A novel method to determine critical CTOA directly by load-displacement curve

2020 ◽  
Vol 230 ◽  
pp. 107013
Author(s):  
Ying Zhen ◽  
Xuyang Li ◽  
Yuguang Cao ◽  
Shihua Zhang
Keyword(s):  
Displacement Curve ◽  
Novel Method ◽  
Load Displacement

scholarly journals Study on the Strength Performance of Recycled Aggregate Concrete with Different Ages under Direct Shearing

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2312
Author(s):  
Xin Liang ◽  
Fang Yan ◽  
Yuliang Chen ◽  
Huiqin Wu ◽  
Peihuan Ye ◽  
...  
Keyword(s):  
Shear Strength ◽  
Shear Force ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Displacement Curve ◽  
Direct Shear ◽  
Replacement Ratio ◽  
Aggregate Concrete ◽  
Concrete Failure ◽  
Load Displacement

In order to study the mechanical properties of recycled aggregate concrete (RAC) at different ages, 264 standard cubes were designed to test its direct shear strength and cube compressive strength while considering the parameters of age and recycled aggregate replacement ratio. The failure pattern and load–displacement curve of specimens at direct shearing were obtained; the direct shear strength and residual shear strength were extracted from the load–displacement curves. Experimental results indicate that the influence of the replacement ratio for the front and side cracks of RAC is insignificant, with the former being straight and the latter relatively convoluted. At the age of three days, the damaged interface between aggregate and mortar is almost completely responsible for concrete failure; in addition to the damage of coarse aggregates, aggregate failure is also an important factor in concrete failure at other ages. The load–displacement curve of RAC at direct shearing can be divided into elasticity, elastoplasticity, plasticity, and stabilization stages. The brittleness of concrete decreases with its age, which is reflected in the gradual shortening of the elastoplastic stage. At 28 days of age, the peak direct shear force increases with the replacement ratio, while the trend is opposite at ages of 3 days, 7 days, and 14 days, respectively. The residual strength of RAC decreases inversely to the replacement ratio, with the rate of decline growing over time. A two-parameter RAC direct shear strength calculation formula was established based on the analysis of age and replacement rate to peak shear force of RAC. The relationship between cube compressive strength and direct shear strength of recycled concrete at various ages was investigated.

Research on the Relationship between Indenter Tip Radius and Hardness with a Self-Designed Nanohardness Test Device

2008 ◽  
Vol 392-394 ◽  
pp. 267-270
Author(s):  
Qiang Liu ◽  
Ying Xue Yao ◽  
L. Zhou
Keyword(s):  
Single Crystal ◽  
Indentation Depth ◽  
Single Crystal Silicon ◽  
Indentation Hardness ◽  
Displacement Curve ◽  
Test Device ◽  
Crystal Silicon ◽  
Load Displacement ◽  
Depth Sensitivity ◽  
Tip Radius

Nanoindentation device has the ability to make the load-displacement measurement with sub-nanometer indentation depth sensitivity, and the nanohardness of the material can be achieved by the load-displacement curve. Aiming at the influence law of indenter tip radius to indentation hardness, testing on the hardness of single-crystal silicon were carried out with the new self-designed nanohardness test device based on nanoindentation technique. Two kinds of Berkovich indenter with radius 40nm and 60nm separately were used in this experiment. According to the load-depth curve, the hardness of single-crystal silicon was achieved by Oliver-Pharr method. Experimental results are presented which show that indenter tip radius do influence the hardness, the hardness value increases and the indentation size effect (ISE) becomes obvious with the increasing of tip radius under same indentation depth.

scholarly journals Analysis of Bearing Strength of Post-Tensioning Anchorage Zone with Respect to Relative Bearing Area and Lateral Confinement Design

2021 ◽  
Vol 11 (18) ◽  
pp. 8386
Author(s):  
Jin-Kook Kim ◽  
Jun-Mo Yang
Keyword(s):  
Error Rate ◽  
Small Diameter ◽  
Average Error ◽  
Displacement Curve ◽  
Proportional Limit ◽  
Lateral Confinement ◽  
Bearing Strength ◽  
Bearing Plate ◽  
Load Displacement ◽  
Post Tensioning

This study aimed to evaluate the bearing strength of the post-tensioning anchorage zone with respect to the relative bearing area and lateral confinement design of spiral and stirrup rebars. Eleven specimens were fabricated and tested to fracture in accordance with EAD 160004-00-0301. Load-displacement curves and fracture modes were analyzed. Then, the conventional design equation for the bearing strength and previous findings on the relative bearing area was re-investigated in comparison with the test results. From the test, the representative findings are as follows: (1) A specimen with relatively small size and less lateral reinforcement is more likely to be affected by the wedge action of the anchorage device; however, a larger specimen is affected by both concrete crushing and/or spalling; (2) The behavior of the anchorage zone is markedly affected by the local behavior near the anchorage bearing plate, and the sectional efficiency is mostly determined by A/Ag; (3) For specimens with A/Ag = 9.52, the proportional limit of the load-displacement curve is determined by the yield of spiral rebar or fracture of the bearing plate, but the later part of the curve is determined by lateral confinement; (4) The maximum A/Ag that could produce 100% sectional efficiency is about 2.0 for the anchorage bearing plate used in the test; (5) For a fully confined specimen with a small-diameter spiral for minimum anchorage spacing, the stirrup rebar design mainly influences crack occurrence and patterns when the size of the specimen is equal to the minimum anchorage spacing; however, the area of the load-displacement curve after the proportional limit as well as crack occurrence and patterns are also influenced by stirrup rebar design when A/Ag is relatively large; (6) Finally, a revised design model is proposed to effectively estimate the ultimate bearing strength of the post-tensioning anchorage zone without respect to A/Ag. From the comparison of the design equations, it was concluded that the proposed equation provides a more reliable prediction with a 14.0% average error rate and 5.7% standard deviation of error rate.

