Advanced Constitutive Model for the Accurate Evaluation of the Structural Performance of Welded Pipes in Offshore Applications

2018 ◽  
Author(s):  
Steven Cooreman ◽  
Dennis Van Hoecke ◽  
Martin Liebeherr ◽  
Philippe Thibaux ◽  
Hervé Luccioni
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Large Scale ◽  
Structural Integrity ◽  
Compressive Strain ◽  
Longitudinal Direction ◽  
Structural Performance ◽  
Isotropic Hardening ◽  
Hardening Models ◽  
Strain Paths

To guarantee the structural integrity of oil and gas transporting pipelines, a detailed analysis of the pipe’s structural response has to be performed. This is of particular importance for offshore applications. As large scale testing is costly and time consuming, one often relies on FE (Finite Element) modelling to accomplish, at least, part of this task. Properties that typically need to be evaluated are compressive strain capacity, collapse resistance and ovalization during reel-lay installation. Furthermore, it can be assumed that those properties are influenced by the pipe forming process, as pipe forming will change the mechanical properties and the level of anisotropy and will modify/introduce residual stresses. Therefore, a first logical step is to simulate pipe forming before evaluating the pipe’s structural performance, to account for these effects. The reliability of FE simulations largely depends on the capability of the constitutive model to accurately describe the mechanical behaviour of the material being studied. Most commercial FE codes only offer combined kinematic-isotropic hardening models. Those models cannot capture the so-called cross-hardening effect and can therefore not predict the evolution of anisotropy during pipe forming. The present paper discusses the implementation and calibration of a more advanced constitutive model, more specifically the Levkovitch-Svendsen model, which accounts for isotropic, kinematic and distortional hardening. The model was implemented in Abaqus/Implicit through a UMAT user subroutine. An inverse modelling approach was applied to calibrate the constitutive model, whereby an extensive set of mechanical tests, involving cyclic tension-compression tests and tests with changing strain paths, was conducted. To assess the model’s performance, it was used in two case studies. The first study focused on the evolution of mechanical properties during spiral pipe forming. The results show that the Levkovitch-Svendsen model allows prediction of the properties in both the transverse and longitudinal direction on pipe. When applying a kinematic-isotropic hardening law only, the properties in the longitudinal direction are significantly underestimated. In the second study, different hardening models were used to predict the evolution of ovality during reel-lay installation. It was observed that the predictions made with the Levkovitch-Svendsen model were much closer to the experimental values than the results obtained by means of a kinematic-isotropic hardening model.

Biomechanics of the lung parenchyma: critical roles of collagen and mechanical forces

2005 ◽  
Vol 98 (5) ◽  
pp. 1892-1899 ◽  
Author(s):  
Béla Suki ◽  
Satoru Ito ◽  
Dimitrije Stamenović ◽  
Kenneth R. Lutchen ◽  
Edward P. Ingenito
Keyword(s):  
Mechanical Properties ◽  
Connective Tissue ◽  
Large Scale ◽  
Structural Integrity ◽  
Lung Parenchyma ◽  
The Body ◽  
Biological Macromolecules ◽  
Mechanical Forces ◽  
Connective Tissues ◽  
Architectural Organization

The biomechanical properties of connective tissues play fundamental roles in how mechanical interactions of the body with its environment produce physical forces at the cellular level. It is now recognized that mechanical interactions between cells and the extracellular matrix (ECM) have major regulatory effects on cellular physiology and cell-cycle kinetics that can lead to the reorganization and remodeling of the ECM. The connective tissues are composed of cells and the ECM, which includes water and a variety of biological macromolecules. The macromolecules that are most important in determining the mechanical properties of these tissues are collagen, elastin, and proteoglycans. Among these macromolecules, the most abundant and perhaps most critical for structural integrity is collagen. In this review, we examine how mechanical forces affect the physiological functioning of the lung parenchyma, with special emphasis on the role of collagen. First, we overview the composition of the connective tissue of the lung and their complex structural organization. We then describe how mechanical properties of the parenchyma arise from its composition as well as from the architectural organization of the connective tissue. We argue that, because collagen is the most important load-bearing component of the parenchymal connective tissue, it is also critical in determining the homeostasis and cellular responses to injury. Finally, we overview the interactions between the parenchymal collagen network and cellular remodeling and speculate how mechanotransduction might contribute to disease propagation and the development of small- and large-scale heterogeneities with implications to impaired lung function in emphysema.

