Stress Analysis Of Sports Shoes

As everyone knows, Sole Unlike the vamp, it carries the weight of a person's body, and even gets about 2~4 times the weight when running fast. Not only that, it also requires wearable, shockproof, elastic, skid resistant, springproof, comfortable air permeability, soft hardness, light weight and flexural resistance. So how can we achieve so many requirements? This requires that shoes should be subjected to force analysis from the positioning of sports shoes, and the sole design should be done by means of testing and analysis.

Provide basis. The influence of several main properties of sneakers on the force of sole is analyzed, which will be referenced by the industry.

1. flexural flexibility

　　 Gym shoes The folding resistance is a priority factor for consumers. It is also a physical index that the domestic quality supervision department attaches great importance to. Its testing method is the national standard of GB /T3903.1 - 1994. It cuts 5mm long at the soles of the soles and soles of the sole of the soles, and tests the flexure frequency of about 4 times per second. Therefore, when designing and producing sole, the thickness of the bending groove and the toughness of the bottom should be considered. Generally, the design of curved crevice is mainly circular arc, which can avoid stress concentration, play the role of dispersing bending force and extension force. At the same time, the back of the bent groove should be thickened to more than 2.0mm by means of reinforcing bars.

2. wear resistance

At present, China is still at a relatively low level of consumption. Gym shoes The wearability is undoubtedly the most concern of consumers. Apart from the folding resistance of sole, wear resistance is also one of the determinants of wearability.

2.1 peripheral wear

Normally, Sole The 10~1 5mm of the periphery (the front, middle, and heel) is the most worn part, but the degree of grinding is less than that of the toe and heel. The reason is that thumb, thumb and heel three points are the main force parts.

2.2 toe wear

The shoe toe is less worn than the heel, and the outside of the toe is less worn than the inside of the toe. The reason is that when walking or running, the heel first touchs the ground, and when the foot is lifted off the ground, the thumb finally raises and advances forward and produces friction.

2.3 heel wear

The heel is the main part of wear. According to statistics: over 80% of the feet are located on the outside side of the heel, and because the feet are in the starting and landing, they are oriented towards the inner side, so the degree of grinding is greater than the inside.

2.4 wear resistant design

According to the above analysis, some sports shoes (such as sneakers) with high requirements for grinding function must be made of rubber with good wear resistance, such as the vibra rubber base with super strong wear resistance in Italy. Or wear the rubber patch specially designed inside the outside of the toe and side of the heel. The best test method at present is SATRA TM1 74-94 for DIN test and evaluation.

3. skid resistance

When playing basketball, there are frequent stops and sharp movements. At this time, sports shoes (such as basketball shoes) are required to have higher slip resistance. Otherwise, they will not only cause a bad match, but also cause injuries to athletes. However, when other conditions of sole are not changed, wear resistance and skid resistance are inversely proportional. Wear resistance is better, which means that the skid resistance decreases; the better the skid resistance, the worse wear resistance. Therefore, we should find the best combination point of wear resistance and skid resistance through a large number of test comparisons to design and produce. Of course, we should also consider the design of the sole's texture from the function of the sports shoes, so as to determine the best balance between wear resistance and skid resistance.

4. permeability

Air permeability is not limited to Shoe upper The sole also requires air permeability. Because in normal wearing shoes, the temperature of human feet can reach 34~35 degrees centigrade, while when heated, the temperature will reach 43~49 degrees. In addition, the coarser and more complicated the design of the bottom, the greater the friction force and the higher the heat. Therefore, the design of the sole's air permeability is very necessary, but at the same time, we should consider its waterproof property. Generally, we use a waterproof glue that can be breathed on the window, or adopt the GORE TE TE material of American company.

5. supporting force

Supporting force is a more complex problem. In particular, it is through the tight design of sports shoes to ensure the foot's strong support for the human body. This kind of retrenchment design can overcome the force scattered around the feet, thus ensuring the upward support. Generally, hard support film (such as TPU) extends from the waist of the shoe to the heel, inserting the middle sole or between the sole and the middle sole. It can stabilize and stabilize the human foot and prevent the sprain in the movement.

