Stress relaxation

About: Stress relaxation is a research topic. Over the lifetime, 12959 publications have been published within this topic receiving 270815 citations.

The Influence of the Support Structure on Residual Stress and Distortion in SLM Inconel 718 Parts

Abstract: The effect of support structure and of removal from the base plate on the residual stress state in selective laser melted IN718 parts was studied by means of synchrotron X-ray diffraction. The residual stresses in subsurface region of two elongated prisms in as-built condition and after removal from the base plate were determined. One sample was directly built on a base plate and another one on a support structure. Also, the distortion on the top surface due to stress release was measured by contact profilometry. High tensile residual stress values were found, with pronounced stress gradient along the hatching direction. In the sample on support, stress redistribution took place after removal from the base plate, as opposed to simple stress relaxation for the sample without support. The sample on support structure showed larger distortion compared to sample without support. We conclude that the use of a support decreases stress values but stress-relieving heat treatments are still needed.

Physical aging of amorphous PEN : Isothermal, isochronal and isostructural results

Abstract: The sub-glass-transition viscoelastic and physical aging responses of an amorphous poly(ethylene naphthalate) (PEN) have been studied using uniaxial tension stress relaxation experiments. It is known that PEN exhibits a strong β relaxation that overlaps the α relaxation in the experimental time and temperature ranges studied. In prior work, we had shown that both amorphous and semicrystalline PEN exhibit thermorheologically complex behaviors in that neither time−temperature nor time−aging time superposition apply to the materials. Here we compare results from two-step aging experiments in which the material is first annealed at a temperature near the nominal glass transition temperature of 120 °C. In the second step, the viscoelastic response of the material is tested at a lower temperature, following classical sequential aging techniques. We find, for samples first annealed at 100 °C, that the amorphous PEN shows time−temperature superposition behavior for constant annealing times. The results are interp...

Observed Long-Term Performance of Geosynthetic Walls and Implications for Design

Abstract: Geosynthetic-reinforced walls have been viewed by the civil engineering profession as a new technology whose acceptable long-term performance is yet to be established. Nevertheless, geosynthetic walls have been in use for almost 25 years. Much of the uncertainty associated with acceptance of geosynthetic-reinforced wall technologies is related to time-dependent deformation. This paper summarizes the creep rates measured in full-scale walls and compares them to creep rates measured in-isolation in the laboratory where the applied load level matches values estimated for the same structures in the field. In the majority of cases, the laboratory in-isolation creep rates were the same as or greater than the measured reinforcement creep rates in full-scale walls, corroborating that reinforcement load levels can be estimated from measured strain data. At the end of wall construction, it appears that the reinforcement is primarily exhibiting creep, with only minor stress relaxation. However, in the long-term, the...