scholarly journals Mechanical Properties of Steels for Cold-Formed Steel Structures at Elevated Temperatures

2020 ◽  
Vol 2020 ◽  
pp. 1-18
Author(s):  
Zhen Nie ◽  
Yuanqi Li ◽  
Yehua Wang
Keyword(s):  
Mechanical Properties ◽  
Material Properties ◽  
Elevated Temperatures ◽  
Elasticity Modulus ◽  
Mechanical Performance ◽  
Strain Curve ◽  
Steel Structures ◽  
Test Method ◽  
Stress Relieving ◽  
Cold Formed Steel

It is highly important to clarify the high-temperature mechanical properties in the design of cold-formed steel (CFS) structures under fire conditions due to the unique deterioration feature in material properties under fire environment and associated reduction to the mechanical performance of members. This paper presents the mechanical properties of widely used steels for cold-formed steel structures at elevated temperatures. The coupons were extracted from original coils of proposed full annealed steels (S350 and S420, with nominal yielding strengths 280 MPa and 350 MPa) and proposed stress relieving annealed steels (G500, with nominal yielding strength 500 MPa) for CFS structures with thickness of 1.0 mm and 1.2 mm, and a total of nearly 50 tensile tests were carried out by steady-state test method for temperatures ranging from 20 to 700°C. Based on the tests, material properties including the yield strengths, ultimate strengths, the elasticity modulus, and the stress-strain curve were obtained. Meanwhile, the ductility of steels for CFS structures was discussed. Then, the temperature-dependent retention factors of yield strengths and elasticity modulus were compared to those provided by design codes and former researchers. Finally, a set of prediction equations of the mechanical properties for steels for CFS structures at elevated temperatures was proposed depending on existing tests data.

Mechanical Properties and Dislocation Structure of Single Crystal Cdte Deformed in Compression at 300°C

1976 ◽  
Vol 34 ◽  
pp. 592-593
Author(s):  
Ernest L. Hall ◽  
J. B. Vander Sande
Keyword(s):  
Mechanical Properties ◽  
Single Crystal ◽  
Dislocation Structure ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Strain Curve ◽  
Optical Devices ◽  
Semiconductor Compound ◽  
Wide Range ◽  
Sample Orientation

The present paper describes research on the mechanical properties and related dislocation structure of CdTe, a II-VI semiconductor compound with a wide range of uses in electrical and optical devices. At room temperature CdTe exhibits little plasticity and at the same time relatively low strength and hardness. The mechanical behavior of CdTe was examined at elevated temperatures with the goal of understanding plastic flow in this material and eventually improving the room temperature properties. Several samples of single crystal CdTe of identical size and crystallographic orientation were deformed in compression at 300°C to various levels of total strain. A resolved shear stress vs. compressive glide strain curve (Figure la) was derived from the results of the tests and the knowledge of the sample orientation.

Comparison Analysis on the Mechanical Properties of HSC and NSC after the Action of High Temperatures

2014 ◽  
Vol 1014 ◽  
pp. 49-52
Author(s):  
Xiao Ping Su
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
High Temperatures ◽  
High Strength Concrete ◽  
Elasticity Modulus ◽  
Strain Curve ◽  
Peak Stress ◽  
High Strength ◽  
Peak Strain ◽  
Strength Concrete

With the wide application of high strength concrete in the building construction,the risk making concrete subject to high temperatures during a fire is increasing. Comparison tests on the mechanical properties of high strength concrete (HSC) and normal strength concrete (NSC) after the action of high temperature were made in this article, which were compared from the following aspects: the peak stress, the peak strain, elasticity modulus, and stress-strain curve after high temperature. Results show that the laws of the mechanical properties of HSC and NSC changing with the temperature are the same. With the increase of heating temperature, the peak stress and elasticity modulus decreases, while the peak strain grows rapidly. HSC shows greater brittleness and worse fire-resistant performance than NSC, and destroys suddenly. The research and evaluation on the fire-resistant performance of HSC should be strengthened during the structural design and construction on the HSC buildings.

