Impact Resistance of Steel Materials to Ballistic Ejecta and Shelter Development Using Steel Deck Plates

The destruction caused by ballistic ejecta from the phreatic eruptions of Mt. Ontake in 2014 and Mt. Kusatsu-Shirane (Mt. Moto-Shirane) in 2018 in Japan, which resulted in numerous casualties, highlighted the need for better evacuation facilities. In response, some mountain huts were reinforced with aramid fabric to convert them into shelters. However, a number of decisions must be made when working to increase the number of shelters, which depend on the location where they are to be built. In this study, we propose a method of using high-strength steel to reinforce wooden buildings for use as shelters. More specifically, assuming that ballistic ejecta has an impact energy of 9 kJ or more, as in previous studies, we developed a method that utilizes SUS304 and SS400 unprocessed steel plates based on existing impact test data. We found that SUS304 is particularly suitable for use as a reinforcing material because it has excellent impact energy absorption characteristics due to its high ductility as well as excellent corrosion resistance. With the aim of increasing the structural strength of steel shelters, we also conducted an impact test on a shelter fabricated from SS400 deck plates (i.e., steel with improved flexural strength provided by work-hardened trapezoidal corrugated plates) . The results show that the shelter could withstand impact with an energy of 13.5 kJ (2.66 kg of simulated ballistic ejecta at 101 m/s on impact). In addition, it was confirmed the impact absorption energy is further increased when artificial pumice is used. Observations of the shelter after the impact test show that there is still some allowance for deformation caused by projectile impact, which means that the proposed steel shelter holds promise, not only structurally, but also from the aspects of transportation and assembly. Hence, the usefulness of shelters that use steel was shown experimentally. However, shelter construction should be suitable for the target environment.

Very-High-Cycle Fatigue and Charpy Impact Characteristics of Manganese Steel for Railway Axle at Low Temperatures

Railway vehicles are being exposed with increasing frequency to conditions of severe heat and cold because of changes in the climate. Trains departing from Asia travel to Europe through the Eurasian continent and vice versa. Given these circumstances, the mechanical properties and performance of vehicle components must therefore be evaluated at lower and higher temperatures than those in current standards. In this study, specimens were produced from a commercial freight train axle made of manganese steel and subjected to high-cycle fatigue tests at −60, −30, and 20 °C. The tests were conducted using an ultrasonic fatigue tester developed to study fatigue at low temperatures. Charpy impact testing was performed over the temperature range of −60 to 60 °C to measure the impact absorption energy of the axle material. The material showed a fatigue limit above 2 million cycles at each temperature; the lower the test temperature, the greater the fatigue limit cycles. The impact absorption energy at −60 °C was 81% less compared to the value at 20 °C. The axle material became completely brittle in the temperature range of −30 to −40 °C.

Study on Ductile Brittle Transition Temperature of Q345C Steel MAG Welded Joints

For Q345C steel MAG welded joints, low temperature tensile test was carried out at normal atmospheric temperature, 0°C,-20°C,-30°C and-40°C in the paper, which results in the law of strength change with temperature. The impact absorption energy of the weld seam sample under different temperature conditions was tested, impact fracture morphology was observed and the parentage of the fibrous fracture surface was assessed. The curve of impact absorption energy and the percentage of the fibrous fracture surface with temperature were fitted by using the Boltzmann function, and ductile brittle transition temperature of Q345C steel MAG welded joints was determined. The test results show that the impact absorption energy of the weld seam can reach 71J at-40°C, and the weld seam is prone to brittle fracture under low temperature. The influences of alloying elements and microstructure on the ductile brittle transition temperature and low temperature impact toughness were discussed, and suggestion is put forward to improve the impact toughness and reduce the ductile brittle transition temperature.

IMPACT ENERGY AND DUCTILITY INDEX OF KEVLAR REINFORCEMENT WITH KENAF POLYESTER COMPOSITE

This research focuses on the reinforcement of Kevlar in treated kenaf composite, specifically in the study of impact properties as well as the characteristics. The kenaf was treated with 6% Sodium Hydroxide (NaOH) solution at a specific period of time before being made into laminates. Impact test was conducted using an instrumented drop tower device at 36J level according to the standard ASTM D7136. Microstructures of the fractured specimens were also analyzed. The results of the study indicated that treated kenaf/Kevlar hybrid composite has better impact absorption energy than pure kenaf composite. Compared to the pure kenaf composite, the hybrid composite absorbs more impact energy and appears to have lower impact damage at the same impact energy level. This is because the Kevlar fibres play an important role to prevent and delay the destruction of composites.

Influence of Volume Fraction of Bainite on Mechanical Properties of X80 Pipeline Steel with Excellent Deformability

The pipeline steel with excellent deformability with ferrite and bainite dual-phase microstructure are obtained by inter-critically accelerating cooling method, aiming to get good deformation capability of avoiding failure from the geological disasters such as landslides and earthquake. The influence of volume fraction of bainite on the mechanical properties of dual-phase pipeline steels was investigated by means of microscopic analysis method and mechanical properties testing. The results indicated that both yield strength and ultimate tensile strength of the steels increase almost linearly with the increasing volume fraction of bainite, while ductility, work hardening exponent and impact absorption energy decrease. When the volume fraction of bainite is about 50%, the yield strength, the yield strength/tensile strength ratio (Y/T), work hardening exponent, uniform elongation and impact absorption energy of X80 pipeline steels with excellent deformability is 665MPa, 0.8, 0.12, 8% and 245J respectively.

Finite Element Analysis of Cable Products for High Impaction and Fatigue Resistance with Nonlinear Material Models

This paper presents experimental and numerical simulation for deformation and fatigue life prediction of various cables, such as electrical, optical and network cables. The cable damage is produced by the tensile, bending and torsional action under moving and fixing condition, and by direct external impact. To obtain material responses of the cable, uniaxial tensile tests and drop-weight impact tests were adopted, and the nonlinear constitutive equations based on various strain energy potentials or material models were employed to analyze deformation of polymer sheath and metallic armor layer of the cable. Finite element results were compared with experimental data for deformation and impact absorption energy of the cable during direct external impact. Also, fatigue strength of the cable was predicted from variation of calculated stress level under tensile conditions. Fractured surface of the cable were analyzed by scanning electron microscopy (SEM).