今日看见@超级陆战队 的一个帖子引起了我的兴趣。

《独家干货！围观YYP与众技术宅吵架：评新宝来没后防撞梁！求精》

@版主大人，我这个能不能也取个精啊。

看来看去发现，技术宅前来凯美瑞论坛踢馆，号称要给点“干"货，还欢迎拍砖，好吧，那我也就不客气了。

BTW， YYP评评车赛赛车就好了，和技术宅瞎裹什么乱。

切入正题，鉴于上述背景，特此将我这片老帖子从杰德那边转过来，以求共勉。

传说中神奇的后防撞钢梁（咦？为虾米非得是肛呢？高级车不都是女合金的么？）-哇，听起来好重要好强壮的部件-实际学名叫后包围补强杠 文中简称后杠

是后保险杠的组成结构之一，另一个就是外面的树脂塑料包围。

后保险杠的英文学名叫rear bumper

什么叫bumper。 资料来源自IIHS，NHTSA。和YYP论道的那一群主机厂工程师啥时能和IIHS这样的测试机构水平相仿，中国汽车就有希望了，否则不过是个汽车头号组装消费大国而已。

英语好的人士，想自己研究的，请直接跳过本文，看最后的连接，去IIHS或NHTSA自学，那里有更详尽的介绍。

看完后，你会觉得中国有很多车评人，媒体，汽车专家爆炒这条后杠，都是些人云亦云（思辩能力不足，但还算善良）或者拿钱干活，揣着明白装糊涂的货。

1) What is the purpose of bumpers?

Bumpers are supposed to keep damage away from safety-related equipment such as headlights and taillights and protect vehicle parts such as hoods, fenders, and exhaust and cooling systems that are expensive to repair. 保险杠是用来降低关系到安全装备的损失，比如大灯，尾灯，引擎盖，翼子板，排气管和散热器这些修起来比较昂贵的装置。When bumpers are poorly designed, these parts sustain most of the damage in parking-lot collisions and other low-speed impacts.如果保险杠设计的很差劲，停车或者其他低速碰撞下，这些部件会很受伤 Bills to fix fender-bender damage can add up to thousands of dollars.

维修扳金件的花费可达数千美刀。

Insurance claims related to fender benders add up, too. This is reflected in the premiums consumers pay for auto insurance. More than $6 billion is paid out each year to cover claims of $4,500 or less, the kind of damage claims associated with low-speed collisions.  Such huge damage costs are why it"s important to equip passenger vehicles with bumpers that effectively reduce damage in low-speed collisions. Better bumpers mean less out-of-pocket costs for consumers and lower insurance costs.

 如果有保险杠可以有效地降低低速碰撞的损失，更好的保险杠意味着消费者的荷包不会内牛满面，同时保险花费也会更少。

The car bumper is designed to prevent or reduce physical damage to the front and rear ends of passenger motor vehicles in low-speed collisions. 主要是防治或降低乘用车前后部位在低速碰撞下的物理损伤。Automobile bumpers are not typically designed to be structural components that would significantly contribute to vehicle crashworthiness or occupant protection during front or rear collisions.通常汽车保险杠不是被设计为保障撞击时车辆和成员安全的结构件It is not a safety feature intended to prevent or mitigate injury severity to occupants in the passenger cars.它不是一个用来避免或降低成员受伤程度的安全装置 Bumpers are designed to protect the hood, trunk, grille, fuel, exhaust and cooling system as well as safety related equipment such as parking lights, headlamps and taillights in low speed collisions.

2 What are bumpers made of?

Front and rear bumpers on today"s cars generally consist of a plastic cover over a reinforcement bar made of steel, aluminum, fiberglass composite or plastic. 保险杠是由塑料包围和补强杠（补强杠。。。伟大的防撞钢梁哭晕在厕所）组成的，这个杠子可以是钢制，铝制（解答了@我爱问问题 童鞋的疑问，嗯嗯），玻璃纤维或者塑料材质。Some automakers design the bumper bar and its attachment brackets to crush in a low-speed crash to absorb energy. Polypropylene foam or formed thermoplastic sometimes is used in addition to or instead of crushable brackets and a bar. But frequently their main purpose is to serve as a spacer between the bar and the bumper cover and not as an energy absorber. Very few bumper bars are attached to the vehicle structure through mechanisms like shock absorbers. 这句有点意思，解释了3008前杠的奇葩小火箭式吸能盒（

