Analysis of the trunk oil pipeline survivability in the zone of the butt welded joint

The article describes the development of a technique for analyzing the survivability of the trunk pipeline in the zone of the transverse weld during operation, taking into account the residual welding stresses. The calculation of residual welding stresses was performed by solving the problem of thermoelasto-viscoplasticity for a material with a non-stationary structure by the finite element method. Solving the nonlinear nonstationary heat conduction problem was carried out by the finite difference method using boundary conditions of the third kind. Modeling the kinetics of transformation of austenite into ferrite-pearlite and bainite under non-isothermal conditions during welding was carried out on the basis of the theory of isokinetic reactions. The calculation of survivability is based on the Irwin criterion and the Paris formula.

Effects of Solid Die Types in Complex and Large-Scale Aluminum Profile Extrusion

Increasing customer requirements for quality and productivity in extruding aluminum products has led to the development of different types of extrusion dies. In this study, three different types of dies, including traditional flat die, pocket die and spread die were designed to extrude complex and large-scale solid profiles. The design parameters for these dies were used from actual extrusion experience. The results obtained from steady-state simulation such as velocity, temperature, extrusion force, and die deformation were used to assess the advantages and disadvantages of the dies. Transient simulations were performed to analyze the evolution of transverse weld in the pocket and spread dies. The effects of ram speeds on the related extrusion parameters were also investigated. The research results provide useful guides for designers and engineers in selecting these types of extrusion dies.

Investigation of Failed Wheel Rim Weld Joints

Material used for car sheet wheels production was analyzed due to limited weldability. During the manufacturing of wheel rims, during shaping - cold forming cracks were initiated in the weld joint and in its heat affected zone. The destruction of rims occurred during their shaping. The wheel rims were welded at their manufacturer's site applying the compression technology and using the direct current welding source. Five rims were supplied for the metallographic analysis of which two were with conforming weld joint, and in the case of three rims there was a rupture at the weld joint point; on one them along the whole width of the rim. The rupture of the rim weld joint across its whole width at the weld joint point that was made by diffusionless connection was caused by a low welding input power. The primary cause of the rim cracking initiation on the transverse weld joint was the presence of micro-cracks, micro-notches in the vicinity of the weld joint and the heat affected zone, the notch effect of which was manifested during the rim forming. The occurrence of micro-notches was shown in the heat affected zone as well as on the conforming weld joint of one rim. The carbon equivalent Ce from the measured values of the material chemical composition of all rims was in the range from 0.175 to 0.201. Given the declared weldability guaranteed up to the value of Ce = 0.45, all analyzed materials complied with the requirement. Material cleanliness, grain size and linearity met the requirements of specification for material MW 01. Given the insufficient quality of the material was not the primary cause of the defect, it was recommended to eliminate the occurrence of potential notches in the heat affected zone through slightly planning of the weld collar.