Effect of Direct Cooling Conditions on Characteristics of Drop Forged Ti+V+B Microalloy Steel

AbstractHot deformation and controlled direct cooling of medium carbon HSLA steel 35MnB4 modified with Ti and V is presented. The study of effect of thermomechanical processing (TMP) conditions on grain refinement and precipitation kinetics was oriented at replacement of conventional with direct heat treatment by imposing the varied processing routes on as-forged non-deformed and restored grains, referring to the vital problem of within-part nonuniformity. Examination of microstructure and mechanical properties showed the effect of accelerated-air cooling on deformed and non-deformed sections and conclusions on the response of the microalloy steel to differing TMP conditions in the context of requirements towards parts operating under severe wear-loading conditions. Due to specific requirements of proper strength/ductility balance in locations, target application – a tarmac cutter base was used as a case study of the efficiency of strength/plasticity enhancement, indicating bearing effect of the straining history on microstructure-properties combination, with 700-1100MPa divergence within direct-cooled parts

Fatigue Properties of Polyurethane Foams, with Special Emphasis on Auxetic Foams, Used for Helicopter Pilot Seat Cushion Inserts

Seat cushion inserts in military helicopters crew seats, as suggested by the helicopters manufacturers, are made of traditional polyurethane foams

Comparative Study on Fatigue Life of CFRP Composites with Damages

In this work, the compressive residual strength tests results, Compression After Impact (CAI), are presented. The specimens were made of carbon-epoxy prepreg E722-02 UHS 130-14. Two variants of specimens were tested: samples undamaged and samples with damage that was centrally introduced by a drop-weight impact, as per the ASTM D7136/7136M standard. An impactor with potential energy equal to 15J and the type of support required by the standard were used. The size of impacted damages, defined as an area of damage on a plane perpendicular to the impact direction, and the equivalent diameter were specified using the flash thermography method. The tests were performed using the fixtures manufactured according to the ASTM D7137/7137M standard. The specimens were compressed to determine the residual strength. This value was afterwards used to specify the force levels for the fatigue tests. The fatigue tests were carried out under force control – with a sinusoidal shape, stress ratio R equal to 0.1 and frequency f 1Hz. Maximum force in a loading cycle Pmax was being increased after each thousand of cycles N until its value was close to the residual strength determined in the previously mentioned tests. In this work, the following relationships were presented: force-displacement P-δ for both static and fatigue tests and displacement-loading cycles δ-N for fatigue tests. A method of conducting the fatigue tests of CFRP composite was proposed, in which both the CAI specimens and CAI fixture were used. This allowed researchers to accelerate making initial comparisons between the two groups of specimens with damages – grouped relative to the way of conditioning

Comparative Study on Fatigue Life of CFRP Composites with Damages

In this work, the compressive residual strength tests results, Compression After Impact (CAI), are presented. The specimens were made of carbon-epoxy prepreg E722-02 UHS 130-14. Two variants of specimens were tested: samples undamaged and samples with damage that was centrally introduced by a drop-weight impact, as per the ASTM D7136/7136M standard. An impactor with potential energy equal to 15J and the type of support required by the standard were used. The size of impacted damages, defined as an area of damage on a plane perpendicular to the impact direction, and the equivalent diameter were specified using the flash thermography method. The tests were performed using the fixtures manufactured according to the ASTM D7137/7137M standard. The specimens were compressed to determine the residual strength. This value was afterwards used to specify the force levels for the fatigue tests. The fatigue tests were carried out under force control – with a sinusoidal shape, stress ratio R equal to 0.1 and frequency f 1Hz. Maximum force in a loading cycle Pmax was being increased after each thousand of cycles N until its value was close to the residual strength determined in the previously mentioned tests. In this work, the following relationships were presented: force-displacement P-δ for both static and fatigue tests and displacement-loading cycles δ-N for fatigue tests. A method of conducting the fatigue tests of CFRP composite was proposed, in which both the CAI specimens and CAI fixture were used. This allowed researchers to accelerate making initial comparisons between the two groups of specimens with damages – grouped relative to the way of conditioning

Comparative Study on Fatigue Life of CFRP Composites with Damages

In this work, the compressive residual strength tests results, Compression After Impact (CAI), are presented. The specimens were made of carbon-epoxy prepreg E722-02 UHS 130-14. Two variants of specimens were tested: samples undamaged and samples with damage that was centrally introduced by a drop-weight impact, as per the ASTM D7136/7136M standard. An impactor with potential energy equal to 15J and the type of support required by the standard were used. The size of impacted damages, defined as an area of damage on a plane perpendicular to the impact direction, and the equivalent diameter were specified using the flash thermography method

Examination of Honeycomb Core Compliance in Sandwich Structure

The objective of the research presented in this paper was to determine the honeycomb core compliance of a sandwich structure of the horizontal stabilizer of the MiG-29 fighter jet in the static compression test. The study of the specimen was conducted based on the ASTM C365/C365M standard. The article presents the results of experimentally determined dependencies and strength parameters, i.e. the force-displacement dependence, the compressive modulus and the honeycomb core deformations