Research On Pressure Distribution And Improved Design Of Fall Protection Harness

With the development of the economy,the form of working at heights has become normal.Causing the fall accidents have always been at the top of the "Five Industrial Injuries" list.,and resulting the casualty rate caused by all accidents accounted for more than 50%.As a "life belt" to prevent fall accidents,fall protection harness is one of the most effective fall protection equipment.Its performance research and structural improvement are of great significance for reducing fall accidents.However,it’s also existing some problems such as poor comfort and uneven pressure distribution.Among them,the pressure distribution is a key factor affecting the comfort of the harness,and it is directly related to the wearer’s physical experience and life safety.Therefore,this thesis,the pressure sensitive paper is used to test the pressure distribution of the harness,and its structure has been improved.It mainly discusses the influence of the main structure of the harness,the position of the attachment and the width of webbing on the pressure distribution.Finally,the dynamic model of the human body during the fall is established,and the influence of the webbing width on the dynamic mechanical properties of the harness is also studied.The specific research conclusions are as follows:（1）Three different structures of harnesses and simulated suspension experiments are used to study the influence of harness’ s structure on pressure distribution.The results show that the uneven pressure distribution coefficient p and the maximum pressure differenceΔFmax of each part of the Y-type harness are the smallest.And the pressure value at each part is kept below the pressure comfort critical value,which proves that Y-type structural can evenly distribute the pressure.（2）Combined with the results of pressure distribution,the Y-type adjustable harness was designed,and the influence of the position of the attachment on the pressure distribution of the harness was explored,too.The results show that when the front attachment is adjusted from the lowest position A to the highest position D,the suspension angle gradually decreases.When the attachment is at position B,the pressure comfort and pressure distribution uniformity of the harness are the best.When the position of the back attachment is adjusted from the lowest position a to the highest position c,its uniformity of the pressure distribution gradually decreases.When the attachment is at position c,the comfort of the harness is relatively higher,but the pressure value of the pubic muscle part exceeds the comfort critical value of 38 N.Therefore,the harness’ s structure needs to be further improved.（3）The influence of webbing width on the pressure distribution and dynamic mechanical properties of the harness was discussed,by establishing the dynamic mode of the human body during the fall,and designing the variable-width webbing harness.The variable-width webbing harness and ordinary harness were subjected to dynamic drop test respectively.The results show that as the width of webbing gradually increases,the pressure values at various parts of the human body show a decreasing trend,and the pressure values at the trapezius muscle and the external oblique muscle decrease the most.In the drop test,by comparing the braking force-time curve and acceleration-time curve of these two harnesses,it is found that the variable-width webbing does not weaken the mechanical properties of the harness,indicating that using the variable-width webbing can not only ensure the safety of the harness,but also increase its comfort.