Mechanical Properties Prediction for Cold-formed Steel Angle Connection with Various Flange Cleat Thickness

2015 ◽  
Vol 74 (4) ◽  
Author(s):  
Yeong Huei Lee ◽  
Cher Siang Tan ◽  
Shahrin Mohammad ◽  
Yee Ling Lee
Keyword(s):  
Mechanical Properties ◽  
Numerical Models ◽  
Steel Structures ◽  
Rotational Stiffness ◽  
Steel Angle ◽  
Cold Formed Steel ◽  
Mechanical Properties Prediction ◽  
Thin Walled ◽  
Angle Connection ◽  
Hot Rolled

Connection is an important element in structural steelwork construction. Eurocode does not provide adequate design information for mechanical properties prediction of top-seat flange cleat connection, especially for thin-walled cold-formed steel structures. Adopting hot-rolled design with neglecting thin-walled behaviour could lead to unsafe or uneconomic design. This research aims to provide accurate mechanical properties prediction for bolted top-seat flange cleat connection in cold-formed steel structures. The scope of work focuses on the effect of various thickness of the flange cleat to the rotational stiffness and strength behaviour of a beam-to-column connection. Experimentally verified and validated finite element modelling technique is applied in the parametric investigation. Two categories of flange cleat thickness, ranged from 2 mm to 40 mm are studied. From the developed numerical models, it is observed that Eurocode has overestimated the initial rotational stiffness prediction, calculated with component method. The over-estimation would influence the overall stiffness of structures and force distribution within the components. As a conclusion, a set of newly proposed accurate predictions for initial rotational stiffness and strength of cold-formed steel top-seat flange cleat connection, with the influence of the thickness of flange cleat is presented.

scholarly journals Damage Constitutive Model and Mechanical Performance Deterioration of Concrete under Sulfate Environment

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Peng Liu ◽  
Ying Chen ◽  
Zhiwu Yu ◽  
Zhaohui Lu
Keyword(s):  
Mechanical Properties ◽  
Bearing Capacity ◽  
Elasticity Modulus ◽  
Mechanical Performance ◽  
Sulfate Solution ◽  
Concrete Surface ◽  
Ultimate Bearing Capacity ◽  
Stress Strain ◽  
Before And After ◽  
Relationship Model

The effects of erosion mode, erosion age, and concentration of sulfate solution on mechanical properties of concrete were investigated. The dimensionless relationship model of the stress-strain of concrete on the basis of randomness was proposed. The variation of the elasticity modulus and Poisson’s ratio of the concrete surface attacked by sulfate was studied, and a novel method of using a superficial parameter to characterize the performance change of the concrete surface was recommended. The results showed that the dimensionless relationship model of stress-strain of concrete could be used to represent the variations of mechanical properties of concrete. The differences of load-displacement of concrete before and after sulfate attack were reflected as the change of curve’s slope and ultimate bearing capacity, and the slope of a straight section of the lateral and longitudinal strain curves of concrete surface also varied. The increment rates of ultimate bearing capacity of concrete attacked by 1% and saturated sulfate solution were about 30% and 10%, respectively. However, the decreasing ratio of the ultimate bearing capacity of concrete attacked by saturated sulfate solution was approximately 25%. The damage factor of the elasticity modulus of the concrete surface of C20 and C40 was 0.185 and −0.19, respectively. The obtained results could provide a support for investigating the variations of stress-strain relationship and mechanical performance of concrete under a sulfate environment.

scholarly journals Additive Manufacturing and Mechanical Performance of Trifurcated Steel Joints for Architecturally Exposed Steel Structures

Materials ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1901
Author(s):  
Pengfei He ◽  
Wenfeng Du ◽  
Longxuan Wang ◽  
Ravi Kiran ◽  
Mijia Yang
Keyword(s):  
Finite Element ◽  
Additive Manufacturing ◽  
Process Parameters ◽  
Mechanical Performance ◽  
Steel Structures ◽  
Mechanical Tests ◽  
Test Method ◽  
Finite Element Analyses ◽  
Steel Joint ◽  
Steel Joints

Additive Manufacturing (AM) technology has unique advantages in producing complex joints in architecturally exposed steel structures. This article focuses on the process of manufacturing and investigating the mechanical properties of a reduced scale model of a trifurcated joint using Selective Laser Melting (SLM) method and mechanical tests, respectively. The orthogonal test method was used to optimize the main AM process parameters. Then the trifurcated steel joint was printed using the optimal process parameters and treated by solid solution and aging treatment. To investigate the mechanical performance of the printed joint, an axial compression test and complimentary finite element analyses were carried out. Failure processes and failure mechanisms of the trifurcated steel joint were discussed in detail. The research results show that the preferred process parameters for printing 316L stainless steel powder are: scanning power 150 W, scanning speed 700 mm/s, and scanning pitch 0.09 mm. Using these AM parameters, trifurcated steel joints with good surface quality, geometrical accuracy and tensile strength are obtained after heat treatment. Our mechanical tests and Finite element analyses results indicate that the failure mechanism in the AM trifurcated joint are similar to those of cast steel joints. Based on these results, we conclude that the AM technology serves as a promising new way for the fabrication of joints with complex geometries.

