Subcritical crack development with an extensive prefailure zone in viscoelastic material

1989 ◽  
Vol 25 (7) ◽  
pp. 688-694
Author(s):  
A. A. Kaminskii ◽  
S. V. Mikhailenko
Keyword(s):  
Viscoelastic Material ◽  
Crack Development ◽  
Subcritical Crack Development

A Consistent Implementation of Inelastic Material Models into Steady State Rolling

2016 ◽  
Vol 44 (3) ◽  
pp. 174-190 ◽  
Author(s):  
Mario A. Garcia ◽  
Michael Kaliske ◽  
Jin Wang ◽  
Grama Bhashyam
Keyword(s):  
Steady State ◽  
Numerical Simulations ◽  
Viscoelastic Material ◽  
Rolling Contact ◽  
Arbitrary Lagrangian Eulerian ◽  
Ale Formulation ◽  
Inelastic Material ◽  
Material Formulation ◽  
Steady State Rolling ◽  
Efficient Alternative

ABSTRACT Rolling contact is an important aspect in tire design, and reliable numerical simulations are required in order to improve the tire layout, performance, and safety. This includes the consideration of as many significant characteristics of the materials as possible. An example is found in the nonlinear and inelastic properties of the rubber compounds. For numerical simulations of tires, steady state rolling is an efficient alternative to standard transient analyses, and this work makes use of an Arbitrary Lagrangian Eulerian (ALE) formulation for the computation of the inertia contribution. Since the reference configuration is neither attached to the material nor fixed in space, handling history variables of inelastic materials becomes a complex task. A standard viscoelastic material approach is implemented. In the inelastic steady state rolling case, one location in the cross-section depends on all material locations on its circumferential ring. A consistent linearization is formulated taking into account the contribution of all finite elements connected in the hoop direction. As an outcome of this approach, the number of nonzero values in the general stiffness matrix increases, producing a more populated matrix that has to be solved. This implementation is done in the commercial finite element code ANSYS. Numerical results confirm the reliability and capabilities of the linearization for the steady state viscoelastic material formulation. A discussion on the results obtained, important remarks, and an outlook on further research conclude this work.

Расчетные методы оценки ударной вязкости сварных элементов с трещинами

2020 ◽  
Vol 44 (3) ◽  
pp. 22-36
Author(s):  
Keyword(s):  
Stress Intensity ◽  
Impact Strength ◽  
Welded Joints ◽  
Development Process ◽  
Welded Joint ◽  
Operating Temperature ◽  
Crack Development ◽  
Heterogeneous Structure ◽  
Critical Crack Length ◽  
The Impact