A Study of the Effect of Hardening Model in the Prediction of Welding Residual Stress

2012 ◽  
Author(s):  
Martina M. Joosten ◽  
Martin S. Gallegillo
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Structural Integrity ◽  
Kinematic Hardening ◽  
Welding Process ◽  
Cyclic Hardening ◽  
Welding Residual Stress ◽  
Isotropic Hardening ◽  
Hardening Models ◽  
Set Up

The presence of residual stresses can significantly affect the performance of manufactured products. The welding process is one of the most common causes of large tensile residual stresses, which may contribute to failure by brittle fracture or cause other forms of failure such as damage by corrosion and creep. Welding is a widely used method of fabrication and it can generate high levels of residual stress over significant proportions of the thickness of a component. In order to study the effect of material characterisation on computer based predictions of welding residual stresses, the presented work was carried out as part of the European Network on Neutron Techniques Standardisation for Structural Integrity (NeT). Within the NeT, a task group is investigating a three-pass Tungsten Inert Gas (TIG) weld benchmark. The three-pass specimen offers the possibility of examining the cyclic hardening and annealing behaviour of the weld metal and heat affected zone. A 3D model of the benchmark NeT problem was set up using ABAQUS v6.9.1 and validated against measurements. This paper presents the finite element work. Future papers from the NeT shall present experimental measurements. Different hardening models were considered in order to study their effect on the residual stresses. The different hardening models were isotropic hardening, linear and nonlinear kinematic hardening and combinations of these. Also the effect of annealing on the hardening behaviour is studied. Finally, the results of the simulations are compared to residual stress distributions as given in several standards.

Mechanical Properties and Bending Behaviors of Low Temperature Toughness Linepipe Steels

2007 ◽  
Author(s):  
Seong Soo Ahn ◽  
Woo Yeon Cho ◽  
Tae-Yang Yoon ◽  
Jang-Yong Yoo
Keyword(s):  
Mechanical Properties ◽  
Transition Temperature ◽  
Low Temperature ◽  
Axial Compression ◽  
Large Scale ◽  
Steel Plate ◽  
Compressive Strain ◽  
Compression Force ◽  
X80 Steel ◽  
Low Temperature Toughness

API-X70 and X80 steel with good low temperature toughness were developed. The microstructure and mechanical properties of API-X70 steel plate and pipe were investigated and the buckling behavior of X80 steel pipe was evaluated through large scale deformation tester. API-X70 steels with 30 mm thickness were manufactured by finished rolling below Ar3. The microstructure was composed of polygonal ferrite with subgrain network, degenerated pearlite and bainite. The yield strengths of API-X70 pipes were lower than those of plates, while the tensile strengths were similar in both states. The Charpy upper shelf energy of API-X70 steel plate was about 350 J and the energy transition temperature was below −100 °C. The separations were observed on the DWTT fracture surface of API-X70 steel plate. The DWTT 85 SA% transition temperature of plate was below −30 °C. It was conjectured that the separation associated with the low temperature rolling might increase the strength without deterioration of DWTT properties. API-X80 steels with 19mm thickness were fabricated with finished rolling above Ar3 and pipes with 30” diameter were made with R/B process. The deformation capacity of X80 linepipe was evaluated by large scale deforming machine operating under the loading of bending and axial compression force. It was showed that 2nd moment term should be calculated more correctly to measure the accurate critical compressive strain of pipe in the loading of bending and axial compression force. The compressive axial force had a little effect on the peak moment but changed the deformation pattern and state of critical compressive strain of linepipe. It was found that X80 linepipe used in this study was within the specification of DNV and API codes in terms of buckling capacity.

scholarly journals Production and Characterization of Large-Scale Recycled Newspaper Enhanced HDPE Composite Laminates