6. shockproof

People walk on a weight-bearing state, taking about 600~700 steps per kilometre. This means that every step is one kilometre, and one foot will bear 600~700 gravity impacts. If the motion is intense, the impact force will be greater. Statistics have been made that when a person is running, the impact of the foot on the ground will be 2~4 times that of the human body. If the shoe does not have a good shock absorber system to relieve the impact, it will make both feet feel tired and brain damage. In general, a flexible midsole (such as EVA, PU) or elastic pad (such as EVA and PU) is used to reduce impact force. At the same time, the effect of energy recovery can be achieved (energy recovery) means that the sole will absorb kinetic energy by pressing the deformed elastic body after hitting the ground. Later, before it is off the ground, the energy will be returned to the wearer because of the shape of the elastomer, so that the wearer can run faster and jump higher.

7. resistance to sprain

A human foot is made up of 26 bones. Human walking is a complex and scientific process of coordinated movement of bones and muscles. From touching the ground to lifting the ground, the foot is subjected to an upward force and forward friction. When the foot touches the ground, it is subjected to a great impulse. Before lifting the ground, a certain force must be applied to the ground to obtain the forward friction. In this process, the analysis of the movement of human feet is like this: more than 80% of the people's feet are located on the outside side of the heel. Heel The axis is slightly skewed outward, and the foot is subjected to a great impact, which naturally turns inside to disperse the injury to the foot joints caused by the impact of the ground. Finally, the axis of the heel moves from the outward oblique position to the vertical ground position. Before lifting off the ground, the relevant muscle groups and joints are contracted to provide the force to the ground. At this time, the heel axis moves from the vertical ground position to the outward position to provide the force. In this process, there are usually two kinds of situations: overturning and overturning. If the foot falls to the inside, the axis of the heel is perpendicular to the inside, so when the foot is off the ground, it will not be able to adjust to the outward position, so that the musculoskeleton can not be fully prepared, and it may cause sports sprains. In order to overcome the problem that the flat foot of the arch falls down is prone to the problem of twisting, the sole is generally designed as a double density elastic body, and a relatively high density material is designed in the rear heel position of the sole to resist the sprain caused by the overturn of the human foot. The other is the phenomenon of insufficient turning on the high arches. Because the foot joints of high arch arch people are generally stiff, when feet are landing, they can not be completely turned to the vertical position, which is not enough to defuse the impact of feet and joints, and easily cause sprains. People with such feet often wear more on the outside side of their shoes. Of course, you can also enhance the torque resistance and reduce fatigue from the design of the insole.

8. lightweight

Lightweight is one of the factors that directly affect the comfort of sports shoes, and it is also a key factor for athletes to make best use of them. Because athletes consume a lot of energy when they exercise. They want to reduce the load outside their weight. Sports shoes are the main consideration. We should minimize the weight of shoes and let athletes walk lightly on the basis of ensuring the function of sports shoes. Foreign countries have already set the upper limit on the weight of sports shoes. In recent years, domestic PU.EVA.MD elastomers such as EVA and ejection 400g have been widely used as midsole, or foamed rubber as sole, which has set a more standard density requirement for the base materials. According to the survey, sometimes a pair of sneakers with less than 400g have good flexibility. 在國內運動鞋行業首家通過英國SATRA實驗室認證的泉州寰球鞋服有限公司，在榮獲國家出口免驗、中國名牌和國家免檢的AthIetic產品上，就是結合了專業功能、納米抗菌(國家專利)獨有特性和緊縮的鞋面及包裹式的支撐鞋底減晨設計，使消費者覺得鞋就象長在腳上一樣那么輕盈、舒適，且兼具安全性和環保性國內目前在市場上銷售的運動鞋，嚴格說來，只有慢跑鞋和休閑鞋二類，沒有什么特殊的功能，對以上所述的8個常規性能要求，沒有很好的體現，但隨著2008奧運會的臨近和大多數人生活品位的普遍提高，對運動鞋功能性的要求也愈來愈高，如何針對各類運動鞋(如：藍球鞋、跑步鞋、網球鞋、羽毛球鞋等)的特性，塑造出有自身品牌特色的產品，應是國內鞋業界值得關注的問題。 Therefore, it is necessary to analyze the force of shoes in detail before developing and designing, and use the perfect testing system to evaluate and verify them.