Evaluation of Mechanical Properties of Regenerated Bone by Nanoindentation Technique

2010 ◽  
Vol 654-656 ◽  
pp. 2220-2224 ◽  
Author(s):  
Takuya Ishimoto ◽  
Takayoshi Nakano
Keyword(s):  
Mechanical Properties ◽  
Young’S Modulus ◽  
Bone Tissue ◽  
Material Properties ◽  
Mechanical Performance ◽  
Young's Modulus ◽  
Mechanical Tests ◽  
Long Bone ◽  
Nanoindentation Technique ◽  
Intact Bone

To evaluate the material parameters of regenerated bone, it is important to clarify the mechanical performance of the regenerated portion. In general, the shape and size of regenerated bone tissue is heterogeneous. It is often difficult to elucidate material properties by means of conventional mechanical tests such as compressive and/or tensile tests and bending tests. The nanoindentation technique has been utilized to evaluate the material properties of small or microstructured materials because they do not necessarily require a large well-designed specimen. Thus, this technique may be useful for the evaluation of the material properties of regenerated bone tissue. In this study, this technique was applied for the assessment of the Young’s modulus and hardness of regenerated and intact long bones of a rabbit. The regenerated bone exhibited a significantly lower Young’s modulus and hardness than the intact bone. The regenerated long bone also exhibited impaired mechanical properties, which may have been caused by the difference in the nano-organization of its collagen fibers and mineral crystals (the main components of bone tissue), from that of the intact bone.

Assessment of Mechanical Properties of Cold Formed Steel Material at Elevated Temperature

2016 ◽  
Vol 846 ◽  
pp. 27-36
Author(s):  
Fadhluhartini Muftah ◽  
Mohd Syahrul Hisyam Mohd Sani ◽  
Ahmad Rasidi Osman ◽  
Mohd Azran Razlan ◽  
Shahrin Mohammad
Keyword(s):  
Elastic Modulus ◽  
Elevated Temperature ◽  
Ambient Temperature ◽  
Yield Stress ◽  
Material Properties ◽  
High Efficiency ◽  
Strain Curve ◽  
Ultimate Stress ◽  
Fire Incident ◽  
Cold Formed Steel

Fire accident is considered as the one of most severe environmental hazards to building and infrastructure. Cold formed steel (CFS) beam has been used extensively as primary load bearing structural member in many applications in the building construction due to high efficiency in term of production, fabrication, and assembling in construction. This material must be well perform in fire incident in term of its integrity and stability of structural for a period of time. Hence, the assessment of the material properties of this material is greatly important in order to predict the performance of this structure under fire incident. The tensile coupon tests of CFS are according to BS EN 10002-1:2001. The CFS material G450 with 1.9 mm thickness is used in this study. The elastic modulus, yield stress, correspondent percentage strain at yield stress, ultimate stress, and correspondent percentage strain of ultimate stress was 200.3 GPa, 540.5 MPa, 0.478 %, 618.8 MPa, and 8.701 % respectively. The results of the ambient temperature test have been used to assess the mechanical strength of CFS at elevated temperature. The discussion of material properties is based on EC3-1-2 and proposed model from other researchers. The main material properties discussed is the stress-strain curve, elastic modulus, yield strength at elevated temperature was determined. The actual elastic region is slightly lower than the prediction of EC3-1.2 at ambient temperature, but well fit with two other studies. Besides that, the actual material properties experience strain hardening after yielding and reach a maximum stress up to 618 MPa while EC3-1.2 predict the constant value of the yield stress after yield until 15 % strain,other two study was fit the ambient tensile test up to ultimate stress, and fit until 2 % strain level.