Практика показывает, что для сварных конструкций, эксплуатируемых в условиях Крайнего Севера необходимо уделять внимание работоспособности сварных соединений при низких температурах. Металл сварных соединений в процессе воздействия обработки изменяет свои свойства, снижается ударная вязкость, образуется гетерогенная структура с большой степенью разнозернистости. Чтобы оценивать и иметь возможность правильно контролировать термическое воздействие и последствия сварочного процесса, требуется решить задачу аналитического определения ударной вязкости для всех зон сварного соединения. В настоящей статье представлен инженерный метод оценки ударной вязкости, применимый для любой зоны сварного соединения, в которой имеется острый или особый концентратор напряжений – трещина. Разработанный аналитический метод расчета ударной вязкости отражает качественную и количественную картину взаимосвязи структурно-механических характеристик и работы развития трещины в диапазоне температур 77…300 К. Предложенная схематизация зависимости критического коэффициента интенсивности напряжений от температуры позволила найти коэффициенты, характеризующие свойства материала, и выполнить расчеты изменения предела текучести и предела прочности от температуры эксплуатации. Построены графики зависимости работы развития трещины от температуры эксплуатации для сталей 15ГС и 17ГС, сравнение которых с экспериментальными данными показывает удовлетворительное согласование. Найдено, что при напряжениях предела выносливости отношение работы развития трещины к критической длине трещины постоянно, не зависит от температуры и для сталей 15ГС и 17ГС равно около 10. Ключевые слова: ударная вязкость, работа разрушения, коэффициент интенсивности напряжений, трещина, феррито-перлитная сталь, зона термического влияния. For welded structures under operation in the Far North, attention must be paid to the performance of welded joints at low temperatures. The properties of metal of welded joints are changed in the process of treatment, its toughness decreases, and a heterogeneous structure with a large range of different grain sizes is formed. In order to evaluate and be able to correctly control the thermal effect and the consequences of the welding process, it is necessary to solve the problem of analytical determination of impact strength for all zones of the welded joint. The paper presents an engineering method for evaluation of the impact strength applicable to any area of the welded joint in which there is a sharp or super sharp stress concentrator – a crack. The developed analytical method for calculating the impact strength reflects a qualitative and quantitative codependency of structural and mechanical characteristics and the process of crack development in the temperature range of 77–300 K. The proposed schematization of dependence of the critical coefficient of stress intensity on the temperature made it possible to find coefficients characterizing the properties of the material and to perform calculations of changes in yield strength and tensile strength on operating temperature. Graphs of the crack development process dependency on the operating temperature for 15ГС and 17ГС steels were constructed, and their comparison with experimental data displays satisfactory agreement. It was found that at endurance limit stresses, the ratio of the crack development process to the critical crack length is constant, non-dependent on temperature, and is equal to 10 for 15ГС and 17ГС steels. Keywords: impact strength, fracture work, stress intensity factor, crack, ferrite-pearlite steel, heat affected zone, steel tempering.

scholarly journals Investigation of Microcrack Propagation and Energy Evolution in Brittle Rocks Based on the Voronoi Model

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2108
Author(s):  
Guanlin Liu ◽  
Youliang Chen ◽  
Xi Du ◽  
Peng Xiao ◽  
Shaoming Liao ◽  
...  
Keyword(s):  
Uniaxial Compression ◽  
Damage Evolution ◽  
Rock Sample ◽  
Rock Fracture ◽  
Damage Threshold ◽  
Crack Development ◽  
Energy Evolution ◽  
Shear Cracks ◽  
Compression Tests ◽  
Microcrack Propagation

The cracking of rock mass under compression is the main factor causing structural failure. Therefore, it is very crucial to establish a rock damage evolution model to investigate the crack development process and reveal the failure and instability mechanism of rock under load. In this study, four different strength types of rock samples from hard to weak were selected, and the Voronoi method was used to perform and analyze uniaxial compression tests and the fracture process. The change characteristics of the number, angle, and length of cracks in the process of rock failure and instability were obtained. Three laws of crack development, damage evolution, and energy evolution were analyzed. The main conclusions are as follows. (1) The rock’s initial damage is mainly caused by tensile cracks, and the rapid growth of shear cracks after exceeding the damage threshold indicates that the rock is about to be a failure. The development of micro-cracks is mainly concentrated on the diagonal of the rock sample and gradually expands to the middle along the two ends of the diagonal. (2) The identification point of failure precursor information in Acoustic Emission (AE) can effectively provide a safety warning for the development of rock fracture. (3) The uniaxial compression damage constitutive equation of the rock sample with the crack length as the parameter is established, which can better reflect the damage evolution characteristics of the rock sample. (4) Tensile crack requires low energy consumption and energy dispersion is not concentrated. The damage is not apparent. Shear cracks are concentrated and consume a large amount of energy, resulting in strong damage and making it easy to form macro-cracks.

scholarly journals Vibration Reduction of an Existing Glass Window through a Viscoelastic Material-Based Retrofit

2018 ◽  
Vol 8 (7) ◽  
pp. 1061 ◽  
Author(s):  
Qian Feng ◽  
Liming Fan ◽  
Linsheng Huo ◽  
Gangbing Song
Keyword(s):  
Viscoelastic Material ◽  
Vibration Reduction
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