scholarly journals Mechanical Behavior of Fresh and Tempered Martensite in a CrMoV-Alloyed Steel Explained by Microstructural Evolution and Strength Modeling

2020 ◽  
Vol 51 (10) ◽  
pp. 5077-5087
Author(s):  
Tao Zhou ◽  
Jun Lu ◽  
Peter Hedström
Keyword(s):  
Yield Strength ◽  
Mechanical Behavior ◽  
Total Elongation ◽  
Test Results ◽  
Effective Grain Size ◽  
Fresh Martensite ◽  
The Individual ◽  
Strength Modeling ◽  
Strength And Ductility ◽  
Good Agreement

Abstract The mechanical behavior of a wear-resistant CrMoV-alloyed martensitic steel in quenched and tempered conditions has been investigated and correlated with the microstructure. The steel has a combination of ultra-high tensile strength of 2065 MPa and total elongation of 7.4 pct in the as-quenched condition. The strength and ductility of the steel change initially during tempering and thereafter remain quite stable during tempering at either 450 °C or 550 °C. A good combination of yield strength and total elongation is achieved after tempering at 550 °C for 2 to 8 hours (about 1300 MPa and 14 pct). The evolution of the mechanical properties can be mainly related to an initial condition with high density of dislocations (in the order of 1015) and carbon in solid solution, while quite early during tempering, dislocations will start to annihilate and carbide precipitates form. On the other hand, there is a negligible evolution of the effective grain size during tempering. Modeling of the individual strengthening mechanisms and the overall yield strength is in good agreement with the tensile test results, in particular for the tempered samples. Finally, the relatively low yield strength of the fresh martensite, significantly lower than for the tempered conditions, is discussed in relation to the two available theories.

Paradox of Strength and Ductility in Metals Processed Bysevere Plastic Deformation

2002 ◽  
Vol 17 (1) ◽  
pp. 5-8 ◽  
Author(s):  
R. Z. Valiev ◽  
I. V. Alexandrov ◽  
Y. T. Zhu ◽  
T. C. Lowe
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Grain Size ◽  
Yield Strength ◽  
Mechanical Behavior ◽  
High Strength ◽  
High Ductility ◽  
Elongation To Failure ◽  
Failure Ductility ◽  
Strength And Ductility

It is well known that plastic deformation induced by conventional forming methodssuch as rolling, drawing or extrusion can significantly increase the strength of metalsHowever, this increase is usually accompanied by a loss of ductility. For example, Fig.1 shows that with increasing plastic deformation, the yield strength of Cu and Almonotonically increases while their elongation to failure (ductility) decreases. Thesame trend is also true for other metals and alloys. Here we report an extraordinarycombination of high strength and high ductility produced in metals subject to severeplastic deformation (SPD). We believe that this unusual mechanical behavior is causedby the unique nanostructures generated by SPD processing. The combination ofultrafine grain size and high-density dislocations appears to enable deformation by newmechanisms. This work demonstrates the possibility of tailoring the microstructures ofmetals and alloys by SPD to obtain both high strength and high ductility. Materialswith such desirable mechanical properties are very attractive for advanced structuralapplications.

An Experiment on Bond-Anchoring Property of Prestressing Spiral Groove Tendon

2011 ◽  
Vol 105-107 ◽  
pp. 1685-1688
Author(s):  
Meng Chen ◽  
Pin Wu Guan
Keyword(s):  
Yield Strength ◽  
Failure Modes ◽  
Concrete Strength ◽  
Concrete Cover ◽  
Tensile Yield Strength ◽  
Test Results ◽  
Statistical Regression ◽  
Spiral Groove ◽  
Anchoring Strength ◽  
Good Agreement

Prestressing spiral groove tendon is a new sort prestressing tendon, its characteristic value of tensile yield strength fyk=1000MPa. Firstly, the yield strength, ultimate tensile strength, elastic modulus and elongation are all tested. According to 68 pullout tests, the bond-anchoring curves and failure modes have been studied, and the effects of concrete strength, diameter, anchoring length, thickness of concrete cover and stirrup ratio have been all analyzed. Finally, the equation for ultimate bond-anchoring strength has been suggested by statistical regression, and the test results are in good agreement with values of the suggested equation.

