多功能健身器的設(shè)計【健身器材類機(jī)械】
多功能健身器的設(shè)計【健身器材類機(jī)械】,健身器材類機(jī)械,多功能健身器的設(shè)計【健身器材類機(jī)械】,多功能,健身器,設(shè)計,健身,器材,機(jī)械
機(jī)械設(shè)計準(zhǔn)則
設(shè)計是從實(shí)際或者假想的需要開始的。對于現(xiàn)有的設(shè)備可能需要在耐用性，效率，重量，速度或成本等方面做進(jìn)一些改進(jìn)工作；也可能需要新的設(shè)備完成以前由人來做的工件，例如，計算或者裝配。當(dāng)目標(biāo)完全或部分被確定以后，下一個設(shè)計步驟是對完成所需要功能的機(jī)構(gòu)及其布局進(jìn)行總體設(shè)計。對于此項工作徒手畫的草圖是很有價值的，他不僅可以記錄下我們的想法，而且還有助于與別人進(jìn)行討論，特別是和自己的大腦進(jìn)行交流，從而促進(jìn)創(chuàng)新想法的產(chǎn)生。
當(dāng)一些零件的大致形狀和幾個尺寸確定后，就可以開始認(rèn)真的分析工作。分析工作的目的是要在重量最輕，成本最低的情況下，獲得令人滿意及優(yōu)良的工作性能，并且還要安全耐用。對于每個關(guān)鍵承載截面，應(yīng)該尋求最佳的比例和尺寸，同時要對這幾個零件的受力進(jìn)行平衡。要對材料和處理方式進(jìn)行選擇。只有根據(jù)力學(xué)原理進(jìn)行分析才能達(dá)到這些重要目的。這些分析包括靜力學(xué)原理進(jìn)行分析反作用力和充利用分摩擦力，根據(jù)動力學(xué)原理分析慣性，加速度和能量；根據(jù)彈性力學(xué)和材料力學(xué)分析應(yīng)力和應(yīng)變；根據(jù)流體力學(xué)分析潤滑和流體傳動。
最后，完成基于功能要求和可靠性所進(jìn)行的設(shè)計，且要制作一臺樣機(jī)。如果實(shí)驗(yàn)結(jié)果令人滿意，而且該裝置將要進(jìn)行批量生產(chǎn)，就應(yīng)該對最初提出的設(shè)計方案做些修改，使其能以較低的成本進(jìn)行批量生產(chǎn)。在以后的制造和使用期內(nèi)，如果產(chǎn)生了新的想法或者根據(jù)實(shí)驗(yàn)和經(jīng)驗(yàn)所做的進(jìn)一步分析結(jié)果表明，可以有更好的替代方案，則很可能對原設(shè)計方案進(jìn)行修改。銷售吸引力，客戶的滿意程度和制造成本均與設(shè)計有關(guān)，而設(shè)計能力則與工程創(chuàng)新的實(shí)現(xiàn)是密切相關(guān)的。
為激發(fā)創(chuàng)造性思維，建議設(shè)計人員遵循下列準(zhǔn)則。
1.創(chuàng)造性的利用所需要的物理性能和控制不需要的物理性能。
可以利用自然法則或物質(zhì)的性能（例如柔性，強(qiáng)度，重力，慣性，浮力，離心力；杠桿原理和斜面原理，摩擦，粘性，流體壓力和熱膨脹）和許多電學(xué)，光學(xué)和化學(xué)現(xiàn)象來滿足一臺機(jī)器的設(shè)計要求。一種性能在某種場合下可能是有用的，而在另外一種場合下則可能是有害的。閥門的彈簧應(yīng)該有彈性，閥門的凸輪軸就不需要柔性。離合器結(jié)合面上需要有摩擦，而離合器軸承卻不需要摩擦。設(shè)計時，需要創(chuàng)造性的利用和控制所要的物理性能，將不需要的物理性能減至最小。
2.載重量最輕的情況下，提供合理的應(yīng)力分布和剛度。
對于承受交變應(yīng)力的零件應(yīng)該特別注意減輕應(yīng)力集中和提高圓角，螺紋和配合處的強(qiáng)度。改變零件的形狀可以降低它所承受的應(yīng)力，對零件施加預(yù)應(yīng)力，如表面滾壓和淺表面硬化，均可使其得到強(qiáng)化?？招妮S和空心管道，箱型截面能獲得有力的應(yīng)力分布同時具有強(qiáng)度高而重量輕的特點(diǎn)。曲軸，凸輪軸以及含有軸承支座的外殼和構(gòu)架都應(yīng)有足夠的剛度以保證直線對中精度和接觸表面之間的壓力均勻分布。軸和其他零件須有適當(dāng)?shù)膭偠缺苊猱a(chǎn)生共振。
