Cooling rate optimization of as-cast consciously cast steel

Combination of a finite element method (FEM) algorithm with ANSYS codes and post image processing of NDT ultrasonic images along with laboratory cooling experiments and microstructural analysis provides a guideline to determine the optimum cooling rate for any grade of steel in which the highest productivity can be achieved without any degradation of the cast steel products. The suggested FEM algorithm with ANSYS codes is introduced to develop a quasi real models to simulate quenching of as-cast steel with any cooling rate from any initial temperature below steel's melting point. The algorithm builds a model which is capable to approximate the thermodynamic stresses generated by thermal strain and possible solid-solid phase transformation for as-cast steel with any chemical composition. The model is applicable for any casting geometry (slab, billet and bloom, bar, etc.) and adaptable for any method of cooling (unidirectional or multidirectional). Cooling with any cooling agent can be simulated with the algorithm in an ideal case. The phase transformation of the steel in the algorithm can be controlled by Continuous Cooling Transformation (CCT) Diagram obtained from analytical calculation or real time-temperaturetransformation experiments for the cast steel. A function for optimizing cooling rate is suggested

Manufacture of a four-sheet complex component from different titanium alloys by superplastic forming

A superplastic forming (SPF) technology process was deployed to form a complex component with eight-pocket from a four-sheet sandwich panel sheetstock. Six sheetstock packs were composed of two core sheets made of Ti-6Al-4V or Ti-5Al-4Cr-4Mo-2Sn-2Zr titanium alloy and two skin sheets made of Ti-6Al-4V or Ti-6Al-2Sn-4Zr-2Mo titanium alloy in three different combinations. The sheets were welded with two subsequent welding patterns over the core and skin sheets to meet the required component’s details. The applied welding methods were intermittent and continuous resistance seam welding for bonding the core sheets to each other and the skin sheets over the core panel, respectively. The final component configuration was predicted based on the die drawings and finite element method (FEM) simulations for the sandwich panels. An SPF system set-up with two inlet gas pipe feeding facilitated the trials to deliver two pressure-time load cycles acting simultaneously which were extracted from FEM analysis for specific forming temperature and strain rate. The SPF pressure-time cycles were optimized via GOM scanning and visually inspecting some sections of the packs in order to assess the levels of core panel formation during the inflation process of the sheetstock. Two sets of GOM scan results were compared via GOM software to inspect the surface and internal features of the inflated multisheet packs. The results highlighted the capability of the tested SPF process to form complex components from a flat multisheet pack made of different titanium alloys

Compression of the material characteristics of steel, aluminum, wood and woven graphite epoxy composites in response to high strain rate load

The stresses developed in the material by impact load are analyzed experimentally, numerically, and analytically for specimens out of steel, aluminum, wood and woven graphite epoxy composites to investigate the material response to high strain rate stresses for aforementioned materials. The applied strain rates in experiments were set to be within 950 and 3500 s-1. The thin circular shape specimens were examined with high strain rate laboratory tests using the perforation split Hopkinson pressure bar (P-SHPB) with dimensional ratio accepted for One-dimensional stress analysis hypothesis. The article describes analytical solutions for one dimensional in detail to be implemented for numerical analyzing via trapezoid computation. The graphs of the four listed materials with two different thicknesses are compared for the specimen’s energy absorbed, specimen’s strain rate, stress strain rate relationship of the specimen, maximum energy absorbed, and maximum strain in specimen. It turned out that the dependency of deformation on energy absorption follows a power law for the woven composite and is approximated with linear relationships for aluminum and steel. Studying the effect of thickness in energy absorbed shows that doubling the thickness of the specimen reduces the strain of the specimen by 50 percentages for woven graphite epoxy and wood specimens, but the reduction is 25 percentages in the steel and aluminum specimen

Investigating the edge forming performance of DP600 and FV 607

This paper scrutinises the effect of varying test parameters on two grades of advanced high strength steels (AHSSs) prepared with abrasive water jet (AWJ) machining during hole expansion test (HET). The main objective was to understand the effect of the forming speed and the bottom die geometry on the hole edge forming performance of DP600 and FV 607 AHSSs. The results showed an optimum forming speed exists between 1 and 1.6mm/s and the FV 607 displayed better hole-expansion performance at 2mm/s. This was explained by correlation between the hole expansion ratio (HER) and the flange height. The results showed that the geometry of the bottom die have an influence on the hole-edge forming capability. The sheet thinning tendency was observed more in the bulge die, and particularly at speeds above 1 mm/s which was argued by requirement for larger HER values for more excessive thinning to account for an enhanced deformation. The FV 607 grade exhibited more thinning under all test conditions

Suggesting a full two level experimental factorial model with three factors to optimize Ti-HA biocomposite properties

A metal matrix composites (MMCs) is introduced to serve as synthetic bone grafts. The MMC was synthetized via powder metallurgical method after milling raw powder mixture of hydroxyapatite (HA) particles and pure titanium (Ti) powder. A full two level experimental factorial model with three factors (2^3) was developed to study the effect of three main parameters of synthetizing process on the hardness, density, and crystallite size of the composite. The synthetizing process parameters under consideration were the mechanical alloying time as well as the ceramic powder initial size and its mass fraction in the mixed powder. The results demonstrate that the composite’s hardness is increasing with higher HA mass fraction (W/W) of the composite and longer milling time. The analysis of data also show that the initial HA particle size has insignificant influence on the composite’s hardness, while higher HA content fraction in the MMC decreases the density of the composite