Papers by Keyword: HIC

Abstract: Purpose of this study is investigation of energy absorption capability of the sandwich structures composed of combination of polystyrene and metal foam element and their suitability as new structure for design of protective helmets. Two types of the metal foams were experimentally tested and evaluated: Alporas (Shinko Wire Ltd., Japan) and Aluhab (Aluinvent Plc., Hungary). Samples of the sandwich structure are composed of two layers: bottom expanded polystyrene (EPS 200S) layer and upper metal foam layer which are glued together. Prepared samples are tested using a drop tower experiment to measure sample response (acceleration, reaction force) at different strain rates and energies. From acceleration/time history the Head Injury Criterion (HIC) is calculated as significant parameters in terms of protective helmets. Moreover, measured and derived characteristics are compared with pure EPS samples to obtain comparison of deformation behaviour between conventional structure for protective helmets and designed sandwich structures.

Abstract: Build the model of motocross-style helmet with a dual - density and series-parallel EPS buffer layer and trial-produce helmet samples. Establish the impact experiment of the helmet model and obtain the values of HIC and Peak ACC based on the testing regulations of ECE R22.05. According to the analysis of the test results, the influence law of different EPS material densities to cushioning effect of the helmet was analyzed specifically. Experimental results show that the minimum values of HIC and Peak ACC can be obtained when the density of EPS is designed to be 0.06g/cm³; a dual - density and series - parallel EPS buffer layer has higher than 76 % of the energy absorption efficiency, and this buffer structure well reduces the values of HIC and Peak ACC, and provides effective protection for the head.

Abstract: ntroduction This paper has proved that the HIC of local Car hood crash area is relative to the distance between the crash point and potential secondary crash point, and with the rigidity of the second crash point, in the process of protection for pedestrians. The pertinence formula was built and the high risky spot of each local crash areas was doped out quickly, and the accuracy of the formula is validated by the subsequent real car crash test. When the vehicles and the pedestrian have the crash accident, the pedestrian casualty rate is very high, develops the pedestrian to protect the research positively, particularly the forehead crash trouble-free service, regarding the guardian vehicle crashs in weak one the pedestrian, has the very vital significance.

Abstract: Head injury of pedestrian is the most common and fatal cause of mortality in vehicle-to-pedestrian crash. And the engine hood is most likely to cause harm to pedestrian head. Efforts to improve engine hood design, which minimize the head injury of pedestrian in vehicle-to-pedestrian crash, are becoming more and more important. In this study, an approximate model of hood thickness for three targets: HIC, mass and modality, is established. In order to meet the requirements of lightweight and reducing vibration and noise, approximate models iterate by the NSGA-II genetic optimization algorithm, and select the Pareto optimal solutions for thickness optimization. At last the study re-simulates the collision between pedestrian head and hood to verify the reliability of the obtained optimization results.

Abstract: A low cost, high reliability pendulum impact device is designed and set up with a gas generator and inflator, and a real deploy test is conducted with 45L drive airbags made of Nylon 66. The interaction between the dummy pendulum and the airbag in this simulation is recorded to observe and study the impact and injury to human body. The HIC is calculated and taken as an important basis for the evaluation of airbag performance. This test can also be used on the study and optimization of airbag fabrics.

Abstract: Because of the performance and cost, airbags are mainly made of coated or uncoated Nylon 66 fabrics. Different airbags, which use different fabrics, vary in the inflation and expansion of the airbag and the protecting function on vehicle occupants. Based on HIC drawn from pendulum impact tests conducted with 45L airbags, the paper analyses influence of some special critical characteristics of airbag fabrics into the performance of airbags. The results show that the weight and the air permeability are the main factors that influence protecting function of airbag. Under the condition of enough fabric strength, light and thin fabric is more preferable in making airbags.

Abstract: This paper has proved that the HIC of local engine hood collision area is relative to the distance between the collision point and potential secondary collision point, and with the rigidity of the second collision point, in the process of protection for pedestrians. The pertinence formula was built and the high risky spot of each local collision areas was doped out quickly, and the accuracy of the formula is validated by the subsequent real car collision test.

Abstract: A model, which can be used to illustrate the process of nucleation of hydrogen induced cracking (HIC) in steels during sour service, was developed with the aid of Gibbs theory. A set of criteria for crack nucleation were then derived from the model. Metallurgical parameters influencing the criteria and thusly the susceptibility of the material to HIC, which are measurable and controllable in industrial processing, were also advanced in the present article.

Abstract: Hydrogen induced cracking (HIC) is one of main type of damage to metallic materials in H2S solution. 08Cr2AlMo steel is a type of material developed especially for heat exchanger pipe bundle used under H2S condition in recent years. Calculation models of the construction units in 08Cr2AlMo steel with or without hydrogen were established based on the empirical electronic theory in solid (EET) and valence electron structure of the construction units in this steel was calculated. The results show that hydrogen bond is formed between the hydrogen solved in the steel and other atoms in the steel. The cleavage energy of crystal plane with hydrogen bond is increased and that without hydrogen bond is decreased. Hydrogen results in the remarkable difference of the cleavage energy of different crystal planes and changes the bond distribution in the structure units. The mechanical property of the units has directional properties. In these units, the microcracks propagate along the cleavage plane with small binding energy and so the brittle fracture of the crystal occurs. The elements of Cr, Al, Mo are able to strengthen the basal body without carbon, and have little effect on the plastic nature. In the structure unit with carbon, carbon increases the anisotropy of mechanical property and alloying agents decrease the plastics of the steel further. The alloying agents of Cr and Mo decrease plastic nature loss of the steel due to decrement of the anisotropy of mechanical property in the unit with hydrogen. The alloying agent of Al has little effect on the loss of plastic nature.

Abstract: Susceptibility of hydrogen embrittlement of a super grade AISI 420 tool steel was studied. Tensile samples were cathodically charged to different hydrogen level. Hydrogen induced mechanical property degradation was measured by tensile tests at a low strain rate. Fractography of broken surfaces was observed using SEM. Relationship between hydrogen content and tensile strength and elongation were studied. Critical hydrogen contents were obtained for different heat treatment states. It was found that for annealed materials could stand for a 3.5ppm hydrogen for keeping 80% of original ductility, and the effect of hydrogen on strength was unobvious. However, for material quenched and tempered at 250°C, only 0.3ppm hydrogen could lead the ductility drop to 80% of original. The material quenched and tempered at 500°C was more sensitive on hydrogen, less than 1ppm hydrogen could lead the strength drop to 80% of original.