EFFECT OF STEREOCOMPLEX FORMATION IN D-LACTIDE-CONTAINING PLLA ON THERMAL BEHAVIORS AND MECHANICAL PROPERTY CHANGES USING THE AGEING DEGRADATION TEST

2013 ◽  
Vol 25 (05) ◽  
pp. 1340003
Author(s):  
Tsai-Chin Shih ◽  
Che-Tong Lin ◽  
Sheng-Yang Lee ◽  
Wei-Jen Chang ◽  
Nai-Chia Teng ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Bending Strength ◽  
Mechanical Performance ◽  
Test Method ◽  
Molar Ratio ◽  
Thermal Behaviors ◽  
Binding Strength ◽  
Stereocomplex Formation ◽  
Degradation Test ◽  
Hydrolytic Resistance

Introduction: The formation of a stereocomplex between PLLA and PDLA has been studied intensively because it increases the mechanical performance and thermal/hydrolytic resistance of polylactide-based materials; however, few studies have investigated the stereocomplex formation between PLLA and the (D-lactide)-containing PLLA copolymer. To investigate the effect of the D-lactide content of PLLA on the thermal behaviors and mechanical properties, (5D/95L) polylactide [(5D/95L)PLA], which contains a molar ratio of 5% of the D-form and 95% of the L-form of the monomer, and (15D/85L) polylactide [(15D/85L)PLA], which contains a molar ratio of 15% of the D-form and 85% of the L-form of the monomer, were used in a series of specimens. For the hydrolytic degradation test, the specimens were placed in 20-mL vials, which were filled with phosphate-buffered solution; the vials were allowed to stand at 57°C for 91 days in accordance with the ASTM F1635-95 (2000) standard test method for in vitro studies. The mechanical properties, thermal properties and crystallization behaviors were investigated using DSC and MTS, respectively. Results: The initial bending strength of the (5D/95L)PLA and (15D/85L)PLA were 35.4 and 31.1 N, respectively. After 1 week, the binding strength of the (5D/95L)PLA increased by 9.8%, and the binding strength of the (15D/85L)PLA decreased by 26%. In addition, the DSC curve of the (5D/95L)PLA demonstrated a higher melting temperature in the 1st week, and this Tc was observed in the DSC curve of the (5D/95L)PLA only during this time. The DSC curve of the (15D/85L)PLA was irregular. Discussion & Conclusions: In the (5D/95L)PLA, the recrystallization that occurred during the hydrolysis process was confirmed by the Tc and the increase in the bending strength. The stereocomplex crystallites may be formed in the (15D/85L)PLA during the degradation process. Because of the increase in the D-form monomer, the stereocomplexes were generated more easily and acted as nucleation sites. The PLLA crystal near the stereocomplex crystallites exhibited an incomplete structure, which led to a faster decrease in the bending strength. The low D-lactide content in the matrix of the PLLA did not form a stereocomplex crystallite because the surface area was not large enough to act as a nucleation site. However, the higher D-lactide-containing fraction formed a large stereocomplex crystallite. The (5D/95L)PLA demonstrated better thermal/hydrolytic resistance and mechanical stability than the (15D/85L)PLA.

scholarly journals Experimental and Theoretical Investigation on the Thermo-Mechanical Properties of Recycled Aggregate Concrete Containing Recycled Rubber

2021 ◽  
Vol 8 ◽  
Author(s):  
Yunchao Tang ◽  
Wanhui Feng ◽  
Zheng Chen ◽  
Yumei Nong ◽  
Minhui Yao ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Elevated Temperatures ◽  
Microstructural Analysis ◽  
Strain Curve ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Stress Strain ◽  
Aggregate Concrete ◽  
Recycled Rubber

The utilization of recycled aggregates made from construction wastes and recycled rubber made from waste tires is an effective method to realize the sustainable development. Thus, this study aims to determine the feasibility of using recycled aggregate concrete containing rubber, named rubberized recycled aggregate concrete (RRAC) as a new type of green-building material. The experimental carbon emissions test verified RRAC as a low-carbon material. In addition, the residual mechanical properties of RRAC were investigated under elevated temperatures. After exposure at 200, 400, and 600 C for 60 min, the stress−strain curve, compressive strength, energy absorption capacity, and spalling resistance of RRAC with recycled aggregate replacement ratios of 50 and 100%, rubber contents of 0, 5, 10, and 15% were explored with microstructural analysis. Moreover, empirical models were proposed to describe the effects of heated temperatures and rubber contents on the stress–strain relationship of RRAC. The results indicated that the rubber particles could reduce the spalling of specimens based on the vapor pressure theory. Therefore, this study provided scientific guidance for the design of structures made with RRAC for resisting high temperatures.

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