Fracture Assessment of Weld Joints of High-Strength Steel in Pre-Strained Condition

Unstable fractures tend to occur after ductile crack initiation or propagation. In most collapsed steel structures, a maximum 15% pre-strain was recorded, at the steel structural connections, during the great earthquake of 1995, in Japan. Almost-unstable fractures were observed in the beam-to-column connections, where geometrical discontinuities existed. Structural collapse and unstable failure occurred after large-scale plastic deformations. Ship structures can also suffer from unstable fractures in the welded joints. The fracture resistance of butt-welded joints subjected to tension in the pre-strained condition was estimated by considering the toughness deterioration, due to pre-strain and toughness correction for constraint loss in a tension specimen. The target specimen for this fracture assessment was a double-edged, through-thickness crack panel, with a crack in the weld joint (heat-affected zone (HAZ)). The critical fracture toughness value (crack tip opening displacement (CTOD)) of a large structure with pre-strain, which was applied to the HAZ region, was estimated from a small-scale, pre-stained, three-point bend specimen. Fracture toughness values, evaluated by a CTOD test, were recently mandated for shipbuilding steel plates. The critical fracture toughness value is a very useful parameter to evaluate the safety of huge ship structures.

Data support system for controlling decentralised nuclear power industry facilities through uninterruptible condition monitoring

The article describes the automated uninterruptible multi-parameter system for monitoring operational vulnerability of critical NPP components, which differs from existing ones by being universally applicable for analysing mechanical damage of nuclear power unit components. The system allows for performing routine assessment of metal structures. The assessment of strained condition of a deteriorating component is based on three-dimensional finite element simulation with calculations adjusted with reference to in-situ measurements. A program for calculation and experimental analysis of maximum load and durability of critical area forms the core of uninterruptible monitoring system. The knowledge base on performance of the monitored components in different operating conditions and the corresponding comprehensive analysis of strained condition and deterioration rates compose the basis of control system data support, both for operating nuclear power units and robotic maintenance and repair systems.

Biomechanical analysis of the cancellous screws implantation schemes in surgical treatment of flexible flatfoot in children

Carry out comparative biomechanical analysis of influence of the implantation scheme and characteristic sizes of cancellous screws on parameters of its strained condition, and elaborate guidelines for optimization of implantation parameters and decision for a material metalware choice. Performed mathematical modelling and comparative numerical analysis of the parameters of strained condition, slant and cantilevered schemes of implantation of cancellous screws, applied to a wide range of support loads variations acting on a screw. Made analysis of influence of size parameters (length of the overhanging part, angle with normal at supporting surface, core diameter) on the magnitude of the calculated stress that appear in compressed and extended zones of slant implanted screw. Carried out investigations reveal that short screws, installed on the hard circuit, from the standpoint of operational reliability according to the criteria of strength under static loading (occasional overload) and multicyclic loading have the highest capacity for work. Least favourable in application are slant and cantilevered implanted screws. With increasing length of cantilevered part and angle between axis of a screw and line of loading force calculated values of stress also increases. Screws of heat-treated stainless steel are preferred from the standpoint of saving bearing capacity with unit congestion due to increased plasticity in 4–5 times (residual strain at failure) compared with titanium alloys.

Study on Large Inclined Angle Integrated Caving Hydraulic Support Stability Control

Analyzed the main factors of affecting hydraulic support stability, this paper analyses anti-topple and antiskid technology to apply to inclined angle 15~33°and compatible supports ZF4200/16/26. Through the practical application in shanjia mine, it can meet large inclined angle mine demands. The follows were studied that can influence the stability of support in large inclined angle coal seam. Every roof situation in the direction of large inclined angle suffering different stress lead to different caving property, and the roof motivation can affect other supports strained condition and stability. Caving mechanism behind the caving coal support suffer downward force, and the force is put on caving shield and tail beam, so it makes supports generate angle of bank. The support would lose its stability with working face processing and supports advancing for descending support and losing point of support.

Numerical Simulation Study on Superposed Combined Exterior Protected Structure

In this article, the waterproof curtain, the underground diaphragm wall and the soil between them are regarded as superposed combined exterior protected structure, then build a flexible spring support system. When using senior ANSYS finite element analysis program to simulate the strained condition and displacement of the underground diaphragm wall, we will combine with the monitoring result and the result of traditional comouting method. After contrasting, we can get a conclusion: the strained condition and displacement of the wall of this simulation method are more coincident with practical projects, and can reduce unnecessary waste.