Non-uniformity Of Strain Distribution Research Articles

Accurate monitoring of coal pillar deformation based on distributed optical fiber

In many structural deformation monitoring applications, determination of the response length of embedded optical fibers is difficult due to the use of strain integration method, which increases the measurement errors. For systematic investigation of the deformation law of coal pillars under mining action, distributed fiber optic technology was used herein to analyze its response length. This study discusses how non-uniform strain distribution can increase the accuracy error of fiber optic displacement measurement, and verifies the effectiveness of theoretical analysis by using coupled FEM–DEM numerical simulation method. Furthermore, the relationship between the Brillouin gain spectrum characteristics of different sampling points and the non-uniformity of strain distribution was explained. To reduce accuracy errors, a new method was proposed herein for determining the response length of optical fibers. The feasibility of this method was verified through indoor experiments. Next, this method was applied to the deformation monitoring of coal pillars in a section of Huojitu Well. By using the proposed method, the deformation of coal pillars can be accurately monitored.

Improvement of Plate’s Shape for Ingots Upsetting

A stress-strain state and a resize of an axial defect during upsetting have been investigated in the article. Theoretical research based on a FEM has been conducted. The upsetting of cylindrical steel workpieces which had the axial defect equal to 10 % of the workpiece diameter has been simulated. Upsetting has been carried out by flat, concave-conical and convex plates (solid or with hole). The result of the studies showed that the main influence on the workpiece shape had a ratio of dimensions. The maximal closure of the axial defect provides upsetting by concave-conical solid plates. Upsetting by flat plates does not provide the closure of axial defects. Convex plates provide the uniform stress-strain state along the workpiece cross section. The hole in the plates increases the non-uniformity of strain distribution and also does not provide the axial defects closure.

Numerical Study on Motions of Rolls in Hot Rolling of Titanium Alloy Large Rings

Abstract Titanium alloy is sensitive to strain rate, so motions of rolls are crucial to the hot rolling process of titanium alloy large rings. In the study, firstly, the relative velocity vr was proposed to synthesize motion parameters of rolls, including the rotational velocity of the driver roll n1 and the feed rate of the idle roll v, and then the reasonable range of vr was determined analytically based on the stable forming condition. Secondly, a reliably coupled thermo-mechanical 3D-FE model of the process was developed in the dynamic explicit code ABAQUS/Explicit. Finally, the effect of vr on the process was studied using FE simulation. The results obtained show that although increasing vr by two different ways, i.e., by decreasing n1 or by increasing v, makes the feed amount per revolution Δhi increase, not all of their effects on the process are in agreement, such as for the nonuniformity of strain distribution. An appropriately larger value of vr is helpful to improve the end-plane quality and make strain and temperature distributions in a deformed ring more uniform, but has an adverse influence on the roll force.

Simulation of material behaviour under dynamic loading

Experiments and FE-simulations are carried out in order to characterise the mechanical behaviour of metals at high strain rates between 10 3 s −1 and 10 4 s −1. The non-uniformity of strain distribution is studied for the cases of tensile impact and forging. The behaviour of fibre-reinforced metals is investigated under impact compressive loading regarding the buckling of the slim fibres within the softer matrix. Failure criteria are deduced considering the interaction between mechanical waves and internal inclusions or external notches.

MODIFIED CYCLIC MICROMECHANICAL MODEL FOR CONCRETE

A detailed cyclic micromechanical model based on the micromechanics of granular material is proposed for concrete. In the current study, concrete is idealized to have two kinds of contacts; aggregate-aggregate and aggregate- mortar contacts. The behavior of these contacts is examined and distinguished for both cyclic and virgin loadings. Finally, an explicit formula which expresses the tangent stiffness matrix of the material as a summation of the contributions of all contacts inside any representative volume is derived. Moreover, the nonhomogeniety of the microstructure and the nonuniformity of strain distribution are considered. This is in contrast to Bazant's microplane model in which concrete has been treated as a homogenous brittle aggregate material having a single kind of contact with uniform strain distribution.

Study on refinement of recrystallized grain size of 3S alloy

Precipitation behavior of the precipitates formed during the preheating of Al-Mn(-1.9%), Al-Mn(1.1%)-Fe(-1%), Al-Mn(1.1%)-Si(-0.6%) and Al-Mn(1.1%)-Fe(-1%)-Si(-0.7%) alloys has been investigated by means of measurements of the electrical resistance and micro-hardness, X-ray analysis and microscopical examination.Results obtained are as follows:(1) The precipitates in Al-Mn and Al-Mn-Fe alloys are MnAl6 accompained by G phase (MnAl12), and in the Al-Mn-Si alloy, are α (MnSi) at the first stage and MnAl6 at the second stage. MnAl6 is needle-like and has a property of coarsening the grain by heating, but α (MnSi) is of much finer particles than MnAl6 and has no tendency of grain growth.(2) Addition of Si in the Al-Mn alloy acceralates the velocity of precipitation which takes place more quickly than in the case of Fe in the alloy.(3) The recrystallized grain in the Al-Mn and Al-Mn-Fe alloys becomes finer after heating, but in the Al-Mn-Si alloy, the recrystallized grain is coarser after heating.This peculiar phenomenon may be explained as follows: Al-Mn-Si alloy has an uniform distribution of a great number of fine precipitates which results in an uniform distribution of working strain followed by a slow nucleation rate. The precipitates in the Al-Mn and Al-Mn-Fe alloys, however, are of large grains and have an irregular distribution of particles which result in a non-uniformity of strain distribution followed by a high nucleation rate.