ASTM special technical publications最新文献_第7页

The Role of Cohesive Strength and Separation Energy for Modeling of Ductile Fracture 黏结强度和分离能在塑性断裂建模中的作用

ASTM special technical publications Pub Date : 2000-01-01 DOI: 10.1520/STP13400S

T. Siegmund, W. Brocks

{"title":"The Role of Cohesive Strength and Separation Energy for Modeling of Ductile Fracture","authors":"T. Siegmund, W. Brocks","doi":"10.1520/STP13400S","DOIUrl":"https://doi.org/10.1520/STP13400S","url":null,"abstract":"Barenblatt's idea of modeling the crack process zone by means of a cohesive zone has attracted considerable attention for predicting ductile crack growth. The model allows separation of the energy necessary for material separation from global plastic work. This has been a key problem in ductile fracture when searching for reasons for the geometry dependence of crack growth resistance curves. When using cohesive zone models, the correct determination of the cohesive zone material parameters is of eminent importance. In the past these parameters-the cohesive strength and the separation energy-were assumed to be material constants. However, micromechanical considerations show that this assumption is only an approximation in the case of ductile fracture. Here, the underlying mechanisms of void nucleation, growth, and coalescence are dependent on the stress triaxiality. This effect is accounted for in the new constitutive equation for cohesive zone models as presented here. In this new \"triaxiality-dependent cohesive zone model,\" the cohesive material properties are taken to be dependent on the stress triaxiality in the solid element adjacent to the cohesive element. For low triaxiality, low values of cohesive strength and large values of the separation energy are observed; the opposite holds true for cases of high triaxiality. Ductile crack growth in a mild steel under quasistatic loading was investigated. The results from the use of the triaxiality-dependent cohesive zone model are compared to those of the Gurson-Tvergaard-Needleman (GTN) model as well as to the cohesive zone model with constant material parameters. The dissipation rate is shown to be a favorable measure for the characterization of the crack growth resistance. It allows the description of both the (global) plastic dissipation and the (local) work of fracture.","PeriodicalId":8583,"journal":{"name":"ASTM special technical publications","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90601895","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: 48

Elastic-plastic fracture mechanics: Where has it been? Where is it going? 弹塑性断裂力学:发展到哪里了?它要去哪里?

ASTM special technical publications Pub Date : 2000-01-01 DOI: 10.1520/STP13391S

J. Landes

{"title":"Elastic-plastic fracture mechanics: Where has it been? Where is it going?","authors":"J. Landes","doi":"10.1520/STP13391S","DOIUrl":"https://doi.org/10.1520/STP13391S","url":null,"abstract":"Elastic-plastic fracture mechanics (EPFM) is the name given to a body of fracture technology that includes parameters, test methods, and analysis techniques. EPFM began in the 1960s, soon after it was recognized that the linear elastic approach to fracture mechanics was too limited to cover many engineering applications. It began in response to real engineering problems and continues to develop in the same application-driven mode. The development of EPFM spans more than three decades. It involved many people and a multitude of good ideas. Some of the people have gone on to other pursuits, and many of the ideas have been set aside or discarded in the never-ending debate about which is the best approach. The development of EPFM is not complete, nor is the controversy ended. It is important to look back at the factors that influenced such a vast development of technology before trying to forge ahead. This paper takes a look at the area of fracture mechanics called EPFM. It considers the development of a technology that involved people, places, and a seemingly inexhaustible supply of technical ideas. It considers what happened in the past, what is going on in the present, and speculates about what will happen for the future. Its purpose is to stop for a moment and consider for EPFM: Where has it been? Where is it going?","PeriodicalId":8583,"journal":{"name":"ASTM special technical publications","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90777807","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: 4

A Viscoplasticity Model for Characterizing Loading and Unloading Behavior of Polymeric Composites 表征聚合物复合材料加载和卸载行为的粘塑性模型

ASTM special technical publications Pub Date : 2000-01-01 DOI: 10.1520/STP15838S

Chang-ming Zhu, C. Sun

引用次数: 10

Evaluation of a Terrestrial Foodweb Model to Set Soil Cleanup Levels 陆地食物网模型对土壤清理水平的评价

ASTM special technical publications Pub Date : 2000-01-01 DOI: 10.1520/STP14416S

P. Doctor, K. A. Gano, N. K. Lane

引用次数: 1

Behavior of the High-Temperaturse Titanium Alloy IMI 834 Under Thermo-mechanical and Isothermal Fatigue Conditions 高温钛合金imi834在热-机械和等温疲劳条件下的行为

