【正文】 only if they are incorporated into a designed product will a benefit be derived. It should be recognized, therefore, that a human need must be identified before a particular product is designed.Mechanical design should be considered to be an opportunity to use innovative talents to envision a design of a product, to analyze the system and then make sound judgments on how the product is to be manufactured. It is important to understand the fundamentals of engineering rather than memorize mere facts and equations. There are no facts or equations which alone can be used to provide all the correct decisions required to produce a good design. On the other hand, any calculations made must be done with the utmost care and precision. For example, if a decimal point is misplaced, an otherwise acceptable 工程學院畢業(yè)設計（論文）第 36 頁，共 49 頁design may not function. Good designs require trying new ideas and being willing to take a certain amount of risk, knowing that if the new idea does not work the existing method can be reinstated. Thus a designer must have patience, since there is no assurance of success for the time and effort expended. Creating a pletely new design generally requires that many old and wellestablished methods be thrust aside. This is not easy since many people cling to familiar ideas, techniques and attitudes. A design engineer should constantly search for ways to improve an existing product and must decide what old, proven concepts should be used and what new, untried ideas should be incorporated. New designs generally have bugs or unforeseen problems which must be worked out before the superior characteristics of the new designs can be enjoyed. Thus there is a chance for a superior product, but only at higher risk. It should be emphasized that, if a design does not warrant radical new methods, such methods should not be applied merely for the sake of change. During the beginning stages of design, creativity should be allowed to flourish without a great number of constraints. Even though many impractical ideas may arise, it is usually easy to eliminate them in the early stages of design before firm details are required by manufacturing. In this way, innovative ideas are not inhibited. Quite often, more than one design is developed, up to the point where they can be pared against each other. It is entirely possible that the design which is ultimately accepted will use ideas existing in one of the rejected designs that did not show as much overall promise. Psychologists frequently talk about trying to fit people to the machines they operate. It is essentially the responsibility of the design engineer to strive to fit machines to people. This is not an easy task, since there is really no average person for which certain operating dimensions and procedures are optimum. Another important point which should be recognized is that a design engineer must be able to municate ideas to other people if they are to be incorporated. Communicating the design to others is the final, vital step in the design process. 工程學院畢業(yè)設計（論文）第 37 頁，共 49 頁Undoubtedly many great designs, inventions, and creative works have been lost to mankind simply because the originators were unable or unwilling to explain their acplishments to others. Presentation is a selling job. The engineer, when presenting a new solution to administrative, management, or supervisory persons, is attempting to sell or to prove to them that this solution is a better one. Unless this can be done successfully, the time and effort spent on obtaining the solution have been largely wasted. Basically, there are only three means of munication available to us. These are the written, the oral, and the graphical forms. Therefore the successful engineer will be technically petent and versatile in all three forms of munication. A technically petent person who lacks ability in any one of these forms is severely handicapped. If ability in all three forms is lacking, no one will ever know how petent that person is! The petent engineer should not be afraid of the possibility of not succeeding in a presentation. In fact, occasional failure should be expected because failure or criticism seems to acpany every really creative idea. There is a great deal to be learned from a failure, and the greates。同時，四年來給予我極大幫助和鼓舞周榮安老師、羅金亮老師、彭慶林老師在這里向他們表示衷心的感謝。 【16】 崔海濤，[J].北京工業(yè)大學學報，2022,28（3）：341344 【17】 [M].北京:機械工業(yè)出版社，1991 【18】 [M].北京:航空工業(yè)出版社，2022 【19】 [M].北京:機械工業(yè)出版社，1990工程學院畢業(yè)設計（論文）第 34 頁，共 49 頁謝辭本設計是在指導老師何彬老師和張培陽的悉心指導下完成的。圖 噴嘴座結(jié)構(gòu)通過送粉頭零部件的設計，最終完成送粉頭的總圖設計如下圖 ：圖 送粉頭 工程學院畢業(yè)設計（論文）第 32 頁，共 49 頁參考文獻 【1】 閆毓禾，[M].天津:天津科學技術(shù)出版社，1994.【2】 [J].天津工業(yè)大學碩士學位論.【3】 [J].天津工業(yè)大學碩士學位.【4】 [M].北京:中國計量出版社，1998【5】 [M].1993【6】 99:125131 Hu S Y,LiＹＬ，Ｍunz D,Yang Y,Y. Thermal stresses incoated structures .in laser surface handening of a medium carbon and Coatings Technoligy,1988.【7】 27:12401244 Piliz M, Rsidual stess induced by laser coatings。夾角 的選擇受兩個方面的影響：一是要保證在入粉口的環(huán)形通道要有足夠的?空間，所以嘴角應采用較小的角度，從而減少通道內(nèi)的存粉量；二是錐環(huán)形送粉通道的長度要盡可能長，綜合以上兩點因素，最終可優(yōu)先選擇夾角 大小。合理的設置公差，保證在送粉通道出口處獲得足夠小的環(huán)形間隙，滿足對送粉通道大小的調(diào)節(jié)要求。為了防止送粉氣體由其他位置泄漏?工程學院畢業(yè)設計（論文）第 30 頁，共 49 頁而影響送粉的均勻性，在噴嘴芯中與中間套的配合面必須設置密封圈。根據(jù)激光束聚焦前及聚焦后的光斑直徑，以及聚焦透鏡的的焦距，可估算出激光束的夾角，噴嘴芯內(nèi)錐孔的的錐度應取略大于或等于激光束的夾角，因而可以定出夾角 ，由此又可以?計算出噴嘴芯內(nèi)錐孔直徑 d，噴嘴芯的的外錐面為送粉通道的一部分，外錐面的大小決定了粉末聚焦點的具體位置。而噴嘴的結(jié)構(gòu)及尺寸直接決定了熔覆材料進入激光束的方式分布特征等。 噴嘴芯的設計 噴嘴的結(jié)構(gòu)及尺寸噴嘴的結(jié)構(gòu)和尺寸對激光與粉末的相互作用方式有著直接的影響，而激光與熔覆粉末的相互作用過程中對激光熔覆效率及質(zhì)量有著重要的影響。這種結(jié)構(gòu)的噴嘴能夠滿足激光熔覆對送粉噴嘴的重要要求，且具有以下特工程學院畢業(yè)設計（論文）第 29 頁，共 49 頁點：⑴粉末匯集點與激光束焦點重合，且粉末匯集點相對于激光匯集點的位子在軸向方向上是可調(diào)的。如果需要在大傾斜角度下進行熔覆，設計的噴嘴也應滿足在大傾角度下對粉末匯集的要求。②粉末束流能夠有足夠的能量而熔化。粉末束流落在激光作用區(qū)的位置是影響熔覆層質(zhì)量的關(guān)鍵參數(shù)之一。在實際應用或?qū)嶒炛校煌姆勰┝６?，粒度、以及送粉速度，都會造成粉末匯聚點的位置變化。載氣式同軸送粉可以適應激光熔覆的三維立體成型的制造，因此本設計才用載氣式同軸