ABSTRACT
The characteristics of human body impact response and several impact test objects are analyzed.The strengths and weaknesses of different research methods applied to different human landing impact test objects are contrasted.The relevant experimental findings and evaluation criteria of domestic and international tests on human landing impact are analyzed.The results show that the selected human substitutes in several research tests have some flaws, so it is urgent to formulate regulations on the load characteristics, individual characteristics, the posture of the test object and the protection status, and it is recessary to study impact tolerance and protective methods of corresponding operating personnel for different transports.
ABSTRACT
Objective To study the effect of bone mineral density (BMD) change on response of human spine to landing impact by numerical simulation. Methods The three-dimensional material point model of human head skull, cervical vertebrae, thoracic, lumbar vertebra, pelvis, ligament and disc was constructed from the computed tomography (CT) scanned images, and they were attached together as a human spine model and placed on the backrest of the chair, which was constructed by the MPM3D program. The acceleration loading was applied on the back rest of the chair to simulate the landing impact loading when the human spine model was laid on the back of the chair. The different responses of human spine to landing impact were simulated by changing the BMD and the corresponding elastic modulus. Results The general risk of injury γ value of normal BMD was 1.589 3, and when the BMD was reduced by 2%, 4%, 6%, 8%, 10%, respectively, γ values were 1.608 6, 1.634 7, 1.641 0, 1.662 5, 1.680 5, correspondingly. Conclusions Under the same landing impact loading, the smaller the bone mineral density, the larger the response of human spine to landing impact loading, and human body is more vulnerable to injuries.
ABSTRACT
The purpose of this study was to investigate the landing impacts of falls from short heights with body weight increment. Eight male college students participated as subjects. The body weight increments were gradually increased by 2, 4, 6, 8 and 10 kg by attaching 500 gram iron bars in the pocket of vests that students wore. The subjects performed the landing by falling from a height of 2.7 m above and they landed on the surface of a force plate as softly as possible. The landing impacts, muscular activities, and joint movements of lower limbs during landing were analyzed by a force plate using EMG and VTR programs.The results indicated that there were no significant increments found in maximal landing impact even though the body weight was increased from 2 to 10 kg. The flexion of ankle, knee and hip joints started immediately before landing and increased after landing with the body weight increments. The activity of plantar and dorsi flexor muscles after landing were increased intensively with the body weight increments. Although the body weight increased from 2 to 10 kg gradually, landing impact at fall did not increase. It may be controlled by fast and deep flexing movements of lower limb joints during landing.