Experimental Study of Mechanical Behavior of Concrete Filled Steel Tubular Short Columns after Fire

2010 ◽  
Vol 168-170 ◽  
pp. 674-678 ◽  
Author(s):  
Ming Zhou ◽  
Xin Tang Wang ◽  
Wan Zhen Wang
Keyword(s):  
Mechanical Behavior ◽  
Bearing Capacity ◽  
Test Results ◽  
Fire Load ◽  
Ordinary Concrete ◽  
Short Column ◽  
Short Columns ◽  
Maximum Value ◽  
Bearing Load ◽  
Strength And Ductility

Mechanical behavior and bearing capacity of ordinary concrete filled steel tubular short column (NCSSC) and ceramsite concrete filled steel tubular short column (CCSSC) subjected to fire load are experimentally investigated. Effect of the parameters, such as the maximum value of fire temperatures, fire duration on the strength and ductility of the two types of specimens were especially discussed. The test results show that both of the specimens of NCSSC and CCSSC after fire have higher bearing capacity and better ductility, there was no descent segment in load-displacement curves of the most specimens after the fire load was subjected, and even the case that bearing load increased again after descent segment arose. It was concluded that the maximum response temperature of specimens and fire duration time has great effect on the axial bearing capacity of concrete-filled steel tubular short columns subjected to fire, and there is a turning point of temperature for the influence.

Experimental Study of Mechanical Behavior of Ceramsite Concrete Filled Steel Tubular Columns Subjected to Fire Load

2011 ◽  
Vol 243-249 ◽  
pp. 1228-1232
Author(s):  
Xin Tang Wang ◽  
Zhi Guo Xie ◽  
Ming Zhou ◽  
Jie Yin
Keyword(s):  
Mechanical Behavior ◽  
Bearing Capacity ◽  
Longitudinal Strain ◽  
Test Results ◽  
Fire Load ◽  
Short Column ◽  
Tubular Columns ◽  
Short Columns ◽  
Maximum Value ◽  
Strength And Ductility

Mechanical behavior of a set of ordinary concrete filled steel tubular short column (note as NCSSC) and ceramsite concrete filled steel tubular short column (note as CCSSC) subjected to fire load are experimentally investigated. Effect of the parameters, such as the maximum value of fire temperatures, fire duration on the strength and ductility of the two types of specimens were especially discussed. The test results show that both of the specimens of NCSSC and CCSSC have higher post-fire bearing capacity and better ductility, there was no descent segment in post-fire load-displacement curves of the most specimens subjected to fire load. It was concluded that the maximum response temperature of specimens and fire duration time has great effect on the axial bearing capacity of concrete-filled steel tubular short columns subjected to fire. The maximum longitudinal strain of specimens of CCSSC is less than the corresponding value of the longitudinal strain of NCSSC.

Optimum Dosage of Deformed Steel Fibres in Fibrous Concrete Beams under Predominant Shear

2013 ◽  
Vol 651 ◽  
pp. 18-23
Author(s):  
Constantin E. Chalioris
Keyword(s):  
Concrete Beams ◽  
Volume Fraction ◽  
Analysis Tool ◽  
Test Results ◽  
Steel Fibres ◽  
Flexural Response ◽  
Design Charts ◽  
Fibrous Concrete ◽  
Strength And Ductility ◽  
Good Agreement

This study presents an analytical approach to evaluate an optimum content of deformed steel fibres in shear-dominated fibrous concrete beams in order strength and ductility requirements to be satisfied. The proposed methodology is based on the calculations of the flexural and shear capacities and to the concept that a pure flexural response should be achieved. The goal of this method is to evaluate the minimum required value of the fibre factor, F, which expresses the effect of the volume fraction and the geometrical characteristics of the used steel fibres. The calculation of F is achieved using a cubic formula derived from the described procedure. Fibres can be used either as the only shear reinforcement or in combination with stirrups. Test results from 47 beams of the literature are used to verify and to illustrate the application of the proposed approach. Comparisons between experimental and predicted results showed a very good agreement. Design charts have also been plotted by the implementation of this methodology as an analysis tool.