Estimation of transverse tensile behavior of Zircaloy pressure tubes using ring-tensile test and finite element analysis

2012 ◽  
Vol 227 (6) ◽  
pp. 1177-1186 ◽  
Author(s):  
MK Samal ◽  
KS Balakrishnan ◽  
J Parashar ◽  
GP Tiwari ◽  
S Anantharaman
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Tensile Tests ◽  
Tensile Specimen ◽  
Displacement Curve ◽  
Stress Strain ◽  
Element Analysis ◽  
Transverse Tensile ◽  
Pressure Tubes ◽  
Load Displacement

Determination of transverse mechanical properties from the ring type of specimens directly machined from the nuclear reactor pressure tubes is not straightforward. It is due to the presence of combined membrane as well as bending stresses arising in the loaded condition because of the curvature of the specimen. These tubes are manufactured through a complicated process of pilgering and heat treatment and hence, the transverse properties need to be determined in the as-manufactured condition. It may not also be possible to machine small miniaturized specimen in the circumferential direction especially in the irradiated condition. In this work, we have performed ring-tensile tests on the un-irradiated ring tensile specimen using two split semi-cylindrical mandrels as the loading device. A three-dimensional finite element analysis was performed in order to determine the material true stress–strain curve by comparing experimental load–displacement data with those predicted by finite element analysis. In order to validate the methodology, miniaturized tensile specimens were machined from these tubes and tested. It was observed that the stress–strain data as obtained from ring tensile specimen could describe the load–displacement curve of the miniaturized flat tensile specimen very well. However, it was noted that the engineering stress–strain as directly obtained from the experimental load–displacement curves of the ring tensile tests were very different from that of the miniaturized specimen. This important aspect has been resolved in this work through the use of an innovative type of 3-piece loading mandrel.

scholarly journals Canine Vertebral Screw and Rod Fixation System: Design and Mechanical Testing

2018 ◽  
Vol 31 (02) ◽  
pp. 095-101 ◽  
Author(s):  
Nirut Suwanna ◽  
Björn Meij ◽  
Pakthorn Lewchalermwong
Keyword(s):  
Ultimate Load ◽  
Rapid Prototype ◽  
Biomechanical Properties ◽  
Bending Stiffness ◽  
Displacement Curve ◽  
Connecting Rod ◽  
Mean Values ◽  
Yield Load ◽  
Load Displacement ◽  
Fixation System

Objectives To develop the canine vertebral screw and rod fixation system (CVSRF) and to compare the biomechanical properties between CVSRF and the screw and polymethylmethacrylate (Screw-PMMA) technique for internal fixation of the vertebral column in dogs. Methods The CVSRF consisted of vertebral screws with monoaxial side-loaded head, rods and specific inner screws connecting rod to the screw head. The CVSRF prototype was made from titanium alloy and manufactured by the rapid prototype machine. Vertebrectomy models were simulated by ultra-high-molecular-weight polyethylene blocks and tested with the CVSRF system (n = 8) and the Screw-PMMA technique (n = 8). The models were developed according to the American Society for Testing and Materials (ASTM F-1717–04). The biomechanical parameters were the compressive bending yield load, the compressive bending stiffness, the compressive ultimate load and the load displacement curve. Results The mean values of the compressive bending yield load, compressive bending stiffness and compressive ultimate load of the CVSRF were significantly higher than those of the Screw-PMMA technique (p < 0.01). The load displacement curve of the CVSRF showed higher rigidity and durability than that of the Screw-PMMA technique. Clinical Significance This mechanical study indicated that the CVSRF system can be used for canine vertebral stabilization and the biomechanical properties were better than those for the Screw-PMMA device.

scholarly journals MODELING OF MONOCRYSTALLINE MAGNESIUM MICROBEAM BENDING

2018 ◽  
Vol 15 ◽  
pp. 69-73
Author(s):  
Jiří Němeček ◽  
Jan Maňák ◽  
Jiří Němeček
Keyword(s):  
Focused Ion Beam ◽  
Ion Beam ◽  
Three Dimensional ◽  
Deformation Energy ◽  
Displacement Curve ◽  
Fe Model ◽  
Cantilever Beams ◽  
Elastoplastic Behavior ◽  
Load Displacement ◽  
Micro Cantilever

This paper presents a numerical simulation of a micro-scale experiment on a magnesium alloy. Micro cantilever beams were fabricated using Focused Ion Beam technology in a single crystal of Mg. The cantilever beams have dimensions in the order of a few micrometers and a pentagonal cross section. Nanoindenter was used for cantilever beam bending and load-displacement curve was received. Cantilevers with two different crystallographic orientations were chosen for the experiment. Three dimensional numerical FE model with elastoplastic behavior respecting crystal anisotropy was used to fit experimental load displacement curves. Strengths and deformation energy were evaluated from the models for each cantilever.

