Variation Of Residual Strength Research Articles

Finite element analysis of pitting pit on residual strength of magnesium alloy welded joint

This work analyzes the Tungsten Inert Gas (TIG)welded joint of AZ31 magnesium alloy and the pitting corrosion stress field at different depths under tensile load via the ANSYS finite element method. The strengths of the stress and strain fields inside the corrosion pit were substantially higher than the average strength level of the matrix. Therefore, under the influence of the applied load, the corrosion pit will fail first. Based on the study of pitting corrosion, a model was developed to explain how pitting corrosion cracks propagate in magnesium alloy welded joints. Finally, the variation of residual strength was revealed to study the corrosion dynamic mechanism of the joints.

The variation in low speed impact strength on glass fiber/Kevlar composite hybrids

The aim of this study was to analyze the effect of hybridization on impact and residual strength in composites as well as the types of damage caused by the impacts, quantifying the delaminated area of the test specimens. Two 11-layer composite laminates were developed, one with bidirectional glass fiber woven and the other a hybrid with three layers of bidirectional aramid fiber substituting the outer layers and the middle layer of the glass fiber. The materials revealed that the hybrid laminate obtained greater impact strength withstanding one impact of 76 J, albeit with an increase in the damaged area of between 64 and 85 cm2, resulting in a decline in mechanical properties along nearly the entire test specimen. This contrasts with what occurred in the glass fiber laminates, which recovered over 80% of their mechanical properties for a distance of 35 mm from the edge of the impactor. Moreover, it demonstrated that the variation in residual strength can be represented by an equation and that there is a relation between the damage area and the residual properties of the glass fiber material.

A micro-mechanical parametric study on the strength degradation of concrete due to temperature exposure using the discrete element method

The present paper investigates the extent of damage caused by temperature on concrete samples. This is accomplished by a parametric approach using a 2-phase discrete element model which incorporates temperature as a global variable. Two factors of concrete degradation have been considered in this study: the thermal incompatibility of the aggregates–mortar composite and the degradation of the bonds between the particles. The base models of this parametric study are created using concrete specimens tested in the laboratory after been exposed to elevated temperatures. Using these base models, the coefficient of thermal expansion (CTE) of aggregate and mortar particles are varied independently and the discrete element model is subjected to increasing temperatures. The residual strength of the thermally-cracked particle assembly is then determined under compression. The results of 36 different combinations of the CTE show the extent of damage that can be induced due to thermal incompatibility of the particles. The variation of residual strength and residual stiffness are discussed in terms of the number of inter-particle bonds that break under rising temperature.

Study of Artificial Structural Loess under the True Triaxial Tests

Structure characteristic is the essential property of natural soils. The paper developed an indoor method of artificial structural loess, and studied on the true triaxial tests of artificial structural loess on the base of improving the original true triaxial apparatus. The results show that it is reasonably reliable of this artificial method. At the same time, the variation of failure strength and residual strength of structural loess under complex stress conditions was analysised. When the confining pressure was less than the structural strength of the structural loess, the stress-strain curve was soften, on the contrary the stress-strain curve was harden. In the end the paper analyzed that Mohr-Coulomb strength criterion was accurately to describe the residual strength variation of structural loess but there has much error in describing the peak broken strength, the value was obviously small.

Residual strength distribution of impacted glass/epoxy laminates with embedded shape memory alloy at low temperature

Abstract This paper evaluated the strength reduction and probabilistic behaviors of the residual flexural strength for impacted glass/epoxy laminates with embedded shape memory alloy (SMA) wires at various temperatures. A series of impact tests were performed on base (glass/epoxy laminates without SMA wires) and SMA laminates (glass/epoxy laminates with embedded SMA wires) at temperatures of 293 K, 263 K and 233 K. Three point flexural tests were then carried out so as to investigate the post-impact strength at the aforementioned temperatures. Strength reduction behavior of impacted laminates could be described by Caprino’s residual strength prediction model. A probabilistic model was developed in order to estimate the variation in residual strength of the impacted laminates with temperature. As the temperature decreased, the variation in residual strength increased due to the embrittlement of the constituent materials of the laminates at lower temperatures. When compared to the base laminates, the SMA laminates exhibited a higher variation in residual strength, especially at lower temperatures.

Assessment of the statistical distribution of flexural strength of woven-fabric laminates with impact-induced damage

This paper deals with several statistical distribution functions in order to analyze the strength data of composite laminates with impact-induced damage under low temperature. A series of impact tests were performed on the woven-fabric carbon/epoxy laminates under temperatures of 293 K, 263 K and 233 K. Then, three-point flexural tests were carried out so as to generate post-impact strength at the aforementioned temperatures. Two-parameter Weibull, three-parameter Weibull and normal distributions were used to fit the residual strength data of the woven-fabric composite laminates. The two-parameter Weibull distribution most accurately described the experimentally measured strength data for all of the cases considered. Furthermore, the variation of residual strength is simultaneously affected by the impact energy and the temperature.

A Residual Strength Model for Palmgren-Miner’s Law

Presently welded components subjected to fatigue loading are assessed using Palmgren-Miner’s law. A method of assessment of welded components subjected to fatigue loading based on the variation of residual strength during its fatigue life has been developed using fracture mechanics and plastic deformation theory. Palmgren-Miner’s procedure of assessing components cannot be directly compared with the residual strength method of assessment developed since the basic principles from which these assessment techniques are derived are different. In this paper a residual strength model of Palmgren-Miner’s law is developed using results of a study conducted for determining damage due to variable amplitude loading from constant amplitude residual strength curves and a method of failure of welded components subjected to fatigue proposed earlier. This residual strength model of Palmgren-Miner’s law allows comparison of present techniques of assessment with the residual strength method of assessment proposed.

Residual strength of maraging steel

Surface crack tension (SCT) specimens of 18 Ni 1800 MPa grade maraging steel (parent metal and welded) were used to evaluate the residual strength in 0.015 and 0.03m wide panels. For 0.03 m wide panels which satisfy infinite plate condition up to 0.006 m surface crack length, the residual strength variation between minimum and maximum crack sizes lie within 5% of the ultimate tensile strength (UTS) of weldments. Also for larger crack sizes both 0.015 and 0.03 m wide panels yields comparable values for residual strength. The results have significant bearing on flaw detection by non destructive testing (NDT) method which could be used for quality and reliability check on the fabricated component. Stress intensity values for these data makes an interesting observation on failure mode.