thinking about safety helmet

Safety helmet is a kind of head protection device to prevent head collision when objects hit and fall. 1t is one of the most popular personal safety protection facilities and appliances. 1t is generally made of wicker, rattan or plastic, There are two main forms: one is a shallow dome hat made of steel or similar materials worn by miners and underground engineers to protect their heads, and the other is a light protective helmet usually made of metal or reinforced plastic worn by workers in industrial production environment< Safety helmet is one of the "three treasures of safety" for construction workers. 1t is an important personal protective equipment for construction workers to protect their head, prevent and reduce all kinds of accidents and ensure their life safety, 1t can be described as a worker's "protective umbrella": when the head of the operator is impacted by a falling object, the impact force is first decomposed into the whole area of the skull by using the helmet shell and the helmet liner in an instant, and then most of the impact force is absorbed by using the elastic deformation, plastic deformation and allowable structural damage of the buffer structure of each part of the helmet, Finally, the impact force acting on the head of the operator is reduced to less than 4900n, so as to protect the head of the operator safety helmet products can be divided into two categories: general operation (y) safety helmet and special operation (T) safety helmet. According to different materials and uses, the main categories are shown in the following table: no matter which form, its validity period is calculated from the date of product manufacturing. 1t shall not be more than two years for plant branch woven cap, two and a half years for plastic cap and paper rubber cap, and three and a half years for glass fiber reinforced plastic (vinylon steel) rubber cap