Link between Microstructure and Mechanical Behavior of Double Annealed Medium Mn Steel

2018 ◽  
Vol 941 ◽  
pp. 524-529
Author(s):  
Artem Arlazarov ◽  
Mohamed Goune ◽  
Alain Hazotte ◽  
Olivier Bouaziz ◽  
Frédéric Kegel
Keyword(s):  
Mechanical Behavior ◽  
Intercritical Annealing ◽  
Holding Time ◽  
Low Carbon ◽  
Complete Model ◽  
Microstructural Constituent ◽  
Medium Mn Steel ◽  
The Individual ◽  
Mn Steel ◽  
Good Agreement

Double annealing of low carbon medium Mn steel was studied. The second intercritical annealing was done at 650°C within a range of holding time: 3min to 30h. Tensile properties of the steel were measured as a function of holding time and the relation between microstructure and mechanical behavior was analyzed. Furthermore, a model, based on the mixture law combined with the considerations of equivalent increment of work in each microstructural constituent during mechanical loading, was proposed. The individual mechanical behavior of each considered microstructural constituent was described with the approaches existing in the literature. The complete model shows a very good agreement with the experimental stress-strain curves and predicts well the optimum strength-ductility balance after 2h holding.

Mechanical Strength Modeling of Particle Strengthened Nickel-Aluminum Alloys Strengthened by Intermetallic γ′ (Ni3Al) Precipitates

1999 ◽  
Author(s):  
James M. Fragomeni
Keyword(s):  
Yield Strength ◽  
Misfit Strain ◽  
Nickel Aluminum ◽  
Solid Solution Strengthening ◽  
Peak Aged Condition ◽  
Peak Aged ◽  
Solution Strengthening ◽  
Particle Strengthening ◽  
Strength Modeling ◽  
Good Agreement

Abstract A Nickel-Aluminum alloy strengthened by γ′ (Ni3Al) intermetallic ordered coherent precipitates with a small misfit strain was used a demonstration material to develop a model to predict strengthening behavior during plastic deformation as a consequence of the γ′ particles acting as obstacles to the dislocations and thus impeding their glide motion through the alloy. It was determined that the two most dominate strengthening mechanisms in the Ni-Al system were order hardening when the particles were smaller than the critical looping radius, and Orowan strengthening when the particles were larger than the looping radius. In the overaged condition when the particles are large in size, the dislocations bypass and loop the particles by the Orowan mechanism. In the underaged to peak aged conditions where the particles are usually smaller than the looping radius, the dislocations shear the precipitates during deformation. The total polycrystalline yield strength included contributions from the intrinsic lattice strength, the solid solution strengthening, grain size strengthening, and particle strengthening which included the order hardening and Orowan strengthening contributions. The total mechanical yield strength for a Ni-6.27wt.%A1 alloy was predicted for the peak-aged condition based on the theory for order strengthening and was found to be in good agreement with the experimental peak-strength data for Ni-6.27A1.

scholarly journals Children’s Astronomy. Development of the Shape of the Earth Concept in Polish Children between 5 and 10 Years of Age

2021 ◽  
Vol 11 (2) ◽  
pp. 75
Author(s):  
Jan Amos Jelinek
Keyword(s):  
Mental Model ◽  
Cultural Influences ◽  
Test Results ◽  
The Earth ◽  
Spherical Earth ◽  
The Individual ◽  
High Level ◽  
Cognitive Problems ◽  
Teaching Situations ◽  
Model Approach

