未來幾年，隨著輕質(zhì)車身、閉合板及鋁制材料應(yīng)用的不斷增長，自沖鉚釘也將作為一種大量使用的結(jié)構(gòu)性連接件，在汽車制造領(lǐng)域發(fā)揮更大作用。據(jù)了解，在奧迪（Audi）、寶馬（BMW）、通用（GM）、捷豹路虎（JLR）和特斯拉（Tesla）汽車小范圍使用自沖鉚釘之后，福特（Ford）F系列鋁制皮卡開始將這種鉚釘連接技術(shù)帶入主流市場(chǎng)。
自沖鉚釘與機(jī)械結(jié)構(gòu)性粘合劑的搭配不僅更牢固，而且還具有其他優(yōu)勢(shì)。鉚釘可以將相鄰的金屬板連接在一起，保證粘合劑可以在車輛的整個(gè)組裝過程中充分接觸。專家表示，如果沒有鉚釘，粘合劑連接的組裝速度完全無法與點(diǎn)焊抗衡。
斯坦利工程緊固公司（SEF,前身Emhart Teknologies）的緊固件研發(fā)經(jīng)理Matthias Wissling博士表示，“自沖鉚釘可以將鋁和其他金屬連接在一起。未來幾年中，這種連接件的使用將在世界范圍內(nèi)顯著提高。”
最近，Wissling及另外幾位公司高管在公司位于密歇根特洛伊市的總部接待了《汽車工程》，共同探討自沖鉚釘和其他結(jié)構(gòu)性連接件創(chuàng)新。
自上世紀(jì)90年代首次登陸鋁制車身的奧迪A8后，自沖鉚釘在歐洲汽車廠商心目中的地位相當(dāng)穩(wěn)固。在北美地區(qū)，隨著汽車廠商開始轉(zhuǎn)而使用鋁材，以及其他無法通過傳統(tǒng)焊接技術(shù)連接的輕質(zhì)材料，自沖鉚釘?shù)膽?yīng)用也開始呈上升態(tài)勢(shì)。
根據(jù)達(dá)科咨詢公司（Ducker Worldwide）的2015年全球輕量化汽車鋁材占比研究，到2025年，鋁制車身板與閉合件的用量將從2012年的不到2億磅增長至40億磅。其中，發(fā)動(dòng)機(jī)蓋中的鋁材使用將達(dá)到85%，車門部分達(dá)到46%，完整車身中的使用將達(dá)18%。相比之下，2015年，車身大量采用鋁制材料的比例不到1%。
雖然，點(diǎn)焊仍是目前最常用的鋼制白車身板連接工藝，但高級(jí)機(jī)械緊固技術(shù)也逐漸成為一個(gè)越來越受歡迎的選擇。自沖鉚釘緊固工藝可以連接鋁、鋼、塑料、碳纖維強(qiáng)化復(fù)合材料及各種材料組合，整個(gè)過程均不需要提前打孔。
專家指出，自沖鉚釘?shù)恼麄€(gè)緊固過程不需要加熱，這種工藝可以用于連接白車身上的各種相同或不同材料，比如鋼-鋼和鋁-鋼連接。Wissling博士表示，“這點(diǎn)非常重要，要知道在白車身上每增加一種連接技術(shù)，就會(huì)產(chǎn)生額外的工序和成本。”
SEF公司突破創(chuàng)新副總裁Sivakumar Ramasamy表示，目前公司可以提供多種連接產(chǎn)品，包括金屬夾、鑲嵌件、雙頭螺釘和自接鉚釘?shù)龋€有多種緊固裝配系統(tǒng)。
Ramasamy博士表示，“要達(dá)到2025年的公司平均燃料經(jīng)濟(jì)性（CAFE）標(biāo)準(zhǔn)，汽車廠商需要繼續(xù)擴(kuò)大輕質(zhì)白車身材料的使用，因此未來市面上將出現(xiàn)更多類型白車身緊固技術(shù)和連接產(chǎn)品。”
Ramasamy表示，“我希望公司能夠拿出更多創(chuàng)新解決方案，這可以是新產(chǎn)品、新工藝、新業(yè)務(wù)模型，從而從容應(yīng)對(duì)未來的無線可能性。”Ramasay新組建的工程師與營銷專家團(tuán)隊(duì)將在2017年前，在德國格森附近的辦公室啟動(dòng)工作。這個(gè)團(tuán)隊(duì)唯一的職責(zé)就是創(chuàng)新。
“自動(dòng)汽車可以采用塑料車身嗎？如果可以，那塑料白車身應(yīng)當(dāng)使用何種緊固工藝呢？公司可能會(huì)推出一種符合要求的塑料鉚釘或粘合劑。”Ramasamy博士認(rèn)為，“創(chuàng)新團(tuán)隊(duì)必須追蹤各種新興趨勢(shì)，然后拿出相應(yīng)的解決方案。”
30多年來，SEF公司的核心產(chǎn)品一直是點(diǎn)焊技術(shù)。不過，正如車身材料已經(jīng)有所變化一樣，相應(yīng)的緊固件也已隨之進(jìn)化了。
SEF公司為創(chuàng)新團(tuán)隊(duì)投資了大量經(jīng)費(fèi)，這絕非偶然。“我們希望通過創(chuàng)新增長業(yè)務(wù)。我們希望可以具備連接輕質(zhì)材料的能力。”Ramasamy博士表示，“但這并不是我們的唯一追求。2025年后，行業(yè)內(nèi)可能又會(huì)出現(xiàn)一些新東西，我們必須做好萬全準(zhǔn)備。”
Growth of lightweight vehicle body and closure panel applications in the coming years, and particularly greater use of aluminum, is driving increased use of self-piercing rivets as a high-volume structural joining solution. Ford's aluminum-intensive F-Series program brought rivet-bonding into the mainstream, following lower-volume applications by Audi, BMW, GM (Corvette), JaguarLandRover and Tesla.
