Plasticity of MoSi2 Below 900°C

1993 ◽  
Vol 322 ◽  
Author(s):  
H. Chang ◽  
R. Gibala
Keyword(s):  
Dislocation Density ◽  
Mechanical Behavior ◽  
Yield Point ◽  
Stress Strain ◽  
Temperature Range ◽  
Dislocation Plasticity

AbstractThe mechanical behavior of polycrystalline MoSi2 tested in compression at temperatures from 750°C to 950°C has been investigated. This material can be deformed to several percent strain without fracture at temperatures as low as 900°C. This same material prestrained at 1300°C and subsequently tested at lower temperatures can be deformed to substantial strain at 800°C, and even exhibits modest plasticity at 750°C. Both prestrained and unprestrained materials exhibit microcracking combined with dislocation substructures containing high densities of dislocations. Unprestrained MoSi2 exhibits a yield point in this temperature range which does not exist when it is prestrained. The stress-strain curves of the prestrained material in this temperature range are similar qualitatively to those of the unprestrained material at 1100°C and above. These observations suggest that at these temperatures MoSi2 is a dislocation density limited material which can deform by dislocation plasticity processes if a sufficient dislocation density is available.

Definition of the yield point in plasticity and its effect on the shape of the yield locus

1966 ◽  
Vol 1 (4) ◽  
pp. 331-338 ◽  
Author(s):  
T C Hsu
Keyword(s):  
Yield Point ◽  
Experimental Work ◽  
Strain Curve ◽  
Yield Locus ◽  
Experimental Results ◽  
Stress Strain Curve ◽  
Proportional Limit ◽  
Stress Strain ◽  
Small Section ◽  
Definition Of

Three different definitions of the yield point have been used in experimental work on the yield locus: proportional limit, proof strain and the ‘yield point’ by backward extrapolation. The theoretical implications of the ‘yield point’ by backward extrapolation are examined in an analysis of the loading and re-loading stress paths. It is shown, in connection with experimental results by Miastkowski and Szczepinski, that the proportional limit found by inspection is in fact a point located by backward extrapolation based on a small section of the stress-strain curve, near the elastic portion of the curve. The effect of different definitions of the yield point on the shape of the yield locus and some considerations for the choice between them are discussed.

On the Impact Behavior of a Material With a Yield Point

1949 ◽  
Vol 16 (1) ◽  
pp. 39-52
Author(s):  
Merit P. White
Keyword(s):  
Yield Stress ◽  
Yield Point ◽  
Impact Behavior ◽  
Longitudinal Impact ◽  
Stress Strain ◽  
California Institute Of Technology ◽  
Static Yield ◽  
Institute Of Technology ◽  
Probable Nature ◽  
The Impact

Abstract An analysis of longitudinal impact tests that were made by Drs. D. S. Clark and P. E. Duwez at the California Institute of Technology on an iron and a steel with definite yield points is described. From this analysis is deduced the probable nature of the dynamic stress-strain relations for such materials. These appear to differ greatly from the static stress-strain relations, unlike the case for materials without yield points. As pointed out by Duwez and Clark, the upper yield stress for undeformed material is several times as great under impact as the static yield stress. The present analysis indicates that under impact, the material with a definite yield point is made harder at a given deformation, and ruptures at a higher (engineering) stress and smaller strain than when loaded statically. The critical impact velocity, defined as that at which nearly instantaneous failure occurs in tension, is discussed, and the factors upon which it depends are given.

Mechanical Characterization of Assemblies Bonded With Pressure-Sensitive Adhesives (PSAs)

2015 ◽  
Author(s):  
Hao Huang ◽  
Abhijit Dasgupta ◽  
Ehsan Mirbagheri ◽  
Srini Boddapati
Keyword(s):  
Mechanical Behavior ◽  
Failure Modes ◽  
Mechanical Characterization ◽  
Bonding Temperature ◽  
Process Conditions ◽  
Second Phase ◽  
Loading Conditions ◽  
Stress Strain ◽  
Strain Behavior ◽  
Pressure Sensitive

The focus of this paper is on the stress-strain behavior and creep response of a pressure-sensitive adhesive (PSA) with and without carrier layers. This study consists of two phases. The first phase focuses on understanding of the effects of fabrication profiles, including bonding pressure, bonding temperature, bonding time, and aging time, on the PSA joint strength. This part of the study is used to identify an acceptable bonding and aging conditions for manufacturing a robust PSA bonded assembly. Specimens fabricated with this selected set of bonding process conditions are then used for mechanical characterization. The second phase focuses on the assembly’s mechanical behavior (stress-strain behavior and the creep curves) under different loading conditions, including loading stress, loading rate, and loading temperature. The mechanical behavior of PSA bonded assemblies is affected not only by the loading conditions, but also by the assembly architecture. The mechanical behaviors and failure modes of PSAs with and without carrier layers are compared. The reasons for these differences are also discussed.

scholarly journals The influence of rate of deformation on the tensile test with special reference to the yield point in iron and steel.

1938 ◽  
Vol 165 (923) ◽  
pp. 568-592 ◽  
Author(s):  
C. F. Elam ◽  
Henry Cort Harold Carpenter
Keyword(s):  
Tensile Test ◽  
Special Reference ◽  
Yield Point ◽  
Strain Curve ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Iron And Steel ◽  
Plastic Distortion

The following experiments were carried out with two principal objects in view: (1) to investigate the deformation of those metals, particularly iron and steel, in which the stress-strain curve does not immediately rise at the onset of plastic distortion; (2) to determine the effect of rate of deformation on the yield and subsequent stress-strain curve. It is impossible to give an adequate summary of the literature which deals with this subject, but a bibliography is included in an appendix and some of the most important results are referred to briefly below.