3. 利用基本公式進(jìn)行尺寸計算和尺寸優(yōu)化。
力學(xué)和其他的基本公式進(jìn)行移項而化成特殊形式，以簡化尺寸的計算或者對尺寸進(jìn)行優(yōu)化。例如，用梁的表面應(yīng)力來計算齒輪的輪齒尺寸。在不能采用解析法計算的情況下，可以在基本公式內(nèi)引入系數(shù)。例如，對于薄壁鋼管，考慮到腐蝕性，可將根據(jù)求的厚度增加一些。當(dāng)必須應(yīng)用一個基本公式來確定形狀，材料和使用條件，而這些被確定的量僅僅與在公式推導(dǎo)中的假設(shè)比較接近時，要采取措施是結(jié)果偏于安全。當(dāng)數(shù)據(jù)不完全時，可以應(yīng)用理論公式作為尺寸的指南，在擴(kuò)展后的范圍內(nèi)獲得令人滿意的設(shè)計結(jié)果。
4.根據(jù)性能組合選擇材料。選擇材料時需要考慮有關(guān)的性能組合，不僅考慮強(qiáng)度，硬度和重量，而且有時還要考慮抗沖擊性，抗腐蝕性和耐高溫或低溫的能力。成本和制造性能都是應(yīng)該考慮的因素，這些因素包括可焊接性，機(jī)械加工性能，對熱處理溫度變化的敏感性和所需要的圖層等。
5.在現(xiàn)有零件和整體零件之間進(jìn)行認(rèn)真的選擇。
若一個以前研制的文件能過滿足性能要求和可靠性要求，并使用于所設(shè)計的那臺機(jī)器而無須附加的研制費(fèi)用，那么設(shè)計人員和公司通常會從零件制造廠的現(xiàn)貨中選取零件。但是，只有了解其性能，才能進(jìn)行認(rèn)真的選擇工作，因?yàn)槿魏我粋€機(jī)器零件的失效都會影響公司的信譽(yù)，并使公司承擔(dān)相應(yīng)的責(zé)任。在其他情況下，若及其設(shè)計人員自己來設(shè)計零件，則零件的強(qiáng)度，可靠性和成本等方面的要求就可以更好的得到滿足。可將某個零件與其他零件設(shè)計成一個整體零件，例如將幾個齒輪設(shè)計為一個鍛件或者將齒輪與軸設(shè)計為一體，這種方法的主要優(yōu)點(diǎn)是緊湊。
6.保證零件在裝配中準(zhǔn)確定位和不發(fā)生干涉。
一個良好的設(shè)計能夠保證零件定位準(zhǔn)確，裝配和修理方便容易。軸肩和導(dǎo)向表面在裝配過程中不需要測量就能提供準(zhǔn)確定位。零件的形狀應(yīng)該設(shè)計的保證這個零件不會被裝反或裝錯位置。必須能夠預(yù)見和防止諸如不同的螺紋孔中的螺釘之間的干涉和不同的連桿機(jī)構(gòu)之間的干涉。必須避免部件之間的找正對中誤差和定位誤差，或者必須采用措施，減小任何由此引起的不利的位移和應(yīng)力。
Some Rules of Mechanical Design
Designing starts with a need ,real or imagined.Existing apparatus may need some improvements in durability,efficiently,weight,speed,or cost.New apparatus may be needed to perform a function previously done by men,such as computation,assembly,or servicing.With the objective wholly or partly defined ,the next step in design is the conception of mechanisms and their arrangements that will perform the needed functions.For this ,freehand sketching is of great value ,not only as a record of one’s thoughts and as an aid in discussion with others ,but particularly for communication with one’s own mind ,as a stimulant for creative ideas.