The Earth’s shape concept develops as consecutive cognitive problems (e.g., the location of people and trees on the spherical Earth) are gradually resolved. Establishing the order of problem solving may be important for the organisation of teaching situations. This study attempted to determine the sequence of problems to be resolved based on tasks included in the EARTH2 test. The study covered a group of 444 children between 5 and 10 years of age. It captured the order in which children solve cognitive problems on the way to constructing a science-like concept. The test results were compared with previous studies. The importance of cultural influences connected to significant differences (24%) in test results was emphasised. Attention was drawn to the problem of the consistency of the mental model approach highlighted in the literature. The analysis of the individual sets of answers provided a high level of consistency of indications referring to the same model (36%), emphasising the importance of the concept of mental models.

scholarly journals Spine Examination during COVID-19 Pandemic via Video Consultation

2021 ◽  
Author(s):  
Tom Jansen ◽  
Martin Gathen ◽  
Amadeo Touet ◽  
Hans Goost ◽  
Dieter Christian Wirtz ◽  
...  
Keyword(s):  
Pain Intensity ◽  
Range Of Motion ◽  
Test Results ◽  
Risk Of Infection ◽  
Face To Face ◽  
Reliable Tool ◽  
Provocation Tests ◽  
Active Range Of Motion ◽  
Video Consultation ◽  
Good Agreement

Abstract Introduction During the current COVID-19 pandemic video consultations are increasingly common in order to minimize the risk of infection for staff and patients. The aim of this study was to evaluate the feasibility of a spine examination via video. Methods A total of 43 patients were recruited. Each participant underwent a video-based (VB) and a conventional face-to-face (FTF) spine examination. Pain intensity, active range of motion, inspection, a neurophysiologic basic exam and provocations tests were evaluated using video-based and face-to-face methods. Results The intra-rater reliability (IRR) was measured between both examinations. Good to very good IRR values were obtained in inspection (Kappa between 0,752 und 0,944), active range of motion and basic neurophysiological examination (Kappa between 0,659 und 0,969). Only moderate matches were found in specific provocation tests (Kappa between 0,407 und 0,938). A video-based spine examination is a reliable tool for measuring pain intensity, active range of motion and a basic neurophysiologic exam. Conclusion A basic spine examination during a video consultation is possible. A good agreement of the test results between video-based and face-to-face examination could be found.

Design of combined brake system for light weight scooters

2021 ◽  
pp. 095440702110240
Author(s):  
Yuan-Ting Lin ◽  
Chyuan-Yow Tseng ◽  
Jao-Hwa Kuang ◽  
Yeong-Maw Hwang
Keyword(s):  
Ride Comfort ◽  
Brake System ◽  
Force Distribution ◽  
Test Results ◽  
Systematic Method ◽  
Braking Performance ◽  
Evaluation Indexes ◽  
Low Costs ◽  
Braking Force ◽  
Good Agreement

The combined brake system (CBS) is a mechanism that links the front and rear brakes for scooters. For two-wheeled scooters, a CBS with appropriate braking force distribution can reduce the risk of crashing accidents due to insufficient driving proficiency. The design of the braking force distribution for a CBS is challenging to the designer because it has to fulfill many requirements such as braking performance, ride comfort, reliability, and low costs. This paper proposes a systematic method to optimize the parameters of CBS. The evaluation indexes for the design are first discussed. The steps to determine the critical parameter to meet the indexes and a method to predict braking performance are developed. Finally, driving tests are carried out to verify the effectiveness of the proposed method. Experimental results showed that the deceleration of the tested scooter equipped with the designed CBS achieves an average mean fully developed deceleration (MFDD) of 5.246 m/s2, higher than the homologation requirement. Furthermore, the proposed method’s prediction of braking performance is in good agreement with the test results, with errors <1%.

Sign in / Sign up

Export Citation Format

Share Document