Polymers ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 851 ◽  
Author(s):  
Binwei Zheng ◽  
Litao Guan ◽  
Weiwei Zhang ◽  
Jin Gu ◽  
Dengyun Tu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Composite Laminates ◽  
Large Scale ◽  
Stress Transfer ◽  
Laminated Composite ◽  
Physical And Mechanical Properties ◽  
Longitudinal Direction ◽  
Industrial Applications ◽  
Splicing Pattern

Recycled newspaper (NP)/high density polyethylene (HDPE) laminated composite can reach the physical and mechanical criteria for most industrial applications, which shows the potential of using solid-state waste paper in engineering materials. Herein, the effects of splicing pattern and size on the physical and mechanical properties of the laminated composite were investigated with the ultimate purpose to fabricate a large-scaleale composite. The laminated composite with a stair-like splicing had better physical and mechanical properties than that with a vertical splicing. An efficient stress transfer could be guaranteed when the distance between the two adjacent junctions were greater than a critical proportion of 1/32 of the length at longitudinal direction. The tensile and flexural properties of the large-scaleale composite with a stair-like splicing, which was fabricated at the splicing ratio of 1/32, were 109 ± 4.2 MPa (MOR), 9836 ± 411 MPa (MOE), 119 ± 7.1 MPa (MOR) and 10002 MPa ± 347 (MOE).

Control of humping phenomenon and analyzing mechanical properties of Al–Si wire-arc additive manufacturing fabricated samples using cold metal transfer process

2021 ◽  
pp. 095440622199840
Author(s):  
Yashwant Koli ◽  
N Yuvaraj ◽  
Aravindan Sivanandam ◽  
Vipin
Keyword(s):  
Mechanical Properties ◽  
Additive Manufacturing ◽  
Heat Input ◽  
Large Scale ◽  
High Deposition Rate ◽  
Bead Geometry ◽  
Layer By Layer ◽  
Cold Metal Transfer ◽  
Geometrical Shapes ◽  
Wire Arc Additive Manufacturing

Nowadays, rapid prototyping is an emerging trend that is followed by industries and auto sector on a large scale which produces intricate geometrical shapes for industrial applications. The wire arc additive manufacturing (WAAM) technique produces large scale industrial products which having intricate geometrical shapes, which is fabricated by layer by layer metal deposition. In this paper, the CMT technique is used to fabricate single-walled WAAM samples. CMT has a high deposition rate, lower thermal heat input and high cladding efficiency characteristics. Humping is a common defect encountered in the WAAM method which not only deteriorates the bead geometry/weld aesthetics but also limits the positional capability in the process. Humping defect also plays a vital role in the reduction of hardness and tensile strength of the fabricated WAAM sample. The humping defect can be controlled by using low heat input parameters which ultimately improves the mechanical properties of WAAM samples. Two types of path planning directions namely uni-directional and bi-directional are adopted in this paper. Results show that the optimum WAAM sample can be achieved by adopting a bi-directional strategy and operating with lower heat input process parameters. This avoids both material wastage and humping defect of the fabricated samples.

scholarly journals Constitutive Modeling of the Densification Behavior in Open-Porous Cellular Solids

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2731
Author(s):  
Ameya Rege
Keyword(s):  
Constitutive Model ◽  
Cell Walls ◽  
Compressive Strain ◽  
Pore Collapse ◽  
Compressive Response ◽  
Linear Elastic ◽  
Nonlinear Springs ◽  
Different Types ◽  
Point Of Intersection ◽  
Good Agreement

The macroscopic mechanical behavior of open-porous cellular materials is dictated by the geometric and material properties of their microscopic cell walls. The overall compressive response of such materials is divided into three regimes, namely, the linear elastic, plateau and densification. In this paper, a constitutive model is presented, which captures not only the linear elastic regime and the subsequent pore-collapse, but is also shown to be capable of capturing the hardening upon the densification of the network. Here, the network is considered to be made up of idealized square-shaped cells, whose cell walls undergo bending and buckling under compression. Depending on the choice of damage criterion, viz. elastic buckling or irreversible bending, the cell walls collapse. These collapsed cells are then assumed to behave as nonlinear springs, acting as a foundation to the elastic network of active open cells. To this end, the network is decomposed into an active network and a collapsed one. The compressive strain at the onset of densification is then shown to be quantified by the point of intersection of the two network stress-strain curves. A parameter sensitivity analysis is presented to demonstrate the range of different material characteristics that the model is capable of capturing. The proposed constitutive model is further validated against two different types of nanoporous materials and shows good agreement.