Fracture Toughness Characterization of Carbon Bonded Alumina Using Chevron Notched Specimens

2017 ◽  
Vol 754 ◽  
pp. 71-74 ◽  
Author(s):  
H. Zielke ◽  
Martin Abendroth ◽  
Meinhard Kuna
Keyword(s):  
Fracture Toughness ◽  
Ceramic Material ◽  
Bending Test ◽  
Parameter Study ◽  
Zone Model ◽  
Displacement Curve ◽  
Notched Specimens ◽  
Load Displacement ◽  
Set Up

A new generation of multifunctional filters is made of carbon bonded alumina and is investigated within the collaborative research center 920 (CRC920). These filters are used during a casting process with the aim of reducing non-metallic inclusions in the cast product. The high thermal and mechanical loading of the filter requires a fracture mechanical characterization of the investigated ceramic material. In order to determine the fracture toughness of the ceramic material, a chevron-notched beam method (CNB) is applied. A 4-point-bending test set-up was constructed and brought into service, at which the load-displacement curve of small chevron-notched specimens (5 x 6 x 25 mm3) can be measured. The set-up offers the possibility of testing specimens at temperatures up to 1000oC. Preceding numerically work using the finite element method was performed to identify a suitable notch geometry. For this purpose a cohesive zone model was used. A parameter study is presented, which shows the influence of the notch parameter on the load-displacement curve.

Inverse determination of the flow curve in large range of strains for cylindrical tensile specimen

2020 ◽  
Vol 234 (11) ◽  
pp. 2256-2265
Author(s):  
Junfu Chen ◽  
Zhiping Guan ◽  
Changhai Yang
Keyword(s):  
Tensile Test ◽  
Flow Curve ◽  
Inverse Method ◽  
Large Range ◽  
Cylindrical Specimen ◽  
Uniaxial Tensile ◽  
Model Parameters ◽  
Displacement Curve ◽  
Simulation And Optimization ◽  
Load Displacement

In this study, an inverse method with the integration of finite element simulation and optimization algorithms is proposed to determine the flow curve of cylindrical specimen characterized by the modified Voce hardening model. The tensile test is repetitiously simulated with different combinations of model parameters designed through Latin hypercube design method, where the baseline values and variation ranges of model parameters are identified through Leroy–Bridgman method, obtaining different simulated load–displacement curves. The corresponding response is defined as the sum of the absolute area difference between the simulated load–displacement curves and the experimental one. The relationship between the model parameters and the response is established through response surface methodology and the optimal parameters combination in the modified Voce model is then determined through nonlinear programming by quadratic Lagrangian. In the case of uniaxial tensile test of mild steel Q345, the inversely identified flow curve is validated by numerically reproducing the experimental load–displacement curve and necking profile. The results indicate that the proposed inverse method is capable of evaluating the flow curve in large range of strains for cylindrical specimen accurately.

Nanoindentation response of Fe-10%Cr bi-crystal structures with Σ5〈001〉 and Σ3〈110〉 tilt boundaries: An atomistic study

2015 ◽  
Vol 04 (04) ◽  
pp. 1550022
Author(s):  
Ishraq Shabib ◽  
Mohammad Abu-Shams ◽  
Mujibur R. Khan
Keyword(s):  
Dislocation Density ◽  
Plastic Zone ◽  
Crystal Structures ◽  
Contact Area ◽  
Dislocation Motion ◽  
Displacement Curve ◽  
Slip Planes ◽  
Tilt Boundaries ◽  
Load Displacement ◽  
Early Interaction

In this research, nanoindentation responses of Fe-10%Cr bi-crystal structures containing [Formula: see text][Formula: see text] and [Formula: see text][Formula: see text] tilt grain boundaries (GBs) have been investigated using atomistic simulation technique. Deformation analyses identify the nucleation of [Formula: see text], [Formula: see text] and [Formula: see text] types of dislocations within the material. The [Formula: see text] slip planes are found to be more active than the [Formula: see text] and [Formula: see text] slip planes. Load-displacement response and corresponding changes in contact area have been recorded and used to measure material hardness and reduced modulus. The lengths of the nucleated dislocations are measured and used to estimate dislocation density within the plastic zone beneath the indenter. Dislocation motion has been found to be much easier in model with [Formula: see text]3 boundary and the early interaction of the dislocation with the boundary affects the shape of the load-displacement curve, contact area on the indented surface, and the volume of the plastic zone. The hardness of the material has been found to be affected primarily by the interaction of the dislocation with the boundary, rather than by the dislocation density within the plastic zone. Both the boundaries exhibit maximum resistance to slip transmission even at the maximum indentation depth.

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