be identified by calculating fatigue lives for a variety of locations. The position of the critical location depends on the hypothesis applied for life calculation – besides loading, geometry, material and many other influence factors. For sharp three-dimensional notches the region for the search of the critical location may be restricted considerably. Weld start and stop points are an industrial example for such sharp notches. They are the object of the present investigation. They are exposed to nominal normal and shear loading. The individual hot spots for crack initiation lie necessarily close together. A strong interaction of the loading cases for both proportional and non-proportional loading was experimentally observed. In the numerical investigation notch stresses were calculated using an idealised weld end model. Based on the critical plane approach according to Findley, numerical interaction lines were produced.","PeriodicalId":300868,"journal":{"name":"Fracture and Structural Integrity","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125629088","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
On the use of length scale parameters to assess the static strength of notched 3D-printed PLA 用长度比例尺参数评价缺口3d打印PLA的静强度
Fracture and Structural Integrity Pub Date : 2017-06-28 DOI: 10.3221/IGF-ESIS.41.34
A. Ahmed, L. Susmel
{"title":"On the use of length scale parameters to assess the static strength of notched 3D-printed PLA","authors":"A. Ahmed, L. Susmel","doi":"10.3221/IGF-ESIS.41.34","DOIUrl":"https://doi.org/10.3221/IGF-ESIS.41.34","url":null,"abstract":"This paper aims to investigate the accuracy of the Theory of Critical Distances (TCD) in estimating static strength of notched additively manufactured PLA as both notch sharpness and infill angle vary. The TCD takes as its starting point the assumption that the extent of damage under static loading can be assessed successfully by using two different material parameters, i.e. (i) a critical distance whose length is closely related to the material microstructural features and an inherent (i.e., a defect free) material strength. Plain and notched specimens of 3D-printed PLA were manufactured horizontally by making the deposition angle vary in the range 0?-90?. Using the TCD in the form of the Point Method, failures were predicted by directly post-processing the linear-elastic stress fields estimated through the well-known analytical solutions due to Glinka and Newport. Independently of the notch sharpness, the estimates being obtained were found to be highly accurate, falling within an error interval of about 20%. This result fully supports the idea that the TCD can successfully be used in situations of practical interest to design against static loading notched components of additively manufactured PLA by directly post-processing the results from simple linear-elastic Finite Element (FE) models.","PeriodicalId":300868,"journal":{"name":"Fracture and Structural Integrity","volume":"8 3-4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130236528","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 5
Mid-thickness studies of the stress intensity factor in the bulk of bainitic steel 贝氏体钢体中厚应力强度因子的研究
Fracture and Structural Integrity Pub Date : 2017-06-28 DOI: 10.3221/IGF-ESIS.41.28
P. Lopez‐Crespo, J. Vazquez-Peralta, C. Simpson, T. Buslaps, P. Withers
{"title":"Mid-thickness studies of the stress intensity factor in the bulk of bainitic steel","authors":"P. Lopez‐Crespo, J. Vazquez-Peralta, C. Simpson, T. Buslaps, P. Withers","doi":"10.3221/IGF-ESIS.41.28","DOIUrl":"https://doi.org/10.3221/IGF-ESIS.41.28","url":null,"abstract":"The current work aims at estimating the stress intensity factor deep inside the bulk from elastic strain data measured by synchrotron X-ray diffraction. Key features affecting the evaluation of the stress intensity factor are the number of terms in the analytical model describing the crack tip field, the extension and position of the area of interest of the experimental data, the effect of the experimental data collected within the plastic zone and the number of elastic strain data points used. Here a parametric study of these features is presented in terms of their influence for the stress intensity factor determination. It was found that 3 or 4 terms in Williams’ expansion is often sufficient; the data should be collected from across the full range of angles around the crack tip; and the number of points/number of terms should be greater than 40.","PeriodicalId":300868,"journal":{"name":"Fracture and Structural Integrity","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129574165","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
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