奇葩，傲慢，疯狂的法国人一直很可爱，去造车，可惜了。。。）

A bumper reinforcement bar, shown without the plastic bumper cover

前杠的图例，透视图示显示了保险杠的组成部分。

此图表明IIHS定义中的bumper是包括包围和补强杠的整体概念。企图用塑料包围充当此文保险杠的胡搅蛮缠混淆视听的童鞋退下吧。

4， Does the federal government regulate bumpers? 

联邦政府对保险杠的法规介绍，包括如何测试后杠是否合格。

The U.S. government sets minimum bumper performance requirements for passenger cars, 4 but these regulations don"t apply to vans, SUVs or pickups. The agency issued its first bumper standard for cars in 1971. 

?See NHTSA"s bumper Q&A

Current bumper rules, in place since 1982, 现行法规是从1982年开始实施，specify 10 bumper tests, including pendulum tests and crashes into a fixed flat barrier. The pendulum tests include two front and two rear-corner impacts at 1.5 mph plus two front and two rear tests at 2.5 mph. 摆杆（模拟其他车辆保险杠的主动移动屏障）撞击试验包括2次前角和后角在1.5英里时速下的撞击试验，和2次前部，后部在2.5英里时速下的试验The pendulum has a bumper-shaped protrusion that may impact the vehicles anywhere between 16 and 20 inches from the ground, and the mass of the pendulum equals that of the tested vehicle. Following these tests, the fronts and rears of the vehicles crash into a flat barrier at 2.5 mph. 另外还有车辆前部和后部在2.5英里时速下撞击竖直圆柱试验In these barrier and pendulum tests, unlimited damage is allowed to the bumper, but none is allowed to other parts of the vehicle. The hood, trunk and doors must operate normally. Propulsion, suspension, steering and braking systems also must operate normally. There can be no broken headlights or fuel, cooling or exhaust leaks or constrictions

上面我重点突出的都是关键语句，就不全文翻译了。

综上所述，这个后杠是用来降低低速碰撞（小于2.5mph=4kph）时维修费用的。郭德纲：5迈太~~~刺激了！

对于后杠子，如果没有的话，也许排气管和后尾灯或者尾箱盖会变形或破损。导致维修费保（险赔付费）的大幅上升。

而且后杠子可以由任何材料任何形状构成，联邦法规只规定了测试标准，只要能合格，厂家可以自行设计任何式样。

比如某些韩系车的那种树脂塑料，新宝来，tiida那种纯工程泡沫。

或者有些车干脆没有，比如8代思域，在日本也没有，美国有法规，所以必须要安一个，否则2.5mph碰撞试验可能过不了关。

日版FD3，光屁股。服不服？

日版FD2传说中的神车typeR，也光腚，这时要闹那样？？

本田歧视日本消费者？为了省2碗拉面钱，至日本人民安危于不顾，次奥！本田宗一郎战时反水，被我武工队教育后回国潜伏，尼玛~亡日之心不死啊。

这个东西有比没有强，但是为了无限提高强度做的很重反而得不偿失。

车身吸能结构中，c柱往后都是溃缩区，是抗拉强度270mpa的钢板的重灾区，你就是按个钢轨当后杠，当追尾碰撞是加到材料上的应力大于270mpa时，后尾箱到c柱也是完全报废。

举个夸张但是易懂的例子，新宝来不是没杠子吗，ok，咱给B屁股上焊条钢轨（高铁用的那种），120kph倒车撞墙，钢轨后杠好好的，拿下来按铁路上能资源回收，新宝来？对不起，车全烂了。。。。。

总而言之，把这个后杠子和车身的强度结构还有成员安全联系在一起，纯属扯淡。

http://www.iihs.org/research/qanda/bumpers.aspx#cite-text-0-0

http://www.nhtsa.gov/cars/problems/studies/Bumper/Index.html

原出处，不服不信，自己去看。