When the general shape and a few dimensions of the several components become apparent ,analysis can begin in earnest.The analysis will have as its objective satisfactory or superior performance,plus safety and durability with minimum weight,and a competitive cost.Optimum proportions and dimensions will be sought for each critically loaded section ,together with a balance between the strength of the several components. Materials and their treatment will be chosen.These important objectives can be attained only by analysis based upon the principles of friction ;of dynamics for inertia ,acceleration,and energy;of elasticity 。
Of years manufacture and service ,the design is likely to undergo changes as new ideas are conceived or as further analysis based upon tests and experience indicate altertions .Sales appeal,customer satisfaction,and manufacture cost are all related to design ,and ability ,and ability in design is intimately involved in the success of an engineering venture .
To stimulate creative thought ,the following rules are suggested for the designer .
1.Apply ingenuty to utilize desired physical properties and to control undeired ones .The performance requiement of a machine are met by utilizing laws of nature or properties of matter ( e g ,flexibility ,strength ,gravity ,inertia ,buoyancy centrifugal force ,principles of the lever and inclined plane ,friction ,viscosity ,fluid pressure,and thermal expansion ) ,also the many electrical,optical ,thermal ,and chemical phenomena.However,what may be useful in one application may be detrimental in the next.Flexibility in the valve springs but not in the valve camshaft ;friction is deired at the cluch face but not in the cluch bearing.Ingenuity in design should be applied to utilize and control the phsical proerties that are desired and to minimize those that are not deired .
2.Provide for favorable stress distribute and stiffiness with minimum weight.Oncomponents subjeted to fluctuating stress,particlar attention is given a reduction in stress concentration ,and to an increase of strength at fillets ,theads,holes ,and fits.Stress reduction are made by modification in shape ,and strengthening may be done .by prestressing treatments such as surface rolling and shallow hardening.Hollow shafts and tubing and box sections five a favorable stress distribution,together with stiffness and minimum weight .Sufficient stiffiness to maintain alignment and uniform pressure between contacting surfaces should be provided to crank ,cam ,and gear shafts and for enclosures.and frames containing bearing supports .The stiffiness of shafts and other components must be suitable to avoid resonant vibrations.
3.Use basic equations to calculate and optimize dimensions .The fundamental equations of mechanics and the other sciences are the accepted bases for calculations They are sometimes rearrannged in special forms to facilitate the determination or ptimization pf dimensions ,such as the beam and surface stress equations for determination for determining gear-tooth size .Factors may be added to a fundamental equation for conditions not analtically deteminable .e.g,on thin steed tubes an allowance for corrosion added to the thickness based on pressure . On thin steel tubes ,an allowance for corrosion added to the thickness based on pressure.When it is necessary to apply a fundamental equation to shapes ,materials,or conditions which only approximate the assumptions for its derivation,it is sone in a mannerwhich gives results on the safe side .In situations where data are incomplete ,equations of the science may be used as propotioning guides to extend a satisfactory design to new capacities .
4.Choose material for a combination of properties.Materials should be chosen for a combination of pertinent properties ,not only for stengths ,hardness,and weight,but sometimes for resistance to impact ,corrosion, and low or high temperatures Cost and fabrication properties are factors ,such as weldability,machinability,sensitivity to variation in heat-treating temperatures ,and required coating.
5.Select carefully between stock and integral components. A previously developed component is frequently selected by a designer and his company from the stocks of parts manufactures,if the important meets the performance and reliability requirements and is adaptable without additional development costs to the particular machine being designed.However ,its selection should be carefully made with a full knowledge of its properties ,since the reputation and liability of the company suffer if there is a failure in any one of the machine`s parts .In other cases the strength ,reliability,and cost requirement are better met if the designer of the macine also designs the component , with the particular advantage of compactness if it designs integral with other components ,e.g.,gears to be forged in clusters or integral with a shaft .
6.Provide for accurate location and non-interence of parts in assembly.A good design provides for the correct locating of parts and for easy assembly and repair .Shoulders and pilot surfaces give accurate location without measurement during assembly Shapers can be designed so that parts cannot be assembled backwards or in the wrong place .Interference ,as between screws in tapped holes ,and between linkage must be avoided ,or provision must be made to minimize any resulting detrimental displacements and stresses.
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