Influence of Elastic-Plastic Bending on the Relationship Between Applied Load and Maximum Bending Stress for Straight and Curved Bars

2020 ◽  
Author(s):  
Don Metzger
Keyword(s):  
Plastic Strain ◽  
Plastic Zone ◽  
Yield Point ◽  
Cross Section ◽  
Applied Load ◽  
Bending Stress ◽  
Stress Strain ◽  
Bending Load ◽  
Bending Capacity ◽  
The Relationship

Abstract Bending capacity in excess of the load required to cause yielding is due to a combination of work hardening and the effect of the plastic zone spreading toward the neutral axis. For materials of sufficiently high ductility, a fully developed plastic zone is achieved and the bulk of the section is stressed beyond yield. For lower ductility materials, failure may occur prior to full development of the plastic zone such that only a fraction of the cross section is at or above the yield stress. In such cases, the relationship between applied load and maximum bending stress becomes sensitive to the shape of the stress-strain curve near the yield point. This relationship is examined for straight and curved bars of rectangular and trapezoidal cross-section for tensile stress-strain curves characterized by nonlinear functions. The stress distribution as a function of applied load is determined analytically by enforcing moment equilibrium across the section. The strain distribution is determined through the classical condition of “planes remain plane” during deformation. The solutions provide analytically smooth load curves such that maximum stress can be directly plotted as a function of applied load. These plots exhibit three distinct regimes of response: 1) elastic, 2) development of plastic zone, and 3) fully developed plastic zone. Since the response is analytically smooth, the detailed relationship through the knee of the tensile curve can be examined. The results indicate that bending capacity is influenced significantly by the development of small amounts of plastic strain prior to reaching a yield point defined by the usual 0.2% plastic strain offset method. The results also show how loss of ductility with respect to tensile elongation translates into reduced bending load capacity in a non-linear relationship.

scholarly journals Prediction of Stress–Strain Curves Based on Hydric Non-Destructive Tests on Sandstones

Materials ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3366 ◽  
Author(s):  
Marco Ludovico-Marques ◽  
Carlos Chastre
Keyword(s):  
Physical Properties ◽  
Mechanical Behavior ◽  
Water Absorption ◽  
Analytical Model ◽  
Strain Curve ◽  
Low Pressure ◽  
Design Parameters ◽  
Compression Tests ◽  
Stress Strain ◽  
Non Destructive

The study of the mechanical behavior of building stones is traditionally supported by destructive compression tests carried out on representative specimens. However, in order to respect the monuments’ integrity, the study of the mechanical behavior of stones can be based mostly on physical properties obtained from non-destructive tests (NDT). For this study, a simple and cheap NDT—water absorption under low pressure—was used to carry out fast surveys and to predict the most important design parameters of loadbearing masonry, among which are the compressive strength, strain at failure, and even elastic modulus on monument blocks. The paper presents the results of the experimental work conducted to obtain the physical properties and stress–strain curves of the sandstones tested. Supported by these results, it was possible to correlate the various parameters and develop an analytical model that predicts the stress–strain curve of the sandstones based on water absorption under low pressure tests. A good agreement is observed between the analytical model and the experimental tests.

Thermo-Mechanical Analysis of Chosen Epoxy Resins Used in Aviation Technology

2015 ◽  
Vol 1126 ◽  
pp. 187-193
Author(s):  
Kamil Prusak ◽  
Janusz Zmywaczyk ◽  
Piotr Koniorczyk ◽  
Jan Godzimirski ◽  
Marcin Cegła
Keyword(s):  
Thermal Expansion ◽  
Epoxy Resins ◽  
Loss Modulus ◽  
Testing Machine ◽  
Mechanical Analysis ◽  
Stress Strain ◽  
Temperature Range ◽  
Heating And Cooling ◽  
Tan Δ ◽  
Material Testing Machine

In this paper the results of storage modulus (E’), loss modulus (E’’) and damping parameter tan (δ)=E''/E' of epoxy resins Epidian 57 and L285 with curing agents Z1 and LH285, respectively are presented. In addition to this the stress-strain and thermal expansion characteristics of Epidian 53, 57 and L285 were obtained experimentally in order to compare Dynamic Mechanical Analysis (DMA) results. Temperature range of DMA investigations using Netzsch (Germany) DMA 242C analyzer was from-120 °C to +110 °C at the heating rate of 1 K/min with frequency of {0.1, 1, 10} Hz, respectively. Netzsch DIL 402C dilatometer was used to study the thermal expansion of the tested samples within temperature range from 30 °C to 80 °C at 1 K/min of heating and cooling rates, respectively and Huang TA computer servo control material testing machine HT-2402 was applied to determine the stress-strain characteristics. Measurements of sample elongation ΔL and physical α* were performed twice in heating and cooling cycles. The glass transition temperature Tg determined from maximum of tan (δ) curve at f = 1Hz was equal to 76.7 °C for E57 and 87.2 °C for L285. It has been observed durable deformed shape of L285 sample with deflection in the middle about 5 mm just after finishing the DMA first run of heating which significantly affected DMA results during the second run of heating

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