scholarly journals Influence of Different Percentages of Binders on the Physico-Mechanical Properties of Rhizophora spp. Particleboard as Natural-Based Tissue-Equivalent Phantom for Radiation Dosimetry Applications

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1868
Author(s):  
Siti Hajar Zuber ◽  
Nurul Ab. Aziz Hashikin ◽  
Mohd Fahmi Mohd Yusof ◽  
Mohd Zahri Abdul Aziz ◽  
Rokiah Hashim
Keyword(s):  
Mechanical Properties ◽  
Radiation Dosimetry ◽  
Structural Integrity ◽  
Soy Flour ◽  
Lower Percentage ◽  
Internal Bonding ◽  
X Ray ◽  
Tissue Equivalent ◽  
Tissue Equivalent Phantom ◽  
Edx Analyses

Rhizophora spp. particleboard with the incorporation of lignin and soy flour as binders were fabricated and the influence of different percentages of lignin and soy flour (0%, 6% and 12%) on the physico-mechanical properties of the particleboard were studied. The samples were characterised by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray fluorescence (XRF) and internal bonding. The results stipulated that the addition of binders in the fabrication of the particleboard did not change the functional groups according to the FTIR spectrum. For XRD, addition of binders did not reveal any major transformation within the composites. SEM and EDX analyses for all percentages of binders added showed no apparent disparity; however, it is important to note that the incorporation of binders allows better bonding between the molecules. In XRF analysis, lower percentage of chlorine in the adhesive-bonded samples may be advantageous in maintaining the natural properties of the particleboard. In internal bonding, increased internal bond strength in samples with binders may indicate better structural integrity and physico-mechanical strength. In conclusion, the incorporation of lignin and soy flour as binders may potentially strengthen and fortify the particleboard, thus, can be a reliable phantom in radiation dosimetry applications.

scholarly journals Study of biaxial mechanical properties of the passive pig heart: material characterisation and categorisation of regional differences

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Fulufhelo Nemavhola
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Computational Models ◽  
Heart Diseases ◽  
Interventricular Septum ◽  
Model Material ◽  
Biaxial Test ◽  
Material Behaviour ◽  
Material Parameters ◽  
Biaxial Tests

AbstractRegional mechanics of the heart is vital in the development of accurate computational models for the pursuit of relevant therapies. Challenges related to heart dysfunctioning are the most important sources of mortality in the world. For example, myocardial infarction (MI) is the foremost killer in sub-Saharan African countries. Mechanical characterisation plays an important role in achieving accurate material behaviour. Material behaviour and constitutive modelling are essential for accurate development of computational models. The biaxial test data was utilised to generated Fung constitutive model material parameters of specific region of the pig myocardium. Also, Choi-Vito constitutive model material parameters were also determined in various myocardia regions. In most cases previously, the mechanical properties of the heart myocardium were assumed to be homogeneous. Most of the computational models developed have assumed that the all three heart regions exhibit similar mechanical properties. Hence, the main objective of this paper is to determine the mechanical material properties of healthy porcine myocardium in three regions, namely left ventricle (LV), mid-wall/interventricular septum (MDW) and right ventricle (RV). The biomechanical properties of the pig heart RV, LV and MDW were characterised using biaxial testing. The biaxial tests show the pig heart myocardium behaves non-linearly, heterogeneously and anisotropically. In this study, it was shown that RV, LV and MDW may exhibit slightly different mechanical properties. Material parameters of two selected constitutive models here may be helpful in regional tissue mechanics, especially for the understanding of various heart diseases and development of new therapies.

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