The combination of self-piercing rivets (SPR) and robotically-applied structural adhesives creates a robust joint with other benefits. The rivets clamp the adjacent metal panels together to allow the adhesive-bonding agents sufficient time to cure while the assembly goes through the body and paint shops. Without the rivets, a bonded-only assembly could not be produced at a line rate competitive with spot welding, according to experts.
“Because self-pierce riveting is a solution that can join aluminum and other multi-material designs, we see a significant increase in SPR usage worldwide over the next few years,” said Dr. Matthias Wissling, Manager of Fastener Engineering for Stanley Engineered Fastening (SEF), formerly Emhart Teknologies.
Wissling and other SEF officials recently sat down with Automotive Engineering at the company’s North America automotive headquarters in Troy, MI, to talk about SPRs and structural-joining innovation.
SPRs are well-entrenched on European vehicle applications after their 1990s debut on the aluminum-bodied Audi A8. As automakers in North America turn to aluminum sheet and other lightweight materials that can’t be joined by traditional welding techniques, SPRs are gaining momentum.
Use of aluminum sheet for vehicle body and closure parts is forecast to climb from less than 200 million pounds in 2012 to approximately 4 billion pounds by 2025, according to Ducker Worldwide’s 2015 North American Light Vehicle Aluminum Content Study. Of the total, 85% of the material will be used for hoods, 46% for doors, and 18% for complete bodies. By comparison less than 1% of bodies were aluminum-intensive in 2015, the study noted.
While spot welding remains the most common method for joining steel body-in-white (BIW) panels, advanced mechanical fastening is an increasingly popular option. The SPR process can join aluminum, steel, plastics, carbon-fiber-reinforced composites, and combinations of materials without the need for a pre-drilled hole.
SPRs don’t require heat to complete the assembly process, the experts noted, and the technique can be used to join all joints, such as aluminum-to-steel and steel-to-steel, on the same BIW. “This is important because each additional joining technology used for a BIW adds additional complexity and cost,” said Dr. Wissling.
SEF offers several different joining technologies, ranging from metal clips and inserts to studs and SPRs, as well as various fastening assembly systems, according to Dr. Sivakumar Ramasamy, SEF’s Vice President of Breakthrough Innovation.
“The 2025 CAFE [Corporate Average Fuel Economy] requirements are dictating a greater use of lightweight BIW materials, so that’s driven more types of fastening methodologies for the BIW and for attaching parts to the BIW,” said Dr. Ramasamy.
“My directive is to come up with innovative solutions--which could be products, processes, the way we do business--for whatever is coming next in the industry,” Ramasamy said. His newly-formed team of engineers and marketing specialists will begin their duties from a location near Giessen, Germany prior to 2017. The team’s sole focus is innovation.
“Could the autonomous vehicle be plastic-bodied? If so, what would be the fastening method for that vehicle with all of its body- and closure-attached sensors? It might be a plastic rivet or gluing that meets the requirements,” Dr. Ramasamy opined. “The innovations team needs to understand all of the emerging trends and come up with solutions.”
For more than 30 years, the company’s core product line was spot welding. As BIW materials have shifted, the fastening options have evolved.
The SEF innovation team’s double-digit percentage budget allocation is no accident. “We want to grow this business through innovation. Being able to fasten lightweight materials is one thing,” said Dr. Ramasamy, “But there are other things we can do. Because beyond 2025, something else is coming.”
Author: Kami Buchholz
Source: SAE Automotive Engineering Magazine
Matthias Wissling 博士站在陸虎攬勝運(yùn)動(dòng)款的白車身旁，該車身使用了3,648個(gè)自沖鉚釘以及214個(gè)鋁釘。
SEF 公司設(shè)計(jì)制造的C型框架結(jié)構(gòu)用來裝配自沖鉚釘。
“我們?cè)O(shè)計(jì)，開發(fā)和制造的緊固件及將緊固件裝配到白車身上的裝配系統(tǒng)?！?SivakumarRamasamy 博士站在SEF公司密歇根Troy創(chuàng)新中心的機(jī)器人邊上