ASTM special technical publications Pub Date : 2000-01-01 DOI: 10.1520/STP15251S

P. Pototzky, H. Maier, H. Christ

{"title":"Behavior of the High-Temperaturse Titanium Alloy IMI 834 Under Thermo-mechanical and Isothermal Fatigue Conditions","authors":"P. Pototzky, H. Maier, H. Christ","doi":"10.1520/STP15251S","DOIUrl":"https://doi.org/10.1520/STP15251S","url":null,"abstract":"The high-temperature titanium alloy IMI 834 was studied with regard to the stress-strain response under thermo-mechanical fatigue conditions, the evolution of the microstructure, the relevant damage mechanisms and their implications for fatigue life. For this purpose isothermal and thermo-mechanical fatigue tests were performed in the temperature range from 350°C to 650°C in vacuum and air, respectively, and changes in the microstructure were determined by means of transmission electron microscopy. It was found that planar dislocation slip prevails in all tests in which the temperature does not exceed 600°C. Hence, in this temperature range the stress-strain response under thermo-mechanical conditions can be predicted solely based on the isothermal behavior. By contrast, a transition to wavy slip takes place at higher temperatures, affecting significantly the stresses in the low-temperature part of the corresponding thermo-mechanical fatigue tests. Fatigue life was generally observed to be lower in out-of-phase tests as compared to in-phase loading. Furthermore, the tests performed in high vacuum demonstrated that oxidation strongly affects fatigue life, but does not basically change the influence of testing mode on cyclic life. This can mainly be attributed to the additional effect of the acting mean stress.","PeriodicalId":8583,"journal":{"name":"ASTM special technical publications","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73071576","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

Fatigue life estimation under cumulative cyclic loading conditions 累积循环载荷条件下的疲劳寿命估算

ASTM special technical publications Pub Date : 2000-01-01 DOI: 10.1520/STP14796S

S. Kalluri, M. Mcgaw, G. Halford

引用次数: 5

An overview and discussion of basic methodology for fatigue 疲劳的基本方法综述与讨论

ASTM special technical publications Pub Date : 2000-01-01 DOI: 10.1520/STP14791S

N. Dowling, S. Thangjitham

{"title":"An overview and discussion of basic methodology for fatigue","authors":"N. Dowling, S. Thangjitham","doi":"10.1520/STP14791S","DOIUrl":"https://doi.org/10.1520/STP14791S","url":null,"abstract":"This paper broadly reviews the stress-based, strain-based, and crack growth approaches to fatigue life prediction, and it attempts to suggest some choices and variations of these that might enhance their inclusion in undergraduate education and their more routine use by practicing engineers. For the stress-based approach, emphasis should shift toward the use of data on actual components, and it should be recognized that damage below the usual fatigue limit may occur. Also, evaluation of mean stress effects by the modified Goodman diagram should be replaced by other methods. The usefulness of the strain-based approach for simple situations may be extended by adding empirical adjustments for surface finish and size. It may also be desirable to lower the long-life end of the strain-life curve to obtain agreement with limited component test data, producing a component-specific strain-life curve. Use of the crack growth approach is hampered by the lack of a widely accepted set of materials constants for describing da/dN versus ΔK curves. It is recommended that this situation be remedied by representing the intermediate growth rate region with a Paris-type exponent, an associated coefficient, and a third constant that characterizes the sensitivity to R-ratio according to the equation of Walker. Limits or asymptotic behavior for the low and high growth rate regions should then be handled separately.","PeriodicalId":8583,"journal":{"name":"ASTM special technical publications","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83349510","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: 28

Implementation of Constitutive Model in FEA for Nonlinear Behavior of Plastics 本构模型在塑料非线性有限元分析中的应用

ASTM special technical publications Pub Date : 2000-01-01 DOI: 10.1520/STP15830S

I. Skrypnyk, J. Spoormaker, W. Smit

引用次数: 5

Estimation Procedure for Determination of Fatigue Crack Propagation in Metal Alloys 测定金属合金疲劳裂纹扩展的估计方法

ASTM special technical publications Pub Date : 2000-01-01 DOI: 10.1520/STP13408S

R. Hertzberg

引用次数: 1

Accelerated Strength Testing of Thermoplastic Composites 热塑性复合材料的加速强度试验

ASTM special technical publications Pub Date : 2000-01-01 DOI: 10.1520/STP15841S

J. Reeder, D. Allen, W. Bradley

{"title":"Accelerated Strength Testing of Thermoplastic Composites","authors":"J. Reeder, D. Allen, W. Bradley","doi":"10.1520/STP15841S","DOIUrl":"https://doi.org/10.1520/STP15841S","url":null,"abstract":"Constant ramp strength tests on unidirectional thermoplastic composite specimens oriented in the 90 deg. direction were conducted at constant temperatures ranging from 149 C to 232 C. Ramp rates spanning 5 orders of magnitude were tested so that failures occurred in the range from 0.5 sec. to 24 hrs. (0.5 to 100,000 MPa/sec). Below 204 C, time-temperature superposition held allowing strength at longer times to be estimated from strength tests at shorter times but higher temperatures. The data indicated that a 50% drop in strength might be expected for this material when the test time is increased by 9 orders of magnitude. The shift factors derived from compliance data applied well to the strength results. To explain the link between compliance and strength, a viscoelastic fracture model was investigated. The model, which used compliance as input, was found to fit the strength data only if the critical fracture energy was allowed to vary with temperature reduced stress rate. This variation in the critical parameter severely limits its use in developing a robust time-dependent strength model. The significance of this research is therefore seen as providing both the indication that a more versatile acceleration method for strength can be developed and the evidence that such a method is needed.","PeriodicalId":8583,"journal":{"name":"ASTM special technical publications","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75136824","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